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.