Flow patterns and defect dynamics of active nematic liquid crystals under an electric field.

The effects of an electric field on the flow patterns and defect dynamics of two-dimensional active nematic liquid crystals are numerically investigated. We found that field-induced director reorientation causes anisotropic active turbulence characterized by enhanced flow perpendicular to the electric field. The average flow speed and its anisotropy are maximized at an intermediate field strength. Topological defects in the anisotropic active turbulence are localized and show characteristic dynamics with simultaneous creation of two pairs of defects. A laning state characterized by stripe domains with alternating flow directions is found at a larger field strength near the transition to the uniformly aligned state. We obtained periodic oscillations between the laning state and active turbulence, which resembles an experimental observation of active nematics subject to anisotropic friction.

A Rare Case of Extremely Severe Heterotopic Ossification after Primary Total Hip Arthroplasty due to Persistent Mild Periprosthetic Joint Infection.

Periprosthetic joint infection (PJI) caused by coagulase-negative staphylococci (CNS) can be a mild, persisting infection. Although heterotopic ossification (HO) is common following total hip arthroplasty (THA), the etiology of severe HO remains unclear. Herein, we describe a rare case of extremely severe HO after a PJI associated with a Staphylococcus caprae infection in a 78-year-old male patient. The patient had poorly controlled diabetes mellitus with no diabetic complications. The patient had no previous history of hip surgery, hip injury, or systemic bacterial infection. Immediately after the initial THA, he developed intermittent low-grade fever (37°C), which persisted for 3 months; consequently, he also reported mild hip pain during walking. He experienced a gradual decrease in hip range of motion within 5 years after the surgery, with progressive gait impairment. Two revision surgeries were required for the successful treatment of this difficult case. The patient's hip function improved, and the PJI was controlled following the second revision surgery. Based on the clinical course, CNS-caused PJI may lead to severe HO. This possibility warrants verification from an accumulated number of cases.

Low Back Pain in Adolescent Athletes: Comparison of Diagnoses Made by General Orthopedic Surgeons and Spine Surgeons.

BACKGROUND: Nonspecific low back pain (NSLBP) is a term used to describe low back pain of unknown origin with no identifiable generators. Over a decade ago, it was reported to account for about 85% of all cases of low back pain, although there is some doubt about the frequency. The purpose of this study was to determine the frequency of NSLBP in adolescent athletes diagnosed by general orthopedic surgeons and by spine surgeons. MATERIALS AND METHODS: A total of 69 adolescent athletes consulted our sports spine clinic to seek a second opinion for low back pain. Data on age, sex, type of sport played, the previous diagnosis made by general orthopedic surgeons, and the final diagnosis made by spine surgeons were collected retrospectively from medical records. RESULTS: The frequency of NSLBP diagnosed by general orthopedic surgeons was 18.9% and decreased to 1.4% after careful imaging and functional nerve block examination by spine surgeons. The final diagnoses made by spine surgeons for those patients previously diagnosed as having NSLBP by general orthopedic surgeons were as follows: early-stage lumbar spondylolysis, discogenic low back pain, facet joint arthritis, lumbar disc herniation, and lumbar apophyseal ring fracture. CONCLUSIONS: In adolescent athletes, the rate of NSLBP diagnosed by general orthopedic surgeons decreased markedly when the diagnosis was made by spine surgeons. A thorough medical interview, careful physical examination, appropriate diagnostic imaging, and selective nerve block examination can effectively identify the cause of low back pain.

Comparison of a highly porous titanium cup (Tritanium) and a conventional hydroxyapatite-coated porous titanium cup: A retrospective analysis of clinical and radiological outcomes in hip arthroplasty among Japanese patients.

BACKGROUND: The use of 3-dimensional highly porous acetabular cups is increasing. Their structure and mechanical properties mimic those of natural bone; therefore, they should promote stronger biological fixation. In our experience with total hip arthroplasty, radiolucent lines are observed when a 3-dimensional highly porous cup (Stryker Tritanium) is used. We compared the clinical and radiographic results between a Tritanium cup and a conventional cup (Stryker Trident HA) over a short time period. METHOD: We retrospectively compared consecutive cases of primary total hip arthroplasty using a Tritanium cup (130 cases in 118 patients) and a matched cohort using a Trident cap (130 cases in 130 patients) between January 2011 and December 2014. RESULTS: The mean follow-up duration was 41.3 and 38.1 months (p = 0.06) for the Tritanium and Trident groups, respectively. There were significant differences between the groups for radiolucent lines, cup abduction angle, and cup-center-edge angle. There were no significant differences in the clinical results. Radiolucent lines increased in the Tritanium group (36.1% at 3 months and 60.7% at final follow-up), whereas they decreased in the Trident group (2.5% at 3 months and 0.8% at final follow-up). The occurrence of radiolucent lines was significantly higher in the Tritanium group than in the Trident group at each follow-up period. Radiolucent lines were seen in 36.1% of patients in the Tritanium group during follow-up, without initial gaps. One cup loosening in the Tritanium group was identified at the final follow-up evaluation. CONCLUSION: Both groups showed successful clinical results over short-term follow-up; however, the Tritanium group had a significantly higher rate of radiolucent line occurrence around the cups than did the Trident group. Thus, radiolucent lines can occur when using highly porous titanium cups; these lines indicate the possibility of future cup loosening. Longer follow-up and assessment of the results of using this implant are necessary.

Utility of STIR-MRI in Detecting the Pain Generator in Asymmetric Bilateral Pars Fracture: A Report of 5 Cases.

Lumbar spondylolysis usually occurs as a stress fracture in the pars interarticularis of the vertebra. It is a prevalent sports-related disorder and a common cause of low back pain. We encountered five athletes (4 males, 1 female) with severe low back pain. Mean age was 14.5 years. All five patients were found to have bilateral pars fracture. In all cases, staging based on the findings from computed tomography scan of the right and left pars fracture was different. On short tau inversion recovery magnetic resonance imaging (STIR-MRI) of the comparatively newer more recently injured side, high signal intensity changes were obvious and dominant at the intra- and extraosseous area, which would indicate tissue edema and/or bleeding. Furthermore, the imaging findings corresponded to the side of the low back pain. In conclusion, STIR-MRI can effectively distinguish between painful pars fracture and painless pars fracture.