Survivorship of the fixed-bearing medial unicompartmental knee arthroplasty: mean 14-year follow-up in a single medical center.

BACKGROUND: This study aimed to report the long-term survival of fixed-bearing medial unicompartmental knee arthroplasty (UKA) with a mean of 14-year follow-up, and to determine possible risk factors of failure. METHODS: We retrospectively evaluated 337 fixed-bearing medial UKAs implanted between 2003 and 2014. Demographic and radiographic parameters were measured, including pre-operative and post-operative anatomical femorotibial angle (aFTA), posterior tibial slope (PTS), and anatomical medial proximal tibial angle (aMPTA). Multivariate logistic regression analysis was applied to figure out risk factors. RESULTS: The mean follow-up time was 14.0 years. There were 32 failures categorized into implant loosening (n = 11), osteoarthritis progression (n = 7), insert wear (n = 7), infection (n = 4), and periprosthetic fracture (n = 3). Cumulative survival was 91.6% at 10 years and 90.0% at 15 years. No statistically significant parameters were found between the overall survival and failure groups. Age and hypertension were significant factors of implant loosening with odds ratio (OR) 0.909 (p = 0.02) and 0.179 (p = 0.04) respectively. In the insert wear group, post-operative aFTA and correction of PTS showed significance with OR 0.363 (p = 0.02) and 0.415 (p = 0.03) respectively. Post-operative aMPTA was a significant factor of periprosthetic fracture with OR 0.680 (p < 0.05). CONCLUSIONS: The fixed-bearing medial UKA provides successful long-term survivorship. Tibial component loosening is the major cause of failure. Older age and hypertension were factors with decreased risk of implant loosening.

Clinical outcomes of various types of revision surgeries after unicompartmental knee arthroplasty failure.

PURPOSE: The advantages of unicompartmental knee arthroplasty (UKA) have led to the procedure being increasingly performed worldwide. However, revision surgery is required after UKA failure. According to the literature review, the choice of implant in revision surgery remains a debatable concern. This study analyzed the clinical results of different types of prostheses used in treating failed UKA. MATERIALS AND METHODS: This is a retrospective review of 33 failed medial UKAs between 2006 and 2017. Demographic data, failure reason, types of revision prostheses, and the severity of bone defects were analyzed. The patients were classified into three groups: primary prosthesis, primary prosthesis with a tibial stem, and revision prosthesis. The implant survival rate and medical cost of the procedures were compared. RESULTS: A total of 17 primary prostheses, 7 primary prostheses with tibial stems, and 9 revision prostheses were used. After a mean follow-up of 30.8 months, the survival outcomes of the three groups were 88.2%, 100%, and 88.9%, respectively (P = 0.640). The common bone defect in tibia site is Anderson Orthopedic Research Institute [AORI] grade 1 and 2a (16 versus 17). In patients with tibial bone defects AORI grade 2a, the failure rates of primary prostheses and primary prostheses with tibial stems were 25% and 0%, respectively. CONCLUSIONS: The most common cause for UKA failure was aseptic loosening. The adoption of a standardized surgical technique makes it easier to perform revision surgeries. Primary prostheses with tibial stems provided higher stability, leading to a lower failure rate due to less risk of aseptic loosening in patients with tibial AORI grade 2a. In our experience, we advise surgeons may try using primary prostheses in patients with tibial AORI grade 1 and primary prostheses with tibial stems in patients with tibial AORI grade 2a.

The Risk Factor and Outcome of Metachronous Periprosthetic Joint Infections: A Retrospective Analysis With a Minimum Ten-Year Follow-Up.

BACKGROUND: Patients with multiple prosthetic joints are at risk of developing periprosthetic joint infections (PJIs). We aimed to determine whether PJI development at one site may lead to infection at another prosthetic joint site and assess the risk factors leading to this subsequent infection. METHODS: We reviewed all cases (294 patients with first-time PJI [159 hips, 135 knees]) with PJI treated at our institute between January 1994 and December 2020. The average follow-up period was 11.2 years (range 10.1-23.2). Patients were included if they had at least one other prosthetic joint at the time of developing a single PJI (96 patients). Patients with synchronous PJI were excluded from the study. The incidence of metachronous PJI was assessed, and the risk factors were determined by comparing different characteristics between patients without metachronous PJI. RESULTS: Of the 96 patients, 19.79% developed metachronous PJI. The identified causative pathogen was the same in 63.16% of the patients. The time to developing a second PJI was 789.84 days (range 10-3386). The identified risk factors were PJI with systemic inflammatory response syndrome, ≥3 stages of resection arthroplasty, and PJI caused by methicillin-resistant Staphylococcus aureus. CONCLUSION: PJI may predispose patients to subsequent PJI in another prosthesis with identified risks. Most causative organisms of metachronous PJI were the same species as those of the first PJI. We believe that bacteremia may be involved in pathogenesis, but further research is required.

