Computer-assisted preoperative simulation for positioning of plate fixation in Lefort I osteotomy: A case report

Tomographic analysis of nasomaxillary and zygomaticomaxillary buttress bone thickness for the fixation of miniplates

The purpose of this study was to evaluate the bone thickness of the nasomaxillary and zygomaticomaxillary buttresses to identify the most favourable region for the installation of miniplates. Bilateral tomographic images of 103 individuals were evaluated, for a total of 206 nasomaxillary and zygomaticomaxillary buttresses. Measurements of bone thickness were performed in the parasagittal reconstructions along three vertical lines on the nasomaxillary buttress (21 measurement points) and four vertical lines on the zygomaticomaxillary buttress (28 measurement points). The vertical line measurements for each buttress were compared using the Kruskal-Wallis test. Spearman's correlation coefficient was used to determine the correlation between the thicknesses obtained and patient sex and side (right/left). The level of significance adopted was 5%. The nasomaxillary and zygomaticomaxillary buttresses presented statistical differences in thickness at their respective points (P=0.001). The analysis of the nasomaxillary buttress showed that the thicker bone for the installation of miniplates follows the long axis of the upper canine at a distance of 3mm from the root apex. For the zygomaticomaxillary buttress, thicker bone to install miniplates was found distal to the distobuccal root of the first molar, at a distance of 3.5mm from the limit of the infraorbital foramen.

Do Vertical Soft Tissue and Actual Bony Landmarks Correlate in Le Fort I Orthognathic Surgery?

PURPOSE

Vertical changes in Le Fort I orthognathic surgery are critical to the overall esthetic result. Three-dimensional planning enables vertical measurements from the rendered computed tomographic (CT) scan, but intraoperative points are ascribed partially from soft tissues landmarks. This study compared intraoperative soft tissue vertical measurements with pre- and postoperative CT-based values and attempted to validate intraoperative soft tissue landmarks for vertical positioning.

MATERIALS AND METHODS

In this retrospective single-cohort study, the authors examined orthognathic procedures performed by a single surgeon at their institution. Patients were excluded if measurements or pre- and postoperative CT scans were lacking. Demographic information and soft tissue perioperative data were tabulated. Clinical vertical measurements included the left medial canthus to the central incisor, the left medial canthus to the left canine, and the right medial canthus to the right canine. Bone measurements were calculated using pre- and postoperative cone-beam CT scans for the same clinical landmarks. Statistical analysis, including paired Student t test, was performed using SPSS.

RESULTS

Forty-two patients were identified (mean age, 23 yr; 57% female). The change in pre- and postoperative measurements was analyzed. There was no significant difference in the absolute value pre- and postoperatively between the 2 modalities (P < .2, .1, .1), but there was a significant difference between bony and soft tissue measurements (P < .01). Subset analysis showed differences in postoperative values between Class II and III cases.

CONCLUSIONS

These results show a nonlinear but predictable relation between intraoperative soft tissue (medial canthi and maxillary dentition) and CT-measured bony vertical measurements. Understanding this relation enables effective use of intraoperative measurements to reproducibly achieve the desired bony vertical position and allows adjustments to be made to optimize esthetics.

Midface Fracture Simulation and Repair: A Computer-Based Algorithm

We introduce a novel computer-based method to digitally fixate midfacial fractures to facilitate more efficient intraoperative fixation. This article aims to describe a novel computer-based algorithm that can be utilized to model midface fracture reduction and fixation and to evaluate the algorithm's ability to produce images similar to true postoperative images. This is a retrospective review combined with cross-sectional survey from January 1, 2010, to December 31, 2015. This study was performed at a single tertiary care, level-I trauma center. Ten patients presenting with acute midfacial traumatic fractures were evaluated. Thirty-five physicians were surveyed regarding the accuracy of the images obtained using the algorithm. A computer algorithm utilizing AquariusNet (TeraRecon, Inc., Foster City, CA) and Adobe Photoshop (Adobe Systems Inc., San Jose, CA) was developed to model midface fracture repair. Preoperative three-dimensional computed tomographic (CT) images were processed using the algorithm. Fractures were virtually reduced and fixated to generate a virtual postoperative image. A survey comparing the virtual postoperative and the actual postoperative images was produced. A Likert-type scale rating system of 0 to 10 (0 being completely different and 10 being identical) was utilized. Survey participants evaluated the similarity of fracture reduction and fixation plate appearance. The algorithm's capacity for future clinical utility was also assessed. Survey response results from 35 physicians were collected and analyzed to determine the accuracy of the algorithm. Ten patients were evaluated. Fracture types included zygomaticomaxillary complex, LeFort, and naso-orbito-ethmoidal complex. Thirty-four images were assessed by a group of 35 physicians from the fields of otolaryngology, oral and maxillofacial surgery, and radiology. Mean response for fracture reduction similarity was 7.8 ± 2.5 and fixation plate similarity was 8.3 ± 1.9. All respondents reported interest in the tool for clinical use. This computer-based algorithm is able to produce virtual images that resemble actual postoperative images. It has the ability to model midface fracture repair and hardware placement.

Use of three-dimensional, CAD/CAM-assisted, virtual surgical simulation and planning in the pediatric craniofacial population

OBJECTIVE

Virtual Surgical Planning (VSP) and computer-aided design/computer-aided manufacturing (CAD/CAM) have recently helped improve efficiency and accuracy in many different craniofacial surgeries. Research has mainly focused on the use in the adult population with the exception of the use for mandibular distractions and cranial vault remodeling in the pediatric population. This study aims to elucidate the role of VSP and CAD/CAM in complex pediatric craniofacial cases by exploring its use in the correction of midface hypoplasia, orbital dystopia, mandibular reconstruction, and posterior cranial vault expansion.

