Patient-specific Reconstruction Research Articles

Factors affecting the risk of trismus following maxillary ablative surgery comparing free flap reconstruction to prosthetic obturation: a retrospective observational study

The reconstruction of post-ablative maxillary defects is controversial. It is accepted that quality of life indicators are poorer for maxillary reconstruction compared with mandibular reconstruction. One factor highlighted is that of post-treatment trismus. Rates of trismus are reviewed comparing free tissue transfer to that of prosthetic obturation. A retrospective review was undertaken comparing rates of trismus at twelve months post-surgery between free tissue transfer and prosthetic obturation. A total of 85 patients were identified who met the inclusion criteria. Both reconstruction techniques were significant for developing trismus, with a higher rate in the free flap reconstruction cohort than the prosthetic obturation cohort by a factor of 2.51. Modern reconstructive head and neck surgery has moved away from ‘filling a hole’ to a more bespoke, patient-specific reconstruction. The evidence presented here should allow the reconstructive surgeon to better discuss outcomes with patients when considering surgical options for Class II maxillary defects.

Defining the Patient Acceptable Symptom State Using PROMIS Following Reconstruction of the Progressive Collapsing Foot Deformity

Introduction/Purpose: Although reconstruction of the flexible progressive collapsing foot deformity (PCFD) has been shown to improve patient-reported outcomes (PROs), there is limited data describing postoperative success as defined by patient satisfaction following surgery. Distinct from the minimal clinically important difference (MCID), the patient acceptable symptom state (PASS) is a novel PRO measurement that represents the symptom threshold beyond which patients are satisfied with their postoperative outcome. The primary aim of this study was to use Patient-Reported Outcomes Measurement Information System (PROMIS) Physical Function (PF) and Pain Interference (PI) scores in combination with anchor questions to define PASS thresholds following reconstruction of the flexible PCFD. A secondary aim was to analyze how patient-specific variables and certain PCFD reconstruction procedures may impact the probability of reaching PASS thresholds. Methods: Using data collected from a foot and ankle orthopedic registry at a large academic institution, 109 patients who underwent reconstruction of a flexible PCFD between February 2019 and March 2021, had preoperative and 2-year postoperative PROMIS PF and PI scores, and 2-year postoperative responses to two PASS anchor questions (the delighted-terrible scale and the satisfied scale) were included in the study. Patients who underwent either a double or triple arthrodesis were excluded. Patient responses to the anchor questions were dichotomized and receiver operating characteristic (ROC) curve analyses were performed. Using the Youden Index to balance sensitivity and specificity and maximize the area under the curve (AUC), PASS thresholds with 95% confidence intervals were quantified using 2000 bootstrapped iterations. Lastly, multivariable logistic regressions were performed to analyze the influence of patient demographics, preoperative PROMIS scores, and certain PCFD reconstruction procedures on the probability of reaching the PASS thresholds. Results: The PASS threshold for PROMIS PF was found to be 42.6 using both the delighted-terrible and the satisfied scale and 73.4% of patients (80/109) reached the threshold (both AUCs: 0.91) (Table 1). The PASS thresholds for PROMIS PI defined using the delighted-terrible scale and the satisfied scale were 54.5 (AUC: 0.90) and 57.5 (AUC: 0.91), respectively, with 72.5% of patients (79/109) and 81.7% of patients (89/109) meeting the respective thresholds. Neither patient demographics nor specific PCFD reconstruction procedures affected the probability of meeting the PASS thresholds. However, a lower preoperative PROMIS PF score or a higher preoperative PROMIS PI score significantly decreased the probability of achieving the PASS thresholds. Conclusion: Following reconstruction of the flexible PCFD, PASS thresholds for the PROMIS PF and PI domains were found to be lower and higher, respectively, than population norms. This suggests that patients may be satisfied with the outcome of their surgery despite not returning to the population mean. The probability of achieving the PASS thresholds was influenced by both preoperative PROMIS PF and PI scores but not by patient demographics or certain PCFD reconstruction procedures. In addition to guiding future outcomes research, these results may help foot and ankle surgeons optimize treatment for the flexible PCFD and better manage patient expectations.

