Angel Ferreres, Marc García-Elías, and Andrew Chin
DEFINITION
Scapholunate dissociation (SLD) is the rupture of the anatomic linkage between the scaphoid and lunate and its subsequent progressive dysfunction, with or without carpal malalignment.
Classical radiographic signs occur only when there is permanent carpal malalignment. This is preceded by complete scapholunate disruption together with failure of the secondary scaphoid stabilizers, namely the scaphotrapezial-trapezoid ligament (STT), the scaphocapitate (SC) ligament, and the radioscaphocapitate (RSC) ligament.
However, in many cases, only partial tears or ligament sprains occur and do not produce positive radiologic signs. These injuries are often seen only arthroscopically.
Dorsal capsulodesis of the radioscaphoid joint was first described by Blatt.2 Now it is one of the most commonly used techniques in the treatment of carpal instability. This procedure involves the creation of a dorsal capsular flap.
ANATOMY
Scapholunate ligaments are divided into three fibrous structures:
Dorsal ligament
Volar ligament
Thin proximal membrane
Anatomically, the dorsal scapholunate ligament is the thickest and shortest of the fibrous structures, measuring 2 to 3 mm thick and 2 to 5 mm long. Biomechanically, it is the strongest and most resistant to failure under load (FIG 1A).1 The radioscapholunate (Testut) ligament is only a path for vascularization and innervation of the scaphoid and lunate.
Scaphoid position and relationship with lunate and distal carpal row is maintained by the scapholunate ligaments and by the secondary stabilizers (STT, SC, and RSC ligaments), which prevent excessive scaphoid flexion. These are called secondary stabilizers (FIG 1B).
The flexor carpi radialis tendon is closely related to the scapholunate joint and acts as a crucial dynamic stabilizer of the scaphoid, preventing it from going into excessive flexion and pronation during a firm grip of an object (FIG 1C).
PATHOGENESIS
Injury to the scapholunate ligaments occurs when the wrist is hyperextended, ulnarly deviated, and supinated during a fall on an outstretched hand. Because of the osseous configuration and disposition of the bones of the proximal carpal row, when the hand hits the floor, the tubercle of the scaphoid is pushed dorsally and extended. The lunate is held in position by the volar radiolunate (RL) ligaments and resists the tendency to extension transmitted by the scaphoid. The impact of the hand on the floor also pushes the pisiform against the triquetrum and because of the configuration of the joint between the triquetrum and the hamate, the former turns into flexion. If forces exceed the ligaments' resistance, they will rupture.
The sequence of failure of the ligaments is from palmar to dorsal. The first to tear is the volar scapholunate ligament, the weaker of the two scapholunate ligaments, followed by the dorsal scapholunate ligament.4
The participation of the dorsal intercarpal ligament (DICL) in scapholunate instability has been recently supported by the studies of Mitsuyasu et al.8
NATURAL HISTORY
Most SLDs present as the initial stage of a progressive carpal destabilization. The mechanism of injury produces a spectrum of injuries, ranging from mild scapholunate sprains to complete perilunar dislocations, all being different stages of the same progressive perilunar destabilization process as described by Mayfield et al.9
If only the palmar scapholunate ligament and the proximal membrane are disrupted, minor kinematic alterations result in predynamic instability. There is no gross carpal malalignment but because there is an increased motion between the scaphoid and lunate causing shear stress, these injuries may be sufficient to promote painful synovial inflammation.
Complete disruption of the scapholunate ligament complex leads to substantial alteration in kinematic and force transmission parameters (demonstrated in cadaver specimens), but not necessarily static carpal malalignment.8,13 This results in a dynamic instability. The scaphoid is unconstrained at the proximal end, resulting in increased radiolunate motion and correspondingly decreased radioscaphoid motion. This is accentuated in a loaded wrist.
When the secondary stabilizers start to attenuate after repeated use of the wrist, carpal malalignment develops, eventually resulting in static instability. Initially the scaphoid is still reducible, but over time it becomes permanently flexed and pronated (see “Imaging and Other Diagnostic Studies”).
