＜Editors' Choice＞ The relationship between preoperative foot alignment and postoperative outcomes in patients who underwent initial total knee arthroplasty.

We compared the relationship between foot alignments and quality of life in patients who underwent initial total knee arthroplasty (TKA). Among the patients with knee osteoarthritis (KOA) who underwent TKA from May 2015 to May 2017 at our hospital, we focused on those in whom weight-bearing foot radiographs had been evaluated preoperatively. The hallux valgus angle and Meary angle were measured by preoperative radiography, and those with hallux valgus angles of 20 degrees or more were classified into the hallux valgus (HV) group, and those with Meary angles of 4 degrees or more into the high arch (HA) group. Also knee and ankle range of motion, knee pain Visual Analog Scale, and the 36-item short-form health survey (SF-36) were measured preoperatively and at discharge, and the amount of these changes was compared in the presence/absence of HV and HA. Regarding HV, there were no significant differences in any of these items between the HV and non-HV groups. However, the SF-physical function was significantly lower in the HA group than in the normal group. In addition, ankle dorsiflexion was lower in the HA group than that in the normal group, although this difference was not statistically significant. There was little improvement of the ankle dorsiflexion, and it was associated with deterioration of the physical function items of SF-36. In total knee arthroplasty patients with HA, physical therapy of the ankles and feet, as well as of the knees, was considered to enhance the improvement of physical function.

Hand Grip Strength Assessment Based on Sarcopenia Diagnostic Criteria Predicts Swallowing Function.

The purpose of this study is to clarify whether swallowing function can be inferred from grip strength. Based on the diagnostic criteria of sarcopenia, patients were divided into two groups according to grip strength, and it was analyzed whether there was a difference in the evaluation index for swallowing function between the two groups. Among the cases requesting evaluation of swallowing function from June 10, 2020 to October 28, 2020, 83 cases (mean age: 71.7 years, 59 males and 24 females) who received assessment tests and swallowing endoscopy were included. According to the diagnostic criteria for grip strength in the Asian working group in Sarcopenia, less than 28 kgf and 18 kgf were defined as the weak group for men and women, respectively. Hyodo scores, repeated salivary swallowing tests (RSST), maximum vocalization time (MPT), and dysphagia severity classification (DSS) were compared between the two groups. Of the 83 patients, 29 and 54 were in the normal group and weak group, respectively. In all indicators, the normal group showed significantly better results than the weak group: Hyodo score (2.4 vs. 4.0, p < 0.01), RSST (4.1 times vs. 2.4 times, p < 0.01), MPT (12.1 s vs. 5.9 s, p < 0.001), DSS (4.5 vs. 5.9, p < 0.001), respectively. In multiple regression analysis with DSS as the dependent variable, grip strength was a significant independent variable of DSS even after adjusting for age, gender, and body mass index. Grip strength assessment based on sarcopenia criteria can be a useful tool for estimating swallowing function.

Metabolic syndrome reduces spinal range of motion: The Yakumo study.

BACKGROUND: Excess visceral fat can accumulate owing to lack of exercise. The relationship between metabolic syndrome (MetS) and spinal range of motion (ROM) is not clear. The purpose of this study was to investigate the relationship between MetS and spinal alignment and ROM. METHODS: Orthopedic evaluation was prospectively performed in 544 participants. The participants were classified into two groups on the basis of the Japanese-specific MetS criteria proposed by the Japanese Committee of the Criteria for MetS (JCCMS). Lower back pain (LBP), knee joint pain with the visual analog scale (VAS), Kellgren-Lawrence (K-L) grade for knee osteoarthritis, body mass index (BMI), and spinal alignment and ROM were evaluated. RESULTS: Forty-four (8.1%) were diagnosed as having MetS. The prevalence rate of K-L grade 4 in the MetS group was significantly higher than that in the non-MetS group (p < 0.05). When sex, age, and BMI were evaluated as covariates, there were significant differences in the VAS score for knee pain (non-MetS group vs MetS group: 13.7 vs 23.3, p < 0.05), L1-S1 flexion spinal ROM (44.1° vs 38.1°, p < 0.001), flexion spinal inclination angle (SIA) ROM (107.6° vs 99.3°, p < 0.01), and SIA ROM (135.4° vs 124.0°, p < 0.05). CONCLUSIONS: Knee pain increased and flexion spinal ROM decreased significantly in the MetS group as compared with non-MetS group. Systemic factors associated with MetS may have a specific impact on spinal ROM while promoting knee osteoarthrosis and increased knee pain.

