ABSTRACT. INTRODUCTION Lewinnek et al described a safe zone of acetabular component placement in Total Hip Arthroplasty (THA) to reduce complications. Callanan et al proposed a modified safe zone with a reduced range of acetabular inclination of 30-45 degrees to eliminate the steeper or more inclinated cups2. This study compares the accuracy of cup placement in the safe zones described by Lewinnek et al. and Callanan et al., leg length discrepancy (LLD) and global offset (GO) measurement in THA using five different surgical techniques performed by six different surgeons. METHODS Between June 2008 and April 2014, 2330 THRs were performed by six different surgeons. Post-operative radiographic images were retrospectively reviewed and measured using TraumaCad® software to determine cup placement, LLD, and GOD. RESULTS One Thousand, nine hundred-eighty patients met the inclusion and exclusion criteria. Ninety-three (4.69%) patients underwent robotic-assisted THA anterior approach, 135 (6.8%) had robotic-assisted THA posterior approach, 942 (47.5%) patients underwent fluoroscopic guided THA anterior approach, 708 (35.7%) had THA without guidance using posterior approach, 43 (2.1%) patients underwent navigation-guided anterior approach and 59 (2.9%) patients underwent radiographic-guided posterior approach THAs. Robotic guidance groups had a significantly greater percentage of hips in the Lewinnek’s and Callanan’s safe zone (p < 0.005). Between robotic guidance groups, the group with posterior approach has more cups placed in the Lewinnek’s and Callanan’s safe zone (p < 0.005). The frequency of hips within the Lewinnek’s safe zone was significantly greater in the navigation guided group, compared to the other groups except robotic guided (p < 0.05). Sixty-four (3.2%) of our cases were with LLD greater than or equal to 10mm, five of those cases were (8.5%) in the group treated with x-ray guidance. (p < 0.05). The mean GOD for the overall cohort was 4.0mm ± 0.4mm (p < 0.0001). Mean ages of patients in the treatment groups were significantly different (p < 0.0001). CONCLUSION Robotic assisted surgery was more consistent than the other techniques in placing the acetabular cup into the Lewinnek and Callanan safe zone. The use of robotic assitance in hip arthroplasty surgery is more accurate fulfilling the goals needed to actual hip arthroplasty. Long term follow-up is required to determine clinical impact of increased accuracy.

ABSTRACT. INTRODUCTION Bicompartmental knee arthroplasty (BKA) is an alternative to total knee arthroplasty (TKA) for degenerative joint disease when present in only two compartments. BKA spares the cruciate ligaments and preserves bone in the healthy compartment, possibly leading to better knee kinematics and clinical outcomes when compared to TKA. While BKA is a technically demanding procedure when performed with manual instrumentation, robotic assistance allows for accurate implant placement and soft tissue balancing of the joint. Robotic unicompartmental knee arthroplasty (UKA) has shown favorable clinical outcomes and survivorship at short term (2 year) follow up compared to manual UKA. The purpose of this study is to evaluate the short term functional outcomes and survivorship of patients undergoing robotically assisted BKA.

METHODS 45 patients (48 knees) were identified in an initial and consecutive single surgeon series receiving robotically assisted BKA to correct disease in the medial and patellofemoral compartments. As part of an IRB approved study, every patient in the series was contacted at a minimum two year (±2 months) follow up and asked a series of questions to determine implant survivorship and functional outcomes (using the patient portion of the Knee Society Score). 9 patients were lost to follow up and 1 patient was deceased. 35 patients (38 knees) at a minimum two year follow up enrolled in the study for an enrollment rate of 79%. There are 22 male patients and 13 female patients; the average age at time of surgery is 67.0 ± 6.8 and the average BMI is 29.5 ± 4.6. Five patients in this series also qualified for a 5 year follow up assessment.

RESULTS Only 1 BKA was reported as revised to a TKA at two year follow up. The revision was reported by the patient due to severe pain and occurred 25 months after the index BKA procedure. The patient did not return to the same surgeon for the revision procedure. The average pre-operative Knee Society Function Score was 58.1 ± 9.9 (n=18) and improved at 2 years post-operatively to 81.5 ± 15.9 (n = 36) (p<0.001). Of the 5 patients contacted at a minimum 5 year follow up, there were no reported revisions.

CONCLUSIONS Robotically assisted BKA shows good survivorship and functional outcomes at a short term 2 year follow up. This procedure may be a viable option to patients with only two diseased compartments, as sparing of healthy bone and cruciates may improve overall kinematics and outcomes of the joint. This study remains ongoing to include a larger cohort and longer follow up.

ABSTRACT. Abstract: Background: Preservation of acetabular bone during primary total hip arthroplasty (THA) is important, because proper stability of cementless acetabular cup during primary THA depends largely on the amount of bone stock left after acetabular reaming. Eccentric or excessive acetabular reaming can cause soft tissue impingement, loosening, altered center of rotation, bone-to-bone impingement, intraoperative periprosthetic fracture, and other complications. Furthermore, loss of bone stock during primary THA may adversely affect subsequent revision THA.

Questions/Purposes: The purpose of this study was to compare preservation of acetabular bone stock between conventional THA (CTHA) vs. robotic-guided THA (RGTHA). We hypothesized that RGTHA would allow more precise reaming, leading to use of smaller cups and greater preservation of bone stock.

Methods: Patients who received RGTHA were matched to a control group of patients who received CTHA, in terms of pre-operative native femoral head size (47.8mm - 48.1mm), age (mean 56.9), gender, BMI, and approach. Acetabular cup size relative to femoral head size was used as a surrogate for amount of bone resected. We compared the groups according to three measures describing the acetabular cup diameter (c) in relation to the femoral head diameter (f). These three measures were: (1) c-f, the difference between the cup diameter and femoral head diameter, (2) (c-f)/f, the same difference as a fraction of the femoral head diameter, and (3) (c^3-f^3)/f^3, the same ratio expressed volumetrically.

Results: A total of 57 matched pairs were included in each group. There were no significant differences between groups in terms of gender, age at surgery, or BMI. No differences in femoral head diameter or acetabular cup diameter were observed between groups (p > 0.05). However, measure (2) (c-f)/f and (3) (c^3-f^3)/f^3 did differ significantly between the groups, with lower values in the RGTHA group (p < 0.02).

Conclusion: RGTHA allowed for the use of smaller acetabular cups in relation to the patient’s femoral head size, compared to CTHA. Using acetabular cup size relative to femoral head size as a surrogate measure of acetabular bone resection, these results indicate that greater preservation of bone stock using RGTHA compared to CTHA. This may reflect increased translational precision during the reaming process. However, further studies are needed to validate the relationship between acetabular cup size and loss of bone in THA.

ABSTRACT. Background: The Robotic Spinal Surgery System (RSSS) is a robot system designed for pedicle screw insertion containing image based navigation system, trajectory planning system and force state recognition system. The special force state recognition system can guarantee the safety during the operation. The RSSS is helpful in pedicle screw insertion surgery and it will be applied in clinic in the near future. In this study, we evaluated the accuracy and safety of RSSS in an animal experiment. Methods: Computer tomography (CT) scan data for two anesthetized experimental sheep was acquired using the C-arm and transferred to RSSS for pre-surgery screw trajectory planning. With the assist of RSSS, we inserted 8 and 4 screws into two sheep respectively. Operation time and blood loss during the surgery were recorded, and CT scan was repeated after surgery. Real screw position and trajectory acquired by the post-surgery CT scan and ideal trajectory planned by RSSS were compared to evaluate the accuracy and safety of RSSS. The result is shows as mean+/-SD. Results: We planted totally 12 screws into two sheep. The operation time for each sheep is 140min and 110min, and the blood loss is 100ml and 80 ml respectively. Compared with planned trajectory, the average deviation of the entry points in lateral and axial view are 1.07+/-0.56mm and 1.25+/-0.42mm and the mean screw deviation angles in later and axial view are 1.78+/-0.98°and 2.52+/-1.03°respectively. The RSSS successfully recognized the force stages and guaranteed the safety during the drilling process. There is no penetration in all 12 pedicles, and all the screws fell into group A according to the Gertzbein-Robbins classification. Conclusion: This animal study demonstrated the accuracy and safety of the RSSS, which also supported the potential application in clinic.

