Capsular attachment on the anterosuperior femoral head-neck junction: A hypothesis about femoroacetabular impingement.

Femoroacetabular impingement (FAI), characterized by a pathological contact between the proximal femur and acetabulum, is a common precursor of hip osteoarthritis. Cam morphology is a bony prominence that causes FAI and frequently forms on the anterosuperior femoral head-neck junction. Despite anatomical consensus regarding the femoral head-neck junction as a boundary area covered by the articular cartilage and joint capsule, it remains unclear whether the joint capsule is continuous with the anterosuperior articular cartilage. For the anatomical consideration of cam morphology formation, this study aimed to investigate the histological characteristics of the capsular attachment on the anterosuperior femoral head-neck junction, particularly focusing on the presence or absence of continuity of the joint capsule to the articular cartilage. A total of 21 anterosuperior regions (seven hips each for the 12:00, 1:30, and 3:00 positions) from seven hips (three males and four females; mean age at death, 68.7 years) were histologically analyzed in this study for quantitative evaluation of the capsular thickness using histological sections stained with Masson's trichrome, as well as qualitative evaluation of the capsular attachment. The present study showed that the joint capsule, which folded proximally to the femoral head-neck junction from the recess, exhibited a blend of the fibrous and synovial regions. Notably, it not only continued with the superficial layer of the articular cartilage, but also attached to the articular cartilage via the fibrocartilage. This continuous region was relatively fibrous with dense connective tissue running in the longitudinal direction. The capsular thickness at the recess point (mean, 1.7 ± 0.9 mm) and those at the distal end of the articular cartilage (0.35 ± 0.16 mm) were significantly greater than the control value for the most superficial layer thickness of the articular cartilage (0.019 ± 0.003 mm) (Dunnett's T3, both p-value <0.001). Based on the fibrous continuity between the joint capsule and articular cartilage and its thickness, this study suggests the anatomical possibility that some mechanical stress can be transmitted from the joint capsule to the articular cartilage at the frequent sites of cam morphology.

In vivo interrelationships between the gluteus minimus and hip joint capsule in the hip internal rotation position with flexion.

BACKGROUND: The flexion adduction internal rotation (FADIR) test is performed by the combined motions of hip flexion (with knee flexion), adduction, and internal rotation, and can often reproduce anterior hip pain consistent with an individual's presenting pain. Since it has high sensitivity for intraarticular pathology diagnosis but low specificity, understanding the extraarticular pathology that can induce anterior hip pain in the FADIR test may also be essential. This study hypothesized that the interrelationships between the joint capsule and gluteus minimus differ in individuals with and without FADIR-positive pain and aimed to elucidate the in vivo interrelationships at hip internal rotation in 90°-flexion, which is also often restricted in individuals with FADIR-positive pain. METHODS: Ten hips were included in the FADIR-positive group, and ten hips without hip pain in the FADIR test were included in a control group. Based on the ultrasound images at the four hip rotation conditions (20° and 10° external rotations, 0° external/internal rotation, and 10° internal rotation), orientation measurements of the gluteus minimus (muscle belly portion) and joint capsule were performed and quantitatively compared between the FADIR-positive and control groups. Additionally, 3 hips of 3 participants were randomly selected from each of the control and FADIR-positive groups for magnetic resonance imaging analysis. RESULTS: At 0°-external/internal and 10°-internal rotation, on ultrasound images, fibers of the gluteus minimus and joint capsule in the FADIR-positive group were significantly more oriented in the same direction than those in the control group. Magnetic resonance imaging showed that the loose connective tissue between the gluteus minimus and joint capsule was prominent at 10°-internal rotation in the control group, although this was not apparent in the FADIR-positive group. CONCLUSIONS: At hip internal rotation in 90° flexion, the muscular belly portion of the gluteus minimus and joint capsule were oriented in the same direction to a greater extent in the FADIR-positive group than in the control group owing to a morphological change in the loose connective tissue between them. The pathological changes in the loose connective tissue may inhibit smooth movement of the gluteus minimus relative to the joint capsule in individuals with FADIR-positive pain.

Radiographic and clinical comparisons between loose-fit and press-fit stems in monopolar radial head arthroplasty for comminuted radial head fractures.

