Advanced arthritis of the wrist can cause notable disability. It typically affects middle-aged men during their prime working years. Because joint replacement is associated with marked complications in active individuals, and because total wrist arthrodesis may result in unacceptable compromise of function, other motion-preserving procedures, such as proximal row carpectomy (PRC) and scaphoid excision with intercarpal arthrodesis, have become popular options.1 A comparison of the indications, techniques, and results of these two procedures can help elucidate their relative differences and aid in appropriate patient selection.
Primary osteoarthritis is relatively rare. Most cases of radiocarpal arthritis are secondary to structural changes that result in abnormal mechanics and are usually caused by chronic scapholunate dissociation or rotary subluxation of the scaphoid. The proximal carpal row acts as a mobile, intercalated segment between the rigid distal carpal row and the radius. When ligament disruption occurs between the bones of the proximal row, wrist instability develops. Disruption of the scapholunate interosseous ligament causes the lunate to dorsiflex or extend, creating the so-called dorsiflexed intercalated segment instability.2 The scaphoid flexes palmarly, causing an abnormal distribution of forces across the elliptical radioscaphoid joint and increased contact pressures, resulting in progressive degenerative changes.3 The sequential progression of arthritis that follows is known as the scapholunate advanced collapse (SLAC) wrist.4,5
Radiographic progression of the SLAC wrist is divided into three stages. Stage I consists of degeneration between the radial styloid and the distal pole of the scaphoid. Stage II describes the progression to involvement of the proximal pole of the scaphoid and scaphoid fossa (Fig. 1, A). In stage III, the capitate migrates proximally between the scaphoid and the lunate, resulting in degeneration at the capitolunate articulation (Fig. 1, B).
Chronic scaphoid nonunion follows a similar progression and has been described as the scaphoid nonunion advanced collapse (SNAC) wrist.6,7 Degeneration occurs between the radius and the distal pole of the scaphoid and progresses to involve the capitate-proximal pole articulation, while sparing the proximal poleradius articulation. The radiolunate joint typically is spared, even with advanced degenerative changes. This predictable distribution of arthritis is the basis of Watson's SLAC wrist procedure (capitohamate-lunotriquetral, or four-corner, arthrodesis combined with scaphoid excision), which transfers the loads across the wrist to the preserved radiolunate joint.4
A staged approach is commonly recommended for treatment of the SLAC wrist.7-9 A stage I SLAC wrist often can be managed with splints, nonsteroidal anti-inflammatory medica tions, or cortisone injections, although a radial styloidectomy can relieve symptoms in older, less active patients. For both stages I and II, PRC is preferred because it is simpler to do than the more technically difficult four-corner arthrodesis, has less potential for complications, has better motion recovery, and has proven durable results. The four-corner arthrodesis is preferred in the stage IIISLAC wrist with advanced capitolunate arthritis. This obviates concerns regarding the degenerative capitolunate joint and uses the preserved articulation between the lunate and radius to transfer joint forces. Either procedure can be relatively easily converted to a full wrist arthrodesis should the primary procedure fail and symptoms persist (Fig. 2).
Proximal Row Carpectomy
Stamm10 in 1944 described PRC as a method of restoring function to the wrist by converting it from a complex link system to a simple ball-and-socket joint. Despite favorable reports, PRC remained controversial and poorly accepted until the last decade. PRC works well and endures because the radiocapitate articulation relies on translation as well as rotation for wrist motion; this is because the curvature radius of the capitate is smaller than that of the radiolunate fossa. The translation may allow more dissipation of forces and decreased wear at the radiocapitate joint.11 Reports of wrist weakness and instability were the main argument against PRC. Although this subjective complaint was reported in older studies, more recently good recovery of grip strength and return to occupations requiring manual labor have been demonstrated.8,11-17 Degeneration may occur over time at the new articulation, but symptoms usually are mild (Fig. 3).
