Diaphyseal Fractures of the Forearm

Proximal Radioulnar Joint

The PRUJ is stabilized by the annular ligament, the joint capsule, and the radial collateral ligament of the elbow. The supinator muscle is a dynamic stabilizer of the PRUJ. An in vivo study on 12 healthy adult elbows showed the highest congruency of the PRUJ in supination (92%) followed by the neutral position (83%). The lowest congruency of only 77% was found in pronation.

Distal Radioulnar Joint

The movement of the distal radius around the ulnar head in pronation and supination has both rotational and translational components. In pronation, the ulna head corresponds to the dorsal edge of the sigmoid notch. In supination, the ulna head corresponds to the palmar edge of the sigmoid notch. Therefore the DRUJ does not have a single center of rotation. In an in vivo biomechanical study under three-dimensional computed tomography (CT) control, a translation within the DRUJ of 0.51 ± 1.79 mm in isometric pronation and of 0.13 ± 2.07 mm in isometric supination in 10 healthy young people was found. During forearm rotation, the sigmoid notch slides substantially longitudinally against the ulnar head at each part of the forearm rotation arc. The contact site of the sigmoid notch with the ulnar head moves slightly distally during forearm pronation and proximally during supination. The mobile distal radius is attached to the stable ulna head by the dorsal and palmar radioulnar ligaments and the base of the triangular fibrocartilage complex (TFCC). Newer in vivo studies have shown that the limitation of pronation and supination of the forearm is more complex. Pronation is limited by the dorsal superficial and the palmar deep radioulnar ligaments, and supination is limited by the palmar superficial and the dorsal deep radioulnar ligaments. The extensor carpi ulnaris (ECU) muscle, which runs through a strong sheath at the dorsal side of the ulna head, stabilizes the DRUJ and hinders the ulnar carpus from dislocating palmarly. The pronator quadratus muscle is an active stabilizer of the DRUJ.

Interosseous Membrane

The interosseous membrane combines the shafts of the radius and ulna. The fibers of the membrane show an oblique orientation that allows the radius to turn around the ulna in a limited dimension. The interosseous membrane consists of flexible areas between strong and inelastic bundles. The thickness of the distal interosseous membrane, which originates from the distal one-sixth of the ulna shaft and inserts proximal to the sigmoid notch at the radius, varies widely among specimens, and the distal oblique bundle exists in only 40% of the specimens. The distal oblique bundle was shown to have a significant impact on DRUJ stability. In a cadaver study, the central bundle of the membrane showed the highest stiffness compared with the proximal and distal bundle in forearm position between 45 degrees of pronation and supination. In another study, the maximum load to failure for the interosseous membrane was 1021.50 ± 250.13 N in fresh-frozen cadaver specimens. In 4 of 10 specimens, a fracture of the distal ulna occurred before disruption of the interosseous membrane. These findings give a good impression of the importance of this almost-underestimated membrane for forearm stability.

The ulnar head and the radial head are the keystones for tightening the interosseous membrane and the distal and proximal radioulnar ligaments. The resection of the ulnar or the radial head allows the radius to come nearer to the ulna with narrowing of the interosseous space. This produces a collapse of the tension of the interosseous membrane and results in a longitudinal instability of the radius ( Fig. 43.1 ).

Muscles

Nerves and Vessels

The radial nerve runs cubital from the radial condyle onto the supinator. Its deep branch runs through the supinator muscle belly and the interosseous membrane to its dorsal side, where it runs distally to the wrist (interosseus dorsalis nerve). The superficial branch stays radially and runs beneath the brachioradialis muscle and through the antebrachial fascia to the radial dorsal hand (ramus superficialis radialis nerve).

The median nerve shows high variability in its relation to the pronator teres muscle bellies. Mostly, the deep branch runs through the pronator teres, stays palmar to the interosseous membrane, and runs distally to the wrist (interosseus anterior nerve). The superficial branch runs straight down through the carpal tunnel to the radial fingers.

The ulnar nerve runs through the sulcus ulnaris around the ulnar epicondyle through the flexors and the loge de Guyon to the ulnar fingers.

The brachial artery lies in the middle of the cubita. It is an end artery, so it needs to be reconstructed if injured. In the cubita, the brachial artery bifurcates into the radial and ulnar arteries. The radial artery runs down along the flexor pollicis longus muscle to the wrist, and the ulnar artery runs down palmar to the ulna. At the hand, both arteries build the arterial arcs.

