Q8What are the general treatment principles for LLD according to the predicted discrepancy at skeletal maturity?▸
<2cm: observe
2-5cm: shorten the longer limb by epiphysiodesis if physis open, shortening osteotomy if physis closed
>5cm: lengthen the short limb +/- shorten the long limb
>20cm: consider amputation
Q9Which methods calculate LLD at maturity from a single visit versus multiple visits?▸
Multiple FU: Moseley chart (needs leg length of both LL and hand X-ray for skeletal maturity), arithmetic method, Green-Anderson chart
Single FU: Paley multiplier method (LLD x age and sex factor), simplistic method
Also take into consideration Shapiro's growth pattern
Q10What are the two categories of limb lengthening technique?▸
Acute lengthening
Gradual lengthening - distraction histogenesis and gradual lengthening procedures
Q11Describe the gradual lengthening procedure in distraction histogenesis.▸
Apply ex fix; low energy corticotomy at metaphysis (2/3 circumference + osteoclasis), preserve periosteum, endosteum, medullary content and nutrient artery
Corticotomy vs osteotomy (multiple drill holes + osteotome) - no difference in the literature
Rest 5-7 days, then distract 1mm/day divided into 4 times
Consolidation ~2x the lengthening time; remove ex fix when interzone closes and 2 side neocorticalisation is seen on AP and lateral films
Maximum lengthening each time 20% (Michael To tutorial, JPO 2010: % lengthening related to % of complication); >20% increases complications e.g. non-union, NV injury, infection, contracture
Q12What is chondrodiastasis and what are its problems?▸
Gradual distraction of the physis results in hypertrophy of the cellular layers of the physis without separation (Heuter-Volkman)
Unpredictable results
Initial lengthening is often followed by growth plate fusion
Q13Describe the permanent shortening techniques for the long limb.▸
Open epiphysiodesis (Phemister): remove a rectangular portion of bone containing metaphysis, physis and epiphysis, flip it around and reinsert to create a bone bridge
Percutaneous epiphysiodesis (Bowen): stab wound, longitudinal periosteum split + physis penetration 5mm by osteotome, peripheral 1/3 ablated by curette on both medial and lateral sides
Q14What temporary epiphysiodesis options exist for LLD?▸
Staples
8-plate
Transphyseal screw
Combo procedures (shortening and lengthening combined)
Q15What is the histology of distraction histogenesis?▸
Central fibrous interzone: fibroblasts activated and secrete collagen parallel to distraction force, providing undifferentiated mesenchymal cells that directly transform into osteoblasts -> intramembranous ossification
Zone of microcolumn formation: osteoblasts align collagen into longitudinal columns and promote blood vessel invasion to lay down osteoid
Q16What factors affect distraction lengthening?▸
Stability of fixation
Type and site of osteotomy: Ilizarov compared open, percutaneous corticotomy and complete closed - recommends percutaneous corticotomy; metaphysis has more osteogenic potential and soft tissue better adapted to lengthening
Distraction regime: latency lets the inflammatory phase subside, then distract during the reparative phase
Q17What is the recommended distraction regime?▸
Latency: 3 days for a child, 7-14 days for an adult
Rate 1mm/day
Rhythm: distraction applied 4 times/day; increasing frequency increases distraction
Q18What are the complications of distraction lengthening?▸
Bone related: incomplete consolidation, premature consolidation, fracture, growth disturbance of the lengthened bone
Also angular deformity and fracture due to early removal of the ex fix
Q19What is the structure of the clinical assessment (script) for limb length discrepancy?▸
1. Describe the LLD - in this patient a girl with right side shortening: left side uncompensated LLD without shoe raise, right side compensated LLD fitted with shoe raise
2. Confirm the LLD and define the level of shortening: true and apparent LLD measurement, Galeazzi test, Bryant triangle
3. Pick up signs pointing to the cause of disease: previous surgical scar, sinus tract suggesting previous insult, cafe au lait spots for NF, abdominal exam for hepatomegaly
4. Look for complications of LLD and current functional deficit: assess gait (expect short limb gait), joint contracture (ROM of hip, knee and ankle), back for compensatory scoliosis, muscle wasting
5. Assess skeletal maturity - clinical and radiological (Tanner score) to predict final LLD and its effect on management (shortening/lengthening, timing of operation)
Q20What problems are associated with limb length discrepancy?▸
Deformity: increased energy of gait, needs shoe raise, cosmetic problem, knee pain
Compensation: compensatory scoliosis, pelvic tilting, contralateral hip adduction
Also knee flexion, ipsilateral equinus deformity and OA hip
Left side (uncompensated, no shoe raise): look for shoulder level, scoliosis, pelvic level, contralateral knee flexion, ipsilateral equinus
Right side partially compensated with shoe raise: improved scoliosis and pelvic obliquity
Q21What imaging is available for LLD measurement and what are their drawbacks?▸
Teleoroentgenogram: single film, single exposure; inaccurate due to parallax of the X-ray beam
Orthoroentgenogram: single film, 3 exposures (hip, knee, ankle); more accurate but needs a cooperative patient
Scanogram: separate films, 3 exposures, ruler fixed on X-ray to avoid magnification
CT scanogram: especially for angular deformity, accurate measurement
Standing vs supine: standing film assesses joint line and rotation, which may mask LLD
Q22How do the Paley multiplier and simplistic methods predict LLD at maturity?▸
Paley multiplier: multiplies current discrepancy by a sex and age specific factor
Applicable at the first visit; most accurate in type I growth pattern; uses chronological age
Simplistic: LLD x 1.5 (7-8yo), x 2 (4yo), x 2.5 (2yo)
Q23Describe the Menelaus arithmetic method of LLD prediction.▸
Inhibition is calculated from the discrepancy between 2 visits
Future discrepancy = current discrepancy + (growth remaining x inhibition); most accurate towards end of growth; uses chronological age
Q24Compare the Green-Anderson and Moseley methods of LLD prediction.▸
Green-Anderson: growth remaining data from 1950s American children; based on skeletal age and growth percentile; Heavy reliance on skeletal age, data from a single population
Green-Anderson is for epiphysiodesis only, not lengthening; complex, 2 sets of graphs
Moseley graph: uses skeletal age, accounts for skeletal vs chronological age difference, predicts both epiphysiodesis and lengthening
Moseley assumes a linear growth pattern
Q25What are the advantages and disadvantages of the Menelaus arithmetic method?▸
Advantages: more applicable in the clinical setting, most accurate towards the end of growth
Disadvantages: uses chronological age, not accurate for early projection
Q26What negative findings are noted in this girl with LLD?▸
No syndromal features
No short stature
Limb to trunk is proportional
Q27Why is skeletal maturity assessed in a child with LLD?▸
To predict the final LLD at maturity
It affects the management plan: shortening vs lengthening and timing of operation