Optimal needle electromyography approach to the serratus anterior muscle.

INTRODUCTION/AIMS: There are two conventional needle electromyography (EMG) approaches to the serratus anterior (SA), both of which can result in erroneous insertion into adjacent structures such as the latissimus dorsi (LD), teres major, or external oblique abdominis muscles and pose a risk of long thoracic nerve (LTN) injury. Therefore, we identified a novel needle insertion point for the SA in cadavers that avoids other muscles and LTN injury. METHODS: This study included 17 cadavers: 12 to devise the new method and 5 to verify its accuracy. Novel landmarks were the inferior angle of the scapula (I), sternal notch (S), and xiphoid process (X). The relationships of the LD, pectoralis major (PM), SA, and LTN were determined relative to these landmarks. RESULTS: When inserting a needle into the proximal one third along the line connecting points I and X, there were adequate safety margins around the LD, PM, and LTN, and the new method had excellent accuracy. DISCUSSION: Compared to the conventional midaxillary method, our novel method improved the accuracy of needle EMG of the SA. Follow-up studies using clinical imaging techniques are needed to verify whether above findings are equally applicable in living subjects.

Ultrasonographic Finding of Contralateral Achilles Tendon in Patients With Acute Achilles Tendon Rupture: A Prospective Observational Study.

OBJECTIVE: Although the incidence of contralateral Achilles tendon in patients with Achilles tendon rupture is higher than in the general population, there are no studies evaluating the status of the contralateral Achilles tendon. The aim of this study was to investigate the status of the contralateral Achilles tendon in patients with acute Achilles tendon rupture. DESIGN: Prospective observational cohort study. SETTING: University hospital foot and ankle clinic. PARTICIPANTS: Seventy-five patients with acute Achilles tendon rupture who met the inclusion criteria. INTERVENTION: Ultrasonography performed by an orthopedic surgeon who had 8 years of experience in musculoskeletal ultrasonography. MAIN OUTCOME MEASURES: Ultrasonographic abnormalities of the contralateral Achilles tendon at the time of diagnosis of acute Achilles tendon rupture. Abnormalities were categorized as intratendinous lesions, peritendinous lesions, changes in retrocalcaneal bursa, and Achilles tendon thickening. RESULTS: The maximal Achilles tendon thickness had a mean of 4.8 ± 1.0 mm. Nine patients (12%) showed ultrasonographic abnormalities on the contralateral Achilles tendon, and the presence of exertional pain was the sole associating variable with ultrasonographic abnormalities. CONCLUSION: The prevalence of ultrasonographic abnormalities in the contralateral Achilles tendon shown in this study was not higher than that reported in healthy or asymptomatic Achilles tendon. Therefore, routine evaluation of the contralateral Achilles tendon is unnecessary at the time of acute Achilles tendon rupture.

Value of postoperative computed tomography for the diagnosis of lateral hinge fracture in medial opening-wedge supramalleolar osteotomy.

INTRODUCTION: It remains unclear whether computed tomography (CT) is superior to plain radiography in detecting lateral hinge fractures after medial opening-wedge supramalleolar osteotomy (SMO) of the ankle joint. This study aimed to evaluate the disparity between postoperative plain radiography and CT in detecting lateral hinge fractures after medial opening-wedge SMO and to identify the predictive factors of lateral hinge fractures. MATERIALS AND METHODS: This retrospective study included 39 patients who underwent medial opening-wedge SMO. The immediate postoperative plain radiography and CT scan images were retrieved, and the presence of lateral hinge fractures was independently determined. Depending on the fracture gap, the lateral hinge fractures were subclassified as stable (gap < 2 mm) or unstable (gap ≥ 2 mm) fractures. To investigate the predictive factors, the cases were divided based on diagnostic tools such as plain radiography and CT. RESULTS: The incidence of lateral hinge fractures was 48.7% (19/39) on plain radiographs and 61.5% (24/39) on CT scans. Five cases of lateral hinge fractures additionally detected on CT scans were stable fractures, and all had been classified as no fracture on plain radiographs. The unstable fractures that had been subclassified based on plain radiographs did not change on CT scans. None of the variables were associated with the presence of lateral hinge fractures on plain radiographs and CT scans. CONCLUSIONS: Postoperative CT after medial opening-wedge SMO has no additional diagnostic value if the lateral hinge fracture has already been diagnosed on plain radiography. Therefore, postoperative CT is only recommended when lateral hinge fractures are not visible on plain radiographs.

