Aims. The primary objective of this study was to compare short-term implant survival between cemented and cementless fixation for the mobile-bearing Oxford medial unicompartmental knee arthroplasty (UKA) across various age groups. The secondary objectives were to compare modes of failure and to evaluate patient-reported outcomes. Methods. A total of 25,762 patients, comprising 8,022 cemented (31.1%) and 17,740 cementless (68.9%) medial UKA cases, were included from the Dutch Arthroplasty Register. Patient stratification was performed based on age: < 50 years, 50 to 59 years, 60 to 69 years, and ≥ 70 years. Survival rates and hazard ratios were calculated. Modes of failure were described and postoperative change in baseline for the Oxford Knee Score and numerical rating scale for pain at six and 12 months’ follow-up were compared. Results. The 2.5-year implant survival rate of cementless UKA was significantly higher compared to cemented UKA in patients aged younger than 60 years (age < 50 years: 95.9% (95% CI 93.8 to 97.3) vs 90.9% (95% CI 87.0 to 93.7); p = 0.007; and 50 to 59 years: 95.6% (95% CI 94.9 to 96.3) vs 94.0% (95% CI 92.8 to 95.0); p = 0.009). Cemented UKA exhibited significantly higher revision rates for tibial loosening (age < 50 and 60 to 69 years), while cementless UKA was associated with higher revision rates for periprosthetic fractures (age ≥ 60 years). Patient-reported outcomes were similar between both fixation techniques, irrespective of age. Conclusion. Cementless fixation resulted in superior short-term implant survival compared to cemented fixation among younger patients undergoing Oxford mobile-bearing medial UKA. Distinct failure patterns between fixation techniques emerged across various age groups, with revisions for tibial loosening being associated with cemented UKA in younger patients, while revisions for periprosthetic fractures were specifically identified among elderly patients undergoing cementless UKA. Cite this article: Bone Joint J 2025;107-B(3):329–336

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

The Oxford medial unicompartmental knee replacement was designed to reproduce normal mobility and forces in the knee, but its detailed effect on the patellofemoral joint has not been studied previously. We have examined the effect on patellofemoral mechanics of the knee by simultaneously measuring patellofemoral kinematics and forces in 11 cadaver knee specimens in a supine leg-extension rig. Comparison was made between the intact normal knee and sequential unicompartmental and total knee replacement. Following medial mobile-bearing unicompartmental replacement in 11 knees, patellofemoral kinematics and forces did not change significantly from those in the intact knee across any measured parameter. In contrast, following posterior cruciate ligament retaining total knee replacement in eight knees, there were significant changes in patellofemoral movement and forces. The Oxford device appears to produce near-normal patellofemoral mechanics, which may partly explain the low incidence of complications with the extensor mechanism associated with clinical use

This prospective study describes the complications and survival of the first 688 Phase 3 Oxford medial unicompartmental knee replacements implanted using a minimally-invasive technique by two surgeons and followed up independently. None was lost to follow-up. We had carried out 132 of the procedures more than five years ago. The clinical assessment of 101 of these which were available for review at five years is also presented. Nine of the 688 knees were revised: four for infection, three for dislocation of the bearing and two for unexplained pain. A further seven knees (1%) required other procedures: four had a manipulation under anaesthesia, two an arthroscopy and one a debridement for superficial infection. The survival rate at seven years was 97.3% (95% confidence interval 5.3). At five years, 96% of the patients had a good or excellent American Knee Society score, the mean Oxford knee score was 39 and the mean flexion was 133°. This study demonstrates that the minimally-invasive Oxford unicompartmental knee replacement is a reliable and effective procedure

