Sequential evaluation for bone union of transferred fibula flaps in reconstructed mandibles: panoramic X-ray versus computed tomography

Evaluating the benefit of virtual surgical planning on bony union rates in head and neck reconstructive surgery

OBJECTIVES

Virtual surgical planning (VSP) has gained acceptance because of its benefits in obtaining adequate resection, achieving cephalometric accuracy, and reducing operative time. The aim of this study is to compare the rate of union between VSP and free-hand surgery (FHS), identify predictors of non-union and evaluate the difference in operative time.

METHODS

Post-operative CT were retrospectively reviewed for 123 patients who underwent maxillary or mandibular reconstruction between 2014 and 2021 using either VSP or FHS. Each apposition was graded as complete, partial or non-union. The rate of union, risk difference and inter-rater reliability were calculated. The difference in operative time was assessed. Predictors of non-union were identified using logistic regression.

RESULTS

A total of 326 appositions were graded (VSP n = 150; FHS n = 176). The rates of complete and partial union were higher with VSP than FHS (74.7% vs. 65.3%; 18% vs. 15.9%, respectively, p = 0.01). Non-union was found at a higher rate with FHS than with VSP (18.7% vs. 7.3%). The non-union risk difference was 11.4. FHS, major complications and apposition at the native bone were predictors of non-union (OR 2.9, p = 0.02; OR 3.4, p = 0.01; OR 2.5, p = 0.05, respectively). The mean surgical time was shorter with VSP than with FHS (265.3 vs. 381.5 min, p < 0.001). The inter-rater agreement was high (k = 0.85; ICC = 0.86).

CONCLUSION

VSP demonstrated significantly higher bony union rates and shorter operative time. FHS, development of major complications and apposition with native bone correlated with non-union.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Impact of the adjacent bone on pseudarthrosis in mandibular reconstruction with fibula free flaps

BACKGROUND

Mechanical and morphological factors have both been described to influence the rate of pseudarthrosis in mandibular reconstruction. By minimizing mechanical confounders, the present study aims to evaluate the impact of bone origin at the intersegmental gap on osseous union.

METHODS

Patients were screened retrospectively for undergoing multi-segment fibula free flap reconstruction of the mandible including the anterior part of the mandible and osteosynthesis using patient-specific 3D-printed titanium reconstruction plates. Percentage changes in bone volume and width at the bone interface between the fibula/fibula and fibula/mandible at the anterior intersegmental gaps within the same patient were determined using cone-beam computed tomography (CBCT). Additionally, representative samples of the intersegmental zones were assessed histologically and using micro-computed tomography (µCT).

RESULTS

The bone interface (p = 0.223) did not significantly impact the change in bone volume at the intersegmental gap. Radiotherapy (p < 0.001), time between CBCT scans (p = 0.006) and wound healing disorders (p = 0.005) were independent risk factors for osseous non-union. Preliminary analysis of the microstructure of the intersegmental bone did not indicate morphological differences between fibula-fibula and fibula-mandible intersegmental bones.

CONCLUSIONS

The bone interface at the intersegmental gap in mandibular reconstruction did not influence long-term bone healing significantly. Mechanical and clinical properties seem to be more relevant for surgical success.

Osseointegration and Bone Resorption of Scapula Tip Free Flaps in Mandibular Reconstruction

OBJECTIVES

Bone resorption of more conventional vascularized bone grafts have been well described showing minimal resorption over time. Few studies have evaluated osseous union and bone resorption in scapula tip free flaps (STFF) in the reconstruction of mandibulectomy defects. We aimed to describe our series on STFF with respect to osseous union and bone resorption over time.

METHODS

Retrospective chart review of patients receiving STFF from January 2014-January 2017 (n = 25). A neuroradiologist analyzed follow-up CT scans to assess (1) STFF complete, partial, or no osseous union with native mandible and (2) STFF volume change over time in a subset with multiple follow-up scans (n = 18).

RESULTS

Twenty-three of 25 patients (92%) showed complete or partial STFF osseous union with native mandible either distally or proximally. STFF volume change ranged from +4.8 to -54% (median -0.5%) over median follow-up interval of 23 months. History of chemoradiation therapy, bisphophonate use, sex, age, or smoking history did not correlate with bone resorption.

