Failure of a two-stage exchange arthroplasty for management of periprosthetic joint infection (PJI) poses a major clinical challenge. There is a paucity of information regarding the outcome of further surgical intervention in these patients. Thus, we aim to report the clinical outcomes of subsequent surgical intervention following a failed prior two-stage exchange. Our institutional database was used to identify 60 patients (42 knees and 18 hips) with a failed prior two-stage exchange from infection, who underwent further surgical intervention between 1998 and 2012 and had a minimum of two years follow-up. A retrospective review was performed to extract relevant clinical information, such as mortality, microbiology, and subsequent surgeries. Musculoskeletal Infection Society criteria were used to define PJI, and treatment success was defined using the Delphi criteria as previously reported. Irrigation and debridement (I&D) was performed after a failed two-stage exchange in 61.7% (37/60) patients. The failure rate of I&D in this cohort was 51.3% (19/37). Two patients underwent amputation after I&D due to uncontrolled infection. A total of 40 patients underwent an intended a second two-stage exchange. Reimplantation occurred in only 65% of cases (26/40), and infection was controlled in 61.6% (16/26) of patients. An interim spacer exchange was required in 15% (6/40) of the cases. Of the 14 cases that did not undergo a second stage reimplantation, 5 required amputation, 6 had retained spacers, 1 underwent arthrodesis, and 2 patients died. Further surgical intervention after a failed prior two-stage exchange has poor outcomes. I&D has a high failure rate and many of the patients who are deemed candidates for a second two-stage exchange either do not undergo reimplantation for various reasons or fail after reimplantation. The management of PJI clearly remains imperfect, and there is a dire need for further innovations that may improve the care of these PJI patients.
Periprosthetic joint infection (PJI) is one of
the most feared and challenging complications following total knee arthroplasty.
We provide a detailed description of our current understanding regarding
the management of PJI of the knee, including diagnostic aids,
pre-operative planning, surgical treatment, and outcome. Cite this article:
Periprosthetic joint infection (PJI) is one the most devastating complications of joint arthroplasty. Although PJI is an infrequent complication (the reported incidence is 1%-2% in the United States), it is the most common indication for revision total knee arthroplasty in the Medicare population and the third most frequent indication for revision total hip arthroplasty. Moreover, the prevalence of PJI appears to be on the rise, with a projected number exceeding 60,000 to 70,000 cases in the United States by 2023. It is estimated that more than 25% of revision procedures annually are attributed to PJI and this number is expected to increase in the upcoming years. The increase in the prevalence of obesity, diabetes, and other comorbidities among the patient population and the emergence of resistant infecting organisms are some of the reasons for the expected rise in the number of infections that medical community will witness. The challenges that PJI presents to the orthopaedic community are on many fronts. Prevention of PJI has proven to be a difficult task indeed. Effective strategies for prevention of PJI are being refined. The Center for Disease Control will be publishing its updated Surgical Site Prevention Guidelines in the next few months that consists of specific recommendations for prevention of PJI. In recent years, strides are made in introducing novel molecular techniques for diagnosis of PJI, which may stand to change our practices. The current surgical technique for management of PJI, besides the immense cost, fall short of delivering high success to the patients. The major problem in eradication of infection relates to formation of biofilm, on the implant surface and internalization of the organisms by affected cells. Biofilm is a sophisticated structure comprising of organisms embedded in multiple layers of glycoccalyx that allows the organisms to evade host immunity and is impenetrable to antibiotics. These organisms are capable or communicating through molecular mechanisms such as quorum sensing that affords them advantage for survival in the host environment. In recent years strategies to prevent colonization of the implant surface, an essential first step in formation of biofilm, or biofilm disruption techniques have been introduced. A recent International Consensus meeting on PJI that assembled more than 350 experts identified some of the best practices in this field and identified areas in need of future research. Moving into the future, the field of orthopaedics in general and PJI in particular stand to benefit from the discoveries in the field of molecular diagnostics, metabolomics and epigenetics.
The safety of simultaneous bilateral knee replacement (BTKA) remains controversial. Some studies have proposed a higher incidence of serious complications, even death, following BTKA whilst others refute the latter. The objective of this meta-analysis was to evaluate the safety of BTKA. A computerised literature search was conducted to identify all citations, between 1966 to 2005, concerning BTKA. All the English-language abstracts were obtained. A multistage assessment was then used to identify articles fulfilling the inclusion criteria for the study. All randomised, prospective studies reporting the outcome of BTKA were included. Details of any reported data were extracted and extensive analysis of relevant variables carried out.Introduction:
Methods:
This study assesses oxidation, mechanical behavior and revision reasons of 2nd generation HXLPE used in total hip and knee arthroplasty. While oxidation was low for both X3 and E1 HXLPEs, oxidative regional variations were detected in the sequentially annealed cohort. First generation highly crosslinked polyethylenes (HXPLEs) have proven successful in lowering both penetration and osteolysis rates. However, 1st generation annealing and remelting thermal stabilization have been associated with in vivo oxidation or reduced mechanical properties. Thus, 2nd generation HXLPEs were developed to improve oxidative stability while still maintaining material properties. Little is known about the in vivo clinical failure modes of these 2nd generation HLXPEs. The purpose of this study was to assess the revision reasons, wear, oxidative stability, and mechanical behavior of retrieved sequentially annealed Vitamin E diffused HXLPE in THA and TKA.Summary Statement
Introduction
Fretting and corrosion has been identified as a clinical problem in modular metal-on-metal THA, but remains poorly understood in modern THA devices with polyethylene bearings. This study investigates taper damage and if this damage is associated with polyethylene wear. Degradation of modular head-neck tapers was raised as a concern in the 1990s (Gilbert 1993). The incidence of fretting and corrosion among modern, metal-on-polyethylene and ceramic-on-polyethylene THA systems with 36+ mm femoral heads remains poorly understood. Additionally, it is unknown whether metal debris from modular tapers could increase wear rates of highly crosslinked PE (HXLPE) liners. The purpose of this study was to characterise the severity of fretting and corrosion at head-neck modular interfaces in retrieved conventional and HXLPE THA systems and its effect on penetration rates.Summary Statement
