Degenerative arthritis of the midcarpal joint, commonly from SLAC/SNAC patterns
Critical Must-Knows
- Differentiate midcarpal from radiocarpal arthritis - different surgical solutions
- SLAC wrist progresses through three stages (Stage I radial styloid, II scaphoid fossa, III midcarpal)
- Four-corner fusion preserves 60% wrist motion with 80% grip strength
- Proximal row carpectomy requires intact lunate fossa cartilage
- Total wrist fusion position: 10-15 degrees extension, 5-10 degrees ulnar deviation
Clinical Pearls
- "Know Lichtman SLAC staging system and which stages amenable to motion-preserving surgery
- "Describe physical examination findings: midcarpal shift test, Watson test
- "Explain why scaphoid excision necessary in four-corner fusion
- "Discuss fixation options for four-corner fusion: headless screws vs circular plate vs Spider plate
- "Know contraindications to PRC: lunate fossa arthritis, capitate chondromalacia, inflammatory arthritis
Clinical Warning
At a Glance
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 Lichtman SLAC staging: 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.
RAMSSLAC Wrist Stages - RAMS
| R | R - Radial styloid arthritis (Stage I) |
| A | A - Articulation scaphoid fossa arthritis (Stage II) |
| M | M - Midcarpal arthritis capitate-lunate-hamate (Stage III) |
| S | S - Stage IV adds pancarpal with DRUJ involvement |
| R | R - Radial styloid arthritis (Stage I) | M | M - Midcarpal arthritis capitate-lunate-hamate (Stage III) |
| A | A - Articulation scaphoid fossa arthritis (Stage II) | S | S - Stage IV adds pancarpal with DRUJ involvement |
Hook:RAMS helps remember SLAC progression - think of RAM pushing through the wrist stages
CARTILAGEPRC vs Four-Corner Fusion Decision - CARTILAGE
| C | C - Cartilage lunate fossa must be pristine (Grade I-II only) | L | L - Low demand patients better PRC candidates |
| A | A - Age favors older patients for PRC (greater than 50) | A | A - Arthritis progression risk higher with PRC |
| R | R - Reliability slightly favors 4CF for strength | G | G - Grip strength 5-10% better with 4CF |
| T | T - Time to recovery faster with PRC | E | E - Early mobilization advantage PRC |
| I | I - Inflammatory arthritis contraindication to PRC |
| C | C - Cartilage lunate fossa must be pristine (Grade I-II only) | T | T - Time to recovery faster with PRC | A | A - Arthritis progression risk higher with PRC |
| A | A - Age favors older patients for PRC (greater than 50) | I | I - Inflammatory arthritis contraindication to PRC | G | G - Grip strength 5-10% better with 4CF |
| R | R - Reliability slightly favors 4CF for strength | L | L - Low demand patients better PRC candidates | E | E - Early mobilization advantage PRC |
Hook:CARTILAGE quality determines PRC suitability - perfect mnemonic for cartilage-dependent procedure
CLTDFour-Corner Fusion Bones - CLTD
| C | C - Capitate |
| L | L - Lunate |
| T | T - Triquetrum |
| D | D - Distal (Hamate) |
| C | C - Capitate | T | T - Triquetrum |
| L | L - Lunate | D | D - Distal (Hamate) |
Hook:Remember CLTD like CLT Down to recall the four bones fused
Overview and Epidemiology
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.
Epidemiology
- SLAC wrist: Most common degenerative wrist pattern
- Prevalence increases with age
- Male predominance (3:1)
- Often bilateral involvement (30%)
- Scaphoid nonunion present in 50% trauma cases
- Inflammatory arthritis affects 70% RA patients
Pathophysiology
- Loss of normal carpal kinematics
- Progressive articular cartilage degeneration
- Subchondral sclerosis and cyst formation
- Osteophyte formation
- Synovial inflammation variable
- Capsular contracture develops
Natural History
- SLAC progression over 10-20 years
- Pain typically precedes radiographic changes
- Function declines with advancing stage
- Grip strength reduced 40-60%
- Motion limitation variable
- Spontaneous fusion rare
Etiology and Classification
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.
