Akos Zahar

How Reliable Is the Alpha-defensin Immunoassay Test for Diagnosing Periprosthetic Joint Infection? A Prospective Study

BackgroundA key issue in the treatment of periprosthetic joint infection (PJI) is the correct diagnosis. The main problem is lack of diagnostic tools able to diagnose a PJI with high accuracy. Alpha-defensin has been proposed as a possible solution, but in the current literature, there is a lack of independent validation.Questions/purposesWe performed a prospective study to determine (1) what is the sensitivity, specificity, and positive and the negative predictive values of the alpha-defensin immunoassay test in diagnosing PJI; and (2) which clinical features may be responsible for false-positive and false-negative results?MethodsPreoperative aspiration was performed in all patients presenting with a painful hip/knee arthroplasty, including both primary and revision implants. Metallosis, other inflammatory comorbidities, and previous/concomitant antibiotic therapy were not considered as exclusion criteria. An inadequate amount of synovial fluid for culture was an exclusion criterion. A total of 156 patients (65 knees, 91 hips) were included in this prospective study. At the time of revision, synovial fluid samples were taken to perform the alpha-defensin assay. During surgical débridement of tissue, samples for cultures and histologic evaluation were taken, and samples were cultured until positive or until negative at 14 days. A diagnosis of PJI was confirmed in 29 patients according to the International Consensus Group on PJI.ResultsThe sensitivity of the alpha-defensin immunoassay was 97% (95% confidence interval [CI], 92%–99%), the specificity was 97% (95% CI, 92%–99%), the positive predictive value was 88% (95% CI, 81%–92%), and the negative predictive value was 99% (95% CI, 96%–99%). Among four false-positive patients, two had metallosis and one had polyethylene wear. The false-negative case presented with a draining sinus, and intraoperative cultures were also negative.ConclusionsAlpha-defensin assay appears to be a reliable test, but followup evaluation is needed to estimate longer term performance of the test. The authors believe that alpha-defensin has demonstrated itself to be sufficiently robust that PJI diagnostic criteria now should include this test. Future studies are needed to compare the differences among the diagnostic capability of the available tests, in particular when metallosis is present, because metallosis may predispose the test to a false-positive result.Level of EvidenceLevel I, diagnostic study.

Can Good Infection Control Be Obtained in One-stage Exchange of the Infected TKA to a Rotating Hinge Design? 10-year Results

BackgroundProsthetic joint infection (PJI) occurs in 1% to 2% of total knee arthroplasties (TKAs). Although two-stage exchange is the preferred management method of patients with chronic PJI in TKA in North America, one-stage exchange is an alternative treatment method, but long-term studies of this approach have not been conducted.Questions/purposesWe reviewed our minimum 9-year results of 70 patients who underwent one-stage exchange arthroplasty with a rotating hinge design to determine: (1) What was the proportion of patients free of infection? (2) What was the patient rate of survival free of any reoperation? (3) What were the clinical outcomes as measured by Hospital for Special Surgery scores? (4) What proportion of patients developed radiographic evidence of loosening?MethodsAll one-stage revision TKAs for infection between January 1 and December 31, 2002, with a minimum 9-year followup (mean, 10 years; range, 9–11 years), in which patients had been seen within the last 1 year, were included in this retrospective review. During that period, 11 patients with infected TKAs were treated with other approaches (including two-stage approaches in eight); the general indication for one-stage revision was the diagnosis of PJI with a known causative organism. Exclusion criteria were culture-negative preoperative aspiration, known allergy to local antibiotics or bone cement, or cases in which radical débridement was impossible as a result of the involvement of important anatomical structures. Eighty-one patients with PJI were seen during this period; 70 underwent one-stage exchange using our strict protocol and were reimplanted with a rotating hinge TKA. Eleven patients (15.7%) were lost to followup. Hospital for Special Surgery scores were recorded and all radiographs were evaluated for prosthetic loosening. Failure was defined as revision surgery for infection or any other cause.ResultsOur 10-year infection-free survival was 93% (mean, 4.1; 95% confidence interval [CI], 89%–96%; p < 0.007); and the patient 10-year survival rate free of revision for other causes was 91% (mean, 5.2; 95% CI, 86%–95%; p < 0.002). Mean Hospital for Special Surgery knee score at last followup was 69.6 (± 22.5 SD; range, 22–100) and the mean improvement in Hospital for Special Surgery knee score from preoperative to most recent followup was 35 (± 24.2 SD; range, 13–99). Evidence of radiographic loosening was seen in 11 patients at last followup, whereby in six patients, there was need for revision surgery.ConclusionsOur study results showed an overall infection control rate of 93% and good clinical results using our one-stage approach, which combines aggressive débridement of the collateral ligaments and posterior capsule with a rotating hinge implant. These results are comparable with two-stage techniques at a followup of 10 years; further research into one-stage exchange techniques for PJI in TKA appears warranted.Level of EvidenceLevel IV, therapeutic study.

