Introduction. Stryker computer navigation system has been used for total knee arthroplasty (TKA) procedures since October 2008 at the Russian Ilizarov Scientific Centre for Restorative Traumatology and Orthopaedics. Material and methods. There have been 126 computer assisted TKA that accounted for 11.5 % of primary TKA within this period (1096 procedures). Arthritis of the knee joints with evident pain syndrome was an indication to TKA surgery. Arthritis of the knee joint of 27 patients (21.4 %) was accompanied by femoral deformity of various etiology with debris found in the medullary canal in several cases. The rest 99 patients (78.6 %) were regular cases of primary TKA. Results. We compared the results of correction of lower limb biomechanical axis with TKA employing navigation and without computer assistance. Regular TKA procedures showed no substantial difference in the correction of biomechanical axis. Complete correction using computer navigation was achieved in 85 % of the cases versus 79 % of the patients without navigation. The deformity up to 3° developed in 14 % of navigated cases and in 17 % of the cases without computer assistance. An error of deformity correction was 3–5° in 4 % of the cases without computer navigation. Those were cases of challenging primary TKA. So the advantages of computer navigation have become evident with greater deformities, and in the cases when intramedullary guide can hardly be used due to severe deformities in the femoral metaphysis and diaphysis, after several operative procedures of osteosynthesis with deformed, obliterating bone marrow canal or presence of debris. Complete correction using computer navigation was achieved in 85.2 % cases versus 42.8 % patients without navigation. Postoperative varus of 2° was observed in 14.8 % cases (valgus or varus deformity of 3° developed in 28.6 % of the cases without computer assistance). Conclusion. What is better: special instrumentation or navigation?. Current instrumentation can provide regular mechanical control of the limb axis and is based on the principles of intramedullary, extramedullary and even double guide placement. Image-free navigation and standard surgical techniques can equally be used for simple cases of primary TKA. Same landmarks are used. These landmarks are determined by a surgeon quite subjectively and can lead to inadequate usage of special instrumentation and computer navigation. However, computer navigation should be used in the cases when intramedullary guide can hardly be used, not desirable or possible. Special instrumentation can fail in setting a valgus angle needed with extraarticular femoral deformity. Navigation allows determining rotation more precisely in the cases when posterior femoral condyles contour (posttraumatic condition, hypoplastic condyles) is distorted. Assessment of ligament balance can be rather subjective when special instrumentation is used. Application of computer navigation is helpful for measurements of flexion and extension gaps sixe and regularity. Computer navigation is contraindicated for contractures and ankyloses of the hip joint. For the rest of the cases the choice of instrumentation is a surgeon's decision

Total hip arthroplasty (THA) is an effective treatment for symptomatic hip osteoarthritis (OA). While computer-navigation technologies in total knee arthroplasty show survivorship advantages and are widely used, comparable applications within THA show far lower utilisation. Using national registry data, this study compared patient reported outcome measures (PROMs) in patients who underwent THA with and without computer navigation. Data from Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) PROMs program included all primary THA procedures performed for OA up to 31 December 2020. Procedures using the Intellijoint HIP® navigation system were identified and compared to procedures using other computer navigation systems or conventional instrumentation only. Changes in PROM scores between pre-operative and 6-month post-operative time points were analysed using multiple regression model, adjusting for pre-operative score, patient age, gender, ASA score, BMI, surgical approach, and hospital type. There were 65 primary THA procedures that used the Intellijoint HIP® system, 90 procedures used other types of computer navigation, and the remaining 5,284 primary THA procedures used conventional instrumentation. The estimated mean changes in the EuroQol visual analogue scale (EQ VAS) score and Oxford Hip score did not differ significantly when Intellijoint® was compared to conventional instruments (estimated differences of 2.4, 95% CI [-1.7, 6.5], p = 0.245, and −0.5, 95% CI [-2.5, 1.4], p = 0.592, respectively). The proportion of patients who were satisfied with their procedure was also similar when Intellijoint® was compared to conventional instruments (rate ratio 1.06, 95% CI [0.97, 1.16], p = 0.227). The preliminary data demonstrate no significant difference in PROMs when comparing the Intellijoint HIP® THA navigation system with both other navigation systems and conventional instrumentation for primary THAs performed for OA. Level of evidence: III (National registry analysis)

A cadaver study using six pairs of lower limbs was conducted to investigate the accuracy of computer navigation and standard instrumentation for the placement of the Birmingham Hip Resurfacing femoral component. The aim was to place all the femoral components with a stem-shaft angle of 135°. The mean stem-shaft angle obtained in the standard instrumentation group was 127.7° (120° to 132°), compared with 133.3° (131° to 139°) in the computer navigation group (p = 0.03). The scatter obtained with computer-assisted navigation was approximately half that found using the conventional jig. Computer navigation was more accurate and more consistent in its placement of the femoral component than standard instrumentation. We suggest that image-free computer-assisted navigation may have an application in aligning the femoral component during hip resurfacing

Introduction. Two aspects are very important for knee joint replacement – restoration of biomechanical limb axis and achieving ligaments balance. Computer navigation allows us to do all this. Material and methods. We analysed 94 knee joint replacement surgeries using computer navigation by “STRYKER”. Results. There is no substantial difference between results of correction of biomechanical axis with computer navigation and without it in case of uncomplicated joint replacement. So, completer correction of axis (varus/valgus zero degrees) with computer navigation was achieved in 84% of cases versus 79% without navigation. There was varus or valgus deformity up to two degrees in 12% after surgery (without navigation −17% of cases). Error in deformity correction without application of navigation was three-five degrees in 4% of cases (all were challenging joint replacement). Advantages of navigation are obvious in case of large deformities, and also when insertion of intramedullary guide is undesirable or impossible. Use of navigation requires good skills of joint replacement, because landmarks should be chosen precisely and possibility of error during determining the center of rotation for the femoral head should be taken into consideration. Duration of surgery without navigation is 82.6±16.4 minutes and is much longer in the beginning of the learning curve (one hour longer or more). After acquiring skills the surgery takes 118±15.6 minutes. Conclusion. We evaluate use of navigation system as a modern and in-demand trend. Use of navigation should be started after getting good skills of joint replacement. Violation of the technology of determining landmarks leads to wrong virtual modeling and serious errors in positioning components. Advantages of navigation are obvious in evident bone deformity, when it is impossible or undesirable to open a medullary canal

Individuals learn to master new motor skills (such as learning a new surgical technique) by evaluating available feedback to alter future performance. Continuous concurrent augmented feedback is supplementary information presented to the learner throughout the performance of a task. An example of this type of feedback is the visual information provided by computer navigation during arthroplasty surgery. This type of feedback is a potentially powerful tool for learning because it theoretically guides the learner to the correct response, reduces errors, and reinforces correct actions. However, motor learning theory suggests that this type of feedback may impair learning because of development of dependence on the additional feedback or distraction from intrinsic feedback. In the current era of reduced number of training hours it is essential to assess the role of computer navigation on trainees. Our objective was to determine whether computer navigation influences the learning curve of novices performing hip resurfacing arthroplasty. We conducted a systematic review and critical appraisal of the literature. There is some evidence from randomised controlled trials that navigation use by trainees facilitates accurate placement of arthroplasty components compared to conventional instrumentation. There is no evidence that training with computer navigation impairs performance in retention tests (re-testing on same task after an interval of time) or transfer tests (re-testing in different conditions i.e. without concurrent feedback). We conclude that although there are significant limitations of the published literature on this topic there is no available evidence that supports concerns regarding the theoretical detrimental effects of computer navigation on the learning curve of arthroplasty trainees

Computer navigation in total joint arthroplasty has been shown to be effective in improving the radiographic outcome in patients undergoing both hip and knee arthroplasty. However, critics have argued that the required capital equipment and added time to perform the procedure is cost prohibitive. To test this hypothesis, we compared our hospital discharge experience with computer navigation to national standards published by the Agency for Healthcare Research and Quality for the years 2004 and 2005. In the AHRQ database the average length of stay for DRG 209 in 2004 and 2005 respectively, in the Midwest region was 4.6 days and 4.3 days, with a mean charge of $27,403 and $27,948, with only 40% and 45%, of patients discharged to home with or without home health care. In 2004 and 2005, the senior author performed 125 and 117 Medicare primary hip and knee replacements, respectively, with computer navigation with a mean length of stay of 2.9 days and 2.8 days, with charges of $22,134 and $24,612, and 63% and 71% discharged to home. On a pure charge basis, the senior author experience a decreased overall charge compared to published data. Even if the entire cost of the navigation system in our system $204,000 was spread equally over only the Medicare patients over the two year period, the additional $842/case still results in a case charge below published data. Based on the senior author’s experience with hospitalization cost, length of stay and discharge disposition, computer navigation in total joint replacement is not associated with an increased cost/case and may result in dramatically lower indirect costs due to shorter length of stay and increased number of discharges to home compared to published regional Medicare discharge data

Alignment of the femoral component during hip resurfacing has been implicated in the early failure of this device. Techniques to facilitate a more accurate placement of the femoral component may help prevent these early failures. We aim to establish whether the use of imageless computer navigation can improve the accuracy in alignment of the femoral component during hip resurfacing. 6 pairs of cadaveric limbs were randomized to the use of computer navigation or standard instrumentation. All hips had radiographs taken prior to the procedure to facilitate accurate templating. All femoral components were planned to be implanted with a stem shaft angle of 135 degrees. The initial guide wire was placed using either the standard jig with a pin placed in the lateral cortex or with the use of an imageless computer navigation system. The femoral head was then prepared in the same fashion for both groups. Following the procedure radiographs were taken to assess the alignment of the femoral component. The mean stem shaft angle in the computer navigation group was 133.3 degrees compared to 127.7 degrees in the standard instrumentation group (p=0.03). The standard instrumentation group had a range of error of 15 degrees with a standard deviation of 4.2 degrees. The computer navigated group had a range of error of only 8 degrees with a standard deviation of 2.9 degrees. Our results demonstrated that the use of standard alignment instrumentation consistently placed the femoral component in a more varus position when compared to the computer navigation group. The computer navigation was also more consistent in its placement of the femoral component when compared to standard instrumentation. We suggest that imageless computer navigation appears to improve the accuracy of alignment of the femoral component during hip resurfacing

