title: Computer-assisted planning, stereolithographic modeling, and intraoperative navigation for complex orbital reconstruction: a descriptive study in a preliminary cohort.
abstract: OBJECTIVE
  Post-traumatic or postablative enophthalmos and diplopia and/or facial asymmetry resulting from inaccurate restoration of orbital anatomy remain relatively frequent sequellae of complex orbital reconstruction. Recently, preoperative computer-assisted planning with virtual correction and construction of stereolithographic models have been combined with intraoperative navigation in an attempt to more accurately reconstruct the bony orbit and optimize treatment outcomes. The purpose of the present study is to review the authors' early experience with computer planning, stereolithographic modeling, and intraoperative navigation in a series of patients who underwent surgical treatment for a variety of complex post-traumatic and postablative orbital deformities.
  
  
  METHODS
  The investigators initiated a retrospective chart review, and a sample of patients was derived from the population of patients at Legacy Emanuel Hospital, Portland, OR, between 2007 and 2008. Each patient's anatomy was assessed in multiplanar (axial, coronal, sagittal) and 3-dimensional computed tomography (CT) hard-tissue views; virtual correction was made using the uninjured or anatomically correct side by creating a mirror image that was superimposed on the traumatized side. The internal orbit was reconstructed with the previously contoured titanium mesh. The external orbital frame was reduced or repositioned and stabilized using 1.3-mm and/or 1.5-mm titanium plates and screws. The patient's position was identified with a digital reference frame that was fixed to an adhesive mask. Intraoperative navigation was then used to assess the accuracy of the restored internal and external orbital anatomy by assessing various points on the virtual image at the workstation. All patients received a postoperative CT scan, and the preoperative and postoperative images were compared and subjectively analyzed. To be included in the sample, patients must have undergone reconstruction for complex primary or secondary unilateral orbital deformities secondary to traumatic injury or ablative procedure using computer-assisted treatment during the study enrollment period. Criteria for using computer-assisted navigation were unilateral, clinically significant disruption of the internal and/or external orbit, that involved more than one orbital wall and that resulted in or had the potential to result in enophthalmos, diplopia, ocular dysmotility, or facial asymmetry. Patients excluded from the review were those who underwent orbital reconstructing using traditional (non-computer-assisted) techniques. Demographic, etiological, treatment, and outcome variables were recorded and analyzed. Outcome measures included globe position, ocular motility, facial symmetry, and complications. Poor outcome was defined as clinically perceptible enophthalmos, persistent dipolopia, facial asymmetry/malar flattening, or ocular dysmotility.
  
  
  RESULTS
  Fifteen consecutive patients with complex primary or secondary unilateral post-traumatic and postablative orbital deformities received computer-assisted treatment. Anatomic restoration of internal and external orbital contours was obtained in all but 1 patient based on a comparison of preoperative and postoperative CT scans. Further evaluation of the postoperative CT images compared favorably to the virtually planned reconstructions. Despite favorable restoration of internal and external bony anatomy, the soft-tissue limitations were not completely overcome in some patients with secondary deformities. Suboptimal correction of globe projection occurred in three patients undergoing secondary enophthalmos repair because of severe, intraconal, soft-tissue scarring posterior to the equator of the globe. Complications occurred in 4 patients.
  
  
  CONCLUSIONS
  Preoperative computer modeling and intraoperative navigation provides a useful guide for and presumably more accurate reconstruction of complex orbital injuries and postablative orbital defects. Although probably not necessary for routine use in small orbital blowout fractures, its use in a shattered orbit or high-velocity injury resulting in severe disruption of the internal and external orbit shows promise.
authors.affiliation: Oral and Maxillofacial Surgery Service, Legacy Emanuel Hospital and Health Center, Oregon Health & Science University, Portland, OR, USA. bellb@hnsa1.com
authors.forename: R Bryan
authors.initials: RB
authors.lastname: Bell
authors.forename: Michael R
authors.initials: MR
authors.lastname: Markiewicz
mesh_terms: D000293:Adolescent; D000328:Adult; D003198:Computer Simulation; D015841:Enophthalmos / Q000209:etiology / Q000601:surgery; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009915:Orbit / Q000000981:diagnostic imaging / Q000601:surgery*; D009917:Orbital Fractures / Q000601:surgery; D009918:Orbital Neoplasms / Q000601:surgery; D011859:Radiography; D019651:Plastic Surgery Procedures; D025321:Surgery, Computer-Assisted; D055815:Young Adult