High Yield Overview

LUNATE AND PERILUNATE DISLOCATIONS

Progressive Instability | Mayfield Stages | Emergent Reduction | Ligament Reconstruction

25%Missed on initial X-ray

Stage IIIPerilunate dislocation

Stage IVLunate dislocation (volar)

6-8 hoursWindow for median nerve

MAYFIELD PROGRESSIVE PERILUNAR INSTABILITY

Stage I

PatternScapholunate dissociation

TreatmentClosed reduction + K-wires

Stage II

PatternCapitolunate dissociation

TreatmentOpen repair + ligament reconstruction

Stage III

PatternPerilunate dislocation (lunate in fossa)

TreatmentEmergent reduction + ORIF

Stage IV

PatternLunate dislocation (volar)

TreatmentEmergent reduction + ORIF + CTR

Critical Must-Knows

25% missed initially - always look for carpal arc disruption on lateral X-ray
Spilled teacup sign = Stage IV lunate dislocation (lunate tips volar into carpal tunnel)
Mayfield progression: SL then capitolunate then lunotriquetral ligaments fail sequentially
Acute median nerve symptoms common in Stage IV - urgent reduction required
Greater arc injuries = fracture-dislocations (trans-scaphoid most common)

Examiner's Pearls

"
Lateral X-ray: Lunate should articulate with both radius and capitate
"
Lesser arc = pure ligamentous; Greater arc = bone fractures
"
Trans-scaphoid perilunate = scaphoid fracture + perilunate dislocation
"
Open reduction via combined volar + dorsal approach preferred

Clinical Imaging

Imaging Gallery

2-panel wrist X-rays (PA and lateral labeled a,b) showing posterior perilunate dislocation with ulnar styloid avulsion fracture (white arrowhead on lateral view). — 2-panel wrist X-rays (PA and lateral labeled a,b) showing posterior perilunate dislocation with ulnar styloid avulsion fracture (white arrowhead on laCredit: Chari PR - Indian J Orthop via Open-i (NIH) - PMC2856404 (CC-BY 4.0)

4-panel wrist X-rays (labeled a-d) showing chronic perilunate dislocation: preoperative lateral (a), post open reduction with K-wire fixation PA and lateral (b,c), and 2-year follow-up (d). — 4-panel wrist X-rays (labeled a-d) showing chronic perilunate dislocation: preoperative lateral (a), post open reduction with K-wire fixation PA and lCredit: Dhillon MS et al. - Indian J Orthop via Open-i (NIH) - PMC3162679 (CC-BY 4.0)

3D CT reconstruction of hand showing carpal bones and metacarpals - useful for understanding carpal anatomy and spatial relationships in perilunate injuries. — 3D CT reconstruction of hand showing carpal bones and metacarpals - useful for understanding carpal anatomy and spatial relationships in perilunate inCredit: Open-i / NIH via Open-i (NIH) (CC-BY 4.0)

AP and lateral wrist radiographs showing posterior perilunate dislocation — AP (a) and lateral (b) wrist radiographs demonstrating a posterior perilunate dislocation (Mayfield Stage III). On the AP view, note the disrupted Gilula's arcs and crowding of the carpal bones. On the lateral view (b), the lunate remains in the lunate fossa while the capitate and rest of the carpus are dorsally displaced - this is the key distinction from Stage IV lunate dislocation. Arrowhead indicates an avulsion fracture fragment. These injuries are frequently missed (25%) - always carefully examine the lateral view to confirm the lunate articulates with both radius and capitate.Credit: Chari PR via Indian J Orthop (CC BY)

Critical Perilunate/Lunate Dislocation Points for Exams

25% Missed Diagnosis

One quarter of perilunate/lunate dislocations are missed on initial presentation. Always examine the lateral X-ray carefully - the lunate should articulate with both the radius and the capitate.

Mayfield Progression

Sequential ligament failure: Scapholunate (I) then capitolunate (II) then lunotriquetral (III) then lunate tips volar (IV). Understanding this helps identify the stage and predict associated injuries.