Purpose. This meta-analysis was designed to evaluate the effects of computer navigation on blood conservation after total knee arthroplasty (TKA) by comparing postoperative blood loss and need for allogenic blood transfusion in patients undergoing computer navigation and conventional primary TKAs. Methods. Studies were included in this meta-analysis if they compared change in haemoglobin concentration before and after surgery, postoperative blood loss via drainage or calculated total blood loss, and/or allogenic blood transfusion rate following TKA using computer navigation and conventional methods. For all comparisons, odds ratios and 95 % confidence intervals (CI) were calculated for binary outcomes, while mean difference and 95 % CI were calculated for continuous outcomes. Results. Twelve studies were included in this meta-analysis. The change in haemoglobin concentration was 0.39 g/dl lower with computer navigation than with conventional TKA (P = 0.006). Blood loss via drainage was 83.1 ml (P = 0.03) lower and calculated blood loss was 185.4 ml (P = 0.002) lower with computer navigation than with conventional TKA. However, the need for blood transfusion was similar for the two approaches (n.s.). Conclusions. The primary TKA with computer navigation was effective in reducing haemoglobin loss and blood loss, but had no effect on transfusion requirement, compared with conventional primary TKA. These findings suggest the importance of analysing several blood loss parameters, because each may not always accurately reflect true postsurgical bleeding

Introduction. Restoration of normal hip biomechanics is vital for success of total hip arthroplasty (THA). This requires accurate placement of implants and restoration of limb length and offset. The purpose of this study was to assess the precision and accuracy of computer navigation system in predicting cup placement and restoring limb length and offset. Material and Methods. An analysis of 259 consecutive patients who had THA performed with imageless computer navigation system was carried out. All surgeries were done by single surgeon (KD) using similar technique. Acetabular cup abduction and anteversion, medialisation or lateralisation of offset and limb length change were compared between navigation measurements and follow-up radiographs. Precision, accuracy, sensitivity and specificity were calculated to assess navigation for cup orientation and student t-test used for evaluation of offset and limb length change. A p value of <0.05 was considered significant for evaluation. Results. Mean cup abduction and anteversion was 40.35° (SD, 5.81) and 18.46° (SD, 6.79) in postop radiographs compared to 41° (SD, 5.03) and 14.76° (SD, 6.11) for navigation measurements. Intraoperative navigation measurements had high precision and specificity for determining cup abduction and anteversion (precision >95%, specificity >90%). Accuracy for determining cup abduction was 96.13% compared to 72.2% for cup anteversion. Change in limb length and offset was mean 6.46mm (SD, 5.68) and −1.07mm (SD, 5.75) on radiograph evaluation and 5.41mm (SD, 5.11) and −2.24mm (SD, 5.87) from navigation measurements respectively, the difference being not significant in both (p value > 0.2). Radiograph and navigation had a mean difference of 1.01mm (SD, 2.83) for offset measurements and a mean difference of 1.05mm (SD, 4.37) for postop limb length assessment. Discussion. To the best of our knowledge this is the largest single surgeon study of navigated THA. We found that computer navigation assessment of acetabular cup abduction and anteversion and limb length and offset restoration has high probability of predicting correct placement of implants. To conclude, navigation can serve as an excellent tool for appropriate placement of implants and restoring limb length and offset in THA

Purpose. Patient-matched instrumentation is advocated as the latest development in arthroplasty surgery. Custom-made cutting blocks created from preoperative MRI scans have been proposed to achieve perfect alignment of the lower limb in total knee arthroplasty (TKA). The aim of this study was to determine the efficacy of patient-specific cutting blocks by comparing them to navigation, the current gold standard. Methods. 60 TKA patients were recruited to undergo their surgery guided by Smith & Nephew Visionaire Patient-Matched cutting blocks. Continuous computer navigation was used during the surgery to evaluate the accuracy of the cutting blocks. The blocks were assessed for the fit to the articular surface, as well as alignment in the coronal, sagittal and rotational planes, sizing, and resection depth. Results. All patient-matched cutting blocks were a good fit intra-operatively. Significant differences (p<0.05) in the resection depths of the distal femur and tibial plateau were observed between the cutting blocks and computer navigation for the medial compartment. Cutting block alignment of the femur and tibia in the coronal and sagittal planes also differed significantly (p<0.05) to navigation measurements. The PSCB would have placed 79.3% of the sample within +3° of neutral in the coronal plane, while the rotational and sagittal alignment results within +3° were 77.2% and 54.5% respectively. In addition, intraoperative assessment of sagittal femoral alignment differed to planned alignment by an average of 4.0 degrees (+/−2.3). Conclusion. This study suggests the use of patient-matched cutting blocks is not accurate, particularly in the guidance of the sagittal alignment in total knee arthroplasty. Despite this technique creating well fitting cutting blocks, intraoperative monitoring revealed an unacceptable degree of potential limb mal-alignment, resulting in increased outliers particularly when compared with standard computer navigation. Caution is recommended before PSCB are used routinely without objective verification of alignment

Patient-matched instrumentation is advocated as the latest development in arthroplasty surgery. Custom-made cutting blocks created from preoperative MRI scans have been proposed to achieve perfect alignment of the lower limb in total knee arthroplasty (TKA). The aim of this study was to determine the efficacy of patient-specific cutting blocks by comparing them to navigation, the current gold standard. 25 TKA patients were recruited to undergo their surgery guided by Smith & Nephew Visionaire Patient-Matched cutting blocks. Continuous computer navigation was used during the surgery to evaluate the accuracy of the cutting blocks. The blocks were assessed for the fit to the articular surface, as well as alignment in the coronal and sagittal planes, sizing, and resection depth. Actual postoperative alignment was then assessed by detailed CT scans following the Perth protocol, comparing the results with intraoperative measurements. All patient-matched cutting blocks were a good fit intra-operatively. Significant differences (p<0.05) in the resection depths of the distal femur and tibial plateau were observed between the cutting blocks and computer navigation for the medial compartment. Cutting block alignment of the femur and tibia in the coronal and sagittal planes also differed significantly (p<0.05) to navigation measurements. In addition, intraoperative assessment of sagittal femoral alignment differed to planned alignment by an average of 4.0 degrees (+/−2.3). This study suggests the use of patient-matched cutting blocks is not accurate, particularly in the guidance of the sagittal alignment in total knee arthroplasty. Despite this technique creating well fitting cutting blocks, intraoperative monitoring, validated by postoperative CT scans, revealed an unacceptable degree of potential limb mal-alignment, resulting in increased outliers particularly when compared with standard computer navigation

Arthrodesis is used most commonly as a salvage procedure for failed total knee arthroplasty (TKA). For successful arthrodesis, a stable fusion technique and acceptable limb mechanical alignment are needed. Although the use of intramedullary alignment rods might be helpful in terms of achieving an acceptable limb mechanical axis, fat embolism and intramedullary dissemination of an infection or reactivation of latent infection might occur in failed TKA cases. However, computer-assisted surgery allows precise cuts to be made without breaching medullary cavities. Here, the authors describe a case of knee arthrodesis performed by computer navigation and the Ilizarov method in a patient with a past history of infection. A 45-year-old man visited our hospital with failed total knee arthroplasy. Fortunately, even though infection was treated by debridement with component retention, mild heating was present over the knee, but ESR(erythrocyte sedimentation rate) and CRP(C-reactive protein) were within normal ranges. X-ray showed subsidence of the femoral component and a radiolucent line around the femoral component. Arthrodesis was planned for this patient due to disabling pain, a long-lasting severe functional deficit, failure of the primary TKA for ankylosed knee, and the patient’s poor economic status and his strong desire for arthrodesis. The computer navigation surgery system and the Ilizarov method were used for two reasons. The first reason was that the patient had a past history of infection. At pre-operative evaluation, even though ESR and CRP levels were within normal range, we could not completely rule out the possibility of latent infection due to suspicious findings such as long lasting disabling knee pain, mild heating over the knee, severe osteolytic radiographic changes around the femoral component. In that situation, inserting an IM rod to achieve acceptable mechanical alignment might have reactivated and disseminated a possible latent infection to the femoral or tibial medullary canals. The second reason was that we wanted to reduce the possibility of fat embolism by using computer navigation without instrumentation within the medullary canal. A CT-free, wireless computer navigation system was applied, with trackers fixed to the femur and tibia and no requirement for the use of an IM rod with component retention. Navigated femoral and tibial bone resections were then performed using Stryker software. The femoral resection was conducted at 0° of flexion to the sagittal axis, and the tibial resection at 7 ° of flexion to the sagittal axis. Arthrodesis was held in proper axial and rotational alignment with bone surfaces compressed together. Finally, knee arthrodesis was completed using the Ilizarov method. Based on our experience of the described case, we believe that arthrodesis for failed TKR, especially failure secondary to intraarticular infection, can be considered as another indication for computer navigation

Introduction:. Restoration of normal hip biomechanics is vital for success of total hip arthroplasty (THA). This requires accurate placement of implants and restoration of limb length and offset. The purpose of this study was to assess the accuracy of computer navigation system in predicting cup placement and restoring limb length and offset. Material and Methods:. An analysis of 259 consecutive patients who had THA performed with imageless computer navigation system was carried out. Acetabular cup abduction and anteversion, medialisation or lateralisation of offset and limb length change were compared between navigation measurements and follow-up radiographs. Sensitivity, specificity, accuracy and PPV were calculated to assess navigation for cup orientation and student t-test used for evaluation of offset and limb length change. Results:. Mean cup abduction and anteversion was 40.35° (SD, 5.81) and 18.46° (SD, 6.79) in postop radiographs compared to 41° (SD, 5.03) and 14.76°(SD, 6.11) for navigation measurements. Intraoperative navigation measurements had high PPV and specificity for determining cup abduction and anteversion (PPV >95%, specificity >90%). Accuracy for determining cup abduction was 96.13% compared to 72.2% for cup anteversion. Change in limb length and offset was mean 6.46 mm (SD, 5.68) and −1.07 mm (SD, 5.75) on radiograph evaluation and 5.41 mm (SD, 5.11) and −2.24 mm (SD, 5.87) from navigation measurements respectively, the difference being not significant in both (p value >0.2). Radiograph and navigation had a mean difference of 1.01 mm (SD, 2.83) for offset measurements and a mean difference of 1.05 mm (SD, 4.37) for postop limb length assessment. Discussion:. To conclude, navigation can serve as an excellent tool for appropriate placement of implants and restoring limb length and offset in THA

