Patient-specific implant modification for alloplastic bridging of mandibular segmental defects in head and neck surgery

Evaluation of the resection plane three-dimensional positional accuracy using a resection guide directional guidance slot; a randomized clinical trial

AIM

The study was performed to compare the mandibular resection guide with a directional guidance slot with the conventional guide regarding three-dimensional positional accuracy.

MATERIALS AND METHODS

Twenty-six patients with lateral segmental mandibular defects were selected, and randomly allocated into two groups. All defects were managed with preoperative virtual surgical planning. Resection in the test group was conducted using a resection guide with a directional guidance slot, while a conventional resection guide design was utilized in the control group. The linear and angular deviation of the osteotomy planes was analyzed for both groups, along with the accuracy of the insertion of the reconstruction bone block in the resected defect. Data were documented, absolute deviation was calculated, statistical analysis was performed and significance was set at the 5% level.

RESULTS

The cases conducted with a directional guidance templet reported a statistically significant difference when compared to the conventional edge-cutting guide regarding the linear and angular spatial osteotomy plane position (P < 0.001). The defect span analysis reported excellent levels of agreement in both groups (ICC = 1.00, ICC = 0.995), however, the difference between the groups was statistically significant (P < 0.001).

CONCLUSION

The study demonstrated the enhanced positional accuracy of the resection plane and reconstruction block placement when a directional slot is incorporated in the computer-generated resection guide.

A Novel Method for Secondary Mandible Reconstruction to Re-Achieve a Native Condyle Position Comprising a New Design for Cutting Guides and New Positioning Devices

Secondary mandibular reconstruction using fibular free flaps (FFF) is a technical challenge for surgeons. Appropriate operation planning is crucial for postoperative quality control and is notably necessary for the (re-) achievement of a physiological condylar position, and the sensible expansion and shaping of the transplant. Computer-assisted planning may help to reconstruct mandibular defects in a patient-specific and precise manner. Herein, we present a newly-developed workflow for secondary mandibular reconstruction using FFF; it comprises digital planning and in-house manufacturing to perform precise secondary mandible reconstruction. This method utilizes a newly designed positioning device to ensure the precise positioning of the fibula segments in relation to each other and the mandibular stumps. The presented in-house-printed positioning device made it possible to achieve digital planning with high precision during surgery.

Use of reconstruction plates prebent on three-dimensional models to reduce the complications of mandibular reconstruction

Background/purpose

Though the gold standard method for mandible reconstruction of the defect from segmental mandibulectomy is by osseous flap or graft, using reconstruction plates is still indicated in some cases. Traditionally, the plate is bended immediately after the segmental mandibulectomy by freehand. However, it's difficult to fit well to the original position of mandible, which may result in more complications. This study therefore aimed to investigate whether using prebent plates on computer-aided 3D printing models could reduce the complication rate.

Materials and methods

Patients who received mandible reconstruction by reconstruction plate from 2018 to 2022 were enrolled and evaluated in this study. The data, including demographics, indications for surgery, pre-existed preoperative and postoperative therapies, classification of defects, and postoperative outcomes were collected and analyzed.

Results

A total of 52 patients were enrolled in our study. The prebent group exhibited a significantly lower complication rate than that of the immediately bent group (P = 0.012). Other risk factors of plate complications included postoperative adjuvant radiotherapy (P = 0.017) and previous surgery (P = 0.047). The complication-free survival rate was also better in the prebent group in a 3-year follow-up period (P = 0.012).

Conclusion

Prebent plates on computer-aided printing models proved to be an effective approach to reduce the complications for mandibular reconstruction in segmental mandibulectomy.

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.

Patient Specific Alloplastic Implant Reconstruction of Mandibular Defects-Safe Practice Recommendations and Guidelines

Mandibular continuity defects are commonly seen after tumor resection, osteomyelitis or maxillofacial trauma. Three-dimensional reconstruction of these mandibular segmental defects is critical for proper mandibular functioning and esthetics. Various methods used to reconstruct such defects include bridging reconstruction plates, modular endoprosthesis, non-vascularized and vascularized bone grafting with stock reconstruction plate or patient specific implants (PSI) and tissue engineering bone transfer. But in the recent years, literature documents use of PSI only alloplastic reconstruction as an alternate to microvascular bone flap reconstruction. Representative cases enumerate current practice of 'patient specific implant only' mandibular reconstruction and its pitfalls. This article discusses current status of literature on PSI's, choice of indications for 'PSI only' mandibular reconstruction and also proposes guidelines for safe practice of patient specific implant reconstruction of mandible.

