ABSTRACT. Total knee arthroplasty (TKA) is a common approach to treating end-stage osteoarthritis of the knee while relieving pain and restoring joint function. However, the procedure has produced variations in postoperative outcomes, with up to 20% of patients left dissatisfied. Therefore, it is important to understand the preoperative and intraoperative factors that drive knee function post-TKA. Using intraoperative data acquired from a surgical navigation system and matched with patient pre- and postoperative data, this study aimed to identify preoperative and intraoperative predictors of PROMs measured using the Oxford Knee Score (OKS) at 1-year follow-up. We analysed 363 cases of navigated TKA at our institution and matched them to preoperative and postoperative patient clinical records including age at index surgery, BMI, sex, presence of co-morbidities, EQ5D anxiety/depression score, and preoperative and postoperative OKS. Starting with a base model of 26 predictor variables, a linear regression model with backward elimination was used to identify predictors of postoperative OKS on a training set of 290 patients. 73 patients (20%) were randomly set aside to use as validation. We then used the remaining predictor variables to train two additional regression models: a Support Vector Machine (SVM) and a Boosted Decision Tree then calculated the coefficient of determination (R2) and percent of patients that where the postoperative OKS was correctly identified within the minimally important clinical difference of 4.9 when the models were applied to the validation set. Of the 26 predictor variables, 10 predictors remained in the final model following backwards elimination, including four that directly under the control of the surgeon. The R2 of the linear regression, SVM, and XGBoost models were 0.37, 0.30, and 0.29 respectively within the validation set. Percentages of patients with correctly predicted OKS within the MICD ranged from 52% to 57% (linear regression to SVM). In this study, we identified sets of preoperative and intraoperative factors which are partially predictive of postoperative OKS at 1-year follow-up. Post-operative prediction models such as the models presented here will help to guide continued research into which intraoperative variables, including bony resection depths, implant alignment, and whether to do ligament releases in surgery, most affect implant function post-TKA and to inform patients and clinicians of possible clinical outcomes.

ABSTRACT. Effects of cruciate-retaining total knee arthroplasty (CR-TKA) on the rotational stability are not fully investigated. The aim of this study is to investigate pre and postoperative rotational laxity of CR-TKA. 25 knees which underwent CR-TKA were evaluated. Passive rotational stress were applied to the knees at each flexion angle with image-free navigation monitoring. Internal and external rotational angle were measured at pre and postoperative. The results indicated that the postoperative rotational laxity were significantly lower than those of preoperative level at initial and intermediate flexion. Our study demonstrated that further rotational stability has observed compared to the preoperative levels in CR-TKA.

ABSTRACT. A common goal in total knee arthroplasty (TKA) is to obtain collateral ligament balance in both flexion and extension while maintaining neutral overall coronal alignment. Femoral component rotation is a key variable in achieving this goal. There are two prominent techniques used in TKA to determine implant orientation, measured resection and gap balancing, but there is some controversy over which technique is superior. At our institution, we regularly use both techniques over a wide range of patients with varying degrees of preoperative coronal deformity. We therefore asked, using intraoperative measurements from a surgical navigation system, can we detect significant differences in external rotation of the femoral component between measured resection and gap balancing techniques, and do any such differences occur more frequently or at higher levels at particular values of preoperative coronal deformity? We analysed 3922 navigated TKA cases undertaken at our institution which had complete measurements of preoperative overall coronal alignment and external rotation of the femoral component relative to the dorsal condyles line. We then compared cases using measured resection to those using the gap balancing technique, stratifying patients by degree of preoperative coronal deformity and applying a two-sample t-test. A total of 1969 cases that used measured resection and 1953 cases that used the gap balancing techniques were identified. We found no significant differences between the two techniques across most of the preoperative coronal deformity groupings, though small differences were detected in two specific subgroups: the femoral component was slightly more externally rotated in the measured resection cohort when the preoperative coronal deformity was between neutral and 5⁰ valgus (mean ± standard deviation - measured resection: 3.6⁰ ± 1.1⁰, gap balancing: 3.0⁰ ± 1.1⁰, p < 0.00625) and between 5⁰ valgus and 10⁰ valgus (measured resection: 4.3⁰ ± 1.4⁰, gap balancing: 3.7⁰ ± 1.3⁰, p < 0.00625). This study has shown that there were essentially no substantial differences between the external rotation of the femoral component between the gap balancing and measured resection techniques regardless of the degree of preoperative coronal deformity. Overall, we feel that surgical decisions regarding which technique to use should be based more on any correlations with other patient outcome measures that may be better elucidated in future studies.

ABSTRACT. Introduction: Existence of knee extra-articular deformity has significant implication on the development and management of knee osteoarthritis. Careful preoperative planning is required when considering total knee replacement (TKR) in these cases due to altered mechanics of the knee. Computer-assisted navigation is a powerful tool that can assist in achieving mechanical alignment in TKR. The purpose of this study was to assess the usefulness of using computer-assisted navigation TKR in treating knee osteoarthritis associated with extra-articular deformity.

Methods: This is a retrospective study in which patients with knee osteoarthritis associated with extra-articular deformity, who were treated with computer-assisted navigation TKR in the period between January 2017 and December 2019, were included. TKRs were fitted using OrthoPilot® computer navigation system (BBraun-Aesculap, Tuttlingen, Germany). Preoperative and postoperative radiographs and planning were reviewed. Preoperative and postoperative Oxford Knee Scores were compared.

Results: Twenty-two patients were included in this study. One lost follow up was excluded. The minimum follow up was 24 months. OKS has improved from 18 ± 9 points preoperatively to 38 ± 5 points postoperatively.

Conclusion: Computer-assisted navigation is a powerful tool that can assist in achieving mechanical alignment and improve the outcome in TKR.

ABSTRACT. INTRODUCTION: Excessive post-operative tibiofemoral rotational mismatch can result in inferior patient outcomes. This highlights the importance considering the femoral axial alignment during tibial axial alignment. This study investigates different tibial rotational references including Insall’s axis, Cobb’s axis, and the projection of the TEA on the proximal tibial plateau in the CT, weightbearing and extension distracted positions.

METHODS: All patients obtained a pre-operative long-leg supine CT scan, weightbearing antero-posterior radiograph and an extension distracted radiograph. Each CT scan was segmented and landmarked, and the resulting 3D bone models were registered to the two radiographs. The position of Insall’s axis was determined relative to Cobb’s axis and the projection of the surgical TEA on the proximal tibia in the supine CT, weightbearing and extension distracted positions.

RESULTS: From the 325 joints analysed, the mean external rotation of Insall’s axis relative to Cobb’s axis and the projection of the TEA in the CT, weightbearing and extension distracted positions was 4.84°±3.37°, 9.67°±4.71°, 9.65°±6.59° and 8.31°±6.44°, respectively.

DISCUSSION: Although numerous tibial rotational reference axes exist, there is a lack of consensus amongst surgeons on which is most appropriate during TKA. Since tibial and femoral axial rotation mismatch is associated with post-operative knee pain, it is important to consider references for axial rotation which can be used to align both femoral and tibial components. A better understanding of the different tibial rotational reference axes including functional axes may assist the industry in reaching a consensus on a single or few reference axes for reporting purposes.

ABSTRACT. The aim of this study is to investigate the position of the femur relative to the tibia in total knee arthroplasty (TKA) and access its influence on clinical results. In this study, varus knees underwent TKA using a navigation system was evaluated. The status of the femur relative to the tibia were measured at every 15 degrees before and after TKA. In addition, knee flexion angle at 1year after surgery and tibial slope were investigated to evaluate the relationship with the position of the femur relative to the tibia. The position of the femur relative the tibia after TKA at mid-flexion was statistically anterior than it before TKA. The changes in the position of the femur at mid-flexion after TKA were positively correlated with knee flexion angle. On the other hand, there was no statistically correlation between tibial slope and the translation of the femur. Our findings suggest that the modification of the position of the femur relative to the tibia is a key factor for postoperative clinical results in TKA.

ABSTRACT. The Coronal Plane Alignment of the Knee (CPAK) classification has been used to describe healthy and arthritic knee alignment as well as to predict phenotypes which could benefit from kinematic alignment using soft tissue balancing during TKA. At our institution, we have access to a large database of navigated TKA procedures including intra and postoperative mechanical hip-knee-ankle angle (mHKA) measurements, which are defined differently than the aHKA. It has been previously recognized that these alternative, but related, measures of coronal alignment may have different distributions. The primary aim of this study was therefore to determine if the CPAK classification frequencies described in the original publication by MacDessi et al. for the aHKA are similar to frequencies acquired using the mHKA. A secondary aim was to categorise postoperative TKA alignment at our institution utilising the mHKA-based CPAK classification.

We analysed data from 3947 total knee arthroplasty procedures undertaken using surgical navigation at our institution between March 2007 and October 2022. The mHKA was measured directly during the registration process while JLO was calculated using the mHKA and LDFA (JLO = HKA + 2xLDFA). This was completed twice for each case using the pre and postoperative mHKA and LDFA. Each case was then categorized as one of the nine CPAK phenotypes. The pre-operative mean mHKA was 2.0⁰ varus using surgical navigation (compared to 0.8⁰ varus reported by Macdessi et al. using the aHKA). The pre-operative mean JLO was 175⁰ (versus 174⁰). Using the mHKA as opposed to the aHKA resulted in more knees being categorized as Class I (34.0% vs 19.4% ) or Class IV (17.5% vs 19.8%) and fewer in Class II (19.0% vs 32.2%) and Class V (6.3% vs 14.6%). All other differences in class frequencies were within 4%. For postoperative CPAK classification, a large majority of knees (72.7%) were categorized as Class V. Our study using mHKA determined during navigated TKA showed that the majority of preoperative arthritic knees were Class I, II, and IV in contrast to the original CPAK publication where most preoperative knees were Class I, II, and III. For TKAs at our institution, the goal was to mechanically align knees to neutral mHKA and JLO. This reflects in our postoperative results in that 73% of all postoperative TKAs were categorized as Class V.

