Alex M. Meyers, Alexander H. Payatakes, and Dean G. Sotereanos
DEFINITION
Scapholunate instability is the most common form of carpal instability.
Scapholunate interosseous ligament (SLIL) injury can result in a predictable pattern of arthritis over time: scapholunate advanced collapse (SLAC).12
Acute tears (<6 weeks from injury) versus chronic tears (>6 weeks from injury)
Acute tears tend to be amenable to primary ligament repair.
Chronic tears tend to require ligament reconstruction procedures.
Static or dynamic instability
Static instability: any or all of the five characteristic changes on standard plain radiographs (see below)
Dynamic instability: normal plain radiographs; however, with loaded (grip view) plain radiographs, any or all of the five characteristic changes may become present.10
Fixed versus reducible deformity
Fixed deformity: the static radiographic changes are not passively correctible
Reducible deformity: the static radiographic changes are passively correctible
This distinction can be determined preoperatively by noting improvement in the static changes on plain radiographs of the wrist in radial deviation compared with AP views of the wrist.
ANATOMY, PATHOGENESIS, AND NATURAL HISTORY
See Chapter HA-41.
PATIENT HISTORY AND PHYSICAL FINDINGS
Typical presentation follows a fall on an outstretched hand with acute onset of wrist pain and mild dorsal wrist swelling.
Key physical examination findings are reviewed in Chapter HA-41.
IMAGING AND OTHER DIAGNOSTIC STUDIES
Plain radiographs may reveal five characteristic findings suggestive of SLIL pathology (FIG 1).
Terry Thomas sign: gap between the scaphoid and lunate of more than 3 mm on posteroanterior (PA) radiograph
Cortical ring sign: Cortical hyperdensity is seen on PA radiograph as the scaphoid moves into increasing flexion.1
Angular changes in the carpal rows
Scapholunate angle: Normal is 30 to 60 degrees (mean 46 degrees); with SLIL injury, more than 60 degrees6
Capitolunate angle: Normal is −15 to 15 degrees (mean 0 degrees); with SLIL injury, more than 15 degrees
Radiolunate angle: Normal is −10 to 10 degrees (mean 0 degrees); with SLIL injury, more than 10 degrees
Quadrangular lunate: As the lunate moves into extension it assumes a rectangular appearance on PA radiograph.
Disruption of Gilula’s lines: Gentle concentric arcs follow the proximal and midcarpal rows. These lines are disrupted with SLIL tears as the relationship of the proximal row is lost.
Arthrography: sensitivity 56%, specificity 83%, accuracy 60%13
False-positive results have been documented with communication of contrast shown in asymptomatic patients.1
CT arthrography: sensitivity 86% to 100% (100% sensitive in the detection of dorsal ligament tears), specificity 50% to 79% (79% specific in the detection of dorsal ligament tears), accuracy 78% to 83%7
MRI: sensitivity 25% to 60%, specificity 77% to 100%, accuracy 64% to 78%8
Specifically, palmar tears of the SLIL were identified with a sensitivity of 60% and specificity of 77% in a cadaveric study. However, the more important stabilizing dorsal portion tears were seen in 0 of 9 specimens.7
Ultrasound: sensitivity 46%, specificity 100%, accuracy 89%2
A negative result with various imaging studies does not prove an absence of ligamentous injury. Arthroscopy has become the gold standard for the diagnosis of SLIL tears.
DIFFERENTIAL DIAGNOSIS
Dynamic SLIL instability or partial SLIL tear
Radiocarpal arthritis
Scaphoid fracture
Keinböck or Preiser disease
FIG 1 • AP and lateral plain radiographs of a patient with scapholunate ligament tear.
NONOPERATIVE MANAGEMENT
Nonoperative methods are unsuccessful in treating dynamic or static acute scapholunate ligament injuries.
0 of 19 patients with dynamic instability treated with immobilization, nonsteroidal anti-inflammatories, and activity modification had substantial reduction in symptoms even up to 12 weeks into treatment.14
SURGICAL MANAGEMENT
Indications
Wrist pain with an acute tear (<6 weeks)
These patients may or may not have static radiographic changes.
Should static radiographic changes be present, plain radiographs in radial deviation can show if the radiographic changes are fixed (and therefore are not amenable to soft tissue repairs) or correct in radial deviation (and therefore are amenable to soft tissue repairs).
Wrist pain with dynamic instability
We advocate diagnostic arthroscopy before open treatment.
