Abstract. Background. The Oxford Domed Lateral (ODL) Unicompartmental Knee Replacement (UKR) has some advantages over other lateral UKRs, but the mobile
Aims. The optimal bearing surface design for medial unicompartmental knee arthroplasty (UKA) remains controversial. The aim of this study was to compare outcomes of fixed-bearing (FB) and mobile-bearing (MB) UKAs from a single high-volume institution. Methods. Prospectively collected data were reviewed for all primary cemented medial UKAs performed by seven surgeons from January 2006 to December 2022. A total of 2,999 UKAs were identified, including 2,315 FB and 684 MB cases. The primary outcome measure was implant survival. Secondary outcomes included 90-day and cumulative complications, reoperations, component revisions, conversion arthroplasties, range of motion, and patient-reported outcome measures. Overall mean age at surgery was 65.7 years (32.9 to 94.3), 53.1% (1,593/2,999) of UKAs were implanted in female patients, and demographics between groups were similar (p > 0.05). The mean follow-up for all UKAs was 3.7 years (0.0 to 15.6). Results. Using revision for any reason as an endpoint, five-year survival for FB UKAs was 97.2% (95% CI 96.4 to 98.1) compared to 96.0% for MB (95% CI 94.1 to 97.9; p = 0.008). The FB group experienced fewer component revisions (14/2,315, 0.6% vs 12/684, 1.8%; p < 0.001) and conversion arthroplasties (38/2315, 1.6% vs 24/684, 3.5%; p < 0.001). A greater number of MB UKAs underwent revision due to osteoarthritis progression (FB = 21/2,315, 0.9% vs MB = 16/684, 2.3%; p = 0.003). In the MB group, 12 (1.8%) subjects experienced
Aims. Unicompartmental knee arthroplasty (UKA) has higher revision rates than total knee arthroplasty (TKA). As revision of UKA may be less technically demanding than revision TKA, UKA patients with poor functional outcomes may be more likely to be offered revision than TKA patients with similar outcomes. The aim of this study was to compare clinical thresholds for revisions between TKA and UKA using revision incidence and patient-reported outcomes, in a large, matched cohort at early, mid-, and late-term follow-up. Methods. Analyses were performed on propensity score-matched patient cohorts of TKAs and UKAs (2:1) registered in the New Zealand Joint Registry between 1 January 1999 and 31 December 2019 with an Oxford Knee Score (OKS) response at six months (n, TKA: 16,774; UKA: 8,387), five years (TKA: 6,718; UKA: 3,359), or ten years (TKA: 3,486; UKA: 1,743). Associations between OKS and revision within two years following the score were examined. Thresholds were compared using receiver operating characteristic analysis. Reasons for aseptic revision were compared using cumulative incidence with competing risk. Results. Fewer TKA patients with ‘poor’ outcomes (≤ 25) subsequently underwent revision compared with UKA at six months (5.1% vs 19.6%; p < 0.001), five years (4.3% vs 12.5%; p < 0.001), and ten years (6.4% vs 15.0%; p = 0.024). Compared with TKA, the relative risk for UKA was 2.5-times higher for ‘unknown’ reasons,
Aims. Medial unicompartmental knee arthroplasty (mUKA) is an advised treatment for anteromedial knee osteoarthritis. While long-term survival after mUKA is well described, reported incidences of short-term surgical complications vary and the effect of surgical usage on complications is less established. We aimed to describe the overall occurrence and treatment of surgical complications within 90 days of mUKA, as well as occurrence in high-usage centres compared to low-usage centres. Methods. mUKAs performed in eight fast-track centres from February 2010 to June 2018 were included from the Lundbeck Foundation Centre for Fast-track Hip and Knee Replacement Database. All readmissions within 90 days of surgery underwent chart review and readmissions related to the surgical wound or the prosthesis were recorded. Centres were categorized as high-usage centres when using mUKA in ≥ 20% of annual knee arthroplasties. The occurrence of complications between high- and low-usage centres were compared using Fisher’s exact test. Results. We included 3,757 mUKAs: 2,377 mUKAs from high-usage centres and 1,380 mUKAs from low-usage centres. Surgical complications within 90 days occurred in 69 cases (1.8%), 45 (1.9%) in high-usage centres and 24 (1.7%) in low-usage centres (odds ratio (OR) 1.1 (95% confidence interval (CI) 0.65 to 1.8)). The most frequent complications were periprosthetic joint infections (PJIs) (n = 18; 0.48%), wound-related issues (n = 14; 0.37%), and periprosthetic fractures (n = 13; 0.35%).
Discussion: This study has shown a high dislocation rate for a COP bearing that was reduced to a low dislocation rate by changing the bearing surface to a MOM design. A potential mechanism for this may be the ‘suction fit’ from the surface tension of the low clearance, high tolerance that the metal-on-metal bearing possesses, requiring increased torque to dislocate during impingement.
