WRIST INJURIES

EPIDEMIOLOGY

The annual incidence of carpal fractures in the United States was reported at more than 678,000 in 1995.

Seven percent of distal radius fractures have an associated carpal fracture.

Carpal fractures account for 18% of all hand/wrist fractures.

Approximate incidence of carpal fractures as follows:

Scaphoid (68.2%)

Triquetrum (18.3%)

Trapezium (4.3%)

Lunate (3.9%)

Capitate (1.9%)

Hamate (1.7%)

Pisiform (1.3%)

Trapezoid (0.4%)

ANATOMY

The distal radius has articular facets for the scaphoid and lunate separated by a ridge. The sigmoid notch articulates with the distal ulna.

The distal ulna articulates with the sigmoid notch of the distal radius. The fovea (base) of the ulna styloid process serves as the attachment for the deep band of the triangular fibrocartilage complex (TFCC) while the superficial band inserts directly onto the styloid process of the ulna.

Carpal bones (Fig. 23.1)

• Proximal row: This consists of the scaphoid (an oblique strut that spans both rows), lunate, triquetrum, and pisiform.

• Distal row: The trapezium, trapezoid, capitate, and hamate are connected to one another and to the base of the metacarpals by strong ligaments, making the distal row relatively immobile.

• The lunate is the key to carpal stability.

  • It is connected to both scaphoid and triquetrum by strong interosseous ligaments.

  • Injury to the scapholunate (SL) or lunotriquetral (LT) ligaments leads to asynchronous motion of the lunate and dissociative carpal instability patterns. SL = DISI (dorsal intercalated segmental instability) and LT tear = VISI (volar intercalated segmental instability)

     

     

     

The main articulations are the distal radioulnar, radiocarpal, and midcarpal.

Normal anatomic relationships (see Chapter 22)

• Radial inclination: averages 23 degrees (range, 13 to 30 degrees)

• Radial length: averages 11 mm (range, 8 to 18 mm)

• Palmar (volar) tilt: averages 11 to 12 degrees (range, 0 to 28 degrees)

• The 0-degree capitolunate angle: a straight line drawn down the third metacarpal shaft, capitate, lunate, and shaft of radius with wrist in neutral position on the lateral radiograph

• The 47-degree scapholunate angle (normal range, 30 to 70 degrees); <3-mm scapholunate space

• Carpal height ratio: carpal height (proximal and distal rows)/length of third metacarpal. The average is 0.53; decreased carpal height ratio indicates collapse due to carpal fracture or instability.

Wrist ligaments (Figs. 23.2 and 23.3)

• Extrinsic ligaments connect the radius to the carpus and the carpus to the metacarpals.

• Intrinsic ligaments connect carpal bone to carpal bone (e.g., scapholunate and lunotriquetral

  ligaments).

• The thickest and strongest region of the scapholunate ligament is located dorsally while that of the lunotriquetral ligament is located palmarly.

• Important volar ligaments include:

  • The radioscaphocapitate, which acts as a fulcrum around which the scaphoid rotates and guides scaphoid kinematics

  • The radioscapholunate, also called the ligament of Testut (not a strong ligament, it is a

    neurovascular tuft of synovium derived from the anterior interosseous and radial arteries as well as the anterior interosseous nerve)

  • The short radiolunate which is contiguous with the palmar fibres of the TFCC

  • The radiolunotriquetral (supports the proximal row, stabilizes the radiolunate and lunotriquetral joints)

    • The important dorsal ligaments are:

      • The dorsal intercarpal, which originate from the triquetrum and extend radially to insert onto the lunate, the dorsal groove of the scaphoid, and the trapezium

      • The radiocarpal, which originate from the dorsal margin of the distal radius and attach to

        the lunate and triquetrum.

• The proximal and distal carpal rows are attached by capsular ligaments on each side of the lunocapitate joint.

  • Injury to these extrinsic ligaments leads to abnormal motion between the two rows and to

    nondissociative wrist instability patterns.

• Space of Poirier: This is a ligament-free area situated between the radioscaphocapitate ligament and the long radiolunate ligament at the level of the midcarpal joint, which is an area of potential weakness.

• The TFCC is a major stabilizer of the ulnar carpus and distal radioulnar joint.

  • The TFCC stabilizes the distal radial ulnar joint (DRUJ) and absorbs about 20% of the axial load across the wrist joint at neutral ulnar variance.

  • It consists of several components, including the dorsal and volar radioulnar ligaments,

    articular disc, meniscal homologue, extensor carpi ulnaris subsheath, and origins of the ulnolunate and ulnotriquetral ligaments.

