Joint prosthetic infections: a success story

Effectiveness of topical adjuvants in reducing biofilm formation on orthopedic implants: an in vitro analysis

BACKGROUND AND HYPOTHESIS

The treatment of periprosthetic joint infection is complicated by the presence of residual biofilm, which resists eradication owing to bacterial adherence to orthopedic implants. The purpose of this study was to compare Bactisure (Zimmer Biomet, Warsaw, IN, USA), povidone-iodine (Betadine), and chlorhexidine gluconate solution (Irrisept; Irrimax, Gainesville, FL, USA) in reducing biofilm formation of Staphylococcus aureus, Staphylococcus epidermidis, and Cutibacterium acnes inoculated on cobalt-chrome, titanium, and stainless steel disks, representing metals commonly used for shoulder arthroplasty. The hypothesis was that there would be no significant difference in biofilm reduction among the 3 topical adjuvants.

METHODS

Strains of S aureus (ATCC 35556), S epidermidis (ATCC 35984), and C acnes (LMG 16711) were grown on cobalt-chrome, titanium, and stainless steel disks. For each strain, the disks were divided into 4 groups: (1) control, (2) povidone-iodine (Betadine), (3) chlorhexidine gluconate (Irrisept), and (4) Bactisure. Bacteria were grown on 5% sheep blood agar plates. Biofilm eradication was quantified using adenosine triphosphate bioluminescence and compared with controls 48 and 72 hours after implementation of the topical adjuvant.

RESULTS

At 72 hours after implementation of the topical adjuvant, a statistically significant reduction in colony-forming units was observed for all topical adjuvants across all tested metals, as compared with their respective control. With respect to the topical adjuvants themselves, Bactisure more consistently demonstrated the most significant reduction in colony-forming units across all bacteria when the tested medium was adjusted for, with the exception of S aureus, which showed similar results to Betadine at 72 hours.

CONCLUSION

By use of commonly encountered topical adjuvants on S aureus-, S epidermidis-, and C acnes-inoculated disks of various implant metals, a significant reduction in biofilm production was observed. Bactisure, a recent Food and Drug Administration-approved topical adjuvant, demonstrated the overall greatest efficacy of the agents studied.

Clostridial Infection After Open Fractures of the Lower Extremity - Report of Two Cases and Discussion of Pathomechanism and Treatment

BACKGROUND

Management of post-traumatic open fractures resulting from severe injuries of the lower extremity continues to challenge orthopedic and reconstructive surgeons. Moreover, post-traumatic osteoarticular infections due to Clostridium species are rare, with few reports in the literature. We describe possible pathomechanisms and propose treatment options for cases of delayed diagnosis of osteoarticular infections with Clostridium spp.

CASE REPORTS

Two patients sustained severe osteoarticular infection due to Clostridium spp. after open epi- and metaphyseal fractures of the lower extremity. In combination with radical debridement, ankle arthrodesis and long-term antibiotic treatment, satisfactory results were achieved after a follow-up of 18 months and 24 years.

CONCLUSION

Clostridium species are difficult to identify, treatment is usually delayed and most patients have unfavourable outcomes.

Early Diagnosis of Periprosthetic Joint Infection of the Hip-Current Status, Advances, and Perspectives

Periprosthetic joint infection (PJI) has devastating consequences on joint function and the morbidity and mortality rate of patients who are victims of this serious complication. Although early diagnosis is one of the consensuses with well-established importance, routine workup is still conducted on an empirical, inconsistent, and nonobjective basis in many centers around the world. The present article seeks to contextualize the current state of knowledge about the early diagnosis of PJIs, as well as to discuss the advances and perspectives, within a scenario of its routine use by the healthcare team responsible for managing this dreaded complication.

Osteomyelitis Risk in Patients With Transfemoral Amputations Treated With Osseointegration Prostheses

BACKGROUND

Percutaneous anchoring of femoral amputation prostheses using osseointegrating titanium implants has been in use for more than 25 years. The method offers considerable advantages in daily life compared with conventional socket prostheses, however long-term success might be jeopardized by implant-associated infection, especially osteomyelitis, but the long-term risk of this complication is unknown.

QUESTIONS/PURPOSES

(1) To quantify the risk of osteomyelitis, (2) to characterize the clinical effect of osteomyelitis (including risk of implant extraction and impairments to function), and (3) to determine whether common patient factors (age, sex, body weight, diabetes, and implant component replacements) are associated with osteomyelitis in patients with transfemoral amputations treated with osseointegrated titanium implants.

