Evaluation of Power Wheelchair Dynamic Suspensions for Tip Prevention in Non-ADA Compliant Surfaces

OBJECTIVE

To evaluate the driving performance and usability of a mobility enhancement robot (MEBot) wheelchair with 2 innovative dynamic suspensions compared with commercial electric powered wheelchair (EPW) suspensions on non-American with Disabilities Act (ADA) compliant surfaces. The 2 dynamic suspensions used pneumatic actuators (PA) and electro-hydraulic with springs in series electrohydraulic and spring in series (EHAS).

DESIGN

Within-subjects cross-sectional study. Driving performance and usability were evaluated using quantitative measures and standardized tools, respectively.

SETTING

Laboratory settings that simulated common EPW outdoor driving tasks.

PARTICIPANTS

10 EPW users (5 women, 5 men) with an average age of 53.9±11.5 years and 21.2±16.3 years of EPW driving experience (N=10).

INTERVENTION

Not applicable.

MAIN OUTCOME MEASURE(S)

Seat angle peaks (stability), number of completed trials (effectiveness), Quebec User Evaluation of Satisfaction with Assistive Technology (QUEST), and systemic usability scale (SUS).

RESULTS

MEBot with dynamic suspensions demonstrated significantly better stability (all P<.001) than EPW passive suspensions on non-ADA-compliant surfaces by reducing seat angle changes (safety). Also, MEBot with EHAS suspension significantly completed more trials over potholes compared with MEBot with PA suspension (P<.001) and EPW suspensions (P<.001). MEBot with EHAS had significantly better scores in terms of ease of adjustment (P=.016), durability (P=.031), and usability (P=.032) compared with MEBot with PA suspension on all surfaces. Physical assistance was required to navigate over potholes using MEBot with PA suspension and EPW suspensions. Also, participants reported similar responses regarding ease of use and satisfaction toward MEBot with EHAS suspension and EPW suspensions.

CONCLUSIONS

MEBot with dynamic suspensions improve safety and stability when navigating non-ADA-compliant surfaces compared with commercial EPW passive suspensions. Findings indicate MEBot readiness for further evaluation in real-world environments.

Plantar somatosensory restoration enhances gait, speed perception, and motor adaptation

Lower limb loss is a major insult to the body's nervous and musculoskeletal systems. Despite technological advances in prosthesis design, artificial limbs are not yet integrated into the body's physiological systems. Therefore, lower limb amputees (LLAs) experience lower balance confidence, higher fear of falls, and impaired gait compared with their able-bodied peers (ABs). Previous studies have demonstrated that restored sensations perceived as originating directly from the missing limb via neural interfaces improve balance and performance in certain ambulatory tasks; however, the effects of such evoked sensations on neural circuitries involved in the locomotor activity are not well understood. In this work, we investigated the effects of plantar sensation elicited by peripheral nerve stimulation delivered by multicontact nerve cuff electrodes on gait symmetry and stability, speed perception, and motor adaptation. We found that restored plantar sensation increased stance time and propulsive force on the prosthetic side, improved gait symmetry, and yielded an enhanced perception of prosthetic limb movement. Our results show that the locomotor adaptation among LLAs with plantar sensation became similar to that of ABs. These findings suggest that our peripheral nerve-based approach to elicit plantar sensation directly affects central nervous pathways involved in locomotion and motor adaptation during walking. Our neuroprosthesis provided a unique model to investigate the role of somatosensation in the lower limb during walking and its effects on perceptual recalibration after a locomotor adaptation task. Furthermore, we demonstrated how plantar sensation in LLAs could effectively increase mobility, improve walking dynamics, and possibly reduce fall risks.

Motorless cadence control of standard and low duty cycle-patterned neural stimulation intensity extends muscle-driven cycling output after paralysis

Background

Stimulation-driven exercise is often limited by rapid fatigue of the activated muscles. Selective neural stimulation patterns that decrease activated fiber overlap and/or duty cycle improve cycling exercise duration and intensity. However, unequal outputs from independently activated fiber populations may cause large discrepancies in power production and crank angle velocity among pedal revolutions. Enforcing a constant cadence through feedback control of stimulus levels may address this issue and further improve endurance by targeting a submaximal but higher than steady-state exercise intensity.

Methods

Seven participants with paralysis cycled using standard cadence-controlled stimulation (S-Cont). Four of those participants also cycled with a low duty cycle (carousel) cadence-controlled stimulation scheme (C-Cont). S-Cont and C-Cont patterns were compared with conventional maximal stimulation (S-Max). Outcome measures include total work (W), end power (P_end), power fluctuation (PFI), charge accumulation (Q) and efficiency (η). Physiological measurements of muscle oxygenation (SmO₂) and heart rate were also collected with select participants.

Results

At least one cadence-controlled stimulation pattern (S-Cont or C-Cont) improved P_end over S-Max in all participants and increased W in three participants. Both controlled patterns increased Q and η and reduced PFI compared with S-Max and prior open-loop studies. S-Cont stimulation also delayed declines in SmO2 and increased heart rate in one participant compared with S-Max.

Conclusions

Cadence-controlled selective stimulation improves cycling endurance and increases efficiency over conventional stimulation by incorporating fiber groups only as needed to maintain a desired exercise intensity. Closed-loop carousel stimulation also successfully reduces power fluctuations relative to previous open-loop efforts, which will enable neuroprosthesis recipients to better take advantage of duty cycle reducing patterns.

