gms | German Medical Science

Objectives: Shear wave elastography (SWE) can be used to assess the mechanical properties of tendons by quantitatively analyzing their tissue stiffness. Currently, there are three tendon autografts available for the reconstruction of the anterior cruciate ligament (ACL), the quadriceps tendon (QT), the patellar tendon (PT), and the hamstring tendons (HT). Each tendon autograft has advantages, but also disadvantages regarding their biomechanical properties and the donor site morbidity. So far there is no study available that has investigated the in vivo stiffness of these tendons using SWE.

Methods: Fourty semiprofessional competitive athletes (age: 24±3 years, BMI: 25±3 kg/m², Training workload: 11±3 hours/week) and 40 age-matched healthy controls (age: 24±4 years, BMI: 23±2 kg/m², Training workload: 4±2 hours/week) were recruited for this case-control study. All participants completed a standardized questionnaire, including the Lysholm Score and International Knee Documentation Committee (IKDC) Score. Physical activity was assessed using the Cincinnati Sports Activity Scale (CSAS). Subsequently every participant underwent a standardized multimodal ultrasound protocol consisting of B-mode-ultrasound (B-US), Power Doppler-ultrasound (PD-US). The modified Ohberg Score was conducted and a shear wave elastographic examination of the bilateral QT, PT and HTs was performed. For all examinations, the Siemens S2000 ultrasound machine (Acuson S2000, Siemens Healthineers, Erlangen, Germany) was used. Univariate comparisons between groups were conducted with independent sample t tests. A significance level ofα= 0.05 was defined to indicate statistical significance.

Results and conclusion: Both groups reached full Lysholm (AG: 100±0, CG: 100±0) and full IKDC Scores (AG: 100±0%, CG: 100±0%), while AG showed higher CSAS Scores (AG: 100±0, CG: 70±10). None of the participants showed any signs of neovascularization throughout the tendons, indicating a modified Ohberg Score of 0. Median QT and PT stiffness was significantly higher in semiprofessional athletes (QT: AG, 4.44m/s vs CG, 3.95 m/s, p=0.032; PT: 4.72 m/s vs 3.82 m/s, p=0.028). There was no significant difference in HT stiffness between AG and CG (ST: 5.11 m/s vs 4.77 m/s, p=0.062).

This is the first study to evaluate in vivo mechanical tendon properties of tendons used for ACL reconstruction. Semi-professional athletes have greater tendon stiffness than healthy controls in QT and PT, potentially caused by long-term adaptations to heavy tendon loading.Interestingly, no differences were found between the groups for HT. The quantitative information obtained by SWE could be of particular interest for graft choice for ACL reconstruction.