Lacertus Fibrosus Versus Achilles Allograft Reconstruction for Distal Biceps Tears: A Biomechanical Study

Abstract

Background: The bicipital aponeurosis, or lacertus fibrosus, can potentially be used as a reconstruction graft in chronic distal biceps tendon tears. Purpose: To evaluate construct stiffness, load to failure, and failure mechanism with lacertus fibrosus versus Achilles allograft for distal biceps tendon reconstruction. Study Design: Controlled laboratory study. Methods: Ten fresh-frozen matched cadaveric pairs of elbows were used. Three centimeters of the distal biceps tendon was resected. Specimens were randomized to the lacertus fibrosus or Achilles tendon group. In one group, the lacertus fibrosus was released from its distal attachment and then tubularized and repaired intraosseously to the radius. In the other group, an Achilles tendon graft was sutured to the biceps muscle and repaired to the ulna. The prepared radii were rigidly mounted at a 45° angle on a load frame. The proximal biceps muscle was secured in a custom-fabricated cryogenic grip. Displacement was measured using a differential variable reluctance transducer mounted at the radius–soft tissue junction and in the muscle- or muscle allograft–tissue junction proximal to the repair. Specimens were loaded at 20 mm/min until failure, defined as a 3-mm displacement at the radius–soft tissue junction. Results: No significant difference was found in mean load to failure between the lacertus fibrosus and Achilles tendon group (mean ± SD, 20.2 ± 5.5 N vs 16.89 ± 4.54 N; P = .18). Stiffness also did not differ significantly between the lacertus fibrosus and Achilles tendon group (12.3 ± 7.1 kPa vs 10.5 ± 5.7 kPa; P = .34). The primary mode of failure in the lacertus fibrosus group was suture pullout from the tissue at the musculotendinous junction (7 of 10). In the Achilles group, failures were observed at the muscle-allograft interface (3) and the allograft-bone (radial tuberosity) interface (3), and 3 suture failures were observed. The button fixation did not fail in any specimens. Conclusion: The mean stiffness and load-to-failure values were not significantly different between a lacertus fibrosus construct and Achilles tendon allograft. Clinical Relevance: Use of the lacertus fibrosus may be a potential alternative to Achilles tendon allograft reconstruction of chronic distal biceps tears when primary repair is not possible.