Selective neural stimulation methods improve cycling exercise performance after spinal cord injury: a case series

BACKGROUND

Exercise after paralysis can help prevent secondary health complications, but achieving adequate exercise volumes and intensities is difficult with loss of motor control. Existing electrical stimulation-driven cycling systems involve the paralyzed musculature but result in rapid force decline and muscle fatigue, limiting their effectiveness. This study explores the effects of selective stimulation patterns delivered through multi-contact nerve cuff electrodes on functional exercise output, with the goal of increasing work performed and power maintained within each bout of exercise.

METHODS

Three people with spinal cord injury and implanted stimulation systems performed cycling trials using conventional (S-Max), low overlap (S-Low), low duty cycle (C-Max), and/or combined low overlap and low duty cycle (C-Low) stimulation patterns. Outcome measures include total work (W), end power (Pend), power fluctuation indices (PFI), charge accumulation (Q), and efficiency (η). Mann-Whitney tests were used for statistical comparisons of W and Pend between a selective pattern and S-Max. Welch's ANOVAs were used to evaluate differences in PFIs among all patterns tested within a participant (n ≥ 90 per stimulation condition).

RESULTS

At least one selective pattern significantly (p < 0.05) increased W and Pend over S-Max in each participant. All selective patterns also reduced Q and increased η compared with S-Max for all participants. C-Max significantly (p < 0.01) increased PFI, indicating a decrease in ride smoothness with low duty cycle patterns.

CONCLUSIONS

Selective stimulation patterns can increase work performed and power sustained by paralyzed muscles prior to fatigue with increased stimulation efficiency. While still effective, low duty cycle patterns can cause inconsistent power outputs each pedal stroke, but this can be managed by utilizing optimized stimulation levels. Increasing work and sustained power each exercise session has the potential to ultimately improve the physiological benefits of stimulation-driven exercise.

Effect of Joint Friction Compensation on a "Muscle-First" Motor-Assisted Hybrid Neuroprosthesis

This study assessed the metabolic energy consumption of walking with the external components of a “Muscle-First” Motor Assisted Hybrid Neuroprosthesis (MAHNP), which combines implanted neuromuscular stimulation with a motorized exoskeleton. The “Muscle-First” approach prioritizes generating motion with the wearer's own muscles via electrical stimulation with the actuators assisting on an as-needed basis. The motorized exoskeleton contributes passive resistance torques at both the hip and knee joints of 6Nm and constrains motions to the sagittal plane. For the muscle contractions elicited by neural stimulation to be most effective, the motorized joints need to move freely when not actively assisting the desired motion. This study isolated the effect of the passive resistance or “friction” added at the joints by the assistive motors and transmissions on the metabolic energy consumption of walking in the device. Oxygen consumption was measured on six able-bodied subjects performing 6 min walk tests at three different speeds (0.4, 0.8, and 1.2 m/s) under two different conditions: one with the motors producing no torque to compensate for friction, and the other having the motors injecting power to overcome passive friction based on a feedforward friction model. Average oxygen consumption in the uncompensated condition across all speeds, measured in Metabolic Equivalent of Task (METs), was statistically different than the friction compensated condition. There was an average decrease of 8.8% for METs and 1.9% for heart rate across all speeds. While oxygen consumption was reduced when the brace performed friction compensation, other factors may have a greater contribution to the metabolic energy consumption when using the device. Future studies will assess the effects of gravity compensation on the muscular effort required to lift the weight of the distal segments of the exoskeleton as well as the sagittal plane constraint on walking motions in individuals with spinal cord injuries (SCI).

Sum of phase-shifted sinusoids stimulation prolongs paralyzed muscle output

Neuroprostheses that activate musculature of the lower extremities can enable standing and movement after paralysis. Current systems are functionally limited by rapid muscle fatigue induced by conventional, non-varying stimulus waveforms. Previous work has shown that sum of phase-shifted sinusoids (SOPS) stimulation, which selectively modulates activation of individual motor unit pools (MUPs) to lower the duty cycle of each while maintaining a high net muscle output, improves joint moment maintenance but introduces greater instability over conventional stimulation. In this case study, implementation of SOPS stimulation with a real-time feedback controller successfully decreased joint moment instability and further prolonged joint moment output with increased stimulation efficiency over open-loop approaches in one participant with spinal cord injury. These findings demonstrate the potential for closed-loop SOPS to improve functionality of neuroprosthetic systems.

Implanted High Density Cuff Electrodes Functionally Activate Human Tibial and Peroneal Motor Units Without Chronic Detriment to Peripheral Nerve Health

OBJECTIVE

Peripheral nerve stimulation via multi-contact nerve cuff electrodes (NCEs) has proved effective in restoring function to individuals with lower-extremity paralysis. This study investigates clinical measures of nerve health over one year post-implantation of a composite flat-interface nerve electrode (C-FINE) on the tibial and peroneal nerves above the knee in a human volunteer. This represents the first deployment of a novel NCE on new neural targets in a uniquely challenging location prone to prolonged externally applied forces, making acute and chronic postoperative observation critical.

MATERIALS AND METHODS

A 27-year-old man with an incomplete spinal cord injury (AIS C) at the C3 to C4 level received eight-contact C-FINEs bilaterally on the tibial and peroneal nerves, proximal to the knee. Access to four contacts per cuff exhibiting the most desirable responses was externalized via temporary percutaneous leads. Percutaneous leads were later removed, with contacts generating the best dorsiflexion (two of four) and plantar flexion (one of four) reconnected to a permanently implanted pulse generator. For 13 months post-implantation, nerve health and cuff performance were assessed through motor nerve conduction velocity (MNCV) studies, clinical needle electromyography, compound motor action potential (CMAP), sensory nerve action potential (SNAP), stimulation-evoked tetanic moment collection, and lower-limb circumference measurements.

