A Biomechanical Comparison of Extensor Carpi Ulnaris Subsheath Reconstruction Techniques

Several surgical stabilization techniques have been described to address pathological subluxation of the extensor carpi ulnaris (ECU) tendon, with no comparative data available. This study compares ECU stability after subsheath reconstruction, with and without ulnar groove deepening, to stability with an intact subsheath in a cadaveric model.

Position of the ECU tendon relative to the ulnar groove was measured in 5 human cadaveric specimens with the subsheath intact, sectioned, and after 3 reconstruction scenarios: reconstructed, reconstructed with ulnar groove deepened, and ulnar groove deepened with subsheath sectioned. Position of the tendon relative to the radial side of the ulnar groove was recorded with digital calipers in 9 combinations of wrist/forearm positions (wrist flexion, extension, and neutral; forearm pronation, supination, and neutral). Dislocation events, defined as the tendon being completely ulnar to the groove, were recorded.

Extensor carpi ulnaris tendon displacement was not significantly different between intact subsheath, subsheath reconstruction, and reconstruction with groove deepening (1.5 mm vs 0.5 mm vs -0.3). Extensor carpi ulnaris tendon displacement after groove deepening with the subsheath sectioned was not significantly different from displacement with a fully sectioned subsheath. Sectioning of the subsheath induced dislocation events of the ECU tendon in multiple positions. Subsheath reconstruction with and without groove deepening allowed no dislocation events.

In this cadaveric model, groove deepening did not improve stability of the ECU tendon compared with the reconstructed subsheath, and reconstruction alone was equally effective at eliminating dislocation events.

Stabilization techniques that focus on restoration of the important ulnar attachment of the ECU subsheath are favored over routine deepening of the ulnar groove in attempts to stabilize the ECU tendon.