     

     

     

     

     

Vascular supply (Fig. 23.4)‌

• The radial, ulnar, and anterior interosseous arteries combine to form a network of transverse arterial arches both dorsal and volar to the carpus.

• The blood supply to the scaphoid is derived primarily from the radial artery, both dorsally and

  volarly. The volar scaphoid branches supply the distal 20% to 30% of the scaphoid, whereas branches entering the dorsal ridge supply the proximal 70% to 80%, via interosseous blood supply, similar to the femoral head.

• The lunate receives blood supply from both its volar and dorsal surfaces in most cases (80%).

  About 20% of lunates have only a volar blood supply.

   

   

   

Kinematics

• The global motion of the wrist is composed of flexion and extension, radioulnar deviation at the radiocarpal joint, and axial rotation around the DRUJ.

• The radiocarpal articulation acts as a universal joint, allowing a small degree of intercarpal

  motion related to rotation of individual carpal bones.

• The forearm accounts for about 140 degrees of rotation.

• Radiocarpal joint motion is primarily flexion and extension of nearly equal proportions (70 degrees), and radial and ulnar deviation of 20 and 40 degrees, respectively.

• The scaphoid rests on the radioscaphocapitate ligament at its waist. Using the ligament as an

  axis, it rotates from a volar flexed perpendicular position to a dorsiflexed longitudinal position. With the wrist in radial deviation, the scaphoid flexes; with ulnar deviation, the scaphoid extends.

Pathomechanics (Fig. 23.5)

• Classically, the radius, lunate, and capitate have been described as a central “link” that is colinear in the sagittal plane.

• The scaphoid serves as a connecting strut. Any flexion moment transmitted across the scaphoid

  is balanced by an extension moment at the triquetrum.

• When the scaphoid is destabilized by fracture or scapholunate ligament disruption, the lunate

  and triquetrum assume a position of excessive dorsiflexion (dorsal intercalated segmental instability [DISI]) and the scapholunate angle becomes abnormally high (>70 degrees).

• When the triquetrum is destabilized (usually by disruption of the lunotriquetral ligament complex), the opposite pattern (volar intercalated segmental instability [VISI]) is seen as the lunate (intercalated segment) volar flexes.

   

   

   

  MECHANISM OF INJURY

The most common mechanism of carpal injury is a fall onto the outstretched hand, resulting in an axial compressive force with the wrist in hyperextension. The volar ligaments are placed under tension with compression and shear forces applied dorsally, especially when the wrist is extended beyond its physiologic limits.

Excessive ulnar deviation and intercarpal supination result in a predictable pattern of perilunate injury, progressing from the radial side of the carpus to the midcarpus and finally to the ulnar carpus.

Direct mechanisms of injury such as crush injuries should alert the clinician to the possible development of compartment syndrome of the hand.

CLINICAL EVALUATION

The clinical presentation of individual carpal injuries is variable, but in general, the most

consistent sign of carpal injury is well-localized tenderness.

Gross deformity may be present, ranging from displacement of the carpus to prominence of individual carpal bones.

A complete evaluation of the median, radial, ulnar, and digital nerves is warranted as well as assessment of capillary refill, color, and temperature.

Provocative tests may reproduce or exacerbate pain, crepitus, or displacement indicative of individual carpal injuries (see specific carpal injuries).

RADIOGRAPHIC EVALUATION

Posteroanterior (PA), oblique, and lateral x-rays are each taken with the wrist in the neutral position.

• Gilula lines (three smooth radiographic arcs) should be examined on the PA view. Disruption of these arcs indicates ligamentous instability.

For further diagnosis of carpal and mainly scaphoid fractures:

• A scaphoid view (anteroposterior [AP] x-ray with wrist supinated 30 degrees and in ulnar deviation) is obtained.

• A pronated oblique view is indicated.

If there is the suspicion of carpal instability, additional views in maximal radial and ulnar deviation are recommended as well as bilateral clenched-fist PA to look for widening of the scapholunate interval.

Further views can be done in maximal flexion and extension.

Arthrography, magnetic resonance (MR), wrist arthrography, videoradiography, and arthroscopy can assist in the diagnosis of carpal ligament injuries.

Computed tomography (CT) scans are helpful in evaluating carpal fractures, malunion, nonunion, and bone loss.

Magnetic resonance imaging (MRI) scans are sensitive to detect occult fractures and osteonecrosis of the carpal bones as well as detecting soft tissue injury, including ruptures of the scapholunate ligament and TFCC.

CLASSIFICATION

Orthopaedic Trauma Association Classification of Carpal Fractures and Fracture-Dislocations

See Fracture and Dislocation Compendium at http://ota.org/.compendium/index.htm.