Patient factors influencing a delay in diagnosis in pediatric spinal cord tumors.

The diagnosis of pediatric spinal cord tumor is frequently delayed due to the presence of non-specific symptoms. We investigated the factors influencing the delay between the first symptom presentation and the diagnosis for pediatric spinal cord tumor. We retrospectively analyzed 31 patients of age <20 years (18 men, 13 women) who underwent surgery for spinal cord tumor at a single center during 1998-2018. We extracted the relevant data on patients' symptoms, affected spinal location (cervical: C1-7, thoracic: T1-T12, and lumbosacral: L1-S), and tumor anatomical location (extradural, intradural extramedullary, and intramedullary tumor) that could potentially affect the duration of symptom presentation prior to the diagnosis. The most common symptom presented in the patients was pain (n = 22, 71.0 %). Motor symptoms such as paralysis was associated with early diagnosis (P = 0.039). The duration of symptoms prior to diagnosis was found to be significantly longer in patients with spinal tumor in the lumbar-sacral region than in those with the involvement of the cervical and thoracic regions (2.1 ± 1.7 months vs 13.6 ± 12.1 months; P = 0.006 and 2.9 ± 2.2 months vs 13.6 ± 12.1 months; P = 0.012, respectively). Our study results demonstrated that pain was the most common symptom in the examined patients, although it did not affect the delay in diagnosis, whereas the presentation of motor symptoms was helpful in the diagnosis of pediatric spinal cord tumor and the diagnosis could be delayed in lumbar-sacral spinal tumors.

Impact of the hip joint mobility on whole-body sagittal alignment: prospective analysis in case with hip arthroplasty.

PURPOSE: To clarify the impact of restriction of hip extension on radiographic whole-body sagittal alignment with using postoperative changes of radiographical parameters for hip osteoarthritis. METHODS: We prospectively enrolled 68 patients with hip osteoarthritis scheduled for arthroplasty. Variables included manual examination of hip range of motion (H-ROM) and radiographic whole-body sagittal alignment parameters including sagittal vertical axis (SVA), center of acoustic meatus and femoral head offset (CAM-HA), thoracic kyphosis (TK), lumbar lordosis, sacral slope (SS), and knee flexion angle (KF). We divided patients with preoperative hip extension angle < 0 into the extension restriction (ER) + group and ≥ 0 into the ER- group. Differences in H-ROM, radiographic parameters between groups and postoperative changes were comparatively analyzed. RESULTS: Fifty-seven patients (The ER + group included 28 patients and the ER- group included 29 patients.) were available for the analysis. Pre-/postoperative H-ROM were 99.7 ± 24.9/118.1 ± 16.0 degrees (p < .01). Greater increases in SVA (5.4 ± 3.4 vs 3.4 ± 2.8 cm, p = .02) and in CAM-HA (3.9 ± 3.9 vs 2.8 ± 3.4 cm, p = 013) were found in the ER + group versus ER- group. Postoperatively, the ER + group showed an increase in TK (pre-/postoperative: 35.2 ± 9.7/37.4 ± 8.8 degrees, p = .04) and decreases in SS (36.5 ± 9.6/33.7 ± 9.9 degrees, p < .01) and KF (9.5 ± 7.0/6.9 ± 6.0 degrees, p = .02). Postoperative changes in radiographic parameters in the ER- group were not significant. CONCLUSION: Patients with restriction of hip extension showed global spine imbalance, and significant changes in TK, SS, and KF were observed after arthroplasty. The presence of hip joint disorder and H-ROM restriction must be considered when evaluating spinopelvic alignment and whole-body sagittal alignment.

Comparison of Outcomes between Minimally Invasive Lateral Approach Vertebral Reconstruction Using a Rectangular Footplate Cage and Conventional Procedure Using a Cylindrical Footplate Cage for Osteoporotic Vertebral Fracture.

