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Pearls and pitfalls in the treatment of tibial plateau fractures

By Douglas W. Lundy, MD, FACS, and Mary Jo Albert, MD

Tibial plateau fractures are common injuries that affect the articular surface of the proximal tibia. They range from minimally displaced lateral depression fractures to severe bicondylar fractures that may be associated with knee dislocations, compartment syndromes, or vascular injuries.

The options available to stabilize these fractures have multiplied during the past few years and include smaller screw diameters, locking plates, and improved osteobiologic implants. Surgeons who care for patients with tibial plateau fractures will find that an understanding of the complications associated with these injuries will improve the patient’s outcome and decrease the surgeon’s risk of liability.

Goal of surgical treatment
The goal of surgical treatment of tibial plateau fractures is a perfect reduction of the articular surface secured with stable fixation. This will enable less painful motion of the knee in the initial postoperative period, while stabilizing the fracture in the reduced position.

Comminution of the articular surface may be so significant, however, that an exact reduction is impossible. In this situation, the surgeon should endeavor to reduce the fracture as well as possible and maintain the normal mechanical alignment of the knee. Fortunately, the knee can tolerate some degree of articular incongruity, due to the presence of the meniscal cartilage.

Vascular complications
In the treatment of tibial plateau fractures, the associated soft-tissue trauma with the most catastrophic outcome is an injury to the popliteal artery. These injuries are more commonly seen in patients who have medial plateau fractures than in those who have lateral plateau fractures. Patients who experienced a fracture-dislocation of the knee are also at risk of sustaining arterial trauma.

Studies have suggested that patients are very unlikely to have a significant arterial injury if they have a Doppler arterial pressure index (API) of more than 0.9. The Doppler API is determined by dividing the systolic arterial pressure of the injured extremity by the arterial pressure in an uninvolved arm. If an arterial injury is suspected, the orthopaedic surgeon should consult a vascular surgeon immediately.

Patients who have a period of ischemia will require fasciotomies of the calf. After surgery, temporarily spanning the knee joint with an external fixator until the vascular and soft-tissue injuries have recovered adequately may be the most appropriate treatment.

Anteroposterior (left) and lateral (right) views of an unstable Schatzker VI tibial plateau fracture.

Neurologic complications
In addition to documenting the vascular status of the extremity, the surgeon should perform a detailed examination of the neurologic status of the affected limb. The varus force generating medial tibial plateau fractures is sufficient to produce a stretch injury to the peroneal nerve. Patients with tibial plateau fractures are often in significant pain and may be reluctant to enthusiastically participate in a neurologic examination. Documenting a patient’s traumatic “foot drop” before surgery, however, is much better than waiting until several days later.

Fortunately, patients who have peroneal nerve palsies usually recover without any additional surgical intervention. Patients with a foot drop should be maintained in an ankle-foot orthosis (AFO) until active ankle dorsiflexion returns to avoid an Achilles contracture. Using an AFO on all patients who have tibial plateau fractures will help avoid equinus contractures. The AFO is used until the patient is allowed to bear weight on the affected extremity.

Compartment syndrome
Compartment syndrome may also be seen in patients who have tibial plateau fractures. Compartment syndrome is more commonly associated with the severe types of plateau fractures in which the muscle in the proximal posterior calf sustains significant injury.

The compartment syndrome usually manifests itself several hours after the injury. The patient begins to complain of severe, unremitting pain that is out of proportion to the bony injury. The patient’s calf often becomes more firm, and pain with passive motion of the muscles in the affected compartment significantly increases.

Compartment syndrome is a clinical diagnosis, and its presence can go undetected if the surgeon is not aware of its possibility. Although there is some benefit in measuring compartment pressures, a fasciotomy of the affected calf should be performed if the surgeon believes that a compartment syndrome is present or imminent.

The presence of head, spinal cord, or peripheral nerve injuries may mask the presence of a compartment syndrome. Nerve blocks for postoperative analgesia, although well-intentioned, will also mask an impending compartment syndrome. If an emergent fasciotomy is required prior to definitive fixation of the fracture, spanning external fixation across the knee may be the best method of stabilizing the fracture.

Knee stiffness
Knee stiffness is perhaps the most common complication seen after tibial plateau fractures. Although immobilizing the knee is acceptable while bridging a tibial plateau fracture with an external fixator or while waiting for soft-tissue flaps to heal, in most cases, the knee should be moved as soon as possible. Physical therapy should be initiated to obtain full extension and as much flexion as possible.

Knee pain after tibial plateau fractures is often due to arthrofibrosis, and the patient needs to be counseled that the time to achieve knee motion is now—not later when the patient thinks that it will feel better! Unless the surgeon intervenes and encourages early motion, most patients will be content to keep their knee immobilized in 30 degrees of flexion.

Malalignment
Malalignment of the knee is a very undesirable outcome after open reduction and internal fixation of tibial plateau fractures. Isolated lateral depression fractures may result in genu valgum from failure to adequately elevate the deformity of the lateral plateau. Bicondylar fractures and fractures with metaphyseal-diaphyseal dissociation may result in a varus malreduction due to misalignment of the medial fragment.

Certain surgical techniques do allow exposure and fixation of the posteromedial plateau fragment. Although determining the exact mechanical axis of the lower extremity may be difficult to do during surgery, some methods can give the surgeon more information.

The mechanical axis can be better appreciated by stretching the cord of the electrocautery in a straight line from the center of the femoral head to the center of the ankle. The cord should pass through the center or just lateral to the center of the knee joint on the fluoroscopic image.

Most locked lateral tibial plateau plates on the market today will help align the fracture if the proximal screws are placed parallel to the knee joint. The plate should then align itself along the reduction line of the metaphyseal and diaphyseal fragments, hopefully reestablishing a normal mechanical axis.

Ligament and meniscal tears
Knee ligament and meniscal tears are commonly seen in conjunction with tibial plateau fractures. Tears of the anterior cruciate ligament (ACL) occur in 10 percent and meniscal tears occur in 20 percent of tibial plateau fractures. These associated injuries may be very difficult to diagnose prior to surgery, and some surgeons recommend preoperative magnetic resonance imaging to more thoroughly evaluate the injured knee. The surgeon may be able to repair some meniscal tears while stabilizing the plateau fracture. ACL tears, however, should not be reconstructed until after the fracture has completely healed and the hardware is removed. At that point, knee stiffness may reduce the need for ACL reconstruction.

Douglas W. Lundy, MD, FACS, a member of the AAOS Medical Liability Committee, and Mary Jo Albert, MD, practice at Resurgens Orthoapedics in Atlanta. Additional readings on this topic can be found online at www.aaos.org/now.

September 2007 AAOS Now
http://www.aaos.org/news/bulletin/sep07/managing3.asp