SPECIFIC FRACTURES

Scaphoid

Fractures of the scaphoid are common and account for about 50% to 80% of carpal injuries.

About 345,000 scaphoid fractures occur annually in the United States and account for 1 in every 100,000 emergency room visits.

Anatomically, the scaphoid is divided into proximal and distal poles, a tubercle, and a waist; 80% of the scaphoid is covered with articular cartilage (Fig. 23.6).

Eighty percent of scaphoid fractures occur at its waist, 10% to 20% involve the proximal pole, and 5% occur at its distal pole and tuberosity.

Ligamentous attachments to the scaphoid include the radioscaphocapitate ligament, which variably attaches to the ulnar aspect of the scaphoid waist, and the dorsal intercarpal ligament, which provides the primary vascular supply to the scaphoid.

The major vascular supply is derived from scaphoid branches of the radial artery, entering the dorsal ridge and supplying 70% to 80% of the scaphoid, including the proximal pole. The remaining distal aspect is supplied through branches entering the tubercle. Fractures at the scaphoid waist or proximal third depend on fracture union for revascularization (Fig. 23.7).

The most common mechanism is a fall onto the outstretched hand that imposes a force of dorsiflexion, ulnar deviation, and intercarpal supination.

Clinical evaluation: Patients present with wrist pain and swelling, with tenderness to palpation overlying the scaphoid in the anatomic snuffbox or volarly over the distal tubercle. Provocative tests include:

• The scaphoid shift test: reproduction of pain with dorsal-volar shifting of the scaphoid

• The Watson shift test: painful dorsal scaphoid displacement as the wrist is moved from ulnar to radial deviation with palmar pressure on the tuberosity

Differential diagnoses

• Wrist sprain

• Wrist contusion

• Scapholunate instability

• Lunate dislocation

• Flexor carpi radialis tendon rupture

• Radial styloid fracture

• Trapezium fracture

• De Quervain disease

• Carpometacarpal (basal) joint arthrosis

Radiographic evaluation

• This includes a PA view of the wrist in ulnar deviation to extend the scaphoid, a lateral, a supinated AP and pronated oblique view, and a clenched supinated view in ulnar deviation.

• Initial films are nondiagnostic in up to 25% of cases.

• If the clinical examination suggests fracture but radiographs are not diagnostic, a trial of immobilization with follow-up radiographs 1 to 2 weeks after injury may demonstrate the fracture.

• Technetium bone scan, MRI, CT, and ultrasound evaluation may be used to diagnose occult scaphoid fractures.

Classification

• Based on fracture pattern (Russe)

  • Horizontal oblique

  • Transverse

  • Vertical oblique

• Based on displacement

  • Stable: nondisplaced fractures with no step-off in any plane

  • Unstable:

    • >1-mm displacement

    • >10 degrees angular displacement

    • Fracture comminution

    • Radiolunate angle >15 degrees

    • Scapholunate angle >60 degrees

    • Intrascaphoid angle >35 degrees

• Based on location

  • Proximal pole: 10% to 20%

  • Distal pole and tuberosity: 5%

  • Waist: 80%

    Horizontal oblique: 13% to 14%

    Vertical oblique: 8% to 9%

    Transverse: 45% to 48%

  • Proximal pole: 5% to 7%

    Treatment

Indications for nonoperative treatment

• Nondisplaced acute (less than 4 weeks) distal third fracture

• Tuberosity fractures

Nonoperative treatment

• Conventional treatment involves use of a long arm thumb spica cast for 6 weeks to limit forearm rotation with the wrist in slight flexion and slight radial deviation and replacement with a short arm thumb spica cast at 6 weeks until united.

• However, there is controversy over the use of long arm versus short arm immobilization, the optimum wrist position, and the need for thumb immobilization.

• Expected time to union:

  • Distal third: 6 to 8 weeks

  • Middle third: 8 to 12 weeks

  • Proximal third: 12 to 24 weeks

Management of suspected scaphoid fractures

• In patients with an injury and positive examination findings but normal x-rays, immobilization for 1 to 2 weeks (thumb spica) is indicated.

• Repeat x-rays if the patient is still symptomatic.

• If pain is still present but x-rays continue to be normal, consider MRI.

• If an acute diagnosis is necessary, consider MRI or CT immediately.

Healing rates with nonoperative treatment depend on fracture location.

Tuberosity and distal third 100%

Waist 80% to 90%

Proximal pole 60% to 70%

Proximal Fractures Are Prone to Nonunion and Osteonecrosis

Operative treatment

• Indications for surgery

  • >1-mm displacement

  • >10 degrees angular displacement

  • Fracture comminution

  • Radiolunate angle >15 degrees

  • Scapholunate angle >60 degrees

  • Intrascaphoid angle >35 degrees

  • Nonunion

• Surgical techniques

  • Most involve the insertion of screws.