RESULTS

Tibial and peroneal MNCVs remained stable bilaterally above 40 m/sec, with CMAPs increased or stable after six months. SNAPs remained stable across all measurements. CMAP initial charge thresholds remained below 50 nC, with minimal changes to muscle recruitment order in three of four externalized contacts per cuff. Peak tetanic moments remained stable, with bilateral increases in thigh and calf circumferences of 5% and 14% over one year.

CONCLUSIONS

Above-knee tibial and peroneal NCEs can restore stimulated ankle-joint function without chronic nerve health detriments. Alongside previous femoral nerve data, this study demonstrates the ability of NCEs to enhance lower-extremity function with limited neuromuscular impact.

Comparison of strategies and performance of functional electrical stimulation cycling in spinal cord injury pilots for competition in the first ever CYBATHLON

Functional Electrical Stimulation (FES) can elicit muscular contraction and restore motor function in paralyzed limbs. FES is a rehabilitation technique applied to various sensorimotor deficiencies and in different functional situations, e.g. grasping, walking, standing, transfer, cycling and rowing. FES can be combined with mechanical devices. FES-assisted cycling is mainly used in clinical environments for training sessions on cycle ergometers, but it has also been adapted for mobile devices, usually tricycles. In October 2016, twelve teams participated in the CYBATHLON competition in the FES-cycling discipline for persons with motor-complete spinal cord injury. It was the first event of this kind and a wide variety of strategies, techniques and designs were employed by the different teams in the competition. The approaches of the teams are detailed in this special issue. We hope that the knowledge contained herein, together with recent positive results of FES for denervated degenerating muscles, will provide a solid basis to encourage improvements in FES equipment and open new opportunities for many patients in need of safe and effective FES management. We hope to see further developments and/or the benefit of new training strategies at future FES competitions, e.g. at the Cybathlon 2020 (www.cybathlon.ethz.ch).

Detecting destabilizing wheelchair conditions for maintaining seated posture

PURPOSE

The purpose of this study was to detect and classify potentially destabilizing conditions encountered by manual wheelchair users with spinal cord injuries (SCI) to dynamically increase stability and prevent falls.

METHODS

A volunteer with motor complete T11 paraplegia repeatedly propelled his manual wheelchair over level ground and simulated destabilizing conditions including sudden stops, bumps and rough terrain. Wireless inertial measurement units attached to the wheelchair frame and his sternum recorded associated accelerations and angular velocities. Algorithms based on mean, standard deviation and minimum Mahalanobis distance between conditions were constructed and applied to the data off-line to discriminate between events. Classification accuracy was computed to assess effects of sensor position and potential for automatically selecting a dynamic intervention to best stabilize the wheelchair user.

RESULTS

The decision algorithm based on acceleration signals successfully differentiated destabilizing conditions and level over-ground propulsion with classification accuracies of 95.8, 58.3 and 91.7% for the chest, wheelchair and both sensors, respectively.

CONCLUSION

Mahalanobis distance classification based on trunk accelerations is a feasible method for detecting destabilizing events encountered by wheelchair users and may serve as an effective trigger for protective interventions. Incorporating data from wheelchair-mounted sensors decreases the false negative rate. Implications for Rehabilitation SCI has a significant impact on quality of life, compromising the ability to participate in social or leisure activities, and complete other activities of daily living for an independent lifestyle. Using inertial measurement units to build an event classifier for control the actions of a neuroprosthetic device for maintaining seated posture in wheelchair users. Varying muscle activation increases user stability reducing the risk of injury.

Abstract P5-01-10: Clinical-pathological features and outcomes of Invasive lobular (ILC) vs Invasive ductal (IDC) breast cancer (BC): a mono-institutional series

Purpose: The aim of our study was to investigate different clinico-biological behavior associated to ILC compared to IDC evaluating implications on survival outcomes

Methods: We analyzed data from 3749 cases of IBC treated from 1995 to 2008 and categorized as having ILC, IDC and mixed/other. Associations between clinical-pathological variables and the ILC/IDC histotype were assessed using a χ2 test. Log-rank test and Cox regression model were performed to evaluate the impact of hystologic types on overall survival (OS), Event Free Survival (EFS) and Post-Progression Survival (PPS).

Results: We identified 445 (12%) ILC, 3021 (80.5%) IDC, 149 mixed (ductal-lobular) BC (3.9%) and 134 other hystotypes (3.6%). Median age was 61 (25–97) years. Compared with IDC, ILC occurred significantly (p &lt; 0.001) more likely in older age, larger in size (T≥2: 46 vs 34%) with frequent axilla involvement (43 vs 37%). It was associated with better differentiated tumors usually presenting low ki67, high level of ER expression and HER2 negative status. Mastectomies were more frequent (45%) in ILC than in IDC (37%). As ILC showed higher ER expression rates, adjuvant hormonal (± previous chemo) therapy was more frequently given to them than IDC (77 vs 64%). At a median follow up of 77 (0–272) months, there were not significant differences in EFS (81.4 vs 82.1%, p = 0.7) and OS (82.8 vs 84.6%; p = 0.19) between ILC vs IDC. Relapses, contralateral and second tumors were 65 (15%), 9 (2%) and 22 (5%) in ILC vs 404 (13%), 84 (2.8%) and 174 (5.7%) in IDC. Local recurences were 16 (3.6%) vs 175 (5.7%) in ILC vs IDC; preferential sites of distant relapses were similar in both histotypes. Median time to first event was 38.3 in ILC vs 35.23 months in IDC. PPS was 16.5 m (0–100) in ILC and 22.2 m (0–187) in IDC. ILC showed worse prognosis than IDC within luminal A (86.9 vs 93.5%; p = 0.003), C (70.4 vs 88.5%; p = 0.028) and in triple negative subtypes (50 vs 73.1%; p = 0.021). No difference in OS was seen for age, size, hormonal and nodal status, except in N &gt;3 ILC pts, in whom a trend of worse prognosis (55.6 vs 60.2%) was observed.

