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, graf t fixation other than an interference screw may be required. If it is too s hort, selection of another type of graft may be necessary. If the length of the patellar tendon portion of the graft could be accurately predicted, pr eoperative planning could determine the adequacy of this graft and choice o f fixation for the planned procedure. Using lateral radiographs with the kn ee flexed 30 degrees, standard magnetic resonance imaging, and magnetic res onance imaging with supplemental three-dimensional reconstructions, we meas ured the length of the patellar tendon in cadavers and then compared these measurements with the actual patellar tendon length measurements. Linear re gression analysis resulted in r(2) values of 0.80, 0.43, and 0.65 for later al 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 accura te predictors of patellar tendon length.