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Purpose: This study aimed to elucidate the positions of the extended fibers of the alar part of the nasalis (Na), and their connections to the levator labii superioris (LLS), zygomaticus minor (Zmi), and adjacent skin near the nasal ala., Methods: The extended fibers of the Na were investigated in 54 specimens obtained from 27 embalmed adult South Korean cadavers., Results: In 51.9% of the specimens, some fibers of the Na extended over the alar facial crease, intermingling or blending with the LLS or Zmi, and attached to the skin lateral to the nasal ala. The quantity and distribution of these extended fibers varied: some fibers of the Na extended and intermingled or blended with the LLS in 25.9%, while another 25.9% exhibited the Na extending in a distinctive fan shape with longer fibers, and combining with both the LLS and Zmi. However, the Na had no extended fibers that reached the LLS, Zmi, or skin near the nasal ala in 48.1%., Conclusion: Contraction of the Na and its extended fibers can influence the nasal ala and also the laterally located skin and muscles, directing them inferomedially toward the incisive fossa of the maxilla, which is the origin of the nasalis. These insights offer a deeper understanding of the role and actions of facial muscles in facial expression. They will be instrumental in the comprehension and analysis of nose and mouth movements, and in conducting electromyographic analyses in this region., (© 2024. The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.)

Purpose: For basic training in ultrasonography (US), medical students and residents must learn cross-sectional anatomy. However, the present educational material is not sufficient to learn the sectional anatomy for US. This study aimed to provide a criterion for reading ambiguous structures on US images of upper limb through the sectioned images of Visible Korean., Methods: US images of the right arm of a volunteer were scanned (28 planes). For comparison with US images, the sectioned images of the right upper limb (24 bits color, 0.5 mm intervals, 0.06 mm × 0.06 mm sized pixel) were used. After the volume model was constructed from the sectioned images using MRIcroGL, new sectioned images of 28 planes corresponding to the US images of 28 planes were created by adjusting the slope of the volume model. In all images, the anatomical terms of 59 structures from the shoulder to the fingers were annotated., Results: In the atlas, which consists of 28 sets of US images and sectioned images of various slope planes, 59 structures of the shoulder, arm, elbow, wrist, palm, and fingers were observed in detail., Conclusion: We were able to interpret the ambiguous structures on the US images using the sectioned images with high resolution and actual color. Therefore, to learn the cross-sectional anatomy for US, the sectioned images from the Visible Korean project were deemed to be the suitable data because they contained all human gross anatomical information., (© 2024. The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.)

Purpose: The aim of this study was to characterize the origin and course of the zygomaticus major muscle (Zmj) with its topographic relationships with the nasal ala, tragus, philtrum, and lateral canthus., Methods: The Zmj was examined in 50 specimens of 25 embalmed adult Korean cadavers. Facial muscles were dissected to expose the origin and course of the Zmj in 48 specimens of 24 cadavers. The 25th cadaver was sectioned to obtain images of the Zmj., Results: The positional relationships of the Zmj origin with the nasal ala and the tragus were classified into three categories. A horizontal line through the center of the Zmj origin and the nasal ala passed through the tragus in 20 of 48 specimens (41.7%), the intertragic notch in 18 specimens (37.5%), and above the tragus in 10 specimens (20.8%). In a horizontal section of the head, the Zmj origin was located near the level of the nasal ala and tragus. In a coronal section of the head, the fibers of the Zmj arising at its origin were located close to the zygomatic bone, lateral to the zygomaticus minor muscle., Conclusion: By combining dissection with the analysis of sectioned images and ultrasound images of the Zmj, this study has yielded positional information for easily predicting the location of the origin and the course of the Zmj and its related structures underlying the skin., (© 2023. The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.)

