Early Postoperative Change in Hip Rotation Angle and Factors Contributing to It for Patients Undergoing Total Hip Arthroplasty.

OBJECTIVE: A possible impairment in hip proprioception after total hip arthroplasty (THA) has been an issue of concern. The aims of this study were to investigate the extent of early postoperative change in standing hip rotation angle (HRAng) in patients with osteoarthritis (OA) undergoing THA and to consider a possible mechanism behind this. MATERIALS AND METHODS: A total of 82 hips (82 patients; 63 women and 19 men) undergoing unilateral primary THA with total capsulectomy were included. We characterized the standing HRAng and internal/external range of motion (ROM) in the prone position before THA and 2 weeks after THA. Acetabular/cup and femoral/stem anteversion, combined anteversion (CA), and leg length discrepancy were also characterized. Correlations were examined postoperatively between the HRAng and the other analyzed variables. RESULTS: The median standing HRAng showed a significant internal shift from external to more medial position (6.3° to 1.7°) 2 weeks after THA (P<.0001). The postoperative change in standing HRAng was significantly negatively correlated with the difference between the postoperative femoral anteversion and the stem anteversion (rs=-0.429, P<.0001) and with the pre- to postoperative change in CA (rs=-0.3012, P=.0063). CONCLUSION: This study demonstrated that the extent of the rotational shift of the distal femur toward medial direction was significantly associated with increasing stem anteversion and CA. This phenomenon can be interpreted as a compensatory mechanism for maintaining the relative positional relationship between the pelvis and the proximal femur using proprioception. Therefore, we conclude that the extracapsular/extra-articular components may be prominent determinants of joint position sense. [Orthopedics. 2024;47(3):e114-e118.].

Comparison of Intravenous Acetaminophen and Intravenous Patient-Controlled Analgesia Fentanyl after Total Hip Arthroplasty: A Multicenter Randomized Controlled Trial.

BACKGROUND: Opioids often need to be discontinued because they cause nausea, whereas the administration of intravenous acetaminophen (APAP) causes less nausea and vomiting. This study aimed to compare the effects of fentanyl-based intravenous patient-controlled analgesia (IV-PCA) and intravenous APAP on pain and nausea after total hip arthroplasty (THA). METHODS: We prospectively investigated primary THA patients who underwent the anterolateral supine approach at four centers between October 2021 and October 2022. The patients (n = 178) were divided randomly into IV-PCA (n = 88) and APAP groups (n = 90). Rest pain, motion pain, and nausea were assessed using NRS scores. RESULTS: Compared with the APAP group, the IV-PCA group experienced significantly greater resting pain and nausea on postoperative day 1. A correlation was found between preoperative and postoperative pain. Postoperative nausea at 8 h was significantly correlated with pain at rest at 4 h (r = 0.193), 8 h (r = 0.194), day 1 (r = 0.245), and day 2 (r = 0.188) after surgery. Early postoperative pain and nausea correlated with subsequent pain and nausea. CONCLUSIONS: Intravenous APAP is associated with less pain and nausea and is superior to IV-PCA.

Bacterial Contamination in Total Joint Replacement: Should We Change into a New Set of Clean Scrub Suits Whenever Entering the Operating Room?

BACKGROUND: The aims of this study are as follows: (1) to investigate the level and probability of bacterial contamination on scrub suits over time for medical personnel working inside and/or outside the operating room (OR) area; (2) to discuss the protective role of cover gowns against bacterial contamination; and (3) to consider the necessity of changing into clean suits whenever entering the OR in terms of preventing periprosthetic joint infection (PJI) in total joint replacement (TJR). METHODS: The bacterial colony count was examined on the chest area of the scrub suits worn during various daily clinical practices. The genus/species of the contaminants were identified by matrix-assisted laser deposition ionization-time of flight mass spectrometry (MALDI-TOF MS). RESULTS: The scrub suits worn outside the OR area showed a greater level of bacterial contamination than those worn inside the OR area, although the colony counts tended to increase over time both in and out of the area. The probability of contamination involving coagulase-negative staphylococci (CNS) (known as the primary cause of PJI) did not increase significantly in the scrubs worn inside the OR area, but did increase significantly after a long-time departure from the OR area. CONCLUSIONS: Our results suggest that wearing scrub suits outside and/or the long duration of wearing the same suits can significantly increase the level and probability of any bacterial contamination (including CNS) on scrub suits. We also found that wearing a cover gown over scrub suits outside the OR area may have only a limited protective role against bacterial contamination.