Microvascular reconstructions in oral and maxillofacial surgery - Results of a survey among oral and maxillofacial surgeons in Germany, Austria, and Switzerland

This study aimed to evaluate the use of microvascular free flaps (MFF) in oral and maxillofacial surgery (OMFS) in Germany, Austria, and Switzerland. A dynamic online questionnaire, using 42-46 questions, was sent to OMF surgeons based in hospitals in Germany, Austria, and Switzerland. The questionnaire was evaluated internally and externally. Aside from general information, data were collected on organizational aspects, approaches, MFF types and frequency, presurgical planning, intraoperative procedures, perioperative medications, flap monitoring, and patient management. Participants mostly performed 30-40 MFF each year (11/53). Most stated that the COVID-19 pandemic did influence MFF frequency (25/53) to varying extents. Radial forearm flap was most frequently used (37/53), followed by ALT (5/53), and fibula flap (5/53). Primary reconstruction was performed by most participants (35/48). Irradiated bony transplants were mostly used for implant placement after 12 months (23/48). Most participants (38/48) used reconstruction plates, followed by miniplates (36/48), PSI reconstruction (31/48), and PSI miniplates (10/48). Regarding the postoperative use of anticoagulants, low-molecular-weight (37/48) and unfractioned heparins (15/48) were widely used, most often for 3-7 days (26/48). Clinical evaluation was mostly preferred for flap monitoring (47/48), usually every 2 h (34/48), for at least 48 h (19/48). Strong heterogeneity in MFF reconstructions in OMFS was found, especially regarding the timepoints of reconstruction, types of osteosynthesis, and postoperative MFF management. These findings provide the chance to further compare the different treatment algorithms regarding relevant MFF aspects, such as postoperative management. This could create evidence-based treatment algorithms that will further improve the clinical outcomes in MFF reconstructions.

Experimental analysis and numerical fatigue life prediction of 3D-Printed osteosynthesis plates

The trend towards patient-specific medical orthopedic prostheses has led to an increased use of 3D-printed surgical implants made of Ti6Al4V. However, uncertainties arise due to varying printing parameters, particularly with regards to the fatigue limit. This necessitates time-consuming and costly experimental validation before they can be safely used on patients. To address this issue, this study aimed to employ a stress-life fatigue analysis approach coupled with a finite element (FE) simulation to estimate numerically the fatigue limit and location of failure for 3D-printed surgical osteosynthesis plates and to validate the results experimentally. However, predicting the fatigue life of 3D components is not a new concept and has previously been implemented in the medical device field, though without experimental validation. Then, an experimental fatigue test was conducted using a proposed modification to the staircase method introduced in ISO 12107. Additionally, a FE model was developed to estimate the stress cycles on the plate. The stress versus number of cycles to failure curve (S-N) obtained from the minimum mechanical properties of 3D-printed Ti6AI4V alloy according to ASTM F3001-14 to predict the fatigue limit. The comparison between experimental results and fatigue numerical predictions showed very good agreement. It was found that a linear elastic FE model was sufficient to estimate the fatigue limit, while an elastic-plastic model led to an accurate prediction throughout the implant's cyclic life. The proposed method has great potential for enhancing patient-specific implant designs without the need for time-consuming and costly experimental regulatory testing.

[Current Therapy Standards for Soft Tissue Sarcomas in the Head and Neck Area - Part 2]

In September 2021, the first version of the German S3 guideline on adult soft tissue sarcomas, version 1.0 (AWMF register number 032/044OL) was presented as part of the oncology guideline program of the DKG, German Cancer Aid and the AWMF. After the basic features of soft tissue sarcomas were presented in Part 1, Part 2 describes the specific options for surgical therapy depending on the location in the head and neck area.

