Brenton Hordacre

Minimum number of trials required for within- and between-session reliability of TMS measures of corticospinal excitability.

Transcranial magnetic stimulation (TMS)-elicited motor-evoked potentials (MEPs) exhibit considerable trial-to-trial variability, potentially reducing the sensitivity and reproducibility of this measure. While increasing the number of trials will improve accuracy, prolonged recording blocks are not always feasible. In this study, we investigated the minimum number of trials required to provide a measure of human corticospinal excitability that is stable both within and between sessions. Single-pulse TMS was applied to the left primary motor cortex, and MEPs were recorded from the right first dorsal interosseous muscle. Approximately 20-30 trials were required to provide a stable measure of MEP amplitude with high within- and between-session reliability. Extending the number of trials beyond 30 provided no additional benefit. Collecting 30 trials may be optimal for reliably estimating corticospinal excitability using TMS. These findings may have significant implications for using TMS to measure corticospinal excitability in both basic and clinical research settings.

Variability in neural excitability and plasticity induction in the human cortex: A brain stimulation study

BACKGROUND The potential of non-invasive brain stimulation (NIBS) for both probing human neuroplasticity and the induction of functionally relevant neuroplastic change has received significant interest. However, at present the utility of NIBS is limited due to high response variability. One reason for this response variability is that NIBS targets a diffuse cortical population and the net outcome to stimulation depends on the relative levels of excitability in each population. There is evidence that the relative excitability of complex oligosynaptic circuits (late I-wave circuits) as assessed by transcranial magnetic stimulation (TMS) is useful in predicting NIBS response. OBJECTIVE Here we examined whether an additional marker of cortical excitability, MEP amplitude variability, could provide additional insights into response variability following application of the continuous theta burst stimulation (cTBS) NIBS protocol. Additionally we investigated whether I-wave recruitment was associated with MEP variability. METHODS Thirty-four healthy subjects (15 male, aged 18-35 years) participated in two experiments. Experiment 1 investigated baseline MEP variability and cTBS response. Experiment 2 determined if I-wave recruitment was associated with MEP variability. RESULTS Data show that both baseline MEP variability and late I-wave recruitment are associated with cTBS response, but were independent of each other; together, these variables predict 31% of the variability in cTBS response. CONCLUSIONS This study provides insight into the physiological mechanisms underpinning NIBS plasticity responses and may facilitate development of more reliable NIBS protocols.

Physiotherapy Rehabilitation for Individuals with Lower Limb Amputation: A 15-Year Clinical Series

BACKGROUND AND PURPOSE Individuals with amputations are a core group in Australian rehabilitation units that have a long index length of stay. The Repatriation General Hospital (RGH) offers general rehabilitation services to the population of Southern Adelaide (a population of 350,000) and includes an on-site prosthetic manufacturing facility. Using a physiotherapy database at the RGH, we sought to answer the following questions: What are the demographic and clinical characteristics of patients admitted for lower limb prosthetic rehabilitation over 15 years? What are the times to rehabilitation outcomes? How have these changed over 15 years with changes in service delivery? METHODS This paper is a retrospective observational study using a physiotherapy clinical database (1996-2010) of 531 consecutive individuals with lower limb amputation at one South Australian hospital (RGH). There were two changes in service delivery: 1) a multidisciplinary interim prosthetic programme (IPP) introduced in 1998 and 2) removable rigid dressings (RRDs) introduced in 2000. Outcome measures were patient demographics, clinical characteristics and time to rehabilitation outcome markers. RESULTS Mean age was 68 years (standard deviation [SD]: 15), with 69% male, 80% dysvascular and 68% transtibial. The overall median inpatient rehabilitation length of stay (RLOS) was 39 days (interquartile range [IQR]: 26-57). Individuals with amputation entering rehabilitation each year had a higher number of co-morbidities (β: 0.08; 95% confidence interval: 0.05-0.11). Introduction of the IPP was associated with a significant reduction in time to initial prosthetic casting, independent walking and inpatient RLOS. Introduction of RRDs was associated with a significant reduction in time to wound healing, initial prosthetic casting and independent walking. CONCLUSIONS Individuals with amputation were typically elderly dysvascular men with transtibial amputations. Introduction of the IPP and RRDs successfully reduced time to rehabilitation outcomes including independent walking, an outcome that is rarely reported but is of significance to patients and physiotherapists.

Use of an activity monitor and GPS device to assess community activity and participation in transtibial amputees

This study characterized measures of community activity and participation of transtibial amputees based on combined data from separate accelerometer and GPS devices. The relationship between community activity and participation and standard clinical measures was assessed. Forty-seven participants were recruited (78% male, mean age 60.5 years). Participants wore the accelerometer and GPS devices for seven consecutive days. Data were linked to assess community activity (community based step counts) and community participation (number of community visits). Community activity and participation were compared across amputee K-level groups. Forty-six participants completed the study. On average each participant completed 16,645 (standard deviation (SD) 13,274) community steps and 16 (SD 10.9) community visits over seven days. There were differences between K-level groups for measures of community activity (F(2,45) = 9.4, p < 0.001) and participation (F(2,45) = 6.9, p = 0.002) with lower functioning K1/2 amputees demonstrating lower levels of community activity and participation than K3 and K4 amputees. There was no significant difference between K3 and K4 for community activity (p = 0.28) or participation (p = 0.43). This study demonstrated methodology to link accelerometer and GPS data to assess community activity and participation in a group of transtibial amputees. Differences in K-levels do not appear to accurately reflect actual community activity or participation in higher functioning transtibial amputees.

