The use of high-resolution ct (HRCT) of the temporal bone for accurate preoperative prediction of stapes prosthesis length in patients with otosclerosis

Introduction Otosclerosis is managed surgically by stapedotomy or stapedectomy with the insertion of a stapes prosthesis. An ideal prosthesis length and accurate placement are crucial for good surgical and hearing outcomes. Methods This retrospective review was conducted on 179 ears diagnosed with otosclerosis that underwent stapes surgery at our institution between January 2014 and March 2023. Preoperative high–resolution computed tomography (HRCT) imaging of the temporal bone was used to measure the distance between the long process of the incus and the stapes footplate. The measurements were independently obtained by two otolaryngologists (observers 1 and 2) and a radiologist (observer 3). The actual measured and rounded values were analyzed and compared along with the inter-observer agreement for prosthesis length and accuracy predictability. Results The mean radiological distance measured from preoperative HRCT imaging was 4.25 mm (range = 4.1 to 4.4 mm). The interobserver agreement was moderately reliable between observer 1 and 2 (ICC 0.57; 95% CI: 0.43, 0.68); between observer 2 and 3 (ICC 0.58; 95% CI: 0.43, 0.68); between observer 3 and the actual length of prosthesis used (ICC 0.50; 95% CI: 0.32, 0.62). When measurements by the radiologist were rounded to the nearest 0.25 mm, 43% (78) of cases matched exactly with the prosthesis used intraoperatively, 22% ( n = 39) showed a value 0.25 mm higher, and 16% ( n = 29) showed a value 0.25 mm lower than the actual length of the prosthesis used. Conclusion Although radiological measurements from HRCT imaging cannot replace the current method of intraoperative measurement of stapes prosthesis length, when the measurement process is difficult, the values measured by a radiologist could be used to estimate the prosthesis length required.