Purpose: The aim of this study was to determine the width of the fibers that extend from the orbicularis oculi muscle (OOc) to the upper lip, and the lateral and inferior lengths of the OOc at the lateral canthus level., Methods: The OOc was investigated in the 40 hemifaces of 20 Korean cadavers. The lateral fibers of the OOc (OOc lat) were traced to determine whether or not these fibers extended to the upper lip., Results: The OOc lat extended to the upper lip at the lateral canthus level in 31 of the 40 specimens (77.5%), whereas some inferolateral fibers of the OOc that extended to the upper lip were observed near the level of the lower margin of the OOc in the other 9 specimens (22.5%). The mean ± SD and maximum widths of the OOc lat that extended to the upper lip at the lateral canthus level were 6.9 ± 3.3 mm and 14.3 mm, respectively., Conclusion: The obtained data will be helpful to distinguish the muscles that underly the wrinkles around the lateral canthus for safer and more-efficient BoNT-A treatments for crow's feet., (© 2023. The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.)

Purpose: Potential asymmetries of the C2 posterior elements pose a problem for the spine surgeon seeking to make the best choice for spinal stabilization while reducing morbidity., Methods: A digital caliper was used to measure the pars interarticularis height and length on left and right sides of 25 adult C2 vertebrae. The pars interarticularis was defined as the bone between the posterior most aspect of the superior articular process and the anterior most aspect of the inferior articular process of C2. Also, the C2 vertebrae from 49 patients were scanned by CT. Parasagittal images were reviewed and using the same definitions as were used for the skeletal specimens, the length and the height of the C2 pars interarticularis from both the left and right sides were measured using CT. The image slices were acquired at 3 mm intervals. The pars interarticularis height was determined on sagittal CT reconstruction, while the pars interarticularis length was calculated on the basis of the axial images., Results: The lengths and the heights of the left and right pars interarticularis were compared using CTs of patients and skeletal specimens. No significant differences were found in the length and height measurements of the CT images on both sides. However, in the skeletal specimens, the left and right pars interarticularis did not differ significantly in length but differed significantly in height (p = 0.003). The mean height of the left pars interarticularis was approximately two times larger than the right in the skeletal specimens. Absolute differences were calculated between the side with the greater length and height and the side with the lesser length and height irrespective of their left-right orientations. For CT measurements, most differences in length and height between the greater pars interarticularis and lesser pars interarticularis occurred between 0 and 1 mm with each successive disparity interval yielding lower numbers. Skeletal measurements revealed a similar length disparity distribution to the CT measurements. However, height measurements in the skeletal specimens varied widely. Eight pars interarticularis specimens demonstrated a height difference between 0 and 1 mm. No dry bone pars interarticularis specimens demonstrated a height difference between 1 and 2 mm. The pars interarticularis of nine specimens demonstrated a height difference between 2 and 3 mm. Two demonstrated a height difference between 3 and 4 mm. Four demonstrated a height difference between 4 and 5 mm and two demonstrated a height difference greater than 5 mm. The greater pars interarticularis lengths and heights were combined and compared to their lesser counterparts on CT and skeletal measurements. In all measurements of this type, significant differences were found in the pars interarticularis length and height, whether measured through CT or via digital calipers., Conclusion: Asymmetry between the left and right C2 pars interarticularis as shown in the present study can alter surgical planning. Therefore, knowledge of this anatomical finding might be useful to spine surgeons., (© 2022. The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.)

Purpose: Since cone-beam computed tomography was developed, a number of radiological studies on the bifid mandibular canals (BMCs) and trifid mandibular canals (TMCs) have been reported. However, many of the suggested subtypes of the BMC described in the literature seem to be normal branches of the inferior alveolar nerve. This might be due to a lack of revisiting classic anatomical studies in the field of radiology. Therefore, such studies are revisited here., Methods: A database search using PubMed and Google Scholar was conducted on BMC and TMC. Eighty-nine articles underwent full-text assessment. The reported three classifications of BMC and the six modified classifications were reviewed and compared to the intramandibular inferior alveolar nerve branches., Results: Some subtypes of BMC and TMC simply represent normal inferior alveolar nerve branches, i.e., retromolar branch, molar branch (alveolar branch/dental branch), large mental branch, or communicating branch. Others such as Naitoh's type III BMC and forward canal might be a true BMC., Conclusion: We found that the bifid mandibular canal is an additional intramandibular canal running parallel to the mandibular canal with/without confluence with the main canal through comparison of classifications of BMC/TMC between the radiology and anatomy fields., (© 2021. The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.)

