Influence of microvascular mandibular bony reconstruction on the posterior airway space: A retrospective cohort study.

INTRODUCTION: The posterior airway space (PAS) is a common site of passive obstructions with high morbidity. Surgical changes to the craniomandibular system may affect the PAS. Data regarding the effects of mandibular reconstruction using vascularized bone flaps on PAS are insufficient. This retrospective cohort study aimed to investigate changes in PAS after mandibular reconstruction. MATERIALS AND METHODS: Pre- and post-reconstructive computed tomography scans of 40 patients undergoing segmental mandibulectomy and mandibular reconstruction with deep circumflex iliac artery or fibula flaps were analyzed. Absolute differences in PAS geometry and relative trends of PAS volume changes were compared within the study population and between subgroups formed according to the extent of resection, timing and type of reconstruction, and presence of pre-reconstructive radiotherapy. RESULTS: Irradiated patients were characterized by an increase in PAS volume after reconstruction. Absolute differences in total PAS volume after reconstruction were significantly different (p = 0.024) compared to non-irradiated patients. Reconstruction of central mandible segments resulted in decrease of the cross-sectional PAS areas. Absolute differences in middle cross-sectional PAS area after reconstruction were significantly different (p = 0.039) compared to non-central reconstructions. Patients who received radiotherapy were less likely to show a total PAS volume reduction after reconstruction (OR: 0.147; p = 0.007), with values adjusted for gender, age, body mass index, timing and type of reconstruction, and transplant length. CONCLUSIONS: Mandibular reconstruction causes changes in PAS geometry. Specifically, reconstructions of central mandibular segments can lead to a reduction in the cross-sectional areas of PAS, and mandibular reconstructions in irradiated sites may cause an increase in PAS volume.

Dimensions of perforator flaps on the lower leg depending on localization.

INTRODUCTION: The soleus perforator flap and the peroneal perforator flap could be alternatives to the radial forearm flap for head and neck reconstruction. However, their flap dimensions remain unknown. This study aims to determine the dimensions of both flaps and allow preoperative planning for reconstruction based on clinical parameters. MATERIALS & METHODS: Computed tomography records of 296 patients dated from 2009 through 2019 were retrospectively analyzed. Virtual three-dimensional flap models of the soleus perforator flap and peroneal perforator flap were aligned to segmented leg models, and flap thickness and volume were determined. Associations of flap thickness and volume with clinical parameters were evaluated, and a calculation method was derived. RESULTS: The soleus perforator flap had an average thickness of 8.7 mm (4.8 mm) and an average volume of 0.9 cm³ (0.5 cm³) per square centimeter surface area. The peroneal perforator flap had an average thickness of 6.4 mm (3.8 mm) and an average volume of 0.8 cm³ (0.4 cm³) per square centimeter surface area. The soleus perforator flap was thicker and more voluminous than the peroneal perforator flap (both p<0.001). For both flaps, leg circumference was the strongest predictor of flap thickness (ß=0.524, p<0.001 and ß=0.700, p<0.001, respectively) and flap volume (ß=0.535, p<0.001 and ß=0.712, p<0.001, respectively). CONCLUSION: Dimensions of the soleus perforator and the peroneal perforator flaps are similar to those of the radial forearm flap. Preoperative planning of flap dimensions, such as flap thickness and volume, can help the surgeons select the appropriate flap.

Comparison of soft tissue simulations between two planning software programs for orthognathic surgery.