Accuracy of surgical navigation for patient-specific reconstructions of orbital fractures: A systematic review and meta-analysis

This systematic review and meta-analysis aimed to review the recent literature on the technical accuracy of surgical navigation for patient-specific reconstruction of orbital fractures using a patient-specific implant, and to compare surgical navigation with conventional techniques. A systematic literature search was conducted in PubMed (Medline), Embase, Web of Science, and Cochrane (Core Collection) databases on May 16, 2023. Literature comparing surgical navigation with a conventional method using postoperative three-dimensional computed tomography imaging was collected. Only articles that studied at least one of the following outcomes were included: technical accuracy (angular accuracy, linear accuracy, volumetric accuracy, and degree of enophthalmos), preoperative and perioperative times, need for revision, complications, and total cost of the intervention. MINORS criteria were used to evaluate the quality of the articles. After screening 3733 articles, 696 patients from 27 studies were included. A meta-analysis was conducted to evaluate volumetric accuracy and revision rates. Meta-analysis proved a significant better volumetric accuracy (0.93 cm3 ± 0.47 cm3) when surgical navigation was used compared with conventional surgery (2.17 cm3 ± 1.35 cm3). No meta-analysis of linear accuracy, angular accuracy, or enophthalmos was possible due to methodological heterogeneity. Surgical navigation had a revision rate of 4.9%, which was significantly lower than that of the conventional surgery (17%). Costs were increased when surgical navigation was used. Studies with higher MINORS scores demonstrated enhanced volumetric precision compared with traditional approaches. Surgical navigation has proven effective in reducing revision rates compared to conventional approaches, despite increased costs.

Vascularized fibular flap and custom-made synthesis in post-traumatic ulnar diaphyseal pseudarthrosis: a case report

BackgroundAlthough isolated fractures of the ulnar shaft are considered common and relatively benign injuries, numerous complications can arise especially in the context of suboptimal care pathways. For pediatric patients, however, there is no single indication of the surgical approach. In the context of the management of these complications, it is known that the vascularized fibular graft has numerous advantages and indications in the treatment of recurrent pseudarthrosis. However, in revision surgery the frequent occurrence of anatomical subversions requires the use of fixation means adapted to the individual patient. We present a clinical case of an adult patient suffering from post-traumatic ulnar pseudarthrosis treated with autologous vascularized fibula grafts and 3D-planned custom-made plate.Case presentationA 38-year-old Ivorian woman came to our attention with a painful nonunion of the ulnar shaft and significant dysmorphism of the left forearm, with shortening and flexion of the limb as an outcome of unspecified road trauma in childhood. No alterations of the nerve compartment were reported. As far as detectable, she had undergone autologous bone grafting and implantation of questionable synthetic means, without acute treatment. Since we evaluated the patient (2012), we have performed two debridement surgeries, associated with autologous avascular bone graft from the iliac crest and plate fixation (2012 and 2014). In both cases, rupture of the fixation media was observed. In 2021, the pseudarthrosis was treated with a vascularized fibular bone graft. The subverted radius and ulna anatomy and poor bone quality required patient-specific reconstruction of the pseudarthrosic ulna from a 3D scan and the production of custom-made plate and screws, supported by the creation of special guides for drilling and by optimizing the positioning of screws with preoperative digital models. In the postoperative period, regular follow-up visits with X-rays evaluations were performed at 1, 3 and 6 months after surgery. No inflammatory reactions or local rejection were found. The fibula graft healed at the proximal ulnar junction six months after the operation while it took eight months to heal at the distal junction. Functionally, we observed a pain reduction and a range-of-motion preservation.ConclusionsThe multiple failures of diaphyseal reconstruction with avascular bone grafts have forced the indication to the vascularized fibular flap. This case is a unique experience but we believe that the association between vascularized bone graft and the potential for customization through 3D planning represents a valid surgical potentiality in complex cases of post-traumatic reconstruction.

