LLD Assessment & Quantification

Quantification of LLD




1. Teleroentgenogram

- single exposure both legs

- long film with ruler

- Parallax errors


2. Orthoroentgengram

- same long Xray

- separate exposures hip, knee & AJ 

- eliminates parallax error

- problem artefact 


3. Scanogram

- similar separate exposures

- film moved between exposures

- smaller film

- multiple exposures


CT scan


Software measures distances 

- accurate to 0.2 mm

- legs must be in same position

- fast


Skeletal Age


1. Greulich- Pyle Atlas


Xray Left hand (non dominant)

- correlated with Green- Anderson table LL

- less accurate < 6

- improved accuracy by focusing on hand bones rather than carpal bones


2. Tanner- Whitehouse Atlas

- more refined

- 20 landmarks graded L Hand

- more accurate

- can't use as not correlated with LL


Prediction of Growth


Note that all methods have an inherent error of 12 months

- gives accuracy to 1.5 cm


Need > 3 measures 4/12 apart for all methods

- If inadequate data wait till older or wait till skeletally mature

- If acquired event caused LLD, can plot onto graph


1.  Menelaus "Rule-of-thumb" Method


Less accurate

- based on chronological age

- only valid from age ten

- convenient / easy / simple


Basic rules

- girls stop growing at 14 

- boys stop growing at 16

- distal femur 9 mm 

- proximal tibia 6 mm 

- distal tibia / proximal femur 3 mm 


Calculate how much growth lost from fusion of physis / Predict effect of epiphysiodesis

- Effect = Physis rate x years of growth Left


2.  Green & Anderson tables


Growth remaining method

- uses skeletal age

- requires graph

- estimates growth potential in distal femur and proximal tibia at various skeletal ages

- separate charts for girls and boys


3.  Moseley


Straight - Line Graph Method  

- uses Green & Anderson data

- applied to a chart


At least 3 measurements each time

1.  Length long leg

2.  Length short leg

3.  Skeletal age


Do so 3 times separated by 3-6 months

- accuracy improves with increased plotting


Plot the points for long and short leg on a vertical line for chronological age of either boy or girl

- create 2 lines for short and long leg over time

- line of best fit

- gives LLD at maturity at right of graph



- plot Long leg length on long leg line against skeletal age

- plot Short leg length on short leg line against skeletal age

- able with at least 3 measures to create line of best fit

- extend lines to maturity

- difference is LLD


Growth rate of each leg = slopes

- parallel or divergent 

- AKA static or progressive


Then use Menelaus rule of thumb to determine appropriate age for epiphysiodesis


4.  Paley multiplier


State of the art

- 2000

- take LLD for boy or girl

- multiplier for chronological or skeletal age

- predicts LLD at maturity


Patterns of LLD


Adds to difficulty

- static

- progressive

- regressive




1982 5 developmental patterns

- 75% types I and II


I Increasing

- LLD increases at constant rate

- hemihypertrophy / atrophy

- tibial pseudoarthrosis


II Increasing plateau

- similar early, but annual rate of increase diminishes thereafter

- Perthes


III  Plateau

- discrepancy increases, then stabilises

- fracture femur


- Polio


IV Increasing- decreasing

- similar to III, then late increase at end of growth


- hemihypertrophy


V Decreasing

- Initial increase, steady, then decrease


Progressive LLD


Progression Rate = Change LLD / Time


Final LLD

- add Current LLD to Prog Rate x Time to Skeletal maturity