Investigation of the effectiveness of intermittent electromagnetic field stimulation for early internal cartilaginous ossification in prechondrocytic ATDC5 cells.

Pulsed electromagnetic field (PEMF) stimulation has been widely applied clinically to promote bone healing; however, its detailed mechanism of action, particularly in endochondral ossification, remains elusive, and long-term stimulation is required for its satisfactory effect. The aim of this study was to investigate the involvement of the mammalian target of rapamycin (mTOR) pathway in chondrocyte differentiation and proliferation using a mouse prechondroblast cell line (ATDC5), and establish an efficient PEMF stimulation strategy for endochondral ossification. The changes in cell differentiation (gene expression levels of aggrecan, type II collagen, and type X collagen) and proliferation (cellular uptake of bromodeoxyuridine [BrdU]) in ATDC5 cells in the presence or absence of rapamycin, an mTOR inhibitor, was measured. The effects of continuous and intermittent PEMF stimulation on changes in cell differentiation and proliferation were compared. Rapamycin significantly suppressed the induction of cell differentiation markers and the cell proliferation activity. Furthermore, only intermittent PEMF stimulation continuously activated the mTOR pathway in ATDC5 cells, significantly promoting cell proliferation. These results demonstrate the involvement of the mTOR pathway in chondrocyte differentiation and proliferation and suggest that intermittent PEMF stimulation could be effective as a stimulus for endochondral ossification during fracture healing process, thereby reducing stimulation time.

A novel diagnostic examination for dropped head syndrome (DHS) (Prone position cervical extension test; DHS test).

BACKGROUND: Dropped head syndrome (DHS) is followed by severe cervical extension muscle weakness that results in chin-on chest deformity. However, maintaining a neutral cervical position can be temporarily possible, and the diagnosis of DHS might sometimes be difficult. The purpose of the present study is to examine a novel clinical test (DHS test) as the diagnostic utility for objective evaluation that focuses on cervical extension condition in the prone position. METHODS: One hundred subjects were diagnosed with isolated neck extensor myopathy (INEM)-DHS at our hospital (17 men and 83 women, mean age 75.0 ± 8.5 years), and 62 subjects were enrolled as age-matched controls. The DHS test consisted of three examinations; the first was "Ceiling gazing test" in standing position, the second was horizontal gazing in "Sphinx prone position test", and the third was horizontal gazing in "Hands and knees prone position test". We investigated the sensitivity and specificity of the DHS test for DHS. RESULTS: The patients showing positive in the INEM-DHS group were 63/100 in Ceiling gaze test, 73/100 in the Sphinx prone position test, and 91/100 in the Hands and knees prone position test. In the control group, 0/62 patients presented positive in the Ceiling gaze test, 4/62 in the Sphinx prone position test, and 0/62 in the Hands and knees prone position test. Sensitivity and specificity of the DHS test were 63.0%/100%, 73.0%/93.5%, and 91.0%/100% in the Ceiling gaze test, Sphinx position prone position test, and Hands and knees prone position test, respectively. CONCLUSION: The prone position cervical extension test (DHS test) would be useful as a novel objective diagnostic tool for INEM-DHS.

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.

Prostaglandin E2 induces dual-specificity phosphatase-1, thereby attenuating inflammatory genes expression in human osteoarthritic synovial fibroblasts.

Characteristic features of osteoarthritis (OA) are joint pain and cartilage degeneration. The degeneration is caused by excess induction of matrix metalloproteinases (MMPs) and the pain is caused by nerve growth factor (NGF)-dependent nerve invasion into synovial tissue in addition to nociceptive pain by prostaglandin (PG)E2. The objective of this study was to clarify the suppressive mechanism of PGE2 on the regulation of MMPs and NGF by focusing on mitogen-activated protein kinases (MAPKs) and their endogenous phosphatase, dual-specificity phosphatase (DUSP)-1 in human synovial fibroblasts. PGE2 strongly increased DUSP-1 and suppressed IL-1ß-induced MAPKs phosphorylation. Inhibition of MAPKs by selective inhibitors differentially regulated the IL-1ß-induced expression of MMPs and NGF expression. IL-1ß-induced MAPKs phosphorylation was prolonged and enhanced in DUSP-1 knockdown cells and the expression of MMPs and NGF was also increased. This study revealed that PGE2 has novel biological activity that suppresses NGF and MMPs expression by inducing DUSP-1 expression.

