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Home / Limbs Dysplasia Deformity / Elbow - radial head dislocation
Limbs Dysplasia Deformity

Elbow - radial head dislocation

Elbow radiographs of radial head dislocation in the adult and the skeletally immature patient.

15 questions 2 source pages

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15 questions
Q1Describe the X-ray findings in congenital radial head dislocation.▸
  • Posterior dislocation of the radial head
  • Convex radial head with long radial neck
  • Hypoplasia of capitellum, valgus deformity
  • No fracture of the proximal ulna; no bony exostosis along forearm
  • Check whole forearm for bowing/exostosis and the contralateral side (60% bilateral)
Q2What clinical clues suggest congenital radial head dislocation?▸
  • History of trauma
  • Bilateral involvement
  • Other congenital abnormalities: achondroplasia, arthrogryposis, Larsen syndrome, nail patella syndrome, HME, ulnar club hand
  • Symptoms: cubital valgum, prominence over radial head, decreased range and limited supination
Q3What are the causes of radial head dislocation?▸
  • Congenital: achondroplasia, nail patella syndrome, Larsen syndrome (and congenital radioulnar synostosis)
  • Acquired: HME
  • Traumatic (missed Monteggia)
  • Paralytic disorders (CP, polio)
Q4What is the treatment for congenital radial head dislocation?▸
  • Excision when mature if symptomatic
Q5Describe the X-ray findings and explain why this is likely congenital.▸
  • Radioulnar synostosis bilaterally
  • Left anteriorly dislocated radial head with malformation
  • Cleary classification type I on the right, type IV on the left
  • Likely congenital: bilateral (60%), continuity of IM canal and matrix
  • Autosomal dominant with variable penetrance, failure of segmentation
Q6What would you comment on if shown a clinical photo of this patient?▸
  • Asymmetry in resting position, any compensation with shoulder adduction
  • Presence of an elbow crease
Q7What history and examination findings are relevant in radioulnar synostosis?▸
  • History of forearm fracture; current disability; bilateral involvement
  • Look for forearm bowing; assess function - depends on the fused position
  • Most are in pronation (>50% >50deg pronation)
Q8What is the pathogenesis of congenital radioulnar synostosis?▸
  • Failure of segmentation
  • Longitudinal segmentation starts at 6 weeks, distal to proximal
  • Forearm lies in pronation at the time (limb rotation complete at 9 weeks)
  • Always in pronation -> radioulnar growth not in proportion -> radial head dislocation
Q9What syndromes and associations should be looked for in congenital radioulnar synostosis?▸
  • Look for other associations: Apert syndrome (acrocephalosyndactyly)
  • Carpenter's syndrome (acrocephalopolysyndactyly)
  • Arthrogryposis
  • Klinefelter's syndrome - chromosome analysis for sex-chromosome duplication
Q10What is the differential diagnosis and how do congenital and acquired synostosis differ?▸
  • Ddx: acquired (post-traumatic) radioulnar synostosis, radiohumeral synostosis
  • Congenital: always proximal, from failure of division from distal to proximal
  • Continuity of the IM canal; 60% bilateral
  • Radial head dislocation: mushroom radial head, hypoplastic capitellum, long radial neck, radial bow rather than ulnar bow (old Monteggia)
Q11How does acquired (post-traumatic) radioulnar synostosis differ?▸
  • Injury factors: fracture of both bones at the same level, crush/ burn, head injury
  • Intervention factors: surgical delay >2 weeks, single incision, disruption of interosseous membrane, infection
  • Treatment: physiotherapy, radiotherapy, NSAID, proximal radial excision
Q12What is the management of congenital radioulnar synostosis?▸
  • No intervention if ADL coped well (wrist usually more mobile than normal)
  • Surgery for functional deficit: pronation >60 degrees
  • Timing 5yo; rotational osteotomy at the level of the synostosis
  • Prophylactic fasciotomy and PIN nerve release; at most 80deg correction in each OT
  • Position: unilateral 20 degrees pronation; bilateral dominant 30-45 pronation, non-dominant 20-35 supination
  • Complications: PIN injury, compartment syndrome (resection has high recurrence)
Q13Why is the rotational osteotomy performed at the level of the synostosis?▸
  • Large contact area
  • Less compartment syndrome
  • Along the axis of rotation
  • High power of correction
  • Resection of the synostosis has a high chance of recurrence
Q14Describe the embryological development of the limb.▸
  • 4 weeks: limb bud from 8th to 10th somites (mesoderm + ectoderm), formation of the anlage
  • 5 weeks: neural plexus; 6 weeks: differentiation of mesenchyme into cartilage (chondrification) + segmentation (formation of primitive joint)
  • 7 weeks: primary ossification centre (complete by 12 weeks); intramembranous at periosteal sleeve, enchondral at central hypertrophied cartilage
  • 9 weeks: limbs rotate (UL 90 ER, LL 90 IR); 36 weeks: secondary ossification centre
  • 3 axes of limb patterning: AER, ZPA, Wnt pathway
Q15What are the 3 axes of limb patterning?▸
  • AER (apical epidermal ridge): proximodistal, secretes FGF (e.g. radial club hand)
  • ZPA (zone of polarizing activity): anteroposterior, secretes Shh (e.g. mirror hand)
  • Wnt pathway: dorsoventral, secretes LMX1 (e.g. nail patella); ventral en-1, dorsal WNT7a
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