The severity of preoperative bone marrow oedema negatively influences short‐term clinical outcomes following arthroscopic bone marrow stimulation for osteochondral lesions of the talus.

Purpose: The purpose of this study was to study the effects of the severity of preoperative bone marrow oedema (BME) on the postoperative short‐term outcomes following bone marrow stimulation (BMS) for osteochondral lesions of the talus (OLTs) and to propose a new metric that combines volume and signal density to evaluate BME. Methods: Sixty‐five patients with symptomatic OLTs (<100 mm2) and preoperative BME, who received BMS in our institution from April 2017 to July 2021 with follow‐ups of 3, 6 and 12 months, were analysed retrospectively. The area, volume and signal value of the BME were collected on preoperative magnetic resonance imaging. The enroled patients were divided into two groups according to the BME index (BMEI), which was defined as the product of oedema relative signal intensity and the relation of oedema volume to total talar volume. Visual analogue scale, American Orthopedic Foot and Ankle Society (AOFAS), Tegner, Foot and Ankle Ability Measure (FAAM)–activities of daily living (ADL) and Sports scores were assessed before surgery and at each follow‐up. The relationship between the scores and the volume, relative signal intensity and BMEI was explored. Results: Sixty‐five patients with preoperative BME were divided into the mild (n = 33) and severe (n = 32) groups based on the BMEI. A significant difference was found for each score with the general linear model for repeated measures through all follow‐up time points (p < 0.001). For the preoperative and 12‐month postoperative changes of the enroled patients, 53 patients (81.5%) exceeded the minimal clinically important difference of AOFAS and 26 (40.0%) exceeded that of FAAM‐sports in this study. The mild group showed significantly more improvement in AOFAS scores at 12 months (89.6 ± 7.0 vs. 86.2 ± 6.2) and FAAM‐ADL scores at 6 months (83.6 ± 7.6 vs. 79.7 ± 7.7) and 12 months (88.5 ± 8.5 vs. 84.4 ± 7.7) than the severe group (p < 0.05). No significant difference of all the scores between the groups was found at 3 months. No significant correlation was found in each group between BMEI and clinical outcomes. Conclusion: The severity of the preoperative BME negatively affected short‐term clinical outcomes following arthroscopic BMS for OLTs. Worse clinical outcomes were shown at postoperative 6 and 12 months in patients with a high preoperative BMEI, which could be a favourable parameter for assessing the severity of BME and assist in developing personalised rehabilitation plans and determining the approach and timing of surgery. Level of Evidence: Level III. [ABSTRACT FROM AUTHOR]