12.33 Forearm fractures

The function of the arm is to position the hand in space. Functional recovery after forearm fracture is dependent on the full return of forearm rotation, wrist and elbow function, and hand grip strength. The muscle envelope surrounding the forearm bones normally controls hand positioning but creates complex deforming forces in a fractured forearm. Complete recovery is reliant on the anatomical alignment and relationship of the radius and ulna. The intimate relationship between the radius and ulna and the articulation at each extremity makes management of these injuries challenging.

In the adult skeleton, forearm fractures are associated with high energy, and are consequentially seen more commonly in men. Open injuries are commoner in the forearm than any other bone excepting the tibia. Due to the high-energy nature of adult forearm injuries they not uncommonly present as multifragmentary fractures, often in the polytrauma patient.

In the elderly population diaphyseal forearm fractures are uncommon. A fall to the outstretched hand in the elderly usually presents with the more common distal radial or supracondylar fractures.

The forearm consists of the shorter radius laterally and the longer ulna medially (Figure 12.33.1). The relationship of the two bones is maintained by the distal radioulnar joint (DRUJ), interosseous membrane and proximally by the radial head and annular ligament. The interosseous membrane is the strongest of these elements and provides 75% of the stability.

The lateral bow of the radius allows the radius to cross the straight ulna mid-shaft in full pronation.

The radial tuberosity is found posteriomedially on the proximal radius allowing the biceps which inserts here to act as a forearm supinator as well as a flexor. Brachioradialis inserts into the styloid and acts as a pure flexor of the forearm. Distally the radius is grooved medially forming the sigmoid notch articulation with the DRUJ.

The olecranon process, of the proximal ulna, articulates with the trochlear groove of the humerus. The triceps tendon inserts into the olecranon posteriorly and brachialis into the coronoid anteriorly. Distally the head of the ulna articulates with a groove in the distal radius to form the DRUJ, the fulcrum for distal forearm rotation.

On the flexor surface three layers of muscles form the anterior compartment along with median, radial, and ulnar nerves. The first (superficial) layer is formed by brachioradialis with the muscles of the common flexor origin (pronator teres (PT), flexor carpi radialis (FCR), palmaris longus (PL) and flexor carpi ulnaris (FCU)). Flexor digitorum superficialis (FDS) lies deep to these and forms the second layer. The final third layer is formed radially by flexor pollicis longus (FPL), distally by pronator quadrates (PQ) and flexor digitorum profundus (FDP) lies on the ulna aspect.

The muscles of the common flexor origin arise from the medial humerus, proximal radius, and ulna. The flexor carpi radialis and ulnaris (FCU) cross the forearm without attachments to these bones. The deep flexors, unlike the superficial muscles, all originate from the forearm bones and interosseous membrane. The deep flexors arise more distally, FDP originates from the proximal two-thirds of the ulna, and the FPL originates from the middle third of the radius. Aside from the pronators, all forearm flexors insert into the bones of the hand.

The muscles on the radial side of the forearm include the extensor carpi radialis brevis and longus, and the brachioradialis. They all originate from the lateral humerus, and only the brachioradialis inserts on the forearm at the radial styloid. The common extensor origin is located on the lateral aspect of the forearm. It gives rise to extensor digitorum, extensor digiti minimi, and extensor carpi ulnaris. The deep extensors all originate on the dorsal surface of the forearm and interosseous membrane. From proximal to distal they are the abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, and extensor indicis.

The radial nerve divides into its two terminal branches, the superficial radial nerve and posterior interosseous nerve as it passes over the lateral epicondyle. The superficial branch passes over supinator and pronator teres before passing deep to brachioradialis and travelling down the forearm with the radial artery. The median nerve enters the forearm through the two heads of pronator teres. As it crosses the ulna artery it gives rise to the anterior interosseous nerve (supplying FPL, FDP and PQ). It passes between FDS and FDP before passing into the carpal tunnel medial to FCR. The ulnar nerve passes into the forearm through the cubital tunnel. It passes between the two heads of FCU and passes with the ulnar artery down the forearm. It enters the hand through Guyon’s canal.

The radius and ulna articulate proximally at the radial head and distally at the distal radial-ulna joint (DRUJ) while the interosseous membrane connects both bones along their length passing obliquely downwards from radius to ulna. The interosseous membrane functions to transmit load from the carpus through the radius to the ulna.