Classification
Lichtman SLAC Staging:
-
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
Post-Traumatic:
- Perilunate dislocation sequelae
- Trans-scaphoid perilunate fracture-dislocation
- Axial loading injuries
- Distal radius malunion
Inflammatory:
- Rheumatoid arthritis (70% wrist involvement)
- Psoriatic arthritis
- Systemic lupus erythematosus
- Crystal arthropathy (gout, pseudogout)
Degenerative:
- Primary osteoarthritis (rare in wrist)
- Kienbock disease (avascular necrosis lunate)
- Preiser disease (avascular necrosis scaphoid)
Clinical Assessment
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.
Key History Elements:
- Pain location: Dorsal midcarpal vs radial styloid
- Onset: Acute injury vs insidious progression
- Mechanical symptoms: Catching, clicking, giving way
- Functional limitation: Grip strength, keyboard use, weight-bearing
- Prior treatment: Injections, splinting, therapy
- Occupational demands: Labor vs sedentary
Physical Examination Findings:
Inspection:
- Dorsal prominence from carpal collapse
- Muscle atrophy (late finding)
- Skin condition (plan incisions)
- Prior surgical scars
Palpation:
- Point tenderness over scapholunate interval
- Midcarpal joint line tenderness
- Radial styloid tenderness (Stage I SLAC)
- DRUJ stability and tenderness
Range of Motion:
- Flexion-extension arc (compare to contralateral)
- Radial-ulnar deviation
- Forearm rotation
- Measure and document baseline
Special Tests:
- Watson test (scaphoid shift): Positive with SL instability
- Midcarpal shift test: Clunk with ulnar to radial deviation
- Shear test: Pain with axial loading
- Grip strength: Typically 40-60% reduction
Clinical Pearl
Midcarpal Shift Test Technique: Stabilize the proximal carpal row dorsally with one hand. With the other hand, grasp the metacarpals and translate the distal row palmarly. A palpable clunk indicates midcarpal instability. Perform wrist in neutral, then in ulnar and radial deviation. Positive test suggests capitolunate instability or midcarpal pathology.
Imaging Studies
Plain Radiographs (Essential):
Standard wrist series including PA, lateral, and bilateral clenched-fist views.
PA View Findings:
- Scapholunate interval widening (greater than 3mm)
- Scaphoid ring sign (flexed scaphoid)
- Radial styloid beaking
- Joint space narrowing
- Subchondral sclerosis and cysts
- Osteophyte formation
Lateral View Findings:
- Scapholunate angle (normal 30-60°, DISI greater than 70°)
- Radiolunate angle (normal 0±10°)
- Carpal height ratio (Revascularization Index less than 0.5 abnormal)
- Capitate migration (proximal relative to radius)
Clenched-Fist PA View:
- Accentuates scapholunate gap
- Dynamic instability assessment
- Comparison to relaxed PA view
Advanced Imaging:
CT Scan:
- Detailed assessment of arthritis extent
- Preoperative planning for four-corner fusion
- Evaluate lunate fossa cartilage (PRC planning)
- Assess subchondral bone quality
- 3D reconstruction for complex cases
MRI:
- Soft tissue assessment (rarely needed for arthritis)
- Evaluate ligament integrity in early disease
- Rule out avascular necrosis
- Assess for concurrent pathology
Wrist Arthroscopy:
- Gold standard for cartilage assessment
- Can perform limited debridement
- Confirm staging before definitive surgery
- Identify salvageable joints
Non-Operative Management
Initial treatment focuses on symptom control and functional optimization. Many patients achieve acceptable outcomes avoiding surgery.
