Significant Factors Influencing the Effectiveness of Cranial Remolding Orthoses in Infants with Deformational Plagiocephaly

Abstract

Infants with deformational plagiocephaly may be indicated for a cranial remolding orthosis (CRO) depending on the severity of deformation. Studies have found torticollis and prematurity to be risk factors for the development of deformational plagiocephaly^1,2 and indicate younger infants have faster and greater correction^1,2,3. However, clinical decisions about which infants should be recommended for CRO treatment differ among healthcare providers⁴ and insurance coverage criteria varies. In order to provide insight into treatment recommendations, this study aims to examine the influence of 4 specific factors on CRO treatment time and the infant’s resultant post-treatment head shape. Results indicate that presenting age, presenting severity, and the presence of torticollis significantly influence treatment duration. Presenting age and severity were found to significantly influence final head shape. The presence of prematurity was not found to be significant when infants were categorized by their corrected postpartum ages.

INTRODUCTION

In 1992, the American Academy of Pediatrics (AAP) released the recommendation that infants be placed in the supine position when sleeping in order to decrease the risk of sudden infant death syndrome (SIDS)⁵. Since this protocol has been implemented by parents and caretakers, the incidence of plagiocephaly in infants has increased by an estimated 600%⁶, with some studies reporting up to 45% of infants at 2 months of age having cranial deformation⁷. While repositioning therapy can be an effective treatment, instances of plagiocephaly beyond a mild case are often treated with cranial remolding orthoses (CROs). The success of CRO treatment has been debated in studies and as such, there remains a large variation in reported cranial correction through the use of CROs. However, a growing body of evidence is being gathered which demonstrates CRO treatment to be more effective in reducing cranial asymmetry than other conservative treatments such as physical therapy or repositioning therapy^4,8.

The term plagiocephaly describes a flattening to the skull. It is characterized by a difference in the diagonal measurements of the cranium, as measured at a cross-section of the greater equator of the skull. Typically, the measurements are taken from the fronotzygomaticus to the opposite posterior urion as shown in Figure 1. Deformational plagiocephaly is a type of flattening of the skull caused by constant external directional force, which frequently occurs due to preferential positioning of the head or prenatal constrictions. Risk factors also documented with deformational plagiocephaly include multiple births, congenital anomalies, prematurity, male sex, and congenital muscular torticollis (CMT)¹. Treatments for these infants have been, for the most part, repositioning strategies, physical therapy, and cranial remolding orthoses (CROs)^4,5. Although studies have suggested torticollis and prematurity are risk factors for plagiocephaly^1,2, they have not examined the effect of these factors on achieving a desired final head shape through cranial remolding treatment.

Figure 1.

Diagonal Cranial Measurements

Cranial remolding orthoses are referred to by many different names: helmet, cranial orthosis, cranial orthotic device and orthotic headband. These devices are custom made though a plaster cast that has been taken of an infant’s head or through a 3D shape capture system. The goal of the device is designed to snugly fit over the bossed areas of the skull and leave gaps over the flattened areas to allow for directional growth of the cranium^1,7. Patients are informed and expected to comply with frequent clinic follow up visits for growth adjustments and 23 hour per day wearing schedule of the CRO over the course of treatment, which can last for several months⁴.

This retrospective chart review was performed to assess clinical findings about the influence of certain intake factors on treatment outcomes of CROs. Specifically, this study aims to examine the statistical effect of a patient’s initial deformational severity, age of initiation of CRO treatment, presence or absence of torticollis, and presence or absence of prematurity on the outcome of a patient’s CRO treatment. The outcome measures of orthotic treatment being examined in this study are total CRO treatment time and final head shape.

MATERIALS AND METHODS

Expedited IRB approval for this retrospective chart review and waiver of consent was obtained through the University of Texas Southwestern Medical Center and a Data Transfer Agreement was set up between UT Southwestern and Level 4 Prosthetics & Orthotics. Electronic patient charts were reviewed from three Level 4 patient care centers (one office in Addison, TX and two in San Antonio, TX). For inclusion in the study, the infant must have undergone CRO treatment for a deformational plagiocephalic head shape, have been 3–18 months of postpartum age at start of treatment, not have been diagnosed with significant commodities (other than prematurity or torticollis), and have completed treatment between January 2013 and June 2017. Subjects born prior to 38 weeks gestation were age-adjusted to account for prematurity. The corrected age was calculated by using the postpartum age minus the number of weeks of prematurity, then rounding to the nearest whole month. Infants with corrected ages were recorded as having prematurity present. For example, a 4 month old subject born at 36 weeks gestation was categorized as a 3 month old subject with prematurity. Subjects previously diagnosed with torticollis and subjects noted by the treating orthotist to have a clinically significant lack of neck range of motion were considered positive for torticollis. Subjects who dropped out of treatment, subjects who did not complete treatment despite practitioner recommendation, and subjects who were lost to follow up were excluded from this study.

