IntroductionPatients with Craniofacial Microsomia (CFM) mandibles Types I/IIa benefit from combined LeFort 1 osteotomy and Mandibular Distraction Osteogenesis (LeFort + MDO); Type IIb from LeFort + MDO or Bimaxillary osteotomy (BiMax); and Type III from BiMax (with 50% of cases having preceding mandibular procedures, including patient-fitted prosthesis); as seen in Part 1. This leads to the question how maxillary and mandibular hypoplasia are correlated and influence the types of maxillary correction. Material and methodsA retrospective chart study was conducted including patients diagnosed with CFM from 2 large craniofacial units. Radiographic and clinical information were obtained. Unilateral affected patients with available (ConeBeam) CT-scan of the maxillary-mandibular complex, without treatment of the upper jaw prior to the CT-scan were included. A maxillary cant grading system was set up and evaluated. Pearson correlation coefficients were used to correlate the maxillary cant and the severity of the mandibular hypoplasia. ResultsEighty-one patients were included, of whom 39.5% had a Pruzansky-Kaban type III mandible and 42% a mild maxillary cant. There was a significant positive correlation between severity of the mandibular hypoplasia and the categorized canting (r = 0.370; p < 0.001; n = 81). Twenty-four patients had maxillary surgery, mainly a BiMax. ConclusionThere is a positive correlation between the severity of mandibular hypoplasia and maxillary cant. The severity of mandibular hypoplasia seems to dictate an intervention for both maxillary and mandibular surgery.