METHODS

We retrospectively analyzed our first 96 patients receiving femoral implants (102 implants; mean implant time, 95 months) treated at our center between 1990 and 2010 for osteomyelitis. Six patients were lost to followup. The reason for amputation was tumor, trauma, or ischemia in 97 limbs and infection in five. All patients were referred from other orthopaedic centers owing to difficulty with use or to be fitted with socket prostheses. If found ineligible for this implant procedure no other treatment was offered at our center. Osteomyelitis was diagnosed by medical chart review of clinical signs, tissue culture results, and plain radiographic findings. Proportion of daily prosthetic use when osteomyelitis was diagnosed was semiquantitatively graded as 1 to 3. Survivorship free from implant- associated osteomyelitis and extraction attributable to osteomyelitis respectively was calculated using the Kaplan-Meier estimator. Indication for extraction was infection not responsive to conservative treatment with or without minor débridement or loosening of implant.

RESULTS

Implant-associated osteomyelitis was diagnosed in 16 patients corresponding to a 10-year cumulative risk of 20% (95% CI 0.12-0.33). Ten implants were extracted owing to osteomyelitis, with a 10-year cumulative risk of 9% (95% CI 0.04-0.20). Prosthetic use was temporarily impaired in four of the six patients with infection who did not undergo implant extraction. With the numbers available, we did not identify any association between age, BMI, or diabetes with osteomyelitis; however, this study was underpowered on this endpoint.

CONCLUSION

The increased risk of infection with time calls for numerous measures. First, patients should be made aware of the long-term risks, and the surgical team should have a heightened suspicion in patients with method-specific presentation of possible infection. Second, several research questions have been raised. Will the surgical procedure, rehabilitation, and general care standardization since the start of the program result in lower infection rates? Will improved diagnostics and early treatment resolve infection and prevent subsequent extraction? Although not supported in this study, it is important to know if most infections arise as continuous bacterial invasion from the skin and implant interface and if so, how this can be prevented?

LEVEL OF EVIDENCE

Level IV, therapeutic study.

Rivaroxaban and early periprostethic joint infection: our experience

BACKGROUND AND AIM OF THE WORK

Periprostethic joint infection (PJI) is a severe post-operative complication after Primary Total Hip Arthroplasty (THA). According to the classification of PJI early acute PJI occurs within 4 weeks from surgery. Some authors think that Rivaroxaban is a risk factor in the incidence of early acute PJI. We analyze our experience about this item.

MATERIALS AND METHODS

We analyze our experience from 1st January 2015 to 31th December 2016. We consider all consecutive hip arthroplasty implants in this period.

RESULTS

In the 205 patients analysed we not find early acute PJI in Rivaroxaban group nor in the others assuming another kind of thromboprophylaxis.

CONCLUSIONS

In our series there is no evidence of association between Rivaroxaban and early acute PJI. This is a retrospective cohort study, so we need more studies and more robust experimental designs to confirm these results.

Rivaroxaban Use for Thrombosis Prophylaxis Is Associated With Early Periprosthetic Joint Infection

BACKGROUND

Periprosthetic joint infection is a disastrous complication after total hip arthroplasty (THA) and total knee arthroplasty (TKA). The use of certain agents to prevent deep vein thrombosis after arthroplasty has been linked to an increased risk of adverse effects including wound drainage and infection. Adverse effects of one alternative, rivaroxaban, was studied in a single community hospital.

METHODS

International Classification of Diseases, Clinical Modification 9 codes were used to identify primary THAs and TKAs in an administrative database at one large-volume community hospital performed in 2012. Patients were divided into 2 groups: the study group received rivaroxaban, whereas the control group received another form of chemical thromboprophylaxis for at least 2 weeks postoperative. Demographics, risk factors, and illness severity scores were collected for each group. The primary measured outcome was the incidence of deep surgical site infection (SSI) within 30 days postoperative.

RESULTS

A total of 639 TKA or THA patients were included, with 159 patients who received rivaroxaban and 480 who received another form of chemical thromboprophylaxis. There were no significant differences between groups regarding demographics, risk factors, or illness severity scores. Incidence of early deep SSI in the rivaroxaban group was higher than in the control group (2.5% vs 0.2%; P < .015).

CONCLUSION

The use of rivaroxaban for thromboprophylaxis led to a significantly increased incidence of deep SSI in a continuous series of patients undergoing primary THA and TKA in a single institution.

Evaluation of Elution and Mechanical Properties of High-Dose Antibiotic-Loaded Bone Cement: Comparative "In Vitro" Study of the Influence of Vancomycin and Cefazolin

Use of antibiotic-loaded bone cements is one of the most effective methods for the prevention and treatment of prosthetic joint infection. However, there is still controversy about the optimal combination and doses of antibiotics that provide the maximum antimicrobial effect without compromising cement properties. In this study, vancomycin and cefazolin were added to a bone cement (Palacos R+G). Antibiotic release, fluid absorption, and mechanical properties were evaluated under physiological conditions. The results show that the type of antibiotic selected has an important impact on cement properties. In this study, groups with cefazolin showed much higher elution than those containing the same concentration of vancomycin. In contrast, groups with cefazolin showed a lower strength than vancomycin groups.