ABSTRACT. Patellofemoral arthroplasty (PFA) is a delicate and challenging procedure. A PFA application has been developed for the Navio semi-active robotic platform (“NavioPFA”), to facilitate both planning and bone preparation. NavioPFA combines image-free navigation and planning with robotically assisted bone shaping, and is open to any implant design, provided that the feasibility and accuracy is confirmed in sawbones and cadaver tests. In this abstract we describe the accuracy tests of NavioPFA, with results for four different implant designs. The accuracy of prosthesis placement with Navio is evaluated by independent measurements that compare the final placement to the planned position.

ABSTRACT. Among many factors that influence the outcomes of Total Knee Arthroplasties (TKAs), the mechanical alignment has played major roles for the success of TKA, the survival rates of the implants, and patient functionality. Most, but not all, studies have shown that alignment of the mechanical axis in the coronal plane within a range of 3° varus/valgus is associated with improved long-term function and increased survival rates. Robot-assisted TKA has been developed to improve improves the accuracy and precision of component implantation and mechanical axis (MA) alignment. We hypothesized that robot- assisted TKA would lead to a more accurate leg alignment and component implantation, and thus, improve radiological and clinical outcomes. Between January 2003 and December 2004, A total of 98 primary TKA procedures were compared: 49 using a robotic-assisted procedure and 49 using conventional manual techniques. The cohorts were followed for 121.2 and 119.5 months on average, respectively. Radiographic assessments of the patients were performed preoperatively and at final follow-up and made according to the Knee Society Roentgenographic Evaluation System (KSRES) which included measurements of the coronal mechanical axis and sagittal and coronal inclinations of femoral and tibial components. The radiographic measurements were made using a PACS (Picture Archiving and Communication System). Clinical assessments were performed preoperatively, and at a final follow-up date that was a minimum of postoperative nine years. The clinical results included ranges of motion (ROM), Hospital for Special Surgery (HSS) scores, Western Ontario and McMaster University (WOMAC) scores (for pain and function). The radiographic results showed no statistical differences when comparing the means of the two groups. When considering outliers (defined as error ≥ ±3°) for the mechanical axis, femoral coronal and sagittal inclinations, and tibial coronal and sagittal inclinations, the ROBODOC group had zero outliers for all measurements except for one in tibial sagittal inclination. On the other hand, the conventional group had 12 outliers for mechanical axis, 2 for femoral coronal inclination, 3 for femoral sagittal inclination, 3 for tibial coronal inclination, and 4 for tibial sagittal inclination. However, there were no statistically significant differences between groups for ROM, HSS, or WOMAC scores at the final follow-up. The results of this study support previous work and demonstrate that the ROBODOC-assisted implantation of TKA results in better radiographic outcomes and better ligament balance with equivalent safety when compared to conventional TKA at a minimum follow-up of nine years.

ABSTRACT. Muscle atrophy and degeneration around the hip joint have been two-dimensionally (2D) evaluated using computer tomography (CT) or magnetic resonance imaging. However, how closely such 2D measurements actually reflect three-dimensional (3D) measurements are unclear. The present study aimed to determine correlations between 2D and 3D measurements of muscle atrophy and degeneration around the pelvis and thighs of patients with unilateral hip diseases using CT images. Fourteen muscles of each side were extracted using semi-automated segmentation methods from CT images of 20 patients who underwent primary total hip arthroplasty to unilateral hip disease. We then manually modified these muscles. We calculated the volume ratio of the affected side to the healthy side as muscle amount analysis, and evaluated the difference between the affected and healthy sides based on radiographic density that reflects muscle degeneration using 2D and 3D measurements. Two dimensional measurements were taken at 1-cm intervals from anatomical bony landmarks. The following muscles were measured at each bony landmark: the anterior superior iliac spine for the gluteus medius, gluteus minimus, iliacus and psoas major; the tip of the great trochanter for the gluteus, the lesser trochanter for the tensor fasciae latae and pectineus, and the middle of the femur for the adductors, biceps femoris, rectus femoris, semi-membranosus, semi-tendinosus, vastus lateralis/intermedius and vastus medialis. We assessed correlation coefficients between 2D and 3D measurements and the cross-sectional level that correlated the closest with the 3D measurement. Analysis of muscle amount showed that seven (50%) muscles had correlation coefficients of > 0.7 between the 2D and 3D measurements with the ratio of the affected to the healthy side determined at anatomical bony landmarks. The mean required translation of the cross-sectional level from bony landmarks was 5.5 (2 – 12) cm. When based on radiographic density, 12 (86%) muscles had correlation coefficients > 0.7 between 2D and 3D measurements with a difference between the affected and unaffected sides. The mean required translation of cross section levels from landmarks was 4.3 (1 – 9) cm. 2D measurements of muscle atrophy on each anatomical landmark plane does not correlate well with 3D measurements in half of the muscles of patients with unilateral hip diseases. The positions of transverse planes must be changed to maximize correlations. On the other hand, it was possible to evaluate muscle degeneration with 2D measurements on the anatomical landmark planes in 86% of the muscles.

ABSTRACT. Distal radius fractures are common, with surgical fixation often necessary for intra-articular or comminuted fractures. This study investigated whether non-locked plating was significantly different from locked plating during a simulated six–week postoperative healing period using an AO C2 fracture model. Fractures were induced in fourth generation plastic bone models that were then fixated using volar locking plates. One group of five received non-locking screws while another five received locking screws. A custom, four-bar, remote center of compliance linkage was used to apply an anatomically representative axial load to the specimens. Specimens were loaded cyclically according to a simulated postoperative period; changes in dorsal tilt, overall fracture gap shortening, articular surface displacement and step-off were measured using calipers and compared after every 1000 cycles using a rank sum test. The failure criteria were: dorsal tilt of greater than 10 degrees, fracture gap shortening greater than 3mm, or articular displacement or step-off greater than 2mm. No statistically significant differences were found between locking and non-locking constructs. None of the non-locking specimens failed according to study criteria, however two showed instability post test (when unloaded), due to screw loosening. Two of the locking constructs failed, one during 400N loading and one during 800N loading, from articular surface displacement; findings that could challenge the current trend towards locked plating. Three of the locking constructs also fractured during testing and, from micro-CT analysis, the fracture propagated from the cancellous foam of the plastic bone to the cortical surface, which could result from limitations of the plastic bone models.

ABSTRACT. The paper has analyzed the effects of soft tissue deformation on the measurement accuracy of skin markers. These skin markers were placed at different locations of the medial side of the lower limb. All the measured data were compared with the bone markers as the ground truth. Error sources of skin marker in measuring the bone spatial information have also been investigated. It is concluded that an innovative design of skin marker and the associate software, different from bone markers, may be needed before the skin marker can be applied in computer assisted orthopaedic surgery.

ABSTRACT. Optical-based computer-assisted orthopaedic surgery (CAOS) relies on clear line-of-sight (visibility) between the localizer and the trackers. During a total knee arthroplasty (TKA), the trackers may not always be optimally positioned for the establishment of line-of-sight, sometimes forcing the surgeon to move the patient’s leg or the camera to maintain tracker visibility. Limited information is known about tracker visibility under clinical settings. This study quantified the rotational limits of the trackers in a CAOS system for maintaining visibility across the surgical field. A CAOS system (ExactechGPS®, Blue-Ortho, Grenoble, FR) was set up in an operating room. A grid was placed at the quadrant of the surgical table associated with the TKA surgical field. The localizer was set up to aim at the center of the grid. A TKA surgical procedure was then initiated using the CAOS system. Once the trackers-localizer connection was established, the CAOS system constantly monitored the accuracy by measuring the root mean square error (RMS) of each tracker. The connection was immediately aborted if the measured RMS was above the defined threshold. Therefore, “visibility” was defined as the tracker-localizer connection with proper accuracy level. An F tracker from the tracker set (3 trackers with similar characteristics) was placed at the center of each cell on the grid. The minimum and maximum angles of rotation around the table normal (Z) axis (RAZ_MIN and RAZ_MAX) and table long (X) axis (RAX_MIN and RAX_MAX) for maintaining tracker visibility were identified. For each cell, the rotational limit of the tracker was calculated for each axis of rotation (RLX and RLZ). The tracker rotation limits were 144.7±3.9° for RLZ (136-152°), and 150.5±3.9° for RLX (143-158°). RLX was significantly higher than RLZ across the field (difference in means = 5.8°, p<0.01). Along the X axis, the rotational limit decreased slightly for RLZ, but increased slightly for RLX. The results demonstrated that ExactechGPS provides tracker visibility for >135° rotation across the surgical field. Moreover, the system is placed inside the sterile field, eliminating the potential blockage of the optical localizer by the surgical staff, further ensuring tracker visibility. The slight rotational limits trends along the X axis may be due to camera placement at one side of the surgical table. The current methodology may be applied to other CAOS systems to quantify the tracker visibility in a clinical environment.

