The Reliability of Assessing Radiographic Healing of Osteochondritis Dissecans of the Knee

Background: The reliability of assessing healing on plain radiographs has not been well-established for knee osteochondritis dissecans (OCD).

Purpose: To determine the inter- and intrarater reliability of specific radiographic criteria in judging healing of femoral condyle OCD.

Study design: Cohort study (Diagnosis); Level of evidence, 3.

Methods: Ten orthopedic sports surgeons rated the radiographic healing of 30 knee OCD lesions at 2 time points, a minimum of 1 month apart. First, raters compared pretreatment and 2-year follow-up radiographs on "overall healing" and on 5 subfeatures of healing, including OCD boundary, sclerosis, size, shape, and ossification using a continuous slider scale. "Overall healing" was also rated using a 7-tier ordinal scale. Raters then compared the same 30 pretreatment knee radiographs in a stepwise progression to the 2-, 4-, 7-, 12-, and 24-month follow-up radiographs on "overall healing" using a continuous slider scale. Interrater and intrarater reliability were assessed using intraclass correlations (ICC) derived from a 2-way mixed effects analysis of variance for absolute agreement.

Results: Overall healing of the OCD lesions from pretreatment to 2-year follow-up radiographs was rated with excellent interrater reliability (ICC = 0.94) and intrarater reliability (ICC = 0.84) when using a continuous scale. The reliability of the 5 subfeatures of healing was also excellent (interrater ICCs of 0.87-0.89; intrarater ICCs of 0.74-0.84). The 7-tier ordinal scale rating of overall healing had lower interrater (ICC = 0.61) and intrarater (ICC = 0.68) reliability. The overall healing of OCD lesions at the 5 time points up to 24 months had interrater ICCs of 0.81-0.88 and intrarater ICCs of 0.65-0.70.

Conclusion: Interrater reliability was excellent when judging the overall healing of OCD femoral condyle lesions on radiographs as well as on 5 specific features of healing on 2-year follow-up radiographs. Continuous scale rating of OCD radiographic healing yielded higher reliability than the ordinal scale rating. Raters showed substantial to excellent agreement of OCD overall radiographic healing measured on a continuous scale at 2, 4, 7, 12, and 24 months after starting treatment.