Evaluation of the Accuracy of Three-Dimensional Virtual Surgical Planning for Reconstruction of Mandibular Defects Using Free Fibular Flap

Accuracy of the surgical execution of virtually planned deep circumflex iliac artery flaps and their appropriateness for masticatory rehabilitation

BACKGROUND

Tumorous diseases of the jaw demand effective treatments, often involving continuity resection of the jaw. Reconstruction via microvascular bone flaps, like deep circumflex iliac artery flaps (DCIA), is standard. Computer aided planning (CAD) enhances accuracy in reconstruction using patient-specific CT images to create three-dimensional (3D) models. Data on the accuracy of CAD-planned DCIA flaps is scarce. Moreover, the data on accuracy should be combined with data on the exact positioning of the implants for well-fitting dental prosthetics. This study focuses on CAD-planned DCIA flaps accuracy and proper positioning for prosthetic rehabilitation.

METHODS

Patients post-mandible resection with CAD-planned DCIA flap reconstruction were evaluated. Postoperative radiograph-derived 3D models were aligned with 3D models from the CAD plans for osteotomy position, angle, and flap volume comparison. To evaluate the DCIA flap's suitability for prosthetic dental rehabilitation, a plane was created in the support zone and crestal in the middle of the DCIA flap. The lower jaw was rotated to close the mouth and the distance between the two planes was measured.

RESULTS

20 patients (12 males, 8 females) were included. Mean defect size was 73.28 ± 4.87 mm; 11 L defects, 9 LC defects. Planned vs. actual DCIA transplant volume difference was 3.814 ± 3.856 cm³ (p = 0.2223). The deviation from the planned angle was significantly larger at the dorsal osteotomy than at the ventral (p = 0.035). Linear differences between the planned DCIA transplant and the actual DCIA transplant were 1.294 ± 1.197 mm for the ventral osteotomy and 2.680 ± 3.449 mm for the dorsal (p = 0.1078). The difference between the dental axis and the middle of the DCIA transplant ranged from 0.2 mm to 14.8 mm. The mean lateral difference was 2.695 ± 3.667 mm in the region of the first premolar.

CONCLUSION

The CAD-planned DCIA flap is a solution for reconstructing the mandible. CAD planning results in an accurate reconstruction enabling dental implant placement and dental prosthetics.

Functional and esthetic outcomes of virtual surgical planning versus the conventional technique in mandibular reconstruction with a free fibula flap: A retrospective study of 24 cases

This study aimed to compare the functional and esthetic results in patients following mandibular reconstruction with a free fibula flap (FFF) by virtual surgical planning (VSP) versus the conventional technique. Patients who had undergone mandibular reconstruction with a FFF by VSP or the conventional technique were retrospectively assessed. The two groups were compared regarding functional and esthetic variables with appropriate scales preoperatively, intraoperatively, and postoperatively. Twenty-four patients were evaluated in two groups: conventional (n = 8) and VSP (n = 16). The mean amount of mandibular asymmetry was 2.62 mm (SD = 1.59) in the conventional group and 1.19 mm (SD = 1.32) in the VSP group. Of the patients who underwent conventional surgery, 12.5% had mandibular asymmetry of <2 mm and 87.5% had asymmetry of 2-5 mm. Of the VSP patients, 61.5% had mandibular asymmetry of <2 mm and 38.5% had mandibular asymmetry of 2-5 mm (p = 0.03). The mean difference in size of mandibular angle on the surgical and control sides was not significantly different between the two groups (p = 0.62). The difference in mean length of the mandibular body on the surgical side relative to the control side was not significant between the two groups (p = 0.75). Differences in functional variables between the two groups were not significant. Within the limitation of the study, it seems that the VSP technique resulted in better facial symmetry and superior esthetic outcomes compared with the conventional technique.

In-house virtual surgical planning and guided mandibular reconstruction is less precise, but more economical and time-efficient than commercial procedures

BACKGROUND

To compare an in-house and a commercially available surgical planning solution for mandibular reconstruction in terms of postoperative reconstruction accuracy and economic benefit.

METHODS

Twenty-nine consecutive patients with advanced oral squamous cell carcinoma (OSCC) requiring segmental mandibular reconstruction were enrolled. Fifteen patients underwent in-house surgical planning and 14 patients underwent a commercially available planning solution. A morphometric comparison of preoperative and postoperative computed tomography (CT) data sets and a cost-benefit comparison were performed.