ABSTRACT. Introduction: In our previous studies, we reported that the use of image-free navigation in THA could achieve improved accuracy and consistency in cup positioning. Since 2011, we have used advanced version of navigation system (Orthopilot ver3.3 and Ortopilot THApro B/BRAUN-Aesclap) which enables intraoperative assessment of stem AT. The purpose of this study was to assess the accuracy of this advanced-version navigation system in determining positioning of both cup and stem components by postoperative CT examination. Methods: Seventy patients underwent primary THA using the imageless navigation for assessment and adjustment of cup and stem positioning during December 2011 and January 2015. Surgeries were performed by Modified-Hardinge approach and Antero-spine-approach. All THAs were implanted with cementless cup and stem. Intraoperatively, the cup inclination, anteversion (AV), and stem AT and leg length were measured by the use of the navigation system. Postoperative CT was performed for all patients and position and orientation of the implants were measured using 3D template software (Zed hip, LEXI). Results: Intraoperative assessment by the navigation system indicated that the average cup inclination and cup AV values were 38.5° ± 2.7° and 16.4° ± 6.0° respectively, while the average stem AT was 16.0° ± 10.3°. Postoperative CT evaluation indicated that calculated cup inclination , cup AV, and stem AT values averaged 36.1° ± 5.2°, 20.6° ± 6.9°, and 21.0° ± 9.9°respectively. In the comparison of intraoperative navigated and postoperative CT evaluated values, the median of absolute discrepancies between the intraoperative and CT measurement results in each subject were 2.7° for cup inclination, 5.3° for cup AV, and 4.7° for stem AT Discussion and Conclusion: It has been already shown that conventional-version image-free THA navigation could provide accurate cup placement for the inclination and AV. The present study conformed the accuracy of the navigation system for the stem AT adjustment by the use of the advanced-version software. Comparison of the intraoperative and postoperative data showed intraoperative navigation assessment indicated slightly higher value for cup inclination (by 2° on average) and lower value for cup AV (by 4° on average). Regarding stem AT, the navigation assessment indicated lower value by 5° as compared to the postoperative CT results. IN the use of this advance-version navigation system, these discrepancies should be taken into consideration.

ABSTRACT. Since many years surgeons are trying to optimise pedicle screw placement in spine surgeries to reduce severe complications. Intraoperative image guidance could improve the accuracy in pedicle screw placement. With the implementation of robotic 3D flat-panel detectors in hybrid operating rooms a new form of navigation is now accessible. A 3D scan (Dyna-CT) of the target area is acquired. After image reconstruction a start- and endpoint can be planned. Afterwards the C-arm is able to automatically move into different position always visualising the planned route. With the help of an integrated laser crosshair the endpoint and the angulation of the planned line can be seen. This enables the surgeon to align his tools and puncture with a needle or implant a wire. Until now this planning tool has only been used for needle procedures. The aim of our study was to find out, if Syngo iGuide® (Siemens, Germany) is feasible for pedicle screw placement in an ex-vivo model. 5 synthetic lumbar spine models embedded in a blinding, radiolucent material with surrounding foam were used for this study (SYNBONE AG, Switzerland). Two orthopaedic surgeons implanted 10 screws (L1-L5) on each model using the new laser guided fluoroscopic method. For this purpose a Dyna-CT of the lumbar spine models was acquired with the Artis zeego® (Siemens, Germany) leading to a 3D reconstruction image. In these images a start- and endpoint was planned for each screw. Afterwards the C-arm was automatically positioned in the “Bulls-eye”-position. After insertion of a k-wire a cannulated screw was implanted over the guidance wire (USS MIS, DePuy Synthes Spine, USA). A separate planning had to be performed for each screw. After implantation of 10 screws in a singular model another Dyna-CT was performed to check implant position. Mean planning and implantation time was 5.73 minutes per screw. Mean fluoroscopy time was 0.2 minutes. In two cases, it was impossible to implant the screws in the fifth lumbar vertebra using the guiding system. In this cases the inclination of the C-arm was to strong, leading to a collision with the OR table or the model. In all other models, screw implantation with the new Syngo iGuide® device was rated succesfull. The system was helpful to place screws in the upper lumbar spine. This is the first time pedicle screws were implanted using with this laser guided technique. The feasibility of this system could be shown. We believe that route planning in 3D reconstruction images will optimise screw position. In many hospitals this system is already installed without the orthopaedic surgeon knowing about it. Yet it could be an essential help in placement of pedicle screws in challenging anatomic regions without the acquisition cost of a navigation system.

ABSTRACT. Introduction Coronal tibiofemoral (CTF) subluxation is a common radiographic finding in knee osteoarthritis (OA) which may be related to poor pain scores and tibial spine impingement. However, the published data regarding CTF subluxation is limited. The purpose of the study was to analyze knees in varying stages of OA for the presence and the severity of CTF subluxation. Methods We retrospectively evaluated coronal tibiofemoral (CTF) subluxation and limb alignment in 113 patients with different stages of knee osteoarthritis (OA) who were being considered for an arthal tibiofemoral (CTF) subluxation and limb alignment in 113 patients with difroplasty procedure. Knee OA was classified as “Mild” or “Severe” according to Kellgren-Lawrence scale. CTF subluxation was measured in the 40 knees of healthy controls and in the study groups using special software developed based on Iterative Closest Point mathematical algorithm. Results Mean CTF subluxation in the control group was 1.4 %( ±1) of the tibial plateau. However, mean CTF subluxation in the “Mild OA” and “Severe OA” groups was 3.5 % (±2) and 3.5% (±5) of the tibial plateau, respectively. For both the “mild” and “severe” OA groups. CTF subluxation was significantly increased compared to the CTF subluxation in the control, (p < 0.0001) and (p = 0.012), respectively. There was no significant difference in CTF subluxation between the “Mild OA” and “Severe OA” groups (p = 0.75). Lower limb alignment in the “Mild OA” was 3.6˚ (± 2.2) and in the “Severe OA” 5.3˚ (± 2.6), both were significantly higher comparing to the control group with (p < 0.0001) in both cases. In addition, lower limb alignment was significantly higher in the “Severe OA” group comparing to the “Mild OA” group (p = 0.0003). Conclusions CTF subluxation is a radiographic finding related to knee OA which occurs mainly in the early stages of the osteoarthritic process, and stagnates as OA progresses. However, lower limb malalignment is an ongoing process throughout all the various stages of OA which may contribute to OA progression.

