Institutional-based and commercial virtual surgical planning in maxillomandibular reconstruction - Comparing the digital plan and postoperative scan

Computer-Assisted Surgery in Mandible Reconstruction

Computer-assisted surgery is the most significant recent advancement in osseous head and neck reconstruction. Computer-aided design (CAD) software allows computerized planning of resection and reconstruction. Computer-aided manufacturing (CAM) can be used to create models, cutting guides, and patient-specific plates. Several studies have shown that these techniques are more accurate and result in decreased flap ischemia times compared with conventional techniques. CAD also facilitates the immediate placement of dental implants. The most useful application of computer-assisted surgery is delayed reconstruction, in which soft tissue contraction and the absence of a specimen as a reference make accurate estimation of the defect challenging. The drawbacks of CAD/CAM are lack of intraoperative flexibility and cost. Some centers have created in-house CAD/CAM processes using open-source software and commercially available three-dimensional printers.

A comparison of preoperative soft tissue contour versus bone accuracy as a predictor of quality of life outcomes in osseous free flap jaw reconstruction using occlusal-based virtual surgical planning

OBJECTIVES

Occlusal-based virtual surgical planning (VSP) prioritises the placement of endosseous dental implants, over replicating native bone contour. This may compromise facial aesthetics. This study aimed to compare function and health-related quality of life (HRQOL) following maxillomandibular reconstruction according to the ability to replicate preoperative soft-tissue contour and virtual plan.

MATERIALS AND METHODS

Patients who underwent occlusal based VSP osseous free flap reconstruction of the maxilla or mandible with high-resolution pre- and post-operative facial computerised tomography imaging and completed the FACE-Q questionnaire were retrospectively identified. Accuracy of reconstruction compared to preoperative soft tissue contour and virtual plan, was measured using 3DSlicer® and CloudCompare® in three dimensions. Random effects modelling determined the associations between bony and soft tissue accuracy and HRQOL/functional domains.

RESULTS

Twenty-two patients met the inclusion criteria. For mandibular and maxillary reconstructions, better soft tissue accuracy was associated with improved appearance (p = 0.048) and appearance distress (p = 0.034). For mandibular reconstructions, better soft tissue accuracy was associated with improved smile (p = 0.039) and smile distress (p = 0.031). For maxillary reconstructions, better bony accuracy was associated with improved appearance (p = 0.023) and drooling distress (p = 0.001). Unexpectedly, better bony accuracy was associated with worse eating and drinking (p = 0.015), oral competence (p = 0.005) and eating distress (p = 0.013) in mandibular reconstructions.

CONCLUSION

Whilst soft tissue accuracy was associated with better functional and HRQOL outcomes, bone accuracy was associated with worse oral function or distress in mandibular reconstruction. These results require validation but should be considered when performing occlusal-based VSP, which prioritises dental rehabilitation over replicating facial bony contour.

What is the force required to treat trismus in patients undergoing oral cavity free flap reconstruction?

BACKGROUND

Trismus therapy is often delayed after jaw reconstruction to avoid hardware failure or non-union. The aim of this study is to document the forces that have been applied to patients undergoing free flap reconstruction of the oral cavity in the 12 months following oral cavity reconstruction, and to analyze the associations between force and maximal interincisal opening (MIO) over time.

METHODS

Participants with trismus after free flap reconstruction of the oral cavity completed a 10-week jaw stretching program using Restorabite™. Primary outcome measures included the minimum and maximal force applied by a trismus device during rehabilitation, MIO, bone union, and health-related quality of life outcomes up to 12 months postoperatively.

RESULTS

A mean of 20.6 Newtons (N) was used during passive exercises and 38.9 N during active exercises was used during trismus therapy. The mean increase in MIO for the 45 participants after 10 weeks, 6 months, and 12 months of therapy was 8.4 mm (p < 0.001), 12.6 mm (p < 0.001), 12.7 mm (p < 0.001), respectively. There was no significant difference in the mean minimal (p = 0.37) or mean maximal (p = 0.08) force applied between those who underwent osseous free flap reconstruction compared to fasciocutaneous only, respectively. In patients who underwent osseous reconstruction, 25 (67.6%) had complete bone union and 12 (32.4%) had partial union at 12 months postsurgery.

CONCLUSIONS

In participants undergoing osseous free flap reconstruction, there was no association between the force applied to the rates of bone union. Further research to define safe and optimal loading may benefit patients undergoing jaw reconstruction.