Lower-limb amputee rehabilitation in Australia: analysis of a national data set 2004–10

OBJECTIVE Examine demographics, clinical characteristics and rehabilitation outcomes of lower-limb amputees, using the Australasian Rehabilitation Outcomes Centre (AROC) database. METHODS Lower-limb amputee rehabilitation separations between 2004 and 2010 were identified using AROC impairment codes 5.3-5.7.(1) Analysis was conducted by year, impairment code, Australian National Sub-acute and Non-Acute Patient (AN-SNAP) classification (S2-224, Functional Independence Measure (FIM) motor(Mot) score 72-91; S2-225, FIM (Mot) score 14-71) and states of Australia. RESULTS Mean length of stay (LOS) for all lower-limb amputee episodes was 36.1 days (95% confidence interval (CI): 35.4-36.9). Majority of episodes were unilateral below knee (63.6%), males (71.8%) with a mean age of 67.9 years (95% CI: 67.6-68.3). Year-on-year analysis revealed a trend for increasing LOS and decreasing age. Analysis by impairment code demonstrated no significant difference in rehabilitation outcomes. Analysis by AN-SNAP found that LOS was 16.2 days longer for S2-225 than for S2-224 (95% CI: 14.7-17.8, P<0.001), and FIM (Mot) change was 12.0 points higher for S2-225 than for S2-224 (95% CI: 11.5-12.6, P<0.001). Analysis by states revealed significant variation in LOS, FIM (Mot) change and FIM (Mot) efficiency which may be associated with variations in organisation of rehabilitation services across states. CONCLUSION Although amputees represented a comparatively small proportion of all rehabilitation episodes in Australia, their LOS was significant. Unlike many other rehabilitation conditions, there was no evidence of decreasing LOS over time. AN-SNAP classes were effective in distinguishing rehabilitation outcomes, and could potentially be used more effectively in planning rehabilitation programs.

Assessing Gait Variability in Transtibial Amputee Fallers Based on Spatial-Temporal Gait Parameters Normalized for Walking Speed

OBJECTIVE To determine whether normalizing spatial-temporal gait data for walking speed obtained from multiple walking trials leads to differences in gait variability parameters associated with a history of falling in people with transtibial amputations. DESIGN Cross-sectional study. SETTING Rehabilitation center. PARTICIPANTS People with unilateral transtibial amputations (N=45; mean age ± SD, 60.5±13.7y; 35 men [78%]) were recruited. INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES Participants completed 10 consecutive walking trials using an instrumented walkway system. Primary gait parameters were walking speed and step-length, step-width, step-time, and swing-time variability. A retrospective 12-month fall history was obtained from participants. RESULTS Sixteen amputees (36%) were classified as fallers. Variation in gait speed across the 10 walking trials was 2.9% (range, 1.1%-12.1%). Variability parameters of normalized gait data were significantly different from variability parameters of nonnormalized data (all P<.01). For nonnormalized data, fallers had greater amputated limb step-time (P=.02), step-length (P=.02), swing-time (P=.05), and step-width (P=.03) variability and nonamputated limb step-length (P=.04) and step-width (P=.01) variability. For normalized data, only 3 variability parameters were significantly greater for fallers. These were amputated limb step-time (P=.05), step-length (P=.02), and step-width (P=.01) variability. CONCLUSIONS Normalizing spatial-temporal gait data for walking speed before calculating gait variability parameters may aid in discerning variability parameters related to falls histories in people with transtibial amputations. This may help focus on the initial rehabilitation efforts of amputees with a fall history.

Ipsilateral corticomotor excitability is associated with increased gait variability in unilateral transtibial amputees

Ipsilateral primary motor cortex (M1) reorganisation after unilateral lower‐limb amputation may degrade function of the amputated limb. We hypothesised unilateral lower‐limb amputees would have a bilateral increase in corticomotor excitability, and increased excitability of ipsilateral M1 would be associated with increased step‐time variability during gait. Twenty transtibial amputees (16 male) aged 60.1 years (range 45–80 years), and 20 age‐ and gender‐matched healthy adult controls were recruited. Single‐pulse transcranial magnetic stimulation assessed corticomotor excitability. Two indices of corticomotor excitability were calculated. An index of corticospinal excitability (ICE) determined relative excitability of ipsilateral and contralateral corticomotor projections to alpha‐motoneurons innervating the quadriceps muscle (QM) of the amputated limb. A laterality index (LI) assessed relative excitability of contralateral projections from each hemisphere. Spatial‐temporal gait analysis was performed to calculate step‐time variability. Amputees had lower ICE values, indicating relatively greater excitability of ipsilateral corticomotor projections than controls (P = 0.04). A lower ICE value was associated with increased step‐time variability for amputated (P = 0.04) and non‐amputated limbs (P = 0.02). This association suggests corticomotor projections from ipsilateral M1 to alpha‐motoneurons innervating the amputated limb QM may interfere with gait. Cortical excitability in amputees was not increased bilaterally, contrary to our hypothesis. There was no difference in excitability of contralateral M1 between amputees and controls (P = 0.10), and no difference in LI (P = 0.71). It appears both hemispheres control one QM, with predominance of contralateral corticomotor excitability in healthy adults. Following lower‐limb amputation, putative ipsilateral corticomotor excitability is relatively increased in some amputees and may negatively impact on function.