Three-Dimensional Printed Plate Template Versus Hemipelvis Model in Patient-Specific Plate Preparation for Posterior Wall Acetabular Fractures.

The application of three-dimensional (3D) printing technology in the management of posterior wall acetabular fractures can greatly reduce surgical invasiveness and operative time and simplify the procedure of reconstruction plate contouring, but the cost and time of patient-specific plate preparation on the basis of traditional 3D-printed pelvis model should not be neglected. We described a new method for patient-specific plate preparation by using 3D-printed plate template. The study aimed to assess the effectiveness and feasibility of the 3D-printed plate template in patient-specific plate preparation for posterior wall acetabular fractures. A total of 65 cases of posterior wall acetabular fractures with surgical treatment from December 2012 to December 2020 were chosen. According to the different plate contouring methods, the 65 cases were divided into three groups, which were group A (21 cases), group B (20 cases), and group C (24 cases). In group A, the 3D-printed plate template was used to contour the patient-specific reconstruction plate before surgery, whereas the 3D-printed hemipelvis model was adopted for group B. In group C, the reconstruction plate was contoured intraoperatively. Among the three groups, the instrumentation time, surgical time, blood loss, patient-specific plate preparation time, complications, reduction quality, and hip function were compared. The Kruskal-Wallis test was used to analyze the reduction quality and hip function among three groups. In comparison with group C, patients in groups A and B were featured by obviously shorter instrumentation time (-22, -23 min), shorter surgical time (-46, -44 min), and less intraoperative blood loss (-110, -122 mL). Compared to the hemipelvis model in group B (2.29 ± 0.56 vs. 12.70 ± 3.79 days), the 3D printing time for plate templates in group A was significantly shorter. The reduction quality and hip function had no obvious statistical difference among the three groups. The complication rate within group A (3/21) and group B (3/20) were both slightly lower than group C (5/24), with no obvious difference. Both the patient-specific pre-contoured plate fixation methods based on the 3D-printed hemipelvis model and plate template can achieve satisfactory clinical efficacy, with the advantage of shorter instrumentation and surgical time, and less intraoperative blood loss. However, 3D printing of plate template is easier and less time-consuming, considering the shorter time and less cost for 3D printing of physical model.

Comparison of Laser-Sintered and Milled Patient-Specific Reconstruction Plates for Complications and Outcomes in Mandibular Defects-Comparative Analysis of a Single-Center Cohort.

CAD/CAM-manufactured implants are increasingly becoming the standard in current therapy. The question of whether the manufacturing-related rougher surface of selective laser fusion plates compared to milled, smoother reconstruction plates leads to increased postoperative complications such as infections, plate exposure, and fistulas has not yet been determined. A retrospective analysis of 98 patients who underwent surgical treatment with either a selective laser fusion plate or a milled reconstruction plate at our hospital was performed. The only significant predictors of the revision risk were the operation time and use of antiresorptive medication. In the KLS Martin® group, the risk of revision decreased by approximately 20% for each additional hour by which the operation time was increased (OR = 0.81). In the Depuy Synthes® group, the risk of revision increased by approximately 11% with each additional hour of operative time (OR = 0.81 × 1.37 = 1.11). Both groups showed no significant differences in the number of necessary revision surgeries as well as inpatient complications. In summary, we can say that the assumption that additively manufactured reconstruction plates have a rougher surface due to selective laser melting and thus make plaque accumulation and revisions more likely has not been confirmed. Overall, it seems imperative to select further studies regarding the clinical outcome depending on the selected plate system.

LatentPCN: latent space-constrained point cloud network for reconstruction of 3D patient-specific bone surface models from calibrated biplanar X-ray images.

