When assessing a patient with a suspected radiographically occult fracture, there are two options for the emergency physician: more tests or more time.

More tests equates to additional X-ray views or advanced imaging (CT or MRI).

More time means treating the patient for the suspected diagnosis and arranging for a serial assessment.

I will discuss three cases and explore the ED management options.

Case 1: Occult Scaphoid Fracture

A 26-year-old female fell on an outstretched hand and has isolated wrist pain, tender snuff box, and scaphoid tubercle. X-rays of the wrist with scaphoid views are normal.

Diagnosis: suspected occult scaphoid fracture.

Follow-up studies have shown that 75 to 80 percent of patients with an ED diagnosis of a “suspected scaphoid fracture” do not have a fracture.^1,2 There is concern that many patients are unnecessarily immobilized and require a low-yield follow-up appointment. These concerns have led some emergency departments to institute a wrist CT protocol during the initial visit in an attempt to definitively rule in or rule out a scaphoid fracture. A meta-analysis showed the sensitivity and specificity of CT for occult scaphoid fractures were 0.72 (95% CI, 0.36–0.92) and 0.99 (95% CI, 0.71–1.00), respectively.³ Even the CT may not definitively rule out a fracture and may be falsely reassuring. Additionally, if a patient’s radial-sided wrist pain comes from a partial scapholunate ligament (SLL) injury, the CT may be normal. If a patient subsequently falls during SLL healing (which may take weeks to months), the second force may convert a partial tear to a complete one, requiring operative management.

MRI is often considered the best advanced imaging option, as it shows the bone and soft tissues. A meta-analysis reported the sensitivity and specificity of MRI for occult scaphoid fractures were 0.88 (95% CI, 0.64–0.97) and 1.00 (95% CI, 0.38–1.00), respectively.³ Another smaller study showed early MRI missed 20 percent of radiographically occult scaphoid fractures.⁴ Therefore, normal MRI may not definitively rule out a fracture either. Additionally, high cost and low access prevent MRI from playing a role as an advanced imaging option for suspected occult scaphoid fractures during ED visits.

A bone scan may be considered due to a high sensitivity, though this modality is fading from common use. The sensitivity and specificity of bone scan for occult scaphoid fractures were 0.99 (95% CI, 0.69–1.00) and 0.86 (95% CI, 0.73–0.94), respectively, but there are many downsides to this imaging modality in the emergency department.³ For fracture detection, a bone scan generally requires 48 to 72 hours after injury to become reliably positive (though modern bone scans may need less time). Given its high sensitivity, a negative bone scan at 48 to 72 hours essentially rules out a fracture, but as with CT, a normal bone scan does not rule out a SLL tear. Unfortunately, a positive bone scan is hampered by low specificity. False positives can be generated by any condition that increases metabolic activity in bone, such as a bone contusion, infection, inflammation, degenerative joint disease, and tumors. Additionally, bone scans are associated with significant ionizing radiation (equivalent to 50 chest X-rays). Bone scans are fairly time-consuming and only available during certain working hours, and they require isotope availability. Bone scans miss important information including fracture pattern and/or precise location, making prognosis for that fracture difficult to assess. Therefore, a positive bone scan is often followed by a form of 3-D imaging (typically CT). As a result, radionuclide bone scans for suspected scaphoid fractures in the emergency department are largely impractical.

Similarly, ultrasound (US) is of limited value for occult fracture confirmation. Certainly, US may be helpful with some soft tissue injuries. It is less helpful in fractures. The sensitivity and specificity of ultrasound in diagnosing radiographically occult scaphoid fracture ranged from 77.8 to 100 percent and from 71.4 to 100 percent, respectively, with pooled estimates of 85.6 percent (95% CI, 73.9–92.6%) and 83.3 percent (95% CI, 72.0–90.6%), respectively.⁵

While there are suggestions in the literature that US may be an option for suspected scaphoid fractures, it is not considered sensitive enough to reliably alter ED management decisions.^3,4

Case 2: Occult Lateral Tibial Plateau Fracture

A 78-year-old male presents with valgus stress to left knee, immediate pain, non-weight-bearing, and swelling within an hour. On exam, the knee is swollen, there is tenderness along the lateral joint line, the ligaments are stable, and soft tissues are intact. X-rays of the knee (four views) show effusion only.

Diagnosis: suspected occult lateral tibial plateau fracture.