Pronation–supination functions around a complex series of movements. The axis ofrotation is from the radial head through the distal ulna into the little finger. During pronation the radius rotates around the ulna at the DRUJ whilst the ulna is abducted (action of anconeus). The centre of rotation of the wrist stays static in space due to the ulna abduction. Conversely during supination, adduction of the ulna occurs (action of supinator) while the radius rotates about its axis. The articulation relies on a bowed radius rotating round a straight ulna to allow for 85 degrees of rotation in each direction.

As both bones work as an articulation with each other throughout their length any fracture within the shaft of either bone must be considered an intra-articular fracture, and this principle forms the cornerstone of management of these injuries.

The deforming forces in forearm fractures have differing affects according to the level of the fracture. In proximal third fractures the proximal fragment is flexed and supinated by biceps and supinator whilst the distal fragment is pronated by pronator teres and quadratus. With middle third fractures the interosseous membrane holds the proximal fragment in neutral while the distal fragment is pronated. In distal third fractures brachioradialis dorsiflexes and radially deviates the distal fragment (Figure 12.33.2).

In indirect injuries the direction of angulation is determined by the rotation of the forearm. When pronated a flexion injury with dorsal angulation will occur while when supinated an extension injury with volar angulation will occur.

The incidence of associated injuries is proportional to the severity and mechanism of the initial trauma. Open forearm fractures are associated with severe initial trauma consequentially the incidence of neurovascular injury is high. Neurological injury is reported to reach 9% in open both-bone forearm fractures. Careful neurovascular examination and documentation of findings is essential prior to any form of intervention, particularly after high energy trauma. It is prudent to take advice from a vascular surgeon prior to intervention in vascular injury as although reduction of the fracture will usually restore circulation there is an appreciable rate of associated intimal tears. The collateral circulation of the forearm and hand is usually excellent, and even in the presence of vascular injury the functional outcome is predominantly determined by associated musculoskeletal or neurologic injuries.

Compartment syndromes may occur in either closed or open forearm fractures but are usually the result of high-energy trauma. Compartment pressures may be elevated in any forearm injury, and are particularly common in the presence of a muscle crush injury. Compartment pressure monitoring should be considered an adjunct to careful clinical examination and is not the basis on which to make a diagnosis or treatment decisions. Complete open forearm fasciotomies of both flexor and extensor compartments should be undertaken immediately when a clinical diagnosis of compartment syndrome is reached or cannot be excluded.

Associated bony injuries have been reported to the scaphoid and floating elbows in adults. Complete examination of the upper limb and x-rays to include the joint above and below are essential to rule out these and other associated injuries.

Forearm fractures are usually described based on the location of the fracture (proximal, middle, and distal thirds) and involvement of the joints at either end. The location of the fracture can be used to determine the deforming forces and the most appropriate surgical approach.

Because the radius and ulna are joined by a proximal and distal joint, it is fundamental in the diagnosis and management forearm fractures that if there is a displaced fracture of one forearm bone, there must be a displaced fracture of the other or a dislocation of the proximal or DRUJ.

The Orthopaedic Trauma Association (OTA) and the AO–ASIF both developed more specific classification systems, which have now been merged. Although most commonly used in research it is simple to use. The classification is based around anatomical location (radius, ulna or both bones) and the increasing degrees of complexity in the fracture pattern (Figure 12.33.3).

The Bado classification is used to classify Monteggia fracture–dislocations based on the type of radial head dislocation, Figure 12.33.4.

If the fracture involves complete cortical and periosteal disruption, displacement consisting of translation, shortening, angulation, and malrotation is not uncommon. Consequently, the clinical signs of a both-bone forearm fracture include obvious deformity, abnormal limb motion, prominent swelling, and severe pain.

The elbow and wrist should be palpated for tenderness, the skin inspected to rule out an open injury, and the forearm compartments evaluated. The competency of the ulnar and radial arteries should be established. A thorough neurologic examination of the radial, median, and ulnar nerves should be performed. All the relevant findings must be documented in the medical records.

Plain anteroposterior and lateral radiographs centred on the forearm are required for diagnosis. The limb’s malposition often prohibits true anteroposterior and lateral radiographs in this case two orthogonal radiographs will suffice. Plain films must include the wrist and elbow joint, but due to the divergence of the x-ray beams separate views should be obtained if there is any clinical suggestion of dislocation or bony injury at these joints. Careful assessment of the elbow is crucial to rule out radial head dislocation, and three views may be required in order to do so.

External support consisting of a splint or rigid arm board should be secured to the traumatized limb to limit further soft tissue injury. If an open fracture exists, the wound must be swabbed, photographed, and a sterile dressing applied which should not be further disturbed until the patient is in the operating room. Although anatomically similar, forearm fractures represent a spectrum of injury mechanisms. Treatment of these injuries varies greatly in different populations and injury types.