Source of the study: University of Auckland, Auckland, New Zealand. Unicompartmental knee arthroplasty (UKA) is effective for patients with isolated compartment osteoarthritis, however the procedure has higher revision rates. Long-term survivorship and accurate characterisation of revision reasons are limited by a lack of long-term data and standardised revision definitions. We aimed to identify survivorship, risk factors and revision reasons in a large UKA cohort with up to 20 years follow-up. Patient, implant and revision details were recorded through clinical and radiological review for 2,137 consecutive patients undergoing primary medial UKA across Auckland, Canterbury, Counties Manukau and Waitematā DHB between 2000 and 2017. Revision reasons were determined from review of clinical, laboratory, and radiological records for each patient using a standardised protocol. To ensure complete follow-up data was cross-referenced with the New Zealand Joint Registry to identify patients undergoing subsequent revision outside the hospitals. Implant survival, revision risk and revision reasons were analysed using Cox proportional-hazards and competing risk analyses. Implant survivorship at 15 years was comparable for cemented fixed-bearing (cemFB; 91%) and uncemented mobile-bearing (uncemMB; 91%), but lower for cemented mobile-bearing (cemMB; 80%) implants. There was higher incidence of aseptic loosening with cemented implants (3–4% vs. 0.4% uncemented, p<0.01), osteoarthritis (OA) progression with cemMB implants (9% vs. 3% cemFB/uncemMB; p<0.05) and
Cementless fixation is an alternative to cemented unicompartmental knee replacement (UKR), with several advantages over cementation. This study reports on the 15-year survival and 10-year clinical outcomes of the cementless Oxford unicompartmental knee replacement (OUKR). This prospective study describes the clinical outcomes and survival of first 693 consecutive cementless medial OUKRs implanted in New Zealand. The sixteen-year survival was 89.2%, with forty-six knees being revised. The commonest reason for revision was progression of arthritis, which occurred in twenty-three knees, followed by primary dislocation of the bearing, which occurred in nine knees. There were two
Source of the study: University of Auckland, Auckland, New Zealand and University of Otago, Christchurch, New Zealand. Patient reported outcome measures (PROMs) are predictors of knee arthroplasty revision. Unicompartmental knee arthroplasty (UKA) is effective for patients with the correct indications, however has higher revision rates than total knee arthroplasty (TKA). Different revision thresholds for the procedures have been postulated. Our aims were to investigate: 1) if PROMs could predict knee arthroplasty revision within two years of the score at six months, five years and ten years follow-up, and 2) if revision ‘thresholds’ differed between TKA and UKA. All TKAs and UKAs captured by the New Zealand Joint Registry between 1999 and 2019 with at least one OKS response at six months (TKA n=27,708, UKA n=8,415), five years (TKA n=11,519, UKA n=3,365) or ten years (TKA n=6,311, UKA n=1,744) were included. were propensity-score matched 2:1 with UKAs for comparison of revision thresholds. Logistic regression indicated that for every one-unit decrease in OKS, the odds of TKA and UKA revision decreased by 10% and 11% at six months, 10% and 12% at five years and 9% and 5% at ten years. Fewer TKA patients with ‘poor’ outcomes (≤25) subsequently underwent revision compared with UKA at six months (5.1% vs. 19.6%, p<0.001), five years (4.3% vs. 12.5%, p<0.001) and ten years (6.4%vs. 15.0%, p=0.02). Compared with TKA, UKA patients were 2.5 times more likely to undergo revision for ‘unknown’ reasons,
Introduction: The results of the mobile bearing Oxford partial knee replacement (PKR) in the lateral compartment have been disappointing with a five year survival of 82%.
