Radioulnar Synostosis


If your baby was born with radioulnar synostosis, we know that you and your family are concerned. So, please know that at Boston Children’s Hospital, we will approach your child’s treatment and care with sensitivity and support — for your child and your whole family.

Radioulnar synostosis is usually congenital (something your child was born with); but it may also occur after a forearm fracture or trauma. Please note that these pages discuss the congenital form of the condition.

Frequently Asked Questions

What is radioulnar synostosis?
Congenital radioulnar synostosis is a rare congenital difference in which there’s an abnormal bony or soft tissue connection between the two bones of the forearm — the radius and the ulna.
What signs or symptoms might my child have?

Radioulnar synostosis can be mild to severe. Signs and symptoms of your child’s condition can range from a minor to a major limitation in her ability to rotate her arm from a pronated (palms down) position to a supinated (palms up) position. She may also carry her elbow at an abnormal angle or have a shortened forearm.

Your child’s doctor will know by physical exam and x-rays that your baby has radioulnar synostosis. The doctor will refer you to an orthopedic surgeon, who will guide you to a more detailed diagnosis and treatment plan.

Can radioulnar synostosis be associated with other conditions?

Yes, radioulnar synostosis can occur as part of an underlying syndrome or with other developmental abnormalities, such as:

  • other skeletal abnormalities (about one-third of the time)
  • problems of the heart, kidneys, nervous system or gastrointestinal system
  • certain genetic syndromes, such as Holt-Oram syndrome (also called hand-heart syndrome) and fetal alcohol syndrome
How does congenital radioulnar synostosis happen?
When your baby is still in the womb, her upper limb develops between the fifth and eighth week of gestation. Initially, the radius and ulna bones are connected. Then, separation occurs and the individual radius and ulna bones form. Congenital radioulnar synostosis results if these bones don’t separate during this time.
Why does it happen?

While most cases of congenital radioulnar synostosis occur by chance (sporadically), about one in five cases is associated with a family history of the same condition.

Congenital radioulnar synostosis can also occur as part of an underlying syndrome or with other developmental abnormalities.

How common is radioulnar synostosis?
The exact incidence of this condition is unknown. Boys and girls are equally affected, and about 60 percent of patients have the condition in both arms.
Does radioulnar synostosis cause my child pain?
No, radioulnar synostosis isn’t usually painful for a baby. But if left untreated or undiagnosed, teens may begin experiencing pain if the top of the radius (radial head) becomes dislocated.
How is radioulnar synostosis diagnosed?

Your child’s doctor will do a thorough medical history and careful physical examination. X-rays and/or CT scans may be used to confirm the diagnosis.

In more serious cases, forearm rotation is much more limited and obvious, so the diagnosis can be made at an earlier age — typically around age 6.

Questions to ask your doctor

If your child is diagnosed with radioulnar synostosis, you may feel overwhelmed with information. It’s easy to lose track of the questions that occur to you. Lots of parents find it helpful to jot down questions as they arise — that way, when you talk to your child’s doctors, you can be sure that all of your concerns are addressed.

Some of the questions you may want to ask include:

  • What is happening to my child, and why?
  • What do the x-rays reveal? How serious is my child’s condition?
  • What actions might you take after you review my child’s condition?
  • Is surgery necessary? Are there alternative therapies?
  • Will my child be OK after surgery?
  • Will my child recover full function of her arm? Will it look OK?
  • Will there be restrictions on her activities or capabilities?
  • What will be the long-term effects?
  • What can we do at home?

For parents

Many parents whose babies are born with radioulnar synostosis feel frustrated that the birth of their child didn’t turn out the way they’d dreamed it would. Your child’s treatment and recovery may be fairly easy. Or, the journey may be more complicated — requiring surgery and care for your child as she grows.

Even though you understand the importance of therapy for your child, you still might experience her treatment and care as a stressful time. If you feel frustrated or depressed, speak to your doctor or counselor to get help. Professionals in Boston Children’s Hale Family Center for Families can provide you with important resources and referrals.

How Boston Children's Hospital approaches radioulnar synostosis

You can have peace of mind knowing that the skilled experts in our Orthopedic Center’s Hand and Orthopedic Upper Extremity Program have treated thousands of babies and children with hand problems, ranging from the routine to the highly complex. So we can provide your child with expert diagnosis, treatment, and care — as well as the benefits of some of the most advanced clinical and scientific research in the world.

Our Orthopedic Center is nationally known as the preeminent center for the care of children and young adults with a wide range of developmental, congenital, neuromuscular, sports related, traumatic, and post-traumatic problems of the musculoskeletal system.


  • The Hale Family Center for Families at Boston Children’s: dedicated to helping families find the information, services, and resources they need to understand their child’s medical condition and take part in their care
  • congenital: present at birth
  • CT scan: (computed tomography): detailed three-dimensional images of your child's bone, tissue, and blood vessels. CT exams in Children’s powerful multi-detector scanners are quick, painless, and non-invasive.
  • embryonic development: development of the fetus in the womb
  • in utero: in the womb (uterus)
  • orthopedics: the medical specialty concerned with diagnosing, treating, rehabilitating, and preventing disorders and injuries to the spine, skeletal system, and associated muscles, joints, and ligaments
  • orthopedic surgeon, orthopedist: a physician specializing in surgical and non-surgical treatment of the spine, skeletal system, and associated muscles, joints, and ligaments
  • osteotomy: surgery that involves cutting bone
  • post-operative (post-op): occurring after surgery
  • pre-operative (pre-op): occurring before surgery
  • pronated (forearm position): “palms down” position
  • proximal (opp. distal): next to or nearest the point of attachment or origin (i.e., closest to the trunk of the body); opp. distal: situated away from the point of attachment or origin (i.e., furthest away from the trunk of the body)
  • radial head: top (most proximal part) of the radius bone closest to the elbow joint; important for rotating the forearm
  • radioulnar synostosis: a deformity in which the forearm bones (radius and ulna) are connected on the proximal side by bony or soft tissue, instead of having completely separated into two distinct bones in utero
  • radius: forearm bone on the thumb side
  • reconstructive surgery: surgery performed to repair and/or restore a body part to normal or as near normal as possible
  • sporadic: occurring without apparent genetic cause
  • supinated (forearm position): “palms up” position
  • synostosis: a union or fusion of bones that are usually distinct from each other
  • ulna: forearm bone on the little finger side
  • x-rays: a diagnostic test that uses invisible electromagnetic energy beams to produce images of internal tissues, bones, and organs onto film