Initial Experience With the Oxford Unicompartmental Knee Arthroplasty

doi:10.1016/j.arth.2010.02.007

The Journal of Arthroplasty

Volume 26, Issue 2, February 2011, Pages 192-197

https://doi.org/10.1016/j.arth.2010.02.007 Get rights and content

Abstract

Our initial experience with mobile bearing medial compartment unicompartmental arthroplasty (UKA) is presented to highlight lessons that have been learned to avoid short-term failures. Consecutive cases of the Oxford medial UKA performed between February 2001 and April 2006 were reviewed to derive those cases that were revised to total knee arthroplasty (TKA). There were 545 patients available with mean age and body mass index of 65.0 and 30.1, respectively. At final follow-up, 32 patients were revised for lateral compartment arthritis, aseptic component loosening, persisting medial or anterior pain and dislocated meniscal bearing. Revisions were performed with primary unconstrained TKA implants with no stems or wedges required. Our results seem to reflect those seen in registries confirming an earlier higher revision rate and highlight the technical issues of overstuffing the compartment, inadequate cementation technique, and strict adherence to patient selection.

Section snippets

Methods

All cases of the Oxford medial UKA phase III were included for study performed between February 2001 and April 2006. The surgical technique included a small medial arthrotomy made possible by the Oxford phase III instrumentation and implants. All participating surgeons but one had attended the company-sponsored Oxford user course preceding their first case. The study was performed in a university-affiliated teaching institution and was approved by our Research Ethics Board. All patients

Results

Five hundred forty-five consecutive cases were available for review between February 2001 and April 2006 to yield a study cohort all with minimum 2-year follow-up and mean follow-up of 45.8 months (range, 27-89 months). The cohort was 57.4% female with mean age of 65.0 ± 10.2 SD (range, 38-89) and mean body mass index of 30.1 ± 5.3 (range, 19.1-52.5). Ten patients (1.9%) were deceased at the time of final review.

At time of final follow-up, 31 patients had come to revision arthroplasty surgery,

Discussion

We were unable to generate the same positive survivorship numbers previously reported by the designing surgeons or some other groups. Murray et al [15] and Svard and Price [14] have reported 10-year survivorships of 98% (95% confidence interval, 93%-100%) and 95.0% (95% confidence interval, 90.8-99.3), respectively, for the Oxford knee. This is less favorable in national registries where revision rates closer to 5% at 3 years are more commonplace, which is double the early revision rate of TKA.

Conclusion

Our initial experience is reported to highlight the pitfalls we encountered that may be of value to others who consider mobile bearing UKA for the treatment of medial compartment osteoarthritis. Although not reported here, most patients have been satisfied with emphasis on less perioperative morbidity and effective symptom control. Our results seem to reflect those seen in registries (and consistent with most UKA) of an earlier higher revision rate but go further by offering a glimpse as to the

Acknowledgments

The authors wish to thank Anna Fazekas for her help with data collection and statistical analysis. Steve Doucette assisted with multivariate analysis and survivorship analysis and Sarah Plamondon assisted with manuscript preparation.

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Cited by (38)