Median Nerve Emergency

Acute carpal tunnel syndrome is common with lunate dislocations (Stage IV). The volarly dislocated lunate compresses the median nerve. Urgent reduction within 6-8 hours is critical.

Greater vs Lesser Arc

Lesser arc = pure ligamentous injury around lunate. Greater arc = fractures through bones (trans-scaphoid most common). Greater arc injuries have better bone healing but worse overall outcomes.

At a Glance

Perilunate and lunate dislocations represent a spectrum of high-energy carpal injuries following the Mayfield progression of ligamentous disruption. Perilunate dislocation (Mayfield Stage III) maintains the lunate in the lunate fossa while the carpus dislocates dorsally. Lunate dislocation (Mayfield Stage IV) shows volar lunate displacement into the carpal tunnel ("spilled teacup" sign). Trans-scaphoid perilunate is the most common greater arc injury. These injuries are commonly missed on initial X-rays (25%). Treatment is urgent open reduction with ligament repair to prevent median nerve damage and progressive carpal instability.

Lunate vs Perilunate Dislocation Comparison

Greater Arc vs Lesser Arc Injuries

MnemonicCards

Mnemonic

S-C-L-TMayfield Stages

Scapholunate

Stage I - SL ligament disruption

Capitolunate

Stage II - Capitate dislocates from lunate

Lunotriquetral

Stage III - Perilunate dislocation complete

Tipped

Stage IV - Lunate tips volar (lunate dislocation)

Memory Hook:S-C-L-T: Scapholunate, Capitolunate, Lunotriquetral, Tipped volar - progressive failure pattern

Mnemonic

BONE vs LIGAGreater vs Lesser Arc

Bone

Greater arc passes through bones

Often scaphoid

Trans-scaphoid most common

Not just ligaments

Fractures present

Easier union

Bone heals better than ligament

Memory Hook:Greater arc = Greater bone involvement; Lesser arc = Less bone, more ligament

Mnemonic

TRAPClosed Reduction Steps

Traction

Longitudinal finger traction first

Recreate

Recreate deformity by extending wrist

Apply pressure

Thumb pressure over dorsal carpus

Push and flex

Push carpus volar while flexing wrist

Memory Hook:TRAP the lunate back in place: Traction, Recreate, Apply pressure, Push and flex

Overview

Perilunate and lunate dislocations represent a spectrum of high-energy carpal injuries characterized by progressive failure of the perilunate ligamentous structures. These injuries are frequently missed on initial presentation (up to 25% of cases), leading to delayed diagnosis and poorer outcomes.

The mechanism involves forced hyperextension, ulnar deviation, and intercarpal supination, typically from a fall on an outstretched hand with the wrist in dorsiflexion. The injury progresses through predictable stages (Mayfield classification) as sequential ligaments fail.

Key Concepts:

Perilunate dislocation: Lunate remains articulated with radius; carpus dislocates dorsally around it
Lunate dislocation: Lunate dislocates volarly while proximal carpal row reduces
Both are part of a continuous spectrum of progressive perilunar instability
Associated fractures (greater arc) are common, especially scaphoid

Anatomy

Perilunate Ligamentous Anatomy

The lunate is the keystone of the proximal carpal row, with critical ligamentous attachments:

Intrinsic Ligaments (Interosseous):

Scapholunate ligament: Strongest dorsally, key stabilizer
Lunotriquetral ligament: Strongest volarly
Both critical for carpal stability

Extrinsic Ligaments:

Volar radiocarpal ligaments: RSC (radioscaphocapitate), LRL (long radiolunate), SRL (short radiolunate)
Dorsal radiocarpal ligaments: DRC (dorsal radiocarpal)
Space of Poirier: Weak zone between RSC and LRL - path of lunate dislocation

Greater Arc vs Lesser Arc

Lesser Arc (Pure Ligamentous):

Injury passes through ligaments only
Arc around the lunate through SL, capitolunate space, LT ligament
Pure soft tissue injury
More challenging reconstruction

Greater Arc (Fracture-Dislocation):

Injury passes through bones
Common fracture patterns:
- Trans-scaphoid (most common)
- Trans-radial styloid
- Trans-capitate
- Trans-triquetral
Bone healing potentially easier than ligament healing

Classification Systems

Mayfield Progressive Perilunar Instability

The Mayfield classification describes the sequential failure of perilunate structures.