Purpose: The aim of this study was to clarify the anatomical relationship of the procerus with the nose, especially focusing on the transverse part of the nasalis, the nasal ala, and the levator labii superioris alaeque nasi (LLSAN)., Materials and Methods: The 53 faces from Korean cadavers were examined anatomically., Results: The procerus originated from the superficial and deep layers in all specimens. Some fibers of the lateral part of the superficial layer extended to connect to the transverse part of the nasalis, while other such fibers extended to attach to the skin of the upper nasal ala in all specimens. The superficial and deep layers of the procerus merged and then intermingled with the frontalis. The anatomical relationship between the superficial layer of the procerus and the LLSAN was classified into the following two categories according to their connections. Some medial originating fibers of the LLSAN extended superomedially to blend in the area between the superficial layer of the procerus and the depressor supercilii (13.5%). And, some medial originating fibers of the LLSAN extended superomedially and then constituted the lateral portion of the superficial layer of the procerus (7.7%)., Conclusion: This study has yielded crucial data for understanding the anatomical relationships and functions of the procerus in relation to the nose. They will be helpful when designing effective therapies involving botulinum toxin type A, performing various types of rhinoplasty and facial surgeries, and in electromyography analyses.

Purpose: The aim of this study was to clarify the origins of the lumbricals of the foot toward a better understanding of its precise action in the gait., Methods: The lumbricals in the foot were investigated in 66 specimens of embalmed Korean adult cadavers., Results: The first lumbrical arose as two muscle bellies from both the tendon of the FDL and the tendinous slip of the FHL in 83.3 %, and as one muscle belly from the tendon of the FDL or the tendinous slip of the FHL in 16.7 %. These two muscle bellies subsequently merged to form the muscle belly of the first lumbrical. The second lumbrical arose from the tendinous slips of the FHL for the second and third toes as well as the tendon of the FDL in all specimens. The third lumbrical arose from the tendinous slips of the FHL for the third and fourth toes in 69.7 %, and the fourth lumbrical arose from the tendinous slip of the FHL for the fourth toe in 18.2 %. Some deep muscle fibers of the fourth lumbrical arose from the tendinous slip of the FHL for the second toe in 4.5 %, for the third toe in 28.8 %, and for the fourth toe in 15.2 %., Conclusions: The results of this study constitute new anatomical knowledge regarding the origin of the lumbricals, and provide insight into their specific role in production of gait. These findings will be useful for various types of surgery, biomechanics research, and rehabilitation programs.

Purpose: The aim of this study was to clarify the prevalence of blending of the lateral deep slip of the platysma into the buccinator, and the morphologic and spatial relationships thereof., Methods: The lateral deep slip of the platysma was investigated in 42 specimens of embalmed adult Korean cadavers., Results: The lateral deep slip of the platysma was observed in 17 of the 42 specimens (40.5 %). When present, it divided from the deep portion (16 specimens, 38.1 %) or the lateral portion (1 specimen, 2.4 %) of the platysma pars modiolaris. The lateral deep slip passed deep to the facial artery, where it blended into the inferior part of the buccinator. The blending site was located inferolateral to the modiolus. After blending into the buccinator, the fibers of the lateral deep slip coursed longitudinally with the inferior fibers of the buccinator., Conclusion: The present description of the topography of the lateral deep slip of the platysma and its relationship with surrounding structures could improve the understanding of the detailed movements of the lower face and the related EMG activities, with the data also being useful when performing facial surgery.

