Scaphoid Fractures

Introduction

The scaphoid is ‘boat’-shaped* bone and is the most common carpus to be fractured.

Scaphoid fractures are most common in men aged 20-30 years and are high-energy injuries. Approximately 10% have an associated fracture.

They are very commonly referred to orthopaedics, due to diagnostic uncertainty; however, only around 1 in 10 referred patients actually have a scaphoid fracture.

*The word scaphoid derived from the Greek word “skaphos”, which means boat 

By TeachMeSeries Ltd (2020)

Figure 1 – The carpal bones

Pathophysiology

The scaphoid is anatomically divided into three parts: the proximal pole, waist, and distal pole.

It is important to appreciate the blood supply to the scaphoid (Fig. 2), which is by branches of the radial artery. The dorsal branch of the radial artery, which supplies 80% of the blood, enters in the distal pole and travels in a retrograde fashion towards the proximal pole.

Consequently, fractures can compromise the blood supply, leading to avascular necrosis (AVN) and subsequent degenerative wrist disease. The more proximal the scaphoid fracture, the higher the risk of AVN.

By Iiibalesiii [CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0)], from Wikimedia Commons

Figure 2 – Blood supply to the scaphoid (a) volar branch (b) dorsal branch (supplying 70-80% blood supply to the scaphoid, travelling towards the proximal pole)

Clinical Features

The scaphoid is fractured following trauma, which is often high energy. Patients will complain of sudden onset wrist pain and bruising may be present.

There is tenderness in the floor of the anatomical snuffbox, pain on palpating the scaphoid tubercle, and pain on telescoping of the thumb.

Differential Diagnosis

The main differentials of radial wrist pain following trauma are distal radial fracture, an alternative carpal bone fracture, fracture of the base of the 1^st metacarpal, ulnar collateral ligament injury, wrist sprain, or De Quervains tenosynovitis.

Investigations

For suspected cases of scaphoid fracture, initial plain radiographs should be taken. A “scaphoid series” should be requested, including anteroposterior, lateral, oblique views.

Scaphoid fractures are not always detected by initial radiographs (especially undisplaced fractures); if there remains sufficient clinical suspicion, despite negative initial imaging, the patient should have the wrist immobilised in a thumb splint and repeat plain radiographs in 10-14 days for further evaluation (Fig. 3).

If repeat radiographic imaging is negative, however clinical findings are still in keeping with a scaphoid fracture, an MRI scan of the wrist is indicated. This is the definitive investigation and, whilst it is awaited, the interim management is as for a fracture.

Adapted from Mohamed Jarraya, Daichi Hayashi, Frank W. Roemer, Michel D. Crema, Luis Diaz, Jane Conlin, Monica D. Marra, Nabil Jomaah, and Ali Guermazi [CC BY 3.0 (https://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons

Figure 3 – (A) Initial AP radiograph showing a subtle linear lucency within the scaphoid (B) more pronounced lucency observed in repeat imaging after 12 days

Management

The treatment of scaphoid fractures is determined by location of the fracture and degree of the fracture.

Undisplaced fractures can typically be managed with strict immobilisation in a plaster with a thumb spica splint. However, undisplaced fractures of the proximal pole have a high risk of AVN and surgical treatment may be advocated, particularly if it is the dominant hand of a working-age patient.

All displaced fractures should be fixed operatively. The most common operative technique is using a percutaneous variable-pitched screw, which can be placed across the fracture site to compress it.

Complications

Avascular necrosis is common complication of a scaphoid fracture (in around 30% of cases), with its risk increasing the more proximal the fracture.

Non-union is the bone failing to heal properly, most commonly due to a poor blood supply. It is particularly common in scaphoid fractures (in around 10% of cases) that go undiagnosed or are inappropriately managed. Such cases can be managed with internal fixation and bone grafts, although the morbidity is high, even with surgical repair.