COVID-19 with Suspected Secondary Pyogenic Arthritis of the Hip: A Case Report and Literature Review

Introduction

COVID-19 may be associated with orthopedic symptoms, including myalgia and joint pain. There are reports of reactive arthritis and acute arthritis diagnosed after COVID-19; however, COVID-19-associated pyogenic arthritis has not been reported.

Case Report

We treated a young woman with secondary pyogenic hip arthritis that started after COVID-19. The patient was a 23-year-old woman who developed acute pain in the right hip 9 days after being diagnosed with COVID-19. Blood cultures revealed methicillin-sensitive Staphylococcus aureus and contrast-enhanced computed tomography revealed joint effusion in the right hip. Although the joint fluid culture results were negative, we suspected pyogenic arthritis of the hip joint and performed curettage and continuous irrigation of the right hip joint. Intraoperative histopathological examination of the synovial membrane revealed numerous neutrophils with segmental nuclei, consistent with a diagnosis of pyogenic arthritis.

Conclusion

To the best of our knowledge, this is the first report of probable secondary pyogenic hip arthritis in a patient with COVID-19.

Two Healthy Elderly Females with Contemporaneous Subchondral Insufficiency Fractures of Bilateral Femoral Heads: A Case Report

Introduction

Unilateral subchondral insufficiency fractures (SIF) of the femoral head have been reported in many cases; however, bilateral cases occurring simultaneously are very rare.

Case Report

We report two cases of relatively active elderly females (aged 73 and 67 years), in which bilateral hip pain appeared simultaneously without any specific triggers. There were no notable lifestyle or medication histories. Imaging and histopathology of the bone excised surgically supported the diagnosis. In Case 1, there was a decrease in bone mineral density and poor congruency between the femoral head and acetabulum. In Case 2, the posterior tilt of the pelvis with aging decreased coverage of the femoral head, and the poor congruency between the femoral head and acetabulum was thought to have contributed to uneven distribution and increased stress in the loading zone.

Conclusion

We encountered two unusual cases with contemporaneous bilateral SIF in the elderly. In recent years, the number of highly active elderly people has increased with the increase in healthy life expectancy. The combined effect of factors such as bone fragility, posterior pelvic tilt, and high activity level likely caused bilateral SIFs, and we should be careful as we expect to see an increase in such cases in the future.

Femoral Bowing Increases Early Postoperative Stress around the Femoral Stem in Humans: A Finite Element Analysis

Background

This study aimed to clarify the characteristics of stress distribution caused by the placement of tapered wedge stems in bowed femurs compared with that in normal femurs and the effect of varus stem placement.

Methods

Models with normal and enhanced bowing were created from the right-side computed tomography data of a 17-year-old woman with the least bowing among 40 participants who underwent anterior cruciate ligament reconstruction or operative treatment for trauma in our hospital between January 2017 and May 2018. Finite element analysis was performed, assuming the tapered wedge stem was placed in the neutral and varus positions.

Results

Varus stem placement on a femur with normal bowing showed a deviation and increase of von Mises stresses in the medial femur. Stem placement on a bowed femur, even when placed in the neutral position, increased stress across the periprosthetic bone. When the stem was placed in the varus position, von Mises stress across the periprosthetic bone increased. Zone 7, with strong bowing, demonstrated 3.6-fold increased stress compared with normal femurs. The maximum tensile principal stress was greatest in zone 6 and increased in zones 3 and 4.

Conclusions

Surgeons should assess femoral bowing preoperatively and pay particular attention to intraoperative stem alignment for femurs with high bowing.

Influence of femoral bowing on stress distribution of the proximal femur: a three-dimensional finite element analysis

BACKGROUND

Whether femoral bowing or its direction has a mechanical effect on the proximal femur is unclear. This study aimed to define the changes in stress distribution in the proximal femur associated with femoral bowing using finite element analysis.

METHODS

We created four femoral models: original, entire lateral bowing, entire anterior bowing, and the middle of both (50% anterolateral bowing) from computed tomography data of women with standard bowing. Each model's stress distribution was compared by two-layering the stress distribution under loading conditions during walking. We also evaluated displacement vectors.

RESULTS

In all directions of femoral bowing, the stress increased in the femoral neck and the femoral trochanter in the 50% anterolateral bowing. The direction of deformation of the vector for the femoral head increased anteroinferiorly in the 50% anterolateral bowing.