Vascular injury during primary total knee arthroplasty: A nationwide study.

PURPOSE: To evaluate the incidence, risk factors, mortality, and complications of direct vascular injury (VI) in patients who underwent primary total knee arthroplasty (TKA) using data from a nationwide database. METHODS: Data were collected from the National Health Insurance Research Database of Taiwan. The study group included 111,497 patients who underwent TKA from January 2004 to December 2011. In total, 15 cases of direct VI were reported (VI group). We analyzed the incidence, risk factors, mortality, complications of direct VI and hospital stays between groups (VI group and non-VI group). RESULTS: Average incidence of VI was 13.74 per 100,000 person-years. No patient-dependent risk factors for VI were identified. Surgeons with low surgical volume highly correlated with incidence of VI (P < 0.05). 90-day mortality was significantly higher (33.3% vs. 0.37%) and length of hospital stay was significantly longer (19.43 days vs. 7.26 days) in the VI group than in the control group. In addition, incidence of periprosthetic joint infection, restenosis at the injury site, and limb loss were significantly higher in the VI group than in the control group. CONCLUSION: VI during primary TKA was associated with significantly higher incidence of periprosthetic joint infection, restenosis at the injury site, and limb loss, as well as higher 90-day mortality. Therefore, surgeons should be aware of VI during primary TKA, especially those with low surgical volume.

One- and two-stage surgical revision of peri-prosthetic joint infection of the hip: a pooled individual participant data analysis of 44 cohort studies.

One-stage and two-stage revision strategies are the two main options for treating established chronic peri-prosthetic joint infection (PJI) of the hip; however, there is uncertainty regarding which is the best treatment option. We aimed to compare the risk of re-infection between the two revision strategies using pooled individual participant data (IPD). Observational cohort studies with PJI of the hip treated exclusively by one- or two-stage revision and reporting re-infection outcomes were retrieved by searching MEDLINE, EMBASE, Web of Science, The Cochrane Library, and the WHO International Clinical Trials Registry Platform; as well as email contact with investigators. We analysed IPD of 1856 participants with PJI of the hip from 44 cohorts across four continents. The primary outcome was re-infection (recurrence of infection by the same organism(s) and/or re-infection with a new organism(s)). Hazard ratios (HRs) for re-infection were calculated using Cox proportional frailty hazards models. After a median follow-up of 3.7 years, 222 re-infections were recorded. Re-infection rates per 1000 person-years of follow-up were 16.8 (95% CI 13.6-20.7) and 32.3 (95% CI 27.3-38.3) for one-stage and two-stage strategies respectively. The age- and sex-adjusted HR of re-infection for two-stage revision was 1.70 (0.58-5.00) when compared with one-stage revision. The association remained consistently absent after further adjustment for potential confounders. The HRs did not vary importantly in clinically relevant subgroups. Analysis of pooled individual patient data suggest that a one-stage revision strategy may be as effective as a two-stage revision strategy in treating PJI of the hip.

Postoperative wound infection after posterior spinal instrumentation: analysis of long-term treatment outcomes.

