Dorsal Bridge Plate
“Internal” distraction fixators (dorsal bridge plates) were originally designed in an effort to mitigate the pitfalls of external fixators. These function to the same extent as external fixators, utilizing traction and ligamentotaxis (applying a longitudinal force to ligaments which then helps to pull the bone they are attached to into the right place) for restoration of the articular surface of the joint.
Securing the plate after traction/distraction allows for restoration of the 3 critical goals of fixing distal radius fractures: restoring radial length, radial inclination and volar tilt (inclination and tilt are anatomical components of the articular surface of the distal radius). While an external fixator functions in a similar kinematic way in order to accomplish the above, there are notable advantages that the dorsal bridge plate has demonstrated in patient studies.
These include improved patient comfort and superior patient outcomes, no risk of pin track infection, and greater biomechanical stability that allows earlier weight bearing. This is particularly important for patients with concomitant lower extremity injuries. Studies have also suggested there is a decreased risk of Complex Regional Pain Syndrome (CRPS) with the use of dorsal bridge plates.
The major drawback of using a dorsal bridge plate is that a secondary surgery is required in order to remove the plate (although external fixator removal may need to be done in the operating room as well, as removal in a clinical setting can cause significant patient discomfort). Compared to external fixators, there is a risk of tendon entrapment during placement of a dorsal bridge plate. This can lead to tendonitis and eventually rupture. This risk can be minimized by securing the plate to the second metacarpal rather than the third, but this is not always possible.
Distal Radius Operative Fixation
A dorsal bridge plate, as the name implies, is applied to the backside (dorsal) part of the radius, proximal to the fracture, and spans the fractured distal radius and wrist joint where it is then secured with screws to either the second or third metacarpal (hand bones of index and middle finger respectively). This thus “bridges” the fractured intra-articular surface of the distal radius.
Application of this plate involves 2-3 incisions. First, two incisions are made, both roughly 5-7cm length: one near the base of the 2nd metacarpal (distal incision) and a second on the dorsal aspect of the forearm in the region of the radial shaft (proximal incision). If significant displacement of the intra-articular fragments is present, an incision directly over the dorsal wrist can be used to assess and reduce/stabilize the articular surface with the use of pins, k-wire, or small metal plates/screws.
The plate is then inserted typical through the distal incision and slid up along the bone to the proximal incision site. The plate is secured to bone with screws. Postoperatively, patients can bear weight/load bear through the forearm and elbow immediately after surgery. This can allow patients to use crutches (platform crutches at first with transition to regular crutches around one month post operatively).
Lifting and carrying is typically restricted to approximately 10lbs until the fracture has healed to minimize stress on the fractured portions of the bone/joint surface. The plate and screws are removed usually no earlies than 12 weeks after injury. At the time of hardware extraction the screws are removed and the plate slid from the incision. A removable short arm splint is worn for 2-3wks after plate removal. Hand therapy at the point is directed at regaining strength and motion, specifically of the wrist.
Distal Radius Fractures
Distal radius fractures are the most common orthopedic-related injury, accounting for 17.5% of all fractures in adults. Fractures are classified as distal radius fractures when they occur in the distal 1/3rdof the radius. Fractures typically occur in older patients with osteopenia/osteoporosis (weak bone) after a fall on an outstretched hand (most common), or in younger patients secondary to high energy trauma (e.g. motor vehicle accidents).
Most distal radius fractures can be reduced (pushed into appropriate alignment) in the emergency department and immobilized in a splint for 4-6 weeks. For those that require surgery, the majority are treated in a one-step procedure with what is known as a volar locking plate. However, when the fracture extends into the diaphysis (shaft of the radius), or there is significant intra-articular comminution (i.e. the joint surface of the radius that articulates with the wrist bones is broken in several pieces), standard volar locking plates are not able to provide adequate stability.
In these situations, there are two surgical options available in order to gain adequate stability of the fracture. Historically, an external distraction fixator has been used, which involves metal pins placed from the skin and into the bone both above and below the fracture site. These pins are then connected with rods outside of the skin. Tension and/or distraction forces can be applied in order to bring the fractured pieces back into close proximity of one another and then the rods are locked in place.
A more novel technique that is now becoming popularized is the use of an internal distraction fixator, commonly referred to as a dorsal spanning bridge plate, or just a dorsal bridge plate. This plate spans the fracture site similar to an external fixator with the major difference being that it is completely internal (i.e. no hardware outside of the skin).
Skeletal Dynamics Dorsal Spanning Plate is designed for distal radius fractures with severe comminution requiring prolonged fixation as an alternative to external fixation. It functions similar to other dorsal bridge plates on the market, designed to optimally restore radial length and neutralize loads on the consolidated fracture fragments.
This plate is specifically designed to avoid Lister’s tubercle (anatomic structure that the extensor tendon to the thumb courses around) and promotes anatomic positioning of fractured fragments. It has a “shovel” tip that aids insertion beneath muscle helping to avoid entrapment of extensor tendons. The plate is also pre-contoured to account for the natural 10 degrees of radial angulation. The plate is equipped to attach to a handle that allows for easy and controlled insertion of the plate.