Virtual planning for mandible resection and reconstruction.

In mandibular reconstruction, computer-assisted procedures, including virtual surgical planning (VSP) and additive manufacturing (AM), have become an integral part of routine clinical practice. Especially complex cases with extensive defects after ablative tumor surgery benefit from a computer-assisted approach. Various CAD/CAM-manufactured tools such as surgical guides (guides for osteotomy, resection and predrilling) support the transition from virtual planning to surgery. Patient-specific implants (PSIs) are of particular value as they facilitate both osteosynthesis and the positioning of bone elements. Computer-based approaches may be associated with higher accuracy, efficiency, and superior patient outcomes. However, certain limitations should be considered, such as additional costs or restricted availability. In the future, automation of the planning process and augmented reality techniques, as well as MRI as a non-ionizing imaging modality, have the potential to further improve the digital workflow.

MRI-detected intraosseous bone marrow edema recedes after effective therapy of periodontitis.

OBJECTIVES: T2 STIR MRI sequences can detect preclinical changes associated with periodontal inflammation, i.e. intraosseous edema in the tooth-supporting bone. In this study, we assessed whether MRI can be used for monitoring periodontal disease. MATERIAL AND METHODS: In a prospective cohort study, we examined 35 patients with periodontitis between 10/2018 and 04/2019 by using 3D isotropic T2-weighted short tau inversion recovery (STIR) and Fast Field Echo T1-weighted Black bone sequences. All patients received standardized clinical exams before and three months after non-surgical periodontal therapy. Bone marrow edema extent was quantified in the STIR sequence at 922 sites before and after treatment. Results were compared with standard clinical findings. Non-parametric statistical analysis was performed. RESULTS: Non-surgical periodontal treatment caused significant improvement in mean probing depth (p < 0.001) and frequency of bleeding on probing (p < 0.001). The mean depth of osseous edema per site was reduced from a median [IQR] of 2 [1, 3] mm at baseline to 1 [0, 3] mm, (p < 0.001). Periodontal treatment reduced the frequency of sites with edema from 35 to 24% (p < 0.01). CONCLUSION: The decrease of periodontal bone marrow edema, as observed with T2 STIR MR imaging, is indicative of successful periodontal healing. CLINICAL RELEVANCE STATEMENT: T2 STIR hyperintense bone marrow edema in the periodontal bone decreases after treatment and can therefore be used to evaluate treatment success. Furthermore, MRI reveals new options to depict hidden aspects of periodontitis. KEY POINTS: • T2 STIR hyperintense periodontal intraosseous edema was prospectively investigated in 35 patients with periodontitis before and after treatment and compared to clinical outcomes. • The frequency of affected sites was reduced from 35 to 24% (p < 0.001), and mean edema depth was reduced from a median [IQR] of 2 [1, 3] mm at baseline to 1 [0, 3] mm 3 months after treatment. (p < 0.001). • T2 STIR sequences can be used to monitor the posttreatment course of periodontitis.

Nodal Disease and Survival in Oral Cancer: Is Occult Metastasis a Burden Factor Compared to Preoperatively Nodal Positive Neck?