Hip Resurfacing is now an established treatment option for young active patients with osteoarthritis. However, there is slow uptake of hip resurfacing by some surgeons, with concern regarding failure from femoral neck fracture, a small but significant risk. Femoral neck fracture may follow notching of the neck, which occurs upon preparing the femoral head after inserting the femoral head/neck guide-wire. The placement of the femoral head/neck guide-wire is a concern for even experienced surgeons routinely, and in difficult cases of femoral head/neck deformity this is especially so. For the first time a preliminary series of Durom hip resurfacings, based on the successful Metasul bearing, were implanted using a computer image guidance system. The aim of computer navigation is to optimally place the femoral prosthesis in the correct degree of valgus with good underlying bone coverage, without notching the femoral neck or over-sizing the femoral component. Preoperative CT scanning was not required. A standard posterior approach to the hip was utilised, and a navigation reference frame was applied to the proximal femur. Then using an image intensifier and the computer navigation system, a guide-wire was passed quickly and easily into the femoral head/neck with a navigated drill guide. The femoral head was then prepared safely for the femoral component of the resurfacing, with minimal risk of femoral neck fracture. Computer navigation systems have an important role to play in hip resurfacing with respect to femoral head/neck preparation, as demonstrated from our preliminary study. This series shows the use of computer navigation in hip resurfacing to be both SAFE and SIMPLE with a quick learning curve. It was shown to be FASTER and MORE ACCURATE in the process of guide-wire placement in the femoral head/neck as compared to conventional jigs. Crucially, femoral neck fractures may even be potentially ELIMINATED using this technique. In the future, hip resurfacing in conjunction with computer navigation systems may allow;. - SAFER hip resurfacing, with reduced rates of femoral neck fractures. - Improved TRAINING to include junior surgeons in hip resurfacing. - Surgeons to operate INDEPENDENTLY initially. - Surgeons to operate on DIFFICULT cases subsequently. - The development of MINIMALLY INVASIVE hip resurfacing. - The development of SPECIALIST centres for teaching and difficult cases

Total hip arthroplasty (THA) is an effective treatment for symptomatic hip osteoarthritis (OA). Computer-navigation technologies in total knee arthroplasty show evidence-supported survivorship advantages and are used widely. The aim of this study was to determine the revision outcome of hip commercially available navigation technologies. Data from the Australian Orthopaedic Association National Joint Replacement Registry from January 2016 to December 2020 included all primary THA procedures performed for osteoarthritis (OA). Procedures using the Intellijoint HIP® navigation were identified and compared to procedures inserted using ‘other’ computer navigation systems and to all non-navigated procedures. The cumulative percent revision (CPR) was compared between the three groups using Kaplan-Meier estimates of survivorship and hazard ratios (HR) from Cox proportional hazards models, adjusted for age and gender. A prosthesis specific analysis was also performed. There were 1911 procedures that used the Intellijoint® system, 4081 used ‘other’ computer navigation, and 160,661 were non-navigated. The all-cause 2-year CPR rate for the Intellijoint HIP® system was 1.8% (95% CI 1.2, 2.6), compared to 2.2% (95% CI 1.8, 2.8) for other navigated and 2.2% (95% CI 2.1, 2.3) for non-navigated cases. A prosthesis specific analysis identified the Paragon/Acetabular Shell THAs combined with the Intellijoint HIP® system as having a higher (3.4%) rate of revision than non-navigated THAs (HR = 2.00 (1.01, 4.00), p=0.048). When this outlier combination was excluded, the Intellijoint® system group demonstrated a two-year CPR of 1.3%. There was no statistical difference in the CPR between the three groups before or after excluding Paragon/Acetabular Shell system. The preliminary data presented demonstrate no statistical difference in all cause revision rates when comparing the Intellijoint HIP® THA navigation system with ‘other’ navigation systems and ‘non-navigated’ approaches for primary THAs performed for OA. The current sample size remains too small to permit meaningful subgroup statistical comparisons

Background: The rates of primary and revision knee arthroplasty in the United States have been increasing. Simultaneously, several studies have reported increased complication rates when these procedures are performed at low-volume centers. One innovation designed to improve knee arthroplasty outcomes is computer navigation, which aims to reduce revision rates by improving the alignment achieved at surgery. The purpose of this study was to examine the impact of hospital volume on the costeffectiveness of this new technology in order to determine its feasibility and the level of evidence that should be sought prior to its adoption. Methods: A Markov decision model was used to evaluate the cost-effectiveness of computer-assisted knee arthroplasty, in relation to hospital volume. Transition probabilities were estimated from the arthroplasty literature, and costs were based on the average reimbursement for primary and revision knee arthroplasty at out institution. Outcomes were measured in quality adjusted life years. Results: The results demonstrate that computer-assisted surgery becomes less cost-effective as the annual hospital volume decreases, as the cost of navigation increases, and as the impact on revision rates decreases. If a center performs 250 cases per year, computer navigation will be cost-effective if the annual revision rate is reduced by 2% per year over a twenty-year period. If a center performs 150 cases per year, computer navigation is cost-effective if it results in a 2.5% reduction in the annual revision rate over a twenty-year period. If a center performs only 25 cases per year, the annual reduction in revision rates must be 13% for computer navigation to be cost-effective. Conclusion: This analysis demonstrates that computer navigation is not likely to be a cost-effective investment in health care improvement in low volume joint replacement centers, where its benefit is most likely to be realized. However, it may be a cost-effective technology for higher volume joint replacement centers, where the decrease in the rate of knee revision needed to make the investment cost-effective is modest, if improvements in revisions rates with the use of this technology can be realized. This illustrates that hospital volume can have a substantial impact on the cost-effectiveness of new technology in surgery, and this should be carefully considered by any center considering such a large capital investment

Background. The literature quotes up to 20% dissatisfaction rates for total knee replacements (TKR). Swedish registry and national joint registry of England and Wales confirm this with high volumes of patients included. This dissatisfaction rate is used as a basis for improving/changing/modernising knee implant designs by major companies across the world. Aim. We aimed to compare post TKR satisfaction rates for navigated and non navigated knees. Methods. This was a retrospective analysis of prospectively collected data. All patients undergo comprehensive preoperative evaluation and comprehensive consent process and same rehabilitation protocols are followed as standard practice. Two groups were established depending on whether surgery was performed with or without computer navigation. We included 229 patients in each group. There were nine bilateral cases in the navigated group giving a total of 238 knees. Both groups were similar at the time of surgery (navigated: 68 years (sd9);; BMI 32.46;; (sd5.19);; OKS: 42.2 (sd7.5);; non-navigated: 70 years (sd9);; BMI 32.36;; (sd5.26);; OKS: 42.4 (sd7.3)). The satisfaction rates are recorded as very satisfied, satisfied, unsure or dissatisfied. Results. Of the 238 navigated knees 227 (95.4%) were very satisfied or satisfied;; while of the 229 non-navigated knees 205 (89.5%) were very satisfied or satisfied. Only 3 (1.3%) navigated knees and 9 (3.9%) non-navigated knees were dissatisfied. Seven (2.9%) navigated knees and fifteen (6.6%) non-navigated knees were unsure. The navigated group showed better satisfaction (p=0.049) compared to the non-navigated group and better satisfaction than previously published satisfaction rates [3]. When combining dissatisfaction and unsure responses the navigated group again performed significantly better than the non-navigated group (p=0.021). Satisfaction rates were also compared with published literature, which suggest that 82–89% of TKA patients are satisfied and that navigation has no effect on satisfaction [3]. Our data for the non-navigated knees are similar to high end of the published data. This goes to show that comprehensive education of patients, high volume surgeons and elective arthroplasty unit along with comprehensive consent process can achieve best results. We have also shown that navigation influences satisfaction rates. There were no differences in 6 week OKS data with scores of 28.1 (sd= 8.0) and 28.8 (sd=7.8) for navigated and non-navigated groups(p=0.623), The same was also true for range of flexion/extension (92.1° [sd=13.4°& 91.3° [sd=14.1°, p=0.360) and length of hospital stay in days (median=5 [min=2, max=37], median=5 [min=2, max=19], p=0.959);; for navigated and non-navigated groups respectively. Of those navigated knees reported as ‘dissatisfied’ and ‘unsure’, 50.0% (5 knees) were due to pain in the knee. For non-navigated knees, 66.7% (16 knees) stated knee pain as the reason for being ‘dissatisfied’ or ‘unsure’. Conclusion. A modern elective arthroplasty service can deliver high satisfaction rates. Use of computer navigation further improves even the best conventional satisfaction rates. Industry should promote better surgical techniques rather than bringing out new implants to improve satisfaction rates in total knee replacements

The Gpsystem Medacta vision system is composed of an infrared camera that produces and receives infrared rays reflected by almost 3 reflectors mounted on different rigid body devices (F=femoral, T=tibial, G=guide), in order to determine its position with an error lower than 0.35mm. Data received from this vision system are than elaborated by the Cinetique Gpsystem Version 1.0 system in order to determine the correct cutting guide positioning both for the femur and the tibia. The cutting guide is moved on different planes by 5 electric engines applied on 5 no ending screws. The first step of this system is determining, with the F and the T rigid bodies, patient’s lower limb kinematic in order to evaluate its mechanical axis, its flexion-extension range of movement and its pathological deviations. The second step is evaluating anatomical landmarks to find out the correct degrees of tibial and femoral cuts: these landmarks are the medial and lateral tibial glena, the distal femoral condyles, the posterior femoral condyles, the anterior femoral cortex, the tibial tuberosity, the Whiteside line and the epycondilar axis (each anatomical landmark is identified by multiple points in order to decrease possible errors). The third step is applying the cutting guide and the Grigid body on the femoral clamp in order to estimate the correct level for the tibial cut than, once the tibial osteotomy is done the vision system controls its correct execution and the soft tissue balancing of the knee. The fourth step is calculating with the Gpsystem the correct orientation of the femoral cutting guide and checking its positioning and cutting execution. The last step is applying the test-prosthesis verifying the mechanical axis of the knee and than assembling the definitive prosthesis. Since now we have applied 10 Cinetique knee prosthesis with the Medacta computer navigation system with good results and good positioning of the prosthesis. Medacta computer navigation system for Cinetique knee arthroplasty is innovative for its simple cutting guide and movement device both in their hardware than in their way of using and for a simpler software interface; these characteristics allows faster surgeon technique learning, shortening of surgical time and a better prosthesis positioning

Accurate implant alignment, prolonged operative times, array pin site infection and intra-operative fracture risk with computer assisted knee arthroplasty is well documented. This study compares the accuracy and cost-effectiveness of the pre- operative MRI based Signature custom made guides (Biomet) to intra-operative computer navigation (BrainLab Knee Unlimited). Twenty patients from a single surgeon's orthopaedic waiting list awaiting primary knee arthroplasty were identified. Patients were contacted and consented for the study and their suitability for MRI examination assessed. An MRI scan of the hip, knee and ankle was performed of the operative side following a set scanning protocol. Following MRI, patient specific femoral and tibial positioning cutting guides were manufactured. Patients then underwent arthroplasty and intra-operative computer navigation was used to measure the accuracy of the custom made, patient specific cutting guides. A cost analysis of the signature system compared with computer navigation was made. Our provisional results show that the accuracy of the pre-operative MRI patient specific femoral and tibial positioning guides was comparable to computer navigation. Pre-operative, patient specific implant positioning cutting guides were as accurate as computer navigation from analysis of our preliminary results. The potential advantages of the MRI based system are accurate pre-operative planning, reduced operating times and avoidance of pin site sepsis. However, further larger studies are required to examine this technique

