Automatic control design for a dynamic knee-brace system

Determination of Gait Events and Temporal Gait Parameters for Persons with a Knee-Ankle-Foot Orthosis

Gait event detection is essential for controlling an orthosis and assessing the patient's gait. In this study, patients wearing an electromechanical (EM) knee-ankle-foot orthosis (KAFO) with a single IMU embedded in the thigh were subjected to gait event detection. The algorithm detected four essential gait events (initial contact (IC), toe off (TO), opposite initial contact (OIC), and opposite toe off (OTO)) and determined important temporal gait parameters such as stance/swing time, symmetry, and single/double limb support. These gait events were evaluated through gait experiments using four force plates on healthy adults and a hemiplegic patient who wore a one-way clutch KAFO and a pneumatic cylinder KAFO. Results showed that the smallest error in gait event detection was found at IC, and the largest error rate was observed at opposite toe off (OTO) with an error rate of -2.8 ± 1.5% in the patient group. Errors in OTO detection resulted in the largest error in determining the single limb support of the patient with an error of 5.0 ± 1.5%. The present study would be beneficial for the real-time continuous monitoring of gait events and temporal gait parameters for persons with an EM KAFO.

Design of an adjustable stance-control knee-ankle-foot orthosis for pediatric population

Conventional knee-ankle-foot orthoses (KAFOs) are generally prescribed for children with lower limb muscle weakness and joint instabilities. The main function of KAFOs is to provide stability during gait by locking the knee in full extension. However, walking with the knee joint in a fully extended position requires excessive energy consumption, leading to early fatigue and inducing non-physiological gait patterns. A new generation of KAFOs was developed to allow free knee flexion during the swing phase and to lock the knee joint during the stance phase to provide the required stability. These are commonly labeled as stance-control knee-ankle-foot orthoses (SCKAFOs). Nevertheless, commercial SCKAFOs are not available for the pediatric population. Especially in early ages, children must frequently replace the orthosis due to their growth. Hence, the proposed design presents a solution for a SCKAFO with adjustable length adaptable to children's dimensions ranging from two to six years old.

Design, construction, and evaluation of "sensor lock": an electromechanical stance control knee joint

BACKGROUND AND AIM

Most currently-available stance control knee ankle foot orthoses (SCKAFOs) still need full knee extension to lock the knee joint, and they are still noisy, bulky, and heavy. Therefore, the aim of this study was to design, construct, and evaluate an original electromechanical SCKAFO knee joint that could feasibly solve these problems, and thus address the problems of current stance control knee joints with regards to their structure, function, cosmesis, and cost.

METHOD

Ten able-bodied (AB) participants and two (knee ankle foot orthosis) KAFO users were recruited to participate in the study. A custom SCKAFO with the same set of components was constructed for each participant. Lower limb kinematics were captured using a 6-camera, video-based motion analysis system.

RESULTS

For AB participants, significant differences were found between normal walking and walking with the SCKAFO for temporal-spatial parameters and between orthoses with two modes of knee joints in the healthy subjects. Walking with stance control mode produced greater walking speed and step length, greater knee flexion during swing, and less pelvic obliquity than walking with a locked knee, for both AB and KAFO users.

CONCLUSIONS

The feasibility of this new knee joint with AB people was demonstrated. Implications for rehabilitation Stance control knee ankle foot orthoses (SCKAFOs) are designed to stop knee flexion in stance phase and provide free knee movement during swing phase of walking. Due to their high cost, size, excessive weight, and poor performance, few SCKAFO were optimal clinically and commercially. The feasibility of the new knee joint with able-bodied people and poliomyelitis subjects was demonstrated.

The influence of a powered knee-ankle-foot orthosis on walking in poliomyelitis subjects: A pilot study

BACKGROUND

Traditionally, the anatomical knee joint is locked in extension when walking with a conventional knee-ankle-foot orthosis. A powered knee-ankle-foot orthosis was developed to provide restriction of knee flexion during stance phase and active flexion and extension of the knee during swing phase of gait.

OBJECTIVE

The purpose of this study was to determine differences of the powered knee-ankle-foot orthosis compared to a locked knee-ankle-foot orthosis in kinematic data and temporospatial parameters during ambulation.

