Leonard L. D'Addesi, Joseph J. Thoder, and Kristofer S. Matullo
DEFINITION
The carpus is a complex, intercalated system of dual rows that allow paired motion within the radial–ulnar and flexion–extension plane. A disruption of the intrinsic ligaments of the carpus or a combination of ligamentous and osseous structures leads to a spectrum of injuries ranging from “wrist sprains” to complex perilunate injuries including lesser and greater arc injuries.
Lesser arc injuries are purely capsuloligamentous.
Greater arc injuries include a range of associated carpal fractures.
Disruptions of the normal kinematics and stability of the carpal row lead to acute failure with a predictable pattern of posttraumatic degenerative changes.
ANATOMY
There are eight carpal bones without tendinous insertions, whose motion is passively transmitted and guided by precise ligamentous architecture and bony geometry.
Volar extrinsic ligaments are the prime stabilizers of the carpus and are oriented in a double-V arrangement with a relative weakness between these V’s called the space of Poirer.
The volar extrinsic ligaments include the inner-V ligaments: long radiolunate (LRL), radioscapholunate (RSL), short radiolunate (SRL), and ulnolunate (UL). The outer V consists of the radioscaphocapitate (RSC) and the ulnotriquetrocapitate complex (UTCC) (FIG 1A).7
The dorsal extrinsic ligaments provide less structural stability and include the radiotriquetral (RT) and dorsal intercarpal (DIC) ligaments (FIG 1B).
The intrinsic ligaments are direct intercarpal connections that provide intra-row stability.
These include the lunotriquetral and the scapholunate ligaments.
Complex, three-dimensional motion occurs with wrist movement: radial deviation and wrist dorsiflexion are paired, as are ulnar deviation and wrist volarflexion.
PATHOGENESIS
These may involve high-energy injuries in which an axial load is applied to a hyperextended and ulnarly deviated wrist, placing the volar structures under tension and the dorsal structures under compression and shear.
The energy dissipates in a radial to ulnar direction.
Lesser arc injuries are purely ligamentous and advance through four progressive stages as originally described by Mayfield et al4 (FIG 2A):
Stage I: the scapholunate ligament
Stage II: the space of Poirer
Stage III: the UTCC and UL ligament
Stage IV: lunate dislocation
Greater arc injuries proceed in the same direction but involve fractures through the radial styloid, scaphoid, lunate, capitate, triquetrum, and ulna, either solely or in combination (FIG 2B).
Perilunate dislocations most commonly occur as dorsal dislocations of the capitate and surrounding carpus with respect to the lunate, which remains in the lunate fossa of the distal radius.
A lunate dislocation often involves volar displacement of the lunate into the carpal tunnel, with the capitate articulating in the lunate fossa of the radius. Median neuropathy is common. The lunate is ousted from the wrist joint through the space of Poirer, creating a rent in the volar capsule that extends medially and laterally along the interval between the V ligaments. The rent is semilunar or crescentic in appearance.
NATURAL HISTORY
Nonoperative management yields predictably poor results, with loss of reduction and progression to wrist deformity and pain.1,2
FIG 1 • A. Volar extrinsic carpal ligaments. LRL, long radiolunate ligament; SRL, short radiolunate; RSC, radioscaphocapitate ligament; UL, ulnolunate ligament; UTCC, ulnotriquetrocapitate complex; *, space of Poirer. B. Dorsal extrinsic carpal ligaments. RTq, radiotriquetral ligament; DIC, dorsal intercarpal ligament; *, scaphoid.
FIG 2 • A. Lesser arc injury. Progression of capsuloligamentous injury from radial to ulnar direction. B. Greater arc injury. Transscaphoid perilunate injury pattern.
Typical instability patterns (depending on extent of injury) include scapholunate advanced collapse, scaphoid nonunion advanced collapse, and volar or dorsal intercalated segmental instability.
Definitive treatment is operative intervention.
PATIENT HISTORY AND PHYSICAL FINDINGS
A typical history may range from a fall and twist on an extended hand to a high-energy event with extreme forces transferred to the wrist. Patients complain of pain and stiffness.