Stage I - Scapholunate Dissociation: Disruption of scapholunate interosseous ligament. Scaphoid flexes, lunate extends (DISI pattern begins). Widened SL interval on PA X-ray (greater than 3mm). Terry Thomas sign (gap between scaphoid and lunate).

Stage II - Capitolunate Dissociation: Space of Poirier disrupts (between RSC and LRL ligaments). Capitate dislocates dorsally relative to lunate. Lunate still articulates with radius. Progressive ligament failure continues.

Stage III - Perilunate Dislocation: Lunotriquetral ligament fails. Entire carpus dislocates dorsally around lunate. Lunate remains in lunate fossa of radius (key point). Capitate no longer articulates with lunate. Lateral X-ray shows dorsal capitate displacement.

Stage IV - Lunate Dislocation: Dorsal radiocarpal ligament fails (final ligament). Lunate rotates and tips volarly out of lunate fossa. Lunate enters carpal tunnel ("spilled teacup"). Median nerve compression very common (60-80%). Surgical emergency if nerve symptoms present.

Pathophysiology

Mechanism of Injury

Typical mechanism:

Fall on outstretched hand (FOOSH)
Wrist in dorsiflexion
Combined hyperextension + ulnar deviation + intercarpal supination
High-energy trauma (MVA, fall from height, sports)

Force transmission:

Axial load through palm
Ground reaction force applied to thenar eminence
Wrist forced into hyperextension
Sequential ligament failure from radial to ulnar side

Median Nerve Emergency

Stage IV lunate dislocations cause acute carpal tunnel syndrome in the majority of cases. The volarly dislocated lunate directly compresses the median nerve. Emergent reduction is required - permanent nerve damage can occur within 6-8 hours of sustained compression.

Clinical Assessment

History

Mechanism:

High-energy trauma typically
Fall on outstretched hand
Motor vehicle accident
Sports injury (contact sports, cycling)

Symptoms:

Severe wrist pain
Rapid swelling
Inability to move wrist
Numbness in median nerve distribution (especially Stage IV)
History may include feeling of "pop" or "shift"

Physical Examination

Inspection:

Marked swelling of wrist
Loss of normal wrist contour
May see dorsal prominence (perilunate) or volar fullness (lunate)
Skin tension assessment critical

Palpation:

Diffuse tenderness
Possible palpable lunate volarly (Stage IV)
Assess for open injury or skin compromise

Neurovascular Examination:

Critical: Median nerve function assessment
Sensation in thumb, index, middle finger
Thenar muscle strength (opponens pollicis)
Two-point discrimination
Compare with contralateral side

Range of Motion:

Severely limited due to pain
Do not force examination
Document baseline for postoperative comparison

Red Flags Requiring Emergent Intervention

Acute carpal tunnel symptoms (numbness, tingling, weakness)
Open injury
Skin blanching or tension
Vascular compromise
Compartment syndrome signs

Investigations

Plain Radiographs

Standard Views:

PA (posteroanterior)
True lateral
Oblique views

PA View Findings:

Normal landmarks (Gilula's arcs):

Arc I: Proximal articular surfaces of proximal row
Arc II: Distal articular surfaces of proximal row
Arc III: Proximal articular surfaces of capitate/hamate

Abnormal findings:

Disruption of Gilula's arcs
Widened SL interval (greater than 3mm = "Terry Thomas sign")
Overlap or crowding of carpal bones
Triangular or pie-shaped lunate = rotated lunate

Lateral View Findings:

Normal alignment:

Radius, lunate, and capitate should be collinear
Lunate "cup" should hold capitate "ball"

Perilunate dislocation (Stage III):

Lunate remains in lunate fossa
Capitate dislocated dorsally
Lunate no longer articulates with capitate

Lunate dislocation (Stage IV):

Lunate tilted volarly out of fossa
"Spilled teacup" appearance
Capitate may partially reduce into lunate fossa

Spilled Teacup Sign

On lateral X-ray, the lunate normally appears like a cup holding the capitate. In Stage IV lunate dislocation, the lunate rotates and "spills" volarly - the spilled teacup sign. This is pathognomonic for lunate dislocation.