Conservative Modalities
Splinting:
- Wrist immobilization splint for acute flares
- Custom thermoplast orthosis for activity
- Night splinting for pain control
- Typically 4-6 weeks trial
Medications:
- NSAIDs first-line for pain control
- Acetaminophen for mild symptoms
- Topical diclofenac gel
- Avoid long-term narcotic use
Corticosteroid Injection:
- Midcarpal injection under ultrasound or fluoroscopy
- Triamcinolone 40mg mixed with local anesthetic
- Relief typically 3-6 months
- Limit to 3 injections per year
- Can help confirm pain generator
Physical Therapy:
- Gentle range of motion exercises
- Strengthening when pain permits
- Activity modification training
- Ergonomic optimization
- Limited efficacy in advanced arthritis
Activity Modification:
- Avoid heavy lifting and impact loading
- Keyboard ergonomics
- Job modification when possible
- Adaptive equipment for ADLs
Indications for Surgery
Surgical intervention considered when conservative measures fail to provide acceptable symptom control or function.
Absolute Indications:
- Severe pain limiting ADLs despite 6 months conservative therapy
- Progressive deformity
- Functional impairment affecting occupation/quality of life
Relative Indications:
- Moderate pain with imaging showing advanced arthritis
- Patient preference after understanding options
- Young patient with high functional demands
Timing Considerations:
- Delay surgery until conservative measures exhausted
- Consider patient age and occupation
- Assess expectations and compliance potential
- Coordinate with other medical conditions
Surgical Options Overview
Multiple surgical procedures address midcarpal arthritis. Selection depends on arthritis extent, patient factors, and surgeon experience.
Surgical Procedures for Midcarpal Arthritis
| procedure | indication | motionPreservation | gripStrength | advantages | disadvantages |
|---|---|---|---|---|---|
| Radial Styloidectomy | SLAC/SNAC Stage I only | 100% preserved | 90-95% preserved | Simple, preserves anatomy, low morbidity | Only for Stage I, progression possible |
| Four-Corner Fusion | SLAC/SNAC Stage II-III | 50-60% arc | 75-80% normal | Reliable pain relief, preserves motion, proven outcomes | Technical demanding, nonunion 5-10%, scaphoid excision required |
| Proximal Row Carpectomy | SLAC/SNAC Stage II-III, low demand | 50-60% arc | 70-75% normal | Single-stage, no implants, lower nonunion risk | Requires intact lunate fossa, progression possible, lower strength |
| Total Wrist Arthrodesis | Stage IV, salvage, high demand | 0% (complete fusion) | 85-90% normal | Definitive, reliable pain relief, maximum strength | Loss of all motion, impacts ADLs, adjacent joint stress |
| Total Wrist Arthroplasty | Pan-arthritis low demand | 60-80% arc | 60-70% normal | Preserves motion, bilateral procedures possible | Implant failure risk, infection, loosening, revision difficult |
Four-Corner Fusion
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.
Four-Corner Fusion Indications:
Ideal Candidate:
- SLAC or SNAC Stage II or III
- Preserved radiolunate cartilage
- Age 30-70 years
- Moderate to high functional demands
- Failed conservative treatment minimum 6 months
- Willing to accept limited postoperative immobilization
Patient Factors Favoring 4CF:
- Manual laborer requiring grip strength
- Active patient desiring motion preservation
- Younger patient (vs total wrist fusion)
- Desire to avoid complete wrist fusion
Contraindications:
- Stage IV with radiolunate arthritis
- DRUJ arthritis (consider total wrist fusion)
- Active infection
- Avascular necrosis lunate (Kienbock)
- Severe osteoporosis
- Poor bone quality preventing fixation
Relative Contraindications:
- Inflammatory arthritis (higher nonunion risk)
- Smoking (counsel cessation minimum 6 weeks)
- Workers compensation (controversial)
- Unrealistic expectations
The procedure achieves pain relief in 80-90% of patients while preserving functional wrist motion and grip strength superior to total wrist arthrodesis.
Proximal Row Carpectomy
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.
PRC Contraindications: Lunate fossa chondromalacia, capitate cartilage degeneration, inflammatory arthritis, and high-demand patients are contraindications. Intraoperative assessment of cartilage quality is essential - if lunate fossa shows Grade III-IV changes, convert to four-corner fusion or total wrist arthrodesis. Do not proceed with PRC if cartilage inadequate.
