A spiral femoral fracture in a non-mobile infant: what the skeletal survey must deliver
A 6-month-old boy is brought to the emergency department by his mother's partner at 22:00 with a swollen left thigh and refusal to move the leg. The history given is that he 'rolled off the sofa' 5 hours earlier. He is afebrile and alert with no bruising, but there is tenderness and swelling of the mid-thigh. A radiograph shows a spiral fracture of the left femoral shaft with 15 degrees of angulation. Because of the mechanism, a skeletal survey is requested. The survey is performed at 23:30 by the on-call radiographer using a single AP view of each region; the report describes the spiral femoral fracture and an additional healing fracture of the left 6th posterior rib. The infant has no neurological symptoms and the fontanelle is normal. The paediatric team asks whether a head CT is needed and when the survey should be repeated.
1. Which features of this case raise concern for physical abuse, and how should the skeletal survey be performed?
Read the worked answer
Concerning features:
- A spiral femoral shaft fracture in a non-ambulant 6-month-old - this mechanism requires considerable rotational force and is not produced by a fall from a sofa.
- A posterior rib fracture, especially healing: posterior and lateral rib fractures have very high specificity for inflicted injury because the leverage required is not generated by ordinary handling or resuscitation.
- Fractures of differing ages (acute femur, healing rib) with no corroborating accidental history.
- History inconsistent with developmental stage and with the injury pattern.
How the survey should be done:
- Follow a recognised standard (RCR/RCPCH in the UK, ACR in the US): AP and lateral skull, AP and lateral thorax (including oblique rib views), AP abdomen, AP pelvis, lateral lumbar spine, AP both upper limbs including coned views of hands, AP both lower limbs including coned views of knees and feet.
- A single AP view per region is inadequate and is the main deficiency here - the lateral skull, lateral spine, oblique ribs and coned metaphyseal views are missing and are exactly the views that detect metaphyseal corner fractures and posterior rib fractures.
- Use a dedicated digital system with a low-dose paediatric protocol; the images must be reviewed by a radiologist before the infant leaves the department, with coned or repeat views as needed. Sedation is rarely required.
- Document image quality and any limitation in the report, and record who was present.
2. Justify the timing of a repeat skeletal survey, and explain what it adds.
Read the worked answer
A repeat survey should be performed about 11–14 days after the initial study.
Reasoning:
- Some fractures - particularly metaphyseal corner fractures, posterior rib fractures and subtle shaft fractures - are radiographically invisible in the first days after injury.
- Healing produces visible callus and periosteal new bone at roughly 7–14 days in an infant, so a second survey at that interval detects fractures that were occult initially.
- It also allows fracture dating: fractures of different apparent ages support a diagnosis of repeated injury, which is powerful evidence for child protection proceedings.
- It is not a substitute for a poor-quality first survey - both should be done properly.
Practical points:
- Do not repeat earlier than about 10 days: callus will not yet be visible and the study adds nothing.
- The repeat should be a full survey, not just a repeat of the symptomatic area, and should be reported by a paediatric radiologist.
- The result must be communicated in writing to the safeguarding lead, and the report should state explicitly whether the findings are consistent with the given history.
- A follow-up skeletal survey is not required if the initial study and the clinical assessment already establish the diagnosis, but it is standard in most safeguarding pathways.
3. How would you image the brain in this infant, and why?
Read the worked answer
This infant needs neuroimaging, even though he is asymptomatic. A significant proportion of infants with inflicted skeletal injury have occult intracranial injury, and missing it risks further harm.
Choice of modality:
- CT head without contrast is first line if there are neurological signs - seizures, reduced consciousness, apnoea, a bulging fontanelle, retinal haemorrhage, or a fracture involving the skull vault. It is fast, excludes acute haemorrhage and skull fracture, and does not need sedation. Its drawback is radiation dose to a young brain.
- MRI brain (including T1, T2, FLAIR, DWI and susceptibility-weighted imaging) is more sensitive for small subdural haematomas, cortical contusion, shearing injury and hypoxic-ischaemic change, and avoids radiation. In an asymptomatic, stable infant with a normal fontanelle and no neurological signs, an urgent MRI within 24–48 hours is a reasonable first choice if it can be obtained promptly without sedation.
- Whichever is used first, the other may still be needed: a normal CT does not exclude a small subdural or shear injury, and a delayed MRI at 48–72 hours may show evolving changes.
Discuss the timing with the paediatric and safeguarding teams, and include the whole spine and cervical spine in the MRI if there is any suggestion of neck injury.