Department of Orthopaedic Surgery, University of California Davis School of Medicine, 4860 Y Street, Suite 3800 Sacramento, CA 95817, USA
Despite improved understanding of carpal mechanics, increased awareness of intercarpal ligament injuries, and improved techniques for treating carpal instability, post-traumatic intercarpal osteoarthrosis remains a common problem. Osteoarthritis of the carpal bones, including scapholunate advance collapse (SLAC) wrist, scaphotrapeziotrapezoid (STT) arthritis, lunotri-quetral arthritis, triquetrohamate arthritis, and pisotriquetral arthritis, follows specific unique patterns, but in each, the final common pathway leads to degenerative change. Injury or deformity leads to instability and altered kinematics producing abnormal joint contact pressures. Cartilage injury and eventual degeneration of the joint follow. The etiology, prevalence, and current evaluation and treatment of these conditions is of importance to hand surgeons.
Scapholunate advanced collapse and scaphoid nonunion advanced collapse wrist
Scapholunate instability and collapse is by far the most frequent cause of noninflammatory degenerative arthritis of the wrist [1,2]. With a fall on an outstretched hand, the wrist moves into dorsiflexion, ulnar deviation, and supination. The first structure injured is the scapholunate in-terosseous ligament; with greater force, the radio-scaphocapitate, long radiolunate, and dorsal radiocarpal ligaments may be torn [3-5]. This progression of injury, described by Mayfield , can be seen radiographically as scapholunate
* Corresponding author. E-mail address: [email protected] (R.M. Szabo).
dissociation, triquetrolunate dissociation, and finally perilunate and lunate dislocation. With disruption of the scapholunate interosseous ligament, the scaphoid assumes a more flexed position; the capitate is able to move proximally, and the lunate, its connection to the triquetrum maintained, assumes a more dorsiflexed position. This pattern of carpal collapse or instability is described as dorsiflexion intercalary segment instability (DISI) (Fig. 1) .
Because of the particular geometry of the scaphoid and distal radius articular surfaces, stress risers develop at abnormal contact points of the articular surface. With time, the abnormal stresses lead to degeneration of the articular cartilage, and a typical pattern of arthritic change develops. The cascade of degenerative change begins with radioscaphoid arthritis, followed by capitolunate and scaphotrapeziotrapezoid arthritis. Ultimately, pan-wrist arthritis results [7,8]. As Watson and Ballet  described, the SLAC wrist pattern is classified into four stages . In Stage I, increased contact pressures lead to beaking of the radial styloid. Narrowing and arthrosis of the ra-dioscaphoid joint indicates progression to Stage II. In Stage III, arthrosis develops between the capitate and the scaphoid or the lunate. There is also proximal migration of the capitate. Finally, at Stage IV, all of the previous stage changes occur, along with degeneration of the radiolunate joint. When arthrosis is limited to the radial sty-loid, reconstructive procedures of the scapholu-nate ligament, along with styloid excision, are the treatment of choice . When there is arthrosis of the radioscaphoid joint (Stage II) or Stage III with additional arthrosis in the midcarpal joint, scapholunate ligament reconstructive procedures are no longer indicated. Stage II disease salvage
procedures such as four-corner fusion or proximal row carpectomy (PRC) preserve wrist motion and are preferable to total wrist fusion [10,11]. If the proximal capitate is arthritic, a PRC is contraindi-cated unless a soft tissue arthroplasty as described by Eaton  is added, and a four-bone fusion procedure is favored . Total wrist fusion is the standard treatment for Stage IV disease, although arthroplasty remains an option in selected patients.
