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. 2023 Jul 26;35(1):21.
doi: 10.1186/s43019-023-00195-1.

Does body mass index influence improvement in patient reported outcomes following total knee arthroplasty? A retrospective analysis of 3918 cases

Kyle W Lawrence  1 , Walter Sobba  1 , Vinaya Rajahraman  1 , Ran Schwarzkopf  1 , Joshua C Rozell  2
Affiliations

Does body mass index influence improvement in patient reported outcomes following total knee arthroplasty? A retrospective analysis of 3918 cases

Kyle W Lawrence et al. Knee Surg Relat Res. .

Abstract

Purpose: The study aimed to determine whether body mass index (BMI) classification for patients undergoing total knee arthroplasty (TKA) is associated with differences in mean patient reported outcome measure (PROM) score improvements across multiple domains-including pain, functional status, mental health, and global physical health. We hypothesized that patients with larger BMIs would have worse preoperative and postoperative PROM scores, though improvements in scores would be comparable between groups.

Materials and methods: Patients undergoing primary TKA from 2018 to 2021 were retrospectively reviewed and stratified into four groups: Normal Weight; 18.5-25 kg/m2, Overweight; 25.01-30 kg/m2, Obese; 30.01-40 kg/m2, and Morbidly Obese > 40 kg/m2. Preoperative, postoperative, and pre/post-changes (Δ) in knee injury and osteoarthritis, joint replacement (KOOS, JR) and Patient-Reported Outcome Measurement Information System (PROMIS) measures of pain intensity, pain interference, physical function, mobility, mental health, and physical health were compared. Multivariate linear regression was used to assess for confounding comorbid conditions.

Results: In univariate analysis, patients with larger BMIs had worse scores for KOOS, JR and all PROMIS metrics preoperatively. Postoperatively, scores for KOOS, JR and PROMIS pain interference, mobility, and physical health were statistically worse in higher BMI groups, though differences were not clinically significant. Morbidly obese patients achieved greater pre/post-Δ improvements in KOOS, JR and global physical health scores. Multivariate regression analysis showed high BMI was independently associated with greater pre/post-Δ improvements in KOOS, JR and global health scores.

Conclusion: Obese patients report worse preoperative scores for function and health, but greater pre/post-Δ improvements in KOOS, JR and physical health scores following TKA. Quality of life benefits of TKA in obese patients should be a factor when assessing surgical candidacy.

Keywords: Body mass index; Knee; Obesity; Patient reported outcomes; Total knee arthroplasty.

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Conflict of interest statement

KWL, WS, VR: Nothing to disclose. RS: AAOS: Board or committee member. American Association of Hip and Knee Surgeons: Board or committee member. Arthroplasty Today: Editorial or governing board. Gauss surgical: Stock or stock Options. Intelijoint: Paid consultant; Stock or stock Options. Journal of Arthroplasty: Editorial or governing board. PSI: Stock or stock Options. Smith & Nephew: IP royalties; Paid consultant; Research support. Zimmer: Paid consultant. JCR: New York State Society of Orthopaedic Surgeons: Board or committee member.

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