Risk stratified usage of antibiotic-loaded bone cement for primary total knee arthroplasty: short term infection outcomes with a standardized cement protocol

Efficacy of antibiotic cement (ALBC) in primary knee arthroplasty (pTKA) has been debated. The study's purpose was to examine efficacy of ALBC versus plain cement (PBC) in preventing infection in high-risk patients undergoing pTKA. 3292 consecutive pTKAs were divided into three cohorts: (1) patients receiving only PBC, (2) patients receiving only ALBC, and (3) only high-risk patients receiving ALBC. Cohorts' infections were compared. The 30-day infection rates for cohorts 1, 2, 3 were 0.29%, 0.20%, and 0.13% respectively. 6-month rates were 0.39%, 0.54% and 0.38%. 1-year rates were 0.78%, 0.61%, and 0.64%. Differences in infection rates at all time intervals were not statistically significant. The study supports that even judicious risk-stratified usage of ALBC may not confer added benefit in decreasing infection at one year.

Infection after total knee replacement: diagnosis and treatment

Infection after total knee replacement (IATJ) is a rare complication. It is associated with increased morbidity and mortality increasing the final costs. Gram positive coccus and Staphylococcus coagulase-negative and Staphylococcus aureus are the most common isolated germs (>50% of the cases). Conditions related to the patient, to the surgical procedure and even to the post op have been identified as risk factors to IATJ. Many complementary methods together with clinical symptoms are useful to a proper diagnosis. Treatment for IATJ must be individualized but generally is a combination of systemic antibiotic therapy and surgical treatment. Prosthesis exchange in one or two stages is the first choice procedure. Debridement with prosthesis retention is an option in acute cases with stable implants and antibiotic sensible germs.

Metal-on-metal joint bearings and hematopoetic malignancy

This is a review of the hip arthroplasty era. We concentrate on new metal bearings, surface replacements, and the lessons not learned, and we highlight recent reports on malignancies and joint implants. A low incidence of blood malignancies has been found in bone marrow taken at prosthetic surgery. The incidence is increased after replacement with knee implants that release very low systemic levels of metal ions. A carcinogenic effect of the high levels of metal ions released by large metal-on-metal implants cannot be excluded. Ongoing Swedish implant registry studies going back to 1975 can serve as a basis for evaluation of this risk.

Dilute betadine lavage before closure for the prevention of acute postoperative deep periprosthetic joint infection

This study evaluated the efficacy of a dilute Betadine (Purdue Pharma, Stamford, Conn) lavage in preventing early deep postoperative infection after total hip (THA) and knee (TKA) arthroplasty. A protocol of dilute Betadine lavage (0.35%) for 3 minutes was introduced to the practice of the senior author in June 2008. A total of 1862 consecutive cases (630 THA and 1232 TKA) performed before this were compared with 688 consecutive cases (274 THA and 414 TKA) after for the occurrence of periprosthetic infections within the first 90 days postoperatively. Eighteen early postoperative infections were identified before the use of dilute Betadine lavage, and 1 since (0.97% and 0.15%, respectively; P = .04). There were no significant demographic differences between the 2 groups. Betadine lavage before wound closure may be an inexpensive, effective means of reducing acute postoperative infection after total joint arthroplasty.

Surgical procedures in the treatment of 784 infected THAs reported to the Norwegian Arthroplasty Register

BACKGROUND AND PURPOSE

Controversies still exist regarding the best surgical procedure in the treatment of periprosthetic infection after total hip arthroplasty (THA). Based on data in the Norwegian Arthroplasty Register (NAR), we have compared the risk of re-revision after 4 different surgical procedures: 2-stage with exchange of the whole prosthesis, 1-stage with exchange of the whole prosthesis, major partial 1-stage with exchange of stem or cup, and minor partial 1-stage with exchange of femoral head and/or acetabular liner.

METHODS

Between 1987 and 2009, 124,759 primary THAs were reported to the NAR, of which 906 (0.7%) were revised due to infection. Included in this study were the 784 revisions that had been performed by 1 of the 4 different surgical procedures. Cox-estimated survival and relative revision risks are presented with adjustment for differences among groups regarding gender, type of fixation, type of prosthesis, and age at revision.

RESULTS

2-stage procedures were used in 283 revisions (36%), 1-stage in 192 revisions (25%), major partial in 129 revisions (17%), and minor partial in 180 revisions (23%). 2-year Kaplan-Meier survival for all revisions was 83%; it was 92% for those re-revised by 2-stage exchange procedure, 88% for those re-revised by 1-stage exchange procedure, 66% for those re-revised by major partial exchange procedure, and it was 76% for those re-revised by minor partial exchange. Compared to the 2-stage procedure and with any reason for revision as endpoint (180 re-revisions), the risk of re-revision increased 1.4 times for 1-stage (p = 0.2), 4.1 times for major partial exchange (p < 0.001), and 1.5 times for minor partial exchange (p = 0.1). With infection as the endpoint (108 re-revisions), the risk of re-revision increased 2.0 times for 1-stage exchange (p = 0.04), 6.0 times for major partial exchange (p < 0.001), and 2.3 times for minor partial exchange (p = 0.02). Similar results were found when the analyses were restricted to the period 2002-2009.

