Introduction. Management of the patellofemoral surface in total knee arthroplasty (TKA) remains a topic of debate. Incidence of anterior knee pain and incidence of repeat operation have been the focus of several recent meta-analyses, however there is little recent data regarding patients” subjective ability to kneel effectively after TKA. The purpose of this study was to compare patient reported outcomes, including reported ability to kneel, after total knee arthroplasty with and without patellar resurfacing. Methods. Retrospective chart review of 84 consecutive patients who underwent primary TKA with patella resurfacing (56 knees) or without patella resurfacing (28 knees) having a minimum of 2.5 year follow up was performed. Oxford knee scores (OKS), visual analog pain scores (VAS), and questionnaires regarding ability to kneel were evaluated from both groups. Inability to kneel was defined as patients reporting inability or extreme difficulty with kneeling. Shapiro-Wilk test was used to determine normality of data. Mann Whitney U test was used to compare the OKS and VAS between groups. Chi square test was used to compare kneeling ability between groups. Statistical analysis was performed with SPSS version 23 (IBM, Aramonk, NY). Results. The 84 patients included 26 males and 58 females with average age 66.5 (range 46–91). Average follow up was 51 months (range 30–85). There was no significant difference in the percentage of female patients (64% vs 79%), age (67.8 vs 63.8), or reoperation rate (4% vs 7%) between the resurfaced and non-resurfaced groups. There was significantly longer follow up in the non-resurfaced group (57 vs 48 months). There was no statistically significant difference between the resurfacing and non-resurfacing group in terms of OKS (39 vs 38) or VAS (2.5 vs 3.0). However, those patients who did not have their patellofemoral joint resurfaced were more likely to report ability to kneel when compared to the resurfacing group (64% vs 39%, p=0.035). Kneeling ability was not correlated with duration of follow up, patient age or VAS. Kneeling ability was higher in female patients (57%) than males (27%), p=0.017. Discussion. There is concern for increased anterior knee pain and reoperation in patients whose patellae are not resurfaced. However, their failure to imnprove after revision to a resurfaced patella has left some room for depate as to whether or not the lack of resurfacing is the cause of their problems. This study did not show any increase in knee pain or reoperation between groups. There was an increased subjective ability to kneel in paients whose patellae were not resurfaced. This may have implications for the subset of paeitnts whose work or hobbies may require kneeling. There have been previous reports that subjective ability to kneel and actual ability may differ, and also that kneeling can be taught by a therapist. Our data also shows that female gender had a higher reported rate of kneeling

Abstract. Objectives. Patella resurfacing in primary total knee arthroplasty (TKA) remains a contentious issue. Australian rates of patellar resurfacing are 66.6%, significantly higher compared to UK rates of 8–15% and Swedish rates of 2%. Resurfacing has gained popularity in Australia since registry data has shown decreased revision rates with no increase in patellar component related complications. We present for discussion an analysis of 113,694 total knee arthroplasties using commonly implanted prostheses in the UK. Methods. We included all TKA's since the Australian register's conception on 01/09/1999 for a primary diagnosis of osteoarthritis involving the use of either the Triathlon or Duracon implant with and without patellar components. The primary outcome of the study was time to revision for Triathlon's resurfaced and non-resurfaced prosthesis compared to the Duracon's equivalent data. We also analysed the reasons for revision between the 4 groups, type of revision and complication rates. We then compared minimally stabilised and posterior stabilised prostheses. Results. The cumulative revision rate for Triathlon prostheses with resurfacing after 12 years was 3.2% (95% CI, 2.9% to 3.6%) compared to 5.6% (95% CI, 5.0% to 6.2%) without resurfacing. Duracon's equivalent data was 6.3% with resurfacing and 5.9% without resurfacing. Triathlon prosthesis with resurfacing have much lower rates of revision due to loosening, patellofemoral pain, patellar erosion compared to unresurfaced Triathlon prostheses. Conclusion. Triathlon with re-surfacing has lower revision rates regardless of age or BMI. Previous concerns regarding patellofemoral loosening, tibial wear, maltracking relate to Duracon only, indicating the importance of implant specific studies. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