Introduction
The safety of simultaneous bilateral knee replacement (BTKA) remains controversial. Some studies have proposed a higher incidence of serious complications, even death, following BTKA whilst others refute the latter. The objective of this meta-analysis was to evaluate the safety of BTKA. A computerised literature search was conducted to identify all citations, between 1966 to 2005, concerning BTKA. All the English-language abstracts were obtained. A multistage assessment was then used to identify articles fulfilling the inclusion criteria for the study. All randomised, prospective studies reporting the outcome of BTKA were included. Details of any reported data were extracted and extensive analysis of relevant variables carried out.Introduction
Methods
Developmental dysplasia of the hip (DDH) is relatively a common condition that can lead to early arthritis of the hip. Although total hip arthroplasty is the surgical treatment of choice for these patients with end stage arthritis, some patients afflicted with DDH may present early. Acetabular osteotomy, in particular Bernese or periacetabular osteotomy (PAO as described by Professor Ganz and Jeff Mast back in 1980s) may be an option with patients with symptomatic DDH who have joint space available. PAO has many advantages. First, it is performed through a single incision (modified Smith Peterson approach) without breaching the abductor mechanism. The periacetabular fragment has, hence, excellent blood supply and avascular necrosis of the acetabular portion is not an issue. In addition, the osteotomy is so versatile allowing for great mobility of the fragment to obtain coverage even in the worst of circumstances. The osteotomy does not affect the posterior column and hence allows for earlier weight bearing. Most joint preservation surgeons in North America and Europe prefer PAO to other types of osteotomy. The indications for PAO are a patient with symptomatic DDH who has good joint space and a congruent joint. The congruency of the joint is usually determined by the abduction views (obtained at 30 degrees abduction and neutral rotation). Although the joint space may be measured on plain radiographs, in recent years some centers have been utilising cross sectional imaging, such as dGEMERIC for evaluation of the articular cartilage, which has been shown to be a good predictor of outcome for PAO.
First generation highly crosslinked polyethylenes (HXPLEs) have proven successful in lowering both penetration and osteolysis rates. However, 1st generation annealing and remelting thermal stabilization have been associated with in vivo oxidation or reduced mechanical properties. Thus, 2nd generation HXLPEs were developed to improve oxidative stability while still maintaining material properties. Little is known about the in vivo clinical failure modes of these 2nd generation HLXPEs. The purpose of this study was to assess the revision reasons, wear, oxidative stability, and mechanical behavior of retrieved sequentially annealed Vitamin E diffused HXLPE in THA and TKA. 251 2nd Generation HXLPE hip and knee components were consecutively retrieved during revision surgeries and continuously analyzed in a prospective, IRB approved, multicenter study. 123 acetabular liners (Implanted 1.2y; Range 0–5.0y) and 117 tibial inserts (Implanted 1.6y; Range 0–5.8y) were highly crosslinked and annealed in 3 sequential steps (X3). Five acetabular liners (Implanted 0.6y; Range 0–2.0y) and six tibial inserts (Implanted 1.3y; Range 0.5–1.8y) were diffused with Vitamin E (E1). Patient information was collected from medical records (Table 1). Linear penetration of liners was measured using a calibrated digital micrometer (accuracy: 0.001 mm). Surface damage of tibial components was assessed using the Hood method. Thin sections were taken from the acetabular liners (along the superior/inferior axis) and the tibial components (along the medial condyle and central spine) for oxidation analysis and analyzed according to ASTM 2102. Mechanical behavior was assessed via the small punch test (ASTM 2183).Introduction:
Methods:
Degradation of modular head-neck tapers was raised as a concern in the 1990s (Gilbert 1993). The incidence of fretting and corrosion among modern, metal-on-polyethylene and ceramic-on-polyethylene THA systems with 36+ mm femoral heads remains poorly understood. Additionally, it is unknown whether metal debris from modular tapers could increase wear rates of highly crosslinked PE (HXLPE) liners. The purpose of this study was to characterize the severity of fretting and corrosion at head-neck modular interfaces in retrieved conventional and HXLPE THA systems and its effect on penetration rates. 386 CoCr alloy heads from 5 manufacturers were analyzed along with 166 stems (38 with ceramic femoral heads). Metal and ceramic components were cleaned and examined at the head taper and stem taper by two investigators. Scores ranging from 1 (mild) to 4 (severe) were assigned in accordance with the semi-quantitative method adapted from a previously published technique. Linear penetration of liners was measured using a calibrated digital micrometer (accuracy: 0.001 mm). Devices implanted less than 1 year were excluded from this analysis because in the short-term, creep dominates penetration of the head into the liner.Introduction:
Patients & Methods:
Previous studies regarding modular head-neck taper corrosion were largely based on cobalt chrome (CoCr) alloy femoral heads. Less is known about head-neck taper corrosion with ceramic femoral heads. We asked (1) whether ceramic heads resulted in less taper corrosion than CoCr heads; (2) what device and patient factors influence taper fretting corrosion; and (3) whether the mechanism of taper fretting corrosion in ceramic heads differs from that in CoCr heads.Background:
Questions/purposes:
The diagnosis of periprosthetic joint infection (PJI) remains a serious challenge. Based on previous work, we believe that biomarkers will become the mainstay of diagnosing PJI in the future. We report on completion of our 8 year comprehensive biomarker program, evaluating the diagnostic profile of the 15 most promising synovial fluid biomarkers. Synovial fluid was prospectively collected from 99 patients being evaluated for infection in the setting of revision hip or knee arthroplasty. All synovial fluid samples were tested by immunoassay for 15 putative biomarkers that were developed and optimized specifically for use in synovial fluid. Sensitivity, specificity and receiver operating Characteristic (ROC) curve analysis were performed for all biomarkers.INTRODUCTION:
METHODS:
Direct anterior approach (DAA) using the Hueter interval for total hip replacement (THA) provides an inter-nervous and inter-muscular access to the hip joint. Although it is technically demanding, the learning curve has been shown to be around 40 cases and 6 months in a high-volume joint surgeon's practice. A level-one study has demonstrated that DAA provides equal or better results and an equivalent rate of complications when compared to the highly utilized direct lateral approach. Using the available evidence to perform a multi-criteria decision analysis we demonstrated that DAA can be the most efficient approach to perform THA. From our standpoint, there is no reason to speculate a surgical approach with such advantages will be abandoned in the future. The DAA is here to stay, and may become the gold standard for THA.
