2015 ISAKOS Biennial Congress ePoster #1503

Clinical Impact of Subchondral Osseous Overgrowth After Microfracture in the Knee

Moiz I. Manaqibwala, MD, Boston, MA UNITED STATES
Kai Mithoefer, MD, Chestnut Hill, MA UNITED STATES

New England Baptist Hospital, Harvard Vanguard Medical Associates and Harvard Medical School, Boston, MA, USA

FDA Status Cleared

Summary: Subchondral osseous overgrowth as a result of aggressive debridement of the calcified cartilage layer, significantly increases the failure rate of microfracture




Subchondral osseous overgrowth has been described with variable frequency after microfracture but little systematic information is available about the clinical incidence, risk factors, and especially the clinical relevance of this phenomenon.


84 patients undergoing microfracture in the knee were prospectively followed up to 6 years postoperatively using cartilage sensitive magnetic resonance imaging (MRI) to detect the incidence of subchondral osseous overgrowth (SOO) and to correlate it to patient and lesion characteristics, surgical technique, validated functional outcome scores, and failure rate.


SOO was detected on MRI in 46 % at an average of 12 months and progressed to 62% at a mean of 34 months after surgery. Most overgrowth was low-grade. Patient and lesion characteristics did not affect the incidence of SOO but intra-operative aggressive debridement of the calcified cartilage layer presented a significant risk factor for SOO (OR 24 (95% CI 5.16-111.56). KOOS scores were not significantly different between patients with or without SOO. However, 93% of patients that failed microfracture demonstrated osseous overgrowth and patients with osseous overgrowth showed significantly higher failure rates than patients without overgrowth (25% versus 3.1%, p<0.01).


Subchondral osseous overgrowth is frequently observed after microfracture surgery but is mostly of low grade. Surgical technique can affect the incidence of this phenomenon. Importanly, subchondral overgrowth significantly increases the rate of postoperative failure following microfracture.