The impact of neck involvement and occult metastasis (OM) in patients with oral squamous cell carcinoma (OSCC) favors an elective neck dissection. However, there are barely any existing data on survival for patients with OM compared with patients with positive lymph nodes detected preoperatively. This study aims to compare survival curves of patients suffering from lymph nodal metastases in a preoperatively N+ neck with those suffering from OM. In addition, clinical characteristics of the primary tumor were analyzed to predict occult nodal disease. This retrospective cohort study includes patients with an OSCC treated surgically with R0 resection with or without adjuvant chemoradiotherapy between 2010 and 2016. Minimum follow-up was 60 months. Kaplan-Meier analysis was used to compare the survival between patients with and without occult metastases and patients with N+ neck to those with occult metastases. Logistic regression was used to detect potential risk factors for occult metastases. The patient cohort consisted of 226 patients. Occult metastases occurred in 16 of 226 patients. In 53 of 226 patients, neck lymph nodes were described as suspect on CT imaging but had a pN0 neck. Higher tumor grading increased the chance of occurrence of occult metastasis 2.7-fold (OR = 2.68, 95% CI: 1.07-6.7). After 12, 24, 48 and 60 months, 82.3%, 73.8%, 69% and 67% of the N0 patients, respectively, were progression free. In the group with OM occurrence, for the same periods 66.6%, 50%, 33.3% and 33.3% of the patients, respectively, were free of disease. For the same periods, respectively, 81%, 63%, 47% and 43% of the patients in the N+ group but without OM remained disease free. The predictors for progression-free survival were a positive N status (HR = 1.44, 95% CI: 1.08-1.93) and the occurrence of OM (HR = 2.33, 95% CI: 1.17-4.64). The presence of occult metastasis could lead to decreased survival and could be a burdening factor requiring treatment escalation and a more aggressive follow-up than nodal disease detected in the preoperative diagnostic imaging.

Cancer testis antigen (PRAME) as an independent marker for survival in oral squamous cell carcinoma (OSCC).

BACKGROUND: The objective was to assess the expression patterns of the cancer testis antigen PRAME, NY-ESO1, and SSX2 in oral squamous cell carcinoma (OSSC) and to correlate the expression with clinical and histopathological parameters including progression-free survival analysis. METHODS: The study variables of this retrospective cohort study (n = 83) included demographic data, histopathological data, and information on progression-free survival. PRAME expression patterns were rated based on immunohistochemistry on tissue microarrays (TMA). The survival rate was assessed by Kaplan-Meier method and Cox regression model. The primary predictor variable was defined as the expression of PRAME and the outcome variable was progression-free survival. RESULTS: Analysis of progression-free survival using Kaplan-Meier method showed that patients with positive expression of PRAME had lower probabilities of progression-free survival (p < 0.001). According to the Cox regression model, the level of PRAME expression had a considerable and significant independent influence on progression-free survival (positive PRAME expression increasing the hazards for a negative outcome by 285% in our sample; HR = 3.85, 95% CI: 1.45-10.2, p = 0.007). The expression of SSX2 (n = 1) and NY-ESO-1 (n = 5) in our samples was rare. CONCLUSION: PRAME is expressed in OSCC and appears to be a suitable marker of progression-free survival, correlates with severe course, and may allow identification of high-risk patients with aggressive progression.

Digital planning and individual implants for secondary reconstruction of midfacial deformities: A pilot study.

Objective: To evaluate the feasibility and accuracy of implementing three-dimensional virtual surgical planning (VSP) and subsequent transfer by additive manufactured tools in the secondary reconstruction of residual post-traumatic deformities in the midface. Methods: Patients after secondary reconstruction of post-traumatic midfacial deformities were included in this case series. The metrical deviation between the virtually planned and postoperative position of patient-specific implants (PSI) and bone segments was measured at corresponding reference points. Further information collected included demographic data, post-traumatic symptoms, and type of transfer tools. Results: Eight consecutive patients were enrolled in the study. In five patients, VSP with subsequent manufacturing of combined predrilling/osteotomy guides and PSI was performed. In three patients, osteotomy guides, repositioning guides, and individually prebent plates were used following VSP. The median distances between the virtually planned and the postoperative position of the PSI were 2.01 mm (n = 18) compared to a median distance concerning the bone segments of 3.05 mm (n = 12). In patients where PSI were used, the median displacement of the bone segments was lower (n = 7, median 2.77 mm) than in the group with prebent plates (n = 5, 3.28 mm). Conclusion: This study demonstrated the feasibility of VSP and transfer by additive manufactured tools for the secondary reconstruction of complex residual post-traumatic deformities in the midface. However, the median deviations observed in this case series were unexpectedly high. The use of navigational systems may further improve the level of accuracy.

Accuracy of free-hand positioned patient specific implants (PSI) in primary reconstruction after inferior and/or medial orbital wall fractures.

