Helmet therapy in infants with positional skull deformation: randomised controlled trialBMJ 2014; 348 doi: https://doi.org/10.1136/bmj.g2741 (Published 01 May 2014) Cite this as: BMJ 2014;348:g2741
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This study by van Wijk et al. in the British Medical Journal reports on data collected from 29 pediatric physical therapy practices and finds no difference in head shape outcomes at 24 months among those assigned to helmet therapy vs. those assigned to no treatment at all. Although timely and intriguing given the prevalence of positional head shape deformity in the wake of the Back-to-Sleep campaign, the study suffers from important and critical weaknesses that warrant mention.
First, subject numbers were particularly small (with 42 patients per group) and infants with “severe” deformities were specifically excluded. Also excluded were infants with torticollis and other developmental neuromuscular delays, making overall conclusions non-generalizable given the estimated 40-50% prevalence of these associated conditions in infants with positional cranial deformities. Second, analysis in this study relied on manual calculations with a non-standard technique (40 degree diagonals rather than 30 degrees), and no such measurements were made during the actual conduct of the study to determine clinical endpoints for helmet wear. Third, 100% of patients in the helmet group were noted to have side effects of wear, including 96% with skin irritation, 76% with unpleasant odor, and 33% with pain. Moreover, 73% admittedly had problems with helmet fit, resulting in shifting or rotating of the orthotic. Fourth, “full recovery” or full normalization of head shape, was seen in only 26 and 23% of helmet and natural course patients, respectively. Such results suggest overall inadequate treatment of the presenting problem and should be considered unacceptable.
In summary, we find significant weaknesses in the methodology employed by van Wijk et al. that necessarily call into question any conclusions about the lack of effectiveness of helmets. Numerous studies have shown excellent results with cranial orthoses that have been fit properly and appropriately monitored by orthotic specialists. While some infants may benefit from “conservative” measures alone (i.e., repositioning therapy and/or physical therapy specifically to address torticollis and core muscular development), we continue to believe that cranial orthoses serve a useful function in regulating growth of the asymmetric infant skull. We would urge parents with questions and pediatricians alike to consult with craniofacial plastic surgeons regarding the appropriate mode and timing of treatment for positional plagiocephaly and/or brachycephaly.
- Section on Plastic Surgery, Executive Committee of the American Academy of Pediatrics
Competing interests: No competing interests
In “Helmet therapy in infants with positional skull deformation: randomised controlled trial” the authors examine an important and timely topic: the use of helmet therapy for positional skull deformation is not undisputed, despite its widespread use, and double blind randomized clinical trials are lacking to examine its effectiveness. Thus, we applaud the authors for their important contribution to the literature.
The authors state that in the long-term, they expect no difference in skull deformation between the helmet and the control condition: “(…) we hypothesized that the natural course of skull deformation would catch up with the effects of helmet therapy and that no clinically meaningful differences would be present between the two groups at 2 years of age”. This makes the study a clear example of a study in which researchers aim to provide evidence in favor of the null hypothesis that there is no effect of the treatment. Regretfully, the null-hypothesis significance tests reported on in the article do not provide evidence in favor of the null hypothesis: the reported tests merely fail to reject the null-hypothesis, which is distinct from providing evidence in favor of the null-hypothesis [1,2]. A failure to reject the null-hypothesis can have a number of causes, such as, a) the study is underpowered, b) the measurements contain too much noise, or c) the null hypothesis in actuality holds. However, these causes cannot be discriminated by the standard null-hypothesis test presented throughout the paper. The large p-values (p=.8 and p=.81) reported in Table 3 should not be interpreted as direct evidence in favor of the null-hypothesis .
As recently advocated by a large number of authors [see, e.g., 1-6], Bayesian methods can be used to quantify the evidence in favor of the null hypothesis. The Bayes Factor (BF) is a statistic that enables direct comparison of statistical models or hypothesis. The BF quantifies the evidence in the data in favor of one hypothesis as opposed to another, competing hypothesis [4,5]. This makes the BF better suited for the purpose of the authors: it can be used to quantify evidence in favor of the null-hypothesis.