Acute hepatitis E virus superinfection increases mortality in patients with cirrhosis.

BACKGROUND: Although acute hepatitis E is not fatal in healthy individuals, it is unclear whether hepatitis E superinfection increases the mortality in patients with pre-existing liver disease. Thus, we investigated the prognosis of patients with acute hepatitis E according to their cirrhosis diagnosis, and the prognosis according to the development of acute-on-chronic liver failure (ACLF) in patients with cirrhosis and chronic liver disease (CLD). METHODS: This study included 74 consecutive patients who were diagnosed with acute viral hepatitis E between January 2007 and December 2019. Of them, 39 patients without CLD, 13 patients with non-cirrhotic CLD, and 22 patients with cirrhotic CLD were analyzed. RESULTS: Among the 74 patients with HEV infection, 7 (9.5%) died within 180 days: 5 with underlying cirrhosis (71.4%) and 2 without cirrhosis (28.6%). The 180-day mortality was significant higher for patients with cirrhosis than for patients without cirrhosis (22.7% vs. 3.8%, P = 0.013). The age- and sex-adjusted proportional-hazard model revealed an approximately eightfold increase in the 180-day mortality risk in patients with cirrhosis compared to patients without cirrhosis. In addition, development of hepatitis E virus-related ACLF due to acute liver function deterioration in patients with pre-existing CLD or cirrhosis worsened the 180-day mortality rate. CONCLUSIONS: Our findings suggest that the acute hepatitis E mortality rate was low in healthy individuals but higher in patients with cirrhosis, and especially high in those with ACLF.

Risk Factors for Persistent Pain Requiring Surgical Treatment in Adult Symptomatic Accessory Navicular.

OBJECTIVE: Identifying the risk factors for persistent pain despite proper conservative treatment in adult symptomatic accessory navicular may reduce the need for surgical treatment. The aim of this study was to identify any such risk factors. DESIGN: Cohort study. SETTING: University hospital foot and ankle clinic. PATIENTS: A retrospective review of 313 patients who presented with adult symptomatic accessory navicular was performed. ASSESSMENT OF RISK FACTORS: Potential risk factors were identified via medical records and foot radiographs. The possible risk factors included age, gender, body mass index, smoking status, occurrence/cause of symptoms, occupation, type of accessory navicular, and radiographic foot parameters. MAIN OUTCOME MEASURES: Predictors that relate to persistent pain requiring surgical treatment in adult accessory navicular were analyzed using logistic regression analysis. RESULTS: Of the 313 patients included, 30 (9.6%) underwent surgical treatment due to failure of conservative treatment. The odds of needing surgical treatment decreased by 0.96 per year of age at symptom onset (P = 0.030), but those odds were 8.52 times higher in patients who had a type IIB accessory navicular (P = 0.001). Other variables did not reach statistical significance. CONCLUSIONS: Younger age at symptom onset and type IIB were the risk factors for persistent pain requiring surgical treatment in adult symptomatic accessory navicular.

Comparison between headless compression screws and tension band wires for the fixation of medial malleolar fractures: a prospective randomized trial.