BACKGROUND: To assess the accuracy with which CAD/CAM-fabricated patient-specific titanium implants (PSI) are positioned for inferior and/or medial orbital wall reconstruction without the use of intraoperative navigation. METHODS: Patients who underwent a primary reconstruction of the orbital walls with PSI due to fractures were enrolled in this retrospective cohort analysis. The primary outcome variables were the mean surface distances (MSD) between virtually planned and postoperative PSI position and single linear deviations in the x-, y- and z-axis at corresponding reference points. Secondary outcome variables included demographic data, classification of orbital wall defects and clinical outcomes. RESULTS: A total of 33 PSI (orbital floor n = 22; medial wall, n = 11) were examined in 27 patients. MSD was on a comparable level for the orbital floor and medial wall (median 0.39 mm, range 0.22-1.53 mm vs. median 0.42 mm, range 0.21-0.98 mm; p = 0.56). Single linear deviations were lower for reconstructions of the orbital floor compared to the medial wall (median 0.45 vs. 0.79 mm; p < 0.05). There was no association between the occurrence of diplopia and the accuracy level (p = 0.418). CONCLUSIONS: Free-hand positioning of PSI reaches a clinically appropriate level of accuracy, limiting the necessity of navigational systems to selected cases.

Geometric accuracy of magnetic resonance imaging-derived virtual 3-dimensional bone surface models of the mandible in comparison to computed tomography and cone beam computed tomography: A porcine cadaver study.

BACKGROUND: Providing accurate 3-dimensional virtual bone surface models is a prerequisite for virtual surgical planning and additive manufacturing in craniomaxillofacial surgery. For this purpose, magnetic resonance imaging (MRI) may be a radiation-free alternative to computed tomography (CT) and cone beam computed tomography (CBCT). PURPOSE: The aim of this study was to assess the geometric accuracy of 3-dimensional T1-weighted MRI-derived virtual bone surface models of the mandible in comparison to CT and CBCT. MATERIALS AND METHODS: Specimens of the mandible from porcine cadavers were scanned with (1) a 3-dimensional T1-weighted MRI sequence (0.6 mm isotropic voxel) optimized for bone imaging, (2) CT, and (3) CBCT. Cortical mandibular structures (n = 10) were segmented using semiautomated and manual techniques. Imaging-based virtual 3-dimensional models were aligned with a high-resolution optical 3-dimensional surface scan of the dissected bone (=ground truth) and global geometric deviations were calculated (mean surface distance [MSD]/root-mean-square distance [RMSD]). Agreement between the imaging modalities was assessed by equivalence testing and Bland-Altman analysis. RESULTS: Intra- and inter-rater agreement was on a high level for all modalities. Global geometric deviations (MSD/RMSD) between optical scans and imaging modalities were 0.225 ± 0.020 mm/0.345 ± 0.074 mm for CT, 0.280 ± 0.067 mm/0.371 ± 0.074 mm for MRI, and 0.352 ± 0.076 mm/0.454 ± 0.071 mm for CBCT. All imaging modalities were statistically equivalent within an equivalence margin of ±0.3 mm, and Bland-Altman analysis indicated high agreement as well. CONCLUSIONS: The results of this study indicate that the accuracy and reliability of MRI-derived virtual 3-dimensional bone surface models is equal to CT and CBCT. MRI may be considered as a reliable alternative to CT and CBCT in computer-assisted craniomaxillofacial surgery.

Prediction of surface area size in orbital floor and medial orbital wall fractures based on topographical subregions.

