the condylar process has been reported as most common site of mandibular fractures , accounting for 29% of all mandibular fractures . surgical treatment of condylar fractures by open reduction and internal fixation ( orif ) demands that internal fixation and anatomic reduction be completed under direct visualization of the fracture . one challenge of open surgery for condylar process fractures is navigating the anatomic complexity of the adjacent vital structures , specifically the facial nerve . several authors have described the location of the facial nerve in the preauricular area . despite this , one of the most common complications of open reduction and internal fixation of subcondylar fractures remains facial nerve paresis and paralysis [ 24 ] . it is our feeling that the novice surgeon can benefit from a system of reference to enable the prediction of critical anatomic structures . this system must be based on anatomical landmarks that are ( 1 ) easily identifiable , ( 2 ) fixed in position during the procedure , and ( 3 ) independent of patient position . this project aimed to describe pertinent anatomic relationships of the facial nerve in the preauricular region and relate these findings to orif procedures of the subcondylar region . specifically , we describe the anatomic relationship of the nerve to subcondylar mandible and to easily palpable topographic landmarks , such as the tragus . we feel that these relationships are especially germane to the less experienced surgeon performing orif for condylar process fractures . an extended preauricular / retromandibular approach was utilized to provide broad exposure of the facial nerve and subcondylar region . the incision was based parallel to the posterior edge of the ramus . once parotid tissue was encountered , blunt dissection was carried out to the facial nerve branches . because of the ease of palpation and fixed location during orif of the subcondylar region , the posterior apex of the tragus and the lateral pole of the condyle were used as reference points for measurements . measurements were made as follows ( figure 1(a)):depth of tissue separating facial nerve from the underlying condylar neck.tragus ( posterior apex ) to the condyle ( lateral pole).tragus ( posterior apex ) to the point where the facial nerve crossed the posterior border of the condylar neck.tragus ( posterior apex ) to the pes anserinus.all dissections were performed by one of two authors ( h. p. barham or a. m. terella ) . tragus ( posterior apex ) to the point where the facial nerve crossed the posterior border of the condylar neck . the temporozygomatic ( upper ) division of the facial nerve was encountered during each of our dissections to the subcondylar region . this division of the facial nerve consistently emerged from posterior and medial to the condylar neck and traveled in an oblique plane . in all cases , the mean depth from facial nerve to underlying condylar neck was 5.5  mm ( standard deviation : 1.2  mm ) . the mean distance from tragus ( posterior apex ) to condyle ( lateral pole ) was 2.20  cm ( standard deviation : 0.04  cm ) , from tragus ( posterior apex ) to the point where the facial nerve crossed the posterior border of the condylar neck it was 2.31  cm ( standard deviation : 0.10  cm ) , and from the tragus to pes anserinus it was 2.25  cm ( standard deviation : 0.10  cm ) ( figure 1(b ) ) . an open approach to the treatment of condylar fractures has become increasingly common , and several surgical incisions including preauricular , rhytidectomy , retromandibular , submandibular , and postauricular incision have been described . a potential and devastating complication of orif in this region is facial paralysis or palsy . the reported incidence of facial nerve palsy varies widely , with a reported incidence of 0% utilizing a high submandibular approach to as high as 30% with a retromandibular approach [ 25 ] ( table 1 ) . our findings support those of authors prior in suggesting that the temporozygomatic division of the facial nerve has an intimate anatomic relationship to the condylar process . we attempt to expand on this work by highlighting the depth of tissue separating the nerve from the underlying condylar process . when approaching the condylar region from a retromandibular approach or preauricular approach , visualization of the facial nerve - condyle relationship is limited , and moderately strong retraction is frequently required to obtain an adequate visual field and working space for osteosynthesis . although the temporozygomatic ( upper ) division of the facial nerve should not be encountered during the submandibular or high submandibular approaches , the nerve is retracted laterally and easily stretched when attempting to achieve an ample working space and optical field . on average , the surgeon must appreciate that blind and aggressive lateral or superior retraction of overlying soft tissue in this region can easily result in stretch injury and neuropraxis . understanding this close relationship should help reduce the incidence of facial nerve injury during orif of the condylar region . additionally , on average , the pes anserinus of the facial nerve was located approximately 2.25  cm anterior - inferior to the tragus , while the facial nerve crossed the posterior border of the mandible on average 2.31  cm anterior - inferior to the tragus . the measurements and relationship of the facial nerve from this study should allow for nerve position to be estimated using the tragus and palpated posterior border of the mandible . it is our opinion that the use of a palpable landmark is of greatest utility to the novice surgeon , less experienced in this region . techniques and measurements to predict nerve location are only estimates and can not replace the need for precise anatomic understanding and cautious dissection in the condylar region . further , they must be interpreted understanding the inherent , well documented anatomic variation of the facial nerve . several studies have demonstrated efficacy of techniques for locating the facial nerve , with the work of de ru et al . being the most complete and showing the single best anatomic landmark for locating the facial nerve trunk to be the tympanomastoid fissure ( tmf ) , usually within 3  mm of this landmark . however , pather and osman noted that the tmf was not an ideal landmark because it often lay behind the sturdy tendon of the sternocleidomastoid muscle , thus requiring a complex dissection . these techniques are excellent in localizing the nerve during dissection but do not help provide a preoperative estimate of nerve location in the condylar region . tissues operated upon following a traumatic insult may undergo distortion due to edema or disruption of soft tissues . presumably , a swelling process would increase distances between structures if uniformly distributed , so it may not significantly change the surgeon 's operative strategy . further , it is acknowledged that even careful anatomic dissection could lead to distortion of tissue in our specimens , thus affecting measurements . lastly , our limited sample size enabled calculation of standard deviations , but not an evaluation of anatomic variation . the temporozygomatic ( upper ) division of the facial nerve has an intimate relationship to the condylar process . it is critical to understanding both the course of the nerve and the depth of tissue separating it from the condylar neck . soft tissue retraction to optimize the optical field can easily stretch the nerve resulting in neuropraxis . understanding this close relationship should help reduce the incidence of facial nerve injury during orif of the condylar region . further the novice surgeon , less experienced in the subcondylar region , can benefit from estimates of facial nerve location using easily palpable topographic landmarks . we suggest that the tragus and lateral pole of the condyle can serve this function .
introduction . 
 the mandibular condyle is the most common site of mandibular fracture . 
 surgical treatment of condylar fractures by open reduction and internal fixation ( orif ) demands direct visualization of the fracture . 
 this project aimed to investigate the anatomic relationship of the tragus to the facial nerve and condylar process . 
 materials and methods . 
 twelve fresh hemicadavers heads were used . 
 an extended retromandibular / preauricular approach was utilized , with the incision being based parallel to the posterior edge of the ramus . 
 measurements were obtained from the tragus to the facial nerve and condylar process . results . 
 the temporozygomatic division of the facial nerve was encountered during each approach , crossing the mandible at the condylar neck . 
 the mean tissue depth separating the facial nerve from the condylar neck was 5.5  mm ( range : 3.5  mm7  mm , sd 1.2  mm ) . 
 the upper division of the facial nerve crossed the posterior border of the condylar process on average 2.31  cm ( sd 0.10  cm ) anterior to the tragus . conclusions . 
 this study suggests that the temporozygomatic division of the facial nerve will be encountered in most approaches to the condylar process . as visualization of the relationship of the facial nerve to condyle 
 is often limited , recognition that , on average , 5.5  mm of tissue separates condylar process from nerve should help reduce the incidence of facial nerve injury during this procedure .