Forearm Fractures

Etiology

The forearm fractures may result from both low energy and high energy trauma. The most common mechanism of injury for such injuries is axial loading applied to the forearm, which is a fall onto an outstretched hand.[6] In adults, the other common mode of injuries that result in forearm fractures are motor vehicle accidents, athletic injuries, and falls from height. These mechanisms of injury can cause either direct or indirect injuries. The other less commonly seen mechanisms of injury to the forearm include gun-shot injuries and nightstick injuries.[7]

Epidemiology

The forearm fractures are common in the pediatric population, with an incidence of around 1 in 100 children each year, and the peak incidence occurs in the 5 to 14 years age group accounting for approximately 34% of the cases. Both bone diaphyseal forearm fractures constitute around 5.4% of all fractures in children under 16 years of age. Among adults, a relatively higher incidence is reported between 25 to 34 years of age group.

In the forearm fractures, the most common site is at the distal radius or ulna (32.9%), and the least common location is the proximal region (2.8%). Open fractures, on the other hand, most commonly involve the diaphyseal region.[8][9]

Pathophysiology

Patho-anatomy and Biomechanics

The forearm unit consists of radius, ulna, proximal and distal radioulnar joints, and secondary soft tissue stabilizers, including a triangular fibrocartilage complex (TFCC) and the interosseous membrane (IOM). Proximally, the elbow joint capsule and annular ligament stabilize the proximal ulna and radial head. Distally, the ulna articulates with the sigmoid notch of the radius and is stabilized by a triangular fibrocartilage complex and the wrist joint capsule.

Interosseous membrane is located between the radius and ulna. It has five components: 1) the central band, 2) the distal oblique bundle, 3) an accessory band, 4) a proximal oblique cord, and 5) a dorsal oblique accessory cord. It provides stability to the distal radioulnar joint, longitudinal stability to the forearm, and also provides an attachment to the forearm muscles.[10][11]

The radius and ulna and the secondary soft tissue stabilizers act as a joint that helps in the pronation and supination movements. The key muscles which help in the supination are the biceps brachii and supinator, whereas pronator teres and pronator quadratus help in pronation; these muscles are the primary deforming forces in the forearm fractures. The various movements that occur at the distal end of the forearm include wrist flexion, wrist extension, ulnar and radial deviation. Similarly, elbow flexion and extension occur at the ulnohumeral joint.[11]

History and Physical

The patients who sustain forearm fractures usually present to the trauma and emergency department with a history of high-velocity trauma. It is of utmost importance to rule out other life-threatening associated injuries with these fractures. A thorough examination should be carried out using the ATLS protocol, including primary and secondary surveys. A structured and systemically performed primary survey is the heart of the ATLS protocol during the initial assessment of trauma patients. The secondary survey includes eliciting a proper history, complete head-to-toe examination, and local examination of the affected parts once the patient is stabilized.[12]

Forearm fractures should be diagnosed through a detailed history, clinical examination, and relevant radiological investigations. The patients usually complain of acute pain, swelling, local tenderness, and visible deformity at the site of trauma or fracture in the forearm. History taking should always be followed by a clinical examination to rule out open fractures and associated soft tissue injuries. A systematically performed neurological examination of peripheral nerves is necessary to rule out any neurological injury in the affected extremity. Once assessed, the patency of the radial and ulnar arteries should be well documented for further reference and treatment prognosis. Early identification of the signs and symptoms of compartment syndrome is necessary to avoid the dreaded complications of tissue necrosis and ischemia.[6]

Evaluation

Plain Radiography

The forearm fractures are routinely diagnosed with the help of plain radiographs, including anteroposterior and lateral views of the forearm. A standard anteroposterior view of the forearm is taken with the elbow extended and the forearm in full supination. These images should involve the elbow and wrist joint for a complete evaluation of either joint. A lateral view can result in overlapping of the radius and ulna; therefore, an oblique view of the forearm can be useful to determine the fracture pattern, whether it’s a simple fracture or comminuted fracture.

There is a high chance of injury to the distal radio-ulnar joint (DRUJ), proximal radio-ulnar joint, and elbow dislocation in forearm fractures. The features suggestive of DRUJ instability are dorsal displacement of the distal ulna, change in ulnar variance, fracture of the base of styloid, and widening of the DRUJ on the PA view. The distal third radius fractures with features of DRUJ instability suggest Galeazzi fracture-dislocation. The associated injuries should be evaluated using anteroposterior and lateral plain radiographs of the elbow and posteroanterior and lateral plain radiographs of the wrist joint.[13][6]

CT Scan

Computed tomography (CT) is only indicated if there is a suspicion of intraarticular distal end radius fracture pattern. However, routinely CT and MRI are not frequently done for the assessment of acute forearm fractures.

