Clinical effects of different center of rotation reconstructions in total hip arthroplasty after femoral neck fractures: a cohort study including a follow-up analysis on patient's mobility and daily living ability.

BACKGROUND: The aim of this study is a clinical evaluation of the center of rotation (COR) placement towards a patient's recovery with respect to daily living ability and mobility. In past experiments based on three-dimensional (3D) models, medialization of the COR in total hip arthroplasty (THA) showed a negative influence on muscle strength of the abductors and reaction force of the hip joint. This contradicts paradigms, where reduced hip loading forces are claimed to increase functional outcomes. METHODS: The plain X-rays of 110 patients who underwent THA after a femoral neck fracture between January 2019 and January 2021 were retrospectively evaluated. A Barthel Index on discharge was obtained in 69 cases. 47 patients were available for a follow-up interview concerning the Barthel Index, Parker mobility score (PMS), and pain levels (NRS) 6 and 12 months after surgery. RESULTS: Medialization of the COR had a significantly negative effect on the need for care (Barthel Index) at patient discharge (Spearman correlation 0.357, p = 0.013). The effect on the PMS is still existent at 6 and 12 months (Spearman correlation 0.471, p = 0.009 at 6 months; 0.472, p = 0.008 at 12 months). Mann-Whitney U tests showed that the groups with medialized COR performed significantly worse than the lateralized groups. This was seen for the Barthel Index at discharge and at 6 months after surgery and for the PMS at 6 and 12 months. The accurately reconstructed CORs showed no significant differences from the lateralized rotation centers in need of care and mobility. The superior COR placement group showed significantly reduced mobility at 12 months in contrast to the inferior COR placement group (p = 0.008), and the group of accurately reconstructed rotation centers showed significantly less pain than the inferior COR placement group (p = 0.007 after 6 months, p = 0.026 after 12 months). Especially the combination of both (superomedialization) leads to reduced mobility (Spearman correlation 0.67, p = < 0.001). CONCLUSIONS: COR superior displacement, COR medialization, and the combination of both (superomedialization, Spearman p = < 0.001) lead to reduced mobility while inferior displacement showed increased pain. According to our results, we recommend an exact vertical COR restoration, while horizontal medial displacement needs to be avoided. LEVEL OF EVIDENCE: III.

Diagnostic accuracy of two commercially available rapid assays for detection of IgG and IgM antibodies to SARS-CoV-2 compared to ELISA in a low-prevalence population.

Background: New commercially available point-of-care (POC) immunodiagnostic tests are appearing, which may yield rapid results for anti-SARS-CoV-2 antibodies. The aim of this study was to evaluate the diagnostic accuracy of rapid antibody detection tests compared to a validated laboratory-based enzyme-linked immunosorbent assay (ELISA) and to investigate infections amongst healthcare workers (HCWs) after unprotected close contact to COVID-19 patients. Methods: Blood serum and whole blood of 130 participants were tested with NADAL® COVID-19 IgG/IgM rapid test and mö-screen 2019-NCOV coronavirus test against a validated ELISA test. Infection status was evaluated using real-time polymerase-chain-reaction. Results: Acute COVID-19 infection was detected in 2.4% of exposed HCWs. Antibody tests showed an overall frequency of IgG and IgM in 5.3%, with 1.6% asymptomatic infections. The NADAL® test showed a sensitivity (IgM/IgG) of 100% (100%/100%), a specificity (IgM/IgG) of 98.8% (97.6%/100 %), a PPV of 76.9% (57.1%/100%), an NPV of 100% (100%/100%), and a diagnostic accuracy of 98.8% (97.7%/100%). The mö-screen test had a sensitivity (IgM/IgG) of 90.9% (80%/100%), a specificity (IgM/IgG) of 98.8% (97.6%/100%), a PPV of 76.9% (57.1%/100%), an NPV of 99.6% (99.2%/100%), and a diagnostic accuracy of 98.5% (96.9%/100%). Conclusions: The frequency of COVID-19 infections in HCWs after unprotected close contact is higher than in the general population of a low-prevalence country. Both POC tests were useful for detecting IgG, but did not perform well for IgM, mainly due to false positive results.

Vitamin D deficiency and benign paroxysmal positioning vertigo.

Benign paroxysmal positional vertigo is a common cause of disabling vertigo with a high rate of recurrence. Although connections between vitamin D deficiency and osteoporosis, as well as between osteoporosis and benign paroxysmal positional vertigo have been suggested respectively in the literature, we are not aware of any publication linking vitamin D and benign paroxysmal positional vertigo. As a hypothesis, we suggest that there is a relation between insufficient vitamin D level and benign paroxysmal positional vertigo. In order to test this hypothesis, in a small retrospective pilot study, 25-hydroxyvitamin D levels in serum of patients with benign paroxysmal positional vertigo and frequency of recurrence after correction of serum level were assessed retrospectively. Patients with idiopathic positional vertigo had a low average serum level of 25-hydroxyvitamin D (23ng/mL) similar to that of the general Austrian population, which has a high prevalence of hypovitaminosis D. In 4 cases with chronically recurrent severe vertigo episodes, average levels of serum 25-hydroxyvitamin D were even significantly lower than in the other vertigo patients, who had their first episode. Vertigo attacks did not recur after supplementation with vitamin D. We raise the possibility that patients with benign paroxysmal positional vertigo who have low vitamin D levels may benefit from supplementation and suggest further epidemiological investigations to determine the effect of correcting vitamin D deficiency on the recurrence of vertigo. Given the many known benefits of vitamin D, the authors recommend the measurement of vitamin D in patients with benign paroxysmal positional vertigo and supplementation if necessary.

Incorporation of tick-borne encephalitis virus replicons into virus-like particles by a packaging cell line.

RNA replicons derived from flavivirus genomes show considerable potential as gene transfer and immunization vectors. A convenient and efficient encapsidation system is an important prerequisite for the practical application of such vectors. In this work, tick-borne encephalitis (TBE) virus replicons and an appropriate packaging cell line were constructed and characterized. A stable CHO cell line constitutively expressing the two surface proteins prM/M and E (named CHO-ME cells) was generated and shown to efficiently export mature recombinant subviral particles (RSPs). When replicon NdDeltaME lacking the prM/M and E genes was introduced into CHO-ME cells, virus-like particles (VLPs) capable of initiating a single round of infection were released, yielding titers of up to 5 x 10(7)/ml in the supernatant of these cells. Another replicon (NdDeltaCME) lacking the region encoding most of the capsid protein C in addition to proteins prM/M and E was not packaged by CHO-ME cells. As observed with other flavivirus replicons, both TBE virus replicons appeared to exert no cytopathic effect on their host cells. Sedimentation analysis revealed that the NdDeltaME-containing VLPs were physically distinct from RSPs and similar to infectious virions. VLPs could be repeatedly passaged in CHO-ME cells but maintained the property of being able to initiate only a single round of infection in other cells during these passages. CHO-ME cells can thus be used both as a source for mature TBE virus RSPs and as a safe and convenient replicon packaging cell line, providing the TBE virus surface proteins prM/M and E in trans.