Good 5-year results and a low redislocation rate using an á la carte treatment algorithm for patellofemoral instability in patients with severe trochlea dysplasia

PURPOSE: Trochlear dysplasia is a major risk factor for recurrent patellar instability, reduced quality of life and osteoarthritis of the patellofemoral joint. Patellar instability in patients with trochlear dysplasia can be treated by trochleoplasty, usually in combination with medial patellofemoral ligament reconstruction (MPFL-R). An á la carte treatment algorithm, which also addresses patella alta, lateralisation of the tibial tuberosity and valgus or torsional malalignment when present has been standard in one clinic for treatment of patellar instability patients since 2009, based on the hypothesis that it results in optimal subjective and clinical outcome, normalisation of the lateral trochlea inclination (LTI) angle and a low rate of patellar redislocation.

METHODS: This prospective study reports the 5-year results for consecutive patients with high-grade trochlea dysplasia operated according to the algorithm 2010-2017, evaluated preoperatively and 1, 2 and 5 years postoperatively. Clinical information on previous surgery and postoperative patellar stability, range-of-motion (ROM) and subsequent surgery were registered. Subjective outcome was evaluated by four patient-reported outcome measures (PROMs): Kujala, Lysholm, International Knee Documentation Committee and Knee injury and Osteoarthritis Outcome Score. The LTI angle was measured pre- and postoperatively on magnetic resonance imaging scans.

RESULTS: There were 131 patients (87 females) with a median age of 22 years (range: 14-38). All had a trochleoplasty and an MPFL-R. Additional procedures (tibial tuberosity medialisation/distalisation and/or femoral/tibial osteotomy) were performed in 52%. All PROM scores improved from preoperatively to 1-year follow-up with further improvement at 2 and 5 years after surgery (p < 0.05). Three patients (2%) had a traumatic patellar dislocation 9, 12 and 24 months postoperatively and 38% underwent subsequent surgery (hardware removal, arthroscopically assisted brisement force, knee arthroscopy). A normalisation of the LTI angle (≥11°) was achieved in 76%.

CONCLUSIONS: Treatment according to the à la carte algorithm for patients with patellar instability and high-grade trochlear dysplasia resulted in significant clinical and subjective improvement in all PROM scores and a very low redislocation rate (2%) 5 years after surgery.

LEVEL OF EVIDENCE: Level II.