A Biomechanical Analysis of Trunk Motion During Stair Descent in Total and Unicompartmental Knee Arthroplasty Patients Compared to Healthy Controls.

M.S. Thesis. University of Hawaiʻi at Mānoa 2018

A Biomechanical Analysis of Total and Unicompartmental Knee Arthroplasty Patients during Stair Negotiation Compared to Healthy Controls.

Ph.D. Thesis. University of Hawaiʻi at Mānoa 2017

Biomechanical demands differentiate transitioning vs. continuous stair ascent gait in older women

Background Stair ascent mechanics change with age, but little is known about the differing functional demands of transitioning and continuous ascent. Work investigating the risky transition from gait to ascent is sparse, and the strategies that older adults adopt to achieve these demanding tasks have not been investigated. Methods This study compared the biomechanics of a 2-step transitional (floor-to-step2) and continuous ascent cycle (step1-to-step3) and investigated the role of limb preference in relation to dynamometer-derived knee strength during this transition. A biomechanical analysis of 36 women (60–83 years) ascending a 3-step staircase was conducted. Findings The 2-step transitioning cycle was completed quicker, with a larger range of motion, increased forces, larger knee flexor and dorsiflexor moments and ankle powers (P ≤ 0.05), but reduced hip and knee flexion, smaller hip extensor moments and hip and knee powers compared to continuous ascent. During the transition, 44% of the participants demonstrated a consistent limb preference. In these cases large between-limb extensor strength differences existed (13.8%) and 71% of these participants utilised the stronger limb to execute the 2-step transitional cycle. Interpretation The preferential stronger-limb 2-step transitioning strategy conflicts with previous recommendations of a stronger lead limb for frail/asymmetric populations. Our findings suggest that most healthy older women with large between-limb differences utilise the stronger limb to achieve the considerable propulsion required to redirect momentum during the 2-step transition. The biomechanical demands of ascent, relative to limb strength, can inform exercise programmes by targeting specific muscle groups to help older adults maintain/improve general functioning

Evaluation of a Soft Robotic Knee Exosuit for Assistance in Stair Ascent

abstract: Muscular weakness is a common manifestation for Stroke survivors and for patients with Anterior Cruciate Ligament reconstruction leading to reduced functional independence, especially mobility. Several rigid orthotic devices are being designed to assist mobility. However, limitations in majority of these devices are: 1) that they are constrained only to level walking applications, 2) are mostly bulky and rigid lacking user comfort. For these reasons, rehabilitation using soft-robotics can serve as a powerful modality in gait assistance and potentially accelerate functional recovery. The characteristics of soft robotic exosuit is that it’s more flexible, delivers high power to weight ratio, and conforms with the user’s body structure making it a suitable choice. This work explores the implementation of an existing soft robotic exosuit in assisting knee joint mechanism during stair ascent for patients with muscular weakness. The exosuit assists by compensating the lack of joint moment and minimizing the load on the affected limb. It consists of two I-cross-section soft pneumatic actuators encased within a sleeve along with insole sensor shoes and control electronics. The exosuit actuators were mechanically characterized at different angles, in accordance to knee flexion in stair gait, to enable the generation of the desired joint moments. A linear relation between the actuator stiffness and internal pressure as a function of the knee angle was obtained. Results from this characterization along with the insole sensor outputs were used to provide assistance to the knee joint. Analysis of stair gait with and without the exosuit ‘active’ was performed, using surface electromyography (sEMG) sensors, for two healthy participants at a slow walking speed. Preliminary user testing with the exosuit presented a promising 16% reduction in average muscular activity of Vastus Lateralis muscle and a 3.6% reduction on Gluteus Maximus muscle during the stance phase and unrestrained motion during the swing phase of ascent thereby demonstrating the applicability of the soft-inflatable exosuit in rehabilitation.Dissertation/ThesisMasters Thesis Biomedical Engineering 201

Effects of Increased Step Width on Knee Joint Biomechanics in Healthy and Knee Osteoarthritis Older Adults During Stair Descent

Stair negotiation is one of the most challenging tasks for older adults especially for those suffering from knee osteoarthritis (OA). To date, no studies have investigated the effects of increased step width (SW) on knee joint biomechanics. The purpose of Study One was to investigate the effects of increased SW on peak internal knee abduction moment and other lower extremity variables during stair descent in healthy older adults. The purpose of Study Two was to investigate the effects of increased SW on peak internal knee abduction moment, knee pain and other lower extremity variables during stair descent in medial compartment knee OA adults. A motion analysis system and an instrumented staircase were used to collect lower extremity joint biomechanics in both studies. Participants performed five stair descent trials at their self-selected speed at preferred, wide and wider SW. Study One: Twenty healthy adults (54.9±9.1 years) were recruited for this study. The preferred normalized SW in healthy adults during stair descent was 20% of leg length. The results indicated that increased SW during stair descent reduced 1st and 2nd peak internal knee abduction moments in healthy adults. These abduction moment reductions may be caused by a less adducted knee with increased SW. These results may have implications in reducing medial compartment knee loads in stair descent in healthy adults to potentially help prevent medial compartment knee OA onset. Study Two: Thirteen medial compartment knee OA patients (62.5±9.0 years) were recruited for this study. Increased SW did not change subjective knee pain in knee OA patients. Preferred SW in knee OA adults during stair descent was 20% of leg length. The increased SW during stair descent reduced 2nd peak knee adduction angle but did not reduce peak internal knee abduction moments in knee OA patients. It appears that earlier timing of 2nd peak adduction angle with increased SW may be related to the unchanged 2nd peak abduction moment. Further studies investigating simulated muscle forces and compartmentalized joint forces in medial compartment knee OA patients during stair negotiation are warranted to obtain a more accurate depiction of medial knee joint loads