The aim of the current study was to compare outcomes between lateral access vertebral reconstruction (LAVR) using a rectangular footplate cage and the conventional procedure using a cylindrical footplate cage in patients with osteoporotic vertebral fracture (OVF). We included 46 patients who underwent anterior-posterior combined surgery for OVF: 24 patients underwent LAVR (Group L) and 22 underwent the conventional procedure (Group C). Preoperative, postoperative, and 1- and 2-year follow-up X-ray images were used to measure local lordotic angle, correction loss, and cage subsidence (>2 mm in vertebral endplate depression). In anterior surgery, the operation time was significantly shorter (183 vs. 248 min, p < 0.001) and the blood loss was significantly less (148 vs. 406 mL, p = 0.01) in Group L than in Group C. In Group C, two patients had anterior instrumentation failure. Correction loss was significantly smaller in Group L than in Group C (1.9° vs. 4.9° at 1 year, p = 0.02; 2.5° vs. 6.5° at 2 years, p = 0.04, respectively). Cage subsidence was significantly less in Group L than in Group C (29% vs. 80%, p < 0.001). LAVR using a rectangular footplate cage is an effective treatment for OVF to minimize surgical invasiveness and postoperative correction loss.

Relationship of frequency of participation in a physical checkup and physical fitness in middle-aged and elderly people: the Yakumo study.

An annual physical checkup is provided as part of the long-term Yakumo study. The checkup is voluntary and there is variation in the frequency of participation. The aim of this study was to examine relationship of physical fitness with frequency of participation in this checkup. The subjects had all attended at least one annual physical checkup from 2006 to 2018. Data from 1,804 initial checkups were used for analysis. At the checkups, age, gender, height, weight, body mass index (BMI), and bone mineral density (BMD) were recorded, and physical activity was measured. The average number of physical checkups per participant for 13 years was 2.4 (1-13). Daily exercise habits were found to be significantly associated with higher participation in physical checkups. Furthermore, between groups with low (1-5 times; <90th percentile of participants) and high (≥6 times) participation, weight and BMI were significantly higher, and BMD, grip strength, 10-m gait time, back muscle strength, and two-step test were all significantly lower in the group with lower frequency of participation in the checkup. In conclusions, our results show that frequency of participation in a voluntary annual physical checkup is significantly associated with physical fitness in middle-aged and elderly people.

Ossification of the posterior longitudinal ligament located on the concave side of the apex vertebra in adult spinal deformity.

A 48-year-old female patient presented with discomfort in the front of the chest. Whole spinal X-ray revealed a thoracic curve of 52°, and thoracic computed tomography (CT) myelography and magnetic resonance imaging (MRI) showed that ossification of the posterior longitudinal ligament (OPLL) on the concave side of the apex vertebra (T9) had highly compressed the spinal cord. Cervical MRI also showed that the C4-C5 intervertebral disc herniation mildly compressed the spinal nerve. In concomitant surgery, the patient underwent cervical laminoplasty, in which OPLL was removed by decompressive laminectomy and posterior correction surgery.In patients with adult spinal deformity (ASD), asymmetric mechanical stress at the apex vertebra can cause various abnormal conditions. Long-term local mechanical stress on the concave side of the apex vertebra might have affected OPLL formation in the present case. This is the first report of a surgical case for an ossification located on the concave side of the apex vertebra in a patient with ASD. Mechanical stress at the concave side of the apex vertebra was suspected to be a cause of formation of OPLL.

Characteristics of cases with and without calcification in spinal meningiomas.

PURPOSE: To quantify calcification in spinal meningiomas using Hounsfield unit (HU) values on CT, and to analyze the characteristics of cases with and without calcification and with different histologic subtypes. METHODS: The subjects were 53 patients who underwent surgical resection of spinal meningioma between January 1999 and December 2019. Clinical and surgical data were collected, and all patients were examined neurologically preoperatively and at final follow-up using the modified McCormick scale and the American Spinal Injury Association scale. Calcification was quantified on CT of the spine prior to surgery. A HU value >60 was considered to indicate calcification. RESULTS: The 53 patients (11 males, 42 females) were aged 62.4 ± 14.3 (range 19 to 91) years at surgery, and had a symptom duration of 10.8 ± 9.0 (1-36) months. The histological type was meningothelial in 35 cases, psammomatous in 13, and others in 5. The mean tumor volume was 1166 ± 350 (593-2176) mm3, and the mean HU value was 212.2 ± 192.8 (43-648). Forty cases (75%) had calcification (HU value > 60). HU values were significantly related to duration of symptoms (R = 0.590, p < 0.05) and significantly higher in psammomatous cases (p < 0.05). Cases with calcification had longer operative times and greater blood loss, and a significantly lower rate of neurological improvement. CONCLUSION: CT was effective for detecting calcification based on HU values. Detection of a HU value > 60 in spinal meningioma may be useful to narrow the differential diagnosis, evaluate the difficulty of resection, and improve intraoperative management, all of which may improve outcomes.