Time is crucial in malignant tumor cases: Speeding up the process of patient-specific implant creation

Purpose

Patient-specific implants are commonly used to reconstruct lower jaw defects following surgical treatment for head and neck squamous cell carcinoma. The planning process of surgery is time-consuming and can delay the “time to surgery,” which should be as short as possible. Therefore, this study aimed to evaluate the planning process to speed up and identify any sources of problems.

Patients and methods

In this retrospective study, we enrolled patients who underwent continuous resection of the mandible in combination with reconstruction with a patient-specific implant between 2016 and 2021. The predictor variables were in-house training of the engineers and implant complexity (complex [with additional features] vs. less complex [resembling standard reconstruction plates]). The outcome variables were the duration of communication, message length, and the need for synchronous communication or modifications to the original design. Descriptive and univariate statistics were computed, and statistical significance was set at P < 0.05.

Results

The data from 83 patients were included in this study. The mean duration of communication was 14.05 ± 13.58 days. The implant complexity and training status of the engineer had no statistically significant influence on the primary outcome variables. As for the secondary outcome variables, the implant complexity significantly influenced the chance that the planned operation had to be postponed (15/16 [93.75%] were complex cases, P = 0.001). The most frequent cause of problems in the planning process was an insufficient dataset, which was not dependent on the type of imaging.

Conclusions

The overall duration of the patient-specific implant creation process is too long to meet oncological requirements. Therefore, standardization of the planning process to accelerate implant creation is of utmost importance. In addition, a common standard imaging format (independent of the type of imaging) for oncological cases could eliminate all delays caused by insufficient datasets in the future.

Pitfalls of Surgeon-Engineer Communication and the Effect of In-House Engineer Training During Digital Planning of Patient-Specific Implants for Orbital Reconstruction

PURPOSE

The use of patient-specific implants for reconstruction of complex orbital floor defects is increasing and requires communication with an industry partner, which warrants investigation. Therefore, the aim of this study was to evaluate the effects of in-house training of engineers on such communication as well as to identify frequent sources of problems and their solutions for improvement of the implant-planning workflow.

METHODS

We conducted a retrospective cross-sectional study and enrolled a sample of patients who had undergone orbital reconstruction with patient-specific implants between 2017 and 2020. The predictor variables were in-house training (additional training completed in hospital or not) and implant complexity (complex [multiwalled implants] vs less complex [isolated orbital floor reconstructions]). The outcome variables were duration of communication, message length, and need for synchronous communication or modifications to the original design. Descriptive, univariate, and multivariate statistics were computed, and statistical significance was set at a P value of < 0.05.

RESULTS

This study included the data of 66 patients (48 men and 18 women, average age: 42.27 years). The complexity of the implant statistically significantly increased the duration of the communication (8.76 vs 16.03 days; P = .004). In 72.73%, the initial design had to be changed. Engineers trained in house required less communication to plan less-complex implants and generally needed fewer corrections to the original design (P = .020 and P = .036, respectively). Problems during planning were observed in 25.76% of the cases, with an insufficient diagnostic 3-dimensional data set being the most common (15.15%).

CONCLUSIONS

In-house training of engineers is time-saving while planning the workflow for patient-specific implants, especially in less-complex cases, given that design changes are not needed often. The high rate of data sets that were insufficient for planning patient-specific implants suggests that diagnostic 3-dimensional data sets should already meet the requirements for such planning.

The Learning Curve of Computer-Assisted Free Flap Jaw Reconstruction Surgery Using 3D-Printed Patient-Specific Plates: A Cumulative Sum Analysis

Background

Computer-assisted jaw reconstruction (CAJR) has benefits in reducing operation time and improving reconstruction accuracy, compared to conventional freehand jaw reconstruction. However, no information is available regarding learning curves in CAJR with the use of 3D-printed patient-specific surgical plates (PSSP). The purpose of this study was to assess surgical outcomes and learning curve for the first 58 consecutive CAJR using 3D-printed PSSP performed by a single surgical team in a single institution.