If the alteration in the motion of the scaphoid persists, the cartilage degenerates and arthrosis develops. This pattern of degeneration is known as scapholunate advanced collapse (SLAC).
Once arthrosis is present, surgical techniques directed at replacing or reconstructing the injured ligaments are no longer options.
SLD is a progressive entity. Therefore, reconstruction is advocated as soon as it is diagnosed.
PATIENT HISTORY AND PHYSICAL FINDINGS
Almost always, patients present after a fall on their outstretched hand. The patient complains of dorsal hand and wrist pain when loading the affected wrist, such as when standing up from a chair.
FIG 1 • A. The elements that maintain the scaphoid in its normal position. B. Volar view of secondary stabilizers. C. The dynamic stabilizer of the scaphoid.
Predynamic and dynamic stages of SLD are often missed or overlooked. The injury usually is the result of isolated trauma, which the patient does not clearly remember, or is masked by other more severe or obvious injuries (eg, fractured scaphoid and distal radius). A high index of suspicion is required.
Weakness of grip strength, occasional swelling over the dorsoradial wrist, point tenderness over the scapholunate interval (more pronounced with gripping), and radial-sided wrist pain after excessive or heavy use are common but subtle physical examination findings.
The examiner should palpate the scapholunate interval dorsally (1 cm distal to the tubercle of Lister) with the wrist in 30 to 50 degrees of flexion.
On palpation of the anatomic snuffbox and palmar scaphoid tubercle, tenderness may also be present, suggesting ligament involvement, synovitis, or an occult ganglion.
Provocative tests such as the Watson scaphoid shift test and resisted finger extension test reinforce the possibility of the diagnosis.
Watson scaphoid shift test: The scaphoid flexes as the wrist goes from ulnar to radial deviation. The examiner's thumb prevents the scaphoid from flexing and if the scapholunate ligament is torn or incompetent, the proximal pole subluxates dorsally out of the scaphoid fossa, causing pain. When the thumb pressure is released, there may be a snap, signifying spontaneous reduction of the scaphoid back into the scaphoid fossa. This test is not highly specific and may signify synovitis, an occult ganglia, or radioscaphoid impingement.
Sharp pain on the resisted finger extension test has low specificity but high sensitivity.
IMAGING AND OTHER DIAGNOSTIC STUDIES
Radiographs
Posteroanterior (PA) view
Elbow flexed at 90 degrees, neutral prono-supination, and the middle finger aligned with the forearm axis. The palm of the hand is in full contact on the film case.
Scapholunate gap greater than 3 mm or wider than the contralateral normal side and a cortical “ring” sign suggest static scapholunate dissociation.
Decreased space between the radius and the scaphoid signifies cartilage loss and arthrosis.
Anteroposterior (AP) view
Forearm is in maximal supination.
This projection puts the scapholunate interval aligned with the beam of the ray.
Lateral view
Elbow at 90 degrees of flexion, middle finger aligned with the forearm, and wrist at 0 degrees of extension or flexion
This projection allows measurement of the scapholunate angle. An angle greater than 60 degrees indicates disruption of the scapholunate ligaments and often corresponds with widening on the PA and AP views.
Clenched-fist AP view demonstrates a widened scapholunate gap compared to the normal side (FIG 2A).
Cineradiography reveals abnormal movements between the scaphoid and lunate and an increase in the scapholunate gap as the wrist moves from radial to ulnar deviation.
FIG 2 • A. Clenched-fist PA view with the wrist in supination that shows a significant increase of the scapholunate interval space. B. CT scan of a patient with pain over the dorsal aspect of his left radiocarpal joint, showing a nonwidened space between scaphoid and lunate.
Arthrography is not specific and may be positive in conditions such as degenerative perforations of the scapholunate membrane and osteochondral defects.
Magnetic resonance imaging does not provide much additional information. Minor, degenerative perforation of the scapholunate membrane may result in a positive test.
