Midcarpal Arthritis

Midcarpal arthritis represents a complex pattern of wrist degeneration affecting the articulation between the proximal carpal row (scaphoid, lunate, triquetrum) and distal carpal row (trapezium, trapezoid, capitate, hamate). Unlike radiocarpal arthritis which affects the radius-carpal interface, midcarpal arthritis frequently results from chronic carpal instability patterns, particularly scapholunate advanced collapse (SLAC) and scaphoid nonunion advanced collapse (SNAC).

The surgical management of midcarpal arthritis has evolved significantly over the past three decades. Motion-preserving procedures including four-corner fusion and proximal row carpectomy offer alternatives to total wrist arthrodesis in appropriately selected patients. Understanding the patterns of arthritis progression, patient factors affecting procedure selection, and technical nuances of each operation is essential for optimal outcomes.

Multiple surgical procedures address midcarpal arthritis. Selection depends on arthritis extent, patient factors, and surgeon experience.

The workhorse procedure for SLAC/SNAC Stage II-III arthritis. Excision of scaphoid eliminates radioscaphoid arthritis while fusing the remaining midcarpal joints preserves the radiolunate articulation.

Alternative motion-preserving procedure removing the proximal carpal row and creating radial capitate articulation. Simpler procedure than four-corner fusion but requires intact lunate fossa cartilage.

Definitive salvage procedure providing reliable pain relief and maximum grip strength at cost of complete wrist motion loss. Indicated for Stage IV SLAC, inflammatory arthritis, and salvage situations.

Motion-preserving alternative for pancarpal arthritis in selected low-demand patients. Limited role given high complication rates but valuable for bilateral disease or specific situations.

SLAC Wrist Progression

Scapholunate advanced collapse represents the most common pattern of degenerative wrist arthritis. The condition results from chronic scapholunate dissociation leading to predictable pattern of cartilage loss.

Watson SLAC Staging (SLAC staging is Watson's; Lichtman staging is for Kienbock disease):

• Stage I: Arthritis between scaphoid and radial styloid

  • Radial styloid beaking
  • Preserved scaphoid fossa
  • Treatment: Radial styloidectomy

• Stage II: Arthritis entire scaphoid fossa (radioscaphoid joint)

  • Scaphoid fossa cartilage loss
  • Capitate migrates proximally
  • Treatment: Four-corner fusion vs PRC

• Stage III: Midcarpal arthritis (capitate-lunate)

  • Preserved radiolunate joint (key feature)
  • Hamate-triquetrum involvement
  • Treatment: Four-corner fusion vs PRC

• Stage IV: Pancarpal arthritis including radiolunate

  • DRUJ arthritis common
  • Motion-preservation not possible
  • Treatment: Total wrist arthrodesis

SNAC Wrist Pattern

Scaphoid nonunion advanced collapse follows identical progression to SLAC but initiates from scaphoid fracture nonunion rather than ligament injury.

Key Differences from SLAC:

• History of scaphoid fracture
• Scaphoid proximal fragment remains attached to lunate
• Distal fragment rotates into flexion
• Same radiographic staging system applies
• Same surgical treatment algorithm

Other Etiologies

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History and Physical Examination

Patients typically present with chronic wrist pain, stiffness, and functional limitation. Distinguishing midcarpal from radiocarpal pathology clinically guides imaging and treatment planning.

Imaging Studies

Plain Radiographs (Essential):

Standard wrist series including PA, lateral, and bilateral clenched-fist views.

Dorsal and radial wrist pain has several causes that mimic or coexist with midcarpal arthritis. Distinguishing them prevents inappropriate salvage surgery.

The topic's very first must-know is to "differentiate midcarpal from radiocarpal arthritis - different surgical solutions", and the whole salvage algorithm depends on it, but the topic never gives the discriminating method. The pivotal question is always the same: is the radiolunate (radiocarpal) joint preserved? - because motion-preserving salvage (4CF, PRC) only works if it is.

