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INTRODUCTION
Because of the unique anatomic position of the scaphoid—in both proximal and distal carpal rows—its integrity is fundamental to the stability of the midcarpal joint and the normal biomechanical function of the wrist. The pivotal role of the scaphoid in carpal mechanics is underscored by the natural history of both chronic scaphoid nonunion and scapholunate dissociation. Although complete scaphoid resection routinely results in carpal collapse and patient dissatisfaction if midcarpal fusion is not performed, there are situations in which partial excision of the scaphoid may be indicated.
In this chapter, three clinical scenarios are addressed for which resection of the distal scaphoid represents a viable treatment option and is unassociated with the carpal dysfunction that results when either the proximal pole or the entire scaphoid is removed. These include (1) excision of the distal fragment of a scaphoid nonunion, (2) distal scaphoid excision for the treatment of scaphotrapeziotrapezoid (STT) arthritis, and (3) distal scaphoid excision in association with radiocarpal fusion.
EXCISION OF THE DISTAL FRAGMENT OF A SCAPHOID NONUNION
Distal pole resection obviously eliminates bone grafting, risk of nonunion, and lengthy immobilization. When the patient is satisfied with preoperative wrist extension, even when a fixed dorsal intercalated segmental instability (DISI) deformity already exists owing to collapse and when arthritis is limited to the radial styloid–scaphoid distal pole, the expected outcome is satisfactory pain relief and functional return. Unless an attempt at scaphoid salvage is contemplated, which might be advisable in the absence of arthritis or previous attempts at obtaining union, there is little downside to this option. If unacceptable carpal collapse occurs after the procedure, midcarpal fusion or proximal row carpectomy can still be used to solve the problem.
Indications
Most waist level and distal scaphoid fractures heal if they are nondisplaced and adequately immobilized until union. Moreover, fixation techniques, largely revolving around the use of headless compression screws, make union likely even when original displacement mandates operative intervention. However, when scaphoid nonunion is chronic, in the setting of periscaphoid arthritis, or when previous attempts at scaphoid union have been unsuccessful, excision of the distal fragment is a feasible alternative to either complete scaphoid excision with midcarpal fusion or proximal row carpectomy ( Fig. 37-1 A–F).
Contraindications
There are really only two contraindications to resection of the distal scaphoid: (1) wrists in which capitolunate or radioscaphoid (proximal pole) arthritis exists, and (2) wrists without a DISI deformity, in which significant carpal collapse may result after partial resection, thereby limiting wrist extension and grip strength.
Surgical Technique
After regional or general anesthesia has been administered and after tourniquet inflation, the hand is supinated and a 3- to 4-cm incision is made over the flexor carpi radialis (FCR), centered at the level of the radial styloid process. After incising the sheath and retracting the FCR tendon radially, the floor of the FCR sheath and the radiocarpal ligaments are incised. The tuberosity of the scaphoid is palpated, the distal fragment is exposed, and the scaphotrapezial joint is opened. The distal pole of the scaphoid is removed. The volar radiocarpal ligaments are closed with absorbable suture, as is the floor of the FCR sheath. The skin is closed with nylon suture, and a thumb spica dressing is placed for 2 weeks.
Results
Malerich and associates reported excellent results in 1999 in a group of patients with periscaphoid arthritis secondary to chronic scaphoid nonunion. Wrist motion and grip strength improved 85% and 34%, respectively. In 2006, Ruch and Papadonikolakis reported similar improvements in 13 patients who were treated with resection of the scaphoid distal pole for persistent nonunion after previous surgical treatment. A volar Russe-type approach is recommended, and the wrist is immobilized in a thumb spica splint for 2 weeks postoperatively.
DISTAL SCAPHOID EXCISION FOR SCAPHOTRAPEZIOTRAPEZOID ARTHRITIS
In light of the normal scaphoid rotation that accompanies radial and ulnar kinematics, it is not surprising that the elimination of this that is a consequence of triscaphe fusion might be problematic. Indeed, painful nonunion, radial styloid impingement, and radioscaphoid arthritis each may complicate outcomes following STT arthrodesis.
Triscaphe arthrodesis may be but one of several options when treating Kienböck’s disease or scapholunate dissociation, but painful STT osteoarthritis has historically required fusion ( Fig. 37-2 ). When pantrapezial disease exists as well, however, the triscaphe disease may be addressed as part of a “basal joint reconstruction,” which includes partial trapezoid excision.
Indications
When isolated STT osteoarthritis is present, another alternative consists of resecting the distal fourth of the scaphoid, with or without soft tissue (dorsal capsule or tendon) interposition.
Contraindications
The only contraindication, as with partial resection for scaphoid nonunion, is when there is already a substantial DISI malalignment pattern, which, if bothersome from the standpoint of lack of wrist extension, will not improve with distal pole resection.
Results
Garcia-Elias and associates reported favorable outcomes with this procedure, successfully avoiding the potential downsides of STT arthrodesis. In 12 wrists the joint defect was filled with either capsular or tendinous tissue, whereas in 9 wrists no fibrous interposition was done. At an average follow-up of 29 months (range 12–61), 13 wrists were pain-free, whereas 8 had occasional mild discomfort. Mean wrist flexion-extension was 119 degrees. Grip and pinch strength improved by an average of 26% and 40%, respectively, compared with their preoperative status. Although patient satisfaction was comparable for both types of treatment, the wrists without fibrous interposition showed significantly greater wrist flexion-extension than wrists with soft tissue interposition. However, removal of the distal scaphoid resulted in a DISI pattern of carpal malalignment in 12 wrists; still, at final follow-up, none of these wrists showed further joint deterioration due to residual malalignment.
Unlike STT fusions, which require lengthy immobilization and are plagued by an array of potential complications, STT resection-interposition arthroplasty is a simple procedure that requires only 2 to 3 weeks of immobilization.
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