Effect of arterial flow on muscle atrophy / 生物医学工程学杂志

This study analyzed the inherent relation between arterial blood mass flow and muscle atrophy of residual limb to provide some necessary information and theoretical support for the clinical rehabilitation of lower limb amputees. Three-dimensional arterial model reconstruction was performed on both intact side and residual limb of a unilateral transfemoral amputee who is the subject. Then hemodynamic calculation was carried out to comparatively analyze the mass flow state at each arterial outlet of both lower extremities. The muscle atrophy ratio of residual limb was calculated by measuring the cross-sectional area of bilateral muscles. Based on the blood supply relationship, the correlation between arterial blood flow reduction ratio and muscle atrophy ratio was discussed. The results showed that the mass flow of superficial femoral arteries and lateral circumflex femoral arteries severely reduced. Meanwhile rectus femoris, vastus lateralis and vastus medialis which were fed by these arteries showed great atrophy too. On the contrary, the mass flow of deep femoral arteries and medial femoral circumflex arteries slightly reduced. Meanwhile gracilis, adductor longus, long head of biceps which were fed by these arteries showed mild atrophy too. These results indicated that there might be a positive and promotion correlation between the muscle atrophy ratio and the blood mass flow reduction ratio of residual limb during rehabilitation.

A numerical analysis of the effects of the lower-limb prosthetic socket on muscle atrophy of the residual limb / 生物医学工程学杂志

Muscle atrophy of the residual limb after lower-limb amputation is a disadvantage of amputees' rehabilitation. To investigate the biomechanics mechanism of muscle atrophy of the residual limb, we built a finite element model of a residual limb including muscle, skeletons and main vessels based on magnetic resonance images of a trans-femoral amputee, and studied the biomechanics effects of the socket of the lower-limb prosthesis on the soft tissue and vessels in the residual limb. It was found that the descending branch of the lateral femoral circumflex artery suffered the most serious constriction due to the extrusion, while that of the deep femoral artery was comparatively light. Besides, the degree of the constriction of the descending branch of the lateral femoral circumflex vein, femoral vein and deep femoral vein decreased in turn, and that of the great saphenous vein was serious. The stress-strain in the anterior femoral muscle group were highest, while the stress concentration of the inferior muscle group was observed at the end of the thighbone, and other biomechanical indicators at the inferior region were also high. This study validated that the extrusion of the socket on the vessels could cause muscle atrophy to some degree, and provided theoretical references for learning the mechanism of muscle atrophy in residual limb and its effective preventive measures.

Residual Limb Volume Change in the Early Post-operative Phase after Below-the-knee Amputation : A Report of Three Cases / The Japanese Journal of Rehabilitation Medicine

<p>For lower limb amputees, good prosthetic fittings are important for wearing prostheses while ensuring gait stability, without skin breakdown. Poor prosthetic fittings tend to occur in the early stage after amputation because of significant changes in residual limb volume. We measured the extent of change in residual limb volume in three below-the-knee amputees by using computed tomography. The measurements were performed before and after inpatient rehabilitation for the first prosthesis. The measurement showed a remarkable change in residual limb volume in a highly active amputee without complications. In contrast, the change in residual limb volume was small in two less active below-the-knee amputees with serious complications, such as heart and renal failures. Generally, to maintain good prosthetic fittings, the first prostheses should be made during inpatient rehabilitation to facilitate maturation of the residual limbs. For the less active below-knee amputees, the prostheses could be made in the outpatient settings because the volume fluctuations of their residual limbs are small and the functional requirements for their daily living are modest.</p>

Non-linear finite element analysis on trans-femoral residual limb during gait phase / 医用生物力学

Objective To investigate biomechanical properties of the contact interface between residual limb and prosthetic socket of the transfemoral amputee during walking by using threedimensional (3D) finite element analysis method, so as to provide references for establishing the complete system of measurement, design and evaluation on prosthetic socket. Methods Based on CT images, two 3D geometric models of a trans-femoral amputee including the femur, soft tissues and transfemoral socket was established, with soft tissues defined as non-linear hyper-elastic and linear elastic material, respectively. The behaviors of the interface between trans-femoral residual limb and prosthetic socket were defined as nonlinear contact. Dynamic loads on the knee joint were applied on distal ends of both the hyper-elastic model and linear elastic model to simulate loading on residual limb-prosthetic socket system during heel strike, mid-stance and toe off phase in a gait cycle, respectively. The stress distributions on interface between trans-femoral residual limb and prosthetic socket were calculated to compare and analyze the effects of different mechanical properties (i.e. hyper-elasticity and linear elasticity) of the femur soft tissue on biomechanical behaviors of the interface. Results For both the hyper-elastic model and linear elastic model, the peak contact pressures were all located on the distal end of the residual femur during different gait phases. The peak contact pressure on the interface of the hyper-elastic model during heel strike, mid-stance and toe off phase was 55.80, 47.63 and 50.44 kPa, respectively, while that on linear elastic model was increased by two times, being 149.86, 118.55 and 139.68 kPa, respectively. Simulation on longitudinal and circumferential shear stress distributions at the limb-socket interface showed that stress on the interface was higher at the distal end of soft tissue during different gait phases. From heel strike to toe off phase, some pressures were transferred from the rear edge to the front edge of the socket. Conclusions The pressure and shear stress distributions on the contact interface between transfemoral residual limb and prosthetic socket were different during different gait phases, thus the relative mechanical properties should be considered in the socket design.

Finite element analysis of interface pressure over the above knee residual limb at mid stance with pre-stress / 医用生物力学

Objective To investigate the interface pressure on above knee residual limb at mid stance during walking，so as to provide basis for the establishment of measurement and evaluation system for the above-knee socket. Methods Based on CT images of the femur, soft tissue and above knee socket of the patient with residual limb, the three-dimensional model was first built, and then to assemble them according to changes of the hip joint in a gait cycle. The finite element model was then established to simulate the loading conditions at mid stance during a gait cycle, and the effect of pre-stress was investigated by nonlinear large deformation analysis. Results If considering the effects such as joint changes and pre-stress, the maximum value by calculation for normal interface pressure distributed on the terminal of stump was 257.66 kPa, which could better match the maximum stress actually measured by the Mflex Sensor Distributing System as 258.9 kPa. Conclusions The three-dimensional finite element model with considering the factors such as hip joint change, pre-stress and friction could effectively simulate the stress condition of patient with residual limb during walking.

Clinical analysis and treatment of poor stumps after lower limb amputation / 中华物理医学与康复杂志

Objective To analyze the cause of poor stumps and to introduce the methods of treatment, so that the rate of poor stump would be decreased. Methods We evaluate 109 cases of lower limb amputees with a total of 110 residual limbs. Evaluation content included: Skin (scars, dermatitis, folliculitis, open wounds, tactile and pain sensation); characteristics of residual limb shape (conical, bulbous, edematous cylindrical); strength of the stump; range of motion of the residual limb; muscle tone; strength of the stump and phantom pain. Results Forty-six cases out of 110 are unqualified. All poor stumps can be fit with the prosthetic through rehabilitation care. Conclusion Poor stumps are those unsuitable for fitting of the prosthetic. Special treatments are required to fit them with prosthetic. Because of the improvement of the prosthetic technology, length of the residual limb is no longer the main obstruction for fitting prosthetic. Instead the skin soft tissue condition of the stump is becoming the main reason of failure in fitting the prosthetic.