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02 Nov 2013 - 03:41:16 pm

Leg Length Discrepancy




Leg Length Discrepancy

Leg Length Discrepancy








Defined
as difference in rate of growth between two limbs:



-
usually
due to abnormal physeal growth



-
fracture
malunions



-
bone
loss from osteomyelitis or tumor resections







Evaluation
includes determination of whether shortening is true or apparent.







Apparent
limb length discrepancy (LLD) may be due to:



-
suprapelvic
obliquity



o scoliosis



-
intrapelvic
obliquity



o pelvic fracture



-
infrapelvic
obliquity



o hip contracture



o knee contracture



o ankle contracture






True Shortening Apparent Shortening








Assessment
of true shortening involves measuring the absolute length of the limbs
involving one of a number of methods:



- tapemeasure



- leveling the pelvis with blocks

















-
scanogram

































































- CT scans




















































-
Long
leg standing films







Why
does leg length inequality matter?



-
back
pain



-
scoliosis



-
hip
and/or knee osteoarthritis







A
study by Gross (1978) showed & recommended:



-
less
than 2.0 cm showed no difficulties



-
more
than 3.5 cm, 80% had complaints



-
LLD
of 3 cm was compatible with high level sports



-
Observation
for less than 2 cm at maturity, especially if the patient has weakness or
spasticity on the short side







Many
options exist for limb lengthening, although are somewhat controversial:



-
skeletally
immature



o stapling



o epiphysiodesis



-
skeletally
mature for discrepancy greater than 3 cm



o lengthening using frame or
IMN



o acute shortening, can fairly
easily accommodate 8 cm in femur or 3 cm in tibia



-
suggested
approaches, given a normal height range are as follows:



o 0 ? 2 cm: no treatment



o 2 ? 6 cm: chow lift,
epiphysiodesis, shortening



o 4 ? 15 cm: lengthening
procedure



o > 15 cm: prosthetic
fitting







Epiphysiodesis



-
first
described by Phemiser in 1933



-
performed
by excising a square of bone from the medial and/or lateral margin of the
growth plate and rotating it 90?



-
permanent,
difficult to undo physeal bar created if not satisfied with result



- complications include
miscalculation of timing and technical errors









Epiphyseal Stapling



-
described
by Blount in 1949



-
potentially
the same problems as the epiphysiodesis



-
staples
may be removed and physis will usually resume growth











The
goal is equal limb length at maturity, unfortunately it is often difficult to
predict future growth in a child.
Stapling may permit less precise estimations whereas epiphysiodesis is
unforgiving. Growth rates have been
extensively studied and growth tables exist to help predict the growth
remaining in a given limb at a given age. Growth is fairly constant from
chronologic ages 6 to 9 with the femur growing roughly 2.0 cm (SD 0.27 cm) and
the tibia 1.6 cm (SD 0.23 cm). During
the adolescent growth spurt, yearly increments are extremely variable. Using bone age, rather than chronological
age is a more useful and reliable gauge in predicting growth. This can be performed using standardized
books containing figures of radiographs of the hand and wrist and comparing
them to the patient. (Greulich)







Acute Shortening Procedures

-
generally
considered for patients with same amounts of LLD as those for epiphysiodesis
but who are too old for correction with physeal closure

-
femoral
shortening usually preferred to tibial shortening

-
up
to 5 cm usually well tolerated in femur (3 cm in tibia), greater resulting in
ineffective recovery of muscle-tendon units

-
involves
open shortening with plate fixation, proximal shortening with blade plate or
newer closed femoral shortening using intramedullary nail





Growth Stimulation



-
multiple
techniques for stimulation of the short extremity have been tried with
irreproducible and clinically insignificant results

o
electrical
stimulation

o
sympathectomy

o
surgical
creation of AV fistulae

o
placement
of foreign bodies next to the physes

o
packing
bone beneath periosteum near physes









Limb Lengthening



-
lengthening
is generally reserved for patients with the most severe deformities

o
multiple
potential complications

?
pin
tract infections

?
joint
contractures

?
joint
subluxation or dislocation

?
nonunion/malunion

o
prolonged
treatment times

-
usually
4 to 20 cm

-
relatively
stable joints above and below are a prerequisite

-
rotational
or angular malalignment usually decreases total length attainable

-
patient
should be emotionally mature (usually older than 8 or 9 years)

-
ring
fixators have focused interest on the biology of lengthening

o
rate
of lengthening is critical

o
osteogenesis
begins in IM canal as multipotential cells diffentiate into osteoblasts

o
bone
formation resembles intramembranous growth (vs endochondral) as no cartilage
matrix is laid down

o
cells
appear to lay down in longitudinal direction of retreating bone end

o
patients
allowed to fully weight bear and to do regular exercise to prevent joint
contractures

-
many
modifications on the original theme (Ilizarov)

o uniplanar frame lengthening
over an IM rod is becoming popular



-
difficult
decision concerning timing of removal of frame











Prosthetic Fitting



-
generally
least desirable form of treatment, but may be best choice with large
discrepancy or severe deformity

-
considered
when predicted discrepancy at maturity exceeds 15 to 20 cm

-
single
operation vs multiple procedures and complications

-
Syme
amputation follows by prosthetic fitting results in a functional BKA that
results in near-normal gait and activity level

o
best
performed when child is younger than 1 year

-
for
patient with severe proximal focal femoral deficiency, Syme with or without a
knee fusion may be the best option

o
Van
Nes rotationplasty, which reverses the ankle joint to power a modified
below-knee prosthesis is also an option (best if completed before 3 to 4 years)











Fortunately, growth disturbances are often
not purely random and unpredictable.
They are usually a progressive inequality due to growth in one extremity
being inhibited. Studies have shown
that 95% of patients with LLD have constant inhibition that is predictable over
time. Polio is one example where the
growth is usually not predictable.