INTRODUCTION: To date, there has been no prospective randomized trial supporting the rationale of the use of headless compression screw (HCS) compared to conventional fixation methods for medial malleolar fractures. This study aimed to prospectively compare the outcomes of the HCS and tension band wire (TBW) for the fixation of medial malleolar fractures. MATERIAL AND METHODS: Sixty patients were randomized to receive either an HCS or a TBW for the fixation of a medial malleolar fracture. Clinical outcomes were assessed using the Olerud-Molander ankle score (OMAS), EuroQoL five-dimensional instrument (EQ-5D) score, visual analog scale (VAS) score, patient satisfaction with implant-related symptoms, operative time, and incision length. Radiographic outcomes were assessed using the presence of nonunion, delayed union, and articular incongruity. Clinical and radiographic assessments were performed at 2 and 6 weeks and 3, 6, and 12 months postoperatively. RESULTS: The OMAS, EQ-5D score, VAS score, and operative time did not differ between the HCS and TBW groups; however, the HCS group had greater satisfaction with implant-related symptoms and smaller incision than the TBW group. There was no difference in the presence of nonunion, delayed union, and articular incongruity. CONCLUSION: HCS fixation for medial malleolar fractures is not inferior to TBW fixation, while reducing implant-related symptoms. These findings suggest that HCS is a viable alternative for the fixation of medial malleolar fractures.

How accurately can surgeons perform angle manipulation? Quantitative assessment of the accuracy of manual angle manipulation of orthopedic surgery: a cadaver study.

INTRODUCTION: To date, only few studies have been performed on the accuracy of manual angle manipulation during orthopedic surgery. This cadaver study was aimed at quantitatively assessing the accuracy of manual angle manipulation performed by orthopedic surgeons according to their surgical experience and comparing it with manipulation performed with the assistance of a digital goniometer. MATERIALS AND METHODS: Six lower-leg specimens of fresh-frozen human cadavers were subjected to angle manipulation performed via Kirschner wire (K-wire) insertion. K-wires were inserted manually and with the assistance of a digital goniometer at target angles of 0°, 30°, and 60° by three operators who had different levels of experience in orthopedic surgery. The accuracy of the insertion angles at the target angles was evaluated using computed tomography. RESULTS: The mean angle error in the manual angle manipulation was 8.8° (standard deviation [SD] 6.0). When the target angles were set to 0°, 30°, and 60°, the identified angle errors were 6.1° (SD 4.3), 8.8° (SD 6.6), and 11.7° (SD 5.6), respectively, and each value did not show any significant difference among the operators. With the assistance of a digital goniometer, the mean (SD) angle error was significantly improved to 2.1° (1.1°) (p < 0.001). The amount of improvement in accuracy significantly increased as the target angle increased (p = 0.01). CONCLUSION: This cadaver study quantified the inaccuracy of manual angle manipulation in orthopedic surgery and showed that these inaccuracies ​​can be improved using an assistive device. These results support the need to develop a device that can compensate manual angle manipulation in orthopedic surgery.

The Influence of Ankle Position on Radiographic Diagnosis of Acute Achilles Tendon Rupture.

No previous study has demonstrated the relationship between the ankle position and radiographic diagnosis of acute Achilles tendon rupture. The purpose of this study was to investigate the influence of ankle position in the presence of diagnostic radiographic signs in acute Achilles tendon rupture. A retrospective review of 154 ankle lateral radiographs of acute Achilles tendon rupture was performed. Ankle position was classified as dorsiflexion, neutral, or plantar flexion by measurement of the tibiotalar angle. Kager's triangle, Toygar's angle, Arner's sign, and thickening of the Achilles tendon were assessed as diagnostic radiographic signs, and their relations to ankle position were analyzed. Interobserver reliabilities of radiographic signs were moderate to substantial (kappa value, range 0.41-0.68). All 4 signs were significantly more visible in ankle plantar flexion than dorsiflexion. The presence of Toygar's angle and positive Arner's sign were significantly increased in ankle plantar flexion compared to neutral, while the presence of Kager's triangle, and thickening of the Achilles tendon did not differ according to ankle position. The diagnostic radiographic signs of acute Achilles tendon rupture were better presented in ankle plantar flexion position than neutral and dorsiflexion positions. Neutral and dorsiflexion ankle positions should be avoided when performing lateral radiographs of patients with suspected acute Achilles tendon rupture.

