Evaluation of harvested and normal patellar tendons: a reliability analyses of magnetic resonance imaging and ultrasonography.

This study compared the reliability (interchangeability) of magnetic resonance imaging (MRI) and ultrasonography (US) examinations of the patellar tendon after using central third patellar tendon autografts during anterior cruciate ligament reconstruction. Nineteen consecutive patients (7 women, 12 men) underwent bilateral MRI and US of the patellar tendons 27 (24-29) months after anterior cruciate ligament reconstruction using ipsilateral central third patellar tendon autografts. Two experienced radiologists blinded to one another evaluated the examinations. Measurements of the length of the noninjured patellar tendon showed the greatest reliability between MRI and US, with no systematic difference (P=0.48), a small mean difference (-0.1 mm), and an interclass correlation coefficient of 0.74. The measurements of the thickness and width of the noninjured side were also judged as reliable. However, on the injured side a lower reliability was found between MRI and US. We conclude that MRI and US are reliable (interchangeable) methods only for evaluating noninjured patellar tendons.