The Relationship between Performance, Satisfaction, and Well Being for Patients Using Anterior and Posterior Design Knee-ankle-foot-orthosis
Ammanath Peethambaran, DPO (India), MS, CO
ABSTRACT
Management of lower extremity musculoskeletal disorders using knee-ankle-foot orthosis (KAFO) represents a complex phenomenon. Much research addressing gait and biomechanics with various KAFO designs has been conducted. The majority of the KAFO users abandon the orthosis primarily because of discomfort and poor ergonomic factors. The purpose of this study was to investigate patients' experiences with two different KAFO designs in relation to performance, satisfaction, and well being.
Five subjects with a primary diagnosis of postpolio paralysis participated in the study. An anterior approach design KAFO and a conventional posterior approach design KAFO were evaluated. Three categories of questionnaires focusing on performance, satisfaction, and well being were administered. The questionnaires measured ease of application and removal, stability, function, and body part discomfort.
The primary conclusion is that in actual practice at home and in the work environment, the anterior approach design is preferred in relation to performance, satisfaction, and well being.
Key Words: Knee-ankle-foot orthosis, satisfaction, performance, well-being, ergonomics
Introduction
Traditionally, a knee-ankle-foot orthosis (KAFO) is used as a therapeutic instrument for the management of lower-extremity musculoskeletal deviations, injuries, or disorders. A KAFO is therefore designed to control motion at the knee, control functional ambulation, and improve general safety during gait. The system also helps to save energy during gait, and to improve balance, endurance, and overall body awareness.
Inman1 states that energy consumption in humans is least when locomotion is in a straight line with a constant velocity requiring only enough force to maintain motion and overcome friction. Gait analysis has shown that the slower the cadence, the greater the energy expenditure. As cadence increased, energy consumption per step decreased at a certain rate of speed. Lehneis,2 investigating energy expenditures of patients with abnormal gait pattern, found that the use of KAFO offered savings in energy from 9% to 14%. A new energy efficient electronically controlled KAFO developed by Kaufman3 provided reduced metabolic energy consumption while providing maximum knee stability during stance and free motion during swing phase of gait.
The basic design used in the fabrication of a KAFO is double uprights, thigh band, calf band, ankle joint, and knee joint, which is attached to the shoe. KAFOs are also fabricated from thermoplastic materials. Traditionally, an orthosis is applied using a posterior approach technique to address the lower extremity segment deviation. Unfortunately, this technique compromises function, comfort, and segment control. Although most researchers have mainly focused on the design basically for ambulation, very little attention has been given to the real potential problems at home and in the workplace environment.
Rationale
KAFOs are recommended to patients who present lower-extremity pathomechanics. It is designed to control undesired motion at the knee, functional ambulation and improve general safety during gait. The system also helps to save energy during gait.
The basic KAFO design consists of a proximal and distal thigh cuffs, calf band, double uprights with mechanical knee joints with or without lock, and an adjustable or fixed mechanical ankle joint with anterior knee flexion control straps. An orthosis so fabricated will allow the patient to balance the body weight over feet with proper trochanter knee-ankle alignment and body posture. Conventional orthoses as described are usually heavy, cumbersome, hard to wear, and ergonomically inefficient. An orthotist mindful of biomechanical principles of gait and availability of materials can properly design a knee-ankle-foot-orthosis to enhance performance for those who are diagnosed with lower extremity dysfunction.
Research Questions
This study seeks answers to the following research questions:
Will patients with lower-extremity musculoskeletal dysfunction experience greater satisfaction in relation to performance and well being using an anterior approach knee-ankle-foot-orthosis when compared with a posterior approach knee-ankle-foot-orthosis?
Will patients with lower-extremity musculoskeletal dysfunction experience improved performance in relation to satisfaction and well being using an anterior approach knee-ankle-foot-orthosis when compared with a posterior approach knee-ankle-foot-orthosis?
Will patients with lower-extremity musculoskeletal dysfunction experience a greater sense of well being in relation to performance and satisfaction using an anterior approach knee-ankle-foot orthosis when compared with a posterior approach knee-ankle-foot orthosis?
Definition of Terms
Performance is defined as the ability of the participant to accomplish the task to be performed within the ergonomic aspects of the orthosis. Questionnaire data is used to measure the participant's performance level (Form 1, Appendix B
).
