SNAC Wrist with Positive Ulnar Variance: Surgical Management
For an adult with SNAC wrist and positive ulnar variance, perform proximal row carpectomy (PRC) as the first-line surgical procedure, with concurrent ulnar shortening osteotomy to address the ulnar positive variance. 1, 2
Rationale for Proximal Row Carpectomy
PRC demonstrates superior outcomes compared to four-corner fusion (4CF) in treating SNAC wrists, with significantly better postoperative range of motion and lower complication rates. 1
- PRC achieves significantly greater postoperative extension, ulnar deviation, and improvement in these parameters compared to 4CF 1
- Visual analog scale pain scores are significantly better with PRC 1
- The reoperation rate requiring arthrodesis is 5.2% for PRC versus 11% for 4CF 1
- 4CF carries an 8.9% nonunion rate and requires hardware removal in 2.2% of cases, complications entirely avoided with PRC 1
Critical Consideration: Addressing Ulnar Positive Variance
The positive ulnar variance must be addressed surgically, as failure to do so can result in new-onset ulnar-sided wrist pain after radiocarpal procedures. 2
- A case report documented ulnar-sided wrist pain developing after four-corner fusion in a previously asymptomatic ulnar positive wrist, requiring subsequent ulnar shortening osteotomy 2
- This highlights that post-traumatic radiocarpal arthrosis can coexist with ulnocarpal pathology that becomes symptomatic after altering radiocarpal mechanics 2
- Perform concurrent ulnar shortening osteotomy at the time of PRC to prevent this complication 2
Alternative Surgical Options (Second-Line)
If PRC is contraindicated or anatomically unsuitable, consider:
- Scaphocapitolunate (SCL) arthrodesis with radial styloidectomy preserves more joint surface and maintains physiologic radiocarpal load sharing 3
- SCL arthrodesis achieved 95% fusion rate (19/20 patients), mean flexion-extension arc of 70 degrees, and pain-free outcomes in 65% of patients 3
- This technique preserves ulnar-sided carpal joints and maintains more normal radiocarpal contact area 3
Common Pitfalls to Avoid
- Do not perform isolated radiocarpal procedures without addressing positive ulnar variance, as this creates ulnocarpal impaction and new pain 2
- Avoid four-corner fusion as first-line treatment given its higher nonunion rate, need for hardware removal, and inferior functional outcomes compared to PRC 1
- Do not attempt scaphoid reconstruction or scapholunate ligament repair in advanced SNAC stages, as these are not reasonable options once degenerative changes are established 4