Optimal Head Position Following Intratympanic Injections of Steroids, As Determined by Virtual Reality.

OBJECTIVES

To study optimal head position after intratympanic steroid injections to enhance drug bioavailability.

STUDY DESIGN

Application of virtual and in vitro models of the intratympanic anatomy.

SETTING

The surgical 3-dimensional printing laboratory of a tertiary academic medical center.

SUBJECTS AND METHODS

A high-resolution computerized tomographic scan of healthy temporal bone and surrounding soft tissue was segmented and reconstructed to a 3-dimensional model. The tympanic membrane was perforated in the posterior-inferior quadrant. Methylene blue-stained 10-mg/mL dexamethasone was administered to the middle ear cleft, after which a 3-dimensional rotation in space was performed to hypothesize the optimal position in relation to gravity. The same stereolithography file used for the actual model was used for a digital virtual liquid flow simulation. The optimal head position was defined as the one with the maximum vertical distance between the round window membrane and the plane of the aditus ad antrum and eustachian tube orifice.

RESULTS

The virtual model yielded the following position of the head as optimal: 53º rotation away from the injected ear in the vertical axis (yaw), 27º rotation toward the noninjected ear in the longitudinal axis (roll), and 10º neck extension in the transverse axis (pitch).

CONCLUSIONS

Virtual imaging determined that 53º and 27º yaw and roll, respectively, away and 10º pitch were the optimal position for drug delivery after intratympanic injection to the middle ear and that an erect head position provided optimal passage of steroids from the middle ear to the inner ear.