Satisfaction is defined as the physical and mental achievement of the functional goal with the orthotic system. Questionnaire data is used to determine the participant's satisfaction level (Form 2, Appendix C
).
Well being is defined as the state of being comfortable mentally and physically within the orthotic system. A body part discomfort chart (Form 3, Appendix D
) is primarily used to determine if the participant experienced perceived discomfort from the use of KAFO system.
Primary components used in the system are lightweight carbon composite material laminate, a laminated foot plate, thigh and leg section incorporated with mechanical knee joint, ankle joint, and cable control knee locking mechanism. The system is created to apply an anterior approach, reducing the strains of donning and doffing, and to allow the lower extremity to maintain an optimal position when effectively applied. Additionally, the orthosis serves to significantly control the knee in sagittal, coronal, and transverse planes.
The purpose of the study is to test the efficacy of an ergonomic model anterior approach KAFO and conventional posterior approach KAFO for patients presenting lower-extremity musculoskeletal pathomechanics and to address performance, satisfaction and well being.
Materials and Methods
Two types of KAFOs were evaluated for patient's performance, satisfaction, and well being.
Anterior approach design KAFO
The design consists of lightweight carbon titanium KAFO with cable control locking mechanism (Figures 1
and 2
). The components identified as necessary for the design and developments of the system are the anterior thigh section, the anterior tibial section, the footplate, the cable control locking mechanism, and the posterior non-elastic strapping system. The system is wet laminated with carbon composite material for strength and durability.
The conventional design KAFO
The conventional design selected for the study consists of standard polypropylene thigh foot and ankle section, mechanical knee and ankle joints, infra and supra patellar straps, and proximal thigh strap attached with Velcro closure for quick and easy removal. The orthosis is applied with a posterior approach technique.
Research Design
The research design is an experimental design. The subjects were selected as convenience sample according to diagnosis and pathomechanical presentation of the lower extremity involved.
Subjects
A sample of convenience consisting of five subjects with postpolio paralysis as primary diagnosis involving one lower extremity was selected. Table 1
shows the characteristics of subjects selected. Three females and two males participated in the study. The sample was limited to five during the study period. The subjects had a mean age of 61.40 years (range, 45-78 years; SD, 12.44). All subjects were patients returning for knee-ankle-foot orthotic management referred by the attending physicians. Participation was voluntary.
The subjects who were selected for the study were required to have lower extremity muscle strength as determined by Manual Muscle Testing4 for hip flexors at greater than or equal to 3, hip extensors greater than or equal to 3, knee extensors and knee flexors shows the subject's muscle strength as determined by manual muscle testing. All subjects had normal range of motion at hip, knee, and ankle. A patient analysis form (Appendix A
) was used for data collection.
Instrumentation
The data collection instruments consisted of performance evaluation questionnaire (Form 1
), satisfaction questionnaire (Form 2
), and a body part discomfort map (Form 3
). Parts of the questionnaire were developed by the Subcommittee on Evaluation, Committee on Prosthetics Research and Development, National Research Council, National Academy of Sciences, Washington, DC.5 The body part discomfort map was developed to identify perceived discomfort experienced by patients wearing KAFOs. It is used to measure the well being of subjects using the orthoses.
The questionnaires on performance evaluation (Appendix B; Form 1
) use a five-point scale (higher scores are better). The data on Form 1
are primarily related to the ease of application, balance, stability, maintenance, and use in sports activities.
The satisfaction questionnaire (Appendix C; Form 2
) uses a five-point scale (higher scores are better). It was used to collect data related to the patient's attitude toward loss of function, appearance, weight, effort, and functional use. It included four questions with "yes" or "no" answers.
A body discomfort map (Appendix D; Form 3
) adapted and modified from Sauter et al.6 was used to evaluate well being. The subjects entered the level of discomfort on the posterior and anterior sections of the extremity using a six-point scale (higher scores indicate increased discomfort). Data are used to evaluate and measure the subject's perceived comfort level in the lower extremity while using the KAFO.
