In the framework of the modiCAS (Modular Interactive Computer Assisted Surgery) Project, which emerged from a collaboration of the University of Siegen and the University of Frankfurt in the fields of mechatronics and medicine, the development of a modular system to assist the surgeon during the whole planning and operation procedure has been started. A completely new realization of a planning system for bone surgery and alloarthroplasty is presented. Characteristics of the new system are generic interfaces for navigation, robotics and real-time data acquisition, graphic interactivity, documentation of each planning-step, a flexible wizard-guided concept and adaptable teaching modes. The system can be configured to any data source such as X-ray, CT, MRI, US with individual calibration. For planning, the data sources can be merged in any user defined way. In contrast to all existing planning systems the presented system can optionally be linked to navigation and robotic systems. The software was realized to run platform-independent on any personal computer surrounding. We used commercially available software libraries for computer graphics and graphical user interface programming. The whole system consists of several modules which are closely linked together and support all major pre- and intraoperative steps of surgery. The user interface remains the same during the planning and the intervention. Preoperative planning is carried out on a totally new planning station comprising an interactive and intuitive graphic interface, while intraoperative features include interactive matching procedures, true real-time-capability and incorporation of navigation and robotics. Initially we realized modules to support total hip allo-arthroplasty. The first application of the system is for a clinical trial on total hip alloarthroplasty. Planning is performed on the basis of radiographs and CT-datasets. Intraoperatively a navigation system and a robotic surgery system are used. Preliminary results show very precise and reproducible plannings that could be achieved in short time without special training of the clinician. Furthermore the unlimited intraoperative access to the whole planning dataset appeared to be very convenient to the surgeon because it allowed immediate response to unforeseen patient specific situations. Future adaptations of the universal planning system will be total knee alloarthroplasty, spine surgery and trauma surgery. The existing system can easily be configured to any surgical procedure because the same basic functionality is used for all applications and only special configurative datasets have to be generated for each application. The open architecture of the system enables easy integration of further input or output devices, an easy adaptation to different interventions, planning styles and operative techniques is possible

Problem. Total hip replacement (THA) is among the most common and highest total spend elective operations in the United States. However, up to 7% of patients have 90-day complications after surgery, most frequently joint dislocation that is related to poor acetabular component positioning. These complications lead to patient morbidity and mortality, as well as significant cost to the health system. As such, surgeons and hospitals value navigation technology, but existing solutions including robotics and optical navigation are costly, time-consuming, and complex to learn, resulting in limited uptake globally. Solution. Augmented reality represents a navigation solution that is rapid, accurate, intuitive, easy to learn, and does not require large and costly equipment in the operating room. In addition to providing cutting edge technology to specialty orthopedic centers, augmented reality is a very attractive solution for lower volume and smaller operative settings such as ambulatory surgery centers that cannot justify purchases of large capital equipment navigation systems. Product. HipInsight™ is an augmented reality solution for navigation of the acetabular component in THA. HipInsight is a navigation solution that includes preoperative, cloud based surgical planning based on patient imaging and surgeon preference of implants as well as intraoperative guidance for placement of the acetabular component. Once the patient specific surgical plan is generated on the cloud-based planning system, holograms showing the optimal planned position of the acetabular component are exported in holographic format to a Microsoft HoloLens 2™, which the surgeon wears during placement of the acetabular component in total hip arthroplasty. The pelvis is registered using the HipXpert™ mechanical registration device, which takes 2–3 minutes to dock in the operating room. The surgeon then is able to view the patient's anatomy and optimal placement of the acetabular component under the skin in augmented reality. The surgeon then aligns the real cup impactor with the augmented reality projection of the cup impactor resulting in precise placement of the cup. Timescales. HipInsight was FDA cleared on January 28, 2021 for intraoperative use for placement of the acetabular component in total hip arthroplasty. The first case was performed in February 2021, and the product was launched to a select group of orthopedic surgeons in March 2021. Funding. HipInsight has been self-funded to date, and is beginning to engage in discussions to raise capital for a rapidly scaling commercial launch

