Real-time elastography of patellar tendon in patients with auto-graft bone-tendon-bone anterior cruciate ligament reconstruction

Patellar tendon donor site has been previously evaluated in patients with auto-graft bone-tendon-bone (BTB) anterior cruciate ligament (ACL) reconstruction using either magnetic resonance imaging or B mode ultrasound. However, donor site patellar tendon strain ratio-reflecting structural features-has not been studied with US elastography. Here, we ascertain real-time elastography properties of patellar tendon donor site and clinical relevance of these properties in patients with auto-graft BTB ACL reconstruction in the postoperative period. Patients who underwent ACL reconstruction using BTB autograft were evaluated. Demographic, operative and clinical data (severity of pain, Lysholm Knee score, sit to stand test, packages/year for smoking amount) were noted. Patellar tendons of the operated knees were evaluated by ultrasound (length and thickness) and sonoelastography (strain ratio). The healthy knees of the patients constituted the control group. Eighteen patients (17 M, 1 F; mean age 30.9 +/- 7 years) were evaluated. Mean postoperative follow-up period was 22.1 +/- 2.6 (range 18-26) months. Patellar tendons were shorter and thicker on the operated side when compared with the contralateral side (both p = 0.001). Patellar tendon strain ratios of the operated side were lower than the contralateral side (harder tendon on operated side). While there was no correlation between strain ratios and clinical variables (age, BMI, postoperative time, severity of pain, Lysholm score, all p values > 0.05), significant negative correlations were detected between strain ratios of proximal, middle and distal thirds of operated side and amount of smoking (p = 0.008, r = -0.607, p = 0.009, r = -0.598, p = 0.023, r = -0.533, respectively). Patellar tendons on the operated sides seemed to thicken and shorten with decreased strain ratios at the donor side compared to the healthy side at an average of 2-year follow-up in patients with ACL reconstruction using BTB autograft, and amount of smoking had negative relationship with strain ratio of donor patellar tendon.