CONCLUSIONS

STFFs shows high rates of osseous union and limited bone resorption that is equivalent to, or less than, vascularized fibular and iliac crest flaps. Clinically, this translates into both optimal healing and functional and cosmetic outcomes, especially in the setting of prior therapies.

LEVEL OF EVIDENCE

4 Laryngoscope, 133:2597-2602, 2023.

Early Second Free Flap is Required in Osteoradionecrosis-related Nonunion after Primary Mandible Reconstruction

Osteoradionecrosis (ORN) manifested as symptomatic nonunion between primary free flap and native mandible after primary bony reconstruction of the mandible is an entity not included in current conventional ORN staging guidelines. This article reports on and proposes early management of this debilitating condition using a chimeric scapular tip free flap (STFF).

Methods

A retrospective review was performed examining cases with bony nonunion at the junction of primary free fibula flap (FFF) and native mandible at a single center over a 10-year duration, which required a second free bone flap. Details of each case (patient demographics, oncological details, primary surgery, presentation, and secondary surgery) were documented and analyzed. Outcomes of the treatment were assessed.

Results

Four patients (two men and two women; age range, 42-73 years) out of a total of 46 primary FFF were identified. All patients presented with symptoms of low-grade ORN and radiological signs of nonunion. All cases were reconstructed with chimeric STFF. The duration of follow-up ranged from 5 to 20 months. All patients reported resolution of symptoms and radiological evidence of union. Two of four patients subsequently received osseointegrated dental implants.

Conclusions

Institutional rate of nonunion after primary FFF requiring a second free bone flap is 8.7%. All the patients of this cohort presented with a similar clinical entity easily discounted as an infected nonunion postosseous flap reconstruction. There is no ORN grading system that currently guides the management of this cohort. Good outcomes are possible with early surgical intervention with a chimeric STFF.

Osseous Union after Jaw Reconstruction with Fibula-Free Flap: Conventional vs. CAD/CAM Patient-Specific Implants

This is a monocentric, retrospective study of patients who underwent successful immediate or delayed maxilla or mandible reconstructions with FFF from January 2005 to December 2021. Panoramic radiograph, computed tomography scans, and cone-beam CTs were analyzed concerning the osseous union of the intersegmental junctions between maxillary or mandibular native jaw and fibular bone. The primary parameter was to estimate the status of osseous union according to osteosynthesis type. A total number of 133 patients (PSI: n = 64, non-PSI: n = 69) were included in the present study. The mean age was 56.7 ± 14.0 (Range: 14.7−82.7); the primary diagnosis was in 105 patients a malignant (78.9%) and in 20 patients a benign (15.0%) tumor. Mandible reconstruction was performed on 103 patients (77.4%), and on 30 patients (22.6%), maxilla reconstruction was performed. The radiographic images provided a rate of incomplete osseous union (IOU) of about 90% in both groups in the first 6 months. Imaging between 6 and 12 months reveals an IOU rate in the non-PSI group of 46.3% vs. 52.5% in the PSI group, between 12 and 24 months, an IOU rate of 19.6% vs. 26.1%, between 24 and 36 months 8.9% vs. 21.7%, and after 36 months the IOU rate decreases to 4.2% vs. 18.2%. Multivariate logistic regression shows that only osteosynthesis type (OR = 3.518 [95%-CI = 1.223−10.124], p = 0.02) and adjuvant radiotherapy (OR = 4.804 [95%-CI = 1.602−14.409], p = 0.005) are independent risk factors for incomplete osseous union. Cox regression revealed that the variables plate-system (Hazard ratio, HR = 5.014; 95 %-CI: 1.826−3.769; p = 0.002) and adjuvant radiotherapy (HR = 5.710; 95 %-CI: 2.066−15.787; p < 0.001) are predictors for incomplete osseous union. In our study, the rate of incomplete bony fusion was significantly higher in the PSI group. Jaw-to-fibula apposition zones were significantly more affected than intersegmental zones. In multivariate analysis, a combination of osteosynthesis with PSI and adjuvant radiotherapy could be identified as a risk constellation for incomplete ossification.

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

OBJECTIVES

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).

METHODS

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.