Purpose:. The use of computer navigation has been shown to improve the accuracy of femoral component placement compared to conventional instrumentation in hip resurfacing. Whether exposure to computer navigation improves accuracy when the procedure is subsequently performed with conventional instrumentation without navigation has not been explored. We examinedwhether femoral component alignment utilizing a conventional jig improves following experience with the use of imageless computer navigation for hip resurfacing. Methods:. Between December 2004 and December 2008, 213 consecutive hip resurfacings were performed by a single surgeon. The first 17 (Cohort 1) and the last 9 (Cohort 2) hip resurfacings were performed using a conventional guidewire alignment jig. In 187 cases the femoral component was implanted using the imageless computer navigation. Cohorts 1 and 2 were compared for femoral component alignment accuracy. Results:. All components in Cohort 2 achieved the position determined by the pre-operative plan. The mean deviation of the stem-shaft angle (SSA) from the pre-operatively planned target position was 2.2 degrees (SD, 2.2°, 95% CI, 0.8°, 3.7°) in Cohort 2 and 5.6 degrees (SD, 4.3°, 95% CI, 3.6°, 7.6°) in Cohort 1 (p = 0.01). Four implants in Cohort 1 were positioned at least 10 degrees varus compared to the target SSA position and another four were retroverted. Conclusions:. Femoral component placement utilizing conventional instrumentation may be more accurate following experience using imageless computer navigation

The presence of retained metalwork, previou fractures or osteotomies makes TKA surgery challenging. Obstructed intramedually canals can produce difficulty with the use of IM instrumentation whilst the altered alignment can result in problematic soft tissue balancing. We present a series of 35 patients with deformity who underwent a successful TKA. Between July 2003 and January 2006 35 patients were operated on between 3 centres. All had extraarticular deformities in either the femur or tibia due to previous fractures or exposure to surgery. All underwent TKA surgery using an image free computer navigation system and extramedullary TKA instrumentation. All patients underwent pre-op and post-operative long eg alignment films. The pre-operative long eg films showed an alignment of 16 degrees varus to 18 degrees of valgus. Post-operative alignment ranged from 3 degrees varus to 4 degrees valgus. The femoral component position ranged from 88-91 degrees from the mechanical axis whilst the tibial component position ranged from 89-92 degrees from the mechanical axis of the limb. Total knee arthroplasty in the presence of extraarticular deformity is fraught with problems in regaining limb alignment and soft tissue balancing. This is the largest combined series of patients in which the same navigation system has been used to provide extramedullary alignment and cuts resulting in excellent component positioning and post-operative alignment. We recommend the routine use of computer navigation in these difficult cases

Introduction: The long-term results of total hip replacement can be improved by accurate placement of the implants, leading to restoration of hip biomechanics and prevention impingement from of implant malposition. Pelvic obliquity from patient positioning during surgery prevents accurate intra-operative assessment of component placement. Computer navigation assisted total hip replacement can potentially eliminate these problems by providing feedback on prosthetic placement during surgery. The purpose of our study was to assess the accuracy of the component placement in computer navigation assisted THRs performed in our institution. Methods: A total of 154 computer navigation assisted total hip arthroplasties performed between January 2004 and January 2005 were prospectively included in this study. Image free optical based navigation system (Navitrack™) was used. All procedures were performed by the senior author using MIS and open posterior approaches. Two independent observers performed analysis of the position of components and leg length discrepancy from standardized hip radiographs. Navigation values during surgery were compared with postoperative radiographic evaluation. Results: The mean abduction and anteversion angles of acetabular component in postoperative radiographs were 41.4 ± 6.1 and 22.6 ± 3.8 degrees respectively, in comparison to the navigation values of 40.9 ± 4.0 and 22.9 ± 3.6 degrees respectively. The femoral neck offset and leg length discrepancy calculated from navigation were with in a mean of 1.5mm and 2.8mm, respectively. There was one complication consisting of a peri-prosthetic femoral fracture that was recognised during surgery and treated with revision of the femoral component to a long-stem prosthesis. There was no early post-operative dislocation or deep infection in this series. Discussion: This study showed that computer navigation assisted THR provided predictable and reproducible results with accuracy in component placement and restorations of femoral neck offset and leg length

Introduction. Computer-assisted hip navigation offers the potential for more accurate placement of hip components, which is important in avoiding dislocation, impingement, and edge-loading. The purpose of this study was to determine if the use of computer-assisted hip navigation reduced the rate of dislocation in patients undergoing revision THA. Methods and Materials. We retrospectively reviewed 72 patients who underwent computer-navigated revision THA [Fig. 1] between January 2015 and December 2016. Demographic variables, indication for revision, type of procedure, and postoperative complications were collected for all patients. Clinical follow-up was performed at 3 months, 1 year, and 2 years. Dislocations were defined as any episode that required closed or open reduction or a revision arthroplasty. Data are presented as percentages and was analyzed using appropriate comparative statistical tests (z-tests and independent samples t- tests). Results. All 72 patients (48% female; 52% male) were included in the final analysis [Fig. 2]. Mean age of patients undergoing revision THA was 70.4 ± 11.2 years. Mean BMI was 26.4 ± 5.2 kg/m. 2. The most common indications for revision THA were instability (31%), aseptic loosening (29%), osteolysis/eccentric wear (18%), infection (11%), and miscellaneous (11%). During revision procedure, polyethylene component was most commonly changed (46%), followed by femoral head (39%), and acetabular component (15%). At 3 months, 1 year, and final follow-up, there were no dislocations among all study patients (0%). Compared to preoperative dislocation values, there was a significant reduction in the rate of dislocation with the use of computer-assisted hip navigation (31% vs. 0%; p<0.05). Discussion. Our study demonstrates a significant reduction in the rate of dislocation following revision THA with the use of computer navigation. Although the cause of postoperative dislocation is often multifactorial, the use of computer-assisted surgery may help to curtail femoral and acetabular malalignment in revision THA

Aim: Accurate soft tissue balance in total knee arthroplasty (TKA) is not only technically challenging but also difficult to teach to trainees; we believe that computer navigation provides a very useful tool for objective and reproducible soft tissue balance. Methods: We studied 52 patients (31 females and 21 males) with knee osteoarthritis and recorded the change of the Medial (MCL) and Lateral Collateral Ligament (LCL) length at full extension and at 90o flexion. Pre- and post-operative results were compared. The assessment was performed by consultant orthopaedic surgeons using trackers and navigation knee replacement software. Data was analysed using the student t-test. Results: The navigation software programme was used to measure the change of the collateral ligament length. Ligament laxity is represented by a negative number and a positive number is used to represent stretching and apparent elongation of the ligament. The medial collateral (MCL) length at full extension ranged from −9mm to 11mm and post-operatively was reduced to −16mm and 8mm, (p=0.042). At 90o flexion the length ranged from −3mm to 9mm and postoperatively was reduced to −8mm and 10mm (p=0.025). The lateral collateral (LCL) length at full extension changed from −10mm to 9mm pre-operatively to −13mm and 6mm post-operatively (p=0.011). At 90o flexion the range from −8mm and 9mm pre-operatively changed to − 5mm and 11mm post-operatively (p=0.005). All the above changes correspond to improvement in the post-operative axial alignment. Conclusion: Our results demonstrate that computer navigation provides a useful adjunct to the accurate and reproducible soft tissue balance in knee arthroplasty which can be used to evaluate results and for training purposes

Introduction: While computer navigation has been shown to improve radiographic alignment and eliminate outliers in limb and component position in total joint arthoplasty, adoption has been relatively slow. One argument against the use of navigation has been the concern about the cost of the capital equipment and surgical disposables. The purpose of this paper was to evaluate whether the direct cost of patient care was greater for the senior author, who navigates all joint replacements, than other surgeons, who perform total joint arthroplasty without navigation. Methods: The author’s institution is a 200 bed community hospital that performs over 1000 joint replacements per year. This study consisted of reviewing the fiscal year 2007 data at the author’s institution and comparing the direct costs of medical care, length of stay and discharge disposition for the senior author to his peers at his institution. Results: In fiscal year 2007, the hospital performed 624 primary total knee and 213 primary total hip replacements of which the senior author performed 284(45%) knees and 156(73%) hips respectively. The average charge for the entire hospital was $38, 877 and LOS was 2.7 days for knees, and charges of $40, 076 and LOS was 2.7 days for hips. The senior authors charges were $33, 801 and LOS was 2.4 days for knees and $36, 403 and LOS 2.4 for hips. 78% of the knees and 81 % of the hips were discharged to home overall for the institution and 86% of both knees and hips by the senior author. The capital equipment purchase for navigation was $204,000 or $463 per primary arthroplasty(senior author). Conclusions: Computer navigation did not increase the direct cost of primary total joint replacement for the senior author relative to his peers even if the entire capital equipment purchase was added to the case cost

The use of a navigation system in musculoskeletal tumour surgery enables the integration of pre-operative CT and MRI images to generate a precise three-dimensional anatomical model of the site and the extent of the tumour. We carried out six consecutive resections of musculoskeletal tumour in five patients using an existing commercial computer navigation system. There were three women and two men with a mean age of 41 years (24 to 47). Reconstruction was performed using a tumour prosthesis in three lesions and a vascularised fibular graft in one. No reconstruction was needed in two cases. The mean follow-up was 6.9 months (3.5 to 10). The mean duration of surgery was 28 minutes (13 to 50). Examination of the resected specimens showed clear margins in all the tumour lesions and a resection that was exactly as planned