New instrumentation system for cementless mobile-bearing unicompartmental knee arthroplasty improves surgical performance particularly for trainees
2021, Knee
Mobile-bearing medial-unicompartmental knee arthroplasty (mUKA) has a documented learning curve. New instrumentation has been designed with the aim of reducing the technical challenges of this procedure. The primary aim of this study was to evaluate the technical performance of mUKA using new (Microplasty) versus older (Phase III) instrumentation, performed by expert surgeons and trainees. Secondary aims were to evaluate functional outcome and mid-term survivorship.
A time-based comparative cohort study was performed between 2009 and 2015 at a high-volume centre. 273 patients (273 knees, 49.5% female) of mean age 67.8 (standard deviation 10.1) years underwent mUKA. 153 (56.0%) procedures used Microplasty instruments and 120 procedures (44.0%) used Phase III instruments.
Non-optimal bearing usage was less frequent with Microplasty than Phase III instruments (24 knees [15.7%] versus 33 knees [27.5%], p = 0.024), with differences due to improved trainee performance. Femoral component sagittal alignment outliers were less frequent with Microplasty, but this was not statistically significant (9 knees [5.9%] versus 13 knees [10.8%], p = 0.18). Post-operative Oxford Knee Scores (OKS) were better with Microplasty (median 42 points [interquartile range 38–44]) compared to Phase III (median 39.5 points [IQR 33–44]), which was statistically significant (p = 0.023), but not clinically meaningful. The overall 5-year Kaplan-Meier (KM) survival estimate was 99.3% (95% CI 97.0–99.8%), with no differences between Microplasty and Phase III instrumentation.
New instrumentation improved the reliability of the proximal tibial resection in trainees. Further research is warranted to investigate whether Microplasty instrumentation shortens the learning curve for medial UKA.
Valgus Subsidence of the Tibial Component Caused by Tibial Component Malpositioning in Cementless Oxford Mobile-Bearing Unicompartmental Knee Arthroplasty
2019, Journal of Arthroplasty
Valgus subsidence (VS) of the tibial component is a rare complication of unicompartmental knee arthroplasty (UKA), and surgeons might consider revision surgery. The present study aimed to identify the factors related to VS of the tibial component after cementless Oxford mobile-bearing UKA.
The study included 120 patients who underwent Oxford mobile-bearing UKA using a cementless tibial component in our center between September 2015 and September 2016. Six showed VS of >2° after surgery. Patients were stratified into 2 groups according to the occurrence of VS of the tibial component (VS group, n = 6; no-subsidence group, n = 114). Postoperative radiographic evaluations were conducted to assess the varus/valgus alignment, rotation, and mediolateral position of the tibial and femoral components. The Oxford Knee Score (OKS) was assessed at 3, 6, and 12 months postoperatively. Positional parameters and sequential change in OKS were compared between the two groups using unpaired t-test (P < .05, statistically significant).
At 3 months postoperatively, an average VS of 3.4° in the VS group was observed, with a significant decrease in OKS. VS was associated with a significantly more medial position and external rotation of the tibial component. After 3 months, VS stopped, and the OKS gradually improved without revision surgery.
VS might be caused by the malpositioning of the tibial component. VS of the tibial component after UKA appears to stop, with simultaneous pain relief, even without revision after 3 months postoperatively.
The Interaction of Caseload and Usage in Determining Outcomes of Unicompartmental Knee Arthroplasty: A Meta-Analysis
2017, Journal of Arthroplasty
Outcomes after unicompartmental knee arthroplasty (UKA) are variable and influenced by caseload (UKA/y) and usage (percentage of knee arthroplasty that are UKA), which relates to indications. This meta-analysis assesses the relative importance of these factors.
MEDLINE (Ovid), Embase (Ovid), and Web of Science (ISI) were searched for consecutive series of cemented Phase 3 Oxford medial UKA. The primary outcome was revision rate/100 observed component years (% pa) with subgroup analysis based on caseload and usage.
Forty-six studies (12,520 knees) with an annual revision-rate ranging from 0% to 4.35% pa, mean 1.21% pa (95% confidence interval [CI], 0.97-1.47), were identified. In series with mean follow-up of 10-years, the revision-rate was 0.63% pa (95% CI, 0.46-0.83), equating to a 94% (95% CI, 92%-95%) 10-year survival. Aseptic loosening, lateral arthritis, bearing dislocation, and unexplained pain were the predominant failure mechanisms with revision for patellofemoral problems and polyethylene wear exceedingly rare. The lowest revision-rates were achieved with caseload >24 UKA/y (0.88% pa; 95% CI, 0.63-1.61) and usage >30% (0.69% pa; 95% CI, 0.50-0.90). Usage was more important than caseload; with high usage (≥20%), the revision-rate was low, whether the caseload was high (>12 UKA/y) or low (≤12 UKA/y; (0.94% pa; 95% CI, 0.69-1.23 and 0.85% pa; 95% CI, 0.65-1.08), respectively); with low usage (<20%), the revision-rate was high, whether the caseload was high or low (1.58% pa; 95% CI, 0.57-3.05 and 1.76% pa; 95% CI, 1.21-2.41, respectively).