PURPOSE: Few clinical studies have compared the operative outcomes between loose- and press-fit stems in radial head arthroplasty (RHA). We aimed to evaluate the radiographic and clinical results of the two radial head implant concepts. METHODS: In this retrospective multicenter study, 32 patients (24 women and 8 men) with a mean age of 63.1 years who underwent RHA for comminuted radial head fractures were reviewed between 2005 and 2021. Seventeen patients underwent RHA with a loose-fit stem (L-group), whereas the remaining fifteen patients underwent RHA with a press-fit stem (P-group). The mean follow-up period was 40.1 ± 9.9 months, with the minimum follow-up duration of 12 months. The radiographic findings were evaluated for periprosthetic osteolysis; furthermore, clinical outcomes were analyzed to measure the range of motion of the elbow. The rate of reoperations and prosthesis removal were also reviewed. RESULTS: The general characteristics of the patients were similar in the two groups. The rate of periprosthetic osteolysis was 17.6% in the L-group, whereas it was 53.3% in the P-group. The mean elbow flexions were 128° and 133° in the L- and P-groups, respectively. The mean elbow extensions were -12° and -9° in the L- and P-groups, respectively. The rate of reoperation was 23.5% in the L-group and 15.2% in the P-group. One patient in the L-group had the prosthesis removed because of surgical site infection, whereas one patient in the P-group had the prosthesis removed owing to painful loosening. CONCLUSIONS: No significant differences in the clinical outcomes and reoperation rate were observed between the two radial head implant concepts in this study. However, osteolysis occurred more frequently in the P-group. Although patients with periprosthetic osteolysis are currently asymptomatic, they should be carefully followed up for the symptoms in the long term.

Anatomical basis for contribution of hip joint motion by the obturator internus to defaecation/urinary functions by the levator ani via the obturator fascia.

The functional association between hip joint motion and defaecation/urinary function has attracted considerable research and clinical attention owing to the potential novel approaches for pelvic floor rehabilitation; however, the anatomical basis remains unclear. This study, therefore, aimed to analyse the anatomical basis of force transmission between the obturator internus, a muscle of the hip joint, and the levator ani, a muscle of the pelvic floor. Twenty-three cadavers were used for macroscopic and histological analyses. The three-dimensional structures of the muscles and fascia were recorded using a high-definition camera and a 3D scanner. The arrangement and attachment of the muscle fibres, tendons and fascia were visualised using histological sections stained with Masson's trichrome. The obturator internus and levator ani were in broad contact through the obturator fascia. The height of their contact area was 24.6 ± 9.1 mm. Histologically, the obturator internus and levator ani shared a large area of the obturator fascia, and the obturator fascia provided the attachment of several muscle layers of the levator ani. The contribution of hip joint motion to defaecation/urinary function can be explained by the broad 'planar' contact between the obturator internus and levator ani. This anatomical feature suggests that movement of the obturator internus creates the foundation for the function of the levator ani and contributes to pelvic floor support through the obturator fascia. This study provides an anatomical basis for the effectiveness of the hip muscles in improving defaecation/urinary function by enabling balanced and proper movements.

Radiation educational program significantly reduces intraoperative fluoroscopy time during locking plate fixation for distal radius fractures.

BACKGROUND: The use of C-arm fluoroscopy poses a risk of radiation exposure to the surgeons. This study aimed to examine the intraoperative fluoroscopy time of the distal radius plating before and after radiation educational program. METHODS: A total of 68 cases (48 women and 20 men; average age, 61.8 years) were reviewed between July 2017 and October 2019. All patients were treated with volar locking plate fixation for distal radius fractures. On October 2018, we had a 1-h radiation educational program for orthopedic surgeons. Intraoperative fluoroscopy time was compared between 34 cases in the preintervention group (group A) and 34 cases in the postintervention group (group B). Radiographic correction loss of the fracture was assessed by ulnar variance (UV), radial inclination (RI), and volar tilt (VT) between immediately after surgery and at the time of bone union. RESULTS: A significant difference was found in intraoperative fluoroscopy time between 329 s in group A and 123 s in group B. ΔUV between immediately after surgery and at the time of bone union was 0.6 mm in group A and 0.3 mm in group B; ΔRI was -0.3° in group A, -0.1° in group B, ΔVT is -0.4° in group A, and -0.1° in group B. No significant difference was found among them. CONCLUSIONS: After an educational program on radiation exposure, the intraoperative fluoroscopy time was significantly saved in the plating surgery for the distal radius fractures. The shortening of the intraoperative fluoroscopy time did not affect the loss of radiographic correction of the fractures.

