PERILUNATE DISLOCATIONS - CARPAL EMERGENCY
25% Missed Initially | Mayfield Stages | Lesser Arc vs Greater Arc
MAYFIELD STAGES
Critical Must-Knows
- 25% missed initially - always look at lateral wrist X-ray
- Lateral X-ray key - capitate should be colinear with radius and lunate
- Lesser arc = pure ligamentous, Greater arc = with fractures (trans-scaphoid)
- Lunate maintains contact with radius in perilunate; loses contact in lunate dislocation
- Urgent reduction - median nerve at risk in carpal tunnel
Examiner's Pearls
- "On lateral: look for colinearity of radius-lunate-capitate
- "Spilled teacup sign = lunate dislocates volarly (Stage IV)
- "Trans-scaphoid perilunate = greater arc injury, better prognosis than pure ligamentous
- "Acute carpal tunnel syndrome common - median nerve compression
Critical Perilunate Dislocation Exam Points
25% Missed
One quarter of perilunate dislocations are missed on initial presentation. The injury is subtle on PA view. Always check the lateral - look for colinearity of radius, lunate, and capitate.
Lateral X-ray Sign
On lateral view: radius, lunate, and capitate should be colinear (like cups stacked). In perilunate dislocation, capitate is dorsal to lunate. In lunate dislocation, lunate tips volarly (spilled teacup).
Median Nerve at Risk
Acute carpal tunnel syndrome occurs in up to 25%. The dislocated bones compress the median nerve in the carpal tunnel. Urgent reduction is required - delays risk permanent median nerve damage.
Lesser vs Greater Arc
Lesser arc = pure ligamentous injury (through Mayfield stages). Greater arc = fracture through bone (trans-scaphoid perilunate most common). Greater arc injuries may have better prognosis.
Quick Decision Guide
| Pattern | Key Finding | Treatment |
|---|---|---|
| Stage I (SL dissociation) | Scapholunate widening, no dislocation | May be isolated or progress |
| Stage II-III (Perilunate) | Capitate dorsal to lunate on lateral | Urgent reduction, operative repair |
| Stage IV (Lunate) | Lunate volarly rotated (spilled teacup) | Urgent reduction, operative repair |
| Trans-scaphoid perilunate | Greater arc with scaphoid fracture | Fix scaphoid + ligament repair |
| With median nerve symptoms | Acute carpal tunnel syndrome | Urgent reduction, consider CTR |
| Delayed presentation (greater than 3 weeks) | Chronic dislocation | Complex reconstruction required |
MAYFIELD - Stages of Injury
Memory Hook:MAYFIELD stages progress from radial to ulnar, lesser to greater severity
SPILLED - Lunate Dislocation Sign
Memory Hook:A SPILLED teacup = lunate dislocation (Stage IV)
LATERAL - X-ray Assessment
Memory Hook:Use LATERAL view to diagnose - look for the three C's colinearity
Overview and Epidemiology
Perilunate dislocations are high-energy injuries representing the most severe end of the carpal instability spectrum. They are frequently missed on initial assessment, with up to 25% of cases not diagnosed at first presentation.
Mechanism of injury:
- High-energy wrist hyperextension
- Motor vehicle accidents
- Falls from height
- Industrial injuries
- Sports injuries - FOOSH with significant force
- Force transmitted through palm causes sequential ligament failure
Energy Required
Perilunate dislocations require significant force - these are not minor injuries. The energy required to cause sequential ligament rupture (or fracture through bone in greater arc injuries) indicates high-energy trauma. Always assess for associated injuries.
Classification:
- Lesser arc injuries: Pure ligamentous (through Mayfield stages)
- Greater arc injuries: With fractures (trans-scaphoid most common - 61%)
- Trans-scaphoid perilunate
- Trans-radial styloid perilunate
- Trans-triquetral perilunate
- Combined patterns
Anatomy and Pathomechanics
Carpal anatomy:
- Proximal row: Scaphoid, lunate, triquetrum (+ pisiform)
- Distal row: Trapezium, trapezoid, capitate, hamate
- Lunate: Central keystone, articulates with radius
- Capitate: Head articulates with lunate concavity
Key ligaments:
- Scapholunate (SL) ligament: Dorsal portion strongest, connects scaphoid to lunate
- Lunotriquetral (LT) ligament: Connects lunate to triquetrum
- Space of Poirier: Weak area between lunate and capitate (volar)
Mayfield pathomechanics:
Mayfield Stages
Progressive perilunar instability (Mayfield):
Mayfield Classification (Progressive Instability):
- Stage I: Scapholunate dissociation
- Stage II: Capitolunate dislocation
- Stage III: Lunotriquetral dissociation (Perilunate dislocation)
- Stage IV: Lunate dislocation (Lunate ejected volar into carpal tunnel)
Lesser vs Greater Arc:
- Lesser arc (pure ligamentous): Injury passes through the ligaments connecting carpal bones
- Greater arc (with fractures): Injury passes through the bones themselves
- Energy dissipated through bone fracture
- Trans-scaphoid perilunate is most common (61%)
- May have better prognosis - bone heals better than ligament
Key concept - Lunate position:
- Perilunate dislocation: Lunate maintains contact with radius; carpus displaces dorsally
- Lunate dislocation: Lunate loses contact with radius; rotates volarly into carpal tunnel
Classification Systems
Mayfield Classification (Stages of Perilunar Instability)
| Stage | Description | X-ray Finding |
|---|---|---|
| I | SL ligament rupture | SL widening (Terry Thomas) |
| II | + Space of Poirier | Capitate starts to dorsally dislocate |
| III | + LT ligament rupture | Complete perilunate dislocation |
| IV | + Dorsal radiocarpal | Lunate dislocates volarly |
Clinical Progression
Injury propagates in an arc from radial to ulnar side. Stage I = SL injury alone. Stages progress as more ligaments fail. Stage III = complete perilunate. Stage IV = lunate pushed volarly into carpal tunnel.
