Phenotypic classification of knee osteoarthritis according to pain mechanisms; a clinical observational study.

BACKGROUND: Pain in knee osteoarthritis is considered to be nociceptive. Recently, involvement of neuropathic pain and psychosocial factors in knee osteoarthritis has been reported. However, the following details are unclear: 1) How often are neuropathic pain and psychosocial factors involved? And 2) Which patients are associated with neuropathic pain and psychosocial factors? METHODS: In 104 patients with knee osteoarthritis, we evaluated neuropathic pain factor with a painDETECT questionnaire and catastrophic thinking using the pain catastrophizing scale. Pain intensity was assessed using the visual analog scale; patients with scores below the median were defined as low-pain group and others as high-pain group. Radiographic severity was categorized according to the Kellgren-Lawrence classification, with grades I-II and III-IV defined as low- and high-grades, respectively. We compared the painDETECT and pain catastrophizing scale scores between the low- and high-pain groups and low- and high-grade groups. Furthermore, the painDETECT and pain catastrophizing scale scores were compared among the following four groups: low-grade/low-pain, low-grade/high-pain, high-grade/low-pain, and high-grade/high-pain. RESULTS: Neuropathic pain factor and catastrophic thinking were found in 16% and 34% of patients, respectively. There were no significant differences in both painDETECT and pain catastrophizing scale scores between the two pain intensity groups. Between the two groups of radiographic severity, there was no significant difference in the painDETECT scores; however, the pain catastrophizing scale score was significantly high in the low-grade group. In addition, there was no significant difference in the painDETECT scores among the four groups; however, the pain catastrophizing scale scores were significantly higher in low-grade/high-pain than in high-grade/low-pain patients. CONCLUSIONS: Therefore, 64% had only nociceptive pain factor. Catastrophic thinking was strong in patients with low radiographic severity, especially in those with high pain intensity. Patients with neuropathic pain factor could not be identified from radiographic severity and pain intensity.

Good Postoperative Flexion Angle Improves Knee Function and Improvement of Flexion Angle Increases Patient Satisfaction After Total Knee Arthroplasty.

BACKGROUND: Total knee arthroplasty (TKA) is a well-established procedure for treating knee joint diseases. However, the postoperative range of motion (ROM) varies and is an important indicator of TKA success. Recently, patient-reported outcome measures (PROMs) and patient satisfaction have drawn attention. However, the relationship between ROM and knee function obtained by PROM and satisfaction is not well understood. METHODS: We retrospectively reviewed the data of 375 patients who underwent 500 primary TKA procedures. We measured the ROM before and after surgery. Knee joint function was evaluated using the Knee Injury Osteoarthritis Outcome Score, a PROM, and patients were classified into good function and poor function groups. Patient satisfaction was evaluated on a 5-graded scale as overall satisfaction, and patients were divided into a satisfied or a dissatisfied group according to the obtained scores. ROM was compared between the 2 groups, then significantly different factors were analyzed using multiple logistic regression analysis. Moreover, cut-off points of ROM for obtaining good function and patient satisfaction were determined using ROC curve analysis. RESULTS: The postoperative flexion angle had a significant effect on knee function (P < .001). The cut-off value of the postoperative flexion angle for good knee function was 120°. The improvement in flexion angle had a significant effect on patient satisfaction (P = .004). The cut-off value for the improvement in the flexion angle was 5°. CONCLUSION: The postoperative flexion angle had a significant effect on knee function and improvement in the flexion angle had a significant effect on patient satisfaction.

Consideration of differences in drug usage between young-onset and elderly-onset rheumatoid arthritis with target of low disease activity.

OBJECTIVES: Elderly-onset rheumatoid arthritis (EORA) is reported to differ from young-onset rheumatoid arthritis (YORA) with regard to patient background and drug treatment. We examined the amount of drug administered to patients who achieved low disease activity (LDA) for rheumatoid arthritis at our hospital. METHODS: Demographics, clinical history, and treatments were compared between patients with EORA (n = 70) and YORA (n = 190). RESULTS: There was a significant difference in the average age (73.8 vs. 57.8 years), disease duration (6.66 vs. 14.7 years), and sex (62.9% males vs. 83.7% females), but no difference in rheumatoid factor positivity (85.3% vs. 80.7%), anti-citrullinated peptide antibody positivity (86.5% vs. 87.7%), simplified disease activity index (4.28 vs. 4.59), or disease activity score 28-CRP (1.99 vs. 2.04) in the EORA and YORA groups, respectively. There were also no significant differences in prednisolone use (37.1% vs. 36.3%), amount of methotrexate administered (MTX) (1.45 vs. 1.41 mg), and MTX use (55.7% vs. 65.3%). However, the MTX dose (2.89 vs. 4.09 mg/week, p = .011) and overall biologics use (32.9% vs. 56.3%, p = .0012) were significantly lower in patients with EORA than in those with YORA. CONCLUSION: Patients with EORA may be able to achieve LDA with lower drug dosage than those with YORA.