Total knee arthroplasty is an operation that can be performed with or without the use of tourniquet. Two systematic reviews and meta-analyses of the available literature have demonstrated that the use of tourniquet leads to a reduction in blood loss and also shortens the operative time. The opponents for use of tourniquet cite development of complications such as skin bruising, neurovascular injury, and metabolic disturbances as a deterrent for the use of tourniquet. Although the latter may be true for some patients such as those with previous vascular grafts, there is little evidence that routine use of tourniquet during TKA results in any of the above complications. The use of tourniquet on the other hand provides a bloodless field that allows the surgeon to perform the procedure with expediency and optimised visualisation. Blood conservation has gained extreme importance in recent years because of increased understanding of problems associated with blood transfusion such as increased surgical site infection (due to immunomodulation effect), increased length of hospital stay, increased cost and so on. Based on our understanding of the available evidence, we believe that routine use of tourniquet during TKA is justified and a good surgical practice.
A novel cementless tapered wedge femoral hip implant has been designed at a reduced length and with a geometry optimized to better fit a wide array of bone types (Accolade II, Stryker, Mahwah, USA). In this study, finite element analysis (FEA) is used to compare the initial stability of the new proposed hip stem to predicate tapered wedge stem designs. A fit analysis was also conducted. The novel stem was compared to a predicate standard tapered stem and a shortened version of that same predicate stem. The novel shortened tapered wedge stem geometry was designed based on a morphological study of 556 CT scans. We then selected 10 discrete femoral geometries of interest from the CT database, including champagne fluted and stove pipe femurs. The novel and the predicate stems were virtually implanted in the bones in ABAQUS CAE. A total of thirty FEA models were meshed with 4 nodes linear tetrahedral elements. Bone/implant interface properties was simulated with contact surface and a friction coefficient of 0.35. Initial stability of each stem/bone assembly was calculated using stair-climbing loading conditions. The overall initial stability of the HA coated surface was evaluated by comparing the mean rotational, vertical, gap-opening and total micromotion at the proximal bone/implant interface of the novel and predicate stem designs. To characterize the fit of the stem designs we analyzed the ratio of a distal (60 mm below lesser trochanter) and a proximal (10 mm above lesser trochanter) cross section. A constant implantation height of 20 mm above the lesser trochanter was used. The fit of the stems was classified as Type 1 (proximal and distal engagement), Type 2 (proximal engagement only) and Type 3 (distal engagement only). The mean % micromotion of the HA coated surface greater than 50 mm was lowest at 40.2% (SD 11.5%) for the novel tapered wedge stem compared to the clinically successful predicate stem design (Accolade TMAZ, Stryker, Mahwah, USA) at 44.9% (SD 13.2%) and its shortened version at 48.5% (SD 9.0%) as shown in Figure 1. Improved initial stability of the new stem was also confirmed for rotational, vertical and gap-opening micromotion. However, there was no statistically significant difference. The novel tapered stem design showed a well balanced proximal to distal ratio throughout the complete size range. The novel tapered stem design showed a reduced percentage of distal engagements (2.8%) compared to the predicate standard stem (17.2%). In the 40 to 60 year old male group the distal engagement for the standard stem increases (28.2%), whereas the distal engagements for the novel stem remains unchanged (1.3%).Methods
Results
Sequentially annealed highly crosslinked polyethylenes (HXLPEs) were introduced in total knee replacement (TKR) starting in 2005 to reduce wear and particle-induced osteolysis. Few studies have reported on the clinical performance of HXLPE knees. In this study, we hypothesized that due to the reduced free radicals, sequentially annealed HXLPE would have lower oxidation levels than gamma inert-sterilized controls. 145 tibial components were retrieved at consecutive revision surgeries at 7 different surgical centers. 74 components were identified as sequentially annealed HXLPE (X3, Stryker) while the remainder (n = 71) were conventional gamma inert sterilized polyethylene. The sterilization method was confirmed by tracing the lot numbers by the manufacturer. The conventional inserts were implanted for 1.7 years (Range: 0.0–9.3 years), while the X3 components were implanted 1.1 years (Range: 0.0–4.5 years). Surface damage was assessed using the Hood method. Oxidation analysis was performed in accordance with ASTM 2102 following submersion in boiling heptane for 6 hours to remove absorbed lipids. 30 of the conventional and 29 of the HXLPE inserts were available for oxidation analysis.Introduction
Methods
