Minimum controlled dynamic foot orthosis (DFO) is a general term that describes a thinly layered shoe insert, which is placed in the shoes of children with motor delays to improve their balance and motor capacities.1,2 A DFO can be used as a therapy device that allows a child with motor developmental delays to quickly (i.e., within days) improve his or her postural control and balance. DFOs are shoe inserts that contain one layer of foam and a thin layer of polyethylene plastic designed to give mild mechanical support and proprioceptive feedback to children with subtle neurological anomalies.1,2
There have been descriptive and observational reports (i.e., anecdotal) on the benefits (e.g., improved balance and motor skills) of DFOs in treating neurological and developmental disorders,1 but there is a paucity of scientific data regarding the effectiveness of DFOs. The purpose of this study is to add to the body of knowledge on DFOs and determine the efficacy of this type of orthosis as it relates to locomotor skills of children with gross motor developmental delays.
A sample-of-convenience method was used to select 25 children with a diagnosis of gross motor delay who were receiving physical therapy. To be eligible to participate in the study, children had to meet the following criteria: a) be below the age of 60 months, b) be diagnosed with gross motor delay, defined as a z score of −1.33 or lower on the locomotion section of the gross motor scales of the Peabody Developmental Motor Scales Test, 2nd edition (PDMS–2),3 c) enrolled in an early intervention program that includes direct physical therapy at least once every week, d) be medically stable for therapy (as determined by the child’s pediatrician), and e) have informed consent of a parent or guardian. Children with uncontrollable seizures, progressive neurological diseases, fetal alcohol syndrome, acquired immunodeficiency syndrome, and blindness were excluded. Two of the selected children were diagnosed with Down syndrome, three with cerebral palsy, and the remainder as motor developmentally delayed. Descriptive characteristics of the participants can be found in Table 1. Approval for the study was obtained from the University Institutional Review Board.
Dynamic Foot Orthosis
The minimum controlled dynamic foot orthosis (DFO) used for this study (PattiBob, Cascade DAFO™, Inc., Ferndale, WA) is a shoe insert consisting of a thin layer of plastic on the bottom of dense foam (aliplast-like material) contoured and shaped to fit the plantar surface of the foot. The PattiBob DFO is constructed of low-density polyethylene, is flexible at the toe, semi-flexible at the arch, and rigid around the heel. Features include an arch support, a metatarsal head depression, heel cup, and toe rise for toes 2 through 5 (Figure 1).
The sizing of the Pattibob DFO correlates to the length of the foot (i.e., the size 4 Pattibob is 4 inches long). Two foot dimensions are measured to determine the size of the PattiBob, length and width (in inches). Fit is determined by using the sizing chart provided by the manufacturer or matching the patient’s foot to the actual product. When fitting the child with the PattiBob, it is important to match the heel and metatarsal heads to the heel pocket and metatarsal depressions, respectively. The generic shape of the PattiBob is based on anthropometric studies of contours and proportions of children’s feet and its genesis of a well-defined footbed for plantar support comes from clinical observations reported by Hylton1,2 (Cascade DAFO, Inc., personal communication, 2003).
Peabody Developmental Motor Scales Test
The locomotion section of the gross motor scales of the PDMS–23 was selected to evaluate the participants’ locomotor abilities. The PDMS–2 has been shown to be a reliable and valid method of determining motor skills in children 0 to 6 years of age.3–8 There are 89 locomotor items ranging from ages 0 month (item 1) to 72 months (item 89). These locomotor items include, but are not limited to: standing, walking up and down stairs, walking fast, walking backward, walking sideways, walking a line, jumping up, jumping forward, jumping down, and running. The PDMS–2 norms are based on scoring each item as 2 (the child performs the item according to the criteria specified for mastery), 1 (the child’s performance shows a clear resemblance to the item mastery criteria but does not fully meet the criteria), and 0 (the child cannot or will not attempt the item, or the attempt does not show that the skill is emerging). The locomotive items that the child enters (i.e., entry point) or begins are based on items in which the child can successfully score 2s. That is, entry point is established when the child receives a score of 2 on three consecutive locomotive items. With each locomotive item there is a chronological age in months that 75% of children in a normative sample at that age can pass (i.e., receive 2s). Once an entry point has been established, the child is given progressively more difficult items until the child scores 0 on each of three items in a row. Raw scores are determined by the total number of points received on each item, and the raw scores are converted into an age-equivalent score. All tests were administered in the same room prepared with the equipment necessary for administering the PDMS–2.
The PDMS–2 was administered to the children four times over a 2-month period. Initially, the children were evaluated before the inserts were placed into the shoes. Following one week of wearing the inserts, the children were reevaluated while wearing the inserts. The children wore the inserts for 2 months and were retested with and without the inserts. Testing with or without the inserts following 2 months was randomly determined. Twenty-five children (Group 1) completed the initial testing, and 17 (Group 2) were tested at 2 months. Eight of the children were unavailable for testing at 2 months because the 2-month time period ended during their summer recess.