The aim of this study was to compare the soft tissue predicative abilities of two established programs depending on the surgical technique and amount of displacement. On the basis of 50 computed tomography images, 11 orthognathic operations with differences in displacement distances and technique (maxillary advancement, MxA; maxillary impaction, MxI; mandibular setback, MnS; mandibular advancement, MnA bimaxillary displacement, MxA/MnS) as well as corresponding soft tissue predictions were simulated using the programs Dolphin (D) and ProPlan (PP). For all the soft tissue predictions by the two programs, eight linear and two angular measurements were performed and compared. The simulation of maxillary impaction showed a similar soft tissue behaviour between the two programs. However, differences or divergent behaviours were observed for other procedures. In the middle third of the face these significant differences concerned in particular the nasolabial angle (Ns-Sn-Ls)(5 mm-MA, D: 119.9 ± 8.6° vs. PP: 129.5 ± 8.4°; 7 mm-MnS: D: 128.5 ± 8.2° vs. PP: 129.6 ± 8.1°; 10 mm-MnA D: 126.0 ± 8.0° vs. PP: 124.9 ± 8.4°; 5 mm-MxA/4 mm-MnS, D: 120.2 ± 8.7° vs. PP: 129.9 ± 8.3°; all p < 0.001) and in the lower third the mentolabial angle (Pog´-B´-Li) (5 mm-MA, D: 133.2 ± 11.4° vs. PP: 126.8 ± 11.6°; 7 mm-MnS: D: 133.1 ± 11.3° vs. PP: 124.6 ± 11.9°; 10 mm-MnA D: 133.3 ± 11.5° vs. PP: 146.3 ± 11.1°; bignathic 5 mm-MxA/4 mm-MnS, D: 133.1 ± 11.4° vs. PP: 122.7 ± 11.9°; all p < 0.001) and the distance of the inferior lip to the aesthetic Line (E-Line-Li) (5 mm-MA, D: 3.7 ± 2.3 mm vs. PP: 2.8 ± 2.5 mm; 7 mm-MnS: D: 5.1 ± 3.0 mm vs. PP: 3.3 ± 2.3 mm; 10 mm-MnA D: 2.5 ± 1.6 mm vs. PP: 3.9 ± 2.8 mm; bignathic 5 mm-MxA/4 mm-MnS, D: 4.8 ± 3.0 mm vs. PP: 2.9 ± 2.0 mm; all p < 0.001). The soft tissue predictions by the tested programs differed in simulation outcome, which led to the different, even divergent, results. However, the significant differences are often below a clinically relevant level. Consequently, soft tissue prediction must be viewed critically, and its actual benefit must be clarified.

Comparison of augmented reality and cutting guide technology in assisted harvesting of iliac crest grafts - A cadaver study.

BACKGROUND: Harvesting vascularized bone grafts with computer-assisted surgery represents the gold standard for mandibular reconstruction. However, current augmented reality (AR) approaches are limited to invasive marker fixation. This trial compared a markerless AR-guided real-time navigation with virtually planned and 3D printed cutting guides for harvesting iliac crest grafts. MATERIAL AND METHODS: Two commonly used iliac crest transplant configurations were virtually planned on 10 cadaver hips. Transplant harvest was performed with AR guidance and cutting guide technology. The harvested transplants were digitalized using cone beam CT. Deviations of angulation, distance and volume between the executed and planned osteotomies were measured. RESULTS: Both AR and cutting guides accurately rendered the virtually planned transplant volume. However, the cumulative osteotomy plane angulation differed significantly (p = 0.018) between AR (14.99 ± 11.69°) and the cutting guides (8.49 ± 5.42°). The cumulative osteotomy plane distance showed that AR-guided navigation had lower accuracy (2.65 ± 3.32 mm) than the cutting guides (1.47 ± 1.36 mm), although without significant difference. CONCLUSION: This study demonstrated the clinical usability of markerless AR-guided navigation for harvesting iliac crest grafts. Further improvement of accuracy rates might bring clinical implementation closer to reality.

Navigation of iliac crest graft harvest using markerless augmented reality and cutting guide technology: A pilot study.

BACKGROUND: Defects of the facial skeleton often require complex reconstruction with vascularized grafts. This trial elucidated the usability, visual perception and accuracy of a markerless augmented reality (AR)-guided navigation for harvesting iliac crest transplants. METHODS: Random CT scans were used to virtually plan two common transplant configurations on 10 iliac crest models, each printed four times. The transplants were harvested using projected AR and cutting guides. The duration and accuracies of the angulation, distance and volume between the planned and executed osteotomies were measured. RESULTS: AR was characterized by the efficient use of time and accurate rendition of preoperatively planned geometries. However, vertical osteotomies and complex anatomical settings displayed significant inferiority of AR guidance compared to cutting guides. CONCLUSIONS: This study demonstrated the usability of a markerless AR setup for harvesting iliac crest transplants. The visual perception and accuracy of the AR-guided osteotomies constituted remaining weaknesses against cutting guide technology.

