Scaphoid Non-Union


Abstract
A 24 year old lady presented with a chronic wrist pain after a motorvehicle accident. She was diagnosed with a non-union of the scaphoid. She was successfully underwent a vascularised bone graft surgery.

Keywords: Scaphoid fracture, non-union, vascularised bone graft.

Introduction
Scaphoid fractures most often occur in young and active patients. Up to 25% remain initially occult.11 Accurate diagnosis and effective management of these injuries are essential, as a failure to achieve these goals may lead to complications such as fracture nonunion, avascular necrosis of the proximal pole, and the development of a progressive of wrist arthrosis termed scaphoid nonunion advance collapse (SNAC), with its associated chronic pain and long-term disability. The ideal treatment of nonunion of the scaphoid remains unresolved and controversial.

Case Report
Ms D, a 24 year old clerk, had a motor vehicle accident on January 13, 2007. She sustained an amputated tip of right little finger and a laceration wound over left foot. She was treated in casualty department and was followed up at an orthopaedic clinic until all wound healed. She resumed her daily activity and returned to work.
However she presented herself again four months later with a complained of persistent right wrist pain. She claimed that the pain already present since the initial injury. A series of wrist radiographs was taken and she was noted to have a neglected fracture of the right scaphoid. A thorough wrist examination was performed. There was no swelling of the right wrist. Mild tenderness was elicited on palpation over the snuffbox. A scaphoid shift test, as described by Watson in 1997, revealed a painful clunk.
A vascularised bone grafting was done on March 3, 2008. She was discharged well and attended regular follow up at Orthopaedic Clinic HTAR.

Discussion
The scaphoid is the most commonly fractured carpal bone, representing approximately 60% of all carpal fractures, 11% of all hand fractures and 2% of all fractures.1,2 It is often misdiagnosed as simple wrist pain. Scaphoid fractures may go on to malunion or non-union. Because of the unique anatomic structure and vascularity, osseous avascular necrosis (AVN) frequently occurs in chronic fractures and may further compromise the healing potential. The scaphoid is almost entirely covered in cartilage, with the exception of a thin dorsal strip of its waist. This reduces it capacity for periosteal healing and increases its propensity to progress to delayed union or nonunion after fracture.
There are two major vascular conduits that supply the scaphoid. One of the two predominant vascular pedicles enters through the scaphoid tubercle and supplies its distal 20% to 30% and the other arising from radial artery forms the dorsal ridge vessels. The dorsal ridge vessels penetrate via several foramina to supply the proximal 70% to 80% of the scaphoid 13. The majority of the vascular foramina are positioned at or distal to the waist of the scaphoid. There is no intraosseoeus anastomoses in between the two arterial systems 13 . Because of its unusual retrograde blood supply, the scaphoid has the greatest risk among the carpal bones for avascular necrosis after fracture.
Despite the advent of newly developed fixation techniques, the nonunion rate in scaphoid fractures remains as high as 10%. Poor results are commonly related to improper fixation, bone graft absorption, and persistent AVN. Vascularized bone grafts (VBGs) have been used to increase the union rate under such circumstances.



Clinical presentation and diagnosis
Patients with scaphoid fractures most often present with radial-sided wrist pain and limited motion after traumatic injuries. The mechanism of injury will often involve falling onto an outstretched wrist. Extreme hyperflexion locks the scaphoid into the scaphoid fossa of the distal radius by producing tension in the volar extrinsic ligaments, and the capitate acts as a fulcrum to the frature. There is mild tenderness on palpation over the anatomic snuff box. The Watson shift test also demonstrates mild tenderness. However there is no subluxation.
A patient with scaphoid nonunion commonly experiences an asymptomatic period following his initial recovery from the acute trauma. The patient can present later with the history of the insidious onset of wrist symptoms. Alternatively, the patient can present after another traumatic event (often not even associated with high energy) with the onset of wrist symptoms.
Plain radiograph is invaluable in detection of bony injury. Standard posteroanterior, lateral, oblique, and ulnar deviation postreoanterior grip views should be obtained. An anteroposterior grip film should be obtained to rule out an isolated or concomitant rupture of the scapholunate ligament. Widening of the joint space between the scaphoid and lunate, seen with rotatory subluxation of the scaphoid (scapholunate dislocation) space is reminiscent of the gap between the teeth of the British comedian Terry Thomas. It has also been called the David Letterman sign or the Lauren Hutton sign (all people with a gap between their two front teeth.) It is an important sign to recognize, since it is a cause of chronic wrist pain and disability if left untreated. Patients with a negative x-ray finding but with clinical signs should be immobilised and x-rays repeated in 10 to 14 days. If a fracture is not seen on the repeat radiographs and a scaphoid fracture is still suspected, a computed tomography scan, a magnetic resonance imaging scan, or a bone scan should be done. No standard diagnostic approach exists for imaging scaphoid fractures, as no single imaging modality has been proven to be ideal in all situations.3,4