Procedure
The purpose and aim of the study was explained to the subjects meeting the criteria for inclusion. They were told that, according to current knowledge, the anterior approach KAFO intervention protocol is considered to be equally effective compared to the conventional posterior approach. A prototype of the KAFO was demonstrated for actual visualization and feel for the system. A drawing of the orthosis with details of materials and componentary and functional advantages and disadvantages was provided. Three outpatient clinic visits were planned. During the initial visit, information from medical records such as name, age, gender, height and weight, and treatments and observations were recorded. A patient analysis form (Appendix A
) was used to record personal information, functional status, and previous orthotic management and lower extremity pathomechanical presentation. All subjects were using a posterior approach KAFO before attending the clinic and all subjects were recommended for the alternate design. At the time of the initial visit, the three sets of questionnaires were administered for an evaluation of their conventional KAFO. The subjects were then evaluated and casting procedures completed for the new KAFO. The KAFO system was ready for application in 3 weeks. The new anterior approach KAFO was worn for 6 weeks. Regular follow-up was carried out to ensure the integrity of the system, its functional fitting, and comfort. During the third visit, the second set of questionnaires (Forms 1
, 2
, 3
) were administered to establish the subjects' responses to the new KAFO.
Data Analysis
Because of the small sample size in the study, the nonparametric Wilcoxon signed rank test was used to compare anterior design KAFO with the posterior design KAFO in terms of performance, satisfaction, and well being. Because it was of interest to determine if the anterior approach design KAFO actually performed better than the posterior approach design KAFO, a one-tailed test was used with alpha = .05 to determine statistical significance. The analysis was performed with SPSS Version 8.0 for Windows software (SPSS, Chicago, IL).
Results
Performance Evaluation
A total of ten questions were asked on Form 1 (Appendix B)
regarding performance using KAFO. Table 3
shows the mean and standard deviations of each of these questions for all five subjects. As indicated in table 3
, the anterior approach design KAFO received the most favorable overall rating. The results of performance evaluation questionnaire are listed in Table 4
.
How easy was the KAFO to put on? 100% (5/5) found that the anterior approach KAFO easy or very easy, as compared with the posterior approach design, of which 60% said very difficult, 20% difficult, and 20% neutral.
How easy were the straps application? 80% (4/5) found no difference between the designs in relation to strap application. One subject said strap application was easy to apply.
How easy was the KAFO to remove? Because of the nature of the design, 60% of the subjects found that it was easy to remove the anterior approach design KAFO as compared with the posterior approach. 100% said it was difficult to remove the posterior approach design
How easy was the shoe to put on? 60% (3/5) indicated that the application of shoe with the anterior design was easy.
How easy was the KAFO cleaning and maintenance? The anterior approach design scored higher with 60% easy, 20% very easy, and 20% neutral.
KAFO adversely affects your balance. 100% strongly disagree or disagree with any adverse affect on balance using the anterior design orthosis, and 80% disagree on adverse affect on using the posterior design.
KAFO interferes with sitting. 100% indicated that the anterior design did not interfere with sitting whereas 100% indicated that posterior design interfered with sitting.
KAFO provided greater sense of stability in level walking. 60% strongly agreed that they felt the anterior design provided a greater sense of stability in level walking.
KAFO provided greater sense of stability on uneven ground walking. All subjects (5/5) felt more stable using the anterior design KAFO, but only three subjects (60%) agreed that they felt stable using the posterior design.
KAFO was adequate during sports activities. All subjects felt that both KAFO designs provided adequate support for their sports activities.
Satisfaction Evaluation
The data analysis shows a significant difference in satisfaction between both designs of orthosis (Table 5
). Subjects accepted the loss of functional ability because of disease and were enthusiastic and comfortable wearing an orthosis, preferring the anterior design to the posterior design. The difference in attitude was the level of confidence and the ergonomic factors associated with the anterior design. Table 6
illustrates the satisfaction questionnaire, the scores on each question, and the significance.
Loss of function. The questionnaire result indicated that the subjects accepted the functional loss because of polio.
Wearing an orthosis. The subjects indicated that wearing an orthosis, whether it is an anterior or posterior design, is acceptable to them. The subjects participating in the study were unable to perform their daily activities without an orthosis.
Comfort. Four out of five subjects (80%) said that they were comfortable most of the time using an anterior design. Only two subjects (40%) indicated the same comfort level using the posterior design.
