Aims. The aim of this study was to develop and evaluate machine-learning-based computerized adaptive tests (CATs) for the Oxford Hip Score (OHS), Oxford Knee Score (OKS), Oxford Shoulder Score (OSS), and the Oxford Elbow Score (OES) and its subscales. Methods. We developed CAT algorithms for the OHS, OKS, OSS, overall OES, and each of the OES subscales, using responses to the full-length questionnaires and a machine-learning technique called regression tree learning. The algorithms were evaluated through a series of simulation studies, in which they aimed to predict respondents’ full-length questionnaire scores from only a selection of their item responses. In each case, the total number of items used by the CAT algorithm was recorded and CAT scores were compared to full-length questionnaire scores by mean, SD, score distribution plots, Pearson’s correlation coefficient, intraclass correlation (ICC), and the Bland-Altman method. Differences between CAT scores and full-length questionnaire scores were contextualized through comparison to the instruments’ minimal clinically important difference (MCID). Results. The CAT algorithms accurately estimated 12-item questionnaire scores from between four and nine items. Scores followed a very similar distribution between CAT and full-length assessments, with the mean score difference ranging from 0.03 to 0.26 out of 48 points. Pearson’s correlation coefficient and ICC were 0.98 for each 12-item scale and 0.95 or higher for the OES subscales. In over 95% of cases, a patient’s CAT score was within five points of the full-length questionnaire score for each 12-item questionnaire. Conclusion. Oxford Hip Score, Oxford Knee Score, Oxford Shoulder Score, and Oxford Elbow Score (including separate subscale scores) CATs all markedly reduce the burden of items to be completed without sacrificing score accuracy. Cite this article: Bone Jt Open 2022;3(10):786–794

Oxford Medial Unicompartmental Knee Replacement (OMUKR) is a well-established treatment option for isolated medial compartment arthritis, with good patient reported outcome measures (PROMs). We present our results of the Oxford Domed Lateral Unicompartmental Knee Replacement (ODLUKR) to establish if patients benefit as much as with OMUKR. Retrospective review of prospectively collected data of a single surgeon series of consecutive UKR from 2007 to 2014 were collated with a minimum 2 years follow-up. PROMs data were collected using pre- and post-operative Oxford Knee Scores (OKS) (best score of 48). One hundred and twenty-eight OMUKR and 27 ODLUKR were performed in the study period. There was no significant difference in the age at time of surgery, but there were significantly more women in the ODLUKR group (74% vs 53%). There was no significant difference in pre-op OKS between the groups (OMUKR = 16/48; ODLUKR = 20/48), or the improvement in OKS post-op (OMUKR = 19 points; ODLUKR = 17 points). One ODLUKR was revised to Total Knee Replacement (TKR) for pain. There were three (11.1%) bearing dislocations, which were treated with thicker bearing exchange, with no subsequent problems. There were no bearing dislocations in the OMUKR. Four OMUKR were revised to TKR due to pain. The overall implant survivorship was 96.3% for ODLUKR and 96.9% for OMUKR. ODLUKR is a good treatment option for isolated lateral compartment arthritis and gives results equivalent to OMUKR. There is, however, an increased risk of bearing dislocation so should be performed by a high volume UKR surgeon

