Review Question - QID 211941

The baker has a RSL fusion non-union with poor motion, which may have been prevented with excision of the distal pole of the scaphoid.

Arthritis of the radioscaphoid and radiolunate joints, in the setting of a preserved mid-carpal joint, may be treated with a RSL fusion. RSL Fusion is an alternative to total wrist fusion and has the benefit of retained motion through the mid-carpal joint. Excision of the distal pole of the scaphoid releases the mid carpal joint and both results in improved range of motion, but also less strain on the fusion mass, likely leading to improved fusion rates. Typically, the distal 20% of the scaphoid may be excised, which would allow the radio-ulnar "dart-thrower's motion" to be unobstructed. In addition to scaphoid excision, some authors additionally advocate for excision of the triquetrum to improve mid-carpal motion.

Bain et al. analyzed wrist motion in a RSL fusion with and without distal scaphoid and triquetrum excision. Wrist motion was best with excision of both distal scaphoid and triquetrum excision, followed by distal scaphoid excision alone, followed by RSL fusion without carpectomy. The authors report that RSL fusion may be a motion-preserving alternative to total wrist fusion.

Muhldorfer et al. retrospectively reviewed 61 patients who were treated for RSL fusion; including those with distal scaphoid pole excision (30) and those that had a RSL fusion alone (31). While 3 RSL fusion alone patients went on to non-union, all of the former group fused. Radial deviation was superior in the distal scaphoid excision cohort. The authors advocated for distal scaphoid excision to improve fusion rates and range of motion after RSL fusion.

Pervaiz et al. analyzed wrist motion in a RSL fusion before and after triquetral and distal scaphoid excision in 10 cadavers. After RSL fusion (as compared to a normal wrist), wrist flexion (39% decrease), extension (46%), radial (65%) and ulnar deviation (71%) decreased. When the distal pole of the scaphoid was also excised, wrist motion improved in terms of flexion (72% of normal) extension (89%) radial (84%), and ulnar (89%) deviation. Excision of the triquetrum further improved motion. The authors recommend excision of the triquetrum and distal pole of the scaphoid for patients undergoing RSL fusion.

Figure A is the radiograph represents a failed RSL fusion (the lunate facet has fused but the scaphoid facet has not).

Incorrect Answers:
Answer 2: The proximal pole must be retained for fusion to the radius.
Answer 3: The proximal pole of the capitate must be retained with its articular surface to allow motion through the mid-carpal joint.
Answer 4: Excision of the scaphoid, lunate, and triquetrum is often performed during a total wrist fusion, but is not performed when preserving the mid-carpal join in a RSL fusion.
Answer 5: Excision of the distal pole of the scaphoid likely increases fusion rate and motion.