  • Controversy exists about open versus percutaneous techniques.

  • Open techniques are needed for nonunions and fractures with unacceptable displacement.

  • Closed techniques are appropriate for acute fractures with minimal displacement.

  • Regardless of technique used, the screw must be inserted in the middle third of the central axis of the scaphoid, as this position provides the greatest stability and stiffness, improves fracture alignment, and decreases the time to union.

• The volar approach between the flexor carpi radialis and the radial artery provides good exposure for open reduction and internal fixation (ORIF) and repair of the radioscapholunate ligament. The volar approach is the least damaging to the vascular supply of the vulnerable proximal pole.

• The type of postoperative immobilization is debatable but usually consists of a short arm thumb spica cast for 6 weeks.

• Return to sports occurs at a minimum of 3 months.

Complications

• Delayed union, nonunion, and malunion: These are reported to occur with greater frequency when there is a delay in treatment, as well as with proximal scaphoid fractures. They may necessitate operative fixation with bone grafting to achieve union.

• Osteonecrosis: This occurs especially with fractures of the proximal pole, owing to the tenuous vascular supply.

• Injury to the dorsal sensory branch of the radial nerve could also occur.

   

  Lunate

The lunate is the fourth most fractured carpal bone after the scaphoid, triquetrum, and trapezium.

The lunate has been referred to as the “carpal keystone,” because it rests in the well-protected concavity of the lunate fossa of the distal radius, anchored by interosseous ligaments to the scaphoid and triquetrum, and distally is congruent with the convex head of the capitate.

Its vascular supply is derived from the proximal carpal arcade dorsally and volarly, with three

variable intralunate anastomoses.

The mechanism of injury is typically a fall onto an outstretched hand with the wrist in hyperextension, or a strenuous push with the wrist in extension.

Clinical evaluation reveals tenderness to palpation on the dorsal wrist overlying the distal radius and lunate, as well as painful range of motion.

Radiographic evaluation: PA and lateral views of the wrist are often inadequate to establish the diagnosis of lunate fracture because osseous details are frequently obscured by overlapping densities.

• Oblique views may be helpful, but CT scanning best demonstrates fractures.

• MRI has been used with increasing frequency to appreciate the vascular changes associated with injury and healing and is the imaging test of choice for evaluation of Kienböck disease.

Classification: Acute fractures of the lunate can be classified into five groups:

• Frontal fractures of the palmar pole with involvement of the palmar nutrient arteries

• Osteochondral fractures of the proximal articular surface without substantial damage to the nutrient vessels

• Frontal fractures of the dorsal pole

• Transverse fractures of the body

• Transarticular frontal fractures of the body of the lunate

Treatment

• Nondisplaced fractures should be treated in a short or long arm cast or splint with follow-up at close intervals to evaluate progression of healing.

• Displaced or angulated fractures should be treated surgically to allow adequate apposition for

  formation of vascular anastomoses.

• Often with displaced lunate palmar lip fractures, the capitate is subluxed volar relative to the lunate and radius. When this occurs, ORIF of the lunate palmar lip is indicated.

Complications

• Osteonecrosis: Depending on the degree of involvement, osteonecrosis may represent the most devastating complication of lunate fractures, with advanced collapse and radiocarpal degeneration. This may require further operative intervention for pain relief, including radial shortening, radial wedge osteotomy, ulnar lengthening, or salvage procedures such as proximal row carpectomy and wrist denervation. (Note: Most cases of Kienböck disease are idiopathic.)

  Triquetrum

The triquetrum is the carpal bone that is most commonly fractured after the scaphoid.

Most fractures of the triquetrum are avulsion or impaction injuries that may be associated with ligament damage.

Most commonly, injury occurs with the wrist in extension and ulnar deviation, resulting in an impingement shear fracture by the ulnar styloid against the dorsal triquetrum.

Clinical evaluation reveals tenderness to palpation on the dorsoulnar aspect of the wrist, directly

dorsal to the pisiform, as well as painful range of wrist motion.

Radiographic evaluation

• Transverse fractures of the body can generally be identified on the PA view.

• Dorsal triquetral fractures are not easily appreciated on AP and lateral views of the wrist owing to superimposition of the lunate. An oblique, pronated lateral view may help to visualize the dorsal triquetrum.

Treatment

• Nondisplaced fractures of the body or dorsal chip fractures may be treated in a short arm cast or splint for 6 weeks.