Conclusions: Despite the quite favorable biological pattern, ILC did not show a better outcomes than IDC.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P5-01-10.

P5-14-23: Clinical Outcomes of Different Subtypes Detected by Immunohistochemistry of Early Invasive Breast Cancers in a Monoinstitutional Series

Background

Early invasive breast cancer (EIBC) is an heterogeneous disease. Immunohistochemical (IHC) markers can be used to classify tumors in different biological subtypes with different clinical behavior.

Purpose: The aim of our study was to evaluate survival outcomes for patients (pts) with different subtypes of EIBC as classified using four ICH markers (ER, PR, HER2 and Ki67).

Methods: We evaluated data from 3403 consecutive cases of EIBC treated from 1995 to 2008 and classified as: luminal A (positive ER and PR, negative HER2 and Ki67&lt; 14%), luminal B (positive ER and/or PR, negative HER2 and Ki67&gt;14%), luminal C (positive ER and/or PR, positive HER2, any Ki67), HER2+ (negative ER and PR, positive HER2, any ki67), triple negative (negative ER and PR, negative HER2, any ki67). Log-rank test and Kaplan-Meyer estimator were performed to evaluate the impact of ICH subtypes on overall survival (OS), Event Free Survival (EFS) and their correlation with other known prognostic factors such as N, G, Size, Age.

Results: We identified 917 luminal A (26.9%), 1731 luminal B (50.9%), 279 (8.2%) luminal C, 183 HER2 + (5.4%) and 293 triple negative (8.6%). Median age was 61 years. Luminal A was more frequently (p&lt;0.001) associated with older age, smaller size, negative axilla involvement, low grading. Observed events (relapses, contralateral and second tumors) were: 54 in luminal A (6%), 215 in luminal B (16%), 40 in luminal C (14%), 42 in HER2+ (23%) and 59 in triple negative (20%). Disease free interval (DFI) was shorter in luminal C, HER2 and TN (median DFI: 30, 26 and 19 months) than in Luminal A and B (median DFI: 51 and 41 month). Luminal A and B presented more bony and less visceral recurrences than luminal C, HER2 and triple negative tumors. At median follow up of 51 months EFS was 94.1% in luminal A, 87.5% in luminal B, 85.5% in luminal C, 76.8% in HER2+ and 79.7% in triple negative. Corresponding OS was 95.3% in luminal A, 89% in luminal B, 89.2% in luminal C, 80.9% in HER2+, 81.9% in triple negative. Different subtypes EFS according to nodal status, grading, tumor size and age, was reported in table 1.

Walking after partial paralysis assisted with EMG-triggered or switch-triggered functional electrical stimulation--two case studies

Functional Electrical Stimulation (FES) facilitates walking after paralysis by activating the muscles of the lower extremities. The FES-assisted stepping triggered either by a manual switch (switch-trigger), or by an electromyogram-based gait event detector (EMG-trigger) were presented in random order to two subjects with incomplete spinal cord injuries (iSCI) during ten trials over two alternate days. Subject iSCI-1 (C6 ASIA C) was non-ambulatory without the assistance of FES and could stand but not initiate a step volitionally. Subject iSCI-2 (T1 ASIA D) could walk only short distances with great difficulty without FES. Gait kinematics and kinetics were captured during FES-assisted over-ground walking with a rolling walker under laboratory conditions. Gait parameters including speed, left and right step length, left and right double support duration, left and right swing phase durations were extracted from the kinematic data. Mean, standard deviation, coefficient of variation, and 95% confidence interval were computed for each gait parameter under each triggering condition. The ground reaction forces were recorded for both the subjects while upper body support provided by the instrumented walker was recorded for iSCI-2. One way analysis of variance (ANOVA) was performed to determine whether significant differences existed in gait parameters between command sources. The left and right double support duration were significantly lower (p<0.05) during EMG-triggered gait than switch-triggered for iSCI-1. The average normal ground reaction force was significantly (p<0.05) higher during EMG-triggered gait than switch-triggered for iSCI-1 and iSCI-2. The average body weight support on the walker was significantly lower for EMG-triggered gait than switch-triggered one for iSCI-2. The results suggest that less user effort was needed when walking with EMG-triggered stepping than with manual switch trigger.

Abstract P3-10-14: The Prognostic Significance of mib-1 (according to St Gallen Criteria) in Patients (pts) with Early Invasive Breast Cancer (EIBC) and Its Relationship with other Biologic Parameters in a Monoinstitutional Series

PURPOSE: To examine interactions between mib-1 and clinical-pathological markers and their impact on outcomes. PATIENTS AND METHODS: Mib-1 was identified by immunohistochemical staining in 3402 EIBC pts treated from 1995 to 2008. Mib-1 was defined as low (15%), intermediate (16%-30%) and high (&gt;30%) value. Correlation between mib-1 and age, tumor size (T), nodal status (N), ER, PR, HER-2, grading (G) was performed by X2 test. Log-rank test and Cox regression model were performed to test mib-1 as prognostic factor for overall survival (OS) and Disease Free Survival (DFS) and its correlation with other known prognostic factors.

