The efficacy and efficiency of gait after functionalsurgery of the lower limb in hemiplegic patients: 3doptoelectronic motion analysis of velocity.

Introduction The efficacy of gait may be characterised through theevaluation of the mean walking velocity. It has beenproved that a significant correlation exists between meanvelocity and the degree of the patient's autonomy ininternal and external environments.The efficiency of gait is correlated to the energyexpenditure necessary to guarantee the subject's ambu-lation and the subject's capability to alternately transferfrom one side to the other the kinetic and potentialenergy generated during the alternation of the stanceand push-off phases. Pathological changes in the sub-ject's capability of load acceptance and progression havea negative influence on these two elements.Hemiplegic patients present a typical asymmetricwalking pattern, a reduced mean walking velocity and adistinct increase in the oxygen consumption per unit ofdistance covered.Subjects and methodsFifteen patients affected by hemiplegia (seven females,eight males, average age 45.8912.7 years, 11 left side,four right side) were analysed prior to and 1 year afterfunctional surgery for equinous varus spastic foot.Changes in the ratio between patients' mean walkingspeed and the mean swing velocity of both the healthyand the plegic lower limb were evaluated. These parame-ters were calculated on the basis of kinematic dataacquired with an optoelectronic 3D motion analyser(Elite system B T S, six Tvc's) with 'Simplified S.A.F.Lo'protocol (nine spherical markers (F15 mm) on bodyland markers of the lower limbs and trunk).Before and after surgery five trials (five complete gaitcycles) were carried out for each single patient.In order to check the trials' repeatability for eachpatient, the homogeneity of the platforms' data wasevaluated through averaging of the five trials and calcu-lation of the standard deviation. When no significantvariation between the trials was appraised, a 3D recon-struction of one of the trials effected was performed.ResultsA significant increase (P0.003) in mean walkingspeed was found 1 year after surgery (from 0.3690.17m:s before surgery to 0.4390.16 m:s).The average velocity during the swing phase of boththe healthy (1.6290.46 m:s before, 1.5590.39 m:s aftersurgery) and the plegic limb (0.8790.31 m:s before,0.9390.38 m:s after surgery) did not change signifi-cantly.The ratio between mean velocity of the lower limbduring swing phase and mean walking velocity hassignificantly decreased both on the plegic side (from2.8390.54 to 2.2690.23 m:s,P0.0004) and on thehealthy side (from 5.2892.75 to 3.7491.69,P0.0008)1 year after surgery.DiscussionThe increase in gait mean velocity after functionalsurgery is evidence of the improvement in the efficacy ofthe walking pattern in patients who underwent this kindof treatment.The reduction in the ratio between mean velocity ofthe lower limbs during swing phase and mean walkingvelocity shows that after functional surgery the patientsare able to transform more efficiently, both on thehealthy and on the plegic side, potential energy (pro-duced during swing phase) in kinetic energy useful to thepropulsion (as proved by the increase of the meanwalking speed).ConclusionsThe ratio between mean velocity of the lower limbduring swing phase and mean walking velocity may beconsidered a new practical kinematic indicator for theevaluation of gait efficiency. It may also therefore beconsidered a useful instrumental parameter for assessingthe results of rehabilitation programs aimed at improv-ing the patients' walking ability.References[1] Whittle M. Gait Analysis: An Introduction, Butter-worth Heinemann, 1991.[2] Prampero PE. La locomozione umana su terra, inacqua, in aria, Edi-ermes, 1985.[3] Perry J et al. Stroke 1995;26:982 - 989.[4] Nadeau S et al. Am J Phys Med Rehabil1999;78:123 - 130.[5] Turnbull GI. Scand J Rehab Med 1995;27: 175 - 182.[6] Von Schroeder HP. J Rehabil Res Dev 1995;32;25 - 31.