Physical examination findings depend on the level of injury and the elapsed time from injury to presentation.
Stiffness, tenderness, crepitus, swelling, and resistance to motion are common findings. Deformity is usually minimal.
Depending on the severity of injury, the findings can be subtle and easily missed. The examiner must maintain a high index of suspicion.
A thorough neurologic examination is critical. Median neuropathy is relatively common and ranges from dysesthesia to overt motor dysfunction. This finding is more common in cases associated with lunate dislocation.
Palpation of individual carpal bones in a greater arc injury may reveal tenderness over specific fractures.
Specific testing of intrinsic and extrinsic ligaments (eg, the Watson test, the lunotriquetral shuck, and the ulnar catch-up) may prove difficult and of little value in an acute setting.
IMAGING AND OTHER DIAGNOSTIC STUDIES
True posteroanterior (PA) and true lateral radiographs should be obtained. The diagnosis is made primarily with these views. These radiographs should be compared with identical radiographs of the uninjured wrist.
Other views such as radial–ulnar deviation, flexion– extension, supinated, and clenched-fist views are often difficult to obtain and are of little additional value.
Perilunate dislocations involve disruption of the lines of Gilula, best seen on the PA radiograph. The lunate assumes a triangular shape, different from its standard trapezoidal shape. On the lateral radiograph, the concentricity of the C's, representing the distal radius, lunate, and capitate, is lost, indicating a dorsal dislocation of the capitate from the lunate fossa (FIG 3A,B).
A lunate dislocation is represented by the “spilled tea cup” sign on the lateral radiograph. The lunate is volarly displaced and flexed. It often lies anterior to the volar cortex of the distal radius. The capitate articulates with the lunate fossa of the radius (FIG 3C,D).
Greater arc injuries must be ruled out. Scaphoid fractures are most common. Capitate and triquetral fractures have been described.
MRI, arthrography, arthroscopy, and bone scan are not indicated in the acute setting after major trauma to the wrist.
DIFFERENTIAL DIAGNOSIS
Given the severity of this injury pattern and the frequency with which it is missed, greater and lesser arc injuries must be ruled out in any situation in which the wrist is traumatized.
Wrist sprain
Triangular fibrocartilage complex (TFCC) injury
Extrinsic or intrinsic ligament disruptions
Carpal fractures
Distal radius or ulna fracture
Median neuropathy
Kienböck disease
Ulnar impaction syndrome
DeQuervain tenosynovitis
Basal joint arthritis
NONOPERATIVE MANAGEMENT
Closed reduction of perilunate dislocations may be achieved by in-line traction and gentle wrist manipulation as described by Tavernier.6and rotates the lunate into extension. The capitate is then translated up and over the lunate while simultaneously flexing the wrist. A snapping sound may be heard when the capitate reduces over the lunate.
In-line traction is helpful for muscle relaxation before reduction and can be applied using finger traps and weights suspended from the arm with the elbow flexed 90 degrees for 10 minutes.
The surgeon extends the wrist and applies gentle manual traction. The surgeon's thumb stabilizes the lunate volarly
FIG 3 • A,B. Perilunate dislocation. A. AP projection demonstrates loss of lines of Gilula. B. Dorsal dislocation of the capitate out of the lunate fossa. C,D. Lunate dislocation. AP and lateral projections demonstrating loss of lines of Gilula and volar dislocation of the lunate into the carpal tunnel, with the capitate articulating in the radial fossa.
Closed reductions of lunate dislocations are frequently unsuccessful. As traction is applied to the wrist, the volar rent narrows to prevent reduction of the lunate into the wrist joint.
Acute carpal tunnel syndrome in this scenario is a surgical emergency.
Long-term outcomes of closed reduction have been shown to be suboptimal, and surgical treatment is warranted.
SURGICAL MANAGEMENT
Preoperative Planning
All radiographs are reviewed.
The surgeon should determine what ligaments are damaged and whether biosuture anchors are needed to augment repair.