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%)
Introduction. The results of the original mobile bearing Oxford unicompartmental knee replacement (UKR) in the lateral compartment have been disappointing because of high dislocation rates (11%). This original implant used a flat bearing articulation on the tibial tray. To address the issue of dislocation a new implant (domed tibia with biconcave bearing to increase entrapment) was introduced with a modified surgical technique. The aim of this study was to compare the risk of dislocation between a domed and flat lateral UKR. Methods. Separate geometric computer models of an Oxford mobile bearing lateral UKR were generated for the two types of articulation between the tibial component and the meniscal bearing: Flat-on-flat (flat) and Concave-on-convex (domed). Each type of mobile bearing was used to investigate three distinct dislocation modes observed clinically: lateral to medial dislocation, with the bearing resting on the tray wall (L-M-Wall); medial to lateral dislocation, out of the joint space (M-L); anterior to posterior dislocation, out of the joint space (A-P). A size C tray and a medium femoral component and bearing were used in all models. The femoral component, tibial tray and bearing were first aligned in a neutral position. For each dislocation the tibial tray was restrained in all degrees of freedom. The femoral component was restrained from moving in the anterior-posterior directions and in the medial-lateral directions. The femoral component was also restrained from rotating about the anterior-posterior, medial-lateral and superior-inferior directions. This meant that the femoral component was only able to move in the superior-inferior direction. Different bearing sizes were inserted into the model and the effect that moving the femoral component medially and laterally had on the amount of distraction required to cause
Background. To evaluate the causes and modes of complications after unicompartmental knee arthroplasty (UKA), and to identify its prevention and treatment method by analyzing the complications after UKA. Materials and Methods. A total of 1,576 UKAs were performed between January 2002 and December 2014 at a single-institution. Postoperative complications occurred in 89 knees (83 patients, 5.6%), and 86 of them were found in females and 3 in males. Their mean age was 61 years (range, 46 to 81 years) at the time of initial UKA and 66 years (range, 46 to 82 years) at the time of revision surgery. We analyzed the complications after UKA retrospectively andinvestigated the proper methods of treatment (Table 1). Results. A total of 89 complications (5.6%) occurred afterUKA. Regarding the type of complications after UKA, there were
Purpose. Unicompartmental Knee Arthroplasty (UKA) has been indicated for inactive elderly patients over 60, but for young and active patients less than 60 years old, it has been regarded as a contraindication. The purpose of this study is to evaluate the usefulness of UKA performed on young Asian patients under 60 years of age by analyzing clinical outcomes, complications and survival rate. Materials and Methods. The subjects were 82 cases, which were followed up for at least 5 years (from 5 to 12 years). Only Oxford phase III® (Biomet Orthopedics, Inc, Warsaw, USA) prosthesis was used for all cases. The clinical evaluation was done by the range of motion, Knee society score (KSS), WOMAC score. The radiographic evaluation was performed on weight bearing long-leg radiographs, AP and lateral view of the knee and skyline view of the patella. The survival rate was estimated by Kaplan-Meier survival analysis. Results. Three
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
Introduction. The results of the mobile bearing Oxford unicompartmental knee replacement (UKR) in the lateral compartment have been disappointing with a five year survival of 82%. Therefore, it is recommended that mobile bearings should not be used for lateral UKR. This low survivorship is primarily due to high dislocation rate, all occurring in the first year. A detailed analysis of the causes of
Introduction: The results of the mobile bearing Oxford unicompartmental knee replacement (UKR) in the lateral compartment have been disappointing with a five year survival of 82%. Therefore, it is recommended that mobile bearings should not be used for lateral UKR. This low survivorship is primarily due to high dislocation rate, all occurring in the first year. A detailed analysis of the causes of
The aim of this study was to evaluate the risk
factors for dislocation of the bearing after a mobile-bearing Oxford medial
unicompartmental knee replacement (UKR) and to test the hypothesis
that surgical factors, as measured from post-operative radiographs,
are associated with its dislocation. From a total of 480 UKRs performed between 2001 and 2012, in
391 patients with a mean age of 66.5 years (45 to 82) (316 female,
75 male), we identified 17 UKRs where
Aims. The aim of this to study was to compare the previously unreported
long-term survival outcome of the Oxford medial unicompartmental
knee arthroplasty (UKA) performed by trainee surgeons and consultants. . Patients and Methods. We therefore identified a previously unreported cohort of 1084
knees in 947 patients who had a UKA inserted for anteromedial knee
arthritis by consultants and surgeons in training, at a tertiary
arthroplasty centre and performed survival analysis on the group
with revision as the endpoint. Results. The ten-year cumulative survival rate for revision or exchange
of any part of the prosthetic components was 93.2% (95% confidence
interval (CI) 86.1 to 100, number at risk 45). Consultant surgeons
had a nine-year cumulative survival rate of 93.9% (95% CI 90.2 to
97.6, number at risk 16). Trainee surgeons had a cumulative nine-year
survival rate of 93.0% (95% CI 90.3 to 95.7, number at risk 35).
