W4 Intramedullary Fixation of Distal Radius Fractures
Our understanding of distal radius fractures has continued to grow exponentially over the last 2 decades. Distal radius fractures are among the most common injuries affecting the musculoskeletal system, and investigators have developed many different methods of treating these fractures over the years. Treatment for these fractures have evolved as recognition of differing fracture types, fracture alignment, and morphology has improved.1 The long-standing treatment of cast immobilization has been used less frequently in recent years as patient demand, improved fracture reduction, and a quicker return to the activities of daily living have driven an increasing trend toward internal fixation. Improved biomaterials and implant technology have led to a veritable deluge of different implants designed to treat fractures of the distal radius. As the elderly population continues to increase in number owing to rapidly improving health care, the incidence of this common fracture will only continue to increase.
Standard treatment for distal radius fractures previously was cast immobilization. Closed reduction and percutaneous pinning came into vogue with the advent of the Kirschner wire. The external fixator began to take root as a viable treatment method as well.2 There were limits to the types of fractures that could be treated closed, however, leading to increasing recognition of the importance of restoring articular congruity and fracture alignment.3,4 This needed to be done in an open fashion, and open reduction and internal fixation became much more common. Various types of plate and screw constructs were used to treat fractures of the distal radius. Plates were applied internally to the distal radius because the idea of rigid fracture fixation with an internal implant was appealing to surgeons and patients.5
This trend has accelerated rapidly over the last decade, and at this point the most commonly used implant to treat fractures of the distal radius has become the volar plate.6 Other pioneers in the field of upper extremity surgery have championed the cause of column-specific fixation with smaller implants addressing specific load-bearing areas of the distal radius in an attempt to provide more rigid fixation with smaller implants.7 These methods all have been tremendously successful in treating fractures of the distal radius; however, problems still remain.8
There is a thin soft tissue envelope surrounding the distal radius, and the neurovascular structures are in very close proximity. Tendon and nerve complications are common with surgery of the distal radius despite advances in implant technology and lower profile implants.9,10 Locking screw technology has definitely improved fracture fixation and allowed for fewer complications because implants are lower profile; however, significant problems remain with tendon irritation and rupture, nerve problems, scar formation, stiffness, and the occasional need to remove implants.
The only type of implant that could potentially avoid these types of complications is an intramedullary one because the implant could be seated completely underneath the cortical surface and not cause impingement on neighboring soft tissue and neurovascular structures. In addition, these implants can be inserted in the most minimally invasive fashion.
As modern medicine has rapidly surged forward, a greater understanding of the basic science of fracture healing has resulted. It has become clear that preservation of the blood supply to fracture fragments can greatly aid in fracture healing and lead to better clinical results. If one could successfully reduce a fracture and maintain its alignment with a minimal amount of soft tissue trauma, while preserving the vascularity of fracture fragments, this would be optimal.
Intramedullary implants have become the standard of care for diaphyseal fractures of the tibia and the femur in patients who need operative fixation.11 These implants have been shown to have excellent results. The benefits of intramedullary fixation include less soft tissue trauma, preservation of the vascularity of fracture fragments, and an implant that acts as a load-sharing device, rather than a load-bearing one. Some prior investigators have examined the concept of intramedullary fixation for fractures of the distal radius, but no specific completely intramedullary implant for the distal radius had been developed.12–19
In an attempt to avoid many of the mentioned complications associated with the current surgical treatment of distal radius fractures, several investigators in conjunction with Wright Medical Technologies, Inc., have developed a novel intramedullary device (MICRONAIL) for fixation of distal radius fractures (Fig. W4-1). This implant uses fixed-angle locking screw technology in conjunction with an intramedullary construct to stabilize fractures of the distal radius rigidly, while preserving fracture fragment vascularity and minimizing soft tissue trauma.
FIGURE W4-1 MICRONAIL distributed by Wright Medical Technologies, Inc. (Arlington, Tennessee) has purple distal fixed-angle locking screws and gold proximal bicortical screws.
Indications
Intramedullary nail fixation is best indicated for extra-articular distal radius fractures that are unstable and cannot be maintained with closed reduction (Fig. W4-2). Simple intra-articular fractures of the distal radius also can be treated with this device, but the fracture should have a minimum number of stable articular fragments and should not have extensive articular comminution. Fractures also should not have excessive metaphyseal-diaphyseal comminution with proximal extension because the proximal fixation point for the device could be compromised resulting in a loss of reduction.
FIGURE W4-2 Virtual image of ideal intramedullary nail position.
The device is an excellent choice for malunion surgery and is best indicated for extra-articular malunions of the distal radius. The device can provide an immediate rigid construct in malunion surgery and better disperse loading forces through the distal radius because it is a load-sharing device rather than a load-bearing one. This immediate rigid construct is of great benefit in malunion surgery because the cortical defect that results after surgical correction can take several months to reintegrate, and during this time plate and screw constructs are subjected to tremendous loads that can lead to implant failure. It is necessary to evaluate carefully the initial injury and postreduction films to determine the appropriate patients amenable to intramedullary fixation.
Preoperative Planning
The preoperative radiographic evaluation follows a detailed history and physical examination and includes standard anteroposterior, lateral, and oblique radiographs of the injured wrist (Fig. W4-3). Careful assessment of the ipsilateral upper extremity, particularly the elbow and forearm, is necessary to rule out more complex injury patterns (e.g., Essex-Lopresti injuries). Further radiographs of the forearm and elbow can be acquired if deemed necessary from the physical examination and history. A thorough neurovascular examination is necessary, and a careful assessment of the associated soft tissue injury is of paramount importance.
FIGURE W4-3 Initial injury films showing dorsal angulation, radial shortening, and loss of radial inclination.
Contralateral radiographs of the opposite wrist are recommended to evaluate carefully each patient’s individualized anatomy of the distal radius and are useful in preoperative templating for implant selection. Postreduction radiographs if available also should be evaluated to assess fracture stability further (Fig. W4-4). Prior history of injury or malunion of the injured distal radius needs to be addressed preoperatively because significant alteration in the normal parameters of the distal radius may prevent implant insertion.
FIGURE W4-4 Postreduction films show fracture instability and lack of alignment.
Necessary Equipment
The minimally invasive surgical technique for intramedullary nail fixation of distal radius fractures described subsequently requires the following specific equipment: (1) Wright Medical Intramedullary Implant System, (2) one 0.62-inch Kirschner wire (K-wire) and two 0.45-inch K-wires, (3) K-wire driver, (4) drill, (5) small rongeur, and (6) intraoperative fluoroscopy.
Surgical Technique
Operative Setup
The versatility of the intramedullary system is that nail fixation can be performed if necessary in a multiply-injured patient, in the supine, lateral decubitus, or prone position. If there is no contraindication, surgery is most easily performed with the patient in the supine position. A standard arm board is attached to the side of the operating room table and is used to support the operative extremity (Fig. W4-5). Alternatively, a hand table can be used, but the single arm board is more versatile because it can be moved out of the way during the procedure when the fluoroscopic unit is in use. A mini-C-arm fluoroscopy unit is preferred because of its decreased radiation exposure, but a standard fluoroscopy unit can be used as well.
Surgical Landmarks
When the patient has been properly positioned, and the arm prepared and draped in the usual sterile fashion, several key surgical landmarks should be identified. The radiocarpal and radioulnar joints should be palpated and identified. The tip and dorsal and volar contours of the radial styloid also should be identified. If excessive soft tissue swelling makes this difficult, fluoroscopy can be used to determine these crucial landmarks, and these areas can be marked on the skin to aid in the proper placement of surgical incisions.