Computer navigation has the potential to revolutionise orthopaedic surgery, although according to the latest 7. th. Annual NJR Report, only 2% of the 5 800 unicompartmental knee replacements (UKRs) performed in 2009 were carried out using ‘image guidance.’ The report also states an average 3-year revision rate for UKRs of 6.5%. Previous NJR data has shown that this figure rises up to 12% for certain types of prosthesis. We suspect that a significant proportion of these revisions are due to failure secondary to component malpositioning. We therefore propose that the use of computer navigation enables a more accurate prosthesis placement, leading to a reduction in the revision rate for early failure secondary to component malpositioning. Our early results of one hundred consecutive computer navigated UKRs are presented and discussed. Ninety-two patients having had one hundred consecutive computer navigated UKRs were reviewed both clinically and radiographically. The Smith & Nephew Accuris fixed-bearing modular prosthesis was used in all cases, with the ‘Brainlab’ navigation system. Pre-operative aim was neutral tibial cut with three degrees posterior slope. Post-operative component alignment was measured with PACs web measuring tools. Patients were scored clinically using the Oxford Knee Score. Our patient cohort includes 54 male knees and 46 female knees. Average age is 66.6yrs. Average length of stay was 3.7 days, (range 2–7.) With respect to the tibial component, average alignment was 0.7° varus, and 2.32° posterior slope. All components were within the acceptable 3 degrees deviation. Functional scores are very satisfactory, with an overall patient satisfaction rate of 97%. To date, only one UKR has required revision. This was due to ongoing medial pain due to medial overhang, not related to computer navigation. There was one superficial infection, with full resolution following a superficial surgical washout, debridement and antibiotics. Unlike complications reported in the NJR, we report no peri-prosthetic fractures or patella tendon injuries. Our results demonstrate accurate prosthesis placement with the use of computer navigation. Furthermore, clinical scores are highly satisfactory. Our current revision rate is 1% at a mean of 27 months post-op. Although longer-term follow-up of our group is required, our results compare very favourably to statistics published in the NJR, (average 3-year revision rate 6.5%.) The only major differences appear to be the type of prosthesis used and the use of computer navigation. It is our proposal that computer navigation reduces the number of revisions required due to component malpositioning and subsequent failure. Furthermore, we believe that this challenging surgery is made easier with the use of computer navigation. We expect our longer-term results to show significant benefits of computer navigation over conventional techniques

Background. Bone preservation is desired for future revision in any knee arthroplasty. There is no study comparing the difference in the amount of bone resection when soft tissue balance is performed with or without computer navigation. To determine the effect on bony cuts when soft tissue balance is performed with or without use of computer software by standard manual technique in total knee arthroplasty. One hundred patients aged 50 to 88 years underwent navigated TKR for primary osteoarthritis. In group A, 50 patients had both soft tissue release and bone cuts done using computer-assisted navigation. In group B, 50 patients had soft tissue release by standard manual technique first and then bone cuts were guided by computer-assisted navigation. In group A the mean medial tibial resection was 5 ± 2.3 mm and lateral was 8 ± 1 mm compared to 5 ± 2 mm (P = 0.100) and 8 ± 1 mm respectively in group B (P = 0.860). In group A the mean medial femoral bone cut was 9 ± 2.9 mm and lateral was 8 ± 2 mm as compared to 9.5 ± 2.9 mm (P = 0.316) and 10 ± 2.2 mm respectively in group B (P = 0.001). Average prosthesis size was 6 (range 3 to 8) in group A as compared to size 5 (range 2 to 7) in group B. Average navigation time in group A was 102 minutes (range 45 to 172) and in group B was 83 minutes (range 42 to 165, P = 0.031). Our results show that performing soft tissue release and bone cuts using computer- assisted navigation is more bone conserving as compared to manual soft tissue release and bone cuts using computer navigation for TKR, thus preserving bone for possible future revision surgery

Correct component positioning in hip resurfacing is a key determinant for a successful outcome. The aim of the study was to compare the radiographic and perioperative clinical parameters between navigated and non-navigated resurfacing groups and to look at the effect of navigation on the learning curve. Pre and post operative radiographs were analyzed with respect to neck-shaft angle, implant-shaft angle, notching, lateral position, and cup inclination. The target implant position was to place the femoral component in relative valgus to the neck-shaft angle using the smallest component without notching the femoral neck. The target cup position was 40–45 degrees inclination. Statistical analysis was performed comparing the two groups with respect to implant position, complications and differences between experienced verses inexperienced surgeons. Data was recorded for 51 patients (24 navigated, 27 conventional). There was no significant difference in implant-shaft angle or presence of notching between the two groups. There were two cases of notching in the non-navigated cohort. Lateral positioning (central placement stem, centering component on shaft) was significantly more accurate for the navigated cases (P< 0. 001). There was no significant difference in cup inclination between the two groups. In the non-navigated group three patients were converted to a total hip replacement (one fracture, one impingement pain, one intra-operative notching) and there was 1 case of medial wall fracture of the acetabulum. There was a 14.8% complication rate for the non-navigated group with no complications in the navigated group. Complications experienced 2.6% vs. training 17.4%. Training navigated 0% vs Training non-navigated 30%; Experienced nav 0% vs. experienced non-navigated 5.5%. Positioning of the femoral component in the lateral plane and A-P head-neck ratios is significantly more accurate with the use of computer navigation. Navigation allows for a relative valgus implant-shaft angle that is as accurate as conventional jigs. Navigation is useful as a teaching tool with a reduction in the learning curve and better radiographic placement of components

Aim: The study was conducted to evaluate differences between simultaneous and sequential cementing of the tibial and femoral components in total knee joint replacement in relation to final component alignment. Our hypothesis was that cementing the components sequentially increases accuracy of the final position. Method: This was a prospective and randomised study, performed using a computer navigation system as the evaluation technique to determine the accuracy of implant positioning. All knee replacements (Scorpio, Stryker) were implanted with the assistance of computer navigation. The patients were divided into two groups of 20 patients each. The first group had implants cemented simultaneously where the tibial and femoral components were implanted with a single mix of cement and then pressurized by extending the leg. The second group of patients had the tibial component inserted with the first mix of cement and then impacted. Then the femoral component was inserted using a second mix of cement. Computer navigation was used to measure varus/ valgus cut of the femur, varus/ valgus cut of the tibia, and sagital slope of the tibia. Measurements were made with the components in place, both before cementing and then after cement cure. Results: Our results show a statistically significant improvement in accuracy of femoral varus/ valgus alignment using the sequential cementing technique

Aims. Due to the complex anatomy of the pelvis, limb-sparing resections of pelvic tumours achieving adequate surgical margins, can often be difficult. The advent of computer navigation has improved the precision of resection of these lesions, though there is little evidence comparing resection with or without the assistance of navigation. Our aim was to evaluate the efficacy of navigation-assisted surgery for the resection of pelvic bone tumours involving the posterior ilium and sacrum. . Patients and Methods. Using our prospectively updated institutional database, we conducted a retrospective case control study of 21 patients who underwent resection of the posterior ilium and sacrum, for the treatment of a primary sarcoma of bone, between 1987 and 2015. The resection was performed with the assistance of navigation in nine patients and without navigation in 12. We assessed the accuracy of navigation-assisted surgery, as defined by the surgical margin and how this affects the rate of local recurrence, the disease-free survival and the effects on peri-and post-operative morbidity. . Results. The mean age of the patients was 36.4 years (15 to 66). The mean size of the tumour was 10.9 cm. In the navigation-assisted group, the margin was wide in two patients (16.7%), marginal in six (66.7%) and wide-contaminated in one (11.1%) with no intralesional margin. In the non-navigated-assisted group; the margin was wide in two patients (16.7%), marginal in five (41.7%), intralesional in three (25.0%) and wide-contaminated in two (16.7%). Local recurrence occurred in two patients in the navigation-assisted group (22.2%) and six in the non-navigation-assisted group (50.0%). The disease-free survival was significantly better when operated with navigation-assistance (p = 0.048). The blood loss and operating time were less in the navigated-assisted group, as was the risk of a foot drop post-operatively. Conclusion . The introduction of navigation-assisted surgery for the resection of tumours of the posterior ilium and sacrum has increased the safety for the patients and allows for a better oncological outcome. . Cite this article: Bone Joint J 2017;99-B:261–6

Purpose: The purpose of this study was to evaluate the accuracy and precision of 3 common methods used to produce posterior tibial slope during total knee arthroplasty. Method: The study population consisted of 110 total knee arthroplasties in 102 patients that underwent total knee arthroplasty. All procedures were performed using a standard medial parapatellar approach and all knees were replaced using the Scorpio Knee System (Stryker, Mahwah, NJ) of implants and instruments. Three treatment groups were identified retrospectively based on the method used to produce the posterior tibial slope. Group 1 used an extramedullary guide with a 0 degree cutting block tilted by placing 2 fingers between the tibia and the extramedullary guide proximally and three fingers between the tibia and guide distally to produce a 3 degree posterior slope (N=40). Group 2 used computer navigation (Stryker Navigation System, Stryker, Mahwah, NJ) to produce a 3 degree posterior slope (N=30). Group 3 used an extramedullary guide placed parallel to the anatomic axis of the tibia with a 5 degree cutting block to produce a 5 degree posterior slope (N=40). Posterior tibial slope was measured from lateral radiographs by 2 independent reviewers that were blinded to the treatment group. The reported posterior tibial slope for each sample was an average of these two measurements. Accuracy of the treatment group was evaluated using a one sample t test. Groups 1 and 2 were tested for an ideal slope of 3 degrees, and Group 3 was tested for an ideal slope of 5 degrees. An a priori sample size calculation with α=0.05 and β=0.20 showed that at least 24 samples in each treatment group were required to determine a difference of 1.5 degrees between the treatment group mean posterior tibial slope and the ideal posterior tibial slope. Results: The mean posterior slope measurements for treatment Group 1 (4.15±3.24 degrees) and treatment Group 2 (1.60±1.62 degrees) were both significantly different than the ideal slope of 3 degrees (p=0.03 for Group 1 and p< 0.01 for Group 2). This indicates that treatment Groups 1 and 2 failed to accurately produce the ideal posterior tibial slope of 3 degrees. The mean posterior tibia slope of treatment Group 3 (5.00±2.87 degrees) was not significantly different than the ideal posterior tibial slope of 5 degrees (p=1.00). This indicates that Group 3 accurately produced the ideal tibial slope of 5 degrees. Conclusion: The most accurate method to produce posterior tibial slope was the 5 degree cutting block with an extramedullary guide. Computer navigation had the lowest standard deviation and therefore was the most precise method. However, computer navigation was not as accurate in producing the desired posterior tibial slope as the extramedullary guide with the 5 degree cutting block. The manual method of producing tibial slope with an extramedullary guide and a 0 degree cutting block was the least precise method and not as accurate as the extramedullary guide with a 5 degree cutting block