• Displaced fractures may be amenable to ORIF via pins/screws into the triquetrum alone or in

  combination with pinning to the lunate or hamate.

• The triquetrum may be removed in its entirety if not amenable to repair.

   

  Pisiform

The pisiform is the last carpal bone to ossify (usually by age 12 years) and may have a nonpathologic fragmented appearance prior to ossification.

Fractures of the pisiform are rare.

The mechanism of injury is either a direct blow to the volar aspect of the wrist or a fall onto an outstretched, dorsiflexed hand.

Clinical evaluation demonstrates tenderness on the volar aspect of the ulnar wrist with painful passive extension of the wrist as the flexor carpus ulnaris is placed under tension.

Radiographic evaluation: Pisiform fractures are not well visualized on standard views of the wrist; special views include a lateral view of the wrist with forearm supination of 20 to 45 degrees (Beware of getting called to the emergency department for a carpal bone dislocation that is just the pisiform being seen on the supinated lateral film!) or a carpal tunnel view (20-degree supination oblique view demonstrating an oblique projection of the wrist in radial deviation and semisupination).

Treatment of nondisplaced or minimally displaced fractures consists of a short arm splint or short arm cast for 6 weeks. Displaced fractures may require fragment excision, either early, in the case of a severely displaced fragment, or late, in the case of a pisiform fracture that has resulted in painful nonunion after 2 to 3 months.

Trapezium

Fractures of the trapezium comprise approximately 3% to 5% of all carpal bone fractures.

Fractures of the body of the trapezium nearly always involve one of its four articular facets and lead to subluxation of the thumb and carpometacarpal (CMC) joint.

About 60% of the reported cases have an unsatisfactory outcome secondary to degenerative changes.

Most are ridge avulsion fractures or vertical fractures of the body.

The mechanism of injury is axial loading of the adducted thumb, driving the base of the first

metacarpal onto the articular surface of the trapezium.

• Avulsion fractures may occur with forceful deviation, traction, or rotation of the thumb.

• Direct trauma to the palmar arch may result in avulsion of the trapezial ridge by the transverse carpal ligament.

Clinical evaluation reveals tenderness to palpation of the radial wrist, accompanied by painful

range of motion at the first CMC joint.

Radiographic evaluation: includes standard PA, lateral, and Robert views of the thumb

• Superimposition of the first metacarpal base may be eliminated by obtaining a Robert view, or a true PA view of the first CMC joint and trapezium, taken with the hand in maximum pronation.

• A carpal tunnel view may be necessary for adequate visualization of dorsal ridge fractures.

Treatment

• Nondisplaced fractures are generally amenable to thumb spica splinting or casting to immobilize the first CMC joint for 6 weeks.

• Indications for ORIF include articular involvement of the CMC articulation with >1-mm step-

  off, comminuted fractures, and displaced fractures.

• The surgical approach is via a “Wagner” approach with a curvilinear incision between the glaborous and nonglaborous skin over the radial border of the thenar eminence.

• Comminuted fractures may require supplemental bone grafting.

Complications

• Posttraumatic osteoarthritis may result in decreased or painful range of motion at the first CMC joint. Irreparable joint damage may necessitate fusion or CMC arthroplasty.

  Trapezoid

Because of the shape and position of the trapezoid, the trapezoid is the least fractured carpal bone. An axial load transmitted through the second metacarpal may lead to dislocation, more often dorsal, with associated capsular ligament disruption.

Direct trauma from blast or crush injuries may cause trapezoid fracture, although this is often in conjunction with other injuries.

Clinical evaluation demonstrates tenderness proximal to the base of the second metacarpal with a variable dorsal prominence representing a dislocated trapezoid. Range of motion of the second CMC joint is painful and limited.

Radiographic evaluation: Fractures can be identified on the PA radiograph based on a loss of the normal relationship between the second metacarpal base and the trapezoid. Comparison with the contralateral, uninjured wrist may aid in the diagnosis. The trapezoid, or fracture fragments, may be superimposed over the trapezium or capitate, and the second metacarpal may be proximally and dorsally displaced.

• Oblique views or CT may aid in the diagnosis if osseous details are obscured by overlap.

Treatment

• Nondisplaced fractures may be treated with a splint or short arm cast for 6 weeks.

• Indications for ORIF include displaced fractures, especially those involving subluxation of the CMC articulation. These may be addressed with closed reduction and percutaneous pinning or ORIF via a standard dorsal approach with Kirschner wires or screws with attention to restoration of articular congruity.

Complications

• Posttraumatic osteoarthritis may result at the second CMC articulation if joint congruity is not restored.

  Capitate

Isolated injury to the capitate is uncommon, owing to its relatively protected position.

