Approximately 50,000 Americans are diagnosed with Parkinson disease (PD) each year, with more than half a million persons affected.1 This chronic progressive disease causes limitations across the model of disablement for this population of individuals. Given the rapidly increasing demographic for this pathology, the health care system should be driven to develop patient management strategies that are effective and will help control the anticipated increase in the economic burden of care for this group of individuals.
Because of the disease pathology and the concomitant impairments, postural instability is often present and gait is typically slow with high variability of spatial/temporal gait kinematics.2 Walking capacity is critical to performance of activities of daily living and participation in community activities. Alterations in biomechanics of gait can change the energy requirements of mobility resulting in a higher percentage of VO2 peak to be utilized.3 The combination of these gait deficits with self-care limitations, history of falls, and disease duration can have a significant impact on health-related quality of life (QOL).4
Persons with PD present with many impairments including bradykinesia, freezing of gait, rigidity, tremor, and postural instability.5 There is also associated muscle weakness in the lower limbs, particularly the plantarflexors and hip extensors.6–8 Weakness in the plantarflexors impacts gait kinematics in individuals with PD, especially in regards to velocity,6,9 decreased step length, and decreased excursion of plantarflexors.8,10 This reduced muscle strength has been shown to contribute to reduced balance and falls in people with PD.9,11,12 Decreased ankle plantarflexion in individuals with PD at toe-off may contribute to a shortened stride length as it does in elderly individuals.6
Recent studies in persons with PD suggest that sensory abnormalities, including sensorimotor integration and peripheral sensory function, play an essential role in feedback to the motor system and thus could produce motor deficits.13 Impaired proprioception has been cited as contributing to the postural abnormalities as well as hypokinesias for this population of individuals.9
The impaired central mechanism combined with the sensorimotor impairments results in postural instability for this patient population. Postural instability has a marked impact on the walking pattern in people with PD as it compromises the ability to maintain the center of mass over a narrow base of support.14,15 One recent study showed that individuals with PD had a smaller displacement of center of pressure movement before stepping, which may impair step initiation.16 The movement of the center of pressure before stepping is part of the anticipatory postural adjustments (APAs) that are typically generated before a step. Reduced APAs are another common abnormality in individuals with PD that can create significant balance and gait problems.17 Mancini et al.17 reported that individuals with early PD have a significantly smaller lateral APA. These changes in APA are considered the major pathophysiological mechanism that underlies hindered gait initiation in PD subjects.18 Rocchi et al.18 also concluded patients with PD often have a narrow base of support to decrease the amount of distance they have to move during an APA.
As noted, individuals with PD have significant gait impairments that impact their mobility, and this is often one of the early signs of PD.19 The reduction of stride length is one of the most prominent features of PD gait and is often accompanied by a slower walking speed and often a tendency for a longer duration in the double-support phase of stance.20,21 Persons living with PD ambulate at 0.88 m/second in the community compared with 1.06 to 1.35 m/second for age-matched healthy individuals. Other hallmark gait deficits include reduced or absent arm swing, reduced trunk rotation, and decreased amplitude of motion at the hips, knees, and ankles.22
Improving gait mechanics in this population is challenging, and few studies report effective long-term interventions.23 Ankle-foot orthoses (AFOs) could be considered for individuals with PD considering deficits in strength, sensory impairments, and changes in the APA. Ankle-foot orthoses are frequently prescribed to minimize the consequences of gait dysfunction for various populations with neurologic impairments including individuals with spinal cord injuries, multiple sclerosis, and individuals poststroke.24–26 There are a variety of orthotic designs that are utilized in the neurologic population. Lower-limb AFOs have been found to improve mediolateral ankle stability, improve foot position, increase walking speed, and decrease energy expenditure.27–29 However, to our knowledge, no studies on the use of these devices with PD have been published, as utilization of orthoses for individuals with PD is not considered current standard of care.
The purpose of this study was to investigate the impact of a hinged orthosis with a Tamarack joint and an adjustable check strap (TCS-AFO) on functional gait capacity, electromyography (EMG), and QOL in select individuals with PD.
The study sample included three persons who were clients at the Gait Disorders Clinic at the University of Texas Southwestern (UTSW) Medical Center. The study was approved by the UTSW Medical Center institutional review board, and each subject gave written consent to participate in the study. Each participant had a confirmed diagnosis of PD. The age of the participants ranged from 62 to 72 years. The median age after diagnosis was 9.3 years. All the participants were males (see Table 1 for summary of participant demographics). Each participant had at least neutral dorsiflexion in supine with knee extended and no significant hip or knee contractures.