PURPOSE: Postoperative spinal implant infection (PSII) places patients at risk for pseudarthrosis, correction loss, spondylodiscitis, adverse neurological sequelae, and even death; however, prognostic factors that predict long-term treatment outcomes have not been clearly investigated. In addition, few studies concerning the feasibility of reconstructing the failed spinal events have been published. METHODS: We performed a cohort study of 51 patients who contracted PSII in the posterolateral thoracolumbar region at a single tertiary center between March 1997 and May 2007. Forty-seven patients (92.2 %) had one or more medical problems. Isolated bacterial species, infection severity, treatment timing, and hosts' defense response were evaluated to assess their relationship with management outcomes. The use of implant salvage, or removal subsequent with a revision strategy depended on the patient's general conditions, infection control, and implant status for fusion. RESULTS: The most common infective culprit was Staphylococcus spp. found in 35 of 60 (58.3 %) isolates, including 20 methicillin-resistant species. Gram-negative bacilli and polymicrobial infection were found significantly in patients presenting early-onset, deep-site infection and myonecrosis. Prompt diagnosis and aggressive therapy were responsible for implant preservation in 41 of 51 cases (80.4 %), while implant removal noted in 10 cases (19.6 %) was attributed to delayed treatment and uncontrolled infection with implant loosening, correction loss, or late infection with spondylodesis. The number of employed debridements alone was not significantly correlated with successful implant preservation. Delayed treatment for infection >3 months significantly led to implant removal (p < 0.05) and a higher number of failed spinal events. Patients with significant comorbidities, malnutrition, severe trauma, neurological deficits, long-level instrumentation, and delayed treatment had poor outcomes. Sixteen patients (31.4 %) exhibited probable nonunion or pseudarthrosis, and eight symptomatic patients among them underwent successful revision surgery. CONCLUSIONS: Retention of the mechanically sound implants in early-onset infection permits fusion to occur, while delayed treatment, severe malnutrition and multiple comorbidities will most likely result in a lack of effectiveness in eradicating the infecting pathogens. Restoring optimal physiological conditions is imperative in high-risk patients to allow for further healing. When loosened screws cause peridiscal erosion and incapacitating motion pain, premature implant removal possibly results in failed fusion and correction loss. Reconstruction for a failed spinal event is feasible following infection control.

The effects of necrotic lesion size and orientation of the femoral component on stress alterations in the proximal femur in hip resurfacing - a finite element simulation.

BACKGROUND: Due to the advantages of its bone-conserving nature, hip resurface arthroplasty (HRA) has recently gained the interest of orthopedic surgeons for the treatment of young and active patients who have osteonerosis of the femoral head. However, in long-term follow-up studies after HRA, narrowing of the femoral neck has often been found, which may lead to fracture. This phenomenon has been attributed to the stress alteration (stress shielding). Studies addressing the effects of necrotic size and the orientation of the implant on stress alterations are lacking. METHODS: Computed tomography images of a standard composite femur were used to create a three-dimensional finite-element (FE) intact femur model. Based on the intact model, FE models simulating four different levels of necrotic regions (0°, 60°, 100°, 115°) and three different implant insertion angles (varus 10°, neutral, valgus 10°) were created. The von Mises stress distributions and the displacement of the stem tip of each model were analyzed and compared for loading conditions that simulated a single-legged stance. RESULTS: Stress shielding occurred at the femoral neck after HRA. More severe stress shielding and an increased displacement of the stem tip were found for femoral heads that had a wider necrotic lesion. From a biomechanics perspective, the results were consistent with clinical evidence of femoral neck narrowing after HRA. In addition, a varus orientation of the implant resulted in a larger displacement of the stem tip, which could lead to an increased risk of implant loosening. CONCLUSIONS: A femoral head with a wide necrotic lesion combined with a varus orientation of the prosthesis increases the risk of femoral neck narrowing and implant loosening following HRA.

Intra-articular bupivacaine reduces postoperative pain and meperidine use after total hip arthroplasty: a randomized, double-blind study.

One hundred patients receiving unilateral total hip arthroplasty (THA) were randomized to receive an intra-articular injection of 300mg bupivacaine or normal saline after completion of surgery. Pain scores of the bupivacaine group were significantly lower than those of the control group the first 12hours postoperatively (all, P<0.001). A significantly lower dose of meperidine was used in the study group than in the control group the first 24hours postoperatively (median, 25 vs. 45mg, P<0.001). Nineteen patients in the study group required meperidine the first day after surgery, as compared to 45 patients in the control group. We conclude that intra-articular injection of bupivacaine after THA reduces pain and meperidine use in the first 12hours after surgery.

Key risk factors and adverse outcomes in metachronous vertebral osteomyelitis following periprosthetic joint infection: A 5-year retrospective study.

