Arthroscopic Measurements Predict Knee Chondral Lesion Size More Accurately than Magnetic Resonance Imaging, and Mechanism of Injury Influences Ability of Either Technique to Predict Graft Size

Abstract

PurposeTo compare osteochondral defect size measurements and characteristics across magnetic resonance imaging (MRI), arthroscopy, and at the time of implantation with osteochondral allograft (OCA) transplantation or autologous chondrocyte implantation (ACI). MethodsPatients who underwent ACI and OCA transplantation at a single institution between 2015 and 2019 were retrospectively identified. Patients were excluded if they had severe osteoarthritis, if MRIs were not available for review, if surgical records did not include defect sizing necessary for analysis, and if operative reports were not available. Osteochondral lesion characteristics including size were collected preoperatively from MRI and arthroscopy and at the time of definitive open surgical intervention. Subgroup analysis was performed comparing measurement techniques depending on the corrective surgical approach used as well as depending on the mechanism of chondral injury to determine if these had any effect on the ability of arthroscopy or MRI to predict graft size. ResultsOverall, 136 chondral lesions were addressed with restoration procedures in 117 patients (mean age 32.5 years). Average difference between final graft size and lesion area measured with index arthroscopy was 116 mm2, while average difference between final graft size and lesion size measured with preoperative MRI was 182 mm2 (P < .001). Depending on surgical technique, measurements with MRI were more similar to final graft size when a patient underwent OCA transplantation versus ACI (P = .007). Depending on mechanism of injury, MRI measurements of lesions were closer to graft area when lesions resulted from trauma (P = .047). ConclusionChondral lesion size determined by preoperative MRI imaging is less accurate than arthroscopic measurements. The mechanism injury leading to chondral damage and degree of damage may influence the ability of MRI and arthroscopy to accurately measure chondral lesions and predict the final graft size used in surgical correction. Level of EvidenceRetrospective Cohort Study (Level III)