CHAPTER 33 Arthroscopic Wafer Resection

Ulnar impaction syndrome or ulnocarpal abutment refers to impaction of the ulnar head against the ulnar carpus, which results in persistent ulnar-sided wrist pain. Additional symptoms may include decreased range of motion, weakness of grip, and clicking of the wrist.¹ A positive or neutral ulnar variance is present in 70% of cases as seen on standardized radiographs.² However, ulnar-negative wrists may present with dynamic ulnar impaction with forceful grip, axial load, forearm pronation, and wrist ulnar deviation.^1,3 A positive ulnar variance may be a normal anatomical variant or result after a traumatic injury or abnormal development. Frequent causes include distal radius malunion with loss of radial height, premature distal radial physeal closure, and proximal radial migration after radial head excision. Developmental causes include Madelung’s deformity and multiple enchondromatoses, among others, that affect the distal radius.^4,5

Injury to the triangular fibrocartilage complex (TFCC) occurs early in the disease process and has been staged by Palmer as a class II TFCC abnormality (Box 33-1).^6,7 Chronic ulnar impaction results in a degenerative TFCC wear, chondromalacia of the lunate or ulnar head, attenuation or tearing of the lunotriquetral interosseous ligament, and, lastly, osteoarthritis of the ulnar carpus. This spectrum of findings has been termed “ulnar impaction syndrome.” TFCC traumatic injuries or class I injuries respond well to repair or débridement.⁶ However, TFCC tears in degenerative ulnar impaction syndrome have a failure rate as high as 25% with TFCC débridement alone.^8–11

Treatment for ulnar impaction syndrome has focused on mechanically unloading the ulnar side of the wrist. Palmer and Werner demonstrated that load distribution across the distal radius and ulna is dependent on ulnar variance.¹² In an ulnar-neutral wrist, 82% of force transmission crosses the radiocarpal joint and 18% crosses the ulnocarpal joint. With 2.5 mm of ulnar lengthening, the force across the ulnocarpal joint increases to 41.9%. When the ulna is shortened 2.5 mm from neutral, force transmission across the ulnocarpal drops to 4.3% and the radiocarpal force transmission increases to 95.7%. The force across the ulnocarpal joint is constant in the native wrist regardless of ulnar variance.^5,13 This is because the thickness of the TFCC is variable. It is thicker in an ulnar-negative wrist and thinner in an ulnar-positive wrist. Disruption of the ulnar variance from its native state will alter the ulnocarpal mechanics. Procedures designed to mechanically unload the ulnocarpal joint include an ulnar-shortening osteotomy, open wafer resection, and arthroscopic wafer resection. More invasive procedures include distal ulnar resection (Darrach), the Sauvé-Kapandji procedure, and the hemi-resection interpositional arthroplasty. These techniques should be reserved as salvage procedures. Of these, only the Darrach resection completely unloads the ulnocarpal joint.^7,14

Ulnar shortening has given excellent results in the treatment of ulnar impaction syndrome. Milch first described an ulnar shortening in 1941 for a malunited Colles fracture.¹⁵ Subsequent modification of the subperiosteal cuff resection by substituting the AO-ASIF principles of rigid plate fixation produced excellent to good results in 93% of patients treated with an ulnar shortening osteotomy for ulnar impaction syndrome.^5,16–18 On average, 3 months of postoperative immobilization is required. Complications from an ulnar-shortening osteotomy include extensor carpi ulnaris tendinitis from hardware irritation and delayed union and nonunion of the osteotomy. Tendinitis necessitating removal of the plate has been reported to be as high as 52%.¹⁹ Delayed union (>3 months) of the osteotomy has been reported in 18% to 22% of cases.²⁰

An open wafer distal ulnar resection was first published by Feldon and associates in 1992.² This procedure does not require internal fixation, and it does not require union of an osteotomy. However, it is contraindicated in patients with degenerative arthritis or instability of the distal radioulnar joint (DRUJ) or an ulnar variance greater then 4 mm positive. It is performed through a dorsal approach between the fifth and sixth extensor compartments, as described by Bowers. A radially based, U-shaped flap of the DRUJ capsule is created to expose the DRUJ, TFCC, and proximal articular surfaces of the lunate and triquetrum. After inspection, an osteotome is used to remove 2 to 4 mm of the ulnar head, including articular cartilage and subchondral bone. Care is taken to preserve the styloid process and all TFCC attachments. In addition, the majority of the cartilage articulating with the sigmoid notch of the radius is retained to preserve DRUJ function (forearm rotation). Débridement or repair of the TFCC is also performed. Intraoperative fluoroscopy is used to ensure that 2 mm of ulnar-negative variance is created. Good to excellent results have been obtained in 85% to 100% of patients with near full recovery of motion and grip strength.^2,16,21–23 However, tendinitis of the extensor carpi ulnaris sheath occurred in up to 31% of patients.²¹ When compared with an ulnar-shortening osteotomy for initial treatment of ulnar impaction syndrome, no clinical difference in outcome has been found.¹⁹

Arthroscopic wafer distal ulna resection was first reported in the early 1990s for patients presenting with extensive degenerative TFCC tears, chondromalacia of the ulnar head, or arthritis of the DRUJ.⁸ In one biomechanical study it was shown that excision of the centrum of the TFCC and resection of the radial two-thirds width of the ulnar head to a depth of subchondral bone revealed statistically significant unloading of the ulnar aspect of the wrist.⁷ It was also shown that ulnocarpal force transmission decreased with continued ulnar recession with maximal unloading at 3 mm of subchondral resection where force was reduced to 10.8%. No correlation with ulnar variance and resection level was observed. However, a trend was observed between optimal unloading and stage. Stage IIB wrists were unloaded with central TFCC excision. Stage IIC wrists tended to be unloaded after TFCC excision and one-third ulnar articular cartilage resection. Lastly, stage IID wrists were unloaded after resection into subchondral bone.⁷ In 12 wrists with ulnar-positive variance, Tomaino found 67% of patients to be completely pain free and 33% to have minimal symptoms at 14 months after arthroscopic wafer resection.¹¹ All patients were satisfied, and all had a negative ulnocarpal stress test. Preoperative ulnar variance averaged 2 mm positive and was neutral postoperatively. It has also been shown in patients presenting with ulnocarpal abutment syndrome that patients treated initially with an arthroscopic wafer resection had no statistically significant difference in outcome than those treated with arthroscopic TFCC débridement and an ulnar-shortening osteotomy.²⁰

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