Efficient Reject Options for Particle Filter Object Tracking in Medical Applications.

Reliable object tracking that is based on video data constitutes an important challenge in diverse areas, including, among others, assisted surgery. Particle filtering offers a state-of-the-art technology for this challenge. Becaise a particle filter is based on a probabilistic model, it provides explicit likelihood values; in theory, the question of whether an object is reliably tracked can be addressed based on these values, provided that the estimates are correct. In this contribution, we investigate the question of whether these likelihood values are suitable for deciding whether the tracked object has been lost. An immediate strategy uses a simple threshold value to reject settings with a likelihood that is too small. We show in an application from the medical domain-object tracking in assisted surgery in the domain of Robotic Osteotomies-that this simple threshold strategy does not provide a reliable reject option for object tracking, in particular if different settings are considered. However, it is possible to develop reliable and flexible machine learning models that predict a reject based on diverse quantities that are computed by the particle filter. Modeling the task in the form of a regression enables a flexible handling of different demands on the tracking accuracy; modeling the challenge as an ensemble of classification tasks yet surpasses the results, while offering the same flexibility.

Evaluation of a novel algorithm for automating virtual surgical planning in mandibular reconstruction using fibula flaps.

Virtual surgical planning plays an increasingly important role in jaw reconstruction. The aim of the present study was the evaluation of the clinical applicability of a novel algorithm for automating virtual mandibular reconstruction using fibula flaps. The software uses Computed-Tomography of the facial skeleton and the lower leg of 63 subjects, implemented in Python programming language. The developed algorithm is based on individual bone curvatures of the mandible and fibula. Ten different defects were generated for each mandible by virtually defined cutting planes. Three experienced surgeons reviewed all reconstruction proposals generated by the algorithm according to a visual analogue scale. The possible correlation between the ratings and the prioritization of the algorithm and the calculation time for the reconstructions were analyzed. Spearman analysis showed a strong correlation -0.613 (p < 0.001) between the deviation of the reconstruction result from the target line and the average assessment of the surgeons as well as a moderate correlation -0.448 (p = 0.013) between surgeons' assessments and the prioritization by the algorithm. The calculation time for twenty reconstructions per defect took between 4.99 s and 483.5 s depending on defect size and location. The evaluated algorithm automatically creates valid reconstruction results with acceptable computation time, which have received a high level of confirmation from experienced surgeons.

Three-dimensional evaluation of the posterior airway space: differences in computed tomography and cone beam computed tomography.

OBJECTIVES: Obstructive sleep apnea syndrome (OSAS) becomes increasingly important. For diagnosis and surgery, computed tomography (CT), and cone beam computed tomography (CB-CT) are used equally, although in most of cases, patient positioning differs between supine positioning (CT) and upright seating positioning (CB-CT). We measured volumetric and anatomical changes in the posterior airway space (PAS) between upright and supine positioning in a three-dimensional set up. MATERIALS AND METHODS: Coherent CT and CB-CT scans of 55 patients were included in the study. Using Brainlab ENT 3.0, image data was superimposed, and three-dimensional models were segmented. PAS height, cross-sectional area, vertical and horizontal position of the mandible and hyoid, and volumetric analyses of the three-dimensional models were measured. RESULTS: PAS height and cross-sectional area were significantly higher in CB-CT compared to CT scans (p < 0.001). In the vertical dimension, the mandible and hyoid were localized more caudally in CB-CT in contrast to CT scans (p < 0.04; p < 0.001). Three-dimensional evaluation showed a greater volume of the PAS in CB-CT (p < 0.0001). Pearson correlation coefficient showed a correlation between vertical positioning of the mandible and hyoid compared to the positioning of the patient. CONCLUSIONS: Patient positioning during CT and CB-CT has an effect on the location of anatomical structures like the mandible and hyoid and changes the dimensions and volume of the posterior airway space significantly. CLINICAL RELEVANCE: The radiological technique used and the positioning of the patient should be taken into account when considering further surgical therapy.

Stress distribution in mandibular donor site after harvesting bone grafts of various sizes from the ascending ramus of a dentate mandible by finite element analysis.