INTERPRETATION

In the Norwegian Arthroplasty Register, the survival after revision of infected primary THA with 2-stage implant exchange was slightly superior to that for 1-stage exchange of the whole prosthesis. This result is noteworthy, since 2-stage procedures are often used with the most severe infections. However, debridement with exchange of head and/or liner but with retention of the fixed implant (minor revision) meant that there was a 76% chance of not being re-revised within 2 years.

[Comparative serologic proteome analysis of Staphylococcus aureus and S. epidermidis exoproteins in prosthetic joint infections]

AIM OF THE STUDY

Staphylococci such as Staphylococcus aureus and S. epidermidis are the most frequently pathogens associated to prosthesis joint infections (PJI), counting for 75% among the isolated bacteria. In this study, we identified PJI-related antigens using two-dimensional immunoblots of S. aureus and S. epidermidis exoproteins probed with serum samples from patients with confirmed PJIs. We further analysed by ELISA tests the response of patients to the identified proteins.

PATIENTS AND METHODS

Secreted proteins from Mu50 strain (S. aureus) and RP62A strain (S. epidermidis) were separated by 2D gel electrophoresis and analyzed by western blot with serum samples from patients with confirmed S. aureus and S. epidermidis PJIs. Recombinant proteins corresponding to the identified proteins were expressed and screened with an in-house ELISA to evaluate their interest for the diagnosis of S. aureus and S. epidermidis PJIs.

RESULTS

Fifty-two antigenic exoproteins were identified: 42 belonging to Mu50 strain, and 10 to RP62A strain. Twenty-two proteins were identified as S. aureus specific. Among these proteins, five were most frequently recognized by patients with S. aureus PJI.

CONCLUSION

Our results showed that few exoproteins were antigenic by RP62A strain compared to Mu50 strain. We identified five antigenic and S. aureus specific proteins, which may contribute to diagnosis, prevention and treatment of these infections.

One-day antibiotic infusion for the prevention of postoperative infection following arthroplasty: a case control study

Intravenous antibiotics effectively reduce the prevalence of postoperative infection. However, Japanese orthopaedic surgeons have no consensus with regard to the optimal duration of prophylaxis. The aim of this study is to compare the outcome of one-day intravenous antibiotic administration with that of long-term intravenous antibiotic administration. Patients who underwent total hip or knee arthroplasty were divided into 2 groups to receive one of 2 prophylactic protocols retrospectively. Group A (223 patients) received intravenous antibiotics twice only on the day of surgery, whereas Group B (104 patients) received intravenous antibiotics for at least 3 days after surgery. We analyzed the wound infection rate and monitored liver and renal functions. None of these patients had a postoperative infection. No liver dysfunction and renal dysfunction were observed. One-day antibiotic infusion was as effective as long-term antibiotics in preventing infection after arthroplasty and achieved greater cost effectiveness.

Incidence of prosthetic joint infections after primary knee arthroplasty

We report the 1-year incidence of postoperative infections in an unselected series of 2647 consecutive primary knee arthroplasties (3137 knees) performed in a modern specialized hospital dedicated solely to joint arthroplasty surgery in 2002 to 2006. The rates of superficial and prosthetic joint infections were 2.9% and 0.80%, respectively. Prospective surveillance by hospital infection register failed to detect 6 of the 24 prosthetic joint infections. Increased rate of prosthetic joint infections was associated with complex surgery and with several patient-related factors, for example, comorbidity, obesity, and poor preoperative clinical state. The rate of prosthetic joint infections in contemporary knee arthroplasty is low and mainly related to patient-related factors, of which patient comorbidity has the most profound effect on the infection rate.

Inadequate timing of prophylactic antibiotics in orthopedic surgery. We can do better

BACKGROUND AND PURPOSE

There are rising concerns about the frequency of infection after arthroplasty surgery. Prophylactic antibiotics are an important part of the preventive measures. As their effect is related to the timing of administration, it is important to follow how the routines with preoperative prophylactic antibiotics are working.

METHODS

In 114 consecutive cases treated at our own university clinic in Lund during 2008, the time of administration of preoperative prophylactic antibiotic in relation to the start of surgery was recorded from a computerized operation report. In 291 other cases of primary total knee arthroplasty (TKA), randomly selected from the Swedish Knee Arthroplasty Register (SKAR), the type and dose of prophylactic antibiotic as well as the time of administration in relation to the inflation of a tourniquet and to the start of surgery was recorded from anesthetic records.

RESULTS

45% (95% CI: 36-54) of the patients operated in Lund and 57% (CI: 50-64) of the TKAs randomly selected from the SKAR received the preoperative antibiotic 15-45 min before the start of surgery. 53% (CI: 46-61) received antibiotics 15-45 min before inflation of a tourniquet.

