Bowing fracture

Bowing fractures are incomplete fractures of tubular long bones in pediatric patients (especially the radius and ulna) that often require no intervention and heal with remodelling.

Epidemiology

Bowing fractures are almost exclusively found in children. However, there have been several case reports of bowing in adult bones. These injuries usually occur in children although adolescents may be affected.

The radius and ulna are the most commonly affected bones, followed by the fibula. However, bowing fractures of all long bones have been described.

Clinical presentation

Children present with pain and swelling following a fall, usually on an outstretched hand. This is often after falling from furniture or climbing equipment, especially monkey bars.

Pathology

When an angulated longitudinal force is applied to a bone, the bone bends. Pediatric bones have a degree of elasticity and therefore, if the force is low and subsequently released, the bone returns to its normal position and no lasting evidence of that bowing is seen radiographically.

This ability to bend occurs because the cortex is thinner in absolute and relative terms compared to adult bones and because of the way the cortex and periosteum bind to each other in the developing skeleton.

If the force is greater than the mechanical strength of the bone, the bone undergoes plastic deformation and when the force is released, the bone remains in its bowed position.

Microscopic examination of the bone reveals that there are microfractures along the concave border of the bowed bone, but these are not visible radiographically.

Radiographic features

Plain film

On a plain film, bowing of the bone can be visualized provided that the view is in a different plane to the direction of bowing. If the view is in the plane of the bow, the bone may appear completely normal ¹. The bowing tends to be fluid and blend into the normal bone at either end.

There is no fracture line or visible cortical injury.

There is usually an accompanying fracture of a paired bone, e.g. radius, and this is usually diaphyseal (either greenstick or complete). In some cases, there may be dislocation of the paired bone, e.g. radial head dislocation.

Treatment and prognosis

Bowing fractures usually accompany another fracture and in those cases, treatment is determined according to the type and severity of the accompanying injury.

In isolation, treatment of bowing fractures is debated ². Some advocate the reduction of a bowing fracture where angulation exceeds 20 degrees. Most authors agree that where angulation is less than 20 degrees, manipulation for reduction is not required and only symptomatic support is required: this is usually in the form of a removable splint.

Differential diagnosis

• greenstick fracture: accompanying bowing, there is a visible fracture
• buckle fracture: there is cortical irregularity
• physiological bowing
• stress fracture: there is a periosteal reaction