Oval Window Size and Shape: a Micro-CT Anatomical Study With Considerations for Stapes Surgery.

Background: The oval window is an important structure with regard to stapes surgeries, including stapedotomy for the treatment of otosclerosis. Recent study of perioperative imaging of the oval window has revealed that oval window niche height can indicate both operative difficulty and subjective discomfort during otosclerosis surgery. With regard to shape, structures incorporated into the oval window niche, such as cartilage grafts, must be compatible with the shape of the oval window. Despite the clinical importance of the oval window, there is little information regarding its size and shape.

Methods: This study assessed oval window size and shape via micro-computed tomography paired with modern morphometric methodology in the fetal, infant, child, and adult populations. Additionally, the study compared oval window size and shape between sexes and between left- and right-sided ears.

Results: No significant differences were found among traditional morphometric parameters among age groups, sides, or sexes. However, geometric morphometric methods revealed shape differences between age groups. Further, geometric morphometric methods provided the average oval window shape and most-likely shape variance.

Conclusion: Beyond demonstrating oval window size and shape variation, the results of this report will aid in identifying patients among whom anatomical variation may contribute to surgical difficulty and surgeon discomfort, or otherwise warrant preoperative adaptations for the incorporation of materials into and around the oval window.