BlOMECHANlCAL CHARACTERISTICS OF THE LOWER EXTREMITIES OF AMPUTEE VERSUS NORMAL SUBJECTS

Abstract

The purpose o f this study was t o determine whether biomechanical characteristics of the non-amputated leg of unilateral lower extremity amputees significantly differed from the dominant leg of normal subjects. A comparison was made of the mean peak isokinetic knee extensor and ankle plantar flexor torques and mean performance in one- legged static and countermovement vertical jumps. Peak isokinetic torque was measured by a Cybex 11 a t 60 degrees.s. Vertical jump performance was captured on video tape and analysed using the Peak 2D Motion Measurement System. The heights o f the jumps were calculated from the difference in the position of the centre of gravity o f the body as determined by the segmentation method. Stump anthropometrics. Hanavan's (1964) model. and density data from Dempster (1955) were used t o c a l c u l a t e the volume. mass. and position of the centre of gravity of the residual limb of the amputee subjects. Four unilateral lower extremity .amputees, age 31.5 + 4.9 years and height 179.7 + 2.3 cm, were compared w i t h four normal subjects. age 31.1 + 4.1 years and height 179.2 + 1.8 cm. The result revealed that the mean peak isokinetic knee extensor (190+19nm) and ankle plantar flexor (84 +20nm) torques for the amputees were less than but not significantly (p<0.05) different from the flexor (115+21nm) torques of the normal subjects. The normal subjects attained a higher mean rise of the centre of gravity of the body during one-legged countermovement (14.6+2.6cm) and static (11.1+0.5cm) jumps than the amputee subjects (13.1+1.9cm for countermovement, 10.6+1.1cm for static jumps) but the difference was not significant (p<0.05). It was concluded that the normal subjects did not have superior knee extensor or ankle plantar flexor strength and unilateral lower extremity amputees would not be disadvantaged in their standing one-legged jumping ability.