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InFocus: ED Evaluation of Occult Hip Fractures

Roberts, James R. MD

doi: 10.1097/01.EEM.0000414931.92050.28
InFocus

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.

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This elderly woman with osteoporosis had a minor fall but full hip range of motion and very minimal pain

This elderly woman with osteoporosis had a minor fall but full hip range of motion and very minimal pain

Figure

Figure

The ubiquitous occult hip fracture is perhaps an even bigger challenge than the tibial plateau fracture. It has the potential for nasty complications if mishandled. Hip fractures are relatively common, but they are not always readily diagnosed by plain films.

Clinicians need to maintain a high index of suspicion with any pathology in emergency medicine, and not simply rely on luck or clinical insouciance when vile pathology is present but not staring you right in the face.

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Imaging Choices in Occult Hip Fracture

J Cannon, et al

J Emerg Med

2009;37(2):144

The authors review the literature on clinicians' ability to detect hip fractures and the advantages and limitations of numerous imaging modalities to ferret out this occasionally elusive diagnosis. A fractured hip is not an unusual injury, and about 15 percent of the population will experience this skeletal insult by age 80. The article contains impressive x-rays depicting a classic scenario where plain films failed to detect an intertrochanteric fracture, leading the physician to discharge the patient with a groin strain, only to have him return with an obvious displaced fracture.

The elderly can fracture a hip with seemingly minor forces applied to the femur

The elderly can fracture a hip with seemingly minor forces applied to the femur

A delay in surgical treatment for this weight-bearing bone has proven to be problematic, doubling mortality and markedly increasing morbidity. (J Bone Joint Surg Am 1995;77[10]:1551.) The downside of missing a hip fracture is not merely theoretical babble.

ED imaging of a painful or traumatized hip usually begins with plain radiography, and this modality reveals most hip fractures. Occult hip fractures are not infrequent, however, and they are more prevalent than most neophyte clinicians appreciate. An impressive incidence of occult fractures is well supported in the literature. The published consensus is that about three to five percent of patients with negative x-rays in a setting suspicious for hip fracture will have an occult fracture eventually diagnosed. The sensitivity of conventional radiographs to detect hip fractures is between 90 and 98 percent overall. This, of course, assumes the film was read appropriately and accurately by the emergency physician, and the radiologist does not spot the fracture with ease. Any life-threatening injury that defies detection by plain x-rays in 10 percent of cases is indeed a cause for concern.

This article emphasizes the need to stratify patients into high- and low-risk groups. Those at high risk with a negative plain film require additional investigation. High-risk criteria clearly include advancing age or osteoporosis and female gender, but also inability to bear weight, pain on range of motion, pain with straight leg raising, and internal and external rotation. Although not 100 percent sensitive, these physical findings and a negative plain film should alert the clinician to a possible occult fracture. Low energy force, such as a simple fall from standing, is probably the most common cause of hip fracture in the elderly. Osteoporotic bone will fracture with one-third the force required to fracture normal bone.

A different kind of occult fracture

A different kind of occult fracture

A hip fracture is largely the albatross around the neck of the older population. Many elderly patients view a hip fracture as a harbinger to the end of their life, and sadly, it is a common companion to one's demise. A hip fracture should prompt at least a reasonable attempt to define the etiology of the fall. Culprits include arrhythmia, cerebral vascular disease, and a zillion systemic problems. New onset atrial fibrillation, a seizure, and a hard-to-detect CVA are not exotic or unusual underlying causes of hip fracture. If properly vetted, these comorbidities are brought to the clinician's attention by the hip fracture. Most hip fractures will end up in the OR, but catching one before it displaces may save a patient from the surgeon or initiate a less invasive procedure.

Osteoporosis not only tends to increase the chance of fracture after an otherwise minor fall, it decreases the ability of plain films to detect the fracture line. CT is readily accessible in the ED, and is a common modality for evaluating injured patients, including the hip and pelvis. Surgeons think the whole body CT pan scan is nirvana and all they need to order. While an easy way to detect fractures in the young motor vehicle crash patient, it is limited in its ability to detect hip fractures in the ubiquitous osteoporosis seen in elderly patients.

The hip contains trabecular, not cortical, bone, and the former does not readily reveal its characteristics to the CT scanner. In reality, evidence to support CT for diagnosing hip fractures is rather scant, and all erudite reviews conclude that the MRI is the modality of choice. Clinicians have come to rely on CT to guide many medical decisions, but this study has significant limitations for the occult hip fracture.

The now largely antiquated bone scan was traditionally ordered when one suspected an occult fracture. While clinicians have relied on bone scanning for decades, MRI makes this test nearly obsolete. Note that the bone scan may require 24 to 72 hours to be completely sensitive for fracture, so it's usually not an ED test. MRI will rapidly differentiate between arthritis, synovitis, tumor, inflammation, and fracture while a bone scan will be positive for all of these conditions. The delay required to obtain a bone scan also can be a deal breaker in today's mandated near-light speed medical pace.

These authors conclude that MRI is the modality of choice for evaluating selected patients at risk for hip fracture who have normal plain radiographs. MRI is highly sensitive, and can differentiate a slew other pathologies. The key, of course, is deciding when to use this ideal technique.

A specific benefit of MRI is that unsuspected malignancy may be the source of hip pain or facilitate a pathologic fracture. Sankey et al (J Bone Joint Surg 2009;91[8]:1064) reported a 10 percent incidence of MRI detected malignancy in 98 patients with occult hip fractures.