METHOD/DESCRIPTION

A retrospective analysis of thirteen patients who underwent 3d, CAD/CAM- assisted preoperative surgical planning between 2012 and 2016 was performed. All CAD/CAM assisted surgical planning was done in conjunction with a third party vendor (either 3D Systems or Materialise). Cutting and positioning guides as well as models were produced based on the virtual plan. Surgeries included free fibula mandible reconstruction (n = 4), lefort I osteotomy and distraction (n = 2), lefort II osteotomy with monobloc distraction (n = 1), expansion of the posterior vault for correction of chiari malformation (n = 3), and secondary orbital and midface reconstruction for facial trauma (n = 3). The patient's age, diagnosis, previous surgeries, length of operating time, complications, and post-surgery satisfaction were determined.

RESULTS

In all cases we found presurgical planning was helpful to improve accuracy and significantly decrease intra-operative time. In cases where distraction was used, the planned and actual vectors were found to be accurate with excellent clinical outcomes. There were no complications except for one patient who experienced a wound infection post-operatively which did not alter the ultimate reconstruction. All patients experienced high satisfaction with their outcomes and excellent subjective aesthetic results were achieved.

CONCLUSIONS

Preoperative planning using CAD/CAM and VSP allows for safe and precise craniofacial reconstruction in complex pediatric cases with a reduction of operative time.

Application of Three-Dimensional Visualization Technology in Laparoscopic Partial Nephrectomy of Renal Tumor: A Comparative Study

PURPOSE

To compare the effectiveness and safety of individualized three-dimensional visualization technology (3DVT) on surgical planning and perioperative outcomes in laparoscopic partial nephrectomy (LPN) for renal cell carcinoma (RCC) with routine computed tomography (CT) examination in the treatment of renal tumor.

METHODS

From May 2015 to March 2016, a total of 94 patients with cT1 RCC who underwent surgical treatment in our department were analyzed retrospectively. Among these patients, a total of 49 cases received LPN with operation plan based on 3DVT. Surgical plan was obtained by virtual operation and morphometry on 3D reconstruction model. The remaining 45 cases received surgical treatment with traditional CT examination. Patient demographic, surgical outcome, and postoperative parameters were compared between these two groups.

RESULTS

No significant difference was found in blood loss volume, postoperative complication, selective clamping success rate, changes in postoperative renal function, and operative and ischemic time between the two groups. However, when handling complicated tumor with R.E.N.A.L score ≥8, operation time (126.7 ± 36.4 versus 154.8 ± 34.7, P = .018) and occurrence of postoperative urinary leak (0 versus 4, 0% versus 22.2%, P = .033) were diminished significantly in the 3DVT group.

CONCLUSIONS

3DVT provided precise information of anatomical structure in the operative area and reliable guidance for preoperative plan design. Our results indicated that 3DVT facilitated accurate visible image-guided tumor resection with ideal renal function preservation in LPN for renal tumor of high complexity.

The use of virtual surgical planning and navigation in the treatment of orbital trauma

Virtual surgical planning (VSP) has recently been introduced in craniomaxillofacial surgery with the goal of improving efficiency and precision for complex surgical operations. Among many indications, VSP can also be applied for the treatment of congenital and acquired craniofacial defects, including orbital fractures. VSP permits the surgeon to visualize the complex anatomy of craniofacial region, showing the relationship between bone and neurovascular structures. It can be used to design and print using three-dimensional (3D) printing technology and customized surgical models. Additionally, intraoperative navigation may be useful as an aid in performing the surgery. Navigation is useful for both the surgical dissection as well as to confirm the placement of the implant. Navigation has been found to be especially useful for orbit and sinus surgery. The present paper reports a case describing the use of VSP and computerized navigation for the reconstruction of a large orbital floor defect with a custom implant.

Evolution of design considerations in complex craniofacial reconstruction using patient-specific implants

Previously published evidence has established major clinical benefits from using computer-aided design, computer-aided manufacturing, and additive manufacturing to produce patient-specific devices. These include cutting guides, drilling guides, positioning guides, and implants. However, custom devices produced using these methods are still not in routine use, particularly by the UK National Health Service. Oft-cited reasons for this slow uptake include the following: a higher up-front cost than conventionally fabricated devices, material-choice uncertainty, and a lack of long-term follow-up due to their relatively recent introduction. This article identifies a further gap in current knowledge – that of design rules, or key specification considerations for complex computer-aided design/computer-aided manufacturing/additive manufacturing devices. This research begins to address the gap by combining a detailed review of the literature with first-hand experience of interdisciplinary collaboration on five craniofacial patient case studies. In each patient case, bony lesions in the orbito-temporal region were segmented, excised, and reconstructed in the virtual environment. Three cases translated these digital plans into theatre via polymer surgical guides. Four cases utilised additive manufacturing to fabricate titanium implants. One implant was machined from polyether ether ketone. From the literature, articles with relevant abstracts were analysed to extract design considerations. In all, 19 frequently recurring design considerations were extracted from previous publications. Nine new design considerations were extracted from the case studies – on the basis of subjective clinical evaluation. These were synthesised to produce a design considerations framework to assist clinicians with prescribing and design engineers with modelling. Promising avenues for further research are proposed.