Elbow Resources

Radioulnar synostosis (R) Radioulnar synostosis (R)


Radio-ulnar synostosis
This is classified as either congenital or post-traumatic. Both result in loss of forearm rotation. The functional arc of forearm rotation is 100 degrees, although most ADLs can be performed with an arc of 60 degrees.

Congenital radio-ulnar synostosis

Epidemiology
Rare – 350 cases described to 1994
Condition is bilateral in around 50%.

Embryology
The radius begins to chondrify at 41 days and the ulna at 44 days. For a short period of time the two are connected proximally. Failure of segmentation results in synostosis. Because the forearm is held in midpronation in utero the patient will present with some degree of pronation.
Congenital synostosis is associated with numerous other abnormalities, and these occur in around 1/3 of cases. Apert's syndrome, Carpenter's syndrome, arthrogryposis, Kleinfelter's syndrome and Williams's syndrome are syndromes that have been associated. Upper limb abnormalities associated include polydactyly, syndactyly, Madelung's deformity, carpal coalition and thumb aplasia. Thus, all children with congenital limb anomalies should be checked for congenital radio-ulnar synostosis.

Clinical presentation
Diagnosis is often delayed, the diagnosis on average being made at 6 years.
Children may find certain tasks difficult.
They have a forearm fixed in pronation, usually full flexion and a mild fixed flexion deformity usually less than 30 degrees.
Pain is not typically a symptom until radial head subluxation occurs in the teens.

Classification

Cleary and Omer
Type 1 -Fibrous synostosis with a normal and reduced radial head
Type 2 -Visible bony synostosis with a normal and reduced radial head
Type 3 -Bony synostosis, radial head is hypoplastic and dislocated posteriorly. Most common.
Type 4 -Radial head is dislocated anteriorly.

Natural history
Patients tend to compensate for their lack of forearm rotation through wrist hypermobility and shoulder abduction.
In a 22 year follow up of 23 patients treated non-operatively Cleary and Omer found 39% of patients had heavy labour intensive jobs and 96% reported none or mild limitation in ADLs hence they recommended non-operative treatment.
Other authors have found that patients with more than 60 degrees of fixed pronation have difficulty in ADLs and should be treated operatively.
Because of these conflicting findings Sacher et al recommend derotating one arm in a child with severe bilateral pronation.
Symptomatic subluxed radial heads can be excised.

Operative treatment
Attempted takedown of the synostosis usually results in recurrence. The contracted soft tissues will also prevent any meaningful return of motion.
Derotation and fixation in the derotated position is preferred.
The fusion mass is identified through an incision along the subcutaneous border of the ulna between anconeus and extensor carpi ulnaris. An osteotomy is carried out through the fusion mass and the forearm derotated to the desired position and fixed with K-wires
What is the preferred position for the derotation?
Around 10 to 20 degrees of pronation for the dominant hand and neutral for the other hand. Patients with the most dissatisfaction are those placed in supination.
Postoperatively the patient needs to be watched like a hawk for compartment syndrome. One series had a rate of 18% of vascular compromise requiring a decrease in the amount of rotation or fasciotomies.

Post-traumatic radioulnar synostosis

Epidemiology
This is much more common
Rate between 2-6% (the latter figure in a series which used a single incision approach to the forearm).

Aetiology
Any trauma that creates a haematoma between the radius and ulna or disrupts the interosseous membrane can cause a synostosis.
• Operatively treated forearm fractures – most common
• Non-operatively treated forearm fractures
• Stab wounds
• Repair of distal biceps tendon ruptures (via two incision technique particularly) – this has led to the modified Boyd-Andersen technique where the periosteum of the ulna is not violated.

Risk factors
Single incisions for both bone fractures
High energy fractures
Head injuries
Monteggia fractures and more proximal fractures
Surgical technique
Leaving bone fragments behind
Creation of communicating haematoma between radius and ulna

Treatment
The synostosis is excised and some material interposed to prevent recurrence. Many materials have been tried, including fat, fascia, muscle, silicon and cellophane. Ideally 15mm of free space between the radius and ulna is created.
Whilst resecting the synostosis it is essential to perform the minimal possible dissection.
Timing of surgery: perform after the synostosis has matured on bone scan. The literature supports the idea of operating between one and three years after injury.

Results
Until recently, fair at best. Two large series report a poor result rate of 68%, and it is common for up to half of the arc achieved in theatre to be subsequently lost.
Jesse Jupiter has done better in a recently published article, with 17 of 18 patients regaining 139 degrees of forearm rotation.

Bibliography
Frassica et al: Ectopic ossification around the elbow. In: Morrey: The elbow and its disorders, 2 nd Ed. WB Saunders and Co. 1983. pp508-510.
Jupiter JB et al: Operative treatment of post-traumatic proximal radioulnar synostosis. JBJS(A),80A,Feb1998pp248-257.
Sachar K et al. Radioulnar synostosis. Hand Clinics Vol.10.No3.Aug1994pp399-404.

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