Although there was no differences in implant survival between consultants
and trainees (p = 0.30), there was a difference in failure pattern
whereby all re-operations performed for
The aim of this study was to describe the pattern of revision indications for unicompartmental knee arthroplasty (UKA) and total knee arthroplasty (TKA) and any change to this pattern for UKA patients over the last 20 years, and to investigate potential associations to changes in surgical practice over time. All primary knee arthroplasty surgeries performed due to primary osteoarthritis and their revisions reported to the Danish Knee Arthroplasty Register from 1997 to 2017 were included. Complex surgeries were excluded. The data was linked to the National Patient Register and the Civil Registration System for comorbidity, mortality, and emigration status. TKAs were propensity score matched 4:1 to UKAs. Revision risks were compared using competing risk Cox proportional hazard regression with a shared γ frailty component.Aims
Methods
When the Oxford unicompartmental meniscal bearing arthroplasty (UCA) is used in the lateral compartment of the knee 10% of the bearings dislocate. An in-vitro cadaveric study was performed to investigate if the anatomy and joint geometry of the lateral compartment was a contributory factor in
Background. A commonly held belief amongst surgeons and patients is that progression of disease (arthritis) to other compartments is a major cause of early failure of UKRs. Methods. We analysed the NJR database records of 17,643 primary UKRs performed between April 2003 and April 2009. Where these had been revised the reason for revision was noted. Results. Of the 17,643 primary UKRs, 308 had died and were excluded from the analysis. Of the living, 505 had been revised (3%) at a mean 3.45 years (range 2-6 years) following the primary procedure. Reason for revision was recorded in 472 cases (93%). Aseptic loosening was the commonest cause for revision in 154 cases (33%), followed by non specific pain in 129 cases (27%),
The August 2023 Knee Roundup360 looks at: Curettage and cementation of giant cell tumour of bone: is arthritis a given?; Anterior knee pain following total knee arthroplasty: does the patellar cement-bone interface affect postoperative anterior knee pain?; Nickel allergy and total knee arthroplasty; The use of artificial intelligence for the prediction of periprosthetic joint infection following aseptic revision total knee arthroplasty; Ambulatory unicompartmental knee arthroplasty: development of a patient selection tool using machine learning; Femoral asymmetry: a missing piece in knee alignment; Needle arthroscopy – a benefit to patients in the outpatient setting; Can lateral unicompartmental knees be done in a day-case setting?
The results of mobile bearing Oxford unicompartmental knee replacement (UKR) in the lateral compartment have been disappointing (five-year survival: 82%). Therefore, it is recommended that mobile bearings should not be used for lateral UKR. This low survivorship is primarily due to a high dislocation rate. A detailed analysis confirmed the elevated lateral tibial joint line to be a contributory factor to
The aim was to identify frequency and pattern of early UKR failure in New Zealand. We analysed data from the New Zealand National Joint Register in a 44 month period of 2000–2003. Thirty-five percent of the 1790 registered UKRs were performed in the last 8 months [ie. in 18% of the total time period]. The ratio of UKRs to TKRs performed was 1:6.25. Fifty two revisions meant a failure rate of 2.9% for UKR (n=1790) compared with 1.6% for TKR (n=11243). The most commonly used implants were the Oxford P3 (68% of total with 2.2% revision rate), MG uni (14.6% with 4.6% revision rate) and Preservation (7% with 5.6 revision rate). The most common reasons for revision (n=52) were aseptic loosening (28%),
Purpose: To analyze the clinical and radiographic results of patients treated by Oxford minimally invasive unicompartmental knee arthroplasty. Materials and Methods: We have operated 166 patients 188 knees of minimally invasive unicompartmental knee arthroplasty(Oxford Uni. ®. ) from January 2002 to December 2005. The mean ages was 65.3 (44–82) years and 16 cases of male and 150 cases of female. The mean follow-up period was 57 (36–77) months. Preoperative diagnosis were osteoarthritis in 166 cases, avascular necrosis of medial femoral condyle in 20 cases and chondrocalcinosis in 2 cases. The clinical results were evaluated using the HSS knee score and the range of motion of knee preoperatively and at the final follow up. At the final follow up, the ability of the patient to assume the squatting and cross-leg position were checked. The tibiofemoral angle was measured preoperatively and postoperatively. Component loosening, radiolucent lines were checked. Result: The HSS knee score was 67.5 (52–86) preoperatively and 89.9 (59–100) at the final follow up. The mean preoperative flexion contracture was 6.5° (0–20) and 0.81 (0–5) at the final follow up. Active full flexion was possible within postoperative 2 months. The squatting position was possible in 133 patients (80.1%) and the cross-leg position was possible in 152 patients (91.6%). The tibiofemoral angle was improved varus 1.5° to valgus 4.8°. Complication occurred in 14 cases (7.4%). Meniscal