Accurate three-dimensional (3D) models play crucial roles in computer assisted planning and interventions. MR or CT images are frequently used to derive 3D models but have the disadvantages that they are expensive or involving ionizing radiation (e.g., CT acquisition). An alternative method based on calibrated 2D biplanar X-ray images is highly desired. A point cloud network, referred as LatentPCN, is developed for reconstruction of 3D surface models from calibrated biplanar X-ray images. LatentPCN consists of three components: an encoder, a predictor, and a decoder. During training, a latent space is learned to represent shape features. After training, LatentPCN maps sparse silhouettes generated from 2D images to a latent representation, which is taken as the input to the decoder to derive a 3D bone surface model. Additionally, LatentPCN allows for estimation of a patient-specific reconstruction uncertainty. We designed and conducted comprehensive experiments on datasets of 25 simulated cases and 10 cadaveric cases to evaluate the performance of LatentLCN. On these two datasets, the mean reconstruction errors achieved by LatentLCN were 0.83mm and 0.92mm, respectively. A correlation between large reconstruction errors and high uncertainty in the reconstruction results was observed. LatentPCN can reconstruct patient-specific 3D surface models from calibrated 2D biplanar X-ray images with high accuracy and uncertainty estimation. The sub-millimeter reconstruction accuracy on cadaveric cases demonstrates its potential for surgical navigation applications.

Patient-specific miniplates versus patient-specific reconstruction plate: A biomechanical comparison with 3D-printed plates in mandibular reconstruction

BackgroundPatient-specific 3D-printed miniplates for free flap fixation in mandibular reconstruction were recently associated with enhanced osseous union. Higher mechanical strains resulting from these plates are discussed as reasons, but biomechanical studies are missing. This study aims to examine, whether patient-specific 3D-printed miniplates provide an increased interosteotomy movement (IOM) and lower stiffness compared with reconstruction plates. MethodsPolyurethane (PU) mandible and fibula models (Synbone AG, Malans, Schweiz) were used to simulate mandibular reconstruction with a one segment fibula flap equivalent. Osteosynthesis was performed using either four patient-specific 3D-printed miniplates (3D-Mini) or one patient-specific 3D-printed reconstruction plate (3D-Recon). Mastication was simulated using cyclic dynamic loading with increasing loads until material failure or a maximum load of 1000 N. Continuous IOM recording was carried out using a 3D optical tracking system (ARAMIS, Carl Zeiss GOM Metrology, Braunschweig, Germany). FindingsThe averaged stiffness at a load of 100–300 N load did not differ between the groups (p = 0.296). There was a faster 1.0 mm vertical displacement in the 3D-Mini group (26 376 ± 14 190 cycles versus 44 817 ± 30 430 cycles, p = 0.018). The IOM were higher with miniplate fixation in the distal gap (p = 0.040). In the mesial gap, there was no significant difference between the groups (p = 0.160). InterpretationFixation with patient-specific 3D-printed miniplates results in higher mechanical strains. Lower rates of pseudarthrosis, as seen in clinical studies, might be caused by this phenomenon. Surgeons should evaluate the primary use of 3D-printed miniplates in mandibular reconstruction due to advantages of intraoral plate removal alongside safe osteosynthesis.

Comparative evaluation of a patient-specific customised plate designs and screws for partial mandibular reconstruction.

Mandibles with odontogenic tumors are often partially reconstructed with a metallic bone graft analogue with dental roots, crowns, along with a customized plate fixed with monocortical or bicortical screws, following resection of the tumor. In this study, two different designs of patient specific customized Ti reconstruction plates, solid and plate with holes, were considered. Fixation through both bicortical and monocortical screw types were investigated. FE models of the reconstructed mandibles were developed to analyse the influence of the plate-screw type combination on the load transfer across the mandibles under a mastication cycle. The effective homogenized orthotropic material properties of the lattice structures with 0.6mm fibre diameter with 0.5mm inter-fibre space were assigned to material properties for the bone graft analogue. The study shows that the combination of plate and screw types influences the state of stresses in the reconstructed mandible. Based on the results of this patient specific study, following resection of the tumor, either solid Ti plate with bicortical screws or Ti plate with holes along with monocortical screws may be used for partial mandibulectomy. It should also be noted that stresses in none of the plates or screws exceeded the yield limit for Ti under the mastication cycle indicating that the components are safe for mandibular reconstruction. However, the choice of this combination of reconstruction plates and screws is dependant on the condition and severity of the tumor in the diseased mandible.

