Case Study: Detecting Limb Length Difference with Pressure Mapping
The F-Scan® enables you to identify several factors that may indicate limb length differences (LLD) and helps determine the proper orthotic modifications.
by Bruce E. Williams, DPM
Merrillville, IN
Using Plantar Pressures to Detect Limb Length Discrepancy
Normal Patterns:
1) Notice the higher pressure under the 1st metatarsal head on the right foot. This can be an indication of a short side limb.
2) The Center of Force (CoF) icon on the right has accelerated faster than the CoF icon on the left.
3) Notice the early loss of heel pressure on the shortside limb.
LLD Left Side Pressure Profile (Before):
Displayed at left is an example of a patient with a short limb on the left side. The patient has a 3/8" LLD left foot. Notice the early reduction of heel pressure left, and the faster acceleration for the CoF icon. There is also greater sub 1st mpj pressure on left. The above indicate the presence of left side LLD.
Pressure Profile After Heel Lift Added:
Displayed at left is the same patient after addition of a 3/8" korex heel lift on the left orthotic. Notice that left vs. right heel pressures are much more symmetrical, as is the pressure under the 1st metatarsals. The CoF icons are also at the same level, indicating equalization in the acceleration.
TYPICAL PRESSURE SENSOR MODEL USED FOR Detecting Limb Length Difference
- Sensor Model 3000E
Sensing Area Total Width Height Sensels Sensel Density 4.20 in. 12.00 in. 954 25.0 in.2 106.7 mm 304.8 mm 954 3.9 cm2
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