The adult skeleton has no capacity to remodel and as whole forearm functions like a joint treatment should be aimed at anatomical reduction and fixation to minimize residual deformity and functional impairment. Open reduction and internal fixation is the treatment option of choice in all but totally undisplaced fractures of a single bone. If possible absolute stability and direct bone healing should be obtained by use of a lag screw and neutralization plate or by compression plating. In those circumstances where the state of the soft tissues or the fracture pattern make this undesirable, bridging plate fixation is an option. Temporary external fixation can be considered as a second line treatment, though this will often lead to some loss of function.

Manipulation and casting has no place in the management of adult forearm injuries. As adults have a thin periosteum it is impossible to effectively manipulate and hold a both bone forearm fracture closed. Cast bracing can only be considered for select fractures that are non-displaced and minimally swollen in patients who can reliably tolerate the treatment. This group of patients will require frequent follow-up and may have to accept mild loss of motion and the risk of surgical intervention in the event of loss of position or non-union.

Plating is a type of fixation, not a mode of fixation or a type of healing. Plates can be used in the forearm in a variety of ways and it is important to decide on the aims of fixation prior to treatment.

Achieving absolutely stable fracture fixation is the conventional way of managing a displaced forearm fracture in the adult. In an oblique fracture patterns this is best achieved with a lag screw and neutralization plate, while compression plating is required for transverse fractures. Preoperative planning is mandatory, and the surgeon should have decided the method and mode of use of the plate for each forearm bone before the operation starts. In normal adult forearm bone, conventional screws are normally adequate. Standard compression type plates should be used The lighter one-third tubular type plates have no place in the stable fixation of adult diaphyseal forearm fractures, although they can be used in small children. Compression plating in this manner has been shown to give a high union rate with a low rate of complications in children and adults (Figure 12.33.6).

Bridging plating in forearm fractures should be reserved for cases where there is extensive fracture comminution and/or soft tissue damage. This makes any attempt to achieve absolutely stable fixation likely to cause devascularization of bone fragments, which would lead to non-union. Although anatomical reduction of the fracture is not obtained, overall anatomical alignment of the radius and ulna is still necessary to prevent loss of pronation/supination. In using a bridging plate the surgeon is accepting some loss of function in an attempt to maintain blood supply to the fracture fragments and get them to heal.

Where the bone is of poor quality or the plate is used for bridging, then ideally a locking plate should be used. The advantage of the additional purchase provided by locking screws and no requirement to contour the plate accurately to the bone, may well justify their increased cost.

Elastic nailing in the adult is inappropriate as it does not provide stable anatomical fixation. Contoured interlocking intramedullary nailing systems are now available. Good early clinical results have been reported in small studies.

External fixation should be considered a temporary treatment for open injuries with significant soft tissue damage. It is not common practice to use external fixation for these injuries. However, in some circumstances with extensive soft tissue trauma and bone loss, temporary external fixation may provide stability whilst awaiting definitive internal fixation.

The anterior approach to the distal radius as described by Henry (Henry 1927), provides access to the distal two-thirds of the radius and may be extended proximally if required. The approach makes use of the plane between brachioradialis and FCR.

Position the patient supine with the arm supinated on an arm table. A curvilinear skin incision is made over the palpable border of FCR and extended proximally to within 5cm of the elbow crease. Identify the interval between brachioradialis and the flexor carpi radialis. The radial artery and the superior cutaneous branch of the radial nerve lie in this interval and must be identified before proceeding. Take the artery medially and the nerve laterally. Develop the plane with blunt dissection—a well-placed finger is often safest—to reflect the muscles. Pronation of the forearm will expose the radial boarder and FPL and PQ can be elevated on a subperiosteal flap, though in practice the fracture has often done this already (Figure 12.33.7).

Boyd describes a proximal approach to the radius which makes use of the plane between FDP and ECU. This is the authors’ preferred proximal approach to the forearm for Monteggia and radial head fractures as it may be extended proximally into a Kocher’s approach to the distal humerus and elbow if required.

The patient is positioned spine with the forearm pronated on the arm table. Make a skin incision from the lateral part of the distal 2cm of the triceps insertion, over the palpable radial head and along the subcutaneous border of the ulnar 6cm distally. Identify the radial boarder of the triceps tendon and the interval of ECU and FDP distally. Divide the ulnar insertion of anconeus and reflect the insertion remnant and FDP towards the flexor compartment as a subperiosteal flap (Figure 12.33.8). Lifting the belly of anconeus exposes the ulnar origin of supinator. Detach supinator carefully as a flap at its ulnar origin and reflect the muscle radially to protect the posterior interosseous nerve. This exposes the radial head and the proximal shaft of the radius.