All participants were provided custom-fabricated articulating TCS-AFOs; all were fabricated by the same orthotist and were not tuned. The participant was positioned for casting by the orthotist with knee flexion, with the ankle set at 90° and in subtalar neutral. The materials for fabrication included 3/16-inch polypropylene plastic, Becker Tamarack joints (85 or 95 durometer), and the check strap designed using 1.5-inch Dacron reinforced hook and pile Velcro and a 1.5-inch stainless chafe. The AFOs had full-length foot plates with enough flexibility to allow for toe extension at terminal stance with sidewall trimlines proximal to the metatarsophalangeal joints. None of the AFOs were intrinsically or extrinsically posted. The height of the AFO was approximately 25 mL distal to the fibular head with approximately a 3-mm clearance from each malleolus. The Tamarack joint was placed just anterior to the apex of the malleoli. Patients were instructed to purchase flat-soled shoes, a half- size larger than their typical shoe size, with moderate flexibility and a minimal heel, with Velcro or lace closure. Leg length was assessed with AFOs donned in a supine position, and a full-length shoe insert was used to correct any differences. The Tamarack joint in the TCS-AFO provided dorsiflexion assistance during swing limb advancement, and the trimlines did not obstruct ankle plantarflexion at loading response. The adjustable posterior check strap provided stance phase stability in the presence of plantarflexion weakness by controlling tibial advancement. The ankle angle in the AFOs during midstance was customized per each participant to facilitate the most normal gait kinematics. All participants had sufficient ankle range of motion to allow for adequate dorsiflexion during terminal stance and to allow the foot to remain neutral. The participants were educated on the benefits of staying mobile with PD and the purpose of the orthoses for improving their walking. They received a wearing schedule to increase tolerance in the braces with a goal of wearing them 8 hrs a day. Each participant was trained in a customized home walking program including walking, posture exercises, and fall education. Proper gait mechanics (heel first contact, posture, step length) were taught for the focused walking practice. The focused walking program was set according to participant capabilities with a goal of working toward 30 minutes of total walking every day. The aim was to practice perfect walking and begin to increase daily walking to promote strengthening and cardiovascular health.30 Each participant completed 10 weeks in the study that included three gait training sessions in the clinic, which were at weeks 1, 2, and 7. Each session was 45 minutes in duration. The clinic sessions focused on fit of the orthoses, assessing the individual’s walking progress, practicing gait activities, and making necessary adjustments to the walking program or orthoses.
MATERIALS AND METHODS
All participants were tested at the David M. Crowley Research and Rehabilitation Laboratory at the UTSW Medical Center, Dallas, TX. Testing was completed at initial visit, week 5, and week 10.
GAIT ENDURANCE, TEMPORAL, AND SPATIAL GAIT PARAMETERS (GAITRite)
The 6-minute walk test (6MWT) has been found to be a reliable measure of walking capacity in individuals with PD.31,32 The minimal detectable change (MDC) has been established at 82 m or 269 ft over the 6MWT.32 The participants were instructed to walk at a pace they could maintain for 6 minutes on level surfaces with minimal turns. No verbal encouragement was provided, and the distance was recorded with a measuring wheel.
The GAITRite computerized gait analysis system (CIR Systems, Havertown, PA, USA) was used to measure temporal and spatial gait parameters. This system has been demonstrated to be reliable and valid with individuals with PD.33 The system consists of a 16-ft pressure-sensitive mat with an area of activation measuring 24 in (61 cm) wide and 192 in (487 cm) long with a total of 18,432 sensors. Data were sampled at 1000 Hz. Participants walked over the walkway a total of four times per walking condition, first at a self-selected walking velocity (SSWV) and then at a fast walking velocity (FWV) in conjunction with collection of EMG data. Participants used their TCS-AFOs for testing on week 5 and 10. Data collected included velocity, step length, and percentage of gait cycle spent in double limb support.
The EMG activities of the bilateral vastus lateralis (VL), anterior tibialis (AT), and medial gastrocnemius (GN) muscles were recorded at initial and week 10 testing times using MyoPac/DataPac fiber-optic hardware (Run Technologies, Pasadena, CA, USA). Electromyographic signal was recorded at a sampling rate of 1 KHz using bipolar paired Ag-Cl surface electrodes (Blue Sensor; Ambu, Denmark). Electrode diameter was 10 mm, with an interelectrode distance of 20 mm (center to center). Electrode sites were prepared by shaving the skin and mildly abrading the skin with prep paper and alcohol, with skin impedance for the electrodes maintained below 10,000 Ω resistance. A reference ground electrode was placed over the patellar surface. Pressure-sensitive foot switches were used to determine stance and swing phases of gait. In addition, a sync pulse transmitted from the GAITRite system at the initial contact of each walking trial was recorded concurrently with the EMG data. Four individual walks were recorded for each of the SSWV trials in conjunction with the GAITRite data.