Challenges for Joint Commission International accreditation: performance of orthopedic surgeons based on International Patient Safety Goals.

The Joint Commission International (JCI) is a US-based organization that accredits and certifies hospitals worldwide. Among the requirements for accreditation, the JCI emphasizes continuous quality improvement (CQI) with regard to international patient safety goals (IPSGs). Our university hospital treats about 26,000 hospitalized patients and 600,000 outpatients annually, and our goal is patient safety in compliance with IPSGs. The purpose of this study is to examine the activities of orthopedic surgeons in preparation for JCI accreditation, including clear identification of patients, preoperative timeout and marking to ensure correct surgery, timely approval of CT/MRI reports, care with pain management, prevention of infection, setting of quality indicators and daily monitoring, and teamwork. Examiners from the JCI visited our hospital to review medical records and documents, and to interview patients, nurses and doctors. There were 1270 evaluation items covering 16 fields, including reviews of IPSGs, patient evaluation and care, infection prevention and control, and governance and leadership. Most importantly, the efforts of all the medical staff in our hospital in obtaining the first JCI accreditation among national university hospitals in Japan have promoted the safety and quality of medical care from the perspective of the patient.

Development and characterization of optical readout well-type glass gas electron multiplier for dose imaging in clinical carbon beams.

The use of carbon ion beams in cancer therapy (also known as hadron therapy) is steadily growing worldwide; therefore, the demand for more efficient dosimetry systems is also increasing because daily quality assurance (QA) measurements of hadron radiotherapy is one of the most complex and time consuming tasks. The aim of this study is to develop a two-dimensional dosimetry system that offers high spatial resolution, a large field of view, quick data response, and a linear dose-response relationship. We demonstrate the dose imaging performance of a novel digital dose imager using carbon ion beams for hadron therapy. The dose imager is based on a newly-developed gaseous detector, a well-type glass gas electron multiplier. The imager is successfully operated in a hadron therapy facility with clinical intensity beams for radiotherapy. It features a high spatial resolution of less than 1 mm and an almost linear dose-response relationship with no saturation and very low linear-energy-transfer dependence. Experimental results show that the dose imager has the potential to improve dosimetry accuracy for daily QA.

Overcoming locomotive syndrome: The Yakumo Study.

OBJECTIVES: Improvement of life expectancy is increasingly important with the aging of society. The aim of the study was to compare physical performance in elderly people in two 3-year periods (2001-2003) and (2016-2018). METHODS: The participants were healthy Japanese elderly adults who attended public health check-ups in Yakumo. Results for 10 m gait time, two-step test, back muscle strength, and grip strength were examined prospectively for participants in 2001-2003 (Group A: n = 488) and 2016-2018 (Group B: n = 309) by gender and age (65-74 and 75-84 years). RESULTS: There were significant differences between Groups A and B for 10 m gait time (age 65-74: male: 5.6 vs. 5.2 s, female: 6.3 vs. 5.5 s; age 75-84: male: 6.1 vs. 5.5 s, female: 6.7 vs. 5.8 s; all p < .05) and two-step test (age 65-74: male: 1.41 vs. 1.48, female: 1.35 vs. 1.44; age 75-84: male: 1.32 vs. 1.41, female: 1.30 vs. 1.38; all p < .05), but not for back muscle strength or grip strength. CONCLUSION: Our results suggest a phenomenon of 'overcoming locomotive syndrome', in which physical performance changed by aging, including motor functions such as 10 m gait time and two-step test, has improved in the current population compared with a similar population from 15 years ago.

Poor derivation of Tc-MEP baseline waveforms in surgery for ventral thoracic intradural extramedullary tumor: Efficacy of use of the abductor hallucis in cases with a preoperative non-ambulatory status.

