Unnecessary contraindications for mobile-bearing unicompartmental knee replacement

Abstract

The contraindications for unicompartmental knee replacement (UKR) remain controversial. The views of many surgeons are based on Kozinn and Scott's 1989 publication which stated that patients who weighed more than 82 kg, were younger than 60 years, undertook heavy labour, had exposed bone in the patellofemoral joint or chondrocalcinosis, were not ideal candidates for UKR. Our aim was to determine whether these potential contraindications should apply to patients with a mobile-bearing UKR. In order to do this the outcome of patients with these potential contraindications was compared with that of patients without the contraindications in a prospective series of 1000 UKRs. The outcome was assessed using the Oxford knee score, the American Knee Society score, the Tegner activity score, revision rate and survival. The clinical outcome of patients with each of the potential contraindications was similar to or better than those without each contraindication. Overall, 678 UKRs (68%) were performed in patients who had at least one potential contraindication and only 322 (32%) in patients deemed to be ideal. The survival at ten years was 97.0% (95% confidence interval 93.4 to 100.0) for those with potential contraindications and 93.6% (95% confidence interval 87.2 to 100.0) in the ideal patients. We conclude that the thresholds proposed by Kozinn and Scott using weight, age, activity, the state of the patellofemoral joint and chondrocalcinosis should not be considered to be contraindications for the use of the Oxford UKR.

Evidence-Based Indications for Mobile-Bearing Unicompartmental Knee Arthroplasty in a Consecutive Cohort of Thousand Knees

“…Previous shorter term studies have also shown that patients treated with the mobile-bearing 258 UKR that have the proposed contra-indications have similar functional outcomes and survival 259 as those considered ideal [16,17]. This study has however shown that patients with contra-260 indications actually have better results.…”

Does obesity influence early outcome of fixed-bearing unicompartmental knee arthroplasty?

“…In a study by Xing et al 21 with 178 patients, the outcome of UKA was not influenced by patient's age, BMI and early degeneration in the PFJ. Furthermore, the clinical outcome of the 1000 mobile-bearing UKA at a mean of 5.6 year in a prospective study by Pandit et al 22 was similar for both patients weighing less and more than 82 kg. Tabor et al 23 reported higher survivorship among obese patients compared with those who were not obese in a 20-year follow-up study of 82 patients.…”

Does body mass index affect the outcome of unicompartmental knee replacement?

“…Preoperative data including patient demographics as well as the patient's height and weight were recorded on dedicated databases. Data from centre 1 has already been used in a study of UKR on patients with weight above or below 82 kg and data from centre 2 has been used in a similar study with BMI above or below 32 13,16 .…”

“…More recent work, reviewing 40 fixed bearing UKRs with a BMI > 35, and a matched group with a BMI < 35, demonstrated higher revision rates in those with a BMI > 35 12 . Conversely, Pandit et al have shown that a weight > 82 kg was not associated with a higher failure rate using a mobile bearing UKR but they did not study the impact of BMI 13 .…”