Computer assisted reduction malarplasty using angled double L-shaped osteotomies

Objective To assess the clinical outcome of the novel computer assisted reduction malarplasty using angled double L-shaped osteotomies. Methods Retrospective analysis of the 35 female patients who received reduction malarplasty surgery during June 2014 to April 2019 was conducted. Patients were divided into the conventional surgery group (9 cases) and the computer assisted surgery group (26 cases) based on their personal will. For the conventional surgery group, the zygomatic arch was repositioned inwardly after L-shaped osteotomy, and was rigidly fixed with miniplates and screws. The computer assisted reduction malarplasty was as follows: computer assisted angled double L-shaped osteotomies with surgical guide was performed intraorally, and the pre-bent titanium was used to setback the resected zygoma bone, which was then fixed with titanium miniplates and screws. Operation time, patients’ satisfaction (3-month follow-up) and postoperative complications (asymmetry and bone nonunion) were recorded and assessed. CT scans were performed to compare the preoperative design and 3-month postoperative follow-up for the computer assisted patient group. For statistical analysis, independent sample t test was used to analyze operation time of the 2 groups and chi-square test was used to analyze the data of patients’ satisfaction and asymmetry occurrence. P<0.05 was considered as statistically significant. Results The mean operation time was (85.1 ± 17.8) min during computer assisted surgery versus (62.2±11.7) min during conventional surgery. The difference between the two groups was statistically significant (t=3.53, P=0.020). Neither group showed noticeable resected bone shifting or soft tissue drooping. One patient in the conventional surgery group had bone nonunion on the right zygoma and partial absorption of the left zygomatic bone. The incidence of asymmetry in the computer-assisted group was 3.8% (1/26, surgical correction was not required), and 33.3% in the conventional surgery group (3/9, one patient required surgical correction). There was a statistically significant difference between the two groups (χ2=6.179, P=0.046). Patients’ satisfaction in the computer-assisted group was 100% (26/26), and 78% (7/9) in the conventional surgery group (χ2=7.929, P=0.019). Comparisons between the postoperative CT and preoperative simulation CT images showed that the position deviation of the resected bones was (0.21 ± 0.19) mm. Conclusions In the present study, improved precision of zygomatic bone resection and bone setback was achieved in reduction malarplasty by using the angled double L-shaped osteotomies with computer assistance. Moreover, complication occurrences (asymmetry, bone nonunion etc.) were significantly decreased. Also, patients’ expectation was better achieved with this method. Key words: Zygomatic hypertrophy; Surgery, computer-assisted; Osteotomy, L-shaped; Surgical guide