While clinically important improvements in Oxford Shoulder Scores have been defined for patients with general shoulder problems or those undergoing subacromial decompression, no threshold has been reported for classifying improvement after shoulder replacement surgery. This study aimed to establish the minimal clinically important change (MCIC) for the Oxford Shoulder Score in patients undergoing primary total shoulder replacement (TSR). Patient-reported outcomes data were sourced from the Australian Orthopaedic Association National Joint Replacement Registry Patient-Reported Outcome Measures Program. These included pre- and 6-month post-operative Oxford Shoulder Scores and a rating of patient-perceived change after surgery (5-point scale ranging from ‘much worse’ to ‘much better’). Two anchor-based methods (using patient-perceived improvement as the anchor) were used to calculate the MCIC: 1) mean change method; and 2) predictive modelling, with and without adjustment for the proportion of improved patients. The analysis included 612 patients undergoing primary TSR who provided pre- and post-operative data (58% female; mean (SD) age 70 (8) years). Most patients (93%) reported improvement after surgery. The MCIC derived from the mean change method was 6.8 points (95%CI 4.7 to 8.9). Predictive modelling produced an MCIC estimate of 11.6 points (95%CI 8.9 to 15.6), which reduced to 8.7 points (95%CI 6.0 to 12.7) after adjustment for the proportion of improved patients. For patient-reported outcome measures to provide valuable information that can support clinical care, we need to understand the magnitude of change that matters to patients. Using contemporary psychometric methods, this analysis has generated MCIC estimates for the Oxford Shoulder Score. These estimates can be used by clinicians and researchers to interpret important changes in pain and function after TSR from the patient's perspective. We conclude that an increase in Oxford Shoulder Scores of at least 9 points can be considered a meaningful improvement in shoulder-related pain and function after TSR

While clinically important improvements in Oxford Shoulder Scores have been defined for patients with general shoulder problems or those undergoing subacromial decompression, no threshold has been reported for classifying improvement after shoulder replacement surgery. This study aimed to establish the minimal clinically important change (MCIC) for the Oxford Shoulder Score in patients undergoing primary total shoulder replacement (TSR). Patient-reported outcomes data were sourced from the Australian Orthopaedic Association National Joint Replacement Registry Patient-Reported Outcome Measures Program. These included pre- and 6-month post-operative Oxford Shoulder Scores and a rating of patient-perceived change after surgery (5-point scale ranging from ‘much worse’ to ‘much better’). Two anchor-based methods (using patient-perceived improvement as the anchor) were used to calculate the MCIC: 1) mean change method; and 2) predictive modelling, with and without adjustment for the proportion of improved patients. The analysis included 612 patients undergoing primary TSR who provided pre- and post-operative data (58% female; mean (SD) age 70 (8) years). Most patients (93%) reported improvement after surgery. The MCIC derived from the mean change method was 6.8 points (95%CI 4.7 to 8.9). Predictive modelling produced an MCIC estimate of 11.6 points (95%CI 8.9 to 15.6), which reduced to 8.7 points (95%CI 6.0 to 12.7) after adjustment for the proportion of improved patients. For patient-reported outcome measures to provide valuable information that can support clinical care, we need to understand the magnitude of change that matters to patients. Using contemporary psychometric methods, this analysis has generated MCIC estimates for the Oxford Shoulder Score. These estimates can be used by clinicians and researchers to interpret important changes in pain and function after TSR from the patient's perspective. We conclude that an increase in Oxford Shoulder Scores of at least 9 points can be considered a meaningful improvement in shoulder-related pain and function after TSR

Background. Unexplained pain is one of the most common complications after Oxford UKAs. We have retrospectively reviewed the patients who underwent Oxford UKAs and investigated those patients with prolonged pain and found that many of these patients had strong tenderness over the Hunter canal and they were well treated with Hunter canal block or administration of Pregabalin. We have checked the details of these prolonged pain and key to the treatment will be discussed. Methods. Between May 2006 and September 2014 we have performed 316 Oxford UKAs. There were 47 males and 269 females with average age of 70.4 years old (46–90). The patients were followed up for at least 6 months (6 months to 8.0 years, mean follow-up period of 3.1 years). The patients were examined both clinically and radiologically. Result. There were 30 knees (9.5%) that showed prolonged pain continuing more than 3 month after the operation(Fig.1). Of these 30 knees, 17 knees had strong tenderness over the Hunter canal, and many patients had numbness and radiating pain toward medial side of the lower extremities. They were diagnosed as having Hunter canal syndrome clinically. Of these 17 knees 5 were treated successfully with Hunter canal block with Lidocaine. Remaining 12 knees were treated with Pregabalin or with Tramadol. All but 1 knee, pain disappeared within 3 months after starting the treatment as we stated. There were 3 cases that were finally diagnosed as having lumbar canal stenosis and L3 root block was effective. For the 10 knees not diagnosed as having Hunter canal syndrome without any tenderness over the Hunter canal, the pain disappeared spontaneously in 2 knees, and the pain disappeared with administration of Pregabalin or Tramadol in 6 knees. Two patients didn't respond to any treatment, they were referred to psychiatrist and diagnosed as having mental problems. There was no abnormal radiolucency, which suggested loosening of the component. As a result, true unexplained pain that continued more than a year was only 1. Discussion. 17 knees out of 30 unexplained pain knees after Oxford UKAs had strong tenderness over the Hunter canal, and the pain disappeared after the saphenous nerve block or adminestration of Pregabalin except for 1 knee. Patients without the diagnosis of Hunter canal syndrome also responded well to either Pregabalin or Tramadol. The pain continuing for more than 3 months after Oxford UKA is usually self-limited and well treated conservatively. With these results, when you see the prolonged pain after Oxford UKA, we strongly recommend just wait and see by conservative treatment with Pregabalin, Tramadol or saphenous nerve block, and do not revise the implant

