gms | German Medical Science

Objectives/Interrogation: The role of anconeus in elbow stability has been a long-standing debate. Anatomical and electromyographic studies have suggested a potential role as a stabilizer. However, to our knowledge, no clinical or biomechanical studies have investigated its role in improving the stability of a lateral collateral ligament (LCL) deficient elbow.

Methods: Seven cadaveric upper extremities were mounted in an elbow motion simulator in the varus position. An LCL injured model was created by sectioning of the common extensor origin, and the LCL. The anconeus tendon and its aponeurosis were sutured in a Krackow fashion and tensioned to 10 N and 20 N using a transosseous tunnel placed through the lateral epicondyle. Varus-valgus angles and ulnohumeral rotations were recorded using an electromagnetic tracking system during simulated active elbow flexion with the forearm pronated and supinated.

Results and Conclusions: During active motion, the injured model resulted in a significant increase in varus angulation (5.3°±2.9°, P=.0001 pronation; 3.5°±3.4°, P=.001 supination) and external rotation (ER) (8.6°±5.8°, P=.001 pronation; 7.1°±6.1°, P=.003 supination) of the ulnohumeral articulation compared to the control state (varus angle -2.8°±3.4° pronation, -3.3°±3.2° supination; ER angle 2.1°±5.6° pronation, 1.6°±5.8° supination).

Tensioning of the anconeus significantly decreased the varus angulation (-1.2°±4.5°, P=.006 for 10 N in pronation; -3.9°±4.0°, P=.0001 for 20 N in pronation; -4.3°±4.0°, P=.0001 for 10 N in supination; -5.3°±4.2°, P=.0001 for 20 N in supination) and ER angle (2.6°±4.5°, P=.008 for 10 N in pronation; 0.3°±5.0°, P=.0001 for 20 N in pronation; 0.1°±5.3°, P=.0001 for 10 N in supination; -0.8°±5.3°, P=.0001 for 20 N in supination) of the injured elbow.

In the highly unstable varus elbow orientation, anconeus tensioning restores the in vitro stability of an LCL deficient elbow during simulated active motion with the forearm in both pronation and supination. These results may have several clinical implications. Our results suggest that strengthening of the anconeus may play a role in improving the varus and posterolateral instability of an LCL deficient elbow and reducing the "sagging" of the elbow in patients with radiographic drop sign after an elbow dislocation. Finally, in the surgical approaches used in the management of patients with pre-existing elbow instability secondary to LCL injury, the origin of the anconeus and its innervation should likely be protected.