ABSTRACT. CORONAL KNEE LAXITY MEASURED DURING COMPUTER-ASSISTED TOTAL KNEE ARTHROPLASTY Y Dai*, G Bras, D Liu† *Exactech Inc, Gainesville, FL, 32653, USA, Yifei.dai@exac.com †The Gold Coast Centre for Bone and Joint Surgery, Queensland, AU, dliu01@bigpond.com

Knee laxity studied in vitro and in vivo often did not reproduce test conditions under the clinical reality. Recently, computer-assisted orthopaedic surgery (CAOS) systems provide tools for measuring ligamentous balance intraoperatively during total knee arthroplasty (TKA) to inform surgical decisions. This study quantified coronal laxity of the knee before and after TKA implantation using a CAOS system. Fifty-six CAOS TKAs performed by the surgeon author were reviewed. Coronal laxity was compared between arthritic and TKA knees at flexion angles of 0°, 40°, and 90°. The maximum varus and valgus laxity angles, size and asymmetry of the laxity envelope were assessed. OA knees exhibited elevated varus and valgus laxity during mid-flexion (40°) compared to 0° and 90° flexion, and an asymmetric laxity envelope at full extension. After trial insertion, an elevated mid-flexion laxity was no longer observed. The maximum varus and valgus laxity angles were generally consistent across the flexion range and both size and asymmetry of laxity envelope significantly decreased from the OA knee. This study provides insight into the clinically observed laxity tested intraoperatively in arthritic and TKA knees. The elevated mid-flexion coronal laxity may indicate reduced rotational support provided by passive joint structures in the arthritic knees. TKA surgery significantly reduced varus/valgus laxity across the flexion range and removed the pattern of elevated mid-flexion laxity, reflecting stabilization of the knee joint by the surgical intervention. Studying intraoperatively measured knee laxity may improve the understanding of ligament balancing and enhance knowledge of what constitutes appropriate soft tissue balance.

ABSTRACT. INTRODUCTION The hypothesis of this study will be that the 10 to 15 year survival rate of this TKA will be improved in comparison to historical papers when analyzing survival rates and knee function as evaluated by the Knee Society Score (KSS).

MATERIAL AND METHODS All patients operated on between 2001 and 2004 for implantation of a navigated TKA in the two participating centers were eligible for this study. Usual demographic and peri-operative items have been recorded. All patients were prospectively followed with clinical and radiological examination. All patients were contacted after the 10 year follow-up for repeat clinical and radiological examination (KSS, Oxford knee questionnaire and knee plain X-rays). Patients who did not return were interviewed by phone call. For patients lost of follow-up, family or general practitioner was contacted to obtain relevant information about prosthesis survival. Survival curve was plotted according to Kaplan-Meier, using the occurrence of TKA revision for mechanical reason as end-point.

RESULTS 578 TKAs were implanted during the study time-frame. 537 cases had an optimal lower limb axis (HKA angle between 177° and 183°) after TKA (93%). 116 patients deceased prior to the 10 year follow-up(20%). Final follow-up (including death or revision) was obtained for 439 cases (76%). Clinical status after 10 years was obtained for 341 cases (59%) (KSS, 254 cases – Oxford questionnaire, 299 cases – radiologic evaluation, 197 cases). 10 prosthetic revisions were performed for mechanical reasons during the follow-up time (2%). The global 10 year survival rate was 95.5%, and it decreased to 91.5% at 15 years. The 10 year survival rate for mechanical revision only was 98.0%, and decreased to 96.2% at 15 years (figure 1). The mean KSS at the last follow-up was 188 points, and the mean Oxford score was 55 points. No component was considered loose at the final radiographic evaluation. No polyethylene wear was detected at the final radiographic evaluation. No difference was observed between the two participating centers for any baseline or follow-up data.

DISCUSSION The present study represents the longer follow-up of navigated TKAs published in the literature. This study confirms our initial hypothesis, namely quite satisfactory results of navigated implanted TKA after more than 10 years. A more consistent anatomical reconstruction and ligamentous balance of the knee should lead to more consistent survival of the TKA.

ABSTRACT. Aim: In varus osteoarthritic knees using Computer Assisted Surgery (CAS), assess the correlation between the degree of pre-operative varus deformity, both in extension and in flexion, and the degree of external rotation required to align the femoral component with Whiteside’s axis.

Material and Methods: This was a single centre computer navigation based study of 106 consecutive Indian varus osteoarthritic knees undergoing primary Total Knee Arthroplasty( TKA). The angle of rotation between the Posterior Condylar Axis (PCA) and Whiteside’s line was calculated using CAS and the measured external rotation was set using the 4-in-1 cutting block. The nature of the anterior cut, notching of the lateral or medial cortex and the need for lateral retinacular release were recorded. The efficacy of CAS in setting optimal femoral component rotation is not clear. Setting a fixed rotation of 3 degrees from PCA may lead to rotational malalignment in several patients. The aims of this study were to establish the relationship between Whiteside’s axis and the PCA to address issues with patellar tracking. All collected data was tabulated and statistically analyzed using SPSS13.0 software. 2-tailed test was used to establish correlation. Results: The mean femoral component external rotation with respect to the PCA was 4.25° ± 2.2°. There is a positive correlation between the degree of varus deformity in extension/ flexion and external rotation (r = .225, .477). Discussion: The external rotation with respect to the posterior condylar axis to align the femoral component to Whiteside line varies with each knee (range:0-14 degrees). The external rotation required in a varus knee increases with the degree of varus deformity in extension as well as in flexion. Computer assisted navigation helps in obtaining an optimal rotational alignment of the distal femur when Whiteside line is taken as a reference.

ABSTRACT. INTRODUCTION: To measure functional outcome of a total knee arthroplasty, Patient Reported Outcome Measures (PROMs) are frequently used. However, while easy to perform, the results are not entirely objective, indicating a supplementary measure for objective functional data. Biomechanical tests such as gait analysis, muscle strength and timed functional tests require complex and expensive equipment and technical expertise. But recently some tests have been simplified by using wearable sensors. Hence a simple biomechanical functional test could now be a quick and efficient objective indicator of function. The purpose of this study was to identify objective biomechanical parameters, as a test to supplement PROMs. The hypothesis was that a foot sensor insole would be a valid approach for comparing function on a right-left knee basis.

METHODS: Patients were in three study groups: intact knees as a control, pre-operative about to undergo total knee surgery, and post-operative total knee at 1 to 2 year follow up. The selection criteria included no major comorbidities that could impair lower-limb function. The patients completed the KSS Short Form. Then, the foot pressure sensor insoles measured forces and motion, while patients performed a timed-up-and-go (TUG) test and a sit-to-stand (STS) test. The following were measured: TUG Time, Cadence, Stance Time Ratio, Gait Force Ratio, and STS Force Ratio. The last three compared the right-left legs. SPSS software was used for statistical analysis.

