INTRODUCTION: The controversy of allograft versus autograft bone-patellar tendon-bone anterior cruciate ligament (ACL) reconstruction is highly debated in the literature. While allografts offer the benefits of decreased morbidity due to graft harvest (e.g. anterior knee pain, patella fracture, weakness), shorter surgical times, and faster recovery, others suggest allograft failure rates are 3-4 time greater than autograft and result in greater knee laxity and worse functional outcomes particularly in younger patients. The purpose of this study was to investigate differences in failure rates and functional outcomes between BPTB autograft and allograft ACL reconstruction in patients <30 years of age.
METHODS: All patients from 17 to 30 years of age who underwent a BPTB allograft or autograft ACLR with bioabsorbable interference screws (ConMed Linvatec, Largo, FL) by a single surgeon (KDP) (1995-2016) were included. Exclusion criteria were follow-up <2 years, osteochondral drilling, revision ACLR and multi-ligamentous injuries. Allograft source was always five years younger than patient age and not terminally irradiated. A notchplasty was performed in all patients to enhance visualization and optimize tunnel placement. Transtibial femoral drilling with the knee in hyperflexion to access the 2:30 and 10:30 positions was used to attempt to restoration of the anatomic footprint. Meniscal repairs were completed as necessary. All patients completed a conservative rehabilitation program with bracing and return to pivoting sports at no sooner than 6 months. An independent physical exam including knee range of motion (ROM) and stability testing, including KT-1000, Lachman, and pivot shift, was performed. Patients completed Lysholm, International Knee Documentation Committee (IKDC), and Tegner questionnaires to assess clinical outcomes. Failure was defined as recurrent subjective knee instability or positive Lachman and/or pivot shift test. Independent samples t-tests were used to assess differences between patients with allograft and autograft ACLR. Significance was set at p<0.05.
RESULTS: 35 patients with BPTB autograft ACLR (8 females, 22.0±4.4 years of age) and 13 patients with BPTB allograft ACLR (8 female, 23.8±3.9 years of age) were included. Average follow-up was 8.7±5.2 years in the autograft group and 6.7±3.7 years in the allograft group (p=0.155). Postoperative VAS pain score was 2.7±1.0 in autograft group and 2.6±0.7 in allograft group (p=0.0872) and postoperative flexion ROM did not differ between the groups (p=0.1218). Postoperative IKDC score was 82.6±16.4 in autograft group and 92.2±7.0 in allograft group (p=0.0259). Postoperative Lysholm score was 89.3±7.0 vs. 93.4±8.0 (p=0.1538). Manual maximum KT-1000 knee stability did not differ between the groups (p=0.740). All patients returned to preoperative sport at Tegner score of 5 or greater. The overall failure rate was 2.1% (1/48). There were no failures in the allograft group and 1 failure in the autograft group (2.9%, 1/35) which occurred 4 years postoperatively. The patient underwent revision BPTB allograft ACLR without recurrence at 15 year follow up. 
DISCUSSION: Allograft BPTB ACLR is a good alternative graft option to return young patients <30 years of age to pre-operative sports with no evidence of increased failure rates. We believe that graft selection with allograft source always 5 years younger than patient’s age without terminal irradiation and a slow, conservative rehabilitation program with objective return to sport criteria are keys to a successful outcome.
SIGNIFICANCE/CLINICAL RELEVANCE (1-2 sentences): 
Anterior cruciate ligament reconstruction graft selection with allograft source always 5 years younger than patient age without terminal irradiation and a slow, conservative rehabilitation program with objective return to sport criteria can yield successful outcomes in young athletes.

1830 - Failure Rates and Functional Outcomes of Allograft and Autograft Bone-Patellar Tendon-Bone (BPTB) Anterior Cruciate Ligament Reconstruction in Patients <30 Years Old