Lateral angle: A method for sexing using the petrous bone

Abstract

We report on the results of applying the so-called lateral angle method for sex determination on skeletal remains. The lateral angle denotes the angle of the internal auditory canal in relation to the medial surface of the petrous part of the temporal bone. The method involves making a small cast of the proximal part of the internal acoustic canal and determining the angle at which the canal opens up to the surface of the petrous bone. The method has the great advantage of utilizing one of the sturdiest bone elements of the human skeleton, and may thus be especially suited for analyses of very fragmented skeletal remains or cremated bones, where the petrous bone may still be readily recognizable. The method was tested using a forensic sample of 113 petrous bones with known sex. Intra- and interobserver testing was also performed. We found a statistically significant difference in angle size between males and females (mean angle size of males, 39.3 degrees ; mean angle size of females, 48.2 degrees ; P < 0.001). There was no bilateral difference in angle size. In blind trials, 83.2% of petrous bones were assigned to the correct sex. We also tested the lateral angle method against an archaeological skeletal sample. True sex was not known for this sample; instead, sexing had been carried out by assessing pelvic and cranial morphology in independent trials. We found a higher concordance between the lateral angle and "pelvic" sex than for lateral angle and "cranial" sex. Finally, we note that subadult sexing may also be possible with this method.

Sexual dimorphism of the lateral angle of the internal auditory canal and its potential for sex estimation of burned human skeletal remains

“…Although similar outcome has been attained previously in unburned bones [12], this comes in contrast with the results from other investigations [5,8,10,13], especially with the one from Masotti et al [6] which also focused on burned remains. This may have been because of our difficulty in applying the method-evidenced by a large inter-observer error-and to the possible impact of heat-induced shrinkage and warping on the natural sexual dimorphism of the internal auditory canal, as suggested by Masotti et al [6].…”

“…For that purpose, the procedure of Norén et al [5] was followed, by using Coltène President©-a silicone lightbodied dental casting material-which was applied to the IAC after the surface was cleaned and coated with Vaseline. This was done in order to facilitate the removal of the cast after drying.…”

“…The shots were taken on an orthogonal plane. The lateral angle is formed by the intersection of the posterior external surface of the petrous bone and the adjacent surface of the IAC [5,[8][9][10]. The median value of three attempts of measurement was used for the analysis.…”

“…Several authors have proposed the petrous pyramid of the temporal bone for the development of sexing methods since it tends to preserve well in contexts involving burned remains [2][3][4][5][6]. Evidence of that is the fact that 82 % of 320 calcined temporal bones from individuals cremated in Italy and examined by Masotti et al [6] were sufficiently preserved to allow for the estimation of sex.…”

Çok Kesitli BT ve MRG’de İnternal Akustik Meatus Lateral Açısının Ölçümü Yoluyla Cinsiyet Tayini

“…Bu hususta geçmifl-ten günümüze, insan kemikleri üzerinde yap›lan anatomik ölçümlere dayanan birçok kadavra çal›flmas› mevcuttur. Temporal kemik petröz parças› insan iskeletindeki en sa¤lam yap›lardan biri olup yanm›fl cesetlerde dahi bütünlü¤ünü korudu¤undan bu tür çal›flmalarda en çok tercih edilen yap› konumundad›r (1)(2)(3)(4). BT kullan›larak canl›lar üzerinde yap›lm›fl tek çal›flma örne¤i olan Akansel ve arkadafllar›n›n çal›flmas›nda yüksek rezolüsyonlu BT cihaz› kullan›lm›fl olup 18 yafl alt›ndaki kifliler ele al›nd›¤›nda temporal kemik internal akustik kanal meatus lateral aç›s›nda, kad›nlar ile erkekler aras›nda istatistiksel olarak anlaml› farkl›l›k elde edilememifltir (5).…”