Ultrasonographic images and correspondence with real color sectioned images of the upper limb.

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.

Positional relationships of the origin and course of zygomaticus major with the nasal ala, tragus, philtrum, and lateral canthus for aesthetic treatments and surgeries.

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.

What is a superior labial frenulum? An anatomical and histological study.

Anatomy of the superior labial frenulum (SLF), at first glance, seems to be well established. However, existing studies on the SLF lack description of the incisivus labii superioris (ILS), which cannot be ignored when discussing the SLF. We believe that thorough understanding of the SLF necessitates the anatomical knowledge of the ILS. This study aimed to elucidate the anatomical relationship between the orbicularis oris (OO), ILS, and SLF. A total of 20 formalin fixed human cadaveric specimens were used for gross anatomical and/or histological observation. For histological observation, all specimens were stained with Masson-trichrome. The SLF was a mucosal fold between the gingival mucosa and alveolar mucosa with connective tissue deep to it. The connective tissue attached to the alveolar bone in the junction between the right and left ILS. Skeletal muscle fibers other than orbicularis oris was found in one specimen, which were considered the ILS. During a frenulectomy, removal of the connective tissue bundle is required to prevent recurrence of the high SLF insertion.

Width of the orbicularis oculi fibers extending to the upper lip with the lateral and inferior lengths of the orbicularis oculi at the lateral canthus level: application to botulinum neurotoxin type A injection for crow's feet.

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.

Detethering the superficial temporal artery: Application to tension free superficial temporal artery-middle cerebral artery bypasses.

Extracranial-intracranial bypass has been shown to be effective in the surgical treatment of moyamoya disease, complex aneurysms, and tumors that involve proximal vasculature in carefully selected patients. Branches of the superficial temporal artery (STA) are used commonly for the bypass surgery; however, an appropriate length of the donor vessel must be harvested to avoid failure secondary to anastomotic tension. The goal of this cadaveric study was to investigate quantitatively operative techniques that can increase the STA length available to facilitate tension-free STA-middle cerebral artery (MCA) bypass. We conducted a cadaveric study using a total of 16 sides in eight cadavers. Measurements of the STA trunk with its frontal branch (STAfb) were taken before and after skeletonization and detethering of the STA with the STAfb and mobilization of the parietal branch of the STA. A final measurement of the STA with the STAfb was taken for the free length gained toward visible proximal cortical branches of the MCA. Paired student's t-tests were used to compare the mean length before and after mobilization and unpaired t-tests to analyze according to laterality. The mean length of the STA with the STAfb was 9.0 cm prior to modification. After skeletonization and mobilization, the mean lengths increased significantly to 10.5 and 11.3 cm, respectively (p < 0.05). Especially in the cases that had the coiled and tortuous STA, skeletonization was considerably effective to increase the length of the STA with the STAfb. After simulating a bypass by bringing the STAfb to the recipient MCA site, the mean extended length of the STA with the STAfb was 3.0 cm. There were no statistically significant differences between sides in all measurements. We report a significant increase in the mean STA length available (3.0 cm) following skeletonization and mobilization. Clinical applications of the extended length of the STA with the STAfb may facilitate tension-free STA-MCA bypasses and improve outcomes. Further studies are needed in a clinical context.

Asymmetry of the C2 pars interarticularis: a clinical anatomical study with relevance to screw placement.

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.

What are the retromolar and bifid/trifid mandibular canals as seen on cone-beam computed tomography? Revisiting classic gross anatomy of the inferior alveolar nerve and correcting terminology.

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.

Longitudinal muscular column in the prostatic urethral wall: Its form, shape, and possible function based on mathematical simulation in ejaculation.

BACKGROUND: The shape and function of the longitudinal muscular column (LMC) of the prostate have not been established in detail. The present study was undertaken to elucidate the roles of the LMC of the posterior wall of the prostatic urethra (PSU) in the emission phase of ejaculation by investigating the form and muscular arrangement of the LMC. METHODS: Prostates and urinary bladders were obtained from 14 Korean adult cadavers. Nine specimens were histologically analyzed using hematoxylin and eosin, Masson's trichrome, and Verhoeff-van Gieson staining. Two specimens were scanned using microcomputed tomography (micro-CT), and all scanned images were reconstructed into a three-dimensional model. RESULTS: At the proximal level of the prostate, the ejaculatory ducts (EDs) and prostatic utricle (PU) together were surrounded by circular smooth-muscle fibers. However, at the seminal colliculus (SC) where the EDs and PU opened, they were mainly surrounded by an abundance of longitudinal fibers. The longitudinal fibers posterior to the EDs and PU formed a distinctive LMC in the posterior urethral wall. In histologic sections and micro-CT images, the LMC extended distally from the level of the SC to the level of the membranous urethra (MBU). We simulated a potential mechanism of LMC using a mathematical model of its movements. CONCLUSIONS: Comprehensive analyses based on in-depth assessment of histologic characteristics and micro-CT images demonstrated extension of the LMC from the level of the SC to the level of the MBU, enabling a better understanding of ejaculation physiology involving the LMC. These results suggest that the LMC in the posterior wall of the PSU is a critical component of ejaculation by facilitating the ejection of seminal vesicle fluid into the PSU via well-coordinated contractions.