The purpose of this study was to evaluate 3 methods used to produce posterior tibial slope. Methods. 110 total knee arthroplasties performed during a 4 year period were included(2005 to 2009). All operations were performed by 2 surgeons. Group 1 used an extramedullary guide with a 0 degree cutting block tilted by placing 2 fingers between the tibia and the extramedullary guide proximally and three fingers distally to produce a 3 degree posterior slope (N=40). Group 2 used computer navigation to produce a 3 degree posterior slope (N=30). Group 3 used an extramedullary guide placed parallel to the anatomic axis of the tibia with a 5 degree cutting block to produce a 5 degree slope (N=40). Posterior tibial slope was measured by 2 independent blinded reviewers. The reported slope for each sample was the average of these measurements. All statistical calculations were performed using SPSS Windows Version 16.0 (SPSS Inc., IL, USA). Results. There was excellent agreement for the mean posterior slopes measured by the 2 independent reviewers. The linear correlation constant was 0.87 (p<0.01). The paired t test showed no significant difference (p=0.82). The measurements for Group 1 (4.15±3.24 degrees) and Group 2 (1.60±1.62 degrees) were both significantly different to the ideal slope of 3 degrees (p=0.03 for Group 1 and p<0.01 for Group 2). The mean posterior tibial slope of Group 3 (5.00±2.87 degrees) was not significantly different to the ideal posterior tibial slope of 5 degrees (p=1.00). Group 2 exhibited the lowest standard deviation. Discussion. The most accurate method was the extramedullary 5 degree cutting block. Computer navigation was the most precise method, but was not accurate in producing the desired slope of 3 degrees. The manual method with an extramedullary guide and a 0 degree cutting block is neither accurate nor precise

Computer navigated total knee arthroplasty (TKA) has several proposed benefits including reduced post operative blood loss. We compared the total blood volume loss in a cohort of morbidly obese (BMI> 40) patients undergoing computer navigated (n=30) or standard intramedullary techniques (n=30) with a cohort of matched patients with a BMI< 30 also undergoing navigated (n=31) or standard TKA (n=31). Total body blood loss was calculated from body weight, height and haemotocrit change, using a model which accurately assesses true blood loss as was maximum allowable blood loss. The groups were matched for age, gender, diagnosis and operative technique. The mean true blood volume loss was significantly (p< 0.001) less in the computer assisted group (1014±312mls) compared to the conventional group (1287±330mls). Patients with a BMI > 40 and a computer navigated procedure (1105 ±321mls) had a significantly lower (p< 0.001) blood volume loss compared to those who underwent a conventional TKA (1399±330mls). There was no significant difference in the transfusion rate or those reaching the maximum allowable blood loss between groups. This study confirms a significant reduction in total body blood loss between computer assisted and conventional TKA in morbidly obese patients. However computer navigation did not affect the transfusion rate or those reaching the transfusion trigger in the morbidly obese group. Therefore computer navigation may reduce blood loss in the morbidly obese patient but this may not be clinically relevant to transfusion requirements as previously suggested

Posterior slope of the tibial component is an important factor in overall alignment of Total Knee Arthroplasty. The purpose of this study was to compare the accuracy and reproducibility of tibial bone cuts utilizing traditional extramedullary 0 degree and angled 5 degree cutting blocks, and computer aided navigation, in primary total knee arthroplasty. We identified 3 groups of patients. Group one were primary total knees performed using an extramedullary 0 degree cutting block for posterior slope, group 2 were performed using an extramedullary 5 degree cutting block and the third group were performed with computer navigation. Patients in all 3 groups were age and sex matched. All operations were performed by residents or clinical fellows, under the supervision of the senior authors. Lateral digital radiographs were reviewed and posterior slope was determined in a standardized fashion. Two independent blinded researchers assessed the posterior slope using Siemens Magicweb software version VA42C_0206. The average difference from the ideal posterior slope in navigated knees was lower than with non-navigated knees, however this was not significant (p=0.086). The average difference from the ideal posterior slope in computer navigated knees was 1.77 degrees (95% CI=1.28 to 2.26) compared to 2.37 degrees (95% CI=1.56 to 3.17) with the 5 degree cutting block and 2.70 degrees (95% CI=1.73 to 3.66) with the 0 degree block. No absolute significant difference was highlighted between the 3 groups using ANOVA testing (p=0.22). All three techniques used to obtain ideal tibial slope were accurate. Accuracy was not increased by the use of computer navigation; however navigation resulted in less variation in outcome. The two jig based methods produced similar outcomes and either technique can be used successfully

Introduction: This study aimed to determine the accuracy of computer navigation in simulated fixation of femoral neck and supracondylar femoral fractures using different sizes of guidewires and drills from commercially available cannulated screw systems. Methods: Simulated fracture fixation was performed with 2.5mm, 2.8mm and 3.2mm threaded guidewires and 3.2mm and 5mm drill bits using 20 4th generation synthetic femurs. The drill or guide wire was inserted in the synthetic femurs, using fluoroscopy based computer navigation (24 drills/guidewires in each group). Pre and postoperative fluoroscopy images were acquired with the C-arm and synthetic bone in the same orientations. Virtual and real wire/drill positions were compared, and errors calculated for each diameter of drill/guidewire (sum AP + Lateral error (mm)). Errors were compared using a general linear model with Tukey adjustment for multiple comparisons. Statistical significance at a two-tailed p-value < 0.05. Results: The mean error for the 5.0mm drill (3.20mm) was significantly less than all the threaded wires (p< 0.05). The mean error for the 3.2mm drill (5.68mm) was significantly less than the 2.5mm guidewire (9.27mm) p< 0.05, and less than the 2.8mm (8.19mm) and 3.2mm (7.14mm) threaded wires. Discussion: For cannulated screws, the 3.2mm drill was the most accurate size tested. The most accurate drill, 5mm, would allow solid screw insertion. However, its large size may preclude screw repositioning, and unlike a cannulated screw, would not maintain fracture position whilst the screw was being inserted

Extensive release of postero-lateral structures may be required to correct rigid and severe valgus deformities during total knee arthroplasty. Current techniques are technically difficult, may not accurately restore soft tissue balance, and are associated with postoperative complications. We evaluated the results of using computer navigation for lateral epicondylar osteotomy during total knee arthroplasty for rigid severe valgus arthritis. We had performed this procedure during navigated TKA in 10 valgus arthritic knees (2 bilateral TKAs) in 8 patients (1 male and 7 female). The mean age at the time of surgery was 65.7 years (range, 48–77 years) and the mean preoperative valgus deformity was 19.25° (range, 10°–36.5°). The mean postoperative limb alignment at the end of a mean follow-up of 20 months (range, 14–31 months) was 0.5° valgus (range, 2° varus–1.8° valgus). None of the patients had any complications related to the procedure with no obvious clinical mediolateral instability and complete union at the osteotomy site was noted in all patients radiographically at the last followup. Computer navigation allows for precisely measuring the difference between medial and lateral gaps as well as the limb alignment and to determine the effect of sequential soft-tissue releases on both. Our technique takes advantage of this feature to accurately re-position the lateral epicondylar block in order to equalize medial and lateral gaps thereby ensuring a stable knee. Internal fixation with compression screws coupled with large contact surfaces of cancellous bone at the osteotomy site allow for early post-operative rehabilitation and ensure union at the osteotomy site

Total knee arthroplasty (TKA) is one of the commonest orthopaedic procedures. Traditionally the surgeon, based on experience, releases the medial structures in knees with varus deformity and lateral structures in knees with valgus deformity until subjectively they feel that they have achieved the intended alignment. The aim of this prospective study was to record the frequency of medial and lateral releases for computer navigated TKAs. Seven four consecutive patients operated on by a single surgeon were included in this study. All patients had TKA using either Stryker or Orthopilot computer navigation systems. The implants used were Scorpio NRG or Columbus. The biomechanical axis was taken as the reference for distal femoral and proximal tibial cut. The trans-epicondylar axis was taken as the reference for frontal femoral and posterior condylar cuts. A soft tissue release was undertaken after the bony cuts had been made if the biomechanical axis did not come to within 2° of neutral as shown by computer readings in extension. The post-operative alignment was recorded on the navigation system and also analysed with long leg hip knee ankle radiographs. There were 43 female and 31 males in the study, 34 left and 40 right knees with an age range of 43 to 87 years. The range of pre-operative deformities on long leg radiographs was 15° varus to 27° valgus with a mean of −5.0° and SD 7.4°. Only two patients needed a medial release. None of the patients needed a lateral release. The fixed flexion deformities needed posterior release. None of the patients needed lateral release for patellar tracking. Post-operative alignment was available for 71 patients. The post implant navigation value was within 2° of neutral in all cases. The mean biomechanical axis on radiographs was 0.1° valgus with a SD 2.1° and range from 6° varus to 7° valgus. From the radiographs six patients were outside the ±3° range. If one sticks to biomechanical axis and transepicondylar axis as the reference for bony cuts, there will be minimal requirement for medial or lateral soft tissue release. According to our results the use of computer navigation gives a low frequency of medial and lateral release in total knee replacement. Other authors have also found that navigation data can help to give a lower rate of soft tissue release, such as Picard et al. who had decreased their soft tissue release to 25%

Introduction/Aims: Early results of a prospective randomised control trial suggested improved position of components implanted during primary hip replacement. The aim of this study is to definitively show the benefit of computer aided navigation in hip arthroplasty with regard to acetabular component position, stem position and leg length. Method: Eighty consecutive patients were prospectively recruited. Patients were quasi-randomised, on an alternating basis, to undergo hip arthroplasty conventionally or with imageless computer navigation. Postoperatively, a CT scan was performed of the pelvis and lower limb. Using a dynamic CT planning software package, the cup and stem position was measured and compared to the position expected by the three operating surgeons in control cases and the position given by the navigation unit in the study group. Change in leg length was measured clinically and compared with the navigation predicted leg length change. Statistical analysis was performed by a statistician. Results: Thirty nine navigated hips (29 female, 10 male) and forty one control hips (26 female, 15 male) were recruited. In the navigated group, the mean age was 65.7 and mean BMI was 29.1. In the control group, the mean age was 64.7 and the mean BMI was 29.4 in the control group. Uncemented, securfit/trident hips were used in 18 navigated cases and 20 control cases, with all other cases being cemented Exeter stems and contemporary cups. None of these differences were significant using the Mann-Whitney test. The mean operating time was 128 minutes for navigated hips and 84 minutes for controls, the difference significant at p< 0.005 using t-test. There was no significant correlation between clinical leg length change, measured in the operating theatre and the leg length change predicted by navigation. Accuracy of cup and stem placement was assessed by comparison of the homogeneity of variances, the Levene statistic, in the navigated and control groups. The range of cup inclination, cup version and stem version was significantly narrowed in the navigation group (p< 0.05). Conclusion: Computer navigation improves the accuracy of component placement in hip arthroplasty with respect to cup version, cup inclination and stem version with either cemented or uncemented hips