Abstract. Background. Since 2012 we have routinely used the cementless Oxford medial unicompartmental knee arthroplasty (mUKA), with microplasty instrumentation, in patients with anteromedial osteoarthritis (AMOA) meeting modern indications. We report the 10-year survival of 1000 mUKA with minimum 4-year follow-up. Methods. National Joint Registry (NJR) surgeon reports were interrogated for each senior author to identify the first 1,000 mUKAs performed for osteoarthritis. A minimum of 4 years follow-up was required. There was no loss to follow-up. The NJR status of each knee was established. For each mUKA revision the indication and mechanism of failure was determined using local patient records. The 10-year implant survival was calculated using life-table analysis. Results. The 1,000 mUKA cohort represented 55% of all primary knee replacements in the period, with an average age of 67.7 years and a 54%/46% male/female split. There were 17 revisions (11 for arthritis progression, 4 infections, 1 dislocation and 1 aseptic loosening). The 10-year survival was 98% (44 at risk in 10th year). One patient sustained a periprosthetic fracture at 3 weeks, treated with buttress plate fixation. Discussion. This is the first detailed series reporting the long-term outcome of the cementless Oxford mUKA implanted using microplasty instrumentation. There was a low failure rate, with only one revision for aseptic loosening. Lateral progression was the commonest cause for revision, with an incidence of 1%. This report provides evidence that the combination of evidence-based indications, well-designed instrumentation and cementless fixation can provide excellent long-term survival for the Oxford mUKA in treating AMOA

To report a 15-year survival analysis of the Oxford Medial Unicompartmental Knee Arthroplasty (Oxford UKA) in an independent series. We report the results of a series of 420 Oxford UKAs performed between 1983 and 2000. Indications for surgery were primary antero-medial osteoarthritis of the knee with an intact ACL, correctable varus deformity of < 15° and < 15° fixed flexion deformity. The state of the patello-femoral joint was not used as a selection criterion. Patients were contacted by a postal questionnaire or by telephone. The outcome of all 420 knees was established, with none lost to follow-up. Seventy-six knees were in patients who had died and the state of each arthroplasty was determined from hospital and GP records. Seventeen patients (4%) had required revision. Indications for revision were lateral compartment arthrosis (7), component loosening (4), bearing dislocation (4) and infection (2). There were no failures for polyethylene wear. Cumulative survival at 15 years was 94.3% [95% CI 3.8%]. The worst case scenario was 94.3% as none were lost to follow-up. The results from an independent series are important, as they avoid bias. The 15-year results of this independent series are better than any other reported series of unicompartmental device at 15 years and as good as the published independent 15 year survival results for total knee arthroplasty. The data illustrates that excellent long-term survival can be achieved with the Oxford UKA, allowing patients to benefit from the advantages that unicompartmental arthroplasty offers. We believe that provided patients are selected appropriately, this device provides the treatment of choice for anteromedial osteoarthritis of the knee

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 bearing dislocations, one medial tibial collapse and one lateral osteoarthritis occurred, so the complication rate was 6.1% (5/82). Among the 3 cases of bearing dislocation, 2 cases were resolved by replacing with a thicker bearing and 1 case was converted to TKA due to repeated dislocation. One case of medial tibia collapse and one lateral osteoarthritis were converted to total knee arthroplasty (TKA). All clinical outcomes measured by KSS scores and WOMAC score showed a statistically significant difference (p<0.001). The 10 year cumulative survival rate using Kaplan-Meier survival method was 94.7% (95% CI: 88.7%–100%). Conclusion. The clinical outcomes and the survival rate of young asian patients less than 60 years of age who underwent Oxford medial UKA showed good clinical results and a good survival rate in the mid-term results. However, long-term follow-up is needed for more reliable clinical results