Based on the details provided in Table 3 it is straightforward to compute a t-value for the null hypothesis test of the Plagiocephaly change score and the Brachycephaly change score. For the Plagiocephaly score, assuming equal variances in both groups, we find a t-value of (2.9-3.1) / sqrt(2.92/39 + 3.32/40) = -.268. Similarly, for the Branchycephaly change score we obtain a t-value of .209. Subsequently, using a standard JZS prior as suggested by Rouder at all [see for more info 4] we obtain a BF of 5.61 and 5.71 respectively (specified in favor of the null hypothesis versus the two sided alternative).
Bayes Factors are often interpreted according to the cut-offs presented by Kass and Raftery , where a BF in the range of 5 to 10 is considered to provide positive, but not very strong, evidence in favor of the null-hypothesis. A BF of 1 is indecisive, as it indicates equal evidence in the data in favor of the null-hypothesis and the alternative hypothesis. A BF > 20 is often regarded as decisive evidence in favor of the null-hypothesis . For a thorough introduction to the use of Bayes Factors and their interpretation we refer the reader to .
From this alternative analysis of the primary outcome measures used in the article we can conclude that while the null-hypothesis was not rejected, the study also provides only limited to moderate evidence in favor of the null hypothesis. We would therefore encourage a larger double blind clinical trial, and perhaps a better development of the primary outcome measures such that these contain less (measurement) variance, before deciding to adopt or reject helmet therapy. Furthermore, we would like to encourage researchers to examine alternatives to the classical null-hypothesis significance test if the aim is to gather evidence in favor of a null-hypothesis .
Maurits Kaptein PhD
Assistant Professor Research Methods and Statistics
Tilburg university, Tilburg, the Netherlands
Rosa Geurtzen MD
Department of Pediatrics
Radboud university medical center, Nijmegen, Netherlands
 Rouder, J. N., Speckman, P. L., Sun, D., Morey, R. D., and Iverson, G. (2009), “Bayesian t tests for accepting and rejecting the null hypothesis”. Psychonomic bulletin & review, 16 (2): 225–37.
 Goodman, S. N. (1999), “Toward evidence-based medical statistics. 2: The Bayes factor”. Annals of internal medicine, 130 (12): 1005–13.
 Wetzels, R., Raaijmakers, J. G. W., Jakab, E., and Wagenmakers, E.-J. (2009), “How to quantify support for and against the null hypothesis: a flexible WinBUGS implementation of a default Bayesian t test”. Psychonomic bulletin review, 16 (4): 752–760.
 Robert E. Kass and Adrian E. Raftery (1995). “Bayes Factors”. Journal of the American Statistical Association, 90 (430): 791.
 H. Jeffreys (1961). The Theory of Probability (3 ed.). Oxford. p. 432.
 Kruschke, J. K. (2010), “Bayesian data analysis”. Wiley Interdisciplinary Reviews: Cognitive Science, 1 (5): 658–676.
Competing interests: No competing interests
I read with interest this article on the use of helmets to prevent head deformation of term babies after birth due to sleeping position.
My response is not based on scientific study, but from observation and ancestral guidance.
When I had my children I was advised to gently massage the newborn's head in a circular manner at the time of bathing. As the head is soft and malleable it eventually gets a good shape. This is done regularly by experienced women who are actually employed to bath the babies for up to 40 days after birth. The baby is massaged with olive oil and not only the head, but the face trunk and limbs are massaged gently, limbs are flexed and extended several times and after about 1/2 an hour the baby is bathed in warm soapy water.
The other technique used is using a small pillow filled with mustard seeds, This allows the head to roll without friction and the baby's head is not misshapen. A pillow wth foam beads as used in a bean bag may do the trick. This has helped me and some of my friends.
Competing interests: No competing interests
We are not in agreement with the results.