Proximal Row Carpectomy Indications:
Ideal Candidate:
- SLAC or SNAC Stage II
- Intact lunate fossa articular cartilage
- Intact capitate articular cartilage
- Low to moderate functional demands
- Age typically greater than 50 years
- Desire for motion preservation
- Failed conservative treatment
Advantages Over Four-Corner Fusion:
- Single-stage procedure (no waiting for fusion)
- No implants (no hardware complications)
- No nonunion risk
- Simpler technique
- Shorter operative time
- Lower cost
Disadvantages Compared to 4CF:
- Requires excellent cartilage (strict criteria)
- Lower grip strength (70-75% vs 75-80%)
- Progressive arthritis risk higher
- Less predictable long-term outcomes
- Not suitable for inflammatory arthritis
Absolute Contraindications:
- Lunate fossa chondromalacia (Grade III-IV)
- Capitate head cartilage degeneration
- Inflammatory arthritis (RA, psoriatic)
- Prior Kienbock disease
- Avascular necrosis capitate
- SLAC Stage IV
Relative Contraindications:
- High-demand manual laborer
- Young patient (less than 30 years)
- Tobacco use
- Workers compensation (controversial)
Preoperative Assessment:
- CT scan to evaluate lunate fossa
- Consider wrist arthroscopy to confirm cartilage quality
- Intraoperative decision-making paramount
- Have backup plan (4CF or total wrist fusion)
The procedure works best in older, lower-demand patients with well-preserved cartilage discovered intraoperatively.
Total Wrist Arthrodesis
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.
Total Wrist Arthrodesis Indications:
Primary Indications:
- SLAC/SNAC Stage IV (pancarpal arthritis)
- Failed four-corner fusion
- Failed proximal row carpectomy
- Severe inflammatory arthritis
- Post-traumatic pancarpal arthritis
- High-demand patient requiring maximum strength
- Salvage for infection/osteonecrosis
Patient Factors Favoring Total Fusion:
- High-demand manual laborer
- Bilateral disease (can fuse dominant, preserve motion contralateral)
- Desire for maximum pain relief and strength
- Understanding of functional limitations
- Failed motion-preserving procedures
Advantages:
- Definitive pain relief (90-95%)
- Maximum grip strength (85-90% normal)
- Predictable union (95% with modern fixation)
- Single definitive procedure
- Allows heavy labor/impact activities
Disadvantages:
- Complete loss of wrist motion
- Impact on ADLs (hygiene, typing, driving)
- Adjacent joint stress (CMC, elbow)
- Irreversible procedure
- Psychosocial impact
Position Planning:
- Dominant hand: 10-15° extension, neutral deviation
- Non-dominant: 0-10° extension, 5-10° ulnar deviation
- Bilateral: Different positions optimize function
- Consider patient occupation and activities
This procedure represents the gold standard for definitive treatment when motion preservation is not possible or has failed.
Total Wrist Arthroplasty
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.
Indications:
- Bilateral wrist arthritis (preserve motion one side if fusion contralateral)
- Low-demand elderly patient
- Inflammatory arthritis with good bone stock
- Patient unable to tolerate wrist fusion limitations
Contraindications:
- High-demand activities
- Poor bone quality
- Active infection
- Inadequate soft tissue envelope
- Young patient
- Manual labor
Implant Designs:
- Universal 2 (commonly used)
- Maestro (modular)
- ReMotion (third generation)
- Evolving technology
Expected Outcomes:
- Motion: 60-80° flexion-extension arc
- Grip: 60-70% normal
- Revision rate: 15-25% at 10 years
- Complications: Loosening, subsidence, dislocation, infection
Role in Midcarpal Arthritis:
- Very limited application
- Reserve for exceptional cases
- Total wrist fusion more reliable
- Consider bilateral wrist disease
Differential Diagnosis
Dorsal and radial wrist pain has several causes that mimic or coexist with midcarpal arthritis. Distinguishing them prevents inappropriate salvage surgery.
