Clinical measurement of patellar tendon: accuracy and relationship to surgical tendon dimensions.

Patellar tendon width and length are commonly used for preoperative planning for anterior cruciate ligament reconstruction (ACLR). In the study reported here, we assessed the accuracy of preoperative measurements made by palpation through the skin, and correlated these measurements with the actual dimensions of the tendons at surgery. Before making incisions in 53 patients undergoing ACLR with patellar tendon autograft, we measured patellar tendon length with the knee in full extension and in 90° of flexion, and tendon width with the knee in 90° of flexion. The tendon was then exposed, and its width was measured with the knee in 90° of flexion. The length of the central third of the tendon was measured after the graft was prepared. Mean patellar tendon length and width with the knee in 90° of flexion were 39 mm and 32 mm, respectively. No clinical difference was found between the estimated pre-incision and surgical widths. However, the estimated pre-incision length with the knee in full extension and in 90° of flexion was significantly shorter than the surgical length. Skin measurements can be used to accurately determine patellar tendon width before surgery, but measurements of length are not as reliable.