About a CT scan of the upper arm
The upper arm runs from the shoulder to the elbow and contains one long bone, the humerus, surrounded by muscles such as the biceps and triceps, along with major nerves and blood vessels. A CT (computed tomography) scan uses X-rays and a computer to make detailed cross-section pictures of the bone, which can be turned into 3D images.
An upper arm CT may be used to look at:
- complex fractures of the humerus, especially those near the shoulder or elbow, to help surgeons plan an operation
- fractures that have not healed (non-union) or have healed in the wrong position, and how a fracture is healing around plates or nails
- bone lumps and lesions, to show their size, shape and effect on the bone, and whether the bone is at risk of breaking
- bone infection (osteomyelitis) affecting the bone
For muscle and tendon injuries, such as biceps or triceps tears, and for soft tissue lumps and nerve problems, an upper arm MRI or ultrasound is usually better. For problems in the joints at each end, see shoulder CT or elbow CT. When you book, choose the left or right side.
What happens during the scan
You lie on your back on the scanner bed with your arm by your side, or sometimes raised, and pads to help keep it still. The bed moves through a short, open ring while your upper arm is scanned. If you have a cast, brace or sling, it can usually stay on. The radiographer controls the scanner from the next room, but can see, hear and talk to you throughout. The scan itself takes only a few minutes. Contrast dye is not usually needed, but may be used to look at a lump or infection; where contrast is needed, it is charged separately.
Is CT safe?
CT uses X-rays, which are a type of ionising radiation. An upper arm CT gives a low dose, because the arm contains few organs that are sensitive to radiation. Part of the chest may be included when the top of the arm is scanned. The risk from a single scan is very small, and every CT scan is checked by a radiologist or radiographer to make sure the benefit of the scan outweighs the risk, as required by the Ionising Radiation (Medical Exposure) Regulations. If you have had other CT scans recently, tell us when you book.
What the scan can show
A CT scan of the upper arm can help to look at:
- complex fractures of the humerus
- non-union and malunion
- fracture healing around plates and nails
- bone lumps, cysts and tumours
- bone infection (osteomyelitis)
- planning for surgery
When to get urgent help: go to A&E if your arm looks misshapen after an injury, you cannot move it, or you cannot lift your wrist or your hand feels numb, cold or looks pale. See a GP if you have bone pain that does not go away, is worse at night, or comes with a lump or swelling.
Preparing for your scan
No special preparation is needed, and you can eat and drink normally. Wear a top that is easy to remove, or you may be asked to change into a gown. Upload any previous X-ray or scan reports and letters from your surgeon when you book, and remember to choose the correct side.
Wear loose, comfortable clothing without metal zips, poppers or buttons, and leave jewellery at home, as metal in the scan area can affect the pictures. You may be asked to change into a gown. Unlike MRI, CT is not affected by pacemakers or most metal implants, and the scanner is a short open ring rather than a tunnel, so it is usually easier for people who feel anxious in enclosed spaces.
Tell the team before your scan if you are, or might be, pregnant or breastfeeding, if you have kidney problems, diabetes (especially if you take metformin), asthma, thyroid problems or allergies, or if you have had a reaction to contrast dye before. If you need contrast, you may be asked for a recent kidney blood test result.
Frequently asked questions
Is CT or MRI better for my upper arm?
CT is best for the bone, such as complex fractures, non-union and bone lumps. MRI is better for muscles, tendons and nerves. Your referrer will say which is needed; if you are unsure, contact us before booking.
I have a plate or nail in my arm. Can I have a CT?
Yes. Modern CT scanners use techniques to reduce the effect of metal on the pictures, and CT is often used to check healing around metalwork. Tell us about any implants when you book.
Do I need to choose a side?
Yes. Choose the left or right upper arm when you book. If both arms need scanning, contact us so the centre can plan the appointment.
Do I need a referral?
Because CT uses radiation, each scan has to be justified by a qualified professional before it can go ahead. Upload a referral from your GP or consultant when you book if you have one. If you do not, select “no referral” and the scanning centre will review your request and confirm the next steps with you, which may include arranging a referral.
Sources
- Humeral shaft fractures: national trends in management (PMC)
- Classification and treatment of proximal humerus fractures: agreement across imaging modalities (PMC)
- NHS – Broken arm or wrist
- NHS – Bone cancer
- NHS – CT scan
- UKHSA – Patient dose information: guidance
The information on this page has been gathered from various sources and is provided for general information only. It is not medical advice. TOP MRI is not liable for the accuracy or completeness of this information. Please speak to your doctor or the scanning centre about your own situation.