3D CT Scans Reveal Hidden Ear Bone Defects Before Hearing Surgery

Deep inside the temporal bone, three of the smallest bones in the human body work in concert to carry sound from the eardrum to the inner ear. When this ossicular chain fails, sound no longer reaches the cochlea efficiently, and the result is conductive hearing loss. The diagnostic puzzle is most frustrating when the eardrum looks perfectly normal, because the structural culprit can hide anywhere along the chain. A new retrospective study from Xi’an Jiaotong University, published in BMC Medical Imaging, shows how high-resolution computed tomography combined with physician-directed three-dimensional reconstruction can sharpen the preoperative picture in exactly these cases, and how far the technology still falls short.

The research team, led by Heng Li, Ying Cheng, Xiaotong Zhang and corresponding author Weijun Ma, reviewed 33 consecutive patients representing 35 operated ears treated between June 2018 and August 2024. Every patient underwent the same triad of assessments: audiologic testing to quantify the hearing deficit, temporal-bone high-resolution computed tomography with post-processing guided by the treating physicians, and exploratory tympanotomy, the surgical exploration of the middle ear that served as the definitive anatomic reference. Ossicular reconstruction was carried out whenever it was technically feasible and judged safe, which ultimately applied to all 33 ears for which hearing outcomes were analyzed.

What the surgeons found at the operating table was strikingly different from what a casual reading of hearing tests might suggest. Eight ears were diagnosed with otosclerosis, the abnormal fixation of the stapes footplate, and in every one of those ears the footplate was indeed immobile at surgery. The remaining diagnoses were dominated by congenital ossicular anomalies, which accounted for 25 ears, while traumatic ossicular discontinuity explained just two. That distribution underscores why imaging matters: congenital malformations of the middle ear bones can produce significant hearing loss behind an entirely intact tympanic membrane, and their anatomy varies from patient to patient in ways that directly shape the surgical plan.

The headline number from the study is a 97.0 percent patient-level agreement between the integrated preoperative diagnostic impression and the principal operative diagnosis, with the impression matching surgery in 32 of 33 patients. The authors are careful, and rightly so, about what this figure means. It reflects the combined weight of clinical examination, audiometry and CT findings, not the diagnostic accuracy of CT alone. The Wilson 95 percent confidence interval, ranging from 84.7 to 99.5 percent, also reminds readers that with a sample of this size the true rate could be somewhat lower. The single discordant case was a fibrous incudostapedial connection, a soft-tissue bridge between the incus and stapes that CT could not resolve.

That limitation is not a footnote; it is central to the study’s message. The authors explicitly note that stapes fixation and fibrous ossicular connections may remain occult on CT. Otosclerosis, in particular, is often a diagnosis of exclusion supported by audiometric patterns and surgical palpation rather than by direct visualization on a scan. Fibrous bands, being soft tissue of similar density to surrounding structures, sit below the resolution threshold of even high-resolution temporal bone protocols. Surgeons reading these images must therefore hold two possibilities in mind simultaneously: the anatomy the CT displays, and the pathology it cannot.

Where the imaging genuinely shines is in anticipating reconstruction requirements. Multiplanar reformation allows radiologists and surgeons to scroll through the ossicular chain in axial, coronal and sagittal planes, while three-dimensional reconstruction renders the malleus, incus and stapes as discrete, rotatable structures. For congenital anomalies, in which a crura may be absent, an incus may be fused or displaced, and the spatial relationships between ossicles and the facial nerve can be unpredictable, this preoperative map changes how the operation is approached. The study frames CT as providing anatomic information for integrated preoperative assessment and helping anticipate possible reconstruction needs, a formulation that respects both the power and the boundaries of the technique.

The hearing outcomes provide the most compelling evidence that this integrated approach translates into real benefit for patients. Mean air-conduction pure-tone average improved from 65.4 plus or minus 14.0 dB HL before surgery to 31.9 plus or minus 9.2 dB HL at three months, a mean paired improvement of 33.5 dB with a 95 percent confidence interval of 28.2 to 38.9. The air-bone gap, the standard measure of how much sound is being lost in the middle ear, fell from 40.9 plus or minus 13.1 dB to 12.1 plus or minus 7.3 dB, a mean closure of 28.8 dB. Both comparisons reached statistical significance at P less than 0.001.

Perhaps the most intriguing audiometric finding is that mean bone-conduction threshold improved by 4.7 dB, with a confidence interval of 1.7 to 7.7 dB and a P value of 0.003. Bone conduction bypasses the middle ear entirely, so an improvement in this measure after ossicular reconstruction is generally interpreted as a reduction in the masking effect of middle ear pathology, sometimes described as a correction of the air-bone gap’s contribution to measured bone thresholds, or as resolution of a mild sensorineural component that was masked preoperatively. Whatever the precise mechanism, the practical consequence is that patients did not merely close the conductive gap; their overall hearing function improved as well.

By the conventional surgical benchmark of a postoperative air-bone gap below 20 dB, 28 of the 33 reconstructed ears, or 84.8 percent, achieved a successful outcome. For a cohort dominated by congenital ossicular anomalies, which are among the most technically demanding middle ear reconstructions, that success rate is notable. It suggests that when surgeons enter the operating room with a detailed three-dimensional understanding of the patient’s unique anatomy, they can select appropriate prostheses, plan their approach and anticipate complications before the first incision.

The study, supported by the National Natural Science Foundation of China and the Shaanxi Provincial Science and Technology Program, carries the usual caveats of a retrospective, single-center, selected surgical series. The patients all came to exploratory tympanotomy, meaning the cohort is enriched with cases where imaging and audiology pointed to surgically correctable disease. The authors themselves caution against over-reading the 97.0 percent correspondence as a statement about CT in isolation. Still, for a condition in which the eardrum looks normal, the audiogram shows a gap, and the cause remains a mystery, the message is clear: modern temporal bone imaging, wielded with clinical judgment, turns much of that mystery into a map, while honestly acknowledging the soft-tissue shadows that remain beyond its sight.

Subject of Research: Preoperative CT imaging and 3D ossicular reconstruction for diagnosing conductive hearing loss with an intact tympanic membrane

Article Title: Preoperative high-resolution computed tomography and three-dimensional reconstruction of the ossicular chain in conductive hearing loss with an intact tympanic membrane: a retrospective imaging-surgical case series

Article References: Li, H., Cheng, Y., Zhang, X., & Ma, W. (2026). Preoperative high-resolution computed tomography and three-dimensional reconstruction of the ossicular chain in conductive hearing loss with an intact tympanic membrane: a retrospective imaging-surgical case series. BMC Medical Imaging. https://doi.org/10.1186/s12880-026-02910-2

Image Credits: AI Generated

DOI: 10.1186/s12880-026-02910-2

Keywords: conductive hearing loss, high-resolution computed tomography, three-dimensional reconstruction, ossicular chain, otosclerosis, congenital ossicular anomalies, exploratory tympanotomy, tympanic membrane, hearing outcomes, temporal bone imaging, ossicular reconstruction, BMC Medical Imaging