2015 ISAKOS Biennial Congress Paper #0

Physiologic Tensioning During Lower Trapezius Transfer For Irreparable Posterosuperior Rotator Cuff Tears Is Important For Improvement Of Shoulder Kinematics

Lukas Nawid Muench, MD, Munich GERMANY
Marco-Christopher Rupp, MD, Munich, Bavaria GERMANY
ELIFHO OBOPILWE, ME, BSc, Farmington, Connecticut UNITED STATES
Julian Mehl, MD, Munich, Bavaria GERMANY
Bastian Scheiderer, MD, Munich, Bavaria GERMANY
Sebastian Siebenlist, MD, MHBA, Prof., Munich, Bavaria GERMANY
Bassem T. Elhassan, MD, Boston, MA UNITED STATES
Augustus D. Mazzocca, MS, MD, Waltham, MA UNITED STATES
Daniel P. Berthold, Association.-Prof., Munich GERMANY
University of Connecticut Health Center, Farmington, Connecticut, UNITED STATES

FDA Status Not Applicable

Summary: Lower trapezius transfer was most effective in improving glenohumeral kinematics following an irreparable posterosuperior rotator cuff tear when maintaining the physiologic tension of the lower trapezius muscle. However, the lower trapezius transfer did not completely restore native kinematics, regardless of tensioning.

Abstract:

Background

Lower trapezius transfer (LTT) has been proposed for restoring the anteroposterior muscular force couple in the setting of an irreparable posterosuperior rotator cuff tear (PSRCT). Adequate graft tensioning during surgery may be a factor critical for sufficient restoration of shoulder kinematics and functional improvement. The purpose of this study was to evaluate the effect of tensioning during LTT on glenohumeral kinematics using a dynamic shoulder model. It was hypothesized that an LTT, maintaining the physiologic tension of the lower trapezius muscle, would improve glenohumeral kinematics more effectively than an under-tensioned or over-tensioned LTT.

Methods

Ten fresh-frozen cadaveric shoulders were tested using a validated shoulder simulator. Glenohumeral abduction angle (gAA), superior migration of the humeral head (SM) and cumulative deltoid forces (cDF) were compared across five conditions: (1) native; (2) irreparable PSRCT; (3) LTT with 12N load (under-tensioned); (4) LTT with 24N load (physiologic cross-sectional area ratio); (5) LTT with 36N load (over-tensioned). gAA and SM were measured using 3-dimensional motion tracking. cDF was recorded in real time throughout dynamic abduction motion by load cells connected to actuators.

Results

The physiologically tensioned (Delta 13.1°), under-tensioned (Delta 7.3°), and over-tensioned LTT (Delta 9.9°) each significantly increased gAA compared to the PSRCT (P<.001, respectively). The physiologically tensioned LTT achieved a significantly greater gAA than the under-tensioned (Delta 5.9°;P<.001) or over-tensioned LTT (Delta 3.2°;P=.038). SM was significantly decreased in LTT compared to the PSRCT, regardless of tensioning. The physiologically tensioned LTT resulted in a significantly lower SM compared to the under-tensioned LTT (Delta 5.3mm;P=.004). A significant decrease in cDF compared to the PSRCT was only observed in the physiologically tensioned LTT (Delta -19.2N;P=.044). However, compared to the native state, LTT did not completely restore native glenohumeral kinematics, regardless of tensioning.

Conclusion

LTT was most effective in improving glenohumeral kinematics following an irreparable PSRCT when maintaining the physiologic tension of the lower trapezius muscle. However, the LTT did not completely restore native kinematics, regardless of tensioning. Tensioning during LTT for an irreparable PSRCT is important to sufficiently improve glenohumeral kinematics and may be an intraoperatively modifiable key variable to ensure postoperative functional success.