QUADRICEPS ATROPHY IN THE TRANSTIBIAL AMPUTEE: THE EFFECT OF LINER TYPE ON MUSCLE ACTIVATION PATTERNS IN NORMAL ACTIVITIES
Jessie Beard, BP&O(Hons)
Supervisor: Dr. T. M. Bach, National Centre for Prosthetics and Orthotics, La Trobe University
Introduction
Thigh muscle atrophy on the amputated limb is common in transtibial amputees (TTA). This atrophy is somewhat localised to the quadriceps muscle group1 and is thought to be due to disuse of this muscle in daily life. TTAs have been shown to be able to produce higher peak mean torques when wearing a silicon liner compared to a pelite liner and stair ambulation has been reported to be easier whilst wearing a silicon liner. Increases in thigh circumference have been found in TTAs wearing silicon liners (Renstrom et al., 1983). The purpose of this study was to investigate the relationship between liner type, thigh muscle atrophy and peak muscle activation levels during various common activities.
Method
Ten able-bodied (AB) subjects and 16 unilateral TTAs, 7 wearing silicon liners and 9 wearing pelite liners, participated in this study. Peak EMG data was recorded bilaterally for the vastus lateralis (VL) and biceps femoris long head (BF) muscles during the activities of level walking, sitting, standing, ascending and descending stairs. Data was analysed using three-way ANOVAs with age entered as a covariate. Thigh circumference was recorded bilaterally at the height of the VL electrode. Thigh circumference measurements were corrected for height and analysed using a one-way ANOVA.
Results & Discussion
The activities of stair ascent and sit to stand required significantly higher peak EMG of the VL compared to walking in the AB group (p<0.01). Figure 1 shows that the prosthetic limb displayed reduced peak activation compared to the sound limb in these activities.
The silicon prosthetic limb had peak EMG levels higher than the pelite prosthetic limb in sit to stand and ascending stairs (p<0.01) indicating that that silicon liners allow better utilisation of the VL muscle during these activities. Atrophy on the silicon prosthetic limb was less than that on the pelite prosthetic limb. Peak BF was was not significantly higher than in normal walking in any of the activities tested. This finding is consistent with the finding that atrophy is mainly confined to the quadriceps group.
Conclusion
Results indicate that TTAs utilise their quadriceps musculature on the amputated side more effectively in activities requiring high peak quadriceps activity when wearing a silicon liner as compared to a pelite liner.
References
Dasgupta et al., (1997) Occ. Med. 47(4): 228-236
Renstrom et al., (1983) Scand. J. Rehab Med. 9: 150-162
Figure 1: Peak vastus lateralis (VL) EMG during sit to stand and stair ascent activities.
EFFECTIVENESS OF DYNAMIC ANKLE-FOOT ORTHOSES (DAFO) IN THE MANAGEMENT OF SPASTIC CEREBRAL PALSY GAIT
Kirrily Brown, BP&O(Hons)
Supervisors:
Dr. T. M. Bach,National Centre for Prosthetics and Orthotics, La
Trobe University
Ms. R. Boyd, Royal Children's Hospital, Melbourne
Introduction
Dynamic ankle-foot orthoses (DAFOs) have in the past three decades, being reported in the paediatric cerebral palsy and adult hemiplegic literature as a form of orthotic intervention. Based on inhibitive casting techniques, DAFOs are utilised as an adjunct to physical therapy. Although widely prescribed overseas, DAFOs are yet to be recognised as a viable alternative to current AFO prescription in Australia. Previous research into this area has attempted to assess DAFO effectiveness via the measurement of functional skills and gait characteristics. Focused on paediatric CP and adult hemiplegic populations, previous investigations lack consistency in their results and methodology.
The aim of this investigation was to examine the effectiveness of DAFOs in the management of children with spastic cerebral palsy. Based on the results of previous research it was hypothesised that compared to a conventional AFO, subjects gait kinematics and kinetics will be no different when wearing a DAFO.
Method and Apparatus
Two subjects were recruited to participate in this study with the assistance of the Hugh Williamson Gait Laboratory at the Royal Children's Hospital in Melbourne. Three-dimensional gait analysis was undertaken utilising a VICON 370 motion analysis system and concealed force plate data.
Conventional AFO fit was assessed as adequate and DAFOs fabricated. Gait analysis was performed after the subjects randomly wore the DAFOs and AFOs on alternate days for a two week period. Dynamic trails were randomly collected for the DAFO, conventional AFO and a shoes condition.
A subjective questionnaire was utilised in an attempt to gauge feedback with regard to DAFO and DAFO. Parents were asked to rate factors such as comfort and cosmesis on a five point scale.
Results and Discussion
Case study 1.
Subject AWP displayed more normalised ankle pattern in shoes, but better baseline function in the DAFO and AFO conditions. Due to orthosis restriction there was uncontrolled rocker transition and a decrease in ankle power generation at double support. This decrease in power generation was compensated for by an increase in hip power generation at IC. Here quadriceps were acting to "pull" the limb off the ground, rather than the plantarflexors "pushing" the limb off the ground. Most importantly for this subject an increase in knee extension was displayed in the DAFO and AFO conditions, therefore acting to stretch the tight hamstrings musculature.
