Wrist, Carpal, Metacarpal, and Hand Fractures and Dislocations

Introduction

The fractures and dislocations of the wrist and hand, taken together, account for nearly 30 percent of all upper extremity injuries presenting to emergency departments and represent a domain in which functional outcome depends critically on early recognition, precise reduction, and intelligent rehabilitation. The mechanical demands of the hand — fine prehension, power grip, opposable thumb, sensory and dexterous manipulation — combine with a small, articular, and ligamentously-stabilized skeleton that tolerates malreduction less well than the proximal upper limb. The orthopedic adage that “the hand is the eye of the patient” captures the disproportionate functional cost of even modest residual deformity, particularly malrotation. This chapter addresses the scaphoid (the keystone of the carpus and the most commonly fractured carpal bone), the perilunate dislocations and other carpal injuries, the metacarpal fractures including the named Bennett and Rolando patterns, and the phalangeal fractures and dislocations. The chapter draws principally on Rockwood and Green’s Fractures in Adults, Apley & Solomon’s, Miller’s Review of Orthopaedics, Dutton’s Orthopaedic Examination, and Netter’s Concise Orthopaedic Anatomy.

Carpal Anatomy and Biomechanics

The carpus consists of two rows of four bones each — the proximal row (scaphoid, lunate, triquetrum, pisiform) and the distal row (trapezium, trapezoid, capitate, hamate) — connected by an intricate network of intrinsic and extrinsic ligaments. The proximal row acts as an “intercalated segment” between the relatively stiff distal row and the forearm, with carpal stability depending on the balance between the flexion vector of the scaphoid (linking proximal and distal rows) and the extension vector of the triquetrum (through the triquetrohamate articulation). The intrinsic ligaments — particularly the scapholunate (SL) interosseous ligament and the lunotriquetral (LT) interosseous ligament — couple the proximal row bones. The extrinsic ligaments connect the carpus to the forearm and to the metacarpus and include both the volar (palmar) and dorsal radiocarpal ligaments. The scaphoid is the largest bone of the proximal row and is unique in spanning both the proximal and distal carpal rows. Its volar position, its tubercle, and its proximal articular pole make it the most commonly fractured carpal bone (60 to 70 percent of all carpal fractures). The blood supply enters the scaphoid predominantly through the dorsal ridge vessels (branches of the radial artery, supplying approximately 70 to 80 percent of the bone in retrograde fashion) and a smaller volar contribution to the distal pole. This retrograde vascular pattern means that proximal pole fractures interrupt the blood supply to the proximal fragment and are at high risk of avascular necrosis and nonunion. The lunate is the central keystone of the proximal row, articulating with the radius proximally and the capitate distally. Its blood supply is from volar and dorsal vessels, with

a small subset of patients (about 25 percent) having a single volar nutrient artery that predisposes to Kienböck’s disease (avascular necrosis, discussed in Topic Orth-9).

Scaphoid Fractures

Anatomy and Classification The classical Russe classification (1960) divides scaphoid fractures by the orientation of the fracture line: horizontal oblique, transverse, and vertical oblique. The vertical oblique pattern is the most unstable. The Herbert classification (1984) subdivides by displacement, location, and stability into types A (stable acute), B (unstable acute), C (delayed union), and D (nonunion), each with subtypes. The Mayo classification subdivides by location into distal pole (10 percent of fractures, generally heal well in cast), waist (70 percent, the most common, intermediate prognosis), and proximal pole (20 percent, high risk of AVN and nonunion). Clinical and Radiographic Diagnosis The classical mechanism is a fall on the outstretched hand with the wrist in dorsiflexion and radial deviation. Clinical features include pain on the radial aspect of the wrist with tenderness in the anatomic snuffbox, scaphoid tubercle tenderness, and pain with axial compression of the thumb. These findings together have a sensitivity approaching 100 percent for scaphoid fracture but specificity is poor (positive in approximately 20 percent of patients ultimately diagnosed with fracture). Plain radiographs in the four scaphoid views (PA, lateral, ulnar deviation PA, and 45- degree pronated oblique) detect approximately 60 to 80 percent of scaphoid fractures at initial presentation. The remaining fractures are radiographically occult — the clinical scaphoid fracture syndrome with negative initial radiographs. The traditional management has been to immobilize all clinically suspected scaphoid fractures in a thumb spica cast and re-image at 10 to 14 days, when callus may be visible. Modern practice has shifted toward early MRI or CT in clinically suspected scaphoid fractures with negative radiographs, with MRI being the gold standard for definitive diagnosis or exclusion. Bone scintigraphy is an alternative but is non-specific. Treatment of Acute Scaphoid Fractures Non-displaced scaphoid fractures can be treated either non-operatively in a cast or operatively with percutaneous screw fixation. The traditional non-operative approach uses a thumb spica cast for 8 to 12 weeks for waist fractures and 12 to 16 weeks for proximal pole fractures, with union rates of 90 to 95 percent for distal and waist fractures and 60 to 80 percent for proximal pole fractures. The classical above-elbow versus below-elbow cast debate has been largely resolved in favor of below-elbow casting in most cases, with the position of the wrist (radial deviation, slight flexion or extension) being controversial; the practical approach is a comfortable position in slight flexion and ulnar deviation. The inclusion of the thumb is now considered unnecessary in many practices, with a simple short-arm cast (without thumb spica) being equally effective in selected non-displaced fractures.