In vivo creep and wear performance of vitamin-E-diffused highly crosslinked polyethylene in total hip arthroplasty.

INTRODUCTION: An acetabular liner thickness of around 6 mm remains the "gold standard" in total hip arthroplasty. Some surgeons have been recommending the use of the thickest possible liner because contact stress and strain in articulating surfaces decrease with increasing the wall thickness. The purpose of this study was to determine whether in vivo creep and wear performance could be enhanced using a thicker liner over the standard thickness in vitamin-E-diffused highly crosslinked polyethylene (HXLPE). MATERIALS AND METHODS: One hundred and twenty-two hips were allocated to age-matched, sex-matched, and body mass index-matched two subgroups implanted either with a 6.8- or 8.9-mm-thick vitamin-E-diffused HXLPE liner against 28-mm cobalt-chrome femoral head, and followed-up for 7 years. Linear and volumetric penetration of femoral head into the liners attributed to creep and wear were analyzed for each group. RESULTS: Compressive creep strain generated at the initial 6 months was significantly larger in the 6.8-mm group (2.6%) than in the 8.9-mm group (2.2%). The linear steady-state wear observed after 2 years was 0.0019 and 0.0015 mm/year, whereas the volumetric steady-state wear was 0.54 and 0.45 mm3/years in the 6.8- and 8.9-mm-thick groups, respectively. Although less strain in the thicker group resulted in a slightly less wear, it did not reach significant differences in the steady-state wear rates between the groups. CONCLUSION: No clinical significance for using a thicker liner over the standard thickness (6.8 mm → 8.9 mm) was confirmed in the vitamin-E-diffused HXLPE according to the 7-year follow-up. The wear rates for both thicknesses were very low enough to prevent osteolysis, and no mechanical failure was observed at any follow-up interval. Nevertheless, since the significantly higher strain was seen in the thinner liner, further follow-up is needed to compare the longer term wear and the incidence of osteolysis and component fracture.

Do polyethylene wear particles affect the development of pseudotumor in total hip arthroplasty? A minimum 15-year follow-up.

BACKGROUND: Adverse local tissue reactions have been problematic as an implant-related complication in total hip arthroplasty (THA). Despite the absence of significant metal wear and corrosion, granulomatous pseudotumor has been reported to be caused by polyethylene wear. We performed a long-term follow-up study investigating the relationship between polyethylene wear and pseudotumor formation in THA. METHODS: This study included 57 patients (64 hips) that underwent primary THA with metal-on-polyethylene or ceramic-on-polyethylene bearing over a minimum follow-up of 15 years. They were stratified into pseudotumor and non-pseudotumor groups and their linear wear rates of polyethylene liner and serum cobalt (Co) and chromium (Cr) ion levels were compared. Pseudotumor was diagnosed on metal artifact reduction sequence-MRI according to its composition and wall thickness using the Hauptfleisch classification. RESULTS: The incidence of pseudotumor was 34% (22/64 hips) at the mean follow-up of 16.9 years. Metal ion levels did not differ between the pseudotumor and non-pseudotumor groups, and none of the patients exceeded the Co/Cr ratio of 2.0 µg/L. Moreover, the wear rate in the pseudotumor group was 1.8 times greater than in the non-pseudotumor group (0.14 vs. 0.08 mm/year, P < 0.001). According to an analysis of the receiver operating characteristic curves, the cutoff level of the wear rate to discriminate between pseudotumor and non-pseudotumor patients at 15 years was 0.11 mm/year (area under the curve = 91%; sensitivity = 95%; specificity = 78%; accuracy = 87%). CONCLUSIONS: Our results might provide new insights into excessive polyethylene wear potentially leading to the future development of both pseudotumor and osteolysis. Further studies are needed to clarify the direct relationship between polyethylene wear and pseudotumor and the mutual effects of osteolysis and pseudotumor in particle reactions.

To what extent could the acetabular liner thickness be reduced yet remaining tribologically acceptable in metal-on-vitamin E-diffused crosslinked polyethylene hip arthroplasty?