Methods

In a prospective study, consecutive patients who underwent free flap CAJR using 3D-printed PSSP were included. The determination of proficiency, based on the cumulative sum of surgical success (no major adjustment of 3D-printed PSSP, flap survival) passing the acceptable boundary line of cumulative sum analysis, was the primary outcome. To find out any potential factors influencing the learning curve, baseline characteristics of patients were compared before and after proficiency achievement. Secondary outcomes included inflexion points of the total operation time, blood loss, length of hospital stay, and bone graft deviation, measured by the cumulative sum analysis.

Results

From December 2016 to November 2020, 58 consecutive cases underwent surgery performed by a single surgical team. The overall surgical success rate was 94.8% (55/58). A three-stage learning curve of primary outcome was observed. The proficiency was achieved after 23 cases. The proportions of advanced tumor staging and concomitant surgery after obtaining proficiency were significantly higher than those before achieving proficiency (p = 0.046 and p < 0.001, respectively). Mean values of operation time, intraoperative blood loss, length of hospital stay, and bone graft deviation were 532.5 ± 119.2 min, 1,006.8 ± 547.2 ml, 16.1 ± 6.3 days, and 0.9 ± 1.2 mm, respectively. Two trends of learning curve were observed in the CUSUM analyses of total operation time, length of hospital stay, and bone graft deviation, in which the first and second inflexion points occurred between 8 and 17 cases and between 43 and 46 cases, respectively.

Conclusion

Our results revealed a three-stage learning curve of CAJR with the use of PSSP, including initial learning, plateau, and overlearning. Based on CUSUM analysis, the surgical proficiency was achieved after 23 cases, and total operation time, length of hospital stay, and bone graft deviation stabilized after 8–17 cases.

3D printing in oral and maxillofacial surgery: a nationwide survey among university and non-university hospitals and private practices in Germany

OBJECTIVES

Oral and maxillofacial surgery (OMFS) has undergone pioneering progress through the development of three-dimensional (3D) printing technologies. The aim of this study was to evaluate the use of 3D printing at OMFS university and non-university hospitals and private practices in Germany.

MATERIALS AND METHODS

For explorative assessment, a dynamic online questionnaire containing 10-22 questions about the current use of 3D printing and the reasons behind it was sent to OMFS university and non-university hospitals and private practices in Germany by the study group from the German Association of Oral and Maxillofacial Surgery (DGMKG).

RESULTS

In total, 156 participants responded from university (23 [14.7%]) and non-university hospitals (19 [12.2%]) and private practices without (85 [50.5%]) and with 29 (18.6%) inpatient treatment facility. Highest applications of 3D printing were in implantology (57%), microvascular bone reconstructions (25.6%), and orthognathics (21.1%). Among the participants, 37.8% reportedly were not using 3D printing. Among the hospitals and private practices, 21.1% had their own 3D printer, and 2.5% shared it with other departments. The major reason for not having a 3D printer was poor cost efficiency (37.6%). Possessing a 3D printer was motivated by independence from external providers (91.3%) and rapid template production (82.6%). The preferred printing methods were stereolithography (69.4 %) and filament printing (44.4%).

CONCLUSIONS

OMFS 3D printing is established in Germany with a wide range of applications.

CLINICAL RELEVANCE

The prevalence of 3D printing in hospitals and private practices is moderate. This may be enhanced by future innovations including improved cost efficiency.

Impact of Planning Method (Conventional versus Virtual) on Time to Therapy Initiation and Resection Margins: A Retrospective Analysis of 104 Immediate Jaw Reconstructions

Simple Summary

Computer-aided design and manufacturing of osseous reconstructions are currently widely used in jaw reconstructive surgery, providing an improved surgical outcome and decreased procedural stumbling block. However, data on the influence of planning time on the time-to-surgery initiation and resection margin are missing in the literature. This retrospective, monocentric study compares process times from the first patient contact in hospital, time of in-house or out-of-house biopsy for tumor diagnosis and surgical therapy of tumor resection, and immediate reconstruction of the jaw with free fibula flaps (FFF). Two techniques for reconstruction are used: Virtual surgical planning (VSP) and non-VSP. A total of 104 patients who underwent FFF surgery for immediate jaw reconstruction from 2002 to 2020 are included. The study findings fill the gaps in the literature and obtain clear insights based on the investigated study subjects.