ABSTRACT. Background: Micro-arc oxidation (MAO) is an electrochemical method used to treat metal surfaces. It provides nanoporous pits, and thick oxide layers, and incorporates calcium and phosphorus into the coating layer of titanium alloy. This modification on the surface of titanium alloy by MAO coating would improve the ability of cementless stems to osseointegrate. In spite of these structural and chemical advantages, clinical study of total hip arthroplasty (THA) using MAO coated stem has not yet been reported. In this study, we evaluated the clinical and radiographic results associated with cementless grit-blasted tapered-wedge stems that were identical in geometry but differed with regard to surface treatment with or without MAO coating. Materials & Methods: We performed a retrospective review of 141 THAs using MAO coated stem for a minimum of 5 years and compared them to 219 THAs using the same geometry stem without MAO coating. A cementless Bencox femoral component was used in all hips. It is made of titanium alloy with a straight, double wedged, tapered stem with a rectangular cross-section. Surface treatment was performed using grit blasting with a roughness of 5.5ųm that was available either with or without MAO coating. Clinical and radiographic evaluations were performed preoperatively and at 6 weeks, 3 months, 6 months, and 1 year postoperatively, and then annually. Results: In the MAO coating group, the mean Harris hip score improved from 43.7 points preoperatively to 93.9 points postoperatively. The mean WOMAC score and UCLA activity score at the final follow-up was 17 points (range, 6-34 points) and 6.9 points (range, 5-10 points), respectively. Thigh pain at final follow-up was reported in 2 hips (1.4%), but neither of these hips showed signs of implant loosening or limited daily activities. Complications included one squeaking, one iliopsoas tendonitis, and one deep vein thrombosis. Postoperative Harris hip scores, WOMAC scores, UCLA activity scores, and complication rates did not differ between the two groups. In both groups, no femoral or acetabular component showed radiographic evidence of mechanical loosening, and no components had been revised at the final follow-up. Conclusions: Primary THA using a cementless grit-blasted tapered-wedge stem with MAO coating showed encouraging medium-term outcomes. Further prospective controlled study is required to investigate the long-term implant survival, possible complications, and cost-effectiveness of utilizing MAO coating in THA.

ABSTRACT. We have been developing an automated preoperative planning system for total hip arthroplasty (THA). The system determines the most suitable size, position and orientation of the implants using the 3D bone models segmented from the CT of diseased hips. Since implants have various designs, the system needs to be adapted to several types of them for clinical use. In this study, we propose a new automated planning method for femoral stem using partial least squares regression for estimation of the stem anteversion angle and previous method based on the contact pattern between stem and femoral bone. In the experiment, we used two types of stem called anatomical stem and taper wedge stem. We compared the average differences of sizes, positions, and rotations of the plans, which were determined with the proposed and previous methods, with surgeon's plans. For the anatomical stem, the differences of anteversion angles were almost same, besides, for the taper wedge stem, those decreased 2.4 degrees, respectively. The differences of positions was almost equivalent to the previous ones for both types of stems. These results showed the usefulness of the proposed method.

ABSTRACT. The technology and the feasibility of computer aided orthopaedic surgery have been widely studied and discussed in the past few years. Surgical accuracy is one of the most essential indicators of the success of the technology. However, a reliable method for postoperative assessment is still not yet well developed and adopted. This study investigated the application of 2D / 3D registration method for postoperative analysis of accuracy in corrective osteotomy by patient specific instruments, in a repeatable, reliable and quantified way making use of a set of preoperative CT scan and postoperative x-rays. Three female patients with hypophosphatemia rickets were included in this study. Two patients were treated with unilateral femoral supracondylar osteotomy while one patient was treated with bilateral femoral supracondylar and bilateral proximal tibial osteotomies. All patients underwent multi-planar corrections with the guidance of patient-specific instrument. Postoperatively, relative positions of bone fragments were compared to the 3D surgical plan by manual and automatic 2D/3D registrations using the medical image processing software (Mimics®). The relative bone fragment position difference between the preoperative and postoperative bone models was calculated. Standing X-ray images were also taken to evaluate the mechanical alignment. The average residual centre of mass translational difference between preoperative plan and postoperatively measurement was 5.47mm ± 2.43mm. The mean tibiofemoral angle of all cases was recorded -0.38˚ ± 2.72°. The residual displacements in this study were 1.61±1.65 (Δx), 3.98±1.83 (Δy), and 2.34±2.3 (Δz) mm. Residual rotations were 8.08°±4.64° (Δφx), 8.87°±4.51° (Δφy), and 5.67°±1.86° (Δφz). Although the mechanical alignment was improved by adopting patient-specific instrument, the position inaccuracy of the realigned bone fragments during intraoperative execution persisted. The need for using a reliable and repeatable workflow for postoperative analysis of corrective osteotomy is apparent. Our preliminary results show that the method we used is promising for postoperative assessments.

ABSTRACT. Intraoperative 3D-imaging in spine surgery is used for navigation and immediate intraoperative control. Major limitation is the image quality and postoperative computed tomography (CT) remains the standard. Another concern is the exposure to radiation. Aim of this study was to determine the effective dose of different imaging protocols of a robotic 3D flat panel C-arm in comparison to CT. Dose measurements were performed with a Rando-Alderson-Phantom equipped with thermoluminescense dosimeters (TLD). The phantom was exposed to different scanning protocols of the 3D C-arm (Artis zeego®, Siemens, Erlangen, Germany) (high definition, high definition with collimation, low dose with collimation) as well as routine and low dose CT. For each technique, images were obtained of the thoracic spine (focus: Th6) and the thoracolumbar junction (focus: L1). At the thoracolumbar junction, the effective dose was comparable for images of the 3D fluoroscope without collimation (4.4 mSv), with collimation (4.3 mSv) and the routine CT protocol (5 mSv). A relevant reduction was achieved with the 3D low dose protocol (1.0 mSv) as well as with the low dose CT protocol (2.9 mSv). The most exposed organs at the thoracolumbar junction were the stomach and the liver. Focusing on the middle thoracic spine (centre Th 6), the effective dose of 3D fluoroscopic images was lower in comparison to the CT protocols. For 3D images without collimation, the effective dose was 1.1 mSv, with collimation 0.8 mSv; the low dose 3D images required only 0.2 mSv. The routine CT images caused an effective does of 2.3 mSv, the low dose CT required 1.8 mSv. At the middle thoracic spine the most exposed organs were the lung and the oesophagus. In general, the effective dose was higher for all images at the thoracolumbar junction in comparison to the thoracic spine. However, the sensitive thyroid gland was more exposed in imaging of the thoracic spine. Modern intraoperative 3D-C-arms produce images of CT-like quality, allowing immediate control of implants. Even with low dose protocols a sufficient assessment of screw position is possible. Beside the image protocol, the quality depends on the screw material. Titan screws produce significant fewer artifacts and should be preferred with intraoperative 3D imaging. In normal weight patients low dose protocols should be applied.

ABSTRACT. Background: Recently, two topical issues in total hip arthroplasty (THA) can be a robot-assisted surgery and use of a short bone-conserving stem. However, there is a potential risk of stem malalignment, stem subsidence leading to unstable fixation, and the possibility of intraoperative femoral fracture when short bone-conserving stems are used. To address these limitations, robot-assistance could provide be a solution. The purpose of this study was to evaluate the effects of robotic milling on the accuracy of short bone-conserving stem positioning and on the short-term clinical outcome in THA using a prospective, randomized design. Materials & Methods: From November 2011 to June 2012, a total of 54 patients scheduled for primary THA using a short bone-conserving femoral stem were randomized into two groups, either robotic milling group or manual rasping group. Three patients (3 hips) in the robotic milling group and two patients in the manual rasping group were lost to follow-up, leaving 24 patients (24 hips) in the robotic milling group and 25 patients (25 hips) in the manual rasping group. The Tri-Lock Bone Preservation Stem was used in all hips and all operations were performed through an anterolateral approach by one surgeon in the lateral decubitus position. New femoral fixator clamp attached to the femoral head was used to decrease soft tissue dissection and nerve injury. A pinless version of the ROBODOC system using a MicroScribe 3D digitizer for femoral registration was used. The patients were assessed clinically and radiographically at 8 weeks, 5 months, 12months, and 24 months. Results: Robotic milling group had a significantly longer operation time, requiring on average 8.9 minutes for registration and 11.2minutes for milling. On the other hand, robotic milling group showed superior results in terms of stem alignment and leg length equality. Two intraoperative femoral fractures occurred only in manual rasping group. Harris hip scores and WOMAC scores at 24 months postoperatively were similar in both groups. No complications including stem loosening, infection, nerve palsy, or dislocation encountered in either group during the follow-up period. Conclusions: The present study suggested that robot-assisted short bone-conserving THA could increase the accuracy of stem alignment, improve leg length equality, and help reduce the risk of intraoperative femoral fracture as compared with manual rasping. However, the clinical outcome scores did not differ between the two groups at the time of short-term follow-up. Long-term follow-up is needed to determine whether there will be a long-term clinical relevance of robot-assisted implantation of short bone-conserving stems in THA.

