Radioulnar Synostosis Clinical Presentation

Updated: Jun 02, 2022
  • Author: Raymond Wurapa, MD; Chief Editor: Harris Gellman, MD  more...
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History and Physical Examination

Functional deficits associated with congenital radioulnar synostosis depend on the severity of the deformity and on whether or not it is bilateral. In cases involving severe, fixed forearm pronation deformity, the patient cannot compensate for the resulting functional limitations by using scapular and glenohumeral motion. The forearm usually lies in the pronated or hyperpronated position.

Hypermobility at the midcarpal and radiocarpal joints can disguise this lack of forearm rotation, particularly with neutral or mild pronation deformities. There is usually full or nearly full elbow range of motion, with flexion contractures rarely exceeding 30º. An abnormal carrying angle of the elbow or a shortening of the forearm may be observed.

Pain is usually not a presenting symptom until the teenage years, when progressive and symptomatic radial head subluxation may be noted. This accounts for the delayed clinical diagnosis in many cases, but it also indicates that function may be satisfactory. The disability is most significant in bilateral cases with severe pronation. Children may initially have a reduced radial head and in adolescence may develop symptomatic radial head subluxation. Therefore, radiographic follow-up is necessary.



Wilkie divided congenital synostosis into the following two types on the basis of the proximal radioulnar junction [21] :

  • Type 1 - Complete synostosis has occurred, with the radius and ulna fused proximally for a variable distance
  • Type 2 - Less involved, and may exist as a partial union; this type involves the region just distal to the proximal radial epiphysis and is associated with radial head dislocation

Cleary and Omer described four types of congenital synostosis, as follows [18] :

  • Fibrous synostosis
  • Bony synostosis
  • Associated posterior dislocation of the radius
  • Associated anterior dislocation of the radius

Simmons et al considered congenital synostosis to be a spectrum of anomalies in which the synostosis occurred in varying lengths, with or without involvement of the radial head. [22]

Posttraumatic radioulnar synostosis has been classified into the following three types on the basis of location:

  • Type 1 - Occurs in the distal forearm (least common)
  • Type 2 - Occurs in the midforearm
  • Type 3 - Occurs in the proximal forearm