INTERPRETATION

The inadequate timing of prophylactic antibiotics indicates that the standards of strict antiseptic and aseptic routines in arthroplasty surgery are falling. The use of a simple checklist to ensure the surgical safety may be one way of reducing infections in arthroplasty surgery.

Cost-effectiveness of antibiotic-impregnated bone cement used in primary total hip arthroplasty

BACKGROUND

Antibiotic-impregnated bone cement is infrequently used in the United States for primary total hip arthroplasty because of concerns about cost, performance, and the possible development of antibiotic resistance and because it has been approved only for use in revision arthroplasty after infection. The purpose of this study was to model the use of antibiotic-impregnated bone cement in primary total hip arthroplasty for the treatment of osteoarthritis to determine whether use of the cement is cost-effective when compared with the use of cement without antibiotics.

METHODS

To evaluate the cost-effectiveness of each strategy, we used a Markov decision model to tabulate costs and quality-adjusted life years (QALYs) accumulated by each patient. Rates of revision due to infection and aseptic loosening were estimated from data in the Norwegian Arthroplasty Register and were used to determine the probability of undergoing a revision arthroplasty because of either infection or aseptic loosening. The primary outcome measure was either all revisions or revision due to infection. Perioperative mortality rates, utilities, and disutilities were estimated from data in the arthroplasty literature. Costs for primary arthroplasty were estimated from data on in-hospital resource use in the literature. The additional cost of using antibiotic-impregnated bone cement ($600) was then added to the average cost of the initial procedure ($21,654).

RESULTS

When all revisions were considered to be the primary outcome measure, the use of antibiotic-impregnated bone cement was found to result in a decrease in overall cost of $200 per patient. When revision due to infection was considered to be the primary outcome measure, the use of the cement was found to have an incremental cost-effectiveness ratio of $37,355 per QALY compared with cement without antibiotics; this cost-effectiveness compares favorably with that of accepted medical procedures. When only revision due to infection was considered, it was found that the additional cost of the antibiotic-impregnated bone cement would need to exceed $650 or the average patient age would need to be greater than seventy-one years before its cost would exceed $50,000 per QALY gained.

CONCLUSIONS

When revision due to either infection or aseptic loosening is considered to be the primary outcome, the use of antibiotic-impregnated bone cement results in an overall cost decrease. When only revision due to infection is considered, the model is strongly influenced by the cost of the cement and the average age of the patients. With few patients less than seventy years of age undergoing total hip arthroplasty with cement in the United States, the use of antibiotic-impregnated bone cement in primary total hip arthroplasty may be of limited value unless its cost is substantially reduced.

Potential for infection in orthopaedic practice due to individually packaged screws

The use of implants is widespread in orthopaedic practice. In recent times screws and plates have increasingly been supplied individually pre-packaged. We hypothesised that there is a potential for an increased risk of infection associated with the practice of using individually packaged screws. In this study an attempt was made to recreate as closely as possible the standard practice of opening screw packets in the operating theatre. The exterior of 50 screw packets was cultured. The outer screw packets were then opened over a draped instrument table above a petri dish. As a control, petri dishes were left open to the air in the same theatre environment. The packet exteriors grew cultures of organisms in 24/50 cases. The act of opening the packets yielded a growth in 7/50 cases. There was no growth on the control petri dishes. The significance of the result and potential solutions are discussed.

Novel model for studying hematogenous infection in an experimental setting of implant-related infection by a community-acquired methicillin-resistant S. aureus strain

The aim of this study is to establish a new experimental model of hematogenous implant-related infection (IRI) by a community-acquired methicillin-resistant S. aureus (CA-MRSA) strain. Cylindrical porous tantalum intramedullary implants were inserted in the proximal right tibia of 30 male white rabbits after administration of antibiotic prophylaxis. Four weeks later and without antibiotic prophylaxis, 20 animals received 1 ml of inoculum of two different concentrations (study groups A and B) of CA-MRSA strain through an ipsilatelar femoral artery catheter. The remaining 10 received normal saline instead (control group C). Surviving animals were sacrificed 4 weeks later. Sterile bone, bone marrow biopsies, and implants were harvested for culture and histological evaluation. Ten animals receiving 5 x 10(8)cfu/ml (group A) died within 48-72 h due to septic shock. Blood cultures were positive; histology demonstrated acute infection. Ten animals received bacterial load of 3 x 10(8)cfu/ml (group B) and all survived; two had negative Gram-stain and cultures but PCR and RT-PCR results demonstrated the viability of the microorganisms, while periprosthetic osteolysis and histological evaluation indicated subacute osteomyelitis; eight animals established periprosthetic infection, osteomyelitis, and septic arthritis documented by positive Gram-stain, cultures, subperiosteal reaction, and chronic infection on histology. Control group specimens demonstrated no signs of infection. Histopathological semiquantitative scoring was used to compare the three groups. Comparison of groups A and B with control group and between group A and B showed statistically significant difference (p < 0.05) in all parameters except for periosteal reaction between groups B and C (p = 0.354). This novel, reproducible experimental model will facilitate the study of hematogenous CA-MRSA IRIs.

