PRS Global Open Article Discussion: “Surgical Classification of the Mandibular Deformity in Craniofacial Microsomia Using 3-Dimensional Computed Tomography”

by Chad Purnell, MD (@ChadPurnellMD)

Craniofacial microsomia is a congenital facial malformation that commonly results in a decrease in the size of one or both sides of the mandible.  The Pruzansky classification (1) and its 1998 modification by Kaban et al (2) is how plastic surgeons have classified and communicated the mandibular deformity in these patients almost universally.  However, as technologies for imaging have changed, so has our understanding of this mandibular problem.  In their PRS Global Open article from January 2016, Drs. Swanson et al suggest an updated classification system that leverages current 3D-CT scan technology. (3)  Initially, they propose a new classification with 4 groups.  Type 1 has mild hypoplasia that can likely be treated with orthodontics or orthognathic surgery.  Type 2 has a moderate loss of vertical ramus height with a normal condyle, which likely would require treatment with distraction osteogenesis.  Type 3 has significant hypoplasia of the condyle which will likely require costochondral grafting for reconstruction.  Finally, Type 4 has hypoplasia of both the condyle and the mandibular body which would likely require a vascularized bone flap for reconstruction.

What makes this article interesting is they then compare the new classification system to the Kaban modified Pruzansky classification with regards to inter-rater reliability.  The authors sent 43 3D-CT scans to 15 craniofacial surgeons and had them classify patients using their new rating scale.  In a previous paper (4) the authors had done the same with the Pruzansky classification.  The new rating scale resulted in about 10% improved agreement amongst surgeons when compared to the older classification system.  Overall, the authors present a classification system that is repeatable, easy to understand, and has clear implications for treatment of the mandible.  The study does have several limitations, which the authors discuss.  As new treatment modalities are developed for craniofacial microsomia, this rating system that suggests treatments based on a given classification will need to be amended.  Additionally, Any classification system will come short to some degree in craniofacial microsomia because the mandible deformity is a continuous spectrum and not a set of artificial categories, just as the treatments of these deformities are not clear-cut either.

As technology and understanding in plastic surgery changes, it is important to continue to re-evaluate existing literature, classification systems, and treatments.  Swanson et al describe a new classification of the mandible deformity in craniofacial microsomia that allows clear communication and guides treatment with current modalities.  They also show that the new system allow more reliable rating between different surgeons.  With their new system, the authors provide an improved ability for surgeons to communicate about craniofacial microsomia patients and their treatment.

References

  1. Pruzansky S. Not all dwarfed mandibles are alike. Birth Defects. 1969;5:120.
  2. Kaban LB, Padwa BL, Mulliken JB. Surgical correction of mandibular hypoplasia in hemifacial microsomia: the case for treatment in early childhood. J Oral Maxillofac Surg. 1998;56:628–638.
  3. Swanson JW, Mitchell BT, Wink JA, et al. Surgical classification of the mandibular deformity in craniofacial microsomia using 3-dimensional computed tomography. Plast Reconstr Surg Glob Open 2016;4:e598
  4. Wink JD, Goldstein JA, Paliga JT, et al. The mandibular deformity in hemifacial microsomia: a reassessment of the Pruzansky and Kaban classi cation. Plast Reconstr Surg. 2014;133:174e–181e.
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