Introduction: Increasing experiences in determining the indication for UKA and improvements in design and materials of the prosthesis led to better results. The AMC-Uniglide has an unconstrained mobile bearing with congruent area contact. This ensures complete freedom to rotate and slide upon one other with physiologic kinematic and low intrinsic stability. Material and Methods:. Minimal-invasive technique 30 patients with minimal-invasive AMC-Uniglide implantation technique were compared with 30 conventional implanted AMC’s and 30 total knee replacements in regard to rehabilitation and accuracy of implantation. 361AMC-Uniglides 361 consecutive patients were investigated after AMC-Uniglide implantation. The mean duration of follow-up was 5.5 (2.3-12.5) years. Patients were reviewed using the American Knee Society Rating System. The roentgenographic analyses were performed with the American Knee Society Evaluation System. Results:. Minimal-invasive technique The comparison of 30 minimal-invasive UKA with 30 conventional UKA and 30 total knee replacements show an advantage of minimal invasive technique with regard to a reduced time of rehabilitation. The accuracy of implantation was comparable between the conventional and the minimal-invasive technique. 361 AMC-Uniglides Ninety-five percent of patients had no pain or slight pain at the latest follow-up, ninety-two percent had good or excellent clinical outcome. Three knees were revised for mobile
Unicompartmental knee arthroplasty (UKA) has a higher risk of revision than total knee arthroplasty (TKA), particularly for younger patients. The outcome of knee arthroplasty is typically defined as implant survival or revision incidence after a defined number of years. This can be difficult for patients to conceptualize. We aimed to calculate the ‘lifetime risk’ of revision for UKA as a more meaningful estimate of risk projection over a patient’s remaining lifetime, and to compare this to TKA. Incidence of revision and mortality for all primary UKAs performed from 1999 to 2019 (n = 13,481) was obtained from the New Zealand Joint Registry (NZJR). Lifetime risk of revision was calculated for patients and stratified by age, sex, and American Society of Anesthesiologists (ASA) grade.Aims
Methods
INTRODUCTION. Wear and polyethylene damage have been implicated in up to 22% of revision surgeries after unicompartmental knee replacement. Two major design rationales to reduce this rate involve either geometry and/or material strategies. Geometric options involve highly congruent mobile bearings with large contact areas; or moderately conforming fixed bearings to prevent
Background. The purpose of this study is to report the outcome of navigation-assisted cruciate-retaining total knee arthroplasty (TKA) using one type of cemented, second-generation, floating-platform (FP), mobile-bearing system. Methods. We retrospectively reviewed 42 patients (51 knees) who underwent cruciate retaining TKAs using e.motion-FP prostheses under navigational guidance. The preoperative diagnosis was osteoarthritis in all knees except one rheumatoid arthritis. There were 2 men (2 knees) and 40 women (49 knees) with a mean age of 64.0 ± 4.7 years (range, 51 – 76 years) at the time of index surgery. The mean follow-up was 120.0 months (range, 106 – 126 months). Clinical and radiographic results as well as mechanical survival rate of this type prosthesis were investigated at a mean follow-up of 10 years. Results. The mean mechanical femorotibial angle was improved from 11.7° ± 3.3° (range, 5.0° to 19.7°) preoperatively to 1.4° ± 1.7° (range, −2.9° to 6.4°) at the latest follow-up. No prosthesis-related complications such as
The dual mobility (DM) bearing concept was introduced to reduce the risk of dislocation in total hip arthroplasty (THA). Our aim was to evaluate the early outcomes following the utilisation of DM in primary and revision THA in our unit. Prospectively collected data on all patients undergoing a DM bearing at was reviewed between July 2012and December 2015. The primary outcome assessed was dislocation, with a secondary outcome revision for any reasons. All data was gathered from patient clinical records and the digital picture archiving and communication system (PACS). 30 primary THA were undertaken and 54 revision THAin the time period described. 11 of the procedures involved a proximal femoral endoprosthesis. The mean age in the primary setting was 65 and 73 in the revision population. The main indications for using DM bearing in the primary setting were; trauma (40%), residual dysplasia (40%) and malignancy (17%). There were no dislocations in the primary THA category. Indications in the revision THA cohort included 33% for aseptic loosening, 11% for instability, 18% for ALVAL reactions, 20% for infection, 18% for fracture. 1 out of the 54 revision THA had one large
It is very important for implanting tibial component to prevent
Uncemented mobile bearing designs in medial unicompartmental knee arthroplasty (UKA) have seen an increase over the last decade. However, there are a lack of large-scale studies comparing survivorship of these specific designs to commonly used cemented mobile and fixed bearing designs. The aim of this study was to evaluate the survivorship of these designs. A total of 21,610 medial UKAs from 2007 to 2018 were selected from the Dutch Arthroplasty Register. Multivariate Cox regression analyses were used to compare uncemented mobile bearings with cemented mobile and fixed bearings. Adjustments were made for patient and surgical factors, with their interactions being considered. Reasons and type of revision in the first two years after surgery were assessed.Aims
Methods