ABSTRACT. Purpose It is now well established that the coronal anatomy of the lower limb is highly variable both in non-arthritic subjects and in subjects undergoing total knee arthroplasty (TKA). Two new classifications were recently described independently, but never compared: phenotypes classification and coronal plane alignment of the knee (CPAK) classification. The objective of this study was to compare the phenotype classification and the CPAK classification in the same patient at the time of TKA.

Methods Five hundred and twenty cases were randomly selected among patients operated on for a TKA with navigation assistance. Anatomical parameters were collected during surgery, and the corresponding data of the CPAK classification were calculated. The numerical value of measured Hip-Knee-Ankle angle (HKA) and arithmetic Hip-Knee-Ankle angle (aHKA) in the same subject was compared.

Results The measured HKA had a mean of 3.0° (standard deviation of 6.0°). The calculated aHKA had a mean of 1.8° (standard deviation 4.8°). There was a significant difference between the value of the two measurements in the same subject (p=0.005). There was a weak negative correlation between the values of the two measurements in the same subject. In addition, there was no relationship between HKA values and joint line obliquity values or CPAK class.

Conclusion There was a significant difference and a weak correlation between the values of the HKA and aHKA measures in the same subject. The two analysis techniques used provide different information, and their correlation is only partial. These two techniques therefore appear to be complementary rather than exclusive. The clinical relevance of using these techniques during TKA remains unknown.

ABSTRACT. Background: We developed and released an AR-based portable navigation system, in which AR technology and gyro sensor of smartphone allows surgeons to detect the functional pelvic plane (FPP) and the placement angle of the acetabular cup during total hip arthroplasty (THA).

Methods: We retrospectively reviewed 912 hips in 834 patients underwent THA between May 2020 and December 2022 in a single institution. All THAs were performed via anterolateral surgical approach with patient in the lateral decubitus position. The conventional cup alignment guide was used for cup placement in 268 hips (conventional group), and AR- based Navigation was used in 644 hips (AR Navigation group). We compared the absolute value of the difference between the angles displayed on the smartphone display and postoperative measured placement angle with X-ray taken 1 months after surgery between groups.

Results: The mean differences between the angles displayed on the smartphone display and postoperative measured angle were significantly smaller in the AR Navigation group than the conventional group (2.7° ± 2.1° versus 3.6° ± 2.7°, P = 0.002 and 2.6° ± 2.1° versus 6.4° ± 4.2°, P = 0.001 respectively).

Conclusion:An AR-based portable navigation system provided accurate and precise inclination and anteversion angles of acetabular cup compared with the conventional freehand technique during THA with patients in the lateral decubitus position.

ABSTRACT. Aims We sought to compare the radiographic parameters concerning the sagittal alignment of the standing whole-body skeletons between the knee extension group and control group using the low-dose biplanar X-ray system in a young adult population without knee pain, and to investigate the associated variables for the sagittal knee angle (sagKA) among the radiographic parameters of global sagittal alignment. Methods We reviewed whole-body standing sagittal radiographs of 124 young adults taken from December 2018 to May 2020 in a single institution. We compared the radiographic parameters concerning the lower extremity sagittal alignment and global sagittal alignment between the knee extension group and control group. The factors correlated with sagKA were evaluated using multiple linear regression analysis. Results The sagittal vertical axis (SVA), the horizontal offset between the gravity line (GL) and the posterior edge of S1 endplate (GL-S), and the horizontal offset between the GL and the hip center (GL-H) were -11.6±21.3 mm, 5.1±23.8 mm, and -25.1±27.1 mm in the knee extension group, respectively, which were significantly smaller than those in the control group. The C7 plumb line (C7PL) and GL were deviated posterior to the sacrum and the hip center in the knee extension group, with the mean sagKA of -5.6° in young adults. Conclusion The GL-H using GL, not the SVA using C7PL, was a significant radiographic factor associated with the sagKA.

ABSTRACT. Background: Several robotics of TKA has been introduced for improving outcomes. As with all new technology, the new system is associated with a learning curve. Therefore, the aim of this study is to determine the learning curve necessary to minimize the operative time and to evaluate the alignment accuracy when using advanced active robotic (AR) TKA (AR-TKA). Methods: In AR TKA, advanced active robotic technology refers to the use of a robot for planning and bone preparation by a milling tool under surgeon guidance and control. Operative times, implant and limb alignment were evaluated. Sixty patients were classified into 6 groups according to the day of surgery. The differences among 6 groups were analyzed to assess learning curves for operative time, implant alignment and lower leg alignment. The cumulative summation analysis(CUSUM) was performed for learning curve assessment. Results: AR-TKA was associated with a learning curve of more than 40 cases for operative time (p<0.001). After 40 cases, the operative time was significantly decreased by approximately 15-20 minutes. The precision of implant positioning and lower limb alignment showed no learning curve. An average deviation for the coronal planes of the femoral and tibial implants from the preoperative plan was observed less than 1.0°. Limb alignment showed a mean deviation of 1.6° towards varus postoperatively compared to the intraoperative plan. The inflection point of CUSUM analysis was found as 39 cases from the initial case. Conclusion: Active Robotic total knee arthroplasty is associated with a learning curve of 40 cases for operative time. There was no learning curve-associated component position. This study demonstrated a high degree of accuracy with regards to implant position and lower limb alignment.

ABSTRACT. Robot assisted anterior cruciate ligament (ACL) reconstruction generally requires preoperative computed tomography images. In this study, we proposed a handheld robotic system for cruciate ligament reconstruction that used intraoperative arthroscopic images as in the conventional procedure, and a cadaver study was performed. A smart handheld tool was developed by our team, which consisted of active tracking system and semi-active robot at the end effector. A skeletal optical marker was placed at proximal tibia via the same incision where entry of tibial tunnel was expected. Under direct arthroscopic vision, point clouds on the surface of medial and lateral tibial plateau were collected by a probe to create a tibial plane, and the targeted intra-articular exit of the guiding pin for tunneling was also marked with the probe Furthermore, point cloud of the proximal medial tibial surface was then collected from the same wound to obtain another plane for tunneling. An angle of 45o in respect to the tibial plateau was set for the tibial tunnel, and the axis of guiding pin was planned. As the surgeon held the robot near the entry point of tunnel, the auto-adjusting function of the end-effector was activated to maintain at the drilling path, allowing surgeons to carry out precise placement of the guiding pins. This was a cadaver study in which we proved the concept of using arthroscopic views, in combination with our smart handheld tool to perform tibial tunneling for anterior cruciate ligament reconstruction.

ABSTRACT. Most CAOS for THA is used only for cup placement. Only Stryker Navigation provides real time navigation for stem insertion, however, few surgeons use this system during stem insertion because its accuracy is believed to be low. We analyzed whether the additional reference points on distal femur improve the accuracy of stem placement. Sixty-three hips of 57 cases (13 males, 44 females, average age: 65.9 y.o.) were analyzed in the study. Proximal registration group (36 hips) were registered with 30 arbitrary points on proximal femur and distal registration group (27 hips) were registered with additional 4-8 points on the distal femoral condyle in addition to 30 arbitrary points on proximal femur. The differences (average ± standard deviation of absolute values) between the pre- and post-operative angles of stem anteversion were 3.7 ± 3.5°in the only proximal registration group, and 3.8 ± 3.1° in the distal addition group. The differences (average ± standard deviation of absolute values) between the pre- and intra-operative angles of stem anteversion were 3.6 ± 2.2° in the proximal registration group and 1.6 ± 1.7° in the distal registration group. Registration with additional distal reference points on femur did not improve accuracy and precision for stem placement. However, addition distal reference points provided intraoperative replication of preoperative planning. Future modifications are needed to improve accurately for stem insertion.

ABSTRACT. Few surgeons use computer assisted surgery for stem placement in THA because its accuracy is not sufficient rather than that for acetabular cup placement. Recently, cemented stem can be available in CT-based navigation, however, accuracy and precision of cemented stem alignment has not been reported. We compared accuracy and precision between cementless and cemented stems using the same CT-based navigation (Stryker hip navigation). We analyzed 43 cases (10 men, 33 women; average age 69.3 years) using cementless and cemented stem (Accolade II stem and Exeter stem [Stryker]) after CT-based navigation assisted THA. The differences (average ± standard deviation of absolute values) between the pre- and post-operative angles of stem anteversion were 3.8 ± 3.0° in the cementless group, and 2.4±1.8° in cemented group, respectively. There was a significant difference in precision in stem anteversion between the two groups. The accuracy and the precision of stem anteversion using the taper-wedge stem in this study was comparable to the previous reports using CT-based navigation. However, the precision of stem alignment with cemented stems was more accurate. When we used cemented stem, stem alignment consisted of 4 factors (stem flexion, varus, anteversion, and depth) could be completely controlled by checking the numbers on the navigation screens until bone cement hardened. Therefore, precision of cemented stem alignment using CT-based navigation are more accurate than that of cementless stems.