The aim of the present study was to evaluate how much reduction in acetabular liner thickness could be tribologically acceptable in metal-on-vitamin-E diffused highly crosslinked ultra-high molecular weight polyethylene (Vit-E XLPE) bearings for total hip arthroplasty. We tested thick- (10.3 mm), moderate- (6.3 mm), and thin- (4.3 mm) Vit-E XLPE liners coupled with 28-mm cobalt-chromium femoral heads on a hip simulator to 5 million cycles, and peak contact stress was predicted based on mathematical modeling. Wear damage was also evaluated in terms of surface topology and morphology. Wear simulation demonstrated that the 2-4 mm thickness reduction (6.3 → 4.3 mm and 10.3 → 6.3 mm) did not significantly affect the wear rate for Vit-E XLPE liner, whereas 6-mm reduction (10.3 → 4.3 mm) significantly increased liner wear (by 309%) and head roughness (by 415%). This effect was attributed to a contact stress increase (by 24-41%). However, the wear rates for all thicknesses tested were much lower than those previously reported for thicker non-crosslinked materials. The original crystalline morphology was maintained in all liners after wear. Our results suggest that the 2-4 mm thickness reduction may be tribologically acceptable in Vit-E XLPE liners. However, more severe and longer term simulations are necessary to determine a minimum acceptable thickness.

Risk factors for preoperative nasal carriage of methicillin-resistant bacteria in total hip and knee arthroplasty patients.

BACKGROUND: The present study aimed to identify risk factors for preoperative nasal carriage of resistant bacteria - MRSA methicillin-resistant Staphylococcus (S.) aureus, MRSE (methicillin-resistant Staphylococcus epidermidis), and MRCNS (methicillin-resistant coagulase negative staphylococci) in total hip and knee arthroplasty (THA and TKA) patients. METHODS: Nasal cultures were obtained from 538 patients before THA (262 primary and 26 revision) and TKA (241 primary and 9 revision). These were classified either as methicillin-resistant bacteria (group MR) or methicillin-susceptible bacteria (including culture-negative) (group MS). Patient characteristics were compared between these groups using logistic regression models. RESULTS: The resistant bacteria were preoperatively present in 33.1% (178 patients) among all patients. MRSE, MRCNS, and MRSA were detected in 27.5% (148 patients), 3.7% (20 patients), and 1.9% (10 patients). In the unadjusted comparisons of the patient characteristics between the groups MR and MS, a significant difference was found in the percentages of diabetic patients (15.2% vs. 9.2%, P = 0.04); the association remained after the multivariable adjustment for possible risk factors (P < 0.001). In addition, the diabetic patients in the group MR showed a higher percentage of receiving insulin injection than those in the group MS (25.9% vs. 6.1%, P = 0.063), and their mean levels of HbA1c were significantly higher in the group MR than the MS (6.8% vs. 6.4%, P = 0.03). CONCLUSIONS: We identified diabetes as a risk factor for the preoperative nasal carriage of resistant bacteria. Our results suggest that, in order to prevent a surgical site infection (SSI), extra care should be taken in performing joint arthroplasties for diabetic patients, especially using insulin and with high HbA1c levels (≥6.6%) prior to the surgical procedures.

Adverse Tissue Reactions and Metal Ion Behavior After Small-Head Metasul Hip Arthroplasty: A Long-Term Follow-Up Study.

