Approach Considerations
Asymptomatic scapholunate advanced collapse (SLAC) wrist generally does not warrant treatment, though some patients may require surgery for secondary problems (eg, carpal tunnel syndrome). Mild symptomatic SLAC also can often be managed nonoperatively.
For more symptomatic SLAC, operative intervention is warranted. Surgical planning is based on symptoms, physical findings, radiographic findings, and the surgeon's preference. Because more motion occurs at the radiocarpal joint than at the midcarpal joint and because the radiolunate joint is generally spared, a limited wrist fusion with scaphoid excision is an option, though a total wrist fusion is often more predictable in alleviating pain. In stage 1 SLAC with sparing of the capitolunate joint, a proximal-row carpectomy (PRC) may also be used to preserve partial wrist motion.
In a small study (13 wrists), Noback et al described good results with arthroscopic synovectomy, radial styloidectomy, and neurectomy for advanced (symptomatic stage 2 or 3) SLAC wrist. [16] Functional outcomes were good, and most patients experienced a reduction in pain with the ability to return to work.
Medical Therapy
It is not uncommon to encounter a patient with an asymptomatic SLAC wrist. [17] The patient should be informed of the problem but may not require any treatment. If symptoms are present, the patient should be informed of the various options for treatment.
Mild symptomatic SLAC can often be managed nonoperatively with periodic steroid injections, splinting, and NSAIDs. If the grip strength of the SLAC wrist is greater than 80% of that of the uninvolved wrist and the condition is not giving rise to significant impairment, then living with SLAC is a valid option. [18]
Surgical Therapy
SLAC reconstruction (limited wrist fusion)
A SLAC reconstruction involves excision of the scaphoid and arthrodesis of the capitate, lunate, hamate, and triquetrum. [19]
Two parallel dorsal transverse incisions, a lazy S incision, or a central longitudinal incision over the distal radiocarpal joint and styloid process is made. The extensor retinaculum is incised through the third dorsal compartment. The terminal branch of the posterior interosseous nerve in the floor of the fourth extensor compartment can be sacrificed as an adjunctive pain relief measure. The wrist capsule is opened over the capitolunate joint.
The scaphoid is resected in piecemeal fashion. Articular cartilage and subchondral bone are removed from the capitate, lunate, hamate, and triquetrum. Care should be taken to maintain the anatomic relations of the intercarpal intervals. Cancellous bone is harvested from the distal radius, the proximal ulna, or the iliac crest.
Lunate dorsal intercalated segment instability (DISI) should be corrected, and five percutaneous Kirschner wires (K-wires) are used. Two wires are placed through the capitate into the lunate, one each through the hamate and through the triquetrum into the lunate, and a fifth through the triquetrum into the capitate. Cancellous bone graft is packed between the interstices of the four bones.
A long arm splint is placed after the procedure. After a week, the splint is replaced with a long arm cast, which is maintained for 3 weeks. A short arm cast is then placed and maintained for an additional 2-4 weeks. The cast and wires are removed when fusion is evident on radiographs. (See the images below.)
Scapholunate advanced collapse (SLAC) wrist from nonunion of the scaphoid. The patient underwent 4-bone fusion.
Scapholunate advanced collapse (SLAC) wrist from nonunion of the scaphoid. The patient underwent 4-bone fusion.
Some fixation methods in this four-quadrant fusion include the use of intercalary screws and a dorsal carpal plate marketed especially for this fusion. The relevant question is whether the increased cost of such devices results in improved outcomes. More solid fixation does allow the use of a short arm cast and earlier initiation of wrist range-of-motion (ROM) therapy. [20] In a study by Tielemans et al, a four-corner fusion that used a locking plate without a bone graft yielded results equal to those reported with grafting. [21]
Arthroscopic assistance may be considered. [22] Arthroscopic four-corner arthrodesis is technically demanding and has a steep learning curve. [23]
Patients with radiolunate changes are not candidates for SLAC reconstruction. A wrist arthrodesis should be performed instead.
Proximal-row carpectomy
PRC requires resection of the proximal row of wrist bones to allow articulation of the capitate within the lunate fossa. [24, 25, 26]
For a successful procedure, both the proximal capitate articular surface and the lunate fossa should ideally be free of pathology. The procedure is usually effective only when the disease is restricted to the radioscaphoid joint. PRC yields the best ROM (average arc, 71°) but may be associated with painful narrowing of the radiocapitate joint. It is not indicated for stage 2 SLAC wrist. It may serve as a salvage procedure for stages 1A and 1B when limited wrist fusion is not indicated. If PRC fails, conversion to wrist arthrodesis is necessary.
A dorsal longitudinal or transverse incision is made. The extensor tendons are retracted. A longitudinal capsulotomy is extended radially and ulnarly. The capitate is identified, and its articular surface is inspected. In the presence of capitate degenerative changes, the procedure should not be performed.
If both the proximal capitate articular surface and the lunate fossa are free of pathology, the scaphoid, lunate, and triquetrum are excised. Both the radioscaphocapitate ligament and the long radiolunate ligament are preserved. Wrist collapse follows, with placement of the capitate head in the lunate fossa along with radial deviation of the wrist. If impingement between the radial styloid and the trapezium is present, a limited radial styloidectomy is performed. The capsulotomy incision is closed snugly.
After the procedure, the wrist is splinted for 4 weeks. Early active digital flexion and extension are recommended. ROM exercises start 4 weeks after the procedure. Strengthening exercises and heavy lifting may begin 3 months after the procedure.
