FRACTURE OF DISTAL RADIUS
Approximately 80% of fractures of the forearm involve the distal radius and the DRUJ. Fractures of the distal radius are common injuries in children, adults, and elderly persons, usually resulting from a fall on the outstretched hand. Significantly more force is required to fracture this part of the radius in adolescents and young adults than in older adults with severe osteoporosis. Fractures that involve the joint are usually caused by high impact.
Evaluation of any injury in the distal radius must include radiographs of the wrist, forearm, and elbow. True anteroposterior, lateral, and sometimes oblique views are required to determine the extent of the injury. If intra-articular involvement is suspected, computed tomography can be performed to determine the degree of joint displacement and guide management. Fractures of the distal radius may be stable or unstable, depending on the degree of comminution and initial fracture displacement. Associated injuries to the carpal bones and/or ligaments of the wrist must be evaluated for and managed appropriately.
The precipitating injury of the extension/compression, or Colles, fracture is a fall on the outstretched hand. The deformity is caused by dorsal displacement of the distal radius and swelling of the distal portion of the forearm and is referred to as a “silver fork” deformity. Successful treatment involves restoration of (1) the radius to its proper length, (2) the radial inclination and volar tilt of the distal radius, and (3) the congruity of the articular surface of the distal radioulnar and radiocarpal joints. Loss of more than 5 mm of radial length (easily measured by using the styloid process of the ulna as a reference point) may result in disability. Restoration of the volar tilt of the distal radius is critical to long-term outcomes and diminishes the risk of altered carpal kinematics, which would lead to degenerative changes of both the radiocarpal and midcarpal joints.
If more than 50% of the metaphysis of the distal radius is comminuted, the fracture is probably unstable and reduction is difficult to maintain in a plaster cast alone. This type of fracture is best visualized on the lateral radiograph. Definitive treatment is determined not only by the injury but also by the patient’s age and occupation. Anatomic restoration is more important in younger, working patients, whereas some loss of radial length and tilt may be more acceptable in sedentary patients.
Fracture of Articular Margin of Distal Radius
Fractures of the articular margin, called Barton fractures, represent a small percentage of fractures of the distal radius. This type of fracture is best described as a fracture-dislocation of the wrist. Correct diagnosis of Barton fracture is very important because it is an inherently unstable injury and therefore difficult to manage with the traditional closed method. The injury is further defined by the direction of the dislocation. If the dorsal aspect of the articular margin, or rim, is fractured and the carpus is displaced dorsally, the injury is termed a dorsal Barton fracture; conversely, the more common volar Barton fracture refers to a fracture in which the dislocation is displaced volarly. In many cases, however, the Barton fracture is nondisplaced and can be treated with immobilization in a plaster cast with weekly follow-up and repeat radiographs.
A fall on the outstretched hand is the most common cause of the Barton fracture. The impact wedges the lunate against either the dorsal or the volar margin of the articular surface of the radius. The lunate acts as a lever against the articular surface, causing it to fracture. The carpus is then dislocated along with the fragment of the articular margin of the radius.
The stability of the closed reduction depends on the integrity of the radiocarpal ligament on the side opposite the injury. For example, the stability of the reduction of a dorsal Barton fracture is best preserved by positioning the wrist in extension to take advantage of the intact volar carpal ligament.
Reduction of a Barton fracture is difficult to maintain with an external fixator or with pins and plaster; there-fore, treatment with open reduction and internal fixation (ORIF) is usually indicated for fracture-dislocations that have large fragments. Barton fractures that involve a significant portion of the articular surface are usually unstable and must be treated with ORIF, using a small buttress plate to maintain the reduction. Buttressing the distal fragment maintains joint congruity. It is not absolutely necessary to insert screws into the distal fragment (which may be significantly comminuted) to maintain the reduction.