Comparison of ceftriaxone and cefazolin as prophylactic antibiotics for surgical site infection in orthopedic upper extremity surgery: The nationwide shortage of cefazolin in March 2019.

BACKGROUND: Due to the nationwide supply shortage of cefazolin in March 2019 in Japan, ceftriaxone was used as an alternative prophylaxis antibiotic agent. This retrospective study was designed to investigate the impact of cefazolin and ceftriaxone as a prophylactic antibiotic agent for surgical site infection (SSI) in orthopedic upper extremity surgery. METHODS: We used cefazolin for antibiotic prophylaxis to prevent SSI before March 2019. Because of cefazolin shortage, ceftriaxone was used as an alternative agent in our hospital. From April 2014 to May 2021, 2493 upper extremity surgeries were reviewed. The exclusion criteria in this study were as follows: patients aged under 16 years, those with an open wound, those with infectious diseases, those who underwent trigger finger surgery, and those who underwent percutaneous pinning surgery. The incidence of deep SSI was evaluated according to the Centers for Disease Control and Prevention guidelines. RESULTS: Among the 2493 eligible cases, 1674 were included in this study. In the cefazolin group, 1140 cases were included, whereas, in the ceftriaxone group, 534 cases were included. No significant differences in the demographic data of the patients were observed between the two groups. The incidence of deep SSI was 0.08% (1/1140 cases) in the cefazolin group and 1.1% (6/534 cases) in the ceftriaxone group, with a significant difference between the two groups (odds ratio, 12.9; p = 0.005). CONCLUSIONS: This study indicated that the use of ceftriaxone instead of cefazolin after upper extremity surgery increases the risk of deep SSI.

High diagnostic accuracy of magnetic resonance imaging in detecting subscapularis tendon tears by focusing on the most superior portion of the subscapularis tendon.

PURPOSE: This study aimed to test the hypothesis that identifying the exact location of the most superior portion of the subscapularis tendon using magnetic resonance imaging (MRI) provides high diagnostic accuracy in detecting subscapularis tendon tears. METHODS: This study included 157 patients who underwent primary arthroscopic rotator cuff repair between 2014 and 2017. All patients underwent conventional 1.5-T MRI in our hospital, within 3 months before surgery. We retrospectively compared the diagnosis of subscapularis tendon tears using MRI based on an anatomical concept focusing on the superior-most insertion point of the subscapularis tendon with intraoperative arthroscopic findings. RESULTS: Subscapularis tendon tears were detected in 80 (51.0%) of the 157 patients during arthroscopic evaluation. The overall sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of the MRI examination were 90, 83, 85, 89, and 87%, respectively. With a kappa score of 0.83, the concordance rate between the two raters was almost perfect (95% confidence interval, 0.75-0.92). The sensitivities of the oblique-sagittal and axial sequences were 84 and 79%, respectively. CONCLUSIONS: Preoperative MRI evaluation focusing on the most superior portion of the subscapularis tendon demonstrated high diagnostic accuracy in detecting subscapularis tendon tears. To find the most superior portion of the subscapularis tendon tears, it was essential to check the slice at the level of the lesser tubercle tip and its adjacent slice. In addition, the combined observation of oblique-sagittal and axial sequences helped to detect subscapularis tendon tears with higher sensitivity.

Medial patellofemoral ligament is a part of the vastus medialis obliquus and vastus intermedius aponeuroses attaching to the medial epicondyle.

