THE BIOMECHANICS OF PARTIAL FOOT AMPUTEE GAIT
Michael Dillon1 and T.M. Bach2
2North West Hospital, Melbourne, Australia
2, La Trobe University, Melbourne, Australia
A biomechanical analysis of the gair patterns of four normal and ten partial foot amputees including one chopart, five transmetatarsal (TMA), and four metaatarsophalangeal (MTP) amputees was undertaken in order to obtain basic kinetic and kinematic data. The Chopart amputee was fitted with a PTB clamshell prosthesis while the others were fitted with AFOs or EVA insoles.
Testing involved documentation of a medical history, physical examinationa and gait analysis usint VICON 3D motion analysis system and Kistler force platform. Affected limb kinetic and kinematic data were collected and anlaysed for the sagittal; plane only. kinematic and kinetic patterns were averaged within each group.
The results showed a significant psoitive correlation between residual foot length and centre of pressure (CP) excursion (r = .898) across the MTP and TMA amputees indicating that the EVA insloes and AFOs did not substantially resotre excursion of the CP. A significant relationship was found between residual foot length and peak plantarflexor power generation (r =.814). It appeared that once the metatarsal heads had been compromised, powere generation at the ankle was neglibible regardless of residuum length. The Chopart and TMA amputees showed substantial alterations in the normal kinetic patterns seen at the hip and the knee. The patterns observed at the other lower limb joints were consistent with an attempt to compensate for a lack of power generation at the ankle. No significant alterations were observed in passive ROM between groups (F = 1.56, df = 12; p=.2572). The varaibility observed within groups would make socket prescription based on ankle ROM inappropriate. The successful utilisation of the available ankle motion, measured by power generation at the ankle would appear to be a better prescription principle.
The gait patterns observed may have been confounded by the type of prosthetic fitting. Further research shoudl assess the biomechanical effects of prosthetic fitting.
BIOMECHANICAL ANALYSIS OF THE GAIT OF CHILDREN WITH PROXIMAL FEMORAL FOCAL DEFICIENCY (PFFD)
Fatone, S.1, Bach, T.M.1, and Graham, H.K.2
1La Trobe University, Melbourne, Australia
2Royal Children's Hospital, Melbourne, Australia
PFFD is a rare, congenital, partial limb deficiency of unknown aetiology that affects the formation of the proximal femur and acetabulum. The main biomechanical losses resulting are: (1) a limb length discrepancy of approximately 50% or more, (2) severe malrotation, (3) inadequate proximal musculature, and (4) instability of the hip and knee joints. The variable nature of the deficiency and the small number of diagnosed cases contribute to the lack of research in this area. The purpose of this study was to analyse the gait of children with PFFD and establish a data base for future study.
Four limb deficient (PFFD) children were analysed using a VICON 3D motion analysis system and AMTI force plates. Retroreflective markers were placed on the pelvis and lower limbs. An OXYLOG portable consumption meter was used to measure walking oxygen consumption.
Analysis of the results revealed large variability in kinematic and kinetic data between subjects. This variability may have been a result of differences in age, the severity of the deficiency, prosthetic prescription and type of surgical management. Pelvic kinematics were abnormal and extreme in range. Overall orientation of the pelvis was the same across subjects (excess anterior pelvic tilt, elevation and internal rotation of the involved side). Further investigation of the implications of excess pelvic motion on long term back problems and possible prosthetic modifications to stabilize the pelvis, appear warranted. Lower walking velocities were recorded during energy expenditure testing. The difference between velocities measured by the VICON and during energy expenditure testing may reflect the effects of encumbrance by testing equipment during ambulation.
INTEROBSERVER RELIABILITY OF OBSERVATIONAL GAIT ANALYSIS IN TRANSTIBIAL PROSTHESIS ALIGNMENT.
Ford, N. E., Poole, B. D., and Bach, T. M.
La Trobe University, Melbourne, Australia
Reliability in clinical decision making is essential for high standards of professional practice. This investigation was carried out to determine the ability of prosthetists to detect gait deviations requiring alignment changes and the extent to which prosthetists agree on these decisions.
Nine experienced prosthetic clinicians who participated in the study viewed videotaped footage of three amputee subjects ambulating on optimally aligned or intentionally misaligned prostheses. Clinicians were required to assess the videotaped sequences and indicate the direction and magnitude of the alignment correction required. In a second phase, clinicians were asked to make the same decisions after viewing videotaped sequences and being provided with subjective feedback from the amputee subjects which was obtained at the time of videotape recording.
Cohen's Kappa was used to express inter-observer agreement rates without and with subjective feedback from the subjects. Kappas of 0.36 for mediolateral and 0.08 for anteroposterior alignment changes indicated poor to slight agreement without subject feedback. When subject feedback was provided, kappas improved to 0.46 and 0.30 for mediolateral and anteroposterior alignments respectively. Only decisions about mediolateral alignment changes with subject feedback could be considered moderately reliable.