Natural Shaping of Acellular Dermal Matrices for Implant-Based Breast Reconstruction via Expansile Kirigami.

To complete a successful and aesthetic breast reconstruction for breast cancer survivors, tissue reinforcing acellular dermal matrices (ADMs) are widely utilized to create slings/pockets to keep breast implants or autologous tissue transfer secured against the chest wall in the desired location. However, ADM sheets are 2D and cannot completely cover the entire implant without wrinkles. Here, guided by finite element modeling, a kirigami strategy is presented to cut the ADM sheets with locally and precisely controlled stretchability, curvature, and elasticity. Upon expansion, a single kirigami ADM sheet can conformably wrap the implant regardless of the shape and size, forming a natural teardrop shape; contour cuts prescribe the topographical height and fractal cuts in the center ensures horizontal expandability and thus conformability. This kirigami ADM can provide support to the reconstructed breast in the desired regions, potentially offering optimal outcomes and patient-specific reconstruction, while minimizing operative time and cost.

3D modeling and printing for complex biventricular repair of double outlet right ventricle.

Double outlet right ventricle (DORV) describes a group of congenital heart defects where pulmonary artery and aorta originate completely or predominantly from the right ventricle. The individual anatomy of DORV patients varies widely with multiple subtypes classified. Although the majority of morphologies is suitable for biventricular repair (BVR), complex DORV anatomy can render univentricular palliation (UVP) the only option. Thus, patient-specific decision-making is critical for optimal surgical treatment planning. The evolution of image processing and rapid prototyping techniques facilitate the generation of detailed virtual and physical 3D models of the patient-specific anatomy which can support this important decision process within the Heart Team. The individual cardiovascular anatomy of nine patients with complex DORV, in whom surgical decision-making was not straightforward, was reconstructed from either computed tomography or magnetic resonance imaging data. 3D reconstructions were used to characterize the morphologic details of DORV, such as size and location of the ventricular septal defect (VSD), atrioventricular valve size, ventricular volumes, relationship between the great arteries and their spatial relation to the VSD, outflow tract obstructions, coronary artery anatomy, etc. Additionally, physical models were generated. Virtual and physical models were used in the preoperative assessment to determine surgical treatment strategy, either BVR vs. UVP. Median age at operation was 13.2 months (IQR: 9.6-24.0). The DORV transposition subtype was present in six patients, three patients had a DORV-ventricular septal defect subtype. Patient-specific reconstruction was feasible for all patients despite heterogeneous image quality. Complex BVR was feasible in 5/9 patients (55%). Reasons for unsuitability for BVR were AV valve chordae interfering with potential intraventricular baffle creation, ventricular hypoplasia and non-committed VSD morphology. Evaluation in particular of qualitative data from 3D models was considered to support comprehension of complex anatomy. Image-based 3D reconstruction of patient-specific intracardiac anatomy provides valuable additional information supporting decision-making processes and surgical planning in complex cardiac malformations. Further prospective studies are required to fully appreciate the benefits of 3D technology.

Towards mechanobiologically optimized mandible reconstruction: CAD/CAM miniplates vs. reconstruction plates for fibula free flap fixation: A finite element study.

Due to their advantages in applicability, patient-specific (CAD/CAM) reconstruction plates are increasingly used in fibula free flap mandible reconstruction. In addition, recently, CAD/CAM miniplates, with further advantages in postoperative management, have been introduced. However, biomechanical conditions induced by CAD/CAM systems remain partially unknown. This study aimed to evaluate the primary fixation stability of CAD/CAM fixators. For a patient-specific scenario, the biomechanical conditions induced in a one segmental fibula free flap stabilized using either a CAD/CAM reconstruction plate or CAD/CAM miniplates were determined using finite element analysis. The main output parameters were the strains between intersegmental bone surfaces and stresses in the fixation systems due to different biting scenarios. CAD/CAM miniplates resulted in higher mechanical strains in the mesial interosseous gap, whereas CAD/CAM reconstruction plate fixation resulted in higher strains in the distal interosseous gap. For all investigated fixation systems, stresses in the fixation systems were below the material yield stress and thus material failure would not be expected. While the use of CAD/CAM miniplates resulted in strain values considered adequate to promote bone healing in the mesial interosseous gap, in the distal interosseous gap CAD/CAM reconstruction plate fixation might result in more beneficial tissue straining. A mechanical failure of the fixation systems would not be expected.