PURPOSE: Harvesting bone from the ascending ramus of the mandible is a common procedure. However, mandibular fracture may occur after grafting bone blocks. This study aimed to investigate the resulting force distribution of stress and strain in the mandibular donor site after harvesting bone grafts of different sizes and various loadings. METHODS: Finite element analysis was performed for virtual harvesting of bone blocks of nine different sizes between 15 × 20 and 25 × 30 mm and three different chewing loads (incisal, ipsilateral and contralateral). von Mises stress and first principal stress distributions were measured. RESULTS: von Mises stress was distributed between 35.01 (10 × 15 mm graft, incisal load) and 333.25 MPa (30 × 20 mm graft ipsilateral load), whereas first principal stress distributions were between 48.27 (10 × 15 mm graft, incisal load) and 414.69 MPa (30 × 20 mm graft ipsilateral load). In general, the least stress was observed with incisal load followed by ipsilateral load and finally contralateral load. The critical value of 133 MPa was found after removing almost all grafts with a width of 20 or 30 mm. CONCLUSIONS: Incisal loading led to less stress compared with contralateral and ipsilateral loads. Increasing graft size led to increasing weakness of the donor site. Graft width exerted a greater influence on stress development than its height. CLINICAL RELEVANCE: Ipsilateral chewing and increasing width of the bone graft result in maximum stress in the mandibular donor side, and critical values regarding to the possibility of fractures are already to expect from a graft size of 20 × 15 mm.

Perioperative safety and complications in treatment of oral and maxillofacial surgery patients under general anesthesia with obstructive sleeping disorders.

Patients with sleeping disorders, such as obstructive sleep apnea, (OSA) have a higher risk for postoperative complications after maxillofacial surgery under general anesthesia. The aim of this study was to detect specific complications after oral and maxillofacial surgery. Sixty-nine cases of patients with middle or severe sleep apnea who underwent an operation under general anesthesia in the oral and maxillofacial region were retrospectively analyzed. This group was compared with an age and diagnosis matched group without sleep apnea receiving the same operative treatment. We found a significant difference between the two groups concerning body mass index, the ASA-Index, the Cormack-Mallampati Index, the number of pre-existing conditions, and home medication (p < 0.05). Concerning the length of stay, overrun of estimated mean length of stay, and number of surgical complications and hypertonic events, no difference could be detected. Almost 28% of the patients with OSA in our study suffered a substantial respiratory complication even under intensive care observation. The number of patients with oxygen desaturation was 9% in the control group, which differed significantly (p = 0.0093) from the number of such patients in the OSA group. In this study, we have shown that the presence of OSA in patients undergoing elective maxillofacial surgery is associated with a considerable number of comorbidities in the postoperative period. Through preoperative OSA screening and OSA evaluation, an improvement in management of surveillance resources could be achieved and the OSA-specific risk could be assessed more precisely and also reduced.

Introduction of an algorithm for planning of autologous fibular transfer in mandibular reconstruction based on individual bone curvatures.

BACKGROUND: Reconstruction of the mandible with autologous transplants is a challenging task and current computer-aided surgical planning remains cumbersome. Thus, the aim of the present study was to create an automated computational approach for this procedure. METHODS: The developed algorithm is based on curves following characteristic anatomical features. Geometrical data from a physiological mandible and a fibula were used to generate six different defects, and geometrical accordance was investigated to demonstrate the applicability of the method with different reconstruction parameters (n = 309). RESULTS: The method proved to be applicable, it recognized given clinical constraints and the values of accordance could be used to quantify the success of reconstructions. CONCLUSIONS: With the present approach, the complex three-dimensional task of mandibular reconstruction was simplified, and thus it allows implementation in clinical routine. The computational planning that is proposed may be used to design cutting guides or as geometrical input data for real-time navigated surgery.

Peri-implant Crestal Bone Changes Around Zirconia Implants in Periodontally Healthy and Compromised Patients.

