Age, Sex, and Location Impact Osteochondritis Dissecans Lesion Depth and Their Relation to the Physis in Skeletally Immature Knees

Purpose To characterize the size of medial and lateral femoral condyle osteochondritis dissecans (OCD) lesions and their relation to the physis in skeletally immature patients. Methods Skeletally immature patients from 2008 to 2023 with medial or lateral femoral condyle OCD lesions on magnetic resonance imaging were included. At the center of each OCD lesion, 2 reviewers independently measured on coronal and sagittal cuts: (1) lesion depth, (2) shortest distance from subchondral bone to open physis, and (3) shortest distance from cartilage to open physis. Intraclass correlation coefficients for inter‐rater reliability and a mixed effects regression model were used to determine repeatability and between‐group differences. Results A total of 123 surgically treated knees from 101 patients were included. Among 82 medial lesions, mean lesion depth from the subchondral bone was 7.51 mm [range 4.10‐12.8], mean distance from subchondral bone‐to‐physis was 27.6 mm [19.1‐36.8], and mean distance from cartilage‐to‐physis was 30.3 mm [21.9‐38.1]. Subchondral bone‐to‐physis distance was smaller in women versus men ( P = .026) and in patients under 13 versus over 13 ( P = .006). For the 41 lateral OCD lesions, mean depth was 7.97 mm [3.78‐12.5], subchondral bone‐to‐physis was 21.4 mm [14.8‐26.5], and cartilage‐to‐physis distance was 24.4 mm [19.0‐28.7]. Subchondral bone‐to‐physis distance did not substantially differ between men and women ( P = .560); however, subchondral bone‐to‐physis distance was smaller in those under versus over age 13 ( P = .027). The mean distance between the OCD lesion base and the physis (safe zone) was 20.0 mm [12.0‐28.3] for medial lesions and 13.4 mm [5.33‐17.5] for lateral lesions. Conclusions OCD lesion characteristics in skeletally immature knees vary by age, sex, and location with younger patients (<13), female patients, and lateral lesions being closer to the physis than their counterparts. In our cohort, a drill or screw length of 16 mm would allow complete lesion penetration while leaving a minimum 3 mm safe zone. Level of Evidence Level IV, retrospective case series.