ABSTRACT. Hip instability has been reported to relate with the progression of Developmental Dysplasia of the Hip (DDH). However, previous studies utilized the evaluation methods in non-weight bearing, therefore it still remains unclear about the influence of morphological characteristics on joint instability in weight bearing. The aim of our study is to measure joint stability in weight bearing, and to evaluate its relationship with the progression of DDH. We evaluated 13 hips with symptomatic DDH. Image acquisition was performed using a CT scanner and an X-ray flat panel detector system (FPD). The CT data were then converted to voxels to construct a 3D gray-scale digital image. Virtual 2D images generated from the 3D gray-scale model were then matched with the X-ray images acquired using the FPD both in supine and standing position. A negative correlation between femoral head displacement distance and CE angle in DDH with a CE angle of less than 18°, which was consistent with previous findings, but the results showed that the hip was unstable in borderline DDH (BDDH) with preserved bony coverage. Based on the results of our study and those of previous studies, we hypothesized that hip instability may exist in DDH, which does not necessarily correspond to the CE angle, and that dynamic instability may be involved in the appearance of symptoms in BDDH.

ABSTRACT. Background: Kinematic alignment technique has shown promising results, but there might be a risk of failure in the patient with extreme deformities. In order to prevent the risk of failure, modified Kinematic alignment (mKA) technique was proposed to achieve (safe) range of alignment by limiting the position of implant within 5° of femoral & tibial mechanical axis. Functional alignment (FA) technique is a relatively new concept to consider not only patient’s specific anatomy, but also to aim achieving balanced gap with respecting the native soft tissue envelope. The purpose of this study to compare the difference in the flexion and extension gap balance and bony resection depth between mKA and FA. Methods: 100 TKAs were preformed with an CT-based MAKO robot. Gap balancing was evaluated real-time during operation, mKA plan was considered to be successful when the medial-lateral gap difference within 2mm. When gap balancing was failed, implant position was changed within 5° of mechanical axis according to FA concepts until satisfactory gap balance was achieved. Bony resection depth, implant position, final tibio-femoral gap balance in extension and 90° flexion were compared with the mKA plan. Results: A mKA plan achieved successful gap balancing in 85% for the extension gap (18.33 ± 1.7mm) and 43% for the flexion gap (21.72 ± 2.3mm). After FA adjustment, gap balance was achieved in the extension gap (18.93 ± 1.2mm) and flexion gap (21.55 ± 1.4mm) in all cases. To achieve gap balancing, final femoral component position was more externally rotated relative to the posterior condylar axis (0° with mKA compared to 2.5° with FA, p=0.00), and more flexed relative to the sagittal plane (1.64° with mKA compared to 2.11° with FA, p=0.00). All bone resection depth were significantly less for FA compared to mKA. Conclusion: This study indicates that the use of FA significantly contributes to gap balance and less bone resection compared to mKA by more external rotation and flexion of the femoral component.

ABSTRACT. Purpose This study aimed to investigate whether acetabular cup positioning in robotic arm-assisted THA (rTHA) was accurate that than in computed tomography (CT) -based navigation THA (nTHA) performed through anterolateral approach. Methods This is a retrospective case-control study, which comprised of 19 patients who underwent rTHA and 16 patients who underwent nTHA. All procedures were performed by senior surgeons, using a modified Watson–Jones approach. Clinical data (surgical time, intraoperative blood loss, and total perioperative blood loss), and radiographic parameters, using pre and postoperative CT (inclination and anteversion angles) were statistically compared between the two groups. Result No significant differences were observed in surgical time, intraoperative blood loss, and total perioperative blood loss between the rTHA and nTHA groups. For rTHA group cup aligment, the mean RI was 39.0°±1.9° and the mean RA was 15.2° ±1.8°. With nTHA group, the mean RI was 40.8° ±2.6° and the mean RA 17.6° ±3.3°. For both measurements there was a significant heterogeneity of variances. The mean absolute difference was 1.5°±1.0° in RI and 1.4°±1.0° in RA in rTHA. That was 2.2°±2.0° in RI and 3.1°±3.5° in RA in nTHA. For both of RI and RA, rTHA was significantly smaller than nTHA. Conclusion The cup positioning through anterolateral approach was more accurate in robotic arm assisted THA than in CT-based navigation THA.

ABSTRACT. Aims: There have been some reports that navigation systems during total hip arthroplasty (THA) are useful in preventing malposition of the acetabular cup. However, there have been few reports from low volume hospital. The aim of this study was to compare the accuracy of acetabular cup placement between using and without portable navigation system in our hospital, which is low volume hospital, and to investigate the usefulness of navigation system.

Methods: We analyzed retrospectively. We compared acetabular cup placement between navigation group (n=16) and conventional group (n=22). The cup position was determined by postoperative computed tomography (CT) scan. We analyzed the angle of radiographic inclination and radiographic anteversion, and the difference between postoperative angle and target angle.

Results: The mean cup inclination was 40.9° ± 3.6° in navigation group, and 40.8° ± 7.9° in conventional group. And the mean cup anteversion was 19.5° ± 4.3° in navigation group, and 25.4° ± 7.8° in conventional group. The mean absolute difference of cup inclination was 2.7° ± 2.9° in navigation group, and 5.9±5.4 in conventional group. There were significant differences (p = 0.03 and p = 0.01), and navigation group were more accurate regarding to cup placement.

Conclusion: Using portable navigation system can leads to appropriate cup placement in low volume hospital.

ABSTRACT. Purpose: Curved varus osteotomy (CVO) is a good surgical option to preserve a hip joint affected with osteonecrosis of the femoral head (ONFH). However, the osteotomy design on the axial plane has not been well discussed. The purpose of this study was two folds: one is to evaluate the variation of the osteotomy angle on the axial plane of CVO and the other is to evaluate the effect of the variation in the osteotomy angle on the axial plane on the bone union and the post-operative intact ratio. Methods: The subjects were ten patients with ONFH of Type C1, which had undergone CVO. The progression of collapse, osteoarthritic change and fragment displacement were reviewed on serial radiographs. The osteotomy angles relative to the posterior condylar and the femoral neck axis on the axial plane were measured on post-operative CT images. Results: The mean post-operative intact ratio was 45.6%. The mean the osteotomy angle to posterior condylar axis was 0.2° (-9.2-19.4). The mean the osteotomy angle to the femoral neck axis was 15.3° (-7.4-41.3). The osteotomy angle to the femoral neck axis was significantly negatively correlated with post-operative intact ratio. In two of three cases in which the osteotomy line was directed >25° anteromedial to the femoral neck, post-operative translation of the osteotomy site was occurred. Conclusion: The osteotomy angle to the femoral neck axis on the axial plane affected the bone union and post-operative intact ratio.

ABSTRACT. During bone drilling, the hard contact of the tool to the bone surface usually causes the drill bit deviated from the desired path. In this paper, a handheld orthopedic robot is equipped with a force control to adjust the contact compliance of the drill to the bone surface. With the proper contact compliance, the drill can maintain a proper contact with the bone surface, and will eventually be directed to the target entry point. The experiment on vertebra phantom shows that the robot under the proposed contact compliance visual feedback control can effectively stabilize the drill tip on the target path.

ABSTRACT. Object The aim of this study was to evaluate the usefulness of the latest version of the navigation system, version 2.6 (BrainLAB, Feldkirchen, Germany), in obtaining the optimal coronal alignment after total knee arthroplasty (TKA). Materials and methods Fifty cases which underwent TKA under the assistance of the latest version of the computer navigation system (BrainLAB version 2.6) from March 2017 to July 2017 were assigned to Group 1. Fifty cases which underwent TKA under the assistance of the previous version of the computer navigation system (Brain-LAB AG Ci Knee essential 2.1.1 system) from March 2012 to December 2012 were assigned to Group 2. Fifty cases which underwent conventional TKA from March 2007 to December 2007 were assigned to Group 3. We compared the intraoperative mechanical hip knee ankle (HKA) axis recorded in the navigation system (Group 1 and 2) and the mechanical HKA axis measured by scanogram at 3 months after surgery in the three groups.

Results At full extension, the average mechanical HKA angle of the navigation recorded after the insertion of the actual implant was -0.54° ± 1.34° in the latest-version navigation group (Group 1), and -0.63° ± 1.12° in Group 2. Intraoperative coronal alignment of 0° ± 2° was achieved in all cases of Group 1 and 2. The average mechanical HKA angles of the group 1, 2 and 3 in scanogram taken at 3 months after surgery were -0.87° ± 2.10°, -1.08° ± 1.82° and -1.23° ± 2.26°, respectively. In Group 1, coronal alignment of 0° ± 3° was achieved in 46 cases (92%) and coronal alignment of 0° ± 5° (100%) was achieved in all cases. Also, group 2 was the same as group 1. In an analysis of the outlier, however, the previous-version navigation showed larger maximal difference range of HKA (3°) than the latest-version navigation (2°) between intraoperative record and scanogram taken at 3 months after surgery. In the conventional group, coronal alignment of 0° ± 3° was achieved in 44 cases (88%) and coronal alignment of 0° ± 5° was achieved in 48 cases (96%). Conclusion Compared with the previous-version navigation, the latest navigation of version 2.6 (BrainLAB, Feldkirchen, Germany) system showed less HKA difference between an intraoperative record and scanogram at 3 months after surgery.

