A Functional Comparison Of Solid And Articulated Afos During Walking And Running In Children With Spastic Hemiplegic Cerebral Palsy

Bridget M. Lawler, CO Michael Oros, CPO Jason Wening, MS, CP


Abstract

While previous research with Cerebral Palsy has focused on hemiplegia and diplegia, Botox injections, and gait patterns with and without ankle foot orthoses in standing, walking, and stair climbing compared to barefoot ambulation, none of this research has included AFOs' effects on running. The purpose of this study was to compare gait parameters of children with spastic hemi-plegic cerebral palsy wearing solid and articulated AFOs during walking and running. It was hypothesized the articulated AFO significantly improves gait parameters for walking and running when compared to a solid AFO. Seven children aged 5-10 years with a diagnosis of spastic hemi-plegia secondary to cerebral palsy participated. All subjects were current AFO users capable of walking and running without an assistive device. Subjects were fit with an articulated and solid AFO fabricated from the same positive model. Ten walking and running trials with subjects wearing each AFO were collected using the GAITRite system. No significant difference in walking gait parameters was detected between the AFOs. A significant difference (p<0.05) in favor of the articulated AFO was noted in the running trials for velocity, step length of the affected and non-affected sides, and stride length of the affected and non-affected sides. It is hoped that the results of this study will aid in the decision of functional orthotic management of children with spastic hemiplegia, especially those with the ability to run.

Introduction

Cerebral palsy (CP) is currently the leading cause of disability in children, occurring in 2-5 per 1000 births and in 15% of premature births 1. It is defined as a nonprogressive, chronic, involuntary movement disorder secondary to an injury or lesion of the immature brain 1. Seventy percent of CP diagnoses are of the spastic type and in some cases a cognitive deficit may also be present. There are a variety of treatments available for CP, which aim to improve function for activities of daily living, while reducing pain and spasticity 2. More specifically, the goals of orthotic management are to facilitate function by preventing deformity, supporting normal joint alignment, reducing tone and spasticity, improving proprioception and balance, and reducing energy expenditure in gait 3.

Previous literature has attributed specific gait patterns to hemiplegia. Equinus in stance is common due to soleus contractures, gastrocnemius insufficiency, and plantarflexor spasticity during loading response 4,5,6,7. This causes a decrease in one's ability to adapt for stability. The knee can present two ways: in hyperextension secondary to weak quadriceps or an extensor synergy pattern; or more commonly in flexion due to hamstring or gastrocnemius contractures and over-powering of the extensors 8,9. According to Buckon et al. active hip and knee flexion are limited and there is an inability to overcome tone 10. Together, these factors limit forward progression through stance. Studies also indicate over 50% of hemiple-gic and diplegic children present with equinovarus, in-toeing, and a stiff knee during the swing phase of gait 7. Scissoring may also be present in cases where tight hip adductors are present 11. The children compensate via circumduction and hip hiking for toe clearance through swing 12.

A vast amount of research has been done in regards to cerebral palsy and orthotic management. Multiple studies focused on gait deviations without orthotic intervention 4,7,11,12,13,14. While others compared barefoot gait with gait while using an ankle-foot orthosis 3,5,15,16,17. Results of these studies showed that the use of any AFO is better than no AFO 5,17,18. Three of the studies concluded that AFOs reduce equinus through the gait cycle by limiting plantarflexion range 9,16,17. It has also been shown that AFOs accounted for an increase in speed, step and stride length when compared to walking without an orthosis 16,17.

