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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


  • Failure of differentiation: forearm begins as a single cartilaginous anlage that divides from distal to proximal in the 7th 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 populations2,6,11

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
ICD-10 Codes

    Diagnostic Guide Name


    ICD 10 Diagnosis, Single Code, Left Code, Right Code and Bilateral Code


    ICD-10 Reference

    Reproduced from the International statistical classification of diseases and related health problems, 10th revision, Fifth edition, 2016. Geneva, World Health Organization, 2016

Clinical Presentation Photos and Related Diagrams
Congenital radioulnar synostosis
  • Congenital radioulnar synostosis Wilkie Type I with no proximal radius.
    Congenital radioulnar synostosis Wilkie Type I with no proximal radius.
  • Congenital radioulnar synostosis Wilkie Type II with a proximal radius present.
    Congenital radioulnar synostosis Wilkie Type II with a proximal radius present.
Forearm fixed in intermediate position or in pronation
Moderate-to-severe hand disability affecting everyday life
Shortening of the affected forearm
Hypermobility of the wrist
Painless restriction of motion
Present at age 2-6 years old due to lack of forearm rotation requirement as infants/toddlers
Typical History

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

Positive Tests, Exams or Signs
Work-up Options
Treatment Options
Treatment Goals

Maintain or improve function without causing serious side effects.


Conservative Management3

  • Suggested for patients with mild synostosis (0–15° fixed pronation)
  • Included ergonomics and activity modification

Surgical Treatment2,7–10

  • Surgical interventions can be divided into two specific categories based on the goals of treatment
  • Restoration of active motion
    • Mobilization (removal of the synostosis) with placement of an interpositional vascularized fascio-fat grafts8,12
    • Most studies show unsatisfactory results with minimal restoration of motion
  • Static rotational deformity correction
    • Indicated for patients with > 60 degrees of fixed pronation, especially with patients with bilateral deformities
    • Derotation for > 85 degrees of correction should be done in two stages to minimize risk of soft tissue constriction/neurovascular compromise
    • Double level osteotomy – radius and ulna osteotomies performed at two different levels to distribute rotational correction and minimize soft tissue constriction
    • Radial diaphyseal osteotomy alone – indicated in younger children
    • Internalized transfixation devices (Kirschner wires, staples) to be used with caution
    • Osteotomy to correct wrist angulation
    • Osteotomy with gradual correction using an external fixation device such as an ilizarov frame
    • Static positioning recommendations
      • Unilateral cases: fix in 0-30 degrees of pronation
      • Bilateral cases
        • Dominant arm – fix in 0-15 degrees of pronation
        • Non-dominant arm – fix in neutral

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.

Key Educational Points
  • 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.


  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


  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


  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