Comparison of Audioarthrography and Magnetic Resonance Imaging for Diagnosis of Patellofemoral Cartilage Damage

PURPOSE To determine the diagnostic accuracy of patellofemoral audioarthrography for cartilage damage assessment as compared with arthroscopy and magnetic resonance imaging. METHODS Ninety patients were tested with Patellofemoral Audioarthrography (PFAA) prior to knee arthroscopic surgery for meniscal or anterior cruciate ligament lesions. All patients had a preoperative standard MRI with a cartilage damage diagnosis. An arthroscopic evaluation of cartilage damage of patella and trochlear groove was done using the International Cartilage Repair Society (ICRS) cartilage damage score (a-ICRS). These findings were compared with the preoperative PFAA score (PFAA-ICRS) and MRI expected ICRS scores (MRI-ICRS). We performed a paired-design study that compared indirect information of patellofemoral cartilage damage as an anatomical measurement. The concordance of arthroscopic findings, ICRS’s expected score with PFAA or MRI were assessed. The diagnostic accuracy of the PFAA was evaluated, and the area under the receiver operating curve (ROC) curve, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and probability ratios were calculated. RESULTS Sixty three patients (70%) had some degree of cartilage damage diagnosed by arthroscopy. The scores matched in 78 patients when compared with PFAA (87%), and in 48 patients with MRI (53%). Accuracy was better with PFAA than MRI in 33% of patients with a-ICRS 1, 38% in a-ICRS 2, 34% in a-ICRS 3 and 15% in a-ICRS 4. Arthroscopic and PFAA ICRS scores were statistically similar in all age groups (p=0.82). The a-ICRS scores were significantly lower than MRI-ICRS scores in the 35-45 years of age group (p=0.028). Specificity Likelihood Ratios for PFAA were LR+ of 8.43 and an LR- of 0.10, and for MRI were LR+ of 2.80 and an LR- of 0.38. When comparing arthroscopic findings with the MRI-ICRS and PFAA-ICRS scores, the Kappa Weighted Value matches were 0.53 and 0.91 respectively. CONCLUSION Our study showed that PFAA was able to determine the degree of patellofemoral cartilage damage when compared and confirmed with arthroscopy. Its diagnostic accuracy was consistently better than MRI in all degrees of chondral injury. PFAA had a favorable and accurate predictive value for patellofemoral cartilage lesion diagnosis. In our study, it exceeded the diagnostic capability of conventional MRI, and should be considered as a future non-invasive and cost-effective diagnostic option for joint monitoring and prevention of patellofemoral osteoarthritis.