Background

 

 

 

Incidence

 

Leg length discrepancy (LLD) < 1 cm seen in 90% of population

 

Etiology

 

Functional LLD

- LLD caused by contracture

- knee and hip fixed flexion deformity (sagittal plane)

- hip adduction / abduction contractures, knee varus / valgus (coronal plane)

 

Structural LLD

- true LLD

- short femur / tibia / hip

- multiple causes

 

Hemihypertrophy / atrophy	Growth plate arrest	Hip	Congenital femoral  deficiency	Leg
Idiopathic Klippel-Trenaunay-Weber syndrome Proteus syndrome Beckwith-Weiderman syndrome Russel-Silver syndrome (atrophy)	Trauma Infection Radiotherapy Tumour	PFFD Coxa vara SUFE DDH Perthe's Infection		Fibula hemimelia Tibial hemimelia Bowing

 

Congenitally short femur                                  Short femur from distal femur growth arrest

 

Issues

 

Short leg gait / increased energy expenditure 

 

Khamis et al Gait Posture 2017

- systematic review of effect of LLD and gait

- LLD > 1 cm affected gait

 

Compensatory scoliosis

 

Hamada et al Strategies Trauma Limb Recon 2022

- 113 patients with LLD

- LLD 2 cm correlates with Cobb angle of 10 degrees

 

Low back / hip / knee pain

 

Gordon et al J Pediatr Orthop 2019

- systematic review

- some evidence of low back pain / hip / knee pathology with LLD > 2 cm

 

Pelvic obliquity and scoliosis secondary to LLD

 

Growth

 

	Proximal femur	Distal femur	Proximal tibia	Distal tibia
Growth	3 mm / year	9 mm / year	6 mm / year	3 mm year
% total leg	15%	37%	28%	20%
% femur	30%	70%
% tibia			60%	40%

 

Growth cessation

- girls: 14-15 

- boys: 16-17 

 

Examination

 

Look

 

 

Pelvic obliquity - corrects with blocks

Scoliosis - corrects with sitting

Long leg - knee held flexed

Short leg - foot in equinus

 

Gait

 

Options

- walk on toes with short leg - most common

- walk with flexed knee on long leg - high energy expenditure

 

Short leg gait - head moves up and down as walk from long leg to short leg

 

Measure LLD
 

 

Functional LLD	Apparent LLD	True LLD
Use blocks under short leg - correct pelvic tilt / scoliosis - correct knee flexion	Xiphisternum to medial malleolus   No correction for contractures - hip / knee / foot - coronal and sagittal plane	ASIS to medial malleolus   Correct for contractures in coronal and sagittal plane - hip: exclude hip adduction or abduction contractures - hip: compensate for hip FFD with pillow under other hip - knee: compensate for knee FFD with pillow under other knee
Measure desired correction

 

Identify site of shortening

 

Long right femur

 

Galeazzi

- hips and knees flexed side by side

- look for tibial / femoral shortening

 

 

Bryant's triangle

- detects shortened femur above greater trochanter in hip

- distance between lines perpendicular to GT and ASIS

- compare each side

 

Examine knee

 

Conditions such as fibula hemimelia associated with ACL deficiency

Can cause issues with femoral lengthening procedures

 

Four outcomes

 

Symmetrical Stance Level Pelvis	Symmetrical Stance Oblique Pelvis	Asymmetrical stance Level Pelvis	Asymmetrical stance Oblique pelvis
No LLD   Bilateral symmetrical deformity	Uncompensated LLD   Hip / knee / ankle normal position	Fully compensated LLD   Flexed hip Flexed knee Equinus ankle	Partially compensated LLD   Partly flexed hip / knee / ankle

 

X-ray

 

Teleroentgenogram	Orthoroentgengram	Scanogram
Single exposure Single film	Multiple exposures hip / knee / ankle Single film	Multiple exposures hip / knee / ankle Separate film hip / knee / ankle
Parallex error	Parallex error

 

 

 

Skeletal Age

 

 

 Greulich-Pyle atlas using PA xray of the left hand

- estimate skeletal age

- peak growth boys skeletal age 14

- peak growth girls skeletal age 12

- 2 years of growth after distal phalanges have fused

 

12 year old versus 14 year old hand xray.  Distal phalanges have fused in 14 year old. 

 

Comprehensive guide to skeletal age: www.radiologykey/skeletal-age

 

 Shapiro's development patterns of LLD

 

Shapiro et al JBJS Am 1982

- longitudinal study of 800 patients with LLD

- age versus LLD with varying causes

- 5 main patterns of LLD over time

 

Type I	Type II	Type III	Type IV	Type V
PFFD Growth arrest	Polio Juvenile RA	Femoral fracture overgrowth	Hip pathology	Juvenile RA

 

Growth prediction

 

Concept

- predict LLD at maturity

- enables decision making on timing of eiphysiodesis

 

Menelaus Rule of Thumb

- girls stop growing at 14 / boys stop growing at 16

- distal femur 9 mm / year
- proximal femur 3 mm / year
- proximal tibia 6 mm / year
- distal tibia 3 mm / year

 

Green and Anderson growth remaining tables

- measured longitudinal growth in normal white children

- tibia and femur

- plotted average growth per year by skeletal age with standard deviations

 

Green and Anderson growth remaining tables

 

Moseley straight line graph

- converted Green and Anderson table to straight line

- three measures: length long leg, length short leg, skeletal age

- plot measures over three time periods

- estimate LLD at skeletal maturity

 

Moseley straight line graph

 

Paley multiplier method

- converted Green and Anderson table to a multiplier for tibia and femur over time
- use established multiplier for age and sex to determine LLD at maturity

- only works with Shapiro Type I LLD patterns

 

Paley growth multiplier app