Impact of Obesity and Preoperative Knee Subcutaneous Fat Indices as Predictors of Postoperative Functional Outcomes Following Total Knee Arthroplasty: A Comprehensive Retrospective Review

TL;DR

This study found that obesity does not significantly affect the outcomes of knee replacement surgery, though obese patients tend to have the procedure at a younger age.

Contribution

The study provides new insights into the relationship between obesity, subcutaneous fat, and TKA outcomes using a comprehensive retrospective analysis.

Findings

Obesity did not independently affect postoperative functional outcomes following TKA.

Higher BMI correlated with younger age at the time of TKA.

BMI and subcutaneous fat indices showed weak predictive value for functional recovery.

Abstract

Introduction: Total knee arthroplasty (TKA) effectively relieves pain and improves functional capacity in end-stage knee osteoarthritis (OA). However, the influence of obesity, particularly as measured by body mass index (BMI), on TKA outcomes remains a subject of debate. This study aimed to investigate the relationship between BMI, knee subcutaneous fat measurements, and postoperative functional outcomes following TKA.

Methods: A retrospective analysis was conducted that included 100 patients (31 men and 69 women) who underwent primary TKA at a single university hospital. Patients were categorized based on BMI (kg/m2) into three groups: control (BMI <30), obese (BMI 30-39.9), and morbidly obese (BMI ≥40). Data collection included measurements of BMI, radiological fat indices, and assessment of joint function recovery using the 12-item Forgotten Joint Score (FJS-12) and flexion scores. Statistical analysis was performed to evaluate correlations and differences between BMI groups.

Results: The majority of patients were women (69%), with no significant BMI difference between genders. The surgical indication was predominantly OA, with a higher frequency seen in groups with BMI ≥30. Patients with a higher BMI underwent TKA at a younger age (p<0.00001). There was no significant difference in postoperative FJS-12 and flexion scores among BMI groups. Correlation analysis showed weak positive correlations between BMI/subcutaneous fat indices and functional outcomes. In addition, complication rates were low, with no reported infections.

Conclusion: Obesity did not independently affect TKA outcomes, with equivalent results observed across BMI groups. However, a higher BMI correlated with younger age at TKA. BMI and knee subcutaneous fat indices showed a poor predictive value for postoperative functional recovery. This study underscores the increasing proportion of obese patients undergoing TKA and the need for further research to understand the complex relationship between obesity, subcutaneous fat distribution, and TKA outcomes.

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