One-Stage Revision for Infected Total Hip Arthroplasty

Prosthetic joint infection (PJI) is a challenging complication following total hip arthroplasty (THA). Two-stage exchange arthroplasty is preferred for treating chronic PJI of THA, although specialized centers have reported comparable outcomes with protocol-based, 1-stage exchange arthroplasty. A main requirement is presurgical determination of the infecting organisms sensitivity. The therapeutic goal is control of the infection and maintenance of joint function. It offers advantages, including a single operative procedure, fewer antibiotics, and reduced hospitalization time and relative overall costs.

Management of Fungal or Atypical Periprosthetic Joint Infections

ConsensusA fungal or atypical PJI is an infection of a jointarthroplasty caused by fungi or atypical bacteria.Delegate VoteAgree: 89%, Disagree: 7%, Abstain: 4% (Strong Con-sensus)JustificationGenerally a fungal or atypical PJI is believed to existwhen fungal organisms or atypical bacteria are isolat-ed from the joint fluid or intraoperative tissue samplesand these organisms are believed to be the dominantinfecting agents in the prosthetic joint.Fungi may be moulds/molds, yeasts, or dimorphicfungi. Moulds are fungi that grow in the form ofmulticellular filaments called hyphae. The vast majori-ty were Candida infections (which represent morethan 80% of PJIs). In contrast, fungi that can adopt asingle celled growth habit are called yeasts. Dimorphicfungi can exist as mold forms or as yeast. Atypicalbacteria are bacteria that have deviations of one ormore of the following characteristics of a typicalbacterium: cell wall (containing peptidoglycan), cellmembrane, no nuclear membrane, reproduction by cellfission, and susceptibility to antibiotics but not toantifungal agents.

Intrapelvic Dislocation of a Femoral Trial Head During Primary Total Hip Arthroplasty Requiring Laparotomy for Retrieval

Background and Purpose: Total hip arthroplasty (THA) is a safe and reliable surgical procedure. However, THA also has intra- and postoperative complications. A dreaded and frustrating intraoperative complication during total hip arthroplasty is dislocation of the femoral trial head from the neck into the pelvis. Methods: Here, we report on the case of a 71-year old female patient with osteoarthritis of the left hip. Total hip arthroplasty was performed in a lateral position through a standard posterior approach. During intraoperative trial reduction, the femoral trial head dissociated from the taper and dislocated into the psoas compartment. Several unsuccessful attempts, including an additional ventral approach, were made to immediately retrieve the femoral trial head. Results and interpretation: Postoperative a Computerized Tomography (CT) was performed to locate the trial head, a secondary explorative laparotomy was undertaken to retrieve it. The retrieval of the femoral trial head should be performed in a planned second surgical procedure to avoid possible complications during the manipulation necessary for retrieval.

One-stage exchange for prosthetic joint infection of the hip.

Exchange arthroplasty remains the gold standard of treatment of established prosthetic joint infection. This can be achieved using a one or two stage approach. The ENDO-Klinik, in Hamburg, has pioneered the one-stage technique since 1970 utilising antibiotic loaded acrylic cement (ALAC). This editorial discusses the relevant literature and describes the indications and surgical technique employed by the ENDO-Klinik Hamburg.

In vitro efficiency of vancomycin containing experimental drug delivery systems.

Biofilm-forming Staphylococcus epidermidis strains are common cause of the periprosthetic infection. The treatment of the periprosthetic infection is very problematic, so the prevention of these infections by an antibiotic containing prothesis could be an option for prevention.The purpose of the present study was to examine the in vitro effects of drug delivery systems (DDSs), namely Wax 1 and Wax 2 with different vancomycin content: 0.5, 1, 2 and 4 mg. In order to control the antibacterial activity of DDSs killing curve study was performed and in order to determine the antibiotic release and the antibiotic peak concentration from the DDSs biological assay was carried out.The time kill curve studies showed, that both DDSs with all vancomycin concentration decreased significantly the bacterial counts, however, Wax 2 with 4 mg vancomycin significantly decreased the bacterial count than all the other groups.The vancomycin release was the best with the highest peak concentration from DDSs with 4 mg vancomycin contain; it was significantly better than in the other groups, however, no significant difference was observed between Wax 1 and Wax 2 in this respect.These findings suggest that Wax 2 with 4 mg vancomycin content could be a potential agent for clinical use.

