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BET 2: CT versus MRI for occult hip fractures
  1. Bernard A Foex,
  2. Anna Russell
  1. Emergency Department, Manchester Royal Infirmary, Manchester, UK
  1. Correspondence to Dr Bernard A Foex; bernard.foex{at}mft.nhs.uk

Abstract

A short-cut review was carried out to establish whether CT or MRI is better at detecting an occult hip fracture. Six studies were directly relevant to the question. The author, date and country of publication, patient group studied, study type, relevant outcomes, results and study weaknesses of these papers are tabulated. The clinical bottom line is that CT is a valid first-line investigation for a suspected plain X-ray occult hip fracture. If clinical suspicion remains after a negative CT scan, then MRI should be used.

  • emergency care systems

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Three-part question

In (elderly patients who present to the ED with suspected hip fracture and inconclusive plain X-rays), is (CT or MRI) better at detecting (occult hip fracture/fractured neck of the femur)?

Clinical scenario

A 75-year-old female patient presents by ambulance to the ED after a fall from standing on to her left hip. On clinical examination she is unable to straight leg-raise and cannot weight-bear. You suspect a fractured neck of the femur. Plain radiographs of her pelvis and hip are inconclusive. You remain suspicious for a hip fracture. Is CT or MRI the next most appropriate imaging modality?

Search strategy

Ovid MEDLINE(R), 1946 to January week 1 2018.

(exp Tomography, X-Ray Computed/or CT.mp. AND exp Magnetic Resonance Imaging/or MRI.mp.) AND (hip fracture.mp. or exp Hip Fractures/OR exp Femoral Fractures/or femur fracture.mp. OR exp Femoral Neck Fractures/or neck of femur.mp.) AND (occult.mp. OR suspected.mp.)

Search outcome

From this search strategy 38 papers were found, of which 6 were relevant. One review article published in 2011 identified only one paper, which compared MRI and CT imaging. This study is included in the table.

Data from the studies are shown in table 1.

Table 1

CT versus MRI for occult hip fractures

Comments

A small but significant proportion of hip fractures are missed on plain X-rays. In the studies presented this is around 1%. Timely diagnosis of hip fracture is important to ensure early fixation and to improve outcome. This literature search showed six relevant papers. All were cohort studies and only one was prospective. Only three studies made direct comparisons of CT and MRI scans. Both Collin et al and Haubro et al show variability in the interpretation of CT scans depending on the expertise of the radiologist. Rehman et al showed a significantly longer time to perform MRI compared with CT scan. MRI scans did pick up a small number of missed fractures. In Haubro et al less than 1% of hip fractures were missed on the initial X-rays. Of the 67 patients who had both CT and MRI scans, only 6 showed a discrepancy between CT and MRI diagnoses, and in only 3 did the MRI confirm a fracture, which needed surgery. In the earlier study by Lubovsky et al, the CT diagnosis was incorrect in four out of six cases after MRI. However, in this latter study CT slices were much thicker than in Haubro et al (3.2 mm vs <1 mm). The National Institute for Health and Care Excellence Hip Fracture Management Guideline (CG124, published in 2011) clearly states that MRI is the investigation choice for an occult hip fracture, with CT as second line if MRI is contraindicated or cannot be obtained within 24 hours. The evidence from this best evidence topic suggests a more pragmatic approach is valid with early/out-of-hours CT if readily available, as in practice there will often be a 24-hour delay to MRI scan.

Clinical bottom line

CT is a valid first-line imaging technique in suspected occult hip fracture and is easily accessible in most centres. Early diagnosis is important for patient outcomes. Reporting variability of CT scans means that an experienced musculoskeletal radiologist should review negative or inconclusive CT scans. However, when a clinical suspicion remains, despite a normal or inconclusive CT scan, an MRI scan is warranted.

References

Footnotes

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Patient consent Not required.

  • Provenance and peer review Not commissioned; internally peer reviewed.