PURPOSE: This study aimed to investigate the bony surface characteristic of the femoral attachment of the medial patellofemoral ligament (MPFL) and the correlation between the relevant layered structures, including muscular aponeurosis and the joint capsule, which contribute to patellofemoral joint (PFJ) stability. METHODS: The morphology of the medial aspect of the medial condyle using micro-computed tomography and analysed cortical bone thickening in 24 knees was observed. For the macroscopic and histological analyses, 21 and 3 knees were allocated, respectively. The Kruskal-Wallis one-way analysis of variance test with Dunn post hoc testing was performed for statistical analysis. RESULTS: At the level of the adductor tubercle, there were no significant differences in cortical bone thickness. At the level of the medial epicondyle (MEC), cortical bone thickness was considerably greater than that in other areas of the medial condyle (mean ± standard deviation, 0.60 ± 0.20 mm; p < 0.0001). Macroscopic analysis revealed that the deep aponeurosis of the vastus medialis obliquus and the tendinous arch of the vastus intermedius distally formed the composite membrane and adjoined to the joint capsule to firmly attach to MEC, which was located at 41.3 ± 5.7 mm posterior and 14.2 ± 3.1 mm superior to the joint cartilage. Histological analysis showed a composite membrane and adjoining capsule attached to MEC via fibrocartilage. CONCLUSION: MPFL could be interpreted as part of the deep aponeurosis of the vastus medialis obliquus (VMO) and the tendinous arch of the vastus intermedius, which combined with the joint capsule to attach to MEC. The cortical bone thickening indicated that the tensile stresses were loaded on MEC in aged cadavers. Involvement of VMO and vastus intermedius aponeuroses in restored graft of MPFL could utilise the dynamic stability of surrounding muscles to mimic a native structure.

Understanding the susceptibility to lateral condyle fracture by analyzing unaffected Baumann's angle in children with distal humeral fracture.

BACKGROUND: Previous studies have shown that posttraumatic cubitus varus deformity in children is somehow related to subsequent humeral lateral condyle fracture. Moreover, we had previously encountered an exactly similar case. In this study, we aim to understand whether there is a morphological difference between pediatric supracondylar and lateral condyle fracture of the humerus by comparing Baumann's angle of the unaffected elbow. METHODS: We conducted a retrospective evaluation of 40 cases of supracondylar fractures (36 boys, 4 girls) and 20 cases of lateral condyle fractures (16 boys, 4 girls) at a single facility between January 2014 and December 2018. The unaffected Baumann's angles and lateral capitellohumeral angles of both groups were measured by two orthopedic surgeons and analyzed using Welch's t-test. The effect size was also calculated using Cohen's d, and intraclass correlation coefficients were applied for intra-rater and inter-rater reliability. RESULTS: The average age of patients in the supracondylar fracture group was 6.78 years and that in the lateral condyle fracture group was 5.70 years. No significant differences were observed between gender and fracture type, between laterality and fracture type, and in the lateral capitellohumeral angles between the groups. Baumann's angle was significantly less in the lateral condyle fracture group (17.27° ± 4.68°) than in the supracondylar fracture group (20.28° ± 3.10°) as analyzed by Welch's t-test (p = 0.015). The effect size was 0.76. Each of the intra-rater reliabilities were 0.97 and 0.96, whereas the inter-rater reliability was 0.75. CONCLUSIONS: A significant morphological difference was found between the supracondylar fracture group and the lateral condyle fracture group. The loss of Baumann's angle which tends to occur after the healing of supracondylar fracture may increase the susceptibility to lateral condyle fracture. Orthopedic surgeons should repair and fix supracondylar fractures appropriately to avoid an ipsilateral second fracture, such as lateral condyle fracture.

Anatomy of inferior end of palatopharyngeus: its contribution to upper esophageal sphincter opening.

PURPOSE: The palatopharyngeus is one of the longitudinal pharyngeal muscles which contributes to swallowing. It is reported that the palatopharyngeus has muscle bundles in various directions and with attachment sites, and each muscle bundle has a specific function. Although previous reports suggest that the palatopharyngeus is partly interlaced with some parts of the inferior constrictor, the precise relationship remains unclear. The purpose of this study was to examine the precise manner of the connection between the palatopharyngeus and inferior constrictor, and to examine the histological characteristics of this connection. METHODS: We examined 15 halves of nine heads from Japanese cadavers (average age: 76.1 years); 12 halves, macroscopically, and three halves, histologically. RESULTS: Our observation suggests that the palatopharyngeus spreads radially on the inner aspect of the pharyngeal wall. The most inferior portion of the palatopharyngeus extended to the inner surface of the cricopharyngeal part of the inferior constrictor. Histological analysis showed that the inferior end of the palatopharyngeus continued into the dense connective tissue located at the level of the cricoid cartilage. The dense connective tissue not only covered the inner surface of the inferior constrictor but also entered its muscle bundles and enveloped them. CONCLUSION: Therefore, the palatopharyngeus interlaced the cricopharyngeal part of the inferior constrictor through the dense connective tissues. The findings of this study show that the palatopharyngeus may act on the upper esophageal sphincter directly and help in its opening with the aid of the pulling forces in the superolateral direction.