DYNAMIC BALANCE ASSESSMENT
The Dynamic Gait Index (DGI) was used to assess dynamic balance. This test assesses individual’s ability to modify balance while walking and attending to external demands. This test has 8 items with a maximum score of 24, which indicates no limitations. Items include tasks such as walking with head turns, changing speeds, and stairs. The test has adequate discriminative ability for individuals with PD between fallers and nonfallers based on a cutoff score of less than 19.34 It also has excellent test-retest reliability (ICC, 0.84).35 The MDC is 2.9 for individuals with PD.36
QUALITY OF LIFE
The Parkinson Disease Questionnaire 8 (PDQ-8) was used to assess the individual’s QOL and the impact of PD on their lives. The PDQ-8 is derived from the PDQ-39. This test is valid and reliable with individuals with PD.37–39 There is one question from each of the eight domains on the PDQ-39 (mobility, ADLs, emotional well-being, stigma, social support, cognition, communication, and bodily discomfort). Each question is scored from 0 to 4 points, and the scores are summed. The summed score is then divided by total possible score and given as a percentage score out of 100. A lower score indicated less impact of the PD on the individual and an improved QOL.
The 6MWT was used as a measure of endurance. Although the participants did not meet the MDC set at 82 m (269 ft) for individuals with PD at a Hoehn and Yahr stage of 2,32 two of the three participants reached the (MCID) set at 50 m for elderly individuals.40 The third participant was lacking 6 m from reaching the MCID for elderly individuals (Table 2).
TEMPORAL AND SPATIAL GAIT PARAMETERS (GAITRite)
The GAITRite was used to measure temporal and spatial gait parameters. All participants had an improvement in their step length bilaterally from the time of initial testing to the completion of the study. The increases in step length ranged from 2.2 to 9.8 cm for the participants. Two of the participants had a greater increase from initial testing to testing at week 5, which could be related to early compliance. Subjects 1 and 2 had a slight decrease in their double limb stance times. The trend for GAITRite velocity was to increase, although there was some variance in this data (see Table 2 for gait and balance outcomes).
Figure 1 represents the EMG profiles of each participant at their SSWV at initial testing and 10 weeks. The EMG data in two of the subjects (1 and 3) showed that the braces may have assisted in decreasing excessive activation of the VL at initial contact and loading response. All of the participants in this study exhibited muscle firing in the lower limb, potentially indicating preserved muscle activation throughout the gait cycle.
QUALITY OF LIFE
The PDQ-8 was used to assess the impact PD-associated impairments have had on QOL. Two of the three participants met the MCID for the PDQ-8 at 5.78 to 7.4 points.41 Participants 2 and 3 had a change of 18.7 and 12.5, respectively. Participant 1 rated his QOL as excellent at all testing points.
DYNAMIC BALANCE ASSESSMENT
The DGI was used to assess dynamic balance. Two of the participants met the MDC of 2.9 for the DGI.36104
The purpose of this case series was to describe the impact of lower-limb bracing on gait characteristics, balance, muscle activation patterns, and QOL in three adults with PD who used a TCS-AFO for the duration of a 10-week home walking program. Outcomes of interest included gait velocity, step length, time spent in double limb support, endurance, dynamic balance, and QOL. The participants in this study showed improvement in their step length, endurance, velocity, and dynamic balance with the use of AFOs.
There is evidence in the literature that AFO design can impact gait outcomes for patients with neurologic dysfunction. For example, the use of bracing for restoring gait is well documented for individuals after stroke. Miyazaki et al.42 suggested that brace design could significantly impact gait across the gait cycle and that muscle activation can change substantially with peripheral mechanical input afforded by an AFO. Bracing improves stance stability and foot position, increases walking speed, and decreases energy expenditure.25,27–29 Ankle-foot orthoses can supplement decreased plantarflexion strength, which provides stability in mid to late stance.42,43 Although there is foundational evidence for the benefits of AFOs in the literature with various populations, there is little evidence regarding the use of AFOs for individuals with PD. Petrucci et al.44 designed a portable powered AFO (PPAFO) designed to provide mechanical assistance for dorsiflexion and plantarflexion as well as somatosensory cues for individuals with PD. Although they have not yet tested this on patients with PD, they believe that the mechanical assist may help to facilitate the necessary weight transfer and thus limb unloading behaviors to allow patients to improve their step. Similarly, the TCS-AFO design used in this study provided anterior stability through a posterior check strap. This allowed stability during stance phase, which assisted in compensating for lower-limb weakness that might otherwise prevent sufficient weight transfer required to initiate a step. The inability to compete the weight transfer to the stance leg secondary to decreased stability might be a contributing factor to the festination of gait. Although no formal testing was done to examine this in this study, it is an area that requires further research.