The surgeon should assess osseous structures and determine whether fractures need to be stabilized with hardware such as Kirschner wires or dual-pitch screws.
If median neuropathy is present or impending, a carpal tunnel release should be performed.
Positioning
Supine positioning with a well-padded pneumatic tourniquet on the upper arm
The use of a radiolucent hand table with fluoroscopic imaging aids in repair and reduction.
Approach
Surgical approaches to this injury include dorsal approach, volar approach, and combined dorsal and volar approach.
The dorsal approach uses the universal dorsal wrist incision and the interval between the third and fourth compartments to expose the dorsal capsule and gain access to the joint.
The dorsal approach is helpful for open reduction of the dislocation and direct assessment of articular injuries. However, great difficulty may be encountered if attempting to reduce a lunate dislocation through only a dorsal approach.
Direct or augmented repair of the scapholunate ligament and open reduction and internal fixation of any concomitant carpal fractures are accomplished through this approach.
The volar approach is performed through an extended carpal tunnel incision. Retraction of the carpal tunnel contents allows visualization of the volar capsuloligamentous structures and the semilunar rent. Decompression of the carpal tunnel, evacuation of any hematoma, and tenosynovectomy of the digital flexor tendons is accomplished.
Open reduction of a volar lunate dislocation is facilitated by this approach.
Repair of the volar capsuloligamentous injuries can also be performed to further stabilize the carpus.
An exclusive volar approach does not allow precise repair of the intercarpal ligaments, and bony fixation is difficult.
The combined dorsal and volar approach is preferred: this is the only method that allows true assessment of the pathology and anatomic repair of all injured structures.
TECHNIQUES
DORSAL APPROACH
Incision and Dissection
A universal dorsal skin incision is made under tourniquet control. The extensor retinaculum is exposed, raising medial and lateral skin flaps. Access to the dorsal capsule is gained through the 3–4 extensor compartment interval (TECH FIG 1A).
The extensor pollicis longus (EPL) tendon is dissected distal to the extensor retinaculum and the third compartment is incised. The EPL is transposed radially to prevent injury to the tendon during manipulation and stabilization of the carpus (TECH FIG 1B).
The fourth extensor compartment is incised longitudinally and the tendons are retracted. The dorsal capsule is now visible.
One centimeter of the posterior interosseous nerve is excised as part of the procedure (TECH FIG 1C).
A transverse rent extending through the dorsal capsule and radiotriquetral ligament is often found. This rent should be extended in both the radial and ulnar directions to allow visualization of the capitolunate interval.
TECH FIG 1 • A. Universal dorsal skin incision for the dorsal approach. B. The third extensor compartment is incised and the extensor pollicis longus (EPL) is transposed radially. The extensor digitorum communis (EDC) tendons are visible. (Thumb is at top left and wrist is to the right.) C. The fourth extensor compartment is incised and the EDC tendons are retracted ulnarly. The sensory branch of the posterior interosseous nerve to the wrist (vessel loop) is sacrificed. D. A ligament-sparing capsular incision may be made to visualize the carpus. Sc, scaphoid.
A more extensile ligament-sparing incision can also be used to gain considerable access to the carpus.
Incise the capsule in a radial direction along the dorsal distal radial lip, leaving a small cuff of tissue attached to the radius for later repair.
Incise ulnarly, along the dorsal radiotriquetral ligament and dorsal intercarpal ligament. This generates a radially based capsular flap (TECH FIG 1D).
If the dislocation was not reducible closed, the capitate is prominent and the absence of the lunate is evident.
The articular injury can now be assessed.
In combination with manual traction and volar pressure on the lunate, insert a Freer elevator into the capitolunate joint around the proximal pole of the capitate and shoehorn the lunate into place.
Reduction and Fixation
Scaphoid
Before reduction of the dislocation–subluxation, 0.045 or 0.062-inch Kirschner wire transfixation pins are inserted into the triquetrum and scaphoid through the dorsal incision in an in-to-out fashion. These pins are later driven back into the lunate to stabilize the reduction.