OBJECTIVE: This retrospective study evaluates the occurrence and frequency of different fracture patterns in a series of computed tomography (CT) scans in terms of the AOCMF Trauma Classification (TC) orbit module and correlates the assigned defects with measurements of the fracture area in order to get an approximate guideline for fracture size predictions on the basis of the classification. MATERIAL AND METHODS: CT scans of patients with orbital floor fractures were evaluated using the AOCMFTC to determine the topographical subregions. The coding consisted of: W = orbital wall, 1 = anterior orbit, 2 = midorbit, i = inferior, m = medial. The 3-dimensional surface area size of the fractures was quantified by the "defect body" method (Brainlab, Munich, Germany). The fracture area size and its confidence and prediction interval within each topographical subregion was estimated by regression analysis. RESULTS: A total of 137 CT scans exhibited 145 orbital floor fractures, which were combined with 34 medial orbital wall fractures in 31 patients. The floor fractures - W1(i)2(i) (n = 86) and W1(i) (n = 19) were the most frequent patterns. Combined floor and medial wall fractures most frequently corresponded to the pattern W1 (im)2 (im) (n = 15) ahead of W1 (im) 2(i) (n = 10). The surface area size ranged from 0.11 cm2 to 6.09 cm2 for orbital floor and from 0.29 cm2 to 5.43 cm2 for medial wall fractures. The prediction values of the mean fracture area size within the subregions were computed as follows: W1(i) = 2.25 cm2, W2(i) = 1.64 cm2, W1(i)2(i) = 3.10 cm2, W1(m) = 1.36 cm2, W2(m) = 1.65 cm2, W1(m)2(m) = 2.98 cm2, W1 (im) = 3.35 cm2, W1 (im) 2(i) = 4.63 cm2, W1 (im)2(m) = 4.06 cm2 and W1 (im)2 (im) = 7.16 cm2. CONCLUSION: The AOCMFTC orbital module offers a suitable framework for topographical allocation of fracture patterns inside the infero-medial orbital cavity. The involvement of the subregions is of predictive value providing estimations of the mean 3-D fracture area size.

Magnetic resonance imaging as a diagnostic tool for periodontal disease: A prospective study with correlation to standard clinical findings-Is there added value?

AIM: To evaluate the correlation between standard clinical findings, radiographic (OPT) and magnetic resonance imaging (MRI) as well as to assess whether MRI is capable of providing additional information related to the severity and extent of periodontal disease. METHODS: 42 patients with generalized periodontitis received pre-interventional MRI scans. These were compared to MR images of a periodontal healthy control group (n = 34). The extent of the osseous oedema, detected by MRI, was set in correlation with clinical periodontitis-associated findings. RESULTS: A highly significant correlation between bone oedema and clinical testings such as probing depth (p < 0.0001) and bleeding on probing (p < 0.0001) was revealed. The oedema exceeded the extent of demineralized bone. Patients with a positive BOP test showed a 2.51-fold increase in risk of already having a bone oedema around the respective tooth even if probing depth was ≤3 mm (logistic binary regression analysis, OR 2.51; 95% CI: 1.54-4.11; p < 0.0001). CONCLUSION: MRI findings correlated with standard clinical findings, and MRI was able to depict intraosseous changes before any osseous defect had occurred.

Magnetic resonance imaging based computer-guided dental implant surgery-A clinical pilot study.

BACKGROUND: Computer-guided implant surgery is currently based on radiographic techniques exposing patients to ionizing radiation. PURPOSE: To assess, whether computer-assisted 3D implant planning with template-guided placement of dental implants based on magnetic resonance imaging (MRI) is feasible. MATERIALS AND METHODS: 3-Tesla MRI was performed in 12 subjects as a basis for prosthetically driven virtual planning and subsequent guided implant surgery. To evaluate the transferability of the virtually planned implant position, deviations between virtually planned and resulting implant position were studied. Matching of occlusal surfaces was assessed by comparing surface scans with MRI-derived images. In addition, the overall image quality and the ability of depicting anatomically important structures were rated. RESULTS: MRI-based guided implant surgery with subsequent prosthetic treatment was successfully performed in nine patients. Mean deviations between virtually planned and resulting implant position (error at entry point 0.8 ± 0.3 mm, error at apex 1.2 ± 0.6 mm, angular deviation 4.9 ± 3.6°), mean deviation of occlusal surfaces between surface scans and MRI-based tooth reconstructions (mean 0.254 ± 0.026 mm) as well as visualization of important anatomical structures were acceptable for clinical application. CONCLUSION: Magnetic resonance imaging (MRI) based computer-assisted implant surgery is a feasible and accurate procedure that avoids exposure to ionizing radiation.

