RADIOULNAR SYNOSTOSIS CONGENITAL

Congenital radioulnar synostosis (CRUS) is a rare anomaly characterized by a bony or fibrous fusion between radius and ulna at birth.^1,2 The condition results from failure of longitudinal separation of radius and ulna during the seventh week of gestation, leading to mild-to-severe functional impairment. In cases of severe deformity, patients will be unable to perform daily activities, such as getting a cup to the mouth, using eating utensils or accepting objects in an open palm.^2–5 In cases of mild deformity, conservative management through occupational therapy, activity modification and an ergonomic working environment is recommended. For severe deformity, recent consensus favors surgical management.^2,7–10

Pathophysiology

• Failure of differentiation: forearm begins as a single cartilaginous anlage that divides from distal to proximal in the 7^th week in utero.  Failure of this process leads to CRUS.  This is why the synostosis is typically seen in the proximal forearm
• Exact etiology is not known
• Chromosomal or other genetic abnormalities such as Klinefelter syndrome, XXXY syndrome, Apert syndrome, Crouzon syndrome, Carpenter syndrome, arthrogryposis, Treacher Collins syndrome, Williams syndrome, amegakaryocytic thrombocytopenia, and Holt-Oram syndrome can be associated with CRUS
• Some sources cite autosomal dominant inheritance in some European populations^2,6,11

Classification - Wilkie

• Type I:
  • Lack of proximal portion of radius
  • Bony fusion for 3-6 cm
  • Radius and ulna are connected at medullary canal
• Type II:
  • Normal radius
  • Synostosis is located just distal to proximal radial epiphysis
  • Radial head is dislocated anteriorly or posteriorly

Cleary and Omer¹

• Type I: Lacks bone involvement, reduced normal appearing radial head.
• Type II: Distinct osseous synostosis , but otherwise normal findings
• Type III: Distinct osseous synostosis with hypoplastic and posteriorly dislocated radial head
• Type IV: Short osseous synostosis, Anteriorly dislocated radial head, Radial head usually with a mushroom shaped deformity

Related Anatomy

• Radius
• Ulna
• Humerus
• Elbow joint

Incidence and Related Conditions

• CRUS is a rare condition with ~400 reported cases worldwide since first anatomic description in 1793
• Familial CRUS is rare⁴ but a positive family history has been reported in up to 20% of cases.
• Bilateral synostosis is seen in 60% of CRUS patients
• Higher frequency of CRUS is seen in patients with chromosomal abnormalities
• Up to 30% ovf CRUS cases may be associated with other congenital musculoskeletal disorders such as congenital hip dislocation, clubfeet, polydactyly, syndactyly, thumb hypoplasia
• Concomitant radial head dislocation 
• Associated syndromes: Apert's syndrome, arthrogyposis, fetal alcohol syndrome, Klinefelter's syndrome

Differential Diagnosis

• Congenital subluxation of radial head
• Acquired radial head subluxation (nursemaid’s elbow)
• Greenstick fracture of the humerus
• Monteggia fractures of the ulna
• Hypoplastic radial heads

A 3-year-old boy presented with decreased mobility of the forearm in both hands. Height and weight of the boy were within normal ranges. At the time of his birth, limitation of forearm pronation in both hands was noted. His maternal uncle and a great uncle also had a history of decreased mobility of the forearm. His mother noticed the boy facing difficulty in brushing his teeth and his hair and backhanded position in holding bottles and toys. There was no previous history of trauma, pain or swelling.^3–5

Complications of surgery ^2,7

• Wound Infection
• Osteotomy slipping from the original position of correction
• Postoperative circulatory compromise
• Compartment syndrome
• Transient anterior interosseous nerve palsies in large corrections

• In severely affected patients, improvement in hand function can be obtained through surgery.