High bacterial contamination rate of electrocautery tips during total hip and knee arthroplasty

PurposeThe aim of the study was to quantify the bacterial contamination rate of electrocautery tips during primary total joint replacement (TJR), as well as during aseptic and septic revision TJR.MethodsA total of 150 electrocautery tips were collected between April and July 2017. TJR surgeries were divided into three groups: (1) primary, (2) aseptic and (3) septic revisions. In each group, a total of 50 electrocautery tips were collected. A monopolar electrocautery with a reusable stainless-steel blade tip was used in all cases. The rate of bacterial contamination was determined for all groups. Correlation of exposure time and type of surgery was analyzed.ResultsThe overall bacterial contamination rate was 14.7% (95% CI 9.4 to 21.4%). The highest contamination rate occurred in the septic revision group (30.0%; 95% CI 17.9 to 44.6%), followed by the primary cases group (10.0%; 95% CI 3.3 to 21.8%) and the aseptic revision group (4.0%; 95% CI 0.5 to 13.7%). Exposure time did not affect the bacterial contamination rate. In 12 out of 15 (80%) contaminations identified in the septic group, we found the same causative microorganism of the prosthetic joint infection on the electrocautery tip.ConclusionsThe bacterial contamination of the electrocautery tips is relatively high, especially during septic hip revision arthroplasty. Electrocautery tips should be changed after debridement of infected tissue.

One-stage Exchange Arthroplasty for Periprosthetic Hip and Knee Joint Infections

Background: Periprosthetic joint infection (PJI) is a devastating complication of joint replacement surgery. In an aging population of the developed world, the increasing numbers of hip and knee replacements will inevitably lead to increasing incidence of PJI, carrying with (it) significant patient morbidity and cost to the health care system. Two-stage exchange arthroplasty is currently the gold standard but it is associated with multiple operations, prolonged hospitalization and impaired functionality. One-stage exchange arthroplasty is similar to the two-stage procedure but the interval between removal of the prosthesis and reimplantation of a new one is only a few minutes. It has the theoretical benefits of a single anesthetic, shorter hospitalization, less cost and improved function. Methods: We reviewed the current literature regarding the outcomes of one-stage exchange arthroplasties focusing on re-infection rates and functional outcomes. Results: Current themes around the one-stage exchange procedure include the indications for the procedure, definition of re-infection, surgical techniques used to provide fixation and differences in approach for hip and knee replacements. Conclusion: The current literature on one-stage exchange procedure is promising, with comparable results to two-stage revisions for hips and knees in selected patients. However, there is a great need for a large multi-centred randomized control trial, focusing on re-infection rates and functional scores postoperatively, to provide concrete guidelines in managing this complex condition.

Conversion arthroplasty of the hip: Mid-term results are good

The historical mid-term results of conversion total hip arthroplasty (THA) are acceptable; however, the complication rates are high. In total, 39 patients (45 hips) from 2 institutions underwent conversion THA from 1993-2006 and were retrospectively evaluated. The mean age was 48.3 years, the mean follow-up time was 8.7 years, and the mean duration arthrodesis prior to conversion THA was 18.2 years. The outcomes included operative time, blood loss, leg-length discrepancy (LLD), thigh circumference, Harris Hip Score (HHS), complications, and radiographic evaluation. A total of 34 THAs were cemented, and 11 were uncemented. The mean operative time was 102 minutes, and the mean blood loss was 1019 ml. The mean HHS improved from 32.4 to 82.5 (p<0.01). The mean LLD decreased from 4.2 to 1.1 cm, while the thigh circumference increased by a mean of 1.6 cm. Complications included: a positive Trendelenburg gait (6), early haematoma that required surgical evacuation (5), dislocation (2), deep infection (1), and early aseptic loosening of the components (2). In conclusion, the functional results of the conversion THA using predominantly cemented components are good at mid-term follow-up; although the complication rates remain higher than a standard primary THA, aseptic loosening rates of the cemented components is low at mid-term follow-up.