The primary indication for PRC is pain relief in patients with radiocarpal arthritis, which usually results from a SLAC or SNAC wrist after failure of nonsurgical treatment. The SLAC or SNAC wrist can have multiple etiologies, including scapholunate dissociation, scaphoid nonunion, and residual incongruencies from a perilunate dislocation. Patients with calcium pyrophosphate deposition disease also may develop a SLAC pattern of arthritis that may be amenable to PRC. Other inflammatory arthritides, however, such as rheumatoid arthritis, have not responded to PRC, and the procedure therefore is not indicated.17 Prerequisites for PRC are preservation of the capitate head articular cartilage and the lunate facet. However, Eaton et al18 reported satisfactory results with the use of fascial interposition even in patients with more advanced changes.
Scapholunate Advanced Collapse Procedure
The management procedure proposed by Watson and Ballet4 takes advantage of the spared radiolunate joint by redirecting the forces across the wrist through the remaining healthy articulation. The proposed advantages of the SLAC procedure over PRC include the following: (1) There is a better match of the radius of curvature of the lunate with the radius compared with the capitate (ie, the natural articulation is retained). (2) Degenerative changes at the capitolunate joint are not a contraindication to performing a four-corner fusion, as they are for performing a PRC. (3) The muscle-tendon units that cross the wrist maintain their relative lengths, thus decreasing the risk of weakness.4,5 Calandruccio et al19 described a modification of the procedure in which only the capitate and lunate are fused and both the scaphoid and triquetrum are excised.
Arthritis secondary to either SLAC or SNAC is the primary indication for the four-corner arthrodesis with excision of the scaphoid (Fig. 4). Similar to PRC, four-corner arthrodesis is not indicated in the patient with in-flammatory wrist arthritis and is contraindicated if the radiolunate articulation is degenerated.
Proximal Row Carpectomy
The carpus is typically exposed through a dorsal longitudinal incision through the third dorsal compartment; however, a transverse dorsal incision also has been described.20 The lunate is excised first because it is usually the easiest. Whenever possible, the triquetrum and scaphoid are then excised sharply; if that is not possible, they can be excised piecemeal. A threaded Kirschner wire (K-wire) can be used as a joystick to gain purchase on these small bones. Care should be taken to preserve the radiocarpal ligaments to prevent postoperative ulnar translocation of the carpus. Most surgeons no longer routinely do a radial styloidectomy during this procedure. Some authors have reported a slight increase in radial deviation after styloidectomy, but overall outcome is not notably improved.11,17 The dorsal wrist capsule is then repaired with sutures. Pin fixation of the carpus to the radius is not recommended because it does not improve outcome and is a frequent source of complications (eg, infection, migration). 8 The patient is immobilized postoperatively for a minimum of 2 weeks in a short arm cast, primarily for comfort, although slightly longer periods of immobilization have been recommended. Radiographs are obtained after 2 weeks to make sure the capitate is located in the lunate facet of the radius. The patient is placed in a removable splint and started on range-of-motion and strengthening exercises; activities are progressed as tolerated. Maximum strength may take 1 year or longer to achieve.
Four-Corner Arthrodesis With Scaphoid Excision
The wrist is exposed in a fashion similar to that described for a PRC. The scaphoid is then excised either sharply or, more often, piecemeal. Care should be taken not to transect the radioscaphocapitate ligament. If it is cut, there is a risk of destabilizing the remaining carpus and of possible ulnar translocation. The opposing surfaces of the capitate, hamate, lunate, and triquetrum are decorticated and the interstices filled with cancellous bone graft. Iliac bone graft is preferred, but the distal radius can be used as the donor site. The anatomic position of the four bones is maintained by leaving the volar capsular attachments and ligaments intact. The lunate is reduced relative to the capitate head to correct any extension malalignment of the lunate or carpal collapse. The bones are then stabilized with K-wires, staples, or small bone screws. Some newer implant devices have been developed specifically for this procedure, but there are no published series evaluating their efficacy. A Silastic scaphoid was inserted in the original description of the SLAC procedure.4 However, scaphoid replacement is unnecessary and to avoid the potential for silicone synovitis is not recommended.1,7-9 An alternative technique is to excise the scaphoid and triquetrum and fuse the capitate to the lunate with small bone screws.19 Results with this technique are comparable to those in other series of scaphoid excision and capitohamate-lunotriquetral arthrodesis. The wrists are immobilized postoperatively for 6 to 8 weeks in a short arm cast, after which the pins are removed. The duration of immobilization may be modified depending on radiographic evidence of fusion. A removable splint is then fashioned, and the patient is started on range-of-motion and strengthening exercises.