Differential Diagnosis of Dorsoradial Wrist Pain
| condition | keyFeature | radiology | distinguisher |
|---|---|---|---|
| SLAC / SNAC midcarpal arthritis | Chronic pain, prior SL injury or scaphoid fracture | Radioscaphoid then capitolunate narrowing; radiolunate spared until late | Watson/scaphoid-shift positive; staged collapse pattern |
| Radiocarpal (radiolunate) arthritis | Pain over proximal dorsal wrist | Radiolunate joint narrowing and sclerosis | Radiolunate involvement contraindicates motion-preserving salvage |
| Kienbock disease (lunate AVN) | Central dorsal wrist pain, no clear injury | Lunate sclerosis, fragmentation, collapse (Lichtman) | Lunate is the primary problem; PRC contraindicated if capitate involved |
| Scaphotrapeziotrapezoid (STT) arthritis | Pain at thumb base or distal scaphoid | STT joint narrowing, distal and radial | Tenderness distal to anatomical snuffbox, not dorsal midcarpal |
| First CMC (thumb base) osteoarthritis | Pain with pinch and grip at thumb base | Trapeziometacarpal narrowing and subluxation | Grind test positive; pain volar-radial, not dorsal carpal |
| Dorsal wrist ganglion (incl. occult) | Dorsal swelling or activity-related ache | Normal radiographs; cyst on ultrasound or MRI | No joint-space loss; transilluminates when visible |
| Inflammatory arthritis (RA / psoriatic) | Bilateral, morning stiffness, systemic features | Periarticular erosions, uniform joint-space loss, osteopenia | Serology and synovitis; contraindicates PRC, alters fixation expectations |
Controversies and Areas of Uncertainty
- 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.
Evidence Base and Outcomes Studies
4CF vs PRC for SLAC/SNAC: Systematic Review & Meta-Analysis
- 61 studies, 3,174 wrists (54% PRC, 46% 4CF); weighted mean follow-up 61 months
- PRC had significantly greater postoperative extension and ulnar deviation
- No significant difference in grip strength between procedures
- Conversion to arthrodesis: 5.2% (PRC) vs 11% (4CF)
- 4CF nonunion rate 8.9% (57/640); hardware removal 2.2% after 4CF
PRC vs 4CF for Post-Traumatic Arthropathy: Systematic Review
- 7 studies (Levels I-III), 240 patients, 242 wrists
- Flexion-extension arc better after PRC: 75 degrees vs 62 degrees for 4CF
- Grip strength better after 4CF: 74% vs 67% of contralateral
- Radial deviation better after 4CF
- Overall complication rate 29% (4CF) vs 14% (PRC); nonunion 7% after 4CF
SLAC Wrist Salvage: Scaphoid Excision and Limited Fusion (Landmark)
- 100 cases of scaphoid excision plus limited (four-corner) fusion; mean follow-up 44 months
- Flexion-extension averaged 72 degrees (53% of normal contralateral)
- Grip strength 80% of the opposite side; pain relief good to excellent in most
- Radiolunate joint preserved in 98/100 despite long follow-up
- Nonunion in 3 cases; dorsal capitate-radius impingement in 12% (technique-related)
Degenerative Sequence of Scaphoid Nonunion (SNAC, Landmark)
- 64 untreated symptomatic scaphoid nonunions analysed radiographically
- Radioscaphoid changes in 75% by 4 years; midcarpal changes in 60% by 9 years
- Pattern follows SLAC (now termed SNAC) from rotary subluxation of the distal fragment
- Radius-proximal fragment and radiolunate joints consistently spared
- Instability progression associated with earlier arthritis onset
PRC vs Scaphoid Excision + 4CF: Cohort Comparison
- Two cohorts of 19 patients each (PRC vs scaphoid excision + 4CF) for SLAC
- Flexion-extension arc near-identical: 81 degrees (PRC) vs 80 degrees (4CF)
- Grip strength 71% (PRC) vs 79% (4CF) of contralateral
- 4CF preserved greater radial deviation
- Pain relief and overall patient satisfaction equivalent at short-term follow-up
PRC vs 4CF for SLAC: Complications and Recovery
- Non-randomised retrospective study of 30 wrists; mean follow-up 3.5 years
- Pain relief and functional gain equal between PRC and 4CF
- Higher complication rate after 4CF, partly from internal fixation
- Higher incidence of carpal tunnel syndrome after 4CF
- Shorter hospital stay and postoperative sick leave favoured PRC
