Effect of robotic arm-assisted bi-unicompartmental knee arthroplasty versus total knee arthroplasty on objectively measured physical activity: secondary outcomes of a randomised controlled trial
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Accepted version
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Type
Journal Article
Abstract
Aims: Bi-unicompartmental knee arthroplasty (Bi-UKA) is a bone-conserving, cruciate-sparing alternative to total knee arthroplasty (TKA). Patient-reported outcome measures (PROMs) do not differ between procedures. Conflicting data exist on gait preservation, and little is known about physical activity (PA) outcomes. PA is understudied in arthroplasty, despite its links with all-cause mortality. We compared PA volume and intensity in patients randomised to Bi-UKA or TKA.
Methods: We analysed 38 TKA and 31 Bi-UKA patients from a prospective randomised controlled trial. A triaxial accelerometer was worn on the surgical thigh for seven days, with a three-day minimum wear criterion. Data were collected preoperatively, and at one and two years postoperatively. Outcomes were PA energy expenditure (PAEE), moderate-to-vigorous intensity PA (MVPA), light intensity PA (LPA), and sedentary time (ST), plus proportional PAEE by intensity. Group differences were assessed with mixed-effects models including baseline PA and biphasic gait as covariates. Spearman’s rank correlation between PROMs and PA was performed.
Results: Preoperative characteristics were comparable. Activity levels were higher following surgery, but postoperative differences in PAEE, MVPA, LPA, or ST between groups failed to reach statistical significance. Baseline PAEE (β=+0.27, p=0.04) and MVPA (β=+0.25, p=0.02) predicted improvements in postoperative activity. Postoperative correlations between PROMs and objective PA were weak across groups, and appeared to diminish over time.
Conclusion: Though free-living PA improved following Bi-UKA and TKA, differences between groups failed to reach statistical significance. Across both procedures, habitual and behavioural factors appear to be stronger determinants of postoperative PA than surgical procedure, as reflected by the limited correlation between PROMs and objective PA. Larger, long-term randomised studies are needed to confirm these findings.
Methods: We analysed 38 TKA and 31 Bi-UKA patients from a prospective randomised controlled trial. A triaxial accelerometer was worn on the surgical thigh for seven days, with a three-day minimum wear criterion. Data were collected preoperatively, and at one and two years postoperatively. Outcomes were PA energy expenditure (PAEE), moderate-to-vigorous intensity PA (MVPA), light intensity PA (LPA), and sedentary time (ST), plus proportional PAEE by intensity. Group differences were assessed with mixed-effects models including baseline PA and biphasic gait as covariates. Spearman’s rank correlation between PROMs and PA was performed.
Results: Preoperative characteristics were comparable. Activity levels were higher following surgery, but postoperative differences in PAEE, MVPA, LPA, or ST between groups failed to reach statistical significance. Baseline PAEE (β=+0.27, p=0.04) and MVPA (β=+0.25, p=0.02) predicted improvements in postoperative activity. Postoperative correlations between PROMs and objective PA were weak across groups, and appeared to diminish over time.
Conclusion: Though free-living PA improved following Bi-UKA and TKA, differences between groups failed to reach statistical significance. Across both procedures, habitual and behavioural factors appear to be stronger determinants of postoperative PA than surgical procedure, as reflected by the limited correlation between PROMs and objective PA. Larger, long-term randomised studies are needed to confirm these findings.
Date Acceptance
2026-06-08
Citation
Bone & Joint Research
ISSN
2046-3758
Publisher
The British Editorial Society of Bone & Joint Surgery
Journal / Book Title
Bone & Joint Research
Copyright Statement
Copyright This paper is embargoed until publication. Once published the Version of Record (VoR) will be available on immediate open access.
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Publication Status
Accepted