Percutaneous screw fixation of non-displaced waist fractures using a headless compression screw (Herbert screw, Acutrak, Synthes screws) has gained popularity because of the substantial reduction in immobilization time (typically 2 weeks in a removable splint, with return to light activity at 4 weeks). The SUSS trial (Dias et al., 2008) and subsequent studies have shown faster return to work and equivalent functional outcomes, though long-term differences are small. The procedure is technically demanding and requires precise central screw placement to maximize fixation strength. Displaced scaphoid fractures (>1 mm displacement, >15 degrees angulation, or >10 degrees of intrascaphoid angulation) and proximal pole fractures are generally treated operatively because of the high nonunion rates with conservative management. Open reduction and internal fixation through a volar approach (Russe approach, between the FCR tendon and the radial artery) or dorsal approach (with the wrist in volar flexion to expose the proximal pole) achieves anatomical reduction and rigid fixation with a headless compression screw. Scaphoid Nonunion Scaphoid nonunion, despite its frequency and clinical importance, remains a challenging problem. The classical pattern is the dorsal intercalated segmental instability (DISI) that develops with progressive collapse of the scaphoid — flexion of the distal fragment and extension of the lunate — producing the scapholunate angle >70 degrees and the humpback deformity of the scaphoid. The progression follows the SNAC (scaphoid nonunion advanced collapse) sequence: stage 1 radial styloid arthritis, stage 2 mid- carpal radioscaphoid arthritis, stage 3 capitate-lunate arthritis. Treatment of established scaphoid nonunion is by open reduction with bone grafting and internal fixation using a corticocancellous bone graft from the iliac crest (Russe technique) or distal radius (Matti- Russe technique) to restore the humpback geometry and stabilization with a compression screw. Proximal pole nonunion with AVN may require vascularized bone graft — typically the 1,2-intercompartmental supraretinacular artery (1,2-ICSRA) pedicled graft from the distal radius or a free vascularized graft from the medial femoral condyle.

Other Carpal Fractures

The remaining carpal fractures collectively account for 20 to 30 percent of carpal injuries. Triquetrum fractures are the second most common carpal fracture, with the dorsal cortical avulsion being typical, recognized on the lateral radiograph by the “pooping duck sign” — a small dorsal chip. Most heal in a short-arm cast or splint for 4 to 6 weeks. Hamate fractures include the body fracture and the hook of hamate fracture (typically occurring in racquet sport athletes and golfers from impact of the handle with the hypothenar eminence); the hook of hamate is best imaged with the carpal tunnel view or CT, and treatment is excision of the hook for symptomatic nonunion. Capitate fractures are uncommon in isolation but may be part of a perilunate injury (the scaphocapitate syndrome of Fenton); the proximal pole of the capitate has retrograde blood supply analogous to the scaphoid. Pisiform fractures are rare and typically heal without specific treatment. Trapezium, trapezoid, and lunate body fractures are rare; the lunate body fracture is significant for its association with Kienböck’s disease.

