Hidden Long Head of the Biceps Tendon Instability and Concealed Intratendinous Subscapularis Tears

BACKGROUND: Few studies have described the characteristics of a concealed intratendinous subscapularis tear (CIST), and there is a lack of research on the preoperative predictability of such lesions. PURPOSE: To describe the characteristics of a CIST as seen on magnetic resonance imaging (MRI) and intraoperatively and to develop a scoring system for predicting such lesions. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Retrospectively, we identified 43 patients with CISTs among 442 consecutive patients who had undergone rotator cuff repair from July 2014 to June 2016. Range of motion, visual analog scale results for pain and function, and patient-reported outcome scores were evaluated preoperatively and at 1 and 2 years postoperatively. CISTs were classified arthroscopically as small (<5 mm), medium (5-10 mm), and large (>10 mm). We performed repair (≥50%) or debridement (<50%) depending on the total subscapularis tendon tear size including the CIST. Preoperative MRI findings were analyzed by 2 observers and were correlated with the arthroscopic findings. A 10-point scoring system was developed based on characteristics during the physical examination (anterior tenderness, bear hug sign), MRI (biceps tendon displacement and subluxation, subscapularis signal change just lateral to the lesser tuberosity), and arthroscopic surgery (medial biceps tendon lesion, combined subscapularis tendon tear), with a cutoff value of ≥7 predicting a CIST. After the retrospective study, we prospectively enrolled 95 patients to validate the 10-point CIST scoring system. RESULTS: All 43 patients diagnosed with a CIST during the retrospective study improved both range of motion and functional scores at 1 year postoperatively. The interrater agreement of the 2 observers was substantial for the evaluation of all parameters except for subscapularis tear classification, which was moderate. On arthroscopic surgery, 11 small, 19 medium, and 13 large CISTs were detected. The preliminary prospective study showed a sensitivity of 61.9%, specificity of 94.3%, positive predictive value of 89.0%, negative predictive value of 75.7%, and accuracy of 80.0% when the cutoff value was set at ≥7 on the CIST scoring system. CONCLUSION: A CIST can be suspected using a combination of preoperative MRI and intra-articular diagnostic arthroscopic findings, but a definitive diagnosis requires an arthroscopic view. On the 10-point CIST scoring system, a score of ≥5 can be suggestive of a CIST, and a score of ≥7 is most likely to predict a CIST.