ß-Angles of hips with femoroacetabular impingement versus asymptomatic normal hips in a Japanese population: A CT-based observational clinical study.

BACKGROUND: The beta angle (ß-angle)-although used to assess femoroacetabular impingement (FAI)-has not been well evaluated. This study aimed to measure the ß-angle on multiradial computed tomography (CT) slice images of both hips with symptomatic FAI and asymptomatic normal hips to determine its optimal cutoff value for detecting FAI in a Japanese population. METHODS: CT was performed with each subject supine. The ß-angle was measured on seven radial slices (designated R0, R15, R30, R45, R60, R75, R90) that were generated at 15° intervals from the oblique axial slice through the center of the femoral neck. An a priori power analysis was performed. The measurements were made in 20 FAI hips (FAI group) and 23 asymptomatic normal hips (ANH group). Cutoff values were evaluated using receiver operating characteristic curves. RESULTS: The mean ß-angles of the FAI and ANH groups at R0, R15, R30, R45, R60, R75, and R90° were, respectively, 73.6° and 84.2°, 66.0° and 79.3°, 57.2° and 69.2°, 48.1° and 63.1°, 46.7° and 62.5°, 50.0° and 63.7°, and 53.7° and 65.9°. For all slices, the ß-angle was significantly smaller in the FAI group than the ANH group. The optimal ß-angle cutoff values for diagnosing FAI at R0, R15, R30, R45, R60, R75, and R90 were 73.9°, 70.2°, 61.4°, 55.7°, 53.6°, 59.4°, and 60.9°, respectively. The respective specificities and sensitivities of the cutoff values at R0, R15, R30, R45, R60, R75, and R90 were 78.3% and 65.0%, 82.6% and 70.0%, 73.9% and 60.0%, 73.9% and 75.0%, 95.7% and 75.0%, 69.6% and 95.0%, and 78.3% and 80.0%. CONCLUSIONS: In all radial slices, the ß-angle was significantly smaller in the hips with symptomatic FAI than in the asymptomatic normal hips. The most useful cutoff value for diagnosing FAI was a ß-angle of 53.6° at R60.

[A Case of Intussusception Caused by Cancer of the Sigmoid Colon in an Adult].

A 55-year-old man complaining of difficulty in defecation was referred to our hospital. A digital examination and abdominal CT led to a diagnosis of intussusception due to tumor of the sigmoid colon. The intussusception was successful reduced by enema. Following colonoscopy and abdominal enhanced CT, a sigmoid colon cancer(cT3, cN1b, cM0, cStage Ⅲb)was detected. A laparoscopic sigmoidectomy and lymph node dissection were performed on 23 days after the hospitalization. Postoperative course was uneventful. Preoperative reduction of the intussusception in this case enabled us to perform an elective surgery. We report this case with a review of the relevant literature.

Sleep education in primary school prevents future school refusal behavior.

BACKGROUND: Sleep disorders, along with extreme difficulty in awakening, are one of the main causes of school refusal. The accumulation of chronic sleep deprivation accompanied by a late-night lifestyle is considered the basic inciting factor. METHODS: From 2007, we initiated a sleep education program (Min-Iku) in Fukui, Japan, with the aim of improving pupil lifestyle and preventing future school refusal. All grade 1-6 Miyake-primary school (M-PS) pupils participated in this program and gave their informed consent. The Min-Iku included (i) implementation of a "daily life rhythm survey" by recording the sleep-wake rhythm in a table for 14 days; (ii) evaluation of the sleep table according to the classifications A-D; (iii) interviews of stage D children and their guardians; (iv) lectures on the importance of daily life rhythms for parents and teachers; and (v) 45 min classwork for all participating pupils. RESULTS: In 2007, 10% of M-PS graduates developed school refusal behavior after entering Kaminaka junior high school (K-JHS). The incidence of school refusal, however, decreased each year after the implementation of the Min-Iku program and finally reached 0 by 2012. The sleep onset time of pupils improved each year, with the most common sleep time reaching 9:30 p.m. on both weekdays and holidays. With an earlier sleep time, the night-time sleep duration was significantly extended (P < 0.001 vs 2007 data). CONCLUSION: The Min-Iku program for primary school pupils successfully achieved a more routine night-time sleep pattern and a regular life rhythm, which prevented school refusal during the subsequent JHS years.

