Summary: purpose. The looseness of Circle ligament of children may cause a feint of dislocation of the upper radioulnar joint.
Method: disection and relocate the ulna. Then bend the joint and fix it with plaster.
Result: the X-ray photo taken two weeks after the operation shows the upper end of the radio- is dislocated from the shoulder bone Comparing with the other healthy arm, the X-ray photo shows the extended line of the radio-'s y-axis does not go through the center of the smaller lower joint of the shoulder bone.
Conclusion: when child's upper ulna breaks with the upper radiojoint dislocation from the shoulder bone, the doctor should take X-ray photo of the other healthy arm for comparision to avoid misdiagnosis.