RESULTS: When comparing the pre-op to the post-op and intact, significant differences were found in Cadence, TUG Time, and STS Force Ratio. There were no significant differences between post-op and intact patients. There were no within-group differences between the affected and contralateral knee in the TKA group and no differences between knees in the intact group.

CONCLUSIONS: Although Cadence and TUG time gave significant p-values, scores were too close to provided a useful comparison between right-left knees. The most useful measure was the STS Force Ratio as it showed clear differences between and within groups. Hence the STS Force Ratio was a simple measure that could provide a simple and efficient way of determining whether a post-op total knee was performing equal to or better than the opposite side; and indicating if remedial action was needed if not.

ABSTRACT. INTRODUCTION The primary hypothesis of this study was that the 10 year survival rate of mobile bearing TKAs will be improved in comparison to historical papers when analyzing survival rates and knee function as evaluated by the Knee Society Score (KSS). The secondary hypothesis was that the use of navigation assistance during implantation will improve the 10 year survival rate in comparison to conventionally implanted TKAs.

METHODS All patients operated on between 2001 and 2004 in all participating centers for implantation of a mobile bearing TKA (whatever design used) were eligible for this study. All patients were contacted after the 10 year follow-up for repeat clinical and radiological examination.Survival curve was plotted according to the actuarial technique, using the occurrence of TKA revision for mechanical reason as end-point. The influence of the implantation technique was assessed with a logrank test at a 0.05 level of significance.

RESULTS 1,604 TKAs were implanted during the study time-frame. There was no difference in any baseline criteria between conventional (968 cases) and navigated (636 cases) TKAs. 289 patients deceased before the 10 year follow up (18%). Final follow-up was obtained for 926 cases (58%). 26 prosthetic revisions were performed for mechanical reasons during the follow-up time (2%). The global 10 year survival rate was 93.9%. The 10 year survival rate for mechanical revision was 98.6%. The 15 year survival rate for mechanical revision was 96.0%. No component was considered loose at the final radiographic evaluation. No polyethylene wear was detected at the final radiographic evaluation. Considering mechanical revision only, the 10 year survival rate of conventional TKAs was 98.6% vs 98.7% for navigated TKAs (NS). However, the 13 year survival rate were 97.2% and 98.3% respectively (p<0.05) (figure 2). The survival curves could not be plotted to the 15 year follow-up because of low remaining cases.

DISCUSSION This study confirms the satisfactory results of mobile bearing TKAs after more than 10 years. Navigated TKAs experienced a small but significant better long term survival after 10 years in comparison to conventional TKAs. A more consistent anatomical reconstruction and ligamentous balance of the knee may lead to more consistent survival of the TKA by decreasing microscopic polyethylene wear, this decreasing third body wear and synovitis.

ABSTRACT. Collateral soft tissue release is practiced commonly in total knee arthroplasty (TKA) with minimal basic science evidence to support it. With the advent of computer navigation, and better means of testing and measuring, it is now possible to objectively assess and evaluate each step of the procedure. The authors question the existing dogma of collateral release.

Part 1 of the study was cadaveric, in which sequential medial release (Luring et al) was performed in 12 cadaveric lower limbs, and Femoro-Tibial Mechanical Angle (FTMA) was measured throughout the range of motion (extension, 0°, 15°, 30°, 45°, 60°, 90° and maximum flexion), in unstressed, 10 Nm varus and valgus stress. The sequential steps were- 1: 2 cm release of anteromedial tibial sleeve, 2: Posteromedial release, 3: 4cm medial sleeve release, 4: 6cm medial sleeve release, 5: Deep medial collateral ligament release, 6: posterior cruciate ligament (PCL) release of medial half only, 7: release of entire PCL.

Part 2 of the study was clinical, in which 224 consecutive computer-navigated TKAs were performed with collateral release withheld until stage of trialling the prosthesis components. Release was performed only if deformity beyond 0±2 degrees or soft tissue imbalance was noted at this stage. Patients were followed up and assessed clinically and radiologically.

In Part 1, most of the initial release steps (6/7) had very little effect on FTMA without force application, especially in the initial 60° of flexion. Application of 10 NM varus force demonstrated very small changes at all points of flexion in all the steps of release. Application of 10 NM valgus force demonstrated little change in initial arc of flexion until step 5/7 was reached.

In Part 2 (clinical), even with pre-operative FTMA ranging from 27° valgus to 25° varus (mean: 4.5° SD 7.6), soft tissue release was needed only in 5 of 224 knees (2.2%). 210 knees (96%) were within 0 ± 5° of neutral on weight bearing long leg radiograph, with 91% patient satisfaction at one year and improvement in Oxford Knee Score from 42 to 23.

The initial steps of sequential medial collateral tissue release have negligible, if any, effect on coronal alignment, thus may not be advisable. In the vast majority of cases, good outcomes in terms of coronal alignment, range of movement, function and patient satisfaction can be achieved without undue collateral ligamentous release.

ABSTRACT. “STANDARD” VERSUS “CHALLENGING” PATIENTS - EARLY OUTCOMES USING COMPUTER-ASSISTED TOTAL KNEE ARTHROPLASTY Y Dai*, MP Bolognesi, SS Wellman, T Seyler, Q Cui, Y Najmabadi, D Liu† *Exactech Inc, Gainesville, FL, 32653, USA, Yifei.dai@exac.com †The Gold Coast Centre for Bone and Joint Surgery, Queensland, AU, dliu01@bigpond.com

Patient conditions have been shown to impact the results of conventional total knee arthroplasty (TKA). This study investigated if computer-assisted (CA) TKA exhibits differences between challenging and standard cases in early outcomes, similar to those observed with conventional TKA. A multicentre, consecutive CA TKA series was conducted in a total of 51 patients. “Challenging” cases were identified with one or more of the following conditions: 1) age > 80 years, 2) BMI > 35, 3) coronal deformity >15°, and 4) ROM <90°. Six-month outcomes (ROM, HSS, KSS, KOOS, patient satisfaction VAS) were compared between the standard and challenging groups. The challenging patients (N=19) had approximately 9° less flexion compared to the standard patients (N=32). Challenging cases tended to improve more outcome scores. No significant difference was found between the two groups in both absolute and improvement in outcome scores, as well as patient satisfaction. Both groups gained well above the Minimal Clinically Important Difference (MCID) in clinical scores, suggesting significant improvement in the patient condition after TKA. No implant related early complications were reported. Contrary to conventional TKA, CA TKA with challenging conditions did not exhibit inferior early outcomes except for ROM, compared to the standard cases. Even with the slight less ROM in the challenging patients, both group achieved on average ≥110° flexion, sufficient for most daily activities. Longer-term follow-up is needed to determine the stabilized clinical outcomes. This study suggested that CA TKA may be an effective and appealing option for challenging patient conditions.

