Abnormalities of the lesser tuberosity on radiography and MRI: association with subscapularis tendon lesions

OBJECTIVE: The objective of our study was to retrospectively evaluate the association between abnormalities of the lesser tuberosity and subscapularis tendon lesions. MATERIALS AND METHODS: Cortical irregularities and cysts of the lesser tuberosity were evaluated on radiographs and MR images in 70 patients: 31 with normal subscapularis tendons and 39 with subscapularis tendon tears. These imaging findings were correlated with subscapularis tendon tears diagnosed during arthroscopy and with fatty atrophy of the subscapularis muscle seen on MR images. Correlations between imaging findings, patient age, history of trauma, and the reference standards were assessed using gamma coefficients. Interreader agreement was calculated using kappa values. RESULTS: For the diagnosis of subscapularis tendon tears, the sensitivity of cortical irregularities and cysts on radiographs was 44%/51% (reader 1/reader 2) and 21%/21%, respectively; specificity was 65%/68% and 87%/87%. The sensitivity of cortical irregularities and cysts on MRI was 64%/72% and 36%/39%. Specificity was 48%/45% and 81%/77%. For fatty atrophy of the subscapularis muscle, the sensitivity of cortical irregularities and cysts on radiographs was 67%/73% and 17%/27%, respectively; the specificity was 63%/63% and 83%/85%. Significant (p > 0.05) positive correlations were found between cortical irregularities and surgical grade of subscapularis tendon tear for reader 2 (radiography, gamma = 0.39; MRI, gamma = 0.45) and between lesser tuberosity abnormalities and patient age (gamma = 0.11 and 0.43) for both readers. Interobserver agreement of imaging findings varied from moderate to substantial (kappa = 0.50-0.76). CONCLUSION: Abnormalities of the lesser tuberosity are moderately associated with subscapularis tendon tears and patient age. Cysts seen in the lesser tuberosity on shoulder radiographs or MR images are relatively specific for subscapularis tendon tears and muscle atrophy.