Scapholunate ligaments can be seen clearly only on transverse cuts that pass through the two horns of the lunate.
MRI plays an important role in excluding other differential diagnoses.
Computed tomography scans do not give additional information except for providing a more accurate measurement of the parameters involved in the diagnosis of static SLD (eg, scapholunate distance and angle; FIG 2B).
It is useful in looking for other osseous anomalies of the wrist (eg, impacted fracture of the radius, scaphoid fracture).
Arthroscopy is the gold standard for diagnosing and staging SLD. It allows grading of the instability (Geissler classification) and therefore determination of the degree of injury to the ligament complex.4
It is also useful in assessing the condition of the cartilage and in locating concomitant carpal injuries that might negatively affect the outcome of a capsulodesis (Table 1).
DIFFERENTIAL DIAGNOSIS
Occult ganglia
Synovitis
Scaphoid fracture, nonunion, and avascular necrosis
Radiocarpal arthrosis
Radioscaphoid impingement
NONOPERATIVE MANAGEMENT
Initial conservative management aims at resting the injured limb and decreasing edema. Adequate immobilization with casting or splinting is advocated.
This immobilization is frequently therapeutic for patients with predynamic SLD.
Elevation of the limb and active finger motion minimize edema.
Anti-inflammatory medications can be given for pain relief.
Physiotherapy may have a role if a Geissler grade 1 is diagnosed by arthroscopy. As the ligaments have not lost their integrity, a period of short immobilization (2 weeks), followed by proprioception re-education of the flexor carpi radialis (FCR), as dynamic stabilizer of the scaphoid, is suggested.
Nonoperative treatment is seldom indicated when a significant disruption is diagnosed.
SURGICAL MANAGEMENT
Capsulodesis is part of the surgical armamentarium for the treatment of SLD. It is indicated for predynamic SLD, resulting from an isolated partial tear of the scapholunate ligament, and for dynamic SLD when the following criteria are fulfilled:
Complete disruption of all scapholunate components (palmar and dorsal)
Technically repairable dorsal ligament that has good healing potential
Intact secondary stabilizers
No cartilage degeneration
Capsulodesis is not indicated when static SLD is present.
Capsulodesis is used either as an isolated procedure together with Kirschner wire stabilization of the scapholunate joint in predynamic cases, or in combination to augment a direct repair of the dorsal scapholunate ligament in dynamic cases.
Due to its structure and position within the wrist, the scaphoid has an inherent tendency to flex and pronate, especially when the wrist is in flexion and radial deviation. The capsular flap created during dorsal capsulodesis acts as a checkrein to tether the scaphoid, preventing it from going into excessive flexion and pronation.
Preoperative Planning
All preoperative radiographs and diagnostic studies, especially arthroscopic findings, are reviewed.
Positioning
The patient is under anesthesia and in the supine position with hips and knees flexed at 30 degrees for low back comfort. The arm is exsanguinated and the tourniquet inflated at 250 mm Hg.
The arm is on the hand table in pronation, presenting the dorsal aspect of the wrist.
TECHNIQUES
BLATT CAPSULODESIS
Exposure
The tubercle of Lister and the radial styloid are identified by palpation.
An oblique skin incision is made following a line from a point 1 cm distal and ulnar with respect to the tubercle of Lister, to a point 1 cm distal to the radial styloid (TECH FIG 1).
Veins are coagulated or ligated.
Care is taken to identify the branches of the superficial radial nerve and mobilize and retract them with the subcutaneous tissue. This is accomplished taking all the fat with the skin as a flap.
Communicating vessels from the superficial layers to the deep arches are divided and coagulated.
The extensor retinaculum overlying the fourth dorsal extensor compartment is incised. The extensor retinaculum is then raised as two flaps, radially and ulnarly based, to free the extensor tendons from the second to fourth compartments.
A neurectomy of the posterior interosseous nerve can be performed at this point.
The extensor digitorum communis (EDC) is retracted ulnarly and the extensor pollicis longus (EPL) and extensor carpi radialis brevis (ECRB) radially to expose the dorsal capsule.
