Determining the optimal osteotomy distance with the fibula free flap in mandibular reconstruction

Biomechanical evaluation of CAD/CAM magnesium miniplates as a fixation strategy for the treatment of segmental mandibular reconstruction with a fibula free flap

Titanium patient-specific (CAD/CAM) plates are frequently used in mandibular reconstruction. However, titanium is a very stiff, non-degradable material which also induces artifacts in the imaging. Although magnesium has been proposed as a potential material alternative, the biomechanical conditions in the reconstructed mandible under magnesium CAD/CAM plate fixation are unknown. This study aimed to evaluate the primary fixation stability and potential of magnesium CAD/CAM miniplates. The biomechanical environment in a one segmental mandibular reconstruction with fibula free flap induced by a combination of a short posterior titanium CAD/CAM reconstruction plate and two anterior CAD/CAM miniplates of titanium and/or magnesium was evaluated, using computer modeling approaches. Output parameters were the strains in the healing regions and the stresses in the plates. Mechanical strains increased locally under magnesium fixation. Two plate-protective constellations for magnesium plates were identified: (1) pairing one magnesium miniplate with a parallel titanium miniplate and (2) pairing anterior magnesium miniplates with a posterior titanium reconstruction plate. Due to their degradability and reduced stiffness in comparison to titanium, magnesium plates could be beneficial for bone healing. Magnesium miniplates can be paired with titanium plates to ensure a non-occurrence of plate failure.

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.

Patient-specific 3D-printed mini-versus reconstruction plates for free flap fixation at the mandible: Retrospective study of clinical outcomes and complication rates

This study aimed to compare the clinical outcomes and complication rates of patient-specific 3D-printed mini- and reconstruction plates for free flap fixation in mandibular reconstruction. A retrospective monocentric study was carried out between April 2017 and December 2021 to analyze patients undergoing immediate mandibular reconstruction using fibula free flaps and osteosynthesis using patient-specific 3D-printed implants. Eighty-three patients with a mean age of 63.6 years were included. The mean follow-up period was 18.5 months. Patient-specific 3D-printed plates were designed as reconstruction plates (38 patients), miniplates (21 patients) or a combination of reconstruction- and miniplates (24 patients). With miniplates, plate removal was performed significantly more often via an intraoral approach (p < 0.001) and in an outpatient setting (p = 0.002). Univariate analysis showed a higher fistula rate with reconstruction plates (p = 0.037). Multivariate analysis showed no significant differences in complications. Case-control matching demonstrated significantly lower rates of fistula (p = 0.017) and non-union (p = 0.029) in the combined group. This retrospective study shows a tendency towards reduced complication rates with patient-specific 3D-printed miniplates in comparison to patient-specific 3D-printed reconstruction plates for immediate mandibular reconstruction with fibula free flaps.

Mandibular reconstructions with free fibula flap using standardized partially adjustable cutting guides or CAD/CAM technique: a three- and two-dimensional comparison

Background

Mandibular reconstruction with the fibula free flap (FFF) is performed freehand, CAD/CAM-assisted, or by using partially adjustable resection/reconstruction aids. The two latter options represent the contemporary reconstructive solutions of the recent decade. The purpose of this study was to compare both auxiliary techniques with regard to feasibility, accuracy, and operative parameters.

Methods and materials

The first twenty consecutively operated patients requiring a mandibular reconstruction (within angle-to-angle) with the FFF using the partially adjustable resection aids between January 2017 and December 2019 at our department were included. Additionally, matching CAD/CAM FFF cases were used as control group in this cross-sectional study. Medical records and general information (sex, age, indication for surgery, extent of resection, number of segments, duration of surgery, and ischemia time) were analyzed. In addition, the pre- and postoperative Digital Imaging and Communications in Medicine data of the mandibles were converted to standard tessellation language (.stl) files. Conventional measurements - six horizontal distances (A-F) and temporo-mandibular joint (TMJ) spaces - and the root mean square error (RMSE) for three-dimensional analysis were measured and calculated.

