Bowing injury of forearm in an adult

Introduction

Injuries of the forearm bones in adults usually result in a complete fracture of one or both bones with displacement. Most often these require surgical treatment to regain full function. Traumatic bowing of the forearm in children is a definite clinical entity which can be explained by the plastic deformation of bones in children. We have not come across any report of bowing injury of the forearm in an adult.

Case report AP, a 30 year-old-labourer caught his left forearm between the two rollers of a roller machine.

He was brought to hospital with bowing of the middle third of the left forearm. There was no neurovascular deficit or evidence of compartment syndrome.

Plain radiographs showed bowing of the left forearm with an angulation of approximately 24". There was no break in the continuity of bones or subluxation of the radioulnar joints ( Figure I). We did not do a skeletal survey to look for any generalized disorder as the bone texture on the radiographs appeared normal.

Closed manipulation was done under anaesthesia. The bowing could be corrected completely. The forearm was immobilized in an above-elbow plaster cast for 6 weeks.

Three years after injury, the patient had no restriction of function. Radiograph of the forearm did not reveal any residual angulation and the radioulnar joints were normal ( Figure 2).

Discussion

Traumatic bowing of the forearm in children is well recognized. Borden1 reported eight cases of traumatic bowing of forearm bones in chiIdren. The mode of injury in all cases was a fall on to the outstretched hand. There was no evidence of generalized bone disease and all patients were successfully managed by closed reduction. He proposed that when the naturally curved tubular bones are subjected to longitudinal compressing forces, the curvature further increases. Up to a certain force, the bone responds in an elastic manner and loses all deformation once the force is removed. Beyond this force, the bone deforms plastically; that is, when the force is removed some bowing persists. With increasing force the bone progressively weakens and finally breaks. Chamay2f3 and Tschantz4 have confirmed the elastic and plastic properties of bone experimentally in the normal dog ulna in vitro and in vine. They found that an ulna stressed at forces in the elastic deformation range was histologically normal. They demonstrated microscopic fatigue lines (microfractures) with progressive stresses.

Currey and Butlers studied the mechanical properties of bone tissue in children and compared them with the bone in adults. They concluded that the bones in children have a low modulus of elasticity, a lower bending strength and a lower ash content. The bones in children absorb more Figure I. Initial radiograph of left forearm showing bowing of both bones.

Injury: International

Journal of the Care of the Injured Vol. 26, No. 4, 1995 shown that the tensile strength and modulus of elasticity of bone tissue of children under 7 months old were less than those of bone from a lb-year-old child. Borden' observed difficulty in reduction and restriction of pronation and supination in significant number of cases.

We have not come across any report of bowing injury of the forearm in an adult. The mechanism of injury in our case was characteristic and not like the one reported in bowing injuries in children. There was no functional loss in our case 3 years after injury and the bowing was satisfactorily corrected. energy before breaking which is the result of the ability of these bones to undergo plastic deformation. This explains the occurrence of bowing injuries in children.

Earlier studies by Hirsch and Evans6 and Vinz' have also