The scaphoid is a component of the proximal carpal row and is the only bone to bridge both proximal and distal rows. It is an important component in normal wrist function. While it is the most commonly fractured bone of the carpus, fractures are uncommon in children and it remains cartilaginous. Approximately 80% of the surface is covered with articular cartilage, leaving a thin strip around the dorsal waist where most blood supply enters. The scaphoid has two (not one) vascular pedicles, both of which originate from the radial artery: one at the distal tubercle, supplying 20%, and the other along the dorsal ridge which supplies the remaining 80%. There are no vessels entering proximal to the wrist, hence the higher rate of nonunion and avascular necrosis with proximal fractures. During surgery, care should be taken to preserve the dorsal ridge region of vascular supply. The dorsal scapholunate ligament is far stronger than its volar counterpart and this serves to prevent excessive flexion of the scaphoid relative to the lunate.1–4
The standard approach to imaging for suspected scaphoid fractures is five-view radiographs. There are variations between institutions regarding the series of images acquired. A typical series includes posteroanterior (PA), lateral, oblique, clenched fist, and scaphoid views. Despite this, normal radiographs cannot always exclude a scaphoid fracture, so they may need to be repeated after 2 or 3 weeks or augmented by additional investigations. CT imaging can provide a more detailed examination of the scaphoid. After a few weeks, bone scans can also be useful because they show increased isotope activity along the fracture line. However, they may tend to overdiagnose fractures. While CT is helpful in identifying the scaphoid and its alignment, MRI is preferred by many in the acute phase, as other causes of pain (such as bone contusions) may also be demonstrated. However, the cost of this modality and the difficulties in getting timely access to scans precludes its routine use in most patients. Furthermore, MRI and CT may each still underdiagnose scaphoid fractures. There are two main mechanisms of injury for scaphoid fracture: axial loading from a punch injury and hyperextension injuries, such as occurring during a fall onto the outstretched hand. Axial loading frequently results in fractures of the scaphoid waist. Although tenderness in the anatomic snuffbox is common in scaphoid fractures, it is nonspecific and is seen in some normal people and with many other conditions. When there is an acute scaphoid fracture present, there is normally additional volar or dorsal tenderness identified.1–5
Most nondisplaced scaphoid fractures heal well with immobilization. However, internal fixation is recommended for proximal pole fractures because of high rates of nonunion. Otherwise, internal fixation is usually reserved for displaced fractures and those with delayed union. Internal fixation uses a solid or cannulated screw placed across the fracture site. Screws with a differential pitch are preferred to provide compression across the fracture site. Nonoperative management requires an extended duration of immobilization for a total of 6 to 12 weeks depending on the fracture location. There is debate surrounding the type of cast. Some would recommend that the first 6 weeks should be in a long-arm thumb spica cast and the second 6 weeks in a short-arm thumb spica cast, whereas others would recommend leaving the thumb free and splinting in slight dorsal extension for 6 to 12 weeks until clinical union.1 Consequently, a patient’s profession should be taken into account when selecting treatment, as internal fixation may be preferable to reduce the immobilization period. It is not the main factor, however, in guiding treatment for a proximal pole fracture. Either a dorsal or volar approach can be used for internal fixation, but the dorsal approach provides a better exposure of the proximal pole.1–3
4. Gelberman RH, Panagis JS, Taleisnik J, Baumgaertner M. The arterial anatomy of the human carpus. Part I: The extraos- seous vascularity. J Hand Surg Am 1983;8(4):367–375
5. de Zwart AD, Beeres FJ, Rhemrev SJ, Bartlema K, Schipper IB. Comparison of MRI, CT and bone scintigraphy for suspected scaphoid fractures. Eur J Trauma Emerg Surg 2016;42(6):725–731
The trapezoid is the least commonly fractured carpal bone, as it is well protected by the surrounding osseous anatomy and the strong carpal ligaments surrounding tissues. However, it may be injured during significant trauma to the wrist in conjunction with other associated injuries. Displaced fractures should be treated with anatomic reduction and fixation. Chronic injuries may require second CMC joint arthrodesis. The scaphoid is the most commonly fractured carpal bone, accounting for 70% of all such fractures. It may be injured by either forced hyperextension or severe axial loading of the wrist. The triquetrum is the second most commonly fractured carpal bone and occurs most often as an avulsion fracture secondary to ligamentous injury pulling small bony fragments off the dorsal rim. Trapezium and lunate fractures are both rare fracture types. Trapezium fractures are not usually seen in isolation and tend to be associated with ligamentous injury. They can occur secondary to a crush injury against the radial styloid or with first metacarpal base fractures. Lunate fractures usually occur in association with ligamentous injuries of the wrist or from axial compression between the capitate and lunate fossa on the radius.1,2
Kienbock’s disease is a condition of avascular necrosis of the lunate. It may occur spontaneously or following a nonunion of a lunate fracture. Kienbock’s disease may first present with a pathologic fracture of the lunate. Prompt management of displaced lunate body fractures is therefore advocated to minimize the risk of nonunion and subsequent development of Kienbock’s disease. Overall, lunate fractures are thankfully rare and occur in association with ligamentous wrist injuries. Kienbock’s disease most commonly occurs in young adult males and the main presenting symptom is dorsal wrist pain which tends to be activity related. Management will depend on severity of the condition. This includes conservative options with nonsteroidal anti-inflammatory drugs and immobilization as well as operative options including radial wedge osteotomy, partial wrist fusion, complete wrist fusion, proximal carpectomy, total wrist arthroplasty, or vascularized bone grafts.1,2
mechanism.” The capitate is at risk of transverse body fracture during forced hyperextension when it is forced against the distal radius through the anvil mechanism (Fig. 73.1). This can result in 180-degree rotation of the proximal fragment which cannot heal without formal reduction and stabilization. Patients remain at risk of avascular necrosis of the proximal fragment.1 Fig. 73.1 Anvil mechanism resulting in capitate body fracture.
Hamate fractures may be subdivided as either hamulus fractures (hook of hamate) or hamate body fractures. Hook of hamate fractures occur secondary to direct trauma to the hand while holding an object such as a bat or racket. Alternatively, they may occur during falls onto the outstretched hand. Untreated hook fractures can present with delayed spontaneous rupture of the little finger flexor tendons. Attrition ruptures of the tendon occur secondary to degenerative bony changes at the fracture site where nonunion has occurred. In this case, the hamulus fragment should be excised in addition to addressing the flexor tendon ruptures. Hamate body fractures tend to be associated with fourth and fifth metacarpal base fractures rather than delayed tendon injuries. A careful ulnar nerve examination is needed in hook of hamate fractures as the deep motor branch is particularly at risk of injury.1–5
Hook of hamate fractures are demonstrated in lateral, oblique, and carpal tunnel views. The AP view of wrist is a core component of a wrist series. The 45-degree pronated oblique view is used to image the triquetrum. AP in ulnar deviation is a component of a scaphoid series. The reverse oblique view is a 45-degree supination view with the wrist extended that demonstrates pisiform fractures.1,2