Results

In total, 40 patients were enrolled (20:20). Overall operation time, ischemia time, and the interval between ischemia time start until end of operation showed no significant differences. No significant difference between the two groups were revealed in conventional measurements of distances (A-D) and TMJ spaces. The Δ differences for the distance F (between the mandibular foramina) and the right medial joint space were significantly lower in the ReconGuide group. The RMSE analysis of the two groups showed no significant difference (p=0.925), with an overall median RMSE of 3.1 mm (2.2-3.7) in the CAD/CAM and 2.9 mm (2.2-3.8) in the ReconGuide groups.

Conclusions

The reconstructive surgeon can achieve comparable postoperative results regardless of technique, which may favor the ReconGuide use in mandibular angle-to-angle reconstruction over the CAD/CAM technique because of less preoperative planning time and lower costs per case.

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.

[Application of personalized guide plate combined with real-time navigation in repairing mandibular defect using fibula muscle flap]

OBJECTIVE

To explore the application of personalized guide plate combined with intraoperative real-time navigation in repairing of mandibular defect using fibula muscle flap, providing the basis for the precise repair and reconstruction of mandible.

METHODS

The clinical data of 12 patients (9 males and 3 females) aged from 23 to 71 years (mean, 55.5 years) between July 2019 and December 2021 were recorded. These patients were diagnosed as benign or malignant mandibular tumors, including 2 cases of ameloblastoma, 6 cases of squamous cell carcinoma, 2 cases of osteosarcoma, 1 case of adenoid cystic carcinoma, and 1 case of squamous carcinoma. All patients were treated with mandibular amputation, and then repaired by double-stacked three-segment fibula muscle flap. Preoperative virtual design scheme and guide plate were performed. During the operation, personalized guide plate combined with real-time navigation was used for fibular osteotomy and shaping. Thin-slice CT examination was performed at 2-3 weeks after operation, and was fitted with the preoperative virtual design scheme. The difference between the distance of bilateral mandibular angles relative to the reference plane in three-dimensional directions (left-right, vertical, and anterior-posterior) and the difference of the medial angle of the lower edge of the mandible reconstructed by fibula were measured, and the mean error of chromatographic fitting degree was calculated.

RESULTS

The guide plate and navigation were applied well, and the fibula shaping and positioning were accurate. The fibula muscle flap survived, the incision healed well, and the occlusal relationship was good. All 12 patients were followed up 1-29 months, with an average of 17 months. There was no significant difference on the distance of bilateral mandibular angles relative to the reference plane in the left-right [(-0.24±1.35) mm; t=-0.618, P=0.549], vertical [-0.85 (-1.35, 1.40) mm; Z=-0.079, P=0.937], and anterior-posterior [(-0.46±0.78) mm; t=-2.036, P=0.067] directions. The difference of the medial angle of the lower edge of the mandible reconstructed by fibula was also not significant [(-1.35±4.34)°; t=-1.081, P=0.303)]. Postoperative CT and preoperative virtual design fitting verified that there was no significant difference in the change of the mandibular angle on both sides, and the average error was (0.47±1.39) mm.

CONCLUSION

The personalized guide combined with intraoperative real-time navigation improves the accuracy of peroneal muscle flap reconstruction of the mandible, reduces the complications, and provides a preliminary basis for the application of visual intraoperative navigation in fibula muscle flap reconstruction of the mandible.

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.

Practice patterns of virtual surgical planning: Survey of the reconstructive section of the American Head and Neck Society

PURPOSE

Virtual surgical planning (VSP), with custom made implants and guides represents a recent major advance. Nonetheless, knowledge related to practice patterns is limited. The purpose of this study was to provide data from the AHNS Reconstruction Section related to practice patterns, perceived value of VSP, as well as elucidate specific situations which represent high value for the application of VSP.

MATERIALS AND METHODS

A multi-center web-based survey consisting of 30 questions regarding practice patterns related to VSP practices delivered via email to 203 members of the AHNS Reconstructive Surgery Section at institutions across North America.