Purpose: The aim of this study was to clarify the location of termination of the ligamentum venosum (LV) and topographic relationships between the left portal vein (LPV), left hepatic artery (LHA), and LV in the fissures for ligamentum teres and LV., Methods: Anatomical examination was performed on 50 livers from embalmed Korean adult cadavers., Results: The LV originated from a point between the transverse and umbilical portions of LPV (Tr-Um point) in all specimens, and terminated in the common trunk of the middle hepatic vein and left hepatic vein (LHV) (61%) or in the LHV (39%). In the fissures for ligamentum teres and LV, the courses of the LHA relative to the LV and the LPV varied, such that four main patterns could be discerned. In type I (48%), the LHA crossed the inferior surface of Tr-Um point and passed just left of the origin of LV. In type II (20%), the LHA crossed the inferior surface of umbilical portion of LPV. In type III (10%), the LHA crossed the inferior surface of Tr-Um point to pass just left of origin of LV, with one branch of the right hepatic artery crossing the inferior surface of umbilical portion of LPV. In type IV (12%), no arterial branches ran on the inferior surfaces of transverse and umbilical portions of LPV., Conclusion: These details may play a role as external landmarks for facilitating preestimation of intrahepatic structures during various surgical procedures involving the liver.

Purpose: The fibularis quartus muscle (FQ) is an accessory fibular muscle that can be found in humans, reportedly in up to 22%. The aim of this study was to classify morphological patterns of the FQ and its anatomical variations., Methods: Eighty lower limbs of 40 formalin-fixed adult Korean cadavers were used in this study., Results: The FQ was present in 13 of 80 specimens (16.3%). In two specimens, each specimen had two FQs with different origins and insertion sites. Thus, 15 cases of FQ were found in 13 specimens. The FQ originated from the fibularis brevis muscle (FB) in 12 cases (15%). In these cases, the FQ arose either as a muscle or as a tendon. The muscle fibers of the FQ merged into a tendon (8 of 12 cases) that inserted variously into (1) the tendon of the FB (three cases, 3.8%), (2) the lateral surface of calcaneus (two cases, 2.5%), (3) the inferior peroneal retinaculum (two cases, 2.5%), or (4) the dorsal surface of the base of fifth metatarsal bone (one case, 1.3%). The FQ arose as a tendon from the FB in 4 of 12 cases. In three of the four cases, the FQ inserted into the lateral surface of calcaneus. The FQ arose from structures other than the FB (three cases, 3.8%)., Conclusion: The present study has demonstrated a new classification for the FQ and its anatomical variations, and provided detailed data for its accurate identification of a muscle and relevant surgical procedures.

The coracobrachialis muscle (Cb M) receives nerve branches from the musculocutaneous nerve (Mc N). Many textbooks describe that the Cb M is innervated by the C5, C6, and C7 spinal nerves. The present study was performed to identify the spinal nerve composition of the nerve branches innervating the Cb M and to evaluate the number of myelinated axons of the nerve branches. Two types of spinal nerve compositions were observed: type I, composed of both C6 and C7 nerves, comprised 88.9% (40/45) of the sides; and type II, composed of only C7 nerves, comprised 11.1% (5/45) of the sides. Of the type I branches, 245.4 +/- 26.3 (mean +/- SD, range 201-267) of the myelinated nerve fibers were derived from C6 and 520.0 +/- 41.8 (range 469-567) of the fibers were derived from C7. Of the type II branches, 836.4 +/- 125.5 (range 709-991) of the nerve fibers were derived from C7. Imbroglio Modometer version 2.0 was used to count the number of fibers innervating the Cb M. The main component of these nerve branches was the C7 spinal nerve. The C5 spinal nerve, did not contribute to innervating the Cb M in the present study. The number of branches varied from one to four, with C7 being concentrated in the first and second branches. Therefore, these two branches may be suitable for the neurotization procedure as a donor nerve at the upper trunk (C5 and C6) lesion of the brachial plexus.