The aim of our study was to compare the precision and effectiveness of a CT-free computer navigation system against conventional technique (using a standard mechanical jig) in a cohort of unselected consecutive series of hip resurfacings. One hundred and thirty nine consecutive Durom hip resurfacing procedures (51 navigated and 88 non-navigated) performed in 125 patients were analysed. All the procedures were done through a posterior approach by two surgeons and the study cohort include the hip resurfacings done during the transition phase of the surgeons’ adoption of navigation. There were no significant differences in the gender, age, height, weight, BMI, native neck-shaft angles, component sizes and blood loss between the two groups. There was a significant difference in the operative time between the two groups (111 minutes for the navigated group versus 105 minutes for the non-navigated group; p=0.048). There were 4 cases of notching in the non-navigated group and none in the navigated group. There were no other intra-operative technical problems in either of the groups nor were there any femoral neck fractures. No significant difference was found between the mean post-operative stem-shaft angles (138.5° for the navigated group versus 139.0° for the non navigated group, p=0.740). However there was a significant difference in the difference between the planned stem-shaft angle versus the post-operative stem-shaft angle (0.4° for the navigated group versus 2.1° for the non-navigated group; p=0.005). There was significantly more scatter in the difference between the post-operative stem-shaft angle and the planned stem-shaft angle in the non-navigated group (standard deviation = 3.6°) when compared with the navigated group (standard deviation = 0.9°; Levene’s test for equality of variances = p≤0.01). No case in the navigated group showed a post-operative stem-shaft angle of more than 5° deviation from the planned neck-shaft angle when compared to 33 cases (38%) in the non-navigated group (p≤0.001). While only 4 cases (8%) in the navigated group had a postoperative stem-shaft angle deviating more than 3° from the planned stem-shaft angle, this occurred in 50 cases (57%) in the non-navigated group (p≤0.001). Hip resurfacing is a technically demanding procedure with a steep learning curve. Varus placement of the femoral component and notching have been recognised as important factors associated with early failures following hip resurfacing. While conventional instruments allowed reasonable alignment of the femoral component, our study has shown that use of computer navigation allows more accurate placement of the femoral component even when the surgeons had a significant experience with conventional technique

Implant alignment in knee arthroplasty has been identified as critical factor for a successful outcome. Human error during the registration process for imageless computer navigation knee arthroplasty directly affects component alignment. This cadaveric study aims to define the error in the registration of the landmarks and the resulting error in component alignment. Five fresh frozen cadaveric limbs including the hemipelvis were used for the study. Five surgeons performed the registration process via a medial parapatellar approach five times. In order to identify the gold standard point, the soft tissues were stripped and the registration was repeated by the senior author. Errors are presented as mm or degrees from the gold standard registration. The error range in the registration of the femoral centre in the coronal plane was 6.5mm laterally to 5.0mm medially (mean: −0.1, SD: 2.7). This resulted in a mechanical axis error of 5.2 degrees valgus to 2.9 degrees varus (mean: 0.1, SD: 1.1). In the sagittal plane this error was between −1.8 degrees (extension) and 2.7 degrees (flexion). The error in the calculation of the tibial mechanical axis ranged from −1.0 (valgus) to 2.3 (varus) degrees in the coronal plane and −3.2 degrees of extension to 1.3 degrees of flexion. Finally the error in calculating the transepicondylar axis was −11.2 to 6.3 degrees of internal rotation (mean: −3.2, SD: 3.9). The error in the registration process of the anatomical landmarks can result in significant malalignment of the components. The error range for the mechanical axis of the femur alone can exceed the 3 degree margin that has been previously been associated with implant longevity. The technique during the registration process is of paramount importance for image free computer navigation. Future research should be directed towards simplifying this process and minimizing the effect of human error

Introduction. It is widely accepted that computer navigation more reliably restores neutral mechanical alignment than conventional instrumentation in total knee arthroplasty (TKA) surgery. Recently, magnetic resonance (MR) based instrumentation has been introduced to the market with a rapid growth in usage. However, a paucity of comparative data still exists on the precision of magnetic resonance (MR) based instruments in achieving acceptable lower limb alignment when compared to other validated techniques. In this analysis, we compare the radiographic outcomes of 3 techniques to achieve satisfactory prosthetic alignment by 2 surgeons using the same prosthesis and surgical technique. Methods. A series of 180 patients who had undergone TKA surgery were included in this study. Two fellowship-trained knee surgeons performed all surgeries using the same cemented, posterior stabilized implants (NexGen, Zimmer, Warsaw, In). Patients were stratified in to 3 groups according to the technique used to align the knee; 1. Conventional Intra-medullary Instrumentation, 2. Computer Navigation (Orthosoft), and 3. MR-based guides (Zimmer PSI). All patients underwent a post-operative CT Perth Protocol to assess coronal, sagittal and rotational alignment of the femoral and tibial implants. A radiographer who was blinded to the alignment technique used performed all radiographic measurements. Outliers were defined at a deviation of more than 3 degrees from the mechanical axis in all planes of motion. Results. The radiographic outcome measures will be presented to highlight the significant differences between 3 groups. In addition, the early surgical experience with the introduction of MR based instruments will be reviewed along with the early problems encountered from tibial sagittal alignment that became apparent with time. Conclusion. The rapid introduction of MR based instruments in to the market by several prosthetic companies has occurred without adequate pre-release analysis. This study will allow surgeons to make an informed decision on whether to use this technology based on validated radiographic measures, when compared to both conventional alignment techniques and computer navigation

Purpose: The aim of our study was to compare the precision and effectiveness of a CT-free computer navigation system against conventional technique (using a standard mechanical jig) in a cohort of unselected consecutive series of hip resurfacings. Method: 139 consecutive Durom hip resurfacing procedures (51 navigated and 88 non-navigated) performed in 125 patients were analysed. All the procedures were done through a posterior approach by two surgeons and the study cohort include the hip resurfacings done during the transition phase of the surgeons’ adoption of navigation. Results: There were no significant differences in the patients caracteristics, native neck-shaft angles, component sizes and blood loss between the two groups. There was a significant difference in the operative time between the two groups (111 minutes for the navigated group versus 105 minutes for the non-navigated group; p=0.048). There were 4 cases of notching in the non-navigated group. There was no other intra-operative technical problem in either of the groups nor were there any femoral neck fractures. No significant difference was found between the mean post-operative stem-shaft angles (138.5° for the navigated group versus 139.0° for the non navigated group, p=0.740). However there was a significant difference in the difference between the planned stem-shaft angle versus the post-operative stem-shaft angle (0.4° for the navigated group versus 2.1° for the non-navigated group; p=0.005). While, none of the cases in the navigated group had a post-operative stem-shaft angle with more than 5° deviation from the planned neck-shaft angle when compared to 33 cases (38%) in the non-navigated group (p≤0.001). For a given patient with a target angle set, it is estimated that positioning precision using the navigation is 1.3° +/− 0.9°, compared to 4.4° +/− 3.6° without navigation (p< 0.0001). Conclusion: Hip resurfacing is a technically demanding procedure with a steep learning curve. Varus placement of the femoral component and notching have been recognised as important factors associated with early failures following hip resurfacing. While conventional instruments allowed reasonable alignment of the femoral component, our study has shown that use of computer navigation allows more accurate placement of the femoral component even when the surgeons had a significant experience with conventional technique

Introduction. Surgical techniques for implant alignment in total knee arthroplasty (TKA) is a expanding field as manufacturers introduce patient-specific cutting blocks derived from 3D reconstructions of pre-operative imaging, commonly MRI or CT. The patient-specific OtisMed system uses a detailed MRI scan of the knee for 3D reconstruction to estimate the kinematic axis, dictating the cutting planes in the custom-fit cutting blocks machined for each patient. The resulting planned alignment can vary greatly from a neutral mechanical axis. The purpose of this study was to evaluate the early fixation of components in subjects randomized to receive shape match derived kinematic alignment or conventional alignment using computer navigation. A subset of subjects were evaluated with gait analysis. Methods. Fifty-one patients were randomized to receive a cruciate retaining cemented total knees (Triathlon, Stryker) using computer navigation aiming for neutral mechanical axis (standard of care) or patient-specific cutting blocks (OtisMed custom-fit blocks, Stryker). Pre-operatively, all subjects had MRI scans for cutting block construction to maintain blinding. RSA exams and health outcome questionnaires were performed post-operatively at 6 week, 3, 6, and 12 month follow-ups. A subset (9 subjects) of the patient-specific group underwent gait analysis (Optotrak TM 3020, AMTI force platforms) one-year post-TKA, capturing three dimensional (3D) knee joint angles and kinematics. Principal component analysis (PCA) was applied to the 3D gait angles and moments of the patient-specific group, a case-matched control group, and 60 previously collected asymptomatic subjects. Results. Five MRI scans for surgical planning were not useable due to motion artifacts, with 2 successfully rescanned. Ligament releases were performed in 62% of navigation cases and 32% of patient-specific cases. One patient-specific case was revised for failure of the cruciate ligament, resulting in a polyethylene liner exchange for a thicker, cruciate substituting insert. Implant migration at 1 year was 0.40±0.25 mm for the patient-specific group and 0.37±0.20 mm for the navigation group (maximum total point motions; t-test P=0.65). EQ-5D scores, Oxford Knee scores, satisfaction, pain, and range of motion were not different between groups at any follow-up to 1 year, including the polyethylene liner exchange case. The gait analysis showed that there were no statistical differences between groups. PCA captured a lower early stance phase flexion moment magnitude in the patient-specific group than the computer navigated recipients, bringing patterns further away from asymptomatic characteristics (flexion moment PC2, P=0.02). Conclusions. Implant migration was not different between groups at 1 year despite differences in implant alignment methods. Subject function and satisfaction were also not different between groups, despite significantly fewer ligament releases in the patient-specific group. However, gait analysis of a subgroup has not shown an improvement towards restoring asymptotic gait. It should be acknowledged that the production of patient-specific cutting blocks may not be possible for all patients due to the MRI scanning requirements. Continued evaluation with RSA to 2 years will be performed to monitor these subjects over the longer term

Introduction We present our earliest series of computer assisted minimally invasive fixation of intertrochanteric hip fractures using the dynamic hip screw. Methods The first five cases of computer assisted minimally invasive dynamic hip screw fixation of intertro-chanteric femur fracture are presented. We used the Medivision Computer Navigation system. Our operative techniques, pitfalls and tricks are presented. All were performed in the standard lateral approach to the femur on a traction table. The minimally invasive cases had a incision length of 5 cm compared with an average length of 13.9 cm for the conventional procedure. Results Technical difficulties in screw placement exists and screw head positions tends to be superior. There was one case of implant cutout. The others recovered uneventfully. Fluoroscopy time is halved, sparing the surgeon from excessive radiation. Operative time is prolonged by about 20 minutes. Patient satisfaction has been very good. Conclusions Our procedure is safe and predictable. Patient satisfaction is high. The small wound allows for less pain and tissue dissection enabling faster and more effective rehabilitation. The instrumentation is based on the existing DHS system and there is no need to change inventory. The option of day surgery and same day discharges for hip fracture patients using this technique is tantalising

