Steven E. Irby

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.

Optimization and application of a wrap-spring clutch to a dynamic knee-ankle-foot orthosis

A dynamic knee-brace system (DKBS) has been designed which provides stance phase stability and swing phase freedom. A wrap-spring clutch controls knee flexion. Clutch optimization was performed minimizing clutch length. Kinematic tests on a normal subject using the DKBS document nearly normal dynamic knee flexion during swing (38 degrees versus 53 degrees for normal).

Automatic control design for a dynamic knee-brace system

A self-contained electronically controlled dynamic knee-brace system (DKBS) has been designed and tested which allows knee flexion during swing phase, but restricts flexion during the stance phase of gait. Cardiovascular energy measurements indicate that DKBS use allowed a more energy efficient gait.

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.

Rhomboid muscle electromyography activity during 3 different manual muscle tests

OBJECTIVE To determine which of 3 previously published rhomboid manual muscle tests (MMTs) elicits the maximal rhomboid electromyographic activity in an asymptomatic population. DESIGN Criterion standard. SETTING Motion analysis laboratory at tertiary care medical center. PARTICIPANTS Eleven male volunteers (age range, 24-40y) without shoulder or neck pain. INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES Peak 1-second normalized electromyographic activity in the rhomboid muscle during 8 different MMT positions, including 3 different rhomboid MMT positions (Kendall, Kendall-Alternative, Hislop-Montgomery). RESULTS The Kendall MMT (78% maximal voluntary contraction [MVC]) produced higher rhomboid electromyographic activity than the Kendall-Alternative (71% MVC) or the Hislop-Montgomery MMT (52% MVC), but the differences were not statistically significant. The posterior deltoid MMT generated the greatest rhomboid electromyographic activity of all MMTs, and 4% to 30% greater rhomboid electromyographic activity than the 3 rhomboid MMTs (P=.0001; posterior deltoid > Hislop-Montgomery). Electromyographic profiles of the Kendall and Kendall-Alternative MMTs were similar, whereas the Hislop-Montgomery MMT produced less upper trapezius activity (P=.0001 vs Kendall and Kendall-Alternative) and more latissimus dorsi activity (P=.0001 vs Kendall-Alternative). The standard MMT positions for the middle trapezius, levator scapula, posterior deltoid, and latissimus dorsi produced the maximal electromyographic activity for their respective target muscles. CONCLUSIONS The posterior deltoid MMT position should be used to produce maximal rhomboid electromyographic activity for normalization purposes during kinesiologic studies. The Kendall and Kendall-Alternative rhomboid MMT are likely to be clinically indistinct. It is unlikely that clinicians can use standard MMT positions to distinguish rhomboid strength from synergists, such as the levator scapula and middle trapezius muscle, for diagnostic purposes.

Ambulatory KAFOs: A Biomechanical Engineering Perspective

Kenton R. Kaufman, PhD, PE Steven E. Irby, MS Individuals with proximal weakness of the lower extremity are often prescribed knee-ankle-foot orthoses (KAFOs), also known as long-leg braces, to compensate for severe weakness of the lower limb muscles. More than 1.5 million people in the United States have partial or complete paralysis of the extremities. 1 Prevalence of paralysis increases with age ( Figure 1 ), and it is not surprising that the mobility of individuals with neuromuscular disorders is one of the most common and complicated issues treated by rehabilitation professionals. Many of these individuals require assistive technology (AT) in the form of an orthosis to enhance mobility ( Table 1 ). 2 It is important to note that although there is a greater need for assistive technology as age increases ( Figure 1 ), the use of AT actually decreases with age ( Figure 2 ). 3 This usage with age is due, in part, to consumer rejection of KAFO designs.

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.