PURPOSE: No consensus regarding the efficacy of zirconia implants in maintaining peri-implant hard and soft tissue health has yet been obtained. The aim of this retrospective follow-up study was to gain knowledge about peri-implant bone behavior and about implant survival and success after treatment with zirconia dental implants in patients with normal and compromised soft and hard tissue conditions. MATERIALS AND METHODS: This follow-up study involved 86 patients with 123 zirconia implants (Straumann PURE Ceramic Implant) that were radiographically investigated directly after implant placement (day 0), 3 months after placement, and 1 year after the definitive implant crown placement. The clinical assessment was done at the 1-year postloading appointment and also included the modified Plaque Index, modified Sulcus Bleeding Index, and sulcus pocket depths. Eighteen patients with periodontally compromised conditions were compared to 68 patients with healthy periodontal conditions. RESULTS: The survival rate was 100% and success rate was 94.5%, with no differences between the two groups. The alveolar crest around the ceramic implants showed no significant difference between day 0 and 1 year postloading for both groups (P > .05). There was also no significant difference at 1 year postloading between the groups in the distance from the implant shoulder to the peri-implant bone crest (P = .67) or in pocket depth (P = .07). CONCLUSION: No significant peri-implant bone loss was observed in the first year. The survival and success rates showed no differences between the periodontally healthy and periodontally compromised groups; however, only a limited number of patients with periodontally compromised conditions were included in this study.

Fracture patterns after bilateral sagittal split osteotomy of the mandibular ramus according to the Obwegeser/Dal Pont and Hunsuck/Epker modifications.

The aim of this study was to compare the fracture patterns after sagittal split osteotomy according to Obwegeser/Dal Pont (ODP) and Hunsuck/Epker (HE), as well as to investigate the relationship between lateral bone cut ending or angle and the incidence of unfavorable/bad splits. Postoperative cone-beam computed tomograms of 124 splits according to ODP and 60 according to HE were analyzed. ODP led to 75.8% and HE led to 60% lingual fractures with mandibular foramen contact. Horizontal fractures were found in 9.7% and 6.7%, respectively, and unfavorable/bad splits were found in 11.3% and 10%, respectively. The lateral osteotomy angle was 106.22° (SD 12.03)° for bad splits and 106.6° (SD 13.12)° for favorable splits. Correlations were found between favorable fracture patterns and split modifications and between buccal ending of the lateral bone cut and bad splits (p < 0.001). No relationship was observed between split modifications (p = 0.792) or the osteotomy angle (p = 0.937) and the incidence of unfavorable/bad splits. Split modifications had no influence on the incidence of unfavorable/bad splits, but the buccal ending of the lateral bone cut did have an influence. More lingual fractures with mandibular foramen contact are expected with the ODP modification. The osteotomy angle did not differ between favorable and bad splits.

Evaluation of bone resorption in fibula and deep circumflex iliac artery flaps following dental implantation: A three-year follow-up study.

Long-term results of dental implant treatment in fibula free and deep circumflex iliac artery (DCIA) free flaps are scarce. The purpose of this study was to assess and compare peri-implant bone resorption of vascularized bone flaps treated with dental implants. A total of 28 patients, 14 fibula and 14 DCIA flaps, respectively, underwent reconstruction of the lower and upper jaw by the use of vascularized bone flaps and were treated with dental implants. Peri-implant bone resorption was measured using digital panographs up to 3 years. Radiographic pictures were taken immediately after implant surgery before prosthetic rehabilitation (T0), the second after 6-12 months (T1), the third after 13-24 months (T2), and the fourth after 25-36 months (T3). Over a period of 3 years, implant resorption changed significantly over time (pD1 = 0.0113, pD2 = 0.0232, pD3 = 0.0143). However, a significant difference in overall resorption between implants with fibula flaps and DCIA could not be detected for the patient average or within the implant-level analysis. Flaps presented minimal resorption from beneath (mean resorption DCIA 0.65, fibula = 0.26). Strong peri-implant bone resorption changed significantly over time. However, no significant difference was observed between fibula and DCIA flaps.

Evaluation of ultrasonic and conventional surgical techniques for genioplasty combined with two different osteosynthesis plates: a cadaveric study.