Purpose: Periprosthetic joint infection (PJI) is a leading cause of joint arthroplasty failure, potentially leading to critical complications like vertebral osteomyelitis (VO). The factors contributing to VO after PJI and the outcomes for these patients are not well understood. Our study aims to (1) identify risk factors for VO following PJI and (2) assess the clinical outcomes in these cases. Methods: We included PJI patients treated surgically at our centre from January 2006 to December 2020, excluding those with simultaneous VO post-PJI. Our focus was on patients with VO occurring after PJI, monitored for at least 5 years. Analysis included patient comorbidities, PJI treatment approaches, pathogen identification and clinical outcomes. Results: Of 1701 PJI cases, 21 (1.23%) developed VO. Key risk factors for VO post-PJI were identified: systemic inflammatory response syndrome, substance misuse, polymicrobial infection and undergoing at least three stages of resection arthroplasty (odds ratios: 1.86, 54.28, 52.33 and 31.88, respectively). Adverse outcomes were noted in VO patients, with recurrent VO in 6/21 and repeated PJIs in 18/21 cases. Conclusions: Patients with PJI, especially those with certain risk factors, have an increased likelihood of developing VO and encountering negative outcomes. The potential role of bacteremia in the development of VO after PJI needs further exploration. Level of Evidence: Level III.

What is the success of treatment of hip and knee candidal periprosthetic joint infection?

BACKGROUND: Fungal infection at an arthroplasty site is rare and poses a therapeutic challenge. To the best of our knowledge, no reports have been published thus far on the success rate of prosthesis reimplantation after fungal prosthetic joint infections. QUESTIONS/PURPOSES: We asked: (1) What is the success rate in terms of infection eradication using a two-stage exchange arthroplasty in patients with hip or knee fungal periprosthetic joint infections, particularly focusing on Candida infections? (2) What patient-, infection-, and treatment-related variables are associated with the success or failure of treatment? METHODS: From January 2000 to December 2010, 16 patients with hip or knee candidal periprosthetic joint infections were treated with two-stage exchange arthroplasty at our institute. Treatment success was defined as a well-functioning joint without relapse of candidal infection after prosthesis reimplantation, while treatment failure was defined as uncontrolled or relapse of candidal infection or mortality. Variables, including age, sex, comorbidities, microbiology, antimicrobial agents used, and operative methods, were analyzed. Minimum followup was 28 months (mean, 41 months; range, 28-90 months). RESULTS: At latest followup, the treatment failed to eradicate the infection in eight of the 16 patients, and there were four deaths related to fungemia. Four patients required permanent resection arthroplasty owing to uncontrolled or recurrent candidal infections. All eight patients (50% successful rate) who had their infections eradicated and successful prosthesis reimplantation had prolonged treatment with oral fluconazole before (mean, 8 months) and after (mean, 2.2 months) prosthesis reimplantation. The antifungal therapy correlated with successful treatment. Renal insufficiency, hypoalbuminemia, anemia, and chronic obstructive pulmonary disease were significantly more prevalent in the treatment-failure group than in the treatment-success group. CONCLUSIONS: Half of the patients treated with two-stage exchange arthroplasty for fungal periprosthetic joint infections had recurrence or lack of control of the infection. A prolonged antifungal therapy appeared to be essential for successful treatment of candidal periprosthetic joint infections. The presence of renal insufficiency, hypoalbuminemia, anemia, or chronic obstructive pulmonary disease might be associated with a poor outcome.

The influence of storage temperature on the antibiotic release of vancomycin-loaded polymethylmethacrylate.

Periprosthetic joint infection is devastating and increases medical expenditure and socioeconomic burden. Antibiotic-loaded cement spacer is useful in the interim period before the reimplantation surgery. Prefabricated antibiotic-loaded cement spacers can decrease operation time but have been limitedly used clinically. In the literature, there is no clear recommendation on the storage temperature for the prefabricated cement spacers. We used an in vitro model to analyze whether the storage temperature at 25°C, 4°C, or -20°C for 2 weeks or 3 months could affect the release of vancomycin from the cement. We found that the storage temperature and time had no significant effects on the pattern and amount of vancomycin release. The patterns of vancomycin release from the cement stored at different temperatures were similar with an abrupt release in the first 3 days and steadily declined in the following period. This study provides a preliminary result to justify the storage of fabricating antibiotic-loaded cement spacer sterilely packed at room temperature. Further studies to examine the effects of storage temperature on the mechanical strength and the release pattern of other antibiotics should be done to provide more evidence to support the clinical use of prefabricated ready-to-use antibiotic-loaded cement spacer.

Molecular diagnosis of periprosthetic joint infection by quantitative RT-PCR of bacterial 16S ribosomal RNA.