It is very important for implanting tibial component to prevent bearing dislocation in Oxford UKA. One of the keys is accurate rotational position of tibia. But the problem remains what is accurate rotation of tibia in UKA. Oxford Signature decided the rotation of tibia component from MRI images. We measured the component rotation of tibia using CT after operation. Patients and Methods. 14 patients were operated by Oxford Signature and 11 patients were operated by Microplasty method. Patients were examined by CT 2 or 3 weeks later after operation. We compared component axis of tibia and A-P axis by best fit circle, Akagi's line. Results. In Oxford Signature group, component angle were 7.1 degree external rotation compared with A-P axis by best fit circle and were 3.6 degree external rotation compared with Akagi's line. In Microplasty group, component angle were 8.1 degree external rotation compared with A-P axis by best fit circle and were 3.8 degree external rotation compared with Akagi's line. Discussion. It is difficult to decide accurate position of tibial component for UKA. The A-P axis by best fit circle and Akagi's line are reliable methods for tibial axis in TKA. We examined component axis of Signature Oxford and Microplasty, these were same tendency toward external rotation

The Oxford mobile bearing knee prosthesis (Zimmer Biomet Inc, Warsaw, Ind) is considered a good treatment option for isolated medial compartment knee arthrosis. From February 2001 until August 2016, 1719 primary Oxford medial unicompartmental knee replacement procedures were completed at our center by a group of seven surgeons. We undertook this study to examine the long-term survivorship of the Oxford unicompartmental knee replacement looking at survivorship and reasons for failure. A retrospective consecutive case series review was completed, and all revisions and re-operations were identified. Conversion to total knee replacement (TKA) was considered a failure. Kaplan-Meier survival analysis was used to calculate the 15-year survivorship of the group overall. We specifically looked at age, gender, BMI and surgeon caseload in addition to the reasons for failure. A statistical analysis was performed and differences in survivorship were compared for the variables listed. A logistic cox regression was performed to explore predictors of revision. Overall 15-year survivorship was 89.9%. Female survivorship of 88.1% was statistically worse than the male group at 91.8% (p=0.018). Younger patients (75yrs of age (p= 0.036). There was a large range in surgical case load by individual surgeons (range 17–570 knees). There were no statistically significant differences in age, BMI, or gender when comparing the individual surgeon groups. There was a large range in 15-year survivorship between individual surgeons (range 78.3% – 95%). Overall the most common reason for revision was due to wear of the unreplaced portion of the knee (lateral and/or patella-femoral joint) followed by aseptic loosening, polyethylene dislocation, infection or persistent pain. The 15-year survivorship results of the Oxford medial unicompartmental knee replacement at our center compares favourably to other published series and large registry data series. We found a reduction in survivorship in female patients and younger patients (< 5 5yrs). There were also significant differences in survivorship based on the individual surgeon. A more selective patient approach yielded the best long-term survivorship and equivalent to that of total knee replacement. We therefore suggest using a more selective approach when choosing patients for a medial unicompartmental knee replacement with the Oxford mobile bearing prosthesis in order to enhance long-term survivorship

