Hong-Tae Kim

Background: The distal oblique bundle (DOB) of the interosseous membrane (IOM) has been recognized as an important stabilizer of the distal radioulnar joint (DRUJ). However, its prevalence, morphology, and distal attachments—particularly its relationship to the articular disc and the extensor carpi ulnaris (ECU) tendon sheath—remain inconsistently described. Clarifying these anatomical details is essential for understanding DRUJ stability and guiding surgical reconstruction. Methods: The distal IOM was examined in 48 specimens from 24 embalmed Korean cadavers. In 46 dissected specimens, the presence, morphology, and attachment sites of distal interosseous structures were documented, and attachment levels were measured. In 38 specimens, attachment to the articular disc was assessed. In addition, serial transverse sections from one cadaver were analyzed to confirm three-dimensional relationships. Results: Two morphological patterns were identified: a distinct DOB (21/46, 45.7%) and, when absent, a membranous thickening of the distal IOM (25/46, 54.3%). The mean attachment level was 39.1 ± 9.7 mm for the DOB and 25.4 ± 4.8 mm for the membranous thickening. Both structures assumed an oblique orientation, fanning palmarly toward the capsule and articular disc and dorsally toward the ECU tendon sheath and dorsal septum. In 26 of 38 specimens (68.4%), these structures attached to the proximal palmar portion of the articular disc. Serial transverse sections confirmed this oblique configuration, linking palmar and dorsal stabilizers of the DRUJ. Conclusions: The distal IOM consistently forms specialized structures—either a DOB or a membranous thickening—that integrate with the triangular fibrocartilage complex. By bridging palmar and dorsal stabilizers, these structures contribute to joint congruency and load transfer during forearm rotation. A refined anatomical understanding of these patterns provides clinically relevant insights for surgical preservation or reconstruction, with the potential to improve outcomes in patients with chronic DRUJ instability.

Latissimus dorsi (LD) tendon transfer is widely used to treat irreparable rotator cuff tears, particularly in cases with posterosuperior and anterosuperior tear patterns. We conducted a comprehensive anatomical analysis of the attachment of the LD tendon to the humerus, focusing on its morphological patterns and morphometric features, which are critical for optimizing the surgery. Dissection of 32 LD tendons in 16 Korean cadavers revealed three insertion patterns: fully combined (40.6%), partially combined (34.4%), and fully separated (25.0%). The mean width, length, and thickness of the tendons were 48.4, 56.2, and 6.2 mm, respectively. There were significant asymmetries in tendon dimensions. There were also tendinous slips connecting the LD tendon to the triceps tendon, adjacent brachial fascia, coracoid process, and anterior joint capsule of the shoulder in nine specimens, emphasizing the anatomical variability relevant to surgical planning. These findings provide insights for determining surgical approaches on the basis of patient anatomy, and whether to use LD transfer alone or combined LD and teres major transfers. Understanding the anatomical variations will help to make interventions more precise, which in turn should enhance the efficacy of tendon transfer procedures and improve functional outcomes for patients with complex shoulder pathologies.

Background/Objectives: Anatomical variations in the biceps brachii muscle (BBM) are extremely frequent, leading to developmental and clinical implications. We studied the topography of the BBM and analyzed its correlations with other structures in the brachial region. Methods: A total of 103 cadaveric upper extremities were dissected. The length of the upper extremities was utilized as a reference line. The origin and insertion of the BBM, the coracobrachialis muscle (CBM), and the related neurovascular system were evaluated. Results: Each variable was calculated as a percentile and compared according to the presence of the considered variation; in particular, a supernumerary head of the BBM was found in 12/103 (11.65%) of upper extremities and was associated with a longer upper limb (506.25 ± 32.55 mm vs. 484.27 ± 30.41 mm, p = 0.022). When the variables were standardized by the length of the upper limb, the accessory head of the BBM was associated with the distal insertion point of the CBM (28.18 ± 3.54% vs. 30.59 ± 2.94%, p = 0.011) and BBM length (55.11 ± 2.17% vs. 58.18 ± 3.72%, p = 0.006). Other variables did not present significant differences with respect to the presence of the supernumerary head of the BBM. Conclusions: BBM variations may affect the topography of other structures, such as the length of the upper extremities, insertion of the CBM, and length of the BBM. Further studies are required to elucidate its clinical implications.

