Perilunate Dislocation ICD-9
- 833.03 (closed midcarpal dislocation)
- 833.13(open midcarpal dislocation)
Perilunate Dislocation Etiology / Epidemiology / Natural History
- Mechanism of injury: hyperextension, ulnar deviation, intercarpal suppination
- Perilunate dislocation = carpal bones displaced dorsally while lunate remains attached to the radius. Hand may snap back into place, forcefully levering the lunate out and displacing it volarly (lunate dislocation). If scaphoid remains attached to the radius a fracture may occur throught the scaphoid waist (trans-scaphoid perlilunar dislocation).
- Untreated leads to progressive arthritis, pain, dysfunction
Perilunate Dislocation Anatomy
- lunate=keystone of carpus
- proximal connected together by interosseous ligaments: injury=dissociative carpal instability
- proximal row attached to distal row by capsular ligaments: injury=nondissociative carpal instablity
- Space of Poirier: V-shaped area of weakenss in the palmar wrist fromed by the palmar carpal ligaments. The lunate can dislocate palmarly through this space.
Perilunate Dislocation Clinical Evaluation
- digits held in semiflexed postion, passive extension causes pain
- may note abnormal carpal alignment
- may have median nerve paresthesias if lunate dislocated into carpal tunnel
Perilunate Dislocation Xray
- true P/A and lateral xray mandatory
- lateral view = loss of colinearlity between radius, lunate, capitate
- “spilled teacup sign” = lunate rotated on its attached palmar ligaments so that concavity faces downward-PA view=loss of normal smooth greater and lesser carpal arcs, overlapping carpal bones
- PA-lunate normally trapezoidal will appear triangular or wedge-shaped when rotated
- evaluate closely for associated fxs
- post reduction clenched fist A/P useful for checking for residual scapholunate or lunotriquetral dissociation or fx.
- Signs of scapholuate dissociation=Terry Thomas Sign)scapholunate widening). Loss of parrallelsm between scaphoid and lunate articular arcs, scaphoid ring sign(volar flexion of the scaphoid), abnormal scapholunate angle on lateral view(normal =30-60 degrees).
- CT, MRI, Bone scan, Arthrography generally not helpful.
Perilunate Dislocation Classification/Treatment
- trans means associated fx. Transcaphoid perilunate dislocation(de Quervain injury)=perilunate dislocation with a scaphoid fx.
- Mayfield biomechanical classification (Mayfield, J Hand Surg 5A:226:1980)
- Stage I=disruption of scapholunate ligamentous complex=scapholunate dissociation
- Stage II=force propagates trhough space of Poirier interruption lunocapitate complex=lunocapitate disruption
- Stage III=lunotriquetral connection violated, entire carpus separates from lunate=lunotriquetral disruption
- Stage IV=lunate dissociates from its fossa into carpal tunnel=lunate dislocation
- ORIF indicated acutely unless swelling is excessive(then CR, delayed ORIF)
- CR =requiresmuscle relaxation (general or regional block), 10-15 pds longitudinal traction for 10 minutes to regain length then manipulate the dislocated carpus to lunate using thumb of one hand. Evaluate reduction with c-arm.
- CRPP=0.045 K-wires. Pin lunate in place after reduction verified by passing wire through radius. Pin triquetrum to lunate. Next pin reduced scaphoid to lunate, then pin scaphoid to capitate. Scaphoid reduction(wrist extension, ulnar deviation, direct pressure) is very difficult and impossible with scaphoid fx.
- ORIF=preferred technique. Dorsal approach=best exposure of carpus, scaphoid & capitate fx can be fixed antegrade. Volar approach=allows carpal tunnel decompression, direct repair of palmar capsular ligaments. Dorsal approach: longitudinal incision; expose capsule between 3rd and 4thcompartments; may use k-wires as joysticks for reduction; place suture to repair interosseous ligaments; percutaneous pin scapholunate, then scaphocapitiate, then trapeziolunate.
- Late/chronic treatment=triscaphe fusion, proximal row carpectomy, wrist fusion
- Transcaphoid peri-lunate dislocation JBJS example case
Perilunate Dislocation Associated Injuries
- Radial styloid fracture
- Scaphoid fracture (trans-scaphoid perilunate dislocation)
- Median nerve palsy (acute carpal tunnel syndrome)
Perilunate Dislocation Complications
- missed diagnosis common, often associated with poor xrays
- median nerve injury
- transient ischemia of lunate, chondrolsys, carpal instability, scaphoid nonunion, malunion, traumatic arthritis
- late flexor tendon rupture
- Loss of motion
- Posttraumatic arthritis
- Carpal tunnel syndrome
Perilunate Dislocation Follow up care
- loss of ROM inevitable. 50% loss of wrist motion, 60% decreased grip strength with treatment
- Short arm cast for 6 weeks. Followed by protected motion program with a thumb spica splint.
- K-wires are generally removed at 3 months followed by an intensive therapy program.
- Kozin, JAAOS 6:114;1998
- Herberg G, J Hand Surg 18A:768;1993°
- AAOS The Fractured Wrist DVD.