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BRIEF REPORTS Prevalence of Traumatic Hip and Pelvic Fractures in Patients with Suspected Hip Fracture and Negative Initial Standard Radiographs—A Study of Emergency Department Patients Shari Dominguez, MD, Patrick Liu, MD, Catherine Roberts, MD, Mark Mandell, MD, Peter B. Richman, MD Abstract Objectives: To determine the prevalence of hip and pelvic fractures in emergency department (ED) patients with hip pain and negative standard initial radiographs. Methods: This was a retrospective, cohort study at an academic, community-based ED. ED patients presenting during a oneyear period with hip pain for whom a plain-film radiograph was obtained were included. Eligible patients were identified by query of electronic records. Plain radiographs and magnetic resonance images (MRIs) were ordered at the discretion of the treating physician. Initial plain radiographs were read at the point of care by board-certified radiologists. MRI images were reviewed by radiologists with fellowship training in musculoskeletal imaging. Structured follow-up at more than one month postvisit was conducted to rule out a subsequent diagnosis of hip fracture. Ninety-five-percent confidence intervals (95% CIs) and kappa (k) were calculated as appropriate. Results: Seven hundred sixty-four of 895 patients (85.3%) had follow-up completed (study group). Within the study group, 219 patients (29%) had
evidence of fracture on initial radiographs. Of the 545 patients with negative initial radiographs, 62 patients (11.4%) underwent hip MRI during the ED visit. MRI identified 24 additional patients with hip fractures. Interobserver agreement for the presence of fracture on MRI was very good (k = 0.847). For patients with negative initial plain radiographs who did not have a hip MRI, follow-up did not identify any of these patients as having a subsequent diagnosis of fracture. Thus, 24 of 545 (4.4%; 95% CI = 3.0% to 6.5%) patients with negative initial plain radiographs had a hip fracture. Conclusions: In this cohort of ED patients with symptoms suspicious for hip fracture who had negative standard radiographs, the authors found that 4.4% were subsequently diagnosed as having fracture. Further studies are warranted to identify characteristics of patients requiring advanced hip imaging studies. Key words: hip fracture; MRI; emergency department. ACADEMIC EMERGENCY MEDICINE 2005; 12:366–370.
Hip pain is a common presenting complaint to the emergency department (ED). In the United States, there are more than 250,000 hip fractures annually, with an incidence of 80 per 100,000 population.1 This number is expected to double by the year 2040.2 As most of these patients are elders, evaluation of hip pain and fractures represents a growing burden on the government-funded Medicare system. In the majority of patients, hip fracture is easily detected with a suspicious history, obvious physical examination findings (e.g., severe pain, leg shortened and rotated), and clear plain radiographic abnormal-
ities indicating fracture. However, it is known that a fraction of patients have clinically significant fractures that are not radiographically apparent on initial plain radiographs. The challenge for emergency physicians is to diagnose this subset of patients at the point of care, because significant morbidity can result when a patient ambulates on an unrecognized hip fracture. Surprisingly, there are limited data as to the overall incidence of hip fracture that is not radiographically apparent on plain radiographs, particularly with respect to patients presenting to the ED with hip injury.3–5 The purpose of our current study was to address this concern.
From the Departments of Emergency Medicine and Radiology, Mayo Clinic Hospital (SD, PL, CR, PBR), Phoenix, AZ; and the Department of Emergency Medicine, Morristown Memorial Hospital (MM), Morristown, NJ. Received July 23, 2004; revision received October 27, 2004; accepted October 27, 2004. Address for correspondence and reprints: Peter B. Richman, MD, Department of Emergency Medicine, Mayo Clinic Hospital, Phoenix, AZ 85054. Fax: 480-342-1774; e-mail:
[email protected]. doi:10.1197/j.aem.2004.10.024
METHODS Study Design. This was a retrospective cohort study conducted to determine the prevalence of hip and pelvic fractures in ED patients with hip pain and negative initial standard radiographs. Our hospital’s institutional review board approved the study protocol.
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Study Setting and Population. This study was based in the ED of Mayo Clinic Hospital (Phoenix, AZ). It is an academic, community ED with an annual patient census of 27,000. Adult patients (age $ 18 years) presenting to the ED during a one-year period, from January 2001 to December 2002, with hip pain, and for whom standard radiographs were obtained were eligible for data analysis. The final study group comprised eligible patients for whom follow-up was available via electronic medical records and/or onemonth post-ED telephone survey.
interobserver agreement for the presence of hip fracture on MRI. The primary outcome parameter of the study was to determine the prevalence of hip and pelvic fractures in patients with initial negative standard radiographs.