Valgus stress with immediate pain, rapid swelling (implying acute hemarthrosis), and non-weight-bearing suggest a lateral tibial plateau fracture, especially in older patients with osteoporosis. On exam, the swollen knee, lateral joint line pain, and inability to bear weight are consistent with a likely tibial plateau injury. Even in the face of normal X-rays, the high clinical suspicion should make one pause and consider occult fracture. Such fractures are at risk of displacing if the diagnosis is missed in the emergency department and the patient is allowed to weight-bear.⁶

More tests? Or “treat and more time?” The option for treat and more time means immobilization, crutches, and non-weight-bearing. In many older patients, this proposition is very risky, so the push would be for advanced imaging (a CT scan) as soon as can be reasonably arranged. The patient should be kept non-weight-bearing until the diagnosis is clarified. A younger patient with a similar assessment may be more likely to manage crutches. Therefore, the option of immobilization, crutches, strict non-weight-bearing, and close follow-up (ideally within a week) may be more reasonable, depending on your local resources and preferences.

Case 3: Occult Hip Fracture

A 74-year-old female slips and falls. She has pain to the right hip and is non-weight-bearing. There is no limb-shortening or external rotation. She has a tender right hip and significant decreased range of motion (passive and active). X-rays of the hip and anteroposterior pelvis are normal.

Diagnosis: suspected occult hip (neck of femur) fracture.

The incidence of radiographically occult hip fracture (neck of the femur) is estimated to be between 5 and 10 percent—and more likely in elderly patients.

A few important warnings about ED patients with hip fractures. The “classic” patient with a hip fracture has fallen and cannot walk, and their leg is short and externally rotated. Shortening and external rotation indicate a displaced fracture. However, an undisplaced hip fracture will not have the classic short and externally rotated presentation—it will have symmetric alignment to the contralateral leg. While most patients with a hip fracture are unable to walk, a minority of patients with an impacted, undisplaced hip fracture may be able to, albeit with a painful limp. In some cases, history (or lack thereof) can mislead us; hip fractures can occur without falling. In patients with an osteoporotic (weak), arthritic (stiff) hip, a vigorous twist can produce enough torque to cause a fracture. Not realizing this can be a diagnostic pitfall.

Often, an occult hip fracture needs surgical management. Delay in diagnosis increases morbidity as diagnostic delay is associated with greater displacement and more extensive surgery.³ Even mortality increases with delay to surgery.⁷ A 13 percent increase in the risk of mortality for every day of delay in surgery has been reported.⁸ Ideally, patients with a hip fracture should be operated on within 24 to 28 hours. However, the decision to operate cannot be made until the diagnosis is confirmed.

This case highlights that a greater imperative exists to diagnose these injuries, requiring more tests on the index visit. However, if the clinical setting is such that advanced imaging is not available, then bed rest and non-weight-bearing are mandated until a diagnosis is confirmed. Ideally, arrangements for advanced imaging should be made.

Two additional points: Older patients with osteoarthritis can have marginal osteophytes. On CT, these marginal osteophytes can simulate fractures in their periphery. Osteoporosis can also accentuate lucencies and nutrient vessels, again mimicking fractures and leading to false positive reads.

Analysis

In determining a management strategy (more tests versus more time), three main factors should be considered for patients with a suspected occult fracture:

• Diagnosis in question
• Patient in question
• Available resources
• Diagnostic Factors

For some occult fractures, the plan of immediate immobilization and delaying diagnostic confirmation is reasonable since this strategy would not adversely affect outcome. However, diagnostic delay of other radiographically occult fractures can be harmful.⁹ Suspected scaphoid fractures with negative X-rays are the classic example. Suspected distal radius fractures can be approached similarly. Most pediatric cases of suspected occult fractures can be managed this way.

Suspected occult hip fractures, tibial plateau fractures, and cervical spine fractures, however, require immediate further evaluation, as they are more likely to displace if missed in the emergency department and not managed appropriately.⁹ These displacements can lead to more extensive surgery or surgery that may have been avoided altogether.⁹ In these cases, the need for advanced imaging during the index visit is evident.

Patient Factors

Patient factors also play a role. Because of the tendency to displace with weight-bearing, patients with suspected tibial plateau fractures should be kept non-weight-bearing until confirmed or reassessed. For older patients, the strategy to immobilize, provide crutches, and require no weight-bearing can be a dangerous combination; fall risks are high. But younger patients may safely tolerate this approach, permitting immobilization and delayed advanced imaging in many instances. Patient factors around compliance and availability for follow-up should also influence our choice between more tests and more time.

Imaging Modalities

Advanced imaging for occult fractures in the emergency department generally refers to CT and MRI. Each has respective pros and cons.