Classification
Herbert and Fisher have classified scaphoid fractures and nonunions into four types 14 .Type A is a stable acute fracture. Type B is an unstable acute fracture. Type C is a delayed union. Type D is an established nonunion. Type D is further divided into 5 types as described by Herbert (Figure 1).15 If previous surgery has failed, a scaphoid non union should be classified one stage worse than is suggested by its radiographic appearance. The scaphoid nonunion may not be readily identifiable because the cartilage may be partially intact or fibrous tissue may be present.

Figure 1: Herbert’s five stages of scaphoid nonunions.
The Mayo classification16 of scaphoid nonunions is based on location and displacement. By location, scaphoid nonunions are classified into the following types: Type 1 is a fracture that involves the tuberosity. Type 2 is a fracture that involves the distal articular surface. Type 3 is a fracture that involves the middle one-third of the scaphoid. Type 4 fractures involves waist or proximal one-third and type 5 fracture involves the proximal pole of the scaphoid.

Natural history
Natural history studies of scaphoid nonunions suggest progression to wrist instability and subsequent wrist arthritis.5,6,7 Surgical treatment is usually indicated for patients with stages Dl and D2 regardless of the presence or degree of symptoms.8,9 Stages D3 and D4 have the presence of progressively more severe osteoarthritis, more loss of motion, and lower union rates. For patients with stages D3, D4, and D5 the patient’s age, symptoms, occupation, and needs should be taken into consideration when deciding among conservative treatment, scaphoid reconstruction, and a salvage procedure. A humpback deformity of the scaphoid is a relative contraindication for a vascularised, pedicled bone graft because correction of the deformity is very difficult. For patients with stage D5 who do not have significant osteoarthritis and do not have a humpback deformity, a vascularized, pedicled distal radius bone graft can be considered.

Management
Non surgical option includes no treatment, immobilization in a splint or cast or electrical stimulation. The surgical options included an anterior (palmar) Russe versus dorsal approach, conventional nonvascularized bone graft (cancellous or corticocancellous) versus vascularized, pedicled bone graft from the distal radius, and fixation options including no fixation, Kirschner wires (K wires), or screw fixation.
A vascularised distal radius corticocancellous bone graft can be used to bridge the two segments. The approach was palmar or dorsal according to the location of the nonunion and the graft that would be subsequently used. For nonunions at the waist of the scaphoid a pedicular graft from the palmar aspect of the distal radius was selected, whereas for nonunions of the proximal third of the scaphoid, a dorsal graft was preferred. The palmar approach was selected for this patient.
The surgery was performed under general anaeasthesia. The patient was placed in supine position and a brachial tourniquet was applied. The upper extremity was exsanguinated with elevation rather than by using an eshmarch, so the vascular pedicle could be readily identified. After resection of the nonunion, the freshly prepared surfaces of both fragments of the scaphoid were inspected for punctuate bleeding and in the absence of bleeding points on the proximal fragment, further sclerotic bone was curreted, preserving the overlying cartilage. A wedge-shaped cortico-cancellous graft (12 mm×10 mm×10 mm) was separated and carefully elevated from the distal radius (ulnar side). The graft was pedicled on the palmar carpal artery, running on the distal edge of pronator quadratus. The wedge shaped graft was then inserted into the nonunion (intercalary graft) with particular care to reduce the height and axis of the scaphoid and to avoid damage to the vessels. Fixation was obtained with two Kirschner wires. A long arm cast was applied for 6 weeks. The disadvantages of the pedicle were that the arc was too short and the muscle bulk limited adequate visualization of the reduction. Contraction of the muscular pedicle sometimes caused loss of reduction.

