Does the Lateral Cubital Retinaculum Isolation or Repair in the Triceps Tongue Approach Affect Elbow Extension? A...

Previous studies suggest that the retinaculum on the lateral side of the triceps brachii muscle, often referred to as the lateral cubital retinaculum (LCR), contributes to elbow extension. The LCR provides continuity of the extensor mechanism with the ulna and contributes to the stable transmission of elbow extension force. However, its precise anatomical definition and biomechanical roles remain unclear. In addition, surgical approaches such as the triceps fascial tongue technique, which is commonly used by elbow surgeons to provide wide posterior access, risks the detachment of the LCR insertion area.

We sought to investigate the anatomical features of the retinaculum and assess its biomechanical role during the triceps tongue approach by answering the following questions in a cadaver study: (1) What kind of anatomical characteristics (the length and width of the LCR and the olecranon width) are present at the ulnar insertion of the LCR? (2) Does isolation of the LCR affect extensor lag of the elbow in the triceps fascial tongue approach? (3) Can surgical repair of the LCR restore extensor lag of the elbow? We defined "extensor lag" as changes in elbow angle due to the dissection or repair of the LCR or the triceps tendon compared with the intact condition when a constant tension was applied to the triceps tendon.

In total, 24 fresh-frozen upper extremities from 3 female and 15 male cadavers (mean ± SD age 84 ± 7 years) were included. Fourteen specimens from 8 cadavers were used in the anatomical study of the LCR. After exposing the triceps brachii and antebrachial muscles, the triceps tendon and lateral spreading fibers of the LCR were identified. The width and length of the lateral insertion of the LCR to the ulna were measured. Biomechanical studies were performed using the remaining 10 elbows to investigate the role of the LCR in elbow extension while elevating the triceps fascial tongue with a posterior surgical approach to the elbow. To determine whether isolation and repair of the LCR affects extensor lag, we measured elbow angle changes under 2 kg and 4 kg of traction, which is 10% to 20% of maximal muscle strength. The elbow was fixed in a custom jig, and a three-dimensional (3D) motion-tracking tool was used for spatial analysis. Elbow flexion angles under 2 kg and 4 kg of triceps traction were measured using the 3D motion tracking system. The measurements were performed under the following conditions: (1) intact LCR and triceps tendon, (2) elevation of a triceps fascial tongue flap with intact LCR in a surgical posterior approach, (3) additional LCR isolation from the ulna (1 to 5 cm), and (4) LCR repair. Repeated-measures ANOVA was used to evaluate interactions between traction force and elbow angle, with post hoc Holm tests. A p value < 0.05 was considered significant.

At the tip of the olecranon, the width of the LCR was 18 ± 3 mm and the length of the ulnar insertion area was 43 ± 5 mm. Isolation of the LCR using a triceps tongue approach resulted in a larger elbow flexion angle under 2 kg or 4 kg of load than was observed when an approach that involved elevating the triceps only was used (2 kg: 83° ± 4° versus 79° ± 5°, mean difference 4° [95% confidence interval (CI) 1° to 7°]; p = 0.049; 4 kg: 80° ± 7° versus 73° ± 8°, mean difference 7° [95% CI 3° to 11°]; p = 0.008). Repair of the LCR resulted in a smaller flexion angle under 2 kg or 4 kg of load than was observed when isolating the LCR using a triceps tongue approach (2 kg: 80° ± 5° versus 83° ± 4°, mean difference 3° [95% CI 1° to 7°]; p = 0.049; 4 kg: 75° ± 7° versus 80° ± 7°, mean difference 5° [95% CI 3° to 9°]; p = 0.008).

Quantitative anatomical and biomechanical studies have shown that isolation and repair of the LCR during the triceps tongue approach affects the angle of the elbow. Based on these results, we concluded that isolation of the ulnar insertion of the LCR may cause elbow extension impairment and that repair may improve this condition.

Preservation or repair of the LCR may help prevent postoperative extension force transmission disorders in elbow arthroplasty and trauma surgery using the triceps fascial tongue approach. Future research should focus on evaluating the effects of LCR isolation and repair through clinical studies.