RESULTS: Median mib-1 was 25%. Mib-1 was low in 1135, intermediate in 1094 and high in 1173 pts. Median age was 62 years. High mib-1 was significantly (P&lt;0.001) associated with younger age, ductal type, greater size, positive N, poor G, absent or low ER and/or PR expression level, positive HER-2, triple negative subtypes, larger use of chemo±hormonotherapy. High mib-1 was a significant predictor of worse

DFS and OS (P&lt;0.001). At median follow up of 42 months DFS and OS were 83.1 and 84.8% respectively in high, 88.9 and 89.3% in intermediate, 92.7 and 93.6% respectively in low Mib-1 group. There were 401 relapses (12%): 197 (6%) in high, 121 (3.5%) in intermediate and 83 (2,5%) in low mib-1 group. BC deaths were 368 (10.8 %): 178 (5.2%) in high, 117 (3.4%) intermediate and 73 (2.2%) in low mib-1 group. High mib1 was predictive of poorer prognosis in &gt; 40 years pts (P&lt;0.001), small tumors (T1) (P&lt;0.001), N+ (P&lt;0.001) and N0 (p=0.007), G1 (p=0.02), ER+ and/or PR+ (P&lt;0.001), negative HER-2 (p=0.007), ductal type (P&lt;0.001) respect to intermediate and low Mib1. At Cox regression analysis Mib1 showed independent prognostic value. According to the median value, high mib-1 (&gt;25%) resulted a prognostic factor of worse outcome (P&lt;0.001, HR=1.81, 95% CI=1.42-2.29), along with positive lymph nodes (P&lt;0.001, HR=2.14, 95% CI=1.67-2.74), age&lt;40 yrs (p=0.002, HR=1.93, 95% CI=1.30-2.86), greater tumors (P&lt;0.001, HR=3.11, 95% CI=2.21-4.39), and ER/PR positive tumors (P&lt;0.001, HR=1.742, 95% CI=1.305-2.327).

CONCLUSIONS: In our experience, Mib-1 confirms to be a significant prognostic biomarker for DFS and OS in EIBC, providing additional information besides other clinico-pathological parameters to help decision-making of treatment.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P3-10-14.

Prognostic Value of mib-1 in Patients with Early Invasive Breast Cancer and Its Correlation with Other Biologic Parameters in a Monoinstitutional Series

INTRODUCTION: Mib-1 is a proliferation biomarker and a prognostic factor for breast cancer as reported in several studies.PURPOSE: The aim of the present study was to examine interactions between mib-1 and other clinical-pathological markers and their impact on outcomes in early invasive breast cancer.PATIENTS AND METHODS: Mib-1 was identified by immunohistochemical staining in 2660 EIBC patients treated in our institution from 2000 to 2008. Mib-1 was dichotomized at the value of 20%. Correlation between mib-1 (&gt; or ≤10620%) and age, tumour size (T), nodal status (N), ER, PR, HER-2, grading (G) was performed by χ2 test. Log-rank test and Cox regression model were performed to test mib-1 as prognostic factor for overall survival (OS) and Disease Free Survival (DFS) and evaluate its correlation with other known prognostic factors.RESULTS: Mib-1 was &gt; 20% in 1276 and ≤106 20% in 1384. Mib-1&gt; 20% was significantly (p=.000) associated with younger age, greater size, positive lymph nodes, poor grading, absent or low ER and/or PR expression level, HER-2 over-expression or amplification with or without co-expression of ER and/or PR, triple negative subtypes. Mib-1 was a significant predictor of worse DFS and OS (p=.000). At a median follow up of 32 months the DFS and OS were 97.4 and 99.2% respectively in Mib-1 ≤20% group and 92.4 and 97.2% respectively in Mib-1 &gt; 20%. There were 195 relapses (7,3%): 139 (5.2%) in Mib-1 &gt; 20% and 56 (2.1%) in Mib-1 ≤ 20%. Breast cancer related deaths were 74 (2.8%) with 58 (2.2%) in mib-1 &gt; 20% group and 16 (0.6%) in mib-1 ≤ 20%.Mib1 &gt;20% was predictive of poorer prognosis in &gt; 40 years patients, small tumors (T1), lower grading (G1 and G2), positive ER and/or PR group with high or intermediate expression, negative HER-2 tumors. However, in Cox multivariate analysis mib-1 didn't maintain independent prognostic value.CONCLUSIONS: In our experience, Mib-1 confirms to be a significant prognostic biomarker for DFS and OS in early breast cancer. It could provide additional information beside other clinico-pathological parameters to perform the risk stratification of early breast cancer patients.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 6054.

Invasive breast carcinoma of 1 cm or smaller: risk of nodal involvement and prognosis

Abstract #1075

Background: Screening mammography has increased the frequency of diagnosis of small (≤1 cm) invasive breast cancer (BC), for which the prognosis after locoregional therapy remains controversial.&#x2028; Patients and methods: We have performed a retrospective analysis of 882 patients with ≤1 cm BC and positive or negative-nodes, treated in our Institution from 1990 to 2005. Risks of axillary nodes involvement (ANI), relapse-free (RFS) and overall survival (OS) were analyzed according to: age, tumor size, histologic type and grading, ER and PgR status and MIB-1, HER-2 and p53 immuno histochemical expression.&#x2028; Results: Median age at diagnosis was 57 years (range: 20 - 86 years). Tumor size was: 71 Tmic (a single focus of invasive carcinoma ≤ 2 mm or up to 3 foci ≤1 mm in greatest dimensions, according to Silver and Tavassoli), 225 T1a (&gt;2 -5 mm) and 586 T1b (&gt;5–10 mm). ANI was found in 122 cases (13,8%): only 1 inT1mic (1,4%), 21 in T1a (9,3%) and 100 in T1b (17%). Tumor size, young age, poor differentiation and ductal histology were significantly associated with ANI (p=0.01). Local relapses were: 3 in Tmic pts(2 DCIS and 1 invasive), 13 in T1a, 22 in T1b. Distant metastases were: 1 in Tmic pts, 11 in T1a, 17 in T1b. At a median follow up of 92 months, RFS was 86,4% (Tmic: 86,8%, T1a: 86,2%; T1b: 86,2%). BC-specific mortality was 2% for T1mic, 3,3% for T1a, 3,8% for T1b accounting for an OS of 96,6%. Nodal involvement was the more relevant prognostic factor for survival, followed by young age, poor differentiation, high MIB-1 and p53.&#x2028; Conclusions: In pts with 1 cm or smaller Invasive Breast Carcinoma, the risk of ANI is low, but not negligible, particularly for T1b tumors. Furthermore, the prognosis of these pts is influenced by high histological grade and young age.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 1075.