MRI Scan

Magnetic resonance imaging (MRI) helps to diagnose DRUJ injury and associated TFCC injury.[14]

Classification

Although a number of classification systems exist to describe forearm fractures, only a few are practically useful in providing prognostic information and guiding treatment. No single classification takes into account all the types of forearm fractures. Due to this reason, anatomic descriptions of the fracture location, fracture pattern, degree of angulation, displacement, and associated soft tissue injuries are typically used to describe the forearm fractures.[15]

The AO/OTA classification is an alpha-numerical classification that is widely used for forearm fractures. Gustilo and Anderson classification and the OTA open fracture classification systems are used for open forearm fractures, whereas Monteggia and Galeazzi fractures have their own subclassifications.[5][16][17]

Treatment / Management

The ultimate goal of fracture management is to obtain acceptable reduction, stable fixation and bony healing, early return to activities of daily living, preservation of function, and minimizing complications.[15] In the case of forearm fractures, it is essential to achieve proper cortical contact, regain length, axial and rotational alignment to gain a good functional outcome.[18]

Conservative Management

There are only limited indications for conservative management in forearm fractures like unicortical fracture and undisplaced or minimally displaced fracture (<50% displacement, <10 degrees of angulation). Isolated ulna fractures have shown high success rates in non-operative management, including long-arm cast, functional brace, and close follow-up by serial x-rays.[19][6]

Operative Management

The forearm fractures are usually managed by surgical fixation, including closed or open reduction and internal fixation. Open reduction helps achieve anatomic reduction, stable fixation, and an early range of motion, thereby enabling patients to return to their pre-injured state as early as possible. Closed reduction and internal fixation can be performed using an intramedullary nail as a minimally invasive procedure which has a good favorable outcome in the pediatric population. At the same time, it is less preferable in adult forearm fractures since adequate reduction is difficult to achieve in a closed fashion.

Open Reduction with Plate and Screw Fixation

In both-bone forearm fractures, the order of fixation for the radius and ulna is based on fracture pattern and comminution. Initial fixation of the fracture with less comminution will restore the length and facilitates reduction of the other bone. When both the fractures are simple, preferably radius should be fixed first as it makes the forearm more stable and makes it easy to address the ulna. Placement of the plate is usually preferred on the volar surface. It provides proper seating of the plate and adequate soft tissue coverage; however, placement of the plate on the dorsal (tension) surface is biomechanically better.[6]

The management of open fractures depends on the grade of the fracture according to Gustilo and Anderson's classification. Grade 1 and 2 fractures with minimum contamination can be managed with definitive fixation after adequate debridement in a single setting. On the other hand, grade 3 and highly contaminated wounds should be managed by debridement and external fixation followed by staged internal fixation.[20]

Surgical Approaches

The majority of the forearm fractures are surgically approached, with the patient lying in the supine position. For volar approaches in the supine position, the limb can be abducted onto the hand table, whereas for dorsal and subcutaneous approaches limb can be adducted and internally rotated at the shoulder joint. The prone position allows access to the dorsal forearm. Using an individualized approach for both ulna and radius is preferable as a single incision approach will lead to cross union and restriction of supination and pronation.

A surgical approach to the radius is considered more difficult than approaching the ulna as the radius is surrounded by a muscular envelope and closely associated with neurovascular structures, particularly in the proximal third. The most commonly used approaches for radius include the volar Henry approach and the dorsolateral Thompson approach.

The Thompson approach is considered the best approach for the proximal and middle third of the radius; it uses the interval between the extensor carpi radialis brevis and the extensor digitorum communis. The most common complication associated with this approach is the injury to the posterior interosseous nerve; this can be prevented or reduced by supinating the radius, allowing safe elevation of the supinator from its insertion. The distal third of the Thompson approach is relatively subcutaneous and is considered to be safe.[21]

The volar Henry approach is an extensile approach to the radius. In this approach, the line of skin incision is from the lateral aspect of the biceps tendon to the radial styloid. The inter nervous plane depends on the area of the fracture. The benefit of this approach is that it allows better visualization of the proximal, middle, and distal parts of the radius.[22] Other volar approaches to the radius include FCR (Flexor carpi radialis) and modified FCR approach, which are slight modifications of the conventional volar Henry approach.