ABSTRACT. Patient satisfaction after total knee replacement is directly related to knee stability and proprioception, particularly for high-demand, active patients. While preservation of all intact and healthy ligaments may be the key to achieving such results of satisfaction, balancing four ligaments in a bi-cruciate preserving knee replacement is technically challenging. Robotics-assisted arthroplasty has been gaining popularity as a tool to increase accuracy and precision of implant positioning. In this study, we are introducing a semiautonomous handheld robotic system support for a bi-cruciate retaining knee implant design. The system supports image-free anatomic data collection and streamlined intraoperative surgical planning with dynamic gap balancing before any bone preparation. In this study, we evaluate the accuracy of implant placement in bi-cruciate preserving TKA in synthetic bone and cadaver experiments. We compared the planned and final implant placement in a total of 24 cadaveric femurs, 8 synthetic femur bones, 2 cadaveric tibias and 10 synthetic tibia bones using the bi-cruciate retaining knee implant design Journey II XR (Smith and Nephew), implanted with the Navio surgical system. Final implant position was measured and compared to the surgical plan using a separate position tracking camera and analysis software. A quantitative analysis was performed to determine the translational, angular, and rotational differences between the planned and achieved positions of the implants. The root mean square (RMS) errors of femoral varus/valgus, rotation and distal resection, were 0.7°, 0.7° and 0.86 mm; respectively. The RMS errors of tibial posterior slope, varus/valgus and resection depth were 0.88°, 0.69° and 0.68 mm, respectively. The image-free handheld robotic tool achieved accurate implementation of the surgical plan with small errors in implant placement.

ABSTRACT. LEARNING OF A CAOS ENHANCED MECHANICAL INSTRUMENT SYSTEM FOR TOTAL KNEE ARTHROPLASTY: A CUSUM ANALYSIS Y Dai*, JI Huddleston III, M Rueff, L Angibaud, DF Amanatullah† *Exactech Inc, Gainesville, FL, 32653, USA, Yifei.dai@exac.com † Dept of Orthopaedic Surgery, Stanford University School of Medicine, Redwood City, CA, USA, dfa@stanford.edu

Adopting computer-assisted orthopaedic surgery (CAOS) in total knee arthroplasty (TKA) usually requires switching to CAOS-specific instruments. This study applied an advanced method (CUSUM) to assess the learning curve of a new CAOS system designed to enhance conventional instrumentation. Two senior and two fellow surgeons with no CAOS experiences each performed resections on six knee models using conventional instrumentation, and six more with CAOS enhancement to the same instrumentation. CUSUM chart was plotted for each surgeon on surgical time. The case number signified the stabilization of the process was identified form the chart, marking the completion of learning. The impact of surgeon experience on learning was assessed. The increase in surgical time during and after learning was compared to the conventional group. No substantial difference was found between senior and novice surgeons in the speed of learning (2-3 cases). The fellow surgeons exhibited slightly steeper learning curve by adding 3-4 minutes more to their learning cases. Compared to the conventional TKA, adding CAOS technology to conventional instruments slightly increased surgical time by 4-6 minutes during learning, and the difference reduced to 2-3 minutes after learning. No significant difference in surgical time was found between senior and fellow surgeons after they mastered the CAOS system. The results demonstrated minimum learning effort and extension of operative time, independent of surgeon’s TKA experience level, by introducing CAOS guidance to the existing conventional mechanical instruments, offering the proven benefit of CAOS technology without major disruption in the surgical tools the surgeons are already familiar with.

ABSTRACT. INTRODUCTION The primary hypothesis of this study will be that the 10 year survival rate of navigated TKAs for severe coronal deformation will be improved in comparison to conventional TKAs when analyzing survival rates.

METHODS All patients operated on between 2001 and 2004 in all participating centers for implantation of a TKA (whatever design used) were eligible for this study.All patients were contacted after the 10 year follow-up for repeat clinical and radiological examination. Conventional and navigated TKAs were paired according to age, gender, body mass index and severity of the coronal deformation (with steps of 5°). Survival curve was plotted according to the actuarial technique, using the revision for mechanical reaosn as end-point. The influence of the implantation technique was assessed with a logrank test at a 0.05 level of significance.

RESULTS 1,604 TKAs were implanted during the study time-frame. 658 cases could be paired in conventional (329 cases) and navigated (329 cases) groups: in each group, 277 cases with a coronal deformation less than 10° and 52 cases with a coronal deformation over 10°.15 prosthetic revisions were performed for mechanical reasons during the follow-up time (2%). There was no significant difference between the 12 year survival rates of conventional (97%) and navigated (98%) TKAs in cases without severe coronal deformation. There was a significant difference between the survival rates of conventional (93%) and navigated (98%) TKAs in cases with severe coronal deformation.

DISCUSSION This study confirms our initial hypothesis: navigated TKAs experienced a small but significant better long term survival after 12 years in comparison to conventional TKAs when a severe pre-operative coronal deformation was present, while no difference was observed in the opposite situation. A more consistent anatomical reconstruction and ligamentous balance of the knee with severe coronal deformation might be the explanation for this more consistent survival of the TKA in these challenging cases, while an optimal reconstruction is more consistently obtained with conventional implantation technique for less severe deformation. This study suggests that navigation implantation should be the default technique for pre-operative coronal deformation greater than 10°.

ABSTRACT. Introduction: Well balanced knees with good alignment are essential for a well-functioning TKA with long survival of its implants. The purpose of this prospective comparative study was to compare long term clinical and radiographic outcomes for patients that underwent robot assisted TKA or conventional TKA using fixed bearing implants at a mean follow-up of ten years.

Methods: A randomized controlled study was conducted to compare the clinical and radiographic outcomes of robot assisted and conventional TKA in 97 consecutive patients who underwent primary TKA using fixed bearing implants for knee osteoarthritis. Mean follow-up of the patients was 10.3 years in the robot group and 10.1 years in the conventional group. Clinical outcomes were evaluated using range of motion, HSS, WOMAC, KS total scores. Radiographic outcomes were assessed using mechanical axis, coronal and sagittal alignments. Perioperative complications and revision rate were also evaluated.

Results: We found no significant differences in clinical outcome parameters between both groups except lower WOMAC score after robot assisted TKA (7.6 ± 10.3, 12.6 ± 14.5, p=0.027). Radiological outcomes showed that the robot assisted TKA group had more neutrally positioned femoral components in the coronal and sagittal plane with fewer mechanical axis outliers that were classified patients with more than 3 degree of mechanical axis. (4 cases vs 7 cases, p=0.260). Complications in conventional TKA group included 1 case of instability. In robot assisted TKA group, 1 case of infection underwent revision surgeries occurred (p>0.05).

Conclusions: This study demonstrated that robot assisted TKA significantly contribute to the desired mechanical axis and improved femoral prosthetic placement without any difference in functional parameters and revision rate when compared to conventional TKA.

