Bicortical suspensory button fixation yields greater ultimate load to failure over unicortical all-suture anchor fixation in distal biceps brachii tendon repair.

Abstract

Various distal biceps tendon repair techniques exist, each with their own biomechanical profile. Recently, all-suture anchor fixation has recently become an intriguing option for distal biceps fixation, compared with the proven track record of the suspensory cortical button. In addition, intramedullary techniques have been utilized as a means to avoid complications such as nerve damage seen with extramedullary fixation. The purpose of this study is to perform a comparative biomechanical analysis of 4 unique distal biceps tendon fixation methods: Unicortical/intramedullary all-suture anchor fixation (UIAS), Bicortical/extramedullary all-suture anchor fixation (BEAS), Unicortical/intramedullary suspensory button fixation (UISB), and Bicortical/extramedullary suspensory button fixation (BESB). Controlled Laboratory study. 24 fresh-frozen cadaveric elbows were randomized into 4 groups providing data from 6 specimens, with each group undergoing a different repair technique. The specimens underwent 2 studies: Cyclic loading and Ultimate Load to failure (ULTF) testing. The repaired elbows were cycled 3000 times between 0 and 90 degrees of flexion, with displacement under cyclic loading at the repair site measured using a differential variable reductance transducer. ULTF test was performed with the elbow flexed at 90 degrees. The modes of failure were recorded. The mean cyclic displacements between the 4 groups were as follows: UIAS: 1.45 ± 1.04 mm; BEAS: 2.75 ± 1.32 mm; UISB: 1.45 ± .776 mm; BESB: 2.66 ± 1.18 mm (p= 0.077). Bicortical repairs displayed greater displacement after cyclic loading when compared with unicortical repairs regardless of anchor used (p= 0.007). The mean ULTF for each group was as follows: all-suture intramedullary: 200 N; all-suture extramedullary: 330 N; cortical-button intramedullary: 256 N; cortical-button extramedullary: 342 N). All-suture unicortical/intramedullary repair had a significantly lower ULTF (200 N) compared with cortical-button Bicortical/extramedullary repair (342 N) (p=0.043). Bicortical/extramedullary suspensory button fixation demonstrated a greater ultimate load to failure when compared with unicortical/intramedullary all-suture anchor fixation. These findings suggest that bicortical/extramedullary suspensory cortical button fixation is a biomechanically superior construct as compared to unicortical/intramedullary all-suture anchor fixation. However, there was no significant difference in ULTF between extra-medullary, Bicortical button or Bicortical, all-suture anchor fixation.