No Difference in Failure Rates Between Hybrid Grafts Compared with Hamstring Autografts Following ACL Reconstruction

Background: Hamstring tendon autografts, for ACL (anterior cruciate ligament) reconstruction, have demonstrated a higher re-rupture rates when graft diameter of <8 mm is chosen. In the event that an autograft yield a graft diameter <8 mm, augmentation with allograft creates a hybrid graft with increased diameter. Clinical outcomes of this hybrid graft have yet to be established. Purpose: To assess clinical outcomes and failure rates of an adult population who undergo augmentation with allograft compared to patients with hamstring autograft alone. Methods: A retrospective chart review of primary ACL reconstructions performed by 4 sports fellowship trained surgeons at a single institution between 2010-2016 identified 23 patients with hamstring autografts and allograft augmentation. A comparison group of 23 patients consisted of patients who underwent ACL reconstruction with hamstring autograft of >8 mm diameter was then selected. The comparison group was matched based on age within 3 years. Graft failure was defined as revision ACL reconstruction or evidence of graft failure on clinical exam (no end point on lachman or pivot shift) or MRI evidence of retear. International Knee Documentation Committee (IKDC), Marx Activity, and Knee injury Osteoarthritis and Outcome (KOOS) scores were obtained. Patients were contacted to obtain information regarding outcome scores, revision procedures, return to sport, and complications. A minimum follow up time was set at 12 months. Results: Forty-six patients met criteria for inclusion in this study and had follow up data. The hybrid group had a total of 23 patients consisting of 7 men and 16 women with an average age of 31 years (Range 17-51 years). The autograft group had a total of 23 patients consisting of 17 men and 6 women with an average age of 33.3 years (Range 15-48). The average follow-up between both groups was 31.5 months (range 12-63 months). The graft failure rate in the hybrid group was 8.7% (2 of 23 patients), while the autograft group demonstrated a graft failure rate of 4.3% (1 of 23 patients) (p=0.49). In the hybrid ACL group, the mean IKDC was 67.8 (CI 59.8-75.9) compared to 73.8 (CI 66.6-80.9) in the autograft group (p=0.26). The average KOOS scores for the hybrid group was 75.8 (CI 67.5-84.1) compared to 86.5 (CI 81.4-91.7) in the autograft group (p=0.03). Conclusions: In an adult population, allografts augmented hybrid ACL grafts showed no statistically significant difference compared to hamstring autograft in graft failure rates. The autograft ACL group demonstrated a higher KOOS score, though the IKDC was equivalent.