Kathie A. Bernhardt

Gait of stance control orthosis users: the dynamic knee brace system.

Individuals with weak or absent quadriceps who wish to walk independently are prescribed knee-ankle-foot orthoses (KAFOs). New stance control orthosis (SCO) designs automatically release the knee to allow swing phase flexion and extension while still locking the joint during stance. Twenty-one participants were fitted unilaterally with the Dynamic Knee Brace System (DKBS), a non-commercial SCO. Thirteen subjects were experienced KAFO users (average 28 ± 18 years of experience) while eight were novice users. Novice users demonstrated increased velocity (55 vs. 71cm/sec, p = 0.048) and cadence (77 vs. 85 steps/min, p < 0.05) when using the DKBS over the traditional locked KAFO. Experienced KAFO users tended to have reduced velocity and cadence measures when using the SCO (p < 0.10). Knee range of motion was significantly greater for the novice group than for the experienced group (55.2 ± 4.8 vs. 42.6 ± 3.8°, p = 0.05). Peak knee extension moments tended to be greater for the experienced group (0.29 ± 0.21 vs. 0.087 ± 0.047 Nm/kg, p = 0.09). This report describes gait changes during the introductory phase of DKBS adoption. Experienced KAFO users undoubtedly had ingrained gait patterns designed to compensate for walking with a standard locked KAFO. These patterns may have limited the ability of those users from taking full and immediate advantage of the SCO capabilities. Also, alternate SCO systems may engender different results. Comparison studies and longer term field studies are needed to clarify benefits of the various bracing options.

Effect of local alignment on compartmental patterns of knee osteoarthritis.

BACKGROUND Previous studies have shown that lower-extremity malalignment increases the risk and rate of progression of knee osteoarthritis. The authors of such studies have used full-length lower-extremity radiographs to quantify alignment. However, a radiograph that includes only the knee is commonly ordered for a patient with early symptoms of knee osteoarthritis. The purpose of this study was to investigate whether local malalignment, as determined with use of a standing short knee radiograph, is associated with an increased risk of having osteoarthritis and having more severe compartmental disease. METHODS Short fluoroscopically guided standing anteroposterior knee radiographs of 306 patients (608 knees) with radiographic evidence of knee osteoarthritis were used to determine the compartment-specific Kellgren-Lawrence grade of osteoarthritis and the local (distal femoral to proximal tibial) knee alignment. The relationship between local alignment and compartmental patterns of osteoarthritis was assessed. RESULTS Each degree of increase in the local varus angle was associated with a significantly increased risk of having predominantly medial compartment osteoarthritis, even when we adjusted for age, sex, and body mass index (odds ratio, 1.39; 95% confidence interval, 1.29 to 1.49; p < 0.001). A similar association was found between valgus angulation and lateral compartment osteoarthritis (odds ratio, 1.55; 95% confidence interval, 1.36 to 1.75; p < 0.001). Analysis of the 362 knees with predominantly medial compartment osteoarthritis showed that each degree of increase in the varus angle was associated with a significantly increased adjusted risk of having severe medial disease (odds ratio, 1.52, p < 0.001). In the forty-seven knees with predominantly lateral compartment osteoarthritis, a similar trend was found between an increase in the valgus angle and the severity of the lateral disease, with the results approaching but not reaching significance. CONCLUSIONS In patients with early symptomatic knee osteoarthritis, there is a clear relationship between local knee alignment, as determined from short standing knee radiographs, and the compartmental pattern and severity of the knee osteoarthritis. This study provides data with which physicians can assess how knee alignment contributes to the observed patterns and severity of osteoarthritis in an individual patient.

Gait changes over time in stance control orthosis users

This report presents objective motion analysis measurements of 14 stance control orthoses (SCO) users during a prospective open-enrollment 6-month clinical field trial. Participants were fitted with a Dynamic Knee Brace System (DKBS) which is a novel electromechanical SCO developed by the authors. Seven of the 14 subjects that had been prescribed but did not use a KAFO at the time of enrollment were defined as novice users. Those subjects who at the time of enrollment were using a locked KAFO for ambulation were defined as experienced users. Results showed that all subjects significantly increased peak knee flexion from 49.0 ± 15.5° to 55.9 ± 11.4° between the initial and six month tests (p = 0.02). They also tended to increase peak hip flexion from 39.6 ± 13.4° to 46.0 ± 14.5° between the 3 month and 6 month tests (p = 0.09). Novice users significantly increased velocity from 74.7 ± 19.4 cm/s to 81.2 ± 19.0 cm/sec between the initial and 3-month tests (p = 0.005). These same users increased stride length from 109 ± 15.3 cm to 112 ± 16.6 cm over the same time period (p = 0.008). Experienced KAFO users, however, tended to increase velocity from 68.8 ± 20.5 cm/s to 83.2 ± 16.8 cm/s at 3 months (p = 0.06). This was combined with a significant increase in cadence from 76.2 ± 14.1 steps/min to 83.9 ± 8.3 steps/min between the initial and 3 month tests (p = 0.05). Joint kinetics showed no changes for users over the duration of the testing period. These results indicate that KAFO users make significant gains in temporodistance measures, while changes in joint kinematics take longer to develop.