Wear debris generation in metal-on-metal (MOM) total hip arthroplasty (THA) has emerged as a compelling issue. In the UK, clinically significant fretting corrosion was reported at head-taper junctions of MOM hip prostheses from a single manufacturer (Langton 2011). This study characterizes the prevalence of fretting and corrosion at various modular interfaces in retrieved MOM THA systems used in the United States. 106 MOM bearing systems were collected between 2003 and 2012 in an NIH-supported, multi-institutional retrieval program. From this collection, 88 modular MOM THA devices were identified, yielding 76 heads and 31 stems (22 modular necks) of 7 different bearing designs (5 manufacturers) for analysis. 10 modular CoCr acetabular liners and 5 corresponding acetabular shells were also examined. Mean age at implantation was 58 years (range, 30–85 years) and implantation time averaged 2.2 ± 1.8 years (range, 0–11.0 years). The predominant revision reason was loosening (n=52). Explants were cleaned and scored at the head taper, stem taper, proximal and distal neck tapers (for modular necks), liner, and shell interfaces in accordance with the semi-quantitative method of Goldberg et al. (2002).Introduction
Methods and Materials
The purpose of this multicenter study was to assess the oxidative stability, mechanical behavior, wear and reasons for revision of 2nd generation sequentially annealed HXLPE, X3, and compare it to 1st generation XLPE, Crossfire. We hypothesized that X3 would exhibit similar wear rates but lower oxidation than Crossfire. 182 hip liners were consecutively retrieved during revision surgeries at 7 surgical centers and continuously analyzed over the past 12 years in a prospective, multicenter study. 90 were highly crosslinked and annealed (Crossfire; Implanted 4.2±3.4 years, max: 11 years), and 92 were highly crosslinked and annealed in 3 sequential steps (X3; Implanted 1.2±1.5 years; max: 5 years). Oxidation was characterized in accordance with ASTM 2102 using transmission FTIR performed on thin sections (∼200μm) from the superior/inferior axis. Mechanical behavior was assessed via the small punch test (ASTM 2183).Introduction
Methods
The diagnosis of Periprosthetic Joint Infection (PJI) is a considerable challenge in total joint arthroplasty. The mainstay for diagnosis of PJI is a combination of serological markers, including C-reactive protein (CRP), along with joint aspirate for white cell count, differential and culture. The aim of this study was to examine the use of synovial fluid CRP in the diagnosis of PJI. Synovial fluid samples were collected prospectively from patients undergoing primary and revision knee arthroplasty. Samples were assessed for CRP, cell count and differential. Three groups were analyzed; those undergoing primary knee arthroplasty, aseptic knee arthroplasties and infected arthroplasties. Demographic data, along with associated medical co-morbidities, were collected,. Statistical analysis was performed. Synovial fluid CRP was correlated with serum CRP values. Sensitivity and specificity were calculated.Background
Material & Methods
The origins of the uncemented tapered wedge hip stem design currently offered by several orthopaedic device companies can be linked back to the cemented Straight Mueller type stem design first used in 1977. The design, a wedge shape with a taper angle of 6 degrees, maintains a single medial curvature for all sizes and increases laterally in the width to accommodate different size femurs. Although evolutionary improvements have been made over the years the basic body geometry of the stem has stayed mainly unchanged with excellent clinical survivorship. Over the past decade, the demographics of hip replacement have changed, with a large increase in younger male patients in the age range of 40 to 60 years. In this study the femoral fit of a novel tapered stem, designed to fit a wide array of patient types, is compared to a standard predicate tapered stem design. A bone morphology study was performed on a patient population of 556 patients using three dimensional digital data from CT-scans. To characterize the fit of the stem designs we analyzed the ratio of a distal (60mm below lesser trochanter) and a proximal (10mm above lesser trochanter) cross section. The same measurements were taken with the standard tapered stem design and the novel tapered stem design, with a given constant implantation height of 20mm above the lesser trochanter. The fit of the stems was classified as Type 1, where there was both proximal and distal engagement, Type 2, proximal engagement only, Type 3, distal engagement only. The distal and proximal engagement, Type 1, was specified with a maximum engagement difference of 2mm proximal to distal.Introduction
Methods
Infection poses one of the greatest medical challenges, one further complicated by bacterial biofilm formation that renders the infection antibiotic insensitive. The goal of this investigation was to covalently link the antibiotic vancomycin (VAN) to a bone allograft so as to render the tissue inhospitable to bacterial colonization and the subsequent establishment of infection. We could achieve uniform tethering of the antibiotic to the allograft with minimal disruption of the underlying bone structure. The tethered VAN remained active against gram-positive organisms with no detectable S.aureus colonization. Additionally, the grafted VAN prevented biofilm formation, even in protected topographical niches. Attachment of the antibiotic to the allograft surface was robust-the stabilized VAN remained active for long time periods. Osteoblasts cultured on the VAN-allograft evidenced no changes in cellular phenotype. We opine that this new chimeric construct represents a superior transplantable substrate with a plethora of applications in medicine, dentistry and surgery.