Impact of acute kidney injury on mortality in patients with acute variceal bleeding.

BACKGROUND: The effect of acute kidney injury (AKI) on patients with acute variceal bleeding (AVB) using the recently proposed International Club of Ascites (ICA) criteria is unclear. This study aimed to evaluate the incidence of AKI using the ICA criteria and factors associated with the outcomes in cirrhotic patients with AVB. METHODS: This retrospective cohort study included data of cirrhotic patients with AVB from two centers in Korea. The association of the ICA criteria for AKI with 6-week mortality was analyzed through univariate and multivariate analyses using the Cox proportional hazard model. RESULTS: In total, there were 546 episodes of AVB in 390 patients, of which 425 and 121 episodes were due to esophageal and gastric variceal bleeding, respectively. Moreover, 153 patients fulfilled the ICA criteria for AKI, and 64, 30, 39, and 20 patients were diagnosed with stages 1a, 1b, 2, and 3, respectively. Conversely, 97 patients developed AKI within 42 days as per the conventional criteria. The 6-week mortality rate was significantly higher in patients with ICA-AKI than in patients without ICA-AKI; the occurrence of ICA-AKI was an independent factor for predicting the 6-week mortality. CONCLUSION: The ICA criteria could help diagnose renal dysfunction earlier, and presence of AKI is a predictor of mortality in patients with cirrhosis and AVB.

Bone Defects After Surgery for Displaced Intraarticular Calcaneal Fractures Spontaneously Improve Without Bone Grafting.

BACKGROUND: Most intraarticular displaced calcaneal fractures are accompanied by bone defects after surgical treatment, but the concern about negative effects of bone defects has not been resolved yet owing to the few studies on this issue. Therefore, studies on volumetric changes in bone defects over time and the correlation between postoperative outcomes and residual bone defects will be helpful to address the controversy on the necessity of bone grafting in bone defects of calcaneal fractures. QUESTIONS/PURPOSES: (1) Do bone defects change in size in the first year after surgical treatment of displaced intraarticular calcaneal fractures? (2) Does the size of residual bone defects correlate with postoperative radiographic or clinical outcomes? METHODS: Between 2015 and 2019, 99 patients with displaced intraarticular calcaneal fractures visited the investigators' institution, of whom 95 received surgical treatment. Of the patients treated with surgery, 25% (24 of 95) did not undergo open reduction and internal fixation via an extensile lateral approach, and 19% (18 of 95) had multiple fractures, bilateral fractures, open fractures, or a history of previous surgery on the calcaneus; all of these patients were excluded. During the study period, CT was routinely performed for calcaneal fractures immediately after and 12 months after the surgery, but 6% (6 of 95) of the patients had insufficient CT data due to loss to follow-up before 12 months or other reasons, leaving 47 patients for evaluation in this retrospective study. Fractures were fixed with plate and screws, and bone grafting was not performed in all patients. To answer our first question, which was on the changes in bone defects over time, volumetric measurements of the bone defect were performed using CT via the ITK-SNAP software. The percentage of volumetric change was calculated as a fraction of the volumetric change over 12 months from the initial volume. The percentage of the residual bone defect was calculated as a fraction of the volume of the residual bone defect relative to the volume of the entire calcaneus. To answer our second question, which was on the correlation between residual bone defects and postoperative outcomes, we assessed the Böhler angle, Gissane angle, calcaneal height, Olerud-Molander Ankle Score (OMAS), and VAS score for pain and compared these parameters with the size of the residual bone defect using the Pearson correlation coefficient. The OMAS and VAS scores for pain were evaluated and recorded during patient visits, and we obtained the scores through a chart review. All volumetric measurements and radiographic evaluations were performed by two orthopaedic surgeons, and the intraobserver and interobserver reliability were assessed using the intraclass correlation coefficient. RESULTS: The mean volume of the bone defect measured using CT was 4 ± 3 cm3 immediately after surgery and 1 ± 1 cm3 12 months after surgery. During the first 12 months after surgery, the mean volume of the bone defect was reduced by 77% (95% confidence interval 73% to 80%). The mean residual bone defect in the entire calcaneus was 2% (95% CI 1% to 2%), and none of the postoperative outcomes were correlated with the residual bone defect. CONCLUSION: As bone defects substantially resolve without treatment, surgeons do not need to use bone graft for the surgical treatment of displaced intraarticular calcaneal fractures. Future studies that include patients who underwent bone grafting for the treatment of calcaneal fractures are needed to confirm our findings and to further investigate whether bone grafting has additional benefits for the recovery of bone defects. LEVEL OF EVIDENCE: Level III, therapeutic study.