Perilunate and Lunate Dislocations

The perilunate dislocation is a complex carpal disruption that occurs in distinctive stages described by Mayfield (1980). The mechanism is high-energy hyperextension, ulnar deviation, and intercarpal supination, typically from a fall from height or motor vehicle accident. The Mayfield stages describe progressive ligamentous disruption around the lunate from radial to ulnar: • Stage I: Scapholunate ligament disruption (scapholunate dissociation). • Stage II: Disruption of the capitolunate articulation (perilunate dislocation). • Stage III: Lunotriquetral ligament disruption (the capitate and triquetrum now both displaced relative to the lunate). • Stage IV: Lunate dislocation into the carpal tunnel, with the rest of the carpus now reduced. A useful conceptual framework is that stages II and III are dorsal dislocations in which the lunate remains in the lunate fossa while the rest of the carpus dislocates dorsally; stage IV is the volar lunate dislocation in which the lunate is displaced volarly into the carpal tunnel while the rest of the carpus is essentially aligned with the forearm. The lateral radiograph is essential for diagnosis: in a normal wrist, the radius, lunate, and capitate are collinear; in a perilunate dislocation, the capitate is displaced dorsally relative to the lunate while the lunate remains aligned with the radius; in a lunate dislocation, the lunate is displaced volarly with the “spilled teacup sign.” The trans-scaphoid perilunate dislocation (or “greater arc” injury) is the variant in which the dislocation pattern passes through the scaphoid as a fracture rather than rupturing the SL ligament; the purely ligamentous “lesser arc” injury ruptures all the intrinsic and extrinsic ligaments around the lunate without bony fracture. Treatment The perilunate dislocation requires urgent reduction by traction with hyperextension followed by flexion. Closed reduction is usually achievable in the acute setting, but maintenance of reduction without operative fixation is generally impossible because of the ligamentous disruption. The standard treatment is open reduction with combined volar and dorsal approaches, repair of the scapholunate and lunotriquetral ligaments with suture anchors, K-wire fixation across the SL and LT joints (typically maintained for 8 to 12 weeks), and median nerve decompression. For trans-scaphoid variants, scaphoid fixation with a compression screw is performed simultaneously. The functional outcomes after perilunate dislocation are generally less than perfect even with appropriate treatment, with most patients retaining 60 to 80 percent of contralateral motion and grip strength and developing some degree of mid-carpal arthritis over time. Missed or chronic perilunate dislocations (the unrecognized injury that presents weeks to months later) have substantially worse outcomes and may require salvage procedures such as proximal row carpectomy or total wrist fusion.

Metacarpal Fractures

Metacarpal fractures are the most common hand fractures, accounting for approximately 40 percent of hand injuries. The mechanisms range from low-energy punch injuries (the “boxer’s fracture”) to high-energy crush injuries. The classification is by location: head, neck, shaft, and base. Boxer’s Fracture (Fifth Metacarpal Neck) The fracture of the fifth metacarpal neck, the classical “boxer’s fracture” produced by striking a hard object with a closed fist, is extremely common. The deformity is volar angulation of the metacarpal head from the pull of the intrinsic muscles. The acceptable angulation is generous because of the mobility of the fifth carpometacarpal joint: up to 40 degrees of volar angulation is well-tolerated in the fifth metacarpal (less in the more lateral metacarpals — 30 degrees in the fourth, 20 degrees in the third, 10 degrees in the second). Rotation is not acceptable at any metacarpal — even a few degrees of rotation produces overlap of the fingers in flexion and substantial functional impairment. Treatment of the typical boxer’s fracture is closed reduction (the Jahss maneuver with the MCP joint flexed to 90 degrees and pressure on the flexed PIP to push the head dorsally) followed by short-arm cast or splint in the intrinsic-plus position (MCP joints flexed 60 to 90 degrees, IP joints extended) for 3 to 4 weeks. Selected unstable patterns, severely angulated fractures, multiple metacarpal fractures, or rotational malalignment require operative fixation, typically by closed reduction and percutaneous K-wire fixation (the bouquet pinning of Foucher using flexible intramedullary nails inserted at the base of the fifth metacarpal is a classical alternative) or open reduction and plate fixation. Metacarpal Shaft Fractures Metacarpal shaft fractures (transverse, oblique, spiral, comminuted) follow similar principles. Transverse shaft fractures angulate apex-dorsally from the pull of the intrinsic muscles. Spiral and oblique shaft fractures tend to shorten and rotate. Acceptable parameters are: up to 5 mm shortening, up to 10 to 20 degrees angulation depending on the metacarpal, no rotation. The treatment is similar to metacarpal neck fractures — non- operative for stable patterns within acceptable parameters, K-wire or plate fixation for unstable or unacceptable patterns. Multiple adjacent metacarpal fractures destabilize each other and have a lower threshold for operative fixation. First Metacarpal Base — Bennett and Rolando Fractures The Bennett fracture (Edward Hallaran Bennett, 1882) is an intra-articular fracture- dislocation of the base of the first metacarpal with a small volar-ulnar fragment held in place by the anterior oblique (deep beak) ligament, while the metacarpal shaft dislocates proximally and radially under the pull of the abductor pollicis longus. The injury is unstable and requires anatomical reduction, almost always operatively. The classical treatment is closed reduction with percutaneous K-wire fixation (typically two wires, one across the CMC joint and one across the fracture into the second metacarpal), with the