Use of allograft bone has become standard for bridging defects unlikely to heal by simple fixation and routinely used in revision arthroplasties for implant stabilization. Unfortunately, this decellularized allograft provides an ideal surface for bacterial colonization, necessitating repeated surgeries, extensive debridement and lengthy antibiotic treatments. With up to 18% infection rate following allograft surgeries, a need for more effective means to prevent this process is evident. We describe a novel modification of native bone allografts that renders their surface bactericidal while increasing the effectiveness of systemic antibiotic treatments. Allograft modification: Morselized human bone was washed extensively and sequentially coupled: 2X with Fmoc-aminoethoxyethoxyacetate (Fmoc-AEEA); deprotected with 20% piperidine in Dimethylformamide (DMF); and then coupled with vancomycin (VAN) for 12–16 hours. The VAN-bone was washed extensively with DMF and PBS for at least 1 day. VAN immuno-fluorescence: Control or VAN-bone was washed 5X with PBS, blocked with 10% FBS (1hr), incubated with rabbit anti-VAN IgG (4oC, 12h) followed by an Alexa-Fluor 488-coupled goat anti-rabbit IgG (1hr), and visualized by confocal laser microscopy. Antibiotic Activity. Equal dry weights of control and VANbone were sterilized with 70% ethanol, rinsed with PBS, and incubated with either Staphylococcus aureus (S. aureus) or Escherichia Coli (Ci=104 cfu) in TSB, 37oC, for 2, 5, 8 and 12 hrs. Antibiotic treatment: Clinical grade vancomycin was added to the solution with bacteria or following infection at a final concentration of 10μg/ml. Bacterial counts: Non-adherent bacteria were removed by washing and adherent bacteria suspended by sonication in 0.3% Tween-80 for 10mins followed by plating on 3M® Petrifilms. Bacterial visualization: Non-adherent bacteria were removed by washing extensively with PBS and adherent bacteria stained with the Live/Dead BacLight Kit (20mins, RT) to cause viable bacteria to fluoresce green. Samples were visualized by confocal microscopy. In comparison to controls, VAN-bone consistently reduced the graft bacterial load by ~90% at all time points. After staining and visualization of adherent bacteria, biofilm formation was apparent on controls by 12 hrs and absent from VAN-bone. E.coli, a gramnegative organism that is not sensitive to VAN, readily colonized both control and VANbone, confirming retention of VAN specificity. We then evaluated VAN-bone activity in a system that modeled systemic antibiotic therapy and antibiotic prophylaxis. In the absence of solution antibiotics, VAN-bone exhibited a significant decrease in bacterial colonization as compared to controls. When 10 μg/ml VAN was added to the medium for the last 4 h (modeling systemic antibiotic therapy), colonization of control surfaces was reduced, while colonization of VAN-allograft was almost eliminated. When 10 μg/ml VAN was added concomitantly with S. aureus, VAN-bone colonization was undetectable, while colonization of control surfaces still occurred. We have previously described an antibiotic-tethered allograft that resists bacterial colonization. In this abstract, we test this technology with an vitro model of bone implantation in the presence of solution antibiotics. In these models, solution antibiotics failed to prevent infection of control bone while completely clearing the bacteria on VAN-bone. Furthermore, VAN bone exhibited high activity against S. aureus, a gram positive organism, whereas it was ineffective against E. coli, a gram negative organism. The specificity of the tethered antibiotic supported the view that the antibacterial properties of the allograft were related to the tethered antibiotic and not to undefined aspects of the attachment chemistry. In terms of antibacterial activity, when challenged with 104 CFU S. aureus (with concentrations reaching >
107 CFU by 24 h), the antibiotic -modified allograft consistently decreased bacterial colonization by >
90%; S. aureus inocula <
102 CFU resulted in no detectable colonization of the VAN-allograft. Thus, development of these allografts may not only combat allograft colonization but increase the effectiveness of prophylactic antibiotics to ultimately result in a new therapy for allograft-associated infection.
Persistent wound drainage after total joint arthroplasty (TJA) has been associated with a higher incidence of superficial and deep periprosthetic infection but the predictors for prolonged drainage and its outcome have not been thoroughly studied. A consecutive series of 7,153 TJA cases performed between 2000 and 2006 at our institute, were recruited into this study. There were 301 cases (4.2%) of persistent wound drainage, defined as discharge from the wound for >
48 hours. The cases were matched in a 2:1 ratio for type of surgery, joint replaced, and date of surgery. This study identified higher BMI (p<
0.005), malnutrition as defined by serum albumin<
3.4g/dl (p<
0.04), longer operative time (p<
0.01), and higher medical comorbidities, in particular diabetes (p<
0.001) as important risk factors for persistent wound drainage. In addition, patients in the drainage group were more likely to have a peak INR of >
1.5 (p<
0.001) during their hospital stay. Patients with wound drainage had a significantly lower hemoglobin postoperatively (p<
0.01) that necessitated greater number of postoperative allogenic transfusions (p=0.004). The hospital length of stay for the drainage group was also significantly higher (p<
0.005). One of the major risk factors for development of deep infection was prolonged drainage (>
7 days). In the deep hematoma and periprosthetic subgroups, the mean of delay in treatment was 6 days in those with retention of the prosthesis and successful outcome, and 9.5 days for those with failure of incision and drainage leading to resection arthroplasty (p= 0.03). 72% of the patient were successfully treated by oral or intravenous antibiotics. 27% required at least one re-operation for deep hematoma and 13% developed deep periprosthetic infection, resulting in 6% rate of resection arthroplasty. 1.5% of those with drainage remained in girdlestone status. This study suggests early surgery for persistent drainage and avoidance of aggressive anticoagulation.