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Study Protocol. The lead investigator conducted a structured chart review to record pertinent clinical and demographic data. Eligible patients were identified by query of a searchable electronic radiographic log and medical record. Standard hip radiographs [standard views included anteroposterior (AP) pelvis, lateral hip, and AP hip views] and magnetic resonance images (MRIs) were ordered at the discretion of the treating attending emergency physician during the index ED visit. MRI is the advanced imaging modality of choice at our center for patients with negative standard radiographs of the hip but for whom clinical suspicion for fracture remains high. The initial plain radiograph readings were provided at the point of care by a board-certified radiologist and results were called to the emergency physician in real time. All MRI images were interpreted as to the presence or absence of fracture by a radiologist with fellowship training in musculoskeletal imaging. For the purposes of the study, a second similarly trained radiologist who was blinded to the initial radiologist’s MRI reading subsequently provided her interpretation to assess for interobserver agreement for the diagnosis of fracture. We defined hip and pelvic fractures as any one of the following: 1) fracture evident on initial plain radiograph, 2) fracture evident on MRI of the hip performed at the time of ED care, or 3) subsequent diagnosis of hip and/or pelvic fracture as determined through follow-up. As the majority of our patients receive their medical care within our institution’s clinic system, their subsequent outcome/follow-up, including clinic visits and additional radiographs obtained, was easily tracked through electronic record review. Due to institutional concerns with Health Insurance Portability and Accountability Act (HIPAA) compliance in the setting of a retrospective investigation, we were unable to conduct telephone follow-up on patients who could not be tracked through our health system. Data Analysis. Continuous data are presented as means 6 standard deviations (6SD). Categorical data are presented as means. Ninety-five-percent confidence intervals (95% CIs) were calculated as appropriate. Kappa (k) was also calculated to determine
RESULTS A total of 895 patients had hip radiographs ordered during the study period. Seven hundred sixty-four patients (85.3%) had follow-up completed; these patients composed the study group. Their mean age was 66.7 (620.6) years, and 62.3% were female. Within the study group, the large majority of the patients (95.6%) presented with a history of blunt trauma, including 85.4% who were injured in a fall and 0.2% who were involved in motor vehicle crashes (MVCs). Two hundred nineteen patients (29%) had evidence of a fracture on initial plain radiographs. With respect to fractures identified by plain radiograph, the most common fractures involved the femoral neck (35.6%) and the intertrochanteric region (28.8%). Sixty-two (11.4%) of the 545 patients with negative plain radiographs underwent MRI of the hip ordered by the emergency physician at the index ED visit. MRI identified a total of 29 fractures in 24 patients (9.9% of all patients with fractures in the study group). Of the patients with negative radiographs but positive MRI for fracture, 22 (91.7%) were 65 years of age or older, 16 (66.7%) were female, 16 (66.7%) were injured in a fall, and only one (4.2%) was involved in an MVC. Of the fractures identified by MRI, 34.5% involved the pubic rami, 27.6% the sacrum, 13.8% the femoral neck, 6.9% the intertrochanteric region, 3.4% the femoral head, 3.4% the acetabulum, and 10.3% other. When a blinded study radiologist independently read each MRI, the interobserver agreement for the presence of fracture on MRI was very good (k = 0.847). For patients with initial negative radiographs who did not have an MRI, follow-up did not identify any of these patients as having a subsequent diagnosis of fracture. Thus, 24 of 545 (4.4%; 95% CI = 3.0% to 6.5%) patients with negative plain radiographs had a hip fracture identified by MRI, and 9.9% of all fractures, 24 of 243, were not identified by initial radiographs at the point of care. Of note, only one patient in the follow-up group underwent computed tomography (CT) imaging of the hip rather than MRI.