Case Study 2.
Gait analysis of subject JDW indicates that in this instance DAFOs did not appear to provide more normalised biomechanical function when compared to the AFO. In the AFO JDW displayed normalised ankle patterns, with smooth1st-2nd rocker transition. Relatively normal ankle power generation was evident as was knee hyperextension control.
In reference to subjective questionnaire feedback, DAFOs were the preferred form of orthotic intervention. Compared to conventional AFOs, DAFOs were superior in comfort, cosmesis, subject compliance, and function. However, increased difficulties were experienced in donning and doffing the orthosis, and placing the DAFO into footwear.
Conclusion
Compared with conventional AFOs, subjects gait kinematics and kinetics are altered when wearing DAFOs. In one case DAFOs were identified as a possible form of orthotic intervention, while for another an unsuitable option.
Although the results of this study do not provide definitive support for the use of DAFOs, possible areas for further research were identified. These areas may include appropriate determination of DAFO prescription populations, and direct measurement of DAFO design on hypertonicity via electrophysiological means.
PRESSURE SENSITIVITY AND PAIN THRESHOLDS IN THE RHEUMATOID FOOT
Denise FetterBP&O(Hons)
Supervisors:
Ms. M. C. Hodge, National Centre for Prosthetics and Orthotics, La
Trobe University
Dr. T. M. Bach,National Centre for Prosthetics and Orthotics, La
Trobe University
Introduction
Previous research has established that up to 42% of Rheumatoid Arthritis (RA) sufferers experience peripheral neuropathy (O'Brien et al., 1997). However, this research has failed to address the clinical fact that peripheral neuropathies in adults with RA are more severe in the lower limbs and usually affect sensory nerve function more than motor nerve function. RA affects the feet of 85% of RA sufferers (D'Amico, 1976) with 90% of those patients experiencing foot pain throughout the disease process (O'Brien et al., 1997). McGuigan and associates (1983) investigated the relationship between foot pain and sensory nerve function and failed to identify significant findings.
The aim of this study was to investigate the following hypotheses:
Method
Ten RA subjects and ten age- and sex-matched control subjects were recruited. The age, weight, experiences of paraesthesiae and callus pattern were recorded. The disease duration of all RA subjects was also recorded.
Both feet of each subject were tested. Each foot was mapped with the 19 plantar regions to be tested and the subjects' view of their feet was obstructed. Five Touch Test Evaluators (Semmes-Weinstein monofilaments) were used to test the pressure sensitivity of each subjects' feet. Subjects were instructed to indicate when they felt the application of a monofilament. Each monofilament was applied perpendicular to the skin at each region until all regions recorded a positive response.
The pain threshold at each region was measured using a Mecmesin force gauge applied perpendicular to the skin surface. Subjects indicated when the pain response was initiated and the force was removed. The maximal force applied at each region was recorded. The data was analysed using multiple ANOVA's and Spearman's Rank Order Correlations. A significance level of alpha = 0.05 was set for all analyses.
Results and Discussion
A significant effect of region effect was found for pressure sensitivity. Post hoc analysis identified that the hindfoot was significantly less sensitive than the rest of the foot, the distal forefoot was significantly less sensitive than the midfoot and the distal forefoot was less sensitive than the toes in the RA group only.
Statistically significant group and region effects were identified for the pain threshold data. Significant differences exist between the toes and distal forefoot, toes and midfoot and hindfoot and all other regions.
Significant correlation coefficients were also obtained for both groups, indicating that pressure sensitivity is predictive of pain thresholds in both groups. However, the two groups were not significantly different from one another.
Thus, it was found that sensory nerve function in the RA group was altered from normal. The findings challenge common clinical belief and show that sensory nerve function alters to protect the RA foot from injury.
Conclusion
RA significantly affects sensory nerve function. The knowledge gained through this study can be used to improve orthotic management of the RA foot, thereby improving the quality of life of RA sufferers.
References
D'Amico, J.C. J. American Podiatry Ass. Vol 66(4), April, 1976
McGuigan, L. et al. Annals of the Rheumatic Diseases. Vol 42,
1983
O'Brien, T.S. et al. Clinical Orthopaedics and Related Research. No.
340, July 1997
THE EFFECT OF PROSTHETIC SOCKET CONSTRUCTION ON STUMP TEMPERATURE
Geoff Hill, BP&O(Hons)
Supervisors:
Dr. T. M. Bach,National Centre for Prosthetics and Orthotics, La
Trobe University
Mr. David Lee Gow, Caulfield General Medical Centre, Melbourne
Introduction
Wearing a prosthetic socket may cause the stump to experience elevated temperatures. This may be uncomfortable and may influence other aspects of health such as sweating, healing, blood supply, stump integrity, pain and oedema. A model has been developed which uses mathematical descriptions of heat flow to quantify the effects of socket construction on stump temperature. This model predicts that socket thickness will have little impact on stump temperature due to:
The model can be challenged on a number of issues. These challenges mean that experimental verification of the model is necessary. This study aims to do this.
