MRI Accurately Predicts Quadrupled Semitendinosus Autograft Size Using Posterior Hamstring Harvest for ACL Reconstruction

Abstract

Purpose: To determine the effectiveness of preoperative magnetic resonance imaging (MRI) measurements of the cross-sectional area (CSA) of the semitendinosus tendon in predicting the intraoperative quadrupled semitendinosus graft diameter of a posteriorly harvested hamstring autograft for anterior cruciate ligament (ACL) reconstruction. Methods: A retrospective review of patients who underwent ACL reconstruction with autograft using a posterior hamstring harvest was performed. Patient demographics and operative reports were reviewed, and measurements of the CSA of the semitendinosus on MRI were performed. Multiple linear regression was used to analyze the predictors for graft diameter. A P value < .05 was considered statistically significant. Interrater and intrarater reliability were calculated. Results: 280 patients were included. Patient height (P < .0001), and CSA of the semitendinosus (P < .0001) were significant predictors. Patients shorter than 63 inches had an average graft diameter of 7.89 mm compared to 8.69 mm for patients above 63 in (P < .001). The formula for the model is as follows: Graft diameter (mm2) = 2.74 + .067·Height (in) + .00009 · Weight (lbs) + .0018 · Age (years) +.12·Gender (1 if M, 0 if F) + 8.56 · CSA (cm2). The R2 for the model (0.5620), was greater than models using only height (R2 = .4092) or only CSA Semitendinosus (R2 = .3932). None of the interaction terms between covariates (e.g., height, weight, age, gender) were significant. Age (P =.6400), weight (P = .9970), and gender (P = .6700) were not significant predictors. Both intraclass (ICC = 0.864, 95% CI=[0.791, 0.912]) and interclass correlation (ICC=0.827, 95% CI=[0.715, 0.894]) showed good reliability. Conclusion: CSA semitendinosus tendon and patient height independently perform similarly as predictors of graft diameter. When used together, CSA and height accurately predict the graft diameter. In particular, for patients under 63 in tall who demonstrated an average graft diameter below the minimum 8 mm, as suggested by the literature, this may be a useful tool for preoperative planning of patients intending to undergo ACL reconstruction with posterior hamstring harvest. Level of Evidence: Level III, diagnostic: retrospective cohort study.