Scaphoid nonunion advanced collapse (SNAC) wrist is analogous to the more common SLAC wrist . The natural history of scaphoid nonunion is one of progressive wrist arthritis [15,16]. In a retrospective review of 102 patients who had scaphoid nonunions, Inoue and Sakuma  found that the prevalence of arthritis was 22% in nonunions of less than 5 years duration, 75% in nonunions of 5 to 9 years duration, and 100% in nonunions of 10 years or more duration. Arthritic changes initially appear at the radiosca-phoid joint as radial styloid beaking and dorsal scaphoid osteophyte formation. Later changes include arthritis of the radioscaphoid, midcarpal arthritis, and finally pan-wrist arthritis. This pattern is very similar to that of the development of SLAC wrist, although with SNAC wrist, the radial fossa that articulates with the proximal pole of the scaphoid escapes degenerative changes until late in the disease process. The prevalence of a DISI deformity increases with time after nonunion . The four stages of progression of SNAC wrist are similar to the patterns seen with SLAC wrist, as have been described .
After obtaining a complete history of the patient's previous injuries, including location, duration, work history, aggravating factors, previous treatments, and job status, it is important to search for potential systemic causes of arthritis. Crystalline arthropathy or rheumatoid disease may cause an SLAC wrist pattern that may also involve the radiolunate joint [19,20]. Physical examination should include palpation for areas of maximal tenderness, which is actually one of the most useful tools for diagnosis of patients who have chronic wrist problems [21,22]. Areas to palpate include the scapholunate ligament area, STT joint, and the radial border of the scaphoid. Range of motion, grip strength, and neurovascu-lar status should also be assessed, and if indicated, appropriate provocative tests such as the scaphoid shift test are performed. It is important to note if a particular range of motion produces pain. For example, pain in radial deviation is common with early SLAC and SNAC wrist.
The initial radiographic evaluation should include at least four views of the wrist. These include a posteroanterior (PA) view, a lateral view, a clenched-fist ulnar deviation PA (scaphoid) view, and a 45° semipronated view. The PA view should be done with the patient's elbow flexed to 90° and the shoulder abducted 90°, with the forearm in neutral rotation (ulnar variance view). In the PA view without radial or ulnar deviation, Gilula's lines can be drawn and should be smooth. In addition, an abnormal outline of the lunate on the PA view may indicate a DISI or volar intercalated segment instability (VISI) deformity . The PA radiograph of a wrist with a DISI deformity shows the lunate with a wedge-shaped ulnar corner pointing toward the medial side of the wrist, whereas radiographs of a VISI deformity wrist tend to show the lunate with a C-shaped outline. The lateral of the wrist must be a true lateral, with the wrist in neutral rotation. In the true lateral view, the pisiform lies between the scaphoid tuberosity and the capitate head . The semipronated view places the dorsoulnar and radiopalmar portions of the wrist in profile. Additional views such as an AP clenched-fist view may help to assess the radiocarpal joint, the midcarpal joint, and the relationship of the scaphoid to the lunate (Fig. 2).
The treatment of SLAC wrist is controversial. Earlier stages of scapholunate dissociation may be treated with a combination of ligament repair and dorsal intercarpal ligament capsulodesis. Reported results of series by Blatt , Wyrick and colleagues , Szabo and coworkers , and Wintman and coworkers , indicate improvements in alignment and pain, although there is concern of these results diminishing with time. When diagnosis of the scapholunate ligament injury is delayed, the exact chronicity of the problem may be difficult to determine. Therefore, choosing the best surgical treatment option may be challenging, especially in cases of carpal collapse in combination with beginning osteoarthro-sis of the radial styloid and the proximal pole of the scaphoid (Fig. 3). Wieloch and colleagues  reported on eight patients who had Stage I SLAC wrist and underwent scapholunate ligament reconstruction. This was performed on average 66 months after the initial injury. At 2 years, five of eight patients reported wrist improvement after the scapholunate ligament reconstruction; however, three of eight patients reported worsening wrist symptoms. All of the patients had abnormal carpal height ratios, both pre- and postoperatively and at follow-up. The study authors' conclusions were that scapholunate dissociation with early stages of arthritis remains an unsolved problem . In a survey of American and Canadian hand surgeons, Zarkadas and colleagues  noted that, although there was a consensus on the treatment of early scapholunate ligament injuries, the treatment of chronic injuries was highly variable.
