Subscapularis repair after shoulder arthroplasty: Biomechanical and clinical validation of a novel technique

Hypothesis

We hypothesized that releasing the subscapularis with lesser tuberosity bone may improve strength of fixation of the subscapularis during total shoulder atthroplasty (TSA).

Materials and methods

In 15 cadaveric humeri, all musculature was removed except the subscapularis. A standard humeral head osteotomy was performed for TSA. The subscapularis was released with a fleck of lesser tuberosity bone in 10 specimens from five matched pairs, and a tenotomy was performed in five. Five osteotomies were repaired with single-row heavy non-absorbable sutures and five with an additional double-row. Repairs were subjected to cyclical loading at 180 newtons for 400 cycles, increasing by 180 newtons to failure. A retrospective review of 100 consecutive patients who underwent dual-row repair of the subscapularis fleck osteotomy following TSA was also performed with minimal follow-up of 24 months (24-48).

Results

Both single (430 N) and double-row (466 N) fixation of the fleck osteotomy were significantly stronger than tenotomy suture repair (252 N) (p < .04). There was no significant difference between single and double-row ultimate strengths. Qualitatively, double-row fixation fixed the fleck osteotomy more securely to the donor site with respect to gross rotational motion. At final clinical review, the lift-off test was rated as normal in 79%. The belly press was rated as normal in 86%. Eighty-two percent were able to tuck in their shirts.

Conclusion

Subscapularis release with fleck osteotomy provides superior biomechanical ultimate strength compared to standard tenotomy. There was no visible motion during biomechanical testing with dual-row osteotomy fixation compared to single-row fixation. Clinical results of this dual-row technique document showed good restoration of subscapularis integrity for activities of daily living.

Level of evidence

Basic science study and level 4; retrospective review, case series, no control group.