Subscapularis muscle (SSc) is one of the critical components of rotator cuff muscles, the largest and strongest muscle in the rotator cuff muscle group, and the only rotator cuff muscle located in front. SSc is a robust internal rotator and dynamic anterior stabilizer of the glenohumeral joint, so the integrity of the SSc tendon is essential. However, SSc tendon injury is often overlooked, so it is named a "forgotten tendon". SSc tendon tear is not rare. According to previous literature reports on open shoulder surgery and cadaver studies, the prevalence of SSc tendon tear is 3.5%-29.4%. However, with the progress and widespread use of shoulder arthroscopy technology, the prevalence of SSc tendon tear is much higher than 29.4%. The incidence of SSc tear in arthroscopic rotator cuff surgery is 31.4%-69.5%. Missed diagnosis of SSc tendon tear can lead to postoperative symptom residue and poor functional recovery, which are potential risk factors for medical disputes. Therefore, accurate preoperative prediction of SSc tendon tear is significant for both patients and shoulder surgeons. Despite the breakthroughs in high-resolution magnetic resonance imaging technology, diagnosing SSc tendon tears is still challenging due to the relatively particular anatomical structure of the insertion site of the SSc tendon, especially in patients with partial or minor tears. In addition, MRI is currently one of the large-scale examinations that cost a lot of money and time in China; in primary hospitals, the conditions for high-resolution MRI examinations may not be available. Therefore, if there is an inexpensive, accurate, and repeatable physical examination of the shoulder joint that can detect SSc tendon tears early, it can reduce the waste of medical resources and the economic burden on patients. In foreign countries, there have been relevant special physical examination tests of the shoulder joint for the diagnosis of SSc tendon injuries, such as the lifting test, abdominal pressure test, bear-hug test, and internal rotation hysteresis test, etc., and have been confirmed to have high sensitivity and moderate specificity. However, most of these tests are carried out alone and have a small sample size. In addition, there has been no research report on the physical examination of the shoulder joint for the diagnosis of SSc tendon injuries in China.

To investigate the value of special physical examination tests for shoulder joints in diagnosing subscapular tendon tears.

A retrospective analysis was performed on 211 patients admitted to the hospital for shoulder arthroscopy treatment with rotator cuff injury from January 1, 2021, to December 31, 2022. Special physical examination tests for shoulder joints were performed before surgery: lifting test, abdominal compression test, bear-hug test, and internal rotation hysteresis test. With intraoperative arthroscopy results as the gold standard, the sensitivity, specificity, and area under the ROC curve of the four physical examination tests for diagnosing subscapular tendon injury were compared and analyzed.

Arthroscopy confirmed that 108 of the 211 patients had intact subscapular tendons, 72 had partial tears of the subscapular tendon (Lafossa type I), and 31 had full-thickness tears (Lafossa type II-V). For Lafossa type I-V injuries, the sensitivity of each physical examination test was bear-hug test (81.6%) > lifting test (71.8%) > abdominal compression test (68.0%) > internal rotation hysteresis test (48.5%), the specificity was internal rotation hysteresis test (71.3%) > bear-hug test (63.0%) > lifting test (50.0%) > abdominal compression test (46.3%), and the area under the ROC curve was bear-hug test (0.609) > lifting test (0.573) > abdominal compression test (0.568) > internal rotation hysteresis test (0.538). For Lafossa II-V injuries, the sensitivity of physical examination tests was bear hug test (93.5%) > abdominal compression test (80.6%) > lifting test (77.4%) > internal hysteresis test (45.2%), and the specificity was internal hysteresis test (62.8%) > lifting test (57.8%) > bear hug test (47.2%) > abdominal compression test (42.3%). The area under the ROC curve was the bear hug test (0.682) > lifting test (0.644) > internal hysteresis test (0.599) > abdominal compression test (0.571). The above tests could not distinguish between partial and full-thickness tears of the subscapularis tendon (P >0.05). Combined tests can improve the sensitivity (84.5%) and area under the particular physical examination tests' ROC curve (0.723) .

Among the 4 shoulder joint special physical examinations included in the study, the bear hug test has the highest diagnostic efficacy, especially for full-thickness tears of the subscapularis tendon. It is also recommended to perform a combined examination of the four physical examination tests to improve the diagnostic efficacy further. Despite this, there are still missed diagnoses of subscapularis tendon tears, especially for partial tears. Therefore, to prevent missed diagnoses of subscapularis tendon tears, it is necessary to explore the subscapularis tendon during arthroscopic surgery carefully.