ABSTRACT. Computer assisted surgery is well known to improve the accuracy of component placement and restoration of mechanical alignment in total knee arthroplasty. This in turn is likely to improve the long term survivorship of the components. We did a retrospective comparative study of accuracy in achieving final component alignment in varus deformities <15ᴼ(mild-moderate) and >15ᴼ(severe) Materials and Methods: Our study included 137 primary total knee arthroplasties performed between Jan and Dec 2015 using Orthopilot 5.1 B Braun Aesculap - Image free computer navigation system. We excluded 16 patients with valgus deformity, rheumatoid arthritis, hip stiffness and revision surgery. A total of 121 patients with varus deformity were included in the final study. The mean age of patients in both the groups was 64 years. All the surgeries in both groups were done by the senior author (KKE) with Aesculap Columbus cruciate retaining design using sub-vastus approach. After registration of the bony reference points and kinematic hip ,knee, and ankle centres, medial soft tissue release and osteophyte removal, the amount of varus deformity as depicted on the navigation screen was recorded and patients were grouped accordingly into mild-moderate (Group A) and severe(Group B). Group A included 95 patients with varus <15ᴼ (mean +/-SD 7.6ᴼ+/-4.6ᴼ;range 3-14ᴼ) and group B included 26 patients with varus >15ᴼ (mean+/-SD 18.4ᴼ+/-2.0ᴼ;range 15ᴼ-21ᴼ). With a sequential medial soft tissue release, the amount of correctable varus deformity was also recorded before the bony cuts were made. All the procedures were done by the femur first measured resection technique and the final component alignment was recorded. Postoperative full length weight bearing scannograms were taken to evaluate the FCA (Femoral component angle) and TCA (Tibial component angle) and the final mechanical alignment was calculated. Results: The final mechanical alignment was within 3ᴼ in 96.15 % of the patients in mild-moderate varus group and in 95.75 % in the severe varus group. A statistical analysis showed that this difference in the final alignment was not statistically significant (p>0.05). Conclusion: Our study shows that irrespective of the severity of deformity, with meticulous , sequential soft tissue release and using computer assisted surgery we can accurately quantify the degree of deformity, the amount of correction done and also achieve the desired, acceptable final component alignment.

ABSTRACT. Although exercises improve the outcome of patients with osteoarthritis, patient compliance is poor. Behaviour modification and measuring compliance remain the Holy Grail of healthcare professionals. Increasing demands on reducing healthcare resources have made this a priority for governments across the globe. Physiotherapy and exercise have been repeatedly demonstrated to be beneficial for both prehab and post-operative/post injury rehabilitation. However, studies show that up to 70% of patients do not do their exercises as prescribed. The reasons include a lack of understanding or forgetting how or how often to do them, pressures of work or social life and simply finding them boring. Gamification has been seen as a method of sustaining the interest of the target patient population. The widespread availability and increasing processing power of smartphones have facilitated the development of augmented reality apps. Quads AR is an augmented reality app for lower limb exercise. It encourages the user to perform variations of lower limb movements through gamification. The core functionality is the ability to interact with a variety of augmented reality objects using the interaction of the user’s foot with virtual objects superimposed on a live real world visual field The responses of focus group of 20 volunteers to a novel automatic compliance recording augmented reality exercise app were studied. Full compliance was achieved in all cases and was measured and recorded by the app. Overall, the app itself received favorable responses regarding the user interface and user experience.

ABSTRACT. This is a Custom made guides or patient specific instruments (PSI) for knee replacement is currently used to replace or guide conventional instruments by pin locating techniques. All currently available PSI techniques are company specific and can only be used for certain implants produced by the specific company. This new method is meant to integrate important parts of conventional instruments to the parts or templates of PSI. It includes 10 different methods and techniques to fit currently available conventional instruments regardless of the implant manufacturers.

The integration is used to transfer the preoperative planning built in PSI to different pieces of conventional instruments allowing the machining of bone according to the preoperative plan. The method is used for any cutting blocks and instruments regardless of manufacturing companies. The methods based on different designs and shapes of custom made guides (PSI) to fit available cutting blocks. These methods give surgeons a variety of techniques to be used for any on shelf implants and any patient specific knee instruments. Using the specific software, these methods are modified to fit any new cutting blocks or conventional instruments that will be introduced in future.

ABSTRACT. Treating an infected femur in total hip replacement using conventional spacer with limitation of 3 size, which may lead to under and over sizing of required spacer size. Using of custom made spacer helping the surgeons to determine the except size and shape of the spacer, which resulting a secure and favorable clinical outcome.

We designed two types of spacers, one of them was produced directly from the 3D printer with NYLON filament. It is implanted to the patient with the suitable cement and antibiotic (Fig 1). The other one was produced from a plastic mold. The two spacers are custom made and patient specific, it based on CT-scan images which transferred to a specific software to construct a 3D model of bone. And another 3D modeling software which construct the model of spacer and the mold . The 3D printing (FDM) machine is used to produce the custom made spacer and mold. We use nylon filament for printing of the custom mad spacer and ABS filament for the custom made mold. The spacer was successfully implanted, the hip joint working and it is achieve its function. The spacer mold was produce a successful and complete pacer part and its working with a good manner.

ABSTRACT. Custom-made implants have been used for bone tumours for over 20 years. However, PST has not been repeatedly used for bone tumour surgeries. Fractures could happen in beginning tumors; and the fixation is usually challenging when it is close to the physis. This work explores additional benefits of computer-assisted orthopaedic surgical techniques.

CT-based, patient-specific templates (PST) were used for benign tumour surgery. A 12-year-old child presented with an aneurysmal bone cyst (ABC) in skeletally immature lower tibia complicated with non-united fracture. CT scanning of the lower half of the tibia was done and the affected bone was 3D printed as a model (plastic bone). Then, simulation of surgery was done preoperatively to determine the direction and length of the screws to avoid insertion into the tumour. The best plate was selected to fit onto the bone without bending the plate.

It was possible to outline the upper and lower limits of the tumour preoperatively. It was possible to detect the trajectory of the screws keeping away from the tumour and the growing plate (physis). PST was applicable for benign tumour surgery and it appears the same principle can be applied for surgery of malignant tumours and fracture fixation. The use of computer-assisted surgery with PST is gaining more attention. The technique has shown high success rate in joint replacement, osteotomy and hip resurfacing. Thus, it has been now applied in more sophisticated surgeries such as pedicle screw fixation and tumour resection. The use of both patient-specific guides and implants can further enhance the use of computer technology in orthopaedic surgeries.

