Body sway in below-knee amputees

The purpose of the present study was to test the hypothesis that below-knee amputees have less standing stability than normal persons. Twenty below-knee amputees were tested with the quantified Romberg test. All amputees below 59 years and all women above 59 years had a decreased sway compared with matched control groups of normal persons. Amputated men above 59 years did not show any difference in sway compared with the matched control group. Presuming that small sway excursions can be interpreted as a stable standing position, the study shows that a well fitted PTB-amputee stands at least as safely as a normal person.     

Running gait impulse asymmetries in below-knee amputees.

In running, large gait asymmetry is expected due to the inability of the foot prosthesis to comply with the kinematic demands and produce a powerful plantarflexion moment. In this work, interlimb asymmetry in below-knee (BK) amputee running gait was assessed for one rigid and three flexible keel prostheses, using vertical and anteroposterior ground reaction forces and respective impulses. Nine BK amputees and 6 controls participated in this study. The running speed was monitored by two light sensitive detectors while the ground reaction forces were measured with a Kistler force plate. Between the prosthetic side and the sound limb the impulse indicator showed greater asymmetry than the force. Interlimb asymmetry was very much present in all types of prosthesis tested but is less pronounced in the flexible keel prostheses. In the latter, the asymmetry may be associated with the force-time history modulation rather than its magnitude alone. Generally, the impulses better describe interlimb asymmetry and the forces allow a greater discrimination between prosthetic foot types.     

Computer aided design of prosthetic sockets for below-knee amputees

A computer-aided sculpting system for use in prosthetics is described. The prosthetist's sculpting tools now consist of a computer, a graphics terminal, a mouse and an on-screen moveable cursor. Accompanied by the system software, these tools allow systematic modification of a primitive socket using techniques analogous to those used by a prosthetist working with rasps and plaster.     

Dynamic electromyography in active and limited walking below-knee amputees

Walking electromyography was performed in 12 below-knee amputees, who were amputated for peripheral vascular insufficiency. All were at least 1 year post-surgery and had no problems with the fit of their prostheses. Seven were community walkers and five were limited household ambulators. The quadriceps and hamstring muscles exhibited electrical activity during 60% and 64.7% of the gait cycle, respectively, in the active walkers, compared with 44.6% and 53.8% in the limited walkers. Quadriceps muscle activity was initiated almost 10% earlier in the active walkers, while hamstring muscle initiation was similar in both groups. The active walkers were able to maintain quadriceps and increase hamstring muscle activity to compensate for their absent ankle motors, while the limited walkers showed decreased activity in both muscle group. The results of this preliminary study suggest that the dysvascular limited walking below-knee amputee does not use the quadriceps and hamstring muscles for propulsion during walking, and does not appear to reap the benefits of knee joint preservation.     

Functional evaluation by gait analysis of various ankle-foot assemblies used by below-knee amputees.

Twelve different prosthetic feet were tested by 10 male subjects with right below-knee amputations. Level walking with each prosthetic foot was investigated using a pair of force plates. Five parameters were selected to compare the functional characteristics of the feet: 1) step length, 2) walking velocity on the sound side in relation to the prosthetic side, 3) depth of valley in the pattern of the vertical component of the floor reaction force, 4) efficiency of the deceleration and acceleration by the prosthetic foot, and 5) irregular patterns in the wave form of the fore and aft components of the floor reaction force. Each of the above parameters was rated numerically. The total score of the objective evaluation attained by analysing the five parameters showed some coincidence to the results of subjective evaluation. However, a good correlation existed between the objective negative score and the subjective negative rating (p < 0.05). Non-axial feet developed recently, such as the SAFE II and Seattle Light feet achieved higher scores in the older age group, while single-axis feet, such as the LAPOC and Otto Bock feet achieved higher scores in the younger age group (p < 0.05).     

Gait kinematics in below-knee child amputees: a force plate analysis

A complete gait analysis was performed on six children with below-knee amputations to determine the kinematics and kinetics of amputee gait in children. A relatively new method of analysis--the inverse dynamic relationship--was used to determine the joint moments in the sagittal plane of the joints in the intact limb and the remaining portion of the amputated limb. The joint moments in the sagittal plane of the intact limb in the child amputee were found to be normal or below normal during level walking. From this study, it was concluded that providing a child amputee has a good prosthetic fit, there will be no increased forces across the joints of the intact or amputated limb and consequently no predisposition to premature degenerative arthritis.     