P2X7 ionotropic receptor is functionally expressed in rabbit articular chondrocytes and mediates extracellular ATP cytotoxicity.

Extracellular ATP regulates various cellular functions by engaging multiple subtypes of P2 purinergic receptors. In many cell types, the ionotropic P2X7 receptor mediates pathological events such as inflammation and cell death. However, the importance of this receptor in chondrocytes remains largely unexplored. Here, we report the functional identification of P2X7 receptor in articular chondrocytes and investigate the involvement of P2X7 receptors in ATP-induced cytotoxicity. Chondrocytes were isolated from rabbit articular cartilage, and P2X7 receptor currents were examined using the whole-cell patch-clamp technique. ATP-induced cytotoxicity was evaluated by measuring caspase-3/7 activity, lactate dehydrogenase (LDH) leakage, and prostagrandin E2 (PGE2) release using microscopic and fluorimetric/colorimetric evaluation. Extracellular ATP readily evoked a cationic current without obvious desensitization. This ATP-activated current was dose related, but required millimolar concentrations. A more potent P2X7 receptor agonist, BzATP, also activated this current but at 100-fold lower concentrations. ATP-induced currents were largely abolished by selective P2X7 antagonists, suggesting a predominant role for the P2X7 receptor. RT-PCR confirmed the presence of P2X7 in chondrocytes. Heterologous expression of a rabbit P2X7 clone successfully reproduced the ATP-induced current. Exposure of chondrocytes to ATP increased caspase-3/7 activities, an effect that was totally abrogated by P2X7 receptor antagonists. Extracellular ATP also enhanced LDH release, which was partially attenuated by the P2X7 inhibitor. The P2X7 receptor-mediated elevation in apoptotic caspase signaling was accompanied by increased PGE2 release and was attenuated by inhibition of either phospholipase A2 or cyclooxygenase-2. This study provides direct evidence for the presence of functional P2X7 receptors in articular chondrocytes. Our results suggest that the P2X7 receptor is a potential therapeutic target in chondrocyte death associated with cartilage injury and disorders including osteoarthritis.

Perforated gastrointestinal stromal tumor (GIST) in a true jejunal diverticulum in adulthood: report of a case.

A 61-year-old man was referred to us for investigation of acute abdominal pain. Computed tomography showed a 5.9 × 5.3 × 5.0 cm lump of food residue in the jejunum, and a large amount of free air and ascites around the liver and right paracolic gutter. He underwent emergency laparotomy for suspected peritonitis from perforation by a foreign body in the small intestine. We identified purulent exudate in the abdominal cavity and perforation of a jejunal cystic mass, attached ~40 cm from Treitz's ligament at the anti-mesenteric side of the jejunum. Based on a diagnosis of jejunal duplication with perforation, we resected that part of the small intestine and performed intra-abdominal drainage. Pathological findings confirmed the diagnosis of a perforated gastrointestinal stromal tumor (GIST) in a true jejunal diverticulum. Histopathological evidence suggests that intestinal pressure and/or hemorrhage can cause perforation in the background of a true jejunal diverticulum. To our knowledge, this is the first case report of a perforated GIST in a true jejunal diverticulum.

[A case of malignant peritoneal mesothelioma diagnosed with laparoscopic biopsy].

A 66-year-old woman was admitted to our hospital for massive ascites of unknown origin. Peritoneal mesothelioma was suspected because of her history of asbestos exposure. Diagnostic laparoscopy with biopsy of the peritoneum and greater omentum was performed. Pathological examination with immunostaining provided a definite diagnosis of malignant peritoneal mesothelioma. The patient underwent early postoperative induction therapy with pemetrexed and carboplatin, which resulted in a reduction in ascites. Laparoscopic biopsy contributed to the definite diagnosis of malignant peritoneal mesothelioma, and thereby, early induction of chemotherapy.

[A case of breast cancer treated with chemotherapy after resection of giant ovarian metastasis].