ABSTRACT. In this paper, an efficient wearable glasses system is proposed for the application of preoperative spinal surgery. The technology is essential to generate a virtual space with a 3D model of the patient from CT images while marker attached [7]. The 3D model is then used to fit the poses of the phantom during surgery by using the PnP method. The patient’s preoperative 3-D image model is registered by projecting it onto the phantom such that the synthetic 3-D model merges with the real patient image, enabling the surgeon to see-through the patient’s anatomy. Glasses with camera are then used to capture the relative pose between patient’s body and viewing direction of the surgeon by marker detection [4] and localization. Experimental results validate on a phantom, and shown the effectiveness of the proposed method. The foremost objective is to assist the surgeons to see-through the vertebral and surgical planning for a minimally invasive spinal surgery.

ABSTRACT. Fluoroscopy is typically used as the intraoperative imaging modality for bone boundary visualization in computer assisted orthopaedic surgery. The associated radiation poses risks to patients and surgical teams that gave rise to recent interest in safer real-time intraoperative imaging alternatives such as ultrasound.

Despite recent advancements in ultrasound intensity-based automatic bone segmentation, results remain unpredictable due to the high levels of speckle noise, reverberation, and signal drop out. Recent work on local image phase feature-based bone segmentation addressed some of these limitations, but remains prone to false positive bone responses at soft tissue interfaces.

In this paper, we present a method for robust bone boundary localization based on the fusion of strain imaging and envelope signal power. To fuse these maps, we introduce a linear weight-based on the echo de-correlation measure between the pre- and post-compression RF frames. We also use a data driven scheme to detect any bone discontinuity in the scanned image. In addition, we introduce Gaussian mixture regression model that better preserves the curvature features in the bone boundary than a linear regression model.

Our quantitative results demonstrate a marked reduction in false positive responses at soft tissue interfaces and an increase in bone delineation accuracy. Comparisons to the state-of-the-art on a finite-element-modelling phantom show an improvement in mean absolute error between actual and estimated bone boundaries of approximately 25%. Finally, we qualitatively validate on clinical in vivo data of the human bones that demonstrate similar improvements to those observed on phantom.

ABSTRACT. Introduction: The treatment of dislocated fractures of the acetabulum is standardized and performed under fluoroscopic guidance. Despite the visualization of the fracture a closed reduction can be performed using a minimal invasive approach positioning the screws under navigational guidance. The aim of the study was the investigation of the clinical outcome of patients with an acetabulum fracture who were treated with an minimal invasive navigated screw osteosynthesis. In addition the reduction of the fracture was analyzed comparing the pre- and postoperative fracture position in 3D fluoroscopy. The study was conducted as a single-center retrospective trial in a primary care institution.

Patients/Material and Methods: Retrospectively data of 16 patients with dislocated acetabulum fractures between 2001 and 2013 were analysed. The patients were treated minimal invasively with closed reduction and a navigated screw osteosynthesis. The study was setup as a case-control study. The following parameter were conducted: range of motion (ROM), Harris-Hip-Score, Merle d’Aubigné, Postel Score and the SF-12 questionnaire, measurement of fracture gap reduction in mm in the standard planes in the preoperative CT-scan and the intraoperative 3D scan.

Results: 16 patients (age: 53.13 ± 13.7) were examined after an average of 4.13 ± 3.11 years to the initial trauma. The fracture patterns were classified according to Letournel in simple (75%) and complex (25%) fractures. The SF-12 score averaged 53.5 ± 6.9 and the Harris-Hip Score 88.75 ± 17.16. On average 16.72 ± 1.94 points were achieved in the Merle d’Aubigné Score during the examination. The fracture reduction in the sagittal plane was conducted from 5.05 ± 4.51 mm to 3.57 ± 3.34 mm. In the coronar plane the fracture reduction was achieved from 7.27 ± 4.20 mm to 5.16 ± 2.99 mm. In the axial plane the fracture was reduced from 6.84 ± 4.07 mm to 5.17 ± 3.23 mm.

Conclusion: The study analysis the clinical results after the treatment of dislocated fractures of the acetabulum with a navigated screw osteosynthesis. Especially the clinical examinations show promising results and satisfying outcomes in the clinical scores. Long term clinical results have not been published so far. Additionally an investigation of the clincial outcomes of patients in combination with the fracture reduction using 3D fluoroscopy after navigated screw osteosynthesis of the acetabulum has not been described before.

ABSTRACT. Current C-arm devices are rarely used for quantitative measurement during orthopaedic surgeries. The most important limitation for this is the lack of a comprehensive C-arm tracking system that is capable of estimating the real time location of the transmitter-detector set. There has recently been a considerable amount of interest and research for developing off-line C-arm joint tracking systems, however, they are limited to a stationary base. This study provides a framework for a single camera odometry system for localizing a surgical C-arm base. An application-specific monocular visual odometry system is proposed in this research. The main sensory unit utilized for this purpose is a consumer-grade camera that is rigidly attached to the C-arm base and is downward looking. The cumulative dead-reckoning estimation of the moving base is extracted based on frame-to-frame homography estimation and decomposition. Optical flow results are utilized to feed the odometry estimation system. On-line positional and orientation parameters are then reported. Positional accuracy of better than 2% (of the total traveled distance) for most of the cases and 4% for all the cases studied and angular accuracy of better than 2% (of absolute cumulative changes in orientation) is achieved with this method. This study provides a robust and accurate tracking framework that not only can be integrated with the current C-arm joint tracking (e.g. TC-arm) system to provide more generic C-arm localization outcomes, but also is capable of being employed for similar applications in other fields (e.g. robotics).

ABSTRACT. Background Ossification of the ligamentum flavum (OLF) has been widely recognized as one of the main causes of thoracic spinal canal stenosis and thoracic myelopathy. Decompression is the only effective strategy for treating thoracic myelopathy caused by OLF. The purpose of this study was to describe the clinical outcomes of computer assisted minimally invasive spine surgery (CAMISS) for posterior decompression in patients with thoracic myelopathy caused by OLF. Methods This study included 14 consecutive patients with thoracic OLF (eight men and six women; mean age, 55.2 years) who underwent surgical treatment in our department from 3 January 2006 to 9 June 2012. In all cases the surgical procedure was performed with the assistance of an intraoperative three-dimensional navigation system. Decompression of the spinal cord was performed with a high-speed drill; the supraspinal ligaments and spinous process were partially preserved. The outcomes were evaluated by a modified Japanese Orthopedic Association (JOA) scoring system and recovery rates. Results The mean duration of follow-up for the 14 cases was 3.9 years. All patients experienced neurological recovery, the mean JOA score improving from 6.1 points preoperatively to 8.6 points at final follow-up and the mean rate of recovery being 52.7% (excellent in two cases, good in eight, fair in three, and unchanged in one). Conclusions CAMISS is a safe and effective procedure for resection of the OLF in the thoracic spine.

ABSTRACT. Uni-compartmental Knee Replacement (UKR) is an orthopaedic surgical procedure to reduce pain and improve function in the knee. Postoperative radiological assessment of the implant alignment is an important predictor of the success of the procedure. Load-bearing long-standing anterior-posterior (AP) x-rays are typically used postoperatively to measure the varus/valgus implant orientation. In this assessment, errors arise due to using 2D measurements to make 3D alignment evaluations. These errors are aggravated when the implants have out-of-plane rotations. Inter-user variability and variations in x-ray acquisition parameters also contribute to errors in this assessment. Previously, Lonner et al. and Radtke et al. studied the effect of foot rotation and knee flexion on assessment of knee alignment in total knee arthroplasty. However, we are not aware of any previous work on effect of x-ray acquisition parameters and varying implant orientations on the accuracy of implant varus/valgus measurements using AP long-standing x-rays. In this paper, we present work to evaluate inter-user variability in assessment of implant varus/valgus angles when using long-standing AP x-ray measurements under varying implant out-of-plane rotations, and variations in the x-ray acquisition process. Our results indicate that manual measurements of implant orientation from long-standing AP x-rays is very unreliable.

