The effect of repair of the lacertus fibrosus on distal biceps tendon repairs: a biomechanical, functional, and anatomic study.

Abstract

To date, repair of the lacertus in distal biceps tendon ruptures, recommended by some, has not been evaluated. The goal of these biomechanical experiments was to evaluate the degree to which its repair increases the strength of a distal biceps tendon repair. An intact or repaired lacertus fibrosus will increase the strength of a distal biceps tendon repair. Controlled laboratory study. Four matched pairs of fresh-frozen human cadaveric upper extremities were prepared by isolating the lacertus fibrosus and the distal biceps tendon. The extremity was placed in a custom-built rig with the distal biceps brachii clamped and affixed to a stepper motor assembly. The distal biceps tendon was sharply removed directly from the radial tuberosity and repaired through a bony tunnel in all specimens. One side of each pair was randomized to also receive repair of the lacertus. The specimens were pulled at a constant rate until failure. The mean failure strength, defined as maximal strength to 15 mm of displacement, was higher in specimens with a repaired lacertus (250.2 N vs 158.2 N; P =.012), as was mean maximum strength (256.8 N v. 164.5 N; P =.0058). Mean stiffness was not significantly different (16.36 N/mm vs 13.8 N/mm; P =.58). All specimens failed due to fracture at the bony bridge. Repair of the lacertus strengthened distal biceps tendon repair in a controlled laboratory setting. Repair of the lacertus fibrosus as an adjunct to distal biceps tendon repair strengthens the repair in the laboratory setting. Clinical testing is needed to verify that this increased strength improves clinical results. Surgeons should be cautioned to protect the underlying neurovascular structures during repair of the lacertus fibrosus and to avoid an overly tight repair.