Incus Necrosis and Blood Supply: A Micro-CT and Synchrotron Imaging Study.

BACKGROUND: Incus necrosis is a common complication following stapes surgery and is associated with impaired microcirculation. The objective of this study was to investigate the vascular anatomy of the human incus by using light microscopy, micro-computed tomography (micro-CT), and synchrotron phase-contrast imaging (SR-PCI) for a novel three-dimensional (3D) analysis of the middle ear, mucosal folds, major vascular pathways, and intraosseous vascular bone channels. METHODS: One-hundred-and-fifty temporal bones from the Uppsala collection were analyzed under light microscopy. Twenty temporal bones underwent high-resolution micro-CT scanning, and an additional seven specimens underwent SR-PCI at the Canadian Lightsource in Saskatoon, Canada. One of these specimens was from an individual who had undergone stapes surgery. Data were processed with volume-rendering software to create 3D reconstructions using scalar opacity mapping for bone transparency, cropping, and soft tissue analyses. RESULTS: Micro-CT and SR-PCI with 3D rendering revealed the extensive vascular plexus within the un-decalcified incus bone communicating with the exterior surface. The relationship between the vessels, lenticular process, and incudostapedial joint were clearly observed. SR-PCI allowed for histologic-level detail while preserving the specimen and its 3D relationships. CONCLUSION: SR-PCI with 3D reconstructions confirmed the main vascular supply to the lenticular process along the intraosseous lenticular vessels. This is the first synchrotron analysis of a patient having undergone stapes surgery, and it suggests that incus necrosis associated with stapes surgery may be caused by a disruption of the lenticular blood flow induced by the prosthesis loop, and not by strangulation of mucosal vessels as has been previously described.

Necrosis of the long process of the incus following stapes surgery: new anatomical observations.

OBJECTIVES/HYPOTHESIS: The most frequent complication (generally recognized during revision procedures) following seemingly successful stapedotomies and stapedectomies is necrosis of the long process of the incus. This is currently ascribed to a malcrimped stapes prosthesis or to a compromised blood supply of the incus. The two-point fixation can cause a mucosal injury with a resulting toxic reaction, and also osteoclastic activity. An important aspect in the engineering of ideal stapes prostheses is that they should be fixed circularly to the long process of the incus with appropriate strength. The objective of this study was to compare current knowledge relating to the blood supply of the ossicular chain with the present authors' observations on cadaver incudes. Most of the papers dealing with this issue appeared in the mid-20th century. METHODS: The published data were compared with the authors' findings gained from photodocumentation on 100 cadaver incudes. The photos were taken with a Canon EOS 20 digital camera (Canon, Inc., Lake Success, NY) with a 5:1 macro-objective. The long processes of the incudes were examined from four directions under a Leica surface-analyzing microscope (Leica Microsystems GmbH, Wetzlar, Germany). RESULTS: Analysis of the positions of the entrances of the feeding arteries (nutritive foramina) on the incudes revealed 1-4 nutritive foramina on the long processes of 48% (24) of the left-sided incudes and 56% (28) of the right-sided incudes. The positions of these foramina differed, however, from those previously described in the literature. They were mostly located not on the medial side of the incus body or on the short process or on the cranial third of the long processes, but antero-medially, mostly on the middle or cranial third. In 48% of all the incudes examined, an obvious foramen was not observed either in the body or in the long process of the incus. No relationship was discerned between the chronological age of the incus specimens and the numbers and/or locations of the nutritive foramina. In each case, the opening of the foramen was the beginning of a tunnel running obliquely and medially upward through the corticalis of the long process of the incus. The foramina are thought to be capable of ensuring a richer blood supply between the surface and the inside of the long process, allowing the arteries to run in and out. CONCLUSIONS: These observations indicate that conclusions drawn from classical anatomical works appear to need reconsideration. The present authors consider that the reason for the necrosis of the long process of the incus is not a compromised blood supply, except in some exceptional anatomical situations. They discuss the possible reasons why malcrimping may lead to necrosis of the long process of the incus. To prevent such malcrimping, attention is paid to the new generation of prostheses.

Middle ear pathology in ancient and modern populations: incudal osteoma.

CONCLUSIONS: Osteomas of the incus were found in surprisingly high numbers in ancient and modern populations. The coexistence of osteoma formation and unique vascularization on the medial surface of the incus alludes to a relationship between the two findings. OBJECTIVE: Osteomas involving the middle ear ossicles are rare. The aim of this study was to compare the incudal pathology of ancient and recent periods using the recent literature. MATERIAL AND METHODS: Pathologies encountered in 1170 human incudes belonging to different populations from ancient and recent periods were studied. Most of the ossicles were found in the middle ear of dry skulls or during dissection. The observations were done with a binocular microscope and a Nikon Profile Projector. RESULTS: A total of 47 incudes (4.01%) presented with a variety of pathologies, osteomas being found in 19 cases (1.62%). The osteomas were noted only on the medial surface of the incus. Other findings, including prominent erosions, multiple nutrient foramina and pitting, were also found on the medial side of the incus. The incidence of osteoma was found to be more common in ancient populations (1.88%) and most prevalent among Bedouins (4.55%).

[Posttraumatic aseptic necrosis of the lenticular process of the incus (author's transl)]. / Posttraumatische aseptische Nekrose des Processus lenticularis des Amboss.

More than two years after a basal fracture an aseptic necrosis of the lenticular process was found. The cause of the necrosis is probably the chronic impairment of blood supply.

The histopathology of the incus after stapedectomy.

Twenty-two temporal bones subjected to stapedectomy were examined by light microscopy for histological changes in the long process of the incus. In 19 cases a stainless steel wire technique had been used and in three a polyethylene tube operation had been performed. Twenty healthy unoperated ears were examined as controls. In all operated ears fibrosis and reduced vascularity of the mucosa was noted. In the polyethylene tube group, 1 ear showed the growth of new bone into the lumen of the tube and 1 showed minor resorption of the long process of the incus. In the stainless steel wire group bone resorption of the long process of the incus. In the stainless steel wire group bone resporption was seen in 5 cases and 1 incus also showed an area of necrosis adjacent to the tip; 2 of the 5 incudes showed some loss of the lenticular process. The main factor relating to bony resorption in this group was the presence of other histological changes resulting from postoperative inflammation. These findings represent a critical histological examination; the hearing results obtained appear to be good, although full audiometry is lacking.