The sesamoid bone in the long abductor muscle tendon of the first digit in the dog

Abstract

The sesamoid bone in the tendon of the m. abductor digiti primi longus is considered present in most dog breeds and is described to be radiologically detectable at the level of the carpus from the age of 4 months. However, an extensive investigation of this sesamoid bone has not been conducted before. The aim of this study was therefore to determine its prevalence in different dog breeds, to describe its histological development, and to determine the age at which it becomes radiologically visible. The prevalence of the sesamoid bone was assessed on radiographic images of the carpus or by dissection of the carpal region in 743 adult dogs of 115 breeds. Its development was studied by dissection and histological analysis in 45 puppies and its timing of radiological appearance was evaluated in 209 puppies. At least one sesamoid bone was present in all adult dogs, except for 14 dogs of six breeds of predominantly the small breed category. The lowest prevalence rate of 38.46% was exhibited in the French bulldog. The histological development could be divided into five stages. The first radiographic appearance corresponded to the coalescence of smaller ossification centers into one big nucleus (stage 4). The mean time of radiographic appearance was 108.4 days. This study provides extensive data on the prevalence and timing of the radiographic appearance of a sesamoid at the carpus of the dog. The data on radiographic appearance may be helpful in the age estimation of puppies.

Age estimation of puppies based on the radiographically assessed development of ossification centres in the carpal and metacarpal regions

“…The clinical differences between the sexes were small (maximum of 5 days' difference in median age), but there was a tendency for an earlier onset of ossification in female puppies. Most previous studies on the occurrence of OCs or growth plate closure in dogs did not distinguish between female and male dogs 15,24,30,34,36,37,39,41,46,48 ; our results are consistent with the few studies that did make a distinction. 25,28,49,50 In human research, it is generally reported that OCs appear significantly earlier in females than in males, with the consequence that standardised methods to evaluate skeletal development have to be gender differentiated.…”

“…45 The majority of the dorsopalmar radiographs (215 carpi of 109 dog cadavers and 140 carpi of 100 dogs in the retrospective study) were previously studied to evaluate the absence or presence of the sesamoid bone. 46 Adding additional radiographs did not change the conclusions of this study regarding the timeline of ossification of the carpal sesamoid bone, namely, that a sesamoid bone is visible on radiographs in the majority of puppies from 121 days onwards. Presence in 100% of the dogs studied may not be achieved as the carpal sesamoid bone may be radiologically absent in some breeds, such as the French Bulldog and Chow Chow.…”

“…Adding additional radiographs did not change the conclusions of this study regarding the timeline of ossification of the carpal sesamoid bone, namely, that a sesamoid bone is visible on radiographs in the majority of puppies from 121 days onwards. Presence in 100% of the dogs studied may not be achieved as the carpal sesamoid bone may be radiologically absent in some breeds, such as the French Bulldog and Chow Chow 46 . Some nuance is therefore in order.…”

“…Apart from the latter, our chronology of first appearance of OCs in the carpal region corresponded very well to the chronology described in their study 45 . The majority of the dorsopalmar radiographs (215 carpi of 109 dog cadavers and 140 carpi of 100 dogs in the retrospective study) were previously studied to evaluate the absence or presence of the sesamoid bone 46 . Adding additional radiographs did not change the conclusions of this study regarding the timeline of ossification of the carpal sesamoid bone, namely, that a sesamoid bone is visible on radiographs in the majority of puppies from 121 days onwards.…”

“…Presence in 100% of the dogs studied may not be achieved as the carpal sesamoid bone may be radiologically absent in some breeds, such as the French Bulldog and Chow Chow. 46 Some nuance is therefore in order. In our study, 100% was demonstrated in the oldest class, but it did not contain puppies belonging to these breeds.…”