Dynamic changes of the joint capsule in relation to the zona orbicularis: An anatomical study with possible implications for hip stability mechanism.

The zona orbicularis, which comprises the inner circular fibers of the joint capsule, is vital for hip stability in distraction. Despite the proximity of the whole joint capsule to the zona orbicularis, their anatomical relationship remains unclear. The aim of this study is to investigate the characteristics of the inner side of the joint capsule comprehensively. Twelve hips from nine bodies donated to science were examined. Six and three of the donated bodies, respectively, were embalmed using 8% formalin and Thiel's method. The joint capsules in three formalin-embalmed bodies were sturied by micro-computed tomography. During formalin fixation of six hips from these three bodies, one side was maintained at hip extension and the other at flexion. The remaining three formalin-embalmed bodies were examined histologically. Micro-computed tomography images revealed that the inward protrusion of the joint capsule narrowed the articular cavity, and the ratio of its narrowest area to that of the femoral neck was less at hip extension than at hip flexion. The Thiel's method specimens showed that the inner surface of the joint capsule protruded inward toward the femoral neck during hip extension. This inward protrusion was not histologically independent of the joint capsule. The zona orbicularis was interpreted as the inward protrusion caused by dynamic change of the joint capsule, rather than the local collar. In other words, the joint capsule could change its morphology dynamically depending on the hip position.

New insight into the iliofemoral ligament based on the anatomical study of the hip joint capsule.

The iliofemoral ligament, which plays an important role in hip joint stability, is formed on the anterosuperior region of the hip joint capsule. Although the tendon and deep aponeurosis of the gluteus minimus and iliopsoas are partly connected to the same region of the capsule, the precise location of the connections between the joint capsule and the tendons and deep aponeuroses remains unclear. The locations of the tendinous and aponeurotic connections with the joint capsule may clarify whether the iliofemoral ligament can be regarded as the dynamic stabilizer. This study investigated the relationships between the anterosuperior region of the joint capsule and the tendon and deep aponeurosis of the gluteus minimus and iliopsoas. Fourteen hips from nine cadavers (five males; four females; mean age at death 76.7 years) were analyzed. Ten hips were macroscopically analyzed, and four were histologically analyzed. During macroscopic analysis, the joint capsule was detached from the acetabular margin and the femur, and its local thickness was measured using microcomputed tomography (micro-CT). The gluteus minimus tendon was connected to the joint capsule, and the lateral end of this connection was adjoined with the tubercle of the femur at the superolateral end of the intertrochanteric line. The deep aponeurosis of the iliopsoas was also connected to the joint capsule, and the inferomedial end of its anterior border corresponded with the inferomedial end of the intertrochanteric line. In the micro-CT analysis, capsular thickening was observed at the base of the connection to the gluteus minimus tendon and at the anterior border of the deep aponeurosis of the iliopsoas. A histological study showed that the gluteus minimus tendon and the deep aponeurosis of the iliopsoas were continuous with the hip joint capsule. Based on the morphology of the tendinous and aponeurotic connections, local capsular thickening and histological continuity, the transverse and descending parts of the iliofemoral ligament were the joint capsules, with fibers arranged according to the connection with the gluteus minimus tendon and the deep aponeurosis of the iliopsoas, respectively. Therefore, the so-called iliofemoral ligament could be regarded as the dynamic stabilizer, with the ability to transmit the muscular power to the joint via the capsular complex. This anatomical knowledge provides a better understanding of the hip stabilization mechanism.

Anatomical relationship between the morphology of the styloid process of the ulna and the attachment of the radioulnar ligaments.