RESULTS

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).

CONCLUSIONS

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.

Strategy for preventing skin paddle necrosis in mandibular reconstruction with free fibula osteocutaneous flap

BACKGROUND

Non-thrombotic skin paddle necrosis occasionally occurs during mandibular reconstructions with free fibula osteocutaneous flaps. The number of perforators, size of the skin paddle, and ischemia time of the flap are considered as causes of skin paddle necrosis. The importance of donor side selection has also been highlighted. This study aimed to investigate the leading cause of skin paddle necrosis and the optimal reconstructive procedure.

METHODS

A total of 66 patients who underwent mandibular reconstruction using a free fibula osteocutaneous flap were retrospectively analyzed. Skin paddle necrosis, number of cutaneous perforators, size of the skin paddle, and ischemia time of the flap were investigated. An incorrect "laterality" was defined as a skin paddle (septum) covering the reconstruction plate. Donor-site morbidity was recorded.

RESULTS

Skin paddle necrosis occurred in 15.2% of patients. An incorrect laterality was associated with a higher incidence of skin paddle necrosis (odds ratio, 22.0; 95% confidence interval, 2.5-195; p = .005). Donor-site morbidity was noted in 18.8% of the patients, without any significant difference in terms of the donor side with and without skin graft (p = .592). The postoperative activities of daily living were not affected.

CONCLUSIONS

To prevent skin paddle necrosis, donor side selection is an important safety strategy during mandibular reconstruction with free fibula osteocutaneous flap. The postoperative activities of daily living were found to be little affected by differences in the donor side.

Patient-Specific 3D-Printed Miniplates for Free Flap Fixation at the Mandible: A Feasibility Study

Background

This study was conducted to evaluate the feasibility, clinical outcomes, and accuracy of patient-specific 3D-printed miniplates for mandible reconstruction with fibula free flaps.

Methods

A feasibility study was conducted with 8 patients. Following virtual planning, patient-specific 1.0 mm titanium non-locking miniplates were produced via laser selective melting. 3D-printed cutting and drilling guides were used for segmental mandible resection and flap harvesting. Flap fixation was performed with two 4-hole miniplates and 2.0 mm non-locking screws (screw length 7 mm) for each intersegmental gap. Clinical follow-up was at least 6 months. Preoperative and postoperative CT/cone beam CT data were used for 3D accuracy analysis and evaluation of bone healing. Plate-related complications were monitored clinically.

Results

Patient-specific miniplate fixation of all flaps was successfully conducted (4 mono-segmental, 4 dual-segmental) with high accuracy (3.64 ± 1.18 mm) between the virtual plan and postoperative result. No technical complications were encountered intraoperatively. Osseous union occurred in all intersegmental gaps (1 partial, 18 complete) after 10 ± 2 months. No material fracture, dislocation, or plate exposure was observed.

Conclusions

Based on this pilot observational study including a limited number of patients, free flap fixation for mandibular reconstruction with patient-specific 3D-printed miniplates is feasible and associated with high accuracy, bone healing, and remote soft tissue complications.

Bone Union of Osseous Microvascular Free Tissue Transfer in Mandibular Reconstruction

Objectives

Osseous microvascular free tissue transfer (MFTT) is the gold standard for reconstruction for most segmental mandibulectomy defects. The most common osseous MFTT utilized in reconstruction is the fibular, scapular, and osteocutaneous radial forearm (OCRF) free flap. We evaluated postoperative bone union as well as clinical complications following MFTT and the impact of various patient and reconstructive characteristics, including type of osseous MFTT.

Study Design

Retrospective cohort study.

Setting

Tertiary care academic hospital.

Methods

This study examined patients who underwent osseous MFTT for mandibular defects from January 2017 to January 2019.

Results

An overall 144 osteotomies in 58 patients were evaluated. Of the 144 junctions, 28 (19.4%) showed radiographic nonunion. Patients who underwent preoperative (odds ratio [OR] = 0.30, P = .027) and postoperative (OR = 0.28, P = .003) radiation had a significantly lower bone union score. Time from surgery to postoperative imaging was associated with higher bone union scores (OR = 1.07, P = .024). When bone union scores were compared among types of MFTT, fibular (OR = 5.62, P = .008) and scapular (OR = 4.69, P = .043) MFTT had significantly higher scores than OCRF MFTT. Twelve (20.7%) patients had postoperative complications. There was no statistically significant correlation between clinical complications and various variables, including type of osseous MFTT.

