Increased Tibial Tubercle–Trochlear Groove Distance and Sulcus Angle Are Associated With Patellar Osteochondritis Dissecans in Pediatric Patients

Abstract

Background:

Osteochondritis dissecans (OCD) lesions in the knee are most commonly found in the medial femoral condyle (MFC). However, a paucity of literature has explored the characteristics or morphology of patellar OCD lesions.

Purpose/Hypothesis:

The purpose of this study was to analyze patellar tracking and patellofemoral measurements of pediatric patients with patellar OCD compared with patients with MFC OCD. It was hypothesized that the patients with patellar OCD would demonstrate an increased bony sulcus angle, cartilaginous sulcus angle, and tibial tubercle–trochlear groove (TT-TG) distance compared with patients with MFC OCD.

Study Design:

Case series; Level of evidence, 3.

Methods:

Patients aged ≤18 years diagnosed with either a patellar or MFC OCD lesion at a single tertiary care hospital between January 2016 and May 2023 were analyzed. Patients with a history of patellar instability were excluded. The Caton-Deschamps index, cartilaginous bony height, trochlear depth, patellar tilt, lateral patellar displacement, cartilaginous sulcus angle, bony sulcus angle, and TT-TG distance were assessed on magnetic resonance imaging (MRI). Patients were matched 1:2 based on sex and chronological age within 2 years between the patellar and MFC OCD groups.

Results:

A total of 40 extremities in 34 patients with patellar OCD were matched to 80 extremities in 73 patients with MFC OCD. The mean age at the time of MRI was 14.1 ± 2.3 years, and 23% were female. Compared with patients with MFC OCD, patients with patellar OCD had a significantly greater TT-TG distance (11.55 ± 4.15 vs 13.35 ± 4.07 mm, respectively; P = .03). The cartilaginous sulcus angle (150.63°± 7.20° vs 128.09°± 14.07°, respectively; P < .001) and bony sulcus angle (144.70°± 7.78° vs 137.37°± 9.62°, respectively; P < .001) were higher in the patellar OCD group compared with the MFC OCD group. Of patients with patellar OCD, 40% had a TT-TG distance >15 mm, and of patients with MFC OCD, 20% had a TT-TG distance >15 mm. The patellar OCD group had 3.7 times the risk of having a patellar dislocation compared with the MFC OCD group.

Conclusion:

An increased TT-TG distance and sulcus angle were associated with patellar OCD in pediatric patients. Patients with abnormal patellofemoral morphology who undergo treatment for a patellar OCD lesion may subsequently develop a patellar dislocation; in this study, patients with patellar OCD without a history of patellar dislocations demonstrated a nearly 4-fold higher dislocation rate compared with an age- and sex-matched group of patients with MFC OCD.