The purpose of this study was to establish the long-term clinical outcome of the Oxford Medial Unicompartmental Knee Arthroplasty (UKA). Methods: A continuous series of 420 patients underwent medial Oxford UKA. Indications were anteromedial osteoarthritis with full thickness lateral compartment cartilage, a functioning anterior cruciate ligament and correctable varus deformity. Survival analysis with all cause revision as the endpoint was carried out for the entire group. At the time of this study 121 were still alive at 10 years and pre/post-operative 10-year clinical data had been prospectively recorded for them from which the AKS and HSS scores were calculated. Results: Seventeen patients required revision (4%) and the fifteen year survival rate was 94.3% (95% CI 85.6 - 100%). At ten years AKS and HSS scores were: AKSS (Knee) pre 30 / post 90, AKSS (Function): pre 42/ post 69 and HSS pre 56/ post 86. The differences were statistically significant (p< 0.01). Discussion and Conclusion: We conclude that providing careful patient selection is maintained, meniscal bearing medial unicompartmental knee arthroplasty has clinical and survival results comparable to modern total knee arthroplasty. The advantages of lower morbidity and earlier return to function, enhanced by the introduction of minimally invasive techniques may make this the treatment of choice for suitable patients with anteromedial osteoarthritis of the knee

The purpose of the study was to investigate the outcome of Oxford medial unicompartmental knee replacement (UKR) in patients over 70 years old and also to assess their ability to kneel. We identified from our prospectively collected knee database 90 patients (98 knees) undergoing Oxford medial UKR who were 70 years or older on the day of surgery. Oxford Knee Scores (OKS) were collected pre-operatively and also post-operatively at the following intervals: 3 months, 6 months, 1 year, 2 years, 5 years and then annually after this. The mean patient age at surgery was 73.2 years (range 70.2 – 84.3 years). The OKS pre-operatively had a mean of 35.8/60 (range 22-55) and improved to 23.6/60 post-operatively (range 14-34). Patient follow-up was 44.3 months and ranged from 12-111 months. Two patients were lost to follow-up, 1 was converted to a total knee replacement and 3 died of causes unrelated to the knee surgery. 91.7% of patients still had their original prostheses at last follow-up. Forty percent of patients stated they were able to kneel pre-operatively which improved to 50.2% postoperatively. This was consistent throughout all the follow up intervals that were assessed. Specific kneeling score from the OKS showed no statistically significant change with a mean of 3.94/5 pre-operatively and a mean of 3.54 averaged over all the post-operative follow up intervals. We conclude that medial Oxford UKR is a reliable operation in patients over 70 years old. Previous studies include a younger age group which potentially encourages the less familiar surgeon to use a UKR for the young active patient but continue with a total knee arthroplasty for the older patient. Our study suggests age should not be a factor when considering performing Oxford UKR. Ability to kneel is not altered significantly by UKR in this age group

We describe the outcome of a series of 124 Oxford meniscal-bearing unicompartmental arthroplasties carried out for osteoarthritis of the medial compartment. They had been undertaken more than ten years ago in a non-teaching hospital in Sweden by three surgeons. All the knees had an intact anterior cruciate ligament, a correctable varus deformity and full-thickness cartilage in the lateral compartment. Thirty-seven patients had died; the mean time since operation for the remainder was 12.5 years (10.1 to 15.6).

Using the endpoint of revision for any cause, the outcome for every knee was established. Six had been revised (4.8%). At ten years there were 94 knees still at risk and the cumulative survival rate was 95.0% (95% confidence interval 90.8 to 99.3). This figure is similar to that reported by the designers of the prosthesis and to the best published results for independent series of total knee replacement. If patients are selected appropriately, this implant is a reliable treatment for anteromedial osteoarthritis of the knee.

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 bearing dislocation in 8 cases (4.3%). Tibial components loosenig in 3 cases (1.6%). Femoral components loosening in 2 cases (1.1%). The average time of meniscal bearing dislocation was 11.3 (3–24)months postoperatively. Six cases returned to the predislocation level of activity with the insertion of thicker bearings and 2cases required TKR conversion.

Conclusion: Minimally invasive unicompartmental knee arthroplasty(Oxford Uni^®) provides rapid recovery, good pain relief and excellent function quite suitable to Korean life-style. But given the high complicate rate in mid-term results. Oxford Uni^® gives less reliability compared with TKR.

