Radioulnar Synostosis Treatment & Management

Indications for surgical treatment of congenital radioulnar synostosis remain somewhat controversial but are related to bilaterality and to the degree of deformity. Patients with neutral rotation, mild pronation, or rare supination positions can compensate somewhat with ipsilateral shoulder motion. Wrist hypermobility allows further functional compensation. Severe pronation deformities (specifically, >60º) cause significant functional difficulty, especially with activities requiring supination. Therefore, indications for surgery must be based more on individual functional limitations than on absolute forearm position.

It is recommended that surgery be performed in childhood before patients reach school age. In patients with symptomatic subluxation of the radial head, the radial head may be excised at maturity. Appropriate workup includes plain radiography performed in orthogonal planes (eg, posteroanterior [PA] and lateral views).

The indication for surgery in posttraumatic radioulnar synostosis is functional limitation of forearm rotation. This limitation must be assessed on an individual basis. An appropriate workup includes taking plain radiographs in orthogonal (eg, PA and lateral) planes.

Surgery should be performed after the synostosis has matured and distinct radiographic borders are observed, so as to decrease the likelihood that the synostosis will recur. Waiting more than 3 years, however, adversely affects final outcome, probably because of soft-tissue contracture. A 100º arc of motion is desired so that the patient can perform all activities of daily living (ADLs), and a 60º arc is required to perform most ADLs without assistance.

The only contraindication for surgical correction is the presence of milder deformity in an older patient, if the patient has only minimal functional deficit and has already made adjustments in his/her activities to accommodate the synostosis.

Attempts to achieve and maintain motion at the synostosis site usually are not successful. Synostosis typically recurs despite excision, the use of various medications, or the interposition of silicone, fat, or muscle. However, success has been reported with excision of the bony bridge and the interposition of vascularized fat graft, with an average rotation range of 74º being maintained at 2 years after surgery. ^[24]

Some mobilization procedures are combined with tendon transfers to achieve supination. The flexor carpi ulnaris can be transferred dorsally around the ulna, and the extensor carpi radialis longus can be transferred to the volar aspect of the wrist.

Congenital radioulnar synostosis

Overall, the preferred surgical procedure has been osteotomy and derotation through the fusion mass, along with fixation with transcutaneous pins. ^{[25, 26, 27]}

The optimal position of correction varies according to the degree of involvement, the bilaterality of the synostosis, and the amount of compensatory shoulder or radiocarpal motion that the patient has. Severe deformities do not allow one-stage correction, because of the tension on vascular and fibrous structures. Gradual correction using a multiplanar external fixator decreases the risk of neurovascular compromise and allows the patient to select the most functional position.

In general, neutral rotation is used for unilateral deformities; for bilateral deformities, one side is placed in 20-30º of pronation and the other in 20-30º of supination. ^[28] Shortening of the forearm to decrease the risk of neurovascular compromise has also been recommended.

A long arm cast with 90º of elbow flexion is utilized postoperatively for 8 weeks. Transcutaneous pins have generally been recommended for fixation after derotation. Unlike techniques that require open operative exposure, this pinning can easily be reversed if postoperative vascular compromise develops. ^{[8, 29]}

Simcock et al described the use of derotational osteotomy to treat 31 forearms in 26 children with congenital radioulnar synostosis and functional limitations. ^[30]  In all cases, union was successfully achieved by 8 weeks. No instances of compartment syndrome, vascular compromise, or loss of fixation occurred. The overall rate of complications was 12%, including two transient anterior interosseous nerve palsies (both in patients with rotational corrections >80º), one transient radial nerve palsy, and one symptomatic muscle herniation.

Hwang et al studied the use of one-stage rotational osteotomy of the proximal third of the ulna and the distal third of the radius with segmental bone resection to treat congenital radioulnar synostosis in 25 patients (28 forearms). ^[31] In group 1, the ulnar osteotomy was stabilized with an intramedullary pin, whereas in group 2, no fixation was used. Surgical outcomes did not differ significantly between the two groups. The authors concluded that one-stage rotational osteotomy of the proximal third of the ulna and the distal third of the radius with segmental bone resection was simple and safe in this setting and that internal fixation at the osteotomy site seemed to be unnecessary.