The variety of AFO styles utilized for testing created difficulty when comparing previous studies to each other. The types of ankle-foot orthoses that were used previously include solid, hinged (articulated), posterior leaf spring, and dynamic AFOs 3,5,6,10,16,17,18. These orthoses were analyzed during standing, walking and stair climbing. Significant results allowed the following conclusions to be drawn from these studies:

  1. Articulated AFOs are better than solid AFOs 5,9,17.

  2. Hinged (articulated) and posterior-leaf spring (PLS) AFOs increase the dorsiflexion range of motion 5,11.

  3. Posterior leaf spring (flexible) AFOs provide improved clearance in swing 3.

  4. Energy efficiency is greatest with the PLS and hinged style AFOs 3,10.

  5. AFO use does not impair stair ambu-lation in children 5.

The purpose of this study is to determine if there is a significant functional difference between solid and articulated AFOs during both walking and running activities in children with spastic hemiplegic cerebral palsy. It is proposed that articulated ankle-foot orthoses allow for improved gait as compared to solid AFOs. The hypothesized results of the articulated AFO as compared to the solid AFO in both walking and running are:

  1. an increase in velocity

  2. a decrease in cadence

  3. an increase in step length on the non-affected side

  4. an increase in step time on the affected side

  5. an increase in stride length on the affected and non-affected side

  6. an increase in step symmetry

  7. an increase in time spent in stance on the affected side

  8. a decreased base of support.

Methods

A convenience sample of subjects was recruited from Scheck and Siress Prosthetics, Orthotics, and Pedorthics. The subjects were to have a diagnosis of spastic hemiplegia secondary to cerebral palsy; between 5-12 years of age; a passive dorsiflexion range of at least 5 degrees; no surgical intervention; have been an active AFO user for over one year; able to walk and run without the use of assistive devices; have no confounding pathologies, and be able to follow instructions.

Figure , Figure

The subjects were asked to participate in two sessions. The initial session was comprised of an interview with the guardian regarding medical history and previous treatment modalities; a clinical evaluation; and the measurement and impression taking procedures of the affected lower extremity. The second session included the fitting of the AFOs, acclimation, and gait analysis.

During the interview, the subjects' guardians were asked about previous and ongoing alternative treatments including physical therapy, Botox injections, serial casting, surgery, and the dates of the last treatment. Clinical evaluation of the subjects involved height and weight measurements, full passive range of motion analysis of the lower extremity, and measurement of leg lengths. Measurements of joint angles were taken at R2. Any noted leg length discrepancy was compensated for prior to gait analysis with a shoe lift of the appropriate height. The impression was taken with Delta-Lite conformable casting tape in a non-weight bearing position with the talocural joint, hindfoot and forefoot in neutral.

A solid and an articulated AFO were fabricated from the same positive mold. The AFOs were made of 5/32" polypropylene with padded leather instep and calf straps and toe extension pads. Modifications of each positive mold included the Carlson modifications, tone reduction modifications, full length foot plate, and a proximal flare. The articulated AFOs had Tamarack joints aligned to the anatomical ankle joint axis and adjustable plantarflexion stops.

The second session consisted of the fitting of both the solid and articulated AFOs. Any adjustments needed to ensure optimal fit and function were subsequently made to both orthoses. The subjects were asked to ambulate in the solid AFO for at least 15 minutes to acclimate to the device, followed by five minutes of rest. The GAITRite, a 14' portable walkway that measures temporo-spatial parameters, was utilized for data collection. Each subject was asked to perform ten walking trials and ten running trials, per each AFO for a total of 40 trials. There was a five minute rest period between each set of trials.

Data was analyzed for each subject comparing the solid AFO to the articulated AFO using a two-tailed T-test. The subjects were compared to each other using a paired T-Test to analyze the difference between the solid and articulated ankle-foot orthoses. Significance was established at a p-value of less than 0.05 and a trend indicated by p-value less than 0.10.

The parameters analyzed using data collected from the GAITRite were: velocity, cadence, step time on the affected side, step time of the non-affected side, step length on the affected side, step length of the non-affected side, stride length of affected side, stride length of the non-affected side, stance time of affected side, stance time of the non-affected side, support base of affected side, and support base of the non-affected side.

