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)

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

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. 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

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

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

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 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

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

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

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

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

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

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

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

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