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Paper text:
hearing impairment frequently follows head trauma . the hearing impairment can be sensorineural , conductive , or a mix - ed hearing loss according to the area affected by the trauma . when head trauma patients suffer acute conductive hearing loss , the most common etiology except traumatic drum perforation is an intratympanic hemorrhage due to temporal bone fracture .
if the conductive hearing loss has not resolved several months later , ossicular disruption due to head trauma is suggested.1,2,3 ) the most common forms of traumatic ossicular disruption are incus - stapes or malleus - incus dislocation .
almost all ossicular problems caused by trauma result from direct pressure on the temporal area or the effects of a temporal bone fracture . consequently , disruption between the incus and stapes or malleus and incus is more common than ossicular fractures because these portions are the most vulnerable portions of the ossicles . in our case ,
the ossicular pathology was very unusual because an anterior crus fracture occurred , while the remaining ossicles were normal .
stapes fractures without other ossicle problems are rare and ossicle problems due to explosion pressure are also rare.4,5 ) we report a very rare transverse fracture of the stapes anterior crus caused by the blast pressure from a land mine explosion and discuss the pathophysiology with a literature review .
a 40-year - old man was admitted to our hospital with a lumbar vertebral fracture .
a land mine had exploded near where he was working . on admission , he had hearing loss in both ears .
temporal bone computed tomography detected no abnormal findings on the right , but revealed partial soft tissue haziness of the left mastoid and mesotympanum ( fig .
after tympanomeatal flaps were elevated , normal mobility of the ossicles was seen ( fig .
the air - bone gap had improved on the left , while minimal change occurred on the right ( fig .
after repositioning the elevated tympanomeatal flap on the external acoustic meatus , we checked the subjective hearing gain using the whispered voice test during the operation .
however , no hearing improvement was evident , and so we re - examined the ossicles .
1d ) . moving the incus long process using an angled pick did not affect the footplate mobility .
therefore , we tried removing the stapes suprastructure to insert a total ossicular replacement prosthesis ( torp ) , but failed because of normal footplate mobility .
consequently , the torp was inserted through the under - portion of the suprastructure without removing the suprastructure .
seventeen weeks after the revision exploratory tympano - tomy , the air - bone gap on the right side was minimal ( fig . 2c )
, we see traumatic drum perforation with a slap to the head , but the air pressure during a slap is insufficient to induce ossicular fracture .
when people are close to an exploding bomb , 27.6 - 62% of them experience perforated eardrums.6,7,8 ) although south and north korea fought each other during the korean war from 1950 to 1953 , an armistice since then has been imposed .
consequently , although the risk of the explosion of a land mine buried near the cease - fire line is low , the high air pressure resulting from an exploding mine may be sufficient to induce ossicular problems via drum perforation .
the anterior crus is hidden behind the stapedial tendon and incus long process when a transmeatal approach is used for surgery .
consequently , checking the condition of the anterior crus during an exploratory tympanotomy is difficult . in standard practice , the movement of the stapedial tendon or stapes outline is checked when we test the mobility of the incudostapedial joint or footplate . in our case
, we missed the patient 's main problem ( the anterior crus fracture ) because the mobility of the stapedial head and tendon was normal during the first tympanoplasty and the first attempt during the revision exploration tympanotomy .
the drum perforation had been corrected , another problem about hearing conduction had to be responsible .
the stapes crura are very thin structures ; typically , the anterior crus is 0.219 mm thick and the posterior crus 0.113 mm.9 ) so when the intact crus is disconnected from the other crus , mechanical sound energy is no longer conducted .
simmons and parkins10 ) refuted the hypothesis that a fracture of one ( the anterior ) stapedial crus will significantly alter ossicular sound transmission in an experimental animal model .
however , the three - dimensional anatomy differs between humans and rats.11 ) consequently , the contribution of the human anterior crus to hearing transmission differs from that in rats or other animals .
we postulated that the pathophysiological mechanism of the injury was an effect of high air pressure in contact with the ear drum damaging the ossicles directly through the drum .
the protective effect of the tensor tympani and stapedial tendon was negated by the very high air pressure and the rapidity of the explosion .
consequently , the air pressure acted on the ossicles , including the stapes , as a single body .
since the posterior crus was hidden behind the posterior bony annulus and was supported by the stapedial tendon , the mechanical energy might be focused on the anterior crus , which fractured although the anterior crus is thicker than the posterior crus ( fig .
the fracture was like a compression wedge fracture of a vertebral body due to pressure induced vertically because the vertebral body is supported by the back muscles and tendons posteriorly .
vertebral spine fractures are classified into compression fractures , burst fractures , seat - belt type fractures , and fracture dislocations.12 ) of these , compression fractures have a pattern similar to the fracture in our case .
a compression fracture involves failure of the anterior column only , while the middle and posterior columns remain intact .
in contrast , the other types of fracture all involve failure of all three columns .
cadaveric studies have revealed that when specimens are loaded in neutral alignment , a vertebral compression - type deformity often results , and the ligament complex of the posterior element is important at the limit of flexion.13,14 ) few studies have reported on trauma to the stapes.5,15 ) the stapes is a very small , vulnerable structure , so the effects of trau - ma are variable .
our case was unusual because it was an isolated anterior crus fracture without damage to the other ossicles .
our case was similar to two cases in yetiser 's report , al - though yetiser , et al.5 ) did not propose a pathophysiological me - chanism .
as this case suggests , a close examination of the ossicles is necessary during an exploratory tympanotomy .
stapes fractures without other ossicle problems are rare and ossicle problems due to explosion pressure are also rare . we describe a very rare case of stapes anterior crural fracture resulting from a land mine explosion . 
 as this case suggests , a close examination of the ossicles is necessary during an exploration tympanotomy .