Effect of weekend physiotherapy provision on physiotherapy and hospital length of stay after total knee and total hip replacement

OBJECTIVE The aim of the present study was to investigate a change in physiotherapy provision from a 5- to 7-days-a-week service on both physiotherapy and hospital length of stay (LOS) after total knee (TKR) and total hip (THR) replacement. METHODS A retrospective analysis of a clinical database was conducted for patients who received either a TKR or THR between July 2010 and June 2012 in one regional hospital. RESULTS There was a significant decrease in physiotherapy LOS from 5.0 days (interquartile range (IQR) 5.0-6.0 days) for a 5-day physiotherapy service, to 5.0 days (IQR 4.0-5.0 days) for 7-day physiotherapy service (U=1443.5, z=-4.62, P=0.001). However, hospital LOS was not reduced (P=0.110). For TKR, physiotherapy LOS decreased significantly by 1 day with a 7-day physiotherapy service (U=518.0, z=-4.20, P=0.001). However, hospital LOS was again no different (P=0.309). For THR there was no difference in physiotherapy LOS (P=0.060) or hospital LOS (P=0.303) between the 5- and 7-day physiotherapy services. Where physiotherapy LOS was less than hospital LOS, delayed discharge was due primarily to non-medical issues (72%) associated with hospital organisational aspects. CONCLUSIONS Increasing the provision of physiotherapy service after TKR provides an increase in physiotherapy sessions and has the potential to reduce hospital LOS. To be effective this must align with other administrative aspects of hospital discharge.

Resting state functional connectivity measures correlate with the response to anodal transcranial direct current stimulation

Responses to non‐invasive brain stimulation are highly variable between subjects. Resting state functional connectivity was investigated as a marker of plasticity induced by anodal transcranial direct current stimulation (tDCS). Twenty‐six healthy adults (15 male, 26.4 ± 6.5 years) were tested. Experiment 1 investigated whether functional connectivity could predict modulation of corticospinal excitability following anodal tDCS. Experiment 2 determined test–retest reliability of connectivity measures. Three minutes of electroencephalography was recorded and connectivity was quantified with the debiased weighted phase lag index. Anodal (1 mA, 20 min) or sham tDCS was applied to the left primary motor cortex (M1), with a change in motor evoked potential amplitude recorded from the right first dorsal interosseous used as a marker of tDCS response. Connectivity in the high beta frequency (20–30 Hz) between an electrode approximating the left M1 (C3) and electrodes overlying the left parietal cortex was a strong predictor of tDCS response (cross‐validated R2 = 0.69). Similar relationships were observed for alpha (8–13 Hz; R2 = 0.64), theta (4–7 Hz; R2 = 0.53), and low beta (14–19 Hz; R2 = 0.58) frequencies, however, test–retest reliability of connectivity measures was strongest for the high beta frequency model (ICC = 0.65; good reliability). Further investigation of the high beta model found that greater connectivity between C3 and a cluster of electrodes approximately overlying the left parietal cortex was associated with stronger responses to anodal (rho = 0.61, P = 0.03), but not sham tDCS (rho = 0.43, P = 0.14). Functional connectivity is a strong predictor of the neuroplastic response to tDCS and may be one important characteristic to assist targeted tDCS application.

Community activity and participation are reduced in transtibial amputee fallers: a wearable technology study

Wearable technology is an important development in the field of rehabilitation as it has the potential to progress understanding of activity and function in various patient groups. For lower limb amputees, falls occur frequently, and are likely to affect function in the community. Therefore, the purpose of this study was to use wearable technology to assess activity and participation characteristics in the home and various community settings for transtibial amputee fallers and non-fallers. Participants were provided with an accelerometer-based activity monitor and global positioning system (GPS) device to record activity and participation data over a period of seven consecutive days. Data from the accelerometer and GPS were linked to assess community activity and participation. Forty-six transtibial amputees completed the study (79% male, 35% identified as fallers). Participants with a history of falls demonstrated significantly lower levels of community activity (p=0.01) and participation (p=0.02). Specifically, activity levels were reduced for recreational (p=0.01) and commercial roles (p=0.02), while participation was lower for recreational roles (p=0.04). These findings highlight the potential of wearable technology to assist in the understanding of activity and function in rehabilitation and to further emphasise the importance of clinical falls assessments to improve the overall quality of life in this population.