CT Scan

Indications:

Confirm diagnosis
Identify associated fractures (greater arc injuries)
Pre-operative planning
Assess reduction quality post-operatively

Key Findings:

Fracture lines in scaphoid, capitate, triquetrum, or styloid
Extent of articular involvement
Fragment size and displacement

MRI

Indications:

Usually not needed acutely
May help assess ligament integrity subacutely
Useful for planning staged reconstruction

Findings:

Ligament tears (SL, LT)
Bone bruising pattern
TFCC injury assessment

Management Algorithm

Initial Assessment and Closed Reduction

Initial Assessment:

Assess neurovascular status immediately (critical: median nerve function)
Document mechanism of injury
Assess skin integrity and tension
Obtain PA, lateral, and oblique X-rays
Splint in position of comfort initially

Indications for Emergent Closed Reduction:

Acute carpal tunnel syndrome (Stage IV lunate dislocation)
Skin compromise or threatened skin
Open injury
Vascular compromise

Closed Reduction Technique (TRAP):

Traction: Apply longitudinal traction through fingers
Recreate: Initially increase wrist extension to disengage and recreate deformity
Apply pressure: Thumbs over dorsum, apply pressure over dorsal carpus
Push and flex: Push carpus volarly while flexing wrist
Verify reduction: Immediate post-reduction films
Analgesia: Regional block or procedural sedation required

Post-Reduction Management:

Splint in neutral position
Repeat neurovascular examination
Confirm reduction on X-ray
Arrange definitive surgery within 24-72 hours (within 7-14 days ideally)

Critical Note: Closed reduction is temporizing only. ALL perilunate/lunate dislocations require definitive surgical treatment. Closed treatment alone results in unacceptable rates of instability and arthritis.

If Closed Reduction Fails: Emergent open reduction in operating theater. Interposed tissue is preventing reduction.

Surgical Technique

Surgical treatment sequence for neglected perilunate dislocation — Surgical treatment of a neglected perilunate dislocation. (a) Preoperative lateral radiograph showing persistent perilunate dislocation 1.5 years after injury. (b-c) Post-operative AP and lateral views demonstrating anatomic reduction maintained with K-wire fixation. (d) Two-year follow-up showing maintained reduction. Even delayed cases (greater than 6 months) can achieve acceptable outcomes with open reduction, though results are inferior to acute treatment.Credit: Dhillon MS et al. via Indian J Orthop (CC BY)

Positioning and Preparation

Patient Positioning:

Supine position
Arm on hand table
Upper arm tourniquet applied
Exsanguinate with elevation (avoid Esmarch if concern for fracture displacement)

Approach Selection: Combined volar plus dorsal approach preferred for all perilunate/lunate dislocations. Volar approach performed first for carpal tunnel release and lunate visualization. Dorsal approach then used for definitive reduction and fixation. Single approach inferior to combined approach which provides better visualization and outcomes.

Complications

Early Complications

Median Nerve Injury:

Acute compression from displaced lunate (Stage IV)
Iatrogenic during reduction
Carpal tunnel syndrome post-operatively
Usually improves with reduction and CTR

Infection:

Higher risk with open injuries
Standard surgical infection risk

Failure of Reduction:

Interposed tissue (capsule, tendons)
Inadequate surgical technique
May require repeat surgery

Late Complications

Post-traumatic Arthritis:

Most common long-term complication
Occurs in 50-70% at long-term follow-up
May be asymptomatic
Radiocarpal and midcarpal joints affected

Carpal Instability:

Recurrent SL or LT dissociation
Progressive collapse patterns (SLAC, SNAC equivalent)
May require salvage procedures

Scaphoid Nonunion:

In trans-scaphoid perilunate injuries
Risk factors: Delay, inadequate fixation, smoking
Requires revision surgery with bone grafting

AVN of Lunate:

Rare but devastating
Blood supply vulnerable during injury
May lead to Kienböck's pattern
Limited salvage options

Stiffness:

Expected to some degree
ROM typically 50-70% of normal
Grip strength 60-80% of normal
Therapy critical for optimization

Complex Regional Pain Syndrome

Rare but serious complication
Early recognition and treatment essential
Multidisciplinary approach required

Postoperative Care

Immediate Postoperative (Day 0-2):

Strict elevation to reduce swelling
Neurovascular checks every 2 hours initially
Watch for compartment syndrome (rare but catastrophic)
Pain control with multimodal analgesia
Finger range of motion exercises started immediately

Week 0-2:

Volar splint or short arm cast
Strict wrist immobilization
Continue finger ROM
First dressing change at 2 weeks
Wound check and suture removal

Week 2-6:

Continue immobilization
May transition to removable splint for hygiene
No active wrist motion yet
K-wires remain in situ
Serial X-rays every 2 weeks to assess alignment

Week 6-8 (K-wire Removal):

X-rays to confirm maintained reduction
K-wire removal in clinic (local anesthesia)
Begin gentle active ROM exercises
Avoid forceful grip or loading
Hand therapy initiated

Week 8-12:

Progressive ROM exercises
Begin gentle strengthening
Therapist-supervised program
May use heat before exercises
Continue to protect from forceful loading

Week 12-16:

Unrestricted ROM exercises
Progressive strengthening with weights
Putty and grip exercises
Functional activities

Month 4-6:

Return to work (light duty may be earlier)
Sports return based on individual progress
Heavy labor typically 6 months minimum
Expect ROM 50-70% of normal long-term
Expect grip strength 60-80% of normal

Long-Term Follow-Up:

X-rays at 6 months and 1 year
Monitor for post-traumatic arthritis development
Counsel regarding arthritis risk (50-70%)
Salvage options if symptomatic arthritis develops

Outcomes/Prognosis

Functional Outcomes

Range of Motion:

Expect 50-70% of normal wrist ROM long-term
Extension typically most affected (loss of 30-40 degrees)
Flexion loss of 20-30 degrees
Radial/ulnar deviation relatively preserved
Forearm rotation usually normal

Strength:

Grip strength typically 60-80% of contralateral side
Improves with therapy and time
Plateaus around 12-18 months

Pain:

Most patients have some residual pain
Usually activity-related
May worsen with arthritis development
Pain scores improve with time if no arthritis

Return to Activities:

Light work: 3-4 months
Heavy labor: 6 months minimum
Contact sports: 6-9 months
Full recovery plateau: 12-18 months

Prognostic Factors

Good Prognosis Factors:

Early treatment (within 7-14 days)
Anatomic reduction achieved
Secure ligament repair
Greater arc injury (paradoxically - better bone healing)
Young patient with good bone quality
Compliant with therapy

Poor Prognosis Factors:

Delayed diagnosis (over 4 weeks)
Incomplete or malreduced carpus
Failed ligament repair
Lesser arc injury (poorer ligament healing)
Associated nerve injury
Multiple carpal fractures
High-energy mechanism

Long-Term Arthritis Risk

Post-Traumatic Arthritis:

Develops in 50-70% of patients by 5-10 years
Radiographic arthritis often asymptomatic initially
Risk factors:
- Residual carpal malalignment
- Articular cartilage damage at injury
- Chronic instability
- Delayed treatment

Arthritis Patterns:

Radiocarpal joint most commonly affected
Midcarpal joint (capitolunate) also common
May progress to scaphoid nonunion advanced collapse (SNAC) or scapholunate advanced collapse (SLAC) equivalent pattern

Management of Symptomatic Arthritis:

Conservative: NSAIDs, activity modification, splinting
Injections: Corticosteroid for temporary relief
Salvage surgery options:
- Proximal row carpectomy (if capitate articular surface intact)
- Four-corner fusion
- Total wrist fusion (last resort for severe symptoms)
- Wrist denervation for pain relief

Evidence Base

Mayfield Progressive Perilunar Instability

Mayfield JK, Johnson RP, Kilcoyne RK • J Hand Surg Am (1980)

Key Findings:

Described the four stages of progressive perilunar instability based on cadaveric and clinical studies. Established that injury progresses sequentially through SL, capitolunate, LT, and finally lunate dislocation.

Clinical Implication: Foundation for understanding perilunate injury spectrum and staging

Missed Perilunate Injuries

Herzberg G, Comtet JJ, Linscheid RL • J Hand Surg Am (1993)

Key Findings:

25% of perilunate dislocations are missed on initial presentation. Delay in diagnosis significantly worsens outcomes.

Clinical Implication: High index of suspicion required; careful examination of lateral X-ray essential

Surgical Treatment Outcomes

Souer JS, Rutgers M, Andermahr J • J Hand Surg Am (2007)

Key Findings:

Combined volar-dorsal approach provides better visualization and outcomes compared to single approach. Open reduction with ligament repair results in 70% good-excellent outcomes.

Clinical Implication: Combined approach preferred for definitive surgical treatment

Long-Term Outcomes of Perilunate Injuries

Komurcu M, Kurklu M, Ozturan KE • J Hand Surg Am (2008)

Key Findings:

Even with optimal treatment, 50-70% develop radiographic arthritis at long-term follow-up. However, clinical outcomes often better than radiographic appearance suggests.

Clinical Implication: Counsel patients about long-term arthritis risk; radiographic changes don't always correlate with symptoms

Trans-Scaphoid Perilunate Dislocations

Budoff JE, Shin S • Hand Clinics (2000)

Key Findings:

Trans-scaphoid perilunate fracture-dislocations represent the most common greater arc injury. Scaphoid fixation with headless screws combined with ligament repair provides optimal outcomes.

Clinical Implication: Greater arc injuries require both fracture fixation and ligament management

Viva Scenarios

Exam Viva Scenarios

Practice these scenarios to excel in your viva examination

VIVA SCENARIOStandard

Missed Perilunate Dislocation

EXAMINER

"A 35-year-old motorcyclist presents 2 weeks after a fall with persistent wrist pain and weakness. Initial X-rays at another hospital were reported as 'normal'. Current examination shows median nerve paresthesias. You review the original X-rays."

EXCEPTIONAL ANSWER

Exceptional Answer Framework:

This scenario illustrates the commonly missed perilunate injury - 25% are missed initially (Herzberg 1993). The key to diagnosis is careful examination of the lateral X-ray: the lunate should articulate with both the radius and the capitate. If the capitate is dorsal to the lunate, it's a perilunate dislocation (Stage III); if the lunate has tipped volar, it's a lunate dislocation (Stage IV).

Clinical assessment: Median nerve symptoms suggest significant injury. I would examine for acute carpal tunnel syndrome - sensory loss in median territory, thenar weakness, Phalen's and Tinel's positive.

Management of delayed presentation:

Urgent CT to assess reduction status and identify any fractures
Surgery indicated despite delay - outcomes worse but still better than non-operative
Combined volar-dorsal approach: Volar for CTR and direct visualization of lunate; Dorsal for ligament repair
Ligament repair may be more difficult due to scarring
Consider ligament reconstruction if primary repair not possible

Counsel patient: increased risk of stiffness and arthritis with delayed treatment. Expected ROM 50-70% of normal. Radiographic arthritis develops in 50-70% long-term.