Clinical Presentation and Assessment
History:
- High-energy mechanism
- Time since injury
- Hand dominance
- Symptoms of carpal tunnel (median nerve)
- Associated injuries
Physical examination:
Physical Examination Findings
| Finding | Significance | Action |
|---|---|---|
| Significant wrist swelling | High-energy injury | X-rays including lateral |
| Wrist deformity | Obvious dislocation | Urgent reduction |
| Reduced grip strength | Carpal instability | Careful examination |
| Median nerve symptoms | Carpal tunnel compression | Urgent reduction, CTR consideration |
| Tenderness over carpus | Carpal injury | X-rays, possible CT/MRI |
| Limited ROM (especially extension) | Mechanical block | Likely dislocation |
Median nerve assessment:
Acute Carpal Tunnel
Assess for acute carpal tunnel syndrome:
- Numbness/tingling in median nerve distribution (thumb, index, middle, radial ring)
- Weakness of thenar muscles
- Two-point discrimination impaired This is an urgent indication for reduction. May need carpal tunnel release at time of surgery.
Key examination points:
- Neurovascular status - especially median nerve
- Wrist ROM - often significantly limited
- Swelling pattern
- Skin integrity - rare to be open
- Associated injuries - other wrist/hand structures
Investigations
Radiographic assessment:
Standard views (CRITICAL):
- PA wrist - may appear near-normal; look for:
- Scapholunate widening (Terry Thomas sign)
- Loss of normal carpal arcs (Gilula's lines)
- Overlapping carpals
- "Crowded" carpus appearance
- Lateral wrist - KEY DIAGNOSTIC VIEW:
- Assess colinearity of radius-lunate-capitate
- Normal: Three C's line up (like stacked cups)
- Perilunate: Capitate dorsal to lunate; lunate-radius contact maintained
- Lunate: Lunate tilts volarly (spilled teacup); loses radius contact
Gilula's Carpal Arcs
Gilula's lines are three smooth arcs on PA X-ray:
- Arc 1: Along proximal carpal row proximal surface
- Arc 2: Along proximal carpal row distal surface
- Arc 3: Along proximal capitate/hamate surfaces
- Arc 3: Along proximal capitate/hamate surfaces Disruption indicates carpal instability or dislocation.
Why 25% are missed:
- PA view may look relatively normal
- Lateral view not obtained or not carefully assessed
- Swelling makes interpretation difficult
- Focus on obvious injury misses carpal dislocation
CT imaging:
- Characterize fractures (greater arc injuries)
- Assess reduction after closed reduction
- Surgical planning
- Evaluate articular involvement
MRI:
- Assess ligament injuries
- Evaluate scaphoid blood supply (if trans-scaphoid)
- Usually post-acute phase for surgical planning
- May assess chronic cases for reconstruction options
Management
Emergency management:
- Neurovascular status (median nerve critical)
- Skin integrity
- Associated injuries
- Adequate X-rays (PA AND lateral)
- Indicated for all perilunate/lunate dislocations
- May be done in ED with sedation
- Traction + manipulation technique
- Confirm with post-reduction X-ray
- Splint wrist in neutral to slight flexion
- Re-assess median nerve function
- Arrange definitive surgical treatment
Closed Reduction Technique
Reduction technique:
- Finger-trap traction for 10-15 minutes
- Extend wrist while applying pressure to carpus
- For lunate: direct pressure on dislocated lunate from palmar side
- Flex wrist to lock reduction
- Confirm with X-ray
- Splint in slight flexion Even with reduction, surgical treatment is almost always required.