Three
common methods of predicting the future difference in LLD have been described:







-
White
and Menelaus (arithmetic method)



o Distal femur grows 0.9 cm/yr



o Proximal tibia grows 0.6
cm/yr



o Inaccurate in young children



o Uses chronological age, not
skeletal



o Until maturity (15 1/4 for a
girl and 17 1/4 for a male)



o Simplistic, but a good guide
for timing of epiphysiodesis







-
Green
and Anderson (growth-remaining method)



o 100 kids from Boston (50%
with polio) had their normal leg evaluated



o correlated growth to
skeletal maturity with Greulich and Pyle bone age atlas



o accuracy improved by
plotting over 3-4 yrs to assess growth inhibition



-
Moseley
(straight-line graph method)



o Derived from Green and
Anderson data/tables



o Use more complicated straight
line tables







In
evaluating the various techniques used to assess limb-length discrepancy,
studies vary with respect to interpretation of success. General success has been reported with both
of these methods, although a recent review has reported rather disappointing
results with all three commonly used methods, suggesting further refinement is
needed.











Determining Leg Length Discrepancy:



The Arithmetic Method



Leg Length Data



(same data for all threesamples)



Sex: Female







Age (yr) Skeletalage (yr) Right leglength (cm) Left leglength (cm)



7 + 10 8 + 10 66.0 58.2



8 + 4 9 + 4 64.4 61.9



9 + 3 10 + 3 70.0 66.2







Prerequisite growth information







Distal femoral plate grows10 mm/yr. Girls stop growing at 14 years of age.



Proximal tibial plategrows 6 mm/yr. Boys stop growing at 16 years of age.







Assessment of past growth







1. Longest time interval for data



= age at last visit ? age at first







2. Years of growth remaining



= 14 (16 for boys) ? age at last visit



3. Past growth of legs



= present length ? first measured length



4. Growth rate of long leg







5. Growth inhibition























1. Longest time interval for data



= 9 yr 3 mo ? 7 yr 10 mo = 1 yr 5 mo



= 1.42yr



2. Years of growth remaining



= 14 yr ? 9 yr 3 mo = 4 yr 9 mo = 4.75 yr



3. Past growth of:



Long leg = 70 ? 60 = 10.0 cm



Short leg = 66.2 ? 58.2 = 8.0 cm



4. Growth rate of long leg



= 7.04 cm/yr



5. Inhibition



= 0.2 cm



Prediction of future growth







1. Future growth of long leg



= years remaining X growth rate



2. Future increase in discrepancy



= future growth of long leg X inhibition



3. Discrepancy at maturity



= present discrepancy + future increase















1. Future growth of long leg



= 4.75 X 7.04 = 33.4 cm



2. Future increase in discrepancy



= 33.4 X 0.2 = 6.7 cm



3. Discrepancy at maturity



= (70.0 ? 66.2) + 6.7 = 10.5 cm



Prediction of effect of surgery







Effect of epiphysiodesis



= growth rate X years remaining











Effect of epiphysiodesis



Femoral = 0.9 X 4.75 = 4.28 cm



Tibial = 0.6 X 4.75 = 2.85 cm



Both = 1.6 X 4.75 = 7.13 cm







Taken from Chapman?s Volume
4, p. 4347.











Determining Leg Length Discrepancy:



The Growth Remaining Method



Prerequisite growth information







Distal femoral plate grows10 mm/yr. Girls stop growing at 14 years of age.



Proximal tibial plategrows 6 mm/yr. Boys stop growing at 16 years of age.







Assessment of past growth







1. Growth of both legs



= present length ? first length







2. Present discrepancy



= length of long leg ? length of short leg







3. Growth inhibition



























1. Growth of long leg



= 70.0 ? 60.0 = 10.0 cm







1. Growth of short leg



= 66.2 ?58.2 = 8.0 cm







2. Present discrepancy



= 70.0 ? 66.2 = 3.8 cm



3. Growth inhibition



= 0.2



Prediction of future growth







1. Plot present length of long leg on Green-Anderson leg length graphfor appropriate sex







2. Project to right parallel to standard deviation lines until maturityto determine mature length of long leg







3. Future growth of long leg



= mature length ? present length







4. Future increase in discrepancy



= future growth long X inhibition







5. Predicted discrepancy at maturity



= present discrepancy + future increase











1.





2. Length of long leg at maturity = 81.1







3. Future growth of long leg



= 81.1 ? 70.0 = 11.1 cm







4. Discrepancy at maturity



= 3.8 + 2.2 = 6.0 cm







Prediction of effect of surgery







1. The effect of epiphysiodesis of the distal femoral and proximaltibial plates for a given sex and skeletal age can be determined by theGreen-Anderson growth = remaining graph.



2. The effect of lengthening is not affected by growth.











1. Correction from proximal tibial arrest



= 2.7 cm







Correction from distal femoral arrest



= 4.1 cm







Correction from combined arrest



= 2.7 + 4.1 = 6.8 cm















Taken from Chapman?s Volume
4, p. 4348.







Moseley
Straight-line Graph Method

























































































































Generously
donated by James Roach, M.D.







Most images and much of thegeneral information from this section were ?borrowed? from a powerpoint presentationby James Roach, M.D. Much was also?borrowed? from Chapman?s, Volume 4, Chapter 170 ?Limb-Length Discrepancyin Children?.














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