Mithoefer Kai, Venugopal Vivek, Manaqibwala Moiz
Department of Orthopedics and Sports Medicine, Harvard Vanguard Medical Associates, Boston, Massachusetts, USA
Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA.
Am J Sports Med. 2016 Aug;44(8):2057-63. doi: 10.1177/0363546516645514. Epub 2016 May 17.
Subchondral bone overgrowth has been described with variable frequency after microfracture, but little systematic information is available about the clinical incidence, risk factors, or clinical relevance of this phenomenon.
Subchondral overgrowth (1) occurs with high incidence and various degrees after microfracture, (2) is associated with risk factors, and (3) affects clinical outcome score and failure rate.
Cohort study; Level of evidence, 3.
A total of 84 patients undergoing microfracture in the knee were prospectively followed up to 6 years postoperatively through use of cartilage-sensitive magnetic resonance imaging to detect the incidence of subchondral bone overgrowth. The quantity of the overgrowth was graded systematically and was then correlated to patient and lesion characteristics, surgical technique, validated functional outcome scores, and failure rate.
Subchondral bone overgrowth was observed in 62% of patients at a mean of 22 months after surgery. Most bone overgrowth (64%) was low grade and developed during the first 12 months after microfracture. Risk factors for bone overgrowth included high body mass index, defects on the lateral femoral condyle, and aggressive debridement of the calcified cartilage layer. Knee injury and Osteoarthritis Outcome Score results were not significantly different between patients with or without subchondral bone overgrowth. However, 93% of patients who failed microfracture demonstrated osseous overgrowth, and patients with osseous overgrowth showed a significantly higher failure rate (25%) than patients without overgrowth (3.1%; P < .01).
Subchondral bone overgrowth is frequently observed after microfracture surgery but is mostly of low grade. Several risk factors were identified that can affect the incidence of this phenomenon. Importantly, subchondral overgrowth is associated with an increased rate of postoperative failure after microfracture.
微骨折术后软骨下骨过度生长的发生率各不相同，但关于这一现象的临床发生率、风险因素或临床相关性的系统性信息较少。
（1）微骨折术后软骨下骨过度生长发生率高且程度各异；（2）与风险因素相关；（3）影响临床结局评分和失败率。
队列研究；证据等级，3级。
对84例行膝关节微骨折手术的患者进行前瞻性随访，术后6年通过使用软骨敏感磁共振成像检测软骨下骨过度生长的发生率。对过度生长的量进行系统分级，然后将其与患者和病变特征、手术技术、经过验证的功能结局评分以及失败率进行关联分析。
62%的患者在术后平均22个月时观察到软骨下骨过度生长。大多数骨过度生长（64%）为低度，且在微骨折后的前12个月内出现。骨过度生长的风险因素包括高体重指数、外侧股骨髁缺损以及对钙化软骨层的积极清创。有无软骨下骨过度生长的患者之间，膝关节损伤和骨关节炎结局评分结果无显著差异。然而，微骨折失败的患者中有93%出现了骨过度生长，有骨过度生长的患者的失败率（25%）显著高于无过度生长的患者（3.1%；P <.01）。
微骨折手术后经常观察到软骨下骨过度生长，但大多为低度。已确定了几个可影响这一现象发生率的风险因素。重要的是，软骨下骨过度生长与微骨折术后失败率增加相关。