For treatment of patients with proximal pole nonunions, a dorsal approach with a curvilinear transverse incision made at the level of Lister's tubercle, just proximal to the radiocarpal joint, extending from the radial styloid to the midportion of the ulnar head. A longitudinal extension is added over the interval between the first and second dorsal compartments. It is important to achieve good visualization through the ulnar extent of the incision. The 1,2 supraretinacular intercompartmental artery are visualized after careful exposure of the extensor retinaculum. The superficial branch of the radial nerve which runs superficial to the extensor retinaculum must be protected.
The artery and venae comitantes were dissected gently toward their distal anastomosis. An interval was developed between the first and second dorsal compartments that were opened at the graft elevation site. A graft sufficiently large to fill the scaphoid defect was raised containing the vessels and cuff of the retinaculum between the first and second compartments. The center of the graft was 1.5 cm proximal to the radiocarpal joint to include the nutrition vessels. The pedicle was dissected gently to its distal radial artery anastomosis. The tourniquet was briefly released to check bleeding on the surface of the vascularized bone graft. After re-inflation of the tourniquet, the graft was transposed to reach the nonunion site where it was gently impacted into position and placed as a dorsal inlay.
Many different methods have been reported for obtaining vascularized grafts. Guimberteau and Panconi reported a vascularised cortical and cancellous bone graft from the ulna17. The vascular pedicle was obtained from the ulnar artery. The disadvantages of this procedure included a long operating time and the need to reconstruct the ulnar artery with a venous graft. In addition, the procedure was associated with a risk of fracture of the ulna.
Brunelli et al. described a bone graft that was obtained from the distal part of the second metacarpal.18 The vascularity of the graft was derived from the deep artery of the first web space on the lateral aspect of the metacarpal. Gabl et al. described free vascular bone grafts from the iliac crest.19 Kazuteru et al. described free vascular bone grafts harvested from the femoral supracondyle.20 The results of their studies were all good but the procedures needed microscopic vessel anastomosis and required long operative times.

Postoperative Care and Evaluation
A short arm thumb spica cast was applied and the Kirschner wires were removed after 6 weeks postoperatively. A removable short thumb-spica splint used for another 4 weeks. Full weight-bearing activity was not permitted until 6 months after the operation. Posterior-anterior (PA) and lateral radiographs were taken every 4 weeks postoperatively. Bone healing was evaluated and unions were confirmed when trabecular bridging of the scaphoid fragments had occurred. The assessments were made on PA views of neutral and deviation position and lateral views
with the forearm in neutral rotation. The severity of collapse were measured based on intrascaphoid (IS) angle and scapholunate (SL) angle. Determination of the intrascaphoid angle can be difficult to make on conventional radiographs and is usually more easily made on a tomographic image. Amadio and colleagues used trispiral tomography scanning to determine the normal and abnormal intrascaphoid angle.12 The articular surfaces were identified, and a line was drawn to connect the extremes of the proximal and distal convex articular surfaces. A perpendicular to each line was drawn, and the resultant angle was noted. The intrascaphoid angle was evaluated in the coronal and sagittal planes. The normal sagittal, intrascaphoid angle was 15-34. An abnormal intrascaphoid angle is greater than 35°. An intrascaphoid angle that is greater than 45° is associated with a poor clinical outcome. Often, this angulation is associated with a dorsal intercalated segmental instability (DISI). Scapholunate angle is measured through the long axis of scaphoid and lunate. The normal angle is 30 – 60 degree.
An MRI is an invaluable imaging tool in determining the vascularity throughout the scaphoid including the graft and the proximal pole, and to confirm healing at the two osteosynthesis sites.10
Functional evaluation was performed using the modified Mayo wrist scoring system (Table 1). Range of motion, grip strength, and pain were measured. Range of motion was reported as both the absolute measurement and that compared with the contralateral side. Maximal grip strength on the injured side was measured and was reported as a percentage of maximal strength on the contralateral side. The pain scale was self-reported and graded with the use of a questionnaire. With the addition of the satisfaction score, a modification of the Mayo Wrist Scoring Chart was used for functional assessment, allowing for a total count of 100 points in four categories.

Conclusion
Scaphoid fracture is a common carpal bone fracture. Careful initial assessment of the injury decreases the incidence of complication such as non-union. A vascularised bone graft is a viable option for the treatment of scaphoid non-union.

Category Score Findings
Pain 25 No pain
(25 points) 20 Mild pain with vigorous activity


20 Pain only with weather changes


15 Moderate pain with vigorous activity


10 Mild pain with activities of daily living


5 Moderate pain with activities of daily living


0 Pain at rest
Satisfaction 25 Very satisfied
(25 points) 20 Moderately satisfied


10 Not satisfied, but working


0 Not satisfied, unable to work
Range of motion 25 100% percentage of normal
(25 points) 15 75% - 99% percentage of normal


10 50% - 74% percentage of normal


5 25% - 49% percentage of normal


0 0% - 24% percentage of normal
Grip strength 25 100% percentage of normal
(25 points) 15 75% - 99% percentage of normal


10 50% - 74% percentage of normal


5 25% - 49% percentage of normal


0 0% - 24% percentage of normal
Final Results 90 – 100 Excellent
(total points) 80 – 89 Good


65 – 79 Fair


< 65 Poor

Table 1: Mayo Wrist Scoring System.


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