Development of an implanted intramuscular EMG-triggered FES system for ambulation after incomplete spinal cord injury

Ambulation after spinal cord injury is possible with the aid of neuroprosthesis employing functional electrical stimulation (FES). Individuals with incomplete spinal cord injury (iSCI) retain partial volitional control of muscles below the level of injury, necessitating careful integration of FES with intact voluntary motor function for efficient walking. In this study, the intramuscular electromyogram (iEMG) was used to detect the intent to step and trigger FES-assisted walking in a volunteer with iSCI via an implanted neuroprosthesis consisting of two channels of bipolar iEMG signal acquisition and 12 independent channels of stimulation. The detection was performed with two types of classifiers- a threshold-based classifier that compared the running mean of the iEMG with a discrimination threshold to generate the trigger and a pattern recognition classifier that compared the time-history of the iEMG with a specified template of activity to generate the trigger whenever the cross-correlation coefficient exceeded a discrimination threshold. The pattern recognition classifier generally outperformed the threshold-based classifier, particularly with respect to minimizing False Positive triggers. The overall True Positive rates for the threshold-based classifier were 61.6% and 87.2% for the right and left steps with overall False Positive rates of 38.4% and 33.3%. The overall True Positive rates for the left and right step with the pattern recognition classifier were 57.2% and 93.3% and the overall False Positive rates were 11.9% and 24.4%. The subject showed no preference for either the threshold or pattern recognition-based classifier as determined by the Usability Rating Scale (URS) score collected after each trial and both the classifiers were perceived as moderately easy to use.

Electromyogram-Triggered Functional Electrical Stimulation-Assisted Walking After Partial Paralysis

Objective: Functional Electrical Stimulation (FES) triggered by manual switch provides brace-free ambulation to wheelchair dependent individuals with spinal cord injuries. An electromyogram (EMG)-based trigger can enhance the coordination between FES-assisted and volitional actions. This study evaluated the gait speed modulation and coordination of the actions of the EMG-triggered FES with the volitional movements during stand-to-walk transition after incomplete spinal cord injury. Methods: two incomplete spinal cord injured (iSCI) subjects (iSCI1: 24years, C7 motor & C6 sensory; iSCI2: 34years, T1 motor & C5 sensory) volunteered for this study. Four able-bodied volunteers provided the normative gait data. The Vicon WorkstationTM (Vicon Peak, USA) software acquired lower-body kinematics data using a seven camera motion capture system during stand-to-walk transition. The FES-assisted swing-phase in iSCI subjects was triggered with three command interfaces—manually triggered with a switch, triggered with EMG-based GED, triggered automatically at a user-selected rate. Results and Discussion: The Euclidean distance from origin of the perturbations of 18 joint angles and 18 joint velocities during stand-to-walk transition converged towards zero. It was found from the Mahalanobis distances between each pair of group means that the EMG-triggered FES-assisted iSCI gait was closest to the able-bodied normative gait clusters.

Retrospective analysis of clinico-pathological features and outcomes of 2,686 hormone receptors-positive breast cancer (HR+) patients in a consecutive mono-institutional series

11036

Background: Clinico-pathological patterns, management and outcomes of HR+ vs HR- have been evaluated in a retrospective study. Methods: A series of 2686 BC patients (pts), treated at our institution from 1988 to 2000 with known immunohistochemical receptor status was investigated. Correlation between HR status and tumour size (T), nodal status (N), grading (G), mib-1, HER-2 and p53 and was evaluated by χ square test. Statistical analysis was performed to test the interaction between HR status and Disease Free Survival (DFS) and with specific and overall survival, using the log-rank test. Results: Among 2686 patients, 467 HR- (17%) and 2219 (83%) HR+ (364 pre and 1855 postmenopausal) were observed, with 1586 ER+PgR+, 555 ER+PgR-, 78 ER-PgR+. Pts with positive HR status showed a statistically significant correlation with lower T, G, mib-1, HER-2 and p53 expression.Chemotherapy was administered to 681 HR+BC (31% ) and to 301 HR-BC (65%), according to stage, age, and G. Tamoxifen based endocrine therapy was administered to 1167 HR+BC (53%) (associated to chemotherapy in 428 and alone in 739 pts). At a median follow up of 108 months, 499 relapses occurred in HR+ (22%) , and 141 in HR- pts (30%), with a 5,10, 15y DFS of 83%,72%, 62% in HR+ and 72%,66%, 57% respectively in HR- pts. More frequent sites of relapse were soft tissue (46%) and bone (35%) in HR+ and soft tissue (50%) and visceral (30%) in HR- pts. Seven hundred sixty pts have died: 576 HR+ (26%) and 184 HR- (39%), with a 5, 10, 15y specific survival of 90%, 84%, 75% which was significantly superior to the 78%, 73%, 69% respectively of HR-. However, considering that 230 HR+ and 44 HR- pts died without relapse, the 5,10,15y overall survival was 90%, 75% 61% for HR+ and 78%, 67%, 60% respectively for HR-. It appears therefore that the specific survival advantage in early years in favour of HR+ is progressively reduced by non specific mortality in late years which results in similar 15 y OS rates among HR+ and HR- pts. Conclusions: Our series appear to confirm the relationship between HR+ status and other more favourable clinical-pathological features, although long term OS is not apparently affected.