Bone regeneration of minipig mandibular defect by adipose derived mesenchymal stem cells seeded tri-calcium phosphate- poly(D,L-lactide-co-glycolide) scaffolds.

Reconstruction of bone defects represents a serious issue for orthopaedic and maxillofacial surgeons, especially in extensive bone loss. Adipose-derived mesenchymal stem cells (ADSCs) with tri-calcium phosphates (TCP) are widely used for bone regeneration facilitating the formation of bone extracellular matrix to promote reparative osteogenesis. The present study assessed the potential of cell-scaffold constructs for the regeneration of extensive mandibular bone defects in a minipig model. Sixteen skeletally mature miniature pigs were divided into two groups: Control group and scaffolds seeded with osteogenic differentiated pADSCs (n = 8/group). TCP-PLGA scaffolds with or without cells were integrated in the mandibular critical size defects and fixed by titanium osteosynthesis plates. After 12 weeks, ADSCs seeded scaffolds (n = 7) demonstrated significantly higher bone volume (34.8% ± 4.80%) than scaffolds implanted without cells (n = 6, 22.4% ± 9.85%) in the micro-CT (p < 0.05). Moreover, an increased amount of osteocalcin deposition was found in the test group in comparison to the control group (27.98 ± 2.81% vs 17.10 ± 3.57%, p < 0.001). In conclusion, ADSCs seeding on ceramic/polymer scaffolds improves bone regeneration in large mandibular defects. However, further improvement with regard to the osteogenic capacity is necessary to transfer this concept into clinical use.

Comorbidity Assessment in Patients With Oral Squamous Cell Carcinoma: Can Imaging Techniques (Fludeoxyglucose Positron-Emission Tomographic Computed Tomography and Contrast-Enhanced Computed tomography) Provide Additional Information?

PURPOSE: This study evaluated the role of imaging staging examinations (positron-emission tomographic computed tomography [PET/CT] and contrast-enhanced computed tomography [ceCT]) for the assessment of the comorbidity status of patients with oral squamous cell carcinoma (OSCC). A binary null hypothesis was drafted: 1) imaging staging examinations do not augment knowledge about the comorbidity status of patients with OSCC and 2) there is no difference between PET/CT and ceCT in this regard. MATERIALS AND METHODS: A retrospective cohort study design was selected to address the research question. Patients with histologically confirmed OSCC who underwent whole-body staging by PET/CT or ceCT from 2012 through 2015 were considered for inclusion according to predefined criteria. Data collection was performed by the review of patient charts and histology, radiology, and nuclear medicine reports. The Charlson Comorbidity Index (CCI) was chosen to quantify comorbidity and was calculated before and after staging and then compared. The type of imaging staging examination (PET/CT or ceCT) served as the predictor variable and the CCI was determined as the primary outcome variable. Descriptive and inferential statistics were computed for the variable scale. The significance level was set at a P value less than or equal to .05. RESULTS: The sample was composed of 178 patients (71 women, 107 men; average age, 64.2 yr) of whom 109 (61%) underwent PET/CT and 69 (39%) underwent ceCT staging. The pre- and post-staging CCI notably differed. Neither imaging technique showed superior results. CONCLUSION: Relevant and otherwise covert comorbidities can be found by the performance of imaging staging examinations. This enables clinicians to better assess the peri-therapeutic risk and prognosis of patients with OSCC. Therefore, a detailed evaluation of incidental findings on imaging studies is warranted and recommended.

Clinical analysis of MatrixMANDIBLE Preformed Reconstruction Plate design.