OBJECTIVE: To investigate the long-term survivorship, incidence of adverse reactions to metal debris (ARMD), and metal ion behavior in patients who underwent small-head Metasul metal-on-metal (MoM) total hip arthroplasty (THA). METHODS: Between February 1998 and September 2003, a retrospective study was performed on 43 consecutive patients (43 hips) who underwent unilateral cementless Metasul MoM THAs at our institution. Of them, 35 patients (nine males and 26 females) who were available for follow-up more than 15 years after THA were enrolled in this study and underwent metal artifact reduction sequence magnetic resonance imaging (MARS-MRI) to identify ARMD. The mean age at surgery of the patients was 59.7 years old (range, 31-83). Clinical and radiographic outcomes were evaluated retrospectively. Clinical examinations were conducted using the Harris Hip Score (HHS). Serum cobalt (Co) and chromium (Cr) ion levels and Co/Cr ratio were assessed at different postoperative periods of <5, 5-10, 11-14, and ≥15 years. RESULTS: The mean follow-up period for the 35 patients included was 18.1 years (range, 15-22). The mean HHS significantly improved from 44.6 ± 11.3 points preoperatively to 89.4 ± 7.9 points at the final follow-up (P < 0.0001). ARMD was found in 20% of the patients using MARS-MRI. No signs of stem loosening were found clinically or radiographically, whereas cup loosening and ARMD were observed in three patients (9%), for whom revision THAs were performed. The Kaplan-Meier survival rates with revision for any reason as the endpoint were 90.9% at 5 years, 84.8% at 10 years, 84.8% at 15 years (95% CI, 67.1-93.6), and 70.3% at 20 years (95% CI, 43.6-87.0). The survival rates with revision for ARMD as the endpoint were 100% at 5 years, 96.6% at 10 years, 96.6% at 15 years (95% CI, 77.2-99.7), and 80.1% at 20 years (95% CI, 45.3-95.2). Serum Co ion level peaked at 5-10 years after THA, which was significantly higher than that <5 years; however, it decreased to the initial level after 15 years. In contrast, serum Cr ion level significantly increased at 5-10 years and then remained almost constant. Significant differences in Cr ion levels (1.0 vs 2.0 µg/L, P = 0.024) and Co/Cr ratio (1.3 vs 0.9, P = 0.037) were found between non-ARMD and ARMD patients at >11 years postoperatively. CONCLUSION: Our results suggest that increased Cr ion levels and decreased Co/Cr ratio may be signs of ARMD in patients who underwent small-head Metasul MoM THA.

IL-17A-Mediated Immune-Inflammatory Periarticular Mass and Osteolysis From Impingement in Ceramic-On-Ceramic Total Hip Arthroplasty.

We present a rare case of symptomatic adverse local tissue reaction in a 54-year-old female patient who had undergone total hip arthroplasty with ceramic-on-ceramic bearing. Inflammatory periarticular mass and osteolysis developed in the absence of cobalt chrome alloy interfaces and a modular neck component. On the pathologic images, there was no clear evidence of gross metal staining of tissues, metal corrosion, and ceramic or metal wear particles. However, there were impingement scars on the titanium alloy femoral neck and acetabular cup associated with a high combined anteversion angle of 75° (stem: 40° and cup: 35°), suggesting titanium debris release in vivo. Immunohistochemical staining proved a predominant infiltration of CD4+ T cells and the corresponding IL-17A response to metal. We conclude that neck-rim impingement may lead to the development of adverse local tissue reaction (periarticular mass and osteolysis) due to a metal hypersensitivity with the production of proinflammatory cytokines (IL-17A) by CD4+ T cells even in ceramic-on-ceramic total hip arthroplasty.

Sacral incidence to pubis: a novel and alternative morphologic radiological parameter to pelvic incidence in assessing spinopelvic sagittal alignment.

BACKGROUND: Although pelvic incidence (PI) is a key morphologic parameter in assessing spinopelvic sagittal alignment, accurate measurements of PI become difficult in patients with severe hip dislocation or femoral head deformities. This study aimed to investigate the reliability of our novel morphologic parameters and the correlations with established sagittal spinopelvic parameters. METHODS: One hundred healthy volunteers (25 male and 75 female), with an average age of 38.9 years, were analysed. Whole-body alignment in the standing position was measured using a slot-scanning X-ray imager. We measured the established spinopelvic sagittal parameters and a novel parameter: the sacral incidence to pubis (SIP). The correlation coefficient of each parameter, regression equation of PI using SIP, and regression equation of lumbar lordosis (LL) using PI or SIP were obtained. The intraclass correlation coefficient (ICC) was calculated as an evaluation of the measurement reliability. RESULTS: Reliability analysis showed high intra- and inter-rater agreements in all the spinopelvic parameters, with ICCs > 0.9. The SIP and pelvic inclination angle (PIA) demonstrated strong correlation with PI (R = 0.96) and pelvic tilt (PT) (R = 0.92). PI could be predicted according to the regression equation: PI = - 9.92 + 0.905 * SIP (R = 0.9596, p < 0.0001). The ideal LL could be predicted using the following equation using PI and age: ideal LL = 32.33 + 0.623 * PI - 0.280 * age (R = 0.6033, p < 0.001) and using SIP and age: ideal LL = 24.29 + 0.609 * SIP - 0.309 * age (R = 0.6177, p < 0.001). CONCLUSIONS: Both SIP and PIA were reliable parameters for determining the morphology and orientation of the pelvis, respectively. Ideal LL was accurately predicted using the SIP with equal accuracy as the PI. Our findings will assist clinicians in the assessment of spinopelvic sagittal alignment. TRIAL REGISTRATION: This study was retrospectively registered with the UMIN Clinical Trials Registry ( UMIN000042979 ; January 13, 2021).