It is very important to choose orthotic treatment in a Clinic of Orthopaedics really specialized in head orthosis and with results that guarantee it.
I urge readers to consult our Web site: www.clinicasalcedo.com, Plagiocefalia section and see our information of results from more than 30 cases.
We have more than 10 years of experience in head orthosis treatment with spectacular results. We have a photographic file of more than 2500 babies we have treated with head orthosis from 2004.
The success of our tailored orthosis treatment is based on taking measurements of the skull of the baby with stucco bandage and not with a scanner; we manufacture for each individual and with manual rectification of the mold, individualized adaptation and revisions every 3 weeks. The helmet in each revision is at the speed and evolution of the growth and improvements of the baby and is rectified and adapted individually.
In this way, the deformity is practically corrected in 3 months.
The helmet by itself does not serve. The success of our treatment is based on the manufacture exclusively to size and the individual and on exhaustive and individualized revisions every 3 weeks for under 1.000€.
We guarantee correction of head deformity in more than 80% of cases in only 3 months.
This does not guarantee any other Orthopaedics in Spain. For that reason we are a referral clinic for Orthopaedics in Spain for the treatment of head deformities of the baby with our orthosis treatment.
Competing interests: To consider that the treatment of head deformities in babies is not effective using any orthopaedic helmet made by nobody orthopaedic is false and harms the image of the professionals and true specialists in head orthosis like us with an historical one of demonstrable spectacular results for more than 10 years.
Dear Editor, we have read with great interest the paper of van Wijk et al. Helmet therapy in infants with positional skull deformation: randomised controlled trial. BMJ 2014;348:g2741. The authors present a single-blinded, randomised controlled trial (HEADS, HElment therapy Assessment in Deformed Skulls) with 84 infants aged 5 to 6 months with moderate to severe skull deformation who were randomly assigned to 6 months of helmet therapy (n=42) or to natural course (n=42) . The improvement assessed by anthropometric measurements showed no differences at 24 months, although the parents of infants in the helmet therapy group showed slightly higher satisfaction scores and lower anxiety levels. The authors discourage the use of a helmet therapy as a standard treatment for healthy individual with moderate to severe skull deformation based on the equal effectiveness of both treatment options and the high prevalence of side effects.
We agree with the authors conclusion that future research should determine the effects of helmet therapy in very severe skull deformation. However, we disagree with the authors statement to discourage the use of helmet therapy for our young patients with moderate to severe skull deformation. It is generally accepted that a positional skull deformation is a rather cosmetic problem. Nonetheless, a persisting severe skull deformation may affect the child psychologically. Besides, the putative distress to parents and caregivers cannot be disregarded. In practice quite often parents relate the story of friends who regret not having shown there child to a sepcialist because the deformity is still visible at 3 years of age. Thus, in a proportion of cases, children can escape the expected course of natural resolution.
Although it is generally accepted that most cases improve spontaneously (up to 70%), and several conservative treatment options have been established including regular changes of head position, physiotherapy and osteopathy, but also cranial remodelling helmets for moderate to severe asymmetry . The latter is a generally well-tolerated method to correct positional skull deformation . Six months of helmet therapy is rather long, as it is gerenally accepted that the effectiveness of helmet therapy diminishes with increasing age, particularly after 9 months of age . Therefore, we recommend to start helmet therapy, if necessary, at the age of 5 to 6 months, for a duration of 2 to 3 months. In van Wijk and colleagues’s study, all parents of the infants in the helmet group reported one or more side effects related to helmet therapy: problems with acceptance of the helmet (8/33, 24%), skin irritation (32/34, 96%), augmented sweating (24/34, 71%), unpleasant odour of the helmet (25/33, 76%), pain associated with the helmet (9/27, 33%), and feeling hindered from cuddling their child (24/31, 77%). A recently published review article showed that most reported complications of helmet therapy are minor and self-limiting . Furthermore, Wilbrand et al. concluded that most complications can easily be avoided or eliminated by proper education of parents . We agree and think that most of the side effects reported in the present study are likely to be avoidable with a regular follow-up, meticulous maintenance of the helmet and a shorter duration of therapy.
