Allograft Augmentation of Hamstring Anterior Cruciate Ligament Autografts Is Associated With Increased Graft Failure in Children and Adolescents

Background: Anterior cruciate ligament (ACL) reconstruction in adolescents is commonly performed with hamstring tendon autografts. Small graft diameter is one risk factor for graft failure and options to upsize the autologous hamstring graft include allograft augmentation and tripling one or both of the hamstring tendons. Purpose: To evaluate the association of upsized hamstring graft constructs and graft rupture after ACL reconstruction. Study Design: Cohort study; Level of evidence, 3. Methods: A retrospective review was performed of patients 19 years of age and younger who underwent hamstring autograft ACL reconstruction with or without soft tissue allograft augmentation from 2012 to 2016. All patients were skeletally mature or had less than 2 years of growth remaining. Graft constructs included 4-strand doubled semitendinosus and gracilis autograft (4-STG), 5-strand tripled semitendinosus and doubled gracilis autograft (5-STG), and 6-strand doubled gracilis and semitendinosus autograft augmented with a soft tissue allograft (6-STGAllo). The primary outcome measure was graft rupture. Results: A total of 354 patients with a mean age of 15.3 years (range, 10-19 years) were included. Graft constructs included 4-STG (198 knees), 5-STG (91 knees), and 6-STGAllo (65 knees). The average diameter of the graft constructs was 8.3 mm for 4-STG, 8.9 mm for 5-STG, and 9.2 mm for 6-STGAllo (P < .001). The mean follow-up was 26 months (range, 6-56 months). There were 50 (14%) graft ruptures and 24 (7%) contralateral ACL tears. The graft failure rates were 14% for 4-STG, 12% for 5-STG, and 20% for 6-STGAllo (P = .51). The average time to graft failure was 16 months (range, 2-40 months). After adjusting for age and graft size, patients who had allograft-augmented grafts (6-STGAllo) had 2.6 (95% CI, 1.02, 6.50) times the odds of graft rupture compared with 4-STG. There was no significant difference in failure rate between patients who had 5-STG grafts compared with 4-STG (OR, 1.2; 95% CI, 0.5, 2.7). Conclusion: ACL reconstruction with hamstring tendon autografts augmented with allografts has a significantly increased risk of graft rupture compared with comparably sized hamstring tendon autografts. In situations where the surgeon harvests an inadequately sized 4-strand autograft, we recommend obtaining a larger graft diameter by tripling the semitendinosus rather than augmenting with an allograft.