The diagnosis of periprosthetic joint infection is sometimes straightforward with purulent discharge from the fistula tract communicating to the joint prosthesis. However it is often difficult to differentiate septic from aseptic loosening of prosthesis because of the high culture-negative rates in conventional microbiologic culture. This study used quantitative reverse transcription polymerase chain reaction (RT-qPCR) to amplify bacterial 16S ribosomal RNA in vitro and in 11 clinical samples. The in vitro analysis demonstrated that the RT-qPCR method was highly sensitive with the detection limit of bacterial 16S rRNA being 0.148 pg/ µ l. Clinical specimens were analyzed using the same protocol. The RT-qPCR was positive for bacterial detection in 8 culture-positive cases (including aerobic, anaerobic, and mycobacteria) and 2 culture-negative cases. It was negative in one case that the final diagnosis was confirmed without infection. The molecular diagnosis of bacterial infection using RT-qPCR to detect bacterial 16S rRNA around a prosthesis correlated well with the clinical findings. Based on the promising clinical results, we were attempting to differentiate bacterial species or drug-resistant strains by using species-specific primers and to detect the persistence of bacteria during the interim period before the second stage reimplantation in a larger scale of clinical subjects.

Antibacterial activity of joint fluid in cemented total-knee arthroplasty: an in vivo comparative study of polymethylmethacrylate with and without antibiotic loading.

The objective of this study was to evaluate the antibacterial activities of joint fluids of patients undergoing total-knee arthroplasty (TKA). Thirty patients who were scheduled for primary cemented TKA were enrolled in the study. The patients were grouped on the basis of whether the cement was without antibiotic loading (control group) or loaded with oxacillin (oxacillin group) or vancomycin (vancomycin group). Cefazolin was administered to every patient as the perioperative prophylactic antibiotic. Samples of joint fluids were collected from the knee joints at 8, 16, 24, 32, 40, and 48 h after prosthesis implantation. We assessed the bioactivities of the joint fluids against methicillin-susceptible Staphylococcus aureus (MSSA) and methicillin-resistant S. aureus (MRSA). The antibiotic contents of the joint fluid samples were further evaluated by using high-performance liquid chromatography. Against MSSA, all joint fluid samples exhibited at least 24 h of bacterial inhibition activity. The oxacillin (43.2 h ± 2 h) and vancomycin (40.8 h ± 1.8 h) groups exhibited significantly longer durations of antibacterial activities than the control group (28 h ± 1.3 h; P < 0.05). However, antibacterial activity against MRSA was observed only in the vancomycin group. In conclusion, cefazolin, which was administered as a prophylactic antibiotic in TKA, exhibited good ability for knee joint penetration and was sufficient to inhibit MSSA during its administration. The use of antibiotic-loaded cement can prolong the antibacterial activity of joint fluid in TKA. Further, vancomycin-loaded cement had antibacterial activity against MRSA superior to that of cement loaded with oxacillin or without antibiotic loading.

Acute delirium and poor compliance in total hip arthroplasty patients with substance abuse disorders.

From the joint registry of 2831 primary total hip arthroplasties (2351 patients) performed between 1998 and 2003, we identified 15 patients (16 hips) who had a documented history of substance abuse disorders at the time of the index surgery. The patients included 13 men (14 hips) and 2 women (2 hips), with the mean age of 49 years (range, 29-65 years). On the basis of the criteria specified in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, 13 patients had alcohol abuse disorders, 1 had amphetamine abuse disorder, and 1 had heroin abuse disorder. We found high rates of postoperative substance withdrawal delirium and psychosis (46%), late complication (25%), and lost to follow-up (27%) in these patients. Because patients with substance abuse disorders have unexpected perioperative psychotic episodes, poor compliance, and a tendency to not follow medical advice after surgery and show early discontinuation of follow-up, we suggest that surgeons should work with other medical professionals and carefully perform total hip arthroplasty in such patients.

Pain distribution and response to total hip arthroplasty: a prospective observational study in 113 patients with end-stage hip disease.

