External fixation for distal radius fracture (from OTA)

External Fixation
OTA BFC Lecture
External fixation has been used increasingly to treat unstable fractures of the distal radius. Indeed, fracture care in part involving the use of external fixation is probably the treatment of choice for unstable extra- articular injuries with extensive comminution (in which percutaneous pinning techniques have a significant incidence of failure) and for the majority of unstable, comminuted intra-articular injuries. Several retrospective and prospective studies have documented that both the anatomic and functional results with external fixation are superior to cast treatment of these fractures. ~ However, enthusiasm over the use of external fixation in these fractures must be tempered by a thorough understanding of the indications, theoretical basis, limitations, and complications of these devices.

Commonly cited indications for external fixation of distal radius fractures include unstable extra- articular fractures with significant comminution, comminuted intra-articular fractures, fractures that have failed to maintain reduction with other treatment modalities, open fractures, and fractures in a polytrauma patient. Volarly displaced and comminuted injuries usually require formal volar exposure and open reduction and internal fixation (ORIF); however, external fixation is often used to augment stability when less than rigid fixation is achieved because of small bony fragments or osteoporosis.

External fixation devices provide fracture reduction and maintenance of that reduction through constant ligamentotaxis. Various fixator designs are available and these vary greatly in their biomechanical properties as well as in their specific techniques. Advantages offered by more recent fixator designs include the ability to apply the fixator prior to fracture reduction, a system for controlled adjustment of traction force during the course of treatment, ability to apply traction force in multiple planes, ability to place pins in a converging pattern, and ability to position the wrist in extension while maintaining fracture reduction. The comparison of reported results with these various fixators is not yet possible because a controlled study comparing these devices has not been conducted.
Despite excellent reduction of radial length and inclination, it had become evident from early reports that restoration of palmar tilt of the distal radius as well as anatomic reduction of the radiocarpal joint surface often were not achieved with external fixation. The strong palmar ligaments have been shown to become taut and limit radiocarpal distraction, while the weaker, Z-shaped dorsal ligament complex has yet to reach maximum length.{36} This prevents purely longitudinal traction from restoring palmar tilt. Similarly, the dorsomedial radiocarpal fragment is not reduced.

Complications with the use of these devices have been many, ranging from 15% to as high as 60% in early reports. Complications related to achieving and maintaining reduction include failure to restore palmar tilt or radiocarpal alignment, overdistraction, late fracture displacement, and nonunion. Complications related to the pins include pin tract infection, pin breakage, pin loosening, fracture through pin sites, and injury to the iatrogenic nerve and to tendons. Complications related to distal radius fractures in general include median neuropathy, reflex sympathetic dystrophy, and decreased motion and grip strength.

Recent reports of the results of external fixation for distal radial fractures have shown a dramatic decrease in the complication rate because potential complications are better appreciated. The failure of longitudinal traction to restore palmar slope and radiocarpal alignment in some injuries must be recognized at the time the fixator is placed. Agee has introduced the concept of triplanar ligamentotaxis with palmar translation of the carpus utilized to achieve restoration of palmar slope in response to this problem.{37} Supplementing longitudinal traction with limited open reduction techniques and internal fixation in order to correct both palmar slope and radiocarpal alignment has been described.38~39 These techniques involve reduction through a small dorsal incision and radiographic ally controlled elevation of articular fragments with an awl or elevator followed by pin fixation of these fragments. As greater duration and magnitude of distraction force have been shown to be associated with posttreatment stiffness and decreased strength regardless of anatomic result (especially when associated with resultant radiocarpal lengthening or positioning of the wrist in flexion during fixator treatment), care has been taken to limit radiocarpal distraction to 5 mm or less and to maintain the wrist in neutral or extension during the course of external fixation.{40,41} The theoretical value of segmentally decreasing traction force after 3 weeks has not yet been specifically documented, and this practice has been associated with loss of reduction by some authors. Cancellous bone grafting of the metaphyseal region has been advocated in order to improve reduction and decrease the duration of external fixation to 3 weeks without this complication.{42} Pin complications may be minimized by meticulous detail to identification of nerves and tendons, predrilling, appropriate pin sizing, and release of skin tension.{43} The importance of early aggressive treatment of pain, limited motion, and median neuropathy cannot be overstated and includes organized and frequent occupational therapy, edema control, adequate pain control, and carpal tunnel release when indicated. In 1987, the concept of dynamic external fixation of these injuries as a means of allowing radiocarpal flexion and extension during treatment was introduced. Potential advantages cited included better restoration of function as well as improved cartilage healing. Studies of cadaveric specimens, however, have documented fracture site movement during wrist motion with these devices. A prospective study comparing dynamic fixation to static fixation with the AO frame documented a higher incidence of loss of reduction and technical complications, as well as poorer functional results in the dynamic fixator group.{44} At present, no study favors these devices over conventional fixators.

Utilization of these new concepts has led to improved results and a dramatic decrease in complications with external fixation. Successful anatomic and functional outcomes have been documented in 80% to 90% of patients studied with few major complications despite high-energy comminuted injuries.{37,45,46} The choice of fixator at this time remains up to the individual surgeon. The principles of anatomic extra-articular and intra-articular reduction, strict attention to fixator application, and augmentation with internal fixation and/or bone grafting, when needed, should be followed closely.