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Maintain mechanical axis when rebuilding proximal tibial plateau fractures
Surgeon uses laterally based locking plates for specific bicondylar plateau fracture patterns.
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New or minimally invasive approaches show promise for producing better outcomes with proximal tibia and tibial plateau fractures. They include rafting plating techniques, percutaneous screws and periarticular locking plates.
Before surgeons can apply these advanced techniques appropriately, they must understand the fracture’s three-dimensional (3-D) anatomy, according to J. Tracy Watson, MD.
“We’re all going to a ‘no-touch,’ or limited incision, technique … To do that you have to know exactly where the fracture lines are located as well as where to position the plates, screws and other percutaneous fixation adjuvants,” he said during a symposium at the American Academy of Orthopaedic Surgeons 74th Annual Meeting.
Watson stressed the importance of correctly diagnosing these fractures and analyzing them looking at the base and orientation of the condylar fracture components to determine if they are comminuted or not. This is the first step, he said, that will aid in selecting the most effective fixation technique.
Diagnostic techniques
Evaluating fractures with plain radiographs is the first step to understanding the 3-D anatomy. AP, lateral and oblique views may be sufficient, but for proximal tibial fractures or polytrauma situations Watson recommended getting films with the limb in distraction, which also may aid in visualizing the sometimes complex fracture pathology. A simple traction view of the knee gives you an idea or a sense of the overall fracture pattern, and in complex fractures, visualizing the medial tibial condyle is important,” he said.
Transverse, sagittal and coronal plane computed tomography (CT) may be effective once the patient’s fracture is distracted achieving a simplistic reduction via ligamentotaxis. “CT also helps to highlight a bicondylar fracture’s anatomy, and for high-energy injuries, a CT scan performed with the fracture in distraction (temporary knee spanning external fixation) provides information that will be useful during surgery. Information such as the degree of condylar comminution, articular impaction and diametaphyseal shaft extension helps to determine which fixation methodology would be appropriate whether it would be locking plates or in some severe instances, small external fixators,” he said.
Some surgeons find MRI useful for visualizing meniscal tears associated with split depression fractures along with the collateral and cruciate ligaments’ status. Its diagnostic usefulness depends on the magnitude of the injury, so it may not be practical or helpful in the multiply injured patient or in those patients who are initially treated with a spanning external fixator frame, Watson said. “Certainly for the most common type of plateau injuries, I think an MRI is probably invaluable in that it not only gives us the most useful information with regard to the 3-D anatomy of the skeletal injury, but also highlights potential soft tissue injuries present.”
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Images: Watson JT |
Assessing the fracture
The following are some indications for operatively reducing proximal plateau and tibial fractures:
- knee instability with the knee in extension for medial/lateral instability;
- dynamic axial deviation of the leg’s mechanical axis secondary to the plateau fracture; and,
- any medial tibial plateau fracture that has the potential to develop any varus tilt.
Watson will assess the degree of the plateau impaction. If the defect is clinically significant, meaning it allows dynamic deviation of the mechanical axis, or if it will become such that it shifts the axis further, or, may settle with further depression, he usually operates.
He keeps one treatment goal in mind: “You have to maintain the overall mechanical axis of the limb … Mild to moderate articular impaction can certainly be tolerated as long as the overall mechanical axis is well maintained and no axial malalignment occurs once the articular surfaces have healed.”
Schatzker classification
When considering the use of contemporary fixation approaches, surgeons should evaluate for comminution at the base of the condylar fracture lines, it also helps to determine the Schatzker classification and whether it is a low- or high-energy mechanism of injury, Watson said.
If done early, treating noncomminuted Schatzker Type 1 fractures without a meniscal tear is fairly straight forward. When bone-on-bone apposition is attainable at the condylar fracture lines, the surgeon can use percutaneous techniques with tenaculum forceps with cannulated screws.
Split-depression Schatzker Type 2 fractures are amenable to raft plating techniques: a precontoured periarticular plate fixed with small diameter, 3.5-mm, screws that completely span the metaphyseal region such that the rear and far and cortices serve as supporting structures. The screws act like the rafters in a roof and support the newly elevated articular surface. Several manufacturers offer such plates. “Because of the preshaped contour of these periarticular plates, it may actually help you reduce the fracture,” Watson said.
Type 3 fractures of the lateral tibial plateau are amenable to arthroscopic treatment, but must be carefully identified. Central depression fractures with lateral wall comminution are problem fractures if the lateral wall comminution is not adequately buttressed with small fixation hardware. “Arthroscopy … in these select cases does give you excellent joint visualization,” he said.
Type 4-6 fractures
Buttress plates work reliably in higher-energy Schatzker Type 4 medial condylar plateau fractures, but must be located at the apex of the medial condylar fracture. This may be located anterior, anterolateral, directly medial or even posterior in terms of major fracture-line orientation. If the buttress plate is not positioned correctly at the apex, the high stresses across the medial condylar region can produce deformity with subsequent varus collapse and malunion, he said.
The newer periarticular locking plates are indicated for high-energy Schatzker Type 5 and 6 fractures that involve both the medial and lateral condyles as well as shaft extension.
“The advantage of a locking plate in these situations is that you can treat these significant fractures without having to perform large extensile exposures. These can now be treated with a percutaneous submuscular approach,” said Watson, who treats these severe injuries with a staged approach based on the competency of the soft tissues.
Condylar fractures
Of 42 bicondylar tibial plateau fractures in which the medial condylar fracture line was reduced with ligamentotaxis and had a noncomminuted base (ie., bone-to-bone apposition as visualized on distraction CT scan) Watson treated, 97% were reduced anatomically and maintained with a laterally based locking pate and raft-type screws.
The hybrid-technique utilized nonlocking screws which compressed the intra-articular condylar fracture lines. He then applied the subchondral locking raft screws, using an alloplastic bone void filler to maintain the subchondral defect following joint elevation, and placed the shaft locking screws last.
With effective periarticular locking plates now available, Watson has reduced his use of ring fixators, reserving them for the “worst-of-the-worst” cases.
“Ring fixators do produce good function, if you are able to respect the mechanical axis, and are indicated for high-energy injuries, poor quality soft tissue, concomitant compartment syndrome, and extensive comminution of the diametaphyseal region with smaller articular fragments.
For more information:
- J. Tracy Watson, MD, can be reached at St. Louis University Hospital, 7th Floor, Desloge Towers, 3635 Vista Ave., St. Louis, MO 63110; 314-577-8850. He is a consultant to Smith & Nephew. His department received research support from Wright Medical Technology.
Reference:
- Watson JT. Tibial plateau/proximal tibia fractures. Symposium W: Fractures about the knee: New treatment methods and stabilization choices. Presented at the American Academy of Orthopaedic Surgeons 74th Annual Meeting. Feb. 14-18, 2007. San Diego.