A fracture of the capitate is more commonly associated with greater arc injury pattern (transscaphoid transcapitate perilunate fracture-dislocation). A variation of this is the “naviculocapitate syndrome,” in which the capitate and scaphoid are fractured without associated dislocation.

The mechanism of injury is typically direct trauma via a crushing force or axial loading along the middle finger ray that results in associated carpal or metacarpal fractures.

Clinical evaluation reveals point tenderness as well as variable painful dorsiflexion of the wrist as the capitate impinges on the dorsal rim of the radius.

Fractures of the capitate can usually be identified on standard scaphoid views.

Diagnosis may require a CT scan.

Treatment: Displaced capitate fractures require reduction to diminish the risk of osteonecrosis. If closed reduction is unattainable, ORIF are indicated, usually with Kirschner wires or lag screws, to restore normal anatomy.

Complications

• Midcarpal arthritis: This is caused by capitate collapse as a result of displacement of the proximal pole.

• Osteonecrosis: This is rare but results in functional impairment; it emphasizes the need for

  accurate diagnosis and stable reduction.

  Hamate

The hamate may be fractured through its distal articular surface, through other articular surfaces, or through its hamulus, or hook.

A distal articular fracture accompanied by fourth or fifth metacarpal subluxation may occur when axial force is transmitted down the shaft of the metacarpal, such as with a fist strike or a fall.

Fractures of the body of the hamate generally occur with direct trauma or crush injuries to the hand.

Fracture of the hook of the hamate is a frequent athletic injury sustained when the palm of the hand is struck by an object (e.g., baseball bat, golf club, hockey stick). Generally, it occurs at the base of the hook, although avulsion fractures of the tip may occur.

Clinical evaluation: Patients typically present with pain and tenderness over the hamate. Ulnar and median neuropathy can also be seen, as well as rare injuries to the ulnar artery, which is located in

close proximity to the hook of the hamate, in Guyon’s canal, along with the ulnar nerve.

Radiographic evaluation: The diagnosis of hamate fracture can usually be made on the basis of the PA view of the wrist. A fracture of the hook of the hamate can be visualized on the carpal tunnel or a 20-degree supination oblique view (oblique projection of the wrist in radial deviation and semisupination). The CT scan is the best radiographic test to visualize the fracture. A hamate fracture should not be confused with an os hamulus proprium, which represents an ossification center that has failed to fuse.

The classification of hamate fractures is descriptive.

Treatment

• Nondisplaced hamate fractures may be treated with immobilization in a short arm splint or cast for 6 weeks.

• Displaced fractures of the body or fractures with associated subluxation of the fourth or fifth

  metacarpals are amenable to Kirschner wire or screw fixation. Fractures of the hook of the hamate may be treated with excision of the fragment for displaced fragments or in cases of symptomatic nonunion, as ORIF of isolated hook of hamate fractures are associated with high rate of complication.

Complications

• Symptomatic nonunion: This may be treated with excision of the nonunited fragment.

• Ulnar or median neuropathy: This is related to the proximity of the hamate to these nerves and may require surgical exploration and release.

• Ruptures of the flexor tendons to the small finger: They result from attritional wear at the

  fracture site.

  PERILUNATE DISLOCATIONS AND FRACTURE-DISLOCATIONS

The lunate, which is normally securely attached to the distal radius by ligamentous attachments, is commonly referred to as the “carpal keystone.”

Greater arc injury: This passes through the scaphoid, capitate, triquetrum, or distal radial styloid and often results in transscaphoid, transcapitate, or transradial styloid perilunate fracture-dislocations (Fig. 23.8).

Lesser arc injury: This follows a curved path around the lunate, involving only the capsuloligamentous tissues through the midcarpal joint, scapholunate and lunotriquetral ligaments and results in perilunate and lunate dislocations.

The most common injury is transscaphoid perilunate fracture-dislocation (de Quervain injury).

Disruption of the normal kinematics and stability of the carpal row leads to acute failure with a predictable pattern of posttraumatic changes.

Mechanism of injury

• Perilunate injuries: Axial load is applied to the thenar eminence, forcing the wrist into extension.

• Injury progresses through several stages (Mayfield progression):

  • It usually begins radially through the body of scaphoid (fracture) or through scapholunate interval (dissociation), although both are possible in the same injury (rare).

  • Force is then transmitted ulnarly through the space of Poirier (between the lunate and

    capitate).

  • Subsequently, force transmission disrupts the lunotriquetral articulation (Fig. 23.9).

  • Finally, the lunate can dislocate volarly out of the lunate fossa of the distal radius, in which case it is called the lunate dislocation.