For Stage II disease, traditionally, a four-bone fusion (capitate, hamate, lunate, triquetrum) along with scaphoid excision was recommended for active patients. PRC was reserved for patients who had lower demands and who were also less tolerant of a longer period of immobilization . There has not been a randomized study comparing these two operations, but Cohen and Kozin  reported results of PRC versus four-corner fusion in two comparable groups of patients. In the study, two cohorts of patients from separate institutions performing exclusively either a scaphoid excision and four-corner arthrodesis or PRC for SLAC wrist were compared. In both groups, there were 19 patients who were comparable with respect to age, gender, dominance, stage of arthritis, or preoperative measures of pain and function. The length of the follow-up period averaged 28 months for the four-corner arthrodesis group and 19 months for the PRC patients. At follow-up, there were no significant differences in the wrist flexion-extension arc, averaging 81° in the PRC patients and 80° following four-corner ar-throdesis. Grip strength of the affected hand compared with the opposite hand averaged 71% for the PRC group compared with 79% for the four-corner arthrodesis patients.
Recently, Baumeister and colleagues  reported on a series of 38 patients who had Stage II disease—SNAC-wrist (n = 29) or SLAC-wrist (n = 9). Postoperative examination included range of motion and grip strength. Mean extension and flexion of the wrist reached 75°, which was 57% of that of the contralateral hand. Mean radial and ulnar deviation was 33°, compared with 52% of that of the contralateral hand. The average grip
strength was 50% of the unaffected side. Pain with strenuous activity was reduced by 40%, and resting pain was reduced by 77%. Three patients showed radiological signs of a radiocapitate ar-throsis. One patient needed conversion to a complete wrist arthrodesis. These results were noted at an average of 27 months after surgery, and were in agreement with the rest of the literature; however, consistent with other reviews of proximal row carpectomy, the long-term results are not known. In a separate study, Dacho and colleagues  reviewed their results in 49 patients at 47 months after midcarpal arthrodesis . Active range of motion was 56% of that of the nonoperated wrist and grip strength was 76%. Forty-five patients demonstrated bony consolidation; however, 6 patients needed further treatment with a total wrist arthrodesis because of pain or absence of bony consolidation. Overall, 77% of the patients returned to their original occupation, and 80% were satisfied with the final result.
Both PRC and scaphoid excision with four-corner arthrodesis are motion-preserving options for the treatment of SLAC arthritis, with minimal subjective or objective differences in short-term follow-up evaluations. Scaphoid excision and four-corner fusion is indicated in more severe disease, and appears to offer the potential for longer durability; however, there is little objective evidence to support this assertion (Fig. 4).
For early SNAC wrist, Soejima and coworkers  reported on a series of 9 patients in whom excision of the distal pole of the scaphoid gave good results at an average of 28.6 month follow-up. Before surgery, all patients had recalcitrant scaphoid nonunions and associated degenerative arthritis. Patients underwent excision of the distal scaphoid fragment. At an average of 28.6 months follow-up, wrist range of motion had improved from 51.4% to 94% of that of the opposite wrist. Grip strength improved from 40% to 77% of that of the opposite wrist. Based on a modified Mayo wrist scoring chart, clinical results were excellent in 6 patients and good in 3. Eight patients showed no radiographic progression of arthritis, whereas one patient who had a Type II lunate (facet articulation with hamate ) did progress to arthritis. Malerich and colleagues  reported on a series of 19 patients who underwent distal scaphoid excision for degenerative arthritis secondary to scaphoid nonunion. They also noted improvement in pain, grip strength, and range of motion with this procedure, although they cautioned that in patients who had capitolunate arthritis, symptoms tended to persist and degenerative changes progressed. Overall the results are encouraging for a procedure that is simpler and requires less immobilization than a four-corner fusion, at least in patients who had no capitolunate arthritis.
Fig. 4. (A) Patient with Stage III SLAC wist including capitolunate arthritis. (B) After partial scaphoid excision and four-corner fusion.
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