Definition
Concept of distraction osteogenesis
Popularised by Ilizarov in the Soviet Union
- initially in the 1940's
- popularised in the 1980's
- also created the circular fixator
Corticotomy
- low energy osteotomy
- attempt to minimise damage to blood supply and periosteum
- avoid use of saw
- minimise thermal necrosis
Callotasis
- gradual incremental distraction of a fracture callous after a latency period
- intramembranous ossification in zone of distraction
- type 1 collagen with osteoid laid on collagen
Advantage
Maintains height & proportions
- Avoids operating on normal side
Disadvantage
Difficult
- steep learning curve
- complication rate 10 - 250%
Indications
General rules
- LLD 6-15 cm
- over 15 cm risks outweigh benefits
- < 20% limb
- 5cm in femur / 5 cm in tibia
Limitation is due to muscles / ligaments / nerves
- can repeat at staged procedures
- i.e. 5 cm per bone at any given time
Site
Site of deformity best
Metaphyseal lengthening easiest
- large cancellous surface area
- thin cortex
- best blood supply
Contra-indications
Mentally or medically unstable
- long and demanding process
- 12 months or more
Unstable joints
Associated neurology
- Weakness / Insensate
Technique
1. Osteotomy & Frame / Nail
2. Latency Period
3. Distraction Period
4. Consolidation Period
Maintaining blood supply via periosteum is the key
1A. Osteotomy with Periosteal Preservation
Open Corticotomy
Drill-holes & closed osteoclasis / Di Bastiani
Used in the femur
- percutaneous skin incision
- multiple drill holes first to weaken bone
- osteotome to complete
- apply force to complete fracture
Usually stablise initially with temporary external fixator
- perform osteotomy
- insert nail / ISKD
- remove frame
Tibial technique with Gigli saw
Proximal corticotomy in metaphyseal bone
- below tibial tuberosity
- frame on initially to stabilise
- incision lateral crest tibia, elevate periosteum lateral tibia
- incision medial border tibia, elevate periosteum medial tibia
- pass artery clip between periosteum and bone on one side
- pass wire on other side, retrieve with clip
- pass suture, then pass gigli saw
- perform subperiosteal corticotomy, periosteum intact
Wagner Osteotomy
Contra-indicated now
- osteotomy and acute resection
- distraction
- bone grafting and plating
- superceded by lizarov techniques
1B. Devices
Need stable device or risk non-union with fibrocartilage
Uniplanar Device
- Wagner, Orthofix
- simple
- no angular correction
- "Cantilever Loading"
- problems with pin loosing
- often necessary in femur
Ilizarov
- multiplanar correction
IM nail / ISKD
Self lengthening nail
- movement of leg induces lengthening mechanism
- maximum of 5 cm
- if only want 3 cm, lengthen 2cm before insertion
Advantage
- all internal
- no pin site complications
- easier for patient
Disadvantage
Runaway nail
- lengthens too quickly
- cause contractures and nerve injury
- nothing can be done about this
- incidence 5%
Jammed nail
- take to theatre to unblock
- may have to debride callus if lengthening too slow
2. Latency period
Usually 1/52
- allow callus to form before distraction
- reduce latency period in child as may start to ossify
- increase latency period in diabetics / steroids
3. Distraction Period
Rate / Regenerate
Optimum 1mm / day turning 4x / day
- balance premature union vs non union
- slower in adults / diabetics
- i.e. 2-3 x day
Stop if
- poor new bone formation
- nerve palsies
- joint subluxation
- joint contracture
4. Consolidation
1 month per cm or
Double the distraction period
Complications
Pin infection
Management
- early oral antibiotics
- patient should have script at home
- take if pin site appears red or begins leaking fluid
- increase frequency of pin site cleaning
Prevention
- tight well tensioned pins
- don't place pins throught muscle
Nerve injury
- demyelinate if lengthen > 6%
Contractures
- muscle elongates poorly
- max 1mm / day
- congenital LLD more susceptible than acquired
Risk
- T achilles contracture in tibia
- FFD / adduction femur
- knee FFD
Device failure
- broken pins, loss of position
Fracture
- inadequate consolidation before device removal
- 10 - 15% incidence
- can result in loss of length or angular deformity
Premature Consolidation
- unable to distract
- break pins / wires
Poor regenerate
- inadequate latency period
- too rapid distraction
- poor blood supply
Joint subluxation
- ligamentous insufficiency
Delayed or non union
- constant observation
Bone growth impairment
- damage to physis
- likely secondary to pressure
- best if delayed until after skeletal maturity
Psychological Stress
Distraction Physiolysis
Concept
- tibial lengthening by distraction across physis
- similar results to metaphyseal lengthening
Indications
- need extra length in skeletally immature
Complication
Physeal injury risk
Chondrodiastasis if < 1mm / day