Elution characteristics and mechanical properties of calcium sulfate-loaded bone cement containing teicoplanin

BACKGROUND

Acrylic bone cement is the most widely used drug delivery system clinically. It has already been shown that antibiotic release is significantly increased when calcium sulfate-loaded acrylic bone cement is used. However, there is no information yet about the mechanical responses of these composite materials. Thus, the purpose of this study was to investigate the effect of calcium sulfate on the elution characteristics and mechanical behavior of teicoplanin-loaded acrylic bone cement.

METHODS

Four groups of acrylic bone cements (GI, GII, GIII, GIV) were prepared using the same liquid/powder ratios. After mixing, the bone cement and additive mixtures were packed into different-type molds to prepare the specimens for the elution and mechanical tests. All of the specimens were tested for two conditions (dry and human plasma solution). The mechanical tests included the setting time (hardness) and tensile, bending, and compression strengths. The fracture surfaces of the failed samples were also examined by scanning electron microscopy.

RESULTS

Teicoplanin release in the calcium sulfate powder added groups (GIII and GIV) was higher than that of GII. When the calcium sulfate and teicoplanin were added on acrylic bone cement, the compressive, bending and tensile strength, hardness values, and elastic modulus decreased. Also, further reductions were evident in human plasma solution.

CONCLUSIONS

Although mechanical properties of tested specimens decreased, all of the results obtained were higher than those required by the American Society for Testing and Materials Standards, but further investigations are necessary before making definitive statements for clinical applications.

Antibiotic-loaded bone cement for infection prophylaxis in total joint replacement

Use of antibiotic-loaded bone cement for prophylaxis against infection is not indicated for patients not at high risk for infection who are undergoing routine primary or revision joint replacement with cement. The mechanical and elution properties of commercially available premixed antibiotic-loaded bone-cement products are superior to those of hand-mixed preparations. Use of commercially available antibiotic-loaded bone-cement products has been cleared by the United States Food and Drug Administration only for use in the second stage of a two-stage total joint revision following removal of the original prosthesis and elimination of active periprosthetic infection. Use of antibiotic-loaded bone cement for prophylaxis against infection in the second stage of a two-stage total joint revision involves low doses of antibiotics. Active infection cannot be treated with commercially available antibiotic-loaded bone cement as such treatment requires higher doses of antibiotics.

[Early results of one-stage septic revision arthroplasties with antibiotic-laden cement. A clinical and statistical analysis]

BACKGROUND

Periprosthetic infections will generally require revision arthroplasty. The one-stage revision arthroplasty with antibiotic-laden cement is hence an attractive therapeutic option, since it only requires one operation, has a low morbidity and, if successful, is cost-efficient.

MATERIALS AND METHODS

We performed one-stage revision arthroplasties. The exchanged prostheses were fixed with antibiotic-laden cement after biotic resistance was determined. All patients were treated with postoperative systemic antibiotics.

RESULTS

After a mean postoperative examination period of 18.4 months, we confirmed eradication of infection in 14 of 15 knee joints and in 15 of 16 hip joints. The mean duration of hospital stay was 23 days. Patients' satisfaction was high (93.55%) and the clinical results were satisfactory.

CONCLUSION

Our analysis shows that our low early reinfection rate (6.45%) is within statistical expectation. Furthermore, we have showed that there is evidence to suggest that the rate of successful outcomes in one-stage revision arthroplasties, at least at the hip, is not different from the rate of two-stage revision arthroplasties and that the difference may be interpreted as stochastic deviation (p=0.264494). According to existing studies, an analogy to knee arthroplasties can be assumed. We demonstrated that one-stage revision is an adequate therapeutic option if patients are carefully selected and under the supervision of an experienced surgeon.

Reduction of orthopaedic wound infections in 21 hospitals

INTRODUCTION

The German national nosocomial infections surveillance system (KISS) has been collecting surveillance data from hip and knee prosthesis operations since 1997. The purpose of this article is to investigate whether surveillance and feedback of surgical site infection (SSI) information to the physicians and nurses of participating hospitals lead to reduced SSI rates or not.

MATERIALS AND METHODS

Only information from hospitals previously participating for at least 3 years was used for the analysis. Monthly SSI rates were pooled over the 36-month period, beginning in each clinic's case with its first month of participation, the rates then being compared for 12-month periods. Relative risks were calculated for comparison of the SSI rates in the first and third years of participation. A multiple logistic regression analysis with stepwise variable selection was performed to identify significant risk factors, including the year of surveillance after starting surveillance activities.

