Antispasticity Contracture Bracing

Many bracing specialists find it very challenging to provide contracture management orthoses to patients with significant limb spasticity. At the root of this dilemma is the need for a thorough understanding of the etiology of spasticity and adequate best-practices guidance for bracing patients with this condition. This article reviews the etiology of upper motor neuron (UMN)-related limb spasticity and orthotic technologies that can be effectively utilized as antispasticity bracing. Spasticity Spasticity is often defined as “a motor disorder with a persistent increase in the involuntary reflex activity of a muscle in response to stretch.” 1 This definition describes the symptoms of spasticity as opposed to identifying the root cause of spasticity and would imply that stretching is to be avoided when using antispasticity bracing. But the clinical evidence suggests that it is erroneous to conclude that stretch is contraindicated for effective spasticity treatment. Spasticity is usually related to a disorder of the UMN, which originates in the brain, that results in a reduction of the inhibitory signals from the brain to the lower motor neuron (LMN), running from the spinal cord to the end of the limbs. 2 The greater the disruption of inhibitory signals from the brain, the greater the degree of spasticity. Common causes of UMN-related spasticity include stroke, traumatic brain injury, cerebral palsy, and multiple sclerosis. Limb spasticity is most pronounced in the flexor muscles of stroke patients. Often our experience with manual stretching of a spastic limb reinforces a belief that stretching is contraindicated for patients with spasticity; during passive stretching, the spastic limb can provide significant resistance to stretch. However, clinical evidence finds that sustained muscle stretch of ten minutes led to significant reduction in spastic hypertonus in the elbow, hand, and finger flexors. 3 This article outlines effective antispasticity bracing characteristics that can be used to provide neurorehabilitation while the patient is wearing an antispasticity brace. All antispasticity braces when used as directed provide sustained stretching that will not initiate a stretch reflex. Motor Nerves There are two primary motor nerves that control smooth muscle movement, the muscle spindle and the Golgi tendon organ (GTO). Muscle spindles and GTOs work in pairs to create smooth muscle function. The muscle spindle is located in the muscle belly and detects the degree and rate of muscle lengthening or shortening. It is responsible for muscle contraction and is therefore referred to as the excitatory motor nerve. The GTOs are found in bundles located at the tendon muscle junction at the distal and proximal ends of the muscle. The GTO senses muscle tension and is responsible for muscle inhibition. Muscle spindles and GTOs communicate with one another to manage smooth, energy-efficient work. If a five-pound weight is placed in an outstretched hand, the GTO senses the tension (load) placed onto the arm and controls muscle spindle–related muscle contraction that is ideal for efficiently holding the weight. When working properly, the GTO regulates the muscle contraction with an inhibitory influence such that the muscle spindle only contracts to the degree necessary to complete the work needed to hold the object. After a UMN injury, the reduction of inhibitory influence from the brain to the GTOs in the LMN results in hyperactivity of the muscle spindles and involuntary muscle contractions. The imbalance of the muscle spindle and GTO-pair functioning can be referred to as an abnormal reflex arc. To rehabilitate the abnormal reflex arc, two things are needed: GTO excitement initiated locally by braces that initiate gentle sustained tension into the spastic muscle, and improved GTO/muscle spindle–communication to reduce muscle hyperexcitability over time. During sustained stretch with an antispasticity brace, muscle spindle/GTO communication is partially restored. Over time, the abnormal reflex arc therapy provided by an antispasticity brace can provide significant neurorehabilitative benefits. Since the brain is not providing adequate inhibitory influence signals to the spastic limb, the clinician needs to focus on creating sustained gentle tension on the affected limb to increase GTO inhibitory influence. The good news is that for the majority of UMN dysfunction patients, the UMN insult has not affected the GTO motor nerves. Since GTOs are not getting adequate excitation from the brain, they need to be excited locally using manual techniques, neuroinhibiting modalities, and gentle, sustained tension initiated by antispasticity orthoses. Antispasticity Orthotic Design [caption id="attachment_250272" align="alignright" width="300"] DynaPro Flex Elbow.[/caption] Traditionally, ball hand splints were recommended as the ideal positioning splints for a spastic hand. While maintaining an optimal resting alignment positioning of the wrist/hand/fingers, static splints do not allow the spastic muscle to shorten during an involuntary muscle contraction. This can result in orthotic discomfort and the possibility that the static splint may “feed into tone” (the affected spastic muscles are agitated when the muscles contract involuntarily and cannot shorten to reduce muscle spindle hyperexcitability). With newer bracing designs and technologies, once spasticity is observed in a limb, static splints should be avoided when possible. Antispasticity orthoses should have the following characteristics to be effective: The brace must flex during a significant involuntary muscle contraction. Muscle spindle hyperexcitability is reduced when the muscle is allowed to shorten slightly. When applied, the brace should initiate gentle tension to both excite the GTO (inhibitory excitement) and increase paired GTO/muscle spindle communication. The brace must have a negative nonlinear spring force or a constant linear spring force tension when applied to avoid feeding into tone. Flexibility During Spastic Episodes Patients with spasticity have episodes of involuntary muscle spasms. Spasms can be limb related (stretched too far or too fast) or nonlimb related (during sit to stand, coughing, etc.). An antispasticity brace must allow the muscles to shorten slightly during involuntary muscle contractions to reduce muscle spindle excitability while providing sustained gentle tension to create GTO inhibitory influence. Pneumatic air orthoses, static-dynamic antispasticity orthoses, and constant linear tension spring-loaded orthoses all have sufficient flexibility to allow the spastic muscle to adequately shorten when necessary. Initiate Gentle Tension to the Spastic Muscle [caption id="attachment_250271" align="alignright" width="300"] DynaPro Flex Finger.