Introduction. Lesion location and volume are critical factors to select patients with osteonecrosis for whom resurfacing arthroplasty is appropriate. However, no reliable surgical planning system which can assess relationship between necrotic lesions and the femoral component has been established. We have developed a 3D-MRI-based planning system for resurfacing arthroplasty. The purpose of the present study was to evaluate its feasibility. Methods. The subjects included five patients with osteonecrosis of ARCO stage 3 or 4 who had undergone resurfacing THA at our institute. All patients had an MRI before surgery using 3D-SPGR sequences and fat suppression 3D-SPGR sequencea. In cases where it was difficult to distinguish bone marrow edema and reparative zone on 3D-SPGR images, fat suppression 3D-SPGR sequences were used. Simulation of resurfacing arthroplasty was performed on image analysis software where multidirectional oblique views could be reconstructed. The femoral neck axis was determined by drawing line through centers of two spheres which were fitted to the normal portion of the femoral head and the mid-portion of femoral neck. A femoral component was virtually implanted to align the femoral neck axis and match the implant center and femoral head center. Results. Planning could be performed within 10 minutes in every case. In all cases, size selection of acetabular and femoral component was within 1 size of actually implanted components. This 3D-MRI based planning system was useful to assess proportion and location of necrotic lesion in the preserved portion of femoral head in resurfacing THA. Conclusion. This preliminary study demonstrated that a 3D-MRI based planning system was useful in surgical planning of resurfacing arthroplasty for patients with osteonecrosis

Introduction. The achieved anteversion of uncemented stems is to a large extent limited by the internal anatomy of the bone. A better understanding of this has recently become an unmet need because of the increased use of uncemented stems. We aimed to assess plan compliance in six degrees of freedom to evaluate the accuracy of PSI and guides for stem positioning in primary THAs. Materials and Methods. We prospectively collected 3D plans generated from preoperative CTs of 30 consecutive THAs (17 left and 13 right hips), in 29 patients with OA, consisting of 16 males and 13 females (median age 68 years, range 46–83 years). A single CT-based planning system and cementless type of implant were used. Post operatively, all patients had a CT scan which was reconstructed using state-of-the-art software solution: the plan and CT reconstruction models were. Outcome measures: 1) discrepancy between planned and achieved stem orientation angles Fig.2&3; 2) clinical outcome. Results. 1) The mean (±SD) discrepancy was low for: Varus-valgus −1.1 ± 1.4 deg (IQR −2.2 – 0.3 deg); Anterior-posterior 0.1 ± 1.6 deg (IQR −0.7 – 1.3 deg). The discrepancy was higher for femoral version −1.4 ± 8.2 deg (IQR −8.3 – 7.2 deg). 3D-CT planning correctly predicted sizes in 93% of the femoral components. 2) There was no intra-operative fracture, no case showed evidence of early periprosthetic osseous injury. Discussion. Surgeons and engineers should be cautious with their expectation of achieving the planned femoral stem version of an uncemented femoral stem from the pre-operative 3D-CT plan. Conclusion. This is the first study to 3D-mensionally evaluate 3D-printed patient-specific instrumentation and guides for achieved femoral stem component orientation vis-à-vis to the plan. The tools allow accurate implant orientation, however there is still potential for improvement. For any figures or tables, please contact the authors directly

Recent innovations in total ankle replacement (TAR) have led to improvements in implant survivorship, accuracy of component positioning and sizing, and patient outcomes. CT-generated pre-operative plans and cutting guides show promising results in terms of placement enhancement and reproducibility in clinical studies. The purpose of this study was to determine the accuracy of 1) implant sizes used and 2) alignment corrections obtained intraoperatively using the cutting guides provided, compared to what was predicted in the CT generated pre-operative plans. This is a retrospective study looking at 36 patients who underwent total ankle arthroplasty using a CT generated pre-operative planning system between July 2015 and December 2017. Personalized pre-operative planning data was obtained from the implant company. Two evaluators took measurements of the angle corrected using pre- and post-operative weight bearing ankle AP X-rays. All patients had a minimum three-month follow-up with weightbearing postoperative radiographs. The actual correction calculated from the radiographic assessment was compared with the predicted angles obtained from pre-operative plans. The predicted and predicted alternative component sizes and actual sizes used were also compared. If either a predicted or predicted alternative size was implanted, we considered it to be accurate. Average age for all patients was 64 years (range 40–83), with a body mass index of 28.2 ± 5.6. All surgeries were performed by two foot and ankle surgeons. The average total surgical time was 110 ± 23 minutes. Pre-operative alignment ranged from 36.7 degrees valgus to 20 degrees varus. Average predicted coronal alignment correction was 0.8 degrees varus ± 9.3 degrees (range, 18.2 degrees valgus to 29 degrees varus) and average correction obtained was 2.1 degrees valgus ± 11.1 degrees. Average post-op alignment was consistently within 5 degrees of neutral. There were no significant differences between the predicted alignments and the postoperative weightbearing alignments. The predicted tibia implant size was accurate in all cases. The predicted sizes were less accurate for talar implants and predicted the actual talar implant size used in 66% of cases. In all cases of predicted talar size mismatch, surgical plans predicted 1 implant size larger than used. Preliminary analyses of our data is comparable to previous studies looking at similar outcomes. However, our study had higher pre-operative deformities. Despite that, post-op alignments were consistently within 5 degress of neutral with no significant difference between the predicted and actual corrections. Tibial implant sizes are highly accurate while talar implant sizes had a trend of being one size smaller than predicted. Moreover, this effect seems to be more pronounced in the earlier cases likely reflective of increasing surgeon comfort with the implant with each subsequent case. These results confirm that pre-operative cutting guides are indeed helpful in intra-operative implant selection and positioning, however, there is still some room for innovation

