objectives:
1- Evaluate the risk of ossicular
chain trauma and injuries due to
different middle ear endoscopic
techniques and maneuvers.
2- Describe types, incidence and
causes of these injuries.
3- Suggest methods to avoid them.
Methods:
Thirty temporal bones were ap-
proached utilizing 0°, 30° and
70°otoendoscopes with 2.7 mm and
4 mm diameters. Three areas were
systematically approached in each
bone: retrotympanum, protympanum
and epitympanum. They were also
manipulated using three sets of otologic
surgical instruments: regular
straight,
regular curved and especially
designed for endoscopic ear surgery. The most common injury was the
fracture of the posterior stapedial
crus (27%). Other types were incudostapedial
joint dislocation (23%),
fracture
of foot plate (23%), stapes
dislocation
(17%), fracture both stapedial
crura (13%), fracture of the incus
long process (6%) and incudomalleolar
joint dislocation (3%).
Single
injuries were 44% and combined
or multiple injuries were 56%.
Highest
incidence of injuries was
with
the 70°otoendoscope
(89%) and
with
both the straight and curved
regular
instruments (67%). The diameter
of otoendoscopes did not affect
the number of injuries. Positioning
of the scopes and familiarity with
the
technique reduced the incidence
of
trauma.
Conclusions:
Middle ear endoscopy can lead to a significant risk of ossicular chain
injuries with their sequelae on hearing.
Minimizing this risk necessitates
adequate
familiarity with the anatomy,
techniques and otoendoscopes
and
usage of especially designed
surgical
instruments. In addition,
combining
both microscopic and
otoendoscopic
approaches or surgically
assisted otoendoscopic approaches
can reduce this risk considerably.