Fracture of Styloid Process of Radius
Most nondisplaced fractures of the styloid process of the radius can be treated with immobilization in a plaster cast. Displaced fractures must be anatomically reduced and held with either a pin or a screw. Often, treatment with closed reduction and percutaneous pin fixation is sufficient. Fractures of the styloid process are frequently accompanied by dislocations of the lunate. Thus, with any fracture of the styloid process, the carpus should be examined for other injuries. Some surgeons are utilizing wrist arthroscopy to aid in the treatment of these injuries. Advantages of arthroscopy include direct inspection of the articular reduction, as well as the ability to identify associated ligamentous injuries that commonly occur with this injury pattern. Closed reduction and immobilization in a plaster cast constitute a dependable treatment for many fractures of the distal radius, but after satisfactory manipulative reduction some fractures (particularly unstable injuries in young, active adults) require operative fixation. Current fixation options include closed reduction and percutaneous pin fixation, external fixation, or ORIF with a recent trend toward volar locked plating.
The best determinants of how to treat fractures of the distal radius are the character of the fracture, whether it is stable or unstable or intra-articular or extra-articular; the life style and age of the patient; and the experience of the treating surgeon.
Closed Reduction and Plaster Cast Immobilization
Colles fractures can often be reduced using manipulation or traction. After a sterile preparation of the forearm, local infiltration of lidocaine into the hematoma at the fracture site often provides adequate anesthesia for manipulating the fracture. Regional anesthesia, either an axillary or a Bier block, is also commonly used; but if the patient is very apprehensive or a more extensive procedure is needed, then general anesthesia may be required.
Traction using fingertraps and weights is an effective method of reducing Colles fractures. The fingertraps are secured to the middle and index fingers and the thumb to suspend the arm; 10- to 15-lb weights are attached by a sling to the upper arm to provide countertraction. Gentle manual manipulation is often needed to fully reduce the fracture. Hyperextension or re-creation of the deformity should be avoided, if possible.
If the surgeon decides to manipulate the fracture without using fingertraps, an assistant is needed to hold the proximal forearm and provide countertraction. The fracture is then reduced with gentle longitudinal traction. A sugar tong splint or a long-arm circular cast is applied after reduction. The sugar tong splint is easier to apply than the long-arm cast and can be tightened on follow-up visits. To maintain the reduction, it is important to mold the plaster snugly to the forearm using three-point molding. The final position of the wrist within the splint/cast must avoid extreme positions (especially wrist flexion) because these can exacerbate nerve compression, specifically the median nerve within the carpal tunnel. Patients must be monitored on a weekly basis for the first 3 weeks with radiographs at each visit confirming maintained reduction. Six weeks of immobilization is the standard length of immobilization, followed by protected motion and progressive strengthening.
Closed Reduction and Pin Fixation
Fractures that do not remain in acceptable alignment after closed reduction require operative fixation. Patients with excellent bone quality and an intact (i.e., noncomminuted) volar cortex are candidates for closed reduction and pin fixation. The most common method is “intrafocal” pinning and utilizes Kirschner wires that are placed distal to proximal both through the radial styloid as well as dorsally into the fracture site and then engaging the volar cortex. This method is not acceptable for fractures with metaphyseal comminution or intra-articular involvement. The pins can be removed at 4 weeks, and protected motion is started. The most common complication with this treatment method is pin site infection requiring antibiotic treatment or early removal of the pins. The most feared complication is complex regional pain syndrome arising from injury to the superficial radial nerve braches during placement of the Kirschner wire.
Fractured associated with severe, open soft tissue injuries or fractures that undergo either pin or plate fixation that is tenuous benefit from external fixation. The most common method of external fixation is a spanning wrist fixator. Threaded pins are placed into both the second metacarpal as well as the distal third of the radius and connected with clamps and bars to maintain length and neutralize forces. Newer devices have been developed that do not cross the wrist and show promise in the treatment of complex distal radius fractures. Pin track infections are common. Complex regional pain syndrome is also a risk from both sensory nerve injury and overdistraction of the wrist.