Patient specific bony and soft-tissue fibular reconstruction: Perforator virtual surgical planning technique

Recent development in Virtual Surgical Planning (VSP) allows for planning of both the bony and soft tissue reconstruction by incorporating skin paddle perforator planning to the 3D planning module. This study aims to describe the perforator planning technique and report on its intraoperative predictability. MethodsA retrospective chart review identified all cases of fibular free flap reconstruction in which VSP was used in combination with perforator soft tissue planning from 2016 to 2022. Data collection included the accuracy of perforator location based on VSP planning versus clinical insitu measurements. ResultsOf 61 patients that underwent free flap reconstruction between 2016 and 2022, a total of 19 patients were identified to have undergone fibula free flap reconstruction with the aid of virtual surgical planning utilizing the perforator planning technique. The average number of fibular segments utilized per patient were 2.15. The mean size of the skin paddle harvested was 5.75 cm × 7.25 cm.The VSP planned perforator vessels were identified clinically in all patients. Exact measurement of the dopplerable skin perforator measured from the lateral malleolus were recorded in 8/19 patients. In the remaining 11 patients estimated data was recorded to indicate whether the perforator was located within 2 cm of the pre-planned VSP perforator location; All 11 perforators were identified within a 2 cm radius.In the 8 cases with exact measurements, the insitu clinical perforator measurements differed by a mean 0.55 cm from the predicted locations (range 0–1.8 cm). In 18/19 cases the perforator was reported to be at the same level or inferior to the predicted perforator location. The pearson correlation coefficient showed a strong correlation between virtual and intraoperative measurements r = 0.984; p < 0.001. ConclusionThe incorporation of perforator planning allows for predictable identification of skin perforators both virtually and intraoperatively. This in turn allows for predictable capturing of the skin paddle perforator within the desired fibular segment allowing for true patient specific bony and soft tissue reconstruction.

Comparison of Titanium and PEEK Medical Plastic Implant Materials for Their Bacterial Biofilm Formation Properties.

This study investigated two of the most commonly used CAD–CAM materials for patient-specific reconstruction in craniomaxillofacial surgery. The aim of this study was to access the biofilm formation of Staphylococcus aureus, Streptococcus mutans, Enterococcus faecalis, and Escherichia coli on titanium and PEEK medical implant materials. Two titanium specimens (titanium grade 2 tooled with a Planmeca CAD–CAM milling device and titanium grade 5 tooled with a computer-aided design direct metal laser sintering device (CAD-DMLS)) and one PEEK specimen tooled with a Planmeca CAD–CAM milling device were studied. Bacterial adhesion on implants was evaluated in two groups (saliva-treated group and non-saliva-treated group) to imitate intraoral and extraoral surgical routes for implant placement. The PEEK medical implant material showed higher bacterial adhesion by S. aureus, S. mutans, and E. coli than titanium grade 2 and titanium grade 5, whereas E. faecalis showed higher adhesion to titanium as compared to PEEK. Saliva contamination of implants also effected bacterial attachment. Salivary coating enhanced biofilm formation by S. aureus, S. mutans, and E. faecalis. In conclusion, our findings imply that regardless of the implant material type or tooling techniques used, salivary coating plays a vital role in bacterial adhesion. In addition, the majority of the bacterial strains showed higher adhesion to PEEK than titanium.

Patient-Specific Image-Based Computational Fluid Dynamics Analysis of Abdominal Aorta and Branches.

