Definition
Abnormal bony connection between then radius and ulna from birth.
Anatomy
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Epidemiology
Approximately 60% bilateral pathology
In some cases appears to be associated with autosomal dominant pattern
Even distribution between males and females (some sources state slightly more common in males 3:2)
30% of cases involved with syndromes – Klinefelter syndrome, XXXY syndrome, Apert syndrome, Crouzon syndrome, carpenter syndrome, arthrogryposis, Holt-Oram syndrome, Williams syndrome.
A>Aetiology
Abnormality of longitudinal segmentation
Radius and ulna initially one anlage which then divides from distal to proximal
Failure of this separation as distal to proximal segmentation occurs causing synostosis
P>Pathology
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N>Natural History
Congenital pathology. Does not progress.
H>History
Frequently unnoticed in first years of life
Pain free
Can present with issues grasping or holding items due to reduced rotational movement – carrying items, keyboard, catching balls and feeding self
Parents or caregivers (teachers, sports coaches) often first to report issue
Exa>Examination
Commonly no obvious deformity, however can have observable bony deformity if severe.
Varying amounts of flexion/extension range of motion depending on extent of synostosis
Pronation/supination range of movement most notably restricted
Forearm shortening and decreased carrying angle can be appreciated
Most common position of fixed pronation is 30 degrees
Compensatory mechanism: shoulder abduction/adduction
Wrist hyper mobility
Dif>Differential Diagnosis
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Cla>Classification: Cleary Classification
Type 1: no osseous involvement, enlocated radial head
Type 2: osseous synostosis on xray, enlocated radial head
Type 3: visible osseous synostosis, hypoplastic and posteriorly dislocated radial head
Type 4: short osseous synostosis, anteriorly dislocated mushrooms shaped radial head
Inv>Investigation
X-ray. Further imaging rarely indicated if management is non-operative. CT can assist with extent of synostosis and 3D modelling for operative management.
Tre>Treatment
Majority of patients managed conservatively – if functional deficit does not significantly impact ability to undertake activities of daily living. This is more common in unilateral disease.
Operative:
Synostosis excision with soft tissue interposition
Forearm de-rotational osteotomy through synostosis or distal
Forearm de-rotational osteotomy with frame