Factors that Predicts the Size of Autologous Hamstring Tendon Graft for Double-Bundle ACL Reconstruction

BACKGROUND: To evaluate the effectiveness of demographic data and radiographic measurements for predicting the diameter and length of autologous semitendinosus (ST) and gracilis (GR) graft. MATERIALS AND METHODS: Fifty-four cases were included to measure the size of 3 or 4 strands of ST and GR tendons retrospectively. The hamstring length on radiograph was defined as the length from the lowest point of ischial tuberosity to intercondylar notch of the femur. The linear and logistic regression analysis was used to assess the roles of the predictor variables, as demographic and radiologic data, in the outcome variables, as diameter of tendon grafts. The cross-validation with hold-out samples and concordance correlation coefficient (CCC) were also calculated. RESULTS: The hamstring and leg length measurement and gender were associated with the diameter of 4-stranded ST tendon graft. The hamstring length measurement, age and BMI were the factors associated with the diameter of 3-stranded ST tendon graft. The hamstring length measurement was found as a common factor for predicting diameters of hamstring tendon with reliable predictability. Moreover, the equation of multivariate regression analysis for the diameter of 4-stranded ST tendon graft showed the most validated power of prediction. All of the cross-validated R(2) values were calculated as similar results of multivariate model, but CCC between the measured diameter and estimated value on the predictive equation showed moderate agreement only (CCC = 0.694). CONCLUSIONS: Combining radiographic length measurements with demographic data showed reliable prediction in identifying the risk of inappropriate graft diameters. LEVEL OF EVIDENCE: Level IV retrospective cohort study.