Lower limb amputation has a significant impact on the movement of the joints and muscles of the lower limb. After amputation, the area of joint motion is often reduced, resulting in undesirable limb contractures that are therefore difficult to compensate for with prostheses. Since lower extremity prostheses are driven by the residual limb, it is important to understand the effects of amputation on the major joints and why such changes occur.
(I) Effects from thigh amputation
The length of the stump has a significant impact on the function of the hip joint. The shorter the stump, the easier it is for the hip to abduct, externally rotate and flex. In other words, on the one hand, the gluteus medius and gluteus minimus, which play a major role in hip abduction, are completely preserved; on the other hand, the adductor muscle group is cut off in the central part, resulting in a decrease in muscle strength.
(II) Effects of lower leg amputation
The amputation had little effect on the range of knee flexion and extension and muscle strength. The quadriceps is the main muscle group for extension and stops at the tibial tuberosity; the main muscle group that plays a role in flexion is the posterior thigh muscle group, which stops at almost the same height as the medial tibial condyle and the fibular tuberosity. Therefore, the above muscles are not damaged within the normal length of the lower leg amputation.
(III) Effects arising from partial foot amputation
Amputation from the metatarsal to the toe had little or no effect on motor function. Amputation from the tarsometatarsal joint (Lisfranc joint) to the center. It causes an extreme imbalance between the dorsiflexors and plantar flexors, which predisposes to plantar flexion contracture and ankle inversion position. This is because after amputation, the function of the triceps calf as the plantar flexor prime mover is completely preserved, while the tendons of the dorsiflexor group are completely amputated, thus losing their proper function.
Post time: Apr-28-2022