Abstract

Virtual surgical planning (VSP) and patient-specific implants are currently increasing for immediate jaw reconstruction after ablative oncologic surgery. This technique contributes to more accurate and efficient preoperative planning and shorter operation time. The present retrospective, single-center study analyzes the influence of time delay caused by VSP vs. conventional (non-VSP) reconstruction planning on the soft and hard tissue resection margins for necessary oncologic safety. A total number of 104 cases of immediate jaw reconstruction with free fibula flap are included in the present study. The selected method of reconstruction (conventionally, non-VSP: n = 63; digitally, VSP: n = 41) are analyzed in detail. The study reveals a statistically significant (p = 0.008) prolonged time to therapy initiation with a median of 42 days when the VSP method compared with non-VSP (31.0 days) is used. VSP did not significantly affect bony or soft tissue resection margin status. Apart from this observation, no significant differences concerning local tumor recurrence, lymph node, and distant metastases rates are found according to the reconstruction method, and affect soft or bone tissue resection margins. Thus, we conclude that VSP for immediate jaw reconstruction is safe for oncological purposes.

Intraoperative real-time navigation and intraoperative three-dimensional imaging for patient-specific total temporomandibular joint replacement

Customized solutions for replacement of the temporomandibular joint (TMJ) along with surgical guides enable precise and fast transfer of the virtual plan to the patient. However, these guides lack information on screw vectors and length, and well-defined borders for bony resections towards the medial skull base. This retrospective study was performed to investigate the feasibility and benefit of real-time navigation and intraoperative three-dimensional imaging during total TMJ replacement (TJR), as well as patient clinical outcomes. Between 2016 and 2020, 26 customized prostheses were implanted in 21 patients either with or without real-time navigation and instrument tracking. The clinical, surgical, radiological, and navigational data were analysed. The accuracy of navigation registration with instrument tracking, precision of screw insertion, and implant and screw positions were analysed by fusion of the virtual plan and surgical outcome. Real-time navigation aided orientation during lateral skull base dissection and resection. However, the results of real-time navigation-aided drilling were inconclusive regarding vector and length control. At a mean 15.3±3.0 months of follow-up, average mouth opening had improved from 21.69±2.80mm to 36.40±1.25mm; the average pain score decreased from 6.18±0.74 to 1.06±0.52. Thus, intraoperative real-time navigation for TJR assists lateral skull base dissection and resection.

Self-centering second-generation patient-specific functionalized implants for deep orbital reconstruction

Deep and complete reconstruction of the orbital cavity has been shown to be essential for preventing enophthalmos and hypoglobus in patients with orbital defects or deformities. Additively manufactured patient-specific titanium implants provide unlimited options in design. However, implant malpositioning can still occur, even when intraoperative imaging and navigation are used. In this study, we investigated novel orbital implants containing features facilitating self-centering. Accuracy of implant placement and reconstruction of the orbital dimensions were compared retrospectively between self-centering second-generation patient-specific functionalized orbital implants (study group) and CAD-based individualized implants (control group). Design features of implants in the study group included functionalization with navigation tracks, a preventive design, and flanges - so called stabilizers - towards opposite orbital walls. Implant position was evaluated by fusion of preoperative virtual plans and the post-therapeutic imaging. Aberrances were quantified by 3D heatmap analysis. 31 patients were assigned to the study group and 50 to the control group, respectively. In the study group, most implants were designed with either one (n = 18, 58.06%) or two (n = 10, 32.26%) stabilizers. Twice (6.45%), one stabilizer had to be shortened intraoperatively. Implant fit analysis revealed a significantly more precise (p < 0.001) positioning in the study group (n = 22/31) than in the control group (n = 42/50). Self-centering second-generation patient-specific functionalized orbital implants showed significantly more accurate implant positioning, facilitating the transformation of virtual plans into patient's anatomy. The presented design provides an additional instrument for intraoperative quality control besides intraoperative imaging and navigation.