Does intraoperative mechanical prophylaxis prevent venous thromboembolism in total knee arthroplasty? - effectiveness of passive-assisted ankle motion in surgical/non-surgical side.

BACKGROUND: Gradual compression stocking (GCS) and intermittent pneumatic compression device (IPCD) are used for intraoperative mechanical prophylaxis against venous thromboembolism (VTE) during total knee arthroplasty (TKA). In this study, we applied a passive-assisted ankle motion in combination with GCS and IPCD during TKA and evaluated its effectiveness in preventing postoperative VTE. METHODS: We included 77 patients who underwent primary unilateral TKA. Patients were divided into group A (53 patients who underwent GCS and IPCD on their non-surgical side limb) and group B (24 patients who underwent passive ankle dorsiflexion motion in addition to GCS and IPCD on their non-surgical side limb). Deep vein thrombosis (DVT) was assessed using lower extremity ultrasonography (US). The incidence of VTE in each affected limb was compared between the two groups. RESULTS: US was performed 4 days after surgery on average. The incidence of DVT in groups A and B was 47.2 and 70.8 %, respectively. In group A, 22.6 % of DVTs were found only on the surgical side, 11.3 % on the non-surgical side, and 13.2 % on both sides. On the other hand, in group B, 41.7 % of DVTs were found only on the surgical side, 4.2 % on the non-surgical side, and 25.0 % on both sides. No significant difference in the incidence of VTE was noted between the 2 groups. CONCLUSIONS: The intraoperative application of passive ankle motion plus GCS and IPCD might not further reduce the incidence of postoperative DVT in TKA patients.

Impact of surgical clothing and footwear on operating room contamination during standstill and intraoperative stepping motion.

BACKGROUND: In view of preventing surgical site infection (SSI) in the orthopedic operating room (OR), evidence concerning types of footwear and clothing is limited. This study aimed to investigate how different footwear and clothing affect the cleanliness of the OR environment. METHODS: The airborne dust concentration in a bioclean room (NASA class 100) was measured around an operator by using a handheld particle counter under the following conditions: (I) wearing a sterilized full-type space suit with OR dedicated clean sandals; (II) wearing a sterilized full-type space suit with non-dedicated (outside) shoes or severely contaminated outside shoes with surgical glove powder (2 µm mean particle size); and (III) wearing an unsterilized medical scrub uniform with OR dedicated sandals. The participant was standing still or stepping in place at 1 Hz during the testing. RESULTS: The concentrations of airborne dusts in the operative field were independent of footwear and clothing types under the stand-still condition. However, these values significantly increased 1.96- to 16.23-fold after simple stepping motion in all the test conditions, and often became dissatisfaction level with the NASA100 requirement for the OR cleanliness. The worst contamination occurred when an operator wore the powder-contaminated shoes and also the unsterilized scrub uniform. CONCLUSION: The present study showed that the stepping motion triggered a considerable contamination in the operative field (beyond the level of NASA100 threshold) particularly when an operator used the outside shoes or unsterilized scrub uniform. Therefore, these results tell us that the one-footwear system (i.e., no use of OR dedicated clean shoes) and unsterilized scrub are likely to be a potential risk factor for SSI. Nevertheless, further studies are necessary to conclude the real efficacy of OR dedicated shoes and sterilized clothes on the SSI prevention.

Do Polyethylene Supra-Macroparticles Lead to Pseudotumor Formation in Metal-on-Polyethylene Total Hip Arthroplasty?