Arbeitsgemeinschaft Für Osteosynthesefragen/Orthopaedic Trauma Association Classification

Today, the comprehensive Arbeitsgemeinschaft für Osteo-synthesefragen/Orthopaedic Trauma Association (AO/OTA) classification is the most common fracture classification. The fracture localization at the diaphyseal forearm is specified by the number 22. The severity of the fracture is classed from A for two-part fractures to B for wedge fractures to C for complex fractures ( Table 43.1 ). This classification is very useful to make clinical studies comparable. In daily communication, the abstract numerical system may lead to misunderstandings. Therefore an additional description of the fracture patterns and the dislocation of the fragments should be given in personal communications. The easiest way to transport the information nowadays is to make the radiographs visible on an electronic medium (e.g., sending the radiographs as DICOM or jpeg files per email).

Monteggia Fracture

In diaphyseal and metaphyseal fractures of the ulna, a special focus has to lay on the PRUJ to detect dislocation and instability of the radial head. A dislocation of the radial head in combination with a proximal ulna shaft fracture was first described by Monteggia in 1814. In 1967, Bado classified four types of injury ( Fig. 43.2 ). The fracture is more common in children. In adults, the more complex type IV lesion, meaning a dislocation of the radial head combined with a fracture of the ulna and the radius, can be seen in high-impact trauma (see Fig. 43.2D ). The Monteggia fracture is often underestimated as an ulna shaft fracture that may be treated conservatively. To avoid this pitfall, additional radiographs of the elbow in two planes are standard in ulna shaft fracture diagnostics. The axis of the radius neck has to run through the center of the capitulum humeri in all planes to exclude a radial head (sub)luxation.

Galeazzi Fracture

A fracture of the radius may be combined with a dislocation of the DRUJ ( Fig. 43.3 ). This type of fracture appears mostly in the distal third of the radius and was first described by Galeazzi in 1934. In highly violent trauma, a dislocation of the DRUJ may also appear in combined fractures of the radius and ulna. In dislocated distal radial fractures, radiographs are often confusing according to the position of the ulnar head because of oblique planes. In case of doubt, a CT scan makes the position of the DRUJ clear.

Essex-Lopresti Lesion

In 1946, Curr and Coe first described a combination of a radial head fracture, a lesion of the interosseous membrane, and an instability of the DRUJ. In 1951, Essex-Lopresti described two cases of such a lesion ( Fig. 43.4 ). He pictured a violent longitudinal compression to the forearm as the mechanism for causing such a lesion. The major lesion is the disruption of the suspension of the radius at the ulna involving the annular ligament, the interosseous membrane, and the capsule and ligaments of the DRUJ. The tension of the muscles leads to a proximalization and dislocation of the radius over time. This results in a painful restriction of elbow movement, limitation of forearm rotation, and reduced weight bearing on the instable forearm as well as complaints in the wrist caused by ulnocarpal impaction. An isolated resection of the fractured radial head increases the instability and should be avoided. Because of the pain caused by the radial head fracture, the lesion may be overlooked at the first presentation after trauma. To avoid underestimation of this injury, it is essential to test the stability of the DRUJ in every case of radial head fracture.

Classification of Associated Soft Tissue Trauma

The associated soft tissue trauma has to be recognized because of its prognostic value for the outcome. The contamination of the wound and denudation of the bone increase the risk for osteomyelitis, nonunion, and delayed union of the fracture. A defect injury of the muscles and nerve injuries result in functional deficiency. The first widely accepted classification system for open fractures was introduced by Gustilo and Anderson in 1976 ( Table 43.2 ). It was initially based on open tibial fractures but was even used for open fractures in other localizations. Despite relatively low interobserver and intraobserver reliability, which was found for this classification by others, using this classification system and the implicated therapy led to a significant decrease of deep wound infections and osteomyelitis. In 2010, the OTA introduced a new classification for open fractures of the extremities and the pelvis, including new strategies for treatment, such as negative-pressure wound therapy (NPWT), to optimize communication for research and clinical care. This new classification accounts for the various injured tissues separately to get a better assessment of the factors that must be considered for treatment. The highest reliability within the OTA classification was found for arterial lesions (kappa value [κ] = 0.9). Lesions of the skin (κ = 0.69), bone loss (κ = 0.65), contamination (κ = 0.48), and muscle injury (κ = 0.40) showed a low reliability. The low κ values show a lower reliability for the newer AO/OTA classification than for the Gustilo and Anderson classification, which is more simple.

Severe soft tissue trauma such as a Morel-Levallée lesion and compartment syndrome may appear without skin lesions. These lesions are much more difficult to detect because the clinical signs appear at least within 72 hours after trauma. This means that the soft tissue has to be reevaluated through the débridements to get an idea of the real dimension of soft tissue damage ( Fig. 43.5 ). The key symptoms of soft tissue trauma are severe pain, swelling, loss of function and sensitivity to touch, white and cold skin, and pulselessness as well as a fluctuating epifascial swelling. Short transverse fractures of the long bones and skin contusions are signs of a high impact with a high risk for a compartment syndrome.

