Relationship Between Revision Rate, Osteoarthritis, and Obesity for ACL Reconstruction: A Nationwide Retrospective Cohort Study

Background: The long-term goal of anterior cruciate ligament (ACL) reconstruction is to prevent secondary osteoarthritis due to instability. Obesity itself is also a risk factor for osteoarthritis and shows an increase in its incidence, but little is known about the relationship between obesity and the outcome of ACL reconstruction. Purpose/Hypothesis: This study aimed to determine the relationship between the outcome of ACL reconstruction and obesity. It was hypothesized that obesity would be associated with the revision rate of ACL reconstruction and additional surgical treatment for osteoarthritis in patients who undergo ACL reconstruction. Study design: Cohort study; Level of evidence, 3. Methods: Claims and health screening data of the National Health Insurance Service were used to analyze patients who underwent ACL reconstruction between January 1, 2003, and December 31, 2021. The association between obesity and risk of revision ACL reconstruction and additional surgical treatment for osteoarthritis or meniscal lesion was analyzed. Body mass index (BMI) was used to classify patients as underweight (BMI, <18.5), normal weight (BMI, 18.5-24.9), overweight (BMI, 25.0-29.9), obese (BMI, 30.0-39.9), or morbidly obese (BMI, >= 40.0). Multivariable Cox proportional hazards model analysis was conducted. Results: A total of 56,734 patients were included. Of them, 311 (0.5%) patients were underweight, 26,613 (46.9%) were normal weight, 24,372 (43.0%) were overweight, 5324 (9.4%) were obese, and 114 (0.2%) patients were morbidly obese. The underweight group showed a significantly lower risk of revision ACL reconstruction than the normal weight group (hazard ratio [HR], 0.54; 95% CI, 0.31-0.93; P = .0273). However, the overweight, obese, and morbidly obese groups had no significant difference from the normal weight group. The risk of high tibial osteotomy (HTO) or total knee arthroplasty (TKA) was significantly high for the overweight (HR, 1.93; 95% CI, 1.70-2.19; P < .0001) and obese (HR, 2.71; 95% CI, 2.23-3.30; P < .0001) groups. Subgroup analysis performed in patients >= 40 years of age for the risk of HTO showed a significant increased risk in the overweight group (HR, 1.889; 95% CI, 1.56-2.29; P < .0001) and obese group (HR, 2.78; 95% CI, 2.10-3.69; P < .0001). Subgroup analysis performed in patients >= 50 years of age for the risk of TKA also showed a significant increased risk in the overweight group (HR, 2.03; 95% CI, 1.67-2.47; P < .0001) and obese group (HR, 2.53; 95% CI, 1.83-3.50; P < .0001). After adjusting for meniscal injury at index surgery by multivariate regression analysis, 1.87- and 2.75-fold increased risks of HTO were identified for the overweight and obese groups, respectively, for patients aged >40 years. For patients aged >50 years, 2.02-fold and 2.52-fold increased risks of TKA were observed for the overweight and obese groups, respectively. The risk of additional surgery due to the meniscal lesion was high for the overweight (HR, 1.09; 95% CI, 1.03-1.15; P = .002) and obese (HR, 1.10; 95% CI, 1.01-1.21; P = .0351) groups, while no significant difference was found for the underweight and morbidly obese groups. Conclusion: This study highlights that obesity does not increase the revision rate of ACL reconstruction. However, the risk of additional surgical treatment for osteoarthritis and meniscal lesions increased as BMI increased. Further investigation is needed to determine the efficacy of ACL reconstruction for preventing osteoarthritis in obese patients.