Samenvatting

A rupture of the anterior cruciate ligament (ACL) is one of the most common sports injuries worldwide, and also one of the most devastating injuries of the knee. An ACL injury happens mostly to young athletes (aged 14-40) who participate in landing, cutting and pivoting sports with fast decelerations, while around 70% of all ACL injuries result from a ‘non-contact’ mechanism.
Rehabilitation after an ACL rupture is prolonged and intensive and is needed to restore the knee function, strength and stability as it was prior to the injury. It is decided during the rehabilitation process in phase 5 if the athlete can return to sport. A triple hop test and a triple crossover hop test are used to assess an athlete’s readiness. A limb symmetry index (LSI) greater than 90% indicates an athlete’s readiness. Despite the fact that athletes can pass these hop tests, the incidence of a subsequent ACL rupture is 6 times as high as an initial rupture. This is partly due to the fact that an ACL injury results in joint specific, bilateral changes of the lower extremity kinematics, while the non-injured leg is also affected due to the long period of inactivity after reconstruction and therefore not the best comparison to use for the LSI. The bilateral changes of the lower extremity kinematics increase the risk for an ACL injury and therefore, should be looked at during the return to sport phase.
The main purpose of this thesis was to find out if the analysis of the lower extremity kinematic symmetry added any value to the ACL reconstruction – return to sport tests. Two criteria were used to do this: an LSI criterion based on the lower extremity kinematics, and a normative data criterion, also based on the lower extremity kinematics. Before both analyses were conducted on athletes with an ACL reconstruction, these criteria needed to be created with help from a healthy peers database. 40 Healthy subjects participated and were divided into 4 groups based on age and gender. The Xsens MVN Awinda was used to obtain the kinematic joint angles of the knee and hip at initial contact and 40ms after initial contact during the landing phase of the triple hop test and the triple crossover hop test.
Data from this study revealed the fact that healthy athletes also show significant differences in the side-to-side hip and knee kinematics during both hop tests. These differences are used to find LSI criteria for each joint motion separately. The exact kinematic data was used to create a normative data criterion for each joint motion separately. Both criteria were used to see how an individual athlete with an ACL reconstruction performed compared to his/her peers. Results showed that the majority of athletes with an ACL reconstruction did pass the hop tests based on their kinematics.
The findings of this study highlight the need for additional assessment of the side-to-side kinematics. While the control groups (based on gender and age) existed of 10 subjects each, more research with a greater amount of controls is needed to create more reliable criteria for kinematic LSI and normative kinematic data.