MatrixMANDIBLE Preformed Reconstruction Plates (MMPRPs) were developed to overcome laborious bending procedures of conventional reconstruction plates. The design comprises three sizes with a nonbendable centerpiece and two bendable sections (proximal and distal). According to the surgical protocol unnecessary parts are trimmed after the last used screw hole. In the present retrospective study postoperative radiographs from 130 patients (average age 63 years) that received treatment with MMPRPs were assessed. There was no statistical correlation between plate-size, location (left/right) or age. 82.98% of the small and 91.80% of the medium MMPRPs were trimmed by at least the terminal screw hole of the ramus part. In all patients receiving a large MMPRP, the terminal screw hole of the ramus was unused accordingly all inserted large MMPRPs were trimmed by at least the terminal screw hole. The majority of the bridged defects were located within the area of the body indicating a feasible plate design. With the emergence of solid free form fabrication of Ti-alloys and economic need to reduce the waste of resources this study may help to further improve the MMPRP design and prevent the loss of medical-grade titanium.

Mechanical and biological effects of infiltration with biopolymers on 3D printed tricalciumphosphate scaffolds.

The aim of this study was to evaluate the influence of infiltrating 3D printed (TCP) scaffolds with different biodegradable polymers on their mechanical and biological properties. 3D printed TCP scaffolds with interconnecting channels measuring 450±50 µm were infiltrated with four different biodegradable copolymers. To determine the average compressive strength, a uniaxial testing system was used. Additionally, scaffolds were seeded with MC3T3 cells and cell viability was assessed by live/dead-assay. Uninfiltrated TCP had an average compression strength of 1.92±0.38 MPa. Mechanical stability was considerably increased in all infiltrated scaffolds up to a maximum of 7.36±0.57 MPa. All scaffolds demonstrated high cell survival rates with a maximum of 94±10 % living cells. In conclusion, infiltration of 3D printed tricalcium phosphate scaffolds with biodegradable polymers significantly improved mechanical properties and biological properties were comparable to those of uninfiltrated TCP scaffolds.

Magnetic resonance imaging of the inferior alveolar nerve with special regard to metal artifact reduction.

PURPOSE: Magnetic resonance imaging (MRI) is an excellent imaging modality for displaying peripheral nerves. Since the knowledge about MRI of the inferior alveolar nerve (IAN) is limited, this pilot study aims to identify the prospects and limitations of MRI of the IAN, with special consideration of metal artifacts. MATERIALS AND METHODS: Initially, in vitro MRI of a dental implant was performed to establish an optimized protocol for metal artifact reduction using WARP sequences (a software package provided by Siemens Healthcare, Erlangen, Germany) including view angle tilting (VAT) and slice-encoding metal artifact correction (SEMAC) techniques. MRI with this optimized protocol was performed in three volunteers and four patients presenting with postoperative IAN impairment. Measuring the evaluable area and the artifact size was performed to assess the benefit of the specific artifact reduction sequences. RESULTS: In vitro imaging of a dental implant demonstrated that WARP sequences with VAT and SEMAC techniques led to a volume reduction of the artifact of up to 69.1%. Observations in both volunteers and patients with neurosensory IAN impairment showed a distinct artifact reduction with the MRI protocol adapted to metallic materials. Additionally VAT and SEMAC techniques improved the imaging due to further artifact reduction. As a main drawback of the VAT technique, the image quality was compromised by a blurring effect. Still, on 3-T MRI the resolution was high enough to reveal even fine structures. Imaging of the IAN was successful in all cases despite metallic material in the region of interest, and structural IAN changes could be detected in correlation with clinical symptoms. CONCLUSION: In contrast to conventional radiography and computed tomography, MRI can directly depict the IAN and provide reliable information on its position and exact course within the mandible. MRI offers an objective assessment of IAN injuries, supporting the decision-making process regarding surgical exploration and microneural repair. With the advent of specialized MRI techniques such as VAT and SEMAC, reduction of metal artifacts is considerably improved.

Comparative 3D micro-CT and 2D histomorphometry analysis of dental implant osseointegration in the maxilla of minipigs.

