The Effects of Vibration on Quadriceps Function and Landing Biomechanics in Individuals with Anterior Cruciate Ligament Reconstruction

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PROJECT SUMMARY The risk of sustaining a second anterior cruciate ligament (ACL) injury is 6 times greater following ACL reconstruction surgery (ACLR) compared to those without a history of ACL injury and poses significant risk to long term knee joint health (i.e., early onset osteoarthritis and poor quadriceps function). Mechanical knee stability is restored after ACLR; however, functional deficits such as quadriceps dysfunction often persist and result in high-risk lower extremity biomechanics and abnormal joint loading that increase the risk of a second ACL injury. Evidence-based return to physical activity (RTPA) criteria have been developed to identify at risk individuals after ACLR based on between limb symmetry (limb symmetry index, LSI) on single leg tasks (i.e. hopping and landing) and quadriceps strength. Meeting RTPA criteria (>90% LSI) can reduce the secondary injury rate by 84%; however few individuals (11-57%) with ACLR treated with standard rehabilitation meet RTPA criteria before reengaging in unrestricted physical activity. As the primary contributor to poor landing biomechanics, failure to meet RTPA criteria, and ultimately secondary ACL injury, there is a need to develop interventions to alleviate persistent quadriceps dysfunction post-ACLR. Whole body vibration (WBV) and local muscle vibration (LMV) excite the quadriceps and increase force production that potentially improves knee stability during landing, hence mitigating risk of second ACL injury. Vibration also acutely improves voluntary quadriceps function (i.e., peak torque, and EMG amplitude) and mitigates aberrant gait biomechanics in individuals with ACLR. To that end, previous clinical trials indicate that vibration (WBV and LMV) embedded in ACLR rehabilitation improves quadriceps function and somatosensory function to a greater extent than rehabilitation alone. However, the longitudinal effects of vibration rehabilitation on quadriceps dysfunction and subsequent reduction in high-risk biomechanics associated with second ACL injury and objective RTPA criteria have not been evaluated. Therefore, the objective of this proposal is to assess the effects of vibration rehabilitation (WBV and LMV) on quadriceps function, landing biomechanics, and the likelihood of meeting RTPA criteria at 6 and 12 months post-ACLR. The central hypothesis is that 1) Vibration rehabilitation will enhance quadriceps function during landing, 2) Vibration rehabilitation will enhance lower extremity biomechanics during lading (i.e. peak sagittal and frontal plane angles and moments and vertical ground reaction force), and 3) the Vibration rehabilitation groups will have greater odds of meeting RTPA criteria than the Standard Rehabilitation group at 6 and 12 months post-ACLR. Completion of this project and the training plan detailed in this application in conjunction with direct interaction with my sponsor and collaborators enable me to develop new skills in clinical trial management, neuromuscular function assessment, and advanced statistical analysis and foster my development as a successful independent clinical researcher.