Undiagnosed or delayed recognized compartment syndrome may lead to Volkmann's contracture with a complete loss of hand function ( Fig. 43.6 ). A decollement of the epifascial soft tissues (Morel-Levallée lesion) may also be overlooked during the first survey. This lesion has to be treated by resection and drainage of the hematoma and compression before the hematoma leads to skin necrosis.

Anamnesis

Fractures of the forearm may occur after different injuries, such as a fall, strike, or distortion. Therefore anamnesis should include the circumstances of the injury to detect the power of the impact on the forearm. Ask for the height from which the patient fell and which part of the body first contacted the ground. How soft or hard was the ground? What were the material, weight, speed, and height of the fall of the object that stroked the forearm? What were the speed and the deformity of the car or the (motor)bike and the helmet, and in the case of a traffic injury, did the airbag inflate? When the patient has injuries with open wounds, ask for the material of the object (e.g., glass, wood, metal) and contamination (e.g., knife used for cutting meat, poison, chemicals). These facts give a first idea of the impact and the contamination. The localization and intensity of pain and the loss of sensitivity and muscle function help to avoid further damage through the physical examination.

Clinical Examination

A careful evaluation of the whole patient is mandatory even in polytrauma patients. In cases of deformation, manipulation should be avoided before a radiologic examination has been completed to avoid further injuries and unnecessary pain for the patient. Neurovascular evaluation should always be performed (see Videos 43.2 and 43.3 ). Be aware that every neurologic symptom of the arm can also be caused by an injury of the cervical spine. Sterile dressings of open wounds should be left in place in the emergency department to avoid further contamination. If there are no signs of fracture or dislocation on the radiographs, the extension and flexion of the elbow should be measured with a goniometer at the radial side. At the elbow, the radial and ulnar epicondyle, the olecranon, and the radial head should be examined for pain under mild pressure. The intensity of the pressure should be increased slowly to avoid pain to the patient. Crepitation at the radial head under passive forearm rotation may be caused by a radial head fracture or synovitis of the elbow. The stability of the collateral ligaments should be tested in full extension and 30 degrees of flexion. The best location for palpation of a hemarthros of the elbow is between the olecranon and the radial condyle in a 90-degree flexed elbow (see Video 43.4 ). Forearm rotation should be measured with the humerus adducted to the thorax to block glenohumeral rotation. The extended thumbs or a pencil in each wrist shows the rotation of the forearm to the humerus. Translation of the PRUJ and DRUJ ( Fig. 43.7 ) should be performed in the plane of the joint at both sides. Because of high interindividual differences in joint mobility, the difference from the uninjured side is much more important than the absolute instability. Beneath the instability, the pain is an important sign for an acute traumatic lesion of the joint (see Video 43.5 ). To avoid overtreatment, be aware that only a difference from the uninjured side is pathologic.

Extension and flexion of the wrist should be measured with a goniometer between the ulna and the fifth metacarpal. Ulnar and radial abduction is measured between the radius and the third metacarpal at the dorsal side. In the initial phase, the radiocarpal and mediocarpal translation, as well as the translation between the carpal bones, gives a good idea of carpal lesions (see Video 43.6 ). Pain to pressure at the dorsoulnar radiocarpal joint and a positive ulnar impaction test are signs of a lesion of the TFCC.

Radiologic Examination

Radiographs of the forearm in two planes in neutral rotation should be performed. In the case of doubt about an injury of the PRUJ or the DRUJ, additional radiographs in two planes of the elbow or the wrist, respectively, should be performed. The axis of the radial neck should run through the center of the capitulum humeri in every plane; otherwise, the radial head is displaced (e.g., Monteggia fracture). A hemarthros of the elbow, as a sign of an articular lesion, can easily be detected by the “fat pad sign” on the lateral radiographs of the elbow ( Fig. 43.8 ). The radial head view is an oblique plane that shows the radial head without overlapping with the ulna ( Fig. 43.9 ). This plane is very useful for the detection of radial head fractures. The right position of the DRUJ is more difficult to detect. Longitudinal displacements of the DRUJ may be stable after reposition of the radius shaft fracture. Palmar or dorsal dislocations of the distal radius are very variable, and exact lateral views are necessary to detect mild dislocations. A fracture of the ulnar styloid may be a sign for DRUJ instability. In simple forearm shaft fractures without additional articular fractures, there are very rare indications for a CT scan. In complex diaphyseal fractures, in which the reference for the osteosynthesis is lost, a three-dimensional CT scan of both forearms may be helpful to use the uninjured forearm bones as a mirrored model for the reconstruction of the fractured bones (see Complex Fracture of the Radius, Ulna Simple or Wedge ). In cases of a pulseless extremity, the vascular injury should be located by a CT scan with contrast medium (CT angiography).