[/caption] Except for very mild spasticity or a flaccid limb, static positioning orthoses are not recommended as they do not provide inhibitory influence on the spastic limb (no sustained tension). The GTOs are activated when there is brace-initiated tension in the affected muscle(s). To be effective, the tension initiated by the brace should be sustained such that constant inhibitory excitement is provided by the brace. Too much tension will have the opposite effect and overexcite the hyperactive muscle spindles. The orthotist can easily assess the affected muscles pre- and post-antispasticity brace fit to confirm the desired inhibitory affect. Pneumatic air bladder technology is excellent as antispasticity bracing. The pneumatic air bladder(s) are inflated until the first pump that is more difficult to insert additional air into the bladder(s). This amount of air initiates the desired inhibitory tension into the spastic muscles. If there is an involuntary contraction of the spastic muscle, the muscle can shorten easily to reduce muscle excitability as the air bladder can be relatively easily squeezed so the muscle will be able to shorten. The correct level of inflation will result in the affected muscles relaxing after several minutes of sustained tension. Static-dynamic orthoses are patented braces constructed in a static orthotic design, but the orthotic inserts are flexible and serve as an antispasticity dynamic spring when applied to the limb as directed. Elbow and knee braces are fitted 15 degrees straighter than the contracted limb. When applied, the brace creates inhibitory sustained tension into the spastic muscles as the flexible uprights flex into the contracture, providing an extension stretch for a flexion pattern of spasticity. Devices for hyperextension tone initiate sustained tension on the extensor muscles. Since the device uprights are flexible, the muscles can shorten during involuntary muscle contractions effectively reducing muscle spindle excitability. Static-dynamic wrist/hand/finger orthoses have a thermoplastic flexible insert that is heat molded so that the fingers are held in full available extension while the wrist is set 30 degrees ahead of comfortable end-range manual stretch. This setting allows the brace to flex into the wrist/hand/fingers, creating an inhibitory effect on the spastic muscles. A static-dynamic AFO has a flexible insert and calf extensions with pull straps to activate an inhibitory sustained stretch. When the AFO is applied and the dorsi-assist straps are tightened, it provides inhibitory excitement to the spastic ankle/foot. A torticollis collar is set to initiate gentle tension onto the laterally contracted neck, creating inhibitory sustained tension within several minutes after device fitting to effectively manage lateral neck spasticity. DynaPro orthoses are second-generation static-dynamic orthoses that were bioengineered using a myotonometer to determine the optimal amount of tension to have an inhibitory effect on the affected spastic muscles within five minutes of brace application. A myotonometer is a device used to test muscle tension, and it can be used to evaluate the effect of various strengths of sustained tension on a spastic muscle to ensure muscle inhibition in most patients. Patients with UMN-related spasticity have an abnormal reflex arc (muscle spindle/GTO imbalance). This means that there is altered muscle spindle/GTO communication. The muscle spindles are hyperexcitable and the GTOs are underperforming. To rehabilitate the abnormal reflex arc, antispasticity braces provide abnormal reflex arc therapy by reactivating GTO influence over the adversely affected muscle spindles. Over time, with daily use of antispasticity braces, the intensity and duration of involuntary muscle contractions should diminish. Muscle Stress-Relax Phenomena Muscle stress-relax in a phenomenon that is described as follows: “When a gentle tension or stress is applied to a muscle that does not cause pain or risk injury to the muscle, the muscle will adapt, and ‘relax’ or elongate as opposed to opposing the gentle stress or stretch. This phenomenon (relaxed elongation) will usually occur within several minutes after applying the gentle stress.” 5 An antispasticity brace is tested by confirming that after several minutes of gentle sustained brace-initiated stress (stretch) that the muscles have relaxed into the fit, and when relaxed they elongate. This phenomenon is evident for all patients, with or without spasticity. Confirmation of stress-relax begins with testing the braced muscle belly immediately after brace-initiated stretch to confirm muscle tension is initiated into the muscle by the brace (muscle is taut). Repalpate the muscle belly five minutes after brace application to confirm stress-relax (muscle softens and elongates slightly). Modify the brace as necessary so that the sustained stretch initiates stress-relax. Confirmation of stress-relax after orthotic fitting is critical for obtaining optimal antispasticity orthotic therapy. The following are the significant clinical benefits of a successful stress-relax fitting: The patient with spasticity will experience a slightly noxious sensation of significant stretch when the brace is initially