We describe 2 cases of pseudotumors induced by an unusual size of polyethylene wear particle after metal-on-polyethylene total hip arthroplasty (MoP THA). The supra-macroparticles of size >100 µm originated from a polyethylene liner with relatively small cup anteversion, potentially leading to excessive loading and increased wear of the anterior edge of the polyethylene liner. Histopathology showed a foreign-body reaction to the polyethylene particles without an adverse reaction to metal debris and with no severe signs of corrosion at the head-neck junction, which have been noted in past reports of pseudotumors in MoP THA. It has been suggested that the large polyethylene wear particles might be the cause of pseudotumor formation in MoP THA.

Wear Simulation of Ceramic-on-Crosslinked Polyethylene Hip Prostheses: A New Non-Oxide Silicon Nitride versus the Gold Standard Composite Oxide Ceramic Femoral Heads.

The purpose of the present study was to compare the wear behavior of ceramic-on-vitamin-E-diffused crosslinked polyethylene (Vit-E XLPE) hip bearings employing the gold standard oxide ceramic, zirconia (ZrO2)-toughened alumina (Al2O3) (ZTA, BIOLOX®delta) and a new non-oxide ceramic, silicon nitride (Si3N4, MC2®). In vitro wear test was performed using a 12-station hip joint simulator. The test was carried out by applying the kinematic inputs and outputs as recommended by ISO 14242-1:2012. Vitamin-E-diffused crosslinked polyethylene (Vit-E XLPE) acetabular liners (E1®) were coupled with Ø28-mm ZTA and Si3N4 femoral heads. XLPE liner weight loss over 5 million cycles (Mc) of testing was compared between the two different bearing couples. Surface topography, phase contents, and residual stresses were analyzed by contact profilometer and Raman microspectroscopy. Vit-E XLPE liners coupled with Si3N4 heads produced slightly lower wear rates than identical liners with ZTA heads. The mean wear rates (corrected for fluid absorption) of liners coupled with ZTA and Si3N4 heads were 0.53 ± 0.24 and 0.49 ± 0.23 mg/Mc after 5 Mc of simulated gait, respectively. However, after wear testing, the ZTA heads retained a smoother topography and showed fewer surface stresses than the Si3N4 ones. Note that no statistically significant differences were found in the above comparisons. This study suggests that the tribochemically formed soft silica layer on the Si3N4 heads may have reduced friction and slightly lowered the wear of the Vit-E XLPE liners. Considering also that the toughness of Si3N4 is superior to ZTA, the present wear data represent positive news in the future development of long-lasting hip components.

A Case of Systemic Lupus Erythematosus/Antineutrophil Cytoplasmic Antibody-Associated Vasculitis Overlap Syndrome with Dissociated Pathological and Immunological Findings.

Systemic lupus erythematosus/antineutrophil cytoplasmic antibody-associated vasculitis overlap syndrome (SLE/AAV OS) describes a pathological condition that presents with overlapping features of two diseases. There have been few reports of SLE/AAV OS and none from Japan. We present the case of a 59-year-old woman admitted with chief complaints of fever and decreased renal function. SLE was suspected due to the identification of four items from the diagnostic criteria of the American College of Rheumatology, including positivity for anti-ds-DNA and antinuclear antibodies. However, pathological findings from the kidney biopsy suggested pauci-immune crescentic glomerulonephritis. She was also diagnosed with AAV according to the Chapel Hill Consensus Conference (CHCC) 2012 definitions and the classification algorithm of AAV. SLE/AAV OS was suspected, we started immunosuppressant therapy, and subsequently her renal function improved. In previous reports, initial immunological and pathological findings generally concur. In cases where clinical and pathological features appear to conflict, as in the present case, a treatment strategy decision should be based on pathological and immunological findings to improve the prognosis of OS.

Does artificial aging correctly predict the long-term in-vivo degradation behavior in zirconia hip prostheses?