OBJECTIVES: The aim of this study was to compare genioplasties performed using traditional saw or piezosurgery combined with different osteosynthesis plates. MATERIALS AND METHODS: Thirty-two genioplasties were first performed on fresh human cadavers using a saw or piezosurgery, followed by chin osteosynthesis with bending or pre-shaped plates. The time required for osteotomy and plate fixation was measured, and the suprahyoid pedicle was inspected. RESULTS: The mean time required was 204 s (SD 43) with the saw and 52 s (SD 67) with piezosurgery. Osteosynthesis fixation time was 100 s (SD 31) for pre-shaped plates and 124 s (SD 24) for individual plates. Statistical differences were found between both osteotomy techniques (p < 0.001) and osteosynthesis plates (p = 0.025). Injuries of the suprahyoid muscle pedicle were found in 10/16 saw cases and 3/16 piezosurgery cases (p = 0.012). CONCLUSIONS: Although piezosurgery is more time consuming compared with saw osteotomy, it is still adequate in time and allows a reduction of the suprahyoid pedicle injuries. Therefore, piezosurgery seems to be a viable alternative technique for genioplasty. From a clinical point of view, the time difference for osteosynthesis fixation has no significance. CLINICAL RELEVANCE: The time taken for ultrasonic surgery is suitable for clinical use and leads additional to less damage to the suprahyoid pedicle.

Intraosseous stability of dental implants in free revascularized fibula and iliac crest bone flaps.

The aim of this study was to investigate the influence of two different microvascular reanastomized bone transplants on primary (PS) and secondary stability (SS) of dental implants. Totally 96 implants (Bone Level, Institut Straumann AG, Basel, Switzerland) were inserted in fibula (n = 50) and iliac crest (n = 46) in mean of 97.7 SD 75.6 weeks after performing reconstructive surgery. For measuring PS and SS the resonance frequency (RFA) analysis was used in mesiodistal and vestibulo-oral direction to quantify the implant stability quotient (ISQ). Mean values (ISQ) for PS in fibula was about 79.48 SD 2.41 and in iliac crest 61.10 SD 3.34 as well as SS in fibula was about 75.59 SD 5.10 and in iliac crest 73.63 SD 5.34. Statistically significant differences between both flaps were found for PS in mesiodistal and vestibulooral direction (p < 0.001). Between the primary and SS a significant decrease was recognized in fibula flap (p < 0.01) as well as an increase in iliac crest flap (p < 0.001). Statistically no difference was found between both bone flaps for SS (p = 0.076). The implant stability in fibula and iliac crest flap after osseointegration is similar to each other. Therefore, it is not important for choosing the suitable donor side.

The use of mobile 3D scanners in maxillofacial surgery.

There are many possibilities for the use of three-dimensional (3D) scanners in maxillofacial surgery. This study aimed to investigate whether the bundling and syncing of two 3D scanners has advantages over single-scanner acquisition in terms of scan quality and the time required to scan an object. Therefore, the speed and precision of 3D data acquisition with one scanner versus two synced scanners was measured in 30 subjects. This was done by analyzing the results obtained by scanning test objects attached to the forehead and cheeks of the subjects. Statistical methods included the Student t test for paired samples. Single-scanner recording resulted in significantly lower mean error of measurement than synced recording with two scanners for length (P < 0.001), all frontal/lateral plane angles (P = 0.034, P < 0.001, P = 0.002, P = 0.003), and side/side plane angles (P = 0.014, P < 0.001, P = 0.015, P = 0.011) of the test object on the cheek. Likewise, the single-scanner method resulted in a significantly lowermean error of measurement than the two-scanner method for frontal/lower plane angles (P < 0.001), right/lower plane angles (P < 0.001), and left/lower plane angles (P = 0.002). Conversely, synced recording of data with two scanners resulted in a significant reduction of scanning time (P < 0.001). Compared to data acquisition with a single 3D scanner, the bundling of two 3D scanners resulted in faster scanning times but lower scan quality.

Three-dimensional evaluation of the different donor sites of the mandible for autologous bone grafts.

