The most commonly performed osteotomy of the lower jaw for occlusal realignment is the sagittal split ramus osteotomy. (SSRO) This cleverly designed osteotomy splits the mandible ramus in a sagittal direction which allows the distal segment containing the teeth to move forward or back. Once the lower teeth are aligned with the upper teeth, the proximal and distal mandibular ramus split segments are then put back together with either bicortical screws or outer cortical plates and screws.
While SSRO mandibular osteotomies have a very high rate of successful bony healing there are changes that can occur in the preoperative shape of the angle bone. This can occur due to changes in its preoperative position, bone resorption from a devascularizing effect, inadvertent fracture of the seaments or some combination of any of these. This can and does typically occur more on one side but can also involve differing shape changes. Corrections of such post-orthognathic surgery jaw angle changes requires a precise method to do so.
In the October 2020 issue of the Journal of Craniofacial Surgery an article was published on this topic entitled ‘Patient Specific Implants to Solve Structural Facial Asymmetry After Orthognathic Surgery’. In this paper the authors describe a single case report of a young male patient who after orthognathic surgery had a right jawline deformity. This was treated by a two-piece PEEK implant generated from a 3D CT scan based on the shape of the left side. It was inserted through an intraoral approach in two pieces and reassembled once inside the elevated subperiosteal pocket. A contralateral reduction as done in the high body area of the mandibular body. After a one year follow-up no infection or complication was observed and facial symmetry was improved.
This single case study is reflective of one of the more common reasons people seek custom jawline implants in my practice. In this paper they choose to call a custom made implant a patient specific implant…but they are one and the same. It is impossible to ever match one side of a jawline bony contour defect to the other normal side without a 3D CT scan and computer design process.
In designing custom jaw angle/jawline implant for previous sagittal split osteotomy sites there almost always is existing plate and screw hardware in the area. This is useful in the implant design process as it can serve as a registration in the implant design for intraoperative implant positioning. Thus rather using this as an opportunity to remove the hardware (which can be very difficult to do) it is used in the implant design to help intraoperatively place the implant.
Dr. Barry Eppley