Overview
Radio-ulnar synostosis, unilateral, refers to a condition where the two bones of the forearm — the radius and the ulna — are fused together on one side of the body. Normally, these two bones are separate and can rotate around each other, which allows you to turn your palm up and down (like turning a doorknob). When these bones are fused, this rotation is limited or completely absent in the affected arm. This condition is present from birth, as the bones fail to separate properly during early development in the womb. This Orphanet entry (295217) is now marked as OBSOLETE, meaning it has been retired or merged into a broader classification of radio-ulnar synostosis conditions. Radio-ulnar synostosis can occur as an isolated finding or as part of a larger genetic syndrome. The unilateral form affects only one forearm, which may make it less noticeable than bilateral (both-sided) cases. Children may adapt well by compensating with shoulder and wrist movements, but some daily tasks like turning objects or carrying items with the palm facing up can be difficult. Treatment is generally supportive and depends on how much the fusion limits function. Mild cases may not need treatment, while more severe cases may benefit from occupational therapy or, in some situations, surgery to improve forearm rotation. Surgical outcomes vary, and the decision to operate is made carefully based on the degree of functional limitation and the position in which the forearm is fixed.
Also known as:
Key symptoms:
Inability to rotate the forearm on one sideDifficulty turning the palm up or downLimited range of motion in one forearmTrouble with tasks like turning doorknobs or using a screwdriverDifficulty carrying objects with the palm facing upwardForearm may appear fixed in one positionCompensatory shoulder or wrist movementsPossible elbow stiffness on the affected sideDifficulty with handwriting or using utensils in some cases
Variable
Can be inherited in different ways depending on the underlying gene
Neonatal
Begins at or shortly after birth (first 4 weeks)
Treatments
No FDA-approved treatments are currently listed for OBSOLETE: Radio-ulnar synostosis, unilateral.
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Specialists
View all specialists →No specialists are currently listed for OBSOLETE: Radio-ulnar synostosis, unilateral.
Treatment Centers
8 centersBaylor College of Medicine Rare Disease Center ↗
Baylor College of Medicine
📍 Houston, TX
🏥 NORDStanford Medicine Rare Disease Center ↗
Stanford Medicine
📍 Stanford, CA
🔬 UDNNIH Clinical Center Undiagnosed Diseases Program ↗
National Institutes of Health
📍 Bethesda, MD
🔬 UDNUCLA UDN Clinical Site ↗
UCLA Health
📍 Los Angeles, CA
🔬 UDNBaylor College of Medicine UDN Clinical Site ↗
Baylor College of Medicine
📍 Houston, TX
🔬 UDNHarvard/MGH UDN Clinical Site ↗
Massachusetts General Hospital
📍 Boston, MA
🏥 NORDMayo Clinic Center for Individualized Medicine ↗
Mayo Clinic
📍 Rochester, MN
👤 Mayo Clinic Center for Individualized Medicine
🏥 NORDUCLA Rare Disease Day Program ↗
UCLA Health
📍 Los Angeles, CA
Travel Grants
No travel grants are currently matched to OBSOLETE: Radio-ulnar synostosis, unilateral.
Community
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Caregiver Resources
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Social Security Disability
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Questions for your doctor
Bring these to your next appointment
- Q1.How much forearm rotation is affected, and in what position is the forearm fixed?,Is this an isolated finding, or could it be part of a genetic syndrome?,Would my child benefit from occupational therapy?,Is surgery recommended, and what are the risks and expected outcomes?,Are there any activities my child should avoid?,Should we consider genetic testing for our family?,What adaptive tools or techniques can help with daily tasks?
Common questions about OBSOLETE: Radio-ulnar synostosis, unilateral
What is OBSOLETE: Radio-ulnar synostosis, unilateral?
Radio-ulnar synostosis, unilateral, refers to a condition where the two bones of the forearm — the radius and the ulna — are fused together on one side of the body. Normally, these two bones are separate and can rotate around each other, which allows you to turn your palm up and down (like turning a doorknob). When these bones are fused, this rotation is limited or completely absent in the affected arm. This condition is present from birth, as the bones fail to separate properly during early development in the womb. This Orphanet entry (295217) is now marked as OBSOLETE, meaning it has been r
At what age does OBSOLETE: Radio-ulnar synostosis, unilateral typically begin?
Typical onset of OBSOLETE: Radio-ulnar synostosis, unilateral is neonatal. Age of onset can vary across affected individuals.