• Clinically. Radioscaphoid/radial-styloid disease gives dorsoradial pain and tenderness over the radioscaphoid joint and radial styloid with a positive Watson (scaphoid-shift) test; midcarpal disease gives central dorsal pain and a positive midcarpal shift (a painful clunk on ulnar-to-radial translation of the distal row). The pattern of tenderness helps, but overlap is common.
• Radiographically (the decisive step). The SLAC/SNAC pattern spares the radiolunate joint: narrowing progresses radioscaphoid → capitolunate (midcarpal) while the radiolunate space stays normal - this is the "midcarpal-salvageable" pattern that permits 4CF or PRC. In contrast, radiolunate/radiocarpal narrowing and sclerosis (e.g. after an intra-articular distal radius fracture, or in inflammatory disease) is the pattern that contraindicates 4CF and PRC, because both rely on a healthy radiolunate (4CF) or lunate-fossa (PRC) surface.
• Confirming it (injection and arthroscopy). When films are equivocal, a selective image-guided diagnostic injection - first the radiocarpal, then the midcarpal joint on separate occasions - localises the pain generator, and wrist arthroscopy directly grades the radiolunate/lunate-fossa and capitate-head cartilage (the true determinant of PRC vs 4CF vs total fusion). This is why arthroscopy is the gold standard for staging before committing to a salvage.

The topic exhaustively covers the midcarpal-salvageable (radiolunate-spared) pattern - 4CF, PRC and total fusion - but never the reciprocal that its own must-know demands: when the radiocarpal (radiolunate) joint is the arthritic one with a preserved midcarpal joint, the motion-preserving salvage is a radioscapholunate (RSL) fusion, not a midcarpal procedure.

• The indication. Isolated radiocarpal arthritis with a healthy midcarpal joint - classically after an intra-articular distal radius fracture (radiocarpal post-traumatic OA), or in some inflammatory and instability patterns - where the pain generator is the radius-to-scaphoid/lunate articulation, not the midcarpal joint.
• The procedure. Fuse the radius to the scaphoid and lunate (the radiocarpal joint), which abolishes the painful radiocarpal articulation while preserving midcarpal motion (the capitolunate and STT joints continue to move) - the mirror image of a 4CF, which sacrifices the midcarpal joint to preserve the radiolunate.
• The refinements that protect motion and union. Adding a distal scaphoid pole excision removes the scaphotrapeziotrapezoid impingement that otherwise limits radial deviation and reduces the fusion surfaces, and some add a triquetrum excision to further unload/increase midcarpal motion; these adjuncts improve range of motion and are thought to lower the historically high RSL nonunion rate.
• The fallback. If the midcarpal joint is also involved (pancarpal disease), RSL is not appropriate and the reliable salvage reverts to total wrist arthrodesis - the same endpoint as a failed 4CF/PRC.

Initial treatment focuses on symptom control and functional optimization. Many patients achieve acceptable outcomes avoiding surgery.

Conservative Modalities

Indications for Surgery

Surgical intervention considered when conservative measures fail to provide acceptable symptom control or function.

Global Epidemiology

• SLAC and SNAC are the most common patterns of degenerative wrist arthritis worldwide; primary midcarpal osteoarthritis is rare.
• Untreated scaphoid nonunion carries a high arthritic burden: radioscaphoid change in roughly three-quarters of patients by 4 years and midcarpal change in around 60% by 9 years (Vender/Watson sequence).
• Scaphoid fractures peak in young men (15-35 years); delayed or missed diagnosis is the dominant driver of the SNAC population globally and is over-represented in manual-labour and resource-limited settings.
• Scapholunate ligament injury underlies the SLAC population and is frequently under-recognised at initial trauma presentation.

Society Guidance: No Single Disease-Specific Guideline

There is no dedicated AAOS, BOA/BOAST, AO or EFORT guideline for midcarpal arthritis; management derives from comparative outcome literature and hand-surgery society consensus. Practice differs mainly in procedure preference rather than indication.

Registry and High-Quality Trial Evidence

• No carpal-specific salvage registry exists; the evidence base is comparative cohorts, systematic reviews and meta-analysis (PRC vs 4CF), now being tested prospectively.
• The multicentre double-blind PROOF randomised non-inferiority trial (NCT04260165) is directly comparing PRC and 4CF with PRWE as the primary endpoint - the highest-level data anticipated in this field.
• Total wrist arthroplasty implant survivorship is captured in national joint registries (e.g. national registries reporting implant outcomes) and remains inferior to arthrodesis durability, supporting fusion as the default salvage in higher-demand patients.