Source of the study: University of Auckland, Auckland, New Zealand and University of Otago, Christchurch, New Zealand. The Oxford Knee Score (OKS) is a 12-item questionnaire used to track knee arthroplasty outcomes. Validation of such patient reported outcome measures is typically anchored to a single question based on patient ‘satisfaction’, however risk of subsequent revision surgery is also an important outcome measure. The OKS can predict subsequent revision risk within two years, however it is not known which item(s) are the strongest predictors. Our aim was to identify which questions were most relevant in the prediction of subsequent knee arthroplasty revision risk. . All primary TKAs (n=27,708) and UKAs (n=8,415) captured by the New Zealand Joint Registry between 1999 and 2019 with at least one OKS response at six months, five years or ten years post-surgery were included. Logistic regression and receiver operating characteristics (ROC) curves were used to assess prediction models at six months, five years and ten years. Q1 ‘overall pain’ was the strongest predictor of revision within two years (TKA: 6 months, odds ratio (OR) 1.37; 5 years, OR 1.80; 10 years, OR 1.43; UKA: 6 months, OR 1.32; 5 years, OR 2.88; 10 years, OR 1.85; all p<0.05). A reduced model with just three questions (Q1, Q6 ‘limping when walking’, Q10 ‘knee giving way’) showed comparable or better diagnostic ability with the full OKS (area under the curve (AUC): TKA: 6 months, 0.77 vs. 0.76; 5 years, 0.78 vs. 0.75; 10 years, 0.76 vs. 0.73; UKA: 6 months, 0.80 vs. 0.78; 5 years: 0.81 vs. 0.77; 10 years, 0.80 vs. 0.77). The three questions on overall knee pain, limping when walking, and knee ‘giving way’ were the strongest predictors of subsequent revision within two years. Attention to the responses for these three key questions during follow-up may allow for prompt identification of patients most at risk of revision

Purpose. the purpose of this study was to compare the rollback ratio in the bi-cruciate substituting BCS-TKA and the Oxford UKA. Methods. 20 subjects (28 knees) who were performed the BCS-TKA (Journey II: Smith and Nephew) and 24 subjects (29 knees) who were performed the Oxford UKA, were included in this study. Approximately 6 months after surgery, and when the subjects recovered their range of knee motion, following the Laidlow's method (The knee 2010), lateral radiographic imaging of the knee was performed with active full knee flexion. The most posterior tibiofemoral contact point was measured for evaluation of femoral rollback (Rollback ratio). Flexion angle was also measured using the same radiograph and the correlation of rollback and flexion angle was analyzed. As a control, radiographs of the contralateral knees of who were performed Oxford UKA were evaluated (29 knees). Results. The rollback ratios of the BCS-TKA, Oxford UKA, and the control knees were 37.9±4.9%, 35.7±4.2%, and 35.3±4.8% respectively from the posterior edge of the tibia. No significant difference in rollback ratio was observed. The flexion angles of the BCS-TKA, Oxford UKA, and the control knees were 121.8±8.4°, 125.4±7.5°, and 127±10.3°, respectively. No significant difference in knee flexion angle was observed. Significant correlation between rollback ratio and knee flexion angle was observed (p=0.002: Pearson's correlation coefficient =−0.384). Conclusion. In conclusion, BCS-TKA showed no significant difference of rollback ratio when compared with the control knees and the Oxford UKA knees. There is the possibility that the design of BCS-TKA could reproduce the native ACL and PCL function