A 49-year-old female patient presented with lower abdominal pain and constipation. Computed tomography revealed left breast cancer with lymph node metastases, a peritoneal metastasis, bilateral hydronephrosis, and ovarian metastasis. The giant ovarian metastasis occupied the pelvic cavity and was responsible for her symptoms of digestive obstruction. Both ovaries were resected as a palliative measure. Three cycles of weekly paclitaxel were successfully administered, leading to the disappearance of malignant ascites. Hence, reduction surgery for ovarian metastasis in the treatment of breast cancer increased the effectiveness of the chemotherapy by improving the patient's general condition.

Molecular phylogenetic analysis of Echinococcus multilocularis from horses raised in Canada or Japan, using mitochondrial cytochrome b gene-targeted PCR.

Alveolar echinococcosis is a zoonotic disease caused by a larval-stage Echinococcus multilocularis infection. Geographical haplotyping targeting the parasite's mitochondrial cytochrome b (cob) gene has been reported for isolates from definitive and intermediate hosts (wild canids and rodents); however, there are limited reports on strain typing for the dead-end host, the horse, which could act as a sentinel for E. multilocularis. Accordingly, we investigated the diversity of E. multilocularis in isolates obtained from slaughtered Japanese and Canadian horses originating from the Iburi and Hidaka regions in Hokkaido and from Alberta, respectively, with PCR and haplogroup analyses targeting cob gene sequences obtained. Seventy horses were diagnosed with alveolar echinococcosis based on histopathology and cob-gene PCR testing. The E. multilocularis detected in these horses was classified as either an Asian (for Hokkaido-raised horses) or a European (for Alberta-raised horses) haplogroup, based on the obtained cob-gene sequence analysis. In addition, haplotype network analysis revealed that E. multilocularis isolated from Hokkaido-raised horses is highly homologous to Kazakhstan isolates, and E. multilocularis isolated from Alberta-raised horses is highly homologous to Austrian isolates. The results of this study suggest that cob-gene-targeted PCR analysis could be useful for the geographical genetic characterization of E. multilocularis isolated from horses.

Cis binding between inhibitory receptors and MHC class I can regulate mast cell activation.

Allergy is caused by immune effector cells, including mast cells and basophils. Cellular signaling that activates these effector cells is regulated by different inhibitory receptors on their surface. We show that human leukocyte immunoglobulin (Ig)-like receptor (LILR) B2 and its mouse orthologue, paired Ig-like receptor (PIR)-B, constitutively associate to major histocompatibility complex (MHC) class I on the same cell surface (in cis). The IgE-mediated effector responses were augmented in beta(2)-microglobulin (beta(2)m) and PIR-B-deficient mast cells. In addition, the increased cytokine production of beta(2)m-deficient mast cells was not affected by the co-culture with MHC class I-positive mast cells, showing that less cis interaction between PIR-B and MHC class I on mast cells led to the increased cytokine release. Thus, the constitutive cis binding between LILRB2 or PIR-B and MHC class I has an essential role in regulating allergic responses.

The COX-2 selective blocker etodolac inhibits TNFα-induced apoptosis in isolated rabbit articular chondrocytes.

Chondrocyte apoptosis contributes to the disruption of cartilage integrity in osteoarthritis (OA). Recently, we reported that activation of volume-sensitive Cl- current (ICl,vol) mediates cell shrinkage, triggering apoptosis in rabbit articular chondrocytes. A cyclooxygenase (COX) blocker is frequently used for the treatment of OA. In the present study, we examined in vitro effects of selective blockers of COX on the TNFα-induced activation of ICl,vol in rabbit chondrocytes using the patch-clamp technique. Exposure of isolated chondrocytes to TNFα resulted in an obvious increase in membrane Cl- conductance. The TNFα-evoked Cl- current exhibited electrophysiological and pharmacological properties similar to those of ICl,vol. Pretreatment of cells with selective COX-2 blocker etodolac markedly inhibited ICl,vol activation by TNFα as well as subsequent apoptotic events such as apoptotic cell volume decrease (AVD) and elevation of caspase-3/7 activity. In contrast, a COX-1 blocker had no effect on the decrease in cell volume or the increase in caspase-3/7 activity induced by TNFα. Thus, the COX-2-selective blocker had an inhibitory effect on TNFα-induced apoptotic events, which suggests that this drug would have efficacy for the treatment of OA.

