The effect of tendon rotation on distal biceps repair

Abstract

BackgroundThe distal biceps tendon externally rotates from proximal to distal before inserting onto the radius. Our hypothesis is that an externally rotated (anatomic) repair would re-create native supination moment arm and flexion force, whereas an internally rotated (nonanatomic) repair would result in reduced force transmission.MethodsThe mechanical tests performed in this study measured isometric moment arms and elbow flexion force using a validated elbow simulator as previously published. Mechanical testing was performed on 8 native cadaveric elbows (61 ± 15 years). The distal biceps tendons in all specimens were then incised from their footprint and repaired with anatomic and nonanatomic tendon rotations. After each repair, the specimens were retested. The repair sequence was randomly assigned.ResultsGross observation showed repair site bunching with the nonanatomic repairs. There was no statistical difference in the moment arms between the native, anatomic, and nonanatomic rotations for the 3 forearm angles (P ≥ .352). Analysis showed no statistical difference in flexion force ratio for the elbow at 90° (P ≥ .283).DiscussionThe study showed that biceps tendon rotation does not play a role in supination moment arm or flexion force. Twisting the distal biceps tendon around the tendon axis does not change the direction of its applied force on the tuberosity. Tendon bunching in nonanatomic reattachments increases repair site width, which may lead to tendon-ulnar impingement during forearm rotation.

Partial Distal Biceps Avulsion Results in a Significant Loss of Supination Force

“…The supination moment arm results are summarized in Tables I and II (with the raw data shown in the Appendix). The native moment arm values were not significantly different from those in our previously published work (p ≥ 0.131) (Appendix) 21,25-27 .…”

“…The elbow flexion force test measured the biceps flexion force efficiency, which is the ratio of flexion load to biceps load (Fig. 5) 21,25,26 . The torque device was removed while maintaining humeral fixation to the simulator.…”

“…Mechanical tests were performed to measure isometric forearm supination moment arms in 60°of pronation, neutral, and 60°of forearm supination and elbow flexion force at 90°as previously reported 21,[25][26][27] . After baseline testing, 9 specimens (the distal-first group) underwent a serial 25%, 50%, and 75% release of the biceps tendon from its insertion, starting distally (Figs.…”

“…The elbow simulator, forearm supination moment arm test, and elbow flexion force test have been previously validated 21,[25][26][27] . The testing apparatus comprised an aluminum frame mounted to a material testing system (MTS) (MTS Systems) (Figs.…”

Acute complete and partial distal biceps tendon ruptures: what have we learned? A review

“… 4 , 5 , 38 Separate anatomical insertion of the short and long head has shown no added benefit compared reinsertion as a single tendon. 39 The two-incision technique has been shown to have less LACN neuropraxia compared to the single-incision technique. Heterotopic ossification (HO), however, remains the major complication of the two-incision technique.…”