Background. Oxford joint scores are increasingly being used in evaluating outcomes following orthopaedic surgery. These patient-reported outcome measures (PROM) have been well validated, but only before and after surgical intervention. We postulated that the scores would deteriorate in the normal population with age. Methods. Members of the public accompanying patients to out-patients and the emergency department in our hospitals were asked to complete an Oxford score questionnaire having ascertained that they had no previous problem with that joint. Exclusions included other multiple joint pathologies and known connective tissue disorders. Power analysis advocated 40 subjects per decade per joint for significance at the 80% mark. 993 subjects between 20 and 80 years of age completed the forms. There were more females than males. The scores were analysed using STATA 8 software. Non-parametric tests of variance, regression analysis, and ANOVA were used. The data were analysed by decades. Results. In all joints (hip, knee, shoulder, and elbow) the mean Oxford score in the 20-30 year olds (third decade) was at least one point below the maximum. The scores then deteriorated with age at the rate of one point per decade. This was statistically significant in all groups (p = 0.002 or less) Sex had no statistical influence on the scores. Conclusion. In our mainly (98%) Caucasian population the Oxford Scores deteriorate with age. We suggest that this should be taken into account when cohort studies are being compared between surgeons and units, especially in units dealing with many younger patients. Oxford scores should be age adjusted, starting at the 3. rd. decade by adding 1 point for the 3. rd. decade, 2 for the fourth, etc. up to 6 points for the eighth decade. Other ethnic groups should also be studied

Aims

Medial unicompartmental knee arthroplasty (UKA) is undertaken in patients with a passively correctable varus deformity. Our hypothesis was that restoration of natural soft tissue tension would result in a comparable lower limb alignment with the contralateral normal lower limb after mobile-bearing medial UKA.

Introduction

The Oxford Unicompartmental Knee Replacement (OUKA) is the most popular unicompartmental knee replacement (UKR) in the New Zealand Joint Registry with the majority utilising cementless fixation. We report the 10-year radiological outcomes.

Excessive under correction of varus deformity may lead to early failure and overcorrection may cause progressive degeneration of the lateral compartment following medial unicompartmental knee arthroplasty (UKA). However, what influences the postoperative limb alignment in UKA is still not clear. This study aimed to evaluate postoperative limb alignment in minimally-invasive Oxford medial UKAs and the influence of factors such as preoperative limb alignment, insert thickness, age, BMI, gender and surgeon's experience on postoperative limb alignment. Clinical and radiographic data of 122 consecutive minimally-invasive Oxford phase 3 medial unicompartmental knee arthroplasties (UKAs) performed in 109 patients by a single surgeon was analysed. Ninety-four limbs had a preoperative hip-knee-ankle (HKA) angle between 170°-180° and 28 limbs (23%) had a preoperative hip-knee-ankle (HKA) angle <170°. The mean preoperative HKA angle of 172.6±3.1° changed to 177.1±2.8° postoperatively. For a surgical goal of achieving 3° varus limb alignment (HKA angle=177°) postoperatively, 25% of limbs had an HKA angle >3° of 177° and 11% of limbs were left overcorrected (>180°). Preoperative HKA angle had a strong correlation (r=0.53) with postoperative HKA angle whereas insert thickness, age, BMI, gender and surgeon's experience had no influence on the postoperative limb alignment. Minimally invasive Oxford phase 3 UKA can restore the limb alignment within acceptable limits in majority of cases. Preoperative limb alignment may be the only factor which influences postoperative alignment in minimally-invasive Oxford medial UKAs. Although the degree of correction achieved postoperatively from the preoperative deformity was greater in limbs with more severe preoperative varus deformity, these knees tend to remain in more varus or under corrected postoperatively. Overcorrection was more in knees with lesser preoperative deformity. Hence enough bone may need to be resected from the tibia in knees with lesser preoperative deformity to avoid overcorrection whereas limbs with large preoperative varus deformities may remain under corrected