Background. Wear and fatigue damage to polyethylene components remain major factors leading to complications after total knee and unicompartmental arthroplasty. A number of wear simulations have been reported using mechanical test equipment as well as computer models. Computational models of knee wear have generally not replicated experimental wear under diverse conditions. This is partly because of the complexity of quantifying the effect of cross-shear at the articular interface and partly because the results of pin-on-disk experiments cannot be extrapolated to total knee arthroplasty wear. Our premise is that diverse experimental knee wear simulation studies are needed to generate validated computational models. We combined five experimental wear simulation studies to develop and validate a finite-element model that accurately predicted polyethylene wear in high and low crosslinked polyethylene, mobile and fixed bearing, and unicompartmental (UKA) and tricompartmental knee arthroplasty (TKA). Methods. Low crosslinked polyethylene (PE). A finite element analysis (FEA) of two different experimental wear simulations involving TKA components of low crosslinked polyethylene inserts, with two different loading patterns and knee kinematics conducted in an AMTI knee wear simulator: a low intensity and a high intensity. Wear coefficients incorporating contact pressure, sliding distance, and cross-shear were generated by inverse FEA using the experimentally measured volume of wear loss as the target outcome measure. The FE models and wear coefficients were validated by predicting wear in a mobile bearing UKA design. Highly crosslinked polyethylene (XLPE). Two FEA models were constructed involving TKA and UKA XLPE inserts with different loading patterns and knee kinematics conducted in an AMTI knee wear simulator. Wear coefficients were generated by inverse FEA. Results. Predicted wear rates were within 5% of experimental wear rates during validation tests. Unicompartmental mobile bearing back-side wear accounted for 46% of the total wear in the mobile bearing. Wear during the swing phase was 38% to 44% of total wear. Discussion & Conclusions. Crosslinking polyethylene primarily decreased (by nearly 10-fold) the wear generated by cross-shear. This result can be explained by the reduced propensity of crosslinked polyethylene molecules to orient in the dominant direction of sliding. A highly crosslinked fixed-bearing polyethylene insert can provide high wear performance without the increased risk for mobile
Background and Purpose of Study. The Valgus knee in total knee Arthroplasty, is considered a more demanding procedure, often with ligament balance a greater challenge than seen with neutral or Varus knees. It has also frequently been suggested that prostheses with higher levels of constraint be used to avoid late-onset instability. Various lateral release techniques have also been suggested in the literature. This study is aimed at assessing the outcomes of an unconstrained, rotating platform designed prosthesis, the LCS, using our technique, in the management of severe valgus deformity. Methods. 44 knees in 42 patients with a pre-operative valgus deformity of more than 10 degrees were included in our retrospective series. We analyzed the radiographs for the degree of correction, the angle of tibial tray implantation, and femoral implantation angle, tibial slope, as well as the presence (or degree) of lift off and any complications were noted. In this group, 7 had a Valgus deformity of greater than 25 degrees, with a mean Valgus deformity of 17,36 degrees. The mean age at operation was 65. Clinical and radiological analysis was done Pre-hospital discharge and again post-operatively 6 weeks. Results. The mean coronal alignment was corrected from 17,36 degrees to 5 degrees of Valgus post operatively. 2 knees were corrected past neutral to varus alignment. There was 1 case of bearing spin out experienced early on in the series. The mean tibial implant angle was 1,7 degrees from neutral. Lift off in the early post-operative X-rays was seen in 6 patients, however at 3 month follow up the knees appeared to be well balanced. There were no infections or revisions for wear, one re-operation for
A review of current literature describes varying 10-year survival rates for the Oxford Unicompartmental Knee Replacement (Biomet Orthopedics Inc, Warsaw, Ind). Application of rigorous indications and meticulous surgical technique are two factors considered to reduce revision rates. A retrospective case-note review was conducted for 96 patients (128 knees) aged 42–89 (mean 57) who had an Oxford unicompartmental knee replacement for medial compartment osteoarthritis between January 2000 and January 2011. All procedures were performed, or directly supervised, by one 5 surgeons. The aim of the study was to ascertain the rate of revision to bicompartmental knee replacement and any associated contributory factors. Of the 128 unicompartmental knees, 10.9% were revised to either mobile- or fixed-bearing total knee replacements due to septic (0.5%) and aseptic (1.5%) loosening, patello-femoral pain (3.9%), periprosthetic fracture (0.8%) and
Bi-unicondylar arthroplasty (Bi-UKA) is a bone and anterior cruciate ligament (ACL)-preserving alternative to total knee arthroplasty (TKA) when the patellofemoral joint is preserved. The aim of this study is to investigate the clinical outcomes and biomechanics of Bi-UKA. Bi-UKA subjects (n = 22) were measured on an instrumented treadmill, using standard gait metrics, at top walking speeds. Age-, sex-, and BMI-matched healthy (n = 24) and primary TKA (n = 22) subjects formed control groups. TKA subjects with preoperative patellofemoral or tricompartmental arthritis or ACL dysfunction were excluded. The Oxford Knee Score (OKS) and EuroQol five-dimension questionnaire (EQ-5D) were compared. Bi-UKA, then TKA, were performed on eight fresh frozen cadaveric knees, to investigate knee extensor efficiency under controlled laboratory conditions, using a repeated measures study design.Aims
Methods
Ultra-high molecular weight polyethylene (UHMWPE) is a commonly used as bearing material in joint replacement devices. UHMWPE implants can be hard to see on a standard X-ray because UHMWPE does not readily attenuate X-rays. Radiopaque UHMWPE would enable direct imaging of the bearing both during and after surgery, providing in vivo assessment of
