Congenital radioulnar synostosis
I share with you a 12 years old case of congenital radioulnar synostosis. He complains of severe limitation of forearm rotation. By Examination, both supination and pronation are blocked with fixed hyperpronation.
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Review of literature
Introduction
Congenital radioulnar synostosis was initially described in 1793 by Sandifort.
It occurs rarely, with only a few hundred cases reported in the literature in the world. Because of its rarity, the diagnosis is often delayed.
It is reported bilaterally in 60–80% of
patients, it can be diagnosed from birth by a clinical examination by testing of the prono-supination of both elbows. It is in fact often discovered later.
Definition
It is a proximal radioulnar fusion, responsible for a limitation of forearm rotation, usually blocked in a neutral position or pronation. This condition results from the failure of the radius and the ulna to separate. The synostosis between the radius and the ulna also occur post-traumatic.
Embryology
Failure of longitudinal segmentation occurs around the 7th week of fetal development.
Genetics
It appears to be inherited as an autosomal dominant disease in some cases. This means that one mutated copy of the gene that causes the disease in each cell is sufficient and can run in the family. It can also be inherited sporadically.
Types
There are 2 types of radioulnar synostosis: type 1 and type 2.
In type 1, the combination includes 2-6 cm of the region between the radius and ulna bones which is nearer to the elbow.
In type 2, the fusion is farther from the elbow and there is dislocation of the head radius.
Age at the time of diagnosis
Diagnosed mainly in preschool-aged children.
Clinical presentation
The proximal congenital radioulnar synostosis manifests by severe limitation of supination and probation. That often results in functional, cosmetic limitations of the upper limb, especially in the bilateral forms. The incomplete type may be manifested by pain. The condition can lead to significant disability, especially if there is hyperpronation or when it is bilateral.
Examination
Pronation and supination blocked both actively and passively.
Imaging
X ray
Ap and lateral views of forearm, elbow and wrist show bony bridge between radius and ulna and may be a valgus deformity.
computed tomography scan
further showed proximal ulna and radius dysplasia.
Treatment
The generally accepted surgical treatment is derotation osteotomy using K-wires or double plates.
While it's rare that surgery can reconstruct the joint between the radius and ulna, some children see significant improvement in function from osteotomy procedures, in which the forearm bones are surgically rotated.
Rotational osteotomy through the synostosis site or double level osteotomy (proximal ulna and distal radius)
Complications of surgery
- loss of correction
- vascular complications such as Volkmanns' ischemia.
- neural complications such as posterior interosseous palsy.
- delayed union.