Assessing Application of the Multicenter Orthopaedic Outcome Network Calculator to Include Quadriceps Tendon Autografts and Older Patients

Anterior cruciate ligament reconstruction (ACLR) is a known risk factor for ipsilateral and contralateral anterior cruciate ligament (ACL) tear, influenced by patient age, activity level, and graft choice. The Multicenter Orthopaedic Outcome Network (MOON) calculator predicts risks post-ACLR, aiding in graft selection and prognosis. The MOON calculator is only validated for those patients under 22 years of age and with patellar bone-tendon-bone (BTB) or hamstring tendon graft options, restricting its applicability. This study assessed the MOON calculator's accuracy in a more diverse patient population, including quadriceps tendon (QT) recipients and patients > 22. With institutional review board approval, registry data were reviewed for patients with primary ACLR at our institution over the past 10 years. Patient information was entered into the MOON calculator, adjusting ages over the calculator's maximum to "22 years" for entry. Patients with QT grafts were entered as BTB. MOON retear and contralateral tear risk predictions were recorded. True outcomes were extracted from medical records. A Brier score of <0.25 was chosen a priori as indicative of acceptable model calibration. An area under the curve (AUC) threshold of 0.70 was determined to indicate acceptable discrimination. A total of 78 patients (49 ≤22 years, 29 23+ years), fulfilled inclusion criteria for analyses. A total of 64 patients received QT grafts (82.1%) and 14 received BTB (17.9%). There were three ACL retears, two QT (3.1%), and one BTB (7.1%) patients. MOON predicted a retear rate of 8.3% for the combined BTB + QT graft group. Brier and receiver operating characteristic curve results suggest poor model calibration, but good discrimination-QT Brier score: 0.89, AUC 0.782, and BTB Brier score: 0.84, AUC 0.846. Analysis restricted to those >22years-QT Brier: 0.84, AUC 0.525, showed poor accuracy and poor outcome discrimination. BTB Brier score: 0.81, AUC 0.778, demonstrated acceptable discrimination. The MOON calculator was not effective in predicting ipsilateral ACL retear risk with the inclusion of patients >22 years and QT grafts. Validating the MOON calculator for a broader age range and QT grafts could enhance its clinical applicability.