FRACTURE OF SCAPHOID
The scaphoid acts as a link between the proximal and distal rows of the carpus and thus is quite susceptible to injury. Most fractures of the scaphoid waist result from an extension force applied to the distal pole, with the proximal pole stabilized by the strong radiocapitate and radioscaphoid ligaments. This mechanism of injury, for example, a fall on the outstretched hand, produces the most common fracture pattern a break through the waist of the scaphoid. Other patterns include fractures of the distal tuberosity and proximal pole and vertical shear fractures of the scaphoid body.
The blood supply to the bone plays an important role in the healing process, and sometimes osteonecrosis is a complication of scaphoid fractures. The major blood supply enters the junction of the waist and distal pole on the dorsal aspect, leaving the proximal pole with a relatively poor vascular supply. Fractures through the waist of the scaphoid disrupt most of the blood supply to the proximal pole, often leading to osteonecrosis.
Fractures of the scaphoid are the most commonly missed fractures of the upper limb; yet, early diagnosis is essential for successful treatment. The initial signs are tenderness and pain over the anatomic snuffbox, with some swelling and loss of the normal concavity of the dorsoradial region of the wrist. Also present is significant discomfort when the thumb is moved or the metacarpal of the thumb is compressed against the proximal carpal row.
Initial radiographs may not accurately demonstrate a fracture of the scaphoid waist. Special views are needed of the hand forming a fist and of the fist in ulnar deviation, positions that bring the scaphoid into extension. An occult fracture of the scaphoid can often be visualized by aiming the x-ray beam parallel to the suspected fracture line rather than at an acute angle to it. However, even with these special views of the wrist, some acute scaphoid fractures are not clearly seen.
If symptoms are present, even if radiographs are normal, the wrist should be immobilized in a thumb spica cast for 2 to 3 weeks. Follow-up radiographs after the plaster cast is removed often reveal a previously occult fracture. If pain persists, the cast is reapplied. Magnetic resonance imaging is another useful tool in evaluating the wrist with a suspected occult scaphoid fracture. Immediate magnetic resonance imaging has been shown to have high sensitivity and specificity for diagnosis of occult scaphoid fractures, as well as a favorable cost-benefit analysis compared with immobilization and repeat plain radiographs.
Most nondisplaced fractures of the scaphoid can be successfully treated by placing the limb in a thumb spica cast with the hand and wrist rigidly immobilized and the thumb in abduction. Some physicians recommend the use of an above-elbow cast, at least for the first 6 weeks of treatment, on the premise that above-elbow casting of scaphoid fractures may enhance union. Prompt recognition, secure immobilization, and careful follow-up remain the essentials of closed treatment. The rate of union in fractures that are immobilized initially is close to 95%. In fractures that are not immobilized initially, the nonunion rate is significantly higher. There is growing support for immediate percutaneous screw fixation of nondisplaced scaphoid fractures. Percutaneous techniques utilizing either volar or dorsal approaches have been shown to diminish the time required for immobilization with a faster return to work and sports. However, the overall union rates between cast immobilization and surgical screw fixation are equivalent. Contemporary management of nondisplaced scaphoid fractures takes into account the location of the fracture (proximal, waist, distal) and individualizes treatment based on the patient’s athletic, recreational, and vocational demands.
Any degree of displacement of a scaphoid fracture may be an indication of wrist instability. Displaced scaphoid fractures are often associated with ligament injuries that ultimately result in persistent wrist instability after the fracture heals. Displaced fractures should be treated with ORIF. Nonunion is much more common after displaced fractures. Therefore, a scaphoid fracture with a displacement greater than 1 mm requires ORIF to ensure union and wrist function.
Indications for immediate operative fixation of scaphoid fractures include displaced fractures, fractures associated with carpal instability, and nonunions. Relative indications for operative fixations include delay in diagnosis (greater than 4 weeks from injury), proximal pole fractures, and malunions.
The cannulated, headless screw, with threads of different pitches at either end, is a very effective device for stabilizing and compressing a scaphoid fracture. There are numerous implants on the market, all with the same goal of compression across the fracture.
Acute Nondisplaced Fractures
Operative fixation of acute, nondisplaced scaphoid fractures is increasing in popularity with the introduction of less invasive surgical techniques and advances in intraoperative imaging and instrumentation. Currently, acute scaphoid fractures can be repaired by means of open volar or dorsal approaches, percutaneous techniques, or arthroscopically assisted procedures. Common to all techniques is the use of biplanar imaging to confirm fracture reduction and central guide wire placement as well as the use of specially designed headless compression screws. Compromising accurate reduction and central screw placement, for the sake of a percutaneous approach, must be avoided. Immediate operative fixation of acute, nondisplaced scaphoid waist fractures has entered clinical practice and is quickly becoming the standard of care. Compared with prolonged cast immobilization, the number of healed fractures is equivalent, but times to fracture healing are significantly reduced. Taras and colleagues reported return to participation in sports averaged 5.4 weeks, with successful fracture union achieved in all patients undergoing percutaneous scaphoid fixation. We counsel our athletes about the risks and benefits of all treatment regimens and advocate percutaneous fixation for all athletes requesting a rapid return to competition. Although both volar and dorsal approaches have been described, we typically employ a dorsal approach to percutaneous internal fixation.
Acute Displaced Fractures
In acute, displaced scaphoid waist fractures, a volar approach to the scaphoid is used to preserve the dorsal blood supply. The fracture is reduced, with careful restoration of length and correction of the “humpback” deformity, and the cannulated, headless compression screw is applied volarly from distal to proximal. The critical step is to ensure appropriate screw position (centered throughout the bone on multiple oblique views).
Acute proximal pole scaphoid fractures should be approached through a dorsal approach. Reduction is confirmed, and a cannulated, headless compression screw is placed with accurate screw placement evaluated and confirmed on multiple radiographic/fluoroscopic images.
The management of the united scaphoid fracture is challenging. Initial diagnosis must be followed by a thorough history regarding the timing of injury and further studies to (1) evaluate for carpal collapse and arthritic destruction, (2) determine the vascularity of the proximal pole of the scaphoid, and (3) define the geometry of the fracture nonunion. All scaphoid non-unions require debridement of the nonunion site and bone grafting. Scaphoid waist nonunions with a viable proximal pole can be managed with a volar approach to the scaphoid, debridement of the nonunion, reduction, and use of autograft bone. Proximal pole nonunions or waist nonunions with avascular change to the proximal fragment require debridement and vascularized bone grafting either from the distal radius, thumb, or a distant site (e.g., medial femoral condyle). Any scaphoid nonunion with advanced degenerative changes is best managed with some type of salvage procedure (proximal row carpectomy, limited arthrodesis, or total wrist arthrodesis).