Yuri Seu, Hyun Jin Park, Jin Seo Park, Yong‑Suk Moon, Hongtae Kim, Mi-Sun Hur. Anat Cell Biol -0001;0:. https://doi.org/10.5115/acb.24.033

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.

The orbicularis oculi (OOc) is a sphincteric muscle of the eyelids, whereas contraction of the orbicularis oris (OOr), another sphincteric muscle, causes narrowing of the lips. Facial muscle fibers normally blend with adjacent muscles. However, muscle fibers connecting the various facial muscles that have different actions and that are located at distant sites, such as the OOc and the OOr have been rarely reported. Herein, we report a rare case of connecting fibers between the inferior margin of the OOc and the OOr. These connecting fibers were blended with the OOr between the inserting fibers of the levator labii superioris and levator anguli oris. Contraction of such variant muscles might affect typical facial expressions.

The precise location of the Master Knot of Henry (MKH) has important clinical significance, but its anatomical definition has not been agreed upon. The purpose of this study is to present a linear regression equation for predicting length variables based on foot length, by evaluating the correlation of length variables related to flexor hallucis longus (FHL) and flexor digitorum longus (FDL), with respect to the location of the MKH. A total of 95 limbs were dissected from 48 adult cadavers, and were fixed in formalin. Measurements were made for the length parameter, with reference to the landmark. The relevance between length variables was analyzed through simple correlation analysis and linear regression analysis. The foot length was 213.69 ± 17.53 mm, MKH-great toe distal phalanx was 140.16 ± 14.69 mm, MKH-FHL insertion was 124.55 ± 13.46 mm, MKH-little toe distal phalanx was 121.79 ± 13.41 mm, MKH-FDL little toe insertion was 109.07 ± 14.16 mm, and the FHL-FDL angle was 33.15 ± 5.39. The correlation coefficient between all the length variables for foot length showed a high positive correlation. We derived a regression equation that can predict the length of each variable. This regression formula is considered to be highly useful because it can estimate the positional relationship of the MKH relatively simply.

This study aimed to determine the anatomical connections between the inferior fibers of M. orbicularis oculi (OOc inf.) and the M. levator labii superioris alaeque nasi (LLSAN), providing anatomical variations of the connecting fibers. This study examined the OOc and LLSAN of 44 specimens from 22 embalmed adult Korean cadavers. Connecting fibers between the OOc inf. and LLSAN were observed in 29.5 % of the specimens. Connecting patterns of the OOc inf. to the LLSAN were classified into three categories according to the directions of the connecting fibers; Type I (13.6 %), in which some of the OOc inf. coursed medially to blend with the lateral originating fibers of the LLSAN. Type II (11.4 %), in which some of the OOc inf. descended vertically to blend with the LLSAN. Type III (4.5 %), in which both types I and II were found simultaneously. Some of the OOc inf. coursed medially to blend with the lateral originating fibers of the LLSAN, and some of the OOc inf. descended vertically to blend with the LLSAN. These findings provide greater knowledge of the connecting fibers between the OOc inf. and LLSAN, thereby helping us understand complicated expressions, inject BoNT-A into related wrinkles, and analyze EMG activities.

Knowledge of anatomical variations of the limb’s main arteries is significant for the clinicians. Thus, this study is aimed at examining the branching pattern and anatomical variations of the axillary artery. We conducted research on 59 upper limbs of adult human donated cadavers. All axillary artery branches’ origins were assessed, and the correlations between points of origins and variations of specific branches were evaluated. The average length of the axillary artery was found to be 11.22 cm, and this length was defined as reference line. Based on this reference line, the first, second, and third parts were 37.56%, 39%, and 30.05%, respectively. The STA was originated from 25.11%. The TAA and LTA were 42.67% and 54.82%, respectively. The SSA, ACHA, and PCHA were 64.72%, 83.89%, and 84.53%, respectively. The origin of LTA was correlated with that of SSA (R = 0.473, P < 0.05) and AHCA (R = 0.307, P < 0.05), respectively. And there was a positive correlation between AHCA and PHCA (R = 0.705, P < 0.05). The number of branches ranged from 3~6, and 9 types were shown. The most frequent branching pattern was common origin of the LTA and SSA (22/59). And AHCA and PHCA were originated together in 19 cases, and both patterns were combined in 12 cases. TTA and LTA branched together in 9 cases, and common trunk for the SSA, PHCA, and AHCA was found in 2 cases. According to this pattern, the origin of LTA and PCHA was significantly different. This information is particularly useful for surgeons and clinicians.