Signal adaptor DAP10 associates with MDL-1 and triggers osteoclastogenesis in cooperation with DAP12.

Osteoclasts, cells of myeloid lineage, play a unique role in bone resorption, maintaining skeletal homeostasis in concert with bone-producing osteoblasts. Osteoclast development and maturation (osteoclastogenesis) is driven by receptor activator of NF-kappaB ligand and macrophage-colony stimulating factor and invariably requires a signal initiated by immunoreceptor tyrosine-based activation motif (ITAM)-harboring Fc receptor common gamma chain or DNAX-activating protein (DAP)12 (also referred to as KARAP or TYROBP) that associates with the cognate immunoreceptors. Here, we show that a third adaptor, YINM costimulatory motif-harboring DAP10, triggers osteoclastogenesis and bone remodeling. DAP10-deficient (DAP10(-/-)) mice become osteopetrotic with age, concomitant with a reduction in osteoclasts. The DAP10-associating receptor was identified as myeloid DAP12-associating lectin-1 (MDL-1), whose physiologic function has not been found. MDL-1-mediated stimulation of osteoclast precursor cells resulted in augmented osteoclastogenesis in vitro. MDL-1 associates with both DAP12 and DAP10 in osteoclasts and bone marrow-derived macrophages, where DAP10 association depends almost entirely on DAP12, suggesting a formation of MDL-1-DAP12/DAP10 trimolecular complexes harboring ITAM/YINM stimulatory/costimulatory motifs within a complex that could be a novel therapeutic target for skeletal and inflammatory diseases.

Mild nonocclusive mesenteric ischemia associated with syncope.

Nonocclusive mesenteric ischemia (NOMI) is a life-threatening disease caused by a reduction in mesenteric blood supply without vascular occlusion. Early diagnosis of NOMI is often difficult because there are no specific findings suggesting NOMI. Here, we report a rare case of a very elderly patient with mild NOMI caused by dehydration due to short-term reduced oral intake and associated with syncope. A 90-year-old man was admitted to our hospital with syncope and melena. The syncope was thought to be caused by orthostatic hypotension due to dehydration owing to reduced oral intake for approximately 24 h. Abdominal computed tomography (CT) revealed marked bowel wall thickening with mesenteric stranding in the ileum and ascending colon, dilated small intestine with thinned bowel wall, collapsed superior mesenteric vein, hemorrhagic ascites, and absence of obvious vascular occlusion in the mesenteric vessels. Abdominal symptoms, laboratory abnormalities, and CT findings improved gradually with the correction of dehydration. Therefore, we diagnosed our patient with mild NOMI. NOMI can be associated with syncope and can occur even with dehydration due to short-term reduced oral intake. When examining elderly patients with hypovolemic signs, such as syncope, who exhibit abdominal symptoms, clinicians must keep in mind the possibility of NOMI.

Knee osteoarthritis with patellar dislocation treated by total knee arthroplasty using a lateral parapatellar approach-ingenuity of exposure and closure.

Knee osteoarthritis with patellar dislocation is a rare and difficult-to-treat condition. Several reports of total knee arthroplasty (TKA) combined with various realignment procedures have been published. A 77-year-old man with knee pain was referred to our hospital. Plain radiography revealed a laterally dislocated patella, with osteoarthritic changes in the femorotibial joint. He simply underwent TKA via a lateral parapatellar approach without realignment. We devised methods of exposure and closure to maximize the effect of lateral release by the lateral parapatellar approach. TKA using the lateral parapatellar approach might be effective in treating knee osteoarthritis with patellar dislocation.

Temporary spontaneous regression of male breast cancer: a case report.

