Ulnar impaction syndrome with different operative methods: a comparative biomechanical study

Objective: Ulnar impaction syndrome seriously impairs wrist and hand function. Three main treatment procedures are available; however, little systematic research on the post-operation changes in wrist biomechanics currently exists. This study aimed to determine the long-term effects of these procedures and the optimal treatment methods for ulnar impaction syndrome.

Methods: Twenty-four cases of fresh upper limb specimens were randomized into four groups: (1) the control group, (2) the ulnar-shortening operation group, (3) the Sauvé-Kapandji procedure group (distal radioulnar arthrodesis and intentional distal ulnar pseudoarthrosis), and (4) the Darrach procedure group (distal ulna resection). After keeping the wrist in a neutral position, a pressure sensitive film was applied. Starting at 0 N, the load was increased gradually at a speed of 0.1 N/s until reaching 200 N and then maintained for 60 s by the CSS-44020 series biomechanical machine. Then, the pressure sensitive films from each group were measured, and the results were analyzed with SPSS software.

Results: The mean pressure and force on the ulna in the groups followed a decreasing trend from the control group, Sauvé-Kapandji procedure group and ulnar-shortening operation group. The mean pressure of the scaphoid fossa and the force on distal aspect of the radius in the groups followed an increasing trend from the control group, Sauvé-Kapandji procedure group, ulnar-shortening operation group and Darrach procedure group. This study found no significant differences in the mean pressure of the scaphoid fossa and the force on distal aspect of the radius between the Sauvé-Kapandji procedure group and the ulnar-shortening operation group. The Sauvé-Kapandji procedure group showed the greatest mean pressure on lunate fossa.

Conclusions: In this comprehensive analysis of wrist biomechanics, the ulnar-shortening operation was superior to the Sauvé-Kapandji procedure and Darrach procedure, which adequately maintained the anatomical relationships of the wrist.