Open Reduction and Internal Fixation ORIF is arguably the current treatment of choice for most unstable, displaced distal radius fractures. Traditionally, plates and screws were placed dorsally along the distal radius, acting as a buttress plate. The intimate relationship of the extensor tendons to the bone led to high rates of extensor tendon complication requiring either hardware removal secondary to extensor tenosynovitis or tendon repair/reconstruction secondary to frank extensor tendon rupture. Locked plating technology, in which the screw heads are threaded into the plate, allows placement of the hardware along the volar cortex of the distal radius. The overlying flexor tendons are protected from the implants by both distance and the pronator quadratus muscle. The “fixed angle construct” buttresses the articular surface with screws/pegs or tines placed immediately subchondral to the articular surface, and then the plate is fixed to the shaft of the radius. Excellent reduction can be obtained, and the rigid constructs allow early mobilization and therapy. Soft tissue irritation and injury from the hardware remain a concern and can be diminished by appropriate position along the bone and avoiding dorsal screw penetration (bicortical fixation is not required with these implants). More complex injuries with comminution of the articular surface or significant volar and dorsal involvement may require ORIF with multiple plates and screws. Fragment-specific fixation is the concept to applying smaller implants to individual fracture fragments, leading to stable fixation and anatomic restoration of complex articular injuries.
The short-term complications associated with all fractures of the distal radius are significant and demand early treatment to prevent long-term residual disability.
To control edema after fracture reduction and casting, the arm is elevated on pillows or in a sling above the level of the patient’s heart and ice bags are applied over the cast. Severe swelling may necessitate splitting the cast, and the cast may need to be trimmed to prevent skin irritation. The physician should encourage frequent and full active range of motion of all the finger and thumb joints to prevent stiffness, which is common, and to reduce swelling. Any persistent pain under the cast should be investigated with the plaster removed entirely.
Acute injury of the median nerve after fractures of the distal radius is an uncommon but debilitating problem. After injury, fracture displacement combined with swelling occasionally distorts and compresses the median nerve, causing pain or numbness. The symptoms of median nerve compression usually subside or disappear when the fracture is reduced. If symptoms persist after reduction particularly if the patient experiences burning pain in the median nerve distribution prompt surgical decompression of the nerve in the carpal tunnel may be necessary. Mild residual numbness and tingling in the median nerve distribution usually subside with time or can be relieved after fracture healing with a carpal tunnel release. Sometimes, acute compartment syndrome of the forearm is associated with fractures of the distal radius. The characteristic symptom is excessive pain combined with numbness and pain on passive movement of the thumb and fingers. Compartment syndromes must be recognized promptly and should be treated with fasciotomy.
Long-term complications develop in 30% to 35% of patients. Loss of the reduction is the most common problem, which can be minimized or corrected by early identification of the displacement with radiographs taken at weekly intervals in the first 3 weeks after injury. Repeat closed reduction and casting may be needed; unstable fractures may require ORIF or application of an external fixator to restore and maintain alignment. After 3 weeks of healing, fractures of the distal radius have stabilized and will rarely settle with further loss of radial length. If the fracture heals with a residual deformity (usually a dorsiflexion deformity), this can be corrected with surgery. Radiocarpal and carpal instability are also associated with injuries of the distal radius. Osteoarthritis of the distal radioulnar joint may produce persistent pain. Fortunately, nonunion is rare, but if it occurs, treatment comprises ORIF and bone grafting.
Rupture of an extensor tendon, most commonly of the thumb, is seen following fractures of the distal radius, as is stenosing tenosynovitis of the first dorsal compartment (de Quervain disease). Reflex sympathetic dystrophy is a very debilitating complication of any musculoskeletal injury. It is frequently a result of hand and wrist fractures, but it develops most often after treatment of unstable fractures with pin fixation, external fixation, or pin and plaster fixation. The early recognition and treatment of reflex sympathetic dystrophy is essential to restore good function.