Although central nervous system pathology impacts normal gait, the frank lower-limb weakness particularly at the ankle and hip in persons with PD also contributes to the dysfunction.6,45 Supplementing plantarflexion strength was the primary purpose of the braces with the participants in this study as they had weak GN muscles. Plantarflexion weakness has been related to increased falls and decreased velocity in individuals with PD.6,9,11,12 During the typical gait cycle, ankle plantarflexion strength is extremely important. Ankle power generation is one of the strongest predictors of step length in healthy elderly subjects.46 Kirkwood et al.45 reported that with decreased duration of GN activation, there was an increase in falls in the elderly population. Likewise, individuals with PD have reduced GN activity during gait using electromyographic activity.9,10,47 There is also decreased ankle plantarflexion at toe-off in individuals with PD.6–8 It is possible that by providing stability for weak plantarflexors with an AFO, the participants were able to increase gait velocity, step length, and gait endurance.
Historically, there has been a concern that AFOs negatively impact muscle activity.48 The use of an AFO does not decrease EMG signals over time.25,49 Likewise, the EMG data in this study revealed that muscle activity was not diminished during AFO use.48 In fact, the EMG data suggested that, in two of the subjects (1 and 3), the braces may have assisted in decreasing excessive activation of the VL at initial contact and loading response as it theoretically provided external support to the participant’s weak plantarflexors. This may have been beneficial for decreasing unnecessary energy expenditure, which is significant with individuals with PD.50
Two studies examined the impact of shoe insoles on gait mechanics in individuals with PD. There is evidence that using a ribbed or textured insole to provide somatosensory input led to an overall improvement in single-limb support time and the sequence of tibialis anterior activation while decreasing postural sway.13,51 Although the insoles were beneficial for providing somatosensory input and therefore improving gait characteristics, they did not provide any significant external stability as is possible with an AFO. In the current study, the brace design may have impacted gait parameters through positive somatosensory input; all had custom footplates as well as the use of a posterior strap to decrease excessive amounts of knee flexion during stance. The strap accomplished two main goals to allow the tibia to advance to approximately 5° of knee flexion and 5° of ankle dorsiflexion to optimally position the GN to activate as well as provide a stop and tactile cues at this angle to improve stability during stance.
Impaired balance is another significant impairment of individuals with PD. Individuals with PD experience deterioration in balance and postural control as well as a progressive reduction in the speed and amplitude of movements (hypokinesia).52 Again, reduced balance is known to be an important risk factor for falls in this population.11,53 Gastrocnemius strength, ankle flexibility, and plantar tactile sensation are associated with balance impairments in older individuals.54 Nam et al.54 also reported that fatigue in the GN muscle, which is closely related to strength, impacts postural control and stability during single-limb standing in the elderly. Likewise, GN strength impacts balance in individuals with PD.9–11 Foot orthoses were shown to improve balance in elderly women.55 The participants in this study also had improvements in their balance after wearing the AFOs, which is important if it translates into fewer falls for this population.
The individuals’ improvements in their gait and balance were especially notable given that the participants had minimal clinical intervention. However, the participants did wear the braces daily for up to 8 hrs. The improvements are likely secondary to the practice and the repetitions they obtained as they consistently participated in their activities of daily living. The minimal clinical visits allowed for a very cost-effective intervention, which is critical in light of today’s health care climate.
Parkinson disease interferes with various aspects of QOL, particularly in relation to physical and social functioning, and deteriorates significantly with increasing disease severity.56 In a recent study, activity limitations were found to be the strongest predictor of health-related QOL.4 In the present study, two of the participants reported significant improvements in their QOL while participating in the study. It is possible that the improvements in QOL were the result of improved gait quality and endurance that resulted from the orthotic intervention.
This case series reported a novel use of AFOs in addressing gait dysfunction in persons with PD. Considering the progressive nature of PD and the need for interventions that can create a long-term impact, lower-limb bracing may be an intervention with potential. The persons in this case report were all trained with a TCS-AFO that was designed to facilitate gait and provide beneficial somatosensory feedback. Each of the participants demonstrated improvements in gait velocity, endurance, dynamic balance, and QOL. Based on the early outcomes from this case series, the laboratory is currently exploring long-term impact of the orthosis on gait parameters and QOL of persons with PD in a randomized 3-group pilot study.
This is a case series with a small homogenous sample, all of whom were males, which does not allow for the findings to be generalized to all persons with PD. This study was of short duration; future studies may benefit from a longer intervention period. Different types of AFOs may also be an avenue for future studies as well as the impact on gait kinematics and falls.
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