RESULTS

Volumes of planned and reconstructed bone segments differed significantly for both in-house planning (p = 0.0431) and commercial planning (p < 0.0001). Significant differences in osteotomy angles were demonstrated for in-house planning (p = 0.0391). Commercial planning was superior to in-house planning for total mandibular deviation (p = 0.0217), intersegmental space volumes (p = 0.0035), and lengths (p = 0.0007). No significant difference was found between the two planning solutions in terms of intersegmental ossification and the incidence of wound healing disorders. In-house planning took less time than commercial planning (p < 0.0001). Component manufacturing costs (p < 0.0001) and total cumulative costs (p < 0.0001) were significantly lower for in-house planning.

CONCLUSIONS

In-house surgical planning is less accurate but has a cost advantage and could be performed in less time.

Reconstruction of the mandible from partial inputs for virtual surgery planning

Statistical Shape Models (SSMs) and Sparse Prediction Models (SPMs) based on regressions between cephalometric measurements were compared against standard practice in virtual surgery planning for reconstruction of mandibular defects. Emphasis was placed on the ability of the models to reproduce clinically relevant metrics. CT scans of 50 men and 50 women were collected and split into training and testing datasets according to an 80:20 ratio. The scans were segmented, and anatomical landmarks were identified. SPMs were constructed based on direct regressions between measurements derived from the anatomical landmarks. SSMs were developed by establishing correspondence between the segmented meshes, performing alignment, and principal component analysis. Anterior and bilateral defects were simulated by removing sections of the mandibles in the testing set. Measurement errors after reconstruction ranged from 1.07˚ to 2.2˚ and 0.66 mm to 2.02 mm for mirroring, from 0.45˚ to 3.67˚ and 0.66 mm to 2.54 mm for the SSMs, and from 1.74˚ to 5.01˚ and 0.64 mm to 2.89 mm for the SPMs. Surface-to-surface errors ranged from 1.01 mm to 1.29 mm and 1.06 mm to 1.33 mm for mirroring and SSMs, respectively. Based on the results, SSMs are recommended for VSP in the absence of normal patient anatomy.

Application of optimized three-dimensional digital surgical guide plates for complex midfacial fractures

INTRODUCTION

The treatment of midfacial fractures is always difficult. The purpose of this study was to verify whether optimized three-dimensional (3D) digital surgical guide plates combined with preformed titanium plates improved the treatment effect in complex midfacial fractures.

PATIENTS AND METHODS

Twenty-six patients with complex midfacial fractures were recruited and randomized into three groups: ten for Group A, eight for Group B, and eight for Group C. Group A was treated with a combination of preformed titanium plates and optimized 3D digital surgical guide plates. Group B was treated with preformed titanium plates only. Group C was treated conventionally. Clinical effects, patient-reported outcome measures (PROMs), midfacial contour, facial symmetry, surgical accuracy, △orbital volume (the absolute value of the bilateral orbital volume difference), and maximum deviation were evaluated in each of the three groups.

RESULTS

Group A had the best postoperative clinical effects and patient-reported outcomes. Significant improvements in midfacial contour (L1[0.72±0.29 mm, P = 0.001], L2[1.04±0.46 mm, P < 0.001]), facial symmetry (S1[0.71±0.30 mm, P < 0.001], S2[0.96±0.58 mm, P < 0.001], S3[0.86±0.40 mm, P < 0.001], S5[0.81±0.16 mm, P = 0.003], S8[0.95±0.30 mm, P < 0.001], S9[1.03±0.38 mm, P < 0.001], S11[0.64±0.46 mm, P < 0.001]) and surgical accuracy (M1[R, 0.82±0.31 mm, P < 0.001], M2[R, 0.87±0.44 mm, P < 0.001], M3[L, 0.88±0.22 mm, P = 0.004], M3[R, 1.06±0.31 mm, P = 0.003], M4[L, 0.96±0.45 mm, P = 0.008], M4[R, 1.11±0.57 mm, P = 0.003], M5[R, 0.76±0.26 mm, P < 0.001], M6[L, 1.00±0.46 mm, P = 0.003], M6[R, 1.00±0.58 mm, P = 0.001], M7[0.87±0.53 mm, P = 0.001], M8[R, 0.91±0.53 mm, P < 0.001], M9[R, 0.81±0.32 mm, P = 0.010], M10[R, 1.19±0.42 mm, P = 0.009], M11[L, 0.85±0.51 mm, P = 0.021], M11[R, 0.96±0.49 mm, P = 0.003]) were found in Group A compared with the other two groups. The results of △orbital volume and maximum deviation analysis showed an ideal surgical treatment effect in Group A.

CONCLUSION

Optimized 3D digital guide plates can accurately locate preformed titanium plates and effectively improve the treatment effect in complex midfacial fractures.