When ACL reconstruction does not help: risk factors associated with not achieving the minimal important change for the KOOS Sport/Rec and QoL

OBJECTIVES: To determine factors associated with not achieving a minimal important change (MIC) in the Knee injury and Osteoarthritis Outcome Score (KOOS) Function in Sport and Recreation (Sport/Rec), and Knee-Related Quality of Life (QoL) subscales 1 year after anterior cruciate ligament reconstruction (ACL-R). METHODS: This study used data from the Swedish National Knee Ligament Registry. Multivariable logistic regression models were used to identify factors associated with not achieving a MIC. The change in the preoperative and postoperative KOOS Sport/Rec and QoL subscale scores were dichotomised based on not achieving MIC for both subscales versus achieving MIC for either one or both subscales. The MICs for the Sport/Rec and QoL subscales were 12.1 and 18.3, respectively, and were used to combine both subscales into a single variable (Sport & QoL). RESULTS: Of 16 131 included patients, 44% did not achieve the MIC for the combined Sport/Rec and QoL subscales 1 year after ACL-R. From the multivariable stepwise logistic regression, older patients (OR 0.91, 95% CI 0.88 to 0.94; p<0.0001), males (OR 0.93, 95% CI 0.87 to 0.99; p=0.034) and patients receiving hamstring tendon autograft ACL-R (OR 0.70, 95% CI 0.60 to 0.81; p<0.0001) had lower odds of not achieving the MIC 1 year after ACL-R compared with younger patients, females and patients receiving patellar tendon autograft. Furthermore, patients with cartilage injuries (OR 1.17, 95% CI 1.09 to 1.27; p<0.0001) and higher pre-operative KOOS Sport/Rec and QoL scores (OR 1.34, 95% CI 1.31 to 1.36; p<0.0001) had higher odds of not achieving the MIC. CONCLUSION: Younger patients, females and patients with cartilage injuries and higher pre-operative Sport/Rec and QoL KOOS scores are less likely to benefit from ACL-R and subsequently, have a lower probability for improved Sport/Rec and QoL scores after ACL-R. Furthermore, graft choice may also affect the risk of not achieving the MIC. LEVEL OF EVIDENCE: Retrospective cohort study, level III.