Wrist Arthrodesis vs Arthroplasty

The management of end-stage wrist arthritis — whether from primary osteoarthritis, rheumatoid arthritis, post-traumatic arthritis (scaphoid non-union advanced collapse — SNAC; scapholunate advanced collapse — SLAC), or inflammatory arthropathy — involves a choice between two fundamentally different surgical approaches: wrist arthrodesis (total wrist fusion) or wrist arthroplasty (total wrist replacement). Wrist arthrodesis provides a painless, stable, durable wrist at the cost of complete loss of wrist motion. Wrist arthroplasty preserves motion but has historically been limited by high implant failure rates, though modern designs have improved outcomes. Partial wrist arthrodesis (four-corner fusion, scaphoidectomy + capitate-lunate-triquetrum-hamate fusion) represents an intermediate option preserving some motion.

• Functional anatomy of the wrist relevant to the arthrodesis vs arthroplasty decision: the wrist provides approximately 70° of flexion, 70° of extension, 20° of radial deviation, and 30° of ulnar deviation in the normal joint; in activities of daily living, a functional arc of approximately 5° of flexion to 30° of extension with 10° each of radial and ulnar deviation is required; complete wrist fusion (arthrodesis) at the ideal position (10–15° of extension and neutral or slight ulnar deviation) allows satisfactory completion of most daily activities but eliminates wrist flexion — activities such as perineal hygiene and some lifting tasks are affected; total wrist arthroplasty preserves motion, which is a significant advantage for bilateral wrist disease (RA — approximately 60% of RA patients have bilateral wrist involvement)
• SNAC and SLAC wrist — the most common indications for total wrist procedures: SNAC (scaphoid non-union advanced collapse) — progressive carpal collapse and OA secondary to chronic scaphoid non-union; SLAC (scapholunate advanced collapse) — progressive carpal collapse and OA secondary to chronic scapholunate ligament disruption; both produce a predictable pattern of radiocarpal OA (radial styloid first, then the whole radiocarpal joint) followed by midcarpal OA; end-stage SNAC/SLAC (Stage III — involving the capitolunate joint) is an indication for either four-corner fusion or total wrist arthrodesis depending on the extent of disease

• Technique: total wrist arthrodesis fuses the radiocarpal and midcarpal joints (and usually the carpometacarpal joints of the ring and little fingers) as a single unit; the standard technique uses a dorsal approach; a dedicated wrist fusion plate (AO/Synthes wrist fusion plate; Trimed; DePuy Synthes) is applied from the dorsal radius to the third metacarpal — spanning the radiocarpal and carpometacarpal joints; the articular cartilage of the radiocarpal, midcarpal, and CMC joints is denuded with an osteotome or high-speed burr; bone graft (autograft from the iliac crest, or allograft, or local bone from the resected carpal bones) is packed into the fusion site; the plate is fixed with screws to the radius proximally and the third metacarpal distally; fusion position — 10–15° of wrist extension, neutral to slight ulnar deviation, and the fingers in a functional position
• Plate vs. pin fixation: the dedicated AO wrist fusion plate is the most widely used fixation method; Steinmann pin (intramedullary rod from the third metacarpal across the carpus into the radius) was historically used (Rush pin, Millender-Nalebuff technique) and remains an option in revision or low-resource settings; the fusion plate provides superior rotational stability and earlier mobilisation of the wrist/forearm
• Position of fusion: 10–15° of extension (functional position allowing grip) is the standard; a position of 15–20° of extension is preferred by some surgeons for grip strength optimisation; neutral position (0°) is preferred when the contralateral wrist is already fused (to allow bimanual tasks); excessive flexion impairs grip; excessive extension impairs digital flexion

• Union rates: approximately 90–95% union with modern plate fixation and autograft; non-union is more common with pin fixation; smoking, RA, and revision surgery increase non-union risk
• Indications for total wrist arthrodesis: post-traumatic OA (SNAC/SLAC Stage III — involvement of capitolunate joint); end-stage RA with bone loss or instability not amenable to arthroplasty; failed wrist arthroplasty (salvage — conversion of failed total wrist replacement to arthrodesis); young patients with high activity demands (arthroplasty is relatively contraindicated in young, high-demand patients); Charcot wrist (neuropathic arthropathy — neuropathic joints require the stability of arthrodesis); wrist septic arthritis sequelae; spastic wrist deformity (cerebral palsy)

