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Commentary: Does Mandibular Distraction Vector Influence Airway Volumes and Outcome?
Accepted Manuscript Commentary: Does mandibular distraction vector influence airway volumes and outcome? Cory M. Resnick, DMD, MD, W. Bradford Williams, DMD, MD PII:
S0278-2391(16)30792-3
DOI:
10.1016/j.joms.2016.08.045
Reference:
YJOMS 57434
To appear in:
Journal of Oral and Maxillofacial Surgery
Received Date: 27 August 2016 Accepted Date: 29 August 2016
Please cite this article as: Resnick CM, Williams WB, Commentary: Does mandibular distraction vector influence airway volumes and outcome?, Journal of Oral and Maxillofacial Surgery (2016), doi: 10.1016/ j.joms.2016.08.045. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
Commentary: Does mandibular distraction vector influence airway volumes and outcome?
RI PT
Cory M. Resnick, DMD, MD1 and W. Bradford Williams, DMD, MD2
1. Instructor, Harvard School of Dental Medicine, Department of Plastic and Oral Surgery, Boston Children’s Hospital, Boston, MA
SC
2. Senior Physician, Kaiser Oakland Medical Center, Department of Maxillofacial Surgery,
M AN U
Oakland, CA
This study compares the airway volumes and outcomes for infants with Pierre Robin sequence who have had mandibular distraction osteogenesis (MDO) using either a horizontal or an oblique vector. The authors found slightly larger increases in airway volumes with a
TE D
horizontal vector, but similar clinical outcomes in both groups.
This topic is of great interest to those of us who perform neonatal MDO as no guidelines currently exist for the method and vector for the mandibular movement and this is the only study
EP
that directly compares distraction vectors. However, there are flaws in the study design and presentation that limit the application of these findings to clinical practice. First, some of the
AC C
study background is misleading, such as a comment regarding the decision to distract the mandible beyond the position of the maxilla, which states that “an overshoot, or creation of anterior skeletal cross-bite, autocorrects, due to continued maxillary growth.” In fact, future growth of the craniofacial skeleton with or without MDO is variable, unpredictable, and likely to be tied to the underlying etiology of the Robin sequence [1]. The reader must recall that Pierre Robin sequence merely refers to a phenotype of sequentially linked events (micrognathia,
1
ACCEPTED MANUSCRIPT
glossoptosis, airway obstruction) which may be caused by any number of syndromic and nonsyndromic etiologies [2]. Next, the manuscript lacks important detail on the methodology of the study. We feel that
RI PT
it is critical to include the study time period, indications for MDO applied at each institution, details about the parameters of the CT scans that were used to assess the airway volumes
(including indication for intubation during the study), and information about the examiners that
SC
assessed these scans (such as if they were blinded to the clinical data and study groupings). It is also noteworthy that the distraction endpoint for the study subjects is vague and is noted only as
M AN U
“device determination”. It is clear in Table 1 that multiple devices were used across the study suggesting that significant differences exist between the magnitude of distraction between subjects.
The results of this study indicate that both groups demonstrated significant volumetric
TE D
and clinical improvement. While our own anecdotal evidence supports this conclusion, we have concerns about the study design that may compromise interpretation of these results. Most notable is that the two cohorts are not comparable. Group 1 had pre- and post-operative CTs at
EP
mean ages of 18.5±19.3 and 124.6±47 days-of-life, respectively, while Group 2 obtained their images at mean ages of 33.5±30.1 and 226.3±308 days. Though the analysis used by the authors
AC C
did not find these ages to be statistically different, we submit that this statistic did not account for the rapid growth that occurs in the first year of life. The nasal airway, for example, has been shown to increase in cross-sectional area by 67% from birth to the first birthday [3]. Calculated at both ends of their standard deviations, the postoperative airway volume of a 77.6-day-old in Group 1 may have been compared to that of a 534.3-day-old in Group 2. Can the airway volume of a 2.5-month-old infant really be measured against that of a 1.5-year-old child?
2
ACCEPTED MANUSCRIPT
Additionally, the authors mention in the Discussion that some subjects were intubated for their CT scans. This is a major confounding variable for volumetric measurements of the dynamic components of the airway. It is intuitive that the presence of an endotracheal tube would
RI PT
alter airway anatomy, and this has been shown to be the case in adults [4]. The positive pressure delivered through the tube during mechanical ventilation, particularly if un-cuffed endotracheal tubes are used, would further deform the airway shape and volume. Additionally, sedation and/or
SC
muscle relaxation used to maintain intubation would alter airway tone. Therefore, we would expect intubation to be an exclusion criterion for any investigation with measurement of three-
M AN U
dimensional airway volumes as a primary outcome variable.
Shortcomings aside, we commend the authors for investigating this important question. No other group has presented a worthier study on this topic to date. While this manuscript may
TE D
not guide treatment decisions for these readers, this is a topic worth further exploration.
References 1.
Rogers GF, Lim AA, Mulliken JB, Padwa BL: Effect of a syndromic diagnosis on
2.
EP
mandibular size and sagittal position in Robin sequence. J Oral Maxillofac Surg 67:2323, 2009 Izumi K, Konczal LL, Mitchell AL, Jones MC: Underlying genetic diagnosis of Pierre Robin
AC C
sequence: retrospective chart review at two children's hospitals and a systematic literature review. J Pediatr 160:645, 2012 3.
Djupesland PG, Lyholm B: Changes in nasal airway dimensions in infancy. Acta
Otolaryngol 118:852, 1998 4.
