ABSTRACT
Abstract Introduction Stapes surgery for otosclerosis is a precise surgical procedure. To achieve excellent hearing results, a firm and stable attachment of the prosthesis to the long process of incus (LPI) is necessary. The present study provides details on the attachment site in two dimensions to choose an appropriate prosthesis and to ensure firm attachment for better surgical outcomes. Objective To study the diameter of the LPI and its relevance in determining the piston, used in stapes surgery by an in vivo method. Methods This study was conducted in 41 patients who underwent stapedotomy, where both Anteroposterior (AP) and Mediolateral (ML) diameters of the LPI were measured at the site of attachment of the piston using specially designed instruments, intraoperatively. Radiological data were obtained to measure the LPI diameter from the normal ears of 46 patients. It was measured from both the right and left side, hence 92 LPI diameters were obtained. Results The most commonly used site for prosthesis attachment is between 1-1.5 mm away from the tip of the LPI. We found great variability in the diameters of LPI in the attachment site, with the AP diameter ranging between 0.6 -1.5mm and the ML diameter ranging between 0.5mm-1.2mm. Conclusion Pistons by design have characteristics of gripping incus that will vary between types. Based on LPI dimensions, ideal piston types with appropriate inner loop diameters are suggested in this study. HRCT before surgery should include measurements of the LPI as a guide to the choice of the prosthesis during surgery.
ABSTRACT
Abstract Introduction Observing the obliquity of stapes by closely scrutinizing the HRCT temporal bone in otosclerosis revealed a reliable and consistent finding. This finding can add to the existing radiological criteria in diagnosis of otosclerosis. Objective The objective of this study is to establish the obliquity of stapes in otosclerosis by radiological measurements using HRCT temporal bone by comparing: (a) the distance between the horizontal (tympanic) segment of facial nerve and stapes head in otosclerotic ears (study group) with non-otosclerotic ears (control group); and (b) the angle subtended by stapes with promontory in the study and control groups. Methods This is a prospective study performed after the institutional Ethics Committee clearance (IEC 3/2013). Results An increased mean distance between the horizontal segment of facial nerve and stapes head in otosclerotic patients (i.e., 2.49mm +/ 0.24mm SD), when compared with the non-otosclerotic patients (i.e., 1.46mm +/ 0.16mm SD) is noted. There is a change in angle (i.e., 64.550 +/ 7.190 SD) subtended by the stapes toward the promontory in otosclerotic ears when compared with that of controls (i.e., 99.700 +/ 40 SD). We applied the Mann-Whitney U non-parametric test and considered p value of < 0.0001 highly significant. Conclusions Obliquity of stapes in otosclerosis referred to as a "Pisa" sign by the senior author has diagnostic value as a new radiological sign in imaging of otosclerosis. This obliquity explains the torsional effect of otosclerosis on the ossicular chain. The findings correlate with late complications and failures in stapes surgery.