CONCLUSIONS

This study showed that the stress distribution at the proximal femur shifted laterally. The high-stress area increased at the femoral neck or trochanter due to increasing femoral bowing. Femoral bowing also increases the anteroinferior vector in the femoral head. This study provides valuable insights into the mechanism of proximal femoral fractures in older adults.

Stress distributions of the short stem and the tapered wedge stem at different alignments: a finite element analysis study

BACKGROUND

The mechanical effects of stem length reduction and stem alignment on the surrounding femur remain unknown. This study directly compared the stress distribution on the surrounding femur of existing tapered wedge stems and short stems and examined the properties of stress distribution at different stem alignments in three dimensions.

METHODS

Finite element analysis was conducted for standing and walking. The cementless stem was appropriately sized to ensure adequate contact with the medial cortical bone line that contours the medullary cavity. The stem neck axis was aligned with the femoral neck axis in the mid-position and placed in 2° of the varus and valgus, 3° of flexion and extension, and 10° and 40° of anteversion.

RESULTS

Regardless of stem length, the trend of stress distribution was similar. The short stem generated less stress around the stem than the tapered wedge stem. In the coronal plane, the effect of varus and valgus deflection was small. In the sagittal plane, the stress generated around the stem was higher in the extended position than in the flexed position. In the horizontal plane, the stress generated around the stem was higher when the stem anteversion was smaller.

CONCLUSIONS

Depending on the design, short stems can reduce the stress on the surrounding bone, compared to a longer tapered wedge with similar stress distribution. Additionally, a short stem can reduce the effect of the varus position. Stems should be placed to achieve stable initial fixation while noting that stresses increase with extension and reduced anteversion.

Survival rates of different bearing surfaces with the same model of stem in total hip arthroplasty: predictive factors for revision surgery

INTRODUCTION

Few studies have examined the survival rates of total hip arthroplasty (THA) with the same femoral stem, and the predictive factors leading to the revision of stemmed metal-on-metal (MoM) THA remain unknown. We determined the long-term survival rate of stemmed MoM THA compared with that of metal-on-polyethylene (MoP) bearing THA, the effect of head size and cup placement angle on revision rate, and predictors of revision.

MATERIALS AND METHODS

A total of 130 hips in 110 patients who underwent primary THA by the same surgeon were included. M2a-RingLoc with a metal-on-polyethylene bearing (group P, 53 hips), M2a-Taper with MoM bearing (group T, 44 hips), and M2a-Magnum with MoM bearing (group M, 33 hips) were used. The mean age at surgery was 63.1 ± 9.5 years, and the mean postoperative follow-up duration was 133.7 ± 39.1 months. Whole blood metal ion concentrations were measured preoperatively and postoperatively, and magnetic resonance imaging was performed to identify aseptic local tissue reactions (ALTRs). Kaplan-Meier survivorship analysis and multiple logistic regression analysis were performed.

RESULTS

The THA survival rate up to the maximum postoperative follow-up period was 96.2% at 173 months, 46.6% at 179 months, and 47.8% at 145 months in groups P, T, and M, respectively, with revision as the endpoint. The stemmed MoM THA recorded a very low survival rate (p < 0.001). The ALTR rates were 70.5% and 63.6% in groups T and M, respectively. The risk factor for revision was the use of MoM bearing, and there was no difference in the results based on the head size in group M. Cobalt levels continued to increase postoperatively, although they were not accurate predictors of revision.

CONCLUSIONS

Stemmed MoM THA has a very low survival rate and should be used with caution. It is important to monitor the patient's symptoms and perform appropriate imaging to ensure timely revision.