Experimental fittings of sockets for below-knee amputees using computer aided design and manufacturing techniques

The experiments showed that it is possible to successfully design a socket using a computer based socket model. Variability of results, however indicates the existence of shortcomings. These were identified as inadequacies in the caliper method used to measure the stumps; inability to make the sockets total contact; lack of flexibility of the design process in the Round #1 computer CASD system. It was shown by results of the MERU fittings that an iterative procedure in the hands of an inexperienced person would lead to a degree of success comparable to that achieved by experienced persons using judgement. Also indicated was that experienced prosthetists were able to transfer their skills to the CASD system. This is indicated by the fact that they achieved 5 Class IV results with 8 sockets as compared to 2 Class IV results with 10 sockets achieved by the inexperienced operator.     

The effect of footwear mass on the gait patterns of unilateral below-knee amputees

This study reports an investigation into the effect of shoe mass on the gait patterns of below-knee (BK) amputees. Ten established unilateral BK, patellar-tendon-bearing prosthesis wearers were assessed using a VICON system of gait analysis. Incremental masses of 50g (up to 200g) were added to the subjects' shoes and data captured as they walked along a 15m measurement field. Coefficients of symmetry of various parameters of the swing phase (knee frequency symmetry, swing time symmetry) were measured and their correlation was tested with the patient's preferred shoe mass and also their own shoe mass, all expressed as a proportion of body mass. The subjects' 'preferred' shoe mass (139-318g) showed the greatest symmetry in all the parameters examined (correlations 0.78-0.81 p less than 0.01 and less than 0.005), whereas there was no correlation between the subjects' own shoe mass (121-325g) and the symmetry coefficients measured.     

Early post-surgical prosthetic limb fitting in dysvascular below-knee amputees with a pre-fabricated temporary limb

Two consecutive series of patients undergoing below-knee amputation for peripheral vascular insufficiency were compared relative to the length of acute-care hospitalization and rehabilitation. The residual limb control group was treated with soft-surgical dressings and non-weight bearing ambulation with referral to the amputee clinic when the residual limb wound was "ready." The residual limb experimental group was treated with rigid plaster (cast) dressings with early post-surgical prosthetic limb fitting and progressive weight bearing ambulation. Acute-care hospitalization following amputation surgery averaged 27.7 days in the control group, and 23.7 days in the treated group. Patients were either re-admitted or transferred to a rehabilitation unit where hospitalization averaged 42.9 days in the control group and 14.1 days in the treated group. This resulted in a cost savings of almost $15,000 per patient based on present hospital fees. The results of this study suggest that early post-surgical prosthetic limb fitting not only hastens recovery amputation, but can be safe and cost effective.     

A Swedish knee-cage for stabilizing short below-knee stumps.

Stump length is an important factor in attaining successful prosthetic rehabilitation in below-knee (BK) amputees. Stability of the stump-prosthesis complex is impaired in the case of a stump shorter than 10 cm. Thus, fitting a prosthesis to a BK amputee with a stump which is very short often requires the use of different prosthetic techniques. In this work, the authors suggest the use of a Swedish knee-cage attached to a conventional patellar-tendon-bearing prosthesis as an alternative solution in the case of a short BK stump. Objective evaluation was performed by an analysis of gait and the foot-ground reaction forces. The results obtained indicate an improvement in all the measured parameters resulting from the modified stump-prosthesis complex.     

A CAD CAM method for custom below-knee sockets.

