Several classification systems have been proposed especially by Pruzansky (1982), Lauritzen et al (1985), David (1987), Vento et al (1991), and Horgan et al (1995). The most comprehensive classification system is OMENS+ as described by Horgan et al. However, surgeons find the classification of the skeletal deformity by Pruzansky, as modified by Kaban (which is incorporated in OMENS+) to be most useful in practice.
OMENS+ subdivides and grades each of the principal deformities. These are: O = Orbit M = Mandible E = Ear N = Nerves S = Soft Tissues + = Extra-craniofacial features
Pruzansky subdivides the ear and the mandible deformities.
I a small ramus with identifiable anatomy
II a functioning TMJ but with an abnormal shape and glenoid fossa (IIa and IIb as modified by Kaban)
IIa the glenoid fossa is in an acceptable functional position
IIb the TMJ is abnormally placed and cannot be incorporated in the surgical construction
III an absent ramus and nonexistent glenoid fossa
This system has two weaknesses.
• It is possible to have a Pruzansky II with a functioning TMJ but with or without a zygomatic arch and glenoid fossa. • It is possible to have a Pruzansky III with no condyle and no functioning TMJ with or without a zygomatic arch and a glenoid fossa.