ABSTRACT. ACCURACY AND RELIABILITY OF FULL-LENGTH LOWER LIMB RADIOGRAPHS IN THE MEASUREMENT OF CORONAL ALIGNMENT Y. Dai*, M Peterson, and K. Wurm *Exactech Inc, Gainesville, FL, 32653, USA, Yifei.dai@exac.com

Full-length lower limb radiograph is the gold standard for measuring alignment in computer-assisted (CA) total knee arthroplasty (TKA). This study assessed the accuracy and reliability of full-length lower limb radiographs in the measurement of alignment outcome of CA TKA and the sensitivity of the measurement to limb rotation. CT scans of 3 cadaveric whole legs in full extension were segmented to surface models, followed by virtual TKA. The “true” postoperative hip-knee-ankle (HKA) angle was determined based on the landmarks on the segmented surfaces. Simulated full-length coronal radiographs were generated from the CT data at the original anteroposterior (AP) view, and at the AP views with 5°, 10°, and 15° of internal or external limb rotation. Three analysts each evaluated the HKA in the radiographs 3 times in blinded fashion. The accuracy (compared to the “true” HKA), and inter- and intra- analyst reliability of the measurements were assessed by Intraclass Correlation Coefficient (ICC). HKA measurements demonstrated sub-degree error and strong inter- and intra- analyst reliability. Rotation of the limb up to 15° had only sub-degree impact on HKA. Measurement with rotated limb exhibited high inter-analyst reliability. High accuracy of using full-length lower limb radiographs for the measurement of postoperative coronal alignment was demonstrated. The measurement did not exhibit sensitivity to limb rotation for up to 15°. Furthermore, strong inter- and intra- analyst reliability was found, confirming the robustness of the measurement method. In conclusion, full-length lower limb radiograph is an accurate and reliable imaging modality for measuring HKA in CA TKA.

ABSTRACT. Introduction: Mobile-bearing total knee arthroplasty (TKA) implant were developed as an alternative to fixed-bearing implants because of their theoretical advantages related to wear and range of motion. However, in TKA choosing fixed-bearing or mobile-bearing prosthesis has been the subject of argument for many years. And there is still no final conclusion. The purpose of this study was to compare the clinical and radiological outcomes of navigation-assisted TKA between fixed-bearing system and mobile-bearing system.

Methods: A retrospective cohort study was conducted to compare the clinical and radiographic outcomes of navigation-assisted TKA using fixed-bearing prosthesis (VEGA® total knee system) in 144 patients and using mobile-bearing prosthesis (e.motion® total knee system) who underwent primary TKA for knee osteoarthritis. Mean follow-up of the patients was 8.3 years in the fixed-bearing group and 11.4 years in the mobile-bearing group. Clinical outcomes were evaluated using range of motion, HSS, WOMAC, KS total scores. Radiographic outcomes were assessed using mechanical axis, coronal and sagittal alignments. Perioperative complications and revision rate were also evaluated.

Results: Clinical outcomes between the two groups showed no significant difference in HSS, WOMAC, ROM, KS pain, and function score at the last follow-up. No significant difference was shown between the groups in the varus and valgus laxity assessment. Mechanical alignment of the lower limb was not significantly difference between the two groups. However, significant difference was observed in the excellent (within 2-degree) and acceptable (within 3-degree) categories. Survival rates were 97.2% in the fixed-bearing group and 97.4% in the mobile-bearing group.

Conclusions: Total knee arthroplasty using navigation show excellent clinical and radiological results and good survival rate. However, there were no clear benefit of mobile-bearing prosthesis with regard to kinematics, ROM, clinical results and survival rate. To ensure good clinical results in both designs, bony alignment and soft tissue balance are more important than type of prosthesis.

ABSTRACT. Low back pain is one of the most common reasons for outpatient service and is associated with high costs.At present, the hierarchical medical system and process of China is not established, and a large number of patients with low back pain have outpatient service in the superior hospital. It caused a conflict between the increasing demand for outpatient visits and limited medical resources and wasted a lot of public health resources. Although the computer technology has broadly applied pre-, intra- and/or post-operatively to improve the outcome of orthopedic surgical procedures, the diagnosis of low back pain with computer technology has very few studies. So we use computer technology to design a system of artificial intelligence, which was named AiKNOWN. Firstly, we hope the system become a assistant of the orthopedic doctor, and help them obtain history of the low back pain patients rapidly, efficiently and accurately. Secondly, we can obtain the Chinese epidemiological data of low back pain. Lastly, we can make the patient education, remote consultation and the guideline of diagnosis and treatment of low back pain.

Before designing the AiKNOWN system, we first builded a medical knowledge graph of low back pain. The knowledge graph was based on European and American guidelines of the low back pain and the medical record data. Based on the knowledge graph, we combined the rules engine and the statistical engine to make knowledge reasoning of medical record data and built the AiKNOWN system.

Using the AiKNOWN system, we will obtain the history and symptom of the patients with low back pain. Then the history will be synchronized to the doctor when the patient visit the doctor. The doctor can directly understand the patient's medical history, and then added physical examination in the medical record on the system. The AiKNOWN system also can prompt the doctor some special information of patients, such as mental illness. This allow doctors make a diagnosis and give treatment to patients more comprehensively and efficiently. At the same time, when the doctors give a diagnosis to the patient, it also will give a feedback to the AiKNOWN system. This will help AiKNOWN system learn deeply, and become a better Assistant of the orthopedic doctor.

Based on the AiKNOWN system, we can make the patient education, remote consultation and the guideline of diagnosis and treatment of low back pain.

ABSTRACT. Purpose: The purpose of our research is to summarize the application of the robot in spinal surgery in the last two years, which improves the accuracy of operation and reduces the radiation. Materials and Methods: From January 2016 to December 2017, 102 patients with spinal diseases were retrospectively analyzed, including 11 cases of spinal deformity, 25 cases of lumbar spondylolithesis, 32 cases of lumbar spinal stenosis, 16 cases of lumbar disc herniation, 12 cases of thoracolumbar fracture, 6 cases of spinal tumors. Robot-related data were recorded prospectively and included demographics, surgeons involved, time of instrumentation, fluoroscopy use, screws executed, and notes on intraoperative adverse events. Results: The accuracy of 102 cases of 743 screws was 99.2%, with an average of 3.5 minutes for each screw. In 11 cases of spinal deformity patients, the time of screw instrumentation is (3.2±0.3) min, (4.6±0.9) min for lumbar stenosis patients, (3.7±0.2) min for lumbar stenosis patients, (4.9±1.1) min for spine fracture patients, (4.1±0.7) min for spinal tumor patients. The number of instrumented screws in the analysis data was negatively correlated with the time taken. In the preparation of 7 screws, due to the deviation of fixed point shift, 3 screws were inserted by traditional method, and 4 screws were inserted by robot de novo. The average intraoperative bleeding was 460ml, and all patients were followed up for more than 3 months, no screw loosening, fracture and other complications were observed. Conclusion: In the preoperative design, not only the model of the screw can be clearly defined, but it is also helpful for the adjustment of the coronal plane screw, saving time for the installation rod3. Planning in a child can include 5-8 vertebral body, in an adult can include 4-5 vertebral body.There are some limitations in the application of robot for severely rotated scoliosis4. The accuracy of the operation can be improved by the precise positioning of the robot, reduce the risk of operation and reduce the incidence of postoperative complications, and also reduce the radiation to patients and doctors. For spinal surgery, especially for minimally invasive technique, it is of great significance for further promoting the clinical application.

