An atypical inferior gluteal artery passing through the piriformis muscle.

PURPOSE: In this article, we report a case of an atypical inferior gluteal artery that passed through the piriformis muscle when it emerged from the pelvic cavity in an elderly Japanese female cadaver. We speculate that this atypical artery could be entrapped and compressed by the piriformis muscle and may therefore be associated with piriformis syndrome; however, the anatomical characteristics of such an atypical artery have not been previously reported. To assess this potential association, the atypical inferior gluteal artery was anatomically examined. METHODS: The cadaver examined in this report was a 97-year-old Japanese female who was donated to The Nippon Dental University for use in medical education and research. The atypical inferior gluteal artery and surrounding structures in half of the pelvis were examined macroscopically. RESULTS: The atypical inferior gluteal artery arose from the common arterial trunk, formed by itself and the superior gluteal artery, passed through the superior proximal part of the piriformis muscle, and left the pelvic cavity. It supplies branches to the lower half of the gluteus maximus and proximal part of the long head of the biceps femoris muscle. The piriformis muscle originates from the 2nd to 4th sacral vertebrae and attaches to the greater trochanter via a single short tendon. CONCLUSION: According to our findings, when the atypical inferior gluteal artery is entrapped and compressed, ischemic signs and symptoms may emerge in the lower buttocks and proximal posterior thigh. These results provide a new perspective for the diagnosis and treatment of piriformis syndrome.

Morphological significance of the medial brachial cutaneous nerve: An anatomical study of the brachial plexus in primates.

The medial brachial cutaneous nerve (MBC) originates from the medial cord of the brachial plexus and innervates the skin sensory in the medial posterior surface of the upper arm. Considering previous reports of the primate brachial plexus, the MBC appeared to be the sole branch in the brachial plexus that only some primates possess. However, the detailed descriptions and records regarding the morphology of the MBC and related nerves, their origins and distributions (dermatomes) in particular, were frequently lacked in the previous reports, and it remains unclear why the difference in the MBC appearance exists among primates. In this study, the brachial plexus and its branches were first re-evaluated and certainly identified in several primates, humans, chimpanzee, macaque monkey, lutung, tamarin, squirrel monkey, and spider monkey. The MBC was identified in humans, chimpanzee, spider monkey, and squirrel monkey. In the other species, the intercostobrachial nerve (ICB) originating from some of 1st to 3rd intercostal nerves developed and distributed instead of the MBC. According to the kinesiological and behavioral studies, the former species possessing MBC show high shoulder joint mobility associated with their locomotive patterns. We speculate that the MBC corresponds to transformed ICB; specifically, where it originates presumably transfers from the 1st and/or 2nd intercostal nerves to the brachial plexus, which allows it to reach the upper arm by coursing the shortest distance even if the forelimb is raised high. Therefore, MBC may embody phylogenetic morphogenesis of the nerve associated with the locomotive evolution and adaptation in primate forelimb.

Anatomical study of the cardiac conduction system in swine hearts.

The cardiac conduction system (CCS) is crucial for regulating heartbeats; therefore, clinicians and comedicals involved in cardiovascular medicine treatment must have a thorough understanding of the CCS structure and function. However, anatomical education of the CCS based on actual dissection and observation is uncommon, although such educational methodology promotes three-dimensional structural understanding of the observed object. Based on previous studies, we examined the CCS structure in the heart of a swine (pig, Sus scrofa domestica) which has been used in the biological, medical and anatomical curricula as science teaching materials, by using macroscopic dissection procedures. Most CCS structures in a young pig heart were successfully identified and illustrated on a macroscopic scale. The atrioventricular bundle (His bundle) was located on the lower edge of the membranous interventricular septum and was clearly distinguished from the general myocardial fibres by its colour and fibre arrangement direction. Following the atrioventricular bundle towards the atrium or ventricle with properly removing the endocardium and myocardium, the atrioventricular node or the right and left bundles appeared respectively. In contrast, the sinoatrial node was not identified. The anatomy of the CCS in young pig hearts was essentially similar to that previously reported in humans and several domestic animals. Our findings of the CCS in young pig hearts are expected to be useful for medical and anatomical education for medical and comedical students, young clinicians and comedical workers.