The ulna is located subcutaneously in the forearm throughout its length; therefore, a subcutaneous approach is used for the ulna exposure and reduction. The only known complication in this approach is the injury to the dorsal branches of the ulnar nerve, especially in the distal third.[21]

Methods of Fixation

Dynamic compression and limited contact dynamic compression are the most commonly used techniques for fixation of the forearm fractures. These are mostly used for simple fracture patterns, especially the transverse and short oblique types. They provide absolute stability at the fracture site and promote primary healing. A lag screw with a neutralization plate is used for oblique fractures. If the fracture is severely comminuted, it should be fixed by bridge plating mode. The intramedullary nail is a load-sharing device that can also be used for the fixation of forearm fractures. The advantages of nailing are preserving the fracture hematoma (closed reduction) and periosteal blood supply in the forearm.[6]

Dynamic Compression Plate

Dynamic compression plating (DCP) has been considered the gold standard treatment in forearm fractures.[21] DCP provides axial compression using an eccentrically placed screw; this screw has a congruent head to plate hole fit. The implant has been used in different modes like compression, neutralization, buttress plate, and tension band. It provides anatomical reduction and absolute stability by compression.[23]

Limited Contact Dynamic Compression Plate

Perren et al. reported the use of limited contact dynamic compression plate (LCDCP) in 1990. The fixation principle of LCDCP is very similar to the DCP. The advantages over the DCP are 1) decreased periosteal compression and damage, 2) preserves blood supply to the bone, 3) wavy surface provides an increased area for bone graft application, 4) altering the load of the plate delivers pure tension on the plate, and 5) avoids implant-related stress riser and thereby re-fracture after implant removal.[23][24]

Bridging Plate

A bridging plate is mainly used for comminuted fractures of the forearm. Minimally comminuted fractures with large fragments can be fixed with multiple lag screws. However, highly comminuted fractures are fixed by bridging proximal and distal fragments after proper reduction.

Intramedullary Nailing

Intramedullary nailing of the forearm shaft fractures has been changed for over a century. Newer trends of fracture treatment have evolved towards the biological fixation of the fracture by minimal handling of the soft tissues and periosteal blood supply. This method is more widely used in children than adults.

Intramedullary nailing can be done by open and closed methods. The advantages of intramedullary nailing over the plating are: 1) preserving soft tissues and primary hematoma,  2) less incidence of neurovascular injury, 3) less risk of infection, 4) minimally invasive and cosmetic, and 5) lowers the incidence of re-fracture.

Previously, solid small diameter nails were used, including Kirschner wires, Steinmann pins, rush pins, and larger V/U rods. The currently used non-locking nails for forearm fractures include square nails, rush pins, and TENS nails. The plating is preferred over the conventional non-locking nailing due to insufficient rotational and linear stability. However, recently a locking intramedullary nail has been introduced for forearm bones which overcomes the stability problem seen with the non-locking nails.[25][18] It can be done through direct visualization, provides sufficient bending, axial and rotational stability with different proximal designs, and does not require fluoroscopy guidance for distal interlocking. The ulna nail has both dynamic and static holes that allow proximal and distal locking. The nails follow the principle of 3-point fixation.[26](B2)

Intramedullary nailing is indicated in pediatric forearm fractures, segmental fractures, polytrauma, osteopenic bones, and those with poor soft tissue envelope. The contraindications for nailing include active infection, narrow intramedullary canal, concomitant metaphyseal or epiphyseal fracture, radial head and neck fractures, ulna, and radial metaphyseal fractures, which do not permit proper locking.[18]

Hybrid Fixation

Hybrid fixation involves the fixation of one bone with an intramedullary nail and the other bone with plating. It also provides good biomechanical stability, preservation of soft tissues, fewer complication, and a good functional outcome. Intramedullary nailing fixation of ulna and plate fixation of radius shows better biomechanical stability than the reversed fixation. In this combination, the plate fixation of radius controls the rotation and provides rigid fixation, whereas nailing is easier in the ulna as it is a relatively straight bone.[27]

Management of Galeazzi and Monteggia Fractures

Principles of management in Galeazzi fractures are the same as that for simple forearm fracture fixation. The adult Galeazzi fractures are highly unstable, so open reduction and stable fixation are required to restore normal anatomy and function. The volar Henry approach is commonly used for these fracture fixations, and plate-fixation is the preferred method of fixation.[28]

Monteggia fracture can be managed by either closed reduction or open reduction, depending on the type of fracture and stability of the radial head. If it is a simple fracture with a stable radial head, it can be managed by the closed reduction in an operative room under fluoroscopic guidance. If the radial head remains unstable even after reduction, the ulna fracture should be managed by internal fixation either by intramedullary nailing or plating, while in comminuted fractures, it should be managed by plate and screw fixation.[29]

Differential Diagnosis

The common differential diagnosis of forearm fractures includes elbow and wrist sprains, elbow and wrist dislocations, olecranon fractures, distal radius fractures, osteomyelitis, neuropathic osteoarthropathy, tenosynovitis, and bursitis. These can be diagnosed separately with the help of meticulous clinical examination along with relevant radiological investigations.