To achieve optimum results, surgeons, whether high or low caseload, should adhere to the recommended indications such that ≥20%, or ideally >30% of their knee arthroplasties are UKA. If they do this, then they can expect to achieve results similar to those of the long-term series, which all had high usage (>20%) and an average 10-year survival of 94%.
Mobile bearing medial unicompartmental knee arthroplasty in patients whose lifestyles involve high degrees of knee flexion: A 10–14 year follow-up study
2017, Knee
Because Asian populations have different lifestyles, such as squatting and sitting on the floor, from those of Western populations, it is possible that the clinical results and survival rate of unicompartmental knee arthroplasty (UKA) for Asian patients may be different. This study described outcomes of mobile bearing medial UKA for Korean patients.
A total of the 164 knees treated with mobile bearing UKAs in 147 patients (14 males and 133 females) were reviewed. The mean follow-up period was 12.1 years (range 10.1–14).
The clinical outcomes, such as the Hospital for Special Surgery Knee score, the Oxford Knee Score and the Knee Society rating system, showed statistically significant improvement from pre-operative to final follow-up (P < 0.05). A total of 26 UKAs (15.8%) required revision; the most common reason was bearing dislocation. The 95% confidence interval of survival rate at 12 years was 84.1%, with revision for any reason as the end point.
Minimally invasive mobile bearing UKA in Asian patients who required high degrees of knee flexion showed rapid recovery and good clinical outcome. However, they also showed relatively high rates of bearing dislocation and aseptic loosening. Therefore, mobile bearing UKA should only be performed in patients whose lifestyle involves high flexions after carefully considering these risks and benefits.
Annual revision rates of partial versus total knee arthroplasty: A comparative meta-analysis
2017, Knee
Utilization of unicompartmental knee arthroplasty (UKA) and patellofemoral arthroplasty (PFA) as alternatives to total knee arthroplasty (TKA) for unicompartmental knee osteoarthritis (OA) has increased. However, no single resource consolidates survivorship data between TKA and partial resurfacing options for each variant of unicompartmental OA. This meta-analysis compared survivorship between TKA and medial UKA (MUKA), lateral UKA (LUKA) and PFA using annual revision rate as a standardized metric.
A systematic literature search was performed for studies quantifying TKA, MUKA, LUKA and/or PFA implant survivorship. Studies were classified by evidence level and assessed for bias using the MINORS and PEDro instruments. Annual revision rates were calculated for each arthroplasty procedure as percentages/observed component-year, based on a Poisson-normal model with random effects using the R-statistical software package.
One hundred and twenty-four studies (113 cohort and 11 registry-based studies) met inclusion/exclusion criteria, providing data for 374,934 arthroplasties and 14,991 revisions. The overall evidence level was low, with 96.7% of studies classified as level III–IV. Annual revision rates were lowest for TKA (0.49%, CI 0.41 to 0.58), followed by MUKA (1.07%, CI 0.87 to 1.31), LUKA (1.13%, CI 0.69 to 1.83) and PFA (1.75%, CI 1.19 to 2.57). No difference was detected between revision rates for MUKA and LUKA (p = 0.222).
Revisions of MUKA, LUKA and PFA occur at an annual rate of 2.18, 2.31 and 3.57-fold that of TKA, respectively. These estimates may be used to inform clinical decision-making, guide patient expectations and evaluate the cost-effectiveness of total versus partial knee replacement in the setting of unicompartmental OA.
Unicompartmental Knee Replacement for Varus or Valgus Malalignment
2017, Noyes' Knee Disorders: Surgery, Rehabilitation, Clinical Outcomes

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Initial Experience With the Oxford Unicompartmental Knee Arthroplasty

Abstract

Section snippets

Methods

Results

Discussion

Conclusion

Acknowledgments

J Arthroplasty

Knee

Knee

Knee

Degenerative arthritis of the knee in active patients: evaluation and management

J Am Acad Orthop Surg

Surgical management of the middle age arthritic knee

Bull Hosp Jt Dis

Surgical treatment of the middle-aged patient with arthritic knees

Instr Course Lect

Unicondylar arthroplasty: redefining itself

Orthopedics

Unicompartmental or total knee replacement

J Bone Joint Surg Br

Revision of failed unicompartmental knee arthroplasty

Clin Orthop Relat Res