The radioulnar ligaments are the major stabilizers of the distal radioulnar joint under dynamic loading; however, anatomical detail regarding their attachment on the middle and distal thirds of the styloid process of the ulna remains unclear. Because previous anatomical studies included only old cadavers, their anatomical findings might not reflect the morphological features of younger and healthy specimens. This study investigated the anatomical features of the distal ulna, particularly the styloid process, to determine the attachment of the radioulnar ligaments to the styloid process and verified their direction and attachment to the styloid process in younger and healthy donors using magnetic resonance imaging (MRI). We investigated the morphological features of the distal ulna of 12 cadaveric wrists using micro-computed tomography (micro-CT). We also visualized and measured the distribution of the cortical bone thickness. We histologically analyzed three specimens in the axial plane and macroscopically analyzed seven specimens to examine the attachment of the radioulnar ligaments to the styloid process. In addition, we evaluated five wrists from living volunteers using 3.0 Tesla MRI. The distal ulna has a ridge on the dorsoradial aspect of the styloid process that corresponds to the attachment of the radioulnar ligaments. Micro-CT images after data processing revealed that the cortical thickness of the dorsoradial quadrant was thicker than that of the other quadrant at the proximal slice of the styloid process (p < 0.01), and that of the dorsoulnar (p = 0.021) and ulnopalmar (p < 0.01) quadrants at the middle slice. Histological analyses showed that the radioulnar ligaments were attached to the middle and distal thirds of the styloid process via chondral-apophyseal entheses. The direction of the fiber was dorsal in the middle third of the styloid process and changed to palmar in the distal third of the styloid process. The direction and attachment of the radioulnar ligaments on the styloid process were confirmed using MRI for younger and healthy participants. The radioulnar ligaments were attached to the dorsoradial ridge of the styloid process, which was confirmed by cortical bone thickening, histology at the attachment sites, and in vivo MR imaging. The directions of the radioulnar ligaments sterically intersected, which would satisfy both slipping stability and rotational mobility. These anatomical findings may provide the basis for biomechanical consideration of distal radioulnar joint stabilization.

Dorsiflexion is more feasible than plantar flexion in ultrasound evaluation of the calcaneofibular ligament: a combination study of ultrasound and cadaver.

PURPOSE: Ultrasound (US) is a valuable tool for the evaluation of chronic lateral instability of the ankle; however, the feasibility of US for calcaneofibular ligament (CFL) assessment remains unknown. This study aimed to depict and compare CFL on US in various ankle positions to determine the optimal method for evaluating CFL with US and to interpret US findings using cadaveric specimens. METHODS: The US study included 43 ankles of 25 healthy individuals. The CFL was scanned with US in 20° plantar flexion, neutral position, 20° dorsiflexion and maximum dorsiflexion. The distances between fibula and CFL were compared. The cadaveric study included macroscopic qualitative observation of the dynamic change of CFL in 7 ankles and quantitative observation of the directions of CFL and footprints in 17 ankles. RESULTS: In the US study, the mean distance (mm) between fibula and CFL was 7.3 ± 1.3 in 20° plantar flexion, 6.7 ± 1.6 in neutral position, 4.3 ± 2.5 in 20° dorsiflexion and 3.1 ± 2.1 in maximum dorsiflexion. The more dorsiflexed the ankle was, the shorter the distance between fibula and CFL was (Jonckheere's trend test p < 0.001). In the cadaveric study, the CFL fibres were aligned parallel between the mid-substance and the fibular attachment in maximum dorsiflexion, whilst CFL was reflected and rotated in plantar flexion. CONCLUSIONS: The whole length of the CFL, including its fibular attachment, is more likely to be visualized with US in dorsiflexion than in plantar flexion due to the direction of the CFL at the fibular attachment, which is parallel with the mid-substance in maximum dorsiflexion. LEVEL OF EVIDENCE: IV.

Device Development for Detecting Thumb Opposition Impairment Using Carbon Nanotube-Based Strain Sensors.