It would have been interesting to see a subanalysis of the anthropometric measurements at 24 months for the infants with helmet therapy with either moderate or severe positional skull deformation compared to natural course, and look forward to seeing a secondary analysis, and longer follow-up of the cohorts.
In our experience, helmet therapy has its justified role for selected infants with moderate to very severe positional skull deformities. Especially for infants with very severe forms, a small study group in van Wijk’s et al. cohort (29/844=3.4%), conservative treatment options do not usually lead to a sufficient correction of the infants head asymetry. Therefore, further randomised controlled trials or well-designed observational studies are of paramount importance in order to find less invasive methods or instruments of reshaping the head of children with plagiocephaly and finding which children benefit best from therapy.
Nonetheless, the authors should be commended for completing the first randomised controlled trial on helmet therapy in infants with positional skull deformities.
1. van Wijk RM, van Vlimmeren LA, Groothuis-Oudshoorn CG, et al. Helmet therapy in infants with positional skull deformation: randomised controlled trial. Bmj 2014;348:g2741 doi: 10.1136/bmj.g2741[published Online First: Epub Date]|.
2. Kluba S, Kraut W, Calgeer B, et al. Treatment of positional plagiocephaly - Helmet or no helmet? Journal of cranio-maxillo-facial surgery : official publication of the European Association for Cranio-Maxillo-Facial Surgery 2013 doi: 10.1016/j.jcms.2013.09.015[published Online First: Epub Date]|.
3. de Ribaupierre S, Vernet O, Rilliet B, et al. Posterior positional plagiocephaly treated with cranial remodeling orthosis. Swiss medical weekly 2007;137(25-26):368-72 doi: 2007/25/smw-11702[published Online First: Epub Date]|.
4. Eppley BL. Re: Helmet versus nonhelmet treatment in nonsynostotic positional posterior plagiocephaly. The Journal of craniofacial surgery 2001;12(1):97
5. Gump WC, Mutchnick IS, Moriarty TM. Complications associated with molding helmet therapy for positional plagiocephaly: a review. Neurosurgical focus 2013;35(4):E3 doi: 10.3171/2013.5.FOCUS13224[published Online First: Epub Date]|.
6. Wilbrand JF, Wilbrand M, Malik CY, et al. Complications in helmet therapy. Journal of cranio-maxillo-facial surgery : official publication of the European Association for Cranio-Maxillo-Facial Surgery 2012;40(4):341-6 doi: 10.1016/j.jcms.2011.05.007[published Online First: Epub Date]|.
Competing interests: No competing interests
As highlighted in the editorial of Collet in The BMJ, the rising incidence of head deformities represents an important health problem of infants in developed countries. With the introduction (and marketing) of orthotic therapy the answer to head deformities seemed to be: "Treatment, not prevention.”
Van Wijk and coworkers have to be congratulated to have undertaken the burdensome task testing helmet therapy in a randomized clinical trial. Results of the study show not only ineffectiveness of helmet therapy but also, that in only one infant out of four head deformities disappear within the first two years of life – regardless of the intervention. Whereas head deformities are found in about 20% of term infants, a much higher prevalence is found in preterm infants1. We have recently shown head deformities in about 30% of preterms at a corrected age of 6 months, suggesting no spontaneous improvement2. Considering the high prevalence, the associated risk of long term sequel and the missing effect of a therapy, the principal of dealing with head deformities has to be changed into: Treatment not, prevention!
