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The Pierre Robin Mandible is Hypoplastic and Morphologically Abnormal
Elizabeth G Zellner1, Russell R Reid, Derek M Steinbacher
1*Division of Plastic and Reconstructive Surgery, The Hospital for Sick Children, Univesity of Toronto, Toronto, ON, Canada †Section of Plastic and Reconstructive Surgery, Department of Surgery, University of Chicago, Chicago, IL ‡Section of Plastic and Reconstructive Surgery, Department of Surgery, Yale University School of Medicine, New Haven, CT.
Insights
Pierre Robin sequence (PRS) affects mandibular morphology, causing smaller volumes and altered angles. Mandibular distraction osteogenesis (MDO) improves PRS mandible size and shape, normalizing angles but altering ramus and body lengths.
Area of Science:
- Craniofacial surgery
- Pediatric orthopedics
- 3D imaging analysis
Background:
- Pierre Robin sequence (PRS) is associated with significant mandibular hypoplasia.
- Detailed 3D characterization of PRS mandibular morphology and the impact of mandibular distraction osteogenesis (MDO) remain incompletely understood.
- Comparison with age-matched controls is essential for understanding PRS-related skeletal differences.
Purpose of the Study:
- To quantitatively assess 3D mandibular morphology in infants with PRS compared to controls.
- To evaluate the effects of MDO on mandibular dimensions and morphology in PRS patients.
- To provide a comprehensive analysis of PRS-related craniofacial skeletal discrepancies.
Main Methods:
- Retrospective analysis of pre- and postoperative CT scans from PRS infants undergoing MDO.
- Inclusion of an age-matched control group with CT scans from a PACS database.
- Measurement of mandibular volume, ramus length, body length, and angles (anterior symphyseal and mandibular).
Main Results:
- PRS patients exhibited significantly reduced mandibular volume, ramus length, and body length compared to controls.
- A reduced anterior symphyseal angle was observed in PRS patients, while the mandibular angle was maintained.
- Post-MDO, mandibular volumes normalized, anterior symphyseal angles were indistinguishable from controls, but mandibular rami remained shorter and bodies longer.
Conclusions:
- The mandible in PRS is characterized by dysmorphia, including smaller volume, shorter ramus, and an obtuse symphyseal angle.
- MDO effectively improves mandibular volume and normalizes the symphyseal angle in PRS patients.
- MDO leads to specific changes in mandibular dimensions, namely a longer body and shorter ramus, compared to controls.
Background:
For Pierre Robin sequence (PRS) patients, there is incomplete characterization of 3D differences and effects of mandibular distraction osteogenesis (MDO) on the mandible compared to normal controls.
Methods:
PRS infants who underwent MDO at 2 craniofacial referral centerals with pre- and postoperative computed tomography (CT) scans were identified. A group of age-matched control patients with CTs were identified in the PACS database. Demographic and perioperative data were recorded. Mandibular lengths, angles, and volumes were measured. Morphologic and outcomes data were analyzed in a case-control comparison.
Results:
Sixty-three CT scans were analyzed. Fifteen pre-op PRS patient and 15 control CTs were well matched in terms of age and sex. Mandibular volume (78%), ramus length (87%), and body length (95%) were all decreased in the PRS patients. Anterior symphyseal angle (84%) was significantly reduced in PRS patients while mandibular angle (102%) was maintained. Eighteen post-op PRS patient and 15 control CTs were well matched in terms of age and gender. Mandibular volumes (106%) were normalized following distraction with shorter mandibular rami (88%) and longer mandibular bodies (109%). Postoperatively, mandibular angle (100%) and anterior symphyseal angle (99%) were ultimately indistinguishable from controls.
Conclusions:
The mandible in PRS is dysmorphic compared to age-matched controls. Overall, they have a smaller volume, shorter ramus, and an obtuse symphyseal angle. MDO improves mandibular volume and normalizes the symphyseal angle, but results in a longer mandibular body and shorter mandibular ramus.
