Simultaneous PSI-Based Orthognathic and PEEK Bone Augmentation Surgery Leads to Improved Symmetric Facial Appearance in Craniofacial Malformations

Abstract

(1) The aim of the present study was to compare the outcome of facial symmetry after simultaneous digitally planned patient-specific implant (PSI-) based orthognathic surgery and polyether ether ketone (PEEK) bone augmentation in patients with craniofacial malformations. (2) To evaluate the outcome of the two different surgical approaches (conventional PSI-based orthognathic surgery versus simultaneous PSI-based orthognathic surgery with PEEK bone augmentation), a comparison of five different groups with a combination of the parameters (A) with vs. without laterognathia, (B) syndromic vs. non-syndromic, and (C) surgery with vs. without PEEK bone augmentation was conducted. The digital workflow comprised cone beam CT (CBCT) scans and virtual surgery planning for all patients in order to produce patient specific cutting guides and osteosynthesis plates. Additionally, deformed skulls were superimposed by a non-deformed skull and/or the healthy side was mirrored to produce PSI PEEK implants for augmentation. Retrospective analyses included posterior-anterior conventional radiographs as well as en face photographs taken before and nine months after surgery. (3) Simultaneous orthognathic surgery with PEEK bone augmentation significantly improves facial symmetry compared to conventional orthognathic surgery (6.5%P (3.2-9.8%P) (p = 0.001). (4) PSI-based orthognathic surgery led to improved horizontal bone alignment in all patients. Simultaneous PEEK bone augmentation enhanced facial symmetry even in patients with syndrome-related underdevelopment of both soft and hard tissues.

Keywords: PEEK; craniofacial malformation; craniofacial reconstruction; digital workflow; orthognathic surgery; patient-specific implants.

Figure 1

Preoperative virtual planning. Baseline situation as identified by CBCT. Color-coded: maxilla (turquoise), corpus mandibulae (yellow), and rami mandibulae (purple).

Figure 2

Preoperative virtual planning. The surgical procedure is planned virtually in advance and the three jaw components (maxilla (turquoise), corpus mandibulae (yellow) and rami mandibulae (purple)) are aligned three-dimensionally in position, tilt, and rotation. (a) Frontal view, (b) lateral view.

Figure 3

Superimposition strategy. Patient skull after virtual planning of PSI-based orthognathic surgery (gray) and standard skull (beige).

Figure 4

Superimposition of patient skull and standard skull (after adjustment of size). Superimposed and color-marked are the planned postoperative hard tissue contours (gray) and the standard skull (beige).

Figure 5

Simultaneous superimposition and mirroring strategy. Superimposed and color-marked are the planned postoperative hard tissue contours (gray), the hard tissue contours mirrored along the median sagittal axis (green), and the standard skull (beige).

Figure 6

Photographic landmarks and axes as described in Table 2. Ideally the vertical midfacial plane (MP) should be perpendicular to all six axes axis of lateral eyebrows (ALE), bipupillary line (BL), axis of tragi (AT), axis of mouth angle (AMA), axis of jaw angles (AJA), and chin base (CB). Midfacial plane is defined as the axis between the glabella (13) and the tip of the nose (14) and represents a continuous perpendicular to the horizontal facial planes.

Figure 7

Radiological landmarks and axes as described in Table 3. Ideally the vertical (MP) should be perpendicular to all six axes axis of lateral orbital walls (ALOR), axis of orbital floors (AOF), axis of temporomandibular joints (ATMJ), occlusal plane (OP), axis of jaw angles (AJA), and chin base (CB).

Figure 8

Radiological distances as described in Table 4. These were divided into a left and right part by midfacial plane (red). Ideally the left part of the distance should be as long as the right part.

Figure 9

Extent of angular normalization in soft tissue after complete surgical treatment. Columns representing mean symmetry changes in degrees of soft tissue in each group. Mean values of preoperative and postoperative symmetry deviations were subtracted resulting in positive values for improvement and deterioration of symmetry. Both axis of lateral eyebrows (ALE) (light blue), bipupillary line (BL) (dark green) as well as axis of tragus (AT) (violet) show only few changes in all groups. Axis of mouth angle (AMA) (orange), axis of jaw angle AJA (dark violet), and chin base CB (green) show improvements in facial symmetry in group 2, 3, 4, and 5. However, largest improvements could be investigated in group 5.

Figure 10

Extent of angular normalization in hard tissue after complete surgical treatment. Each column demonstrates mean values of angular changes in degrees of hard tissue after surgical treatment in each group. Mean values of preoperative and postoperative symmetry deviations were subtracted resulting in positive values for improvement and deterioration of symmetry. Both axis of lateral orbital rim (ALOR) (light blue), axis of orbital floor (AOF) (dark green) as well as axis of temporomandibular joints (ATMJ) (purple) show only few changes. Both axes occlusal plane (OP) (orange), axis of jaw angles (AJA) (dark purple), as well as chin base (CB) (green) show improvements in facial symmetry in group 2, 3, 4, and 5. However, largest improvements could be investigated in group 5.

Figure 11

Comparison of pre- and postoperative discrepancy. Mean percentage discrepancy of facial left side versus right side at different levels (ZB = zygomatic bone (blue), OP = occlusal plane (red), and JA = jaw angle (green)) pre- and postoperative. Deviations on the level of zygomatic bone (blue) stay the same, while each group shows less deviation on the levels of occlusal plane (red) and jaw angle (green) after surgical treatment. Groups 4 and 5, in particular, show massively decreased discrepancy after surgical treatment.

Figure 12

Boxplots displaying change of discrepancy in percentage points subdivided into groups 1–5. Positive values are improvements in symmetry, while negative values mean a deterioration in symmetry. Improvements occur at the levels of jaw angle (blue) and occlusal plane (green). However, there are no changes in the discrepancy at the level of zygoma (red) in any of the groups.

Figure 13

Scatter plot displaying reduction of discrepancy in percentage points (change of discrepancy) vs. amount of preoperative asymmetry (discrepancy pre-op).

Figure 14

Boxplots displaying change of discrepancy in percentage points subdivided into orthognathic surgery only (cumulative groups 1, 2, and 3) and orthognathic surgery with additional PEEK bone augmentation (cumulative groups 4 and 5). Positive values are improvements in symmetry, while negative values mean a deterioration in symmetry. Improvements occur at the levels of jaw angle (blue) and occlusal plane (green) with mean 2.4 percentage points in orthognathic surgery only and mean 8.9 percentage points in orthognathic surgery with additional PEEK bone augmentation. However, there are no changes in the discrepancy at the level of zygoma (red) in any of the groups.

Figure 15

Angular deviation from ideal angle to midfacial plane (90°) after complete surgical treatment.

Figure 16

Linear distance discrepancy of left vs. right facial halves subdivided by all levels after surgical treatment in all five groups.