Prognosis

Overall, forearm fractures have a good prognosis with union rates of approximately 95% to 98%. It has been noted in various studies that the union rate is slightly higher in the case of radius fracture than ulnar fracture.[30][31][32] The plate osteosynthesis shows a slightly better outcome as compared to the third-generation intramedullary nail. In contrast, the first-generation intramedullary nail does not provide rotatory stability, and hence the outcome was poor compared to compressive plating.

The outcome of an open fracture depends on the severity and grade of the injury. Open fractures are associated with a high incidence of complications like infection and non-union, which results in a significant increase in morbidity and overall health care cost.[33]

Complications

Peripheral Nerve Injuries

The common neurovascular injuries associated with forearm fractures include ulnar nerve, radial nerve, and superficial branch of radial nerve injury. During operative procedures, the posterior interosseous nerve and radial nerves can get injured.[1][21][32]

Compartment Syndrome

Fractures are the most common cause of compartment syndrome in the forearm; the distal end of radius fracture is the most common cause. Diagnosis is made by clinical examination and compartment pressure monitoring of the forearm compartments. It is considered a surgical emergency and has to be treated promptly by early fasciotomy of the volar or dorsal compartment. Delayed diagnosis and late management may lead to tissue ischemia and necrosis.[34][35][36]

Infection

Infection is considered to be the most debilitating complication of all. The most common organism causing infection in forearm fractures is staphylococcus aureus. The incidence of infection in the forearm fractures treated with plate and screw fixation is approximately 3% (ranges from 0.8% to 6% in different studies). The common clinical findings include redness, swelling, a local rise of temperature, and tenderness at the infection site. For mild superficial infections, it can be treated with an oral antibiotic course; however, in deep infections, surgical debridement is the mainstay of treatment to prevent non-union and other complications.[32][31][37]

Non-union

The incidence of non-union is estimated to be around 2% to 10% of all forearm fractures. The cause is multifactorial, including lack of mechanical stability (inadequate reduction or fixation construct) and impaired biology of bone healing such as infection and metabolic disorders.[37][38][39] The fracture patterns like comminuted fracture, open fracture, soft tissue stripping, and location of fracture (distal third and middle third junction having least blood supply) also play an important role in the non-union of forearm fractures. Other patient factors like smoking, malnutrition, diabetes, steroid intake, and immunosuppression are also contributing factors leading to non-union.[40]

The management principles of non-union include excision of the non-union site, the opening of the intramedullary canal, anatomic reduction, and stabilization. The surgical intervention should provide stability and functional restoration for the fracture. The addition of bone grafting procedure provides stimulation for bone formation.[11]

Malunion

Malunion in forearm fracture is common, but the exact incidence is not stated in the literature. In a cadaveric study, Mathew et al. demonstrated that angulation of 10 degrees or less did not affect the forearm rotation significantly, even if both bones were mal-aligned. However, angulation of 20 degrees in the ulna or radius in either direction causes loss of pronation-supination of around 30 degrees.[41] In another cadaveric study, Tarr et al. stated that combined total angular deformities (radio-ulnar or dorso-volar) of 10 degrees or less lead to a loss of movement of 18 degrees or less, whereas 15 degrees of total deformity resulted in a loss of motion greater than 27 degrees.[42]

The loss of pronation is greater for angulation at the distal third radius, while the loss of supination is greater for the angulation at the middle third radius. Similarly, deformity of the middle third of the ulna affects more in forearm rotation.[43] Tarr et al. reported that the loss of movement after forearm fractures is equal to the magnitude of the malrotation.[42] On the other hand, Dumont et al. reported that the malunion of the radius in supination causes more loss of rotation than malrotation in pronation.[44]

Radioulnar Synostosis

Post-operative radioulnar synostosis commonly occurs in a single incision approach for both bone forearm fracture fixation. It is rarely seen with separate approaches. Bone grafting in the interosseous space increases the risk of synostosis. Therefore it is usually recommended to put the bone graft on the opposite side of the interosseous space. Various risk factors for the development of radioulnar synostosis include proximal third fracture, infection, head injury, and soft tissue trauma. Few proposed adjuvants to prevent radioulnar synostosis are early commencement of range of motion exercise, indomethacin, low dose radiation, and anconeus muscle interposition and interposition fat grafting.[6]

Refracture

Refracture is one of the least common complications after forearm fractures. The incidence of refracture is more in a patient who had got an implant removed after the union. The forearm fracture fixation with plate osteosynthesis forms a rigid construct that causes stress shielding, reduces vascularity, and causes osteopenia, leading to refracture.[31]