RESULTS

The overall SSI rates were 1.4% for hip prosthesis and 1.0% for knee prosthesis. Fourteen clinics participated in KISS for at least 3 years continuously with HIP prostheses and 21 with knee prostheses. It was possible to include a total of 15,457 hip and 9,011 knee procedures for this analysis. A comparison of data from the first and the third years show a significant SSI reduction with hip procedures, with a relative risk of 0.54 (CI95 0.38-0.77), and a trend towards reduced SSI rates for knee procedures. The multiple logistic regression analysis confirmed that the SSI rate for hip prosthesis was significantly lower in the third year than in the first year of surveillance (OR = 0.57; CI95 0.42-0.78), though for knee prosthesis the level of significance was not achieved.

CONCLUSION

A reduction of SSIs following hip and knee prosthesis operations through the introduction of ongoing surveillance and the possibility of using benchmark data for comparison does seem to be possible in many institutions.

Bacterial contaminants and antibiotic prophylaxis in total hip arthroplasty

We have investigated the contaminating bacteria in primary hip arthroplasty and their sensitivity to the prophylactic antibiotics currently in use. Impressions (627) of the gloved hands of the surgical team in 50 total hip arthroplasties were obtained on blood agar. The gloves were changed after draping, at intervals of 20 minutes thereafter, and before using cement. Changes were also undertaken whenever a visible puncture was detected. The culture plates were incubated at 37°C for 48 hours. Isolates were identified and tested for sensitivity to flucloxacillin, which is a recognised indicator of sensitivity to cefuroxime. They were also tested against other agents depending upon their appearance on Gram staining.

We found contamination in 57 (9%) impressions and 106 bacterial isolates. Coagulase-negative staphylococci were seen most frequently (68.9%), but we also isolated Micrococcus (12.3%), diphtheroids (9.4%), Staphylococcus aureus (6.6%) and Escherichia coli (0.9%). Of the coagulase-negative staphylococci, only 52.1% were sensitive to flucloxacillin and therefore to cefuroxime. We believe that it is now appropriate to review the relevance of prophylaxis with cefuroxime and to consider the use of other agents.

Influence of the method of blending an antibiotic powder with an acrylic bone cement powder on physical, mechanical, and thermal properties of the cured cement

Two variants of antibiotic powder-loaded acrylic bone cements (APLBCs) are widely used in primary total joint replacements. In the United States, the antibiotic is manually blended with the powder of the cement at the start of the procedure, while, in Europe, pre-packaged commercially-available APLBCs (in which the blending is carried out using an industrial mixer) are used. Our objective was to investigate the influence of the method of blending gentamicin sulphate with the powder of the Cemex XL formulation on a wide collection of properties of the cured cement. The blending methods used were manual mixing (the MANUAL Set), use of a small-scale, easy-to-use, commercially-available mechanical powder mixer, OmoMix 1 (the MECHANICAL Set), and use of a large-scale industrial mixer (Cemex Genta) [the INDUSTRIAL Set]. In the MECHANICAL and MANUAL Sets, the blending time was 3 min. In preparing the test specimens for each set, the blended powder used contained 4.22 wt% of the gentamicin powder. The properties determined were the strength, modulus, and work-to-fracture (all obtained under four-point bending), plane-strain fracture toughness, Weibull mean fatigue life (fatigue conditions: +/-15 MPa; 2 Hz), activation energy and frequency factor for the cement polymerization process (both determined using differential scanning calorimetry, at heating rates of 5, 10, 15, and 20 Kmin(-1)), the diffusion coefficient for the absorption of phosphate buffered saline, PBS, at 37 degrees C, and the rate of elution of the gentamicin into PBS, at 37 degrees C (E). Also determined were the particle size, particle size distribution, and morphology of the blended powders and of the gentamicin. For each of the cured cement properties (except for E), there is no statistically significant difference between the means for the 3 cements, a finding that parallels the observation that there are no significant differences in either the mean particle size or the morphology of the blended cement powders. Notwithstanding these results, it is suggested that when the powder mixture is blended in the operating room, using the OmoMix 1 is more likely to produce a more consistent and reproducible mixture than when manual mixing is used.

Acrylic bone cements: clinical developments and current status: Scandinavia

This article focuses on bone cement, the cementing technique used, and their influence on aseptic loosening and infection of acrylic and joint implants--Scandinavian view.