DISCUSSION In recent years, emergency specialists have been provided with numerous clinical algorithms to guide cost-effective ordering of radiographs in the ED.6–10 When one considers the estimated annual cost to care for hip fractures in the United States ($8 billion), it is surprising that there is a current paucity of research
368 with respect to the ED diagnosis/imaging of this condition.1 In a retrospective study, Oka and Monu reported a series of 73 patients with symptoms suspicious for clinical hip fracture and negative radiographs who subsequently underwent MRI.3 Within this group, they found that 46% of patients had fractures. Although the prevalence of fracture identified by MRI was similar to that which we observed (37.8%), the utility of their study as a reference of comparison is limited by the lack of information regarding the initial number of patients evaluated and radiographed for hip pain. Lim et al. performed a prospective study of 422 patients in Singapore who were evaluated for posttraumatic hip pain.4 They reported that the diagnosis of fracture was unequivocally made on the initial plain radiograph in 365 (86%) cases. The remaining 57 patients in the study group underwent limited MRI of the hip and an additional 32 fractures were discovered. Thus, within their cohort, 8% of the fractures were not identified by plain radiograph as compared with 9.9% in our population. At the same time, their overall prevalence of hip fracture seems quite high when compared with our study group (91.7% vs. 31.8%). This difference may reflect a much higher physician threshold to order a radiograph in their setting, or some other divergence in the selection of the study population that is unaccounted for by the authors’ reported methods. Pandey et al. conducted an ED-based study in the United Kingdom that also evaluated the use of MRI in patients with traumatic hip pain.5 Out of the 770 patients seen during the 20-month study period, 33 with suspected hip fractures but negative plain radiographs underwent hip MRI within 48 hours. From this subset, they identified 22 additional fractures (66% of all fractures). Unfortunately, the authors did not follow-up patients and, therefore, one cannot draw a conclusion as to the overall fracture rate of patients with negative plain radiographs who did not undergo advanced imaging. Although our study is retrospective and subject to the risk of unintended selection bias, we believe that our inclusion criteria and use of clinical follow-up provide the most useful data to date with respect to the question of hip fractures that are not apparent on initial standard radiographs in the ED. We found that 24 of 545 (4.4%; 95% CI = 3.0% to 6.5%) patients with negative plain radiographs had a hip and/or pelvic fracture identified by MRI, and 9.9% of all fractures, 24 of 243, were not identified by initial plain radiographs at the point of care. Within our cohort, the most common fractures identified by MRI after negative plain radiographs included the pubic rami (34.5%), the sacrum (27.6%), the femoral neck (13.8%), and the intertrochanteric region (6.9%). Our results suggest that there is considerable potential for the development of a clinical decision
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algorithm to identify ED patients who remain at risk for fracture after negative standard radiographs. While our physicians appeared to have relatively good judgment for the selective use of MRI based on the relatively high yield of fractures observed (24/ 62 = 38.7%), MRI is an expensive test, and the majority of MRIs ordered were negative. In addition, many of the fractures that were identified by MRI (e.g., pubic rami fractures) are typically managed conservatively. ED patients with these fractures, therefore, may not require advanced imaging.
LIMITATIONS In the setting of a retrospective study, there is always risk for selection bias. We believe that it is unlikely that eligible patients would not have been identified by search of our institution’s electronic medical records and radiologic logs. Although the decision to order a radiograph and/or an MRI was determined by the discretion of the treating physician at the point of care rather than by study protocol, this is the current reality of clinical practice. To date, investigators have not defined a well-accepted clinical algorithm to guide the ordering of hip imaging studies. Another limitation of our study is that we are unable to account for the possibility that some of the patients may have been improperly classified as positive or negative for hip fracture on the initial plain radiographs. This limitation is typically mirrored in clinical practice where decisions for follow-up and advanced imaging are based on the initial readings of the radiographs. In all cases at our center, the initial radiograph was read by both a board-certified attending emergency physician and a board-certified attending radiologist at the point of care. We also note that our physicians rarely order additional plain radiographic views (e.g. Judet, inlet, outlet) when there is high suspicion for fracture, despite negative standard views, because MRI imaging is readily available. Within the constraint that we were unable to initiate telephone or other non-chart-review contact with patients, we believe that our 85.3% follow-up rate on a predominantly elder population was excellent. At the same time, we recognize that we cannot account for the outcomes of the 14.7% of patients lost to follow-up and how these might have changed our results. Irrespective of this limitation, our results certainly provide evidence that a significant percentage of ED patients with hip pain and negative plain radiographs require advanced imaging. Such evidence provides a foundation for future prospective studies to further define this population and categorize high-risk patient groups. Indeed, in the next phase of our investigations, we plan to conduct a prospective protocol with the hope of developing a clinical decision rule for the use of both plain radio-
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graphs and advanced imaging for patients who present to the ED with hip pain.
4. Lim K, Eng A, Chng S, Tan A, Thoo F, Low C. Limited magnetic resonance imaging (MRI) and the occult hip fracture. Ann Acad Med Singapore. 2002; 31:607–10. 5. Pandey R, McNally E, Ali A, Bulstrode C. The role of MRI in the diagnosis of occult hip fractures. Injury. 1998; 29(1): 61–3. 6. Stiell IG, McKnight RD, Greenburg GH, et al. Implementation of the Ottawa ankle rule. JAMA. 1994; 271:827–32. 7. Stiell IG, Wells GA, Hoag RH, et al. Implementation of the Ottawa knee rule for the use of radiography in acute knee injuries. JAMA. 1997; 278:2075–9. 8. Seaberg DC, Yealy DM, Lukens T, Auble T, Mathias S. Multicenter comparison of two clinical decision rules for the use of radiography in acute, high-risk knee injuries. Ann Emerg Med. 1998; 32:8–13. 9. Stiell IG, Wells GA, Vandemheen KL, et al. The Canadian Cspine rule for radiography in alert and stable trauma patients. JAMA. 2001; 286:1841–8. 10. Hoffman JR, Mower WR, Wolfson AB, Todd KH, Zucker MI. Validity of a set of clinical criteria to rule out injury to the cervical spine in patients with blunt trauma. National Emergency X-Radiography Utilization Study Group. N Engl J Med. 2000; 343:94–9.