PURPOSE: The aim of this study was to investigate the pain patterns in patients with end-stage hip disease and to assess the response after total hip arthroplasty (THA). METHODS: The pain patterns of patients undergoing THA for end-stage hip diseases were prospectively evaluated by requesting them to mark a map of body areas before and after surgery. Patients were excluded if they had coexisting pathology of the knee or spine. The pain measurements were quantified using visual analog scales, and factors that may contribute to different pain patterns were also evaluated. RESULTS: Among 113 patients (113 hips) enrolled in the study, the groin, anterior thigh, buttock, anterior knee, and greater trochanter were the most common pain locations before THA. Pain over the lower back, shin, and calf areas, which were not generally considered referral pain areas from hip diseases, was present in 21.2, 7.1, and 2.7% patients, respectively. The presence of lower back pain (LBP) was statistically more common in patients with longer duration of hip symptoms. Regardless of the different pain patterns, 97.3% (110 of 113) of patients reported complete pain relief within 12 weeks after THA. CONCLUSIONS: The distribution of pain from end-stage hip diseases is versatile, and presence of pain in areas other than around the hip is not uncommon. LBP was more common in patients with longer duration of symptoms. THA satisfactorily resolves the pain in all areas soon after surgery.

Revision Total Hip Arthroplasty with Primary Stem or Full-Porous-Coated Long Stem for Aseptic Femoral Component Loosening: A Matched-Pair Study.

BACKGROUND: Revision total hip arthroplasty (RTHA) for loosening the femoral stem is a technical challenge. Distally fixed, full-porous-coated long stems are widely accepted as the standard selection for these revisions. However, the success of primary stems in RTHA is not well known. METHODS: This study enrolled 24 patients with aseptic loosening of the femoral stem who underwent RTHA using primary stems. Another 72 patients with aseptic loosening who underwent RTHA using full-porous-coated long stems were matched in terms of operation date, proximal femoral bone stock (Paprosky classification), sex, and age. The primary and secondary outcomes of failure were the need for revision for any reason and the radiographic change in the stem respectively. RESULTS: In the primary stem group, one patient had a periprosthetic fracture and received a second RTHA 2 years after the previous one. The primary outcome's 5-and 10-year survival rates were both 95.8%. For the matched comparison group, one patient had an immediate periprosthetic fracture of the femoral shaft requiring further open reduction internal fixation surgery. Another patient had a full-porous-coated long stem breakage 6 years postoperatively, which required a second RTHA. The primary outcome's 5-and 10-year survival rates were 98.6% and 97.2%, respectively. CONCLUSION: Primary stems can achieve non-inferior clinical success compared to a full-porous-coated long stem for aseptic stem loosening RTHA in patients with adequate proximal femoral bone stock.

Nontuberculous mycobacteria peri-prosthetic joint infection: An outcome analysis for two stage revision arthroplasty.

PURPOSE: Nontuberculous mycobacteria periprosthetic joint infection (NTMPJI) is a rare complication of hip or knee joint arthroplasty. The experience for outcomes of NTMPJI treatment is still limited. The objective of this study was to investigate the outcome of hip or knee nontuberculous mycobacteria periprosthetic joint infection following treatment with two-stage exchange arthroplasty. MATERIAL AND METHODS: From 1995 to 2020, 12 patients with NTMPJI were treated with two-stage exchange arthroplasty at our institution. We collected and analyzed variables including demographic data, comorbidity, microbiological data, treatment outcome and antibiotic formula in bone cement. RESULTS: Mycobacterium abcessus (n = 6) and Mycobacterium chelonae (n = 2) constitute the majority of the cases. Five patients had early-onset PJIs and the other seven patients were late onset. The success rate of two-stage exchange arthroplasty was 66.7% (8 of 12). Three patients experienced infection relapse, and one patient had soft tissue compromise complication. Post-operative antibiotic therapy may not improve the success rate (4 of 6 cases, 66.7%). Based on in vitro study, the most commonly used effective antibiotic in bone cement spacer for nontuberculous mycobacteria was amikacin. CONCLUSIONS: nontuberculous mycobacteria is a rare cause of PJIs and should be suspected especially in relatively immunocompromised patients. Resection arthroplasty with staged reimplantation is the preferred approach. Prolonged post-operative antibiotic therapy before reimplantation may not improve the success rate. Delayed revision surgery may not be needed and can be performed once C-reactive protein level is normal after a drug holiday.

Characterization of the phenotypes of methicillin- and vancomycin-susceptible Staphylococcus argenteus after vancomycin passages.