Creation of the Capsular Flap
A rectangular capsular flap, 25 mm long and 10 mm wide, is created by making a transverse capsular incision just proximal to the vascular dorsal carpal arch and elevating the tissue in a distal to proximal direction, leaving the proximal end still attached to the dorsal rim of the distal radius (TECH FIG 2A).
As the flap is elevated, the scaphoid is exposed (TECH FIG 2B).
At the dorsum of the scaphoid, a trough is created at a point distal to the axis of rotation of the scaphoid (scaphoid neck) (TECH FIG 2C).
Reducing the Instability
If the instability is acute, a primary repair of the scapholunate ligament is performed.
The space between scaphoid and lunate is reduced, using a 1.1-mm Kirschner wire inserted in the scaphoid as a joystick, and then another Kirschner wire is placed in the scaphoid and fixed to the lunate.
This step should be performed under radiologic guidance. The scapholunate angle in which these bones are fixed should be 45 ± 5 degrees.
When fixing the scaphoid to the lunate, ensure that the lunate is in a neutral position.
TECH FIG 1 • Incision site.
TECH FIG 2 • A. The vascular dorsal arch. B. Capsular flap is elevated, allowing visualization of the scaphoid, lunate, and head of the capitate. C. Intraoperative photo showing the scaphoid (S), the capitate (C), and the dorsal scapholunate ligament (SL). A bone trough has been created in the distal scaphoid for insertion of the capsular flap. KW, Kirschner wire in the lunate. (C: Courtesy of A. Lluch, Institut Kaplan.)
If the capsulodesis is being performed for predynamic instability, the scaphoid is fixed to the lunate in its normal alignment. This is also accomplished by means of a Kirschner wire as described earlier.
Another Kirschner wire is passed from the scaphoid into the capitate to avoid flexion and pronation (TECH FIG 3).
Securing the Capsular Flap and Wound Closure
The flap is tightly inserted into the notch created on the dorsum of the scaphoid.
There are two ways of securing the proximally based capsular flap to the scaphoid:
The flap is secured through holes created in the notch and transosseous sutures that are tied on the volar surface of the scaphoid tubercle.
The flap is secured to the sutures of a bone anchor (authors' preferred method) (TECH FIG 4).
The dorsal capsule is left in situ. The extensor retinaculum is closed with resorbable sutures.
Layered closure of the wound and skin is performed.
TECH FIG 3 • Orientation of the Kirschner wires recommended to stabilize the joints and protect the capsulodesis.
TECH FIG 4 • A. Placement of two bone anchors in the distal dorsal scaphoid. B. The proximally based capsular flap is prepared for insertion. C. The Blatt capsulodesis is completed. D. Radiographic PA view after eventual K-wire removal showing placement of the metallic bone anchors. (A: courtesy of A. Lluch, Institut Kaplan.)
HERBERT TECHNIQUE
This method is very similar to Blatt's technique, the difference being that the capsular flap is distally based.
There is no clear advantage to this technique over that described by Blatt.
The same approach is used and the same capsular flap created except that the tissue is left attached to the distal third of the scaphoid.
The flap is incised at the radiocarpal joint, tensioned proximally, and anchored to the dorsal radius using a suture anchor. This force extends the distal pole of the scaphoid, reducing the scapholunate joint (TECH FIG 5).6
TECH FIG 5 • Drawing depicting the distally based capsulodesis described by Herbert.
BERGER CAPSULODESIS
Use the same approach and exposure as described for the Blatt capsulodesis.
Raise a rectangular, radially based, capsular flap to allow exposure of the carpus. Its ulnar margin is the radiotriquetral ligament, its proximal margin is the radius, and its distal margin is the midsubstance of the DICL.
This elevated flap includes the proximal half of the DICL. Separate this portion of the DICL from the capsular tissue in an ulnar to radial direction, maintaining the radial insertion of the ligament.
Transfer this strip of ligament to the dorsum of the lunate into a prepared cancellous trough (TECH FIG 6).