Introduction: For longer lasting and bone conserving cementless stem fixation, stable and physiological proximal load transfer from the stem to the canal should be one of the most essential factors. According to this understanding, we have been developing a custom stem system with lateral flare and an off-the-shelf (OTS) lateral flare stem system was added to the series. On the other hand, dysplastic hips are often understood that they have larger neck shaft angle as well as larger anteversion. In other words they are in the status called “coxa valga.” From this point of view we had been mainly using custom stems for the dysplastic cases before. After off-the-shelf lateral flare stem system; which is designed to have very high proximal fit and fill to normal femora; was added, we have been using 3D preoperative planning system to determine custom or OTS. Then in most of the cases, OTS stem were suitably selected. Our pilot study of virtual insertion of OTS lateral flare stem into 38 dysplastic femora has shown very tight fit in all 38 cases. The reason was analyzed that the excessive anteversion is twist of proximal part over the distal part and the proximal part has almost normal geometry. In the present study, 59 femora were examined by the 3D preoperative planning system how the excessive anteversion effect to the coxa valga status. Materials and Methods: Fifty-nine femoral geometry data were examined by the 3D preoperative planning system. Thirty-three hip arithritis, 3 RA, 2 metastatic bone tumours, 5 AVN, 1 knee arthritis, 12 injuries, and 3 normal candidates were included. Among them one arthritic Caucasian and one AVN South American were included. The direction of the femoral landmarks; centre of femoral head (CFH), lesser trochanter (LTR), and asperas in 3 levels (just below LTR, upper 1/3, mid femur; A1-3); were assessed as the angle from knee posterior condylar (PC) line. Neck shaft angle of each case was assessed from the view perpendicular to PC line and neck shaft angle form the view perpendicular to CFH and femoral shaft (i.e. actual neck shaft angle). Results: Average anteversion was 34.4 +/−9.9 degree. CFH and LTR correlated well (i.e. they rotate together). A1, A2, A3 correlated well (i.e. they rotate together). LTR and A1 correlate just a little, LTR and A2 were independent each other. So the twist existed around A1. Neck shaft angle was 138.7+/−6.6 in PC line view and in actual view 130.3+/−4.4. No excessive neck shaft angle was observed in actual view. Even the case that has the largest actual neck shaft angle (140.4), the virtual insertion showed good fit and fill with the lateral flare stem. Conclusion: In many high anteversion cases, coxa valga is a product of the observation from non perpendicular direction to CFH-shaft plane. Selection or designation of the stem for high anteversion cases should be carefully determined by 3D observation

