Kathie A Bernhardt

Mayo Clinic - Rochester, Rochester, Minnesota, United States

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Publications (11)21.33 Total impact

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    ABSTRACT: 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. 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. 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. 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.
    American journal of physical medicine & rehabilitation / Association of Academic Physiatrists 04/2012; 91(4):300-8. · 1.56 Impact Factor
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    ABSTRACT: 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. 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. 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. 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.
    The Journal of Bone and Joint Surgery 09/2008; 90(9):1961-9. · 3.23 Impact Factor
  • Steven E Irby, Kathie A Bernhardt, Kenton R Kaufman
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    ABSTRACT: 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 degrees to 55.9 +/- 11.4 degrees between the initial and six month tests (p = 0.02). They also tended to increase peak hip flexion from 39.6 +/- 13.4 degrees to 46.0 +/- 14.5 degrees 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.
    Prosthetics and Orthotics International 01/2008; 31(4):353-61. · 0.62 Impact Factor
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    ABSTRACT: To compare the muscle activation pattern in subjects with and without "snapping triceps syndrome" (dislocation of the medial head of the triceps and ulnar nerve over the medial epicondyle). Controlled study. Biomechanics laboratory. Eight male subjects (9 elbows), with symptomatic snapping triceps and 9 male controls. Not applicable. Activation pattern of the 3 triceps heads during active elbow extension at 0 degrees , 45 degrees , 70 degrees , 90 degrees , and 115 degrees of flexion, recorded by fine-wire electromyography. There were no significant differences between subjects and controls in the firing pattern of the triceps heads. The medial head fired first in 6 of 9 symptomatic elbows and in 7 of 9 controls at 90 degrees of flexion, and in 6 of 9 elbows of both subjects and controls at 115 degrees of flexion, positions where snapping typically occurs. There was no significant difference between the groups as to how often the medial head fired maximally. This study suggests the firing pattern of the triceps heads may not contribute to the pathogenesis of this syndrome. Rather, the authors believe the anatomic position of the medial head causes it to dislocate over the medial epicondyle, often resulting in ulnar neuritis.
    Archives of Physical Medicine and Rehabilitation 03/2007; 88(2):239-42. · 2.36 Impact Factor
  • Kathie A Bernhardt, Steven E Irby, Kenton R Kaufman
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    ABSTRACT: Stance control knee orthoses (SCOs) have become very popular recently. However, there is little information regarding opinions of actual orthosis users. The purpose of this study was to quantify the users' opinions of a SCO, and see whether factors found important for knee orthoses in past studies hold true for a stance control orthosis as well. A standardized survey was employed as part of a larger field trial study of the Dynamic Knee Brace System, a SCO developed by the authors. The Dynamic Knee Brace System scored well in areas of effectiveness, operability, and dependability, but areas in need of improvement included weight, cosmesis, and donning and doffing. These findings match well with previous knee orthosis studies. This study shows that wearing a stance control knee orthosis can be a positive experience for an orthosis user.
    Prosthetics and Orthotics International 01/2007; 30(3):246-56. · 0.62 Impact Factor
  • Steven E. Irby, Kathie A. Bernhardt, Kenton R. Kaufman
    Gait & Posture 12/2006; 24. · 1.97 Impact Factor
  • Steven E Irby, Kathie A Bernhardt, Kenton R Kaufman
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    ABSTRACT: 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. 71 cm/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 degrees, 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.
    Prosthetics and Orthotics International 01/2006; 29(3):269-82. · 0.62 Impact Factor
  • Osteoarthritis and Cartilage 01/2006; 14. · 4.26 Impact Factor
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    ABSTRACT: To determine the effect of temperature changes on the shock attenuation of 4 running shoe shock absorption systems. Prospective. Motion analysis laboratory. 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 degrees C, -10 degrees C, 0 degrees C, +10 degrees C, +20 degrees C, +30 degrees C, +40 degrees C, and +50 degrees C. Repeated-measures analysis of variance was used to determine differences between shoes. Shock attenuation as indicated by peak deceleration (g) measured by a mechanical impactor following ASTM Standard F1614-99. 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. 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.
    Clinical Journal of Sport Medicine 06/2005; 15(3):172-6. · 1.60 Impact Factor
  • Medicine &amp Science in Sports &amp Exercise 01/2004; 36. · 4.48 Impact Factor
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    ABSTRACT: 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. Engineering design specifications and testing protocols for orthosis joint designs are available through national and international standards committees. 1-3 Understandably, these standards were developed with respect to the then state-of-the-art orthosis joint components. Testing typically has been conducted with the knee joint locked at full extension. This made sense because the devices are generally locked and loaded during ambulation and unlocked only for transfers and seating. Stance phase control knee brace designs have been developed recently that promise greater functionality. 4 These advanced designs promise dynamic control of the locked and unlocked states, and some provide a multiplicity of locking positions. Current structural testing standards do not address the dynamic nature of this new generation of knee joint designs. 2-4 This is of particular concern with respect to durability because of the increased number of potential failure modes. A new testing protocol needs to be developed to investigate the fatigue and wear properties of stance phase control knee joint mechanisms. Therefore, the purpose of this project is to develop a mechanical fatigue test for the stance phase control knee joints now entering the commercial market. Such a system of hardware and methodology should be scalable according to target population anthropometrics and should simulate anticipated loading patterns. To design a realistic protocol, normal knee kinetics and kinematics were used as a test parameter selection guide. Although knee brace users are not able to reproduce normal knee kinetics or kinematics, we assumed that users would naturally adopt similar patterns based upon esthetics and inherent energy efficiencies. Normal sagittal knee motion can be divided into stance and swing phases (Figure 1). Stance phase begins at foot strike (0 percent of gait cycle) and ends at foot off (approximately 62 percent of gait cycle). Although it is assumed that a locking knee brace will provide stability during stance phase, normal kinematics require approximately 40° of knee flexion at the end of stance. Swing phase begins at foot off and ends at foot strike or 100 percent of the gait cycle. Beyond foot off, the knee flexes another 10° to 20°, then extends to 0° in preparation for the subsequent foot strike and stance phase. Normal sagittal knee kinetics provided an estimate of the character and magnitude of moments about the knee. These data typically are normalized by the product of weight (N) and height (m) of the individual (Figure 2). Peak internal knee extensor moments during stance equal approximately 3 percent of the weight-height product. Of particular note is the second peak that occurs during double limb support and equals approximately 1 percent of the weight-height product. Thus, there exists an internal knee extensor moment when the joint needs to be released and allowed to flex in preparation for swing. Based on this information, the following four principal requirements are set forth for stance phase control devices: 1) lock reliably; 2) unlock reliably under physiologic loads; 3) provide adequate durability; and 4) allow adequate range of motion during swing phase of gait.
    JPO Journal of Prosthetics and Orthotics 09/2003; 15(4):143-147.

Publication Stats

51 Citations
21.33 Total Impact Points


  • 2007–2008
    • Mayo Clinic - Rochester
      Rochester, Minnesota, United States
  • 2006–2007
    • Mayo Foundation for Medical Education and Research
      • • Department of Physical Medicine and Rehabilitation
      • • Department of Orthopaedic Surgery
      Scottsdale, AZ, United States