Periprosthetic infection (PPI) remains the most dreaded and difficult complication of total joint arthroplasty. Although there is no definite diagnostic test for PPI, synovial leukocyte count and neutrophil percentage have been reported to have high sensitivity and specificity. However, leukocytes and neutrophils introduced into the joint during a traumatic aspiration can skew results and undermine the predictive value of this diagnostic test. This study intends to determine the diagnostic value of implementing a corrective formula frequently used in traumatic spinal taps to adjust for serum leukocytes introduced into the joint fluid during a bloody tap. We conducted a review of all TKA aspirations of infected and non-infected patients performed at our institute from 2000 to 2005. The following inclusion criteria were used:
(a) a red cell count (RBC) was performed on the aspirate, and (b) a blood white cell count with differential was done within one week of aspiration. Patients with inflammatory arthropathy or those who underwent reimplantation after PPI were excluded. Strict criteria for diagnosis of PPI were used. We previously determined at our institute the cut-off values for fluid leukocyte count (>
1760 cells/μl) and neutrophil percentage (>
73%). The adjusted fluid leukocyte counts were calculated using the following formula: Wadjusted = WBCobserved – [(WBCblood * RBC-fluid/RBCblood)] predicted. A similar formula was implemented to calculate the adjusted absolute neutrophil counts. Our cohort included 73 infected and 32 aseptic total knee arthroplasties that fulfilled the above criteria. After correcting for introduced red blood cells, cell counts of 3 infected patients dropped below the cut-off value, while the remaining 70 maintained a high cell count. However, the 3 infected patients had initial cell counts below our reported cut-offs. Of the 32 non-infected patients, 10 patients had false positive cell counts due to the presence of extremely high numbers of blood RBC. Five of the 10 false positive aspirates successfully corrected to levels below the thresholds used to diagnose infection. The aspirates that corrected had a greater number of introduced RBCs, an initial higher cell count, and 20 times more fluid WBC deducted from the initial cell count. The corrective formula can safely adjust for RBC found in a traumatic tap and detect false positive results among non-infected TKA without compromising the diagnosis of infection. Adjusted aspirates of non-infected TKA can be expected to decrease below zero due to one of the following: adherence of the introduced systemic WBC to the joint synovium, greater rate of lysis of the introduced systemic WBC compared to the systemic RBC, laboratory errors in performing fluid cell counts.
The differential diagnosis of pain after total knee arthroplasty (TKA) should always include periprosthetic infection (PPI). The current diagnostic tools vary in sensitivity, specificity, and predictive value. Currently there is no test with an absolute accuracy for diagnosis of PPI. Furthermore, cost effectiveness of investigations has become an important issue in recent years as increased expenses can place an unnecessary heavy burden on the medical system. We retrospectively evaluated 296 patients who underwent revision TKA at our institution during 2000–2005 and had preoperative erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) performed. The criteria used for diagnosing infection were a positive intraoperative culture on solid media, presence of an abscess or sinus tract that communicated with the joint, positive preoperative aspiration culture, and/or elevated fluid cell count and neutrophil differential of the aspirated fluid. The sensitivity, specificity, and predictive values of ESR and CRP were determined. Combinations were performed in parallel that necessitate both tests to be negative to rule out infection. The cost of each serological test was compared to that of other commonly used screening modalities. One hundred and sixteen patients (39%) were classified as infected and 180 patients (61%) were considered non-infected. The sensitivity, specificity, positive predictive value, and negative predictive value for the ESR were: 91%, 72%, 68%, and 93%. The sensitivity, specificity, positive predictive value, and negative predictive value for the CRP were: 94%, 74%, 70%, and 95%. The sensitivity and negative predictive value for the combined studies were 96% and 95%, respectively. However, five infected patients (4%) had a normal ESR and CRP. An organism was cultured on solid media in 4 of the 5 cases. ESR and CRP were the least costly of all the preoperative tests including radionuclide imaging and joint fluid analysis. ESR and CRP are important preoperative tests in diagnosis of PPI and their ability to clench the diagnosis in the majority of cases should not be underestimated. When combined, these simple serological tests have improved sensitivity and negative predictive value to rule out infection.
Serological tests including erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are frequently used in the preoperative workup to screen for periprosthetic infection (PPI) in total hip arthroplasty (THA). The cut-off points reported in the literature are arbitrarily chosen by investigators. Similarly, the values used in laboratories to distinguish elevated results vary from one institute to another. Therefore, we intended to define the appropriate cut-off points of ESR and CRP that can be used to differentiate infection from aseptic failure of THA. A review of our joint registry database revealed that 515 THA revisions (131 infected cases) were performed during 2000–2005. Intraoperative samples for culture were taken in all cases. The criteria used for diagnosis of infection were a positive intraoperative culture on solid media, presence of an abscess or sinus tract that communicated with the joint, positive preoperative aspiration culture, and/or elevated fluid cell count and neutrophil differential of the aspirated fluid. Non-infected patients with confounding factors that can elevate ESR and CRP including collagen vascular disease, inflammatory arthropathy, malignancy, and urinary tract infection were excluded. Receiver operator curves were used to determine the ideal cut-off point for both ESR and CRP. The mean value of ESR in the infected group (77mm/ hr) was significantly higher compared to that of the non-infected cohort (29mm/hr) (p=0.0001). Similarly, infected patients presented with a greater mean CRP (9.8 mg/dl) than their non-infected cohort (1.48 mg/ dl) (p=0.0001). The infection threshold for ESR was 45mm/hr with a sensitivity of 85% and specificity of 79%, while the optimal cut-off value for CRP was defined as 1.6 mg/dl which yielded a sensitivity of 86% and specificity of 83%. The optimal threshold values we determined are higher than the arbitrarily chosen values cited in the literature for ESR (30mm/hr) and CRP (1mg/dl). Although it has been previously reported that the sensitivity and specificity of CRP are far greater than that of ESR, we found that the two tests have comparable diagnostic value.
The accurate differentiation of aseptic loosening from periprosthetic infection in the painful hip prosthesis is a major clinical challenge. FDG-PET imaging has shown great promise in various clinical settings for detection of infection. This prospective study was designed to determine the efficacy of FDG-PET imaging in the assessment of patients with painful hip prosthesis. One hundred and thirteen patients with 127 painful hip prostheses were evaluated by FDG-PET. Approximately 60 minutes after the intravenous administration of FDG images of the lower extremities were acquired using a dedicated PET machine. FDG-PET images were interpreted by experienced nuclear medicine physicians. Images were considered positive for infection if PET demonstrated increased FDG activity at the bone-prosthesis interface of the femoral component of the prosthesis. Surgical findings, histopathology, and clinical follow-up served as the “gold standard”. FDG-PET was positive for infection in 35 hips and negative in 92 hips. Among 35 positive PET studies, 28 were proven to be infected by surgical and histopathology findings as well as follow-up tests. Of 92 hip prostheses with negative FDG-PET findings, 87 were proven to be aseptic. The sensitivity, specificity, positive and negative predictive values for FDG-PET were 0.85 (28/33), 0.93 (87/94), 0.80 (28/35), and 0.95 (87/92), respectively. The overall accuracy of FDG-PET in this clinical setting was 90.5% (115/127). The results demonstrate that FDG-PET is a highly accurate diagnostic test for differentiating infected from non-infected painful hip prosthesis. Therefore, FDG-PET imaging is considered the study of choice in the evaluation of patients with suspected hip prosthesis infection.