BACKGROUND: Accelerated hydrothermal aging has long been one of the most widely accepted quality control tests for simulating low-temperature degradation (LTD) in zirconia-containing implants used in total hip arthroplasty (THA). However, it is still unclear how much consistency there is between the experimental prediction from the internationally-standardized tests and the actual measurements from surgically-removed implants after a long period of implantation. This question is fundamentally related to a lack of understanding of mechanical/tribological contribution to the in-vivo LTD kinetics. OBJECTIVE: The main purpose of this study is to validate the clinical relevance of standardized accelerated aging by comparing artificially-aged and in-vivo used prostheses, and to clarify the long-term effects of in-vivo mechanics/tribology on the LTD progression upon service in the body environment. METHODS: Surface magnitudes of phase transformation and residual stress in zirconia femoral head retrievals (13.1-18.4 yrs) were evaluated by using confocal Raman microspectroscopy. RESULTS: The long-term aging behavior in unworn head surface was in agreement with the experimental prediction estimated as 1 h aging at 134 °C = 4 years in-vivo. However, the current aging protocols based on ASTM and ISO criteria were not accurately predictive for the worn surfaces, and the tribologically-induced phase transformation and tensile stress were up to 6.5-times and 3.3-times higher than the environmentally-induced ones. CONCLUSION: Our study suggests that wear/scratching, frictional heating, tribochemical reactions, and metal transfer may become far more intense triggers to phase transformation than the mere exposure to body fluid.

Influence of liner offset and locking mechanism on fatigue durability in highly cross-linked polyethylene total hip prostheses.

Highly cross-linked, ultrahigh molecular weight polyethylene (HXLPE) acetabular liners are inherently associated to a risk of fatigue failure due to femoral neck impingement. Different thicknesses and designs employed with HXLPE liners greatly affect mechanical loading scenario. The purpose of this study was to clarify the influence of liner offset (lateralization) and locking mechanism (presence/absence of anti-rotation tabs in the external surface) on fatigue durability in annealed and vitamin E-blended HXLPE liners with a current commercial design. Each liner tested had six anti-rotation tabs, which were engaged in the 6 of 12 recesses on the metal shell. The remaining six recesses had no direct contact with the liner, where HXLPE was mechanically unsupported by the metal backing. These mated and/or unmated rim regions in the offset (2, 3, 4-mm lateralized) liners were exposed to severe neck impingement until crack propagation was identified. Phase volume percentages (crystalline, amorphous, and intermediate phase contents) of HXLPE liners were compared before and after impingement in order to interpret differences in impingement micromechanics associated with the rim design variations. Our results showed that the presence of unmated recesses served as a stress concentrator due to the formation of millimeter-scale gaps between the liner and shell. Another potential design problem drawn from our study was liner offset associated with a small volume protruding above the metal rim. Therefore, surgeons should take special care in selecting locking designs and geometries especially when using HXLPE offset liners.

A new method for diagnosing biochemical abnormalities of anterior cruciate ligament (ACL) in human knees: A Raman spectroscopic study.

Anterior cruciate ligament (ACL) plays an essential role in knee joint stability and kinematics. The microstructural irregularities such as cellular changes and disorganization of the extracellular matrix (ECM) alter the mechanical properties of the ligament, leading to a significant knee functional instability and progression of osteoarthritis (OA). So far, the identification of the local abnormality in ACL has routinely relied on invasive analytical techniques such as histology or biochemical assays. The non-invasive diagnosis using magnetic resonance imaging (MRI) is still limited to identifying the presence/absence of partial/complete ruptures and mucoid degeneration. In this study, laser micro-Raman spectroscopy with near-infrared excitation (785 nm) was applied to human ACL in order to establish optical algorithms for non-destructively diagnosing a degeneration state at molecular level. Raman spectra were obtained from 44 ex-vivo ACL specimens, and these were subsequently classified as an early (subclinical) and advanced (clinical) level of tissue degradation based on the histopathological scoring system. The significant differences in Raman peak intensities were found between the different degeneration groups, which were assigned to the vibrational modes of nucleic acids in cells, collagens, and phospholipids. Linear discriminant analysis (LDA) was performed to identify cut-off values for the distributions of Raman intensity and intensity ratios, which enable to best discriminate between the early and advanced degenerated tissues. Raman intensity algorithms derived from I1101/I1749, [I1002/I1516vs. I1101/I1749], and [I1002/I1749vs. I1101/I1749], yielded a maximum diagnostic sensitivity of 100%, specificity of 80%, and accuracy of 91% for discriminating the degeneration severity. STATEMENT OF SIGNIFICANCE: In this study, laser micro-Raman spectroscopy was applied to human anterior cruciate ligament (ACL) to establish optical algorithms for non-destructively diagnosing the tissue degeneration at molecular level. To our knowledge, this is the first report on Raman diagnosis for human ACL. Linear discriminant analysis (LDA) was performed to identify cut-off values for Raman intensity and intensity ratios, which enable to best discriminate between an early (subclinical) and advanced (clinical) level of ACL degeneration. The intensity ratios of I1101/I1749, [I1002/I1516vs. I1101/I1749], and [I1002/I1749vs. I1101/I1749] yielded a maximum diagnostic sensitivity of 100%, specificity of 80%, and accuracy of 91% for discriminating the ACL degeneration. The present findings might contribute to expanding clinical diagnostic possibilities for non-invasively identifying tissue degeneration.

