Clean FRCS notes with inline figures
Xray elbow of skeletally immature patient
•Radioulnar synostosis bilaterally
•Left ant dislocated radial head with malformation
•Likely congenital as it is bilateral and there is continuity of IM canal and matrix
•Ddx: acquire RU synostosis, radiohumeral synostosis
•(AD with variable penetrance, Failure of segmentation, 60% bilateral)
•Cleary classification type I on right, type IV on left
•[may also be given a clinical photo: need to comment on asymmetry in resting position, any compensation with shoulder adduction and also presence of elbow crease]
History
History of forearm fracture
•FHx
•Current disability
•Bilateral
Examination
•See if there is any forearm bowing
•Assess function (depends on fused position)
•Most are in pronation (>50% >50deg pronation)
Look for other associations:
•Apert syndrome (acrocephlosyndactyly)
•Carpenter’s syndrome (acropolysyndactyly)
•Arthrogryposis
•Klinefelter’s syndrome
•Xray whole forearm and chromosome analysis (some have duplication in sex-chromosome – Klinefelter syndrome)
Management
•No intervention if ADL coped well (usu. wrist more mobile than normal)
Indications for surgery:
•Functional deficit (pronation >60 degree)
Time of surgery – 5yo
•Rotational osteotomy at level of synostosis
•Large contact area, less compartment syndrome, along axis of rotation, high power of correction
•- Prophylactic fasciotomy and PIN nerve release
•At most 80deg correction in each OT
Position depends on demand
•Unilateral: 20’ pronation (or neutral)
•Bilateral: Dominant hand : 30-45‘ pronation, Non-dominant hand : 20-35’ supination
•Cx: PIN injury, compartment syndrome
•(Resection have high chance of recurrence)
Cleary classification
| Type / group | Definition / note |
|---|---|
| 1 | No osseous synostosis, radial head ok |
| 2 | Osseous synostosis, radial head ok |
| 3 | Long osseous synostosis, radial head posterior dislocated |
| 4 | short osseous synostosis, radial head anterior dislocated |
•Pathogenesis: failed segmentation
•Longitudinal segmentation starts at 6 weeks from distal to proximal
•Forearm at pronation at the time (limb rotation complete at 9 weeks)
•Always at pronation → radioulnar growth not in proportion → radial head dislocation
•C/f Acquired (post traumatic)
•Congenital always proximal due to division from distal to proximal
•Continuity of IM canal
•60% bilateral
•Radial head dislocation: mushroom radial head, hypoplastic capitellum, long radial neck, radial bow rather than ulnar bow (old monteggia)
Risk factor of posttraumatic synostosis :
•Injury factor: 1 # both bones at same level, 2 crush/ burn, 3 head injury
•Intervention factor: 1 surgical delay >2 weeks 2 single incision 3 disruption of IO membrane 4 infection
•→ Rx: physio, RT, NSAID, proximal radial excision
•the embryological development of limb
•4 weeks: Limb bud appearance from 8th to 10th somites as an outpouching composing of mesoderm covered by ectoderm. Formation of anlage.
•5 weeks: Formation of neural plexus
•6 weeks:
•Differentiation of mesenchyme into cartilage (chondrification)
•Segmentation (formation of primitive joint)
•7 weeks: formation of primary ossification centre (complete by 12 weeks)
•Intramembranous ossification at periosteal sleeve
•Enchondral ossification at central hypertrophied cartilage
•9 weeks: limbs rotate (UL90 ER, LL 90 IR)
•36 weeks: formation of secondary ossification centre
•3 axis of limb patterning
•Apical epidermal ridge (AER) – proximodistal (HOX gene, secrete Fbl growth factor) (e.g. radial club hand)
•Zone of polarizing activity – AP (secrete Shh protein) [ Mirror hand ]
•Progress zone: Wnt pathway: Dorsoventral (secret LMX1) [e.g. nail patella]