Background: To undergo a lower limb amputation is a traumatic experience affecting the individual on physical as well as psychological levels and often leading to limitations in a person´s daily life. Following an amputation individual often receive a prosthesis to address impairments in mobility and functioning. The mechanical properties of the prosthesis can vary, and the choice of specific components to include in the device has been demonstrated to influence patient outcomes. Studies investigating the relative effects of different prosthetic knee components have generally focused upon physical and biomechanical outcomes, providing a rather narrow view of health-related states in prosthetic users. There is a need to view health and wellbeing of prosthetic users from a broader perspective by evaluating outcomes that reflect a variety of different factors that can influence their functioning.

Aim: The overall aim of this thesis was to describe and compare functioning in individuals with a trans-femoral amputation or knee disarticulation and to evaluate the relative effects of using non-microprocessor-controlled prosthetic knees (non-MPK) or microprocessor-controlled prosthetic knees (MPK).

Methods: The four studies presented in this thesis used a cross-sectional, quantitative design with different types of data collection methods. These included self-report measures, capacity tests, a survey with two questionnaires and a measure of cortical brain activity during normal level waking and while performing a secondary task. One group of 42 individuals with lowerlimb amputations, using a prosthetic knee with or without microprocessor-control was included in the survey study. Another group of 29 individuals with a lower limb amputation, using a prosthetic knee with or without a microprocessor-control and a control group (n=16) participated in the remaining studies. Statistical tests were used to compare differences between groups using different knee joints, between prosthesis users and controls.

Results: Individuals using a non-MPK had lower self-reported mobility and balance confidence as well as poorer results on mobility tests compared to those using an MPK. Results revealed no significant differences in self-rated health, daily step count or general self-efficacy. Increased cortical brain activity was seen in frontal cortex in individuals using a non-MPK in single-task walking compare to the MPK group and controls. A significant increase in brain activity was also seen in prefrontal cortex in dual-task walking compared to single-task walking in those walking with an MPK and controls.

Conclusion: Combined results of all four studies suggest that persons provided with an MPK had better mobility, both self-rated and objectively evaluated, and better self-rated balance confidence than those who were using a non-MPK. Results also showed that an individual’s belief in their own ability was associated with the number of hours they use their prosthesis per week. Participants using a non-MPK had higher levels of cortical brain activity in the frontal cortex during walking, suggesting that the attentional demand required to walk was greater than for individuals using an MPK. Of particular interest for health professionals involved in prosthetic rehabilitation was the finding that significant increases in attentional demand were not always reflected in temporospatial gait parameters. This suggests that cognitive demands may not always be reflected in variables that are commonly evaluated in the clinical setting.

OBJECTIVE: To explore cognitive load in people with transfemoral amputations fitted with socket or bone-anchored prostheses by describing activity in the left and right dorsolateral prefrontal cortices during single- and dual-task walking.

DESIGN: Cross-sectional pilot study.

PATIENTS: 8 socket prosthesis users and 8 bone-anchored prosthesis users. All were fitted with microprocessor-controlled prosthetic knees.

METHODS: Participants answered self-report questionnaires and performed gait tests during 1 single-task walking condition and 2 dual-task walking conditions. While walking, activity in the dorsolateral prefrontal cortex was measured using functional near-infrared spectroscopy. Cognitive load was investigated for each participant by exploring the relative concentration of oxygenated haemoglobin in the left and right dorsolateral prefrontal cortex. Symmetry of brain activity was investigated by calculating a laterality index.

RESULTS: Self-report measures and basic gait variables did not show differences between the groups. No obvious between-group differences were observed in the relative concentration of oxygenated haemoglobin for any walking condition. There was a tendency towards more right-side brain activity for participants using a socket prosthesis during dual-task conditions.

CONCLUSIONS: This pilot study did not identify substantial differences in cognitive load or lateralization between socket prosthesis users and bone-anchored prosthesis users.