AIM: The bone implant contact (BIC) has traditionally been evaluated with histological methods. Thereupon, strong correlations of two-dimensional (2D) BIC have been detected between µCT and destructive histology. However, due to the high intra-sample variability in BIC values, one histological slice is not sufficient to represent 3D BIC. Therefore, our aim has been to correlate the averaged values of 3-4 histological sections to 3D µCT. MATERIAL AND METHODS: Fifty-four implants inserted into the maxilla of 14 minipigs were evaluated. Two different time points were selected to assess the 3D BIC (distance to implant: 2-5 voxels), an inner ring (6-30 voxels) and an outer ring (55-100 voxels) using µCT (voxel size: 10 µm) and to correlate the values to histomorphometry. RESULTS: Strong correlations (p < 0.0001; 28 days, 56 days, total) were seen between µCT and histomorphometry concerning BIC (r = 0.84, r = 0.85, r = 0.83), the inner ring (r = 0.87, r = 0.87, r = 0.88) and the outer ring (r = 0.85, r = 0.85, r = 0.88). Closer to the implant, µCT values were higher compared with histomorphometry. CONCLUSION: Although 3-4 histological slices per implant seem to predict the 3D BIC, µCT might be advantageous because of its non-destructive 3D character. The healing time may not impact on the comparability.

Micro-CT vs. Whole Body Multirow Detector CT for Analysing Bone Regeneration in an Animal Model.

OBJECTIVES: Compared with multirow detector CT (MDCT), specimen (ex vivo) micro-CT (µCT) has a significantly higher (~ 30 x) spatial resolution and is considered the gold standard for assessing bone above the cellular level. However, it is expensive and time-consuming, and when applied in vivo, the radiation dose accumulates considerably. The aim of this study was to examine whether the lower resolution of the widely used MDCT is sufficient to qualitatively and quantitatively evaluate bone regeneration in rats. METHODS: Forty critical-size defects (5mm) were placed in the mandibular angle of rats and covered with coated bioactive titanium implants to promote bone healing. Five time points were selected (7, 14, 28, 56 and 112 days). µCT and MDCT were used to evaluate the defect region to determine the bone volume (BV), tissue mineral density (TMD) and bone mineral content (BMC). RESULTS: MDCT constantly achieved higher BV values than µCT (10.73±7.84 mm3 vs. 6.62±4.96 mm3, p<0.0001) and consistently lower TMD values (547.68±163.83 mm3 vs. 876.18±121.21 mm3, p<0.0001). No relevant difference was obtained for BMC (6.48±5.71 mm3 vs. 6.15±5.21 mm3, p = 0.40). BV and BMC showed very strong correlations between both methods, whereas TMD was only moderately correlated (r = 0.87, r = 0.90, r = 0.68, p < 0.0001). CONCLUSIONS: Due to partial volume effects, MDCT overestimated BV and underestimated TMD but accurately determined BMC, even in small volumes, compared with µCT. Therefore, if bone quantity is a sufficient end point, a considerable number of animals and costs can be saved, and compared with in vivo µCT, the required dose of radiation can be reduced.

Computer-Assisted Designed and Manufactured Procedures Facilitate the Lingual Application of Mandible Reconstruction Plates.