ABSTRACT. Morpho-functional analysis is a major aspect of preoperative planning for THA. This study aims to investigate whether pain or movement restrictions correlate with the morphofunctional parameters pelvic tilt, pelvic bend and pelvic rotation. Pre- and postoperative CT and EOS images, as well as score values of 201 Japanese patients were analyzed. No statistical relevant correlation between the score values and the parameters could be found (|rmax| = 0,38). However, the statistical power was found to be low for our data ((1-β ~ 0.10). Further research with larger data sets is desirable.

ABSTRACT. Background : The new trend of total knee arthroplasty surgery is encouraging in using Robotic assisted surgery not only more precision and accuracy of surgery but less soft tissue dissection. Ligament balancing plays an important role in prolonging longevity of TKA implant. Inadequate gap balancing produces pain and decreases longevity of implant. In Pre-Resection Balancing technique of robotic TKA, bone resection evaluated by paddle thickness, but unknown tension of gap. Aim of this study was to indicate the tension of gap resection in Robotic total knee arthroplasty Method and material : Seventy-three knees was performed by MAKO robotic assisted total knee arthroplasty. Patients received spinal block&adductor canal block anesthesia. After medial parapatellar approach was performed, deep MCL was released in varus knee, IT band was released in valgus knee. Gap tension was evaluated at extension and flexion position by paddle thickness. Femoral and tibial component position is adjusted to achieve even gap at flexion and extension. Proximal tibial was resected, gap tension was re-evaluated with tension device started from 100N in extension while increasing tension until the gap and planning gap are equal or the gap difference was less than 2 mm. We did the same technique in extension gap and flexion gap. Robotic TKA was performed as usual. Implant was installed with Cemented fixed- bearing TKA (Triathlon, Stryker) Result : The proper soft tissue balance that achieved from robotic assisted total knee arthroplasty was less than 2 mm difference in flexion and extension. Moreover, the difference of medial and lateral gap was less than 2 mm. We found that the mean soft tissue tension of medial extension gap was 165.83±33.81 N and 162.5±28.56 in lateral extension gap. The mean difference in extension gap was 3.33 N (p-value 0.571). The mean soft tissue tension of flexion gap was 166.67±39.77 N in medial side and was 190.83±39.59 N in lateral side. The mean difference in flexion gap was 24.17 N (p-value 0.001) Conclusion : Robotic assisted TKA,150-N was the median of tension in medial and lateral extension gap. However, in flexion gap the median of medial side was 150 N and lateral side was 200 N.

ABSTRACT. Improper functional orientation of the acetabular cup can result in improper positions when dynamic pelvic positions are not considered. The purpose of this study was to evaluate changes on acetabular anteversion according to pelvic tilt under various acetabular inclinations. Two artificial pelvic models were selected for this study. Acetabular inclinations on the coronal plane were 25°, 32°, 50°, and 60°. Acetabular anteversion of all components were 15°. Changes of anteversion according to pelvic tilt were measured at angles of 0°, 10°, 20°, 30°, and 40°. Computer Navigation, PolyWare 3D pro, CT, and plain radiography were used to measure each angle. The anatomical anteversions against pelvic tilt were calculated using the following formulae: anatomical anteversion (°) = −14.48Χ + 90.18 (inclination angle 25°); anatomical anteversion (°) = −12.26Χ + 80.10 (inclination angle 32°); anatomical anteversion (°) = −7.468Χ + 61.13 (inclination angle 50°); and anatomical anteversion (°) = −5.328Χ + 44.84 (inclination angle 60°) (Χ: pelvic tilt angle). Radiographic anteversion against pelvic tilt were calculated using the following formulae: radiographic anteversion (°) = −9.50Χ + 57.09 (inclination angle 25°); radiographic anteversion (°) = −8.577Χ + 50.89 (inclination angle 32°); radiographic anteversion (°) = −6.794Χ + 45.73 (inclination angle 50°); radiographic anteversion (°) = −5.226Χ + 33.08 (inclination angle 60°). In conclusion, changes in anteversion according to pelvic tilt were lesser at higher degrees of acetabular inclination.

ABSTRACT. Introduction: Malalignment of the fibula after fixation of ankle fractures with syndesmostic instability was occurred 25 - 52 % of the cases in some studies. As malalaigment of fibula is difficult to detect with conventional fluoroscopy, some authors recommend an intraoperative control with 3D image. In this study, we present our experience with the intraoperative use of the 3D image (Cios Spin 3D, Siemens Healthineers, Erlangen, Germany) in the treatment of syndesmotic injuries, and compare the accuracy of intraoperative 3D imaging with postoperative CT.

Materials and methods: We treated 25 syndesmotic lesions by fixation using an intraoperative control with 3D image from April 2018. First, osteosynthesis is performed on the fracture sites of the fibula and tibia. Then, the tibio-fibular joint was reduced and temporally fixed by K-wire under conventional fluoroscopy technique. After this fixation, the position of the joint was controlled with a 3D image acquisition. The 3D image takes 100 low-dose shots while automatically rotating 200 degrees in about 1.5 minutes. If the tibio-fibular joint position was wrong, reduction was changed again before definitive fixation. Using intraoperative 3D image and postoperative CT scan, we evaluate about three-dimensional and rotational position of fibula.

Results: Eighteen patients (72%) showed a good reduction result intraoperative first reduction. The other nine patients (36%) needed a change in reduction of the tibio-fibular joint after intraoperative 3D imaging. Two was over 1.5mm shortening of fibular, three was 2mm ventral displace and the other four had over 10 degree rotational malposition. The postoperative CT scan showed 3 patients (12%) had 5~8 degree rotational malalignment.

Discussion: In this cohort, cases of malreduction decreased from 36% after initial reduction to 12% at the end. On the other hand, three cases (12%) of malposition are remained. We could not find it during surgery is caused that the malreduction of posterior maleollar fragment, the resolution of the 3D image is insufficient due to the metal artifacts, and the reduction position changes when the position screw is inserted after 3D image. This part is an issue in the future.

Conclusion: Although exposure to radiation will increase, it is more important to reduce the malreduction rate and reduce the reoperation rate in this study.

ABSTRACT. Utility of O-arm Navigation in Spinal Tumors Excluding Screw Placement

The O-arm navigation system (Medtronic, Dublin) has been introduced in an increasing number of institutions as a tool to assist in spine surgery. It is very useful for accurate screw placement in spine fusion surgery, and our department has been using it since 2012. It is used for screw placement in pediatric scoliosis and other cases, and we report on three cases in which we were able to effectively use it in the treatment of a spinal tumor. Case 1: 46-year-old male. MRI showed extensive brightness changes in the L4 vertebral body. A transpedicular biopsy was performed under C-arm fluoroscopy to confirm the diagnosis, and the results showed no malignant findings and a chronic osteomyelitis-like finding. PET-CT was performed afterward due to the appearance of neuropathy in the lower extremities and showed no FDG accumulation in the L4 vertebral body and accumulation in the surrounding lymph nodes. The right iliac bone was also found to have an accumulation, and at the same time of lumbar decompression, the FDG accumulation site in the iliac bone was sampled using O-arm navigation. The pathology result was Langerhans cell histiocytosis. The patient continues to be an outpatient of the department of internal medicine. Case 2: 56-year-old male, tumor recurrence near L5/S1 facet joint (chondrosarcoma grade 1). The operative orientation became difficult (transverse processes, etc., which were resected at the initial surgery). However, an appropriate approach, tumor resection, and posterior fixation were achieved by O-arm navigation. One year after surgery, the patient is currently under observation with no recurrence. Case 3: 22-year-old male. He was first seen in our department because of severe low back pain, and a bone tumor (osteoid osteoma) was found in the left facet joint at L5/S1 on imaging examination. Using O-arm navigation, the tumor was completely removed while preserving the facet joint as much as possible. His low back pain improved, and he was able to return to sports (track and field). The O-arm navigation system allows easy intraoperative CT imaging. Therefore, in spinal tumor surgery, not only accurate orientation, but also confirmation imaging after tumor resection is possible. In all three cases, safe and effective treatment was achieved by using the "strong point" of the O-arm navigation system.

ABSTRACT. Background: The use of robotics in TKA has been shown to minimize human error, as well as improve the accuracy and precision of component implantation and mechanical axis alignment. Dr LCT (CT based full active, 7 axis arm robotic system) was newly developed in 2021. The present study aimed to demonstrate that robot-assisted TKA using Dr LCT is safe and capable of producing a consistent and accurate postoperative mechanical axis.

Methods: This is prospective randomized controlled study. From June 2021 to September 2021, 50 osteoarthritis patients (average age: 69.7, male: 7, female: 43) was preformed bilateral TKA with mechanically alignment. The operations were performed one Knee with conventional ROBODOC & ORTHODOC and the other knee with Dr LCT, same times or in a week. The radiological evaluations included mechanical axis, implant position (α,β,γ,δ angle) according to the system of American Knee Society. Clinical outcomes and motion were measured preoperatively, 6 weeks, 3 months, 6 months and 1 year postoperatively.

