Keys To Recognizing And Treating Limb Length Discrepancy

Author(s): 
Joseph C. D’Amico, DPM, DABPO

What You Should Know About Functional Symmetry

A level pelvis does not ensure symmetrical function. Equal limb length does not ensure functional symmetry. An individual with a structural LLD may function symmetrically while some individuals with equal length of the extremities may function asymmetrically. Computer-assisted gait analysis may help determine this with in-shoe pressure transducers capable of measuring time, pressure and direction of force.19,42

   It is one thing to measure limb length either clinically or radiographically, and couple the findings with symptomatology and observational gait analysis. However, it is another story to be able to identify and assess symmetry where it matters most: in action. Life is movement and the locomotor system is designed just for that purpose (i.e. to transport the individual to a desired destination in the mot efficient fashion utilizing the least expenditure of energy). Symmetrical function lowers energy requirements and improves efficiency. With the population today living longer, more active lifestyles, it is imperative for patients to maintain the ability to walk without pain. This starts with optimum symmetrical lower extremity alignment and function.

How To Assess And Obtain Functional Symmetry

The first step in assessing and obtaining functional symmetry is to negate all untoward musculoskeletal influences and deficiencies. This includes identification and neutralization of all abnormal pronatory influences and malalignment. This may entail any or all of the following interventions: prescription of foot orthoses; identification and stretching of posterior group contractures (equinus influences); improving restricted ranges of motion, especially in the hip, knee, ankle and subtalar joints; strengthening of weak musculature; strengthening of joint stabilizers in individuals with ligamentous laxity; weight reduction (when appropriate); evaluation and remediation of inappropriate footwear, etc.

   After addressing these factors, one can assess symmetry functionally. In my early years in practice, I would equalize limb length based on clinical and radiographic measurements as well as sacral leveling. Computer-assisted gait analysis taught me that leveling the pelvis or equalizing limb length may in fact create pedal and limb imbalances during gait. This manifests via asymmetrical plantar pressures as well as temporal parameter disturbances.

   The goal of dynamic gait assessment via computer-assisted gait analysis is to identify and reduce torque and stress so the right and left pedal segments spend the same amount of time on the ground, generate the same normal pressure and move with the same speed. It is non-invasive, relevant, repeatable and reliable. It is capable of detecting locomotor events that one cannot observe with the naked eye or time with a stopwatch as well as forces too small or rapid to detect. Gait analysis quantifies and records weight distribution patterns and temporal parameters in a realistic environment (i.e. inside the shoe).

   Perform an initial computer-assisted gait analysis prior to orthotic prescription in order to gauge pre-treatment symmetry or asymmetry, weight distribution patterns, COF and phases of gait. When it comes to assessing symmetry, useful parameters include: stance, single support, propulsion, midstance, heel duration, heel pressure, time speed, center of pressure patterns, etc. Functional limb symmetry or asymmetry following the use of prescription foot orthoses is not predictable with certainty. Accordingly, one should only address this after orthotic realignment.

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