Effect of environmental temperature on shock absorption properties of running shoes.

Objective:To determine the effect of temperature changes on the shock attenuation of 4 running shoe shock absorption systems. Design:Prospective. Setting:Motion analysis laboratory. Interventions:The shock attenuation of 4 different running shoes representing common shock absorption systems (Nike Air Triax, Asics Gel Nimbus IV, Adidas a3 cushioning, Adidas Supernova cushion) was measured at ambient temperatures of −20°C, −10°C, 0°C, +10°C, +20°C, +30°C, +40°C, and +50°C. Repeated-measures analysis of variance was used to determine differences between shoes. Outcome Measures:Shock attenuation as indicated by peak deceleration (g) measured by a mechanical impactor following ASTM Standard F1614-99. Results:Shock attenuation decreased significantly with reduced temperature for each shoe tested. The Adidas a3 shoe exhibited significantly higher peak decelerations (lower shock attenuation) at cold temperatures compared with the other shoes. Conclusions:Cold ambient temperatures significantly reduce the shock attenuation of commonly used running shoes. These findings have important clinical implications for individuals training in extreme weather environments, particularly those with a history of lower limb overuse injuries.

Gait patterns of patients with inclusion body myositis

Inclusion body myositis (IBM) is a progressive, inflammatory muscle disease that is known to cause quadriceps weakness and knee buckling during gait. This is the first known report of gait characteristics in patients with IBM. Nine subjects with IBM and quadriceps weakness underwent gait analysis and quantitative strength testing. A wide range of strength and gait abilities were present in the subject group. Subjects with stronger knee extensors exhibited nearly normal sagittal knee kinematics and kinetics. As quadriceps strength decreased, kinematic and kinetic patterns were increasingly abnormal. Exceptions to this pattern could be explained by examining strength at adjacent joints. Gait analysis and strength testing is a helpful tool in evaluating the functional status of this population and aiding in determination of the needs for interventions such as assistive devices.

Weight Bearing through Lower Limbs in a Standing Frame with and without Arm Support and Low-Magnitude Whole Body Vibration in Men and Women with Complete Motor Paraplegia

Objective The aim of the study was to determine the proportion of body weight borne through the lower limbs in persons with complete motor paraplegia using a standing frame, with and without the support of their arms. We also examined the effect of low-magnitude whole-body vibration on loads borne by the lower limbs. Design Vertical ground reaction forces (GRFs) were measured in 11 participants (six men and five women) with paraplegia of traumatic origin (injury level T3–T12) standing on a low-magnitude vibrating plate using a standing frame. GRFs were measured in four conditions: (1) no vibration with arms on standing frame tray, (2) no vibration with arms at side, (3) vibration with arms on tray, and (4) vibration with arms at side. Results GRF with arms on tray, without vibration, was 0.76 ± 0.07 body weight. With arms at the side, GRF increased to 0.85 ± 0.12 body weight. With vibration, mean GRF did not significantly differ from no-vibration conditions for either arm positions. Oscillation of GRF with vibration was significantly different from no-vibration conditions (P < 0.001) but similar in both arm positions. Conclusions Men and women with paraplegia using a standing frame bear most of their weight through their lower limbs. Supporting their arms on the tray reduces the GRF by approximately 10% body weight. Low-magnitude vibration provided additional oscillation of the load-bearing forces and was proportionally similar regardless of arm position.