The starting point for these pins is through the centroid of the aspect of the proximal pole of the scaphoid and triquetrum that articulates with the lunate (TECH FIG 2).
Transfixation pins are unnecessary in the scaphoid if it is fractured since a screw in the scaphoid will stabilize the radial side of the carpus.
TECH FIG 2 • Transfixation pins are placed through the scaphoid and triquetrum before reduction of the lunate. This facilitates placement of these Kirschner wires and advancement into the lunate after reduction. The entry point is the centroid of the intercarpal joint on the scaphoid and triquetrum. The tips of the Kirschner wires are seen slightly protruding from the scaphoid and triquetrum. The lunate is displaced volarly and is not visible.
Reduce and stabilize carpal fractures.
Attention is first directed toward fixation of an associated scaphoid fracture using proximal to distal (antegrade) fixation.
The scaphoid is usually fractured at its waist or proximal pole.
In a noncomminuted fracture, stabilization is accomplished with a cannulated headless compression screw.
If comminution exists, autologous cancellous bone graft is applied before final tightening of the screw.
Ligament Repair
Intercarpal ligament injuries may now be repaired.
In a transscaphoid perilunate dislocation, the proximal pole of the scaphoid remains attached to the lunate with an intact scapholunate ligament. However, in lesser arc injuries, the scapholunate and the lunotriquetral ligament are disrupted.
Before ligamentous repair, anatomic carpal realignment is ensured.
0.045-mm Kirschner wires are introduced into the scaphoid, lunate, and triquetrum and used as joysticks to align these bones.
The previously set Kirschner wires used as transfixation pins are then advanced from the scaphoid and triquetrum into the lunate.
Transfixation pins are also percutaneously introduced to stabilize the scaphoid and triquetrum to the capitate (TECH FIG 3A).
Intraoperative fluoroscopy aids alignment and placement of Kirschner wires.
The scapholunate angle (40 to 60 degrees), capitolunate angle (less than 15 degrees), and radiolunate angle (less than 15 degrees) should be reduced and verified.
The C shape of the distal radius, lunate, and capitate should be concentric (TECH FIG 3B).
Small (about 2 mm) suture anchors with nonabsorbable suture (2-0 to 3-0) are inserted for reattachment of the scapholunate and lunotriquetral ligaments, avoiding the Kirschner wires.
Most often the ligaments avulse from the scaphoid and the triquetrum; therefore, the anchors are placed in those locations.
When the intercarpal ligaments are beyond repair, suture anchors are unnecessary, and stability is established via extrinsic capsuloligamentous healing.
The dorsal capsular injury and extended capsulotomy is closed with nonabsorbable suture.
The EPL tendon is left transposed in a subcutaneous location (TECH FIG 3C).
The subcutaneous tissue and skin are closed in a standard fashion.
TECH FIG 3 • Transfixation pins are in place protecting the ligament repairs and maintaining anatomic carpal alignment. Suture anchors were not required for repair in this case. The intercarpal ligament injuries were midsubstance. A. The PA radiograph shows the reduced trapezoidal shape of the lunate and restoration of the lines of Gilula. B. The lateral radiograph shows the reduced scapholunate, radiolunate, and capitolunate angles. The three concentric C's are also visible. C. Repair of the extensor retinaculum and transposed extensor pollicis longus.
COMBINED DORSAL AND VOLAR APPROACH (AUTHORS' PREFERRED APPROACH)
Incision and Dissection
A standard extended carpal tunnel approach is performed under tourniquet control (TECH FIG 4A).
The median nerve is completely decompressed.
The contents of the carpal canal are retracted and hematoma is evacuated.
The volar capsuloligamentous injury, which is represented by an apex-distal, semilunar rent, is visualized (TECH FIG 4B).
This rent courses between the RSC and LRL radially, and between the UTCC and ulnolunate ligaments ulnarly.
In the case of a lunate dislocation, the lunate can be visualized within the carpal canal, having been extruded through the capsular tear.
Next, the wrist is exposed dorsally as described above.