This will create a link between scaphoid and lunate, preventing scaphoid flexion and pronation.
The ligament is secured by tying to the suture anchor(s) in the lunate.
This technique represents a variation of a previous version described by Taleisnik and Linscheid15,17 in which the flap was attached to the dorsum of the distal radius.
TECH FIG 6 • Berger's technique involves transfer of the proximal half of the dorsal intercarpal ligament to the dorsum of the lunate.
SZABO TECHNIQUE
The DICL is used to stabilize the scapholunate interval as above except the ligamentous tissue is ulnarly based and is inserted into the scaphoid rather than the lunate (TECH FIG 7).
Typically a longitudinal capsular incision is used to expose the carpus.
Care is taken to avoid incising the DICL.
The DICL is defined and its proximal half separated.
The radial insertion is incised at the level of the trapezium, trapezoid, and distal third of the scaphoid and then transferred to the scaphoid at the level of the scapholunate ligament insertion.
The transferred ligament may also be integrated into the scapholunate ligament repair more proximally.
The transferred ligament is secured using suture anchor(s) into a cancellous trough in the scaphoid.
Like the Berger capsulodesis, this technique does not specifically limit wrist flexion as it does not cross the radiocarpal joint.14
TECH FIG 7 • Szabo's technique involves transfer of the distal half of the dorsal intercarpal ligament from its attachment to the trapezium and trapezoid (x) to the distal third of the dorsum of the scaphoid (y).
POSTOPERATIVE CARE
Blatt recommended wearing a thumb spica cast for 2 months, after which active range-of-motion exercises were begun. The Kirschner wires were left in place for another month before removal, allowing intercarpal motion at 3 months postoperatively. Forceful stress was discouraged for up to 6 months postoperatively.
We prefer 6 weeks of immobilization in a rigid splint, avoiding extreme motions for one additional month. Kirschner wires can be removed at 8 weeks from the time of surgery.
OUTCOMES
A number of clinical series have reported good results with these procedures. 2–4,6,7,10–12,14,16,18,19 The agreement of these series is that tensioning or augmenting the dorsal radioscaphoid capsule offers less surgical morbidity than other alternatives.
At an average of 2 years of follow-up, these studies noted an absence of symptoms in two thirds of patients, with 75% grip strength compared to the contralateral side.
When examined with MRI, these patients demonstrate an increased capsular thickening that prevents rotary subluxation of the scaphoid but with the drawback of limiting wrist flexion by an average of 20 degrees.
The long-term stabilizing efficacy of this capsule, however, has yet to be determined.
Poor results have been reported in some series. This may be due to the use of the technique in cases of static instability or even in irreducible forms of SLD.3,10,11,18,19 This procedure is not recommended if the SLD has progressed to the static form because the pathomechanics from the permanent malalignment will increase the risk of a failed procedure. Studies reporting more favorable outcomes are those in which capsulodesis is used mainly for dynamic SLD.2,7,12,16
FIG 3 • A. The amount of flexion is reduced because of the dorsal restraint. The yellow arrow indicates the origin and insertion of the capsular flap. B. Extension is not restricted by the capsulodesis.
COMPLICATIONS
Reduction of wrist flexion (FIG 3)
Failure
Progression of SLD
REFERENCES
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2. Blatt G. Capsulodesis in reconstructive hand surgery. Hand Clin 1987;3:81–102.
3. Deshmukh SC, Givissis P, Belloso D, et al. Blatt's capsulodesis for chronic scapholunate dissociation. J Hand Surg Br 1999;24B: 215–220.
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15. Taleisnik J, Linscheid RL. Scapholunate instability. In Cooney WP, Linsheid RL, Dobyns JH, eds. The Wrist: Diagnosis and Operative Treatment. St. Louis: Mosby, 1998:501–526.
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18. Wyrick JD, Youse BD, Kiefhaber TR. Scapholunate ligament repair and capsulodesis for the treatment of static scapholunate dissociation. J Hand Surg Br 1998;23B:776–780.
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