Surgical Techniques
Bioactive Glass was used to obliterate mastoid cavities in 55 primary procedures and 35 secondary procedures. 57 ears were approached using a postaural soft tissue approach, 33 via a endaural approach. Table I. shows the classification of cases in both primary and secondary obliteration.
Ossicular status, as recorded in the operative notes, was graded using the Mills Staging System[13], from 0 (Chain intact) to 3 (Erosion malleus, incus and stapes arch). In 23 cases, the ossicular status was not able to be determined. In some cases, this was because the middle ear was not entered during a secondary obliteration (n=14), or revision surgery, and in others where clear documentation was not available at the time of not review (n=9). Chi-squared testing was performed to look for greater representation of one ossicular status than the others, and none was found (p=0.78). Table II. shows the number of cases at each ossicular Mills status. 41 patients underwent ossiculoplasty, the most common means of reconstruction being cartilage reinforced Type III (n = 17), or use of Titanium Partial(n = 12) or Total Ossicular Reconstruction Prosthesis (n = 5).
The 7th cranial nerve (Facial) was exposed as a result of disease in 8 cases. A fistula in the lateral semicircular canal was present in 5 cases. A further 7 patients were found to have both exposed Facial nerve and a fistula in the lateral semicircular canal. The presence of both facial dehiscence and lateral semicircular canal fistula in such a high proportion of patients highlights the need for intraoperative vigilance, in particular where one dehiscence has already been identified. At the time of publication, no patient had suffered delayed complications as a result of the use of Bioactive glass in the presence of a labyrinthine or facial nerve dehiscence.
A number of different graft materials were used for both the tympanic membrane repair and as a covering for Bioactive Glass. The covering graft prevents the bioactive glass from extruding into the external auditory canal and as an autograft provides a framework for epithelial growth (Figure 1).
The diversity of procedures, ossicular status, and the objective of this paper being to assess the use and clinical outcomes of Bioactive Glass mean that assessment of audiological outcomes by subgroup has not been performed. However, the median change of Air Bone Gap between Pre and Post (>6 months) operative audiometry was 1dB, (Range -36dB - +25dB). 31 had change within the margin of error for audiometry (+/-5dB), whilst 19 had a lower hearing threshold post operatively and 21 a higher hearing threshold postoperatively.
Clinical complications of open cavity surgery (dependence on clinical staff for aural toilet, discharging cavity, vertigo in cold air, and need to protect the ear from water) are shown in Figure 2. At the time of publication no patient has demonstrated recurrence. However, 6 patients have demonstrated retraction of the attic, one of whom has underwent exploratory tympanotomy where a suspicious area was found to be scar tissue rather than cholesteatoma pearl. Seven patients had intermittently discharging ears at the time of data collection (one as a result of ventilation tube). However, 18 (20%) (10 Primary, 8 Secondary) reported the presence of discharge and attended the outpatient department frequently for up to 6 weeks post-operatively. This was due to delayed healing of the graft covering of the Bioactive Glass and, in all cases, responded to regular microsuction and the use of topical antibiotic and steroid creams. All healed without deleterious effect on the mastoid obliteration. Further complication was seen in the occurrence of surgical site infection in two patients, both of whom resolved with oral and topical antibiotic treatment. One patient failed to comply with follow up and attended a solitary review at greater than six months post operatively. She had suffered prolonged discharge from the ear that had settled a few weeks prior to review. There had been complete loss of the bioactive glass and covering graft tissue but she had been left with a well healed and dry mastoid cavity.