Intermittent pulsed electromagnetic field stimulation activates the mTOR pathway and stimulates the proliferation of osteoblast-like cells.

Pulsed electromagnetic fields (PEMFs) have been shown to be a noninvasive physical stimulant for bone fracture healing. However, PEMF stimulation requires a relatively long period of time and its mechanism of action has not yet been fully clarified. Recently, the mammalian target of rapamycin (mTOR) pathway has been shown to be involved in bone formation. This study aimed to investigate the effects of PEMFs on osteoblastic MC3T3-E1 cells by examining various cellular responses including changes in the mTOR pathway. Continuous PEMF stimulation induced a transient phosphorylation of the mTOR pathway, whereas intermittent PEMF stimulation (1 cycle of 10 min stimulation followed by 20 min of stimulation pause) revitalized the reduced phosphorylation. Moreover, PEMF stimulation stimulated cell proliferation (bromodeoxyuridine incorporation) rather than differentiation (alkaline phosphatase activity), with a more notable effect in the intermittently stimulated cells. These results suggest that intermittent PEMF stimulation may be effective in promoting bone fracture healing by accelerating cell proliferation, and in shortening stimulation time. Bioelectromagnetics. 2019;40:412-421. © 2019 Bioelectromagnetics Society.

The aging micromechanisms of alumina matrix composite (AMC) used in total hip arthroplasty.

BACKGROUND: The aim of the present study is to simulate and better understand the long-term interplay between alumina matrix composite (AMC) femoral head and aqueous environment. In particular, we focused on clarifying the role of alumina grains on zirconia phase stability and mechanical equilibrium in AMC head during aging processes in a clinically-relevant time frame. METHODS: The tested AMC head consists of an alumina matrix (82 vol.%) reinforced by yttria-stabilized zirconia (17 vol.%), chromium oxide (0.5 vol.%), and strontium aluminate (0.5 vol.%). The accelerated hydrothermal aging testing (at 134 °C, 2-bars pressure) was conducted up to 20 h. According to ASTM standard, 1-h aging under these conditions corresponds approximately to 2 yrs in vivo exposure. Confocal Raman and fluorescence spectroscopy were applied to quantify surface tetragonal-to-monoclinic phase transformation of zirconia and surface stresses in the AMC head. The Mehl-Avrami-Johnson (MAJ) theory was applied, which allowed modeling the micromechanisms of nucleation and growth of monoclinic sites during the transformation process. The obtained results were compared to those of monolithic zirconia (3Y-TZP) femoral heads. RESULTS: The 3Y-TZP head showed a rapid increase of transformation rate beyond the aging time of 5 h (simulated as ∼10 yrs in vivo), suggesting the initiation of the transformation cascade toward the neighboring zirconia grains (growth mechanism). On the other hand, MAJ analysis revealed that the growth mechanism was completely absent and the nucleation of the monoclinic phase was partially prevented in the AMC head even after the 20-h aging (∼40 yrs in vivo). In addition, the stress accumulation in the AMC head was restricted at a quite low level throughout the aging simulation. CONCLUSION: Those results suggest that the presence of stable and hard alumina in the AMC can play a considerable role in slowing down the destabilization processes by spatially encompassing zirconia grains.

Does modern space suit reduce intraoperative contamination in total joint replacement? An experimental study.

BACKGROUND: The purpose of this study was to evaluate a potential risk of intraoperative contamination associated with clothing systems and surgeon's motion in total joint replacement. METHODS: The airborne particle concentrations at different locations around a single operating surgeon wearing standard surgical gown (SG) or modern "space suit" (SS) were compared. The particles in the size of ≥0.5 µm (roughly corresponding to a mean diameter of squamous epithelial cells) were counted at the following three locations: (1) ≈10 cm inferior to the wrist; (2) ≈10 cm posterior to the feet; and (3) near the chest (operative field) under condition either with or without the surgeon's motion (stepping in place at ~1 Hz). RESULTS: The difference in the surgical clothing systems did not significantly affect the mean particle counts detected near the wrist and chest (p = 0.307 and 0.155, respectively). However, the particle count near the feet was 154 times higher in SS than SG (4630 ± 2795 vs. 30 ± 23 N/F3, p = 0.023). The simple stepping of the surgeon with SS increased contaminants near the chest 31 times as compared to the condition without motion (1053 ± 709 vs. 34 ± 31 N/F3, p = 0.0032). Although the particle count was less affected by the motion in SG than SS, contaminants near the chest increased ten times after the stepping in the use of SG (p = 0.032). CONCLUSION: The present results suggest that the intraoperative motion of a surgeon may considerably increase airborne particle/bacterial concentration in the operative field. This can be a much higher likelihood in SS rather than SG because of air blow-off from the incorporated cooling fan.