Muscular Architecture of the Abdominal Part of the Esophagus and the Stomach.

The aim of this study was to clarify the muscular architecture of the abdominal part of the esophagus and the stomach. This study investigated 60 embalmed Korean adult cadavers. The circular and oblique fibers of the stomach that originated from the abdominal part of the esophagus crossed each other in the cardia. The arrangement of the circular fibers of the stomach differed between its anterior and posterior surfaces in all specimens (100%). On the posterior surface of the stomach, the circular and longitudinal fibers on the greater curvature merged and ran parallel toward the fundus. The three layers of the musculature of the stomach have different arrangements in different regions of the stomach and are connected to each other. Understanding the muscular architecture of the stomach and the abdominal part of the esophagus can be helpful when evaluating stomach motility and performing various types of gastrectomy. Clin. Anat. 33:530-537, 2020. © 2019 Wiley Periodicals, Inc.

New Insight Regarding the Zygomaticus Minor as Related to Cosmetic Facial Injections.

The present study aimed to determine the arrangement and terminal attachments of the zygomaticus minor (Zmi) muscle fibers connecting the orbital and mouth regions. The Zmi was examined in 32 specimens of embalmed Korean adult cadavers. The Zmi was present in all 32 specimens (100%). In 31 of the specimens (96.9%), the Zmi that inserted into the upper lip was formed by muscle fibers that arose from the zygomatic bone and muscle fibers that extended from the orbicularis oculi (OOc) muscle. In 14 of the specimens (43.8%), some fibers of the Zmi that arose from the zygomatic bone blended with the inferior margin of the OOc, while the other fibers inserted into the upper lip. After the Zmi fibers blended with the inferior margin of the OOc, these fibers constituted the inferior and medial margins of the OOc. These fibers were then attached to the medial palpebral ligament, the maxilla, the levator labii superioris alaeque nasi muscle, and the depressor supercilii muscle. In 30 of 32 specimens (93.8%), muscle fibers that extended from the OOc constituted the lateral margin of the Zmi, usually descending to the level between the nasal ala and the vermilion border of the upper lip and inserting into the upper lip. The obtained data will be helpful for understanding their connected movements and in kinematics and electromyographic analyses, therapies involving injections of botulinum toxin Type A, and various types of facial surgery. Clin. Anat. 31:974-980, 2018. © 2018 Wiley Periodicals, Inc.

Variations of lumbrical muscle innervation patterns in the hand, focusing on the dual innervation of the third lumbrical muscle.

INTRODUCTION: This study was conducted to clarify the innervation patterns of the lumbrical muscles by identifying the origin of the nerve fascicles innervating these muscles. METHODS: The lumbricals in the hand were investigated in 50 specimens of embalmed Korean adult cadavers. RESULTS: Dual innervation of the third lumbrical was most frequently observed in 64.0%. The third lumbrical was innervated by a branch arising from the median nerve (MN) distal to site at which the superficial branch of the ulnar nerve (sUN) joins the MN in 34%. When separating and tracing the nerve fascicles from the MN distal to the communicating branch from the sUN to MN, the fascicles contained parts of the MN and sUN in 18% and part of the MN in 16%. CONCLUSIONS: These results will be helpful for accurate diagnoses, surgical procedures, and electrophysiological examinations in lesions of the MN and ulnar nerve in the hand. Muscle Nerve, 2016 Muscle Nerve 55: 160-165, 2017.

Anatomical Relationship of the Inferior Bundle of the Incisivus Labii Inferioris With the Depressor Labii Inferioris and the Platysma.

The current study examined the inferior bundle of the incisivus labii inferioris muscle (ILI) and its morphologic and spatial relationships with regard to the depressor labii inferioris muscle (DLI) and the platysma. Incisivus labii inferioris muscles and their inferior bundles were investigated in 50 specimens from embalmed Korean adult cadavers. The inferior bundle of the ILI was divided from the originating fibers of the ILI, and it was present in all specimens (100%). The inferior bundle of the ILI could be distinguished into the transverse and inferolateral slips according to their courses and locations. The inferior bundle of the ILI was classified into 3 types according to the presence of the transverse and inferolateral slips. In Type I (44%), the inferior bundle of the ILI had both the transverse and inferolateral slips. In Type II (48%), the inferior bundle of the ILI had only the transverse slip. In Type III (8%), the inferior bundle of the ILI had only the inferolateral slip. The transverse and inferolateral slips were usually attached to the deep fibers of both the platysma lateral to the DLI and the lateral portion of the DLI via aponeurosis, just below the ILI and above the inferior margin of the mandible, respectively. The new anatomical findings of the present study might contribute to the understanding of the detailed movements required to raise the lower lip. This knowledge will be useful for botulinum toxin type A therapies, various facial surgeries, orthodontic treatment, and electromyographic analyses in this area.

