Articular cartilage defects: In vitro evaluation of accuracy and interobserver reliability for detection and grading with US

PURPOSE: To determine the accuracy and reliability of detecting and grading articular cartilage defects in porcine and human knees by using ultrasonog raphy (US). MATERIALS AND METHODS: US was used to evaluate 175 porcine and 16 human kne e surfaces with a linear 5-12-MHz transducer. Porcine defects of varying di ameter and depth were surgically created. Each porcine surface was independ ently assessed in blinded fashion by two radiologists for the presence and severity of defects. Accuracy of detection, interobserver reliability, and concordance between US and surgical grades were determined. Human specimens were retrieved from knees of patients who underwent joint arthroplasty. De fects in human knees detected with US were correlated with defects seen at direct surface visualization. RESULTS: Sensitivities for detection of porcine defects were 94% and 93% fo r readers 1 and 2, respectively; specificities were 90% and 77%, respective ly; positive predictive values were 98% and 95%, respectively; and negative predictive values were 78% and 73%, respectively. Interobserver agreement was high (weighted kappa = 0.80), and concordance between US and surgical g rades for both readers was high (weighted kappa = 0.90 and 0.78). In human cartilage, the distribution of cartilage denudation determined at US was th e same as that determined at direct visualization. CONCLUSION: High-frequency US was accurate and reliable for detection and g rading of knee articular cartilage defects.