STUDY DESIGN

Quasi-experimental design.

METHODS

Subjects with poliomyelitis (n = 7) volunteered for this study and undertook gait analysis with both the powered and the conventional knee-ankle-foot orthoses. Three trials per orthosis were collected while each subject walked along a 6-m walkway using a calibrated six-camera three-dimensional video-based motion analysis system.

RESULTS

Walking with the powered knee-ankle-foot orthosis resulted in a significant reduction in both walking speed and step length (both 18%), but a significant increase in stance phase percentage compared to walking with the conventional knee-ankle-foot orthosis. Cadence was not significantly different between the two test conditions (p = 0.751). There was significantly higher knee flexion during swing phase and increased hip hiking when using the powered orthosis.

CONCLUSION

The new powered orthosis permitted improved knee joint kinematic for knee-ankle-foot orthosis users while providing knee support in stance and active knee motion in swing in the gait cycle. Therefore, the new powered orthosis provided more natural knee flexion during swing for orthosis users compared to the locked knee-ankle-foot orthosis.

CLINICAL RELEVANCE

This orthosis has the potential to improve knee joint kinematics and gait pattern in poliomyelitis subjects during walking activities.

Gait evaluation of new powered knee-ankle-foot orthosis in able-bodied persons: a pilot study

BACKGROUND

Knee-ankle-foot orthoses are utilized for walking by patients with lower limb weakness. However, they may be rejected by patients due to the lack of knee flexion available when using them for walking activities.

AIM

The aim of this study was to perform a pilot study investigating the effect of a new powered knee-ankle-foot orthosis on walking in healthy persons before testing with patients with lower limb weakness.

METHODS

Walking evaluation was performed on five healthy subjects (mean age: 26 ± 5.6 years). Walking trials were randomly performed in three test conditions: normal walking without an orthosis, walking with a conventional knee-ankle-foot orthosis unilaterally, and also with a new powered knee-ankle-foot orthosis applied to the same leg.

RESULTS

The means of walking speed, cadence, and knee flexion during swing and step length were all decreased. Compensatory motions were increased by both orthoses compared to normal walking. More knee flexion was observed in both swing and stance phases when walking with the powered knee-ankle-foot orthosis compared to the conventional knee-ankle-foot orthosis.

CONCLUSION

The results demonstrated the potential of a powered orthosis in providing improvements in gait parameters compared to a conventional device in healthy subjects but are yet untested in subjects with lower limb weakness.

CLINICAL RELEVANCE

The results of this study demonstrated that a powered knee-ankle-foot orthosis could lock the knee during stance and provide active knee flexion during swing to potentially reduce the tripping during ambulation.

Wearable monitoring devices for assistive technology: case studies in post-polio syndrome

The correct choice and customization of an orthosis are crucial to obtain the best comfort and efficiency. This study explored the feasibility of a multivariate quantitative assessment of the functional efficiency of lower limb orthosis through a novel wearable system. Gait basographic parameters and energetic indexes were analysed during a Six-Minute Walking Test (6-MWT) through a cost-effective, non-invasive polygraph device, with a multichannel wireless transmission, that carried out electro-cardiograph (ECG); impedance-cardiograph (ICG); and lower-limb accelerations detection. Four subjects affected by Post-Polio Syndrome (PPS) were recruited. The wearable device and the semi-automatic post-processing software provided a novel set of objective data to assess the overall efficiency of the patient-orthosis system. Despite the small number of examined subjects, the results obtained with this new approach encourage the application of the method thus enlarging the dataset to validate this promising protocol and measuring system in supporting clinical decisions and out of a laboratory environment.