K-wires removed at 4 to 6 weeks. The open reduction and screw fixation is an alternative for larger volar fragments. The Rolando fracture (Silvio Rolando, 1910) is the comminuted intra-articular fracture of the first metacarpal base — Y- or T-shaped — and is more difficult to manage than the Bennett because of the comminution and articular involvement. Treatment options range from external fixation with traction to open reduction with mini-fragment plate or T-plate fixation, with the prognosis being worse than for Bennett fractures because of the articular comminution. Severely comminuted Rolando patterns may require K-wire fixation alone with limited reduction, or, in late presentation with arthritis, trapeziectomy with ligament reconstruction and tendon interposition. Extra-articular fractures of the first metacarpal base are addressed similarly to other metacarpal shaft fractures, with closed reduction and casting suitable for most patterns and operative fixation for unstable or rotated patterns.

Phalangeal Fractures

Phalangeal fractures of the fingers include the proximal, middle, and distal phalanges and the interphalangeal joints. Proximal and Middle Phalangeal Fractures Phalangeal shaft fractures are common and can be condylar, neck, base, or shaft in location. The acceptable parameters are stricter than for metacarpals: no significant angulation in either plane, no rotation, and minimal shortening. The principal concern is the rotational malalignment that produces overlap of the fingers in flexion — a deformity that demands operative correction. Stable non-displaced and minimally displaced fractures are managed by buddy taping or extension block splinting with early protected motion. Unstable patterns are addressed by closed reduction and K-wire fixation, mini-plate fixation, lag screw fixation for spiral patterns, or intramedullary nailing with a small-diameter intramedullary wire (the Foucher technique adapted for phalanges). The intra-articular phalangeal base fractures of the proximal phalanx, particularly the avulsion of the volar plate with associated PIP dislocation, are a particular concern. Stable injuries with fragments less than 30 percent of the articular surface are treated by extension block splinting with early motion; larger or unstable fragments require open reduction and fixation. Distal Phalangeal Fractures The distal phalangeal tuft fractures are extremely common, typically from crush injuries, and heal reliably with brief splinting; the principal concern is the associated nail bed laceration that may require repair. Mallet fracture (avulsion of the dorsal lip of the distal phalanx with the extensor tendon) is treated by extension splinting of the DIP joint for 6 to 8 weeks for fragments less than 30 percent of the articular surface, and by operative fixation for larger fragments or those with volar subluxation of the distal phalanx. The

