How VSP and 3D-Printed PSI Enable the MI-PSI Approach for Orthognathic surgery

Minimally invasive surgery (MIS) has gained its attention in various surgical disciplines, most notably in laparoscopy and orthopedic arthroplasty, gaining significant momentum in the late 1980s and 1990s. In these fields, the primary objective was the reduction of surgical trauma to accelerate post-operative recovery and minimise cicatricial complications.

In Orthognathic Surgery, the adoption of MIS principles appeared later, primarily due to the anatomical complexity of the maxillofacial skeleton and the critical need for precise occlusal relationships. While the first minimally invasive Le Fort I osteotomies were discussed in the early 2000s [1], the movement remained limited by the inability to visualise the bone through small soft-tissue windows. The emergence of high-resolution Computed Tomography (CT), Virtual Surgical Planning (VSP), and 3D-printed Patient-Specific Implants has since bridged this gap, allowing for precision through guided technology.

Comparison of Orthognathic Surgical Frameworks

1. Conventional Orthognathic Surgery: The traditional approach relies on extensive mucoperiosteal flaps to provide the surgeon with adequate direct visualisation of the osteotomy sites.

• Planning: Manual cephalometric analysis and stone model surgery.

• Hardware: Standard miniplates.

• Challenges: The need for wide exposure increases the risk of post-operative edema, ischemia to the bone segments (potentially affecting stability), and increased risk to neurovascular structures, such as the infraorbital or inferior alveolar nerves [2]

2. Virtual Surgical Planning (VSP)+ Patient-Specific Implant (PSI) with Standard Exposure

The introduction of VSP allowed surgeons to move from the lab to the digital environment.

• Planning: 3D workflows to simulate movements.

• Hardware: A Patient-Specific Implant (PSI) and cutting guides are manufactured via additive manufacturing (3D printing).

• Benefit: Eliminates the error inherent in manual plate bending and intraoperative trial and error positioning. Surgeons still utilise standard incisions to ensure the guide fits perfectly against the bone [3].

3. Minimally Invasive (MI) Patient-Specific Implant (PSI) + Virtual Surgical Planning (VSP)

The current frontier involves combining VSP with limited-access incisions (e.g., small vestibular incisions for Le Fort I).

• Planning: 3D workflows to simulate movements.

• The Workflow: The surgery is performed through smaller access. Because the surgeon cannot see the entire bone, they rely entirely on the accuracy of the 3D-printed guide and the plate.

• Mechanism: Cutting guides are designed to seat on specific anatomical landmarks through small incisions. The Patient-Specific Implant then acts as the final jig, dictating the exact spatial position of the bone segments according to the digital plan.

Clinical Benefits of the MI-PSI Approach

The integration of MI techniques with Patient-Specific Implants offers several documented advantages for both the surgeon and the patient:

• Reduced Post-operative Edema: By maintaining greater soft-tissue attachment and minimising periosteal stripping, lymphatic and venous drainage are better preserved [4].

• Vascular Integrity: Limited dissection preserves the nutrient blood supply to the osteotomised segments, which is theorized to improve healing and long-term skeletal stability.

• Accuracy and Predictability: The use of a Patient-Specific Implant eliminates the need for intraoperative repositioning of the maxillomandibular complex (MMC) using an intermediary splint, which can be a source of vertical error.

• Operative Efficiency: Even though digital planning takes more effort beforehand, the surgery itself is faster because the 3D-printed guides and plates are ready to use [4].

The transition toward minimally invasive orthognathic surgery represents a logical progression in the quest for reduced patient morbidity and increased surgical precision. While the conventional approach remains a reliable and necessary skill set for complex secondary cases or trauma, the MI-PSI framework offers a sophisticated alternative for routine dentofacial deformities.

Ultimately, the choice between conventional and minimally invasive techniques should be dictated by the specific clinical requirements of the case, the surgeon's experience with digital tools, and the patient’s biological needs. As 3D printing technology becomes more accessible, the integration of the Patient-Specific Implant is likely to become an increasingly standard component of the maxillofacial armamentarium, though it remains one tool among many in the surgeon's repertoire.

Reference

[1] P.G. Morselli, Surgical maxillary expansion: a new minimally invasive technique, Journal of Cranio-Maxillofacial Surgery. 1997, 25(2): 80-84.

[2] Kim YK. Complications associated with orthognathic surgery. J Korean Assoc Oral Maxillofac Surg. 2017 Feb;43(1):3-15.

[3] Strujak G, Marlière DAA, Medeiros YL, Guariza Filho O, Carlini JL, Westphalen VPD. Virtual Versus Conventional Planning in Orthognathic Surgery: A Systematic Review and Meta-analysis. J Maxillofac Oral Surg. 2024 Apr;23(2):219-228.

[4] Swennen GRJ, de O. Andriola F, Weinberg Y. A New Concept Toward Minimally Invasive (MI) Orthognathic Surgery. 2023 Nov 28. In: Swennen GRJ, editor. Minimally Invasive (MI) Orthognathic Surgery: A Systematic Step-by-Step Approach [Internet]. Cham (CH): Springer; 2023.