Conclusion

Pre- and postoperative radiation and time from surgery have an impact on bone union. Regarding the type of MFTT, fibular and scapular MFTT appeared to have higher bone union when compared with OCRF. There was no impact of bone union or type of osseous MFTT on clinical complications.

Intensive Care as an Independent Risk Factor for Infection after Reconstruction and Augmentation with Autologous Bone Grafts in Craniomaxillofacial Surgery: A Retrospective Cohort Study

Autologous bone grafts for reconstruction and augmentation are routinely used for maintaining functionality and facial aesthetics. Associated complications, however, have a significant impact on patients and health care systems. This study aims to investigate the possible risk factors associated with the occurrence of complications in order to provide evidence for the outcome of autologous bone graft reconstructive procedures. Patients from 2008 to 2018 who underwent autologous (mostly mandibular) reconstruction were included in the observational study. Clinical, pathological, and therapeutic factors were examined in univariate and multivariate analysis for significance with occurring complications. A multivariate model was used to create a prognostic model predicting the occurrence of complications. Graft complications requiring revision were exhibited by 33/128 patients. Infections were most frequent, with 4/22 patients affected by multi-resistant germs. Multivariate analysis showed radiotherapy (OR = 5.714; 95% CI: 1.839–17.752; p = 0.003), obstructive pulmonary disease (OPD) (OR = 4.329; 95% CI: 1.040–18.021; p = 0.044) and length of defect (in mm) (OR = 1.016; 95% CI: 1.004–1.028; p = 0.009) as independent risk factors associated with graft complications with high accuracy of prediction (AUC = 0.815). Intensive care (OR = 4.419; 95% CI: 1.576–12.388; p = 0.005) with a coefficient between intensive care and OPD (0.214) being low was identified as the most relevant risk factor for infection. Although intensive care is not a classic risk factor, but rather a summation of factors not reaching significance in the individual case, a stay in ICU (intensive care unit) needs to be considered for graft complications. As a clinical consequence, we recommend using the best possible hygienic measures during procedures e.g., while performing dressing and drainage changes in ICU.

Short and long-term outcomes of three-dimensional printed surgical guides and virtual surgical planning versus conventional methods for fibula free flap reconstruction of the mandible: Decreased nonunion and complication rates

BACKGROUND

To determine whether virtual surgical planning and three-dimensional printed cutting guides (3D/VSP) improved radiographic bone union compared to conventional methods (CM) in fibula free flap (FFF) reconstruction of the mandibles.

METHODS

Retrospective study from the years 2000-2018 at a tertiary hospital. Osseous union was evaluated by a radiologist blinded to each patient's treatment.

RESULTS

Two hundred sixty patients who underwent FFF tissue transfer, 28 with VSP and 3D cutting guides. Bony union was not achieved in 46 (20%) patients who underwent CM compared to 1 (4%) of patients with VSP and guides (p = 0.036). FFF complication was significantly higher in CM with 87 patients (38%) compared to three patients (11%) in 3D/VSP (p = 0.005). Median time to bony union for patients who underwent CM was 1.4 years compared to 0.8 years in 3D/VSP.

CONCLUSIONS

3D/VSP reduced the rate of radiographic nonunion and flap-related complications in FFF reconstruction for mandibular defects.

Occurrence and Treatment Outcome of Late Complications After Free Fibula Flap Reconstruction for Mandibular Osteoradionecrosis

PURPOSE

This study aimed to evaluate the occurrence and treatment outcome of late complications after free fibula osteocutaneous flap reconstruction for mandibular osteoradionecrosis (ORN).

METHODS

We enrolled 15 consecutive patients (14 men, one woman; median age 65 years, range 57-80 years) who underwent free fibula reconstruction for advanced mandibular ORN during 2013-2017 with two or more years of follow-up. Late complications included infection, plate exposure, and recurrence at the resection margin. The effect of perioperative antibiotic administration on late complications was also assessed.