Alexopoulos C, Larsson SG, Lindholm CE: The anatomical shape of the airway during
endotracheal intubation. Acta Anaesthesiol Scand 27:331, 1983
3
S0278-2391(16)30792-3
DOI:
10.1016/j.joms.2016.08.045
Reference:
YJOMS 57434
To appear in:
Journal of Oral and Maxillofacial Surgery
Received Date: 27 August 2016 Accepted Date: 29 August 2016
Please cite this article as: Resnick CM, Williams WB, Commentary: Does mandibular distraction vector influence airway volumes and outcome?, Journal of Oral and Maxillofacial Surgery (2016), doi: 10.1016/ j.joms.2016.08.045. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
Commentary: Does mandibular distraction vector influence airway volumes and outcome?
RI PT
Cory M. Resnick, DMD, MD1 and W. Bradford Williams, DMD, MD2
1. Instructor, Harvard School of Dental Medicine, Department of Plastic and Oral Surgery, Boston Children’s Hospital, Boston, MA
SC
2. Senior Physician, Kaiser Oakland Medical Center, Department of Maxillofacial Surgery,
M AN U
Oakland, CA
This study compares the airway volumes and outcomes for infants with Pierre Robin sequence who have had mandibular distraction osteogenesis (MDO) using either a horizontal or an oblique vector. The authors found slightly larger increases in airway volumes with a
TE D
horizontal vector, but similar clinical outcomes in both groups.
This topic is of great interest to those of us who perform neonatal MDO as no guidelines currently exist for the method and vector for the mandibular movement and this is the only study
EP
that directly compares distraction vectors. However, there are flaws in the study design and presentation that limit the application of these findings to clinical practice. First, some of the
AC C
study background is misleading, such as a comment regarding the decision to distract the mandible beyond the position of the maxilla, which states that “an overshoot, or creation of anterior skeletal cross-bite, autocorrects, due to continued maxillary growth.” In fact, future growth of the craniofacial skeleton with or without MDO is variable, unpredictable, and likely to be tied to the underlying etiology of the Robin sequence [1]. The reader must recall that Pierre Robin sequence merely refers to a phenotype of sequentially linked events (micrognathia,
1
ACCEPTED MANUSCRIPT
glossoptosis, airway obstruction) which may be caused by any number of syndromic and nonsyndromic etiologies [2]. Next, the manuscript lacks important detail on the methodology of the study. We feel that
RI PT
it is critical to include the study time period, indications for MDO applied at each institution, details about the parameters of the CT scans that were used to assess the airway volumes
(including indication for intubation during the study), and information about the examiners that
SC
assessed these scans (such as if they were blinded to the clinical data and study groupings). It is also noteworthy that the distraction endpoint for the study subjects is vague and is noted only as
M AN U
“device determination”. It is clear in Table 1 that multiple devices were used across the study suggesting that significant differences exist between the magnitude of distraction between subjects.
The results of this study indicate that both groups demonstrated significant volumetric
TE D
and clinical improvement. While our own anecdotal evidence supports this conclusion, we have concerns about the study design that may compromise interpretation of these results. Most notable is that the two cohorts are not comparable. Group 1 had pre- and post-operative CTs at
EP
mean ages of 18.5±19.3 and 124.6±47 days-of-life, respectively, while Group 2 obtained their images at mean ages of 33.5±30.1 and 226.3±308 days. Though the analysis used by the authors
AC C
did not find these ages to be statistically different, we submit that this statistic did not account for the rapid growth that occurs in the first year of life. The nasal airway, for example, has been shown to increase in cross-sectional area by 67% from birth to the first birthday [3]. Calculated at both ends of their standard deviations, the postoperative airway volume of a 77.6-day-old in Group 1 may have been compared to that of a 534.3-day-old in Group 2. Can the airway volume of a 2.5-month-old infant really be measured against that of a 1.5-year-old child?
2
ACCEPTED MANUSCRIPT
Additionally, the authors mention in the Discussion that some subjects were intubated for their CT scans. This is a major confounding variable for volumetric measurements of the dynamic components of the airway. It is intuitive that the presence of an endotracheal tube would
RI PT
alter airway anatomy, and this has been shown to be the case in adults [4]. The positive pressure delivered through the tube during mechanical ventilation, particularly if un-cuffed endotracheal tubes are used, would further deform the airway shape and volume. Additionally, sedation and/or
SC
muscle relaxation used to maintain intubation would alter airway tone. Therefore, we would expect intubation to be an exclusion criterion for any investigation with measurement of three-
M AN U
dimensional airway volumes as a primary outcome variable.
Shortcomings aside, we commend the authors for investigating this important question. No other group has presented a worthier study on this topic to date. While this manuscript may
TE D
not guide treatment decisions for these readers, this is a topic worth further exploration.
References 1.
Rogers GF, Lim AA, Mulliken JB, Padwa BL: Effect of a syndromic diagnosis on
2.
EP
mandibular size and sagittal position in Robin sequence. J Oral Maxillofac Surg 67:2323, 2009 Izumi K, Konczal LL, Mitchell AL, Jones MC: Underlying genetic diagnosis of Pierre Robin
AC C
sequence: retrospective chart review at two children's hospitals and a systematic literature review. J Pediatr 160:645, 2012 3.
Djupesland PG, Lyholm B: Changes in nasal airway dimensions in infancy. Acta
Otolaryngol 118:852, 1998 4.
Alexopoulos C, Larsson SG, Lindholm CE: The anatomical shape of the airway during
endotracheal intubation. Acta Anaesthesiol Scand 27:331, 1983
3