Pilot study into single limb landing biomechanics following quadriceps tendon autograft anterior cruciate ligament reconstruction

Introduction: As the optimal graft choice for anterior cruciate ligament (ACL) reconstruction continues to be debated, scientific interest into using the quadriceps tendon autograft (QT) has increased. Reported benefits of a QT graft include satisfactory structural size for graft harvesting, similar properties to the native ACL, and similar knee joint stability outcomes compared to other autografts. However, very little is known about biomechanical outcomes following QT ACL reconstruction. Therefore, the purpose of this pilot study was to examine trunk and lower limb kinematic variables of the operated limb and non-operated limb during single limb landings. Methods: Six participants (1 Female/5 Male; Age at testing range 18-29 years; Lysholm range 82-100) who had undergone QT ACL reconstruction (Time since surgery range 2.1-3.2 years) and had returned to either recreational or competitive sports were included in this study. The QT graft was harvested as a soft tissue graft. A three-dimensional motion analysis system was used to collect kinematic data of the trunk, pelvis, hip, knee, and ankle of the operated and non-operated limb for participants during two different single limb landing tasks. (i) Participants used a single limb to propel forward and land at a distance equal to their leg length; (ii) Participants used a single limb to propel themselves as high as possible with the use of arm swing, landing in the same position as take-off. Within-subjects comparisons was performed for kinematic variables using paired t-tests. Results: When looking at the group mean no statistically significant differences in trunk and lower limb kinematic variables were found between the operated limb and the non-operated limb during either landing task. However, individual participant differences were clearly present. Two out of the six participants had more than 10 degrees less peak knee flexion and greater than 10 degrees difference in peak knee coronal plane motion when landing onto the operated limb compared to the non-operated limb. Furthermore, when landing onto the operated limb, three participants during a forward hop and two participants during a countermovement hop had more than five degrees greater peak trunk ipsilateral side lean compared to the non-operated limb. Discussion: Despite all participants being more than two years post QT ACL reconstruction and having returned to sports, some participants had altered landing biomechanics when landing onto the operated limb when compared to the non-operated limb. In these participants the observed patterns of reduced knee flexion, stiffer single limb landings, may have implications for both sport performance and risk of reinjury. Further research exploring movement quality in a larger sample size is warranted. Impact/Application to the field•Knowledge into biomechanical outcomes during high demand tasks following QT ACL reconstruction. Conflict of interest statement: My co-authors and I acknowledge that we have no conflict of interest of relevance to the submission of this abstract.