Lunate Fracture

Populations and Risk Factors

FOOSH injuries with force transmitted through the center of the hand during wrist extension
Less common than scaphoid fractures but carries higher avascular necrosis risk due to precarious blood supply
The lunate forms the "floor" of the wrist's central compartment — injury destabilizes the proximal carpal row
Risk of Kienbock disease (chronic avascular necrosis with bone collapse) as a long-term complication
Negative ulnar variance (short ulna relative to radius) increases mechanical load on the lunate

Mechanism: FOOSH with force transmitted through the center of the hand during wrist extension. The lunate is "trapped" between the radius and the distal carpal row during axial loading
Precarious blood supply: The lunate often has a single, tenuous vascular pedicle, making it susceptible to avascular necrosis after even minor fractures that disrupt blood flow
Kienbock disease: Chronic complication where the bone collapses and undergoes sclerosis (increased density visible as whiteness on X-ray) — can lead to total proximal carpal row collapse within months if untreated
Median nerve compression: Displacement or swelling can compress the median nerve within the carpal tunnel, causing secondary CTS
"Local shock" phenomenon: Immediately after fracture, numbness and flaccid muscles lasting up to 30 minutes can mask the severity of the injury

Murphy's Sign: When making a fist, the head of the 3rd metacarpal is level with the 2nd and 4th (normally it projects distally)
Deep, nagging pain localized to the center of the dorsal wrist, aggravated by weight-bearing or extension
Springy end-feel during passive wrist extension (suggesting scapholunate instability)
Rapid edema and tenderness directly distal to Lister's tubercle
Burning or numbness in the thumb and first two fingers (median nerve compression)
"Local shock" immediately after fracture: numbness and flaccidity masking injury severity
Red flags: Persistent wrist pain after FOOSH must be investigated even if initial X-rays are negative — fractures may not appear for up to 2 weeks; median nerve symptoms require urgent referral

Murphy's Sign is a specific indicator for lunate fracture or displacement
Point tenderness 1 cm distal to Lister's tubercle localizes the lunate
Kienbock disease (avascular necrosis) is the major long-term complication due to precarious blood supply
Minor fractures may not show on radiographs for up to 2 weeks. Persistent localized pain requires follow-up bone scan or MRI
Gilula's arcs disruption or "Terry Thomas sign" on X-ray confirms fracture or displacement

Acute fractures locally contraindicate rigorous massage until the site is medically stabilized
Median nerve risk: Displacement or swelling can compress the median nerve — screen with Phalen and Tinel tests
Post-immobilization: Massage restores joint play, reduces casting-related edema, and addresses forearm muscle atrophy
Focus: Stretch wrist flexors and release the transverse carpal ligament to prevent secondary carpal tunnel entrapment. Restore AP glide of the lunate on the radius
Positioning: Avoid prone positioning requiring weight-bearing through the wrist or forced extension for suspected or healing lunate injuries
"Local shock" awareness: Post-fracture numbness and flaccidity can mask severity — refer for imaging if clinical suspicion exists

The lunate is the carpal bone most prone to dislocation and carries high risk of avascular necrosis due to poor blood supply
Murphy's Sign and point tenderness distal to Lister's tubercle are the key clinical indicators
Kienbock disease (avascular necrosis with bone collapse) is the major long-term complication
Minor fractures may be radiographically invisible for up to 2 weeks. Persistent pain warrants follow-up imaging
Post-immobilization treatment focuses on restoring joint play and preventing secondary carpal tunnel syndrome