RESULTS

There was a 34% response rate (70/203). A majority of the respondents (96%) used VSP in approximately 50% of their mandibular reconstruction cases, and in 42% of maxillary cases. 46% reported using patient specific implants >75% of cases. Respondents estimated that ~17% of patients received dental implant reconstruction. The majority of respondents (71.0%) did not know the cost of VSP at their institution. The remaining respondents indicated the average cost was $6680 per case. VSP was felt to be necessary as a teaching tool by 55.9%.

CONCLUSIONS

Our results demonstrate that a majority of respondents frequently utilize VSP in their practice for head and neck reconstruction. Complex, multi-unit reconstructions were felt to offer the greatest value when utilizing VSP. Future work should focus on increasing the rates of dental implant reconstruction in this population, optimizing value of VSP with careful case selection, and understanding the educational value and costs of these platforms.

Risk Factors for Plate Extrusion After Mandibular Reconstruction With Vascularized Free Flap

PURPOSE

Plate extrusion after mandibular reconstruction is a complication that imposes significant morbidity on the patient. The goal of this study is to estimate the incidence of plate extrusion after mandible reconstruction with a vascularized free flap and to identify the factors associated with plate extrusion.

METHODS

This was a retrospective cohort study involving patients who underwent mandibular reconstruction from October 2008 to July 2019 at LAC + USC or Keck Hospital of USC. Inclusion criteria were age ≥ 18 years, single-stage mandibular reconstruction with vascularized free flap, and follow-up of at least 12 months. Relevant demographic, intraoperative, and postoperative data were collected. The primary outcome was postoperative plate extrusion within the 12-month follow-up. Descriptive, univariate, and multivariate analyses were performed. Statistical significance was set at P ≤ .05.

RESULTS

A total of 102 patients were included in this study. The majority received a fibula free flap (90%) for a malignant neoplasm (76%). All patients had at least 12 months of follow-up. The rate of plate extrusion was 16%, with the majority of those patients undergoing plate removal (69%). After adjusting for postoperative fistula, soft tissue, and length of hospitalization, we found that any history of smoking (odds ratio = 12.8; confidence interval, 1.57 to 104.2), number of osteotomies (odds ratio 3.07; confidence interval, 1.09 to 8.6), flap nonviability (odds ratio = 18.2; confidence interval, 2.22 to 148.8) were associated with plate extrusion on multivariate analysis. Postoperative soft tissue infection approached significance.

CONCLUSIONS

This study demonstrates that smoking history, number of osteotomies, and flap nonviability are associated with plate extrusion after mandible reconstruction. Performing fewer osteotomies when possible to avoid excessively small flap bone segments and minimizing postoperative complications may improve long-term outcomes after mandibular reconstruction.

Application of additive manufacturing in customized titanium mandibular implants for patients with oral tumors

The application of additive manufacturing (AM) technology has been widely used in various medical fields, including craniomaxillofacial surgery. The aim of the present study was to examine the surgical efficiency and post-operative outcomes of patient-specific titanium mandibular reconstruction using AM. Major steps in directly designing and manufacturing 3D customized titanium implants are discussed. Furthermore, pre-operative preparations, surgical procedures and post-operative treatment outcomes were compared among patients who received mandibular reconstruction using a customized 3D titanium implant, titanium reconstruction plates or vascularized autologous fibular grafting. Use of a customized titanium implant significantly improved surgical efficiency and precision. When compared with mandibular reconstruction using the two conventional approaches, patients who received the customized implant were significantly more satisfied with their facial appearance, and exhibited minimal post-operative complications in the 12-month follow-up period. Patients who underwent mandibular reconstruction using a customized titanium implant displayed improved mandibular contour symmetry, restored occlusal function, normal range of mouth opening and no temporomandibular joint related pain; all complications frequently experienced by patients who undergo conventional approaches of mandibular reconstruction.