Do not extend this incision distally beyond the proximal ¼ of the radius as both the dorsal interosseous artery and radial nerve are at risk. It may however be extended proximally to Kocher’s lateral elbow approach.

This approach provides access to the proximal two-thirds of the radial shaft, and makes use of the plane between ECRB and EDC. The patient lies supine with their abducted arm lying on an arm table and the forearm pronated. The incision runs over the proximal two-thirds of a line from 1.5cm anterior to the lateral humeral epicondyle to the centre of the dorsum of the wrist.

Identify and split the interval between ECRB and EDC (Figure 12.33.9). This exposes the underlying supinator muscle. Supinator can be elevated off the radial shaft by subperiosteal dissection reflecting the muscle medially. It is important to start from distally and work proximally protecting the posterior interosseous nerve within the belly of the muscle. This may be helped by supinating the forearm. If required the nerve can be identified emerging from supinator inferiorly or within the muscle belly via a small muscle split.

The subcutaneous approach to the ulna is the only commonly used approach to the ulna shaft. Approach the ulna through an incision just volar to the subcutaneous border. Develop the incision through the deep fascia. Identify the plane between FCU and ECU and part the muscles using blunt dissection. The ulnar nerve lies deep to FCU should be protected throughout the dissection.

The postoperative regimen will vary from surgeon to surgeon and fracture to fracture. Early active mobilization to avoid stiffness is becoming more common after operative fixation, and this is the authors’ practice. Fractures fixed with absolute stability should be aggressively mobilized although dangerous or heavy activities should be restricted until the fracture has united.

There is an appreciable risk of neurovascular damage in open procedures to the forearm, and these injuries represent the majority of interoperative complications. Reduced range of movement can be minimized with anatomical stable reduction that allows early rehabilitation. Other postoperative complica-tions include synostosis, refracture, infection, and loss of reduction.

Synostosis is a recognized complication of both bone forearm fractures. It is associated with high-energy injuries, malreduction, delayed surgery, single incision fixation of both bones, fractures at the same level in both bones, and excision of the radial head. After the ossification has matured (usually 1–2 years) the bone bridge can be excised and interposition performed.

It has been common practice in the past to remove forearm plates, and this is still common practice in children. However, the literature demonstrates a high refracture rate of up to 11% and a significant risk of wound complications and neurological damage particularly when removing plates from the radius. We do not advise or routinely remove plates unless crossing a growth plate or causing symptoms. Elective removal of plates should not be undertaken before 1 year and some authors have argued that the high refracture rate warrants a 2 year delay for plate removal.

It is important in any seemingly isolated ulna fracture to obtain good lateral and AP views of the elbow. Treatment is based around the nature of the ulna fracture, not the type of radial head dislocation. The same principles are used as for other forearm fractures. The radial head cannot be reduced closed in approximately 10% of cases due to soft tissue interposition, and open reduction is indicated. Annular ligament reconstruction is controversial. Bado type IV injuries with radial head fracture dislocations require open reduction and internal fixation of large radial head fragments. If radiocapitellum stability is not compromised, small fragments of the radial head are best excised. Injuries with severe comminution of the radial head and significant ligamentous disruption, require radial head replacement to maintain stability.

A Galeazzi fracture is fracture of the distal third of the radius with an associated dislocation of the DRUJ. Also called the fracture of necessity by Campbell, the injury is often unrecognized and diagnosis relies on true lateral radiographs at the time of injury. Failure to anatomically reduce and hold this fracture pattern will result in almost universal poor outcomes. For this reason the authors advocate open reduction and internal fixation of the radius. This will usually reduce the DRUJ and if it is stable through a full range of pronation/supination then early functional rehabilitation can be considered. If the DRUJ remains unstable other treatment options are required (see Chapter 12.31) (Figure 12.33.10).

The Essex-Lopresti lesion is a fracture of the radial head in combination with a disruption of the interosseous membrane and disruption of the DRUJ. This is an unstable injury as the stabilizing function of the interosseous membrane is lost. Treatment should consist of reconstruction or replacement of the radial head to restore the radial length and stability.

The classic nightstick (truncheon) injury is described as a transverse fracture of the distal ulna. Typically caused by a blow to the ulna border of the forearm in an adult, who raises their arm over their head to ward off a blow, it may occasionally have a less violent aetiology and represent a fragility fracture. Radial fractures and displaced fractures of the ulna have been associated with a high incidence of non-union if managed conservatively. For this reason plate fixation is the treatment of choice.