Results: There was no difference in the postoperative α, β, γ angle and mechanical axis between two groups (p<0.05). In group ROBODOC, mechanical axis angle changed from preoperative varus 8.5 to postoperative varus 0.3° with 1 outlier. In group Dr LCT, mechanical axis angle changed from varus 7.8° to varus 0.2° with 1outliers. In group ROBODOC, the mean α, β, γ, δ angle were 96.2°, 89.9°, 1.5°, 84.3° and 96.2°, 90.2°, 1.4°, 83.4° in group Dr LCT. There was no difference of clinical results between two groups. Mean knee society score was improved in both group, (pain score; from 46.3(preoperative) to 83.4(postoperative) in ROBODOC, from 50.3 to 85.0 in Dr LCT, function score: from 43.2 to 86.7 in ROBODOC, from 39.1 to 86.7 in Fr LCT). WOMAC score showed similar results; 68.1 to 15.6 in ROBODOC, 69.6 to 15.70 in Dr LCT). There was significant difference in surgery times between two groups (Match times (minutes): 7.9 in ROBODOC, 2.8 in Dr LCT, Cut time: 23.5 in ROBODOC, 8.2 in Dr LCT).

Conclusion: On the basis of our results, TKA with ROBODOC and TKA with Dr LCT showed good radiological & clinical results without difference, whereas operative time and cutting time were founded to be less in TKA with Dr LCT. We think that Dr LCT system has clinically safety and effectiveness, comparable to ROBODOC system. However, a long term follow up evaluation will be necessary in Dr LCT system.

ABSTRACT. Due to the complex anatomy of the pelvis, achieving adequate surgical margins and performing limb-sparing resections of pelvic tumors can often be challenging. Marginal resections have a high local recurrence rate, up to 70%, therefore, achieving adequate margins is of paramount importance. We performed CATS for pelvic tumors and selected extremity tumors. We initiated CATS in November 2018 and present here the retrospective analysis of our prospectively maintained database from November 2018 to November 2022. We evaluated the intraoperative feasibility, margin status, and complications in this cohort. A total of 78 cases were planned for CATS during the study period, of which 49 underwent CATS (Navigation group) and 29 were operated without CATS (Non-navigation group). Navigation was successfully executed in 46 cases and failed in three cases. The majority of the cases in the navigation group were of Ewing's sarcoma. The mean time taken for navigation was 25.12 minutes. The average registration error was 1.08mm (range of 0.6 to 1.8mm). There were no margin-positive cases in the navigated group, while in the non-navigated pelvic and sacral tumors, six patients had margin positivity. Intraoperative complications were 18.3% in the navigation group compared to 13.7% in the non-navigated group. Navigation was used to save the sacral roots, save the acetabular roof, and for hemi-cortical excisions. Our early experience suggests that there is a learning curve with the use of navigation. With an increase in experience, the time taken for planning and intraoperative execution decreases considerably. It helps in protecting vital structures like sacral roots while providing adequate margins. There was no increase in intraoperative or postoperative complications observed with the use of CATS, even with prolonged surgical procedures. CATS is an incredible academic tool for teaching complex surgical anatomy and resections.

ABSTRACT. Adequate (femoral) implant sizing in total knee arthroplasty is of high relevance, as it is crucial for recreating both stability and pain-free mobility. Femoral size parameters include the anteroposterior (AP) height and mediolateral (ML) width. We aimed to optimize respective implant size parameters to maximize population coverage for a large database of 85,143 cases, which were provided with patient-specific implants (PSI). For a subset of 1,049 cases, the 3D surface information of the patients’ bones was available. We used this information to evaluate, whether the PSI size is representative of the bone size. The size optimization was conducted using the particle swarm optimization. Deviations between PSI and bone sizes were small and evaluated as clinically insignificant, hence the full database was used for the size optimization. The population coverage showed higher sensitivity regarding tolerated error bounds compared to the number of implant sizes. A population coverage of 84.67% was reached with an exemplary setup of 12 implant sizes and error bounds of +/- 1.5 mm for AP and +/- 3 mm for ML. Maximizing population coverage by increasing the number of implant sizes proved to be ineffective, as even with 30 implant sizes a full population coverage could not be reached. Remaining cases could instead be provided with a PSI.

ABSTRACT. The computer-assisted technique for total knee arthroplasty (TKA) was initially employed to optimize the prosthetic alignment. However, under the computer-assisted TKA, bone cutting can be executed precisely in the extra-medullary way, thus diminishing the violation of the bone marrow cavity. Diminishing bone marrow insult is an additional benefit other than the optimization of prosthetic alignment. Our team has been dedicated in unravelling the biological impacts of intramedullary reaming, and this abstract tries to summarize our serial research findings in terms of the differential biological signatures between CAOS and conventional TKAs.

ABSTRACT. In this paper, we have proposed an effective dangerous region generation method, which can fast and accurately estimate a 3D region that extends the 3D bone tumor uniformly in the 3D space by a safe margin. Guided by our generated dangerous region, the surgeon can conveniently design a set of qualified cut planes with adequate margin against bone tumor just by checking whether each plane locates outside the dangerous region. Efficacy of our method was evaluated on 17 patients receiving bone tumor resection surgery. Results showed that our method could fast generate the dangerous region for each specific patient with bone tumor, i.e., costing only about 0.17 seconds for each specific patient. Moreover, outcomes of the patients using our method are much better than those without using our method, i.e., survival rate: 8/9 versus 5/8, recurrence rate: 0/9 versus 2/8, and metastasis rate: 1/9 versus 3/8. Therefore, our method exhibits great possibility to apply in clinical practices to improve the treatment outcomes of patients with bone tumor.

ABSTRACT. Allograft or combined allograft/autograft reconstruction after oncological resection, using CAS or PSI, a multicenter retrospective study JG Gerbers 1, JJW Ploegmakers 2, RJP van der Wal 1, D Broekhuis 1, PC Jutte 2 1. Leiden University Medical Center, Albinusdreef 2, 2300 RC, Leiden, The Netherlands 2. Department of Orthopedic Surgery, University of Groningen, University Medical Center Groningen, Hanzeplein 1, 9700RB Groningen, The Netherlands

Allograft/autograft reconstruction is associated with significant complication rates. CAS has been described to improved resection and reconstruction accuracy potentially reducing this rate. A retrospective study was performed in two centers: LUMC and UMCG. Patients with oncological resection and graft reconstruction both using PSI/CAS were included. Union: radiologist describing integration/union. 14 patients were included. Average follow-up is 74 months (12-148). 8 patients had a surgery using CAS, 5 using PSI, 1 CAS/PSI hydrid. Location: 13 tibia (6 prox, 8 mid), 1 femur. 11 using allografts, 3 hybrid allograft/ipsilateral fibula autograft. 10 were hemicortical reconstructions, 4 intercallary. Average reconstruction length was 9,9 cm. There was 1 fracture (7%, at 16 months), 2 infections (14%, 1 late/1 early), graft survival was 86%. Union was reported in 12 out of 14 cases, taking on average 14.9 months. Bus et al describe 14% infection, 29% fracture, 40% non-union, 15% failure-rate at 84 months without CAS/PSI. Aponte-Tinao et al described 66 patients using CAS, with a 6% non-union rate, 2% reoperation rate for fractures. Our series had no graft related failures, two were revised due to (suspected) local recurrence. Fracture (7%) rate is better and infection rate (14%) comparable to reported non CAS/PSI series. Union rate was 86%, one likely due to infection/recurrence. Potential improvement point may be a lower threshold for plate fixation as both failures only used screw fixation in significant hemicortical reconstruction. CAS and PSI use can likely improve complication and failure rate in allograft/hybrid graft reconstruction after tumor resection.

ABSTRACT. Introduction In orthopaedic oncology, computer navigation and 3D-printed guides facilitate precise osteotomies only after surgical exposure[1,2]. Mixed Reality is an immersive technology merging real and virtual worlds, and users can interact with digital objects[3]. Through Head-Mounted Displays, surgeons directly visualize holographic models that overlay tumor patients in their physical environment before surgeries start. Clinical reports of MR application are limited, and no data in orthopaedic oncology.

Methods Between July 2021 and October 2022, we retrospectively reviewed eight bone tumor patients undergoing surgeries. A holographic application was created using patients’ 2D medical images. In the conventional 2D method, the surgeon studied 2D images and mentally overlaid the virtual 3D models onto the patients’ bodies. In the MR technology group, the surgeons directly visualized 3D holograms on the patients’ bodies via HMD (Figure 1). For each method, the surgeon completed 1) a Likert-Scale (LS) questionnaire to assess his opinions on the spatial awareness of the bone structures and the effectiveness of surgical planning and 2) The National Aeronautics and Space Administration-Task Load Index (NASA-TLX) score to evaluate the surgeons’ cognitive workload. The results of the two methods were compared using Wilcoxon Signed Rank Test.

Results For the use of MR technology in improving surgeons’ spatial awareness of 3D models, the Likert-scale questionnaire revealed that the 3D holograms in the MR technology group were more effective than the Conventional 2D group. For the cognitive workload for preoperative clinical assessment, the MR technology group received significantly lower “mental,” “temporal,” “performance,” and “frustration” scores; however, they received significantly higher “physical demand” and “effort” ratings than the Conventional group.