Gait. All subjects (100%) felt that their gait has much improved using an anterior design KAFO. Four subjects (80%) indicated some improvement in their gait using the posterior design KAFO.
Appearance. Questionnaire results show that all subjects (100%) approved the anterior design with higher scores and said it is a better design compared with the posterior design.
Effort. All subjects (100%) wearing an anterior design KAFO found that using the anterior design required much less effort. Only 40% found the same effect using the posterior design.
Hours of wearing. There were no difference in using the KAFO and the hours of wearing in both designs. All subjects participating in the study were full-time wearers and were unable to complete the tasks without an orthosis.
Weight. Three of the subjects (60%) felt that the posterior design was lighter than the anterior design. The researcher also found that the laminated design had increased weight because of the lamination process and the materials used in the fabrication.
Support. Although all subjects (100%) felt somewhat secure with the posterior design KAFO during the gait, four subjects (80%) felt that the anterior design provided a more secure base of support during ambulation.
Donning and doffing. All subjects (100%) felt that the anterior design was easy to apply and remove. Two (40%) agreed that it was easy for them to apply and remove a posterior design KAFO.
Catch Clothes. Questionnaire results indicate that the anterior design did not catch clothes; all subjects (100%) using the posterior design said that it did catch clothing. This may be attributable to the fact that there are more exposed parts of mechanical joint and locking mechanisms as compared with the laminated anterior design.
Soil Clothes. All subjects (100%) indicated that the anterior design KAFO did not soil clothes. Three subjects (60%) said that the posterior design did not soil the cloths.
Perspire. Four subjects (80%) complained that both designs made their skin perspire. One subject using the anterior design said "no."
Rub skin. Questionnaire answers indicate that all participants (100%) agreed that the anterior design did not rub or irritate the skin. Two participants (40%) using the posterior design agreed to the same.
Body Part Discomfort Diagram Well Being Questionnaire
KAFO users assume that the aches and pains associated with the use of an orthosis are merely natural. Improper application and poor ergonomic design may lead to uncomfortable experiences with the orthosis. The data collected from the body discomfort diagram (Table 7
) shows majority of the patients experienced pains or discomfort at the back of the thigh section and calf section while using the conventional orthosis. Table 8
shows patient responses to each question and significance.
Thigh (front). There were no differences in the responses, indicating that both designs were equally comfortable at the anterior section of each subject's thigh.
Knee (front). Three subjects (60%) using anterior design were very comfortable and four subjects (80%) using the posterior design felt comfortable at the anterior section of the knee.
Lower leg (front). The posterior design received higher scores on comfort at the anterior section of the lower leg. Three subjects (60%) felt that it was comfortable for them when using the anterior design KAFO.
Foot and ankle. Questionnaire results indicate that both anterior and posterior designs were comfortable at the foot and ankle section, although the anterior design scores were slightly higher in comfort level.
Thigh (back). The results of the questionnaire indicates that all subjects (100%) using anterior design were very comfortable while the subjects using the posterior design indicated discomfort at the posterior section of the thigh.
Knee (back). All subjects with anterior design KAFO felt very comfortable at the posterior section of the knee. Only one subject using the posterior design responded to the same level of comfort.
Lower leg (back). The anterior design KAFO received a high score (100%) on comfort level at the back of the lower leg. Four subjects (80%) said that using the posterior design KAFO was uncomfortable at the back of the lower leg.
Discussion
Over the years there have been numerous developments in the design of lower extremity orthotic systems. These include KAFOs, AFOs, and computerized electrical stimulation for walking. However, none of these designs have proven successful in terms of usage in the community, home, and work place. Certainly, factors such as cosmesis, ease of application and removal, ease of maintenance, ergonomic function, and well being may be far more important than biomechanical performance.
The presently available KAFO designs are mainly focused on substitution of functional deficits. The conventional designs available are fabricated from a metal and leather combination or, more recently, a metal and thermoplastic combination. They are cumbersome and heavy, with many straps attached to control various segment deviations. These mechanical devices sometimes induce potential hazards from the physical and psychological stress of spending long hours wearing them and having activities limited rather than accomplishing important objectives or performance.