PURPOSE: Lingual positioning of mandible reconstruction plates can prevent typical complications such as plate exposure and orocutaneous fistulas. The aim of this study was to evaluate the feasibility and clinical outcomes of lingually applied patient-specific reconstruction plates. MATERIALS AND METHODS: A retrospective cohort study of patients managed with reconstruction plates positioned at the lingual side of the mandible was performed. The following outcome variables were analyzed: feasibility and handling of the lingual application, fitting accuracy, and postoperative complications. RESULTS: The study sample included 8 patients (4 women, 4 men) with a mean age of 68.8 years (range, 43 to 79 yr). The indications for plate use were defect-like zones owing to multiple fractures in the atrophic mandible (n = 2) and segmental defects attributed to squamous cell carcinoma, osteomyelitis, and bisphosphonate-related osteonecrosis (n = 6). Off-the-shelf reconstruction plates, which were intraoperatively bent (n = 2) or pre-bent to a stereolithographic model (n = 1), or fully computer-assisted designed and computer-assisted manufactured (CAD/CAM) patient-specific reconstruction plates (n = 5) were used. Lingual application of reconstruction plates was feasible in all cases and considerably facilitated by the CAD/CAM plates. The fitting accuracy was high. Within an average follow-up period of 15.3 months, no loosening of plates or screws, plate fracture, or orocutaneous fistula occurred and no dysphagia was observed with the exception of 1 case, in which plate exposure was due to extreme soft tissue thinning and tumor recurrence. CONCLUSIONS: Lingual application of CAD/CAM patient-specific reconstruction plates is technically feasible with high accuracy. It has great potential for low complication rates, especially in unfavorable soft tissue conditions.

Iterations of computer- and template assisted mandibular or maxillary reconstruction with free flaps containing the lateral scapular border--Evolution of a biplanar plug-on cutting guide.

BACKGROUND: Computer-assisted planning and intraoperative implementation using templates have become appreciated modalities in craniofacial reconstruction with fibula and DCIA flaps due to saving in operation time, improved accuracy of osteotomies and easy insetting. Up to now, a similar development for flaps from the subscapular vascular system, namely the lateral scapular border and tip, has not been addressed in the literature. PATIENTS/METHOD: A cohort of 12 patients who underwent mandibular (n = 10) or maxillary (n = 2) reconstruction with free flaps containing the lateral scapular border and tip using computer-assisted planning, stereolithography (STL) models and selective laser sintered (SLS) templates for bone contouring and sub-segmentation osteotomies was reviewed focussing on iterations in the design of computer generated tools and templates. RESULTS: The technical evolution migrated from hybrid STL models over SLS templates for cut out as well as sub-segmentation with a uniplanar framework to plug-on tandem template assemblies providing a biplanar access for the in toto cut out from the posterior aspect in succession with contouring into sub-segments from the medial side. CONCLUSION: The latest design version is the proof of concept that virtual planning of bone flaps from the lateral scapular border can be successfully transferred into surgery by appropriate templates.

Are There Clinical or Pathological Parameters of Maxillary Oral Squamous Cell Carcinoma With an Influence on the Occurrence of Neck Node Metastasis? An Appraisal of 92 Patients.

PURPOSE: To determine the proportion of patients with cervical metastases caused by maxillary oral squamous cell carcinoma (OSCC) and to identify any clinical or pathologic parameters that might be associated with the occurrence of metastatic neck disease. MATERIALS AND METHODS: A retrospective cohort study of all patients managed with primary surgical resection of maxillary OSCC at the authors' institution from 2006 through 2013 was performed. Cervical lymph node dissection and adjuvant therapy were performed as warranted by preoperative staging examinations or histopathologic evaluation or as recommended after multidisciplinary consultation, and regular follow-up protocols were followed. In this analysis, each maxillary OSCC was assigned to an anterior or a posterior anatomic group based on the location of the primary lesion, with the anatomic tumor location serving as the predictor variable and the occurrence of cervical lymph node metastases as the outcome variable. Descriptive and inferential statistics were calculated with a significance level set at a P value less than .05 and post hoc power analyses were performed. RESULTS: The study sample was composed of 92 patients (38 women, 54 men; average age, 60.9 yr). Overall, 27 patients developed cervical metastases (29.3%). Neck disease was present in 15 patients (16.3%) at initial presentation. Delayed cervical metastases were diagnosed in 12 patients (13%) and manifested after an average period of 11.17 months. The anatomic location of the OSCC within the maxillary structures (anterior vs posterior) and the histologic grade greatly influenced the occurrence of metastatic neck disease. No associations were found for the variables tumor size and resection status. CONCLUSION: In this series, cervical lymph node metastases were frequent and to some degree predictable based on anatomic location and tumor grade.