Gross anatomy of the gluteal and posterior thigh muscles in koalas based on their innervations.

Morphological and functional comparison of convergently-evolved traits in marsupials and eutherians is an important aspect of studying adaptive divergence in mammals. However, the anatomy of marsupials has been particularly difficult to evaluate for multiple reasons. First, previous studies on marsupial anatomy are often uniformly old and non-exhaustive. Second, muscle identification was historically based on muscle attachment sites, but attachment sites have since been declared insufficient for muscle identification due to extensive interspecific variation. For example, different names have been used for muscles that are now thought to be equivalent among several different species, which causes confusion. Therefore, descriptions of marsupial muscles have been inconsistent among previous studies, and their anatomical knowledge itself needs updating. In this study, the koala was selected as the representative marsupial, in part because koala locomotion may comprise primate (eutherian)-like and marsupial-like mechanics, making it an interesting phylogenetic group for studying adaptive divergence in mammals. Gross dissection of the lower limb muscles (the gluteal and the posterior thigh regions) was performed to permit precise muscle identification. We first resolved discrepancies among previous studies by identifying muscles according to their innervation; this recent, more reliable technique is based on the ontogenetic origin of the muscle, and it allows for comparison with other taxa (i.e., eutherians). We compared our findings with those of other marsupials and arboreal primates and identified traits common to both arboreal primates and marsupials as well as muscle morphological features unique to koalas.

Relationship between the lumbosacral plexus deviation and 12th rib length in Japanese macaques (Macaca fuscata).

The relationship between the lumbosacral plexus (LSP) origin and the 12th rib length was recently determined in humans; cranial and caudal deviations of the plexus origin are related to shortening and elongation of the 12th rib, respectively. However, it remains unclear whether such anatomical correlations are also observed in non-human mammals. To address this issue, in the present study, we evaluated the LSP origin and the 12th rib length in Japanese macaques (Macaca fuscata). In typical cases, the femoral and obturator nerves were derived from both the 4th and 5th lumbar nerves, and the lumbosacral trunk was from the 5th to 7th lumbar nerves. Some of the LSPs exhibited a caudal deviation of their origins; the femoral and obturator nerves were also derived from the 6th lumbar nerve, in addition to the 4th and 5th lumbar nerves; the lumbosacral trunk lost the 5th lumbar nerve origin and arose from the 6th and 7th lumbar nerves. Individuals with the caudal deviation of LSP origin exhibited significant elongation of the 12th ribs, in comparison with individuals with the typical plexus. The present findings indicate that the caudal deviation of LSP origin was correlated to the 12th rib elongation in Japanese macaques, similar to humans. As a future studies, we need to clarify which mammalian groups exhibit such correlation between the deviation of the LSP origin and the lowest rib length, and further to provide evolutionary implications of this correlation.

Anatomic characterization of the tibial and fibular nutrient arteries in humans.

The location of nutrient foramina has been extensively studied in long bones; however, accurate information on the origin and extra-osseous course of the nutrient artery remains clearly defined in some long bones, although it is crucial to protect the nutrient arteries during operative procedures. In this study, we elucidated the origin and extra-osseous course of tibial and fibular nutrient arteries based on the 54 cadaveric legs. The tibial nutrient artery typically arose from the posterior tibial artery. Some of the tibial nutrient arteries arose from the anterior tibial, popliteal, and fibular arteries. The tibial nutrient artery arose from these parent arteries as a long descending branch. It penetrated the most proximal portion of the tibialis posterior or flexor digitorum longus to enter the tibial nutrient foramen. The fibular nutrient artery arose from the fibular artery as a short descending branch in all the cases. The fibular nutrient artery penetrated the flexor hallucis longus to enter the fibular nutrient foramen. Our present and previous findings provide new insight into the anatomical characteristics for the nutrient arteries in the long bones of upper and lower extremities. Namely, the nutrient arteries of the long bones go away from the elbow or knee to enter the nutrient foramina.