New wearable walking-type continuous passive motion device for postsurgery walking rehabilitation

While total knee arthroplasty is useful for treating osteoarthritis of the knee, the success of this treatment depends on effective rehabilitation. The goal of this study was to develop an assistive device for post-total knee arthroplasty patients for walking rehabilitation and for shortening the hospitalization period. We developed a brace electronic assist system termed the knee assistive instrument for walking rehabilitation (KAI-R) to illustrate the need for training during postoperative rehabilitation. Sixteen osteoarthritis patients (1 male and 15 females; average age 68.9 years) who underwent total knee arthroplasty were analyzed before operation and 2-4 weeks after operation, and 25 healthy individuals (14 males and 11 females; average age 26.2 years) formed the control group. Based on the pre- and postoperative data on peak knee flexion angle, foot height, and walking velocity, we developed the KAI-R, which consists of an assistive mechanism for the knee joint, a hip joint support system, and a foot pressure sensor system and is driven by a CPU board that generates the walking pattern. We then tested the walking gait in seven healthy volunteers with and without KAI-R assistance. KAI-R increased the peak flexion angle of the knee and foot height in all seven volunteers; their range of motion of the knee joint was increased. However, KAI-R also decreased the walking velocity of subjects, which was explained by reaction delay and slightly compromised physical balance, which was caused by wearing the KAI-R. KAI-R is useful for gait improvement. In future studies, KAI-R will be investigated in a clinical trial for its ability for walking rehabilitation in post-total knee arthroplasty patients.

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 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.

Gait evaluation of a new electromechanical stance-control knee-ankle-foot orthosis

Commercial versions of a stance-control knee-ankle-foot orthosis (SCKAFO) have emerged to improve gait over conventional knee-ankle-foot orthoses (KAFOs), which lock the knee in full extension in individuals with quadriceps muscle weakness. A new electromechanical SCKAFO was recently designed to address the functional, structural, and cost limitations of these commercial SCKAFOs. This paper presents an evaluation of the new SCKAFO conducted to determine its functional and clinical effectiveness during gait. Three healthy adults (100% male; age, 35.3 +/- 19.7y) and three KAFO users with knee extensor weakness in at least one limb (100% male; mean age, 56.3 +/- 4.0y) participated in the study. The SCKAFO had a minimal effect, as desired, on the kinematics of the able-bodied subjects. KAFO users had a mean increase in knee flexion of 21.1 degrees (sd=8.2) during swing, and a greater total knee range of motion when walking with the new SCKAFO compared to their prescribed KAFO. Two KAFO users experienced a reduction in pelvic obliquity and hip abduction angle abnormalities when walking with the SCKAFO compared to their prescribed KAFO.

Consumer opinions of a stance control knee orthosis

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.

Design and evaluation of a stance-control knee-ankle-foot orthosis knee joint

Conventional knee-ankle-foot orthoses (KAFOs) are prescribed for people with knee-extensor muscle weakness. However, the orthoses lock the knee in full extension and, therefore, do not permit a natural gait pattern. A new electromechanical stance-control knee-ankle-foot orthosis (SCKAFO) knee joint that employs a novel friction-based belt-clamping mechanism was designed to enable a more natural gait. The SCKAFO knee joint allows free knee motion during swing and other non-weight-bearing activities and inhibits knee flexion while allowing knee extension during weight bearing. A prototype SCKAFO knee joint was mechanically tested to determine the moment at failure, loading behavior, and wear resistance. The mean maximum resisting moment of the SCKAFO knee joint over five loading trials was 69 Nm +/- 4.9 Nm. The SCKAFO knee-joint strength and performance were sufficient to allow testing on a 90 kg subject at normal walking cadence. Proper function of the new electromechanical knee joint was verified in walking trials of an able-bodied subject.

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. 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.

A practical guide to gait analysis

The act of walking involves the complex interaction of muscle forces on bones, rotations through multiple joints, and physical forces that act on the body. Walking also requires motor control and motor coordination. Many orthopaedic surgical procedures are designed to improve ambulation by optimizing joint forces, thereby alleviating or preventing pain and improving energy conservation. Gait analysis, accomplished by either simple observation or three-dimensional analysis with measurement of joint angles (kinematics), joint forces (kinetics), muscular activity, foot pressure, and energetics (measurement of energy utilized during an activity), allows the physician to design procedures tailored to the individual needs of patients. Motion analysis, in particular gait analysis, provides objective preoperative and postoperative data for outcome assessment. Including gait analysis data in treatment plans has resulted in changes in surgical recommendations and in postoperative treatment. Use of these data also has contributed to the development of orthotics and new surgical techniques.