The Value of Minimal Clinically Important Difference, Substantial Clinical Benefit, and Patient-Acceptable Symptomatic State for Commonly Used Patient-Reported Outcomes in Recurrent Patellar Instability Patients After Medial Patellofemoral Ligament Reconstruction and Tibial Tubercle Transfer

Abstract

To identify the minimal clinically important difference (MCID), substantial clinical benefit (SCB) and patient acceptable symptomatic state (PASS) for commonly used patient-reported outcomes (PROs) in recurrent patellar instability patients after medial patellofemoral ligament reconstruction (MPFLR) and tibial tubercle transfer (TTT), and to determine the impact of potential prognostic factors on the likelihood of achieving these values. From April 2015 to February 2021, patients who underwent MPFLR and TTT were retrospectively reviewed. PROs included Kujala, Knee Injury and Osteoarthritis Outcome (KOOS), Lysholm, International Knee Documentation Committee (IKDC) and Tegner score. Relevant anchor questions were provided. A distribution- or anchor-based method was adopted to determine the MCID, SCB and PASS. Minimal detectable change (MDC) was included to confirm the validity. Univariate regression analyses were conducted to determine the potential prognostic factors. 142 patients were included. The MCID were 9.1(Kujala), 11.1 (Lysholm), 0.9(Tegner), 9.9(IKDC), 9.0(KOOS-Pain), 10.8(KOOS-Symptoms), 10.0(KOOS-Activities of Daily Living (ADL)), 17.8(KOOS-Sports and Recreation (Sports/Rec)), and 12.7 (KOOS-Quality of Life (QoL)). The SCB were 14.5(Kujala), 12.5(Lysholm), 1.5(Tegner), 14.5(IKDC), 13.9(KOOS-Pain), 14.3(KOOS-Symptoms), 18.4(KOOS-ADL), 47.5(KOOS-Sports/Rec), 15.0(KOOS-QoL). The PASSs were 85.5(Kujala), 75.5(Lysholm), 3.5(Tegner), 73.2(IKDC), 87.5(KOOS-Pain), 73.2(KOOS-Symptoms), 92.0(KOOS-ADL), 77.5(KOOS-Sports/Rec), and 53.1(KOOS-QoL). All SCBs were valid except KOOS-QoL. All MCIDs were valid at the 95% confidence interval (CI) except KOOS scores, the majority of which were valid at the 90% CI. A younger age was an independent prognostic factor of reaching PASS for Lysholm, IKDC, Tegner and KOOS-ADL score. A higher baseline score was a negative prognostic factor for achieving MCID or SCB but had a slightly positive influence on the achievement of PASS. This study established the MCID, SCB, and PASS for commonly used PROs and confirmed their validity in recurrent patellar instability patients after MPFLR and TTT. Younger age and lower baseline scores were prognostic factors of achieving MCID and SCB, while patients with higher baseline scores were more likely to report satisfaction.