BACKGROUND: Spontaneous regression (SR) of a malignant tumor is the partial or complete disappearance of primary or metastatic tumor tissue in the absence of treatment, which can be temporary or permanent. Here, we report an extremely rare case of male breast cancer that exhibited temporary SR followed by reappearance 8 months after tumor disappearance. CASE PRESENTATION: A 70-year-old man presented at our hospital with a primary complaint of pain and a lump in his left breast. Ultrasonography revealed a hypoechoic lesion measuring 12 mm × 10 mm × 8 mm. Fine-needle aspiration cytology revealed numerous necrotic and degenerated cells and few sheet-like clusters of atypical ductal epithelial cells. The atypical cells had mildly enlarged nuclei with nucleoli, were focally overlapped and formed tubular patterns. The cytological diagnosis indicated a suspicion of malignancy. Core needle biopsy (CNB) revealed necrotic and degenerated cells with microcalcification. The pathological diagnosis was indeterminate because there was no area of viable atypical cells. An excisional biopsy of the left breast lesion was scheduled one month later. However, it was difficult to detect the tumor during physical examination and ultrasonography performed 1 month after the patient's first visit. The operation was canceled, and the patient received follow-up observation. After 8 months of follow-up, ultrasonography and computed tomography (CT) revealed reappearance of a 0.6-cm-diameter breast tumor in the same place. CNB was performed again and revealed invasive ductal carcinoma. A total mastectomy with sentinel lymph node biopsy was performed 13 months after the first tumor disappeared. Histopathological examination revealed invasive cribriform carcinoma without sentinel lymph node metastasis. The patient did not have any complications, and adjuvant therapy with tamoxifen was started. The patient was alive without recurrence 7 months after surgery. CONCLUSIONS: Temporary SR followed by tumor reappearance can occur in breast cancer cases, and it is important to follow patients even if their breast tumor has seemingly disappeared. When breast tumors disappear without treatment, clinicians must be aware of the possibility of SR of cancer and should follow the patient for early detection of tumor reappearance.

Effects of malalignment and disease activity on osteophyte formation in knees of rheumatoid arthritis patients.

PURPOSE: Rheumatoid arthritis (RA) patients with secondary osteoarthritis (OA) in a knee joint following a total knee arthroplasty (TKA) procedure have been increasing. Here, we investigated osteophyte formation in knee joints of RA patients and associated factors. METHODS: We retrospectively examined findings of 35 knees in 30 RA patients (26 females, 4 males; mean age: 63.0 years; median disease duration: 15 years) who underwent TKA, including preoperative anteroposterior view radiographs of the knee joint. Using the ImageJ software package, osteophyte size in the medial femur (MF), medial tibia (MT), lateral femur (LF), and lateral tibia (LT) regions was also determined. RESULTS: The mean femorotibial angle was 179°, while Larsen grade was 2 in 1, 3 in 12, 4 in 18, and 5 in 2 patients. Osteophyte sizes in the MF, MT, LF, and LT regions were 37.2, 17.0, 27.2, and 4.57 mm2, respectively, and significantly greater in the medial compartment (MC; MF+MT) than the lateral compartment (LC; LF+LT) (p < 0.001). In varus cases, osteophyte size in the MC was significantly larger than normal and valgus cases (p = 0.0016). Furthermore, osteophyte size in the MC was negatively correlated with the inflammatory markers C-reactive protein (r = -0.492, p = 0.0027) and erythrocyte sedimentation rate (r = -0.529, p = 0.0016), whereas that in the LC was negatively correlated with disease activity (r = -0.589, p = 0.0023). CONCLUSION: Our results suggest that alignment and disease activity influence osteophyte formation in RA patients, with secondary OA a more prominent symptom in RA patients with controlled inflammation.

Is the ischiofemoral space value of Japanese hip joints equal to that of Western populations?

Ischiofemoral space (IFS) is a radiological parameter employed for diagnosing ischiofemoral impingement (IFI). The mean IFS value measured with the leg in natural resting position has been reported as 23.0 mm in males and 18.6 mm in females in a patients-based Western population. The normal value of IFS for an Asian population is unknown. This study therefore aimed to investigate whether the IFS value in Japanese hip joints equals that of the Western population. We retrospectively examined 89 consecutive Japanese individuals (178 hips) (46 male subjects with 92 hips, 43 female subjects with 86 hips; mean age 58.7 ± 15.7 years, range 17-84 years) who had undergone computed tomography (CT) for conditions unrelated to hip disorders and ordered by other departments at our institution. All CT scans were performed in a standardized fashion: patient in a flat spine position, hips and knees in extension, and the leg in its natural resting position. IFS was evaluated on axial images as the shortest distance between the ischium and the lesser trochanter. The mean IFSs of this Japanese patient-based population were 20.5 ± 7.3 mm [95% confidence interval (CI) 19.0-22.0] in the male cohort and 13.9 ± 6.5 mm (95% CI 12.6-15.3) in the female cohort. The IFS value was significantly smaller in female subjects than in male subjects. Taking the lower limit of 95% CI into consideration, the IFSs measured in natural leg-resting position in the Japanese male and female groups were significantly smaller than those of the Western populations.