Leg Length Discrepancy

Considerations:

May lead to

Increased energy expenditure of gait
Cosmetically disturbing gait
Required use of prosthesis or shoe lift
Equinus contracture of the ankle or flexion contracture of the knee not uncommon
Increased incidence of knee pain in athletes
Scoliosis, initially flexible but may become rigid. (30% to opposite side to that expected from LLD)
Low back problems
Late degenerative arthritis in the hip of the long leg due to an adducted stance and reduce area for WB on the acetabulum

Measure LLD from ASIS ® true LLD, measured from umbilicus or symphysis ® apparent LLD (must position limbs in comparable posture, ie correct for fixed deformity)
Blocks account for shortening distal to the malleoli
Distal femoral physis contributes 70% of the length of the femur and the femur 54% of the length of the leg.
Proximal tibial physis contributes 60% of the length of the tibia and the tibia 46% of the length of the leg.

Options:

Lengthen shorter leg, (eg shoe raise, callus distraction) Shortern longer leg, (eg physeodesis, femoral shortening)
Combination of the above
If more than 2.5 cm needs treatment
Shoe raise should be 1cm less than LLD and not greater than 5cm

Assessment

History

cause, pattern or change in discrepancy, prior surgery

Examination

Hip, knee, ankle examination- ROM, joint stability
Real and apparent lengths, galleazi test, Blocks to level the pelvis
Spine for scoliosis
Muscle power (undercorrect in weak or paralysed limbs)

Radiological evaluation of LLD:

Teleroentgenogram: Single exposure hips to ankles over radio-opaque ruler. Error of parallax a problem
Orthoroentgenogram: Separate exposures centred on hip, knee, ankle over a single film with a ruler
Scanogram: Separate exposures centred on the hip, knee and ankle over a radio-opaque ruler on separate films
CT scan: Quick, easy and less radiation

Assessment should be assessed once per year early on and with increasing frequency closer to the time for correction.

Skeletal age should be made at the time of each review using Greulich and Pyle atlas, (comparison of X-Rays of the left hand with standard films, not very accurate)
N.B. Greulich and Pyle data used in the Green-Anderson tables

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Aetiology

1. Congenital

Retardation: Congenital hemiatrophy with skeletal anomalies- eg coxa vara, femoral aplasia, fibular aplasia
Epiphyseal dysplasia, multiple exostoses, CDH, CTEV
Stimulation: Partial giantism with vascular anomalies (Klippel-Trenaunay,Parkes-Weber)
Haemarthrosis in haemophilia

2. Infection

Retardation: Epiphyseal plate destruction - osteomyelitis, TB, Septic arthritis
Stimulation: Diaphyseal osteomyelitis, Brodies abscess,septic arthritis
Syphilis of femur or tibia
Metaphyseal TBof tibia or femur (tumor albus)

3. Paralysis

Retardation: Polio, other spastic paralysis
N.B. The Heuter-Volkmann law suggests that the growth rate of the physis depends of the compression forces across it.

4. Tumours

Retardation: Osteochrondroma, GCT, Neurofibromatosis
Stimulation: Haemangioma, Lymphangioma, GCT, Neurofibromatosis, Fibrous dysplasia

5. Trauma

Retardation: Damage to physeal plate, #'s with overriding of fragments, severe burns
Stimulation: #'s of femur and tibia
Diaphyseal operations- stripping of periosteum, osteotomy

6. Mechanical

Retardation: Immobilisation of long duration by weight relieving braces
Stimulation Traumatic A-V aneurysms

7. Other

Retardation: AVN- Perthes, CDH
SUFE
Post radiation therapy
Stimulation: Pauciarticular JRA-esp if age of onset less than 3

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Leg Shortening

White & Stubbins (1944)

Distal femur grows 3/8" and proximal tibia 1/4" per year. Growth stopped at 17 in boys and 16 in girls. Later modified this to 16 and 15 years.

M.B. Menelaus (1966)

JBJS, 1966;48B Distal femoral physis grows at a rate of 10mm per year
Proximal tibial physis grows at a rate of 6mm per year
Proximal femur & distal femur grow at a rate of 3mm per year
Growth plates stop growing at 16 in boys and 14 in girls

Calculate years of growth remaining
Calculate past growth rate over longest possible time interval as growth per year
Calculate future expected growth of each leg
Predict leg lengths at maturity and final leg length discrepancy
Calculate amount of correction possible by epiphyseodesis from distal femur, proximal tibia and both combined
Calculate result of epiphyseodesis and select site and timing of surgery

Moseley (1977)

Uses special graph to show pattern of past growth and enables prediction of future growth.