No significant financial relationships to disclose.

Clinical presentation and outcomes of 2,924 early breast cancer patients (br.ca. pts) treated in a single institution in a 10-year period with a long follow up

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Background: A consecutive series of br.ca. pts, treated between Jan 1st 1990 to Dec 31st 1999 in our Department, is the basis of our retrospective study, aimed to create a data base on routinary clinical management of early br.ca. pts, to which compare similar series and literature data. Methods: All Clinical Records were reviewed and computerized. Disease free and overall survival were estimated using the product-limit method of Kaplan and Meier. The log-rank test was used to compare prognosis between different subgroups. Results: Among 2924 consecutive br.ca. pts, 836 were younger than 50 years (med. age 44) and 2088 older (med. age 63). Regional nodes were negative (N−) in 1754, positive (N+) in 1027 and unknown in the remaining pts. So, 2593 pts were stage I-II and 301 stage IIIA-B. Hormonal Receptor status (available on 2560 pts) was positive for Estrogen (ER+) in 2021 pts and for Progesterone (PgR+) in 1649 pts. Moreover, 1571 pts were ER+Pgr+, 539 ER-PgR−, 78 ER-PgR+ and 461 ER+PgR−. HER2 was overexpressed in 262/1426 (18%) pts. Tumor grading (available on 2176 cases) was G1–2 in 1411 and G3–4 in 765 cases. After surgery, 731 pts received adjuvant Tamoxifen, 507 pts CMF ± Antracyclines chemotherapy, 434 pts both chemotherapy and Tamoxifen and 958 pts none. (no therapy data are available for the remaining 334 pts). At a median f.up of 9.8 years, 993/2924 pts (33.9%) have recurred, (med. DFS 137 mos) with a 5, 10 and 15 y probability of recurrence of 26, 44 and 63% respectively. Corresponding figures of recurrence for N− pts were 14, 30 and 50% (med. DFS 168 mos), while for N+ pts were 41, 61 and 77% (med DFS 81 mos). For younger N+ pts treated with chemotherapy, the 5 years probability of recurrence was 34% while it was 24% for older ER+ pts treated with hormonal therapy. So far, 794/2924 (27.5%) pts have died, with a 5, 10 and 15 y probability of death of 13, 27 and 41%. This was 5, 16 and 28% for N- pts and 22, 41 and 56% for N+ pts. For younger N+ pts treated with chemotherapy, the 5 y probability of death was 14%, as it was for older ER+ pts treated with Tamoxifen. Conclusions: Although this data are not yet conclusive, it appears that large part of the clinical improvements reported in clinical trials may be achieved in the routine management of breast cancer pts.

No significant financial relationships to disclose.

A model-based study of passive joint properties on muscle effort during static stance

This study examined the impact of lower extremity joint stiffnesses and simulated joint contractures on the muscle effort required to maintain static standing postures after a spinal cord injury (SCI). Static inverse computer simulations were performed with a three-dimensional 15 degree of freedom musculoskeletal model placed in 1600 different standing postures. The required lower extremity muscle forces were calculated through an optimization routine that minimized the sum of the muscle stresses squared, which was used as an index of the muscle effort required for each standing posture. Joint stiffnesses were increased and decreased by 100 percent of their nominal values, and contractures were simulated to determine their effects on the muscle effort for each posture. Nominal muscle and passive properties for an individual with a SCI determined the baseline muscle effort for comparisons. Stiffness changes for the ankle plantar flexion/dorsiflexion, hip flexion/extension, and hip abduction/adduction directions had the largest effect on reducing muscle effort by more than 5 percent, while changes in ankle inversion/eversion and knee flexion/extension had the least effect. For erect standing, muscle effort was reduced by more than 5 percent when stiffness was decreased at the ankle plantar flexion/dorsiflexion joint or hip flexion/extension joint. With simulated joint contractures, the postural workspace area decreased and muscle effort was not reduced by more than 5 percent for any posture. Using this knowledge, methods can be developed through the use of orthoses, physical therapy, surgery or other means to appropriately augment or diminish these passive moments during standing with a neuroprosthesis.

Pressure-induced formation of diblock copolymer "micelles" in supercritical fluids. A combined study by small angle scattering experiments and mean-field theory. II. Kinetics of the unimer-aggregate transition

We developed a simple time-dependent mean-field theory to describe the phase separation kinetics of either homopolymers or AB-diblock copolymers in supercritical (SC) fluids. The model, previously used to describe the phase behavior of AB-block copolymers under the assumption of strong solvent selectivity for just one copolymer chain, has been extended to study the kinetics of the phase separation process. Time resolved small angle x-ray scattering (TR-SAXS) measurements have been performed on different AB-diblock copolymers containing a perfluorinated chain and dissolved in SC-CO2. The data obtained over a wide range of pressure and temperature confirm our theoretical predictions. Particularly interesting is the presence of two relaxation frequencies for the homogeneous solution --> spherical aggregate transition, where the two relaxation processes depend on the depth of the pressure jump and on temperature. The whole phenomenon could be explained as an initial SC solvent/polymer phase separation followed by a slow reorientation process to form spherical aggregates driven by the copolymer solvophilic moiety.

