There are many ways to be brought into a discussion of limb length discrepancy by your patients. They may explain that their PCP wanted someone good in biomechanics to check for a short leg due to the chronic hip and low back pain. They may show the signs we talked about last post in your gait evaluation of head tilt, shoulder drop, asymmetrical arm swing, dominance (or lean) to one side, and asymmetrical pronation. In fact, by definition, when a patient comes in with PTTD on one side they have at least a functional leg length and everything we discuss holds true for them. Most patients with recent hip replacement and knee replacement will have a limb length discrepancy also. So, you can really help with your understanding for this problem, since the treatment can be so dramatic in patients.
40 years ago when I was a Biomechanics Fellow I had my podiatry rotation of 20 students all measure leg length with tape measure of one student. Prior to any measurement, we carefully marked and exposed the ASIS at the hip and bisection of the medial malleolus on both sides. The students were given the tape measure and told to record their findings in secret. We literally had a 20 mm difference in all the measurements with 15 mm short on one side to 5 mm short on the other side. This lead me to look for a better way of teaching about short legs, and this will be presented today. The literature supported this osteopathic approach with 80% accuracy in agreeing with xray evaluation. It became the technique I still use with great success today.
The examination is done with the patient standing. Jackets and belts should be removed for better palpation. The patient is initially standing in RCSP in normal angle and base of gait. What are the four landmarks? These are from the front the Iliac Crests, Anterior Superior Iliac Spines, Great Trochanters, and from the back the Posterior Superior Iliac Spines. These standing landmarks are good ones, but you have to know the nuances of them.
Limb Length Discrepancy being measured can have most of its origins in a pelvic tilt, with or without scolosis, a true structural limb length discrepancy, a functional leg length discrepancy from something happening below the pelvis, and a combination of all three. Your job is to make the observations on the patient and try to make sense. Is there something I can treat? In my 40 plus years, the pros and cons are evident, but the victories are so so sweet.
It is so important to palpate one side at a time with the other side being supported. By this, I mean do not attempt to find your landmarks on the right and left at the same time. The patient will feel that they are being pushed all over. For the Iliac Crests and the Greater Trochanters, our hands lie on top of the boney landmarks, we can ask the patient if they feel in the same spot, and our hands have to be parallel to each other, and easy to observe. For the ASIS and PSIS, you use your parallel thumbs to make the observation.
Here the top of the Iliac Crests (IC) are
palpated. The iliac crests can be off
with limb length discrepancy,
scoliosis, or pelvic tilts. See the
hands are parallel, the shirt does not
get in the way, and the examiner is
at eye level
Here the tops of the Greater Trochanters are palpated. This observation
is the truest for actual limb length discrepancy as it is not influenced by
pelvic tilts. Like the Iliac Crest measurement, the hands should be
parallel.
The ASIS (done here) and PSIS measurements are both done with parallel thumbs.
Find the spot on one side first, while stabilizing the one side with
your hand. Then find the second spot.
The ASIS is one of the most interesting and helpful observations. Even though it is not
a true limb length landmark, since it is so influenced by pelvic tilts, it can be
crucial in our treatments.
Next post I will go over some typical findings and their effect on treatment. I use
inserts 1/8 inch thick to measure the leg difference. If the greater trochanters show
a lower right side, I build up under the right side until the trochanters are level.
I will be talking in a few weeks how to work with lifts when treating a short leg.
One of the first things to do after diagnosis is have the patient walk with both 1/8
and 1/4 inch lifts on the side you feel is short, and get their feedback. Normally,
they feel more centered and stable.