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Leg-Length Discrepancies: Diagnosis and Treatment
By Séamus Kennedy, BEng (Mech), CPed Numerous studies have been conducted. All agree on
the data, but the actions required are unclear. Experts weigh in
with research-supported opinions, but a universal protocol is not
established. Although this may sound like a discussion of the
Social Security system, these statements also apply to the clinical
diagnosis and treatment of leg length discrepancies
(LLDs).
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Séamus Kennedy, BEng (Mech), CPed |
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This is a diagnosis that appears deceptively
simple. There is often more to the apparent difference in limb
length than meets the eye. The symptoms can be diverse, confusing,
and vague, such as complaints of lower-extremity pain or general
backache. Studies have shown that true or
structural LLD is less common than realized, and
that most LLDs are functional in nature, i.e.,
they are the result of a compensation or restriction.
Structural vs. Functional
Structural LLDs are the result of an anatomic short limb. These
may occur due to congenital or developmental factors. Other
conditions such as post-polio syndrome, certain post-op patient
conditions, or trauma cases may lead to a LLD that needs to be
actively managed.
More frequently, patients will display LLDs due to a
functional difference in their biomechanics. For
example, spinal problems, muscular weakness, ligamentous
flexibility, and restricted ranges of motion at the ankle, knee, or
hip can all lead to compensations that result in LLDs. Just because
these LLDs are functional in nature doesn't mean they should be
treated any differently.
Evaluating
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2.5 inch Internal Heel Lift |
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Asymmetry is a clue that a LLD is present. The
center of gravity will shift to the short limb side and patients
will try to compensate, displaying indications such as pelvic tilt,
lumbar scoliosis, knee flexion, or unilateral foot pronation.
Asking simple questions such as, "Do you favor one leg over the
other?" or, "Do you find it uncomfortable to stand?" may also
provide some valuable information. Performing a gait analysis will
yield some clues as to how the patient compensates during
ambulation. Using plantar pressure plates can indicate load
pressure differences between the feet. It is helpful if the gait
analysis can be video-recorded and played back in slow motion to
catch the subtle aspects of movement.
Measuring
One of the golden rules in pedorthics is that you always measure
a patient's two feet before fitting a pair of shoes. You never
trust in the sizing that they tell you. Likewise, it is vital that
you measure the LLD, whether structural or functional, yourself.
Measuring for a LLD is not an exact science; there is no clinical
consensus as to which anatomical references should be used or how
the patient should be positioned. In addition, direct measurement
results with a tape can be difficult to reproduce across
practitioners, and they will only indicate a structural LLD. It may
be best to use several methods to develop a composite picture.
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Internal Heel Lifts |
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For a direct measurement, the method that I
recommend is to measure from the anterior superior iliac spine to
the medial malleolus. This measurement will give you the
actual limb length difference. Other methods
include palpation, frontal plane observation, X-rays, and use of a
measurement screen. However, this is only a starting point for
treatment. There is no agreement as to the amount of a measured
difference that should trigger an intervention! Anecdotally, it
appears that for LLDs greater than ¼" some form of treatment
be suggested to the patient, although many cases greater than this
may be asymptomatic.
My preferred course is to proceed with an indirect measurement.
I am not so much concerned with what the LLD is as I am concerned
with what the patient can tolerate and what makes him or her
comfortable. I prefer to measure the correction.
Correcting
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2 inch External Platform Lift |
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In order to measure for correction, use a series
of blocks or sheets of firm material (cork or neoprene) of varying
thickness, e.g., 1/8", 1/4", and 1/2". Place them under the short
limb, either under the heel or the entire foot, depending on the
pathology, until the patient feels most balanced.
Usually you will not be able to correct for the full amount of
the imbalance at the outset. The longer a patient has had the LLD,
the less likely he or she will be able to tolerate a full
correction immediately. This is a process of incremental
improvements. 2 inch External Platform Lift Bear in mind that the
initial lift may need to be augmented as the patient's
musculoskeletal system begins to adjust. It is often recommended
that the initial buildup should be 50 percent of the total. After a
suitable break-in period, one month say, another 25 percent can be
added. If warranted, the final 25 percent can be added a month
later.
Once you determine how much lift the patient can handle, you
then need to decide how to best apply it. There are certain
advantages and disadvantages to using either internal or external
heel lifts.
Internal heel lifts: Putting a simple heel lift
inside the shoe or onto a foot orthotic has the advantage of being
transferable to many pairs of shoes. It is also aesthetically more
pleasing as the lift remains hidden from view. However, there is a
limit as to how high the lift can be before affecting shoe fit.
Dress shoes will usually only accommodate small lifts (1/8"1/4")
before the heel starts to piston out of the shoe. Sneakers and
workboots may allow higher lifts, e.g., up to 1/2", before heel
slippage problems arise.
External heel lifts: If a lift of greater than
1/2" is required, you should consider adding to the outsole of the
shoe. In this way, the shoe fit remains good. Although some
patients may worry about the cosmetics of the shoe, it does ensure
better overall function. Nowadays with the development of synthetic
foams and crepes, such lifts do not have to be as heavy as the cork
buildups of the past. External buildups are not transferable and
they will wear down over time, so the patient will need to be
vigilant in having them repaired. On ladies' high-heel shoes, it
may be possible to lower one heel and thereby correct the
imbalance.
Compromise is always a worthy attribute, and personally I favor
a blend of both internal and external lifts when more than 1/2" is
necessary. This way, shoe fit is not too affected and yet changes
to the overall look are minimized. A follow-up gait analysis should
reveal a more symmetric gait, more even pressure distribution
across both feet, and an absence of painful symptoms. Séamus Kennedy, BEng (Mech), CPed, is president and co-owner of Hersco Orthotic Labs, Long Island, New York. 
Table Of Contents - August 2005
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