Issue: April 2020
Disclosures: Rambau, Victoria and Wolfe report no relevant financial disclosures.
April 15, 2020
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Front, back reconstruction for scapholunate dissociation restores normal alignment

Issue: April 2020
Disclosures: Rambau, Victoria and Wolfe report no relevant financial disclosures.
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Scapholunate dissociation is a difficult and unresolved problem in orthopedic hand surgery. Scapholunate ligament repair alone leads to failure and progression of scapholunate advanced collapse wrist in 30% of patients within 6 months. Delays in presentation, often years after injury, can dramatically increase the level of complexity and worsen prognosis. Traditionally, the treatment options for advanced arthritis have been bleak, including salvage options such as scaphoid excision and four-corner fusion or proximal row carpectomy. For mostly young and active patients, these options leave them limited in their physical and occupational demands.

The anatomical front and back ligament reconstruction (ANAFAB) is a novel technique developed by Michael J. Sandow, BMBS, FRACS, FAOrthA, of Adelaide, Australia, that addresses this dilemma by restoring the critical ligaments that stabilize the scaphoid and collapsed central column of the wrist. It expands on the simplistic approach of addressing the scapholunate gap and combines multiple techniques to address the complex carpal mechanics. The transosseous reconstruction of four critical ligaments is what distinguishes this innovative procedure. Not simply addressing scapholunate, but reconstructing the scapho-trapezial-trapezoid, dorsal intercarpal and long radiolunate ligaments allows for restoration of carpal mechanics while preserving the native anatomy.

Indications

The finding of a scapholunate gap or the Terry-Thomas sign on the posteroanterior radiograph is the most obvious indicator of ligament rupture. Recent scientific findings have shown dorsal scaphoid translation, marked by abnormal scaphoid rotation and translation, has the highest correlation with patient outcomes (Figure 1). Other radiographic findings, including scapholunate interval greater than 60° and dorsiflexed intercalated segment instability (DISI) are indicative of multiple ligament interruption, in addition to the scapholunate gap. Early grade 1 scapholunate advanced collapse (SLAC) wrist may be present and should not preclude treatment, but is an indication for combined styloidectomy. Preoperative MRI or arthroscopy can help determine the quality of the cartilage and whether reconstruction is appropriate.

Figure1. A patient’s preoperative pencil grip view from November 2019 is shown (a). The scapholunate gap was 9.3 mm. The preoperative lateral view from November 2019 shows dorsal lunate tilt of 13° and dorsal scaphoid translation of 3.8 mm (arrow) (b).Figure 2. The same patient’s postoperative pencil grip view from March 2020 is shown. The scapholunate gap was 3.7 mm (a). The postoperative lateral view from March 2020 shows DISI is corrected to -12° and the dorsal scaphoid translation is 0.0 mm (b).

Images courtesy of Scott W. Wolfe, MD, 2020

Technique

A 4-cm longitudinal incision is made over the dorsum of the wrist just ulnar to Lister’s tubercle and dissection is carried through the fourth dorsal compartment with transposition of the extensor pollicus longus and subsequent posterior interosseous neurectomy. The interval between the third and fourth dorsal compartments is explored and a “window” approach, preserving the dorsal intercarpal ligament and the dorsal radiocarpal ligament is used. The cartilage is inspected, and the lunate and scaphoid mobility interrogated. If reducible and supple with preserved cartilage, then reconstruction is undertaken.

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Tunnel locations are then marked on the scaphoid and lunate, and attention then turned to the volar wrist. A 10-cm hockey stick incision is made overlying the scaphoid tubercle, which is exposed and the surface roughened to accept the tendon graft. Distally, the trapezium is exposed and a 3.5-mm suture anchor is then inserted with a two-ply synthetic surgical tape.

If indicated, a radial styloidectomy is performed. The radial tunnel is then created using a 3-mm cannulated drill over a guidewire, beginning at the origin of the radiolunate ligament and targeting Lister’s tubercle. A K-wire is placed through the scaphoid from the previously marked exit point dorsally through the scaphoid tuberosity. A K-wire joystick can assist with lunate positioning to allow the correct trajectory, which aims to exit at the volar-ulnar lunate surface and tangent to, but not breaching, the mid-carpal joint. All tunnels are over-drilled with a 3-mm drill and copious irrigation.

A 2.5-mm portion of flexor carpi radialis tendon is separated and divided from the muscle belly 15 cm proximal to the wrist crease. Further dissection is performed distal to the scaphoid tubercle, so the distal-based tendon graft will have the appropriate vector to reconstruct the palmar-radial scaphotrapeziotrapezoidal ligament complex. Using a suture shuttle, the tendon slip and two-ply synthetic tape are passed from volar to dorsal through the scaphoid. While holding the construct at maximum tension, a 3-mm x 8-mm interference screw is inserted into the distal scaphoid. The construct is next passed from dorsal to volar through the lunate. Before securing it, 2-0 braided synthetic suture is knotted and placed within the dorsal lunate hole, and the construct is maximally tensioned and secured to the dorsal lunate with a 3-mm x 8-mm interference screw. This braided synthetic suture is later used to reattach the dorsal intercarpal ligament to the dorsal lunate during closure. Lastly, the shuttle and tendon/tape construct are passed from palmar to dorsal through the radial tunnel to reconstruct the critical long radiolunate ligament. The construct is tensioned. A 3.5-mm bone anchor is used to bury the tendon and tape securely into the dorsal radial metaphysis. Final carpal alignment is analyzed with fluoroscopy and the wrist is taken through a full range of motion with confidence. Closure begins with a reapproximation of the dorsal intercarpal ligament and dorsal radiocarpal to the dorsal lunate. The capsular window is closed with 4-0 nonabsorbable braided suture. The skin is then closed in a layered fashion and a thumb spica splint applied. The splint is changed to a short-arm thumb spica cast at suture removal for the remainding 6 weeks. No K-wires are used to stabilize the carpus.

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Patient outcomes

Preliminary data on a cohort of 14 consecutive patients with average follow-up of 4.25 months demonstrated significant improvement in pain and functional scores of the patient-rated wrist and hand evaluation. Postoperative radiographic measurements demonstrated significantly improved scapholunate angle, scapholunate gap, radiolunate angle and dorsal scaphoid translation (Figure 2). Wrist range of motion decreased slightly and further time points are needed to determine final range of motion. One patient’s reconstruction failed by pullout from osteoporotic bone at 10 weeks and it was successfully revised to a proximal row carpectomy. Sandow published on 10 patients who demonstrated maintained scapholunate gap and improved carpal alignment with recovery of 75% grip strength and wrist range of motion at 24 months.

The ANAFAB procedure, although early in practice, shows promising results. It offers a robust restorative option for patients with acute or chronic scapholunate dissociation, characterized by scapholunate gap, scaphoid rotatory subluxation, DISI and dorsal scaphoid translation. It presents a reconstructive option for patients with early SLAC changes that preserves carpal mechanics and should help to avoid a salvage procedure. Further follow-up is needed to monitor the evolution of this technique.

Disclosures: Rambau, Victoria and Wolfe report no relevant financial disclosures.