Stance control orthosis trial in patients with inclusion body myositis

Background: Inclusion Body Myositis (IBM) is an inflammatory myopathy that commonly affects quadriceps strength, resulting in knee buckling and falls. Therefore, patients with IBM should be ideal candidates for stance control orthoses (SCOs). Objectives: Evaluate the effectiveness of SCO use in patients with IBM who have functional deficits due to quadriceps weakness. Study Design: Cohort study. Methods: Nine subjects with IBM were provided a stance control orthosis and followed for six months of home use. All patients had objective testing of their strength and gait and completed a questionnaire at baseline and six months. Gait analysis was performed both with and without the orthosis. Results: Velocity and cadence were lower and step width was higher when using the orthosis. Kinematic measures were largely unchanged with orthosis use. Subjects with less knee extensor weakness had a better outcome than weaker participants. Those who spent more time wearing the orthosis also had a more positive outcome. The participants felt that the SCO was helpful in safeguarding against falls and providing stability. Conclusions: SCO use will benefit patients with IBM, but care should be taken to choose the SCO option that best suits their individual clinical presentation. Clinical relevance This is the first study to examine SCO use in the IBM population. Patients with IBM have quadriceps weakness and will potentially benefit from SCO use. This study suggests that successful SCO management of patients with IBM depends on severity of weakness.

The circumstances, orientations, and impact locations of falls in community-dwelling older women

OBJECTIVE We sought to characterize the circumstances, orientations, and impact locations of falls in community-dwelling, ambulatory, older women. METHODS For this longitudinal, observational study, 125 community-dwelling women age≥65years were recruited. Over 12-months of follow-up, fall details were recorded using twice-monthly questionnaires. RESULTS More than half (59%) of participants fell, with 30% of participants falling more than once (fall rate=1.3 falls per person-year). Slips (22%) and trips (33%) accounted for the majority of falls. Approximately 44% of falls were forward in direction, while backward falls accounted for 41% of falls. About a third of all falls were reported to have lateral (sideways) motion. Subjects reported taking a protective step in response to 82% of forward falls and 37% of backward falls. Of falls reporting lateral motion, a protective step was attempted in 70% of accounts. Common impact locations included the hip/pelvis (47% of falls) and the hand/wrist (27%). Backwards falls were most commonly reported with slips and when changing direction, and increased the risk of hip/pelvis impact (OR=12.6; 95% CI: 4.7-33.8). Forward falls were most commonly reported with trips and while hurrying, and increased the risk of impact to the hand/wrist (OR=2.6; 95% CI: 1.2-5.9). CONCLUSION Falls in older ambulatory women occur more frequently than previously reported, with the fall circumstance and direction dictating impact to common fracture locations. Stepping was a common protective recovery strategy and that may serve as an appropriate focus of interventions to reduce falls in this high risk population.

Fatigue Test Device for Stance Phase Control Knee Orthoses

Mechanical endurance testing is critical to ensuring durability and safety of novel orthosis components. Stance phase control knee orthoses present challenges in this area because of the lock/release mechanisms, dynamic range of joint motion, and in some cases, the capability of locking at different joint positions. A new mechanical fatigue tester has been developed to evaluate stance phase control knee orthosis joint designs. Electromechanical and pneumatic elements of the fatigue tester are under computer control. The user can determine applied maximum load, applied load at release, and range of motion and can set specific failure criteria. The computer control algorithm also provides automated data logging and system diagnostic information. This system has been in operation for more than 2,000,000 cycles. The time to complete one test cycle is 4.3 seconds under a 44.7-Nm load and 50° range of motion.

Net ankle quasi-stiffness is influenced by walking speed but not age for older adult women

BACKGROUND Insufficient plantar flexor resistance due to plantar flexor weakness, an impairment common in patient populations, causes substantial gait deficits. The bending stiffness of passive-dynamic ankle-foot orthoses (PD-AFOs) has the capacity to replace lost plantar flexor resistance. Many patients who are prescribed PD-AFOs are older adults. While PD-AFO bending stiffness should be customized for patients, a method to objectively prescribe this stiffness does not exist. Quantifying natural plantar flexor resistance during non-pathological gait could provide a reference value for objectively prescribing PD-AFO bending stiffness. RESEARCH QUESTION This study investigated the effect of age on plantar flexor resistance in 113 participants above the age of 65 years. We did so while also considering the confounding influence of gait speed, an aspect known to be reduced with old age. METHODS Ambulatory, community-dwelling older adult women (ages 65-91 years) with no current or recent lower-extremity injuries or surgeries underwent an instrumented gait analysis at a self-selected speed. Plantar flexor resistance was quantified via net ankle quasi-stiffness (NAS) defined as the slope of ankle joint moment-angle curve during late stance. RESULTS showed that NAS was not significantly influenced by age (r = -0.11, p = 0.12), and that the confounding factor of walking speed had a significant, positive relationship with NAS (r = 0.59, p < 0.001). SIGNIFICANCE By determining that gait speed, not age, is related to NAS in older adults, this study represents the initial step towards objectively prescribing PD-AFO bending stiffness to achieve a targeted gait speed for older adults with plantar flexor weakness.