We present a comparison of the results of the Oxford unicompartmental knee arthroplasty in patients younger and older than 60 years of age. The ten-year all-cause survival of the < 60 years of age group (52) was 91% (95% confidence interval (CI) 12), while in the ≥ 60 years of age group (512), the figure was 96% (95% CI 3). For the younger group, the mean Hospital for Special Surgery score at ten-year follow-up (n = 21) was 94 of 100, compared with a mean of 86 of 100 for the older group (n = 135). The results show that the Oxford unicompartmental arthroplasty can achieve ten-year results that are comparable to total knee arthroplasty in patients < 60 years of age. We conclude that for patients aged over 50, age should not be considered a contraindication for this procedure.

Background

Unicompartmental knee arthroplasty provides a good alternative to total knee arthroplasty in patients with isolated medial compartment osteoarthritis. There has been variable reporting in the literature as to whether age and sex affect the survival of unicompartmental knee arthroplasty. The aim of this study was to determine whether age and sex were predictors of failure for the Oxford unicompartmental knee arthroplasty.

Background

Unicompartmental knee arthroplasty provides a good alternative to total knee arthroplasty in patients with isolated medial compartment osteoarthritis. There has been variable reporting in the literature as to whether age and sex affect the survival of unicompartmental knee arthroplasty.

Background: Within the scope of the EU project EUPHORIC a methodology for direct comparison of different datasets was developed and applied on a sample of implants, among them the Oxford Unicompartmental Knee Arthroplasty (Oxford Uni). The aim was to identify potential bias factors inherent in the datasets and evaluate the outcome achieved with this implant.

Materials and Methods: A structured comparison was performed of data published on the revision rate of the Oxford Unicompartmental prosthesis. Both clinical follow-up studies published in Medline-listed journals and worldwide Register data were included. The data were stratified with regard to potential influence factors like the individual research groups or the geographical origin of the papers.

Results: A major proportion of the published data, between 50 and 75%, depending on the method of calculation, comes from studies including the developing institution in Oxford. The results published by this group deviates statistically significantly from the reference datasets from Register data or independent research groups. Data from the developing hospital show mean revision rates that are 4.4 times lower than those based on worldwide Register data, and 2.74 times lower than in independent studies. As opposed to this, independent studies on average publish data that are reproducible in Register data.

Conclusion: A conventional meta-analysis of clinical studies is significantly affected through the influence of the developing institution and is therefore subject to a bias. Neither through arthroplasty Register outcome data nor by other research groups that have disclosed outcome information on the Oxford Uni can the excellent results be reproduced that were published by the inventors.

Compared to other implants for unicompartmental knee arthroplasty in worldwide arthroplasty Registers, the Oxford Uni shows good results.

For the assessment of the outcome of implants, register data are to be rated superior and, in terms of reference data for the detection of potential bias factors in the clinical literature, can provide an essential contribution for scientific meta-analyses.

Aims

Our aim was to examine the clinical and radiographic outcomes in 257 consecutive Oxford unicompartmental knee arthroplasties (OUKAs) (238 patients), five years post-operatively.

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.

Patellofemoral joint degeneration is often considered a contraindication to medial unicompartmental knee replacement. We examined the validity of this preconception using information gathered prospectively on the intra-operative status of the patellofemoral joint in 824 knees in 793 consecutive patients who underwent Oxford unicondylar knee replacement for anteromedial osteoarthritis. All operations were performed between January 1998 and September 2005. A five-point grading system classified degeneration of the patellofemoral joint from none to full-thickness cartilage loss. A subclassification of the presence or absence of any full-thickness cartilage loss was subsequently performed to test selected hypotheses. Outcome was evaluated independently by physiotherapists using the Oxford and the American Knee Society Scores with a minimum follow-up of one year.