Comparisons between PRC and other techniques were published by Vanhove et al [27] and Dacho et al. [28] Van Riet and Bain presented findings using memory staples in the three-corner wrist fusion technique. [29] A systematic review and meta-analysis of 15 studies by Ahmadi et al recommended PRC over four-corner arthrodesis as the preferred procedure, though the quality of the evidence was not high. [30]
Total wrist arthrodesis
Total wrist fusion (see the images below) diminishes pain, but wrist function is sacrificed. Patients may have functional limitations that interfere with their lifestyles, and total fusion does not always result in complete pain relief.
A central dorsal longitudinal incision is made, and the extensor retinaculum is incised. The incision is carried down to bone surface from the middle-finger metacarpal to the distal radius, raising capsular and periosteal flaps.
Articular cartilage and subchondral bone are resected from the radioscaphoid, radiolunate, lunocapitate, scaphocapitate, and middle-finger carpometacarpal (CMC) joints. The radioulnar joint should not be entered. The index-finger CMC joint may also be opened for fusion. The radial metaphysis is generally used for the necessary cancellous bone graft, and more distal harvest is not required.
Bone grafts are placed in the radiocarpal, midcarpal, and CMC fusion sites, and a wrist fusion plate is applied. [31] The fusion plate is secured with screws at the middle-finger metacarpal, the capitate, and the radius. The periosteal and capsular flaps are reapproximated. A short arm splint is applied until fusion can be seen on radiographs. Fusion is usually evident in 6-8 weeks. [32, 33]
Total wrist arthroplasty
Total wrist arthroplasty is an alternative for diffuse arthrosis of the wrist, especially in rheumatoid arthritis and in the presence of bilateral disease. [34] With bilateral disease, a combination of a total wrist arthroplasty and a contralateral total wrist fusion is an option. Numerous implants have been used; however, major complications (eg, implant loosening and wear of the components) are common.
Mosillo et al performed a systematic review of seven studies involving the adaptive proximal scaphoid implant (APSI), a device made from pyrocarbon that is used to replace the proximal part of the scaphoid. [35] In all of the studies, grip strength and the flexion extension arch were improved in comparison with preoperative values; 17.3% of patients reported progression of osteoarthritis with the APSI, and the implant mobilization rate was 5.1%.
Complications
SLAC reconstruction
In a series of 250 procedures, Watson and Weinzweig reported nonunion in 1%, wound infection in 1%, reflex sympathetic dystrophy in 1.5%, and capitate-radial impingement necessitating revision arthroplasty in 13%. [36] The high incidence of dorsal impingement was the result of noncorrection of the lunate DISI deformity. A flexion/extension arc of 60-65° can be expected with a four-bone fusion. Brown and Erdmann presented complications after 50 consecutive limited wrist fusions. [37]
Proximal-row carpectomy
Krakauer et al compared SLAC reconstruction with PRC and found that patients with PRC had 71° of motion, whereas patients with SLAC reconstruction had 54° of motion. [38] They recommended PRC for patients without lunate pathology and SLAC reconstruction for patients with capitolunate arthritis.
Wyrick et al presented similar results and recommendations. [39] In the PRC group, total wrist motion was 85° and grip strength 94%; in the SLAC reconstruction group, total wrist motion was 67° and grip strength 74%.
Imbriglia et al presented the results of long-term follow-up after PRC. [40] Four years after the procedure, 26 of 27 patients had pain relief, ROM did not deteriorate, and 80% of patients improved their grip strength.
PRC appears to offers better ROM and almost normal grip strength. In some patients, conversion to wrist arthrodesis may be required because of the persistence of severe pain. [41, 42, 43, 44]
Kiefhaber et al reported a higher number of complications in the four-corner fusion group, including nonunion and hardware-related problems. [45] The failure rate and the need to convert to a fusion were greater in patients who have a PRC and are younger than 35 years. The authors preferred a four-corner fusion for patients younger than 35 years and for middle-aged patients with high demand, while favoring a PRC for all others.
Total wrist arthrodesis
Hastings et al reported a 2% nonunion rate with total wrist fusion. [46] The most common nonunion site was the middle-finger CMC joint. To prevent this complication, complete decortication of the dorsal 80% of the CMC joint is recommended. Other complications were tendon adhesions (in 3.5% of patients), carpal tunnel syndrome, and iliac crest harvest site problems (in 1.7% of patients).
Weiss et al discussed upper-extremity function after arthrodesis. [47] Dacho et al described long-term results. [48]
Total wrist arthroplasty
Major complications, including implant loosening and wear of the components, are common.
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Stage 2 scapholunate advanced collapse (SLAC) wrist.
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Scapholunate advanced collapse (SLAC) wrist from Kienböck disease.
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Scapholunate advanced collapse (SLAC) wrist from nonunion of the scaphoid. The patient underwent 4-bone fusion.
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Scapholunate advanced collapse (SLAC) wrist from nonunion of the scaphoid. The patient underwent 4-bone fusion.
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Scapholunate advanced collapse (SLAC) wrist treated with total wrist fusion.
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Scapholunate advanced collapse (SLAC) wrist treated with total wrist fusion.
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Stage 2 scapholunate advanced collapse (SLAC) wrist treated with 4-bone fusion.
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Stage 2 scapholunate advanced collapse (SLAC) wrist treated with 4-bone fusion.