Four-Corner Fusion: Fixation Method and Outcomes
- 31 patients; fixation with K-wires (14), headless screws (8), or circular plate (9)
- Mean wrist motion 70% and grip strength 85% of contralateral
- Complete radiographic fusion in 90.3%; partial fusion in 9.7% (none reoperated)
- Partial union more common with K-wires
- Complications more common with circular plate (CRPS, painful impingement)
PRC Durability: Average 15-Year Follow-up
- 13 patients with advanced Kienbock disease; average 15-year follow-up after PRC
- 12 of 13 excellent or good clinical results
- Total arc of motion 73% and grip strength 92% of the uninvolved side
- All patients remained employed, including 7 in manual labour
- Radiocapitate degeneration universal but did not correlate with clinical results
Clinical Decision Scenarios
Use these scenarios to practise clinical reasoning and management decisions
"A 55-year-old carpenter presents with chronic dorsal wrist pain following a scaphoid fracture 10 years ago. Radiographs show scaphoid nonunion with arthritis between the proximal scaphoid fragment and radius, as well as between the capitate and lunate. The radiolunate joint appears well preserved. How would you classify and manage this?"
"You perform a dorsal approach for four-corner fusion in a 62-year-old woman with Stage III SLAC wrist. After excising the scaphoid and exposing the midcarpal joint, you inspect the lunate fossa cartilage and find it pristine with no evidence of degeneration. The capitate head also shows excellent cartilage. Your surgical plan was four-corner fusion but the findings suggest PRC might be possible. How do you proceed?"
"A 48-year-old labourer presents 18 months after a four-corner fusion done elsewhere with persistent dorsal wrist pain. Radiographs show a lucent line across the capitolunate interval and CT confirms a fibrous nonunion. The radiolunate joint remains well preserved. How do you assess and manage this failed four-corner fusion?"
MCQ Practice Points
Clinical Pearl
Q: What is the typical progression pattern of SLAC (Scapholunate Advanced Collapse) wrist?
A: SLAC progression: Stage I - radial styloid to scaphoid. Stage II - entire radioscaphoid joint. Stage III - capitolunate joint. The radiolunate joint is spared due to preserved spherical congruency. This pattern guides surgical decision-making: PRC possible if capitate head intact.
Clinical Pearl
Q: What distinguishes SNAC from SLAC wrist arthritis?
A: SNAC (Scaphoid Nonunion Advanced Collapse) results from scaphoid nonunion. SLAC results from scapholunate ligament injury. Both progress similarly through radioscaphoid then capitolunate joints. Key difference: SNAC shows scaphoid nonunion with humpback deformity and DISI pattern. Both spare radiolunate joint.
Clinical Pearl
Q: What are the surgical options for midcarpal arthritis with intact radiolunate joint?
A: Options include: Proximal row carpectomy (PRC) - requires intact capitate head and radiolunate joint; Four-corner fusion (scaphoid excision + capitate-lunate-hamate-triquetrum fusion) - preserves more motion than total wrist fusion. PRC simpler with faster recovery; four-corner preserves more grip strength.
Clinical Pearl
Q: What radiographic measurement indicates scapholunate dissociation leading to SLAC wrist?
A: Scapholunate angle greater than 70° (normal 30-60°) indicates dissociation. Terry Thomas sign - scapholunate gap greater than 3mm (or greater than 2mm difference from contralateral). Scaphoid ring sign on PA view indicates flexed scaphoid. DISI pattern (dorsal intercalated segment instability) shows lunate extended dorsally.
Clinical Pearl
Q: Why is the radiolunate joint preserved in SLAC and SNAC wrist arthritis?
A: The radiolunate joint maintains spherical congruency even with carpal malalignment, distributing load evenly. The radioscaphoid joint has elliptical articulation, making it susceptible to point-loading with scaphoid malposition. This preservation makes PRC and four-corner fusion viable options.