Discussion MR technology improved 3D visualization and spatial awareness of bone tumors in patients’ anatomies and may facilitate surgical planning before skin incisions in orthopaedic oncology surgery. The results concurred with the first case series of MR applications during orthopaedic surgery [4]. With less cognitive load and better ergonomics, surgeons can stay focused on the patients and surgical tasks while keeping their hands free and sterile to manipulate virtual objects [5]. Further studies can investigate whether MR technology translates into better clinical outcomes

ABSTRACT. Short-term clinical & radiologic outcomes of Imageless - robotic assisted total knee arthroplasty versus conventional total knee arthroplasty in Thabo Crown Prince Hospital: Retrospective cohort study Pornpavit Sriphirom1, Pitee Wongyongsilp2, Woraphot wicharn3 Rajavithi Hospital, Bangkok Thailand Thabo Crown Prince Hospital, Nongkhai province Thailand Abstract Introduction: Robotic assisted total knee arthroplasty (RATKA) was proven that improved component position, ligament balanced and decreased outlier leading to improved clinical results and implant survivorship. Aiming of this study is comparison of short-term clinical and radiologic outcomes between RATKA versus conventional TKA (CMTKA) in Thabo Crown Prince Hospital, Thailand. Methods: Retrospective cohort study by single surgeon, from July 2020 to August 2022 compared 51 RATKA and 49 CMTKA. Baseline data and short-term clinical outcomes including knee society score (KSS), operative time, estimated blood loss (EBL), length of stay (LOS), complications and radiologic outcomes were collected at postoperatively 3 months follow up. Results: There was no statistically significant difference in KSS, EBL, LOS and complications between RATKA and CMTKA (P < 0.05). Operative time was significant greater in RATKA (138 vs. 162 min, P < 0.05). Radiologic outcomes in CMTKA, posterior condylar Offset, posterior condylar deviation, tibial slope was significant higher (P < 0.05). In subgroup analysis, patients with post operative tibial slope ≥ 7° (poor clinical outcomes) in CMTKA significantly higher than in RATKA (P = 0.021). Conclusions: Imageless - robotic assisted total knee arthroplasty demonstrated that more benefit in posterior condylar offset and posterior tibial slope restoration and seem to be better in short-term clinical outcomes.

ABSTRACT. In this work, we present a finite element analysis (FEA) in SOLIDWORKS 2018 software to study stress and displacement of normal tibias and tibias implanted with a 4- mm-thick CoCr tibial tray (4mm-tray) and 2-mm-thick titanium alloy (2mm-tray). Under vertical loads of 1000 and 2000 N, the stress and displacement of both tibia tray models were analyzed. The study show that stress concentrated around the central region compared to the peripheral region in all models, which caused more deformation of the material in the central region. However, the 4mm-tray exhibited a more rigid construct compared to the 2mm-tray. Under any load, the 2mm-tray exhibited more tray deformation, with a central–peripheral deformation difference of approximately five times more than the deformation difference for the 4mm-tray. Moreover, stress on the peripheral region of the supported proximal tibia was only 18–22% of that of a normal bone for the 4mm-tray compared to 54–66% for the 2mm-tray. Both tibial tray implant models exhibited some degree of stress shielding on the peripheral region of the supported proximal tibia. However, the greater modulus and thicker baseplate construct

ABSTRACT. Background: Robotic-assisted unicompartmental knee arthroplasty (UKA) has improved component alignments and clinical outcomes. A previous literature review did not report functional outcomes and survivorship in long-term follow-up. Aim of this study was to compare the clinical outcomes, radiologic outcomes, survivorship of implant, and revision rates of robotic-assisted UKA to those of conventional mobile Oxford UKA in long-term follow-up at a minimum of ten years. Method and materials: This is a prospective study, One hundred knees, ninety-two patients with medial unicompartmental osteoarthritis were assigned to treatment with either conventional Oxford mobile UKA or robotic-assisted surgery UKA. Radiographic outcomes and Oxford knee score was evaluated at 1,5 and 10 years after surgery. Revision rates and mode of failure were recorded, compared and analysis. Results: The comparison between the two groups in terms of post-operative radiographic measurement included femorotibial angle (0.02° ± 4.40 vs. 3.38° ±3.45), femoral component alignment (3.13° ± 2.11 vs 8.08° ± 2.99), tibial component alignment (1.47° ± 1.59 vs. 0.33° ± 2.49), posterior slope (3.89° ±3.15 vs 2.02° ±1.87) in robotic group were superior than conventional group. Only ten years survivorship curve in robotic group was lower than conventional group. However, Oxford knee scores of one year, five years, and ten years follow-up were not significant difference for both groups. Conclusion: Robotic-assisted UKA surgery makes prosthesis positioning more accurate than conventional UKA. However, no differences in clinical outcomes and rates of revision were found in the midterm statistically significant. Early revision rates were observed in the robotic-assisted UKA group.

ABSTRACT. Introduction: Robotic-assisted total hip arthroplasty (raTHA) was introduced in recent decades, offering proven advantages in improving the acetabular cup placement. However, raTHA requires specific equipment and additional costs of $1,788 per case which raises the question of its cost-effectiveness. We believe that the use of raTHA may be substantially advantageous in complicated cases such as developmental dysplasia of the hip (DDH) whose anatomy are deformed and hard to get proper prosthesis alignment.

Method: The systematic review and meta-analysis was conducted in accordance with the 2020 PRISMA to review the benefits of raTHA over conventional total hip arthroplasty in DDH patients. From 80 studies that we found, only 3 of them were eligible. We primarily focused on the radiological outcomes and complications.

Results: The analyses proved that raTHA was associated with a significantly increased rate of cup placement within Lewinnek's safe zone from 66.3% to 95.3% with odds ratio of 12.32 and 95% CI (1.40, 108.81; p = 0.02). Similarly, the raTHA was associated with the higher accuracy of cup placement in Callanan’s safe zone from 46.5% to 86% with odds ratio of 11.09 and 95% CI (1.10, 111.64; p= 0.04). All studies had no report of any complications and revisions during the short term follow-up. Functional outcomes were not compared and analyzed since the original studies reported these outcomes in different formats.

Conclusion: This meta-analysis revealed the conceivable benefits of the raTHA in terms of improving radiological outcomes which potentially outweigh the total costs in such well-selected cases. Even though we have provided the first and most-recent evidence-based review of the use of raTHA in secondary osteoarthritis due to DDH, a limited number of studies resulted in low accuracy of statistical results.

ABSTRACT. Background: Since computer assisted surgery total knee arthroplasty (CAS-TKA) could avoid injury to femoral canal and also resulted in less blood loss. We hypothesized that CAS-TKA should resulted in lesser degree of inflammatory response compared to conventional TKA.

Methods: Forty patients whom underwent TKA from May 2019 to May 2020 were randomly divided into two groups. One group underwent CAS-TKA (CAS-group) and the other underwent conventional TKA (CON-group). We compared level of local and systemic inflammatory markers using intra-operative and post-operative blood and joint fluid samples. Knee injury and osteoarthritis outcome score (KOOS) were also evaluated. All patients were followed to observe complication or readmission at least 2 year postoperatively.

Results: Forty patients were divided into 2 groups. There was no statistically significant difference in pre-operative demographic data, tourniquet time and operative time between groups. However, CAS-group exhibited less blood. After operation, both groups showed significantly increase level of Serum IL-6, ESR, CRP, JIL-6 and JCRP levels at all time point. However, CAS-group has statistically significant lower degree of change in IL-6, ESR, CRP levels at 2 weeks. There were no significant differences in KOOS between groups. There was one case of intra-hospital acute ischemic stroke in CON-group and two cases of periprosthetic joint infection in CAS-group at 13 and 20 months follow up period.

Conclusions: CAS-TKA resulted in lower level of inflammatory response after operation compared to conventional TKA in early post-operative period, which could be beneficial for clinical outcomes.

ABSTRACT. Robot assisted anterior cruciate ligament (ACL) reconstruction generally requires preoperative computed tomography images. In this study, we proposed a handheld robotic system for cruciate ligament reconstruction that used intraoperative arthroscopic images as in the conventional procedure, and a cadaver study was performed. A smart handheld tool was developed by our team, which consisted of active tracking system and semi-active robot at the end effector. A skeletal optical marker was placed at proximal tibia via the same incision where entry of tibial tunnel was expected. Under direct arthroscopic vision, point clouds on the surface of medial and lateral tibial plateau were collected by a probe to create a tibial plane, and the targeted intra-articular exit of the guiding pin for tunneling was also marked with the probe Furthermore, point cloud of the proximal medial tibial surface was then collected from the same wound to obtain another plane for tunneling. An angle of 45o in respect to the tibial plateau was set for the tibial tunnel, and the axis of guiding pin was planned. As the surgeon held the robot near the entry point of tunnel, the auto-adjusting function of the end-effector was activated to maintain at the drilling path, allowing surgeons to carry out precise placement of the guiding pins. This was a cadaver study in which we proved the concept of using arthroscopic views, in combination with our smart handheld tool to perform tibial tunneling for anterior cruciate ligament reconstruction.

ABSTRACT. Most CAOS for THA is used only for cup placement. Only Stryker Navigation provides real time navigation for stem insertion, however, few surgeons use this system during stem insertion because its accuracy is believed to be low. We analyzed whether the additional reference points on distal femur improve the accuracy of stem placement. Sixty-three hips of 57 cases (13 males, 44 females, average age: 65.9 y.o.) were analyzed in the study. Proximal registration group (36 hips) were registered with 30 arbitrary points on proximal femur and distal registration group (27 hips) were registered with additional 4-8 points on the distal femoral condyle in addition to 30 arbitrary points on proximal femur. The differences (average ± standard deviation of absolute values) between the pre- and post-operative angles of stem anteversion were 3.7 ± 3.5°in the only proximal registration group, and 3.8 ± 3.1° in the distal addition group. The differences (average ± standard deviation of absolute values) between the pre- and intra-operative angles of stem anteversion were 3.6 ± 2.2° in the proximal registration group and 1.6 ± 1.7° in the distal registration group. Registration with additional distal reference points on femur did not improve accuracy and precision for stem placement. However, addition distal reference points provided intraoperative replication of preoperative planning. Future modifications are needed to improve accurately for stem insertion.

