The scaphoid is the largest bone of proximal carpal row and acts as an important stabilizing link between the proximal and distal rows. Because of its peculiar boat configuration, with the medial and distal concavity, the anatomists have compared this bone to a ship (scaphon in Greek means boat).
One can palpate the waist and distal third of the scaphoid in the middle third of the snuffbox. At the distal end of the snuffbox the Scapho-Trapezio-Trapezoidal (STT) joint is identified. Moving ulnarly to the extensor pollicis longus is a landmark, lister’s tubercle, which is the key to identifying the junction of scapholunate joint and dorsal scapholunate interosseous ligament.
The scaphoid receives the majority of its blood supply via dorsal vessels at or just distal to the waist area, these vessels perfuse the proximal pole in a retrograde fashion (from distal to proximal). This explains the problems of delayed union and non-union with fractures of the proximal pole of the scaphoid. There is a spectrum of movements of scaphoid in two planes. More specifically the scaphoid can flex, translate or supinate on the radius, or more commonly move by combination of two or three of these during radial of ulnar deviation.
Fractures of the scaphoid represent nearly 2% of all fractures. Among all wrist injuries, the incidence of fractures of the scaphoid is second to that of fractures of the distal radius. Fractures of the scaphoid comprise 70% to 80% of injuries to the carpal bones. Scaphoid fracture has been reported in persons from 10 to 70 years of age although it is found most commonly in young adult males. It is caused by a fall on the outstretched palm, resulting in severe hyperextension and slight radial deviation of the wrist. Other mechanisms include palmar flexion, as occurs in an over-the-handle-bars motorcycle accident or twisting injuries in sports.
Despite adequate non-operative treatment, scaphoid fracture nonunion occurs at a rate of 3% to 10%. The rate of nonunion in patients who do not receive treatment for scaphoid fracture is markedly higher. The failure has been attributed to delay in beginning treatment, inadequate immobilization, displacement of the fragments, instability due to ligamentous injury, or inadequate blood supply of the proximal fragment.
A fracture nonunion is defined as absence of evidence of healing at 6 months after injury. A delayed union of fracture is considered to be present if there is no evidence of healing after 3 months. Although other method of diagnosis as magnetic resonance image (MRI), computed tomography (CT) and ultrasound (US) are 100% sensitive and would reduce the disability of unnecessary casting, it is costing and time consuming. Thus clinical assessment is not only essential for accurate diagnosis but also in deciding which patients will benefit from further investigation. The diagnosis of a fracture of the scaphoid is suggested by the patient’s age, the mechanism of injury, and the initial signs and symptoms, but it is only confirmed by a radiographic examination.
As many as 16 views have been proposed for an exhaustive study of the injured wrist, but only 4 must be included in the routine examination: one posteroanterior, one lateral, and
two oblique projections. These four views can detect 97 % of scaphoid fractures.
Established scaphoid non-unions have been successfully treated with a variety of surgical procedures. The success and failure of these procedures depend upon a number of factors, including length of time from original injury, fracture pattern, size of the proximal pole, and vascularity of the proximal pole.
The described treatments for these non-union include, pulsed electromagnetic field and casting, Russe bone grafting, iliac bone grafting and K-wire fixation, lag screw fixation and iliac crest bone grafting, Herbert bone screw with iliac crest bone grafting, Ender compression blade plate, compression staple osteosynthesis, pronator quadratus vascular graft, and distal dorsal vascular graft. The overall success rate of these procedures varies between 71% and 97% union. Although patients with a scaphoid non-union can remain symptom free for many years, it is generally accepted that surgery is indicated when healing cannot be achieved by conservative methods. The aim of the operation is either to achieve bony union or to obtain a good functional wrist, without pain in the absence of union.
Excision of the fibrous tissue or pseudoarthrosis of fracture non-union, correction of malalignment or bone collapse, provision of a bridging bone graft, allowance for mechanical compression and stable fixation, and an adequate period of immobilization are the principles of treatment of scaphoid non-union Russe (1960) used a volar approach to fill an egg-shaped cavity created within the scaphoid and across the fracture site with an oblong cancellous bone peg and additional bone chips. Russe procedure is indicated for all symptomatic, established non-unions and symptomatic delayed unions without osteoarthritis but with satisfactory carpal alignment. In 1970, Fisk observed that in cases with carpal collapse, realignment of the scaphoid fragments creates an anterior wedge-shaped defect that requires an anterior wedge-shaped bone graft. Fisk showed that this procedure would correct the abnormal extension of lunate. Fernandez (1984) has modified Fisk’s technique by inserting a carefully measured wedge or trapezoidal shaped iliac bone graft through a volar approach and using internal fixation. Several screws have been developed such as the universal compression screw, Herbert screw, Herbert-whipple screw, AO 3.5-milimeter canulated screw, and Acutrak screw for fixation of scaphoid non-union.
Most scaphoid fractures that fail to heal with inlay or wedge conventional grafts probably have impaired vascularity as a contributing factor.
As demonstrated by sclerosis of the proximal pole on x-ray and MRI imaging and absence of punctate bleeding at the time of surgery.
Vascularized bone grafts have been proposed as appropriate methods to increase the rate and frequency of healing in fractures with poor prognosis as ( vascularized femoral graft) in avascular fragment.
Salvage and palliative procedures considered if the proximal fragment constitutes less than one fifth of the bone, regardless of its viability. Grafting of such a small fragment usually fails. If the proximal fragment constitutes up to one third of the entire bone and is necrotic sclerotic or severely comminuted. If there is capitolunate arthritis, the degenerative process has progressed too far to have a reasonable chance for a good result from a successful union with surgery. They include proximal raw carpectomy, excision of the entire carpal scaphoid, excision of the proximal fragment, and scaphoid replacement midcarpal arthrodesis.
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