Of the 2,423 charts reviewed, 499 patients were found to meet the inclusion criteria and had complete data for analysis. Data collection from each subject included the corrected age at the start and end of treatment (rounded to the nearest month), presence or absence of prematurity, and presence or absence of torticollis. Also collected was the pretreatment and posttreatment Cranial Vault Asymmetry Index (CVAI) as reported via digital scanning of the infants. The same scanning equipment was used at each of the offices, namely the STARscanner (Vorum Research Corporation, Vancouver, BC). The Cranial Vault Asymmetry Index (CVAI) is the measurement of two-dimensional lateral cranial asymmetry, expressed as a percentage of cranial deformation. It is was calculated by the difference in cranial diagonals (CVA), divided by the larger of the two diagonals, then multiplied by 100. This measurement was automatically calculated by the STARscanner and is a modified version of the CVAI as reported by Loveday and Dorhage in that the denominator is the larger diagonal^3,9. Measurements are taken at the greater equator of the skull (Table 1)¹⁰.

Table 1.

Calculation of CVAI

$\mathit{CVAI}=\frac{\mid \mathit{Diagonal}1-\mathit{Diagonal}2\mid }{\mathit{Diagonal}1\mathit{or}2(\mathrm{whichever}\mathrm{is}\mathrm{greater})}\times 100$

A statistical analysis was performed using 1-way and 2-way ANOVAs in MATLAB to determine the significance of age, severity, torticollis, and prematurity on treatment time and post-treatment measurements, with the significance set to p<0.05. These findings were also examined by the UT Southwestern Center for Translational Medicine Biostatical Department with the support of the National Center for Advancing Translational Sciences of the National Institutes of Health and propensity matching was performed for further analysis. Infants were then grouped according to their age of treatment initiation and the average rate of change of CVAI based on the calculation in Table 2.

Table 2.

Calculation of the Cranial Deformation Rate of Change

$\mathrm{Rate}\mathrm{of}\mathrm{Change}=\frac{{\mathit{CVAI}}_{\mathit{initial}}-{\mathit{CVAI}}_{\mathit{final}}}{\mathrm{Months}\mathrm{of}\mathrm{Treatment}}$

RESULTS

The exclusion breakdown of the 2,423 reviewed electronic charts is as follows: 1,402 had non-plagiocephalic deformational head shapes, 201 had synostotic head shapes, 73 had significant comorbidities (other than prematurity and torticollis), 204 dropped out, 27 were non-compliant, 8 had incomplete data in charts, 4 had treatment extend beyond June 2017, 3 moved out of state during the course of treatment, 1 discharged early, and 1 did not meet the age requirements for the study. This resulted in 499 included subjects.

The included subjects spanned a variety of initial treatment ages and severities. All subjects began treatment at a corrected age between 2 and 17 months and had CVAI measurements spanning from 3.1% to 16.1%. All subjects ended treatment at a corrected age between 5 months and 21 months and had final CVAI measurements between 0.1% and 10.1%. The distribution of patients based on prematurity and torticollis are shown in Table 3.

Table 3.

Distribution of Subjects based on Prematurity and Torticollis (n=499)

	# Patients	% Patients
Prematurity	142	28%
Torticollis	300	60%
Prematurity & Torticollis	93	19%
Neither Prematurity or Torticollis	150	30%

A 2-way unbalanced ANOVA was performed to examine the interaction between the presence or absence of both torticollis and prematurity on the examined outcome measures of CRO treatment. The results of this ANOVA are shown in Table 4. The presence of torticollis was shown to have a statistically significant effect on treatment duration but not on final CVAI. The presence of prematurity was not shown to have a statistical effect on treatment duration or final CVAI. The interaction between the presence of torticollis and prematurity was not statistically significant.

Table 4.

Results of 2-way Unbalanced ANOVAs (n=499)

	Factor p-value
	Treatment Time	Final CVAI
Torticollis	0.0095*	0.3846
Prematurity	0.5659	0.4013
Interaction	0.5681	0.1609

The results of the 1-way ANOVAs are listed in Table 5. When evaluating the treatment time needed to complete orthotic treatment, the following factors were found to be significant: initial age, initial CVAI, and the presence of torticollis. Treatment duration was not found to be affected by the presence of prematurity when postpartum age was corrected by the number of weeks of prematurity. When comparing the post-treatment CVAI, the following factors were found to be significant: age and severity at the initiation of treatment. Both torticollis and prematurity were not found to be significant factors in the overall cranial correction achieved through CRO treatment in this data set.