The purpose of this investigation was to develop a numerical method for fabricating prosthetic sockets for below-knee amputees. An optical/laser digitiser scans an amputee's stump and collects three dimensional numerical data describing the surface of the limb and describing specific modification site locations. The numerical data from the laser camera representing the stump and modification sites are altered by the prosthetist using a custom computer aided design software system running on a personal computer. Using the altered numerical data a programme is created for a high resolution numerically controlled milling machine and a mould is made. The prosthetist then fabricates a socket. While the system has been tested with below-knee amputees it has been designed for application in most areas of prosthetics and orthotics. Utilising this method 15 patients were fitted. All patients subjectively stated that their "computer designed" socket fitted better than their conventionally made socket. As the research progressed and experience was gained with the system patients were normally fitted with the first socket iteration. The system overcomes five limitations existing with some of the other numerical systems: 1) accurate high resolution surface topography, 2) specific identification of subject modification sites, 3) flexible, user friendly software, 4) high resolution numerically controlled milling, and 5) integrated expansion to other prosthetic and orthotic areas.     

Prosthesis-free solution for below-knee amputations

The Ilizarov fixator can be used as a bone regenerator to correct limb-length discrepancies in patients who require limb lengthening.A 17-year-old man presented with 12 cm of left lower-limb shortening and amputation at the left mid-forefoot region, which was the result of severe burns of the left lower limb at 2 years of age. The burns damaged the distal femoral, proximal, and distal tibial physes. Scarring around knee and leg acted as a bowstring and slowed normal longitudinal femoral and tibial bone growth. The patient wished to be prosthesis free. Limb lengthening was performed with the Ilizarov fixator. The patient became prosthesis free and was able to perform activities of daily living wearing normal footwear, which was possible because the patient had a good heel pad. The patient can walk on a normal limb with no prosthesis, the significant advantage being the right proprioceptive feedback it gives the patient during ambulation because it is sensate.This technique can be used in other patients with below-knee amputations in which the tibial amputated end can be given a myoplasty cover or padding nearly as good as a heel. Subsequently, tibiae can be lengthened, and patients can be made to bear weight on artificial heels.     

Cryopreserved saphenous vein allografts for below-knee lower extremity revascularization.

OBJECTIVE: Cryopreserved saphenous vein allografts have been offered as an alternative conduit for bypass in ischemic limbs. The authors examined the efficacy of this conduit for arterial bypass to the distal popliteal and tibial arteries in patients in whom autogenous vein was not available. SUMMARY BACKGROUND DATA: Previous experience with arterial and venous allografts has been unsatisfactory because of aneurysmal degeneration and poor patency. Endothelial loss and host rejection have been suggested as mechanisms of graft failure. Cryopreservation by modern techniques with rate controlled freezing, dimethyl sulfoxide (DMSO), and other cryopreservants, has addressed these issues and rekindled interest in vein allografts. METHODS: Over a period of more than 5 years, 115 cryopreserved vein allografts were implanted in 87 limbs to the distal popliteal (14) or tibial (101) arteries. The indication for surgery was rest pain in 56 procedures (49%), gangrene in 36 (31%), claudication in 21 (18%), and replacement of aneurysmal allografts in 2. Follow-up was 1 to 61 months (mean 25 months). RESULTS: There was no significant difference in patency related to site of proximal or distal anastomosis, patency of runoff vessels, use of anticoagulation, age, sex, diabetes, hypertension, smoking, indication, source of graft, or use of multiple segments. Revision was required in six grafts for aneurysmal dilatation. Histologic examination of explanted sections of allografts showed no immune response, and immunosuppressive drugs were not used. CONCLUSIONS: Although limb salvage has been satisfactory, long-term patency rates for cryopreserved vein allografts are poor when compared with autogenous vein. The cost of cryopreserved allografts far exceeds that of prosthetic grafts, for which comparable and superior results have been reported. Use of cryopreserved vein allografts should be reserved for situations in which adequate lengths of autogenous vein do not exist and the risk of infection of prosthetic grafts is high.     

A plaster-pylon technique for below-knee amputation

We reviewed 83 patients after below-knee amputation. In 56 with 69 amputations early management was by plaster-pylon. A plaster cast is applied in the operating room, and a pylon added one week later, after which full weight-bearing is allowed. We compared these patients with 27 who had soft bandaging. The 'healing' time was reduced from 98 days to 40 days, and there were no major complications in the plaster-pylon group. The technique is simple and cheap and can be used by paramedical staff without specialised training or equipment.