Ulnar Impaction Syndrome

• Age: 40-60 years (degenerative process)
• Gender: Equal distribution
• Occupation: Manual laborers, overhead workers
• Bilateral: Common (50% have bilateral variance)

Chronic overload leads to progressive degeneration.

• Positive ulnar variance (constitutional or acquired)
• Radial shortening after distal radius fracture malunion
• Radial head excision (shifts load ulnarly)
• Essex-Lopresti injury (proximal radius migration)
• Repetitive pronation-supination activities

Any process increasing ulnar variance predisposes to UIS.

With a significant distal radius malunion — large radial shortening, marked dorsal tilt, or DRUJ incongruity — a radial corrective osteotomy restores anatomy and DRUJ congruity, whereas an isolated ulnar shortening only neutralises variance and leaves the radial deformity uncorrected. Assess the magnitude of deformity and DRUJ articular congruity before choosing.

A systematic review of isolated USO performed for distal radius malunion (Laane et al) reported a 33% overall complication rate dominated by implant irritation (removal in about 13%), with nonunion only about 3%, and improved functional and patient-rated scores in most patients. It is a simpler, reliable option for lesser deformity — prefer a buried or low-profile implant to limit hardware irritation.

Every 1mm of positive ulnar variance increases ulnocarpal load. Studies show 2.5mm positive variance increases TFCC load by over 40%. This explains why shortening 2-4mm dramatically relieves symptoms.

Biomechanical correction is the goal of surgery.

Forearm rotation affects variance. Pronation increases positive variance by 1-2mm. Supination decreases it. Always measure in neutral rotation for accuracy. Grip force also increases dynamic loading.

Symptoms worse with pronation and grip.

• Pain: Dorsal-ulnar wrist pain
• Worse with: Ulnar deviation, grip, pronation
• Better with: Rest, avoiding provocative activities
• Clicking: Occasional with forearm rotation
• Weakness: Grip strength reduced
• Occupation: Manual work, repetitive pronation

Insidious onset over months to years is typical.

• Inspection: Minimal swelling usually
• Palpation: Tender over ulnocarpal joint (just distal to ulnar styloid)
• ROM: Normal or slightly reduced
• Provocative tests: Ulnar impaction test, TFCC load test
• Strength: Grip weakness (pain-limited)
• DRUJ: Assess stability (piano key sign)

Ulnar-sided tenderness is hallmark finding.

The variance cut-off for choosing arthroscopic wafer over USO is not firmly evidence-based. Feldon's original description contraindicates wafer above 4mm positive variance, but trials and meta-analysis pooling subtle-variance patients (under 4mm) show equivalent patient-rated outcomes — with the wafer offering faster recovery and fewer complications. Most surgeons reserve wafer for stable-DRUJ, low-variance disease.

Transverse, oblique and step-cut osteotomies are all used. Oblique/step-cut increase the union surface and allow interfragmentary compression, but high-quality comparative data are limited. The dominant complication is implant irritation requiring removal, not nonunion, which has reframed the debate toward low-profile fixation.

Shortening re-tensions the TFCC and can stabilise the DRUJ — but cadaveric data show this only works if the radioulnar ligament remains attached to the fovea. A complete foveal avulsion is not corrected by shortening and requires separate foveal repair.

For end-stage ulnocarpal/DRUJ arthritis there is no consensus winner. Darrach is simple but risks instability and stump convergence; Sauvé-Kapandji preserves an ulnar buttress; ulnar head arthroplasty preserves stability and rotation but has cost and long-term wear uncertainty. Selection is driven by age, demand and resources rather than robust comparative trials.