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InFocus: High-Risk Orthopedic Injuries: Tibial Plateau Fracture

Roberts, James R. MD

doi: 10.1097/01.EEM.0000413883.43046.bc
InFocus
Something is just not right with this knee x-ray, and the novice may be tempted to diagnose degenerative arthritis. But a lateral tibial plateau fracture like this one is a common and easily missed serious knee injury, especially in the elderly. Subtle irregularities in the cortex of the lateral plateau (arrows) are the tipoff. Osteoporosis can obscure obvious black fracture lines seen in younger patients. This 74-year-old woman fell and had a large knee effusion, and further investigation is clearly warranted, even if this subtle fracture is not appreciated. Elderly patients rarely sprain or strain; more often they fracture brittle bones, often with seeming minimal force

Something is just not right with this knee x-ray, and the novice may be tempted to diagnose degenerative arthritis. But a lateral tibial plateau fracture like this one is a common and easily missed serious knee injury, especially in the elderly. Subtle irregularities in the cortex of the lateral plateau (arrows) are the tipoff. Osteoporosis can obscure obvious black fracture lines seen in younger patients. This 74-year-old woman fell and had a large knee effusion, and further investigation is clearly warranted, even if this subtle fracture is not appreciated. Elderly patients rarely sprain or strain; more often they fracture brittle bones, often with seeming minimal force

Draining a large knee effusion provides pain relief and diagnostic information. Clear fluid often means a meniscal tear or inflammatory process, but blood means other badness. Do not throw away the syringe before examining the aspirated blood in a basin with bright overhead lighting. The sheen of fat floating on the surface, easily seen in this case, means that a fracture is present, liberating fat from the bone into the joint space. A CT scan, or preferably an MRI, is the next required investigation

Draining a large knee effusion provides pain relief and diagnostic information. Clear fluid often means a meniscal tear or inflammatory process, but blood means other badness. Do not throw away the syringe before examining the aspirated blood in a basin with bright overhead lighting. The sheen of fat floating on the surface, easily seen in this case, means that a fracture is present, liberating fat from the bone into the joint space. A CT scan, or preferably an MRI, is the next required investigation

Emergency physicians must be aware of the plethora of relatively common and potentially problematic orthopedic injuries lurking out there, just waiting to trip up the less—than-astute clinician. While an in-depth knowledge of exotic or complicated fractures or dislocations need not be in everyone's armamentarium, a number of nasty orthopedic injuries, classically difficult for the uninitiated to suspect let alone diagnose with alacrity, are bread-and-butter emergency medicine. One need attend only a few M&M conferences to become familiar with such puzzlers that have become denizens of many a clinician's “what was I thinking” file.

These injuries mandate one to intuit their presence in real-time, often with a modicum of data but with a surfeit of paranoia, and then to instigate the proper diagnostic and therapeutic interventions in the requisite time frame to ensure the best outcome. Missing a chip fracture that is caught by radiology overread the next day is embarrassing, and while technically it would be considered a “missed fracture,” the consequences rarely wreak havoc on the patient's homeostasis or forever crimp his lifestyle. Failing to suspect or investigate a handful of classic, albeit commonly missed nefarious injuries, is a greater infraction. Some garden–variety traumatic injuries prognosticate real trouble for the patient, even under the best of circumstances. These can be even more serious if the diagnosis is delayed or otherwise flubbed. More seasoned and certainly more prescient and sagacious clinicians, likely after succumbing to these missteps themselves at a younger age, should be better versed on these clandestine orthopedic landmines. The pro can, simply by picking up the chart or glancing at the patient's injured part, readily intuit injuries that are frequently missed or mishandled by the neophyte.

This month's column begins a discussion of these pesky orthopedic injuries with a focus on tibial plateau fractures. The tibial plateau is an important weight-bearing joint, and it must be pristine and intact for normal knee mobility. It may be impossible, however, for a violated articulating surface ever to revert to pristine status. Tibial plateau fractures are relatively common, but they are not always readily diagnosed by plain films. As with any pathology in emergency medicine, one needs to maintain a high index of suspicion and not simply rely on luck or exhibit clinical insouciance when surreptitiously vile pathology is present yet not staring you right in the face.

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MRI Findings in Patients with Acute Tibial Plateau Fractures

Colletti P, et al

Comput Med Imaging Graph

1996;20(5):389

MRI is the best noninvasive technique for defining the nuances of many bony and soft tissue injuries, and this space-age modality can often readily ferret out the presence or extent of internal derangement of the knee. MRI is largely the tool of the consultant, a luxury not afforded many emergency physicians, particularly in off-hours. That alone does not seem fair.

These authors evaluated MRI scans of 29 patients with known acute tibial plateau fractures. Of course, they only evaluated patients who were referred for MRI because of obviously positive plain films. Unlike EPs who must make important clinical calls in the middle of the night with minimal information, these consultants were not forced to make any diagnostic calls without sophisticated MRI technology.