A Preclinical Trial Protocol Using an Ovine Model to Assess Scaffold Implant Biomaterials for Repair of Critical-Sized Mandibular Defects

The present work describes a preclinical trial (in silico, in vivo and in vitro) protocol to assess the biomechanical performance and osteogenic capability of 3D-printed polymeric scaffolds implants used to repair partial defects in a sheep mandible. The protocol spans multiple steps of the medical device development pipeline, including initial concept design of the scaffold implant, digital twin in silico finite element modeling, manufacturing of the device prototype, in vivo device implantation, and in vitro laboratory mechanical testing. First, a patient-specific one-body scaffold implant used for reconstructing a critical-sized defect along the lower border of the sheep mandible ramus was designed using on computed-tomographic (CT) imagery and computer-aided design software. Next, the biomechanical performance of the implant was predicted numerically by simulating physiological load conditions in a digital twin in silico finite element model of the sheep mandible. This allowed for possible redesigning of the implant prior to commencing in vivo experimentation. Then, two types of polymeric biomaterials were used to manufacture the mandibular scaffold implants: poly ether ether ketone (PEEK) and poly ether ketone (PEK) printed with fused deposition modeling (FDM) and selective laser sintering (SLS), respectively. Then, after being implanted for 13 weeks in vivo, the implant and surrounding bone tissue was harvested and microCT scanned to visualize and quantify neo-tissue formation in the porous space of the scaffold. Finally, the implant and local bone tissue was assessed by in vitro laboratory mechanical testing to quantify the osteointegration. The protocol consists of six component procedures: (i) scaffold design and finite element analysis to predict its biomechanical response, (ii) scaffold fabrication with FDM and SLS 3D printing, (iii) surface treatment of the scaffold with plasma immersion ion implantation (PIII) techniques, (iv) ovine mandibular implantation, (v) postoperative sheep recovery, euthanasia, and harvesting of the scaffold and surrounding host bone, microCT scanning, and (vi) in vitro laboratory mechanical tests of the harvested scaffolds. The results of microCT imagery and 3-point mechanical bend testing demonstrate that PIII-SLS-PEK is a promising biomaterial for the manufacturing of scaffold implants to enhance the bone-scaffold contact and bone ingrowth in porous scaffold implants. MicroCT images of the harvested implant and surrounding bone tissue showed encouraging new bone growth at the scaffold-bone interface and inside the porous network of the lattice structure of the SLS-PEK scaffolds.

Trends in free flap reconstruction of the head and neck: a single surgeon series of 1027 free tissue transfers

BACKGROUND

Free tissue transfer has fundamentally changed head and neck surgery, enabling reliable reconstruction of large defects with better function and aesthetics. This study assesses two decades of trends in free flap reconstruction, and how disease incidence, survival, surgeon caseload, team approach, and technology have impacted practice.

METHODS

Retrospective analysis of 1027 head and neck free flaps from 2006 to 2022. Outcomes examined include chronological changes in flap selection, indication, length of stay, incorporation of virtual surgical planning (VSP), annual caseload, survival, and their associations with the single versus multi-team approach.

RESULTS

There were 764 soft-tissue and 263 osseous reconstructions utilizing 21 different flaps. Anterolateral thigh and radial forearm accounted for 76.7% of soft tissue flaps, with recent increase in superficial circumflex iliac perforator flaps in young patients. Osseous flap proportion remained stable, but fibula flaps increased five-fold with more VSP, dental implants, oral cancer, and multi-team surgery. Outcomes such as complication rates, length of stay and disease specific/overall survival have improved over time despite increasing complexity (P = 0.001, P = 0.001, P < 0.001, and P < 0.001, respectively). However, there was no significant difference in operative time, complication rate, or disease specific/overall survival between single team or multi-team approaches (P = 0.45, P = 0.054, P = 0.57, and P = 0.60, respectively).

CONCLUSION

Single and multi-team approaches may have similar fundamental outcomes, but as caseload, complexity, and life-expectancy increases, both patients and surgeons benefit from a collaborative multi-team approach that focuses on improving long-term functional outcomes.

Evolution of Medical Modeling and 3D Printing in Microvascular Midface Reconstruction: Literature Review and Experience at MD Anderson Cancer Center

Reconstruction of the midface represents a challenge for reconstructive microsurgeons given the formidable task of restoring both aesthetics and functionality. In particular, preservation of proper globe positioning and maintaining normal vision are as important as restoring the proper projection of the midface and enabling a patient to speak and eat as normally as possible. The introduction of virtual surgical planning (VSP) and medical modeling has revolutionized bony reconstruction of the craniofacial skeleton; however, the overwhelming majority of studies have focused on mandibular reconstruction. Here, we introduce some novel advances in utilizing VSP for bony reconstruction of the midface. The present review aims (1) to provide a review of the literature on the use of VSP in midface reconstruction and (2) to provide some insights from the authors' early experience.

Clinical application of 3-dimensional tissue volume assessment using CloudCompare

Adjunctive procedures, including autologous fat grafting and surgical debulking, may be required to optimise facial contours following maxillomandibular reconstruction. A standardised method for the quantitative analysis of volumetric change and the impact of restoration of facial symmetry on health-related quality of life remains unclear. We use two case studies to illustrate the value of a combination of objective 3-dimenmsional (3D) measurements, clinical assessments, and patient-reported outcomes, using the FACE-Q questionnaire to elucidate the benefits of adjunctive procedures.