A comparison of preoperative imaging techniques for predicting patellar tendon graft length before cruciate ligament reconstruction.

Autogenous bone-patellar tendon-bone is commonly used as graft material for cruciate ligament reconstructions. If this type of graft is too long, graft fixation other than an interference screw may be required. If it is too short, selection of another type of graft may be necessary. If the length of the patellar tendon portion of the graft could be accurately predicted, preoperative planning could determine the adequacy of this graft and choice of fixation for the planned procedure. Using lateral radiographs with the knee flexed 30 degrees, standard magnetic resonance imaging, and magnetic resonance imaging with supplemental three-dimensional reconstructions, we measured the length of the patellar tendon in cadavers and then compared these measurements with the actual patellar tendon length measurements. Linear regression analysis resulted in r2 values of 0.80, 0.43, and 0.65 for lateral radiographs, standard magnetic resonance imaging, and magnetic resonance imaging with three-dimensional reconstructions, respectively. We concluded that lateral radiographs at 30 degrees of knee flexion are the most accurate predictors of patellar tendon length.