Introduction. Kinematics post-TKA are complex; component alignment, component geometry and the patient specific musculoskeletal environment contribute towards the kinematic and kinetic outcomes of TKA. Tibial rotation in particular is largely uncontrolled during TKA and affects both tibiofemoral and patellofemoral kinematics. Given the complex nature of post- TKA kinematics, this study sought to characterize the contribution of tibial tray rotation to kinematic outcome variability across three separate knee geometries in a simulated framework. Method. Five 50. th. percentile knees were selected from a database of planned TKAs produced as part of a pre-operative dynamic planning system. Virtual surgery was performed using Stryker (Kalamazoo, MI) Triathlon CR and PS and MatOrtho (Leatherhead, UK) SAIPH knee medially stabilised (MS) components. All components were initially planned in mechanical alignment, with the femoral component neutral to the surgical TEA. Each knee was simulated through a deep knee bend, and the kinematics extracted. The tibial tray rotational alignment was then rotated internally and externally by 5° & 10°. The computational model simulates a patient specific deep knee bend and has been validated against a cadaveric Oxford Knee Rig. Preoperative CT imaging was obtained, landmarking to identify all patient specific axes and ligament attachment sites was performed by pairs of trained biomedical engineers. Ethics for this study is covered by Bellberry Human Research Ethics Committee application number 2012-03-710. Results and Discussion. From the 360 Knee Systems database, 1847 knees were analysed, giving an average coronal alignment of 4.25°±5.66° varus. Five knees were selected with alignments between 4.1° and 4.3° varus. Kinematic outcomes were averaged over the 5 knees. The component geometries resulted in characteristically distinct kinematics, in which femoral rollback was most constrained by the PS components, whereas tibiofemoral axial rotation was most constrained in MS components. Patella lateral shift was comparable amongst all components in extension, medialising in flexion. Patella shift remained more lateral in MS components compared to PS and CR. Average patella lateral shift, medial and lateral facet rollback separated by tibial tray rotation are shown for all component systems in Figure 1. Medial and lateral facet rollback in the PS and CR components are symmetrical and opposite, indicating that with tibial tray rotation, the tibiofemoral articulation point balances between component rotation and neutral alignment, reflecting the restoring force exerted by the simulated collateral ligaments. As such, with higher internal tibial rotation and subsequent lateralisation of the tubercle, patella lateral shift increases. MS medial and lateral facet rollback however are not symmetrical nor opposite, reflecting the chirality of the tibiofemoral articulation. With internal tibial tray rotation, relatively high lateral facet rollback is observed, lateralising the femoral component centre, giving the patella component a relatively more medial position. Conclusions. Component geometry was found here to produce characteristically distinct tibiofemoral and patellofemoral kinematics. Medial stabilised components reported asymmetric kinematic changes, compared to either CR or PS components, in which a higher rate of change was observed for internal tray rotation, indicating that neutral or external rotation of medial stabilised components will result in more predictable kinematic outcomes

Introduction: The success of cemenntless THA (total hip arthroplasty) mainly depends on the choices of stem, its size and accuracy of stem orientation. Selection of the optimal stem judging only by plain X-ray is not so easy. Because deformity varies in each case and it is impossible to obtain profile view of the hip. As osteoarthritic patients tend to develop external rotation contractures, radiographic position of the patients with correct rotation is very difficult. To override these problems, we have been using 3-D preoperative planning system. As for the stem selection, we have been mainly using Revelation stem, because it has a structure called lateral flare that provide proximal physiological load transfer. In the present study, the usefulness of our preoperative planning system especially for the determination of the size and stem orientation with Revelation stem. Materials and Method: Pre-operative planning was performed in 55 osteoarthritic hips in 50 patients (10 male and 40 females), and the mean age at the operation was 64.05 years old. The 3-dimensinal geometries of the femora femora were reconstructed from the CAT scan DICOM data. The geometry of femur and components were placed on the same coordinate. Cross-sectional images from many directions were observed, and the optimal location and the size of the stem were selected. According to the result, actual operations were done. Planed sizes and selected sizes at the surgeries were compared. For several patients, post-operative CAT scans were performed, then planed stem position and actual stem position were compared. Result: Stems preoperatively defined were used in 50hips (90.9%),1 size large ones were used in 2 hips (3.6%) and 1 size large ones were used in 3 hips (5.5%). Discussion: As Revelation stems have very high proximal fit-and-fill, the end point of the stem insertion is very definite. The characteristics made the accuracy of the preoperative planning. So it was not so difficult to perform THA according to the preoperative planning as it had been imagined

Aims

To investigate if preoperative CT improves detection of unstable trochanteric hip fractures.