The degree of injury is assessed.
Reduction, Fixation, and Repair
Preset transfixation Kirschner wires as previously described.
Reduce the carpus under direct visualization, with wrist extension and the aid of a Freer elevator to shoehorn the capitate into the lunate fossa.
The volar approach facilitates the reduction by allowing direct access to the lunate.
Surgical extension of the capsular tear between the RSC and LRL ligaments or between the UTCC and ulnolunate ligaments allows greater access to the wrist without further disruption of extrinsic ligaments.
Through the dorsal incision, reduce, stabilize, and repair any associated carpal fractures and intercarpal ligament injuries in the manner described above.
The volar capsuloligamentous rent is closed with nonabsorbable suture (TECH FIG 5).
The flexor tendons may now be assessed. Often the tenosynovium surrounding the tendons within the carpal tunnel is thickened. A tenosynovectomy may be performed.
The EPL should be left transposed dorsally.
The subcutaneous tissue and skin are closed in a standard fashion.
TECH FIG 4 • A. Extended carpal tunnel incision used for the volar approach. B. A volar, semilunar, apex-distal, capsuololigamentous rent is visible at the space of Poirer. The lunate (Lu) is seen protruding from the rent.
TECH FIG 5 • The volar capsule is closed with nonabsorbable suture.
POSTOPERATIVE CARE
The immediate postoperative dressing includes a wellpadded splint immobilizing the wrist and forearm in a neutral rotational position with about 20 degrees of wrist extension.
Edema control and prevention of skin maceration can be accomplished with the addition of sterile gauze dressings between the digits and a bulky dressing within the palm.
Active and passive digital range-of-motion exercises are encouraged immediately to prevent flexor tendon adhesions and digital stiffness.
Sutures are removed at 10 to 14 days and full-time cast or splint immobilization is continued for a total of 8 weeks postoperatively.
Pins may be removed at 8 weeks, and the patient may be converted to a removable splint to promote range of motion of the wrist.
At 12 weeks, strengthening is permitted with progressive resistance as tolerated.
Anticipated return to activities is 6 to 12 months.
OUTCOMES
Outcomes will vary with regard to stiffness and grip strength.
More accurate anatomic reduction will lead to improved results. Sotereanos et al 5 used a dorsal–volar approach in 11 patients with perilunate dislocations and fracturedislocations. Good to excellent results were achieved in 9 of 11 patients.
Up to 50% loss of flexion–extension motion arc can be anticipated.3
Up to 60% diminished grip strength can be anticipated.3
COMPLICATIONS
Missed diagnosis
Postoperative pin-tract infections
Median nerve injury
Transient ischemia of lunate
Chondral injury or chondrolysis
Late carpal instability
Nonunion or malunion of the scaphoid
Posttraumatic arthritis
REFERENCES
1. Adkison JW, Chapman MW. Treatment of acute lunate and perilunate dislocations. Clin Orthop Relat Res 1982;164:199–207.
2. Apergis E, Maris J, Theodoratos G, et al. Perilunate dislocations and fracture dislocations: closed and early open reduction compared in 28 cases. Acta Orthop Scand Suppl 1997;275:55–59.
3. Cooney WP, Bussey R, Dobyns JH, et al. Difficult wrist fractures: perilunate fracture-dislocations of the wrist. Clin Orthop Relat Res 1987;214:136–147.
4. Mayfield JK, Johnson RP, Kilcoyne RK. Carpal dislocations: pathomechanics and progressive perilunar instability. J Hand Surg Am 1980;5:226–241.
5. Sotereanos DG, Mitsionis GJ, Giannakopoulos PN, et al. Perilunate dislocation and fracture dislocation: a critical analysis of the volardorsal approach. J Hand Surg Am 1997;22A:49–56.
6. Tavernier L. Les deplacements tramatiques du semilunaire. These, Lyons, 1906:138–139.
7. Walsh JJ, Berger RA, Cooney WP. Current status of scapholunate interosseous ligament injuries. JAAOS 2002;10:32–42.