Operative management:
Surgical Indications
- Essentially all perilunate/lunate dislocations
- Closed reduction alone has unacceptable outcomes
- Goals:
- Anatomic reduction
- Ligament repair
- Fracture fixation (greater arc)
- Stable fixation allowing early motion
Emergency surgery:
- Unreducible dislocation
- Median nerve symptoms persisting after reduction
- Open injury
All perilunate injuries require surgical stabilization for optimal outcomes.
Surgical Technique
Dorsal Approach (Standard)
Incision and Exposure:
- Longitudinal dorsal incision centered over Lister's tubercle
- Elevate extensor retinaculum between 3rd and 4th compartments
- Retract EPL radially
- Capsulotomy through dorsal radiocarpal ligament
Key Steps:
- Assess carpal alignment under direct vision
- Identify and reduce SL and LT intervals
- K-wire fixation (usually 3-4 wires)
- Repair dorsal intercarpal ligaments
The dorsal approach provides excellent visualization of carpal alignment.
Complications
Complications of Perilunate Dislocations
| Complication | Incidence | Management |
|---|---|---|
| Post-traumatic arthritis | Up to 50% | Activity modification, salvage procedures |
| Carpal instability | 30-50% | Reconstruction, fusion options |
| Median neuropathy (permanent) | 10-15% | Prevention with urgent treatment |
| Scaphoid nonunion (trans-scaphoid) | 5-10% | Revision fixation, bone graft |
| Stiffness | Common | Physiotherapy, capsular release |
| AVN of lunate | Rare with timely treatment | Salvage procedures |
| Complex regional pain syndrome | 5-10% | Early recognition, MDT treatment |
Post-traumatic arthritis:
- Most significant long-term complication
- Radiocarpal and midcarpal joints affected
- May progress despite initial good result
- Treatment: activity modification, fusion procedures
Carpal instability:
- SL ligament heals poorly
- May have chronic SL dissociation despite repair
- Leads to DISI pattern, SLAC wrist
- May need late reconstruction or fusion
Long-Term Prognosis
Despite optimal treatment, post-traumatic arthritis develops in up to 50% of patients over time. Carpal instability is also common. Patients should be counseled that even with good initial treatment, long-term problems may develop.
Median nerve injury:
- Acute compression usually resolves with reduction
- Delayed treatment = higher risk of permanent deficit
- May need neurolysis or secondary procedures
Postoperative Care and Rehabilitation
Postoperative protocol:
- Volar splint, wrist neutral to slight flexion
- Elevation
- Finger motion immediately
- Monitor median nerve function
- Convert to removable splint
- Gentle active wrist ROM
- Continue finger exercises
- Suture removal
- X-ray to assess healing
- Consider K-wire removal (8-12 weeks)
- Progressive ROM
- Light functional activities
- K-wire removal (usually by 12 weeks)
- Progressive strengthening
- Increase ROM exercises
- CT if concerns about union
- Full strengthening program
- Grip strength recovery
- Return to work assessment
- Final outcome evaluation
Key rehabilitation principles:
- Finger motion from day 1 (prevent stiffness)
- Protected wrist motion starts at 2 weeks
- K-wires removed before aggressive ROM
- Grip strength takes 6-12 months to recover
- Long-term monitoring for arthritis
K-wire Duration
K-wires are typically left in place for 8-12 weeks to allow ligament healing. SL ligament is particularly slow to heal. Remove K-wires once adequate healing confirmed, then progress rehabilitation.
Outcomes and Prognosis
Outcome factors:
| Factor | Better Outcome | Worse Outcome |
|---|---|---|
| Arc type | Greater arc (trans-scaphoid) | Lesser arc (pure ligamentous) |
| Time to treatment | Less than 7 days | More than 7 days |
| Reduction quality | Anatomic | Residual malalignment |
| Nerve symptoms | None | Persistent median neuropathy |
| Associated injuries | Isolated | Multiple patterns |
Prognostic considerations:
- Even with optimal treatment, outcomes are guarded
- Post-traumatic arthritis common long-term
- SL ligament rarely heals to normal
- Chronic instability may develop despite repair
- Greater arc (trans-scaphoid) may have better outcomes - bone heals better than ligament
Greater Arc Advantage
Greater arc injuries (trans-scaphoid) may have better long-term outcomes than lesser arc (pure ligamentous). The scaphoid fracture, once healed, provides stability. In lesser arc, the SL ligament rarely heals to normal strength.
Evidence Base
- Described the progressive stages of carpal instability from wrist hyperextension. Four stages from SL disruption to complete lunate dislocation. Established framework for understanding these injuries.
- Reviewed 166 perilunate dislocations. Found 25% missed on initial presentation. Emphasized importance of lateral wrist X-ray. Median nerve symptoms in 25%.