Anatomical relationships of the procerus with the nasal ala and the nasal muscles: transverse part of the nasalis and levator labii superioris alaeque nasi.

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.

Morphological Patterns and Variations of the Nasal Septum Components and Their Clinical Implications.

The aim of this study was to clarify the morphological patterns and proportions of the components of the nasal septum. Anatomical examinations were performed on 70 nasal septums of embalmed Korean adult cadavers. The septal deviation was checked before cutting the nasal cavity midsagittally with the aid of a laryngoscope. The shape of each component of the nasal septum was identified, and photographs were taken from a midline sagittal view. A line was drawn on each photograph between the septal components, and then the area of each septal component was measured using software. The mean area proportions of the septal cartilage (SC), the perpendicular plate of the ethmoid bone (PPE), the vomer, and the nasal crest of the maxilla relative to the total area of the nasal septum were 25.6%, 43.0%, 25.8%, and 5.6%, respectively. The morphology of the nasal septum was classified into 3 main patterns according to the proportion of each septal component. The proportions of the SC, the PPE, the vomer, and the nasal crest of the maxilla were similar to the mean values of the present study in 45.7%. The proportions of the SC, the PPE, and the vomer were similar to each other (with a difference of <15%) in 24.3%. The proportion of the PPE exceeded 50% of the total area of the nasal septum in 22.9%. The results reported herein provide detailed anatomical knowledge that can be used as a valuable reference for rhinoplasty procedures.

Termination of the ligamentum venosum and the topographic relationship between the left portal vein, left hepatic artery, and ligamentum venosum in the fissures for the ligamentum teres and ligamentum venosum.

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.

A new morphological classification for the fibularis quartus muscle.

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.

New insights into the origin of the lumbrical muscles of the foot: tendinous slip of the flexor hallucis longus muscle.

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.

Blending of the lateral deep slip of the platysma muscle into the buccinator muscle.

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.

Spinal nerve composition and innervation of the axillary nerve.

INTRODUCTION: The purpose of this study was to evaluate the spinal nerve composition of the axillary nerve and the contribution of each spinal nerve. METHODS: Thirty brachial plexi extracted from Korean adults (15 men, 14 women, 1 unknown; left side, 13; right side, 17) were examined in this study. RESULTS: The frequency of the contribution of C4 was 13.3%, and it was mainly innervated the deltoid and teres minor muscles. The frequency of inclusion of C7 was 20.0%. C7 fibers were mainly involved in the deltoid and cutaneous branches. The axillary nerve was primarily composed of fibers from C5 and C6 in 66.6%; C4, C5, and C6 in 13.3%; and C5, C6, and C7 in 20.0%. CONCLUSIONS: These findings may be helpful to diagnose damage to axillary nerve structures that occur in such injuries as humerus fractures.

Clinical anatomic considerations of the zygomaticus minor muscle based on the morphology and insertion pattern.

BACKGROUND: The zygomaticus minor muscle (Zmi) is involved in the expression of many different facial emotions. However, the details of its insertion pattern and morphology are not well described. OBJECTIVE: The aim of this study was to clarify the morphology and insertion pattern of the Zmi, and to provide clinical anatomic information that will help elucidate its roles in animation. MATERIALS AND METHODS: Fifty-four embalmed adult hemifaces (18 men and 12 women; mean age, 67.4 years) from 30 cadavers were used in this study. The dissection was performed with the aid of a surgical microscope. RESULTS: This muscle could be classified into 3 types (A-C). Type A, in which the Zmi attached only to the upper lip, was observed in 63.0% of cases (34/54) and could be subdivided into 2 types: straight (A-1; 31.5%, 17 cases) and curved (A-2; 31.5%, 17 cases). Type B, in which the Zmi was attached to both the upper lip and the lateral alar region, occurred in 27.8% of cases (15/54). In Type C (9.2% of cases, 5/54), there was either no or only undeveloped Zmi fibers. CONCLUSION: The present finding of Zmi fibers being attached to the alar region in many cases (27.8%) suggests that this muscle is involved in elevation of both the nose ala and upper lip during various facial animations.