Jordy van Sambeeck

Age at surgery is correlated with pain scores following trochlear osteotomy in lateral patellar instability 5 71 Background Patellar instability is a common problem seen by orthopedic surgeons. The annual incidence of primary patellar dislocation has been estimated at 43 per 100,000 in children under 16 years 5 . Recurrent patellar dislocation occurs in 15% to 45% of primary dislocation cases 6-11 . Patellofemoral stability is maintained by static stabilization of bony and soft tissue structures on the one hand and by dynamic stabilization through the activation of muscles on the other hand. The lateral displacement is statically restrained by the lateral facet of the trochlea and the medial patellofemoral ligament (MPFL) and mechanical alignment. Dynamic stabilization occurs by the activation and relaxation of co-acting muscles and muscle groups that directly or indirectly influence the position of the patella relative to the trochlea. Trochlear dysplasia is a condition in which the development of the trochlea results in an abnormal geometry, with a shallow, flat or a convex shape of the sulcus. It has been identified as the most consistent anatomic factor present in patients with recurrent patellar dislocations 12 . For the surgical treatment of patients with recurrent patellar dislocations and trochlear dysplasia, various surgical procedures have been described to reshape the abnormal trochlea 13, 14 . Trochlear osteotomies directly modify the patellofemoral joint with the risk of causing cartilage damage and alterationof joint kinematics and contact pressures 14 . Normal joint kinematics and contact pressures are fundamental for the long- term joint preservation and abnormalities in these factors could potentially lead to development of early patellofemoral osteoarthritis 13-16 . Due to the presumed susceptibility of complications of a trochlear osteotomy, these procedures are not performed often. However, a systematic review of literature demonstrated that the rate of major complications is comparable to those of other patellar stabilizing procedures 17 . The indication for trochlear osteotomies is still a matter of debate. Combination of the procedure with another bony or soft tissue procedure is often necessary to achieve patellar stability throughout the full range of knee motion. Patellar stability is reported to be restored in a large majority of patients who had a trochlear osteotomy 13, 18, 19 . Next to the anatomical abnormalities such as trochlear dysplasia, patella alta and insufficiency of the MPFL, other patient factors such as their age could be of influence on the results of surgery for patellar instability. Multiple studies have shown that a correlation exists between the age of patients and the risk on recurrent dislocation and the outcomes of surgery. A study of Fithian et al. indicated that patients with initial injury at a younger age had a higher risk of subsequent patellar subluxation or dislocation 11 . Hiemstra et al. found a correlation between age at time of surgery (MPFL-reconstruction) and outcome 20 . Palmu et al. 21 reported a redislocation rate of 67% following operative treatment for acute patellar dislocation in children younger than sixteen years of age, which is much higher than the pooled risk of redislocation of 12% presented by Smith