The complicated abdominal aorta and its branches are a portion of the circulatory system prone to developing atherosclerotic plaque and aneurysms. These disorders are closely connected to the changing blood flow environment that the area’s complicated architecture produces (between celiac artery and iliac artery bifurcation); this phenomenon is widespread at arterial bifurcations. Based on computed tomography angiography (CTA) scans, this current work offers a numerical analysis of a patient-specific reconstruction of the abdominal aorta and its branches to identify and emphasize the most likely areas to develop atherosclerosis. The simulations were run following the heart cycle and under physiological settings. The wall shear stress (WSS), velocity field, and streamlines were examined. According to the findings, complex flow is primarily present at the location of arterial bifurcations, where abnormal flow patterns create recirculation zones with low and fluctuating WSS (<0.5 Pa), which are known to affect endothelial homeostasis and cause adverse vessel remodeling. The study provides a patient-specific hemodynamic analysis model, which couples in vivo CT imaging with in silico simulation under physiological circumstances. The study offers quantitative data on the range fluctuations of important hemodynamic parameters, such as WSS and recirculation region expansion, which are directly linked to the onset and progression of atherosclerosis. The findings could also help drug targeting at this vascular level by understanding blood flow patterns in the abdominal aorta and its branches.

Benefits of Patient-Specific Reconstruction Plates in Mandibular Reconstruction Surgical Simulation and Resident Education.

Poorly contoured mandibular reconstruction plates are associated with postoperative complications. Recently, a technique emerged whereby preoperative patient-specific reconstructive plates (PSRP) are developed in the hopes of eliminating errors in the plate-bending process. This study’s objective is to determine if reconstructions performed with PSRP are more accurate than manually contoured plates. Ten Otolaryngology residents each performed two ex vivo mandibular reconstructions, first using a PSRP followed by a manually contoured plate. Reconstruction time, CT scans, and accuracy measurements were collected. Paired Student’s t-test was performed. There was a significant difference between reconstructions with PSRP and manually contoured plates in: plate-mandible distance (0.39 ± 0.21 vs. 0.75 ± 0.31 mm, p = 0.0128), inter-fibular segment gap (0.90 ± 0.32 vs. 2.24 ± 1.03 mm, p = 0.0095), mandible-fibula gap (1.02 ± 0.39 vs. 2.87 ± 2.38 mm, p = 0.0260), average reconstruction deviation (1.11 ± 0.32 vs. 1.67 ± 0.47 mm, p = 0.0228), mandibular angle width difference (5.13 ± 4.32 vs. 11.79 ± 4.27 mm, p = 0.0221), and reconstruction time (16.67 ± 4.18 vs. 33.78 ± 8.45 min, p = 0.0006). Lower plate-mandible distance has been demonstrated to correlate with decreased plate extrusion rates. Similarly, improved bony apposition promotes bony union. PSRP appears to provide a more accurate scaffold to guide the surgeons in assembling donor bone segments, which could potentially improve patient outcome and reduce surgical time. Additionally, in-house PSRP can serve as a low-cost surgical simulation tool for resident education.

Cutting guides in Mandibular Tumor Ablation: Are We as Accurate as We Think?

The introduction of computer-assisted surgical planning and computer-aided manufacturing in reconstructive surgery has been proven to have many advantages such as decreased operative and ischemic times and superior accuracy.1-3 However, even with the introduction of computer-assisted surgical planning, one of the main challenges is accurate positioning of the surgical cutting guide due to lack of anatomical landmarks and soft tissue interferences during placement. The purpose of this study is to determine the accuracy of osteotomy lines produced by the virtually planned 3-dimensionally printed cutting guides and to assess the overall accuracy of mandibular resection using virtual planning and patient-specific reconstruction plates.

Increased rate of pseudarthrosis in the anterior intersegmental gap after mandibular reconstruction with fibula free flaps: a volumetric analysis.