In total knee replacement (TKR), neutral mechanical alignment (NMA) is targeted in prosthetic component implantation. A novel implantation approach, referred to as kinematic alignment (KA), has been recently proposed (Eckhoff et al. 2005). This is based on the pre-arthritic lower limb alignment which is reconstructed using suitable image-based techniques, and is claimed to allow better soft-tissue balance (Eckhoff et al. 2005) and restoration of physiological joint function. Patient-specific instrumentation (PSI) introduced in TKR to execute personalized prosthesis component implantation are used for KA. The aim of this study was to report knee kinematics and electromyography (EMG) for a number lower limb muscles from two TKR patient groups, i.e. operated according to NMA via conventional instrumentation, or according to KA via PSI. 20 patients affected by primary gonarthrosis were implanted with a cruciate-retaining fixed-bearing prosthesis with patella resurfacing (Triathlon® by Stryker®, Kalamazoo, MI-USA). 17 of these patients, i.e. 11 operated targeting NMA (group A) via convention instrumentation and 6 targeting KA (group B) via PSI (ShapeMatch® by Stryker®, Kalamazoo, MI-USA), were assessed clinically using the International Knee Society Scoring (IKSS) System and biomechanically at 6-month follow-up. Knee kinematics during stair-climbing, chair-rising and extension-against-gravity was analysed by means of 3D video-fluoroscopy (CAT® Medical System, Monterotondo, Italy) synchronized with 4-channel EMG analysis (EMG Mate, Cometa®, Milan, Italy) of the main knee ad/abductor and flexor/extensor muscles. Knee joint motion was calculated in terms of flex/extension (FE), ad/abduction (AA), and internal/external rotation (IE), together with axial rotation of condyle contact point line (CLR). Postoperative knee and functional IKSS scores in group A were 78±20 and 80±23, worse than in group B, respectively 91±12 and 90±15. Knee motion patterns were much more consistent over patients in group B than A. In both groups, normal ranges were found for FE, IE and AA, the latter being generally smaller than 3°. Average IE ranges in the three motor tasks were respectively 8.2°±3.2°, 10.1°±3.9° and 7.9°±4.0° in group A, and 6.6°±4.0°, 10.5°±2.5° and 11.0°±3.9° in group B. Relevant CLRs were 8.2°±3.2°, 10.2°±3.7° and 8.8°±5.3° in group A, and 7.3°±3.5°, 12.6°±2.6° and 12.5°±4.2° in group B. EMG analysis revealed prolonged activation of the medial/lateral vasti muscles in group A. Such muscle co-contraction was not generally observed in all patients in group B, this perhaps proving more stability in the knee replaced following the KA approach. These results reveal that KA results in better function than NMA in TKR. Though small differences were observed between groups, the higher data consistency and the less prolonged muscle activations detected using KA support indirectly the claim of a more natural knee soft tissue balance. References

Anterior knee pain following primary total knee replacement (TKR) is a common problem with average reported rates in the literature of approximately 10%. Symptoms are frequently attributed to the patellofemoral joint, and the treatment of the patella during total knee replacement is controversial. There is no article in the literature that the authors know of that has specifically evaluated the effect of patella rim cautery on TKR outcome. This is a denervation technique that has historically been employed, with no evidence base. A prospective comparative cohort study was performed to compare the outcome scores of patients who underwent circumferential patella rim cautery, with those who did not. Patients who had undergone a primary TKR were identified from the unit's arthroplasty database. Two cohorts, who were age and gender matched, were established. None of the patients had their patella resurfaced, but all had a patellaplasty. The Low Contact Stress TKR (Depuy International) was used in all cases. The effect of circumferential patella rim cautery on the Oxford Knee Score (OKS) and the more anterior knee pain specific Patellar Score (PS) a minimum of 2 years post surgery was evaluated. Previous reports have suggested that a change of 5 points in the OKS represents a clinical difference. A sample size calculation based on an effect size of 5 points with 80% power and a p-value of 0.05 would require a minimum of 76 patients in each group. There were 94 patients who had undergone patellaplasty only, and 98 patients who had supplementary circumferential patella rim cautery during their primary TKR. The mean OKS were 34.61 and 33.29 respectively (p=0.41), while the PS scores were 21.03 and 20.87 (p=0.87). No statistically significant differences were noted between the groups for either outcome score. Patella rim cauterisation is unnecessary in primary TKR