[Intramuscular lengthening and range of motion after local tendon transfer for repair of retracted supraspinatus tendon defects. A biomechanical study].

BACKGROUND

The current cadaver study was performed to evaluate and compare infraspinatus (ISP) vs. subscapularis (SSC) tendon transfer used for the repair of a large supraspinatus (SSP) rotator cuff defect. The main outcome measures were the range of motion and intramuscular length changes during motion.

METHODS

Thirteen fresh-frozen cadaver shoulders were used in the study. A supraspinatus defect extending to the apex of the humeral head (Patte size II) was created. Transosseous repair was then attempted with the ISP and with the SSC in all cases; intramuscular length changes were measured by Hall effect transducers during motion of the arm in steps of 30 degrees.

RESULTS

Repair was successful in all cases when the ISP was used, while use of the SSC resulted in a successful repair in only 8 of the 13 (61.5%). Passive range of motion did not differ between ISP and SSC. ISP was shortened during flexion and abduction in contrast to the SSC that was lengthened during flexion (p<0.05) and shortened to a lesser degree (p<0.05). Length changes during rotation were not significantly different.

CONCLUSIONS

In this cadaver model the ISP proved more favorable than the SSC for covering a Patte size II SSP defect if the assumption is true that lengthening of a muscle is less favorable than shortening because of the vascularization of the tendon.