Purpose. We analyzed the frequency, causes and treatment of dislocation of polyethylene insertion among various causes of failure of unicompartmental knee arthroplasty. Materials and Methods. We studied 69 knee joints of 65 patients who underwent medial unicompartmental knee arthroplasty using from June 2005 to December 2010. Average age was 61.8 and average follow-up period was 20 months. Radiologic results evaluated preoperative and postopertative mechanical axis deviation, tibio-fibular angle and postoperative implant position in total 69 knees(A group), failed 15 cases(B group) and 10 cases(C group) of
Background: Durable long-term independent results with the Low Contact Stress rotating-platform (mobile-bearing) and the Insall Burstein-II (fixed-bearing) total knee prostheses have been reported, but no studies describing either the mid-term or long-term results and comparing the two prostheses are available, to our knowledge. Methods: Thirty-two patients who had bilateral arthritis of the knee with similar deformity and preoperative range of motion on both sides and who agreed to have one knee replaced with a mobile-bearing total knee design and the other with a fixed-bearing design were prospectively evaluated. Comparative analysis of both designs was done at a mean follow-up period of six years, minimizing patient, surgeon, and observer-related bias. Clinical and radiographic outcome, survival, and complication rates were compared. Results: Patients with osteoarthritis had better function scores and range of motion compared with patients with rheumatoid arthritis. However, with the numbers available, no benefit of mobile-bearing over fixed-bearing designs could be demonstrated with respect to Knee Society scores, range of flexion, subject preference, or patellofemoral complication rates. Radiographs showed no difference in prosthetic alignment. Two knees with a mobile-bearing prosthesis required a reoperation: one had an early revision because of
To report mid- to long-term results of Oxford mobile bearing domed lateral unicompartmental knee arthroplasty (UKA), and determine the effect of potential contraindications on outcome. A total of 325 consecutive domed lateral UKAs undertaken for the recommended indications were included, and their functional and survival outcomes were assessed. The effects of age, weight, activity, and the presence of full-thickness erosions of cartilage in the patellofemoral joint on outcome were evaluated.Aims
Methods
Purpose. To identify the causes of failure after unicompartmental knee arthroplasty (UKA), and to evaluate considerations for surgical procedures and the results of revision total knee arthroplasty (TKA) performed after failure of UKA. Materials and Methods. Eight hundreds and fifty-two cases of UKA were performed from January 2002 to June 2011. Forty-seven cases of failures after UKA were analyzed for the cause of the failures, and thirty-five cases of revision TKA after failure were analyzed for the operative findings and surgical technique. The clinical results were measured for thirty cases which were followed-up on at least two years after TKA. The mean duration of follow-up was four years and one month after revision TKA and the mean patient age at the time of surgery was sixty-five years. Results. For the cause of failures after UKA, there were twenty-two cases of early loosening of prosthesis, seventeen cases of simple mobile
Mobile bearings in knee arthroplasty carry the theoretical advantage of lower wearing prostheses. However, dislocating mobile bearings can be a significant issue in mobile bearing knee replacement arthroplasty. Our aim is to report our design alterations to the insert to address bearing spinout. A total of 598 RBK mobile bearing total knee arthroplasties were performed by the senior author over a 10–year period. The standard bearing was subjected to three design changes to address spinout and increase flexion range. The first alteration involved a deeper dish with a higher anterior lip. Subsequently, a reduced footprint insert (RFI) was created. The final modification was a shaved off posterior rim to allow for greater flexion (high flex). An overall
About ten years ago we introduced sophisticated instrumentation and an increased range of component sizes for the Oxford unicompartmental knee replacement (UKR) to facilitate a minimally invasive surgical (MIS) approach. The device is now routinely implanted through an incision from the medial pole of the patella to the tibial tuberosity. This has resulted in a more rapid recovery and an improved functional result. As the access to the knee is limited there is a concern that the long term results may be compromised. The aim of this study was to determine the 10 year survival. A prospective follow up of all Phase 3 minimally invasive Oxford UKR implanted by two senior authors (DWM &
CAFD) has been undertaken. So far 1015 UKRs have been implanted for anteromedial osteoarthritis. All patients received a cemented implant through a MIS approach and were followed up prospectively by an independent observer. The data was collected prospectively regarding pre-operative status, complications and clinical as well as functional outcome at predetermined intervals. The average age of patients was 66.4 years (range: 33 – 88) with mean Oxford Knee Score 41 (SD: 7.9) at the time of last follow up, Knee Society Score (objective) of 84 (SD: 13) and Knee Society Score (functional) of 83 (SD: 21). At ten years the survival of this cohort is 96%. There were 22 revisions including 7 for progression of arthritis, 5 for infection, 5 for