- Long-term follow-up of surgically treated perilunate dislocations. Found 30-50% develop carpal instability, 50% develop arthritis. Trans-scaphoid pattern may have better outcomes.
- Described combined dorsal and volar approach for perilunate dislocations. Volar approach allows carpal tunnel release, direct reduction visualization, and volar ligament repair.
- Chronic perilunate dislocations (greater than 8 weeks) have worse outcomes. Open reduction becomes more difficult. May require salvage procedures including proximal row carpectomy.
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
Scenario 1: Missed Perilunate Dislocation
"A 28-year-old man comes to your clinic referred by his GP. He fell off a motorcycle 3 weeks ago and was seen in another hospital's ED. He was told he had a 'wrist sprain' and given a splint. He has persistent pain and weakness. You obtain new X-rays. What are you looking for and what might you find?"
Scenario 2: Acute Lunate Dislocation with Median Nerve Symptoms
"A 35-year-old woman is brought to ED after a high-speed MVA. She has numbness and tingling in her thumb, index, and middle fingers. Her wrist is swollen and painful. X-rays show a lunate dislocation (Stage IV Mayfield). What is your management?"
Scenario 3: Trans-Scaphoid Perilunate Dislocation
"A 25-year-old construction worker falls from scaffolding onto his outstretched hand. X-rays show a perilunate dislocation with a scaphoid fracture through the waist. How does this change your management compared to a pure ligamentous injury?"
MCQ Practice Points
Mayfield Stages Question
Q: In Mayfield Stage III, which structures are disrupted? A: SL ligament + lunocapitate joint (space of Poirier) + LT ligament. This represents complete perilunate dislocation. Stage IV adds dorsal radiocarpal ligament failure with lunate dislocating volarly.
X-ray Question
Q: What is the key X-ray finding on lateral view for perilunate vs lunate dislocation? A: In perilunate: lunate maintains contact with radius, capitate is dorsal to lunate. In lunate dislocation: lunate loses radius contact and tips volarly ("spilled teacup" sign).
Miss Rate Question
Q: What percentage of perilunate dislocations are missed on initial presentation? A: 25% (approximately one quarter). This is usually due to inadequate lateral X-ray or not recognizing the abnormal carpal alignment. Always look at the lateral view for colinearity of radius-lunate-capitate.
Arc Classification Question
Q: What is the difference between lesser arc and greater arc injuries? A: Lesser arc = pure ligamentous (injury through SL, lunocapitate, LT ligaments). Greater arc = with fractures (most commonly trans-scaphoid - 61%). Greater arc injuries may have better long-term prognosis as bone heals better than ligament.
Nerve Question
Q: Why is median nerve assessment critical in perilunate dislocations? A: Acute carpal tunnel syndrome occurs in up to 25% of cases. The dislocated carpal bones compress the median nerve. This is an urgent indication for reduction - delay risks permanent nerve damage.
Australian Context
Epidemiology:
- High-energy injuries: MVA, motorcycle, industrial
- Young male predominance
- Significant work injury implications
Management considerations:
- Requires subspecialty hand surgery expertise
- Should be managed at centers with hand surgery capability
Transfer considerations:
- Complex injuries may need transfer
- Urgent closed reduction can be done locally
- Definitive surgery at appropriate center
Exam Context
Be prepared to discuss Mayfield stages, X-ray interpretation (especially lateral view), lesser vs greater arc, acute carpal tunnel syndrome, and surgical approach. Understanding why 25% are missed is commonly tested.
PERILUNATE DISLOCATIONS
High-Yield Exam Summary
MAYFIELD STAGES
- •Stage I: Scapholunate ligament rupture
- •Stage II: + Lunocapitate (space of Poirier)
- •Stage III: + Lunotriquetral (complete perilunate)
- •Stage IV: + Dorsal radiocarpal → lunate dislocates volarly
KEY X-RAY FINDINGS
- •LATERAL VIEW IS KEY
- •Normal: radius-lunate-capitate colinear
- •Perilunate: capitate dorsal, lunate maintains radius contact
- •Lunate dislocation: lunate tilts volarly (spilled teacup)
LESSER VS GREATER ARC
- •Lesser arc: pure ligamentous
- •Greater arc: with fractures (trans-scaphoid 61%)
- •Greater arc may have better prognosis
- •Bone heals better than ligament
CRITICAL POINTS
- •25% missed on initial presentation
- •Acute carpal tunnel syndrome in 25%
- •Urgent reduction required
- •Surgery almost always required
SURGICAL APPROACH
- •Combined dorsal and volar approach
- •Volar: CTR, visualize reduction
- •Dorsal: ligament repair, K-wire fixation
- •Fix scaphoid if trans-scaphoid
PROGNOSIS
- •50% develop arthritis long-term
- •30-50% chronic instability
- •SL ligament rarely heals to normal
- •Even optimal treatment has guarded prognosis