ABSTRACT. As advancements are made in the field of total knee arthroplasty (TKA) with respect to instrumentation, implants, surgical techniques and use of computer assistance, the indications for TKA continue to expand and functional expectations continue to rise. However the most important factors affecting the outcome of a TKA are restoring the normal mechanical axis and achieving optimum soft tissue balance. The gap balance technique initially described by Freeman and later modified by Insall et al blends the soft tissue balance with the bony cuts and tries to overcome this problem. The lateral ligaments and soft tissues (in case of OA knee with varus deformity) act as a reference against which the medial soft tissues are balanced. The aim of the present study was twofold: - To describe our methodology of ligament specific navigation assisted gap balance technique and analyze the clinico-radiological outcome of our technique over an eight year follow up. Seventy nine patients (98 knees) with a diagnosis of primary osteoarthritis with varus deformity <20⁰ and flexion deformity of <25⁰ operated with our technique were followed up for an eight year duration. After obtaining an optimum gap balance and neutral axis in extension, tibial osteotomy perpendicular to the mechanical axis in both the coronal and sagittal planes was done. At this stage joint gaps were distracted in extension and 90⁰ flexion. Based on the gap values patients were classified into three groups. Group 1 was the balanced group with flexion extension gap difference ≤2mm, group 2 was the flexion tight group with flexion gap smaller than the extension gap by ≥3mm and group 3 was the extension tight group with the extension gap smaller than the flexion gap by ≥3mm. Thereafter flexion gap balance was achieved only by adjusting the cutting levels of the distal and posterior condyles and adjusting the axial rotation of the femoral component without any further soft tissue release. Intra operative navigation readings were recorded. All patients were followed clinico-radiologically at 1, 4, and 8 years post operatively. The level of posterior condylar cut was significantly higher in the flexion tight group. The level of distal cut was higher in the extension tight group. Mean external rotation of the femoral component was 3.14⁰. Mean joint line change in all patients was < ±2.5mm. There was significant improvement in all the clinical scores, and ROM till the last follow up. There were no differences among the patients in the three groups. The ligament specific navigation assisted gap balance technique is a reliable technique for TKA with excellent clinico-radiological results over an eight year follow up period.

ABSTRACT. Accurate alignment and soft tissue balance are essential for successful total knee arthroplasty (TKA). Mal-alignment and soft tissue imbalance produce unequal loads on the medial and lateral tibial plateaus, and thus, substantially increase component wear. Therefore, in order to obtain well-balanced knees, good varus and valgus alignment and equal flexion and extension gaps must be achieved. The computer assisted navigation systems have been used to help surgeons improve TKA alignment accuracy, and these systems have been demonstrated to reduce some alignment errors. However, despite improved alignment accuracies, soft tissue balancing remains a challenge. To the best of our knowledge, no reports are available on knee stability after TKA performing using a navigation system. We compared the laxity, radiological and clinical outcomes of TKA (total knee arthroplasty) that performed using the navigation system and using the conventional technique at least 7-year follow up. Total of 92 TKAs were included for this study, 47 TKAs were performed by the navigation group and 45 TKAs were performed by the conventional surgery. At the final follow up, to evaluate knee joint laxity, varus-valgus laxities were measured on the stress radiographs taken with varus or valgus loads at 90° of flexion. The radiological measurements with regard to the mechanical axis, the inclination of the femoral and tibial components, femoral posterior condylar off-set difference and radiolucency were compared between two groups. The clinical evaluations were performed using range of motion, Western Ontario and McMaster Arthritis index (WOMAC) scores and Knee Society (KS) score. At a final follow up, the mean of valgus laxities were 3.9° in the navigation group and 4.0° in the conventional group, and the corresponding mean of varus laxities were 4.0° and 4.3° (p=0.19, p=0.22). Although there was no significant difference in the total laxity (7.8° in the navigation group and 8.1° in the conventional group, p=0.35). However, more than 10° of total laxity was significantly reduced in the navigation group (1 knee in the navigation group and 6 knees in the conventional group). The mean of mechanical axis was not statistically different between two groups. In the inclination of the femoral and tibial components, posterior femoral offset difference, radiolucent line, there were no statistical differences between two groups. But, the outlier numbers at mechanical axis, the mean of coronal inclination of the femoral and tibial component and the mean of sagittal inclination of the femoral component in the two groups was significantly different. At the last follow up, the differences in ROM, WOMAC score and KS scores were not observed between the two groups.

ABSTRACT. Operation of a C-arm in the operating room (OR) is typically performed by a radiology technologist (RT). However, C-arm training for an RT is largely limited to theory and lacks hands-on practice in an OR environment. Thus, a large proportion of the learning curve is carried out in the real OR resulting in higher radiation exposures and longer surgery times. A computer-based simulation system may help bridge this experience gap by providing a practical training tool for RT students.

virtX is a simulation package that integrates a real C-arm and manikin with a virtual OR scene. Our goal is to evaluate the value of virtX for training RTs with no prior C-arm experience. We hypothesized that participants who receive training with virtX will perform imaging tasks faster and with fewer X-ray shots than those who do not receive the training. We performed a pilot study with six participants (who are not RT students) to evaluate the virtual component of the virtX system and to refine the protocol for the larger scale RT study. We present the pilot results here, but we plan to carry out this study with 1st year medical radiography students at the British Columbia Institute of Technology shortly.

The pilot study participants were randomized to either the control group (no virtX training) or the intervention group (virtX training).  The intervention group completed two tasks that required taking virtual X-rays of the ankle and pelvis at specified angles. To assess whether virtX training could improve imaging skills, both study groups performed an evaluation exercise using a real C-arm and human knee model. Participants were shown reference radiographs of two desired views (an anteroposterior and lateral view) then replicate these while time and number of X-ray shots were recorded for each task.

The average number of X-rays taken to achieve the desired views was 7 for the control group and 6 for the intervention group, while the average time to achieve the desired views was 188 s and 322 s for the control and intervention groups, respectively. Our results varied greatly, which may be explained by the range of C-arm experience of the participants. Thus, our next step is to collect data on novice users and with the physical virtX module. Despite the lack of demonstrated improvement with the virtual portion of virtX in this pilot study, these results directly inform our next steps in further evaluating virtX training on RT students.

ABSTRACT. INTRODUCTION Congenital proximal radioulnar synostosis (PRUS) is a rare congenital anomaly where the radius and ulna are fused at the proximal portion. PRUS is classified into three types according to radius head position in x-ray, posterior dislocation type, anterior dislocation type and non-dislocation type. However, little information has been available on the 3-dimensional (3D) deformity patterns, including axial rotation deformity. The purpose of this study was to compare the deformities among the three dislocation types of PRUS.

PATIENTS AND METHODS A total of 38 radii and ulnae in 25 patients (mean age: 6 y-o.) were evaluated. 3D computer models of bilateral radius and ulna were created from computed tomography data. We evaluated deformity by superimposing the mirror-image bone model of the contralateral normal bone onto a model of the affected bone.

RESULTS In the posterior dislocation group (n=16), the flexion deformity of radius and pronation deformity of ulna were seen the most severe among 3 groups (p<0.01). In the non-dislocation group (n=8), the pronation deformity of ulna was seen significantly more severe than ant-dislocation group (p<0.01). In the anterior dislocation group (n=14), the extension deformity of ulna was seen the most severe among 3 groups (p<0.01).

DISCUSSION It was considered that non-dislocation type of PRUS was mild deformity in the three types, however our result showed that severe pronation deformity of ulna was found. This suggests that an additional supination osteotomy of the ulna might be required for not only the posterior dislocation type but also non-dislocation type of PRUS.

ABSTRACT. Long term satisfaction of patients with total knee arthroplasty has lagged behind that of total hip arthroplasty. One explanation is a mismatch between the shape of the native distal femur and its shape post-operatively

A technique that would allow for measurement of morphologic concordance between the native femur and implanted femur with no additional imaging requirement could offer a pathway to optimize implant positioning leading to improved function and satisfaction.

The objective of this study was to develop and validate a fitting procedure for a statistical shape model of the distal femur using data collected routinely intraoperatively as part of surgical navigation total knee arthroplasty.

A total of 20 patients who underwent navigated total knee arthroplasty also had an MRI performed within 2 months preoperatively as part of a previous study protocol. These patients data were selected to be used in this study. Of these subjects the first 3 processed cases are presented here.