Purpose. To identify the incidence and reasons for revision of the Oxford prosthesis (OXF) in New Zealand. Methods. Review and compare UKA and TKA data including patient-generated Oxford scores after operation. Results. 105 surgeons performed 3,624 OXF (66.5% of all UKA). UKA made up 12.8% of all knee arthroplasties. There were 216 OXF revisions and revision rate (RR) of 1.39 per 100 component-years (p100cy); for UKA this was 1.42 p100cy, and for TKA 0.54 p100cy (OXF vs TKA p< 0.0001). The indications for OXF revisions were unexplained pain (38.0%); aseptic loosening (38.0%);
Introduction: Unicompartmental knee replacement (UKR) is a popular alternative to total knee replacement (TKR) in medial compartment disease. Early problems include
Introduction. The options for the treatment of the young active patient with unicompartmental symptomatic osteoarthritis and pre-existing Anterior Cruciate Ligament (ACL) deficiency are limited. Patients with ACL deficiency and end-stage medial compartment osteoarthritis are usually young and active. The Oxford Unicompartmental Knee Replacement (UKA) is a well established treatment option in the management of symptomatic end-stage medial compartmental osteoarthritis, but a functionally intact ACL is a pre-requisite for its satisfactory outcome. If absent, high failure rates have been reported, primarily due to tibial loosening. Previously, we have reported results on a consecutive series of 15 such patients in whom the ACL was reconstructed and patients underwent a staged or simultaneous UKA. The aim of the current study is to provide an update on the clinical and radiological outcomes of a large, consecutive cohort of patients with ACL reconstruction and UKA for the treatment of end-stage medial compartment osteoarthritis and to evaluate, particularly, the outcome of those patients under 50. Methods. This study presents a consecutive series of 52 patients with ACL reconstruction and Oxford UKA performed over the past 10 years (mean follow-up 3.4 years). The mean age was 51 years (range: 36–67). Procedures were either carried out as Simultaneous (n=34) or Staged (n=18). Changes in clinical outcomes were measured using the Oxford Knee Score (OKS), the change in OKS (OKS=Post-op − Pre-op) and the American Knee Society Score (AKSS). Fluoroscopy assisted radiographs were taken at each review to assess for evidence of loosening, radiolucency progression, (if present), and component subsidence. Results. Five year survival was 90%. At last follow-up, the mean outcome scores for the group were: OKS 40 (SD: 8.3), objective AKSS 77 (SD: 16.1), functional AKSS 93 (SD: 13.7) and OKS of 11. Complications were recorded in three patients, (one early infection requiring a two-stage revision, a
Aim: This paper presents the 20-year survival and 10-year clinical follow-up results from the entire series of all medial Oxford meniscal bearing unicompartmental knee arthroplasties performed in a single centre in Sweden, between 1985 and 2004. Method: Patients were contacted and information about the state of the knee collected. Revision surgery was used in the life-table survival analysis performed. For the entire cohort clinical follow up at 10-years is routinely performed, using the HSS knee score. Results: The entire group comprised of 683 knees in 572 patients. The mean age at implantation was 69.7 (range 48–94). There had been 30 revision procedures: 8 for lateral arthrosis, 7 for component loosening, 3 for infection, 6 for
Introduction. Radiolucencies beneath the tibial component are well recognized in knee arthroplasty; the aetiology and significance are poorly understood. Non-progressive narrow radiolucencies with a sclerotic margin are thought not to be indicative of loosening. Factors which decrease the incidence of radiolucencies include cementless fixation and the use of pulse lavage. Leg/component alignment or BMI do not influence radiolucency. We are not aware of any studies that have looked at the effect of load type on radiolucency. The Oxford domed lateral tibial component was introduced to decrease the
Introduction: Oxford Unicompartmental knee arthroplasty (UKA) is now performed using a minimally invasive surgical (MIS) technique. Although early results are encouraging, the studies assessing outcome could be criticised for the restricted number of patients and centres involved. A multi-centre follow-up of patients is required to confirm the preliminary findings. Aim: To examine early clinical outcome in patients with minimally invasive Oxford medial UKA using a multi-centre, multi-surgeon design. Materials and Methods: This prospective study was carried out in three centres with involvement of six surgeons. All patients undergoing cemented Oxford UKA for medial OA using MIS were included. 231 consecutive UKAs with a minimum follow up of 2 years (mean: 2.84) were assessed using objective and functional Knee Society Score (KSS). Results: There were 108 females and 102 males (21-bilateral) with average age of 66.8 years (42 – 86). No significant difference was noted between various age groups or between different surgeons. Three knees were revised: one for infection, one for unexplained pain and one for
To identify frequency and patterns of Oxford Phase 3 UKA failure in New Zealand through analysis of national primary and revision data. Retrospective audit examining all revision Oxford Phase 3 UKAs recorded in the New Zealand National Joint Register from January 2000 to October 2003 were analysed along with surgeons’ clinical notes and patient x-rays. Seventy-three Orthopædic Surgeons performed 1216 Oxford UKAs. The average age was 66.4 years (range 35–94). Osteoarthritis was the primary diagnosis for 1163 (96%) patients. Mean time to revision was 437 days (14.4 months). The early revision rate was 2.2% (n=27). The most common reasons for revision were aseptic loosening (n=7, 26%),