Most thoracic intradural extramedullary tumors (IDEMT) are benign lesions that are treated by gross total resection and spinal cord decompression. Intraoperative transcranial-motor evoked potential (Tc-MEP) monitoring is important for reducing postoperative neurological complications. The purpose of this study is to examine the characteristics of Tc-MEP waveforms in surgery for thoracic IDEMT resection based on location of the tumor relative to the spinal cord. The subjects were 56 patients who underwent surgery for thoracic IDEMT from 2010 to 2018. The waveform derivation rate for each lower muscle was examined at baseline and intraoperatively. 56 patients had a mean age of 61.7 years, and 21 (38%) were non-ambulatory before surgery. The tumors were schwannoma (n = 28, 50%), meningioma (n = 25, 45%), and neurofibroma (n = 3, 5%); and the lesions were dorsal (n = 29, 53%) and ventral (n = 27, 47%). There was a significantly higher rate of undetectable waveforms in all lower limb muscles in the ventral group compared to the dorsal group (15% vs. 3%, p < 0.05). In non-ambulatory cases, the derivation rate at baseline was significantly lower for ventral thoracic IDMETs (47% vs. 68%, p < 0.05). The abductor hallucis (AH) had the highest waveform derivation rate of all lower limb muscles in non-ambulatory cases with a ventral thoracic IDMET. Spinal cord compression by a ventral lesion may be increased, and this may be reflected in greater waveform deterioration. Of all lower limb muscles, the AH had the highest derivation rate, even in non-ambulatory cases with a ventral IDEMT, which suggests the efficacy of multichannel monitoring including the AH.

Primary cervical decompression surgery may improve lumbar symptoms in patients with tandem spinal stenosis.

PURPOSE: Tandem spinal stenosis (TSS) refers to coexisting lumbar and cervical canal stenosis. Evidence regarding whether cervical decompression improves lumbar symptoms in TSS is insufficient. Therefore, we determined the effectiveness of cervical decompression surgery for patients with lumbar spinal stenosis (LSS) and cervical spinal stenosis. METHODS: The records of 64 patients with TSS experiencing lumbar symptoms who underwent cervical decompression surgery between April 2013 and July 2017 at a single institution were retrospectively reviewed. We categorized patients into the Non-improved (n = 20), Relapsed (n = 30), and Maintained-improvement (n = 14) groups according to the presence or absence of improvement and relapse in lower limb symptoms in TSS following cervical decompression surgeries. RESULTS: Of 64 patients, 44 (69%) showed improved lower limb or low back symptoms, with 14 (22%) patients maintaining improvement. The preoperative cervical myelopathy-Japanese Orthopedic Association score and the preoperative number of steps determined using the 10-s step test were significantly lower in the Non-improved group than in the Maintained-improvement group. Receiver operating characteristic curve of preoperative 10-s step test results revealed 12 steps as a predictor for maintained improvement. CONCLUSION: The improvement of LSS symptoms following cervical decompression surgeries may be associated with the severity of cervical myelopathy as determined in clinical findings rather than in imaging findings. Patients with TSS having a 10-s step test result of < 12 steps were more likely to experience a relapse of lower limb symptoms following cervical decompression surgeries.

Automated Detection of Spinal Schwannomas Utilizing Deep Learning Based on Object Detection From Magnetic Resonance Imaging.

STUDY DESIGN: A retrospective analysis of magnetic resonance imaging (MRI) was conducted. OBJECTIVE: This study aims to develop an automated system for the detection of spinal schwannoma, by employing deep learning based on object detection from MRI. The performance of the proposed system was verified to compare the performances of spine surgeons. SUMMARY OF BACKGROUND DATA: Several MRI scans were conducted for the diagnoses of patients suspected to suffer from spinal diseases. Typically, spinal diseases do not involve tumors on the spinal cord, although a few tumors may exist at the unexpectable level or without symptom by chance. It is difficult to recognize these tumors; in some cases, these tumors may be overlooked. Hence, a deep learning approach based on object detection can minimize the probability of overlooking these tumors. METHODS: Data from 50 patients with spinal schwannoma who had undergone MRI were retrospectively reviewed. Sagittal T1- and T2-weighted magnetic resonance imaging (T1WI and T2WI) were used in the object detection training and for validation. You Only Look Once version3 was used to develop the object detection system, and its accuracy was calculated. The performance of the proposed system was compared to that of two doctors. RESULTS: The accuracies of the proposed object detection based on T1W1, T2W1, and both T1W1 and T2W1 were 80.3%, 91.0%, and 93.5%, respectively. The accuracies of the doctors were 90.2% and 89.3%. CONCLUSION: Automated object detection of spinal schwannoma was achieved. The proposed system yielded a high accuracy that was comparable to that of the doctors.Level of Evidence: 4.

Age-related Changes in T1 and C7 Slope and the Correlation Between Them in More Than 300 Asymptomatic Subjects.