Introduction. Accurate acetabular cup orientation could lead to successful surgical results in total hip arthroplasty (THA). We introduce a novel CT-based three-dimensional (3D) planning system, HipCOMPASS (Fig.1) and TARGET (Fig.2), which enable to design suitable alignment not only cup also surgical devices calculatingly, according to each pelvic inclination. Patients and Methods. We performed THA in 45 hips in 43 patients (female 37 and 6 men) between April 2014 and October 2015. Average age were 68 years old. THA operation was based on each parameter of the cup and device, providing a preoperative planning by ZedView system. HipCOMPASS and TARGET is linked with ZedView software, which is simultaneously calibrated adjustable parameters on this devices. Cup alignment was assessed by ZedView as well. Results. The differences of component alignment from the preoperative planning were shown in Tables. Conclusion. HipCOMPASS and TARGET might be more accurate than conventional method and more accessible system than navigation system in THA

Trauma surgeries in the pelvic area are often difficult and prolonged processes that require comprehensive preoperative planning based on a CT scan. Preoperative planning is essential for the appreciation and spatial visualisation of the bone fragments, for planning the reduction strategy, and for determining the optimal type, size, and location of the fixation hardware. We have developed a novel haptic-based patient specific preoperative planning system for pelvic bone fractures surgery planning. The system provides a virtual environment in which 3D bone fragments and fixation hardware models are interactively manipulated with full spatial depth and tactile perception. It supports the choice of the surgical approach and the planning of the two mains steps of bone fracture surgery: reduction and fixation. The purpose of the tool is to provide an intuitive haptic spatial interface for the manipulation of bone fracture 3D models extracted from CT images, to support the selection of bone fragments, the annotation of the fracture surface, the selection and placement of fixation screws, and the creation and placement of fixation plates with an anatomically fit shape. The system incorporates ligament models that constrain the bone fragments motions and provides a realistic interactive fracture reduction support feeling to the surgeon. It allows the surgeon to view the fracture from various directions, thereby allowing fast and accurate fracture reduction planning. Two haptic devices, one for each hand, provide tactile feedback when objects touch without interpenetrating. To facilitate the reduction, the system provides an interactive, haptic fracture surface annotation tool and a fracture reduction algorithm that automatically minimises the pairwise distance between the fracture surfaces. For fracture fixation, the system provides a screw creation and placement capability as well as custom anatomical-fit fixation plate creation and placement. The screw placement is facilitated by the transparent viewing mode that allows the surgeon to navigate the screws inside the bone fragments while constraining them to remain within the bone fragments with haptic forces. Our experimental results with five surgeons show that the method allows highly accurate reduction planning to within 1 mm or less. To evaluate the alignment in terms of quantity, we created a model of an artificial fracture in a healthy pelvis bone. The created model is placed in its anatomic location thus allowing us to measure the error in relation to its initial position. We calculate the anatomic alignment error by measuring the Hausdorff distance in mm between the fragment positioned in the desired location and the fragment placed by the surgeon. The new haptic-based system also supports patient-specific training of pelvic fracture surgeries

Introduction. Accurate acetabular cup orientation could lead to successful surgical results in total hip arthroplasty (THA). We introduce a novel CT-based three-dimensional (3D) planning system, HipCOMPASS (Fg.1) and TARGET (Fig.2), which enable to design suitable alignment not only cup also surgical devices calculatingly, according to each pelvic inclination. Patients and methods. We performed THA in 13 patients (10 female and 3 men) between September 2014 and April 2014. Average age were 67 years old. THA operation was based on each parameter of the cup and device, providing a preoperative planning by ZedView system. HipCOMPASS and TARGET is linked with ZedView software, which is simultaneously calibrated adjustable parameters on this devices. Cup alignment was assessed by ZedView as well. Result. The differences of component alignment from the preoperative planning were shown in table. Conclusion. HipCOMPASS and TARGET might be more accurate than conventional method and more accessible system than navigation system in THA

