Basics
Description
- Dislocation of the lunate relative to the radius and distal row of metacarpals, most are volar but can be dorsal.
- Usually from high-energy hyperextension with ulnar deviation of the wrist.
Etiology
- Implies disruption of all 4 perilunate ligaments and radiocarpal ligament (Mayfield classification, stage IV)
- In volar dislocations, median nerve injury occurs in the carpal tunnel.
- Associated fractures of the radial styloid, scaphoid, capitate, and triquetrum are common and, if present, should raise suspicion of an occult perilunate ligamentous injury.
Diagnosis
Signs and Symptoms
Frequently missed injury.
History
- Often from fall or motor vehicle accident.
- Pain and tenderness in the wrist.
Physical Exam
- Mass or swelling in the wrist, either dorsally or volarly, depending on direction of dislocation.
- Gross deformity can be masked by swelling.
- May display signs of median nerve injury.
Essential Workup
- Clinical exam is frequently not diagnostic.
- Assess skin integrity and neurovascular status, including 2-point discrimination.
- Radiographs as outlined below.
Diagnosis Tests & Interpretation
Imaging
- Radiographic imaging to include 3 views of the wrist.
- Lateral view most useful:
- Disruption of the normal imaginary longitudinal line through the centers of the radius, lunate, and capitate indicates dislocation or subluxation.
- In volar dislocations, the lunate is frequently tilted with the opening of the "cup " toward the palm (spilled teacup sign)
- Posteroanterior (PA) view:
- The dislocated lunate has a triangular (as opposed to the usual quadrangular) appearance.
- Disruption of a smooth and continuous arc formed by the radiocarpal row suggests lunate dislocation.
Radiograph can be difficult to interpret unless full ossification is present.
Other fractures are common.
Differential Diagnosis
- Lunate fracture.
- Perilunate dislocation.
- Scapholunate dissociation.
- Scaphoid fracture.
Treatment
Pre-Hospital
- Dress open wounds.
- Immobilize in neutral position.
Initial Stabilization/Therapy
Immobilize in position of comfort with a volar or "sugar tongs " splint.
Ed Treatment/Procedures
- Identify multiple trauma or other injuries.
- Contact a hand surgeon for immediate reduction and possible operative intervention.
- Closed reduction can be difficult or unstable.
- Open reduction and internal fixation are frequently required.
Although serious injury is unusual, children with wrist pain should be splinted and referred for ongoing evaluation of possible occult fractures.
Medication
First Line
Analgesics:
- Morphine:
- Pediatrics: 0.05 " 0.20 mg/kg IV up to 1.5 mg. Use preservative-free formulation q4h
- Adults: 4 " 8 mg IV
- Acetaminophen with hydrocodone:
- Pediatrics >12 yo: 2.5 " 10 mg hydrocodone every 4 " 6 h to max 60 mg/24 h or 4 g acetaminophen/24 h.
- Adults: 5 " 10 mg hydrocodone ever 4 " 6 h as needed not to exceed 60 mg/24 h or 4 g acetaminophen/24 h
- Acetaminophen with codeine (adults):
- Pediatrics: 0.5 " 1 mg/kg/dose based on codeine content PO q4 " 6h; do not exceed 5 doses of 10 " 15 mg/kg/24 h of acetaminophen
- Adults: 30 " 60 mg/dose PO q4 " 6h; do not exceed 4 g/24 h of acetaminophen
- Hydrocodone and acetaminophen:
- Pediatrics <12 yr old: 0.1 " 0.2 mg/kg based on hydrocodone content PO q4 " 6h; do not exceed 5 doses of 10 " 15 mg/kg/24 h of acetaminophen
- Pediatrics >12 yr old: 750 mg apap PO q4h, not to exceed 10 mg hydrocodone per dose
- Adults: Do not exceed 4 g/24h of acetaminophen PO q4 " 6h
Second Line
NSAIDs:
- Ibuprofen:
- Pediatrics: 5 " 10 mg/kg q6 " 8h, max. dose 40 mg/kg/d PO div. TID/QID
- Adults: 600 mg PO q6h
- Naproxen:
- Pediatrics >2 yr old: 2.5 mg/kg/d PO BID (not to exceed 10 mg/kg/d)
- Adults: 250 " 500 mg PO BID
- Acetaminophen with codeine (pediatrics):
- Patients may metabolize codeine at variable speeds: poor metabolizers which may lead to under-response, or "ultra-fast " metabolizers which can lead to high levels of morphine, hence undesirable side effects such asapnea and death.
Follow-Up
Disposition
Admission Criteria
- Admission is often necessary for definitive care.
- Open fracture, presence of multiple trauma, or other more serious injuries mandates admission.
Discharge Criteria
Patients with closed dislocations or fractures that have been adequately reduced and immobilized in the ED may be discharged with orthopedic follow-up.
Follow-Up Recommendations
- For those reduced and discharged with splint, follow-up with orthopedics.
- No return to play until fully healed.
Pearls and Pitfalls
- Failure to diagnose wrist dislocations.
- Missed median nerve injury.
- Avascular necrosis of the lunate (Kienb Άck disease)
- Degenerative joint disease.
Additional Reading
- Budoff JE. Treatment of acute lunate and perilunate dislocations. J Hand Surg Am. 2008;33(8):1424 " 1432.
- Marx JA, Hockberger RS, Walls RM, et al., eds. Rosens Emergency Medicine: Concepts and Clinical Practice. 7th ed. Philadelphia, PA: Mosby, Elsevier; 2010.
- Mayfield JK, Johnson RP, Kilcoyne RK. Carpal dislocations: Pathomechanics and progressive perilunar instability. J Hand Surg Am. 1980;5(3):226 " 241.
- Perron AD, Brady WJ, Keats TE, et al. Orthopedic pitfalls in the ED: Lunate and perilunate injuries. Am J Emerg Med. 2001;19(2):157 " 162.
Codes
ICD9
- 833.02 Closed dislocation of radiocarpal (joint)
- 833.09 Closed dislocation of wrist, other
ICD10
- S63.024A Dislocation of radiocarpal joint of right wrist, initial encounter
- S63.026A Dislocation of radiocarpal joint of unspecified wrist, initial encounter
- S63.096A Other dislocation of unspecified wrist and hand, initial encounter
- S63.025A Dislocation of radiocarpal joint of left wrist, initial encounter
SNOMED
- 110029007 traumatic dislocation of lunate bone (disorder)
- 208819009 Closed traumatic dislocation lunate (volar) (disorder)
- 208820003 closed traumatic dislocation perilunate (dorsal) (disorder)