STUDY DESIGN: A cross-sectional analysis using T1 slope (T1S) and C7 slope (C7S) in asymptomatic individuals. OBJECTIVE: The aim of this study was to identify normative values, ranges of motion (ROMs), age-related changes in T1S and C7S, and correlation between the two slopes. SUMMARY OF BACKGROUND DATA: Few studies have reported age-related changes in the T1S and C7S angles. Additionally, studies investigating the effects of cervical position on these slopes are limited. METHODS: A total of 388 asymptomatic subjects (162 males and 226 females) for whom T1S measurement was performed on radiographs were enrolled in the study. The T1S and C7S angles were measured using neutral radiography of the cervical spine. ROMs were assessed by measuring the difference in alignment in the neutral position, flexion, and extension. RESULTS: The mean C7S and T1S angles were 19.6° (22.2° in males, 17.9° in females) and 24.0° (26.7° in men and 22.1° in women), respectively. The T1S angle was significantly greater than the C7S angle. Both the C7S and T1S angles significantly increased with age. The flexion ROM of C7S was higher than that of T1S, whereas no significant difference was detected between the extension ROMs of the two slopes. The flexion ROMs of the two slopes did not change, whereas the extension ROMs significantly increased with age. A significant positive correlation was observed between the C7S and T1S angles (r2 = 0.75). CONCLUSION: The normative values and age-related changes in C7S and T1S were analyzed. Both the C7S and T1S angles increased with age. The C7S angle was strongly correlated with the T1S angle, suggesting that C7S can substitute T1S on radiographic images.Level of Evidence: 3.

Dynapenia and physical performance in community-dwelling elderly people in Japan.

Aging of society has increased the incidence of physical disability. The goal of this study was to examine the physical ability of elderly people classified as having sarcopenia, presarcopenia, or dynapenia (a low muscle function without low muscle mass) in a community in Japan. The subjects were volunteers aged >60 years who were participants in a health checkup in Yakumo, Hokkaido and were in good general health. Demographic data were collected and physical performance tests were performed to measure grip strength, walking speed, back muscle strength, maximum stride length, and 3-m timed-up-and-go (3m TUG) time. A measurement of skeletal muscle mass was used as a basis for calculating the appendicular skeletal muscle index (aSMI). The rates of sarcopenia, presarcopenia, and dynapenia were 10%, 22%, and 8% in males (n=101, age 69.7±5.4 years), and 19%, 23%, and 13% in females (n=112, 68.5±5.9 years). Body mass index in subjects with dynapenia was significantly higher compared to that in subjects with sarcopenia and presarcopenia (p<0.01). Back muscle strength, maximum stride length and 3m TUG were similar in dynapenia and sarcopenia, but differed significantly with those in presarcopenia in both males and females without the influence of age (p<0.05). Further studies are needed to evaluate the benefits of dynapenia intervention programs and to explore the underlying pathophysiology of dynapenia.

Larger muscle mass of the upper limb correlates with lower amplitudes of deltoid MEPs following transcranial stimulation.

To perform spinal surgery safely, it is important to understand the risk factors, including factors that negatively influence intraoperative neuromonitoring (IONM). Transcranial motor evoked potentials (TcMEPs) are important in IONM. Therefore, we aimed to investigate whether muscle mass affects the waveforms of TcMEPs to understand the risk factors influencing TcMEPs. We enrolled 48 patients with thoracolumbar spinal diseases who underwent surgery at our facility between April 2015 and March 2018. Before surgery, the body composition, including muscle mass and fat mass, of all patients was measured using bioelectrical impedance analysis (BIA). During surgery, cranial stimulation under general anesthesia was used to derive TcMEPs, enabling us to measure the amplitude, using the control wave of the TcMEPs of the deltoid muscles and the abductor digiti minimi (ADM) muscles. We found a negative correlation between the amplitude of deltoid-muscle TcMEPs and muscle mass of the upper limb. The amplitude of deltoid-muscle TcMEPs did not correlate with the skeletal muscle index (SMI), muscle mass of the lower limb, or body fat mass. The amplitude of ADM-muscle TcMEPs did not correlate with SMI, muscle mass of any limb, or body fat mass. In conclusion, a larger muscle mass of the upper limb correlated with a lower amplitude of deltoid-muscle TcMEPs. By contrast, there was no correlation between the muscle mass of the upper limb and the amplitude of ADM-muscle TcMEPs. These findings suggest that TcMEPs of the ADM are less influenced by muscle mass and are more stable than those of the deltoid.