T2-mapping at 3 T after microfracture in the treatment of osteochondral defects of the talus at an average follow-up of 8 years

Abstract

Purpose: To compare repaired cartilage with native cartilage, and inter-observer reliability, using T2 mapping at 3 T for assessing cartilage repair in osteochondral defects of the talus after the microfracture technique.

Methods: We enrolled eight females and seven males undergoing arthroscopic microfracture for osteochondral defects of the talus at an average follow-up of 7.9 ± 2.2 years (range 5-13 years). Cartilage tissue was assessed using a 3-T magnetic resonance imaging unit with an 8-channel phased array foot and ankle coil (gradient strength, 50 mT/m; slew rate, 200 T/m/s). T2 maps were then calculated. Three independent boarded specialists evaluated the images, and magnetic resonance observation of cartilage repair tissue scores was used to assess the cartilage and joint status. Clinical results were assessed using the Hannover Scoring System (HSS) for the ankle and the American Orthopaedic Foot and Ankle Society (AOFAS) hind-foot score.

Results: No significant mean differences were found between the T2 properties of the repair tissue and those of the native reference cartilage (T2 = 38.6 ± 5.3 ms, range 30.2-55.8 ms vs. 40.3 ± 8.5 ms, range 31.4-59.8 ms, respectively; intra-class correlation coefficient = 0.94; confidence interval 0.84-0.99, P ≤ 0.001). Despite ≥50 % defect filling in all patients, subchondral bone changes were considerable. The HSS at the follow-up revealed a mean score of 87 ± 12 (range 51-97), and the AOFAS-Score was 90 ± 13 (range 59-100).

Conclusions: 3 T T2 maps were similar in repaired and native cartilage with good inter-observer reliability.

Level of evidence: IV.