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Radioulnar Synostosis



- Congenital Synostosis:
    - discussion:
           - occurs due to a defect in longitudinal segmentation at the 7th week of development;
           - autosomal dominant inheritance in some cases but often occurs sporatically;
           - bilateral in 60% (most common in males);
           - proximal 1/3 of forearm is most common site of bony union, and the forearm is pronated (avg 30 deg);
    - non operative treatment:
           - patients with a unilateral deformity or with a bilateral deformity & minimal pronation do not need surgery;
           - majority of patients w/ bilateral osseous radioulnar synostosis function adequately despite forearm position;
    - surgical treatment:
           - surgery is rarely indicated for this condition, except for severe pronation deformities (more 60 deg of pronation)
           - resection and interposition procedures fail, and the bridge regrows;
           - in pts w/ severe bilateral hyperpronation, osteotomy of nondominant extremity, to create supination, is indicated.
           - derotational osteotomy through the area of synostosis is recommended, placing one side in 10 to 20 degrees of pronation and the other forearm in a neutral position or slight supination for function;
    - references:
           Congenital proximal radio-ulnar synostosis. Natural history and functional assessment.
           Congenital Proximal Radioulnar Synostosis: Treatment with the Ilizarov Method.
           Congenital radioulnar synostosis.



- Traumatic Synostosis:
    - see discussion of hetertopic ossification and hetertopic ossification of the elbow;
    - discussion:
           - may arise from posterior frx dislocation of the elbow, Monteggia frx dislocation, traumatic rupture of the distal triceps, both bones forearm frx, or from isolated radial head frx;
                  - often these patients have undergone previous surgery;
           - exam findings: absence of forearm pronation and supination;
           - in some patients the hetertopic ossification will extend into the elbow joint which will limit flexion;
    - management:
           - traumatic synostosis is amenable to surgical excision;
           - timing of excision:
                  - traditionally, it has been recommended that hetertopic bone not be excised until there has been maturation (as judge by bone scan or serum alk phos);
                  - this has been challenged by Jupiter et al 1998, who noted no ill effects from excision of synostosis at 6-12 months post injury;
           - surgical approach:
                  - often the synostosis is amenable to excsion via a posterior approach;
                  - w/ proximal synostosis, the ECU and the supinator are elevated off the ulna, which allows exposure of the synostosis and the radius;
                        - w/ proximal synostosis, consider anterior transposition of the ulnar nerve;
                  - denuded bony surfaces are covered w/ a thin layer of bone wax at the end of the case;
           - postoperative care:
                  - in the report by Jupiter and Ring (1998), neither postoperative radiation nor indomethacin was considered essential to prevent recurrence;
                  - head injury patients may be at higher risk for recurrence, and therefore, they may require XRT or NSAIDS
                  - Operative treatment of post traumatic proximal radioulnar synostosis.



Post traumatic radioulnar synostosis.

Post-traumatic proximal radio-ulnar synostosis. Results of surgical treatment.

Cross union complicating fracture of the forearm. Part I: adults.

Treatment of posttraumatic radioulnar synostosis with excision and low dose radiation

Radioulnar synostosis.

Treatment of traumatic radioulnar synostosis by excision and postoperative low dose irradiation.