RESULTS

Late complications occurred in 33.3% (5/15) of patients, including two infections (local and distant), two plate exposures, and two recurrences (plate exposure and recurrence occurred in one patient). Perioperative antibiotic administration duration did not significantly affect the occurrence of postoperative late complications. All late complications were treated without problems.

CONCLUSIONS

Late complications after ORN reconstructive surgery are not uncommon, but can be treated properly.

Comparison of surgical outcomes between primary plate and fibular flap transfer for reconstruction of segmental mandibular defects

PURPOSE

Although two ways of reconstruction have been reviewed for a long period, comparison of large sample size with nearly randomized patient selection is rare. Here, we compare the surgical outcomes of these two methods from two large medical institutes.

METHODS

Totally 176 patients were included from two medical centers with different protocols, 62 patients from MacKay Hospital repair defects with fibula flaps using reconstruction plates. Also 114 patients from Kaohsiung ChangGung Hospital treat with reconstruction plates combine anterior lateral thigh flaps, in which 12 cases had secondary fibula flap after plate exposure. Electronic medical records were reviewed retrospectively. Short (3-12 months) and long-term (>12 months) outcomes were evaluated.

RESULTS

Short-term evaluation revealed that the secondary fibula had a higher rate of vascular complications (33 vs. 6%, p = .02). Primary fibula had a higher risk of post reconstructive surgical debridement (60 vs. 40%, p = .018). Long-term follow-up revealed radiation therapy significantly worsened bone healing (p = .03). Primary fibula had a lower rate of screw loosening (14.0 vs. 40.3%, p = .002). Radiation therapy did not increase the plate exposure rate among the groups (33 vs. 27%, p = .389). Disease free survival showed no significant difference between two groups (53.1 ± 3.5 vs. 47.8 ± 2.8 months, p = .317).

CONCLUSION

Primary fibula reconstruction should be considered whenever possible to reduce the risk of late complications and simplifies the management after a potential plate exposure. Notably, radiation therapy apparently has no significant effect on plate exposure rate both in ALT or fibula groups.

Cancellous Tibial Bone Graft for Malunion after Mandibular Reconstruction in Head and Neck Cancer

OBJECTIVES/HYPOTHESIS

While nonunion after mandibular reconstruction for head and neck surgery is rare, literature exploring management is scarce. Our primary objective was to determine success rates of tibial bone graft (TBG) in achieving mandibular union. Secondary objectives include determining factors that contribute to failure of TBG.

STUDY DESIGN

Retrospective Chart Review.

METHODS

Retrospective chart review between January 1, 2008 and December 31, 2018. Patients who underwent a mandibulotomy or mandibulectomy with osteocutaneous free flap reconstruction were identified. Patients who were pursuing dental rehabilitation, subsequently diagnosed with mandibular nonunion and received a cancellous TBG were assessed.

RESULTS

The 15 patients meeting inclusion criteria were mostly male (67%), white (87%), and nonsmokers (67%) with a median age of 64 (IQR = 60-73). Successful union occurred in 13 of 18 (72%) TBGs and the majority (63%) had a partial union documented at the time of surgery. Five patients (83%) who initially had a mandibulotomy achieved union compared to 78% of those with osteocutaneous reconstruction (P = 1.0). Postoperative radiation did not affect rates of union: 80% for both (P = 1.0). Patients with osteoradionecrosis (ORN) achieved union in 67% of cases compared to 75% of cases who did not have ORN (P = .86). There were similar rates of union for those who required perioperative antibiotics for infection and those without infection (67% vs. 75%, P = .86). Dental rehabilitation was achieved in 55% of patients, most commonly dentures.

CONCLUSIONS

This study shows that TBG can be used to achieve union for patients with malunion after head and neck cancer reconstruction. We show its successful use within the reconstructive algorithm for patients regardless of postoperative radiation for very small defects.