• Four-corner fusion (4CF): scaphoidectomy combined with fusion of the capitate, lunate, triquetrum, and hamate (the `four corners` of the midcarpal row); preserves approximately 40–50% of normal wrist motion; eliminates the degenerate radiocarpal articulation (by removing the scaphoid) while the lunate (which maintains a normal articulation with the radius even in advanced SNAC/SLAC) continues to articulate with the radius; the radiocapitate joint is preserved; appropriate for Stage II–III SLAC/SNAC where the radiolunate joint is preserved but the radioscaphoid joint is degenerate; fixation with a circular plate (Spider plate — Kinetikos Medical/Biomet) or compression screws; union rates approximately 85–90%
• Proximal row carpectomy (PRC): an alternative to four-corner fusion for Stage I–II SLAC/SNAC; the scaphoid, lunate, and triquetrum are excised; the capitate head articulates directly with the lunate fossa of the radius (`neocapitate-lunate` joint); preserves motion comparable to 4CF; technically simpler; no fusion required; union failure not applicable; best results when the capitate head and lunate fossa are not severely arthritic; outcome data show broadly equivalent results to 4CF for SLAC/SNAC at 5–10 years

• Historical context and current designs: early total wrist arthroplasty designs (1970s–1980s) had very high failure rates (50% at 5 years) from implant loosening, dislocations, and bearing failure; this led to near-abandonment of wrist arthroplasty in favour of arthrodesis; modern third-generation implants (Motec — Swemac; Re-Motion — Small Bone Innovations; MAESTRO — Biomet; Remotion — Small Bone Innovations) have improved 5–10 year survival to approximately 80–90%, making wrist arthroplasty a viable option in appropriately selected patients
• Modern TWA design: bicompartmental replacement — a radial component (cemented stem into the distal radius, with a smooth articular surface) and a carpal component (cemented or cementless fixation to the capitate and hamate through pegs or stems, with a polyethylene or pyrocarbon articular surface); provides approximately 40–50° of arc of motion (flexion-extension) post-operatively
• Indications for total wrist arthroplasty: RA with significant bilateral wrist involvement (preserving motion in at least one wrist is important for bimanual activities — particularly perineal hygiene; a bilateral arthrodesis is functionally limiting; TWA in the dominant or non-dominant hand with arthrodesis of the other is sometimes recommended); elderly low-demand patients with end-stage wrist arthritis; patients in whom preservation of wrist flexion is important for occupational or recreational activities; NOT appropriate for young high-demand patients, manual workers, patients with bone loss, or post-traumatic indications in young patients
• Complications of TWA: dislocation (the wrist articular surface has relatively low intrinsic constraint — dislocation rates of 5–10% in historical series; improved with modern designs); aseptic loosening (the most common late failure); infection; implant fracture; periprosthetic fracture of the distal radius (from carpal stem pegs); revision of failed TWA to arthrodesis is the standard salvage and is generally feasible (bone loss permitting)

• Total wrist arthrodesis: dorsal AO fusion plate from distal radius to 3rd metacarpal; fusion position 10–15° extension + neutral/slight ulnar deviation; 90–95% union with plate + autograft; eliminates all wrist motion; excellent durable pain relief
• Arthrodesis indications: post-traumatic OA (SNAC/SLAC III); young high-demand patients; bone loss; failed TWA (salvage); Charcot wrist; bilateral disease without bilateral arthrodesis plan
• Four-corner fusion (4CF): scaphoidectomy + capitate-lunate-triquetrum-hamate fusion; preserves ~40–50% motion; for SLAC/SLAC II–III with preserved radiolunate joint; Spider plate or compression screws; 85–90% union; alternative to PRC in older patients
• PRC: scaphoid + lunate + triquetrum excised; capitate articulates with lunate fossa; motion preserved; no fusion; simpler; best for Stage I–II with healthy capitate head and lunate fossa; equivalent outcomes to 4CF at 5–10 years
• Total wrist arthroplasty: 3rd generation designs (Motec, Re-Motion, Remotion); ~80–90% 5–10 year survival; preserves ~40–50° arc; for RA with bilateral involvement (preserve motion); elderly low-demand; NOT for young/active patients
• Bilateral RA strategy: TWA in dominant hand + arthrodesis of non-dominant (or vice versa); bilateral arthrodesis severely limits bimanual ADLs including perineal hygiene; preserve motion in at least one wrist
• Failed TWA salvage: conversion to arthrodesis; standard and generally feasible; may require structural allograft for bone loss after implant removal
• SNAC vs SLAC: SNAC — scaphoid non-union advanced collapse; SLAC — scapholunate ligament disruption; both produce predictable radiocarpal then midcarpal OA; Stage I (radial styloid); Stage II (entire radioscaphoid); Stage III (capitolunate — end-stage); 4CF or total arthrodesis for Stage III
• Wrist fusion position: 10–15° extension for unilateral fusion; neutral (0°) if contralateral wrist already fused; excessive flexion impairs grip; excessive extension impairs digital flexion