MRI will readily detect otherwise occult fractures of the knee, and also elucidate many associated meniscus and ligamentous injuries. Note that MRI can actually define fat-laden blood in the joint, known as lipohemarthrosis, and differentiate a fracture-initiated hemorrhage from a simple joint effusion. Forty-one percent of the patients in these cases displayed characteristic MRI findings of the lipohemarthrosis. Importantly, a simple joint effusion was found in 60 percent of the patients, so MRI either missed small amounts of fat in the hemarthrosis or it was absent. One wonders if bone-derived fat would have been visible on gross inspection of blood aspirated at the bedside.

This was likely a select population, but the incidence of associated injuries was still amazingly high. I was always happy just to conquer a difficult case by finding a subtle fracture, but I wonder what I have regularly been missing all these years. Almost all patients in this series (28/29) had MRI evidence of associated internal derangement of the knee in addition to the fracture. About 55 percent of patients had a tibial collateral ligament injury, 45 percent had a lateral meniscus tear, 21 percent had a medial meniscus tear, and 41 percent had an anterior cruciate ligamentous injury. MRI also saw a smattering of other soft-tissue injuries. These authors concluded that MRI imaging in patients with acute tibial plateau fractures commonly demonstrates clinically important associated ligamentous or meniscal injuries.

Comment: Hardly a shift will go by when one is not called on to evaluate an injured knee. Many patients will have an array of minor sprains and strains that will get better regardless of ED diagnosis or your intervention, but tibial plateau fractures must be a concern and appropriately suspected under the proper clinical circumstances. EPs should not be naive enough to believe that they have made a complete diagnosis nor pat themselves excessively on the back simply for finding a plateau fracture. This is usually not an isolated injury.

The most common clinical scenario is an elderly person who falls on his knee and has pain for a few days, or who presents with acute swelling consistent with a hemarthrosis. Acute meniscal injuries do not bleed. Anterior cruciate ligament injuries will bleed profusely, but elderly patients rarely sprain, bruise, or strain; they usually fracture brittle bones. Importantly, the little old lady who falls and injures her knee, can't bear weight, and has a hemarthrosis almost certainly has a fracture, regardless of your x-ray interpretation. The presence of osteoporosis makes radiographs much less diagnostic, and places elderly patients at much higher risk for complex f-ractures and higher morbidity.

The elderly fall for a number of reasons, including too much wine with their gargantuan medication load, cerebral vascular insufficiency, outright fainting from new onset atrial fibrillation, or simply from failing strength, waning vision, lack of coordination accompanying diabetic neuropathy, arthritis, or the foibles of advanced age. Many are reticent to tell you exactly what happened or cannot remember, so the mechanism of injury is often difficult if not impossible to reconstruct. One must always be concerned with the etiology of any injury, though the specifics of the event are relatively unimportant for your initial ED evaluation of a simple mechanical fall.

Tibial plateau fractures occur secondary to direct trauma, knee hyperextension, and twisting motions. The knee can be jammed against the dashboard in a motor vehicle accident, and produce trauma to the tibial plateau. Significant pain and swelling can limit your examination and totally obscure findings of importance. But in essence, sophisticated physical exam machinations designed to figure out ligament or meniscal integrity are of only secondary importance to the EP. Clearly ligamentous and meniscal injuries commonly occur in conjunction with tibial plateau fractures, but these injuries are often best diagnosed at an office visit follow-up, usually with the help of MRI or an arthroscope. In the ED, one should strive not to miss a tibial plateau fracture.

A knee that harbors 30 or 40 mls of blood indicates serious internal derangement. Most EPs will drain a large acute hemarthrosis merely for pain relief. Importantly, a fleeting glance at the blood-filled syringe, with a quick toss into the trash can, is an amateur move. If the aspirated blood contains shiny lipid droplets, easily seen as a fat-like sheen on the surface of blood emptied into an emesis basin, you should be convinced that some fracture is spewing blood and fat. The tibial fracture is often the perpetrator.

Standard plain radiographs will identify the majority of tibial plateau fractures. Of course, one has to look specifically at the plateau with a suspicious and paranoid eye and be aware that minor perturbations in the articular surface may mean trouble. As a rule, it's best to look for and always to comment on the tibial plateau surface in the ED chart, convincing everyone that you know such a fracture can exist and that you carefully looked for it. These films are tricky in the elderly, so enlist the help of your friendly radiologist when appropriate.

Tibial plateau fractures occur most commonly in the lateral plateau following a direct blow to the lateral knee. Remarkably minimal trauma is required for an 85-year-old to break the bone, and I have seen fractures in osteoporotic oldsters from stepping off the curb or simply trying to get out of a low chair. Medial tibial plateau fractures require higher forces and are less common. If you are fortunate, a depression of the lateral plateau will be seen easily on plain films, but in more subtle nondisplaced injuries, the x-ray may appear deceptively normal or show only a slight abnormality that may be easily overlooked with a furtive glance during a busy ED shift. Don't let the resident have the only eyes on these radiographs.

The pro will understand that a large hemarthrosis, particularly one harboring fat droplets, requires further investigation in the ED or shortly thereafter. This can be as simple as asking a radiologist or orthopedic surgeon to evaluate the plain film, but these consultants frequently hedge and often request an additional study when they are forced to make decisions that EPs must make on a daily basis with less data.

