Poster 241: Outcomes of Trochleoplasty for Recurrent Patellar Dislocation in Adolescents with Open Physes

Abstract

Objectives: Patellofemoral dislocation, the most severe presentation on the spectrum of patellar instability, is most common in adolescent populations. Trochlear dysplasia is an integral component of the disorder, and procedures aimed at correcting instability by addressing this dysplasia are often necessary. A theoretical risk of injury to the distal femoral physis exists in these surgeries. At our institution, a thick-flap sulcus deepening technique is used to re-shape the trochlear groove. The risk of injury to the physis in this procedure is not clearly delineated in the current literature. We investigated the outcomes in adolescent patients undergoing this procedure, hypothesizing that patients with open distal femoral physes and less than 2 years of remaining growth can safely and successfully undergo thick-flap sulcus deepening trochleoplasty. Methods: Seventeen adolescents (21 knees) with open physes underwent thick-flap trochleoplasty at our institution. Preoperative radiographs were used to evaluate leg axis and patella alta. Preoperative MRI was used to determine trochlear dysplasia (sulcus depth, spur height, patellofemoral index) and tibial tuberosity to trochlear groove distance (TTTG) distance. Preoperative and postoperative AP and lateral radiographs were used to evaluate and compare the lateral distal femoral angle (LDFA) and Blumensaat’s angle (BA). Preoperative and postoperative IKDC and Kujala outcome scores were measured to evaluate clinical improvement. Results: Median age at time of operation was 14.9 years for girls and 15.5 for boys. Mean follow up was 5.4 years from surgery. At two-year follow up, growth plates were closed in all but one knee. No clinical differences to the leg length or alignment were appreciated. There was no statistically significant change in lateral distal femoral angle (mean change 0.74 degrees, p = 0.1074). There was a statistically significant change in Blumensaat’s angle (mean change 0.89 degrees, p = 0.0477). Mean Kujala score improved significantly from 60.19 preoperatively to 90.36 postoperatively, p= 0.0008. Mean IKDC score improved significantly from 59.37 preoperatively to 87.21 postoperatively, p = 0.00064. There was recurrent instability in one knee, requiring revision surgery with distal femur and Fulkerson osteotomies. Conclusions: Adolescent patients nearing skeletal maturity can safely and successfully undergo thick- flap sulcus deepening trochleoplasty for patellar instability resulting from trochlear dysplasia. At follow- up, there was no clinical evidence of growth disturbances, and postoperative imaging demonstrated less than 1 degree difference in LDFA and BA at skeletal maturity, which are unlikely to be of clinical significance. These findings should be interpreted very carefully, as specific patient selection, trochleoplasty expertise, and extreme caution are still necessary to prevent iatrogenic injury to the distal femoral physis.