The questionnaire results from this study indicate that patients with lower extremity impairment were able to enhance their ergonomic function in relation to performance, satisfaction, and well being when using anterior design KAFO compared to posterior design KAFO. In addition to improving sitting comfort (Figure 3
), stability in level walking, and easy application, the anterior design was adequate for use in the sports activities. Strap application (Figure 4
) and effect of balance seemed almost equally effective in enhancing the performance in both designs. Perhaps making the straps adjustable, non-elastic, and soft may increase the comfort level. The study indicates that the anterior design has positive ergonomic attributes, convenience, and usability compared with the posterior design.
Besides the enhanced performance shown in the results from questionnaire Form 1 (Appendix B)
, patients using the anterior design showed satisfaction, especially in the areas of comfort, improved gait, and effort. A particular area where the ratings were least satisfactory was the weight of the anterior design orthosis. The laminated design demonstrated greater weight compared with the posterior design. This may be because of the excess material used in the lamination procedure to maintain the structural strength of the KAFO. A future goal of minimizing the weight by using lightweight material should be considered. However, the subjects participating in the study was very much satisfied with the design, appearance, and the ease of application. All subjects reported that the loss of function was acceptable and that wearing an orthosis was very acceptable and subjects showed equal scores on both designs. Anterior design scored higher values with donning, doffing, and support, and essentially all subjects reported that they were satisfied with the design and the ergonomic factors.
The review of responses summarized in the questionnaire Form 3 (Appendix D)
data indicates a greater perception of body comfort. Two particular areas where the posterior design KAFO received lower comfort ratings were on the posterior sections of the thigh and the lower leg segments. This may be because of the fact that the system KAFO molded sections apply excessive force on the posterior sections of the leg during sitting at the work place or at home. The anterior design scored higher on thigh, knee, and lower leg comfort, enhancing the body comfort level. The questionnaire results indicate that overall, the anterior design resulted in most favorable ratings.
The results of this study can be used to improve the designs of knee-ankle-foot orthoses by considering the negative and positive aspects of the orthoses. It is suggested that the area needing the most attention may concern patient feelings relating to performance, satisfaction, and well being. As the age of polio patients increases, the problems associated with pain, fatigue, loss of muscle strength, and ligament laxity of the lower extremity are also expected to increase. The percentage of time wearing an orthosis may increase considerably and this increase in time would make ergonomic factors more important, especially body comfort, satisfaction, and performance. The data from the study present a considerable amount of information that suggests positive feelings concerning design changes to enhance the satisfaction, performance, and well being of KAFO wearers.
Conclusion
The results of this study indicate that changes in the design of a knee-ankle-foot orthosis can significantly improve the performance, satisfaction, and well being of patients with lower-extremity musculoskeletal dysfunction. Subjects showed improved overall ergonomic function at home and work environment with the anterior design. Although the subjects used both the anterior and the posterior designs full-time, the anterior design was rated higher in satisfaction and body comfort. The data reported in this study and the results of the investigation were considered and the overall opinion of the investigator is that the anterior design KAFO was the better design tested from an ergonomic perspective. The study also suggests that positive design changes can enhance the performance, satisfaction, and well being of patients using knee-ankle-foot orthosis.
Acknowledgements
This study was completed while the author was a graduate student at the University of Connecticut, Storrs, CT. The author is very grateful to Dr. Priscilla Douglas, PhD for her help and support. The author also gratefully acknowledges the contributions of Mark Taylor, MLS, CPO and the O&P practitioners and technicians at the University of Michigan O&P Center, Ann Arbor, MI.
References:
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- Lehneis HR. Bioengineering research and development of LE orthotic devices. Final report, Project 23-P-55029/2-03. New York: NYU Medical Center; 1992.
- Kaufman RK, et al. Energy efficient KAFO: A case study. J Prosthet Orthot. 1996;8:79-85.
- Daniels L, Williams M, Worthingham C. Muscle Testing: Techniques of Manual Examination. Philadelphia: W.B Saunders; 1968.
- National Academy of Sciences Subcommittee on Evaluation, Committee on Prosthetics Research and Development. Clinical Evaluation of a Comprehensive Approach to Below Knee Orthotics. Washington, DC: National Academy of Sciences; 1972.
- Sauter SL, et al. Work posture, work station, design and musculoskeletal discomfort in a VDT data entry task. Hum Factors. 1991;33:151-167.
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