The study raised concerns about the reliability of observational gait analysis as a tool for dynamic alignment of transtibial prostheses. The study indicated that prosthetists are more reliable in judging mediolateral alignment changes than anteroposterior changes and that subjective feedback from the client is an important adjunct to observation. Further investigations designed to identify causes of this unreliability and improved methods of observational gait analysis and training for this task are necessary.
Jarrott, T.J., O'Keefe, C.J., and Bach, T.M.
La Trobe University, Melbourne, Australia
The purpose of this investigation was to determine the effects of a dynamic elastic response prosthetic foot (the SAFE II) on gait patterns of the transtibial amputee. Four unilateral transtibial amputees were fitted randomly with either a SACH or SAFE II foot. Following a one week familiarisation period, electromyographic activity of the quadriceps and hamstrings muscle groups was recorded during gait utilising surface electrodes. Kinematic and kinetic data was also collected using a 3D VICON motion analysis system. After the first testing session, subjects were fitted with the alternate prosthetic foot and the above process was repeated. Comparisons were made between the two foot types for each subject.
The results of this investigation highlighted the individual compensatory mechanisms adopted by each amputee. Varying adaptations to each prosthetic foot type were observed. However, some general trends did appear. Quadriceps activity on the prosthetic limb was slightly reduced in comparison with the sound limb. This contradicts the results of other investigators, who found increased quadriceps and hamstrings activity on the prosthetic limb. When comparing the two different types of prosthetic feet, the SAFE II foot resulted in a slight increase in quadriceps activity in the majority of subjects. However, this was not noticeable in averaged patterns due to the large amount of variability between subjects. This increased quadriceps activity was associated with more normal knee extensor moment patterns with the SAFE II foot.
Reduced hamstrings muscle activity was also observed on the prosthetic limb compared to the sound limb, again in contrast to the results of previous investigators. This observation was more evident when the SAFE II foot was worn. The SAFE II foot may provide propulsion at push off that decreases the requirement of the prosthetic limb hamstring muscles.
Acknowledgement: The prosthetic feet used in this study were generously donated by G. W. Masson & Sons, Melbourne.
Retschko, P. , Wood, M. and Bach, T. M.
La Trobe University, Melbourne, Australia
The purpose of this study was to compare the effects of weight bearing (WB) and non-weight-bearing (NWB) casting techniques on shock absorption in foot orthoses.
Three young adult male subjects with no previous history of heel or foot pathology were cast bilaterally in the neutral position for the WB and NWB conditions. In the WB cast, 15% of body weight was applied through the foot during casting. The resultant positives were cleaned but not modified in any way. Polypropylene (3.2 mm) was vacuum formed over the casts and standard UCBL trim lines applied.
Shock absorption was measured using an accelerometer taped firmly to the tibial flare of the right leg. During impact tests, the leg was flexed to ninety degrees and braced firmly against a brick wall. A 2kg pendular hammer was released from a set position to strike the heel of the subject. An accelerometer on the hammer measured acceleration on impact. An acceleration damping ratio (ADR) was computed as the ratio of the peak leg acceleration to the peak hammer acceleration. During dynamic gait tests, acceleration of the leg was recorded and averaged over a five second period which usually included four heel strike transients.
Results for the walking trial indicated a 14% reduction in heel strike acceleration transients for the NWB orthosis compared to the WB orthosis although this trend was not statistically significant (t=2.6, p=0.12). Results for the impact tests showed a similar difference (16% lower for the NWB orthosis) which was statistically significant, (t=16.8, p=0.003).
The fabrication of UCBL foot orthoses from NWB casts significantly reduces the transmission of shock to the lower limb at heel strike by about 15%. These results can be explained by the containment of the elastic adipose tissue of the heel pad.
Cecilia Tan1, Timothy M. Bach2, Anne-Maree Keenan3
1Prince of Wales Hospital, Sydney, Australia
2La Trobe University, Melbourne, Australia
3University of Western Sydney, Sydney, Australia
This study compared biomechanical effects of two different approaches to design of foot orthoses. The orthoses investigated were a semi-rigid design commonly manufactured by Orthotists and a 25š inverted design commonly manufactured by podiatrists. Eleven patients who exhibited excessive pronation were studied while running on a treadmill. Two dimensional, high speed motion picture analysis was used to examine rearfoot mechanics and oxygen consumption was used to examine running economy. The study consisted of two measurement sessions, after a three week accommodation period, for each pair of orthoses. The rearfoot variables included: maximum calcaneus angle, pronation angle at touchdown, maximum pronation angle, pronation range of motion and maximum pronation velocity.
There were no differences in rearfoot variables between any conditions (semi-rigid, 25š inverted device and no orthosis). Based on this result it was concluded there was no difference in rearfoot mechanics between the two orthoses or between orthosis and no orthosis conditions. In addition, there was no difference in oxygen consumption between the two orthosis connditions indicating no difference in running economy. Despite this failure to detect differences, all subjects reported a subjective improvement in running with the use of orthoses.
The exact mechanisms by which foot orthoses affect the body are unclear. Additional research is necessary to identify both the mechanisms and the effects responsible for the clinical success of foot orthoses and to evalute different designs and differences between designs.