Preoperative Planning
General or regional anesthesia
Equipment
Mini suture anchors (1.8 mm)
Kirschner wire driver and smooth wires (0.045 and 0.062 inch)
Arthroscopic equipment (see Chap. HA-41)
Mini C-arm
Positioning
The patient is positioned supine with a hand table.
The bed is turned such that the hand table faces the corner opposite anesthesia.
Fluoroscopy can then move in and out from the opposite corner perpendicular to the patient.
An upper arm nonsterile tourniquet should be placed.
The operative arm is prepared and draped. Slack is left in the armboard portion of the drape to allow the sterile wrist traction tower to slide under the arm above the elbow.
The operative wrist is suspended in a wrist traction tower.
Approach
A preoperative examination of both wrists is performed and documented, noting passive range of motion, swelling, and the Watson scaphoid shift test.
Arthroscopy is recommended before open reconstruction because of the lack of diagnostic accuracy of available imaging modalities.
Wrist arthroscopy is considered the gold standard for diagnosis of SLIL pathology and can confirm the diagnosis and degree of instability before making a larger skin incision.
Geissler staging of SLIL tears3 is covered in Chapter HA-41.
TECHNIQUES
DIAGNOSTIC WRIST ARTHROSCOPY
See Chapter HA-41.
The 3–4 portal is used for viewing.
The 6U portal is used for outflow (typically an 18-gauge needle with sterile IV tubing).
The 4–5 is used for placement of instruments.
The SLIL is probed in the radiocarpal and midcarpal joints.
A 1-mm arthroscopic probe passable in the scapholunate interval and rotated 360 degrees is indicative of a grade III Geissler lesion.
A “drive-through” sign with a 2.7-mm arthroscope is indicative of a grade IV Geissler lesion.
Midcarpal arthroscopy most effectively reveals the degree of instability.
DIRECT SLIL REPAIR
Specific indications for direct SLIL repair with or without dorsal capsulodesis
Geissler III or IV complete SLIL tear
Injury less than 6 weeks old
It is rare that a repairable ligament is available more than 3 months after injury.
Minimal degenerative changes in the radiocarpal and midcarpal joints
Static radiographic changes that are not fixed
Adequate SLIL tissue
Make a standard longitudinal dorsal incision just ulnar to the tubercle of Lister and dissect to the extensor retinaculum.
Raise flaps at the level of the extensor retinaculum, exposing the retinacular edges proximally and distally.
Superficial radial and ulnar dorsal cutaneous nerve branches will be within these flaps.
Incise the extensor retinaculum over the third extensor compartment and transpose the extensor pollicis longus (EPL) tendon into the radial subcutaneous space.
Expose the dorsal capsule and dorsal extrinsic radiocarpal ligaments (dorsal radiocarpal [DRC] and dorsal intercarpal [DIC] ligaments).
Incise the dorsal capsule, leaving a 1to 1.5-cm ulnarbased flap (TECH FIG 1A).
Leaving the capsule attached ulnarly provides a capsular flap available for capsulodesis or augmentation of a repair if desired.
This flap of tissue will parallel the DIC and include the capsule and portions of the DIC and DRC.
With the scaphoid, SLIL, and lunate exposed, note any arthritic changes, the location of the SLIL disruption (typically it avulses off the scaphoid) (TECH FIG 1B,C), and any injury to the DIC ligament.
In cases of high energy the DIC may avulse off its scaphoid and lunate attachment.
Place joystick Kirschner wires (0.062 inch) into the scaphoid and the lunate.
TECH FIG 1 • A. Intraoperative photo demonstrating the exposure and location of the dorsal capsular ulnar-based flap. The DIC parallels the more distal transverse limb of the flap. S, scaphoid; L, lunate; T, triquetrum. B.Intraoperative photo demonstrating the flexed scaphoid (S), the capitate (C), and the extended lunate (L). A complete disruption of the scapholunate interosseous ligament (SLIL) is noted. The arrow points at the ulnar-based capsular flap. C. Intraoperative photo showing the scaphoid on the left and the SLIL still attached to the lunate on the right (held by forceps). The capitate head is seen distal to the lunate at the top of the photo. D.Intraoperative photo after suture anchor placement into the scaphoid at the dorsal SLIL footprint on the left, then passed through the SLIL shown on the right. The joystick Kirschner wires are placed into the scaphoid and the lunate in such a manner that when they are brought together, the dorsal intercalated segment instability (DISI) deformity will be corrected and the joint reduced. E. Intraoperative photo after reduction of the joint and DISI deformity using the joystick Kirschner wires and suture repair of the avulsed SLIL. The Kirschner wires in the scaphoid and in the lunate have been brought together from their divergent positions and are now in the same plane, correcting the DISI deformity. The two Kirschner wires have been placed from radial to ulnar (seen on the left of the image), passing through the scapholunate interval and scaphocapitate interval. F,G. AP and lateral intraoperative fluoroscopic images demonstrating Kirschner wire placement across the scaphocapitate joint and the reduced scapholunate joint. Suture anchors can be seen in the scaphoid at the dorsal SLIL footprint. This example shows a third, more distal suture anchor at the scaphoid that was used for dorsal capsule augmentation.