Guidelines, Registries & Global Practice
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.
| Theme | Common ground (AAOS / BOA / AO / EFORT-aligned practice) | Where practice varies |
|---|---|---|
| First-line treatment | Conservative trial (NSAIDs, splinting, activity modification, image-guided corticosteroid) before surgery | Threshold/duration of trial (commonly 3-6 months) |
| Staging | Watson SLAC / SNAC staging directs surgical choice | Use of arthroscopy vs CT to confirm capitate-head cartilage |
| Stage II-III salvage | Motion-preserving surgery (PRC or scaphoid excision + 4CF) preferred over total fusion | PRC-first (motion, lower morbidity) vs 4CF-first (grip, demand) |
| Stage IV / failure | Total wrist arthrodesis is the reliable salvage | Selective total wrist arthroplasty in low-demand or bilateral disease |
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.
Clinical summary
SLAC Staging - RAMS
- •R: Radial styloid arthritis (Stage I) - radial styloidectomy
- •A: Articulation scaphoid fossa (Stage II) - 4CF or PRC
- •M: Midcarpal capitolunate arthritis (Stage III) - 4CF or PRC
- •S: Stage IV adds pancarpal + DRUJ - total wrist fusion
- •Radiolunate preserved until Stage IV (key concept)
- •SNAC follows identical staging from scaphoid nonunion
Four-Corner Fusion Essentials
- •Scaphoid excision + fuse capitate-hamate-lunate-triquetrum
- •Preserves radiolunate joint (motion source)
- •Outcomes: 75-80% grip, 50-60% motion, 85-90% pain relief
- •Union rate 90-95% with rigid fixation
- •Immobilize 8-12 weeks until fusion
- •Complications: nonunion 5-10%, hardware prominence 10-20%
PRC vs 4CF Decision
- •PRC requires pristine lunate fossa cartilage (Grade I-II)
- •PRC: faster recovery, no nonunion, 70-75% grip
- •4CF: better grip (75-80%), more predictable long-term
- •PRC contraindications: inflammatory arthritis, poor cartilage, high demand
- •Intraoperative cartilage assessment definitive
- •Both achieve similar 50-60% motion preservation
Total Wrist Arthrodesis
- •Indications: Stage IV SLAC, failed 4CF/PRC, high demand
- •Position: 10-15° extension, neutral to 5-10° ulnar deviation
- •Outcomes: 85-90% grip (best), 90-95% pain relief, 95% union
- •Complete motion loss impacts ADLs significantly
- •Plate fixation most common, allows early mobilization
- •Consider bilateral disease (fuse one, preserve other)
PRC Contraindications
- •Lunate fossa chondromalacia (Grade III-IV)
- •Capitate articular cartilage degeneration
- •Inflammatory arthritis (RA, psoriatic)
- •Kienbock disease (AVN lunate)
- •High-demand manual laborer
- •Young patient (relative, consider 4CF instead)
Physical Examination
- •Watson test: scaphoid shift with SL instability
- •Midcarpal shift test: clunk ulnar to radial deviation
- •Point tenderness scapholunate interval (dorsal)
- •Grip strength typically 40-60% reduced
- •ROM measurement and comparison to contralateral
- •DRUJ assessment (Stage IV consideration)
Imaging Assessment
- •PA wrist: SL gap (greater than 3mm), scaphoid ring sign
- •Lateral: SL angle (normal 30-60°, DISI greater than 70°)
- •Clenched fist: Dynamic SL instability
- •CT scan: Assess arthritis extent, plan fixation, evaluate lunate fossa
- •MRI: Limited role in arthritis (ligament assessment early)
- •Arthroscopy: Gold standard cartilage evaluation
Surgical Pearls
- •4CF: Complete scaphoid excision prevents impingement
- •4CF: Thorough cartilage removal to bleeding bone essential
- •PRC: Don't proceed if cartilage inadequate (convert to 4CF)
- •Total fusion: Position critical (cannot easily revise)
- •All: Preserve soft tissue envelope and blood supply
- •All: Rigid fixation improves union rates
Summary
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.