A CT scan generally has high sensitivity for detecting fractures, and especially with 3-D reconstruction, it is an excellent tool for assessing bony alignment. CT provides little value for soft tissue injuries.

Musculoskeletal CT scans expose patients to ionizing radiation, but that exposure is far less than chest, abdomen, and pelvic protocols. A wrist CT is equivalent to the radiation of just 1.5–3 chest X-rays.^10,11 A chest CT is equivalent to around 70; an abdomen/pelvis CT is equivalent to up to 100.¹²

MRI has advantages over CT. In addition to high sensitivity for fractures, MRIs can assess soft tissue structures—and without any radiation. However, high cost, long scan and radiology reading times, and poorer availability limit its role in the emergency department for occult fractures.

Bone scans and ultrasound in assessing suspected occult fractures are discussed above.

As a final consideration, the ED workup and treatment can vary from hospital to hospital based on local orthopedic preferences. Knowing how your local orthopedic surgeons prefer to manage the spectrum of suspected occult fractures from the outset optimally aligns initial ED care with the follow-up care patients will receive.

Summary

When considering advanced imaging, we are guided by the post-test probability for fracture; knowing the limits of plain films; understanding the complications of the suspected injury; the pros, cons, and indications for advanced imaging; and the proper ED treatment. Combining these helps optimize care.

“X-ray normal” is not a diagnosis. While most ED patients with negative extremity X-rays do not have a fracture, a few will. As clinicians, we see normal X-rays routinely on every shift. We should neither be falsely reassured by them nor unduly afraid of them. Combining the patient’s history with risk factors and the physical exam will determine our proper level of concern.

If significant concern for a fracture remains after negative X-rays, the ideal ED management strategy depends on the diagnosis, the patient, and available resources.

Worrisome diagnoses in less physically robust patients tend to require more urgent diagnostic confirmation. However, in many cases, sturdy patients with a suspected occult fracture can be safely and appropriately managed with an ED plan to treat for the fracture and arrangement of close follow-up.

References

1. Baldassarre R, Hughes T. Investigating suspected scaphoid fracture. BMJ. 2013;346:f1370.
2. Suh N, Grewal R. Controversies and best practices for acute scaphoid fracture management. J Hand Surg Eur Vol. 2018;43(1):4-12.
3. Mallee WH, Wang J, Poolman RW, et al. Computed tomography versus magnetic resonance imaging versus bone scintigraphy for clinically suspected scaphoid fractures in patients with negative plain radiographs. Cochrane Database Syst Rev. 2015;(6):CD010023.
4. Beeres FJ, Rhemrev SJ, den Hollander P, et al. Early magnetic resonance imaging compared with bone scintigraphy in suspected scaphoid fractures. J Bone Joint Surg Br. 2008;90(9):1205-1209.
5. Kwee RM, Kwee TC. Ultrasound for diagnosing radiographically occult scaphoid fracture. Skeletal Radiol. 2018;47(9):1205-1212.
6. Kiel CM, Mikkelsen KL, Krogsgaard MR. Why tibial plateau fractures are overlooked. BMC Musculoskelet Disord. 2018;19(1):244.
7. Lewis PM, Waddell JP. When is the ideal time to operate on a patient with a fracture of the hip? a review of the available literature. Bone Joint J. 2016;98-B(12):1573-1581.
8. Weller I, Wai EK, Jaglal S, et al. The effect of hospital type and surgical delay on mortality after surgery for hip fracture. J Bone Joint Surg Br. 2005;87(3):361-366.
9. Je S, Kim H, Ryu S, et al. The consequence of delayed diagnosis of an occult hip fracture. J Trauma Injury. 2015;28(3):91-97.
10. Iordache SD, Goldberg N, Paz L, et al. Radiation exposure from computed tomography of the upper limbs. Acta Orthop Belg. 2017;83(4):581-588.
11. Biswas D, Bible JE, Bohan M, et al. Radiation exposure from musculoskeletal computerized tomographic scans. J Bone Joint Surg Am. 2009;91(8):1882-1889.
12. Radiation dose to adults from common imaging examinations. American College of Radiology website. Available at: https://www.acr.org/-/media/ACR/Files/Radiology-Safety/Radiation-Safety/Dose-Reference-Card.pdf. Accessed Feb. 13, 2020.

Dr. Sayal is a staff physician in the emergency department and fracture clinic at North York General Hospital in Toronto, creator and director of CASTED ‘Hands-On’ Orthopedic Courses, and associate professor in the department of family and community medicine at the University of Toronto.