In patients with developmental dysplasia of the hip (DDH) chronic joint dislocation induces remodeling of the soft tissue with contractures, muscle atrophy, especially of the hip abductors muscles, leading to severe motor dysfunction, pain and disability (1). The aim pf the present work is to explore if a correct positioning of the prosthetic implants through 3D skeletal modeling surgical planning technologies and an adequate customized rehabilitation can be beneficial for patients with DDH in improving functional performance. The project included two branches: a methodology branch of software development for the muscular efficiency calculation, which was inserted in the Hip-Op surgical planning system (2), developed at IOR to allow surgical planning for patients with complex hip joint impairment; and a clinical branch which involved the use of the developed software as part of a clinical multicentric randomized trial. 50 patients with DDH were randomized in two groups: a simple surgical planning group and an advanced surgical planning with muscular study group. The latter followed a customized rehabilitation program for the strenghtening of hip abductor muscles. All patients were assessed before surgery (T0) and at 3 (T1) and 6 months (T2) postoperatively using clinical outcome (WOMAC, HHS, ROM, MMT, SF12, 10mt WT) and instrumental measures (Dynamometric MT). Pre- and post-operative musculoskeletal parameters obtained by the software (i.e., leg length discrepancy, hip abductor muscle lengths and lever arms) using Hip-Op during the surgical planning were considered. One Way ANOVA for ROM measurement showed a significant improvement at T2 in patients included in experimental group, as well as WOMAC, HHS and SF12 score. The Dynamometric MT score showed significant differences between at T2 (p<0.009). Spearman's rank correlation coefficients showed a significant correlation between both pre- and post-operative abductors lever arm (mm) and hip abductor muscle strength at T2 (ρ = −0.55 pre-op and ρ = −0.51 post-op, p p<0.012 and p<0.02 respectively) and between the operated pre-postoperative leg length variation (mm) and the hip abductor muscle strength (ρ = −0.55, p p<0.013). Results so far obtained showed an improvement of functional outcomes in patients undergoing hip replacement surgery who followed therapeutic diagnostic pathway sincluding a preoperative planning including the assessment of the abductiors lever arm and a dedicated rehabilitation program for the strenghtening of abductios. Particularly interesting is the inverse relationship between the strength of the hip abductor muscles and the variation of the postoperative abductor lever arm

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 anesthetised 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 shown 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 recognised 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

Purpose. The purpose of this study was to evaluate the postoperative maximal flexion of Robotic assisted TKA which does not increase the posterior condylar offset after surgery and compare CT and conventional radiography in measuring the posterior condylar offset changes. Materials and method. 50 knees of 37 patients who underwent Robotic TKA and underwent follow-up minimal one year were evaluated. CT based preoperative surgical planning system was designed not to increase posterior condylar offset (PCO) after surgery. Maximal flexion angle of the knee was evaluated at 1 year after surgery. The change in PCO and joint line on x-ray and CT were evaluated. Results. The mean preoperative knee flexion was 121° (sd: 9.21; range: 80–135), and it was improved to 125.3° (sd: 4.85; range: 115–140) postoperatively. On radiographic evaluation, the mean preoperative PCO was 26.4 mm (sd: 0.5; range: 14.8 mm to 36.3 mm) and the mean postoperative PCO was 23.0 mm (sd: 0.37; range: 16.0 mm to 34.3 mm). On CT evaluation, the mean medial PCO was 28.7± 2.4 mm preoperatively and 24.9± 2.2 mm postoperatively. The mean lateral PCO was 26.3± 2.4 mm preoperatively and 24.9± 2.2 mm postoperatively. There were no significant correlations between x-ray and CT measurement in PCO and joint line. There were no significant correlations between the changes in the posterior condylar offsets and the postoperative knee flexion. Conclusion. After Robotic assisted TKA which is planned not to increase the medial and lateral posterior condylar offset, satisfactory maximal flexion angle of the knee was gained in all patients. Changes in medial and lateral posterior condylar offsets were not correlated with the postoperative knee flexion angle. And changes in PCO and joint line measured by x-ray did not reflect those of the medial and lateral condyle, and joint line on CT

Background. The distal part of the radius is the most common localisation of fractures of the human body. Dislocated intraarticular fractures of the distal radius (FDR) are frequently treated by open reduction and internal fixation with a volar locking plate (VLP) under fluoroscopic guidance. Typically the locking screws are placed subchondral near the joint line to achieve maximum stability of the osteosynthesis. To avoid intraarticular screw placement an intraoperative virtual implant planning system (VIPS) as an application for mobile C-arms was established. The aim of the study was the validation of the implemented VIPS comparing the intraoperative planning with the actual placement of the screws. The study was conducted as a single-centre randomised controlled trial in a primary care institution. The hypothesis of the study was that there is conformity between the virtual implant position and the real implant placement. Patients/Material and Methods. 30 patients with FDR type A3, C1 and C2 according to the AO-classification were randomised in two treatment groups and allocated either in the conventional or in the VIPS group in which the patients underwent an intraoperative planning before screw placement. The randomisation was performed on the basis of a computer-generated code. After fracture reduction an initial diaphyseal fixation of the plate was done. Then the matching of the three-dimensional virtual plate with the image of the real plate in the fluoroscopy shots in two planes was performed automatically. The implant placement was planned intraoperatively in terms of orientation, angulation and length of the screws. After the placement of four or five locking screws the implant position was verified with an intraoperative three-dimensional mobile C-arm scan. The locking screws near the joint line were examined and compared in relation to the actual and the planned inclination angle, the azimuth angle which is determined analogue to a compass rose and the screw-tip distance. The planned and actual parameters of the locking screws were then statistically analysed applying the Shapiro-Wilk - and the Students t-test. Results. 15 patients with FDR were treated in the VIPS arm. In the VIPS group six fractures type A3 one type C1 and eight type C2 were included. The control group showed a similar fracture distribution with six type A3 and nine type C2 fractures. The discrepancy between the actual and the planned screw-tip distance was 2,24 ± 0,97 mm and did not differ significantly (p>0,05). The angle of the planned and actual screw placement also did not vary significantly (p>0,05). The difference of the actual to the planned azimut angle accounted for 18,69°± 29,84. The planned and real inclination of the screws differed by 1,66° ± 4,46. Conclusion. The analysis shows that the screws were almost placed as planned. Differences between actual and planned placement of the screws were observed but were not statistically significant. Therefore the hypothesis of the study can be accepted. We assume, that the precise planning of the screw placement in FDR with VIPS can be transported into the surgical treatment