Research into hand-sensing is the focus of various fields, such as medical engineering and ergonomics. The thumb is essential in these studies, as there is great value in assessing its opposition function. However, evaluation methods in the medical field, such as physical examination and computed tomography, and existing sensing methods in the ergonomics field have various shortcomings. Therefore, we conducted a comparative study using a carbon nanotube-based strain sensor to assess whether opposition movement and opposition impairment can be detected in 20 hands of volunteers and 14 hands of patients with carpal tunnel syndrome while avoiding existing shortcomings. We assembled a measurement device with two sensors and attached it to the dorsal skin of the first carpometacarpal joint. We measured sensor expansion and calculated the correlation coefficient during thumb motion. The average correlation coefficient significantly increased in the patient group, and intrarater and interrater reliability were good. Thus, the device accurately detected thumb opposition impairment due to carpal tunnel syndrome, with superior sensitivity and specificity relative to conventional manual inspection, and may also detect opposition impairment due to various diseases. Additionally, in the future, it could be used as an easy, affordable, and accurate sensor in sensor gloves.

Medial elbow anatomy: A paradigm shift for UCL injury prevention and management.

To improve the management outcomes and diagnostic accuracy of the ulnar collateral ligament (UCL) injury, the anatomy of the medial side of the elbow joint is necessary to be understood in terms of the periarticular surroundings rather than the specific ligaments. The aim of this study was to anatomically clarify the medial side of the elbow joint in terms of the tendinous structures and joint capsule. We conducted a descriptive anatomical study of 23 embalmed cadaveric elbows. We macroscopically analyzed the relationship between the flexor pronator muscles (FPMs) and the joint capsule in 10 elbows, histologically analyzed in 6 elbows, and observed the bone morphology through micro computed tomography in 7 elbows. The two tendinous septa (TS) were found: between the pronator teres (PT) and flexor digitorum superficial (FDS) muscles, and between the FDS and flexor carpi ulnaris (FCU) muscles. These two TS are connected to the medial part of the brachialis tendon, deep aponeurosis of the FDS, and FCU to form the tendinous complex, which linked the humeroulnar joint and could not be histologically separated from each other. Moreover, the capsule of the humeroulnar joint under the tendinous complex had attachment on the ST of 7 mm width. The two TS, the brachialis tendon, the deep FDS and FCU aponeuroses, and the joint capsule linked the humeroulnar joint. These anatomical findings could lead to a paradigm shift in the prevention, diagnosis, and treatment of UCL injuries in baseball players. Clin. Anat. 32:379-389, 2019. © 2018 The Authors. Clinical Anatomy published by Wiley Periodicals, Inc. on behalf of American Association of Clinical Anatomists.

Intramuscular Tendon of the Adductor Pollicis and Underlying Capsule of the Metacarpophalangeal Joint: An Anatomical Study With Possible Implications for the Stener Lesion.

PURPOSE: To identify the layered relationship anatomically between the musculotendinous structures of the adductor pollicis, the ulnar collateral ligament, and the capsule of the metacarpophalangeal joint in terms of understanding the pathomechanism of a Stener lesion. METHODS: We macroscopically analyzed 37 cadaveric thumbs to identify the intramuscular tendon of the adductor pollicis and bony attachments of the joint capsule including the ulnar collateral ligament. In addition, we histologically analyzed 3 thumbs and made a 3-dimensional image of 3 other thumbs, using micro-computed tomography. RESULTS: The adductor pollicis has 3 components of an intramuscular tendon (dorsal, palmar, and distal), which connect to form a lambda shape. The dorsal part inserts into the joint capsule dorsal to the ulnar sesamoid. The palmar part inserts into the ulnar sesamoid. The distal part inserts into the lateral tubercle of the proximal phalanx. The thickened and cord-like part of the joint capsule, which has generally been referred to as the proper ulnar collateral ligament, has a distinct bony attachment on the proximal slope of the lateral tubercle of the proximal phalanx separate from the adductor pollicis insertion. CONCLUSIONS: Of the 3 components of the intramuscular tendon of the adductor pollicis muscle, the dorsal part inserted into not only the aponeurosis but also the joint capsule. CLINICAL RELEVANCE: The results of the current study suggest the anatomic basis for a possible pathomechanism of the Stener lesion.

An anatomic study on the attachment of the joint capsule to the tibia in the lateral side of the knee.