The quickest and easiest additional study to look for a tibial plateau fracture is a CT scan of the knee, with the knowledge that this test will not evaluate a cornucopia of other soft tissues insults to normal knee joint function. While readily available and cool technology in itself, CT is less sensitive in the presence of osteoporosis so be forewarned when using this test on the elderly. The gold standard appears to be MRI because of its ability to better define washed out bone and evaluate associated meniscal or ligamentous injury.

While compression, ice, knee splinting, elevation, and strict non-weight-bearing are fine for the initial treatment of most tibial plateau fractures, such injuries must be referred for orthopedic follow-up. Local custom and the availability of resources dictate the exact scheduling, but there is no downside to having follow-up of even a proven plateau fracture in three to five days. Fractures with significant displacement or depression are best related to your consultant while the patient is still in the ED because operative repair is usually needed.

Occasionally a patient with minimal displacement will be followed without immediate surgery for a few weeks to see if there is any further derangement of the plateau surface. A depression of 4 mm or greater usually spells surgery, and the MRI is the best way to measure this parameter.

It is a fact of life that some tibial plateau fractures will be missed in the ED, especially when one is faced with minimal symptoms and a seemingly normal x-ray. No standard of care mandates routine CT or MRI in all ED cases. Hopefully your sophisticated, proactive, professional, patient-friendly, suave interactions on the first encounter will mollify any callback outrage for a missed x-ray and minimize subsequent animosity. A system that ensures overview of plain films with a turnaround time that allows for appropriate intervention is key. Placing the patient in a knee immobilizer with crutches with strict non-weight-bearing is always a reasonable ED intervention in the middle of the night. Keeping someone in the ED overnight to allow a consultant to share the liability in the morning is an alternative tactic.

Informing patients that they have a sprain or bruise is adequate for the young person with no findings on the normal x-ray, but should not be your mantra in the older individual with a significant hemarthrosis and an x-ray that is difficult to read because of degenerative changes. If you're wrong with “you might have a fracture,” no one cares. Lack of hubris and close follow-up are your friends. But a “no problems with this knee” proclamation is a gutsy move in all but the most benign injuries.

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Dr. Robertsis the chairman of emergency medicine and the director of the division of toxicology at Mercy Catholic Medical Center, and a professor of emergency medicine and toxicology at the Drexel University College of Medicine, both in Philadelphia.

Pain and swelling in the knee after trauma usually means significant internal derangement. The clinician thought the tibial head fracture (arrow) was the cause of a large hemarthrosis, but this is anatomically impossible because this fracture is outside the knee capsule. Once the first fracture was found, however, the EP failed to carefully look at the tibial plateau, the most common missed fracture. The diagnosis is complicated further because the tibial plateau does appear pristine on this view

Pain and swelling in the knee after trauma usually means significant internal derangement. The clinician thought the tibial head fracture (arrow) was the cause of a large hemarthrosis, but this is anatomically impossible because this fracture is outside the knee capsule. Once the first fracture was found, however, the EP failed to carefully look at the tibial plateau, the most common missed fracture. The diagnosis is complicated further because the tibial plateau does appear pristine on this view

This knee joint seems normal, and the physician was initially but naively satisfied. Arthrocentesis was performed solely for pain relief, yielding the lipohemarthrosis in the basin in the photo on page xx. Dr. John Madden, a radiologist from Mercy Hospital of Philadelphia, was then consulted, and he astutely called a probable lateral tibial plateau fracture on one of the projections of the plain radiograph. These are very subtle findings indeed (see arrows) that were not appreciated by the EP. An MRI was then performed.

This knee joint seems normal, and the physician was initially but naively satisfied. Arthrocentesis was performed solely for pain relief, yielding the lipohemarthrosis in the basin in the photo on page xx. Dr. John Madden, a radiologist from Mercy Hospital of Philadelphia, was then consulted, and he astutely called a probable lateral tibial plateau fracture on one of the projections of the plain radiograph. These are very subtle findings indeed (see arrows) that were not appreciated by the EP. An MRI was then performed.

MRI easily found the impressive comminuted tibial plateau fracture that is easily missed or even totally obfuscated on plain radiographs. The MRI also evaluates for common associated injuries, such as meniscus and ligamentous injuries. A CT scan would have sufficed for ED diagnosis of the fracture itself. Had the lipohemarthrosis not been appreciated, this patient would have been discharged with the wrong diagnosis, likely with subsequent increased morbidity. Tibial plateau fractures are easy to miss, and clinical suspicion (AKA paranoia) should run high in the appropriate clinical setting

MRI easily found the impressive comminuted tibial plateau fracture that is easily missed or even totally obfuscated on plain radiographs. The MRI also evaluates for common associated injuries, such as meniscus and ligamentous injuries. A CT scan would have sufficed for ED diagnosis of the fracture itself. Had the lipohemarthrosis not been appreciated, this patient would have been discharged with the wrong diagnosis, likely with subsequent increased morbidity. Tibial plateau fractures are easy to miss, and clinical suspicion (AKA paranoia) should run high in the appropriate clinical setting

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