ABSTRACT. Objective: to study the clinical curative effect of the percutaneous vertebroplasty or "TINAVI" robot assisted in the treatment of osteoporotic fracture. Methods: A controlled randomized clinical trial was conducted from Dec , 2016 to Apr, 2017. A total of 80 patients with osteoporotic fracture were randomized into two groups: A group (percutaneous vertebroplasty) and B group (percutaneous vertebroplasty by leonardo's robot assisted). The condition of patients were assessed by visual analogue scale (VAS) and Japanese Orthopaedic Association Scores (JOA). The Cobb, operating time, the amount of bone cement, number of times of the X ray, postoperative complications, length of stay were compared between the two groups. Results: The VAS and JOA of 80 cases before and after operation, there were there were significant difference between them (P＜0.05). Compared with A group, the operating time, the amount of bone cement, number of times of the X ray were statistical significance (P＜0.05). The postoperative complications, length of stay were no statistical significance (P＞0.05); and the length of stay were statistical significance (P＜0.05). Conclusions: The percutaneous vertebroplasty by "TINAVI" robot assisted is safety and effective, and worthy of clinical application and promotion.

ABSTRACT. Objective To evaluate the effectiveness of osteotomy for spinal deformity using virtual reality platform. Methods 12 patients of spinal deformity from May 2016 to July 2017 were retrospectively reviewed. Among them, 6 patients (VR group) underwent surgery planning and simulating with VR technique: first introduced CT images and constructed 3D models, followed by virtual osteotomy and automatically generate a new model for choice of the most appropriate osteotomy. 6 patients (control group) were treated with conventional osteotomy and correction surgery. The operative time, blood loss, perioperative complications and postoperative correction rate were compared between the two groups. Results 12 patients were successfully completed the operation without neurological damage, dural tear and other complications. The operation time and blood loss of VR group were lower than those of the control group, and the correction rate of Cobb angle and kyphotic angle were higher than those of the control group, but neither of the differences were statistically significant. Conclusion The VR platform can simulate the effect of spine osteotomy, thus has development potential in the individual treatment of spinal deformity osteotomy.

ABSTRACT. Aims Due to the three-dimensional anatomy of the scapula, precise resections of the scapula with antiquate surgical margin, could be very difficult. The computer navigation system has the advantage of pre-operative surgical planning. The purpose of this research is to evaluate the efficacy of computer assisted pre-operative surgical planning for the resection of bone tumors in the scapular. Patients and Methods

Patients and Methods This was a retrospective research. A total of six patients were surgically treated with this technique between 2013 and 2017. There were 3 males and 3 three females. All the patients were histologically diagnosed as low grade chondrosarcoma. The tumor edge was determined in CT images. With the virtual scapula specimen, the planned margin of the tumor resection was 1-2 cm from the tumor edge. The surgical margin was evaluated for each case. Distances between the osteomy planned and the osteomy by free hand were measured. For each case, at least two distances were calculated.

Results All tumors were removed en bloc with a cuff of normal soft tissue completely surrounding the mass. Histological examination of all specimen showed a clear margin in all cases. The minimum of surgical margin width in bone varied from 7 to 13 mm in this series. The differences between the osteomies preoperatively planned and the osteomies achieved by navigation was in a global mean of 2.36 mm (SD: 2.09) in a total of 14 planes. No patient experienced local recurrence or distant metastasis in the 4 of 6 patients, who were evaluated with more than 3 years’ follow-up. The functional MSTS score were 100% for all 6 patients.

Conclusion 3D preoperative planning and surgery using a virtual specimen provide a reasonable premise for partial geographic scapulectomy of the scapular chondrosarcoma.

ABSTRACT. INTRODUCTION Bone tumor surgery can be more accurate under the computer assisted navigation. The researches have shown the benefit of margin control in pelvic, joint sparing surgery. The traditional method for bone cutting in limb salvage was by free hand. There was no literature focused on the comparison of cutting accuracy in bone tumors around the knee joint. The aim of this study was to compare the accuracy for bony resection under navigation and by free hand in limb salvage surgery around the knee.

MATERIALS AND METHODS Thirty-nine cases of bone tumors around the knee joint were resected under navigation in our department from 2008 Sep to 2017 Nov. All the cases were performed intercalary resection in femur or tibia. We used intraoperative navigation to find the cutting plane and use the jig saw to cut the bone. The post-operative specimen was used for verification and compared with the pre-operative plan. The length difference was defined as specimen length minus planning resection length. The control group included 117 cases of tumors around the knee performed limb salvage surgery when bony cutting was achieved by free hand. The method to find the cutting plane was by measuring the length from the joint line to the planned plane by ruler.The length difference was detected in this control group. Then the differences in two groups were compared and analyzed.

RESULTS The resection lengths in navigation group ranged from 85-282mm and in the free hand group the length ranged from 90-330mm. The length difference between post-operative verification and pre-operative plan was detected. In the navigation group, the length difference was 0.5±2.5mm (range ,-5～5mm), while in the free hand group the length difference was 3.4±9.6mm (range ,-20～29mm), P<0.01. For the absolute value differences analysis, the difference was 2.0±1.6mm and 8.3±6.0mm for navigation and free hand group respectively, P<0.01.

DISCUSSION Our study shows that bone cutting with navigation can be more accurate than freehand cutting. The average length difference was 2.0mm (95% CI, 0.4 to 3.6mm) when compared to average 8.3mm (95% CI, 2.3 to 14.3mm). The accuracy with navigation is similar to the previous researches. Our comparison with free hand group gives the data how accurate the navigation can help surgeon to achieve. The result indicates that computer assisted navigation can make a role in limb salvage surgery if the precise resection is required.

ABSTRACT. Background Some malignant pelvic tumor may affect the anterior or posterior column at the acetabula area. The postoperative recurrenceand complication rate are high. Precise resection with safe surgical margin could cure the patients while saving healthier host bone for relative simple reconstruction. Questions/Purposes The purpose of this study is to evaluate the effect of precise single column resection and reconstruction with femoral head plus THR for malignant pelvic tumorswith respect to the (1) surgical safety, (2) oncological outcome and (3) prosthesis survivorship and function. Methods This is a clinical cases study. From 2007 to 2015, 19 patients with primary malignant tumors of the pelvis were enrolled in the study. The diagnosis included 16 cases of chondrosarcoma, 1 case of undifferentiated polymorphic sarcoma, 1 case of Ewing's sarcoma and 1 case of solitary plasmacytoma. All tumors were resected with safe surgical margins, which were proved by the postoperative specimen evaluation. Anterior column was involved in 17 cases and posterior column in 2 cases. Ten of 19 tumors were resected assisted by computer navigation. Femoral heads were used to reconstruct anterior or posterior column defects and fixed by screws; THR was used for the joint reconstruction. Oncologic outcome and function were evaluated by regular follow-up. Results The follow up time was more than 12 months in 14 cases with the average of 58.4 months (median 61, range 13-118) months. Surgical margins contained wide resection in 12 cases and marginal resection in 7 cases. The bony wide resection rate was 90% (9/10) in the navigation group and 77.8% (7/9) in free hand group respectively. One patient with Ewing's sarcoma died 14 months postoperative due to lung metastasis. There was only one case with chondrosarcoma was found recurrence in 61 months postoperatively, who was in the navigation group and having marginal margin resection. There was one prosthesis removed due to prosthesis infection (14 months postoperatively). There were another two patients with minor wound infection. The average MSTS function score was 24.8 (17-29). Conclusions The current treatment method is oncological safe and functional with less complications. The hardware is relatively cost effective and right on the shelf. However, this procedure is highly skill needed.