Bishay prospectively studied 12 consecutive pediatric patients (14 forearms) with severe congenital proximal radioulnar synostosis (mean pronation deformity, 70.7°; range, 60-85°) that was corrected by means of single-session double-level rotational osteotomy and percutaneous placement of intramedullary Kirschner wires (K-wires) in both radius and ulna. ^[32] After a mean interval of 30.4 months (range, 24-36 mo), patients had a mean pronation deformity correction of 59.8°. All 12 patients showed improvement in functional activities; none had any loss of correction or nonunion, circulatory disturbances, neuropathies, or hypertrophic scars.

Satake et al studied the long-term (≥10 y) results of simple rotational osteotomy for congenital radioulnar synostosis in nine patients (12 forearms). ^[33] After the procedure, the forearm was fixed at an average of 4.2° of supination. At final follow-up, the average motion arc of the palm ranged from 26° of pronation to 62° of supination. No postoperative neurologic or circulatory complications were noted. Patients were much better able to perform ADLs, and all were satisfied with the results of surgery. The average score on the 11-item version of the Disability of the Arm, Shoulder, and Hand (DASH) score was 3.79 points at final follow-up.

In a retrospective study of 31 patients (36 forearms) with congenital radioulnar synostosis, Pei et al found that proximal radioulnar derotational osteotomy followed by plate fixation was a safe and feasible procedure with a low complication rate and that the technique could effectively improve the function of the forearm. ^[34]  A study by Hamiti et al also reported good results with this approach. ^[35]

Posttraumatic radioulnar synostosis

In contrast to surgery for congenital radioulnar synostosis, surgery for the posttraumatic form of the condition restores motion through excision of the synostosis area. ^{[5, 6, 36]} Numerous interposition materials—including fat, muscle, fascia, silicone, and cellophane—have been proposed for use after resection to prevent a recurrence of synostosis, but these have met with varying degrees of success. Kelikian and Doumanian developed a metallic swivel prosthesis to restore motion, but no large series has been reported that supports its effectiveness. ^[37]

The goal of treatment, regardless of what interpositional material is used, involves resection of the entire bony synostosis. Careful dissection with minimal periosteal disruption prevents the further stimulation of bone, limiting recurrence. Identification and protection of neurovascular structures is essential, and the final range of motion should be assessed intraoperatively. Minimal postoperative immobilization is recommended.

Giannicola et al evaluated 12 patients with posttraumatic proximal radioulnar synostosis (two with a double synostosis) treated surgically by a single elbow surgeon. ^[38]  The synostosis was excised in 10 cases; in addition, radial head excision was done in one case, radial head arthroplasty in three, and proximal radial diaphyseal resection in two. Final mean extension-flexion and pronation-supination arcs were 116° and 123°, respectively. Significant improvements were found in the Mayo Elbow Performance Score (mean, 24), modified American Shoulder and Elbow Surgeons score (mean, 28), and QuickDASH score (mean, 17). Ther was one synostosis recurrence and one late disassembly of the radial head arthroplasty.

Abdul Azeem et al reported good functional and prophylactic (against recurrence) results with a triple therapy consisting of (1) preoperative radiation therapy, (2) tissue interposition after heterotopic ossification resection, and (3) postoperative adjuvant indomethacin. ^[39]

Although the surgical procedure that is used to treat congenital radioulnar synostosis is not exceedingly difficult, it is associated with significant complications, ^{[40, 41]} including neurovascular compromise and recurrence of ankylosis. The limiting factors for derotation are soft-tissue contracture and neurovascular compromise. Simmons et al recommended that derotations of more than 85º be performed in two stages. ^[22] A low threshold for fasciotomies should be maintained for suspected compartment syndromes.