ABSTRACT. Hip instability has been reported to relate with the progression of Developmental Dysplasia of the Hip (DDH). However, previous studies utilized the evaluation methods in non-weight bearing, therefore it still remains unclear about the influence of morphological characteristics on joint instability in weight bearing. The aim of our study is to measure joint stability in weight bearing, and to evaluate its relationship with the progression of DDH. We evaluated 13 hips with symptomatic DDH. Image acquisition was performed using a CT scanner and an X-ray flat panel detector system (FPD). The CT data were then converted to voxels to construct a 3D gray-scale digital image. Virtual 2D images generated from the 3D gray-scale model were then matched with the X-ray images acquired using the FPD both in supine and standing position. A negative correlation between femoral head displacement distance and CE angle in DDH with a CE angle of less than 18°, which was consistent with previous findings, but the results showed that the hip was unstable in borderline DDH (BDDH) with preserved bony coverage. Based on the results of our study and those of previous studies, we hypothesized that hip instability may exist in DDH, which does not necessarily correspond to the CE angle, and that dynamic instability may be involved in the appearance of symptoms in BDDH.

ABSTRACT. Aims: There have been some reports that navigation systems during total hip arthroplasty (THA) are useful in preventing malposition of the acetabular cup. However, there have been few reports from low volume hospital. The aim of this study was to compare the accuracy of acetabular cup placement between using and without portable navigation system in our hospital, which is low volume hospital, and to investigate the usefulness of navigation system.

Methods: We analyzed retrospectively. We compared acetabular cup placement between navigation group (n=16) and conventional group (n=22). The cup position was determined by postoperative computed tomography (CT) scan. We analyzed the angle of radiographic inclination and radiographic anteversion, and the difference between postoperative angle and target angle.

Results: The mean cup inclination was 40.9° ± 3.6° in navigation group, and 40.8° ± 7.9° in conventional group. And the mean cup anteversion was 19.5° ± 4.3° in navigation group, and 25.4° ± 7.8° in conventional group. The mean absolute difference of cup inclination was 2.7° ± 2.9° in navigation group, and 5.9±5.4 in conventional group. There were significant differences (p = 0.03 and p = 0.01), and navigation group were more accurate regarding to cup placement.

Conclusion: Using portable navigation system can leads to appropriate cup placement in low volume hospital.

ABSTRACT. Purpose: Curved varus osteotomy (CVO) is a good surgical option to preserve a hip joint affected with osteonecrosis of the femoral head (ONFH). However, the osteotomy design on the axial plane has not been well discussed. The purpose of this study was two folds: one is to evaluate the variation of the osteotomy angle on the axial plane of CVO and the other is to evaluate the effect of the variation in the osteotomy angle on the axial plane on the bone union and the post-operative intact ratio. Methods: The subjects were ten patients with ONFH of Type C1, which had undergone CVO. The progression of collapse, osteoarthritic change and fragment displacement were reviewed on serial radiographs. The osteotomy angles relative to the posterior condylar and the femoral neck axis on the axial plane were measured on post-operative CT images. Results: The mean post-operative intact ratio was 45.6%. The mean the osteotomy angle to posterior condylar axis was 0.2° (-9.2-19.4). The mean the osteotomy angle to the femoral neck axis was 15.3° (-7.4-41.3). The osteotomy angle to the femoral neck axis was significantly negatively correlated with post-operative intact ratio. In two of three cases in which the osteotomy line was directed >25° anteromedial to the femoral neck, post-operative translation of the osteotomy site was occurred. Conclusion: The osteotomy angle to the femoral neck axis on the axial plane affected the bone union and post-operative intact ratio.

ABSTRACT. During bone drilling, the hard contact of the tool to the bone surface usually causes the drill bit deviated from the desired path. In this paper, a handheld orthopedic robot is equipped with a force control to adjust the contact compliance of the drill to the bone surface. With the proper contact compliance, the drill can maintain a proper contact with the bone surface, and will eventually be directed to the target entry point. The experiment on vertebra phantom shows that the robot under the proposed contact compliance visual feedback control can effectively stabilize the drill tip on the target path.

ABSTRACT. Object The aim of this study was to evaluate the usefulness of the latest version of the navigation system, version 2.6 (BrainLAB, Feldkirchen, Germany), in obtaining the optimal coronal alignment after total knee arthroplasty (TKA). Materials and methods Fifty cases which underwent TKA under the assistance of the latest version of the computer navigation system (BrainLAB version 2.6) from March 2017 to July 2017 were assigned to Group 1. Fifty cases which underwent TKA under the assistance of the previous version of the computer navigation system (Brain-LAB AG Ci Knee essential 2.1.1 system) from March 2012 to December 2012 were assigned to Group 2. Fifty cases which underwent conventional TKA from March 2007 to December 2007 were assigned to Group 3. We compared the intraoperative mechanical hip knee ankle (HKA) axis recorded in the navigation system (Group 1 and 2) and the mechanical HKA axis measured by scanogram at 3 months after surgery in the three groups.

Results At full extension, the average mechanical HKA angle of the navigation recorded after the insertion of the actual implant was -0.54° ± 1.34° in the latest-version navigation group (Group 1), and -0.63° ± 1.12° in Group 2. Intraoperative coronal alignment of 0° ± 2° was achieved in all cases of Group 1 and 2. The average mechanical HKA angles of the group 1, 2 and 3 in scanogram taken at 3 months after surgery were -0.87° ± 2.10°, -1.08° ± 1.82° and -1.23° ± 2.26°, respectively. In Group 1, coronal alignment of 0° ± 3° was achieved in 46 cases (92%) and coronal alignment of 0° ± 5° (100%) was achieved in all cases. Also, group 2 was the same as group 1. In an analysis of the outlier, however, the previous-version navigation showed larger maximal difference range of HKA (3°) than the latest-version navigation (2°) between intraoperative record and scanogram taken at 3 months after surgery. In the conventional group, coronal alignment of 0° ± 3° was achieved in 44 cases (88%) and coronal alignment of 0° ± 5° was achieved in 48 cases (96%). Conclusion Compared with the previous-version navigation, the latest navigation of version 2.6 (BrainLAB, Feldkirchen, Germany) system showed less HKA difference between an intraoperative record and scanogram at 3 months after surgery.

ABSTRACT. Improper functional orientation of the acetabular cup can result in improper positions when dynamic pelvic positions are not considered. The purpose of this study was to evaluate changes on acetabular anteversion according to pelvic tilt under various acetabular inclinations. Two artificial pelvic models were selected for this study. Acetabular inclinations on the coronal plane were 25°, 32°, 50°, and 60°. Acetabular anteversion of all components were 15°. Changes of anteversion according to pelvic tilt were measured at angles of 0°, 10°, 20°, 30°, and 40°. Computer Navigation, PolyWare 3D pro, CT, and plain radiography were used to measure each angle. The anatomical anteversions against pelvic tilt were calculated using the following formulae: anatomical anteversion (°) = −14.48Χ + 90.18 (inclination angle 25°); anatomical anteversion (°) = −12.26Χ + 80.10 (inclination angle 32°); anatomical anteversion (°) = −7.468Χ + 61.13 (inclination angle 50°); and anatomical anteversion (°) = −5.328Χ + 44.84 (inclination angle 60°) (Χ: pelvic tilt angle). Radiographic anteversion against pelvic tilt were calculated using the following formulae: radiographic anteversion (°) = −9.50Χ + 57.09 (inclination angle 25°); radiographic anteversion (°) = −8.577Χ + 50.89 (inclination angle 32°); radiographic anteversion (°) = −6.794Χ + 45.73 (inclination angle 50°); radiographic anteversion (°) = −5.226Χ + 33.08 (inclination angle 60°). In conclusion, changes in anteversion according to pelvic tilt were lesser at higher degrees of acetabular inclination.

ABSTRACT. Utility of O-arm Navigation in Spinal Tumors Excluding Screw Placement

The O-arm navigation system (Medtronic, Dublin) has been introduced in an increasing number of institutions as a tool to assist in spine surgery. It is very useful for accurate screw placement in spine fusion surgery, and our department has been using it since 2012. It is used for screw placement in pediatric scoliosis and other cases, and we report on three cases in which we were able to effectively use it in the treatment of a spinal tumor. Case 1: 46-year-old male. MRI showed extensive brightness changes in the L4 vertebral body. A transpedicular biopsy was performed under C-arm fluoroscopy to confirm the diagnosis, and the results showed no malignant findings and a chronic osteomyelitis-like finding. PET-CT was performed afterward due to the appearance of neuropathy in the lower extremities and showed no FDG accumulation in the L4 vertebral body and accumulation in the surrounding lymph nodes. The right iliac bone was also found to have an accumulation, and at the same time of lumbar decompression, the FDG accumulation site in the iliac bone was sampled using O-arm navigation. The pathology result was Langerhans cell histiocytosis. The patient continues to be an outpatient of the department of internal medicine. Case 2: 56-year-old male, tumor recurrence near L5/S1 facet joint (chondrosarcoma grade 1). The operative orientation became difficult (transverse processes, etc., which were resected at the initial surgery). However, an appropriate approach, tumor resection, and posterior fixation were achieved by O-arm navigation. One year after surgery, the patient is currently under observation with no recurrence. Case 3: 22-year-old male. He was first seen in our department because of severe low back pain, and a bone tumor (osteoid osteoma) was found in the left facet joint at L5/S1 on imaging examination. Using O-arm navigation, the tumor was completely removed while preserving the facet joint as much as possible. His low back pain improved, and he was able to return to sports (track and field). The O-arm navigation system allows easy intraoperative CT imaging. Therefore, in spinal tumor surgery, not only accurate orientation, but also confirmation imaging after tumor resection is possible. In all three cases, safe and effective treatment was achieved by using the "strong point" of the O-arm navigation system.