Full-thickness cartilage loss on the trochlear surface was observed in 100 of 785 knees (13%), on the medial facet of the patella in 69 of 782 knees (9%) and on the lateral facet in 29 of 784 knees (4%). Full-thickness cartilage loss at any location was seen in 128 knees (16%) and did not produce a significantly worse outcome than those with a normal or near-normal joint surface. The severity of the degeneration at any of the intra-articular locations also had no influence on outcome.

We concluded that, provided there is not bone loss and grooving of the lateral facet, damage to the articular cartilage of the patellofemoral joint to the extent of full-thickness cartilage loss is not a contraindication to the Oxford mobile-bearing unicompartmental knee replacement.

Good mid-term results of Oxford UKA (OxUNI) for anteromedial osteoarthritis (OA) were reported. The designers of prosthesis reported a 98% 10-year survival rate for a combined series of phase I and II, and these findings were supported by published results from other series, with 10-year survival ranging from 91% to 98%. In order to obtain good results, the designers of this prosthesis mentioned the importance of adhering to strict indication for OxUNI, especially only for OA cases with intact anterior cruciate ligament (ACL). OxUNI combined with ACL reconstruction (ACLR) is a viable treatment option for only young active patients, in whom the ACL has been primarily ruptured. On the other hand, it was not clear whether the result of OxUNI combined with ACLR for OA with secondary ruptured ACL was good. In this study we compare the short-term results of OxUNI combined with ACLR for OA with secondary ruptured ACL with that for usual OA with intact ACL.

382 OxUNI were performed at two hospitals by one surgeon between January 2002 and August 2005. Among those, 367 cases, followed over two years postoperatively (272 patients, women: 283, men: 84) were assessed. Follow up ratio was 96.1%. The mean patient age at the time of surgery was 72.0 (47~93) years. The mean follow-up period was 39.3 (24~67) months. Thirty three knees of OA were treated with OxUNI combined with ACLR, by using synthetic graft. Clinical results were assessed by the Oxford Knee Score (OKS) and active range of motion (ROM). Patients are asked a series of 12 questions, and their response scores range from 0 (worse) to 4 (best) for each, yielding an overall score range of 0–48. All living patients were contacted, and the status of the implant was established at the time of last follow from hospital records. We evaluate the survival rate for OxUNI with or without ACLR, using the endpoint of revision for any reason.

The pre-and postoperative clinical scores were compared using the paired Student’s t-test. Survivor-ship curves were constructed using the Kaplan-Meier method, and survivorship between groups was compared using logrank and Wilcoxon methods. All analyses were performed using 95% confidence intervals and a P value of < 0.05 was considered significant.

The mean OKS at final follow-up was 42.1 (preoperative; 21.7), and the mean active ROM was 125.2° (preoperative; 113.4°). OKS and active ROM were significantly improved. There were no significant differences in OKS and active ROM between OxUNI with ACLR and OxUNI with intact ACL. Fourteen knees among 367 knees were revised; nine for loosening of tibial component, four for dislocation of bearing and one for progression of lateral OA. Overall 5-year survival rate was 95.6%. When survival rate was assessed separately with or without ACLR, that of OxUNI with intact ACL was 96.7% and that of OxUNI with ACLR was 83.8%. There was significant worse survival rate between the two groups (P=0.0071).

The 5-year survival rate for OxUNI with intact ACL was 96.7%, which was equivalent to those of original series from Oxford. However, 5-year survival rate for Oxford UKA with ACLR was 83.8% in our series. Four knees in nine of loosening of tibial component were replaced by OxUNI combined with ACLR. Therefore, even if ACL was reconstructed, the results of OxUNI for OA with secondary ruptured ACL was proved to be pessimistic.

There was significantly worse survival rate for OxUNI with ACLR, compared with OxUNI with intact ACL. So we conclude that combined ACL reconstruction and OxUNI for anteromedial OA with secondary ruptured ACL is not recommended, which must be treated with TKA.