Comment: Last month's column raised a similar caveat for knee trauma and seemingly normal x-rays. Tibial plateau fractures, particularly in the elderly, are common serious injuries that are easily missed if one relies only on plain films. Clinicians are usually tipped off to tibial plateau fractures by an associated hemarthorsis, often with fat floating on the top of a visually examined specimen of aspirated blood (lipohemarthrosis). No such aspiration is possible with the hip.

It's a fact of life that not all hip fractures will be diagnosed on the first evaluation. A missed hip fracture not only will yield a surfeit of malice from the patient and family, but it will also garner high interest from the omnipresent plaintiff attorney. Any missed fracture, however noncontributory to a worsened outcome, is popular and relatively easy litigation against EPs. Little judicial cerebration is involved when deciding that something went wrong when an emergency specialist declared a broken bone healthy after an ED evaluation. Anyone can fall prey to an occult fracture, so try to be squeaky clean in your evaluation, charting, and patient satisfaction in the ED. Missing a fibula fracture for a few days is usually nothing more than embarrassment for the clinician and inconvenience for the patient. Not so with a hip fracture.

It is absurd, if not impossible, to obtain an ED-generated MRI on all patients with hip pain and negative plain films, and most do not require it. When it's the classic scenario, however, the seasoned clinician follows this axiom: anyone who falls and has trauma to the hip, can't bear weight, or has significant pain on hip manipulation has a hip fracture until proven otherwise. Proving otherwise can be as simple as having another set of eyes on the plain films or asking a specialist to weigh in. Often our colleagues are as nonplussed and wary as we are, and opt for MRI.

Critical thinking in the ED evaluation of hip pain includes how to proceed if plain films are normal. Hip infections, synovitis, arthritis, aortic disease, and referred pain must be in the mix of your cogitations. Young people will rarely have a hip fracture without a great deal of trauma, obvious symptoms, and an obvious fracture line on plain films. The elderly and those with severe osteoporosis can fracture a hip by simply turning over in bed or trying to get out of a chair. Occasionally, the patient will sense a pop or a crack, but the physical findings can be subtle and misleading, and history can be problematic. Good luck getting pristine information from the elderly patient or the nursing home.

MRI demonstrated a fracture of the hip that was, even retrospectively, invisible on plain x-rays

MRI demonstrated a fracture of the hip that was, even retrospectively, invisible on plain x-rays

One fact known to most veteran clinicians is that hip pain with a normal hip x-ray can be from a rather difficult-to-see and often overlooked pelvic ramus fracture or acetabular fracture. Missing a small pelvic fracture in a patient with hip pain is a common scenario. Do not make the hip your first area of interest, but look at other areas, particularly the pubic ramus.

What is a clinician to do for a patient with traumatic hip pain and an x-ray that everyone agrees is normal? Occasionally this is a bruise, strain, or an inflammatory or degenerative process associated with or exacerbated by minimal trauma. But one should not allow the absence of a significant fall or high-force trauma stop you from considering a hip fracture.

Don't be fooled by patient denial of significant trauma or attempts to walk through pain. A 23-year-old who fell while drunk and readily walks around the ED with a small bruise on the thigh is different from an 85-year-old who can't remember any significant injury or downplays a minor fall. Elderly patients will lie on the floor for 12 hours and then deny slipping or falling, and that history is often obtained when you finally speak to a relative. When your only source is the oldster who does not want to be in the hospital in the first place, always, always, always ask the family or anyone else who knows your patient.

Kirby et al (AJR Am J Roentgenol 2010;194[4]:1054) reviewed MRI studies of the hip and pelvis in 92 patients 19 to 94. Trauma was documented in only 71 percent of the patients, usually a fall in elderly patients or a motor vehicle crash. They demonstrated 23 fractures in 13 patients with a negative plain film, an amazing 15 percent incidence of occult fractures elusive to plain films. Overall, the sensitivity and specificity of plain films is only 57 percent and 85 percent respectively for hip fractures and 52 percent and 99 percent respectively for pelvic fractures. These are indeed disturbing data, and demonstrate the high incidence of occult fractures of the hip and pelvis as well as the absolutely astonishing shortcomings of plain films. Caveats and cautions abound, and EPs need to know their limitations as well as those of plain films. (Acta Orthop 2005;76[4]:524; J Bone Joint Surg 2009;91[8]:1064.)

While the resident may think missing an occult hip fracture is no big deal, these injuries do produce ongoing pain, and tend to make those trying to walk at home fall again. Weight-bearing also causes a nondisplaced fracture to displace. Early surgery, defined as within 72 hours of injury, will reduce a variety of complications, such as pneumonia, bedsores, and venous thrombosis. (Can Med Assoc J 2010;182[15]:1509.) I personally give 5,000 units of subcutaneous heparin prophylaxis in the ED to those with hip fractures, and aggressive surgeons try to operate within 24 hours; the best operate even on weekends.

A hip fracture is rarely lethal, although it can bleed profusely. But this injury is often an indication of the frail elderly patient being near the end of his life. Even in the best of hands, elderly patients with hip fractures do not always fare well, and delaying their care by an unenlightened approach or a hubris-laden evaluation can get you and your patient into trouble. Good luck trying to convince the family that your misstep in the ED did not initiate or exacerbate the inevitable downward spiral of their loved one.

© 2012 Lippincott Williams & Wilkins, Inc.