The accurate diagnosis of periprosthetic infection poses a challenge to the clinician and the imaging specialist alike. In recent years, FDG-PET imaging has shown great promise in the evaluation of occult infection at various anatomic sites. The purpose of this investigation was to determine the accuracy of FDG-PET imaging in diagnosing periprosthetic infection associated with total knee arthroplasty. Sixty eight painful knee prostheses were referred for further evaluation with FDG-PET imaging. Approximately 60 minutes after the intravenous administration of FDG, PET images of both knees were acquired and interpreted by experienced nuclear medicine physicians. PET images demonstrating increased FDG activity at the bone-prosthesis interface were considered infected. Final diagnosis was made on the basis of surgical findings, histopathology, and clinical follow-up. FDG-PET correctly diagnosed 19 of the 22 infected cases for a calculated sensitivity of 86.4% (19/22). FDG-PET correctly predicted the absence of infection in 38 of 46 aseptic knee prostheses for a calculated specificity of 82.6% (38/46). The negative and positive predictive values for FDG-PET imaging in this setting were 92.7% (38/41) and 70.4% (19/27), respectively. The overall accuracy of FDG-PET imaging was 83.8% (57/68). FDG-PET was indeterminate in three cases which were not included in this analysis. These results demonstrate that FDG-PET is a useful diagnostic tool for the evaluation of possible infection associated with knee arthroplasty. Considering the large number of subjects who undergo total knee arthroplasty and the sizable fraction who develop complications following surgery, the impact of FDG-PET imaging could be substantial. Examination of a larger number of patients with painful knee prostheses will further clarify the merit of this powerful technique in this clinical setting.
Currently two-stage resection arthroplasty is the preferred method for surgical treatment of periprosthetic infection in North America. However, the success of this treatment strategy has varied from 54% to 98% based on previous reports. The exact reason for this variation in outcome is not known. The purpose of this study was to determine the efficacy of this treatment modality and delineate patient risk factors that result in recurrent infection and failure. During the period of this study (2000–2005) 77 patients with an infected THA were treated at our institution. Fifty-four patients underwent two-stage exchange arthroplasty while the remaining 22 failed to have the second stage reimplantation due to ill health. The latter 22 were excluded from the analysis. All patients were followed up prospectively for at least two years after reimplantation. Detailed data including demographics, comorbidities, surgical history, and medication intake was collected. Intraoperative data, organism profile, and complications were also documented. Failure was defined as patient requiring additional surgical procedure for control of infection or loosening. Two-stage exchange arthroplasty successfully eradicated infection in 36 patients (67%) without need for further treatment. Seven patients (13%) had recurrent infection that necessitated resection arthroplasty. Eleven (20%) patients required irrigation and debridement for postoperative purulent drainage which successfully treated infection in 8 of the cases. The remaining 3 patients failed and required resection arthroplasty. Three additional patients had early loosening of components and required revision arthroplasty. The exact cause of loosening in these patients could not be determined and despite lack of isolation of organisms infection was suspected. Multivariate analysis identified previous medical comorbidity and postoperative allogenic transfusion as risk factors for failure. Current strategies to treat periprosthetic infection remain imperfect. Two-stage exchange arthroplasty with all its inherent problems and inconveniences imparted a modest success in treatment of PPI at our high volume specialized center. With the increase in the number of virulent and resistant organisms, and the rise in arthroplasties being performed in infirm patients with medical comorbidities the success of this procedure is likely to be jeopardized. Novel treatment modalities to combat this dreaded condition is needed.
Debridement of an infected total joint arthroplasty with retention of mechanically stable components is often performed for acute cases of periprosthetic infection (PPI). However, the reported success of such a procedure to fully eradicate infection has varied widely. The objective of this study was to elucidate the efficacy of debridement in both infected THA and TKA and attempt to identify risk factors responsible for failure. During the years 2000–2005, 71 TKA and 69 THA underwent irrigation and debridement for acute PPI (<
4 weeks). All patients were followed up prospectively for at least two years. Detailed data including demographics, comorbidities, surgical history, and medication intake was collected. Intraoperative data, organism profile, and complications were also documented. Failure was defined as patient requiring additional surgical procedure for control of infection or loosening. Of the 140 patients, 24% required repeat irrigation and debridement for postoperative drainage, hema-toma formation, or systemic symptoms. One third of these revision debridement patients underwent multiple consecutive debridements. Two-stage resection arthroplasty was required in 65 patients (46%) of the entire cohort. Fifty-eight percent of the patients with resection required revision of their cement spacer block due to continuous drainage and systemic symptoms indicative of persistent infection. We noted a total of 86 failures (61%) that required either an additional debridement or resection arthroplasty after the first debridement procedure. The failure rates of THA (62%) and TKA (55%) individually were similar (p=0.253). Although the concept of conservative management of PPI with debridement and retention of components is an attractive alternative to resection arthroplasty, we have found that 60% of patients undergoing this procedure will inevitably undergo two-stage arthroplasty. Furthermore, more than half of the patients that required resection arthroplasty developed infection of their spacer that entailed revision of the cement block. Therefore, we can conclude that this procedure has a high failure rate and should be implemented in only a select group of patients.