applied. There should never be pain or significant discomfort. After several minutes of device wear (three to five minutes), the inhibitory effect of the brace will cause the muscles to relax and elongate slightly. After this stage, although the limb is immobilized in extension (for a flexion contracture), the brace should be comfortable and the sensation of stretch significantly diminished. This increases patient compliance with brace wear. Compliance can be compromised if there is not a stress-relax as the brace will be far less comfortable. There is a slight risk of skin breakdown from the pressure applied to the skin from any orthotic stretching device. Since the patient relaxes into the fit, adverse pressure or force on the skin is significantly reduced or eliminated and skin breakdown should not occur. Since the fit of the brace is intended to initiate stress-relax, the brace is providing the optimal tension necessary to provide abnormal reflex arc therapy on the affected motor nerves. In addition, the gentle tension applied by the brace will provide a lengthening demand to reverse any contracture related adaptive tissue shortening. It is common for patients with spasticity to have involuntary muscle contractions. These contractions initially involve a dynamic muscle contraction followed by a sustained static contraction of the spastic muscle. The antispasticity brace flexes, allowing the dynamic muscle contraction muscle to shorten while eliminating the subsequent longer lasting static contractions by providing GTO tension-related inhibition. The key therapy the brace provides is effectively managing involuntary muscle contraction by keeping the spastic muscles inhibited. Antispasticity Orthotic Spring Force [caption id="attachment_250274" align="alignright" width="172"] Ultraflex spring-loaded AFOs.[/caption] DynaPro braces have a patented negative nonlinear flex force when applied as directed on a spastic limb. A clinical study found that when comparing a positive spring-loaded brace with a negative nonlinear force static-dynamic brace, only the negative nonlinear force characteristics were found to be antispastic. 4 The authors concluded that a negative nonlinear spring force provided the ideal antispasticity tension characteristics. For severe spasticity, use of a negative nonlinear tension brace was recommended for best outcomes. Pneumatic air bladder braces work well for patients with all levels of spasticity. It is important to ensure that each time the brace is inflated, gentle tension is initiated by the brace and that muscle inhibition follows after five minutes of brace application. Modifying the level of inflation to create stress-relax in the spastic muscles is accomplished by using palpation to confirm sustained stretch (muscle belly is taut) immediately after fitting and confirming stress-relax after a few minutes of device wear (muscle belly has softened). Positive linear spring-loaded braces are contraindicated for patients with spasticity. A positive spring force will increase force significantly as the patient flexes into the spring during an involuntary muscle contraction. This increased force with involuntary muscle contractions can easily feed into tone by overexciting the muscle spindles, thereby making the spasticity worse while using the device. There are several companies that make constant linear force spring-loaded braces that can be effectively used on patients with spasticity. Since the spring force is not positive, these braces should not feed into tone if the spring force is set properly. The muscle can easily shorten during an episode of tone while providing constant GTO inhibitory tension into the limb. UltraFlex, EMPI, and the DeRoyal DeROM constant linear spring-loaded braces can all be utilized to effectively treat spasticity. The key to success is using muscle palpation to confirm the correct spring tension is initiated into the muscle immediately after brace application and that within five minutes there is an inhibitory effect on the muscle(s). The spring force is adjusted until stress-relax is evident. Summary There are three types of orthotic design that can be successfully used as antispasticity orthoses: pneumatic air bladder braces, static-dynamic antispasticity braces, and constant linear tension spring-loaded braces. Antispasticity bracing should initiate a sustained gentle tension into the hyperexcitable muscles to initiate an inhibitory effect and will initiate stress-relax into the spastic muscle within several minutes of sustained tension. Antispasticity braces provide abnormal reflex arc therapy. With successful use, the intensity and duration of involuntary muscle contractions should diminish over time. John Kenney, PhD, BOCO, is the inventor of DynaPro antispasticity orthoses and holds five patents on antispasticity brace design. He is the vice president of Clinical Development, Ongoing Care Solutions/Guardian Brace. Credits in order of appearance: Photograph courtesy of John Kenney. Photograph courtesy of John Kenney. Photographs courtesy of Ultraflex. References Glenn, M. B., J. Whyte. 1990. The Practical Management of Spasticity in Children and Adults , Philadelphia. Lea & Febiger. Emos, M. C., and S. Agarwal. 2022. Neuroanatomy, upper motor neuron lesion. In StatPearls [Internet] . StatPearls Publishing. Hummelsheim, H., B. Münch, C. Bütefish, and S. Neumann. 1994. Influence on sustained stretch on late muscular responses to magnetic brain stimulation in patients with upper motor neuron lesions. Scandinavian Journal of Rehabilitation Medicine 26(1):3-9. Leone, D., P. Quesada, and S. Chesser, S. 2000. Investigation of Stiffness Characteristics of Three Low Load Passive Stretch Devices. University of Louisville. Hindle, K., T. Whitcomb, W. Briggs, and J. Hong. 2012. Proprioceptive neuromuscular facilitation (PNF): Its mechanisms and effects on range of motion and muscular function. Journal of Human Kinetics 31:105-13.

Antispasticity Contracture Bracing

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