Place these wires parallel to the scapholunate joint about 5 mm from the articular surface.
The scaphoid joystick should angle proximally and the lunate joystick should angle distally (TECH FIG 1D).
The Kirschner wire joysticks are brought together, taking the scaphoid out of flexion and the lunate out of extension to correct any dorsal intercalated segmental instability deformity and reduce the joint.
Preliminarily reduce the scapholunate joint and identify the anatomic insertion site for the SLIL.
Roughen the SLIL footprint to bleeding bone on the dorsal ulnar portion of the scaphoid and insert one or more mini suture anchors (2.0 or 2.5 mm).
Pass the sutures from the suture anchor through the SLIL stump but do not tie them (TECH FIG 1D).
With the joint reduced via the joysticks, drive two 0.045-inch smooth Kirschner wires from the scaphoid into the lunate across the reduced scapholunate joint and drive one or two 0.045-inch Kirschner wires through the waist of the scaphoid into the capitate (TECH FIG 1E–G).
Secure the SLIL to the prepared site by tying the suture anchor sutures.
Remove the joystick Kirschner wires and cut the remainder of the Kirschner wires below the skin.
Suture anchors are placed at the DIC footprint on the dorsal more distal scaphoid should it be avulsed and need repair or should capsular flap augmentation be desired (see Direct SLIL Repair with Dorsal Capsulodesis).
Close the capsule with 3–0 absorbable suture.
Transpose the EPL tendon subcutaneously and repair the extensor retinaculum with 3–0 absorbable suture.
DIRECT SLIL REPAIR WITH DORSAL CAPSULODESIS
Indications
Tenuous SLIL repair
Chronic scapholunate dissociation (>6 weeks) without arthritis
The deformity must be reducible and not fixed.
Should capsulodesis be required for augmentation, perform the SLIL repair as described above, making the same ulnar-based dorsal capsular incision.
After the SLIL is repaired, swing the ulnarly based capsular flap over the scapholunate interval and plan the location for its attachment to the scaphoid waist.
Plan to secure the flap under tension to further stabilize the scapholunate joint.
Place one or two mini suture anchors (1.8 or 2.0 mm) into the scaphoid at the determined location and another mini suture anchor dorsal-central into the lunate.
With the capsular flap pulled taut, pass the scaphoid suture anchor sutures through the flap. Then pass the lunate sutures through the central aspect of the flap, estimating suture location to maximize stabilization of the scapholunate joint.
Once all sutures from the scaphoid and the lunate are placed through the capsular flap, tie them down (TECH FIG 2).
TECH FIG 2 • Repair augmentation with ulnar-based capsular (CAPS) flap. Note the suture anchor knots (arrows) and the location of the distal suture anchor at the scaphoid at the footprint of the dorsal intercarpal ligament.
POSTOPERATIVE CARE
The wrist is immobilized in a short-arm thumb spica splint immediately after surgery.
Sutures are removed at 2 weeks and the wrist is placed into a short-arm thumb spica cast for 8 weeks.
Radiographs are obtained at 2 and 4 weeks to evaluate reduction and any pin migration.
Pins are removed at 8 weeks and the wrist is placed back into a short-arm thumb spica splint.
Gentle active range-of-motion exercises are allowed at 8 weeks, out of the splint for exercises only.
Immobilization is discontinued at 12 weeks.
Full activities are allowed at 4 to 6 months.
Forced hyperextension (push-ups) and axial loading are especially restricted during the 4to 6-month postoperative period.
OUTCOMES
Results following direct SLIL repair with capsulodesis are highly variable.
By not crossing the radiocarpal joint with the capsulodesis, theoretically wrist motion will be maximized.