OBJECTIVES: For effective placement of endosseous implants, a sufficient volume of bone is required at the recipient site. The aim of this study is to evaluate the density and maximum amount of harvestable bone graft required from the mandible symphysis, coronoid process, and ascending ramus, depending on dentition. MATERIALS AND METHODS: CT data from 42 patients (13 females and 29 males) in DICOM format were read using special planning software. Three different virtual bone grafts were created, and the dimension outcomes, surface, volume, and density were measured in a dentate group (n = 22) and a total edentulous group (n = 20). RESULTS: Comparisons between corresponding bone grafts showed no difference for the symphysis and coronoid process in relation to dentition, and no difference in bone density was observed. However, significant changes between the average values of the ramus were found between the two groups (p < 0.0001). CONCLUSIONS: Appropriate software and CT data can deliver more accurate examinations of the mandible in relation to potential donor sites. Atrophy primarily affects the ascending ramus; the symphysis and coronoid process are only slightly influenced. CLINICAL RELEVANCE: Using appropriate software in conjunction with implant planning, it is possible to analyze potential donor areas within the jaw and create virtual bone grafts.

Computer-Aided Mandibular Reconstruction With Vascularized Iliac Crest Bone Flap and Simultaneous Implant Surgery.

The intention of oral rehabilitation in patients with mandibular defects is an early prosthetic treatment with maximum possible functionality and high accuracy. The present study describes a new computer-aided technique for mandibular reconstruction using a free vascularized iliac flap and simultaneous insertion of dental implants into the flap while it is still pedicled at the donor site. Based on preoperative computerized tomography data of the facial skeleton and the iliac crest donor site, a surgical guide transferred the virtual plan including information on the transplant dimensions and shape as well as the position of the dental implants into real-time surgery. Using postoperative computerized tomography scans, the actual situation were compared with the preoperative simulation. A mean difference of 0.75 mm (SD ± 0.72) for the flap shape and 0.70 mm (SD ± 0.44) for the implant position analysis was determined. A calculation of the closest point distance showed a surface deviation of <2 mm for the shape analysis in 93.3% of the values and <1 mm for implant position in 75.2% of the values. The mean angular deviation was 3.65°. Virtual surgical planning is a suitable method for mandibular reconstruction with vascularized iliac crest flaps and simultaneous implant surgery. It can be used to restore the anatomy of the mandible with a high accuracy and can help to shorten subsequent dental rehabilitation.

The accuracy of computer-assisted primary mandibular reconstruction with vascularized bone flaps: iliac crest bone flap versus osteomyocutaneous fibula flap.

BACKGROUND: The intention of mandibular reconstruction is to restore the complex anatomy with maximum possible functionality and high accuracy. The aim of this study was to evaluate the accuracy of computer-assisted surgery in primary mandibular reconstruction with an iliac crest bone flap compared with an osteomyocutaneous fibula flap. MATERIALS AND METHODS: Preoperative computed tomography data of the mandible and the iliac crest or fibula donor site were imported into a specific surgical planning software program. Surgical guides were manufactured using a rapid prototyping technique for translating the virtual plan, including information on the transplant dimensions and shape, into real-time surgery. Using postoperative computed tomography scans and an automatic surface-comparison algorithm, the actual postoperative situation was compared with the preoperative virtual simulation. RESULTS: The actual flap position showed a mean difference from the virtual plan of 2.43 mm (standard deviation [SD] ±1.26) and a surface deviation of 39% <2 mm and 15% <1 mm for the iliac crest bone flap, and a mean difference of 2.18 mm (SD ±1.93) and a surface deviation of 60% <2 mm and 37% <1 mm for the osteomyocutaneous fibula flap. The position of the neomandible reconstructed with an osteomyocutaneous fibula flap indicated a mean difference from the virtual plan of 1.25 mm (SD ±1.31) and a surface deviation of 82% <2 mm and 57% <1 mm, in contrast to a mean difference of 1.68 mm (SD ±1.25) and a surface deviation of 63% <2 mm and 38% <1 mm for the neomandible after reconstruction with an iliac crest bone flap. For shape analysis, a similarly high accuracy could be calculated for both flaps. CONCLUSION: Virtual surgical planning is an effective method for mandibular reconstruction with vascularized bone flaps, and can help to restore the anatomy of the mandible with high accuracy in position and shape. It seems that primary mandibular reconstruction with the osteomyocutaneous fibula flap is more accurate compared with the vascularized iliac crest bone flap.