Pressure-induced formation of diblock copolymer “micelles” in supercritical fluids. A combined study by small angle scattering experiments and mean-field theory. I. The critical micellization density concept

We developed a simple mean-field theory to describe polymer and AB diblock copolymer phase separation in supercritical (SC) fluids. The highly compressible SC fluid has been described by using a phenomenological hole theory, properly extended to consider the solvent/polymer/vacancy pseudoternary mixture. The model has been applied to describe the phase behavior of AB-diblock copolymers under the assumption of a strong solvent selectivity for just one copolymer chain. In our model the solvent selectivity is a strong function of the external pressure because in compressible fluids vacancies reduce the number of favorable solvent-polymer contacts. The combined effect of the pressure on the average solvent quality and selectivity for a single polymer chain makes the phase behavior of a diblock copolymer in SC fluids quite complex. Small angle neutron and x-ray scattering (SANS and SAXS) measurements have been performed on SC-CO2 solutions of different AB-diblock copolymers containing a perfluorinated chain. The data obtained over a wide range of pressure and temperature confirm our theoretical predictions.

SAXS investigation on aggregation phenomena in supercritical CO2

Synchrotron Small-Angle X-Ray scattering (SAXS) measurements on aggregate formation of a Polyvinyl acetate- b-Perfluoro octyl acrylate (PVAc- b-PFOA) block copolymer in supercritical CO(2) are here reported. Experiments were carried out for a series of different thermodynamic conditions, changing the solvent density by profiling both the pressure at constant temperature and the temperature at constant pressure. This block copolymer and in general fluorocarbon-hydrocarbon di-blocks form aggregates depending on the value of CO(2) density. A sharp transition between monomers dissolved as random coils and micelles characterized by a solvophilic shell and a solvophobic core occurs when the CO(2) density reaches a critical value. Results of critical micellization density (CMD) derived from pressure and temperature ramps experiment along with the comparison with previous SANS results are here reported to give additional experimental support to the solvent density-driven aggregation process.

Effects of stimulated hip extension moment and position on upper-limb support forces during FNS-induced standing--a technical note

This study explores the effects of active hip extension moment produced by electrical stimulation on the support forces the arms must exert through an assistive device during quiet erect standing with functional neuromuscular stimulation (FNS) in individuals with spinal cord injuries (SCI). A static sagittal plane biomechanical model of human standing was developed to predict the effects of stimulated hip extension moment and sagittal plane hip angle on the arm support necessary to maintain an upright posture. Two individuals with complete thoracic SCI were then tested while they stood with continuous stimulation to the knee and trunk extensors. The steady-state active extension moment exerted at the hip was varied by activating different combinations of hip extensor muscles with continuous stimulation while steady-state support forces applied to the arms and feet during standing were measured. The steady-state support forces imposed on the arms during quiet standing decrease with increased stimulated hip extension moment and are highly dependent upon hip flexion angle, as predicted by the biomechanical simulations. Experimentally, the combination of gluteus maximus and semimembranosus stimulation produced three times more steady-state hip extension moment than did stimulation of the gluteus maximus and adductor magnus. This resulted in a ten-fold decrease in body weight supported on the arms. More vertical postures (smaller hip flexion angles) improve the effectiveness of the hip extensor muscles in reducing the support forces placed on the arms. A single Newton-meter of stimulated hip extension moment with the hips fixed at 5 degrees of flexion results in almost five times the reduction in arm support forces as with the hips at 20 degrees. To minimize the forces applied by the arms on an assistive device for support while standing with FNS, these preliminary results suggest that (1) efforts should be made to assume the most erect postures possible and (2) muscles and stimulation paradigms that maximize active hip extension moment should be chosen.

Defective neurogenesis in citron kinase knockout mice by altered cytokinesis and massive apoptosis

Citron-kinase (Citron-K) has been proposed by in vitro studies as a crucial effector of Rho in regulation of cytokinesis. To further investigate in vivo its biologic functions, we have inactivated Citron-K gene in mice by homologous recombination. Citron-K-/- mice grow at slower rates, are severely ataxic, and die before adulthood as a consequence of fatal seizures. Their brains display defective neurogenesis, with depletion of specific neuronal populations. These abnormalities arise during development of the central nervous system due to altered cytokinesis and massive apoptosis. Our results indicate that Citron-K is essential for cytokinesis in vivo but only in specific neuronal precursors. Moreover, they suggest a novel molecular mechanism for a subset of human malformative syndromes of the CNS.

Critical micellization density: A small-angle-scattering structural study of the monomer-aggregate transition of block copolymers in supercritical CO2

In this paper we report a small-angle neutron-scattering investigation of micelle formation by the fluorocarbon-hydrocarbon block copolymer, polyvinyl acetate-b-poly (1,1,2, 2-tetrahydroperfluoro-octyl acrylate) in supercritical CO2 (scCO(2)) at 313 K. At high pressure the copolymer is in a monomeric state with a random coil structure, while at low pressure the polymer forms spherical aggregates stable in a wide range of thermodynamic conditions. By profiling pressure, a sharp monomer-micelle transition is obtained due to the tuning of the solvating ability of scCO(2). We confirm the previous finding that this aggregate-monomer transition is driven by the gradual penetration of CO2 molecules toward the core of the aggregate and is critically related to the density of the solvent, thus giving additional support to the concept of a critical micellization density reported earlier on a similar polymer.