Anterior cruciate ligament injuries in children
Abstract: The thesis discusses the two most common injuries to the anterior cruciate ligament (ACL) in children: The rupture in the substance of the ACL and the anterior tibial spine (ATS) fracture. The latter is an avulsion fracture of the tibial attachment of the ACL. The injuries and their treatment are studied in two clinical papers. Two experimental studies in rabbits are connected to the clinical studies and focuses on two fields of evident interest in the treatment of the injuries: ' The limitations of ACL reconstruction in children, with respect to drilling and tendon grafting across a growth plate (physis), and the risk of growth disturbances. ' The influence of growth on knee laxity after an ATS fracture. Twenty-eight consecutive children with ACL ruptures were followed for 3 - 5 years in order to describe the outcome of nonoperative treatment, to identify variables relevant to failure of nonoperative treatment, and to evaluate an over-the-top procedure for ACL reconstruction avoiding drill holes across the physes. 68% of the patients in whom nonoperative treatment was attempted had been operated on at follow-up, i.e. the injury has a marked impact on knee function in children. The patients not operated on were younger at the time of injury and had a lower activity level at follow-up. The surgical procedure improved knee function, but there was a correlation between high activity level and low subjective knee function indicating that the knee function was not completely restored. A controlled and measurable drill injury was made across the distal femoral physis in rabbits. The relative size of the drill injury necessary to cause growth disturbance was found to be 7 - 9%. A transphyseally placed tendon, even as a free graft, prevented solid bone bridge formation in the drill hole and growth disturbance. The results are of possible clinical significance when discussing improvement of ACL reconstruction in children. The long-term course of ATS fractures sustained in childhood was evaluated 10 - 39 years after injury in 61 adults. Age at injury, residual fracture displacement after healing, and the type of ATS fracture according to Meyers & McKeever were compared with objective and subjective knee function. The injury appears to be a relatively benign injury in the long term. The subjective knee function was excellent or good in 87% of the subjects. Age at injury did not influence the outcome. Only in patients with a totally avulsed ATS fragment (type 111), was there a correlation between residual fracture displacement and knee laxity, which in turn was correlated to subjective knee function. A method to measure anterior knee laxity in rabbits was developed using a materials testing machine. The results of the subsequent experimental study on the influence of growth on knee laxity after healing of a displaced ATS fracture type Ill, support the theory that further growth may reduce the functional elongation of the ACL caused by the fracture.
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