Method
Six sockets were made for a single subject. These sockets were each tested under three environmental conditions
Socket and liner thicknesses were measured. Thermal conductivities were obtained from published sources. Socket temperature was obtained from the average of four thermocouples taped to the residual limb. Correlations between predicted and measured socket temperatures were calculated. Accuracy was estimated by the average magnitude of difference between predicted and measured temperature.
Results and Discussion
Correlation coefficients between predicted and measured temperature were:
The range of measured temperatures was greater than predicted. Accuracies were:
Adjusting the parameters of the model resulted in improvement in the mean accuracy to:
The model can provide reasonable estimations of stump temperature, in still air, for this subject. These results may not be generalisable to amputees with altered physiology. The model identifies the major determinants of stump temperature as being the number of layers in the prosthesis and the thickness and thermal conductivity of those layers. However the boundary layer does not reduce differences between socket constructions as much as predicted. Identifying these factors allows comparisons between prostheses to be made objectively.
Conclusion
The model provides reasonable accuracy for static subjects with normal physiology. The role of the boundary layer requires further investigation. The determinants of stump temperature have been sufficiently well identified to allow comparisons to be made between socket constructions. The model does not apply to dynamic situations.
References
Lee Gow, D., (1997). Prediction of residual limb/prosthetic socket interface temperature. Masters thesis. University of Salford, UK.
AN INVESTIGATION OF PROPRIOCEPTION IN TRANSRADIAL PROSTHESIS USERS AND ABLE BODIED SUBJECTS
Camille Shanahan, BP&O(Hons)
Supervisor: Dr. D. K. Rogers, School of Human Biosciences, La Trobe University
Introduction
It is often assumed that transradial amputees (TRAs) suffer a loss in proprioception on their limb deficient side. This decreased proprioception is assumed due to the loss of proprioceptive mechanisms distal to the point of limb deficiency. The full effect of these distal mechanisms on positioning ability at the elbow joint is unknown.
A relationship between loading of the limb and positioning (matching) accuracy of the limb has been indicated (McCloskey 1973, Worringham et al 1985, Watson et al 1984). Loading conditions of prosthetic forearms are consistently variable. The weight of prosthetic and contralateral forearm is most often not equal and there is no standard weight of transradial prostheses. It was hypothesised that weighting conditions of the prosthetic forearm may have an effect on the limb positioning accuracy of the prosthetic user.
The present study aimed to quantify the loss of proprioception in transradial (TR) subjects compared to able bodied subjects.
Method
Six able bodied and five TR subjects were recruited. All TR subjects were body-powered users with voluntary opening terminal devices and sound contralateral limb. Testing involved elbow angle matching tasks, in the horizontal and vertical planes, at 700 and 1000 of elbow flexion and a range of forearm weighting conditions was used. Mean matching error and variable matching error data were analysed using one, three and four way ANOVAs.
Results and Discussion
In subjects normal weighting conditions no differences in mean or variable matching error were found between the two groups (p=0.29 and p=0.07 respectively). The only difference between the two groups for all weighting conditions was a decreased 0.850 variable error for the able bodied group. The lack of difference in elbow angle matching accuracy between the groups indicates a recalibration of the proprioceptive system in TRAs following limb loss.
The only other difference between the groups was the transradial group were found to be less accurate than the able bodied group at 700 in the vertical plane (p=0.04). The finding of greatly increased mean error and variable error by the TR group at 700 in the vertical plane is probably due to an impingement of the prosthetic socket on the cubital fold. This increased matching error indicates decreased positioning accuracy in activities at this inner range of flexion, in particular when performing hand to mouth activities. Thus the clinician should be aware of providing low anterior socket trim lines and minimising socket movement in relation to the residual limb.
Decreased reliance on sight and increased coordination of bilateral activities have been noted as important areas for improvement in TR prosthetic prostheses (Atkins et al 1984). The findings of this study indicate that there is little if any deficit in proprioception in TRA when compared to able bodied subjects. Further study is required to show how positioning of the prosthetic side may be improved. Activities requiring less conscious attention and/or more complex tasks are possibilities for further research.
TRA show little difference in elbow angle matching ability when compared to able bodied subjects. Differences in matching abilities appear to occur only in conditions of the extreme inner range of flexion in the vertical plane. This difference is most probably occurring due to the impact of the prosthetic socket on the activity rather than any physiological difference between the two groups.
References
Atkins D.J; et al. (1984) JPO 8.1: 2-11.
McCloskey, D.I. et al. (1973) Brain Research. vol. 63: 119-131.
Worringham, C.J et al. (1985) Exp. Brain Res. vol. 61: 38 - 42.
Watson, J.D.G., et al. (1984) Beh. Brain Research. vol. 13: 267-271.
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Last Modified March 25, 1999