Prevention however does have some prerequisites. Firstly, a widely applicable measure of head shape is needed, that provides standardized and reproducible data with appropriate reference values. Whereas the method used by van Wijk is good for research purposes, it will be less appropriate as a standard screening tool for head deformities and represents only a 2-dimensional measurement3. Thus, research is required to develop and test handy and affordable surface imaging systems, which provide standardized 3-dimensional measures and to define age dependent reference values (percentiles). Secondly, early prevention – starting already during neonatal care – is required to reduce the high prevalence of head deformities in preterm infants. Up until now, neonatal care is focused on other morbidities – clinical studies are needed to establish effective preventive interventions. Thirdly, an active educational program for parents is needed to prevent the development of head deformities by simple measures. Whereas special devices have been shown to be effective in preventing deformities in neonates born at term4. More research on the efficacy of non-invasive methods is required.
1 Ifflaender S, Rüdiger M, Konstantelos D, et al. Prevalence of head deformities in preterm infants at term equivalent age. Early Human Development 2013;89:1041–7. doi:10.1016/j.earlhumdev.2013.08.011
2 Ifflaender S, Rüdiger M, Konstantelos D, et al. Individual course of cranial symmetry and proportion in preterm infants up to 6months of corrected age. Early Human Dev Published Online First: 18 April 2014. doi:10.1016/j.earlhumdev.2014.03.008
3 van Adrichem LNA, van Vlimmeren LA, Cadanová D, et al. Validation of a simple method for measuring cranial deformities (plagiocephalometry). J Craniofac Surg 2008;19:15–21. doi:10.1097/scs0b013e31815c93cb
4 Wilbrand J-F, Seidl M, Wilbrand M, et al. A Prospective Randomized Trial on Preventative Methods for Positional Head Deformity: Physiotherapy versus a Positioning Pillow. J Pediatr 2013;162:1216–1221.e1. doi:10.1016/j.jpeds.2012.11.076
Competing interests: No competing interests
In a study of 84 infants with skull deformity randomized to either ‘no-treatment’ or ‘helmet treatment’, van Wijk and associates  found that the deformation was not corrected by either ‘helmet treatment’ or by the natural growth of the skull (i.e., no treatment). Seeing no difference, the authors conclude that “the use of a helmet as a standard treatment for healthy infants” should be discouraged.
We appreciate the investigators desire to address such a timely and difficult topic. Of significance, the authors were able to demonstrate that the ‘natural history’ of plagiocephaly is the skull deformity will not resolve on its own. This is a significant finding which may be overlooked in the hyperbole of their second conclusion, the overreaching dismissal of all helmet therapy. We assert that the author’s second conclusion is egregiously in error, and that the lack of improvement seen in their study was the direct result of their own admittedly ill-fitting helmets.
To understand our concerns, one needs to appreciate why doubters of helmet therapy have called for randomized controlled trials.
In 1979, Sterling Clarren et al.  first introduced helmet therapy for treatment of plagiocephaly. By the mid-1990’s, with what came to be recognized as an “epidemic” of skull deformity , numerous craniofacial centers began developing and using these devices, and subsequently began reporting that infants were successfully responding to treatment. Study after study [4-20] would demonstrate that helmet therapy is an effective treatment for deformational plagiocephaly, and soon invasive surgical interventions would come to be recognized as largely unwarranted [21-23].
Critics (e.g., Moss ) of helmet treatment called for randomized controlled trials, not to determine whether helmet therapy was effective, but rather to determine whether helmet therapy was necessary. The belief was that helmet therapy was not required if one simply allowed cranial growth to run its natural course. In other words, “the head will round out on its own”.
In a truly novel contribution to the medical literature, van Wijk and colleagues have documented that the natural growth did not correct the skull deformation. In other words, they have shown that untreated skull deformities persist. This finding suggests to us that the prevention and treatment of the skull deformation is justified and necessary.
However, at great variance with the medical literature [4-20], van Wijk and colleagues have reported that helmet therapy did not correct the skull deformity. Indeed, in 15 peer-reviewed studies conducted over the past 20+ years [4-20], helmet therapy has been demonstrated as an effective treatment for skull deformation. Based on a single, aberrant study, van Wijk and colleagues have concluded that all helmet therapy should be discouraged.
