Scapholunate advanced collapse (SLAC) is a predictable pattern of degenerative wrist arthritis that develops as a result of scapholunate dissociation. The purpose of this article is to review outcomes for the various motion-sparing surgical treatments for SLAC wrist.
Key points
- •
Scapholunate advanced collapse (SLAC) occurs as a result of altered biomechanics after scapholunate dissociation.
- •
Proximal row carpectomy (PRC), scaphoid excision and four-corner arthrodesis (FCA), and wrist denervation are motion-sparing techniques designed to treat SLAC wrist.
- •
There are no Level I studies comparing PRC with FCA for treatment of SLAC wrist; however, systematic reviews and comparative studies suggest that there are minimal differences between PRC and FCA with respect to functional outcomes.
- •
Specific subgroups of patients may benefit from 1 procedure over the other. PRC may be preferred in smokers, and FCA may be preferred in patients younger than 35 years.
Introduction
Scapholunate advanced collapse (SLAC) is a predictable pattern of degenerative wrist arthritis that develops as a result of scapholunate dissociation. Watson and Ballet described the sequence of degenerative changes starting with narrowing at the radial styloid, progressing to the radioscaphoid joint, and terminating at the capitolunate articulation ( Fig. 1 ). The radiolunate articulation is commonly spared in SLAC. Total wrist arthrodesis is a reliable method for obtaining pain relief but has the disadvantage of sacrificing wrist motion. Motion-sparing procedures have been designed to relieve pain while maintaining some wrist range of motion. The purpose of this article is to review outcomes for the various motion-sparing surgical treatments for SLAC wrist ( Fig. 2 ).
Introduction
Scapholunate advanced collapse (SLAC) is a predictable pattern of degenerative wrist arthritis that develops as a result of scapholunate dissociation. Watson and Ballet described the sequence of degenerative changes starting with narrowing at the radial styloid, progressing to the radioscaphoid joint, and terminating at the capitolunate articulation ( Fig. 1 ). The radiolunate articulation is commonly spared in SLAC. Total wrist arthrodesis is a reliable method for obtaining pain relief but has the disadvantage of sacrificing wrist motion. Motion-sparing procedures have been designed to relieve pain while maintaining some wrist range of motion. The purpose of this article is to review outcomes for the various motion-sparing surgical treatments for SLAC wrist ( Fig. 2 ).
Four-corner arthrodesis
Intercarpal arthrodesis as a treatment for painful degenerative conditions of the wrist was initially proposed by Watson and Ballet when it was noted that many patients with congenital coalitions of the carpal bones had pain-free fully functioning wrists. In their technique, k-wire fixation was used to hold the lunate, capitate, hamate, and triquetrum in position until arthrodesis occurred ( Fig. 3 ). Watson and Ballet reviewed 16 patients treated with scaphoid excision and 4-corner fusion and noted 1 nonunion that was successfully treated with repeat bone grafting. All patients returned to work and had minimal pain at follow-up in this series. Other authors have obtained similarly good results with high union rates using k-wire fixation. Krakauer and colleagues had a 91% union rate (21/23) using mostly k-wires for fixation (19/23). Patients obtained a mean flexion extension arc of 54°, and grip strength improved from 59% to 78.5% of the contralateral wrist. Cohen and Kozin reported a union rate of 95% (18/19) and reported a mean flexion extension arc of 80° and grip strength of 79% of the contralateral side. The disadvantage of this technique is that the patient must return to the operating room, typically 8 to 10 weeks after the index procedure, to have the k-wires removed.
Although high union rates have been reported in the literature (>90%) with k-wire fixation, circular plate fixation was been introduced as alternative to theoretically improve union rates and avoid the need for k-wire removal. Despite the theoretic advantage of increased stability, the nonunion rates in several series have been surprisingly high (25%–63%). Kendall and colleagues reviewed the results of 4 surgeons using the circular plate for the first time. Only 3 of 8 patients who returned for final radiographs achieved union. Grip strength was 56% of the opposite wrist, and the mean flexion extension arc was 61°. Vance and colleagues reviewed 58 patients who had undergone FCA with various techniques. Twenty-seven patients had plate fixation, and 31 patients had traditional fixation (k-wires, Herbert screws, staples). The traditional group had a nonunion rate of 3%, and the plate group had a nonunion rate of 26%. Grip strength and range of motion compared with the opposite side were 70% (plate)/79% (traditional) and 48% (plate)/50% (traditional), respectively. Shindle and colleagues reported on 16 patients undergoing 4-corner fusion with circular plate and had a 25% nonunion rate and a 56% overall complication rate. Circular plates have also been associated with decreased range of motion, compared with k-wires postoperatively. De Smet and colleagues reported on 28 patients undergoing FCA and found that traditional methods had better postoperative flexion than the plate fixation group, 33° versus 23°, respectively. Despite the reports of high nonunion rates, other authors have published union rates as high as 100%. Bedford and Yang reported a 100% union rate on 15 patients undergoing 4-corner arthrodesis with a circular plate. Patients in this series achieved range of motion and grip strength of 71% and 78% of the opposite side, respectively. Merrell and colleagues reported a 100% union rate for the capitolunate articulation in 28 patients using a circular plate. The mean flexion extension arc was 61°, and grip strength was 82% of the opposite side. These authors attributed the high union rate to using bone graft from the distal radius, placement of 2 screws in each bone, and thorough debridement of all chondral surfaces.
The primary goal of an FCA is the fusion of the capitolunate joint. The fusion of the triquetrum and hamate was added, because early reports of isolated capitolunate fusion had higher nonunion rates. Kirschenbaum reported a fusion rate of only 67% (12/18) in patients undergoing an isolated capitolunate fusion with a combination of staples and k-wires. The mean flexion extension arc was 50°, and grip strength was 67% of the opposite side. Calandruccio and colleagues reported on 14 patients who underwent isolated capitolunate fusion with a compression screw with scaphoid and triquetrum excision ( Fig. 4 ). The authors reported a union rate of 86%, mean flexion extension arc of 53°, and grip strength 71% of the contralateral side. Gaston compared 16 patients who underwent capitolunate fusion with 18 patients who underwent traditional FCA. There was a slight increase in the mean flexion extension arc in the capitolunate group (58%) compared with the traditional FCA (48%). The capitolunate group had a 100% union rate, and there were no differences in any other outcome measures; however, 5 patients in the capitolunate group required screw removal for migration. Overall clinical results of isolated capitolunate arthrodesis are similar those of FCA.
