The effect of the number of cross-stitches on the biomechanical properties of the modified becker extensor tendon repair.

Abstract

The optimum number of cross-stitches in modified Becker repair for extensor tendon injury is not known. The purpose of this study was to compare the biomechanical characteristics of 1, 2, and 3 cross-stitches in modified Becker extensor repairs. We used 8 fresh-frozen cadaveric hands (24 fingers). We exposed extensor tendons of the index, middle, and ring fingers over the proximal phalanx, cut them transversely at the mid-portion of zone IV (proximal phalanx), and repaired them in situ with a modified Becker technique with 1, 2, or 3 cross-stitches using 4-0 braided suture. We randomized the tendons within each hand for the number of cross-stitches. Stiffness, yield load, ultimate load, energy absorbed, and gap formation were measured. After a 5 N preload, each repair was cyclically loaded from 5 to 25 N for 30 cycles and from 5 to 35 N for 30 cycles at a rate of 20 mm/min to simulate loads during postoperative rehabilitation. After cyclic loading, the specimens were loaded to failure. The repair with 1 cross-stitch showed superior gap resistance and stiffness during cyclic loading compared with 2 and 3 cross-stitches. One cross-stitch also resulted in higher stiffness and yield strength in load to failure testing. However, 3 cross-stitch configurations displayed higher ultimate strength. All repairs failed by knot slippage. A modified Becker extensor tendon repair with 1 cross-stitch provides superior mechanical properties for loads seen with postoperative rehabilitation compared with 2 and 3 cross-stitches for similar loads. These findings may lead to reduced operative time and decreased tendon damage with superior results.