The differential diagnosis of pain after total knee arthroplasty (TKA) should always include periprosthetic infection (PPI). The current diagnostic tools vary in sensitivity, specificity, and predictive value. Currently, there is no test with an absolute accuracy for diagnosis of PPI. Furthermore, cost effectiveness of investigations has become an important issue in recent years as increased expenses can place an unnecessary heavy burden on the medical system. We retrospectively evaluated 296 patients who underwent revision TKA at our institution during 2000–2005 and had preoperative erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) performed. The criteria used for diagnosing infection were a positive intraoperative culture on solid media, presence of an abscess or sinus tract that communicated with the joint, positive preoperative aspiration culture, and/or elevated fluid cell count and neutrophil differential of the aspirated fluid. The sensitivity, specificity, and predictive values of ESR and CRP were determined. Combinations were performed in parallel that necessitate both tests to be negative to rule out infection. The cost of each serological test was compared to that of other commonly used screening modalities. One hundred sixteen patients (39%) were classified as infected and 180 patients (61%) were considered non-infected. The sensitivity, specificity, positive predictive value, and negative predictive value for the ESR were: 91%, 72%, 68%, and 93%. The sensitivity, specificity, positive predictive value, and negative predictive value for the CRP were: 94%, 74%, 70%, and 95%. The sensitivity and negative predictive value for the combined studies were 96% and 95% respectively. However, five infected patients (4%) had a normal ESR and CRP. An organism was cultured on solid media in 4 of the 5 cases. ESR and CRP were the least costly of all the preoperative tests including radionuclide imaging and joint fluid analysis. ESR and CRP are important preoperative tests in the diagnosis of PPI and their ability to clench diagnosis in the majority of cases should not be underestimated. When combined, those simple serological tests have improved sensitivity and negative predictive value to rule out infection.
Periprosthetic infection (PPI) is one of the most devastating complications of total knee arthroplasty (TKA). It is widely accepted that resection arthroplasty supplemented with intravenous antibiotics and delayed exchange arthroplasty is the treatment modality of choice for infected TKA. However, the outcome after reimplantation has varied and unpredictable results have been reported. This study evaluates the outcome of this treatment strategy in a single high volume specialised center. Furthermore, our study aims to identify the factors that lead to failure of this treatment. A thorough review of our joint registry database revealed that 80 patients with an infected TKA underwent resection arthroplasty at our institution during 2000–2005. Sixty-five patients underwent two-stage exchange arthroplasty while the remaining 15 failed to have the second stage reimplantation due to ill health or underwent arthrodesis or amputation. The latter 15 were excluded from the analysis. All patients were followed up prospectively for at least two years. Detailed data including demographics, comorbidities, surgical history, and medication intake was collected. Intraoperative data, organism profile, and complications were also documented. Failure was defined as patient requiring additional surgical procedure for control of infection or loosening. Two-stage exchange arthroplasty successfully eradicated infection in 45 patients (31%) without need for further treatment. Twelve patients (18%) had recurrent infection that necessitated another resection arthroplasty. Eleven (17%) patients required irrigation and debridement for postoperative purulent drainage which successfully treated infection in 5 cases (46%). The remaining 6 patients failed and required resection arthroplasty. Three additional patients had early loosening of components and required revision arthroplasty. The exact cause of loosening in these patients could not be determined, and despite lack of isolation of organisms infection was suspected. Our analysis identified that irrigation and debridement prior to resection arthroplasty are major risk factors for failure. Current strategies to treat periprosthetic infection remain imperfect. Two-stage exchange arthroplasty with all its inherent problems and inconveniences imparted a modest success in treatment of PPI at our high volume specialised center. The rise in the number of resistant and virulent organisms, increase in the number of patients with severe medical comorbidities who develop infection may account for the decline in the success of two-stage resection arthroplasty. Novel strategies for treatment of PPI are desperately needed.
One of the routinely used intraoperative tests for diagnosis of periprosthetic infection (PPI) is Gram stain that is reported to carry a very high specificity and a poor sensitivity. However, it is not known if the result of this test can vary according to the type of joint affected or the number of specimen samples collected. This study intended to examine the role of this diagnostic test in a large cohort of patients from single institution. A review of our joint registry database revealed that 453 total knee arthroplasty (TKA) and 551 total hip arthroplasty (THA) of which 171 and 150 cases were respectively infected underwent revision surgery during 2000–2005 and had intraoperative cultures available for interpretation. A positive gram stain was defined as the visualisation of bacterial cells or ‘many leukocytes’ (>
5 per high power field) under the smear. The sensitivity, specificity, and predictive values of each individual diagnostic arm of Gram stain were determined. Combinations were performed in series that require both tests to be positive to confirm infection and in parallel that necessitate both tests to be negative to rule out infection. This analysis was performed for THA and TKA separately and later compared for each joint type. The presence of organism cells and ‘many’ neutrophils on a Gram smear had high specificity (98%–100%) and positive predictive value (89%–100%) in both THA and TKA. The sensitivities (30%–50%) and negative predictive values (70%–79%) of the two tests were low as expected among both joint types. When the two tests were combined in series the specificity and positive predictive value were absolute (100%). The sensitivity (43%–64%) and the negative predictive value (82%) improved among both THA and TKA. The presence of organisms or ‘many’ leukocytes on the Gram smear can confirm PPI in TJA. As expected, the sensitivity and negative predictive value of the two tests were low, and therefore infection could not be safely ruled out. Although the two diagnostic arms of Gram stain can be combined to achieve improved negative predictive value (82%), Gram stain continues to have poor value in ruling out PPI. With the advances in the field of molecular biology, novel diagnostic modalities need to be designed that can replace these traditional and poor tests.