Pseudarthrosis after mandibular reconstruction leads to chronic overload of the osteosynthesis and impedes dental rehabilitation. This study evaluates the impact of gap site on osseous union in mandible reconstruction using a new volumetric analysis method with repeated cone-beam computed tomography (CBCT). The degree of bone regeneration was evaluated in 16 patients after mandible reconstruction with a fibula free flap and patient-specific reconstruction plates. Percentual bone volume and width changes in intersegmental gaps were retrospectively analyzed using a baseline CBCT in comparison to a follow-up CBCT. Patients' characteristics, plate-related complications, and gap sites (anterior/posterior) were analyzed. Detailed assessments of both gap sites (buccal/lingual/superior/inferior) were additionally performed. Intersegmental gap width (p = 0.002) and site (p < 0.001) significantly influence bone volume change over two consecutive CBCTs. An initial larger gap width resulted in a lower bone volume change. In addition, anterior gaps showed significantly less bone volume changes. Initial gap width was larger at posterior segmental gaps (2.97 vs 1.65 mm, p = 0.017). A methodology framework has been developed that allows to quantify pseuarthrosis in reconstructed mandibles using CBCT imaging. The study identifies the anterior segmental gap as a further risk factor for pseudarthrosis in reconstructions with CAD/CAM reconstruction plates. Future research should evaluate whether this outcome is related to the biomechanics induced at this site.

A novel conceptual design of a biomimetic oral implant and its biomechanical effect on the repairment of a large mandibular defect

This study aimed to propose a novel biomimetic design strategy of an oral implant and to numerically examine its biomechanical effect according to clinical interests. The designed implant conceptually mimicked the morphology and elastic modulus of the mandibular bone. Basing on a CT-image-based patient-specific reconstruction of the tumor-excised mandible, the biomechanical effects of the implants with three materials (PEEK/n-HA/CF, PEEK/HA and Ti6Al4V), two surgical conditions (removed and retained muscles), and two postoperative stages (early and late) were fully investigated by a static finite element analysis. Moreover, according to clinical interests (e.g. failure and stability of the implant and rivets), maximum von Mises stresses and strains of the implant and rivets, maximum implant-bone gap in the early postoperative stage, and maximum von Mises stress of the mandible were mainly analyzed. The results showed that the implant composed of Ti6Al4V material was suitable for the current design strategy with respect to the other two PEEK-based materials. Although the implants in the muscle-retained surgical condition had relative greater indices compared to the muscle-removed surgical condition, the index difference between the two conditions was slight. The biomechanical indices indicating the failure and loosening risks of implant and rivets were much reduced in the late postoperative stage with respect to the early postoperative stage due to the osteointegration at the implant-bone interface. Generally, the proposed novel design strategy could be useful to guide the design of the oral implant addressing different implant materials and surgical conditions, and further made proper suggestion to clinicians and patients.

Automated 3D thorax model generation using handheld video-footage

PurposeFor the visualization of pulmonary ventilation with Electrical Impedance Tomography (EIT) most devices use standard reconstruction models, featuring common thorax dimensions and predetermined electrode locations. Any discrepancies between the available model and the patient in terms of body shape and electrode position lead to incorrectly displayed impedance distributions. This work addresses that problem by presenting and evaluating a method for 3D model generation of the thorax and any affixed electrodes based on handheld video-footage.MethodsTherefore, a process was developed, providing users with the ability to capture a patient's chest and the attached electrodes via smartphone. Once data is collected, extracted images are used to generate a 3D model with a structure from motion approach and locate electrodes with ArUco markers. For the evaluation of the developed method, multiple tests were performed in laboratory environments, which were compared with manually created reference models and differences quantified based on mean distance, standard deviation, and maximum distance.ResultsThe implemented workflow allows for automated model reconstruction based on videos or selected images captured with a handheld device. It generates sparse point clouds from which a surface mesh is reconstructed and returns relative coordinates of any identified ArUco marker. The average value for the mean distance error of two model generations was 5.4 mm while the mean standard deviation was 6.0 mm. The average runtime of twelve reconstructions was 5:17 min, with a minimal runtime of 3:22 min and a maximal runtime of 7:29 min.ConclusionThe presented methods and results show that model reconstruction of a patient’s thorax and applied electrodes at an emergency site is feasible with already available devices. This is a first step toward the automated generation of patient-specific reconstruction models for Electrical Impedance Tomography based on images recorded with handheld devices.