• Congenital Radioulnar Synostosis is often bilateral.
• Removal of the synostosis can be accomplished, but unfortunately, the improvement in active supination/pronation is usually small.
• Proximal surgical corrections of severe case of radioulnar synotosis can have severe complications, therefore proceed with caution and properly educate the patient the his/her family members.
• Surgery is not indicated for cosmesis alone.

Cited

1. Cleary JE, Omer GE Jr. Congenital proximal radio-ulnar synostosis. Natural history and functional assessment. J Bone Joint Surg Am 1985;67(4):539–45. PMID: 3980498
2. Simmons BP, Southmayd WW, Riseborough EJ. Congenital radioulnar synostosis. J Hand Surg Am 1983;8(6):829–38. PMID: 6643957
3. Tsai J. Congenital radioulnar synostosis. Radiol Case Rep 2017;12(3):552–4. PMID: 28828125
4. Spritz RA. Familial radioulnar synostosis. J Med Genet 1978;15(2):160–2. PMID: 641954
5. Tuli S, Kelly M, Ryan K, et al. A 4-year-old child who could not supinate her forearm. J Pediatr Health Care 2014;28(4):357–60. PMID: 24593870
6. Yammine K, Salon A, Pouliquen JC. Congenital radioulnar synostosis. Study of a series of 37 children and adolescents. Chir Main 1998;17(4):300–8. PMID: 10855298
7. Bishay SN. Minimally invasive single-session double-level rotational osteotomy of the forearm bones to correct fixed pronation deformity in congenital proximal radioulnar synostosis. J Child Orthop 2016;10(4):295–300. PMID:27312798
8. Kanaya F, Kinjo M, Okubo H, Yoneda S. Mobilization of a Congenital Proximal Radioulnar Synostosis with a Vascularized Fascio-fat Graft in 104 Forearms of 87 Patients. J Hand Surg Am 2016;41(9):S47-8.
9. Hung NN. Derotational osteotomy of the proximal radius and the distal ulna for congenital  radioulnar synostosis. J Child Orthop 2008;2(6):481–9. PMID: 19308546
10. Garg G, Gupta SP. Surgical outcome of delayed presentation of congenital proximal radioulnar synostosis. SICOT-J 2015;1:33. PMID: 27163088
11. Barr ML, Carr DH, Pozsonyi J, et al. The XXXXY sex chromosome abnormality. Can Med Assoc J 1962;87:891–901. PMID: 13969480
12. Horii E, Koh s, Harrori T, Otsuka J. Single osteotomy at the radial diaphysis for congenital radioulnar synostosis. J Hand Surg Am. 2014; 39(8): 1553-1557.

New Articles

1. Samson D, Power D, Tan S. Adipofascial radial artery perforator flap interposition to treat post-traumatic  radioulnar synostosis in a patient with head injury. BMJ Case Rep 2015 Epub. PMID: 25725026
2. Kamrani RS, Ahangar P, Nabian MH, et al. Proximal radial diaphyseal segment resection for posttraumatic proximal radioulnar synostosis: a prospective study of 15 cases. J Shoulder Elbow Surg 2014;23(6):855–60. PMID: 24768222
3. Daluiski A, Schreiber JJ, Paul S, Hotchkiss RN. Outcomes of anconeus interposition for proximal radioulnar synostosis. J Shoulder Elbow Surg 2014;23(12):1882–7. PMID: 25304042

Reviews

1. Dohn P, Khiami F, Rolland E, Goubier JN. Adult post-traumatic radioulnar synostosis. Orthop Traumatol Surg Res 2012;98(6):709–14. PMID: 23000035
2. Bergeron SG, Desy NM, Bernstein M, Harvey EJ. Management of posttraumatic radioulnar synostosis. J Am Acad Orthop Surg 2012;20(7):450–8. PMID: 22751164

Classics

1. Vince KG, Miller JE. Cross-union complicating fracture of the forearm. Part I: Adults. J Bone Joint Surg Am 1987;69(5):640–53. PMID: 3110165