During surgery the anterior cortex, the distal and posterior femoral condyles, the medial and lateral epicondyles and the femoral center were digitized. Post-operatively these data were extracted from the navigation unit and imported into Matlab. A statistical shape model adapted from previous work was optimized to approximate the shape of the distal femur from available point clouds.

The MRI data was segmented to develop 3-D models. The segmented MRI data was used as the control against which the statistical shape model was compared.

Comparison of the statistical shape model with the femoral models obtained from the segmented MRI data showed good agreement in all cases. The average error between the statistical shape model and the MRI for the three cases was 1.21, 1.56 and 1.61 mm. The standard deviation was 1.02, 1.07 and 1.15 mm. The root mean squared error was 1.58, 1.89 and 1.85 mm.

As total knee arthroplasty evolves, a patient specific approach is going to be demanded by patients. The results of this study show that with the sparse data set available from routine navigated knee surgery, the statistical shape model can provide an accurate approximation of the distal femur. In the future these models could be incorporated into a surgical navigation unit and provide a surgeon with accurate measurement of the concordance of the proposed femoral component positioning with the native anatomy.

This technique is an important step in the development of a patient morphology-specific TKA protocol and could allow for optimization of implant selection and positioning for patients.

ABSTRACT. Atrophy of the muscles around the hip and thigh occurs in patients with hip osteoarthritis (OA). Total hip arthroplasty (THA) increases activity levels, resulting in the recovery of the muscular strength of the hip and thigh. However, there have been few reports which have quantitatively evaluated the change in the muscle volume after THA, and there are no reports indicating on the volume recovery of gluteus muscles after THA. In this report, we quantitatively evaluated the changes in the hip and thigh muscle volume after THA and also evaluated the related factors. Thirty eight patients (6 men and 32 women, mean age: 58 years) with bilateral hip OA who had undergone unilateral THA, were the subjects of this study. CT images used for measurements were taken 3 weeks after THA (postop-CT) and 4 years (range: 2-8.5 years) after THA (2nd postop-CT). The cross-sectional area (CSA) of gluteus maximus (G-max), gluteus medius (G-med), and thigh muscles (Th) of both hips were measured on the axial plane of the CT images to evaluate the muscle volume change. The factors related to the muscle recovery that were measured and evaluated were: sex, age, days from operation, surgical approach, length change, and femoral offset change. CSAs on the operated side (OS) increased significantly after THA (G-max: 24%, G-med: 16%, Th: 12%). There were no significant correlations between the increased rates of CSAs and the evaluated factors except for a correlation between G-max and age (R=-0.35). By comparing the OS with the contralateral side (CS), all CSAs of the OS were significantly smaller than the CS on postop-CT, but became significantly larger than that of the CS on 2nd postop-CT. CSAs of the gluteus muscles and thigh muscles on the OS significantly increased from the postop-CT to the 2nd postop-CT. This study was the first study to evaluate the muscle recovery after unilateral THA in bilateral OA patients and also the first study to reveal the increase in the gluteus muscles after THA. In the analysis of the related factors, there were no significant correlations seen between the increased rates of CSAs and days from THA. Since all of the patients included in this study had taken 2 CT images with more than 2 years of interval, it can be suggested that the significant increase of the muscle volume happened within 2 years after THA and reached the equilibrium state. In conclusion, the quantity of the gluteus maximus, gluteus medius and thigh muscles increased significantly after THA.

ABSTRACT. Conventional computer-assisted orthopaedic surgery (CAOS) involves many time-consuming and patient-dependent repeatable tasks such as region-of-interest segmentation, implant fitting, and surgical planning. This work proposes an open framework and a core technology for CAOS tasks that enables users to easily exchange modules to customize applications. The framework consists of one core and multiple application modules. The core is a Lie group statistical shape model constructed from an anatomical population. The core constructs a shape model for each region of interest. The core can be used with different application modules. The power of a Lie group is derived from the fact that it is an algebraic group and a smooth manifold at the same time. The core technology was validated using a dataset of 15 human proximal femurs. The study showed that in such a small dataset, the Lie group based model outperformed the linear model in terms of compactness. Linear PCA failed to capture the variations of the dataset, requiring 7 components to capture 95% of the variation within the simple dataset, whereas the product Lie group analysis was able to capture the same percentage using only 3 components. In conclusion, the open framework with a Lie group statistical shape model core promises to enhance the progress of the automation of CAOS repeatable tasks in an accurate and efficient manner. Consequently, this can enhance the outcomes of CAOS procedures.

ABSTRACT. Rotational acetabular osteotomy (RAO) for developmental dysplasia of the hip (DDH) may not restore normal hip range of motion (ROM) due to the inherent deformity of the hip and it may lead to femoro-acetabular impingement. The purpose of this study was to investigate morphological factors of the pelvis and femur influencing on simulated ROM after RAO with a fixed target for femoral head coverage. We retrospectively reviewed CT images of 52 DDHs with an average lateral center edge angle (CEA) of 7.9° (-12° to 19°). After virtual RAO with 30° of lateral CEA and 55° of anterior CEA producing femoral head coverage similar to that of the normal hips, we measured simulated flexion ROM using pelvic and femoral computer models reconstructed from the CT images. Pelvic sagittal inclination, acetabular anteversion, lateral CEA, femoral neck anteversion, femoral neck shaft angle (FNSA), alpha angle and the position of the anterior inferior iliac spine (AIIS) were investigated as morphological factor. When the most prominent point of the AIIS existed more distally than the cranial tip of the acetabular joint line in a lateral view of the pelvis model in supine position, the subjects were defined as AIIS-Type1; the remaining subjects were defined as Type2. There were 10 hips with Type 1 and 42 hips with Type 2 AIIS. The Kappa value of inter-observer reproducibility to classify AIIS was 0.82. Multiple regression analyses were performed to analyze the relationship between ROM and the morphological parameters. We also analyzed the relationship between the probability of flexion ROM being less than 110º and the factors which influenced on flexion ROM. FNSA and AIIS-Type independently influenced on simulated flexion ROM after RAO (standard regression coefficient: -0.51 and 0.37, respectively. p< 0.001). The multiple correlation coefficient was 0.68. Flexion ROM after RAO with a fixed femoral head coverage similar to that of the normal hips ranged from 95º to 141º with an average of 121º±8º. The probability of ROM being less than 110º was significantly higher in subjects with AIIS-Type 1 than in those with Type 2 (odds ratio: 13.3, p<0.01). It was also significantly higher in subjects with more than 135º of FNSA than in those with less than 135º of FNSA (odds ratio: 9.5, p<0.05). FNSA and the type of AIIS influenced on flexion ROM after RAO with approximately 40º of variation in spite of a fixed target for femoral head coverage. A large FNSA and a distal positioning of AIIS were independently associated with smaller flexion ROM after RAO.

ABSTRACT. Purpose: Aim of the study was to assess difficulties and adverse effects in more than 400 CAS hip replacement using a short modular femoral stem to assess their incidence and to determine if this surgical procedure has to be considered as an high demanding surgical technique. Materials and Methods: Since 1998 511 computer assisted hip replacement using a short modular stem were performed in our department. 403 implants were followed for at least 6 months postoperatively and included in the study. All the cases were divided in 3 series according to when the surgery had been performed to consider the evolution of the navigation systems and the surgeons familiarity with this improvements (group A: 1998-2003, group B: 2004-2008 and group C: 2009-2014). All intraoperative problems (difficulties that required no operative intervention to resolve or without any conseguence on the navigation process), intraoperative obstacles (difficulties that required operative intervention or that caused a failure of the navigation process) and complications (intra-operative injuries and all the problems following in the first 6 months postoperatively) were registered. Adverse facts not directly caused by the surgical but derived by other conditions were excluded from the study. Results: There were no differences in number of total problems/complications among the 3 groups. Obstacles were statistically higher in group A where we observed an higher incidence of navigation failures in association both to the first software versions and to a minor surgical experience. We did not registered any statistically significant difference in the number of septic THR (complication) and incidence of superficial pin site infections (complication). One case in group A had to be successfully revised because a proven metal allergy in group B. We registered 8 cases of proximal femur fractures wit different distribution among the 3 groups . In 1 cases in group A we experienced an acetabular fracture during cup impaction managed with rest. No abnormal intra operative or post operative bleeding was registered because of the surgical technique with no statistical difference in clinical evident DVT among the 3 groups. Surgical time was longer in group A with a statistical significant difference in group A compared both to group B and C. Conclusion: In this study the authors registered both a higher rate in navigation failure and longer surgical time in the first cases even because of less advance navigation systems and lower experience with CAS. However in a series of more than 400 CAS THRs using a modular short femoral stem the authors could demonstrated no increased rate of complications compared to traditional techniques.