Results

Currently, seven subjects have met the inclusion criteria for gait analysis with the ankle foot orthoses. The subject demographics are presented in Table 1 .

Alternative treatments used prior to or throughout the course of orthotic management, as reported by the subjects' guardians, are as follows: All seven subjects were actively involved with physical therapy. Five of the subjects had Botox injections within the last year, one of whom had treatment six weeks prior to testing. Two of the subjects had serial casting, one of whom had a cast removed three weeks before testing. Two subjects had leg length discrepancies noted during the evaluation. In both cases, the leg length discrepancy was compensated for with a shoe lift prior to testing.

See Figure 1 for a graphic representation of the significant results, as determined by a p<0.05.

The data suggests that there is no significant functional difference between the articulated and solid AFOs in walking. However, a trend was noted showing improved step symmetry with the articulated AFO in walking (p<0.09). Another trend indicated step time on the affected side, the time from initial contact on the affected side to initial contact on the non-affected side, was increased by the solid AFO (p<0.0816).

Data analysis shows a significant improvement in the running trials for velocity (p<0.008), step length of the affected (p<0.0112) and non-affected side (p<0.012), and stride length of the affected (p<0.0059) and non-affected side (p<0.0161) with the articulated AFO.

Discussion

The initial hypothesis was both upheld and refuted. It was proposed that the articulated AFO would significantly be more functional in both walking and running parameters secondary to anterior translation of the tibia. In theory this would reduce the short step typical of the contralateral limb, thus an increase of the non-affected side step length would contribute to a more symmetrical gait pattern. It would theoretically contribute to an increase in the amount of time spent in stance on the affected side by allowing the subject to utilize more normal rockers.

The parameters are interrelated, thus by allowing anterior translation of the tibia, an overall improvement in function was noted with the articulated AFO. These results are supported by Romkes et al. who determined that an articulated AFO with plantarflexion stop results in a heel-toe gait, increased step and stride length, and reduced power absorption 17.

The significance in the running trials may be attributed to an improved push-off with the articulated AFO. A previous study conducted compared an articulated AFO with plantarflexion stop to a solid AFO and found a significant improvement in push-off with the articulated AFO 5. This finding is important as other research had shown that the equinovarus with clawed toes, typical of hemiplegic gait, is one of the key components in the disturbance of terminal stance in barefoot ambulation 4. It is proposed that the difference in results between the walking and running may be attributed to the increase in force and propulsion in running as compared to walking. There is no current research to support or refute this theory.

It is anticipated that the results of this study will aid as a stepping stone in the research and clinical management of spastic hemiplegia with orthoses. It should aid in the decision process of appropriate treatment as the goals of orthotic management focus on facilitating function while maintaining joint alignment, reducing spasticity and energy expenditure, and improving balance and pro-prioception. All of these are achievable and important goals in the physical and psychosocial development of children with disabilities.

Future of the Study

This is an ongoing study in an effort to gather more data to analyze the function of both the solid and articulated AFOs in walking and running. Due to the abilities of the GAITRite, this study could not focus on joint kinetics and kinematics to provide explanations for the results thus far. However, there have been studies showing that an articulated AFO helps to increase passive ankle dorsiflexion while effectively controlling knee hyperextension 10. This increase in dorsiflexion yields a more normal ankle rocker and gait cycle 10. Since hemiplegic subjects tend to adopt a gait pattern for optimal stability rather than efficiency, it is important to note that while AFOs help maintain normal joint alignment and reduce spas-ticity, the hinged (articulated) AFOs also result in the greatest improvement in energy efficiency 4,10. These are all variables that will be considered for future research endeavors, as well as comparing barefoot walking and running to a posterior leaf spring AFO, solid AFO and an articulated AFO.

Authors Address:

Bridget M. Lawler, CO Oak Park, IL
Bridget.lawler@scheckandsiress.com

Scheck and Siress Prosthetics, Orthotics, and Pedorthics, Oak Park, Illinois

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