Purpose: To measure self-efficacy in a group of individuals who have undergone a lower-limb amputation and investigate the relationship between self-efficacy and prosthetic-specific outcomes including prosthetic use, mobility, amputation-related problems and global health. A second purpose was to examine if differences exist in outcomes based upon the type of prosthetic knee unit being used.

Method: Cross-sectional study using the General Self-Efficacy (GSE) Scale and the Questionnaire for Persons with a Transfemoral Amputation (Q-TFA). Forty-two individuals participated in the study. Twenty-three used a non-microprocessor-controlled prosthetic knee joint (non-MPK) and 19 used a microprocessor-controlled prosthetic knee joint (MPK).

Results: The study sample had quite high GSE scores (32/40). GSE scores were significantly correlated to the Q-TFA prosthetic use, mobility and problem scores. High GSE scores were related to higher levels of prosthetic use, mobility, global scores and negatively related to problem score. No significant difference was observed between individuals using a non-MPK versus MPK joints. Conclusions: Individuals with high self-efficacy used their prosthesis to a higher degree and high self-efficacy was related to higher level of mobility, global scores and fewer problems related to the amputation in individuals who have undergone a lower-limb amputation and were using a non-MPK or MPK knee. Implications for rehabilitationPerceived self-efficacy has has been shown to be related to quality of life, prosthetic mobility and capability as well as social activities in daily life. Prosthetic rehabilitation is primary focusing on physical improvement rather than psychological interventions. More attention should be directed towards the relationship between self-efficacy and prosthetic related outcomes during prosthetic rehabilitation after a lower-limb amputation. 

BACKGROUND

Walking with a lower-limb prosthesis while performing a secondary task (dual-tasking) has been suggested to increase demand on attentional resources, negatively affecting balance and gait performance.[1, 2] Brain imaging research has suggested that microprocessor-controlled prosthetic knees (MPKs) reduce attentional demands during single-task walking.[3] To date the effects of MPK on brain activity during dual-task walking has not been investigated.

AIM

To evaluate effects of single- and dual-task walking on cortical brain activity in individuals using a non-MPK or MPK and controls and compare differences between the 3 groups.

METHOD

A cross-sectional study was performed involving twenty-nine individuals with a transfemoral amputation or knee disarticulation who were provided with either a non-MPK or an MPK, and 16 controls. Functional near-infrared spectroscopy was used to evaluate cortical brain activity (oxygenated haemoglobin (oxyHb) concentration level changes) while participants walked on a stable level surface and simultanously performed 2 dual-task activities; 1) walking while sorting through keys; and, 2) walking in sequence around randomly number cones. Temporospatial variables was recorded for each activity.

RESULTS

Increased brain activity (oxyHb concentration level changes) were observed when a secondary task was added in the MPK-group (p=.000) and in the control group (p=.007). No significant differences were observed between single- and dual-task walking in the non-MPK group (p>.05). Significantly increased brain activity (oxyHb concentrations level changes) was observed during single-task walking in the non-MPK group when compared to the MPK-group and controls. Significantly different results in temporospatial parameters were also observed.

DISCUSSION AND CONCLUSION

Results suggest that dual-task walking increases cognitive demand in individuals fitted with MPKs and controls. The lack of difference with the non-MPK group may suggests that their maximum capacity was already reached during single-task walking.

REFERENCES

[1] Morgan, Prosthet Orthot Int 2016. [2] Nagamatsu, Psychol Aging 2011. [3] Möller, Prosthet Orthot Int 2018.

ACKNOWLEDGEMENTS

Thanks to Jette Schack, Evin Güler, Vera Kooiman, Lamija Pasalic, Promobilia Foundation, ALF/LUA Research Grants, Össur and Team Olmed.