This study aims to correlate Oxford shoulder score (OSS) to EQ5D score in healthy patients presenting to a shoulder clinic with shoulder pain. OSS and EQ5D scores were collected prospectively from 101 consecutive patients presenting with shoulder pain in a shoulder clinic at one specialist centre. Patients with ASA > 2 and other significant joint arthritis were excluded from the study. Scores were collected from electronic patient records. Spearman's rho correlation of oxford shoulder scores and EQ5D scores was completed. Mean age of subjects was 51.8 (range 19.1–81.9) years, 55 of 101 subjects were men (54%). Median OSS was 26 (range 3–48) and median EQ5D score was 0.76 (range 0–0.76). Correlation for all patients was 0.624 (Sig p<0.001). This study demonstrates a strong correlation between Oxford shoulder scoring and EQ5D in a fit and well shoulder surgery clinic population. It is possible that Oxford shoulder scores may be a useful indicator of quality of life in healthy shoulder clinic patients presenting with shoulder pain

Introduction. The Oxford Knee Score is a well validated, commonly used scoring system. Previous studies have suggested that the score is influenced by demographic differences between patients in particular the functional component more than the pain and clinical components. The aim of this study was to further assess this using a large number of patients. Methods. The pre, 3 months and 12 months post-surgical Oxford Knee Scores were collected from 1492 patients from five distinct demographic locations undergoing total knee arthroplasty over twelve years under the care of 8 different consultants. A total of 735 patients had complete data sets. The scores were than analysed to test whether age, postcode, sex or consultant in charge had any significant effects on the outcome. Results. No significant difference in outcome was found between the five locations used in the study. This was also the case when different consultants were compared however when the results are adjusted for age there was a significant difference (p=0.019). In this study female patients had higher scores at both 3 and 12 months (significance p=0.011 and 0.044 respectively). Age of patient was also found to be of borderline significance when determining the post-operative scores. Conclusion. This large patient sample study shows that the Oxford Knee Score in post-operative patients is not as heavily influenced by demography as previously suggested. The results show that patients who are older and/or male will have better outcomes from knee arthroplasty. Individual surgeons do not significantly affect the outcome although some surgeons may have better results when age of patient is taken into account. Lastly, post code and life style has no significant influence on the outcome neither should be taken for any consideration for surgery

A large proportion of wait times for primary total knee (TKA) and hip (THA) arthroplasty is the time from primary care referral to surgical consultation. To our knowledge, no study has investigated whether a referral Oxford Knee or Hip Score (OKHS) could be used to triage non-surgical referrals appropriately. The primary purpose of the current study was to determine if a referral OKHS has the predictive ability to discriminate when a knee or hip referral will be deemed conservative as compared to surgical by the surgeon during their first consultation, and to identify an OKHS cut-off point that accurately predicts when a primary TKA or THA referral will be deemed conservative. We retrospectively reviewed all consecutive primary TKA and THA consultations from a single surgeon's tertiary, high volume practice over a three-year period. Patients with a pre-consultation OKHS, BMI < 4 1, and no absolute contraindication to TJR were included. Consultation knees/hips were categorized into two groups based on surgeon's decision, those that were offered TJR during their first consolation (surgical) versus those that were not (conservative). Baseline demographic data and OKHS were abstracted. Variables of interest were compared between cohorts using the exact chi-square test and Wilcoxon rank-sum test. Spearman's rank correlation coefficients were used to measure association between pre-consult OKHS and the surgeon's decision. A receiver operator characteristic (ROC) curve analysis was used to calculate the area under the curve (AUC) and to identify a cut-off point for the pre-operative OKHS that identified whether or not a referral was deemed conservative. TKA and THA referrals were analyzed separately. The study included 1,436 knees (1,016 patients) with a median OKS of 25 (IQR 19–32) and 478 hips (388 patients) with a median OHS of 22 (IQR 16–29). Median pre-consultation OKHS demonstrated clinically and statistically significant differences between the surgical versus conservative cohorts (p 32 (sensitivity=0.997, NPV=0.992) and for hips is OHS >34 (sensitivity=0.997 NPV=0.978). ROC analysis identified severable potential lower OKHS thresholds, depending on weight of prioritization of sensitivity, specificity, and NPV. Referral OKS and OHS demonstrate good ability to discriminate when a primary TKA or THA referral will be deemed non-surgical versus surgical at their first consultation in a single surgeon's practice. Multiple potential effective OKHS thresholds can be applied as a tool to decrease wait times for primary joint arthroplasty. However, a cost analysis would aid in identifying the optimal cut-off score, and these findings need to be externally validated before they can be broadly applied