Microvascular system of hip joint constituents with special reference to ultrastructural findings and early arteriosclerosis

This study aimed to examine the ultrastructure of the arteries of the synovium, acetabular labrum, and ligamentum teres of the hip joint using light, scanning electron, and transmission electron microscopes to identify features of early arteriosclerosis. Tissues collected from three patients (under 40 years of age) with osteonecrosis of the femoral head were immersed in 8 N HCl at 60 °C for 20 min to digest collagen fibers for scanning electron microscopy. Tortuous arterioles and arteries were noted in the joint components, including the synovium, acetabular labrum, and ligamentum teres. The ultrastructure of the arterioles appeared normal; however, intimal thickening was found in most arteries. The thickened intima had abundant elastic fibers and many smooth muscle cells (which were of a synthetic phenotype because they had a few actin filaments and well-developed rough endoplasmic reticulum). This study illustrates that arteriosclerotic changes are present in tortuous arteries in the synovium, acetabular labrum, and ligamentum teres of the hip joint even from a relatively young age and suggests that meandering blood vessels may be the preferred foci of arteriosclerosis.

Existence of an immunoglobulin G component of naturally occurring HLA class I antibodies that are not directed against self-antigens in human serum

We compared the frequency of immunoglobulin G (IgG) type of human leukocyte antigen (HLA) class I antibodies between patients with systemic lupus erythematosus (SLE) and healthy controls using a highly sensitive FlowPRA method. Sixteen of 130 normal healthy males and 2 of 10 normal females without a history of pregnancy (none had ever been transfused) possessed HLA class I antibodies. In SLE, male, but not female patients, showed a significant increase in the frequency of the antibodies compared with the corresponding controls. The antibodies did not appear to be involved in the development of SLE because of no substantial relationship to the incidence of cytopenia or SLE disease activity index score. Each individual had 1-31 types of HLA class I antibodies. Interestingly, HLA class I antibodies did not correspond to the individual's own HLA antigens. Eight of 32 types of HLA class I antigens detected were rare in the Japanese population. These results suggest that an IgG component of naturally occurring HLA class I antibodies exists in human serum and that these antibodies are not antibodies against self-antigens.

In vitro and in vivo antibacterial activities of L-084, a novel oral carbapenem, against causative organisms of respiratory tract infections

L-084 (a prodrug of LJC 11,036 [L-036]) is a new oral carbapenem. Here we compared the in vitro and in vivo antibacterial activities of L-036 with those of imipenem, faropenem, ceditoren-pivoxil, cefdinir, amoxicillin, and levofloxacin. The MICs at which 90% of the isolates were inhibited of L-036 against methicillin-susceptible staphylococci, Streptococcus pneumoniae including penicillin-resistant organisms, Escherichia coli, Klebsiella pneumoniae, Haemophilus influenzae including ampicillin-resistant organisms, Legionella pneumophila, and Moraxella catarrhalis were equal to or less than 1 microg/ml. In pharmacokinetics studies of L-084 in lungs of mice, the maximum concentration in serum, half-life, and area under the concentration-time curve of this drug were 9.09 microg/g of tissue, 6.18 h, and 31.0 microg. h/ml, respectively. In murine respiratory infection models of penicillin-susceptible and -resistant S. pneumoniae and H. influenzae, the efficacies of L-084 were better than those of reference drugs. Our results indicate that the in vitro high potency and good distribution in the lungs might be the underlying mechanisms of its efficacy in the murine model of pneumonia.

An effective method for isolating alginate lyase-producing Bacillus sp. ATB-1015 strain and purification and characterization of the lyase

A new alginate lyase-producing micro-organism, designated as Bacillus sp. strain ATB-1015, was effectively isolated from soil samples pretreated for 3 months with a substrate of the enzyme, sodium alginate. Alginate lyase activity was assayed by the degrading activity of biofilm of Teflon sheet discs, which was formed by a mucoid strain of Pseudomonas aeruginosa PAM3 selected from clinical isolates. The extracellular alginate lyase was precipitated with ammonium sulphate from the culture broth, and purified by gel filtration and anion exchange chromatography. The molecular weight of the lyase was estimated to be 41 kDa by SDS polyacrylamide gel electrophoresis and Sephacryl S-200 HR column chromatography. The optimum pH and temperature for the enzyme activity were around 7.5 and 37 degrees C, respectively, and the Km value was 0.17% with the substrate, sodium alginate. The lyase activity was completely inhibited by treatment with 1 mmol l-1 of EDTA and the decreased activity was almost completely recovered by the addition of 2 mmol l-1 of CaCl2. The activity was not affected by treatment with the protein denaturants, 0.01 mol l-1 of SDS or 1 mmol l-1 of urea. The lyase had substrate specificity for both the poly-guluronate and poly-mannuronate units in the alginate molecule.