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CONCLUSIONS In our cohort of ED patients with hip pain who had negative plain radiographs, we found that 4.4% were subsequently diagnosed as having fractures. Further studies are warranted to identify characteristics of patients requiring advanced hip imaging studies. References 1. Melton L. Hip fracture: a worldwide problem today and tomorrow. Bone. 1993; 14:51–8. 2. Cummings S, Rubin S, Black D. The future of hip fractures in the United States: numbers, costs, and potential effects of postmenopausal estrogen. Clin Orthop. 1990; 252:163–6. 3. Oka M, Monu J. Prevalence and patterns of occult hip fractures and mimics revealed by MRI. AJR. 2004; 182:283–8.
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[email protected], via phone at 517-485-5484, or via fax at 517-4785-0801.
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REFLECTIONS
REFLECTIONS Time Zones It is 5:45 PM at home in Connecticut. My older son is at soccer practice, and my wife is probably keeping my younger son entertained at the playground near the soccer field. It is around 78°F and sunny—typical early autumn weather in southern New England. It is 23:45 hours local time here in Norway. A group of about 30 students from the disaster management graduate program at Buskerud University College is three days into a five-day field exercise. It is around 6°C and has been raining almost continuously since we arrived—typical early autumn weather in central Norway. It is 21:45 hours Zulu in the exercise, which is run on Greenwich Mean Time. The students have established a United Nations (UN) Emergency Response Team (ERT) camp in an extremely remote area to receive, care for, and evacuate civilian refugees from a fictitious complex humanitarian emergency modeled after the Balkans crisis. Built of Norwegian Civil Defense inflatable tents, the camp consists of a command post, sleeping quarters, a dining hall/personnel shelter, and a medical aid station. There are four instructors: the course director, a Chief Superintendent from the national police academy, a Norwegian Civil Defense captain who served as Commanding Officer (CO) in this exercise last year as a student, and myself. The two students who had been staffing the forward observation post (OP), about a kilometer north of the camp along the dirt road, were taken hostage about an hour ago, and the CO and Executive Officer are debating whether to sit tight and allow the main UN office nearby to handle the crisis, or to send personnel down to the OP to determine whether the hostage taker and students are still there and, if so, begin negotiations. Since the ERT is unarmed, UN Headquarters–Balkans has indicated by radio that the latter course is unwise. Earlier today, a group of 36 refugees was attacked by unknown combatants with grenades approximately half a kilometer north of the ERT camp. Fourteen were wounded in the attack. After mitigating a hazardous materials situation at the scene of the attack, ERT personnel evacuated all 36 to the camp. The 14 injured refugees were triaged, assessed, and treated by the camp nurses; three died of their wounds during the 90-minute wait for evacuation back to the UN security zone to the north. All of the refugees were registered and given blankets and hot beverages while awaiting transport out of camp. It is now 23:00 hours Zulu in the exercise. The other three instructors are heading off to catch some sleep. I will provide information updates regarding the hostage negotiations every half-hour to the CO by radio, and handle whatever logistic needs arise. I will be relieved at about 03:00 Zulu when the hostages are returned to camp. Then off to bed for an hour or two before shelling of the camp at about 05:00 Zulu, and another influx of refugees later in the morning. It is now about 7:00 PM back in Connecticut, and my family is on the way home from the soccer field. A quick dinner, some homework, then off to bed. In the two weeks that I am in Norway, I miss two of my older son’s soccer games, and my younger son’s first piano lesson. My wife is studying for her boards recertification examination and would have more time for studying if I were home. In the years since September 11, many of us who work in emergency medicine and emergency medical services have focused our attention on disaster planning, preparedness, and response. It is a very difficult thing to do, as it is hard to convince ourselves that, for example, all of the training and preparedness in the world would have made any difference on September 11. But we train and prepare anyway, hoping that we will never need to use our training or our plans, but also hoping that if we do need them, they will serve us well. I always learn as much as I teach in Norway, and hope that it is time well spent. David C. Cone, MD Senior Associate Editor Academic Emergency Medicine Section of Emergency Medicine Yale University School of Medicine New Haven, Connecticut The Graduate Program in Disaster Management is run by the Faculty of Health at Buskerud University College in Drammen, in cooperation with the Norwegian Civil Defense Academy at Starum. The 30 to 35 students who participate in the one-year certificate program have backgrounds and experience in the military, national police, fire service, nursing, and international relief. Slightly more than half are women. The program consists of seven one-week on-campus sessions and several practical and field exercises. Approximately onefourth of each year’s graduating class continues the full master’s program.
