Automatic virtual reconstruction of maxillofacial bone defects assisted by ICP (iterative closest point) algorithm and normal people database.

OBJECTIVES: The aim of this study was to propose and validate an automatic approach based on iterative closest point algorithm for virtual complement and reconstruction for maxillofacial bone defects. MATERIALS AND METHODS: A 3D craniomaxillofacial database of normal Chinese people including 500 skull models was established. Modified iterative closest point (ICP) algorithm was developed to complete bone defects automatically. The performances were evaluated by two approaches: (1) model experiment, virtual bony defects were created on 30 intact normal skull models not included in the database. For each defect model, the algorithm was applied to select the reference skull model from the database. 3-Dimensional and 2-dimensional comparison were conducted to evaluate the error between reference skull model with original intact model. Root mean square error (RMSE) and processing time were calculated. (2) Clinical application, the algorithm was utilized to assist reconstruction of 5 patients with maxillofacial bone defects. The symmetry of post-operative skull model was evaluated by comparing with its mirrored model. RESULTS: The algorithm was tested on an CPU with 1.80 GHz and average processing time was 493.5 s. (1) Model experiment, the average root-mean-square deviation of defect area was less than 2 mm. (2) Clinical application, the RMSE of post-operative skull and its mirrored model was 1.72 mm. CONCLUSION: It is feasible using iterative closest point algorithm based on normal people database to automatically predict the reference data of missing maxillofacial bone. CLINICAL RELEVANCE: An automated approach based on ICP algorithm and normal people database for maxillofacial bone defect reconstruction has been proposed and validated.

Correlation Between Soft and Hard Tissue Changes in the Zygomaticomaxillary Region After Bone Contouring Surgery for Fibrous Dysplasia-A Preliminary Study.

PURPOSE: The purpose of the present study was to determine the correlation between the soft and hard tissue changes in the zygomaticomaxillary region after facial bone contouring surgery for patients with craniofacial fibrous dysplasia (FD). MATERIALS AND METHODS: The present study was a retrospective case series that reviewed the cases of 13 patients with craniofacial FD in the zygomaticomaxillary region who had undergone navigation-guided facial bone contouring surgery from January 2013 to October 2017. Pre- and postoperative computed tomography (>3 months) were collected. The pre- and postoperative soft and hard tissues were placed in the same spatial coordinate system using multipoint registration to measure the distances between the corresponding pre- and postoperative points of the soft and hard tissues. The outcome variable was the corresponding soft tissue change. The correlation between the hard and soft tissue changes was obtained using correlation analysis with SPSS software (IBM Corp, Armonk, NY). The linear regression equation of the soft and hard tissue changes was used to predict the corresponding soft tissue changes. RESULTS: The Pearson correlation coefficient of the zygomatic region was 0.954 (P < .001) and the coefficient for the maxillary region was 0.758 (P < .001). The linear regression index (R2) for the zygomatic and maxillary regions was 0.910 (P < .001) and 0.575 (P < .001), respectively. The ß value of the linear regression equation for the zygomatic and maxillary regions was 0.815 (P < .001) and 0.52 (P < .001), respectively. CONCLUSIONS: The soft and hard tissue changes were highly correlated in both the zygomatic area and the maxillary area, and the variance of the maxillary area was slightly greater than that in the zygomatic area. This implied that the change of 1 mm of bone tissue along the tangent direction of the bone contour will cause a change of 0.815 mm in the soft tissue in the zygomatic region and 0.52 mm in soft tissue in the maxillary region.

Reconstruction of Bilateral Post-Traumatic Midfacial Defects Assisted by Three-Dimensional Craniomaxillofacial Data in Normal Chinese people-A Preliminary Study.

PURPOSE: To provide reference data for reconstruction of bilateral midfacial defects for which "mirror technique" cannot be applied. METHODS: The present study included 4 patients (3 males and 1 female) with post-traumatic bilateral midfacial fractures and defects. The most similar model was retrieved from a database of 552 normal Chinese people and used to guide preoperative virtual surgery planning. All patients underwent open reduction, internal fixation, and reconstruction surgery in 1 stage. A custom-made titanium prosthesis was used to repair the defects of frontal and naso-orbital-ethmoid (NOE) region in 1 patient. Two fibular flaps were used to repair the maxillary defects. A deep circumflex iliac artery flap was used to reconstruct large midfacial defects involving the right zygoma. A surgical navigation system was applied in 3 patients. RESULTS: The 4 patients were followed for 6 to 42 months. Two patients had finished all therapies and had satisfactory functional and cosmetic results. The appearance of 1 patient was obviously improved; that patient was still receiving treatment for denture prostheses. One patient had undergone first-stage reconstructive surgery and had normal occlusion at 6 months of follow-up. For 3 patients whose treatment had been assisted by navigation, the average surgical deviation was less than 3 mm (range, 1.5 to 2.2). For the patient whose treatment had not been assisted with navigation, the deviations differed in different areas: 3.47 mm in the right zygomaticomaxillary complex, 5.48 mm in the NOE area, and 5.91 mm in the maxillary area. CONCLUSIONS: For patients with bilateral post-traumatic midfacial defects across the midline, the use of a 3-dimensional craniomaxillofacial database can be considered a feasible method for providing reference data for preoperative planning.