Monobloc and facial bipartition osteotomies: quantitative assessment of presenting deformity and surgical results based on computed tomography scans.

PURPOSE

The results of monobloc (MB) or facial bipartition (FB) osteotomies on 23 consecutive patients operated on between 1987 and 1991 were evaluated.

PATIENTS AND METHODS

A previously described method of clinically relevant linear measurements taken from preoperative and postoperative computed tomographic scans of these patients was used to document their presenting dysmorphology and the results of surgical correction initially and 1 year after operation. These data were compared with control values, and a percentage of normal for each measurement was derived for each patient.

RESULTS

In the patients with craniofacial dysostosis undergoing an MB osteotomy, the initial cranial vault length (87% of normal), medial orbital wall length (87%), zygomatic arch length (84%), and extent of globe protrusion (134%) all indicated horizontal (anterior-posterior) deficiency of the upper and middle face. After surgery, these measurements moved closer to age-matched control values. At the 1-year interval a minor degree of relapse was evident. In the patients with craniofacial dysostosis who were believed to need an FB osteotomy, the globe protrusion (142% of normal), medial orbital wall length (85%), and zygomatic arch lengths (83%) all indicated horizontal (anterior-posterior) deficiency in the upper and middle face. In addition, the anterior interorbital distance (123% of normal), mid-interorbital distance (122%), and intertemporal distance (126%) all indicated upper face hypertelorism. As a result of the FB osteotomy, anterior bony projection was achieved, and the hypertelorism was improved, but fell short of age-matched normal values. In the patients with frontonasal dysplasia, cranio-orbital clefting, and isolated orbital hypertelorism who underwent an FB osteotomy, preoperative measurements showed a distinct widening of the whole upper midface with forward projection of the medial relative to the lateral orbital walls. The orbital measurements revealed a substantially widened anterior interorbital distance (175% of normal), increased mid-interorbital distance (123%), and an increased distance between the lateral orbital walls (106%). After the surgical procedure, these measurements were improved and relatively stable but not completely normalized.

CONCLUSION

The use of quantitative measurements in the initial evaluation, intraoperative skeletal reshaping, and assessment of early and late reconstructive results provides useful benchmarks.