     

     

     

Clinical evaluation: Scapholunate or perilunate injuries typically cause tenderness just distal to Lister tubercle. Swelling is generalized about the wrist with variable dorsal prominence of the entire carpus in cases of dorsal perilunate dislocations.

Radiographic evaluation: PA, lateral, and oblique views should be obtained to confirm the diagnosis and rule out associated injuries. A CT scan may be useful in further defining the injury pattern.

• PA view: The dislocated lunate appears to be wedge-shaped and more triangular, with an elongated volar lip.

• Loss of normal carpal colinear “Gilula lines” and abnormal widening of the scapholunate

  interval >3 mm are noted.

• Look for associated fractures, such as “transscaphoid” injuries.

• Lateral view (most important view): Carefully look at the outline of the capitate and lunate carefully. The “spilled tea cup sign” occurs with volar dislocation of the lunate.

• A clenched-fist PA view obtained after closed reduction of the midcarpal joint is useful for

  checking residual scapholunate or lunotriquetral dissociation as well as fractures.

Classification (Mayfield): A sequence of progressive perilunate instability is seen as the injury spreads:

• From the scapholunate joint (radioscapholunate ligament) → midcarpal joint (radioscaphocarpal ligament) → lunotriquetral joint (distal limb of radiolunotriquetral ligament) → dorsal radiolunotriquetral ligament→ volar dislocation of the lunate

  Stage I: Disruption of the scapholunate joint: The radioscapholunate and interosseous scapholunate ligaments are disrupted.

  Stage II: Disruption of the midcarpal (capitolunate) joint: The radioscaphocapitate ligament is disrupted.

  Stage III: Disruption of the lunotriquetral joint: The distal limb of the radiolunotriquetral ligament and the ulnotriquetrocapitate complex (UTCC) is disrupted.

  Stage IV: Disruption of the radiolunate joint: The dorsal radiolunotriquetral ligament is disrupted, ultimately causing volar dislocation of the lunate.

Treatment

• Closed reduction should be performed with adequate sedation.

• Technique of closed reduction (described by Tavernier)

  • Longitudinal traction is applied for 5 to 10 minutes for muscle relaxation.

  • For dorsal perilunate injuries, the wrist is hyperextended and volar pressure is applied to the lunate to rotate the lunate into extension.

  • Wrist palmar flexion and traction then reduces the capitate into the concavity of the lunate.

  • Closed reduction of lunate dislocations are frequently unsuccessful.

• Early surgical reconstruction is performed if swelling allows. Immediate surgery including open carpal tunnel release is needed if there are progressive signs of median nerve compromise.

• Closed reduction and pinning—for patients who can’t tolerate ORIF

  • The lunate is reduced and pinned to the radius in neutral alignment.

  • The triquetrum and scaphoid can then be pinned to the lunate with additional pins from scaphoid to capitate if stability dictates.

• Transscaphoid perilunate dislocation

  • Most of these injuries are best treated by open volar and dorsal reduction and repair of the injured structures.

  • This requires reduction and stabilization of the fractured scaphoid first.

  • Open repair should be supplemented by pin fixation while ligaments heal.

• Delayed reconstruction is indicated if early intervention is not feasible.

Complications

• Median neuropathy: This may result from carpal tunnel compression, necessitating surgical release.

• Posttraumatic arthritis: This may result from the initial injury or secondarily from small,

  retained osseous fragments and cartilage damage.

• Chronic perilunate injury: This may result from untreated or inadequately treated dislocation or fracture-dislocation resulting in chronic pain, instability, and wrist deformity, often associated with tendon rupture or increasing nerve symptoms. Repair may be possible, via tenodesis or capsulodesis procedures, but a salvage procedure, such as proximal row carpectomy or radiocarpal fusion, may be necessary after a delay in treatment for 1 to 2 months.

  SCAPHOLUNATE DISSOCIATION

This is the ligamentous analog of a scaphoid fracture; it represents the most common and significant ligamentous disruption of the wrist.

The underlying pathologic process is a disruption of the radioscapholunate and the dorsally based scapholunate interosseous ligaments.

The mechanism of injury is loading of the extended carpus in ulnar deviation.

Clinical findings include ecchymosis and tenderness of the wrist. The proximal pole of the scaphoid may be prominent dorsally. Signs of scapholunate dissociation include pain with a vigorous grasp, decreasing repetitive grip strength, a positive Watson test (see earlier, under scaphoid fractures), and painful flexion-extension or ulnar–radial deviation of the wrist.