Szabo et al9 showed mean loss of wrist flexion of 10 degrees, extension of 15 degrees, radial deviation of 20 degrees, and ulnar deviation of 11 degrees at 2 years of follow-up for chronic (>6 weeks) SLIL tears treated with DIC capsulodesis.
Grip strength was unchanged from the preoperative assessment (mean 41).
Results of the procedure typically do not hold over time radiographically.
Minimum 5-year follow-up for chronic SLIL tears treated with DIC capsulodesis showed4 :
Immediate postoperative scapholunate angle of 56 degrees at 5 years increased to 62 degrees
Immediate postoperative scapholunate gap of 2.6 mm at 5 years increased to 3.5 mm
Also, 50% of wrists show arthritic changes at 5 years.
Radiographic changes have not correlated with clinical results over time.4
Wrist flexion decreased 19 degrees at 5-year follow-up compared with preoperative values.
Extension and radial and ulnar deviation remained unchanged at 5 years from the immediate postoperative values shown above.9
Grip strength remained unchanged at 5 years (mean 43).
Outcome instrument scores at 5 years (Mayo Wrist Score)
38% excellent, 19% good, 31% fair, 12% poor outcomes
No correlation between subjective pain scores and radiographic changes has been shown at 5 years.
COMPLICATIONS
Pin tract infections (this risk is minimized with buried pins)
Superficial radial nerve injury
The surgeon should keep skin flaps thick when dissecting on top of the extensor retinaculum (this keeps the superficial radial nerve branches within the flaps).
The surgeon should make a small stab incision to bluntly dissect down to bone to minimize risk of nerve injury during pin placement.
Loss of scapholunate reduction
Arthritic changes in the radiocarpal and midcarpal joints
REFERENCES
1. Blatt G. Capsulodesis in reconstructive hand surgery: dorsal capsulodesis for the unstable scaphoid and volar capsulodesis following excision of the distal ulna. Hand Clin 1987;3:81–102.
2. Dao KD, Solomon DJ, Shin AY, et al. The efficacy of ultrasound in the evaluation of dynamic scapholunate ligamentous instability. J Bone Joint Surg Am 2004;86A:1473–1478.
3. Darlis NA, Weiser RW, Sotereanos DG. Partial scapholunate ligament injuries treated with arthroscopic debridement and thermal shrinkage. J Hand Surg Am 2005;30A:908–914.
4. Gajendran VK, Peterson B, Slater RR, et al. Long-term outcome of dorsal intercarpal ligament capsulodesis for chronic scapholunate dissociation. J Hand Surg Am 2007;32A:1323–1333.
5. Geissler WB, Freeland AE, Savoie FH, et al. Intracarpal soft tissue lesions associated with an intra-articular fracture of the distal end of the radius. J Bone Joint Surg Am 1996;78A:357–365.
6. Linscheid RL, Dobyns JH, Beabout JW, et al. Traumatic instability of the wrist: diagnosis, classification, and pathomechanics. J Bone Joint Surg Am 1972;54A:1612–1632.
7. Schmid MR, Schertler T, Pfirrmann CW, et al. Interosseous ligament tears of the wrist: comparison of multi-detector row CT arthrography and MR imaging. Radiology 2005;237:1008–1013.
8. Schweitzer ME, Brahme SK, Hodler J, et al. Chronic wrist pain: spinecho and short tau inversion recovery MR imaging and conventional MR arthrography. Radiology 1992;182:205–211.
9. Szabo RM, Slater RJ, Palumbo CF, et al. Dorsal intercarpal ligament capsulodesis for chronic, static scapholunate dissociation: clinical results. J Hand Surg Am 2002;27A:978–984.
10. Taleisnik J. Post-traumatic carpal instability. Clin Orthop Relat Res 1980;149:73–82.
11. Viegas SF, Patterson RM, Hokanson JA, et al. Wrist anatomy: incidence, distribution, and correlation of anatomic variations, tears, and arthrosis. J Hand Surg Am 1993;18:463–475.
12. Watson K, Ballet FL. The SLAC wrist: scapholunate advanced collapse pattern of degenerative arthritis. J Hand Surg Am 1984; 9:358–365.
13. Weiss AP, Akelman E, Lambiase R. Comparison of the findings of triple-injection cinearthrography of the wrist with those of arthroscopy. J Bone Joint Surg Am 1996;78A:348–356.
14. Wintman BI, Gelberman RH, Katz JN. Dynamic scapholunate instability: results of operative treatment with dorsal capsulodesis. J Hand Surg Am 1995;20:971–979.