Time analysis from video footage gives a simple outcome measure of surgical practice against a measured model of use. The added detail that can be produced, over simply recording the usual surgical process data such as tourniquet times, allows us to identify and time the sequence of surgical procedures as stages, to describe issues, and the identification of idiosyncratic behaviours for review and comparison. Makoplasty (Mako surgical corp. FL, US) partial knee operation times were compared using this technique with those from the Oxford (Biomet, IN, US) partial knee. Three experienced surgeons were observed over 19 Makoplasty procedures ([Consultant 1] 11, [Consultant 2] 5, [Consultant 3] 3) and 2 experienced surgeons over 11 Oxford partial knee procedures ([Consultant 1] 5, [Consultant 2] 6). Times were refined into separate stages that defined the major operative steps of both the Makoplasty and Oxford processes as used by the surgical team at the Glasgow Royal Infirmary, UK. The videos were reviewed for start and stop times for pre-defined actions that would be expected to be observed during each surgical process and from these stage lengths were calculated. For both the Oxford and Mako system 12 comparable stages were identified for comparison and the timing of the various episodes was tested for statistical significance using a Two-Sample, two tail, t-Test. assuming Equal Variances. [Stages: 1. Setup time, 2. Patient on table, 3. Skin incision, 4. Joint Prep, 5. Robot registration (Not in Oxford), 6. Tibial resection, 7. Femoral resection, 8. Trials, 9. Finishing, 10. Cementing and Washout, 11. Closure and dressing, 12. Off table]. The MAKOplasty procedures were on average longer than Oxfords by 27 minutes. This can largely be accounted for in the additional setup stage 4, where in addition to the usual joint preparation taking a couple of minutes approximately 17 minutes were spent in the MAKO cases undertaking image registration and in stage 5 where nearly five minutes were spent in setting up the robot in the MAKO cases. In conclusion while operative times fell for the Makoplasties across the learning curve they remained elevated once the plateau was reached. It should be remembered that the surgeons had much less experience with the Makoplasty procedure and were undertaking a randomised clinical trial of outcome and hence were not minded to perform the surgery quickly but to the best of their ability and that this may account for some of the elongated surgical time. Indeed other Makoplasty surgeons report an average surgical time of 30–45 minutes per case and 6 cases per day. What is striking is that the additional steps of registration and robot positioning account for a large proportion of the differences and these are mitigated to some extent by quicker trialling of the implant and finishing of the cuts suggesting more confidence in the suitability of the cut surfaces. There is clearly a need to reduce the registration time to produce more cost effective surgeries

The Oxford unicompartmental knee replacement (UKR) was introduced in 1976 with good results. Mobile bearings in the lateral compartment have been associated with unacceptably high bearing dislocation rates, due to greater movement between the lateral femoral condyle and tibia, and the lateral collateral ligament's laxity in flexion. The new domed implant is designed to counter this with a convex tibial prosthesis and a fully-congruent, bi-concave mobile bearing allowing a full range-of-movement (ROM), minimising dislocation risk and bearing wear. We present complication rates and clinical outcomes for a consecutive series of our first 20 patients undergoing Oxford domed lateral UKR, between June 2006 and August 2009, with minimum 6-month follow-up. There was one unrelated death (31 months post-UKR) and one postop MI. We had no bearing dislocations, infections or loosening nor other complications. All patients had post-op Oxford Knee Scores; eleven had pre-op scores and demonstrated a significant improvement – mean pre-op 22.75 to post-op 35.45 (p=0.01). All achieved full extension with average ROM 116°, mean change in ROM was –2.6°(p=0.6). This study adds to previous work in confirming a low level of complications with this new procedure (including the early learning curve), particularly bearing dislocation and demonstrates excellent functional outcomes