Infections Associated with Prosthetic Knee and Prosthetic Hip

Arthroplasty of the knee and hip is a common procedure. There is a risk of infection with primary arthroplasty, with an incidence of 1% to 2%. Significant cost and morbidity are associated with infection of the prosthetic joint. Most infections (60% to 70%) are caused by staphylococci, but approximately 10% are caused by streptococci and/or enterococci, whereas the remainder are caused by gram-negative enteric aerobes or anaerobic flora. Surgical revision is often required for cure because the biofilm that adheres to the infected prosthesis precludes antibiotic therapy from being effective. Biofilm formation occurs consistently as a consequence of host protein deposition on the prostheses, which serve as ligands for bacterial receptors. Once established, biofilm infections require removal of the prosthesis in order to effect a cure. Clinical and radiologic features are not specific for the diagnosis. Culture is specific but not sensitive enough to establish a pathogen in all cases. Surgical approaches are varied and range from debridement with retention of the prostheses to amputation of the limb. The most favored approach is the two-stage delayed reimplantation, in which patients receive specific antibiotic therapy for 6 weeks or more. Several additional antibiotics other than vancomycin are available for methicillin-resistant staphylococcal infection, but these are still unproven in the treatment of osteomyelitis or prosthetic joint infection.

Backgrounds of antibiotic-loaded bone cement and prosthesis-related infection

Antibiotic-loaded bone cement has been in use for over 30 years for the fixation of total joint arthroplasties, although its mechanism of action is still poorly understood. This review presents the backgrounds of bone cements, prosthesis-related infection and antibiotic-loaded bone cements. It is shown that antibiotic-loaded bone cement has a significant effect on bacteria, particularly in animal and clinical studies. However, recently, antimicrobial resistance among bacteria has been ascribed to the antibiotic-loaded bone cement. The unresolved issues both regarding the action of antibiotic-loaded bone cement and the nature of the antimicrobial resistance necessitate further research into the interaction of antibiotic-loaded bone cement and bacteria.

Antibiotic prophylaxis in total hip arthroplasty: effects of antibiotic prophylaxis systemically and in bone cement on the revision rate of 22,170 primary hip replacements followed 0-14 years in the Norwegian Arthroplasty Register

We studied the effects of antibiotic prophylaxis, systemically and in bone cement, on the revision rate of cemented total hip arthroplasties (THAs) in data from the Norwegian Arthroplasty Register during the period 1987-2001. To have comparable groups, only THAs performed because of primary osteoarthritis, using cemented implants with documented good results, and high-viscosity cement were included. If systemic antibiotic prophylaxis had been given, only operations with cephalosporin or penicillin were selected. Cox-estimated survival relative revision risks (RR) are presented with adjustment for differences among groups in gender, age, cement brand, type of systemic antibiotic prophylaxis, type of prosthesis, type of operating room, and duration of the operation. Of 22,170 THAs studied, 696 THAs (3.1%) were revised, 440 (2.0%) for aseptic loosening and 102 (0.5%) for deep infection. We found the lowest risk of revision when the antibiotic prophylaxis was given both systemically and in the cement (15,676 THAs). Compared to this combined regime, patients who received antibiotic prophylaxis only systemically (5,960 THAs) had a 1.4 times higher revision rate with all reasons for revision as endpoint (p = 0.001), 1.3 times higher with aseptic loosening (p = 0.02) and 1.8 times higher with infection as the endpoint (p = 0.01). With the combined antibiotic regime, the results were better if antibiotics were given 4 times on the day of surgery (2,194 THAs), as compared to once (1,424 THAs) (p < 0.001), twice (2,680 THAs) (p < 0.001), or 3 times (5,522 THAs) (p = 0.02). Those who received systemic prophylaxis a single day 1, 2 or 3 times, as compared to 4 times, had a revision rate 1.8-3.5 times higher with all reasons for revision as endpoint, 1.5-3.1 times higher with aseptic loosening, and 2.7-6.8 times higher with infection. When we compared systemic prophylaxis 4 times in 1 day, no further improvement resulted in those given systemic prophylaxis for 2 days (1,928 THAs) or 3 days (717 THAs). In a subset of data including only the Charnley prosthesis, we obtained similar results. This observational study shows that the best results were recorded when antibiotic prophylaxis was given both systemically and in the bone cement, and if the systemic antibiotic was given 4 times on the day of surgery.

Prosthetic joint infections: bane of orthopedists, challenge for infectious disease specialists

Prosthetic joint infections (PJIs) occur in approximately 1.5%-2.5% of all primary hip or knee arthroplasties. The mortality rate attributed to PJIs may be as high as 2.5%. Substantial morbidity is associated with a loss of mobility, although this is temporary. The costs associated with a single episode of PJI are approximately $50,000 per episode, exclusive of lost wages. Risk factors that increase the occurrence of PJI include revision arthroplasty, time in the operating room, postoperative surgical site infection, and malignancy. Pain is the most consistent symptom. Staphylococcus species are the most common organisms isolated from PJI sites. Two-stage revision is superior to single-stage revision or to debridement with prosthesis retention. Long-term antibiotic suppression and/or arthrodesis are useful for patients too frail to undergo extensive surgery. Using an optimal approach, recurrent infection occurs in <10% of previously infected joints.

Human factors and infection in THA

Joint prosthetic infection is a very hot issue, frequently discussed in our meetings and journals. According to Lars Lidgren (6) it is "a success story", but probably not from all points of view.