Polyclinique le Languedoc, avenue de la Côte-des-Roses, 11100 Narbonne 7885. Purpose of the study: The goal of navigation for TKA is to improve the precision of the frontal alignment. Continuing this objective, we were interested in a different option than navigation: we wanted to optimise traditional instrumentation and associated an implantation procedure with a rigorous radiographic planning system. Material and methods: This was a consecutive series of 100 TKA all implanted by the same operator; pre- and postoperative goniometry was performed in the same radiology unit and controlled by the same radiologist. Preoperative planning was based on the weight-bearing goniometry with a femoral valgus varying from 3 to 11, in order to obtain a distal femoral cut strictly orthogonal to the mechanical axis. The tibial cut, independent of the femoral cut was also orthogonal to the tibial axis. The instrument sent enabled in situ correction, with 1° precision, of the angle of the femoral and/or tibial cut if it was different from the preoperative measurement; tibial insertion was mixed (centromedullary and controlled by an extramedullary system). Results: Mean patient age, male-female ratio and varus/valgus were comparable with other series. The mean postoperative HKA angle was 180±2.3°. Alignment varied from 0 to 2° in 70 patients. Defective alignment of 2 to 3° was observed in 14 patients, i.e. 92% of knees within 3°. Eight patients were misaligned at 3 to 5° which was the greatest deviation in this series. Conclusion: These results demonstrate that the quality of TKA implantation can be improved, in particular implant alignment, by optimising the operative technique and the surgical material and associating simple radiographic planning, without necessarily using navigation systematically

NavioPFS™ is a hand-held robotic technology for bone shaping that employs computer control of a high-speed bone drill. There are two control modes – one based on control of exposure of the cutting bur and another based on the control of the speed of the cutting bur. The unicondylar knee replacement (UKR) application uses the image-free approach in which a mix of direct and kinematic referencing is used to define all parameters relevant for planning. After the bone cutting plan is generated, the user freely moves the NavioPFS handpiece over the bone surface, and carves out the parts of the bone targeted for removal. The real-time control loop controls the depth or speed of cut, thus resulting in the planned bone preparation. This experiment evaluates the accuracy of bone preparation and implant placement on cadaveric knees in a simulated clinical setting. Three operators performed medial UKR on two cadaver specimens (4 knees) using a proprietary implant design that takes advantage of the NavioPFS approach. In order to measure the placement of components, each component included a set of 8 conical divots in predetermined locations. To establish a shared reference frame, a set of four fiducial screws is inserted in each bone. All bones were cut using a 5 mm spherical bur. Exposure Control was the primary mode of operation for both condylar cuts – although the users utilised Speed Control to perform some of the more posterior burring activities and to prepare the peg holes. Postoperatively, positions of conical divots on the femoral and tibial implants and on the respective four fiducial screws were measured using a Microscribe digitising arm in order to compare the final and the planned implant position. All implants were placed within 1.5 mm of target position in any particular direction. Maximum translation error was 1.31 mm. Maximum rotational error was 1.90 degrees on a femoral and 3.26 degrees on a tibial component. RMS error over all components was 0.69mm/1.23 degrees. This is the first report of the performance of the NavioPFS system under clinical conditions. Although preliminary, the results are overall in accordance with previous sawbones studies and with the reports from comparable semi-active robotic systems that use real time control loop to control the cutting performance. The use of NavioPFS in UKR eliminates the need for conventional instrumentation and allows access to the bone through a reduced incision. By leveraging the surgeon's skill in manipulating soft tissues and actively optimising the tool's access to the bone, combined with the precision and reproducibility of the robotic control of bone cutting, we expect to make UKR surgery available to a wider patient population with isolated medial osteoarthritis that might otherwise receive a total knee replacement. In addition to accurate bone shaping with a handheld robotically controlled tool, NavioPFS system for UKR incorporates a CT-free planning system. This approach combines the practical advantages of not requiring pre-operative medical images, while still accurately gathering all key information, both geometric and kinematic, necessary for UKR planning

