- Author: Gopikrishna Kakarala, MBBS, MS; Chief Editor: Harris Gellman, MD more...
The forearm is a complex anatomic structure serving an integral role in upper-extremity function. The dexterity of the upper limb depends on a combination of hand and wrist function and forearm rotation. The forearm bones can be considered struts linking the two halves of a condylar joint formed by the proximal and distal radioulnar joints. Thus, any change in the geometry of the radius or ulna alters the congruency and range of motion of this condylar joint.
Malunion, especially shortening and angulation of the radius or ulna, may cause functional problems at the wrist or elbow. If functional disability is to be avoided after fracture, precise anatomic reduction is necessary.
As a result of the complex arrangement of neurovascular structures surrounding the radius and ulna, surgical approaches to the forearm for fracture fixation require particular care in planning and execution. To restore the functional dynamics of the upper limb, very careful attention must be paid to accurate reconstruction of injured structures.
In children, rapid bone-healing times and the possibility of remodeling with growth allow conservative treatment much of the time. In adults, nonoperative treatment in the form of plaster casting is often inadequate to ensure anatomic reduction and healing. Achieving anatomic reduction by closed methods is difficult, and maintaining a reduction is often impossible.
For an optimal result, the basic rule is that a stable anatomic reduction with preservation of mobility must be achieved. Operative treatment is therefore the rule, rather than the exception, in adults, the treatment principles of the AO group (Arbeitsgemeinschaft für Osteosynthese, or Association for the Study of Osteosynthesis) have revolutionized treatment of radius and ulna fractures.
This article addresses injury to the diaphyseal radius and ulna, as well as associated injury to the distal and proximal radioulnar joints.
The radius and ulna function as a unit, but they come into contact with each other only at the ends. They are bound proximally by the capsule of the elbow joint and the annular ligament and distally by the capsule of the wrist joint, the dorsal and volar radioulnar ligaments, and the fibrocartilaginous articular disk.
The ulna is relatively straight, has stable articulation with the distal humerus at the elbow, and runs virtually subcutaneously distally to the ulnar styloid at the wrist. The radius is bowed along its length and thus angles at least 13° opposite to the bow to articulate with the capitellum. The radius and ulna form a joint at the distal end, where the strutlike radius sweeps and rotates around the relatively fixed ulna with pronation and supination.
Between the shafts of the radius and ulna is the interosseous space. The fibers of the interosseous membrane run obliquely across the interosseous space from their distal insertion on the ulna to their proximal origin on the radius. The central portion of the interosseous membrane is thickened and is approximately 3.5 cm wide. Hotchkiss et al showed that making an incision on the central band reduces stability by 71%, whereas making an incision of the triangular fibrocartilage complex and the interosseous membrane proximal to the central band decreases stability by only 11%.
In the treatment of fractures of the forearm, the radial bow and proper interosseous space must be maintained for normal motion to be achieved. Schemitsch et al reported that restoration of the radial bow is related in a linear fashion to the quality of the outcome. The normal maximal radial bow, measured from the area between the radius and the ulna across the interosseous membrane, is 15 mm. To achieve 80% of the normal range of movement, this bow must be within 1.5 mm of normal. The same relationship also applies to grip strength. Both the amount and the location of radial bow are crucial correlates to functional outcome.
Fractures of both bones of the forearm are usually classified according to the level of fracture, the pattern of the fracture, the degree of displacement, the presence or absence of comminution or segment bone loss, and whether they are open or closed. Each of these factors may have some bearing on the type of treatment to be selected and the ultimate prognosis.
Disruption of the proximal or distal radioulnar joints is of great significance to treatment and prognosis. Determining whether the fracture is associated with joint injury is imperative because effective treatment demands that both the fracture and the joint injury be treated in an integrated fashion.
The mechanism of injury is variable. The most common cause is a direct blow to the forearm, producing a single (nightstick) fracture of the ulna, the radius, or both. The next most likely mechanism is a fall on an outstretched hand with the forearm pronated. Other mechanisms of injury include road traffic accidents and athletic injuries. The force generated is usually much greater than that required to cause a Colles fracture. Most forearm shaft fractures resulting from falls occur in athletes or in persons who fall from heights.
Gunshot wounds can result in fracture of both bones of the forearm. These injuries are commonly associated with nerve or soft-tissue deficits and frequently have significant bone loss. Severely debilitating and mutilating injuries are caused by accidents involving farmyard machines and industrial machinery. These severely mangled extremities pose a challenge from the time the decision is made to salvage the limb until the final result.
In 2010, according to data from the 2010 National Electronic Injury Surveillance System (NEISS) database and the 2010 US Census, forearm fractures were the most common type of fracture in the pediatric population (age range, 0-19 years) and accounted for 17.8% of all fractures.
The literature provides few details regarding the incidence of fractures of the radius and ulna in adults. McQueen et al comprehensively analyzed the incidence of forearm fractures seen at the trauma unit of the Royal Infirmary of Edinburgh over a 3-year period. This unit caters exclusively to adult trauma cases in a specified area and population and thus is a very good guide to the epidemiology of forearm fractures in a westernized country.
In this analysis, the causes of injury included direct trauma, fall from a height, road traffic accidents, and sporting injuries. Unlike in other regions, injuries related to gunshots and firearms are not prevalent as a cause of injury in this region. Of the 2812 fractures, just 5% were diaphyseal forearm fractures, and an overwhelming majority of 76% were distal radius fractures.
Data from the National Hospital Ambulatory Medical Care Survey showed that radius and/or ulna fractures accounted for 44% of all forearm and hand fractures in the United States.
The prognosis for adults with fractures of the radius and ulna depends on many factors.[7, 8, 9, 10] However, the factors under the surgeon's control include choice of treatment method, timing of internal fixation in open fractures, soft-tissue handling, and restoration of osseous anatomy.
Anderson reported a union rate of 97.3% for fractures treated with open reduction and internal fixation (ORIF) using compression plates. Of these patients, 90% had satisfactory or excellent function, and only 10% had unsatisfactory or poor function. Sage reported a union rate of 93.8% for fractures treated with triangular nails.
One study compared the complication rates in patients treated with external fixation versus volar plating of distal radius fractures. The volar plate group experienced more tendon and median nerve complications; however, the external fixation group had a significantly higher overall complication rate. While there were no significant differences between the groups in the scapholunate angle or palmar tilt measurements, the volar plate group had significantly better arc of motion in pronation-supination and flexion-extension and better grip strength.
The important feature common to these studies, in which a union rate of more than 90% was reported, was the rigidity of the fixation. If intramedullary nails are used, they must control rotation of the fragments and be sturdy enough to resist angulatory forces. If plates and screws are used, they must be long enough and strong enough to resist loosening and breakage.
The prognosis is more guarded for open fractures of the shaft of the radius and ulna with major skin and soft-tissue loss. In these cases, several operative procedures may be necessary, including initial debridement and stabilization, skin grafting, pedicle or free-flap applications, late reconstruction of the bones, and, frequently, tendon transfers.
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