Azilsartan causes natriuresis due to its sympatholytic action in kidney disease.

The sympathoinhibitory mechanism of azilsartan was investigated in an adenine-induced chronic renal failure model. Azilsartan exerted an antihypertensive effect, though BP elevation induced by adenine was marginal. The creatinine value was significantly lower in the azilsartan group (AZ) than in the vehicle group (VEH); furthermore, proteinuria was suppressed, and sodium excretion was augmented in the AZ group. The low frequency (LF) of systolic BP was suppressed (VEH: 4.07 ± 2.67 mmHg2 vs. AZ: 3.32 ± 1.93 mmHg2 P < 0.001), and the spontaneous baroreflex gain (sBRG) was augmented (VEH: 1.04 ± 0.62ms/mmHg vs. AZ: 1.38 ± 0.69 ms/mmHg, P < 0.001) in AZ. There were no significant differences in ACE1 and ACE2 expression between the groups, which indicated that the action of azilsartan on these components of the intrarenal renin-angiotensin-aldosterone system was comparatively small. Although NHE3, NKCC, and ENaC expression was similar between the groups, NaCl cotransporter (NCC) expression was markedly suppressed by azilsartan (P < 0.05). Thus, in a mild chronic kidney disease (CKD) model with slight BP elevation, the sympatholytic effect of ARB might be expected, and azilsartan might exert its natriuretic effect by NCC suppression achieved by sympathoinhibitory activity.

Clinical course of asymptomatic deep vein thrombosis after total knee arthroplasty in Japanese patients.

PURPOSE: The purpose of the present study was to follow up Japanese patients with deep vein thrombosis (DVT) after total knee arthroplasty (TKA) and also to examine factors associated with residual thrombus within the sixth postoperative month. METHODS: DVT evaluation was performed by noninvasive venous ultrasonography. We retrospectively reviewed 88 Japanese patients (88 knees) receiving primary unilateral TKA, who had no preoperative DVT. We examined the influence of the following four factors on postoperative DVT: (1) patient factors (age, sex, body height, body weight, and body mass index), (2) surgical factors (operation time, bleeding amount, avascularization time, and anesthesia method), (3) postoperative factors (bleeding amount, period to ambulation, period of venous foot pump use, and ratio of graduated compression stocking use), and (4) DVT conditional factors (location, length, number of vein branches, and the presence of >5 mm vasodilatation). RESULTS: The total prevalence of venous thromboembolism (VTE) was 62.5% (55 of the 88 patients). Among the 55 VTE patients, the rates of distal and proximal DVT were 96.4% and 3.6%, respectively. Bilateral DVT was found in 34.5%, while unilateral DVT on the surgical and nonsurgical sides were 52.7% and 12.7%, respectively. Asymptomatic pulmonary embolism was 1.8%. DVT was exacerbated in five patients (11.9%), of whom three showed additional thrombus formation. The remaining two patients had thrombus elongation or propagation from distal to proximal veins. In comparisons between thrombus-unresolved and -resolved groups within the sixth postoperative month, statistical significances were found in the incidence of bilateral DVT (50.0% vs. 15.4%, p = 0.02) and unilateral DVT (43.8% vs. 76.9%, p = 0.02). On the other hand, operation time (107.0 ± 17.3 min vs. 94.5 ± 11.9 min, p = 0.01) and avascularization time (99.8 ± 17.6 min vs. 88.0 ± 11.5 min, p = 0.01) in bilateral DVT patients were significantly longer than in unilateral ones. CONCLUSION: Our results suggest that an extended operation and avascularization time may be a risk factor for bilateral DVT and residual thrombus over 6 months.