Summary

Sulcus-deepening trochleoplasty performed as a closing-wedge osteotomy with a dedicated cutting guide shows promising mid-term results in preserving cartilage and maintaining functional outcomes in patients with patellar instability and high-grade trochlear dysplasia over a 3 to 10-year follow-up period.

Abstract

Background

Recurrent patellar dislocations and trochlear dysplasia are closely linked to cartilage damage and early patellofemoral osteoarthritis (PF OA). While trochleoplasty effectively addresses patellar instability in cases of high-grade trochlear dysplasia, its impact on cartilage degeneration remains uncertain. The traditional Dejour technique for sulcus-deepening trochleoplasty involves uniform subchondral resection, which may inadvertently cause chondral damage and fail to restore optimal trochlear congruency, potentially leading to early PF OA. To improve outcomes, we propose a sulcus-deepening trochleoplasty performed as a closing-wedge osteotomy (CW OT) with a dedicated cutting guide. This approach aims to preserve subchondral bone and optimize cartilage integrity. Unlike conventional radiographic assessments, this study utilizes MRI follow-up to evaluate the impact of this surgical technique on cartilage health. We hypothesize that the use of thick osteochondral flaps and a dedicated cutting guide will prevent secondary PF OA and maintain functional outcomes.

Purpose

The primary objective of this study is to evaluate patellofemoral cartilage integrity at 5 years post-sulcus-deepening trochleoplasty using MRI. The secondary objective is to assess patient-reported outcomes over time, comparing the first 3 years postoperatively with outcomes beyond 3 years.
Study Design: Prospective cohort study; Level of Evidence, 2.

Methods

From 2015 to 2022, all patients with patellar instability and high-grade trochlear dysplasia scheduled for sulcus-deepening trochleoplasty performed as a CW OT with a thick osteochondral flap were included. The procedure was conducted 5mm below the articular surface using a saw blade guided by K-wires positioned with a dedicated guide, allowing for greater resection in the central and proximal trochlea while preserving the medial and lateral edges. Patients were prospectively followed with annual KOOS, Kujala, IKDC, and Lysholm scores, and MRI every 2 years. A radiologist independently measured cartilage thickness on MRI at baseline and final follow-up in four focal regions of the patellofemoral joint, including the medial and lateral facets of the patella and the medial and lateral portions of the trochlea. Results were categorized as good (Modified Outerbridge Classification (MOC) grade <2), fair (MOC grade 3), or poor (MOC grade 4).

Results

A total of 36 consecutive patients were included, with 75% presenting Dejour type B and 25% Dejour type D trochlear dysplasia. The male-to-female ratio was 0.8, with an average age of 23.9 ± 7.3 years and a BMI of 23.2 ± 4.6 kg/m². Trochleoplasty was combined with medial patellofemoral ligament reconstruction in all cases, tibial tuberosity osteotomy in 69%, and lateral patellar retinaculum Z-lengthening in 91%. The mean follow-up period was 5 years (range 3-10 years). The most common postoperative adverse event was arthrofibrosis (14%), successfully treated by arthroscopic arthrolysis in all cases. No significant differences were observed in KOOS subscales, Kujala anterior knee pain scale, or Lysholm scores when comparing results from the first 3 years postoperatively to those beyond 3 years. MRI analysis revealed good outcomes were observed in 68%, fair outcomes in 23%, and poor outcomes in 9%.

Conclusion

Sulcus-deepening trochleoplasty performed as a closing-wedge osteotomy using a dedicated cutting guide shows promising mid-term results for patients with patellar instability and high-grade trochlear dysplasia. The procedure achieves good to fair cartilage preservation in 91% of patients over a 3 to 10-year follow-up period, with functional outcomes remaining stable beyond three years.