Accuracy of Two Different Patient-Specific Drill/Cutting Guides for Maxillary Repositioning When Used for Minimally Invasive Bimaxillary Orthognathic Surgery.

BACKGROUND

Minimally invasive orthognathic surgery (MIOS) involves smaller incisions and minimal tissue dissection. Most MIOS is done using interim splints to position the first jaw. The application of patient-specific implants in MIOS is difficult due to the size of traditional cutting/drill guides, which require larger incisions. As a result, MIOS guides were redesigned for this study to fit into smaller incisions.

PURPOSE: The study purpose was to estimate and compare the accuracy of the smaller and redesigned bone-borne (BB) versus bone/tooth-borne (BTB) cutting/drilling guides used in minimally invasive bimaxillary orthognathic surgery.

STUDY DESIGN, SETTING, SAMPLE: This retrospective cohort study included consecutive MIOS patients treated by a single surgeon at the University of Texas Health San Antonio from June 2023 to September 2024. It included patients that underwent bimaxillary MIOS with complete preoperative and postoperative cone-beam computed tomographic records. Exclusion criteria included craniofacial syndromes, severe medical comorbidities, or single-jaw surgery.

PREDICTOR VARIABLE: The primary predictor variable was the type of cutting/drilling guide (BB vs BTB) used to perform maxillary osteotomy.

MAIN OUTCOME VARIABLE(S): The primary outcome variable was accuracy, defined as mean linear discrepancy that is closest to 0 mm. Linear discrepancies between planned and actual maxillary movements were measured.

COVARIATES: Demographics and malocclusion type.

ANALYSES: χ2 tests compared categorical variables, and Student's t-tests assessed accuracy differences. A P value < .05 was considered significant, with a Bonferroni correction applied for multiple comparisons.

RESULTS

The sample consisted of 20 patients (15 females, 75%; 5 males, 25%; mean age 24 ± 11.3 years) evenly divided into BB (n = 10) and BTB (n = 10) guide groups. The BTB guide demonstrated superior vertical accuracy for the upper incisor (mean difference: 0.67 mm, standard deviation = 0.33, P = .02) and the upper left canine (mean difference: 0.11 mm, standard deviation = 0.04, P = .03) when comparing means. However, no significant differences were found in root mean square discrepancies (P > .2) or other measurements (P > .06).

CONCLUSIONS AND RELEVANCE: Both guides achieved acceptable accuracy overall, with the BTB guide showing superior precision for 2 of the 11 landmarks.