Improved Resistance to Neck-Liner Impingement in Second-Generation Highly Crosslinked Polyethylene-The Role of Vitamin E and Crosslinks.

BACKGROUND: Radiation crosslinking of ultrahigh molecular weight polyethylene (UHMWPE) results in the reduced tensile strength and fracture toughness as an expense of dramatic increase in the wear resistance. Clinical rim fracture has been reported due to neck-liner impingement on a first-generation highly crosslinked UHMWPE acetabular component. The objective of this study was to investigate whether a second-generation, vitamin E-blended highly crosslinked UHMWPE possesses the improved impingement resistance. METHODS: Cyclic impingement testing was performed in a variety of UHMWPE acetabular components (vitamin E free or blended, noncrosslinked or highly crosslinked, and GUR1050 or GUR1020) with the same design specification. The kinematics used to reproduce the neck-liner impingement was a uniaxial fatigue compression in concert with an axial rotational torque. After the test, the geometry and morphological changes were characterized by coordinate measuring machine, scanning electron microscopy, and confocal Raman microspectroscopy. RESULTS: A total of 300-kGy irradiated and annealed GUR1050 liner resulted in a significant geometry change and microcracks on the rim surface after the test. However, regardless of the similar level of crosslinking, much less damage was noted in the 300-kGy irradiated GUR1050 liner blended with vitamin E at a concentration of 3000 ppm. On the other hand, vitamin E-blended noncrosslinked GUR1050 exhibited an extensive microscopic fibrillation and folding on the impinged surface. CONCLUSION: These results suggest that vitamin E-blending into UHMWPE has compensated the negative effect of toughness decrease induced by radiation crosslinking. We concluded that the coexistence of vitamin E and crosslinks can restrain impingement damage more effectively than either of them.

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.].

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.

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.

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.

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.

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.

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.

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.

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.

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.

Cement spacer loaded with antibiotics for infected implants of the hip joint.

It is difficult to treat infected implants of the hip joints. Such treatment involves immeasurable physical and psychological suffering of the patients. We used antibiotic-impregnated cement spacers in 17 cases of infection after total hip arthroplasty and bipolar arthroplasty with good clinical results. We thoroughly removed any foreign material and formed an antibiotic-impregnated cement spacer into a similar shape as that of the implants. A cement spacer enables high-concentration antibiotics to act on infected sites. Also, it can prevent leg length discrepancy and atrophy of bones or muscles. Although cement spacers have been reported to have problems regarding shape and strength, we achieved good results with a cement spacer mold in the present study. No recurring infection has been found at a mean follow-up period of 3 years and 2 months.

Do rim cracks and backside grinding affect the aging kinetics of alumina-matrix composite acetabular liners?

The acetabular liner malalignment and rim impingement have been problematic issues in ceramic-on-ceramic (CoC) total hip arthroplasty (THA). Commercial ceramic liners made of alumina-matrix composite (AMC) have polished articulation and rim, and roughly ground backside with a button-like apical projection (post) to resist tilting. In this study, we hypothesized that rim cracks and backside grind critically affect the aging kinetics of tetragonal zirconia dispersed in AMC structure. We analyzed phase transformation in the zirconia phase and residual stresses in the alumina matrix during aging by Raman and fluorescence spectroscopy. We demonstrated that the polished surfaces showed environmental stability in vitro, while the roughly-ground backside showed a significant stability loss and tensile stress accumulation as a consequence of enhancing the inter-component fixation between the liner and the metallic shell. Rim cracking locally produced a preferential transformation at the tip and the surrounding of the crack. Note that the tensile stress concentration at the crack tip was counteracted by the phase transformation after a few hours of aging. This suggests the presence of a time lag in vivo before further transformation around the crack could provide a crack shielding effect in the material. © 2018 Wiley Periodicals, Inc. J. Biomed. Mater. Res. Part B, 2018. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 791-798, 2019.