summary Metacarpal Fractures are the most common hand injury and are divided into fractures of the head, neck, or shaft. Diagnosis is made by orthogonal radiographs the hand. Treatment is based on which metacarpal is involved, location of the fracture, and the rotation/angulation of the injury. Epidemiology Incidence metacarpal fractures account for 40% of all hand injuries Demographics men aged 10-29 have highest incidence of metacarpal injuries Anatomic location metacarpal neck is most common site of fracture fifth metacarpal is most commonly injured Etiology Mechanism of injury direct blow to hand or rotational injury with axial load high energy injuries (ie. automobile) may result in multiple fractures Associated conditions wounds may indicate open fractures or concomitant soft tissue injury tendon laceration neurovascular injury compartment syndrome closed injuries with multiple fractures or dislocations crush injuries Anatomy Metacarpal anatomy concave on palmar surface 1st, 4th, and 5th digits form mobile borders 2nd and 3rd digits form stiffer central pillar index metacarpal is the most firmly fixed, while the thumb metacarpal articulates with the trapezium and acts independently from the others three palmar and four dorsal interossei muscles arise from metacarpal shafts Insertional anatomy extensor carpi radialis longus/brevis insert on the base of metacarpal II, III (respectively); assist with wrist extension and radial flexion of the wrist extensor carpi ulnaris inserts on the base of metacarpal V; extends and fixes wrist when digits are being flexed; assists with ulnar flexion of wrist abductor pollicis longus inserts on the trapezium and base of metacarpal I; abducts thumb in frontal plane; extends thumb at carpometacarpal joint opponens pollicis inserts on metacarpal I; flexes metacarpal I to oppose the thumb to the fingertips opponens digiti minimi inserts on the medial surface of metacarpal V; Flexes metacarpal V at carpometacarpal joint when little finger is moved into opposition with tip of thumb; deepens palm of hand. Presentation Physical exam inspect for open wounds and associated injuries fight wounds over MCP joint are open until proven otherwise extensor tendon can be lacerated and retracted dorsal wounds over metacarpal fractures are almost always open fractures deformity indicates location deformity at metacarpal base may indicate CMC dislocation shortening can be assessed by comparing contralateral hand may be prevented by transverse intermetacarpal ligaments in isolated fracture of the 3rd or 4th metatcarpal shafts malrotation assessed by lining up fingernail in partial flexion and full flexion if possible, compare to contralateral side motor examination typically no motor deficits unless open wounds present check integrity of flexor/extensor tendons in presence of open wounds neurovascular examination dorsal wounds may affect dorsal sensory branch of radial/ulnar nerve volar wounds can involve digital nerves Imaging Radiographs recommended views PA lateral ER oblique best view to see 4th/5th CMC fracture/dislocation IR oblique best view to see 2nd/3rd CMC fracture/dislocation optional views brewerton best view to see metacarpal head fractures roberts best view to see thumb CMC fracture/dislocation CT indications inconclusive radiographs of CMC fractures/dislocations multiple CMC dislocations complex metacarpal head fractures Diagnosis Radiographic diagnosis confirmed by history, physical exam, and radiographs General Treatment Nonoperative immobilization indications must be stable pattern no rotational deformity acceptable angulation & shortening (see table) Acceptable nonoperative criteria Acceptable shaft angulation (degrees) Acceptable shaft shortening (mm) Acceptable neck angulation (degrees) Index & Long finger 10-20 2-5 10-15 Ring finger 30 2-5 30-40 Little finger 40 2-5 50-70 Operative operative treatment general indications open fx intra-articular fxs rotational malalignment of digit significantly displaced or angulated fractures (see above criteria) multiple metacarpal shaft fractures loss of inherent stability from border digit during healing process postoperative early motion is critical remove pins/ cast at ~ 4 weeks Treatment - Metacarpal Head Fractures Operative ORIF indications no degree of articular displacement acceptable majority requires surgical fixation external fixation indications severely comminuted fractures MCP arthroplasty indications severely comminuted fractures MCP fusion indications arthritis late disease Techniques ORIF approach dorsal incision either centrally split extensor apparatus or release and repair sagittal band fixation hardware cannot protrude from joint surface fix with multiple small screws in collateral recess, headless screws, or k-wires ideal fixation should allow for early motion Complications stiffness most common prevented with early motion Treatment - Metacarpal Shaft Fractures Nonoperative immobilization indications nondisplaced metacarpal neck fractures acceptable angulation (see above table) no malrotation immobilize MCP joints in 70-90 degrees of flexion cast for 4 weeks Operative ORIF vs. CRPP indications open fractures unacceptable angulation (see above table) any malrotation multiple fractures Techniques closed reduction percutaneous pinning place antegrade through metacarpal base or retrograde through collateral recess remove pins at 4 weeks open reductions with lag screw can use multiple lag screws for long spiral fractures try to get at least two lag screws open reduction with dorsal plating works best for transverse fractures try to cover plate with periosteum to prevent tendon irritation begin early motion to prevent tendon irritations intramedullary headless compression screw indicated only for axially stable fractures Treatment - Metacarpal Neck Fractures Nonoperative reduction and casting acceptable degrees of apex dorsal angulation (varies by study, see above table) immobilize MCP joints in 70-90 degrees of flexion, leave PIP joints free cast for 4 weeks reduce using Jahss technique 90 degrees MCP flexion, dorsal pressure through proximal phalanx while stabilizing metacarpal shaft Operative reduction and fixation indications unacceptable angulation (see above table) open fractures any malrotation intraarticular fractures Technique CRPP with MCP's flexed antegrade through metacarpal base retrograde through collateral recess ORIF perform if cannot get reduction for CRPP difficult to plate because limited bone for distal fixation