Hip pain with normal radiographs — suspected occult fracture or osteonecrosis

ACR AC Acute Hip Pain (2024 rev); ACR AC Osteonecrosis (2022 rev)

Persistent hip or groin pain with normal or equivocal radiographs. MRI of both hips with a large field of view is the answer to both halves of the question — the undisplaced proximal femoral fracture in the elderly faller, and early osteonecrosis in the patient with risk factors.

An older patient unable to weight-bear after a fall with normal radiographs, or a younger patient with groin pain and risk factors for osteonecrosis — corticosteroids, alcohol, sickle cell disease, transplantation, chemotherapy.

Referenced decision support — confirm against your local protocol.

Decision support, not a directive. Protocols and timings shown are typical published ones — your local protocol takes precedence, and the vetting radiologist decides.

The request in front of you

Everything is optional. Leave a field alone and the answer assumes nothing — the verdict updates as you go.

Study requested

What the referrer actually asked for. It is evidence of intent, not a constraint on the right answer.

Contrast as written

What the request form says, not what it should say.

Age

Pick a band, or type an exact age if it matters.

years

Pregnancy status

Renal risk factors

The question a vetter can actually answer from the request. An explicit “none known” is a real answer, and it removes checks rather than deferring them.

Previous contrast reaction

The pathway — tap anything already done

Marking a study complete moves the answer on. A patient arrives partway through a pathway far more often than at the start of one.

Accept as requested

MRI Hip — routine

MRI Hip

What we'd amend, and why

Marrow oedema and the fracture line are visible on MRI from the moment of injury, which is why a coronal T1 and STIR pair across the whole pelvis is close to definitive for radiographically occult proximal femoral fracture — and why a negative study lets the patient be mobilised with confidence. The same sequences show the serpiginous demarcation line of early osteonecrosis before any radiographic change, and cover the contralateral hip, where asymptomatic disease is common.

Nothing needs resolving before this goes ahead. Routine checks below are owned downstream.

How was this decided?

pathwayany — All patients
rulerule-mr-device-screening — MR safety screening for implants and foreign bodies; checked by Radiographer at the scanner

Decision support only. Local protocol takes precedence.

Handled at the scanner(1)nothing for you to do

Settled and owned downstream. Each returns to a radiologist only on the stated trigger.

MR safety screening for implants and foreign bodies
Complete the MR safety questionnaire, verify implant labelling and its stated conditions of use against this scanner and this protocol, and ensure no ferromagnetic object enters Zone IV.
Radiographer at the scannerBefore the scan
Flags back if: An implant or retained foreign body that is MR Unsafe, unlabelled, or cannot be identified; or an MR Conditional device whose stated conditions this scanner or the requested protocol cannot satisfy; or a credible unexcluded intraocular metallic foreign body history.
If an implant flags back on an inpatient who cannot weight-bear, do not simply cancel: CT the same day is a reasonable fallback for the fracture question, while a delayed MRI once the device is characterised remains the better test for osteonecrosis. What is not acceptable is leaving an older patient immobile while the implant is chased.

Worth asking the referrer (1)

None of these hold the request up. They sharpen the protocol or the plan that follows.

Can the patient weight-bear, and are there osteonecrosis risk factors such as corticosteroids, sickle cell disease or alcohol excess?
It separates the urgent fracture question from the osteonecrosis question, which changes how quickly the study is needed and what the report should emphasise.

Pathways

Big forks are separate pathways; the first whose conditions match is the one used.

All patients

Matches your inputsDefault

Role	Study & protocol	Why this answers the question
First line	MRI Hip MRI Hip — routine usually appropriate	Marrow oedema and the fracture line are visible on MRI from the moment of injury, which is why a coronal T1 and STIR pair across the whole pelvis is close to definitive for radiographically occult proximal femoral fracture — and why a negative study lets the patient be mobilised with confidence. The same sequences show the serpiginous demarcation line of early osteonecrosis before any radiographic change, and cover the contralateral hip, where asymptomatic disease is common.
Reasonable alternative	CT Extremity / Musculoskeletal CT Extremity — Unenhanced, Thin Section	CT is the substitute when MRI is contraindicated or cannot be obtained quickly enough for an inpatient who needs a decision today. It is good for cortical detail and surgical planning but less sensitive for an undisplaced fracture, and it is insensitive to early osteonecrosis, which is a marrow diagnosis.
Problem solving	Bone scintigraphy Bone scintigraphy — whole body (± three phase)	A distant third option where both MRI and CT are unavailable. Sensitivity is good but uptake takes time to develop in the very elderly, and specificity is poor in a degenerate pelvis, so a positive scan often still needs anatomical imaging to interpret.

Pitfalls

Accepting a single-hip, small field-of-view MRI. The pubic rami and sacrum are frequent alternative fracture sites and the contralateral hip is where asymptomatic osteonecrosis is found.
Reporting a normal hip and stopping, when the patient still cannot weight-bear and the pelvis was not covered.
Assuming that normal radiographs plus a plausible alternative explanation excludes a fracture in an osteoporotic patient.
Calling early osteonecrosis "bone oedema" without describing the demarcating line and the extent of head involvement, which is what determines the risk of collapse and the surgical options.
Delaying the study to the next working day in a patient admitted specifically because they cannot walk.

Priors — what to pull first

Compare with any previous pelvic radiograph or CT; pre-existing degenerative change and old fractures are the commonest cause of misinterpretation.
Where osteonecrosis is suspected, previous imaging that already shows subchondral change moves the patient down the staging pathway rather than the diagnostic one.

What makes a good request

These two presentations share one answer and one pitfall, which is why they sit on one card: normal radiographs do not exclude either diagnosis, and the imaging must cover both hips and the pelvis.
An occult hip fracture is a same-day question. Prolonged immobility in an older patient carries its own well-documented complications.
Where osteonecrosis is the question, ask about the risk factor on the request — it changes the pre-test probability, and steroid exposure often has to be sought actively.

Scoring this once it is done

The classification and risk tools this question ends in.

Garden Classification (Femoral Neck Fractures)Ficat-Arlet / ARCO Staging (Femoral Head AVN)Ottawa Ankle / Knee / Foot Rules Salter-Harris Classification (Physeal Fractures)

How these studies are acquired

Contrast, phases and timing for every study on the pathways above.

MRI Hip — routine CT Extremity — Unenhanced, Thin Section Bone scintigraphy — whole body (± three phase)

Confirm locally

MRI Hip — routine: timings are typical — confirm against local protocol.
Timings, contrast volumes and rates above are typical published values. Your department's protocol, scanner and patient population decide the actual numbers.
Safety thresholds and premedication policy follow local policy where it differs from the cited guidance.

References

Implemented from the cited published sources. Educational and workflow support only; confirm against current guidelines and local policy before clinical use.