Shear-wave Elastography of the Hamstrings Tendon in Pediatric Patients Status Post Autologous-graft ACL Reconstruction: Implications for Rehabilitation, Return to Sport, and Risk for Re-injury

The PI of this project was:

This project was funded by: Radiology RD

The term of this project was: August 2019 to September 2020

The number of subjects scanned during this project was: 20

The incidence of anterior cruciate ligament (ACL) injury among pediatric athletes has significantly increased as more children and adolescents participate in competitive sports. Definitive treatment requires surgical reconstruction using a tendon graft, with the specific technique influenced by skeletal maturity. In adolescents with growth remaining, soft tissue autograft, most commonly the ipsilateral semitendinosus with or without gracilis tendon, is preferred to minimize risk of growth disturbance. In an attempt to utilize more objective criteria for determining readiness for return to activity, testing of an individual’s motion, strength, balance and movement patterns following ACL reconstruction has become a common component of postoperative therapy and return to play criteria. Through this type of testing, persistent hamstring weakness has been documented following ACL reconstruction using hamstring autograft, which is of concern as the hamstrings provide a posteriorly directed force on the tibia that decreases ACL loading. After tendon harvest, Semitendinosus has been shown to have the potential to regenerate tendon-like tissue, although the morphology of the regenerated tendon is altered.
We propose the use of ultrasound shear wave elastography (US-SWE) to noninvasively evaluate hamstring tendon size, tendon strength, and elasticity. In comparison to magnetic resonance imaging (MRI), ultrasound is widely available, rapid, low cost, and dynamic. In addition to the standard morphological information obtained by ultrasound, US-SWE evaluates the mechanical “stiffness” of the interrogated structure, a proxy for tensile strength. We hypothesize that, when applied to the medial hamstrings, this technique may provide information about the tensile strength and elasticity of the regenerated tendon following hamstring tendon harvest for ACL reconstruction. Viewed in the context of functional hamstring muscle testing and clinical outcomes, this data could be a valuable adjunct in advancing rehabilitation, guiding return-to-play decisions, and predicting risk of re-injury.