Validation and cross-cultural adaptation of the Korean translation of the Achilles tendon Total Rupture Score.

BACKGROUND: The Achilles tendon Total Rupture Score (ATRS) is a widely used patient-reported outcome measure to assess clinical outcomes of Achilles tendon rupture, but it has not been validated in Korean yet. The purpose of this study was to translate the ATRS into Korean and evaluate its reliability and validity in a Korean population. METHODS: The ATRS was translated into Korean according to recommended guidelines for forward-backward translation. Thirty-eight patients who underwent surgical treatment for Achilles tendon rupture from 2017 to 2019 were enrolled. Reliability was evaluated by the intraclass correlation coefficient (ICC), standard error of measurement (SEM), and minimal detectable change (MDC). Construct validity was assessed with Spearman rank correlations with the Korean version of the Foot and Ankle Outcome Score (FAOS) and Numeric Rating Scale (NRS) for pain in daily activity. RESULTS: The Korean translation of the ATRS had excellent test-retest reliability (ICC = 0.84) and acceptable internal consistency (Cronbach's alpha = 0.84). The SEM was 6.61, and the MDC was 18.32 at the individual level and 2.97 at the group level. The Korean translation of the ATRS was strongly correlated with the FASO (r = 0.88). Correlation with the NRS in daily activity (r = - 0.66) was moderate. CONCLUSION: The Korean translation of the ATRS showed sufficient reliability and validity for use in the Korean population. LEVEL OF EVIDENCE: II.

Comparison of the intraoperative efficacy of the powered rasp and conventional burr in arthroscopic resection of anterior ankle osteophytes.

BACKGROUND: The efficacy of the powered rasp, a new reciprocating motion device for arthroscopic resection of osteophytes, has not been verified. The aim of this study was to compare the intraoperative efficacy of the powered rasp in arthroscopic resection of anterior ankle osteophytes to that of the conventional burr. METHODS: A total of 49 consecutive patients who underwent arthroscopic resection of anterior ankle osteophytes (26 patients with the conventional burr and 23 patients with the powered rasp) were retrospectively reviewed. The preoperative volume of each osteophyte was measured using computerized tomography scan and three-dimensional software. The resection time was measured by review of the individual arthroscopy video, and the estimated resection rate was calculated as the volume of osteophytes/resection time. RESULTS: The preoperative volume of osteophytes was not different between the two groups (847.8 ± 685.3 mm3 in the conventional burr and 913.3 ± 605.8 mm3 in the powered rasp, p = 0.726). The resection time was 442.4 ± 216.6 s (seconds) in the conventional burr and 386.4 ± 186.3 s in the powered rasp, and the estimated resection rate was 1.8 ± 1.0 mm3/s with the conventional burr and 2.4 ± 1.3 mm3/s with the powered rasp. These measurements were not significantly different between the two groups (p = 0.340 and 0.083, respectively). CONCLUSION: The intraoperative efficacy of the powered rasp did not show superiority to that of the conventional burr in arthroscopic resection of anterior ankle osteophytes. LEVEL OF EVIDENCE: Level III, retrospective comparative study.

Personal audio system for neckband headset with low computational complexity.