Radiographic evaluation: PA, lateral, clenched fist supinated PA, and radial and ulnar deviation views are obtained. Classic signs of scapholunate dissociation on the PA view include:

• The “Terry Thomas sign”: widening of the scapholunate space >3 mm (normal <2 mm)

• The “cortical ring sign” caused by the abnormally flexed scaphoid

• A scapholunate angle of >70 degrees visualized on the lateral view due to extension of the lunate via associated DISI deformity

Treatment

• Arthroscopically assisted reduction with percutaneous pin fixation has been described with variable results.

• An inability to obtain or maintain reduction is an indication for ORIF. This is usually

  accomplished by a dorsal approach with reduction and stabilization of the scapholunate interval dorsally, by repair of SL interosseous ligament, if possible, and dorsal capsulodesis. The construct is held together using Kirschner wires to allow for ligament healing. Wrist ligaments can be repaired via the volar approach, if necessary.

• Chronic scapholunate disruptions can be treated with bone-tendon-bone reconstruction or tenodesis/capsulodesis procedures.

Complications

• Recurrent instability: Failure of closed or open reduction and internal fixation with ligament repair may necessitate ligament augmentation, intercarpal fusion, proximal row carpectomy, or wrist fusion. It may progress to a DISI pattern or a scaphoid–lunate advanced collapse of the wrist.

  LUNOTRIQUETRAL DISSOCIATION

These injuries involve disruption of the distal limb of the volar radiolunotriquetral ligament either as a stage III lesser arc injury of perilunate instability or as a result of a force causing excessive radial deviation and intercarpal pronation. The lunotriquetral interosseous and dorsal radiolunotriquetral ligaments are also injured.

Lunotriquetral ligament disruption can result from acute trauma or degeneration/inflammatory processes.

Clinical findings include swelling over the peritriquetral area and tenderness dorsally, typically

one fingerbreadth distal to the ulnar head. Chronic injuries present with vague ulnar-sided wrist pain.

• Ballottement test (shear or shuck test): Dorsal–volar displacement of the triquetrum on the lunate results in increased excursion as compared with the normal, contralateral side, as well as painful crepitus.

• Ulnar compression test: Involves a painful “snap” with axial compression with the wrist in ulnar deviation during pronation

Radiographic evaluation: PA radiographs of the hand rarely reveal frank gapping of the

lunotriquetral space, but a break in the normal smooth contour of the proximal carpal row can be appreciated.

• Radial deviation view: This may demonstrate the triquetrum to be dorsiflexed with the intact scapholunate complex palmar flexed. A lateral projection may reveal a VISI pattern.

• Bilateral clenched fist view with wrist in maximal ulnar and radial deviation can show lunate–

  triquetral dissociation.

Treatment

• Acute lunotriquetral dissociation with minimal deformity may be treated with a long arm cast for 4 weeks followed by a short arm cast or splint for an additional 4 weeks.

• Closed reduction with pinning of the lunate to the triquetrum may be necessary to maintain

  reduction.

• Angular deformity or unacceptable reduction from nonoperative treatment may necessitate ORIF utilizing a combined dorsal and volar approach, with pinning of the triquetrum to the lunate and ligamentous repair.

Complications

• Recurrent instability may necessitate ligament reconstruction with capsular augmentation. If recurrent instability persists, lunotriquetral fusion may be necessary, with possible concomitant ulnar shortening to tension the volar ulnocarpal ligaments.

  ULNOCARPAL DISSOCIATION

Avulsion or rupture of the TFCC from the ulnar styloid results in a loss of “sling” support for the ulnar wrist.

The lunate and triquetrum “fall away” relative to the distal ulna and assume a semisupinated and palmar-flexed attitude, with the distal ulna subluxed dorsally.

Clinical evaluation reveals dorsal prominence of the distal ulna and volar displacement of the ulnar carpus.

Radiographic evaluation: The PA view may reveal avulsion of the ulnar styloid and widening of the DRUJ. Dorsal displacement of the distal ulna on true lateral views suggests disruption of the TFCC in the absence of an ulnar styloid avulsion fracture.

• MRI may demonstrate a tear of the TFCC and may additionally provide evidence of chondral lesions and effusion.

Treatment: Operative repair of the TFCC may be achieved via a dorsal approach between the fifth and sixth extensor compartments.

• ORIF of large displaced ulnar styloid fragments may be necessary if they involve the base or fovea.

Complications

• Recurrent instability: This may occur with or without previous operative intervention and may result in pain and functional debilitation that may be progressive requiring reconstructive procedures.

• Ulnar neuropathy: Transient sensory symptoms may result from irritation of the ulnar nerve in Guyon canal or its dorsal sensory branch. Permanent damage is rare, but persistence of symptoms beyond 12 weeks may necessitate exploration.