Deformation Assessment of the Manually Pre-bent Titanium Miniplates in Orthognathic Surgery With Finite Element Analysis

Patient-Specific Le Fort I Osteotomy Plates Are More Stable than Stock Plates in Patients with Cleft Lip and Palate

BACKGROUND

There is evidence that patient-specific plate fixation for Le Fort I osteotomies (LFI) is more stable than traditional plate fixation. The purpose of this study was to evaluate stability of LFI in patients with cleft lip and palate and determine stability differences between patient-specific and stock plates.

METHODS

Consecutive patients with cleft lip and palate who underwent isolated LFI by one surgeon (B.L.P.) between 2016 and 2021 were included. The predictor variable was type of plate used for fixation (patient-specific or stock). The outcome variable was magnitude of relapse in the vertical (nasion to A point) and horizontal planes (basion to A point) at 1 year after LFI using 3-dimensional cone beam computed tomography. Statistical analysis included independent samples t , Mann-Whitney U , Fisher exact, and chi-square tests. Values of P < 0.05 were significant.

RESULTS

The sample included 63 subjects; 23 in the patient-specific group (36.5%) and 40 in the stock group (63.5%). Groups were comparable by sex, race, age at surgery, cleft type, presence of pharyngeal flap, and magnitude of horizontal movement ( P > 0.136 for all). Subjects who underwent patient-specific plate fixation were less likely to have greater than or equal to 1-mm change at 1 year in the horizontal (4.3% versus 50.0%; P < 0.001) and vertical planes (4.3% versus 65.0%; P < 0.001) compared with stock plates. For patients who had greater than 10-mm horizontal advancement, the patient-specific plates had significantly less relapse (patient-specific plates, 0.105 ± 0.317 mm; stock plates, 1.888 ± 1.125 mm; P = 0.003).

CONCLUSION

Patient-specific plate fixation of LFI is more stable and demonstrates less relapse after 1 year than stock plates.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, III.

Influence of the Inferior Turbinate on the Accuracy of Superior Maxillary Repositioning

Notably, many studies have focused on the bony interference in the maxillary segment when performing maxillary superior repositioning; however, few reports have described the interference with the inferior nasal turbinate. Therefore, the authors aimed to retrospectively analyze the soft tissue or bone tissue volume of the inferior nasal turbinate and the accuracy of maxillary superior repositioning in Le Fort I osteotomy (LF1). The authors included 83 patients with facial deformities who underwent conventional LF1 (maxillary molar elevation between 4.0 and 6.0 mm) with/without bilateral sagittal split ramus osteotomy. The ratio of the soft tissue of the inferior turbinate to that of the inferior nasal cavity was used to divide the participants into 2 subgroups (large and small ratio). Similarly, the bony tissue volume of the inferior turbinate was used to divide the participants into 2 subgroups (large and small bony tissues), and the planned or actual amount of superior repositioning was compared 3 dimensionally. In the soft tissue group, the subgroups showed no significant differences (P=0.934). However, the actual maxillary superior repositioning was significantly lower in the large bone group than in the planned maxillary elevation group (P<0.01). In cases where the maxillary molar needs to be elevated by >4 mm and the bone tissue of the inferior nasal turbinate is well developed, an adjunctive technique such as horseshoe osteotomy or partial inferior turbinate resection should be considered in addition to LF1 to avoid interference between the inferior nasal turbinate and the maxillary bone fragments.

Accuracy and influencing factors of maxillary and mandibular repositioning using pre-bent locking plates: a prospective study

In-house repositioning methods based on three-dimensional (3D)-printing technology and the use of pre-bent plates has been gaining popularity in orthognathic surgery. However, there remains room for further improvement in methods and investigations on clinical factors that affect accuracy. This single-centre, prospective study included 34 patients and aimed to evaluate the accuracy and factors influencing maxillary and mandibular repositioning using pre-bent locking plates. The plates were manually pre-bent on the 3D-printed models of the planned position, and their hole positions were scanned and reproduced intraoperatively with osteotomy guides. The accuracy of repositioning and plate-hole positioning was calculated in three axes with the set landmarks. The following clinical factors that affect repositioning accuracy were also verified: deviation of the plate-hole positioning, amount of planned movement, and amount of simulated bony interference. The median deviations of the repositioning and hole positioning between the preoperative plan and postoperative results were 0.26 mm and 0.23 mm, respectively, in the maxilla, and 0.69 mm and 0.36 mm, respectively, in the mandible, suggesting that the method was highly accurate, and the repositioning concept based on the plate hole and form matching was more effective in the maxilla. Results of the correlation test suggest that large amounts of bony interference and plate-hole positioning errors in the up/down direction could reduce mandibular repositioning accuracy.

A Novel Orthognathic Surgery With a Half-Millimeter Accuracy for the Maxillary Positioning Using Prebent Plates and Computer-Aided Design and Manufacturing Osteotomy Guide

This retrospective study aimed to assess the accuracy of prebent plates and computer-aided design and manufacturing osteotomy guide for orthognathic surgery. The prebent plates correspondent to the planning model were scanned with a 3-dimensional printed model for guide design and used for fixation. Forty-two patients who underwent bimaxillary orthognathic surgery using computer-aided design and manufacturing intermediate splint with the guide (guided group: 20 patients) or with conventional fixation under straight locking miniplates (SLMs) technique (SLM group: 20 patients) were analyzed. A deviation of the maxilla between the planned and postoperative positions was evaluated using computed tomography, which was taken 2 weeks before and 4 days after the surgery. The surgery time and the infraorbital nerve paranesthesia were also evaluated. The mean deviations in the mediolateral ( x ), anteroposterior ( y ), and vertical directions ( z ) were 0.25, 0.50, and 0.37 mm, respectively, in the guided group, while that in the SLM group were 0.57, 0.52, and 0.82 mm, respectively. There were significant differences in x and z coordinates ( P <0.001). No significant difference in the surgery duration and paranesthesia was seen, suggesting the present method offers a half-millimeter accuracy for the maxillary repositioning without increasing the risk of extending surgery duration and nerve complication.

Evaluation of the Properties of 3D-Printed Ti Alloy Plates: In Vivo and In Vitro Comparative Experimental Study

Titanium (Ti)-based implants play a significant role in rigid internal fixation in maxillofacial surgery. No study has reported that three-dimensional-printed Ti alloy plates (3D-Ti plates) have comprehensively excellent properties similar to standard plates (Matrix-MANDIBLE, SYNTHES, Switzerland) (Synthes-Ti plates). In this work, we manufactured 3D-Ti plates by selective laser melting with Ti6Al4V powder. The surface morphology, mechanical properties, and bone-plate contact rate of the 3D-Ti plates and the Synthes-Ti plates were characterized and compared via electron microscopy, atomic force microscopy, Vickers hardness test, three-point bending test, and software calculation. Human bone marrow stromal cells (HBMSCs) were cultured on the plates to test their biocompatibility. Importantly, the 3D-Ti plates were placed into a mandibular fracture model to assess the effect of medical application for 4 and 24 weeks. The 3D-Ti plates were demonstrated to have similar biocompatibility and stability for rigid internal fixation with the Synthes-Ti plates, lower roughness (106.44 ± 78.35 nm), better mechanical strength (370.78 ± 1.25 HV10), and a higher bone-plate contact rate (96.9%). These promising results indicate the feasibility of using 3D-Ti plates for irregular shapes and complex anatomical structures in a clinical context.