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For decades and for a myriad of pathologies, patients requiring the use of a knee-ankle-foot orthosis or KAFO would find themselves relegated to one of two possible orthotic devices: a “locked-knee” or a “free-knee” orthosis. In exchange for much needed stability while ambulating, patients, therapists, physicians, and orthotists alike historically have made the recommendation for a KAFO with locked knee joints.
The locked-knee KAFO design has become a dreaded option for patients, who usually develop altered gait patterns that include hip hiking, circumduction, and vaulting as a result of not being able to functionally bend their knee. By comparison, these gait deviations are much like those of a low functioning level transfemoral amputee, who is utilizing a manual-locking prosthetic knee on the temporary prosthesis. The gait patterns arise due to the patient’s inability to “shorten” the length of the lower extremity during the swing phase of gait. Furthermore, these compensatory gait efforts lead to increased energy expenditure, which can result in up to a 58% to 79% KAFO rejection rate of the orthosis (Kaufman, 1996).
Stance control (SC) KAFOs offered a solution to the problem, however; traditional SCKAFOs are quickly being considered a “first wave” of potential options for “locked-knee” users. With a SCKAFO, the patient generates a toe-moment and/or a knee extension moment to cause a manually adjusted joint to release just prior to the swing phase of the gait cycle, allowing the knee to flex or bend. Then, during the stance phase of gait, the brace locks to block knee flexion for inherent stability and subsequent increased weight transfer to the brace or affected side.
While these manual, or nonpowered, SCKAFO designs have been used since the 90s, more recently, microprocessor-controlled or electronic options have become available. Not only can these joints be calibrated to the user, they can help the brace adapt to variations in velocity, stride length, and cadence, providing for increased stability and mobility. To allow for dissimilarity among patients’ needs, there are more than five different options of SCKAFOs for patients and orthotists to consider. Models vary with weight and size and to some degree function; understanding the subtleties of each device can lead to increased success when fitting microprocessor-controlled SCKAFOs.
In the United States, there are roughly 989,000 KAFO wearers. Many of these patients could improve their quality of function with a stance control orthosis, specifically a microprocessor-controlled SCKAFO. While all available designs succeed at providing stance-increased ability and stability, they are not without limitations. Understanding appropriate patient selection for this technology is particularly paramount.
One factor for consideration of patient selection is hip strength. It is thought that an appreciable number of patients currently utilizing locked-knee KAFOs possess sufficient hip strength to both control and benefit from a microprocessor-controlled SCKAFO. Currently, these devices can be considered for patients with hip flexor and extensor strength of at least a Grade 3. Furthermore, no diminished hip abductors can be noted in patients who are wearing the braces bilaterally.
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In addition, consideration of the patient’s knees is imperative. Knee extensor paralysis or paresis must be confirmed. Any presence of knee contracture must be less than 15º. Furthermore, any noted knee varum/valgum must be less than 15º. Lastly, hamstring spasticity should be noted, as these braces are ineffectively operated by patients with moderate to severe hamstring spasticity.
Patient weight is also important. While weight restrictions vary with each type of microprocessor-controlled SCKAFO, minimum and maximum weight requirements exist. Many of these SCKAFOs will not support the body weight if the patient stumbles or flexes the knee during standing, or function properly while ascending or descending stairs. Due to the high forces generated when resisting the patient’s knee flexion, joints vary in size with most being on the larger size. If the joints are smaller in dimensions, then the maximum weight limit for that brand of joint is probably fairly low.
In addition to considering patient weight and other issues, more readily quantifiable measures, such as strength and flexibility, cognitive ability, and other potential limitations, must be discussed with the patient. Patients should be able to understand basic “gait” concepts. It helps if the patient has, but doesn’t necessarily need, a general intuition about how the ankle, knee, and hip joints work together to advance a person forward. My experience has been that most patients who have been ambulating in an existing locked-knee KAFO completely understand “how the SCKAFOs are supposed to function” and have good limb awareness and proprioception. In addition, SCKAFOs have just begun to be available in some low profile designs but not without trade-offs. Many of the less bulky designs offer fewer features than the bulky, less aesthetic styles. It is imperative that the orthotist spend as much time with the patient managing expectations as identifying clinical indications.
Lastly, and maybe as important, expectations of function and physical therapy training must be established with every potential patient. This process starts during the initial evaluation/consultation and continues well into the initial fitting of the SCKAFO. To further facilitate this anticipatory guidance, our clinic, Ability Prosthetics & Orthotics Inc, offers “functional fittings” of these devices. Much like a diagnostic “walking” check socket for a prosthetic limb, the orthotist takes an impression of the limb and has a clear plastic KAFO fabricated to include the SCKAFO joints on a trial basis. The patient can then ambulate within the safety of parallel bars. The orthotist can assess any potential fitting issues as they relate to trim-lines, strap placement, and pressure tolerances. Initial potential positive outcomes can be measured—all prior to both the patient and orthotist committing to providing the technology. Some of the following issues can be considered: Does the patient exhibit a normal or near normal knee flexion angle during swing phase? Any reduced pelvic retraction or excursion? Is the patient’s velocity and stride length greater? What does the patient think and feel? And, on the nonbraced side, was there a reduction in vaulting?
At Ability, we have fit 25 patients with microprocessor-controlled SCKAFOs. Patients range in diagnosis from post-polio syndrome to isolated quadriceps weakness to incomplete spinal injury to multiple sclerosis to muscular dystrophy. In addition to strict patient selection criteria, we have found that orthotist knowledge, payor source understanding, physician awareness, and some design factors/limitations and cosmesis also have contributed to a limited emergence of these technologies. Whether a patient meets criteria for a SCKAFO is uncontrollable, but the other barriers noted can be overcome through increased education and awareness.
Part of increasing awareness is to underscore that, for the right patient, the effects of the SCKAFO are tremendous. Many of our patients have quickly gained increased confidence in walking with SCKAFOs, even during these trial sessions. Our advice to patients has been to “just walk.” Like many other microprocessor-controlled devices, the microprocessor-controlled SCKAFO calibrates to the user; thus, the device can support the user within and beyond their function-ability. This is unlike many other devices in both orthotics and prosthetics over the years, as traditionally the patient must operate within the functional limitations of the device.
To allow patients to transcend beyond issues regarding design and function factors, we coordinate physical therapy for our patients who have received a microprocessor-controlled SCKAFO. In fact, we have found it most beneficial for the patient to have a therapist present for the trial fitting. After an average of 4 to 6 weeks, most patients are comfortable within their new brace and rewarded with their increased stability and mobility.
With the limited research available, it is fair to say there is a positive trend toward SCKAFOs, providing increased gait efficiencies while maintaining a user’s stability. Larger sample sizes should be examined to further objectively establish their effectiveness. Other such suggestions to increase usage and applicability would be for more orthotic practices to embrace this offering as a “first choice” for patients who are candidates. The locked-knee KAFO should become a “last resort” brace design. To do this, many practices will need to adapt more of a technology platform. Also, the various orthotics educational programs throughout the country should be implementing this technology to enhance the knowledge of new practitioners entering a quickly evolving market.
Jeffrey M. Brandt, CPO, is a certified prosthetist and orthotist, and is CEO and founder of Ability Prosthetics & Orthotics Inc (www.abilitypo.com), Gettysburg, Pa. The company outsources 100% of its fabrication, employs electronic medical records, and has launched five full-time offices in as many years, with patient care centers in Pennsylvania and Maryland. For additional information, contact .