We report our five-year functional results comparing navigated and conventional total knee replacement. To our knowlege this represents the first Level 1 study comparing function in navigated and conventional total knee replacement at five years. An origianl cohort of 71 patients undergoing Duracon (Stryker Orthopaedics, St. Leonards, Australia) total knee replacement without patellar resurfacing were prospectively randomised to undergo operation using computer navigation (Stryker Image Free Computer Navigation System (version 1.0; Stryker Orthopaedics))(n=35) or a jig-based method (n=36). The two groups were matched for age, gender, height, weight, BMI, ASA grade abd pre-operative deformity. All operations were performed by a single surgeon. Reviews were undertaken by senior physiotherpist blinded to participant status using validated outcome scoring tools (Knee Society Score, WOMAC Score and Short Form SF-36 Score). All patients underwent CT scanning of the implanted prosthesis as per Perth CT Knee Protocol to assess component alignment. After 5 years 24 patients in the navigated group and 22 patients in the conventional group were available for review. At 5 years no statistically significant difference was seen in any of the aforementioned outcome scores when comparing navigated and conventional groups. No statistically significant differencewas seen between 2- and 5-year results for either group. Due to the relatively low numbers in each group these data were compared with retrospective cohorts of navigated (n=100) and conventional (n=70) Duracon total knee replacements performed outwith this study over the same 5-year period. WITHIN the retrospective cohorts no statistically significant differences were found when comparing any of the aforementioned outcome scores. In addition, when comparing parallel scores between prospective and retrospective groups again no statistically significant differences were identified. At 5-years post-operatively the functional outcome between computer navigated and conventional total knee replacement appears to be no different despite the better alignment achieved using navigation

Purpose. Computer navigation for hip resurfacing has been shown to reduce the incidence of technical error during femoral head preparation and provides increased accuracy compared to conventional instrumentation for insertion of the initial femoral guidewire. Limitations to the widespread use of navigation in hip resurfacing include access and cost. A novel, patient specific nylon jig has been developed as a cost effective alternative for placement of the initial guidewire. The purpose of this study was to compare the accuracy of femoral guidewire insertion between imageless navigation, conventional instrumentation and a new type of CT-based custom jig. Method. Six pairs of cadaveric femora were used in the study. Each pair was divided randomly between a group utilizing firstly a conventional lateral pin jig (BHR, Smith & Nephew Inc.) followed by navigation (Vector Vision SR, BrainLAB) and a group utilizing a CT-based, patient specific custom jig (Visionaire, Smith & Nephew Inc.). A single surgeon inserted all guidewires. The planned guidewire position was approximately 10 degrees of relative valgus to the native neck-shaft angle in the coronal plane and neutral version in the sagittal plane. The same coronal alignment angle was used between paired femora. Femurs were positioned in a draped synthetic foam hip model prepared with a standard posterior approach. Guidewire insertion time and placement accuracy for each of the three alignment methods was assessed. Guidewire placement accuracy for coronal inclination and version was assessed by anteroposterior and lateral digital radiographs and was defined as the mean deviation from the planned alignment value. Results. Imageless navigation was more accurate than both the custom and the conventional jigs in coronal guidewire inclination (mean 1.3 degrees, SD 1.2, p<0.047). The custom jig (mean 6.4 degrees, SD 2.9) provided a comparable level of accuracy to that of the conventional jig (mean 5.5 degrees, SD 3.6, p=0.851). Guidewire version using the custom jig (mean 1.0 degrees, SD 0.4) was comparable to imageless navigation (mean 3.9 degrees, SD 2.1, p=0.101) and was superior to the conventional jig (mean 5.6 degrees, SD 2.9, p=0.008). The time required for guidewire insertion using the custom alignment jig was significantly reduced compared to both the conventional jig and imageless computer navigation (p<0.001), with imageless navigation requiring more time than the conventional jig (p=0.038). Conclusion. The CT-based custom alignment jig was superior to conventional instrumentation for guidewire version while providing a similar level of accuracy for coronal guidewire inclination. Imageless navigation provided the highest level of accuracy for coronal guidewire placement. A custom alignment jig may be a better alternative to conventional instrumentation for placement of the initial femoral guidewire in hip resurfacing

Introduction. Blood loss after TKA varied, but not uncommon with up to 1500 ml or a decrease in hemoglobin of 3–4 g/dL. In addition to improving prosthetic alignment, computer-assisted TKAs also contribute to reduced operative blood loss and systemic emboli. These observations imply that navigation TKAs may cause less microvascular endothelial damage than conventional TKAs. Cell adhesion molecules (CAMs) have been employed as markers for endothelial or vascular damage. We hypothesized serum levels of CAMs in patients receiving navigation TKAs may be different from those receiving conventional TKAs. Material and Methods. A prospective comparative study, enrolling 87 patients with osteoarthritic knees was conducted. There were 54 navigation TKAs and 33 conventional TKAs. Levels of cell adhesion molecules (CAM) in sera and hemovac drainage were measured by ELISA before and 24 hours after the surgery. Hb and Ht were checked pre- and post-operatively. The blood loss was calculated though the formula by Nadler and Sehat et al. Results. There were no significant differences in gender, affected side, age or BMI between the two group. The calculated volume of blood loss in the computer navigation group was 955 (772, 1164)mL, significantly lower (p=0.001) than the 1265 (963, 1475)mL in the conventional group. The baseline serum CAMs did not differ before surgery. Postoperative serum ICAM-1, VCAM-1 and PECAM-1 levels in the navigation group were 35.5% (p<0.001), 2.0% (p=0.037) and 49.3% (p<0.001) lower, respectively, than those in the conventional group. Discussion. Complications secondary to bone marrow violation are significant concerns after TKA. We provided novel evidence that patients had decreased blood loss concomitant with mitigated postoperative elevation of levels of CAMs after navigation TKA, which is indicative of its less-invasive nature with regard to the integrity of femoral medullary cavity

We previously compared component alignment in total knee replacement using a computer-navigated technique with a conventional jig based method. Improved alignment was seen in the computer-navigated group (Beaver et al. JBJS 2004 (86B); 3: 372–7.). We also reported two-year results showing no difference in clinical outcome between the two groups (Beaver et al. JBJS 2007 (89B); 4: 477–80). We now report our five-year functional results comparing navigated and conventional total knee replacement. To our knowlege this represents the first Level 1 study comparing function in navigated and conventional total knee replacement at five years. An original cohort of 71 patients undergoing Duracon (Stryker Orthopaedics, St. Leonards, Australia) total knee replacement without patellar resurfacing were prospectively randomised to undergo operation using computer navigation (Stryker Image Free Computer Navigation System (version 1.0; Stryker Orthopaedics))(n=35) or a jig-based method (n=36). The two groups were matched for age, gender, height, weight, BMI, ASA grade and pre-operative deformity. All operations were performed by a single surgeon. All patients underwent review in our Joint Replacement Assessment Clinic at 3, 6 and 12 months and at 2 and 5 years. Reviews were undertaken by senior physiotherapist blinded to participant status using validated outcome scoring tools (Knee Society Score, WOMAC Score and Short Form SF-36 Score). All patients underwent CT scanning of the implanted prosthesis as per Perth CT Knee Protocol to assess component alignment. After 5 years 24 patients in the navigated group and 22 patients in the conventional group were available for review. At 5 years no statistically significant difference was seen in any of the aforementioned outcome scores when comparing navigated and conventional groups. No statistically significant difference was seen between 2- and 5-year results for either group. Due to the relatively low numbers in each group these data were compared with retrospective cohorts of navigated (n=100) and conventional (n=70) Duracon total knee replacements performed outwith this study over the same 5-year period. WITHIN the retrospective cohorts no statistically significant differences were found when comparing any of the aforementioned outcome scores. In addition, when comparing parallel scores between prospective and retrospective groups again no statistically significant differences were identified. At 5-years post-operatively the functional outcome between computer navigated and conventional total knee replacement appears to be no different despite the better alignment achieved using navigation

Purpose. The purpose of this study was to analyze rotational kinematic patterns in knees treated with either cruciate-retaining (CR) or posterior-stabilized (PS) total knee arthroplasty (TKA), using an intra-operative navigation technique, and to clarify the factors that affect of the rotational kinematics and the difference rotational kinematics patterns between CR- and PS- TKA. Methods. A total of 35 knees (35 patients) were included in this study, deformed valgus, sever flexion contractures, and highly unstable knees were excluded. These knees were allocated to CR (NexGen CR-Flex) or PS (NexGen PS-Flex) implants and underwent TKA with a computer navigation technique (precision N Knee Navigation Software v4.0; Stryker). There was no significant difference in pre-operative parameters between CR- and PS-TKA group: age, femorotibial angle (FTA), and chondylar twist angle (CTA). We measured two points during surgery. First, the skin incision was made and subcutaneous tissue was exposed. The joint capsule was temporality closed by three or four strand suture. Second, after the surgery was completed with satisfactory alignment and soft tissue balance, immediately following wound closure the measurement procedure was repeated. The surgeon gently applied a manual range of motion from full extension to flexion. The angle of internal rotation in tibia to the functional plane of tibia and femur was measured automatically at max extension, 0, 30, 45, 60, 90 degrees, and max flexion throughout the passive knee motion. Result. We categorized the post-operative rotational kinematics patterns to five types. Type A was increasing with the internal rotation angle in tibia with knee flexion. Type B was decreasing the internal rotation with knee flexion. Type C was decreasing the internal rotation from 0 to 45 or 60 degrees, Then graduated increasing until full flexion. Type D was the opposite type of type C. Type E was not able to categorize any pattern. (Figure 1) The individual kinematic pattern was variable in pre- and post-operative knee motion. Both CR- and PS-TKA had a tendency to remain the preoperative kinematic pattern (CR-TKA 66% and PS-TKA 59%) by comparing the pre- and post-operative kinematic pattern. But, type A was increased in post-operative PS-TKA. (Figure 2) We analyzed factors (age, pre-operative FTA, CTA, pre-operative knee extension, and post-operative FTA) that affect the change of rotational kinematics patterns before and after TKA. In CR-TKR, there were not any factors that influence with the changes of kinematic pattern. In PS-TKR, pre-operative knee extension angle affected accompanied by significant difference in the change of rotational kinematics patterns. Discussion & Conclusion. We analyzed the rotational kinematics patterns in knees treated with either CR- or PS-TKR, using an intra-operative navigation. Pre- and post-operative knee kinematics of TKA patients had a variety of rotational kinematics patterns. Both CR- and PS-TKA had a tendency to remain the preoperative kinematic pattern by comparing the pre- and post-operative kinematic pattern Pre-operative knee extension affected to the change of rotational kinematics pattern in PS-TKR