Phemister (1933)

Epiphyseodesis by excision of a rectangular block over the growth plate, the growth plate is curetted out and the block inverted and replaced.
® 3% under correction
3% overcorrection
2.5% angular deformity

Blount ® Physeal stapling
Ogilvie ® Percutaneous epiphyseodesis
Limb shortening is restricted almost exclusively to the femur where as much as 6cm shortening can be obtained. In the tibia no more than 2.5 to 3cm can be obtained due to loss of muscle power etc.

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Leg Lengthening

History

DeBastiani (1986 & 1987)
Developed two, single stage modalities for lengthening

Chondrodiastasis (slow stretching of the growth plate) distraction at a rate of 0.5mm per day
Technique reserved for children close to skeletal maturity with no other available healthy sites for lengthening and for angular deformities that have ocurred with partial growth plate arrest
Callotasis (division of cortex with preservation of periosteum) distaction at a rate of 1mm per day

Ilizarov (since 1989 & 1990)
Noted that gradual distraction of living tissues created stresses that stimulated and maintained active regeneration on certain tissue structures (Tension Stress Effect)
Also developed a circular distraction frame that could correct deformity in any plane

Vilarrubias (1990)
Recognised the importance of soft tissue tension as a rate limiting step in lengthening and the cause of joint subluxation

Biology of Lengthening

Corticotomy (separation of medullary canal leaving the periosteum intact) allows restoration of medullary blood flow in 5 - 7 days (Paley 1988) ® delay in commencement of distraction following corticotomy but there is no consensus in the literature regarding the timing of distraction after operation (Ilizarov starts at 5 - 7 days, DeBastiani waits for early callus formation to occur and starts at 7 - 10 days in children and 14 days in adults)

Bone is layed down in a longitudinal pattern and ossification follows an intramembranous process
Aronson (1989) compared distraction osteogenesis using the Wagner and Ilizarov fixators and noted distinct difference in the alignment of collagen and quality of the regenerate
Clinical experience ® days of fixation per centimetre of lengthening varies significantly with technique and pathology but averages 34.9 days per centimitre (range 20 - 70)

Indications

Leg lengthening considered for LLD more than 5 - 6cm.
Probably not indicated if resultant LLD still 2 - 3cm, requiring the use of a prosthesis. Also must be able to afford about one year of disability.
Amount of lengthening obtained will depend to a certain extent on the initial length of the limb therefore best restricted to patients older than 10 - 12 years and best done before the age of 18 years due to better osteogenic potential.

Methods: Callus distraction (Ilizarov)

Physeal Distraction (Montinelli & Spinelli)
External Fixateur, bone graft and plate (Wagner)
Orthofix distracter (De Bastiani) also used for distraction of the growth plate for small discrepancies and only in the last year of growth

Contraindications

Joint instability
Paralysis
Poor bone structure
Mental instability

Principles

Should not lengthen more than 20% of the original length of the limb
Optimal rate 1mm per day (0.25mm 4 times per day)
Lengthening at 2mm per day may ® arrest osteogenesis due to ischaemia consequent upon too rapid distraction of vessels.
0.5mm per day may ® consolidation.

Pre-existing deformities should be corrected before starting
Consolidation of lengthened segment occurs at the rate of one month per centimetre of lengthening

Problems

Foot deformities
Knee deformities & FFD: Muscles crossing two joints are particularly at risk and if unchecked will ® flexion contracture and as the flexion contracture increases the joint will sublux
Any pre-existing contracture in a joint to be involved in distraction should be corrected first and splinted to prevent recurrence
Tibial deformities (ant / medial bowing)
Ankle arthritis ? secondary to the pressure of distraction
Muscle weakness: Nerve palsies which indicate distraction must be slowed or stopped until the situation resolves
Circulatory problems,: Hypertension (? secondary to stretching sympathetic nerve fibres)
Infection: (pins particularly) with 30% of pin sites becomming infected and 1.1% requiring curettage +/- pin removal
AVN: Non union (more common in adults)
Premature consolidation blocking further distraction

Complications

Problems are defined by Paley as difficulties being resolved during lengthening by non operative methods
Obstacles are difficulties being resolved by operative means
Complications were systemic or local difficulties continuing after cessation of the lengthening programme and further subdivided into mild, moderate and severe

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