Stability of Rigid Fixation in Craniofacial Fibrous Dysplasia and Cherubism: Report of Two Cases and Review of the Literature

Fibrous dysplasia (FD) is a rare non-malignant condition that involves the replacement of normal bone and marrow with fibrous tissue and woven bone.  Both monostotic and polyostotic FD frequently involve the craniofacial region.  Cherubism, previously described as familial FD, is genetically distinct from FD but is a related disorder with large fibro-osseous lesions.  Though the majority of individuals with cherubism eventually go into remission and lesions involute, changes may persist in some individuals.  Consequences of craniofacial involvement in FD and persistent cherubism include severe skeletofacial deformity, asymmetry, and malocclusion, and thus, these individuals will often benefit from orthognathic surgery.  When an individual with FD involving the craniofacial region presents for an orthognathic surgery work-up, the question of fixation type arises.  Poor bone quality can make rigid fixation with miniplates and screws challenging intraoperatively.  Although there has been some investigation into the histology of the bone/screw interface in FD, little attention is given to clinical stability from a rigid fixation standpoint.  Here we evaluate the stability of rigid fixation in dysplastic bone after orthognathic surgery in conjunction with a review of the literature. 

The first case reported involves a 16 year-old male with polyostotic craniofacial FD of his right zygoma, maxilla, and mandible, who underwent bilateral sagittal split osteotomies and genioplasty for correction of his skeletofacial deformity.  The second case reported involves a 16 year-old female with persistent cherubism who underwent bilateral sagittal split osteotomies.  Lateral cephalograms were taken immediately postoperatively (T1) and 6 months after orthognathic surgery (T2).  Eight standard cephalometric landmarks and four angular landmarks were measured for T1 and T2 to examine fixation stability.  Literature review included orthognathic surgical procedures with osteotomy site in craniofacial FD involved bone (monostotic or polyostotic) and in cherubism, rigid fixation with titanium miniplates and screws, and follow up > 6 months.  Orthognathic surgery utilizing osteotomies exclusively in nondysplastic bone or those that did not indicate lesion location or fixation type were excluded from the review.

Cephalometric analysis demonstrated consistency in the maxillary-mandibular relationship postoperatively from T1 to T2 in both cases.  Review of the literature revels that to date, 12 individuals with craniofacial FD have had osteotomy sites fixated using titanium miniplates and screws in involved bone.  The review also identified one report of orthognathic surgery with rigid fixation in an individual with cherubism.  The follow up of these patients ranged from 9 months to 9 years.  Unfortunately, fixation stability in patients treated at outside institutions were not evaluated on a cephlometric level.  However, serial clinical exams evaluating for changes in facial appearance and occlusion indicated fixation stability over time.  Although no publications indicated hardware failure, 6 patients with craniofacial FD had fixation hardware removed postoperatively (5 for the purpose of histopathologic analysis). 

In conclusion, when individuals with craniofacial FD and cherubism seek treatment for their skeletofacial deformities, osteotomy fixation type must be carefully considered.  The cases reported here demonstrate that rigid fixation of dysplastic bone is possible and can result in stable outcomes.  Additionally, a review of the literature further supports stability after orthognathic surgery involving fixation of dysplastic bone.  Therefore, although poor bone quality in these individuals can make osteotomy fixation more difficult intraoperatively, if achieved, long-term stability is likely.

SA Sachs, M Kleiman, R Pasternak. Surgical Management of a Facial Deformity Secondary to Craniofacial Fibrous Dysplasia.  J Oral Maxillofac Surg. 42:192-196. 1984.

JS Lee, EJ FitzGibbon, YR Chen, HJ Kim, LR Lustig, SO Akintoye, MT Collins, LB Kaban.  Clinical Guidelines for the Management of Craniofacial Fibrous Dysplasia.  Orphanet Journal of Rare Diseases. 7(suppl 1)L 52. 2012