ABSTRACT. Coupling of intra-operative 3D imaging and surgical navigation or robotics have been introduced for more than a decade. However, existing solutions are not used in clinical routine and many pitfalls have been reported in the literature. To overcome these difficulties, methods of auto-calibration and auto-registration of 3D imaging and surgical navigation for spine surgery are presented, together with a novel fully integrated C-arm/Navigation device. The methods rely on the use of a calibration phantom fixed to the spine using sharp pins, during open or percutaneous surgery. These methods are fully automatic, they do not require the use of trackers fixed to the C-arm, and they compensate for patient breathing or system deformation during 3D image acquisition. These methods are implemented in a novel fully integrated device made of a motorized C-arm and a navigation system (Surgivisio, Grenoble, France). Preliminary results are presented. Benefits in terms of time saved (less than 5 minutes from the first 2D image to surgical navigation), increased accuracy (0.35mm), reasonable x-ray dose, and surgeon satisfaction are reported. It is anticipated that these excellent preliminary results, if they are confirmed by clinical studies, will contribute to wide adoption of 3D imaging and navigation for clinical routine.

ABSTRACT. Objective The second sacral segment iliosacral screw (S2 screw) insertion is a demanding technique, with a high rate of screw malposition due to the complex pelvic anatomy. TiRobot™ is an orthopedic surgery robot which can be used for S2 screw fixation. We carried out a retrospective analysis of the accuracy of S2 screws using robot-assisted navigation. Methods A retrospective analysis of 16 patients admitted and managed by S2 screw fixation for unstable pelvic fractures was carried out for evaluation of its efficacy and safety. all patients with pelvic ring disruptions and sacral dysmorphism were evaluated radiographically and S2 screws were placed using a robot-assisted navigation technique. Screw position was assessed and classified using postoperative computed tomography. Fisher’s exact probabilities test was used to analyse the screws’ positions. Surgical time after reduction of the pelvis, insertion time for guide wire, number of guide wire attempts, and radiation exposure without pelvic reduction were also assessed. Results The excellent and good rate of screw placement was 100%. The fluoroscopy time after pelvic reduction was 7 (7, 9) seconds. The operation time after reduction of the pelvis was 29 (27,33). Time for guide wire insertion was 2.0 (2, 2) minutes. The number of guide wire attempts was 0.0 (0, 0). No postoperative complications or revisions were reported. Conclusion S2 iliosacral screws can be safely and accurately accomplished using a robot-assisted navigation technique in patients with unstable posterior pelvic ring disruptions and sacral dysmorphism.

ABSTRACT. Objective: To evaluate the efficacy and accuracy of posterior hemivertebra resection and deformity correction assisted by intraoperative three-dimensional navigation system for the treatment of congenital kyphoscoliosis due to hemivertebra.

Methods: Seventeen consecutive patients with congenital kyphoscoliosis due to hemivertebra who underwent posterior hemivertebral resection and deformity correction assisted by intraoperative three-dimensional navigation system were investigated retrospectively. The average age of the patients at surgery was 14.7 years and included eight cases at the thoracic spine and nine at the lumbar spine．An intraoperative three-dimensional navigation system was used to guide the pedicle screw placement and hemivertebra resection in real-time. The coronal and sagittal Cobb angles were measured on standing X-ray films to determine the deformity and correction. CT scan was used to evaluate the accuracy of pedicle screw placement. The mean follow-up was over 5 years (range 1 year to 8.5 years).

Results: The mean Cobb angle of the segmental curve was 46.2°preoperatively and 11.5°postoperatively, an improvement of 79.8%. Mean Cobb angle of the main curve was 49.6°preoperatively and 13.3°postoperatively, an improvement of 75.7%. The segmental kyphotic angle curve was 36.5°preoperatively and 9.7°postoperatively, an improvement of 76.6%. Lateral trunk shift improved significantly. No complications of neurovascular injury or implant failures occurred. In total, 116 pedicle screws were placed assisted by the navigation system, and no screw perforated the pedicle more than 2 mm.

Conclusions: The intraoperative three-dimensional fluoroscopic navigation system enables safe and accurate hemivertebral resection via a single posterior approach. It may achieve excellent clinical results with better deformity correction, less invasiveness, and fewer complications.

ABSTRACT. The forgotten joint score (FJS) is a recently developed scoring system to assess the patients' ability to forget the artificial joint in everyday life. The FJS exhibits a substantially lower ceiling effect compared with other patient-reported outcomes measurements and enables discrimination between good and excellent outcomes. Behrend et al. reported that age, body mass index, and gender influence the FJS. However, few studies have evaluated the influence of postoperative coronal and rotational limb alignment on FJS. The aim of this study was to determine the impact of coronal and rotational component alignment on FJS with a minimum follow-up period of 2 years. Eighty-two primary varus osteoarthritis knees undergoing navigated total knee arthroplasty were enrolled. The implants included PS fixed-bearing, PS mobile-bearing and CR mobile-bearing designs. Postoperative mechanical alignment and tibial joint line angle were evaluated at 6 months. The knees were categorized as neutral (0°-3° varus), 4°-5° varus, or ≥ 6° varus. Postoperative rotational component alignment mismatch was calculated using the Baker protocol with CT. The FJS was obtained by phone 2 years after surgery on average. The results revealed that different postoperative mechanical alignment and the tibial joint line angle were not associated with FJS in each prosthesis design. FJS was reduced in the PS mobile-bearing design with excessive internal and external rotational mismatch. Moreover, FJS was reduced in the CR mobile-bearing design with excessive internal rotational mismatch. Only rotational component alignment errors affect the FJS after mobile-bearing TKA navigation.

ABSTRACT. Introduction: The purpose of the present study was to determine which factors affect the positional accuracy of iliosacral screws inserted using 3D fluoroscopic navigation.