LEVEL OF EVIDENCE

3 Laryngoscope, 131:1291-1296, 2021.

Fibula free flap in maxillomandibular reconstruction. Factors related to osteosynthesis plates' complications

The aim of this paper is to identify risk factors associated with the development of osteosynthesis plates' related complications in fibula free flap reconstructions. This is a case series study of consecutive fibula free flaps. Clinical and radiological variables were recorded. Patient outcomes were evaluated with special attention to osteosynthesis plates' related complications; these included plate exposure, plate fracture, loosening of screws, non-union, bone resorption, oro-cutaneous fistulas, and bone exposure. We have done a descriptive analysis, univariate analysis, and multivariate logistic regression model to explore possible risk factors for osteosynthesis plates' related complications. Data analysis was performed using R software (version 3.5.0). 111 fibula free flaps were studied. 29 patients (26.1%) developed osteosynthesis plates' related complications. The mean time to osteosynthesis plates' related complications was 22 months; range (1-120); the median and mode were 12 months. Patients with preoperative radiotherapy (34% vs 14%, p = 0.021), and secondary reconstruction (31% vs 15%, p = 0.053) had a higher incidence of osteosynthesis plates' related complications. In the univariate analysis, "preoperative radiotherapy" (OR 3.07, 95%CI = 1.139-8.242, p = 0.025) and "extraoral soft-tissue defect" (OR 2.907, 95%CI = 1.032-8.088, p = 0.042) were risk factors for osteosynthesis plates' related complications. We have observed an interaction effect: patients with mandibular Brown's classes III + IV and "secondary reconstruction" have a higher risk for osteosynthesis plates' related complications; more than 47.30 times compared to Brown's class I and "primary reconstruction" (p = 0.026). Different factors may contribute to the development of osteosynthesis plates' related complications. Our study adds important information about these. Patients with higher risk of developing complications should be informed that a second intervention to remove the plates might be necessary.

Biomechanical Analysis of Various Reconstructive Methods for the Mandibular Body and Ramus Defect Using a Free Vascularized Fibula Flap

Several different methods exist for reconstructing the mandibular body and ramus defect with the use of a free vascularized fibula flap, but none have adequately addressed the long-term mechanical stability and osseointegration. The aim of this study is to compare the biomechanics of different surgical methods and to investigate the best approach for reconstructing the mandibular body and ramus defect. Five finite element models based on different reconstructive methods were simulated. Stress, strain, and displacement of connective bone sections were calculated for five models and compared. The models were printed using a 3D printer, and stiffness was measured using an electromechanical universal testing machine. The postoperative follow-up cone beam computed tomography (CBCT) was taken at different time points to analyze bone mineral density of connective bone sections. The results showed that the “double up” (DU) model was the most efficient for reconstructing a mandibular body and ramus defect by comparing the mechanical distribution of three sections under vertical and inclined loading conditions of 100 N. The stiffness detection showed that stiffness in the DU and “double down” (DD) models was higher compared with the “single up” (SU), “single down” (SD), and “distraction osteogenesis” (DO) models. We used the DU model for the surgery, and postoperative follow-up CBCT showed that bone mineral density of each fibular connective section increased gradually with time, plateauing at 12 weeks. We conclude that a free vascularized fibula flap of the DU type was the best approach for the reconstruction of the mandibular body and ramus defect. Preoperative finite element analysis and stiffness testing were shown to be very useful for maxillofacial reconstruction.

Heterogeneity of Necrotic Changes between Cortical and Cancellous Bone in Mandibular Osteoradionecrosis: A Histopathological Analysis of Resection Margin after Segmental Mandibulectomy

BACKGROUND

This study aimed to analyze differences in necrotic changes between cortical and cancellous bone in resection margins after segmental mandibulectomy for advanced mandibular osteoradionecrosis.

METHODS

Anteroposterior bone specimens from eleven patients who underwent segmental mandibulectomy with simultaneous free fibula flap reconstruction for advanced osteoradionecrosis were analyzed histopathologically for the presence of necrotic bone based on the presence of blood vessels within Haversian canals.

RESULTS

Ten of eleven (91%) cortices near the inferior border of the mandible at the anterior margins were necrotic. All cancellous bones at the anterior margins were viable. Seven of eleven (64%) cortices near the inferior border of the mandible at the posterior margins were necrotic. Three of eleven (27%) cancellous bones at the posterior margins were necrotic.

CONCLUSION

Necrotic changes are more prevalent in cortices than in cancellous bones in mandibular osteoradionecrosis, probably due to a decrease of periosteal blood supply caused by radiotherapy.