High- vs Limited-Resource Practice Variation

• High-resource settings: routine CT and/or wrist arthroscopy for cartilage assessment, headless-screw or low-profile plate fixation for 4CF, and certified hand-therapy rehabilitation pathways.
• Limited-resource settings: greater reliance on plain radiographs and intraoperative cartilage assessment; PRC is often favoured for its single-stage, implant-free nature, shorter operative time and lower cost (direct surgical costs for 4CF are several-fold higher than PRC, driven mainly by implants).
• Across all settings, late presentation of scaphoid nonunion increases the proportion requiring salvage rather than reconstruction.

Rehabilitation Principles (Universal)

• Post-PRC: early protected mobilisation, typically from 2-3 weeks.
• Post-4CF: immobilisation usually 8-12 weeks until radiographic union, then progressive strengthening.
• Post-total fusion: splint weaning with strengthening once fixation is secure; counsel on compensatory elbow/shoulder/finger motion.
• Return to sedentary work generally precedes return to heavy manual work by several weeks to months in every health system.

• PRC versus four-corner fusion as the default. The largest meta-analysis favours PRC for motion and lower complications with comparable grip, yet many surgeons still default to 4CF in younger, higher-demand patients. True equipoise persists pending the multicentre double-blind PROOF randomised trial (NCT04260165), the first head-to-head RCT.
• Age threshold for PRC. PRC is traditionally reserved for patients over 35-50 years because of radiocapitate contact stress, but long-term series with durable results to 15 years despite universal radiographic change challenge a strict age cut-off. The decisive factor is capitate-head and lunate-fossa cartilage quality, not age alone.
• Fixation for four-corner fusion. Headless compression screws, dorsal circular plates, staples and K-wires all achieve union, but circular plates carry higher hardware-related morbidity and impingement while K-wires show higher partial-union rates. No construct is clearly superior; reported 4CF nonunion remains around 9%.
• Capsular interposition and resurfacing PRC. Dorsal capsular interposition or a resurfacing graft when the capitate head is marginal is proposed to extend PRC indications, but evidence is limited and it is not yet standard.
• Radial styloidectomy with salvage. Routine adjunctive radial styloidectomy to prevent impingement is debated; over-resection risks radiocarpal instability, so most surgeons limit it to a few millimetres and only when impingement is demonstrated.
• Total wrist arthroplasty role. Improving implant designs have renewed interest in motion-preserving arthroplasty for low-demand or bilateral disease, but registry-level survivorship still trails arthrodesis, keeping fusion the reliable salvage in active patients.

Midcarpal arthritis affects the articulation between proximal and distal carpal rows, most commonly from SLAC (scapholunate advanced collapse) or SNAC (scaphoid nonunion advanced collapse) wrist patterns. Know the Watson SLAC staging (SLAC staging is Watson's - do not confuse it with Lichtman, which stages Kienbock): Stage I (radial styloid), Stage II (scaphoid fossa), Stage III (midcarpal), Stage IV (pancarpal with DRUJ). Four-corner fusion (scaphoid excision + capitate-hamate-lunate-triquetrum fusion) is the workhorse procedure, preserving 60% wrist motion with 80% grip strength. Proximal row carpectomy is an alternative requiring intact lunate fossa cartilage. Critical concept: the radiolunate joint remains preserved until late disease - this is why scaphoid excision works.

Midcarpal arthritis represents a complex spectrum of degenerative wrist conditions requiring thorough understanding of carpal biomechanics, staging systems, and surgical options. SLAC and SNAC wrist patterns progress through predictable stages, with radiolunate joint preservation until late disease enabling motion-preserving surgery.

Four-corner fusion and proximal row carpectomy both achieve approximately 50-60% motion preservation with good pain relief in appropriately selected patients. Four-corner fusion provides superior grip strength and more predictable long-term outcomes but requires fusion healing and carries nonunion risk. Proximal row carpectomy offers simpler surgery with faster recovery but demands pristine lunate fossa cartilage and shows higher late progression rates.

Total wrist arthrodesis remains the gold standard for definitive treatment when motion preservation fails or is not feasible, providing maximum grip strength and reliable pain relief despite complete motion loss. Patient selection, understanding individual functional demands, and mastery of multiple surgical techniques are essential for optimal outcomes in this challenging condition.