Biomechanical Study Of Gait Coordination Of Transfemoral Amputees

Currently,there are a large number of amputees living worldwide,with millions in China.Of the amputees,more than 70% were amputated at lower extremity.Compared to other types of lower extremity amputations,transfemoral amputations are more difficult to rehabilitate owing to the loss of more joints,bones,and muscles.Wearing a transfemoral prosthesis has become the most important way for the amputees to restore the ability of bipedal locomotion.Transfemoral amputees usually exhibit changed gait patterns compared to the abled people,which is albeit compensated by the prothesis.Meanwhile,the rehabilitation process for amputation also encounters some pathological problems after wearing the prothesis.These pathological problems occur not only in the residual limb,but also in the intact limb and trunk,such as joint osteoarthritis or lower back pain.Great effort has been made to improve the performance of prosthetic joints or supplement more powerful biomechanical functions for the prostheses over decades.Nevertheless,the defectiveness of the prosthesis design,the altered gait,and the mechanisms of the pathological problems are still lack of enough awareness.One important but often omitted approach to understand the linkage is the gait coordination in walking with the prothesis.Gait coordination relates to the issue whether the patient’s gait is reasonable or healthy.In the past,gait analysis of the transfemoral amputees is largely confined to single joint level,which could not reflect the whole-body movements.And it was not sufficient to reflect the adjustments made by the patients to cooperate multiple joints when they cope with different movement tasks or compensate for movement defects.There are research gaps for the previous studys:1.Lacking of gait coordination study for the amputees.The gait coordination features of transfemoral amputees is still unknown till now,which limit the improvement of prosthesis design and clinical rehabilitation.2.Compared to traditional passive transfemoral protheses,knee-ankle joint linkage prosthesis has the advantages of better restoring the normal gait patterns of human musculoskeletal system,whereby the knee and ankle joints could regain their functional roles in gait coordination.Nevertheless,whether the function can help to improve gait coordination effectively need to be validated.3.Walking speed is an important manifestation of exercise capacity.Human beings,inevitably,need to adopt different walking speeds in their daily walking to cope with the external environment and achieve the purpose of locomotion.However,the ability to control walking speed is much lower in transfemoral amputees than in normal subjects.Amputees normally exhibited a reduction in preferred walking speed and maximum walking speed compared to their abled counterparts.How the walking speed affect the gait coordination need to be revealed.4.The important implication of muscle coordination of the patient’s intact limb was neglected.Previous studies focused more on the intact limb as a comparison of the prosthetic side and paid less attention to the intact limb.However,we believe that the improvement of prosthesis performance should not be made at the expense of ignoring the intact limbs.In the meantime,several studies have shown that the intact limbs also have a high incidence of pathological problems,but there is still a lack of explanation about the causes.Whether the intact limb is adversely affected by the prosthetic gait needs to be studied;on the other hand,muscular coordination of intact limb is another embodiment of gait coordination.Information of muscular coordination can give a better insight of the characteristics of motor control in amputees.Therefore,in this study,gait analysis and inverse dynamics analysis were carried out on eight patients with unilateral transfemoral amputation to comprehend their gait coordination.The study was comprised of four parts as following:1.The general characteristics of gait coordination in patients with transfemoral amputation were revealed.This chapter is based on the study of wearing the passive transfemoral prostheses,which are the most widely used prostheses for patients with transfemoral amputations.The gait was performed at self-preferred comfort speed.Joint coordination,decomposition index and other traditional gait parameters were analyzed and compared to those of abled people.Results of the study showed that,in addition to the changed gait in single joints,a study of coordination unveiled more information regarding the adjustments made by the patients to restore their walking ability.Although different version of prostheses were involved in this study,patients with transfemoral amputation demonstrated common features of gait coordination.The patients adopted a different inter-joint coordination strategy to accommodate walking with the prothesis,which distinguished them from the abled.The adjustment of control strategies of hip and ankle joint in the intact limb is critical for improving gait coordination.The hip joint in the intact limb played a decisive role for maintaining gait steady;while the ankle joint was helpful for motor control by reducing the degree of freedom.The prosthetic knee-ankle coordination was significant different from that of abled.The prosthetic knee joint demonstrated less functional to flex during stance phase,which affected the amputees’ gait and should be improved in the future optimization.2.The effects of prosthetic knee-ankle linkage on gait coordination were evaluated.The prosthetic knee-ankle coordination has been found to be great different from that of abled in the first chapter.In this chapter a series of gait coordination analyses were conducted to the patients when they wore: a)their own passive transfemoral prosthesis;b)knee-ankle linkage prosthesis provided by the investigators.Walking speed was self-selected upon best comfort.Variables of gait coordination were compared between the two prosthesis conditions.The results showed that the knee-ankle linkage prosthesis ensured the similar basic function with other passive thigh prostheses.Nevertheless,the knee-ankle linkage prosthesis produced a higher ankle dorsiflexion during pre-swim than passive transfemoral prosthesis,which facilitated forward rotation of the affected side and increased the overall stride length.Meanwhile,results of this chapter also indicated that gait coordination in knee-ankle linkage prosthesis was mainly fulfilled by the function of“active” plantarflex and dorsiflex of the artificial ankle joint.The prosthetic knee had little contribution to the coordination improvement and was similar to the passive prosthesis in terms of other functions,which should be improved.3.The effects of walking speed on gait coordination in amputees were investigated.In this study,patients wore their own passive transfemoral prostheses and walked at 1)medium speed(their preferred speed);2)faster speed;and 3)slower speed.Gait coordination were analyzed and compared among the conditions.The results showed that walking speed could influence gait coordination.Slow walking is more challenging for the patient’s movement control because of a higher movement control requirement.Adjustment of the hip joint control strategy is crucial to fulfill the gait requirements at different speeds.Additionally,this chapter also found that“preferred” walking speed is the optimal speed in which the patients showed more flexibility in joint motion and easier motor control.4.The muscular coordination of the patient’s intact limb was revealed.In this chapter,the patients walked with the passive transfemoral prostheses at their comfort speed.We analyzed the muscle forces of 24 muscles of the intact limbs through inverse dynamics and compared to those of abled people.The results showed that regulation of muscle coordination was one of the key factors for achieving different demands of joint moments.In addition,the higher flexion moment of the intact knee joints of amputees happed in the end of stance phase attributed little to the muscle coordination.The fixed joint passively balance the external extension moment,which were generated by ground reaction force.The patient’s long-term exposure to this high moment is responsible for the higher prevalence of knee pain or knee osteoarthritis.This chapter also found that the maximum muscle force of some muscles during gait was significantly lower in amputees than in abled people.The low level of muscular output during a long-term may result in weakness of muscle function and thus affect the motor control of patients.In summary,we conducted a systematic investigation of gait coordination for transfemoral amputees.The gait analysis of the transfemoral amputees is brought up to a multi-level study including the interactions of joint-to-joint and muscle-to-muscle.This study provides a new theoretical basis for future prosthetic design and clinic rehabilitation for the patients.