Patients and Methods: We treated 27 patients with pelvic ring fracture by percutaneous iliosacral screw fixation. Pelvic ring fractures were classified as type B1 in 3 patients, B2 in 7 patients, B3 in 1 patient, C1 in 10 patients, C2 in 1 patient and C3 in 5 patients according to the AO-OTA classification. A total of 55 screws were inserted using 3D fluoroscopic navigation combined with preoperative CT-based planning. The positional accuracy of screws was assessed by superimposing the preoperative CT-based plan on the postoperative CT images computationally. The following seven factors that could potentially have affected the accuracy of screw insertion using navigation were evaluated: the planned screw insertion angle formed between the vertical axis and the iliac cortical surface on coronal and axial images, AO/OTA fracture classification, sacral morphology, site of screw insertion, patient position, and type of screw.

Results: The mean deviation between the planned and the actual inserted screw position was 2.9±1.7 mm at the vertebral body center. Multiple regression analysis showed that the screw insertion angle in the axial plane and the use of a transsacral screw correlated with the positional accuracy of screws.

Conclusion: A greater screw insertion angle against the vertical line on the bone surface and the use of transsacral screws increased the positional error of iliosacral screws inserted using 3D fluoroscopic navigation.

ABSTRACT. Introduction: Registration of the patient body and the virtual 3D plan is an initial but very fundamental procedure for the accurate usage of the navigation systems. Currently, there are two commonly used registration methods, i.e., point registration and intraoperative CT registration. These two methods suits for different kinds of operative scenarios. For example, point registration is mainly suitable for those operation sites where could expose large bone surface and contain sufficient landmarks, while intraoperative CT registration suits for most of scenarios but would radiate the patients. By now, no literature has reported about how to choose between these two registration methods during using the navigation systems. In this study, we tested the equivalence of the point registration method and the intraoperative registration method during using the navigation system, simply compared their performance, and shared the surgeons some suggestions about their selection. Materials and Methods: We used 4 artificial pelvises to simulate 8 patients respectively with one tumor. We designed the surgical plans following the standard surgical workflow. Specifically, we designed 3 osteotomy planes for each simulated patient. Then, according to the surgical plans, we performed 8x3 osteotomies and measured the osteotomy errors. Results: T-test results (p<0.001) indicated the intraoperative CT registration performed better than point registration. Besides, equivalence test of the two registration methods (Rg=1.00 mm) suggested that the two registration methods were equivalent while using the navigation systems. Conclusions: Three suggestions about selection of the registration methods are shared with the surgeons: If the operation site could be easily exposed and contain enough landmarks, then we suggest the surgeons to select the point registration method; If only small surface could be exposed or the landmarks are rare, then we suggest the surgeons to perform intraoperative CT registration; If the surgeons want to pursuit more precision, we suggest them to use intraoperative CT registration.

ABSTRACT. “STANDARD” VERSUS “CHALLENGING” PATIENTS - PERIOPERATIVE OUTCOMES USING COMPUTER-ASSISTED TOTAL KNEE ARTHROPLASTY Y Dai*, Q Cui, MP Bolognesi, SS Wellman, T Seyler, Y Najmabadi, D Liu† *Exactech Inc, Gainesville, FL, 32653, USA, Yifei.dai@exac.com †The Gold Coast Centre for Bone and Joint Surgery, Queensland, AU, dliu01@bigpond.com

Results from conventional total knee arthroplasty (TKA) concluded factors such as advanced age, obesity, and coronal deformity increased the risk of inferior outcomes. To date, it remains unclear how perioperative outcomes are impacted by these challenging cases, as compared to the “standard” cases for computer-assisted orthopaedic surgery (CAOS) TKA. This study investigated if there is a difference between challenging and standard cases in terms of perioperative outcomes. A multicentre, consecutive CAOS TKA series was conducted by 5 surgeons 70 patients (72 knees). “Challenging” cases were defined from the series as having one or more of the following conditions: 1) age >80 years, 2) BMI >30, 3) coronal deformity >15°, and 4) ROM <90°. Perioperative outcomes were compared between the standard and challenging case groups. The challenging cases (N=26) tended to require slightly longer surgical time, have more intraoperative blood loss, and lower discharge to home rate than the standard cases, as well as higher variability in intraoperative blood loss and haemoglobin change. However, none of the above differences were significant. No blood transfusion or implant related early complications were reported in the series. Although challenging conditions studied have been shown by previous investigations to impact conventional TKA results, the present data did not suggest inferior perioperative outcomes compared to the standard cases using CAOS. Like previous case studies and clinical series that have proposed the benefits of CAOS in TKA cases with severe coronal deformity, this study highlights the advantages CAOS TKA may offer in demanding cases where patient or joint factors increase the surgical challenges.

ABSTRACT. Computer Assisted Orthopaedic Surgery (CAOS) has been proven beneficial to the surgical outcome, but it clutters an already overcrowded operating theatre, and tends to disrupt the workflow of conventional surgery. In order to provide seamless computer assistance with improved immersion and a more natural surgical workflow, we propose an augmented-reality based navigation system for CAOS. Here, we choose to focus on the proximal femoral anatomy, which we register to a preoperative plan by processing depth information of the surgical site captured by a commercial depth camera. Intra-operative three-dimensional surgical guidance is then provided to the surgeon through a commercial augmented reality headset, to drill a pilot hole in the femoral head, so that the user can perform the operation without additional physical guides. The user can interact intuitively with the system by simple gestures and voice commands, resulting in a more natural workflow. In order to assess the surgical accuracy of the proposed setup, 30 experiments of pilot hole drilling were performed on femur phantoms. The position and the orientation of the drilled pilot holes were measured and compared with the preoperative plan, and the mean errors were within 2 mm and 2°, results which are in line with commercial computer assisted orthopaedic systems today.

ABSTRACT. Aim: Recent advances have made robotic assistance a viable option in total hip arthroplasty (THA). However, the clinical outcomes of this procedure relative to THA without robotic assistance have yet to be reported. This study presents short-term outcomes of robotically assisted THA compared to a pair-matched control group of patients that underwent THA without robotic assistance. Method: Data were prospectively collected on all THAs performed from July 2011 to January 2015. Patients were included if they underwent primary THA treating idiopathic osteoarthritis and were eligible for minimum two-year follow-up. Outcomes were measured using Harris Hip Score (HHS), the Forgotten Joint Score (FJS-12), pain on a visual analog scale (VAS), and satisfaction from 0-10. Patients that underwent THA with robotic assistance were matched 1:1 with THA patients without robotic assistance for age, sex, BMI, and approach. Results: There were 85 patients in each study group. There were no significant differences in the demographic factors matched for. Both HHS and FJS-12 were significantly higher in the robotic assistance group at minimum two-year follow-up. VAS was lower in the robotic assistance group, but this was not statistically significant (p = 0.12). There was a not a significant difference in patient satisfaction. There was no significant difference in the rate of postoperative complications or subsequent revisions between groups. Conclusions: Robotically assisted THA is safe and may lead to superior short-term outcomes compared to THA without robotic assistance.