Helmet therapy, like any other recognized treatments, should be undertaken with a clear treatment protocol—none of which is provided in this study. On the other hand, the authors do report problems that indicate serious deviations from current standards of care. Complaints about skin irritation (96%), ill-fit (73%), pain (33%) and acceptance (24%) raise alarming concerns about treatment fidelity. In other words, was the treatment delivered in an accurate and consistent manner in accord with accepted standards? Unfortunately, the answer to that question is a resounding “no”. The van Wijk helmet therapies do not represent current standards of care and consequently, did not achieve the expected treatment outcomes.
Thus, while we applaud the investigators for documenting the ‘natural history’ of untreated plagiocephaly, we admonish them for hastily dismissing all helmet therapy. Nevertheless, van Wijk and colleagues  have added to our understanding of skull deformation by providing evidence that treatment is necessary.
Kevin M. Kelly, PhD
Associate Research Scientist, College of Public Health
Adjunct Associate Professor, Department of Anthropology,
Adjunct Associate Professor, Department of Community and Behavior Health
Adjunct Associate Professor, Department of Occupational and Environmental Health
The University of Iowa, Iowa City, Iowa, USA
Former Consultant, Cranial Technologies, Inc., Tempe, Arizona, USA
Timothy R Littlefield , MSEng
Vice President, Research and Regulatory Affairs
Cranial Technologies, Inc., Tempe, Arizona, USA
1. van Wijk RN, van Vlimmeren LA, Groothuis-Oudshoorn CGM, Van der Ploeg CPB, IJzerman MJ, Boere-Boonekamp MM. Helmet therapy in infants with positional skull. BMJ 2014; 348:g2741 doi: 10.1136/bmj.g2741
2. Clarren SK, Smith DW, Hanson JW. Helmet treatment for plagiocephaly and congenital muscular torticollis. J Pediatr. 1979 Jan;94(1):43-6.
3. Kane AA, Mitchell LE, Craven KP, Marsh JL. Observations on a recent increase in plagiocephaly without synostosis. Pediatrics. 1996 Jun;97(6 Pt 1):877-85
4. Ripley CE, Pomatto J, Beals SP, Joganic EF, Manwaring KH, Moss SD. Treatment of positional plagiocephaly with dynamic orthotic cranioplasty. J Craniofac Surg. 1994 Jul;5(3):150-9; discussion 160.
5. Littlefield TR, Beals SP, Manwaring KH, Pomatto JK, Joganic EF, Golden KA, Ripley CE. Treatment of craniofacial asymmetry with dynamic orthotic cranioplasty. J Craniofac Surg. 1998 Jan;9(1):11-7; discussion 18-9.
6. Kelly KM, Littlefield TR, Pomatto JK, Ripley CE, Beals SP, Joganic EF.Importance of early recognition and treatment of deformational plagiocephaly with orthotic cranioplasty. Cleft Palate Craniofac J. 1999 Mar;36(2):127-30.
7. Kelly KM, Littlefield TR, Pomatto JK, Manwaring KH, Beals SP.Cranial growth unrestricted during treatment of deformational plagiocephaly. Pediatr Neurosurg. 1999 Apr;30(4):193-9.
8. Mulliken JB, Vander Woude DL, Hansen M, LaBrie RA, Scott RM. Analysis of posterior plagiocephaly: deformational versus synostotic. Plast Reconstr Surg. 1999 Feb;103(2):371-80.
9. Bruner TW, David LR, Gage HD, Argenta LC. Objective outcome analysis of soft shell helmet therapy in the treatment of deformational plagiocephaly. J Craniofac Surg. 2004 Jul;15(4):643-50.
10. Graham JM, Kreutzman J, Earl D, Halberg A, Samayoa C, Guo X. Deformational brachycephaly in supine-sleeping infants. J Pediatr. 2005 Feb;146(2):253-7.
11. Graham JM, Gomez M, Halberg A, Earl DL, Kreutzman JT, Cui J, Guo X. Management of deformational plagiocephaly: repositioning versus orthotic therapy. J Pediatr. 2005 Feb;146(2):258-62.