Influence of Patient Satisfaction of Total Knee Replacement Patients on Stair Negotiation and Walking Biomechanics, Strength, and Balance

Total knee replacement (TKR) patients have shown alterations in lower extremity biomechanics during level ground walking and stair negotiation, strength levels, and balance abilities, however, it is unknown how dissatisfied TKR patients compare to satisfied TKR patients in these activities. Study One examined the lower extremity biomechanics of dissatisfied and satisfied TKR patients during level ground walking. Study Two investigated knee biomechanics during stair ascent and descent activities. Study Three compared isokinetic strength, balance abilities, deep knee flexion abilities, and functional abilities of the dissatisfied patients to the satisfied patients. Study Four performed a logistic regression as a means of examining significant variables in models designed to predict patient satisfaction. Study One found reduced 1st and 2nd peak VGRF, knee flexion ROM, and peak loadingresponse knee extension and abduction moments in the dissatisfied patients compared to healthy controls. First and 2nd peak VGRFs and flexion ROM were reduced in the replaced limb of the dissatisfied patients compared to their non-replaced limb. Study Two showed reduced 2nd peak VGRF and loading-response knee extension moments in the replaced limb of the dissatisfied group compared to their non-replaced limb and to satisfied and healthy groups during stair ascent. 1st peak VGRF and both loading-response and push-off abduction moments showed reduced values in replaced limbs compared to non-replaced limbs for all groups. During stair descent, the dissatisfied group showed reduced loading-response and push-off knee extension moments in their replaced limb compared to their non-replaced limb and the healthy group. The loading-response knee extension and abduction moments were also reduced in the dissatisfied group compared to the satisfied group. Study Three showed reduced peak extension (180°/s) and flexion (60°/s) torque in dissatisfied patients compared to satisfied patients. No balance differences were evident, although an increased percentage of dissatisfied patients were unable to complete the unilateral balance tests. Study Four produced models via the logistic regression analysis which often included peak VGRFs and knee extension moments. Future research should examine the effects of attempting to alter the physical differences between patient satisfaction groups and whether it improves patient satisfaction rates

Moving out of the lab:movement analyses in patients with osteoarthritis of the knee

Osteoarthritis of the knee is one of the main causes of physical limitations. In addition to osteoarthritis, obesity is also a growing public health problem. Research has shown that obese people are almost four times as likely to develop osteoarthritis of the knee. Patients with osteoarthritis of the knee develop compensation mechanisms during daily activities. This dissertation focuses on the analysis of biomechanical components in patients with osteoarthritis of the knee. The focus was on the knee adduction moment (KAM) during walking, stair climbing and sit-to-stand. A high KAM is associated with the onset and progression of osteoarthritis of the knee. Furthermore, this study focused on physical activity in patients with osteoarthritis of the knee with and without obesity. In this way, this research wanted to gain more insight into small changes in movement behaviour in these patients. Accelerometery is a good way to understand quantity and quality of physical activity. Patients with both osteoarthritis of the knee and obesity have a significantly increased KAM compared to healthy subjects. However, presence of only osteoarthritis of the knee, does not result in an increased KAM. Furthermore, more insight was gained into the actual physical activity and limitations in daily life in patients with osteoarthritis of the knee

High-Intensity Variable Stepping Training in Patients With Motor Incomplete Spinal Cord Injury: A Case Series

Background and Purpose: Previous data suggest that large amounts of high-intensity stepping training in variable contexts (tasks and environments) may improve locomotor function, aerobic capacity, and treadmill gait kinematics in individuals poststroke. Whether similar training strategies are tolerated and efficacious for patients with other acute-onset neurological diagnoses, such as motor incomplete spinal cord injury (iSCI), is unknown. Individuals with iSCI potentially have greater bilateral impairments. This case series evaluated the feasibility and preliminary short- and long-term efficacy of highintensity variable stepping practice in ambulatory participants for more than 1 year post-iSCI. Case Series Description: Four participants with iSCI (neurological levels C5-T3) completed up to 40 one-hour sessions over 3 to 4 months. Stepping training in variable contexts was performed at up to 85% maximum predicted heart rate, with feasibility measures of patient tolerance, total steps/session, and intensity of training. Clinical measures of locomotor function, balance, peak metabolic capacity, and gait kinematics during graded treadmill assessments were performed at baseline and posttraining, with more than 1-year follow-up. Outcomes: Participants completed 24 to 40 sessions over 8 to 15 weeks, averaging 2222 ± 653 steps per session, with primary adverse events of fatigue and muscle soreness. Modest improvements in locomotor capacity where observed at posttraining, with variable changes in lower extremity kinematics during treadmill walking. Discussion: High-intensity, variable stepping training was feasible and tolerated by participants with iSCI although only modest gains in gait function or quality were observed. The utility of this intervention in patients with more profound impairments may be limited