Relationship of segmental variations in the human lumbar plexus to the length of the 12th rib.

BACKGROUND: Evaluating segmental variations in the lumbar plexus is crucial for neurological diagnosis. In the present study, we examined the relationship between the segmental composition of the lumbar plexus and length of the 12th rib. PROCEDURES: To evaluate segmental variations in the lumbar plexus, the furcal nerve (Nf) which forms the boundary between the lumbar and sacral plexus, was used as an index of plexus arrangement. MAIN FINDINGS: Segmental variations in the Nf were classified into four groups on the basis of whether the Nf originated from the ventral rami of L3 and L4 (Nf L3 + L4 group), L4 (Nf L4 group), L4 and L5 (Nf L4 + L5 group), or L5 (Nf L5 group). The Nf L3 + L4 group was associated with short 12th rib, and groups Nf L4 + L5 and Nf L5 were associated with long 12th rib. These findings suggest that the segmental variations in the lumbar plexus are related to the length of the 12th rib. CONCLUSIONS: Therefore, the segmental variations in the lumbar plexus can be evaluated non-invasively and easily by measuring the length of the 12th rib. This may contribute to the diagnosis and treatment of various lumbar radiculopathies.

Anatomical study of the soleus: Application to improved imaging diagnoses.

INTRODUCTION: Strains of the soleus are widely found both in amateur and professional athletes. For their accurate regional diagnoses, understanding the anatomy of the spatial relationship between muscular fibers and tendinous structures is important because their interfaces are susceptible sites to muscle strains. Therefore, this study evaluated the precise architecture of the soleus. MATERIALS AND METHODS: We evaluated the precise anatomical architecture of the soleus in 87 formaldehyde-fixed soleus muscles. To calculate mean relative physiological cross-sectional area of each muscular fiber compartment, we measured the fiber length, volume, and pennation angle in isolated compartments. RESULTS: The posterior soleus surface was covered by a broad aponeurotic posterior insertion tendon (PIT), which continued inferiorly to the insertion tendon. The anterior surface had three aponeurotic origin tendons, lateral origin tendon (LOT), medial origin tendon (MOT), and tendinous arch, which were arranged along the soleus margins. The anterior bipennate muscle portion (ABP), surrounded by the three origin structures, terminated as the sagittal insertion tendon (SIT), which continued inferiorly to PIT. The posterior main muscle portion behind LOT and MOT was separated into lateral and medial portions by the SIT. The soleus thus possessed a broad musculotendinous junction. Furthermore, ABP exhibited wide structural diversity in shape and size: in extreme cases, it was duplicated or absent. CONCLUSION: Systematic anatomical descriptions of the soleus will be useful for accurate regional diagnosis of its strains with magnetic resonance imaging and ultrasonography.

Variations in the course of the superior gluteal artery in relation to the lumbosacral plexus.

The course of the superior gluteal artery (SGA) as it passes through the lumbosacral plexus is variable. The variations of the arterial course in relation to the lumbosacral plexus have focused on statistical analysis, and it is limited arterial diversity. In this study, we investigated the positional relation between the SGA and the furcal nerve (FN): guide to segmentation of the lumbosacral plexus, arising from the L4, ie, the contribution to the femoral nerve, obturator nerve, and lumbosacral trunk. We could classify the pathway of the SGA into three types based on its positional relation to the FN. The SGA courses under the ramus from which the FN originates (Type A), under the ramus one segment below the origin of the FN (Type B), or between the obturator nerve and the lumbosacral trunk (Type C). The SGA pathway in Types A and B showed a cranial or caudal shift along with cranial or caudal deviation of the FN. In summary, the variation in the SGA pathway was correlated with cranial or caudal shift of the FN. Our findings indicate that variations of the SGA pathway are associated not only with arterial transformation, but also with diversity of the lumbosacral plexus.