Bone Defect Regeneration and Donor-Site Morbidity After Bone–Patellar Tendon–Bone Anterior Cruciate Ligament Reconstruction: A Prospective Cohort Study

Background and Objectives: This prospective cohort study aimed to assess patellar and tibial donor-site bone defect volume and regeneration on MRI at 4 weeks and 12 months after bone–patellar tendon–bone anterior cruciate ligament reconstruction and to determine their association with knee function and donor-site morbidity at 12 months. Materials and Methods: This single-center prospective observational cohort study included 30 patients who underwent ACL reconstruction with a BTB autograft. Donor-site bone defect volume was estimated on MRI using a triangular prism approximation at 4 weeks and 12 months by two independent evaluators blinded to patient-reported outcome scores. Clinical outcomes were assessed at 12 months using the International Knee Documentation Committee (IKDC) subjective knee form and the Donor Site Morbidity Questionnaire (DSMQ). Associations between MRI-derived parameters and patient-reported outcomes were analyzed using Spearman’s rank correlation coefficient. Results: At 4 weeks, mean donor-site bone defect volume was 2602.4 ± 684.7 mm3 in the patella and 2993.9 ± 714.3 mm3 in the tibia. At 12 months, defect volume decreased to 628.0 ± 279.7 mm3 and 980.8 ± 488.2 mm3, respectively. Tibial defects were significantly larger than patellar defects at both time points, while regeneration was significantly greater in the patella than in the tibia (74.8 ± 11.5% vs. 67.2 ± 15.1%; p = 0.0264). Regeneration was not significantly associated with IKDC or DSMQ scores (all p > 0.05). Larger patellar defect volume at 4 weeks was associated with worse subjective outcomes (both p = 0.0107). Conclusions: After BTB ACL reconstruction, tibial donor-site bone defects were larger, whereas patellar defects showed greater regeneration over time. Larger patellar defect volume at 4 weeks, but not regeneration percentage, was associated with worse subjective outcomes at 12 months.