An investigation of dynamic balance and postural control in persons with below-knee amputation due to a dysvascular condition

Background and aim: Lower limb amputation (LLA) disrupts the typical functioning of an individual with the loss of normal ankle joint, surrounding musculature and associated sensory-motor loop. Although LLA is a peripheral condition, considerable sensorimotor reorganisation is required for relearning of effective postural control subsequent to the amputation. The ability to relearn postural control is affected by various factors such as ageing and disease co-morbidities. However there is insufficient understanding of patient-centred problems due to the fact that postural control research in persons with LLA is complicated by differing levels of amputation, the presence of peripheral vascular disease, age and other confounding factors. Therefore the overall aim of thesis was to explore and compare dynamic balance performance in persons with a dysvascular and traumatic below-knee amputation and, with age matched able-bodied and, able-bodied dysvascular control subjects. Methods and results: The thesis comprises three projects: a systematic review of instrumented measurement of balance in persons with LLA followed by two individual studies in persons with below-knee amputation. The systematic review identified the methodological issues in postural control research in persons with LLA and it was recognised that the dynamic and functional balance needs further attention in persons with LLA. The findings from the systematic review informed the methods used in Study 1 which was undertaken to examine the psychometric properties (feasibility, reliability and validity) of selective tasks in below-knee amputees. In Study 1, 15 persons with a below-knee amputation (8 traumatic amputations and 7 dysvascular amputations) who were 60 years and older completed the Sensory Organization Test (SOT), Sit to Stand (STS), Step Quick Turn (SQT) and the Step Up and Over (SUO) using the NeuroCom® Balance Manager on two occasions approximately two weeks apart. The SOT and SQT tests were determined to be feasible in persons with a below-knee amputation and their measures demonstrated acceptable test-retest reliability (ICC ≥ 0.79, SEM ≤ 10% mean) and concurrent validity (rs≥ 0.56). An exploratory analysis that compared the balance performance of the traumatic and dysvascular amputees with these measures identified a difference in postural strategy in the SOT for conditions 2, 4 and 6 (p< 0.05) and in the Turn Time and Turn Sway variables of the SQT (p<0.05). In Study 2, 19 persons with a below-knee amputation (9 traumatic and 10 dysvascular) and 17 able-bodied control participants (9 with and 8 without dysvascular condition) completed the SOT and three tasks that simulated the turning behaviour. A significant difference was observed in SOT between the dysvascular amputees and able-bodied participants in conditions 1 to 4 (p< 0.05) and between traumatic amputees and able-bodied in conditions 1, 3 and 4 (p<0.05). Although no significant difference was observed between the dysvascular and traumatic amputation groups in centre of pressure measures, a difference was observed in the average ankle muscle activity and ankle co-contraction index of condition 5 (p<0.05). Also, significant differences were observed in the co-contraction index between traumatic amputees and able-bodied group in conditions 2 and 4. Of the three tasks (trunk rotation, weight shifting, shifting and rotation of the trunk) that simulated the turning behaviour, a significant difference was observed between the dysvascular amputees and able-bodied group in the execution and stabilisation phases of trunk rotation and weight shifting (p