Explain the indications, surgical technique, postoperative management, expected outcomes, complications, and alternative procedures for a four‑corner wrist fusion in patients with severe mid‑carpal arthritis, post‑traumatic wrist collapse, or advanced rheumatoid arthritis who have persistent pain despite conservative treatment.

Four-Corner Wrist Fusion: Comprehensive Overview

Definition and Surgical Concept

Four-corner fusion (4CF) is a motion-preserving wrist salvage procedure that involves complete excision of the scaphoid bone combined with midcarpal arthrodesis of the remaining four ulnar carpal bones—the capitate, hamate, lunate, and triquetrum—to eliminate pain while maintaining functional wrist motion through the preserved radiocarpal joint. 1

Primary Indications

• Scapholunate Advanced Collapse (SLAC) wrist, stage III, which develops after traumatic or atraumatic attenuation of the scapholunate ligament leading to abnormal joint kinematics and progressive radiocarpal then midcarpal arthritis 2

• Scaphoid Nonunion Advanced Collapse (SNAC) wrist, stage III, which occurs following untreated scaphoid fracture nonunion that progresses to degenerative arthritis of the radiocarpal articulation followed by carpal collapse and midcarpal arthritis 2

• Post-traumatic degenerative changes with dorsal intercalated segment instability (DISI) deformity where the lunate assumes an extended posture due to loss of scaphoid restraint 2

• Severe mid-carpal arthritis from calcium pyrophosphate deposition disease, rheumatoid arthritis, neuropathic diseases, or β2-microglobulin-associated amyloid deposition when conservative management has failed 2

The fundamental principle is to fuse the arthritic midcarpal joints while preserving motion through the uninvolved radiocarpal joint. 3

Surgical Technique

Fixation Methods

• Variable angle locking circular plate fixation is the preferred modern technique, providing angular stable fixation with locking screws that create a very solid construct and allow early mobilization 1, 4

• The circular plate accommodates both variable angle locking screws and compression screws to firmly fix the plate to the carpal bones, with locking technology producing superior construct stability compared to traditional K-wire fixation 1

• Triangle fixation using three headless compression screws (e.g., Double-threaded Japan screws) is an alternative technique that provides strong compression force in a skewed position, eliminates pin tract infection risk, and avoids hardware removal 5

Operative Steps

• Complete scaphoid excision is performed first to remove the arthritic bone and create space 1, 4

• A specialized reaming-distraction-compression guide is used to countersink the plate on the underlying carpal bone mass and allow distraction of the midcarpal joint for thorough debridement 1

• Cancellous bone graft is interposed at the fusion site after joint surface preparation 1

• The circular plate is positioned dorsally and secured with variable angle locking screws into the capitate, hamate, lunate, and triquetrum to achieve rigid fixation 1, 4

Postoperative Management

• Rigid immobilization for 2 weeks using a short arm splint immediately postoperatively 4

• Removable wrist brace with assisted physiotherapy for 4 weeks (weeks 2-6 postoperatively) to allow protected early motion 4

• Active range of motion exercises initiated at 3-4 weeks when using modern rigid fixation techniques, which is significantly earlier than the traditional 4-8 week immobilization period required with K-wire fixation 4, 5

This accelerated rehabilitation protocol is possible due to the superior stability provided by locking plate or headless screw constructs. 4, 5

Expected Outcomes

• Pain relief during daily activities is the most consistent and statistically significant benefit, with the majority of patients experiencing substantial reduction in pain 4, 2

• Preservation of functional wrist range of motion averaging 50-60% of the contralateral side, with extension-flexion arc typically 60-80 degrees 4, 3

• Grip strength improvement to approximately 70-80% of the contralateral side, though this improvement may not reach statistical significance in smaller series 4

• High patient satisfaction rates with 8 out of 9 patients (89%) reporting satisfaction with functional outcomes in recent series 4

• Reliable bone union with modern fixation techniques showing 100% fusion rates and no nonunions when rigid fixation is achieved 4, 5

• Improved carpal height ratio postoperatively, representing restoration of carpal alignment and prevention of further collapse 4

Complications and Management

• Persistent pain requiring secondary procedures occurs in approximately 10-15% of cases; limited wrist denervation can provide additional pain relief without compromising the fusion 4

• Hardware prominence is less problematic with low-profile locking plates compared to traditional K-wires, which required routine removal 5

• Pin tract infection is eliminated when using buried headless screws or locking plates instead of percutaneous K-wires 5

• Nonunion is rare (<5%) with modern rigid fixation techniques but was more common historically with K-wire fixation and inadequate compression 4, 5

• Radiocarpal arthritis progression can occur over time at the preserved radiocarpal joint, potentially requiring conversion to total wrist arthrodesis or proximal row carpectomy 3

Alternative Procedures

• Three-corner fusion (capitolunate-triquetral fusion with scaphoid and hamate excision) is considered when hamate involvement is minimal, though this is less commonly performed 3

• Proximal row carpectomy involves excision of the scaphoid, lunate, and triquetrum, preserving the capitate-radius articulation; this is indicated when the capitate head and lunate fossa of the radius are relatively preserved without significant arthritis 3

• Total wrist arthrodesis eliminates all wrist motion but provides complete pain relief and is reserved for patients with pan-carpal arthritis or failed motion-preserving procedures 3

• Radioscapholunate arthrodesis with distal scaphoidectomy is preferred when radiocarpal arthritis is present in addition to midcarpal disease, particularly in multi-joint involvement scenarios 6

The choice between four-corner fusion and proximal row carpectomy depends on which joints are involved versus spared—the main principle is to fuse the involved joints and allow motion through the uninvolved joints. 3

Critical Decision-Making Algorithm

When radiocarpal arthritis is absent and midcarpal arthritis is present (SLAC/SNAC stage II-III): Perform four-corner fusion to preserve radiocarpal motion 3, 2

When the capitate head and radial lunate fossa are well-preserved: Consider proximal row carpectomy as an alternative motion-preserving option 3

When pan-carpal arthritis is present: Proceed directly to total wrist arthrodesis rather than attempting motion preservation 3

When severe multi-joint disease involves both wrist and thumb CMC arthritis: Stage the procedures with radioscapholunate arthrodesis plus thumb CMC arthroplasty as the first stage 6

Common Pitfalls to Avoid

• Do not use traditional multiple K-wire fixation when modern locking plate or headless screw options are available, as K-wires require prolonged immobilization (8+ weeks), cause pin tract infections, and necessitate hardware removal 5

• Do not delay early mobilization beyond 4 weeks when rigid fixation has been achieved with locking plates or compression screws, as this leads to unnecessary stiffness without improving fusion rates 4, 5

• Do not perform four-corner fusion when radiocarpal arthritis is already present, as this will lead to persistent pain from the preserved but arthritic radiocarpal joint; consider total wrist arthrodesis or radioscapholunate fusion instead 6, 3

• Do not inadequately debride the fusion surfaces or fail to use bone graft, as this increases nonunion risk despite rigid fixation 1