THE BIOMECHANICAL IMPACT OF WEIGHT ON THE LOWER EXTREMITY

Background: Obesity is a chronic disease characterized by a body mass index (BM1) of ≥ 30 kg/m2 which negatively impacts the musculoskeletal system and has been found to be a major contributing factor to obesity-induced biomechanical alterations during activities of daily living (ADLs). A certain level of mobility is required for all populations to maintain independence and a good quality of life becomes more difficult with excess weight. Using a reduced weight-bearing activity, such as the Alter Gravity treadmill, would be beneficial in an obese population to reduce the load on the joints and potentially decrease the risk of weight bearing injury while maintaining normal gait mechanics. The purpose of this dissertation was to determine the biomechanical effects of excess weight and weight distribution on ADLs. To address this, two different weight gain models were created to simulate central (CL) and peripheral (PL) weight gain compared to an obese group (OW), and normal weight group (UL) during different activities of daily living (ADLs). The purpose of the third study was to compare lower extremity joint kinematics and muscle activation patterns between obese and normal individuals at different levels of body support (100, 75, and 50%) while walking in the AlterG treadmill. Methods: 14 normal weight (BMI: 22.4 ± 1.8 kg/m2, age: 23.4 ± 3.6 yrs) and 17 obese (BMI: 33.2 ± 2.3 kg/m2, age: 31.6 ± 8.0 years) adults participated in different ADLs (gait and descending a set of stairs). Normal weight participants were loaded with two different external loads sufficient to increase their BMI by 5 kg/m2 (~22.6% body mass). Kinematic and kinetic data were collected with 3D motion analysis. Frontal plane hip and knee angles and moments were calculated. Results: During gait, the obese group walked at a significantly slower velocity compared to UL. Step length was 8.7% longer in UL and 7.4% longer in the CL compared to the OW. PL more closely mirrored the OW group in step length, flexion moment and extension moment and the CL more closely mirrored the obese group in sagittal plane knee and hip excursion, and peak hip flexion moment and extension moment during gait During the transition from descending stair walking to level gait, it was found that the PL, but not CL, decreased step length, increased step width, and increased proportion of the gait cycle spent in stance. During the transition from walking down the stairs to level gait it was found that CL and PL affect temporal spatial variables differently. PL also reduced peak hip adduction angle, increased peak hip flexion moment, decreased peak hip extension, decreased sagittal plane hip excursion, and decreased frontal plane hip excursion. Conversely, CL reduced peak hip flexion moment and trended to reduce peak hip extension moment. To determine the effects of reduced body mass per se on improved biomechanics, we needed a model that would prevent associated changes in segmental volume. Therefore, using an AlterG treadmill facilitated this method. At 100 % BW support, mean ST and VM EMG activity were significantly higher in the obese compared to the normal weight groups. There were also differences found at 75 % BW support in ST in the obese being greater than the normal. Conclusions: Combined, the overall results of this dissertation suggest that weight gain is able to be modeled but is variable and task specific. The CL has proven to be the weight gain model that which elicits a better biomechanical obese response when normal weight individuals are loaded. Further work is needed to understand how to truly mimic obesity with an external load

Effects of Wider Step Width on Knee Biomechanics in Obese and Healthy-Weight Participants During Stair Ascent

An increased likelihood of developing obesity-related knee osteoarthritis may be associated with increased peak internal knee abduction moment. Increases in step width may act to reduce this moment. This study focused on how step width influenced the knee joint during stair ascent by healthy and obese participants. Participants ascended stairs while walking at their preferred speed and under one of two step width conditions – preferred and increased. Obese participants experienced greater mediolateral and vertical ground reaction forces (GRFs), as well as increased peak knee extensor moments and push-off peak internal knee adduction moments. The findings of this study indicate that when step width increases, obese participants will experience a disproportionate increase in Loading-response and push-off response peak mediolateral GRF, push-off peak knee adduction moments, and peak knee adduction angle compared to healthy participants. When normalized to lean body mass, obese participants also had greater increases in peak knee extension moments under the increased step width condition. Participants in each group experienced decreased in loading-response peak vertical GRF, loading-response peak knee abduction moment, peak knee internal rotation moment, knee extension range of motion, and knee abduction range of motion, and increased loading-response and push-off response peak mediolateral GRF, push-off peak knee adduction moment, peak knee external rotation moment, peak knee abduction angle, and knee internal rotation range of motion. This study provides important information regarding differences in knee joint biomechanics during stair ascent between obese and healthy populations