Personal audio systems have been developed based on various approaches with the goal of synthesizing an isolated sound zone that avoids disturbing others in different locations. In this work, a near-field solution for a neckband headset using three loudspeakers positioned close to each ear is proposed. In particular, it is an attempt to derive a simple multichannel filter for reducing the computational cost in mobile devices. Unlike super-directive beamforming techniques, the controlled radiation pattern is not highly directional but can boost the near-field sound, thereby providing an extra sound level difference between the listener's ear locations and far-field surrounding areas. For this purpose, a multichannel filter is designed using a conventional pressure matching technique for reproducing a target signal at the ear location while suppressing sound radiation to a far-field. It is shown that the optimal filter weights can be successfully approximated in the form of a simple broadside differential array pattern. The simplified filter structure can be realized using only two second-order infinite impulse response filters for driving the middle and two side loudspeakers. Through various simulations and experiments, it is demonstrated that the proposed solution can effectively realize a personal audio system with a minimal loss of sound isolation performance.

Parametric direction-of-arrival estimation with three recurrence relations of spherical harmonics.

The eigenbeam estimation of signal parameters via the rotational invariance technique (EB-ESPRIT) is a well-known subspace-based beamforming algorithm for a spherical microphone array. EB-ESPRIT uses a recurrence relation to directly estimate directional parameters expressing directions-of-arrival (DOAs) of sound sources without an exhaustive grid-search. In the conventional EB-ESPRIT, the directional parameter along the elevational direction is given by a tangent function, which inevitably produces two shortcomings. First, the tangent function becomes singular for sources near the equator in spherical coordinates. Furthermore, two sources lying in exactly opposite directions in the spherical coordinates are indistinguishable and a strong ambiguity problem arises. In this work, an EB-ESPRIT technique based on generalized eigenvalue decomposition (GEVD) is proposed to resolve the singularity and ambiguity problems. The proposed technique uses three independent recurrence relations for spherical harmonics, thus the singularity problem due to the tangent function can be completely avoided. A common transformation matrix for extracting DOAs from recurrence relations are found from the GEVD, and the use of cosine and sine functions makes it possible to find DOAs without ambiguity and without extra transforms or angle-pairing processes. It is demonstrated that the proposed method not only overcomes the singularity and ambiguity problems, but also outperforms conventional techniques in terms of DOA accuracy.

Direction of arrival estimation using nonsingular spherical ESPRIT.

The eigenbeam-ESPRIT (EB-ESPRIT) is a parametric method that estimates the direction of arrival of source signals using a recurrence relation of spherical harmonics. In EB-ESPRIT, the sound-source elevation angle is estimated from an arctangent function, which diverges near the equator in the spherical coordinate system and inevitably induces an ill-conditioning problem. Here, a nonsingular spherical ESPRIT technique based on sine-based recurrence relations is proposed, in which the elevation angles are estimated from an arcsine function. It is shown that the proposed technique can estimate more sources than the conventional EB-ESPRIT technique while also avoiding ill-conditioning problems.

Multidimensional Anodized Titanium Foam Photoelectrode for Efficient Utilization of Photons in Mesoscopic Solar Cells.

Mesoscopic solar cells based on nanostructured oxide semiconductors are considered as a promising candidates to replace conventional photovoltaics employing costly materials. However, their overall performances are below the sufficient level required for practical usages. Herein, this study proposes an anodized Ti foam (ATF) with multidimensional and hierarchical architecture as a highly efficient photoelectrode for the generation of a large photocurrent. ATF photoelectrodes prepared by electrochemical anodization of freeze-cast Ti foams have three favorable characteristics: (i) large surface area for enhanced light harvesting, (ii) 1D semiconductor structure for facilitated charge collection, and (iii) 3D highly conductive metallic current collector that enables exclusion of transparent conducting oxide substrate. Based on these advantages, when ATF is utilized in dye-sensitized solar cells, short-circuit photocurrent density up to 22.0 mA cm-2 is achieved in the conventional N719 dye-I3- /I- redox electrolyte system even with an intrinsically inferior quasi-solid electrolyte.

