Purpose: Patellofemoral instability is influenced by ligamentous, boney and neuromuscular factors. The most important variables are trochlea geometry, medial patellofemoral ligament (MPFL), patella height, tibial tuberosity-trochlea groove distance (TT-TG) and the extensor muscles. Treatment is complicated by these multifactorial conditions. This prospective study examined the influence of risk factors on clinical results and athletic activities where treatment was confined to ligamentous procedures only.
Methods: Fifty patients with chronic patellofemoral instability were treated with MPFL reconstruction using an autologous gracilis tendon. Clinical data, radiographs and magnetic resonance imaging (MRI) were prospectively evaluated pre- and postoperative (minimum follow-up 12 month) to detect existing risk factors for patellofemoral instability and to evaluate clinical and sport ability scores (Kujala, Valderrabano).
Results: There was a low rate of redislocation (2 %) and an average Kujala score of 87 ± 13 points postoperative. The MRI showed good integration of the reconstructed MPFL and a positive effect regarding the decrease of patella tilt (16.1° to 11.2°). A negative relationship was found between the degree of trochlear dysplasia and outcomes. 80 % of all patients returned to the same or higher level of physical activity.
Conclusions: Addressing only ligamentous factors through MPFL reconstruction leads to satisfying clinical results and low redislocation rates in most patients. In cases with a high degree of trochlear dysplasia and enlarged TT-TG, additional procedures such as trochleaplasty and tibial tuberosity transfer should be considered as well.
Level of evidence: IV.