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Short-Term Functional Outcomes in Patients Undergoing Primary Total Knee Arthroplasty According to Their Body Mass
Ranj Bhakar1, Arjun S Chakrapani1, Arfaz Shaik2,3
1Department of Trauma and Orthopaedics, Torbay Hospital, Torquay, GBR.
Objective:
This study aimed to evaluate the association between body mass index (BMI) and short-term outcomes following primary unilateral total knee arthroplasty (TKA), including functional improvement, perioperative variables, and postoperative complications.
Methodology:
A retrospective case-control study was conducted at a tertiary orthopedic center on 525 consecutive patients who underwent primary unilateral TKA for osteoarthritis between January 2019 and December 2023. Patients were classified according to World Health Organization (WHO) BMI criteria: normal (18.5-24.9 kg/m²), overweight (25.0-29.9 kg/m²), and obese (≥30.0 kg/m²). Collected data included demographics, American Society of Anesthesiologists (ASA) grade, Charlson Comorbidity Index (CCI), glycated hemoglobin (HbA1c), operative time, length of hospital stay, change in Knee Society Score (ΔKSS) at 12 months, patient-reported outcome measures, satisfaction, revision surgery, and postoperative complications. Between-group comparisons were performed using one-way analysis of variance (ANOVA) for continuous variables and chi-square or Fisher's exact tests for categorical variables, with significance set at p < 0.05.
Results:
Baseline characteristics were comparable across BMI groups, except for higher ASA scores and HbA1c levels in obese patients (p < 0.05). Obese patients had significantly longer operative times (95.9 ± 16.8 minutes) and hospital stays (4.8 ± 1.2 days) than normal-weight patients (83.6 ± 14.1 minutes; 3.9 ± 1.0 days, p < 0.01). All BMI groups demonstrated significant improvement in ΔKSS at 12 months, although the gain was lowest in obese patients (34.7 ± 10.5 vs. 41.2 ± 9.6; p = 0.012). Overall complications were highest in the obese group with 16 patients (9.1%), followed by nine patients (5.1%) in the overweight group and seven patients (4.0%) in the normal-weight group, with wound-related issues being the most common. Revision surgery occurred in one (0.6%) obese patient, and no mortality was reported.
Conclusion:
Higher BMI was associated with longer operative times, prolonged hospital stays, increased wound complications, and slightly reduced functional improvement and satisfaction at 12 months after primary TKA. These findings highlight the importance of optimizing metabolic status before surgery and emphasize the need for individualized perioperative risk assessment in patients undergoing knee arthroplasty.