ABSTRACT. Purpose: Implant positioning is one of the critical factors influencing the postoperative outcome in total hip arthroplasty (THA). Conventional (manual) intraoperative stem adjustment may result in variability and inaccuracy of stem antetorsion (AT). Since March 2013, we have measured stem antetorsionwith CT free Navigation system (OrthoPilot Navigation System THA Pro Ver4.2, B/Braun Aesculap Germany: Navi). We have developed a simple instrument, the Gravity-guide (G-guide), for intraoperative assessment and adjustment of stem AT. We evaluated the accuracy and effectiveness of G-guide and navigation software as referenced to postoperative CT evaluation with 3D template system (Zed hip, LEXI, Japan). Method: Between March 2013 and December 2014, 50 patients underwent primary THA were evaluated. Surgeries were performed with routine techniques with a modified Hardinge approach with the patient at a lateral decubitus position in all cases. The G-guide consists of two parts: one attached to the lower leg and the other attached to the handle of the rasp. During surgery, AT value was determined with navigation at the time of final rasping of the femur. Additionally, the G-guide was utilized at the time of final rasp insertion. In intraoperative AT assessment using this instrument, a correction was required considering the discrepancy between the perpendicular to the posterior condylar axis and the longitudinal axis of the lower leg. The angle of discrepancy between posterior condylar line and femoral transepicondyler axis needs to be taken into consideration. Therefore, correction by the angle between the trans-epicondylar and posterior condylar lines (correction angle) was required for each patient when the intraoperative AT as measured by the G-guide. Therefore, the correction angle should be added to the AT value obtained from the G-guide for comparison with postoperative value measured with Zed Hip. Result: The discrepancy between the intraoperative G-guide with correction angle and postoperative Zed Hip measurements was 4.7° ± 3.9°. The discrepancy between Navi AT and postoperative Zed HIP measurements was 5.9° ± 4.1°. A discrepancy was 10° or more were 7 cases in Navi and 4 cases in G-guide. Conclusion: Navi and G-guide measured intraoperative stem antetorsion was comparable utility.

ABSTRACT. Introduction The safe zone of the acetabular cup for THA was discussed based on the AP X-ray films of hip joints. A supine position is still used to determine the cup position for CAOS such as navigation systems. There were few data about the implant positions after THA in standing positions. The EOS X-Ray Imaging Acquisition System (EOS system) (EOS imaging Inc, Paris, France) allows image acquisition with the patients in a standing or sitting position. We can obtain AP and lateral X-ray images with high-quality resolution and low dose radiation exposure. Recently, we have obtained the EOS system for the first time in Japan. We investigated 3D accuracy of the EOS system for implant measurements after THA. Patients and Methods We measured the implant angles of the 68 patients (59 females and 9 males, average age: 61y.o.) who underwent THA using the EOS system. The cup inclination and anteversion were measured in the anterior pelvic plane (APP) coordinate. The femoral stem antetorsion was defined as angles between the stem neck axis and the posterior condylar axis. These data were compared with the implant angles of the same patients measured by the post-operative CT scan images and the 3D image analysis using the ZedHip software (LEXI, Japan). Results The cup inclinations (average ±SE) measured by the EOS system and the CT scan were 40.6 ± 0.64º and 42.9 ± 0.53º, respectively. The cup anteversions were 22.9 ± 1.3º and 22.8 ± 1.0º, respectively. The stem antetorsions were 28.9 ± 1.3º and 29.8 ± 1.6º, respectively. The differences (average ± SE) between the EOS system and the CT scan in the cup inclination, the cup anteversion, and the stem antetorsion were -2.3 ± 0.38º, -0.09 ± 0.82º, and -0.90 ± 0.91º, respectively. There were strong correlations in measurement values between the EOS system and the CT scan (the Spearman’s correlation coefficients of the cup inclination, the cup anteversion, and the stem antetorsion were 0.6521 [p<0.001], 0.7154 [p<0.001], and 0.8645 [p<0.001], respectively). Discussion The EOS system provides acceptable clinical accuracies in measuring acetabular cup and femoral stem angles after THA. The accuracy of the cup angles was accorded with that of the basic experimental data using a dry pelvis. Our data also demonstrated clinically acceptable accuracy in the measurement of stem antetorsion. This system can provide accurate snap shots of variable postures with high resolution. Using the EOS system, we may establish real optimum positions of THA implants by measuring the patients after THA in several postures including standing, squatting or sitting positions which required for Japanese ADL.

ABSTRACT. Introduction In recent literatures dealing with optimization of prosthetic alignment in total hip arthroplasty (THA), the concept of combined anteversion (CA), sum of acetabular anteversion (AV) and femoral antetorsion (AT), has been addressed. We have been using an image-free THA navigation system（OrthoPilot THAPro）to achieve improved overall alignment with both stem and cup. In the use of this system, we have used the stem-first procedure so-called CA technique. In this technique, the femur was prepared first with the target angle corresponding to the native femoral AT and the cup AV was decided considering CA calculated with the formula of Widmer (37.3°= cup AV + 0.7 stem AT). The purpose of this study was to evaluate the accuracy of CA by using CA technique with image-free navigated THA. Methods Fifty hips were underwent primary THA using OrthoPilot THApro with CA technique. In CA technique, the femur was prepared first and the target angle of AT value was basically determined by for the individual native femoral AT angle. After the femur was prepared, the cup AV was decided based on the formula of Widmer. All included patients underwent postoperative CT examination, and the prosthetic alignment was assessed using the 3D-Template system (Zed Hip, LEXI). Results In the assessment of accuracy of the navigation systems in 50 consecutive THA’s, comparison of intraoperative navigation value and postoperative CT evaluation indicated that the absolute discrepancy of cup AV, and stem AT was 4.5° ± 3.5°and 5.9° ± 4.3° respectively. In the assessment of the cup AV with postoperative CT evaluation, the measured values averaged 20.7° ± 6.2° while AT values averaged 20.9° ± 10.6°. Distribution of AT values showed large SD. By contrast, the average Widmer’s CA values (cup AV + 0.7 stem AT) were 35.2° ± 5.7°. In the assessment of overall alignment, the Widmer’s CA values were within 37° ± 5° in 40 hips and 37° ± 10° in 46 hips. Conclusion The present study proposed that the confirming stem AT prior to cup placement could be important to achieve appropriate CA value. CA technique with image-free navigated THA could achieve accurate and consistent control of CA value.

ABSTRACT. The purpose of this retrospective study was to estimate the outcome improvements after Total hip arthroplasty (THA) using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) in patients who underwent THA with a navigation system in our institutions, and to compare them with those undergoing THA without a navigation system that had been reported in the literatures. The subjects in this study comprised 245 patients (39 males, 206 females; mean age, 59.9±12.0 years; mean BMI, 22.8±3.2 kg/m2) who underwent THA. All patients had adequate data to allow complete scoring of the WOMAC for a minimum one-year postoperative follow-up. CT-based navigation was used in all THAs. Postoperatively, no restrictions were imposed. A MEDLINE search was conducted using the search terms ‘Total hip’, ‘Quality of life (QOL)’, and ‘WOMAC’. 10 articles evaluated all WOMAC subscales one to two years after THA. The WOMAC subscale scores were compared statistically between our study and the results reported in the 10 articles using Welch’s t-test. The present physical function subscale scores were the best of the 10 studies, and in 8 of the 10 studies, the differences were significant. WOMAC subscale results in our study were significantly better than those reported in most articles in which THA was performed without navigation. These results show that THA using navigation can improve patients’ postoperative QOL.