Data were analyzed using SPSS (v. 10.1). Means and standard deviations were calculated for all variables. Interrater reliability and test-retest reliability were established for the PDMS–2 based on data obtained for 10 children who were receiving early intervention but who were not part of the study sample. To establish interrater reliability, these children were rated by one author (VCW) and another physical therapist. Both are certified physical therapists and had at least 2 years of clinical experience in the administration of all the domains (i.e., fine and gross motor) of the PDMS–2. Using interclass correlation coefficients, reliability was calculated to be 0.95. To establish test-retest reliability, the same 10 children were retested by the same physical therapist within 1 week. Test–retest correlation coefficients for the two therapists were 0.93 and 0.95, respectively.
For the 25 participants who performed the initial evaluations, a paired t test was performed to determine if differences existed in PDMS–2 raw scores (i.e., total points accumulated), and motor age equivalents of raw scores (in months) with and without the DFO. For the 17 participants tested following 2 months of wearing the inserts, a repeated measures one-way ANOVA followed by a Newman-Keuls multiple comparison was performed to determine if specific differences existed among the four tests (i.e., initially with and without inserts, and following 2 months with and without inserts) for raw scores and motor age equivalents. For all analyses, statistical significance was set at p < 0.05.
Initial raw scores and age equivalent scores with and without inserts are found in Table 2. Significantly higher raw scores and age equivalent scores were seen with inserts when compared to without inserts. Raw scores and age equivalent scores following 2 months of wearing inserts are found in Table 3. Significantly higher raw scores and age equivalent scores were seen for the following comparisons: a) with the inserts following 2 months when compared to the scores without inserts following 2 months and initial scores, with and without inserts; b) without the inserts following 2 months when compared to initial scores without the inserts; and c) initial scores with the inserts when compared to initial scores without the inserts. No significant differences were seen when comparing scores at 2 months without inserts to initial scores with inserts.
Previous anecdotal reports have suggested that DFOs improve balance and motor skills in children with neurological and developmental disorders.1 However, there has yet to be reported research data regarding the effectiveness of DFOs. In this study, a specific type of DFO (Pattibob, Cascade DAFO™ Inc.) was evaluated to determine capacity in improving the locomotor skills of children with motor developmental delays. The results of this study suggest that the DFO used in this study did improve the motor capacities of these children.
Although it was not the purpose of this study to compare improvements among disability categories (i.e., Down syndrome vs. cerebral palsy vs. developmentally delayed), it is of interest that the disability category that demonstrated the largest improvements included those children who were developmentally delayed. For those children with Down syndrome, no initial improvements were seen when comparing scores with and without the insert, and small but nonsignificant improvements were seen following 2 months (see Tables 2 and 3). Similarly, small, but non-significant, improvements were seen for those children with cerebral palsy initially and following 2 months (see Tables 2 and 3). The possibility exists that the DFO did not provide a high enough support for the amount of joint instability and motor control problems in children with Down syndrome and cerebral palsy.9,10 However, the small number of participants with Down syndrome and cerebral palsy prevents any definitive conclusion. Nevertheless, it does suggest that more children with Down syndrome and cerebral palsy need to be included in studies concerning the affect of DFOs on their locomotor capacity to determine efficacy with these populations.
Of interest, eight children who were also enrolled in the early intervention program and were initially screened for participation in this study were not included because their z scores were above −1.33 (Table 4). These children had been previously diagnosed with motor developmental delays (i.e., without Down syndrome or cerebral palsy). As noted above (see Table 2), in the disability category that demonstrated the largest initial improvements were those children who were motor developmentally delayed. However, as shown in Table 4, such is not the case with the eight developmentally delayed children with z scores above -1.33. These data suggest that future research should also include children with z scores above −1.33 to determine if a “threshold” exists for motor improvements while using DFOs.
Even though interrater reliability and test–retest correlation coefficients were high, the physical therapists who tested the children were aware that each child was either with or without inserts during evaluations. Therefore, the possibility exists that this could have subjectively affected the scores to be rated higher while testing the children with the shoe inserts. However, the scores of the children with Down syndrome and cerebral palsy showed little to no improvements initially (i.e., within 7 days) or following 2 months. In addition, during the initial screening, which included the eight children with z scores above −1.33, the physical therapists conducting the PDMS–2 were not aware that only those children with a z score of −1.33 or lower would be included in the study. As reported in Table 4, these eight children also showed little to no improvements. These results suggest that the possibility that higher scores were given to the children while they were wearing inserts was not the case.
In summary, the results of this study suggest that the DFO used in this study did improve the locomotor capacities of children diagnosed with motor developmental delays defined as z scores at or below −1.33. However, more research is needed to determine if these findings can be applied to children diagnosed with Down syndrome or cerebral palsy and whether or not a “threshold” exists for those children diagnosed with z scores above or below −1.33.
We thank Rhonda Davis, RPT, and the staff at Rainbows United Inc., Wichita, Kansas, for their assistance.
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