Jersey finger (avulsion of the flexor digitorum profundus from the volar base of the distal phalanx) is a tendinous rather than purely bony injury, classified by the level of retraction (Leddy and Packer types I, II, III, IV), and requires prompt operative repair, particularly for type I where the tendon has retracted into the palm. Interphalangeal Joint Dislocations The dorsal PIP dislocation is the most common, with the volar plate avulsing from the middle phalangeal base. The treatment is closed reduction followed by extension block splinting; recurrent instability requires volar plate repair. The volar PIP dislocation is less common but more concerning because of the associated central slip rupture that, if untreated, produces a boutonnière deformity (flexion of the PIP and hyperextension of the DIP). After closed reduction, the PIP joint must be splinted in extension for 6 weeks with active DIP motion to prevent boutonnière deformity. The DIP dislocation is uncommon and is reduced by traction; the joint is stable after reduction and is treated by brief splinting. The thumb MCP joint ulnar collateral ligament injury — the gamekeeper’s thumb (chronic) or skier’s thumb (acute) — produces ulnar laxity of the thumb MCP. The Stener lesion is the displacement of the avulsed ulnar collateral ligament superficial to the adductor aponeurosis, preventing healing in non-operative management; clinical examination demonstrating substantial laxity (>30 degrees difference from the contralateral thumb or absolute laxity >35 degrees) and imaging (often MRI) confirm Stener lesion. Treatment of complete UCL tears is surgical repair, with non-operative management reserved for partial tears.

Crush Injuries and Compartment Syndrome of the Hand

The hand has 10 distinct compartments (thenar, hypothenar, adductor, four dorsal interosseous, three palmar interosseous, and carpal tunnel by some accounts), and compartment syndrome of the hand may follow crush injuries, prolonged compression, or severe burns. Recognition by disproportionate pain, tense swelling, and pain with passive stretch is critical because the hand cannot tolerate sustained intracompartmental pressure without permanent damage. Treatment is decompressive fasciotomy through dorsal incisions (two longitudinal dorsal incisions over the second and fourth metacarpals to release the dorsal and volar interossei) and a separate carpal tunnel release if indicated.

Open Hand Injuries

Open injuries of the hand follow the principles outlined in Topic Trauma-5 (open fractures) with specific considerations for the hand. Bite injuries (“fight bite” from human teeth contacting the MCP joint, typical of a closed-fist strike to a tooth) carry a particularly high risk of infection because of human oral flora and the introduction of bacteria into the joint at flexion; treatment requires irrigation and debridement with the joint opened, broad- spectrum antibiotic coverage (with attention to Eikenella corrodens), and tetanus prophylaxis as needed. High-pressure injection injuries appear deceptively benign

initially but may be limb-threatening; urgent extensive debridement and exploration is required. Crush injuries with significant tissue loss may require complex reconstructive procedures including local flaps, regional flaps, or free tissue transfer.

Summary and Take-Home Points

The scaphoid is the most commonly fractured carpal bone, with the retrograde dorsal blood supply placing proximal pole fractures at particular risk of avascular necrosis and nonunion. The clinical scaphoid fracture syndrome — anatomic snuffbox tenderness, scaphoid tubercle tenderness, axial thumb compression pain — is sensitive but not specific; MRI is the modern standard for early definitive diagnosis or exclusion in patients with negative initial radiographs. Treatment is cast immobilization or percutaneous screw fixation for non-displaced waist fractures, and open reduction and screw fixation with bone grafting for displaced or proximal pole fractures. Established nonunion with humpback deformity is treated by anatomical reconstruction with corticocancellous bone graft (Matti-Russe) or, for AVN of the proximal pole, vascularized bone graft (1,2-ICSRA or medial femoral condyle). Perilunate dislocations are recognized by the lateral wrist radiograph and the Mayfield staging from scapholunate dissociation through frank lunate dislocation; treatment is open reduction with ligamentous repair and K-wire stabilization, with median nerve decompression when indicated. Trans-scaphoid perilunate variants require concurrent scaphoid fixation. Metacarpal fractures tolerate considerable angulation (40 degrees at the fifth metacarpal neck, decreasing more radially) but no rotation; the boxer’s fracture is the prototype and is generally treated non-operatively. The Bennett fracture-dislocation of the first metacarpal base requires anatomical reduction and percutaneous or open fixation; the Rolando comminuted variant has a worse prognosis and requires individualized approach. Phalangeal fractures tolerate even less angulation and absolutely no rotation, with operative fixation indicated for any rotational malalignment. Interphalangeal dislocations require recognition of the associated tendinous injuries — central slip rupture in volar PIP dislocation produces boutonnière deformity if untreated; the Stener lesion in thumb UCL injury prevents non-operative healing of complete ruptures. The chapter that follows turns to the pelvic ring, where high-energy mechanism, hemorrhage, and complex bony anatomy combine to produce some of the most challenging injuries in orthopedic trauma.