Method. We prospectively investigated the radiological outcomes of the uncemented Oxford medial compartment arthroplasty in 231 consecutive patients performed in a single centre with a minimum two year follow up. Results. The functional outcome using the Oxford knee score and the High Activity Arthroplasty Score were significantly improved on the pre-operative scores (p<0.001). There were 196 patients with a radiological examination that was acceptable for analysis of the bone-implant interface. Of the six tibial zones examined on the anteroposterior radiograph there were only three with a partial radiolucent line (3 out of 1176 zones). All were present in the medial aspect of the tibial base plate (Zone 1) and all were <1 mm in size. All of these patients were asymptomatic. There were no radiolucent lines seen around the femoral component or on the lateral tibial view. There was one revision for mal-seating of the tibial component. Conclusions. These results confirm that the early results of the uncemented Oxford medial compartment arthroplasty were reliable and the incidence of radiolucent lines was significantly decreased compared to the reported results of the cemented version of this implant. These independent results confirm those of the designing centre

Objective. Mobile bearing unicompartmental knee arthroplasty (UKA) is an effective and safe treatment for osteoarthritis of the medial compartment. However, mobile-bearing UKA needs accurate ligament balancing of flexion and extension gaps to prevent dislocation of the mobile meniscal bearing. Instability can lead to dislocation of the insert. The phase 3 instruments of the Oxford UKA use a balancing technique for the flexion gap (90° of flexion) and extension gap (20° of flexion), thereby focusing attention on satisfactory soft tissue balancing. With this technique, spacers are used to balance the flexion and extension gap. However, gap kinematics in another flexion angle of mobile-bearing UKA is unclear. We developed UKA tensor for mobile-bearing UKA and we assessed the accurate gap kinematics of UKA. Materials and Methods. Between 2012 and 2013, The Phase 3 Oxford Partial Knee UKA (Biomet Inc., Warsaw, IN) were carried out in 48 patients (71 knees) for unicompartmental knee osteoarthritis or spontaneous osteonecrosis of the medial compartment. The mean age of patients at surgery was 71.6 years and the mean follow-up period was 1.7 years. The mean preoperative coronal plane alignment was 7.4° in varus. The indications for UKA included disabling knee pain with medial compartment disease; intact ACL and collateral ligaments; preoperative contracture of less than 15°; and preoperative deformity of <15°. Each surgery was performed by using different spacer block with 1-mm increments and the meniscal bearing lift-off tests according to surgical technique. We developed newly tensor for mobile bearing UKA which designed to permit surgeons to measure multiple range of the joint medial compartment/joint component gap, while applying a constant joint distraction force (Figure 1). We assessed the intra-operative joint gap measurements at 0, 20, 60, 90 and 120 of flexion with 100N, 125N and 150N of joint distraction forces. Results. The gaps measured were 0°: 8.6 ± 1.6, 20°: 9.2 ± 1.4, 60°: 9.6 ± 1.2, 90°: 11.1 ± 1.3, 120°: 11.6 ± 1.8 in 100 N, 0°: 9.7 ± 1.7, 20°: 11.2 ± 1.3, 60°: 11.4 ± 1.3, 90°: 11.9 ± 1.5, 120°: 10.4 ± 1.6 in 125 N, 0°: 11.3±1.4, 20°: 11.8 ± 1.3, 60°: 11.1 ± 1.2, 90°: 12.5 ± 1.3, 120°: 11.9 ± 1.6 in 150N (Figure 2). There was a significant difference between full extension to extension (20° of flexion) and flexion (90° of flexion) to full flexion (120° of flexion). Conclusion. Mobile bearing UKA instrumentation using a balancing technique by spacer block for the flexion gap (90° of flexion) and extension gap (20° of flexion), full extension gap was significantly smaller than extension gap and flexion gap was significantly smaller than full flexion gap in 100N, 125N and 150N of joint distraction forces