Hip resurfacing has advantages over hip replacement for younger, more active patients. However, it requires that surgeons learn new techniques for correctly cutting bone and positioning the components. Pre-operative planning systems exist for conventional hip replacement. Planning software for hip resurfacing is described, with the resulting plans available as a visual aid during surgery, or transferred to the Acrobot. ®. Navigation system for intra-operative guidance. CT data is acquired from the top of the pelvis to immediately above the acetabulae in 4 mm slices, and from there down to just below the lesser trochanter in one mm slices. This keeps radiation doses low while providing high image quality in the important regions for planning. This is segmented semi-automatically, and bone surface models are generated. Frames of reference are generated for the pelvis and femur, and the acetabular and femoral head positions are computed relative to these. Prosthesis components are initially positioned and sized to match the computed anatomy. They can then be adjusted as required by the surgeon. While adjusting their positions, he is able to visualize their fit onto the bone to ensure good placement without problems such as femoral neck notching. Twenty one hip resurfacings have been planned including two navigated cases. In addition, visualization of hip geometry for osteotomy and impingement debridement has been performed on 14 cases, giving the surgeon a good understanding of hip geometry prior to surgery. Initial evidence indicates surgeons find the planner useful, particularly when the anatomy is not straightforward

Introduction. Most surgeons utilize one of three axis options in conventional total knee arthroplasty (TKA), the transepicondylar axis (TEA), Whiteside's line (WSL) or the posterior condylar axis (PCA) with an external rotation correction factor. Each option has limitations and no clear algorithm has been determined for which option to use and when. Many surgeons believe the TEA to be the gold standard for determining rotation however it can be difficult to access intraoperatively. WSL and PCA have been used as surrogates for determining axial rotation in conventional TKA but may also be prone to error. MRI based preoperative planning systems overcome intraoperative limitations while accounting for the individual anatomy of each patient, thus helping optimize femoral component rotation. The goal of this study was to examine if coronal plane deformity had any effect on the relationship of conventional referencing options such as WSL and PCA to the TEA. Methods. Utilizing a preoperative planning software based on MRI, we compared the preoperative posterior femoral condyle resections for three different axis options in 176 TKA. The difference in bone resection amount was used to determine the rotational differences between the axis options in all knees. Assuming that the TEA was the ideal rotational axis, we compared the TEA to both WSL and PCA. A 1-sample t-test and paired t-test were then used to determine if there was a significant rotational difference between the various axis options when accounting for degree and direction of preoperative deformity in the coronal plane. Results. In the overall population of 176 knees (42 valgus, 134 varus), neither WSL or PCA approximated the TEA accurately (p=0.016 and 0.001). In valgus deformity, WSL was found to approximate the TEA (p=0.68) better than the PCA (p=0.21). Minor varus deformity (< 3 degrees) favored the use of PCA (0.53) while moderate varus deformity (3–6 degrees) favored use of WSL (p=0.76). Severe varus (>6 degrees) deformity favored use of PCA due to lower variability. For complete results see Figure 2. Conclusion. Based on MRI data, our study indicates that preoperative coronal plane deformity should help determine the specific referencing option utilized for femoral component rotation in TKA. Broad application of either WSL or the PCA to all patients regardless of preoperative deformity did not accurately approximate TEA in femoral component rotation. Rather, analysis of the degree and direction of preoperative coronal plane deformity indicates that WSL and PCA should be used in specific scenarios to approximate the TEA. When WSL or PCA either both approximate or do not approximate the TEA, we recommend using the option with a lower standard deviation, and thus less variability. Although this MRI based technology is not in widespread use, we believe our findings (Figure 1) can assist the majority of surgeons determine when to use WSL or the PCA based on preoperative coronal plane deformity