A Prospective Randomized Comparison using MRI of Two Distinct Allogenic Tissue Constructs for Anterior Cruciate Ligament Reconstruction

OBJECTIVES: To compare the radiographic and clinical outcomes of anterior cruciate ligament (ACL) reconstruction using quadrupled hamstring tendon (HT) allograft vs. doubled tibialis anterior (TA) allograft. METHODS: Methods: A prospective randomized controlled trial (PRCT) at a single center was conducted with enrollment from 7/2010 to 4/2012. One hundred subjects undergoing primary ACL reconstruction were randomized to either HT or TA allograft (47 vs. 53, respectively). Subjects completed KOOS, IKDC, Tegner, VR-12, and Lysholm outcomes measure pre-operatively, and then post-operatively at the 6 month and 24 month time period. Arthrometric testing using KT-1000 (MEDmetric® Corporation) was applied at 6 months post-operatively. At this time patients also underwent MRI to evaluate allograft integrity and ligamentization. The signal to noise quotient (SNQ) was calculated via the Impax markup tool (Afga HealthCare®) using sagittal non-contrast T2 weighted MRI (Figure 1) as follows: SNQ = (Signal graft - Signal Quadriceps)/Signal Background RESULTS: MRIs were obtained in the HT (n=22, 53%, 205.6 ± 35.7 days) and TA (n=23, 47%, 187.3 ± 26.0 days) groups. The average SNQ for the HT and TA allografts were .94 ± 3.03 and 4.14 ± 3.64, respectively (p = 0.12). There was no correlation between MRI SNQ and subject age, BMI, sex, graft diameter or smoking status. With arthrometric testing there was a trend for the HT allografts to have increased laxity as compared to contralateral side but the magnitude of difference was not clinically relevant (average 0.88 vs. 0.40mm, respectively). At an average of 2.4 ± 0.4 years there was no difference detected between groups in any of the outcomes scores with each showing improvement from baseline (Table 1). Allograft re-tear rates were similar between groups (9.5% HT vs. 4.5% TA, p=1.0). CONCLUSION: Limited data exists directly comparing different ACL allograft soft tissue constructs. Specifically, to the author’s knowledge this is the first prospective RCT comparing quadrupled hamstring tendon and doubled tibialis anterior allografts. Our data indicate no difference in graft failure rate, rate of ligamentization, and similar significant improvement from baseline with respect to subjective outcomes scores between each treatment group after more than two years.