Superior Capsular Reconstruction Combined With Lower Trapezius Tendon Transfer Improves the Biomechanics in Posterosuperior Massive Rotator Cuff Tears.

BACKGROUND: Surgical treatments for chronic posterosuperior massive rotator cuff tear (MRCT) are still controversial. Superior capsular reconstruction (SCR), which provides a static stabilizer to decrease superior humeral head translation, and lower trapezius tendon transfer (LTTT) with centralization of the humeral head, which prevents superior humeral head migration, are potential surgical options. To date, SCR combined with LTTT has not been fully investigated.

HYPOTHESIS: Restoration of static stabilizer and dynamic stabilizer together would effectively improve shoulder kinematics in posterosuperior MRCT.

STUDY DESIGN: Controlled laboratory study.

METHODS: A custom-made shoulder mechanics testing system was used to test 8 fresh-frozen cadaveric shoulders. The testing conditions were as follows: (1) intact; (2) posterosuperior MRCT (supraspinatus and infraspinatus removed); (3) SCR using the fascia lata; (4) LTTT; and (5) SCR combined with LTTT. The total rotational range of motion (ROM), superior translation, anteroposterior translation, and peak subacromial contact pressure were evaluated at 0°, 30°, and 60° of shoulder abduction. Repeated-measures analysis of variance and Tukey post hoc tests were performed.

RESULTS: The total rotational ROM, superior translation, anteroposterior translation, and peak subacromial contact pressure increased in posterosuperior MRCTs (all, P < .05). The rotational ROM, superior translation, anteroposterior translation, and peak subacromial contact pressure at 0° and 30° of shoulder abduction decreased in SCR (all, P < .05). However, there was no significant improvement in rotational ROM, superior translation, and peak subacromial contact pressure at 60° of shoulder abduction ( P > .05). LTTT resulted in a significant decrease in the superior translation, anteroposterior translation, and peak subacromial contact pressure at 0°, 30°, and 60° of shoulder abduction ( P < .05). SCR combined with LTTT restored the total rotational ROM, superior translation, anteroposterior translation, and peak subacromial contact pressure at 0°, 30°, and 60° of shoulder abduction (all, P < .05).

CONCLUSION: In the cadaveric model, SCR combined with LTTT showed improved shoulder kinematics and contact pressures in the posterosuperior MRCT model compared with SCR or LTTT alone.

CLINICAL RELEVANCE: SCR combined with LTTT may be regarded as an alternative surgical procedure for posterosuperior MRCTs.