Straight Egyptian Arabian skull morphology presents unique surgical challenges compared to the Thoroughbred: a computed tomography morphometric anatomical study

Abstract

OBJECTIVE The objective of this study was to compare the skull morphology of the Straight Egyptian Arabian (SEAR) to the Thoroughbred (TB), using computed tomography (CT) in the context of surgical procedures commonly performed on the equine head. ANIMALS Measurements relating to surgical considerations of the equine head were taken from 29 clinically normal adult horses (15 SEAR, 14 TB). PROCEDURES A clinical prospective study. Standing skull CTs were performed. Fourteen gross and 10 CT measurements were taken. RESULTS Several variables showed a significant difference between groups, in all cases greater in TB. Head length (P < .001) and facial crest length (P < .001) were significantly shorter in SEAR than TB. The head length was shorter relative to body height in SEAR (P < .001). The lateral length of a virtual maxillary bone flap was shorter in SEAR (P < .001). SEAR had smaller craniofacial angles than TB (P = .018). CLINICAL RELEVANCE SEAR skull morphology differs significantly from TB, making surgical approaches potentially more challenging. Compared with TB, the shorter facial crest in the SEAR group could contribute to poor surgical access to the maxillary sinus in SEAR due to shorter maxillary flap lengths. Significant differences in the craniofacial angles between SEAR and TB suggest similarities between SEAR and brachycephalic dog breeds, warranting further investigation.

Comparison of Computed Tomography Assisted 3D Cephalometric Measurements in Straight Egyptian Arabian and Thoroughbred Horses

“…Previous findings indicate that there is no significant difference in the lengths of the caudal or rostral maxillary sinuses between the 2 breeds. 8 While this is not directly comparable to the Mxa length in the present study, which was measured as the distance between the superior molar and superior premolar, it does suggest that the difference between the 2 breeds may be attributable to the SEAR having a shorter EtL distance. Again, while not directly comparable, it has been shown that absolute distances from the maxillary septal bulla to the rostral aspect of the cribriform plate are significantly shorter in SEAR compared to TB.…”

“…Again, while not directly comparable, it has been shown that absolute distances from the maxillary septal bulla to the rostral aspect of the cribriform plate are significantly shorter in SEAR compared to TB. 8 It could be theorized that this may have an impact on the length of the EtL in the current study, potentially causing the SEAR to have a shorter EtL and thus a significantly greater Mxa/EtL ratio. However, further investigation is required to understand these differences in more detail.…”

“…All 9 cephalometric measurements were found to be significantly greater in TB than SEAR, in addition to the interincisal angle ( P < 0.05). 8 Even after controlling for horse height, the effect of breed remained the same with TB > SEAR for all measurements ( P < 0.05). It is worth noting the statistically significant differences in 2 of the reported ratios, FL/ML and Mxa/EtL.…”

“…The SEAR has been shown to have significantly shorter head lengths, as well as significantly smaller facial crest length, compared to TB, which likely explains this finding. 8 This could possibly provide an explanation for why it has previously been anecdotally reported that Arabians are predisposed to underjet/prognathism. 2 The relatively shorter facial-to-mandibular length could contribute to the Arabian's dished-face phenotype.…”

“…7 However, the Straight Egyptian Arabian subgroup (SEAR) has been shown to have significantly shorter head lengths and facial crest lengths compared to TBs, as well as smaller craniofacial angles. 8 Potentially this could have implications for the development of malocclusions, resulting in a predisposition for the development of underjet/prognathism. According to one study, certain cephalometric ratios can be useful to predict whether a young warmblood foal born with a physiological malocclusion may spontaneously resolve or progress into an overjet later in life.…”