Lower limb dysmetry, false short leg or true short leg?

Edited by Doctor Ilio Iannone

In the medical field there is often a lot of confusion in the prescription of the lift in cases of leg length discrepancy. All this is due to the lack of clarity and the difficulty of recognizing a real shortening of the lower limb or its false shortening due to other components. .
The prescription of the lift is often done very lightly and without the appropriate clinical evaluations.

It is absolutely essential to ascertain whether there is really a real short leg, which requires the permanent use of a lift, or another phenomenon for which its use - in addition to being useless - can be harmful.
The only diagnostic tool currently used is the radiographic measurement of the acetabular line. However, there are several components that determine a false shortening of the limb:

Valgus of the heel or knee, greater on one side than the other, causes a decrease in the distance from the ground to the cup; lowering the latter causes a false short leg.
The tilting of the iliac bone can influence the height of the cup: an anterior tilting lowers the cup causing a false long leg, a posterior tilting raises the cup causing a false short leg.
The abnormal ossification of the pelvis.
The rotation of the pelvis which generally lowers the cup on the propulsive side.
Lumbar scoliosis.
Visceral fixations.
Muscle retractions of psoas, piriformis (piriformis syndrome), etc ..

For these reasons it is advisable to carefully evaluate the patient before prescribing a lift through instrumental examinations and evaluation tests.

Scansioscintigrafia and RX
Patient observation

When standing, it is necessary to assess whether there is coherence between the inclination of the pelvis and an apparently more deformed lower limb. By evaluating the sitting position, it is possible to eliminate the influence of the lower limbs on the tilting of the pelvis: if in this position the pelvis is perfectly aligned with respect to the standing position, the cause of the tilting is attributable to the lower limb.

Osteopathic tests that evaluate the tilting of the pelvis.

In light of these aspects, the prescription of the increase must be carried out only after numerous investigations. This solution must never have an excessive thickness and it is preferable to consider a few mm less than the real need. It must be placed under the sole of the foot and not just under the heel, as this would favor the shortening of the triceps sural.

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