12. Elwood ET, Petronio J, Wood RJ. Parental satisfaction with the CranioCap: a new cranial orthosis for deformational plagiocephaly. Cleft Palate Craniofac J. 2005 Jul;42(4):340-3.
13. Lee WT, Richards K, Redhed J, Papay FA. A pneumatic orthotic cranial molding helmet for correcting positional plagiocephaly. J Craniofac Surg. 2006 Jan;17(1):139-44.
14. Plank LH, Giavedoni B, Lombardo JR, Geil MD, Reisner A. Comparison of infant head shape changes in deformational plagiocephaly following treatment with a cranial remolding orthosis using a noninvasive laser shape digitizer. J Craniofac Surg. 2006 Nov;17(6):1084-91
15. Lee R, Teichgraeber J, Baumgartner J, Waller AL, English JD, Lasky RE, Miller CC, Gateno J, Xia JJ. Long-term treatment effectiveness of molding helmet therapy in the correction of posterior deformational plagiocephaly: a five-year follow-up. Cleft Palate Craniofac J. 2008;45(3):240–245
16. Thompson JT, David LR, Wood B, Argenta A, Simpson J, Argenta LC. Outcome analysis of helmet therapy for positional plagiocephaly using a three-dimensional surface scanning laser. J Craniofac Surg. 2009 Mar;20(2):362-5. doi: 10.1097/SCS.0b013e3181992382.
17. Lipira AB, Gordon S, Darvann TA, Hermann NV, Van Pelt AE, Naidoo SD, Govier D, Kane AA. Helmet versus active repositioning for plagiocephaly: a three-dimensional analysis. Pediatrics. 2010 Oct;126(4):e936-45. doi: 10.1542/peds.2009-1249.
18. Kluba S, Kraut W, Calgeer B, Reinert S, Krimmel M. Treatment of positional plagiocephaly - Helmet or no helmet? J Craniomaxillofac Surg. 2013 Oct 15. pii: S1010-5182(13)00271-0. doi: 10.1016/j.jcms.2013.09.015.
19. Seruya M, Oh AK, Sauerhammer TM, Taylor JH, Rogers GF. Correction of deformational plagiocephaly in early infancy using the plagio cradle orthotic. J Craniofac Surg. 2013 Mar;24(2):376-9. doi: 10.1097/SCS.0b013e31828010d1.
20. Moghaddam MB, Brown TM, Clausen A, DaSilva T, Ho E, Forrest CR. Outcome analysis after helmet therapy using 3D photogrammetry in patients with deformational plagiocephaly: the role of root mean square. J Plast Reconstr Aesthet Surg. 2014 Feb;67(2):159-65. doi: 10.1016/j.bjps.2013.09.036.
21. Longaker MT, Posnick JC, Rekate HL.Craniosynostosis and skull molding. J Craniofac Surg. 1998 Nov;9(6):572-600.
22. Persing J, James H, Swanson J, Kattwinkel J, American Academy of Pediatrics Committee on Practice and Ambulatory Medicine, Section on Plastic Surgery and Section on Neurological Surgery. Prevention and management of positional skull deformities in infants. Pediatrics. 2003 Jul;112(1 Pt 1):199-202.
23. Laughlin JL, Luerssen TG, Dias, MS, American Academy of Pediatrics Committee on Practice and Ambulatory Medicine, Section on Neurological Surgery. Prevention and Management of Positional Skull Deformities in Infants. Pediatrics 2011;128;1236; doi: 10.1542/peds.2011-2220
24. Moss SD. Nonsurgical, nonorthotic treatment of occipital plagiocephaly: what is the natural history of the misshapen neonatal head? J Neurosurg. 1997 Nov;87(5):667-70.
Competing interests: Kevin Kelly is former research consultant to Cranial Technologies, makers of orthotic helmets. Timothy Littlefield is Vice President, Research and Regulatory Affairs, Cranial Technologies. Together they have published three of the 15 articles cited as evidence against the authors' conclusions.