Introduction: Walking with a prosthesis while performing secondary tasks increases demand on cognitive resources, compromising balance and gait. This study investigated effects of a secondary task on patterns of brain activity and temporospatial gait parameters in individuals using a prosthesis with or without a microprocessor-controlled prosthetic knee(MPK) and controls.Methods: A cross-sectional study with repeated measures was performed. Twenty-nine individuals with amputations and 16 controls were recruited. Functional near-infrared spectroscopy was used to evaluate changes in oxygenated and de-oxygenated haemoglobin in the prefrontal cortex and temporospatial variables during single-and dual-task walking.Results: Differences in brain activity were observed within the MPK-group and controls without changes in temporospatial parameters. The Trail-Walking test was associated with highest levels of brain activity in both groups. No differences were observed between single- and dual-task walking in the non-MPK-group (p > 0.05). The Non-MPK and the MPK-group recorded higher levels of brain activity than controls during single-task walking and poorer results on temporospatial variables compared to controls.Conclusions: For the MPK-group and controls, introduction of a secondary task led to an increase in brain activity. This was not seen in the Non-MPK-group. Significant differences in brain activity were observed in the absence of changes in temporospatial parameters.

Background: Individuals using a lower-limb prosthesis indicate that they need to concentrate on every step they take. Despite self-reports of increased cognitive demand, there is limited understanding of the link between cognitive processes and walking when using a lower-limb prosthesis.

Objective: The objective was to assess cortical brain activity during level walking in individuals using different prosthetic knee components and compare them to healthy controls. It was hypothesized that the least activity would be observed in the healthy control group, followed by individuals using a microprocessor-controlled prosthetic knee and finally individuals using a non-microprocessor-controlled prosthetic knee.

Study Design: Cross-sectional study.

Methods:: An optical brain imaging system was used to measure relative changes in concentration of oxygenated and de-oxygenated haemoglobin in the frontal and motor cortices during level walking. The number of steps and time to walk 10 m was also recorded. The 6-min walk test was assessed as a measure of functional capacity.

Results: Individuals with a transfemoral or knee-disarticulation amputation, using non-microprocessor-controlled prosthetic knee ( n = 14) or microprocessor-controlled prosthetic knee ( n = 15) joints and healthy controls ( n = 16) participated in the study. A significant increase was observed in cortical brain activity of individuals walking with a non-microprocessor-controlled prosthetic knee when compared to healthy controls ( p < 0.05) and individuals walking with an microprocessor-controlled prosthetic knee joint ( p < 0.05).

Conclusion: Individuals walking with a non-microprocessor-controlled prosthetic knee demonstrated an increase in cortical brain activity compared to healthy individuals. Use of a microprocessor-controlled prosthetic knee was associated with less cortical brain activity than use of a non-microprocessor-controlled prosthetic knee.

Clinical Relevance: Increased understanding of cognitive processes underlying walking when using different types of prosthetic knees can help to optimize selection of prosthetic components and provide an opportunity to enhance functioning with a prosthesis.

Background

Walking with a prosthesis requires substantial concentration on behalf of the user and places increased demands on executive functions. Little is known of the effects that prosthetic knee joint prescription may have on executive functioning.

Objectives

Evaluate executive functioning in trans-femoral prosthesis users during single and dual-task walking, before and after they transition to a Microprocessor-controlled prosthetic knee unit.

Study Design

Multiple case-study design.

Methods

Single and dual task gait was evaluated while recording cortical brain activity. Testing occasion 1 occurred prior to participants receiving their microprocessor-controlled prosthetic knee, while testing occasion 2 was conducted a minimum of 8 months after they had been fitted with an microprocessor-controlled prosthetic knee.

Results

During single-task level walking and walking while performing a dual-task key finding test, executive functions, measured as the relative haemodynamic response in the frontal cortex, reduced for most, but not all participants after transitioning to an Microprocessor-controlled prosthetic knee. There did not appear to be any difference when participants performed a trail walk test.

Conclusions

Results suggest Microprocessor-controlled prosthetic knee prosthetic knees may have a positive effect on executive functioning for some individuals who have undergone a lower-limb amputation. A larger, longitudinal study with careful control of extraneous variables (e.g. age, training) is needed to confirm results and determine causality.

Clinical relevance

This article provides some evidence to suggest that prosthetic prescription may influence executive functioning and that microprocessor-controlled prosthetic knee mechanisms may reduce cognitive effort when walking.