PURPOSE: The purpose of the current study was to examine the width, area, and histological characteristics of the capsular attachment to the tibia in the lateral side of the knee. METHODS: A total of 27 knees were used in this study. The joint capsule of the knee was peeled away from the tibia and the width of the capsular attachment to the tibia was measured by two independent observers using a caliper. Interclass correlation coefficients for each value were calculated to evaluate the validity of the measurement. The capsular attachment to the tibia of the seven knees was histologically analyzed using Masson's trichrome staining. RESULTS: At the posterior border of Gerdy's tubercle, the capsular attachment was wide; the average width was 8.6 mm (SD 3.0). Toward the posterolateral aspect of the knee, the capsular attachment gradually tapered. Finally, the capsular attachment was linear at the apex of the head of the fibula. Histological analysis at the posterior border of Gerdy's tubercle revealed developed uncalcified fibrocartilage on the capsular attachment. In contrast, at the apex of the head of the fibula, the joint capsule was adhered to the capsule of the proximal tibiofibular joint. Fibrous connective tissue was directly attached to the calcified fibrocartilage. CONCLUSIONS: The attachment width of the knee joint capsule at the lateral side varied according to location. We consider that this finding on the capsular attachment will facilitate an understanding of the pathology or mechanism of diseases on the lateral side of the knee joint.

Attachment area of fibres from the horns of lateral meniscus: anatomic study with special reference to the positional relationship of anterior cruciate ligament.

PURPOSE: Although studies support the clinical importance of the fibres from the horns of lateral meniscus (LM), few studies have investigated the detailed anatomy. This anatomic study was conducted to analyse the structural details of LM with special reference to (1) the attachment area of the fibres from the anterior and posterior horns and (2) the positional relationship between these fibres and the anterior cruciate ligament (ACL). METHODS: A total of 24 cadaveric knees were used in the macroscopic investigation, and six knees were used in the histological investigation. Micro-computed tomography analysis was also performed to assess the anatomy of the posteriormost fibre from the posterior horn of LM. RESULTS: Based on the macroscopic investigations, the outer fibres from the anterior horn of LM extended to ACL and seemed to intermingle with ACL fibres. However, the histological investigations showed a distinct border between the fibres and ACL. The inner fibres from the anterior horn of LM attached to the lateral intercondylar tubercle serving as a lateral margin of ACL attachment. Fibres from the posterior horn of LM were separated into anterolateral and posteromedial crura which attached to the posterior aspect of the lateral and medial intercondylar tubercles, respectively. These two crura formed the posterior margin of the ACL attachment, except for the central part of ACL. CONCLUSION: The outer fibres from the anterior horn of LM adjoined ACL. The inner fibres from the anterior horn of LM and two crura from the posterior horn of LM formed the border of the attachment area of ACL. The distinctive fibre anatomy from LM could provide a surgical landmark during arthroscopic surgery.

Anatomic study and electromyographic analysis of the teres minor muscle.

BACKGROUND: The teres minor muscle is a focused topic on the treatment of massive rotator cuff tears and reverse total shoulder arthroplasty. Its precise anatomy and function have not been completely investigated. The purposes of this study were to anatomically investigate the muscle and analyze electromyographic (EMG) activities during shoulder motion. METHODS: This anatomic study used 20 shoulders from deceased donors (mean age, 75.0 years). EMG data were recorded from 10 healthy volunteers (mean age, 21.7 years) during flexion, abduction, and external rotations at 0° of abduction, at 90° of abduction, and at 90° of flexion in their dominant arms synchronized with a computerized 3-dimensional motion analysis system. RESULTS: The muscle in all specimens consisted of 2 distinct muscular bundles: the upper and lower portions. The upper portion attached to the round area of the greater tuberosity, and the lower portion inserted into the linear shaped area. Both portions were independent in their origins, insertions, and innervation. The muscle engaged force during each shoulder motion. EMG activities of abduction and the 3 forms of external rotation were similar. Maximal voluntary contraction in the 3 forms of external rotation was 32% in maximum external rotation in the neutral position, 25% in flexion, and 40% in abduction. CONCLUSIONS: The teres minor consists of independent upper and lower portions. The muscle engages force in all ranges of 5 shoulder motions, and maximum external rotation in abduction is a reliable method to evaluate potential activity of the muscle.