The PRC and four-corner arthrodesis with scaphoid excision are both good procedures for preserving motion in the painful posttraumatic arthritic wrist. However, there is controversy as to which procedure is more appropriate. The PRC has been used longer, and clinical results have been documented in multiple series.7-17 The most compelling evidence in support of the procedure is the number of series that corroborate excellent results (Table 1). Because it was introduced later, the SLAC procedure has shorter follow-up periods in published reports, although potential advantages have been indicated.4
Three clinical series have directly compared the two procedures and help to define the criteria for choosing between the two.7-9 The data from these series are similar. Based on the mean of the outcomes from the three studies, range of motion was consistently better in the PRC group, averaging 64% of the opposite side compared with 45% in the four-corner arthrodesis group.7-9 Grip strength varied between the series, but the mean of approximately 75% of the opposite side was not statistically different. 7-9 Pain relief and patient satisfaction were good for both groups; however, the failure rate differed somewhat between the series. Tomaino et al9 and Krakauer et al7 reported an approximate failure rate of 20% after PRC, with failure defined as an unsatisfied patient or conversion to wrist fusion. The failure rate after four-corner arthrodesis was much lower, with reported rates of 0%9 and 7%.7 Wyrick et al8 had a 30% failure rate after four-corner arthrodesis and unanimous patient satisfaction after PRC. The small patient populations probably account for the sometimes substantial percentage difference in outcomes between the three series. However, Cohen and Kozin21 reported no clear advantage of one method over the other in their comparative study of the two procedures.
Risk of complications is the other factor to be considered when choosing a procedure. A markedly higher number of patients have required further surgery to treat complications after four-corner arthrodesis. Most of the complications are implant-related, many caused by the use of staples.7,8 Symptomatic nonunions also can occur, but they are uncommon (<4%) as long as the arthrodesis includes the hamate and triquetrum rather than just fusion of the capitate to the lunate. 19,22 Calandruccio et al19 suggest that capitolunate fusion can be reliably achieved, but Kirschenbaum et al22 found the nonunion rate to be unacceptable. The difference may be related to the fixation method, with headless screws performing better than staples or K-wires.
A staged approach can be used to manage advanced wrist arthritis. A stage I SLAC wrist often can be managed nonsurgically with splints, nonsteroidal anti-inflammatory drugs, or cortisone injections. Occasionally, a radial styloidectomy can relieve the symptoms in the older, less active patient. If this fails or, more commonly, when the patient presents with a stage II SLAC wrist with a preserved capitolunate joint, PRC is preferred because it is technically less demanding and yields durable results. The patient should be made aware that as much as 1 year may be needed to achieve full rehabilitation of the hand and wrist. When salvage is necessary, a PRC can be relatively easily converted to a wrist fusion.7 For the patient with a stage III SLAC wrist, the critical decision is whether a complete or a partial wrist arthrodesis is more appropriate. This decision is usually predicated on patient factors (eg, whether motion needs to be preserved). If motion is a priority, scaphoid excision and four-corner arthrodesis can provide excellent results. Conversion to a total wrist arthrodesis can be relatively easily accomplished as a salvage procedure when pain relief is unsatisfactory.
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