KEY POINTS TO SCORE

25% of perilunate dislocations are initially missed

Key finding on lateral X-ray: Lunate should articulate with both radius and capitate

Median nerve symptoms suggest significant injury - likely lunate dislocation

Delayed treatment worsens outcomes but surgery still indicated

Combined volar-dorsal approach with CTR recommended

COMMON TRAPS

✗Accepting 'normal' X-ray report without reviewing films yourself

✗Not examining median nerve function carefully

✗Recommending non-operative treatment for established dislocation

✗Performing single approach without addressing carpal tunnel

LIKELY FOLLOW-UPS

"How would you counsel the patient about prognosis given the delay?"

"What would you look for on the lateral X-ray?"

"If this were Stage IV, how would you approach surgical planning?"

"What is the risk of post-traumatic arthritis?"

VIVA SCENARIOChallenging

Acute Lunate Dislocation with CTS

EXAMINER

"A 28-year-old man presents to ED 4 hours after a high-speed motorcycle accident. He has severe wrist pain and reports numbness in his thumb, index, and middle fingers that is worsening. X-rays show a Stage IV lunate dislocation with the lunate tilted into the carpal tunnel."

EXCEPTIONAL ANSWER

Exceptional Answer Framework:

This is a surgical emergency. Stage IV lunate dislocation with acute median nerve compression requires urgent intervention. The median nerve can suffer permanent damage with sustained compression beyond 6-8 hours.

Immediate management:

Document neurovascular status carefully (baseline for comparison)
Closed reduction under sedation in ED - do not delay for theater
Technique (TRAP): Traction, Recreate deformity with extension, Apply dorsal thumb pressure, Push volar while flexing
Post-reduction X-ray and neurovascular reassessment
Splint in neutral

If reduction successful: Neurovascular symptoms should improve. Proceed to definitive surgery within 24-72 hours via combined approach with mandatory CTR.

If reduction fails: Emergent open reduction in operating theater. This is an absolute indication for immediate surgery - interposed tissue preventing reduction.

Surgical approach: Combined volar + dorsal approach preferred. Volar for CTR and direct lunate reduction; dorsal for ligament repair and K-wire fixation. Consider suture anchor repair of SL ligament. Cast 6 weeks, K-wires out at 6-8 weeks.

KEY POINTS TO SCORE

Stage IV = lunate dislocation (spilled teacup sign on lateral)

Acute median nerve compression is an emergency

Attempt closed reduction urgently

Even if closed reduction successful, surgical treatment required

Combined approach with CTR mandatory

COMMON TRAPS

✗Delaying reduction to wait for operating theater

✗Not documenting pre-reduction neurovascular status

✗Assuming closed reduction is definitive treatment

✗Performing dorsal-only approach without CTR

LIKELY FOLLOW-UPS

"Describe your closed reduction technique"

"What if closed reduction fails?"

"How long can the median nerve tolerate compression?"

"What is the long-term prognosis for median nerve function?"

VIVA SCENARIOChallenging

Trans-Scaphoid Perilunate Fracture-Dislocation

EXAMINER

"A 32-year-old construction worker fell from scaffolding. X-rays show a perilunate dislocation with a scaphoid waist fracture. The carpus is displaced dorsally with the lunate remaining in the lunate fossa. No median nerve symptoms."

EXCEPTIONAL ANSWER

Exceptional Answer Framework:

This is a trans-scaphoid perilunate fracture-dislocation - the most common greater arc injury. The force passes through the scaphoid (fracture) and then through the LT ligament (disruption), rather than through the SL ligament as in lesser arc injuries.

Key distinction: Greater arc injuries involve bone fractures; lesser arc are pure ligamentous. The scaphoid fracture actually simplifies one aspect - bone heals better than ligament - but we must still address the LT ligament.

Surgical approach:

Combined volar + dorsal approach (even without acute CTS, volar gives scaphoid access)
Reduce and fix scaphoid first - anatomic reduction, headless compression screw (Herbert type)
Dorsal approach for LT ligament repair - suture anchor or direct repair
K-wire augmentation of reduction (LT, possibly SC)
Capsular repair and closure

Prognosis considerations: Interestingly, greater arc injuries may have better overall outcomes than pure ligamentous injuries because bone heals more reliably than ligament. However, scaphoid nonunion is a risk, and post-traumatic arthritis still occurs in 50-70%.

