DEXA Scanning

A DEXA scan (dual-energy X-ray absorptiometry, sometimes written DXA) is a quick, painless test that measures how dense your bones are. It is the standard way of diagnosing osteoporosis — the thinning of bone that makes fractures more likely. In spinal care it matters because weakened vertebrae can fracture with little or no injury, and knowing bone density helps assess that risk and inform decisions about treatment.

The scanner passes two low-energy X-ray beams of different strengths through the body. Bone and soft tissue absorb the two beams differently, and by comparing them the machine can calculate the amount of mineral in the bone — its density. Measurements are usually taken at the lower spine and the hip, the sites most relevant to serious fractures. The result is compared with reference values to produce scores that describe how your bone density compares with a healthy young adult (the "T-score") and with people of your own age (the "Z-score").

You lie on a padded table, fully clothed in most cases, while a scanning arm passes over you without touching you. It is completely painless and takes only around ten to twenty minutes. The radiation dose is very low — far lower than a standard X-ray or CT — but pregnancy is still checked as a precaution. You may be asked to avoid calcium supplements for a short time beforehand and to remove metal items such as belts or jewellery from the area being scanned.

Vertebral fractures from fragile bone are common and can occur with minimal trauma, causing pain, height loss and a stooped posture. A DEXA scan identifies low bone density before such fractures happen, allowing risk to be assessed and, where appropriate, treatment to be started to strengthen bone. It is also used to monitor bone density over time. In spinal surgery, bone quality can influence how well implants hold, so density information can be relevant to planning.

• —National Osteoporosis Guideline Group (NOGG) — Clinical Guideline for the Prevention and Treatment of Osteoporosis
• —Royal Osteoporosis Society — Clinical Guidance
• —Royal College of Radiologists — iRefer: Making the Best Use of Clinical Radiology

This information is for general patient education and is not a substitute for an individual consultation. Always seek personalised advice from a qualified spinal specialist.