Table 5.

Results of 1-way ANOVAs (n=499)

	Factor p-value
	Treatment Time	Final CVAI
Torticollis	0.0072*	0.7347
Prematurity	0.3497	0.1993
Starting CVAI	4.34e-11*	5.28e-21*
Starting Age	0.0046*	3.15e-11*

After propensity matching for initial severity and age for patients with and without torticollis, the statistics we reanalyzed. This new data set included 362 subjects (181 with torticollis, 181 without torticollis). The results of this analysis are summarized in Table 6. The significance described in the full data set was found to be robust in the new propensity-matched data set. Patients with torticollis were generally found to have 12–13 days longer in treatment than their age and severity matched counterparts.

Table 6.

Results of 2-way ANOVAs with propensity matching for patients with and without Torticollis (n=362).

	Factor p-value
	Treatment Time	Final CVAI
Torticollis	0.0225*	0.4417
Prematurity	0.9843	0.4857
Interaction	0.8064	0.9937

The 499 patient sample set was divided into age groups based on the infant’s corrected age at the initiation of treatment (rounded to the nearest month) and the standard error was calculated for each group. Groups with fewer than 5 patients were not included due to the large standard error in these groups. This resulted in a sample set of 490 infants. The average rate of change in CVAI was plotted against the age groups, as shown in Figure 2. In this graph, a positive rate of change indicates a decrease in CVAI, which is an overall improvement in the cranial shape. The number above each bar indicates the number of patients in the sample set.

Figure 2.

Bar graph of the rate of change in cranial deformation for infants undergoing cranial remolding treatment based on their corrected treatment initiation age (n=490).

DISCUSSION

The study results are consistent with other studies and the clinical experience of the author. Based on the results of this study, infants who are older, more severe, and/or have torticollis can expect to need longer treatment durations. However, the presence of torticollis does not preclude achieving similar CVAI correction to infants without torticollis when the torticollis is being concurrently treated with the deformational plagiocephaly.

The presence of prematurity does not seem to affect treatment outcomes when the number of weeks of prematurity is subtracted from the postpartum age. In other words, in classifying the previously mentioned 4 month old infant born at 36 weeks gestation as a 3 month old infant, this infant had clinical outcomes similar to other 3 month old infants. Therefore, based on this study, practitioners may be able “correct” a patient’s age in order to more reliably predict treatment outcomes.

When evaluating an infant for CRO treatment, practitioners must decide if treatment is likely to have a positive outcome. By understanding how different factors influence treatment outcomes, practitioners can make more informed decisions about which patients may benefit from CRO treatment. The results of this study suggest that infants have better treatment outcomes when they are younger, less severe, and without torticollis; however, a longer treatment duration was shown to be successful for patients with torticollis. Since CRO initiation age strongly influences an infant’s rate of correction, parents of older infants should be counseled regarding treatment expectations and understand treatment duration may be substantially longer for older infants. Because the FDA recommends CRO’s to be used only for infants from 3–18 months of age¹¹; older infants with more severe deformations might not be able to achieve the desired cranial correction due to their decreased rate of change of CVAI. Further studies are needed to determine if there is a “cut-off” age at which older infants are unlikely to benefit from a CRO.

The described study does have several key limitations: This study was performed as a retrospective chart review and therefore certain factors such as patient compliance and caregiver education were not able to be directly controlled. These factors were minimized by reviewing the practitioner’s notes to see if non-compliance was suspected and thereby excluding these subjects from the analysis. Also, only 3 offices were used for this study from a single company to limit variations in practitioner training for the treatment of deformational plagiocephaly. The practitioners in these 3 offices were trained in a similar fashion and reported to the same Area Manager. Only a single type of CRO was used (Orthomerica’s STARband, Orlando, FL) and all CRO’s were centrally fabricated in the same facility in Orlando, Florida under FDA regulations.

The assessment of the presence or absence of torticollis was determined by the physical evaluation of the patient done by the treating practitioner instead of via physician diagnosis. This was justified because at the time of the evaluation, many infants had not yet been diagnosed with torticollis, although they had the clinical presentation of it. The orthotists treating patients in this study were trained in the assessment of neck ROM and recommended caregivers seek torticollis treatment if a lack of ROM was noted. Physician records for each patient were not able to be pulled under the existing IRB to confirm the diagnosis of torticollis.

Subjects included in this study had isolated Deformational Plagiocepaly. Any patients with a Cephalic Index (ratio of the width of the cranium to the length of the cranium) greater than 90% were excluded from the study and will be included in future studies when other deformational head shapes are examined such as Deformational Asymmetrical Brachycephaly and Deformational Brachycephaly. Results of this study should not be used in the analysis of non-plagiocephalic deformational head shapes.