Validity and Responsiveness of Measuring Facial Swelling With 3D Stereophotogrammetry in Patients After Bilateral Sagittal Split Osteotomy-A Prospective Clinimetric Study.

Introduction: This study is aimed at determining the validity and responsiveness of three-dimensional (3D) stereophotogrammetry as a measurement instrument for evaluating soft tissue changes in the head and neck area. Method: Twelve patients received a bilateral sagittal split osteotomy (BSSO). 3D stereophotogrammetry, tape measurements, and a global perceived effect scale were performed within the first, second, and third postoperative weeks and at 3 months postoperatively. Distance measurements, mean and root mean square of the distance map, and volume differences were obtained from 3D stereophotogrammetry. Validity and responsiveness were assessed by correlation coefficients. Results: Significant correlations between distances from 3D stereophotogrammetry and tape measurements varied from 0.583 to 0.988, meaning moderate to very high validity. The highest correlations were found for the total sum of distances (r ≥ 0.922). 3D stereophotogrammetry parameters presented weak to high responsiveness, depending on the evaluated head and neck region. None of the parameters for 3D stereophotogrammetry significantly correlated with the global perceived effect scale outcomes for all measurement moments. Conclusion: 3D stereophotogrammetry has high to very high construct validity for the total sum of distances and weak to high responsiveness. 3D stereophotogrammetry seems promising for measuring soft tissue changes after surgery but is not interchangeable with subjective measurements.