X-ray

An X-ray is a test that takes pictures of the inside of the body using a small amount of radiation. A standard X-ray is used mainly to check bones, for example for a fracture after an accident; CT scans, which also use X-rays, give more detail (NHS). For back pain, NICE advises against offering imaging routinely outside specialist settings (NICE).

What an X-ray shows, and what it doesn’t

A standard X-ray is mainly a picture of bone: it shows the shape and alignment of the vertebrae rather than the intervertebral discs, nerves or muscles. When symptoms of a slipped disc don’t get better, the NHS says the next test may be an MRI scan (NHS).

What it does show often isn’t the cause. In 107 people over 45, neck X-rays showed no difference in neck curvature between those with neck pain and those without, and the authors concluded such findings should be considered coincidental (Grob et al., 2007); see cervical lordosis. On CT and MRI scans of 3,110 people with no symptoms, disc degeneration rose from 37% at age 20 to 96% at 80 (Brinjikji et al., 2015).

What NICE and the trials say

NICE’s low back pain guideline says: do not routinely offer imaging in a non-specialist setting, explain that people referred to a specialist may not need imaging, and consider imaging in specialist care only if the result is likely to change management (NICE).

The trials behind that advice:

• A meta-analysis of 6 trials (1,804 people) found no difference in pain or function between immediate lumbar imaging and usual care without it, in the short or long term (Chou et al., 2009).
• In a UK trial of 421 people with low back pain lasting a median of 10 weeks, those randomised to an X-ray were more likely to still report pain at 3 months and consulted their GP more. They were more satisfied with their care at 9 months, and an abnormal finding made no difference to outcome (Kendrick et al., 2001).

When is an X-ray useful for back or neck pain?

When a doctor suspects something specific. NICE asks clinicians to exclude causes such as cancer, infection, trauma and inflammatory disease (NICE); these warning signs are covered under red flags.

• After an injury. For neck injuries, emergency clinicians can use the Canadian C-spine rule. In 8,924 alert trauma patients it picked out all 151 with an important neck injury while flagging about 58% for an X-ray, rather than everyone (Stiell et al., 2001). See whiplash.
• A suspected osteoporotic fracture. Spine X-rays are a standard way to look for a vertebral fracture, though reading them takes care: in one international study, local reports missed 34% of fractures found by expert readers (Delmas et al., 2005).

How much radiation is in a spine X-ray?

UK Health Security Agency figures put a lumbar spine X-ray at about 1.3 mSv, equivalent to roughly 7 months of natural background radiation and an estimated 1 in 15,000 lifetime added risk of fatal cancer. A neck X-ray is about 2 weeks of background radiation and a single chest X-ray about 3 days (UKHSA). The NHS describes the cancer risk from many X-rays as very small and says doctors weigh it before offering one (NHS).

When to see a doctor

Ask for an urgent GP appointment or call 111 if back pain starts suddenly and severely or comes with feeling hot, shivery or unwell. Call 999 or go to A&E if it comes with numbness or weakness in both legs, loss of feeling around the genitals or anus, bladder or bowel changes, or chest pain, or if it started after a serious accident (NHS). For the common causes, see lower back pain from sitting and neck pain from desk work.