An intracortical chondromyxoid fibroma in the diaphysis of the metatarsal.

Chondromyxoid fibromas (CMFs) are rare, benign, primary tumors of bones, and occur in the metaphyses of the medullary canals of the long bones. The occurrence of intracortical CMFs is extremely rare. Very few cases of intracortical CMFs located in the long tubular bones have been reported to date. Moreover, even though the feet are the second most common site for CMF (after the knees), intracortical metatarsal CMF has not been reported previously, to our knowledge. We report an intracortical CMF occurring in the diaphysis of the metatarsal in a 17-year-old man. It showed the same imaging findings as usual intramedullary CMFs, except for its cortical location. The development and serial increase in this tumor over time are also demonstrated in this report. Additionally, we present a review of current literature on intracortical CMFs.

Free-Standing Graphene Thermophone on a Polymer-Mesh Substrate.

A graphene thermoacoustic loudspeaker with a thin polymer mesh is fabricated using screen-printing. An experiment with substrates of various free-standing areas shows that a higher sound pressure level can be achieved as compared to previously reported graphene thermoacoustic loudspeakers. Moreover, a modified equation to predict the sound pressure level of the thermoacoustic loudspeaker with a thin and patterned substrate is proposed and verified by experimental results.

Reproduction of a higher-order circular harmonic field using a linear array of loudspeakers.

This paper presents a direct formula for reproducing a sound field consisting of higher-order circular harmonics with polar phase variation. Sound fields with phase variation can be used for synthesizing various spatial attributes, such as the perceived width or the location of a virtual sound source. To reproduce such a sound field using a linear loudspeaker array, the driving function of the array is derived in the format of an integral formula. The proposed function shows fewer reproduction errors than a conventional formula focused on magnitude variations. In addition, analysis of the sweet spot reveals that its shape can be asymmetric, depending on the order of harmonics.

Gene Expression Patterns Associated with Peroxisome Proliferator-activated Receptor (PPAR) Signaling in the Longissimus dorsi of Hanwoo (Korean Cattle).

Adipose tissue deposited within muscle fibers, known as intramuscular fat (IMF or marbling), is a major determinant of meat quality and thereby affects its economic value. The biological mechanisms that determine IMF content are therefore of interest. In this study, 48 genes involved in the bovine peroxisome proliferator-activated receptor signaling pathway, which is involved in lipid metabolism, were investigated to identify candidate genes associated with IMF in the longissimus dorsi of Hanwoo (Korean cattle). Ten genes, retinoid X receptor alpha, peroxisome proliferator-activated receptor gamma (PPARG), phospholipid transfer protein, stearoyl-CoA desaturase, nuclear receptor subfamily 1 group H member 3, fatty acid binding protein 3 (FABP3), carnitine palmitoyltransferase II, acyl-Coenzyme A dehydrogenase long chain (ACADL), acyl-Coenzyme A oxidase 2 branched chain, and fatty acid binding protein 4, showed significant effects with regard to IMF and were differentially expressed between the low- and high-marbled groups (p<0.05). Analysis of the gene co-expression network based on Pearson's correlation coefficients identified 10 up-regulated genes in the high-marbled group that formed a major cluster. Among these genes, the PPARG-FABP4 gene pair exhibited the strongest correlation in the network. Glycerol kinase was found to play a role in mediating activation of the differentially expressed genes. We categorized the 10 significantly differentially expressed genes into the corresponding downstream pathways and investigated the direct interactive relationships among these genes. We suggest that fatty acid oxidation is the major downstream pathway affecting IMF content. The PPARG/RXRA complex triggers activation of target genes involved in fatty acid oxidation resulting in increased triglyceride formation by ATP production. Our findings highlight candidate genes associated with the IMF content of the loin muscle of Korean cattle and provide insight into the biological mechanisms that determine adipose deposition within muscle.