ABSTRACT. Few surgeons use computer assisted surgery for stem placement in THA because its accuracy is not sufficient rather than that for acetabular cup placement. Recently, cemented stem can be available in CT-based navigation, however, accuracy and precision of cemented stem alignment has not been reported. We compared accuracy and precision between cementless and cemented stems using the same CT-based navigation (Stryker hip navigation). We analyzed 43 cases (10 men, 33 women; average age 69.3 years) using cementless and cemented stem (Accolade II stem and Exeter stem [Stryker]) after CT-based navigation assisted THA. The differences (average ± standard deviation of absolute values) between the pre- and post-operative angles of stem anteversion were 3.8 ± 3.0° in the cementless group, and 2.4±1.8° in cemented group, respectively. There was a significant difference in precision in stem anteversion between the two groups. The accuracy and the precision of stem anteversion using the taper-wedge stem in this study was comparable to the previous reports using CT-based navigation. However, the precision of stem alignment with cemented stems was more accurate. When we used cemented stem, stem alignment consisted of 4 factors (stem flexion, varus, anteversion, and depth) could be completely controlled by checking the numbers on the navigation screens until bone cement hardened. Therefore, precision of cemented stem alignment using CT-based navigation are more accurate than that of cementless stems.

ABSTRACT. This research paper investigates whether robotic total knee replacement (TKR) reduces bone resection compared to conventional TKR using the tibial polyethylene thickness used as a surrogate marker. While TKR is a successful procedure, revision surgery remains a challenge with up to 8.3% of all knee replacement procedures requiring revisions. The study retrospectively analyzed the tibial polyethylene inserts used and bone cuts made in 157 primary TKRs performed by a single surgeon. The results show that 93.3% of robotic TKRs used the base size tibial polyethylene of 9mm, and the average distal femoral cut was 7.4mm and the average tibial cut was 6.4mm, with the minimum being 3mm. The study suggests that robotic TKR reduces bone resection compared to conventional TKR.

ABSTRACT. Background - This study has been conducted to compare the postoperative pain and functional outcome in patients undergoing Conventional Total Knee Arthroplasty and Robotic assisted Total Knee Arthroplasty and to study the advantage of Robotic Assisted TKA in relation to pain and functional outcome.

Methods: An observational comparative study was conducted in tertiary care hospital from December 2018 to December 2021 on postoperative pain and functional outcome in patients undergoing Conventional total knee arthroplasty versus Robotic assisted total knee arthroplasty which included a total of 240 patients and 120 patients in each group. Pain scores were measured using VISUAL ANALOGUE SCALE (VAS), and functional outcomes were measured by KNEE SOCIETY SCORE. All patients were followed weekly once for a period of six weeks post-surgery.

Results: There were no systemic differences in baseline characteristics of the patients. A significant difference was noted in the immediate and early postoperative pain, which was less in Robotic TKA when compared to the conventional group. Comparison of pain using VAS score in both groups showed a significant difference in the first week (P value <0.05) In the first week and fifth week, though the mean knee scores were found to be better in Robotic TKA as compared to Conventional TKA, it was not found to be statistically significant (P > 0.05). Similarly, the mean functional scores of Robotic TKA in the first, second and sixth week were better compared to Conventional TKA but were found to be not significant statistically since P value > 0.05. A significant difference was noted in the hospital stay between these two groups, with the Robotic group requiring less hospital stay. The median hospital stay of patients following surgery in the Robotic group was 3 days and in the conventional group was 4.5 days. Conclusion: Reduced early post-operative pain in patients undergoing Robotic assisted TKA when compared to Conventional TKA, but there was no significant difference in pain at 6 weeks among the two groups. Robotic assisted TKA patients have fewer hospital stay because of less early post-operative pain. Though knee score and functional score in Robotic group showed better scores in the early follow-up, but the final outcome in the both groups showed no difference sixth weeks.

ABSTRACT. Purpose: Based on CT scan to obtain 3D reconstruction and make optimal preoperative planning, the accuracy of implant placement may be impaired by lack of identifiable bony landmarks in robotic-assisted total hip arthroplasty (THA). Whether robotic-assisted THA can achieve the same accuracy of cup positioning in both standard and complex cases is unknown. The aim of this study is to compare the accuracy of acetabular cup placement between robotic-assisted standard and complex THA. Methods: In this study, 51 patients (17 males, 34 females; 63 hips) underwent robotic-assisted THA using the Mako system (Stryker, Kalamazoo,MI, US) between July 2020 and February 2021 at our institution were collected. Approval of this study was obtained from our institution’s Institutional Review Board. 29 Patients (36 hips) without easily recognized hip landmarks were assigned to the complex THA group (Fig 1), including dysplastic hip, ankylosed hip, protrusio acetabuli, prior hip fracture, skeletal dysplasia, and previous hip surgery. The other 22 patients with recognizable bony landmarks (27 hips) were assigned to the standard THA group. Postoperative standard anteroposterior (AP) radiographs were used to assess cup position. Results: All patients received the same cementless cup (Trident, Stryker). There was no significant difference in the mean post-operative cup inclination and anteversion between the groups (Table 1). The mean cup inclination was 41.0° ± 3.1° and 41.2° ± 2.6° in the complex THA and standard THA groups, respectively. The mean cup anteversion was 16.9° ± 3.4° and 17.1° ± 3.0° in the complex THA and standard THA groups, respectively. With regard to Lewinnek safe zone, there were two outliers of cup position in the complex THA group, while all cups in the standard THA group were placed within Lewinnek safe zone (Fig 2). However, the difference was not significant different between the two groups (p = 0.226). Regarding Callanan safe zone, there was significant difference between the groups (p = 0.004). 8 outliers were found in the complex THA group, while only one outlier was in the standard THA group. Conclusion: Robotic-assisted THA showed less precise cup placement with higher variation and more outliers in complex cases.

ABSTRACT. The study aimed to evaluate the short-term outcomes, length of stay, operative time, complications, and immediate postoperative pain when using the ROSA robotic-assisted device for total knee arthroplasty (TKA). The study included 71 patients who underwent ROSA-assisted TKA between June 2021 and December 2022. Patient-reported outcome measures (PROMs) were collected at preoperative, 6 weeks, and 1-year postoperative time points. The results showed that the average preoperative Oxford Knee Score was 18.3(SD of 6.3), and the 6-week postoperative score was 32.6(SD of 9.3) for 37 knees. At 1 year postoperative, the mean Oxford score was 34 (SD of 12.3), and the mean forgotten joint score was 50.9 (SD of 9) for. The mean length of stay in the hospital was 3.9 days (SD 3.34), and the average operative time for the ROSA cases was 97 minutes (SD 17.5, Range 69 to 172). The postoperative pain scores on the first and third days were 1.25 and 1.61, respectively (on a scale of 0-3). The length of stay in the hospital may have been slightly longer due to several factors such as transportation to remote areas, increased medical complexity of the patients, and the admission the day before surgery. The operative time for ROSA-assisted TKA was slightly longer than manual TKA, but it may decrease with increasing experience with the system. In this study, three patients required conversion to manual due to unsatisfactory femoral registration, and one patient suffered from a venous thromboembolism postoperatively. Further analysis and auditing may provide a clearer picture of the use of ROSA in TKA.

ABSTRACT. Background: Robot-assisted total knee arthroplasty (r-TKA) can reportedly achieve more accurate implant positioning than conventional total knee arthroplasty (c-TKA), although its learning curve is controversial. Moreover, few studies have investigated r-TKA in Asians, who have different anatomical characteristics. This study aimed to determine the learning curve for r-TKA and compare implant positions between r-TKA and c-TKA according to the learning curve in Asian patients. Methods: This prospective study included 50 consecutive c-TKAs (group C), followed by 50 consecutive r-TKAs conducted using the MAKO robotic system (Stryker, USA). Cumulative summation analyses were performed to assess the learning curve for operative time in r-TKA. Accordingly, the r-TKA cases were divided into the initial (I group) and proficiency cases (P group). The femoral and tibial component positions in the coronal, sagittal, and axial planes and lower limb alignment were compared among the three groups. Results: r-TKA was associated with a learning curve for operative time in 18 cases. The operative time was significantly shorter in groups C and P than that in group I, with no significant difference between groups C and P. Groups I and P demonstrated fewer outliers with respect to lower limb alignment, femoral component coronal position, axial position, and tibial component sagittal position than those in group C, with no significant difference between groups C and P. Conclusion: The operative time did not differ significantly between r-TKA and c-TKA after the learning curve. Surgeons could expect more accurate and reproducible lower limb alignment and implant positioning with r-TKA in Asian patients, irrespective of the learning curve.