KEY POINTS TO SCORE

This is a greater arc injury - trans-scaphoid perilunate fracture-dislocation

Most common greater arc pattern

Requires both scaphoid fixation AND ligament repair

Scaphoid fracture fixation typically with headless compression screw

LT ligament still disrupted and needs repair

COMMON TRAPS

✗Treating only the scaphoid fracture and ignoring ligament injury

✗Using K-wires only for scaphoid (screws provide better compression)

✗Not addressing the LT ligament

✗Forgetting to assess for carpal tunnel symptoms

LIKELY FOLLOW-UPS

"How does this differ from a lesser arc injury?"

"What is your surgical sequence?"

"How do you fix the scaphoid?"

"What determines prognosis - the fracture or the ligament injury?"

MCQ Practice Points

Mayfield Staging Question

Q: In Mayfield Stage III perilunate instability, where is the lunate located?

A: In Stage III (perilunate dislocation), the lunate remains in the lunate fossa of the radius. The capitate and rest of the carpus dislocate dorsally around it. In Stage IV (lunate dislocation), the lunate tips volarly out of the fossa.

Lateral X-ray Interpretation Question

Q: What is the "spilled teacup" sign?

A: The spilled teacup sign is seen on lateral X-ray in Stage IV lunate dislocation. Normally, the lunate looks like a cup holding the capitate. When the lunate dislocates volarly and rotates, it appears to have "spilled" out of its normal position - pathognomonic for lunate dislocation.

Greater vs Lesser Arc Question

Q: What is the difference between greater and lesser arc injuries in perilunate dislocations?

A: Lesser arc injuries are pure ligamentous - the injury arc passes through the SL ligament, around the lunate, and through the LT ligament. Greater arc injuries involve fractures - the arc passes through bones (most commonly trans-scaphoid). Greater arc injuries have fractures that need fixation in addition to ligament repair.

Emergency Management Question

Q: What is the urgency of treatment for a Stage IV lunate dislocation with median nerve symptoms?

A: This is a surgical emergency. The volarly dislocated lunate compresses the median nerve in the carpal tunnel. Urgent closed reduction should be attempted immediately (within hours), and definitive surgical treatment with carpal tunnel release is required. Permanent median nerve damage can occur with compression beyond 6-8 hours.

Missed Diagnosis Question

Q: What percentage of perilunate/lunate dislocations are missed on initial presentation?

A: 25% (one quarter) of these injuries are missed initially. This emphasizes the importance of careful examination of the lateral X-ray and maintaining high clinical suspicion. The lunate should articulate with both the radius and the capitate on a normal lateral view.

Australian Context

Perilunate and lunate dislocations in Australia are typically managed through major trauma networks. High-energy injuries presenting to emergency departments are triaged to Level 1 trauma centers with hand surgery support available 24/7. Inter-hospital transfer may be required from regional centers to ensure timely definitive surgical management.

Advanced imaging including CT scanning is readily available at major trauma centers and is essential for identifying greater arc fractures and planning surgical fixation. CT helps distinguish trans-scaphoid perilunate injuries from pure ligamentous injuries, guiding the surgical approach and fixation strategy.

Hand therapy services play a critical role in rehabilitation and are accessible through both public and private sectors across Australia. Coordinated postoperative therapy programs focus on progressive range of motion and strengthening exercises, with typical return to heavy manual work occurring around 4-6 months post-surgery. Access to experienced hand therapists is generally good in metropolitan areas but may be limited in rural and remote regions.

For workplace injuries, WorkCover and workers' compensation systems (which vary by state) provide coverage for treatment and rehabilitation. Motor vehicle accidents involving perilunate injuries fall under state-based compulsory third party (CTP) insurance schemes. Documentation of mechanism of injury, initial neurovascular status, and functional impairment is important for medico-legal purposes. Permanent impairment assessments may be required if residual stiffness or pain persists beyond 2 years.