Wrist kinetics after scaphoidectomy

Isolated Osseous Excision in the Adult Carpus: A Narrative Review

Various pathologies of the adult carpus result in clinical scenarios where excision can be considered and even recommended. In the appropriate patient population, isolated carpal excision can alleviate pain and improve mobility. Excisions of the pisiform, trapezium, and trapezoid have abundant literature evidence to support positive long-term functional outcomes. In contrast, isolated excision of the capitate, hamate, and triquetrum has limited support in the literature secondary to compromise of carpal mechanics and lead to recurrent pain. Additionally, isolated scaphoid and lunate excision are best avoided secondary to carpal collapse and should be paired with concomitant stabilizing procedures in the carpus. This article provides a comprehensive literature review of isolated excision of each osseous carpal bone, their indications, and previously assessed outcomes.

How Much Scaphoid Can be Safely Resected? A Biomechanical Analysis of the Effects of Distal Scaphoid Resection

BACKGROUND

Resection of the distal pole of the scaphoid has been advocated as a simple alternative to other wrist salvage procedures for scaphoid nonunion advanced collapse and scaphotrapezio-trapezoid arthritis. However, the extent of scaphoid that may be resected without adversely affecting carpal kinematics has never been clearly defined.

METHODS

Seven cadaveric upper extremities were tested in a custom motion wrist simulator. A 3-stage sequential sectioning of the distal scaphoid protocol was performed in 25% increments then cyclic active wrist flexion-extension and dart thrower's motion trials were recorded.

RESULTS

The extent of distal scaphoid resection had no effect on overall wrist range of motion. The lunate assumed a more extended position following resection of the distal scaphoid compared to intact. At 25%, 50%, and 75% of distal scaphoid resection, the lunate extended to 13.32° ± 9.4°, 23.43° ± 7.5°, and 15.81° ± 16.9°, respectively. The capitate migrated proximally with 25% and 50% distal scaphoidectomy, and proximally and radially with 75% of the scaphoid resected. Resection of 75% of the scaphoid resulted in unstable wrist kinematics.

CONCLUSIONS

Resection of up to 25% of the distal scaphoid did not significantly influence carpal kinematics and induced mild lunate extension deformity. Resection of 50% of the scaphoid induced further and potentially clinically significant lunate extension and dorsal intercalated segment instability. Further removal of 75% of the distal scaphoid induced capitate migration radially and unpredictable wrist kinematics. Consequently, removal of over 25% of the scaphoid should be avoided or supplemented with partial wrist fusion.