OBJECTIVES: Staphylococcus argenteus is generally more susceptible to antibiotic treatments than Staphylococcus aureus; however, the study showed that the daptomycin/vancomycin-resistant S. argenteus was isolated from a patient with repeated antibiotic treatments. In this study, the methicillin- and vancomycin-susceptible S. argenteus isolates were used to characterize the phenotypes of S. argenteus after vancomycin passages in vitro. METHODS: Eleven S. argenteus isolates were used for passaging under different concentrations of vancomycin. The minimal inhibitory concentration (MIC) of vancomycin was determined by the agar dilution assay, and the biofilm mass of the passaged variants was quantified by the crystal violet staining assay and observed under the confocal microscope. RESULTS: The MIC of vancomycin for eight of 11 S. argenteus isolates was increased from ≤2 µg/mL to ≤4-8 µg/mL after vancomycin passages. Two variants with the high-level vancomycin-intermediate (vancomycin MIC ≤8 µg/mL) phenotype were identified, and the parental strains of these variants did not have the heterogeneous vancomycin-intermediate population determined by the population profile analysis. Further, three S. argenteus isolates showed an increase in biofilm production and icaA transcription after the low-dose (2 µg/mL) vancomycin passages. CONCLUSIONS: S. argenteus is capable of acquiring a vancomycin-tolerant phenotype and/or converting to a strong biofilm producer after vancomycin passages, which could contribute to the decrease of their antibiotic susceptibility.

In vitro activities of daptomycin-, vancomycin-, and teicoplanin-loaded polymethylmethacrylate against methicillin-susceptible, methicillin-resistant, and vancomycin-intermediate strains of Staphylococcus aureus.

The objective of this study was to evaluate the antibacterial effects of polymethylmethacrylate (PMMA) bone cements loaded with daptomycin, vancomycin, and teicoplanin against methicillin-susceptible Staphylococcus aureus (MSSA), methicillin-resistant Staphylococcus aureus (MRSA), and vancomycin-intermediate Staphylococcus aureus (VISA) strains. Standardized cement specimens made from 40 g PMMA loaded with 1 g (low-dose), 4 g (middle-dose) or 8 g (high-dose) antibiotics were tested for elution characteristics and antibacterial activities. The patterns of release of antibiotics from the cement specimens were evaluated using in vitro broth elution assay with high-performance liquid chromatography. The activities of broth elution fluid against different Staphylococcus aureus strains (MSSA, MRSA, and VISA) were then determined. The antibacterial activities of all the tested antibiotics were maintained after being mixed with PMMA. The cements loaded with higher dosages of antibiotics showed longer elution periods. Regardless of the antibiotic loading dose, the teicoplanin-loaded cements showed better elution efficacy and provided longer inhibitory periods against MSSA, MRSA, and VISA than cements loaded with the same dose of vancomycin or daptomycin. Regarding the choice of antibiotics for cement loading in the treatment of Staphylococcus aureus infection, teicoplanin was superior in terms of antibacterial effects.

Outcome and cost analysis of primary total knee arthroplasty in end-stage renal disease patients: A nationwide population-based study.

BACKGROUND: A number of patients with end-stage renal disease (ESRD) undergo total knee arthroplasty (TKA) due to advanced knee joint osteoarthritis. There are few studies describing the incidence, morbidities, mortality rate, and cost analysis regarding ESRD patients receiving TKA. METHODS: We retrospectively retrieved patient data from National Health Insurance Research Database in Taiwan during 2005-2011, and evaluated the outcomes of TKA in patients with (ESRD group) and without ESRD (non-ESRD group). Patients' demographic data, comorbidities, mortality, and in-hospital cost were recorded. RESULTS: A total of 578 TKAs and 110,895 TKAs were identified in the ESRD and non-ESRD group, respectively. The incidence of patients receiving TKA was higher in the ESRD than in non-ESRD group by at least 2 folds. The ESRD group showed significantly more medical complications (pneumonia, peptic ulcer disease, and acute myocardial infarction) after surgery. In prosthesis-related complications, the ESRD group also had more periprosthetic joint infections, and prosthetic loosenings by one year. The one-year mortality rate was more than 6 times higher in the ESRD than in the non-ESRD group. The ESRD group had higher in-hospital medical expense than the non-ESRD group, especially when there were complications, even when the dialysis-related costs were exempted. CONCLUSION: The complication rate, mortality rate, and cost were higher in the ESRD patients receiving TKA. When considering TKA in ESRD patients, it is crucial to weigh the risks against benefits of TKA, and have a thorough discussion with the patients.