The effect of body mass index on the outcomes of cementless medial mobile bearing unicompartmental knee replacements

Hasan Raza Mohammad, Stephen Mellon, Andrew Judge, Christopher Dodd, David Murray

Research output: Contribution to journalArticle (Academic Journal)peer-review

1 Citation (Scopus)
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Abstract

Purpose: Given an increasingly overweight population, unicompartmental knee replacements (UKRs) are being performed in patients with higher body mass indices (BMIs). There are concerns that cemented fixation will not last. Cementless fixation may offer a solution, but the long term results in different BMI groups has not been assessed. We studied the effect of BMI on the outcomes of cementless UKRs.
Methods: A prospective cohort of 1000 medial cementless mobile bearing UKR with a mean follow up of 6.6 years (SD 2.7) were analysed. UKRs were categorised into four BMI groups: (1) ≥18.5 to <25 kg/m2 (normal), (2) 25 to <30 kg/m2 (overweight), (3) 30 to <35 kg/m2 (obese class 1) and (4) ≥ 35 kg/m2 (obese class 2). Implant survival was assessed using endpoints reoperation and revision. Functional outcomes were assessed.

Results: Ten year cumulative revision rate for the normal (n=186), overweight (n=434), obese class 1 (n=213) and obese class 2 (n=127) groups were 1.8% (CI 0.4-7.4), 2.6% (CI 1.3-5.1), 3.8% (CI 1.5-9.2) and 1.7% (CI 0.4-6.8) with no significant differences between groups (p=0.79). The 10 year cumulative reoperation rates were 2.7% (CI 0.8-8.2), 3.8% (CI 2.2-6.6), 5.2% (CI 2.5-10.7) and 1.7% (CI 0.4-6.8) with no significant differences between groups (p=0.44). The 10 year median Oxford Knee Score were 43.0, 46.0, 44.0 and 38.0 respectively.

Conclusion: Cementless mobile bearing UKR has low 10 year reoperation and revision rates across in all BMI groups, and there are no significant differences between the groups. Although higher BMI groups had slightly worse functional outcomes, the improvement in function postoperatively tended to be better. This study suggests that BMI should not be considered a contraindication for the cementless mobile bearing UKR.
Original languageEnglish
Number of pages11
JournalKnee Surgery, Sports Traumatology, Arthroscopy
Early online date17 Apr 2021
DOIs
Publication statusE-pub ahead of print - 17 Apr 2021

Bibliographical note

Publisher Copyright:
© 2021, The Author(s).

Keywords

  • body mass index
  • cementless fixation
  • mid-long term outcomes
  • unicondylar knee arthroplasty

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