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: Bone Joint J 2015;97-B(10 Suppl A):20–9.

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.

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.

Summary Statement

This study assesses oxidation, mechanical behavior and revision reasons of 2^nd 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.

Summary Statement

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.

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.

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.

Introduction:

First generation highly crosslinked polyethylenes (HXPLEs) have proven successful in lowering both penetration and osteolysis rates. However, 1^st generation annealing and remelting thermal stabilization have been associated with in vivo oxidation or reduced mechanical properties. Thus, 2^nd 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 2^nd 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.

INTRODUCTION:

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.

Background:

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.

Introduction:

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.

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.

Introduction

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.

Introduction

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.

Introduction

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 1^st generation XLPE, Crossfire. We hypothesized that X3 would exhibit similar wear rates but lower oxidation than Crossfire.

Background

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.

Introduction

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.

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.

Purpose: Recently an orthopedic manufacturer has introduced a gender specific knee design implying that there is a substantial anatomical difference between the genders. If such concept is true then TKA prosthesis implanted in the female population over the last decades, by definition, must have suboptimal outcome when compared to the male patients. The purpose of this study was to examine the functional outcome, the incidence of complications, and the need for revision between the two genders receiving the same knee design.

Method: The study selected a matched group of 150 men and 250 women undergoing TKA at our instituion. The patients were matched for age, BMI, pre-op diagnosis, comorbidities, race, mode of fixation, and the type of implant. Other demographic, surgical, and medical factors between the two genders were similar. Both pre-op and post-op functional scores were compared between the two groups. Pre-op and post-op radiographic images were assessed for implant fit.

Results: There was a significant improvement in functional outcome as measured by Knee Society score, WOMAC, and SF-36 for all patients. The improvement in functional outcome was not different between the two groups. The incidence of complications, reoperations, and need for revision between the two genders was also not significantly different.

Conclusion: Total knee arthroplasty continues to be an effective surgical procedure. Both genders appear to enjoy relief of pain and improvement of function equally. Based on this retrospective study the use of non-gender specific knee prosthesis did not seem to result in suboptimal outcome in female patients. There appears to be little merit in introduction of gender specific knee designs when previous non-gender specific prosthesis appeared to function well in both genders.

Purpose: Hip arthroscopy has been used at an increasing frequency over the last few years. Majority of patients undergoing hip arthroscopy are young and active individuals who seek definitive therapy for a painful hip condition and wish to avoid undergoing a hip replacement. Although relatively successful, complications following hip arthroscopy occur. This multi-institutional study presents a worrisome and previously unrecognized complication of hip arthroscopy, namely chondrolysis that lead to accelerated development of end-stage arthritis.

Method: Using the computerized database in each institution, patients undergoing total hip arthroplasty between 1999–2008 who had received hip arthroscopy prior to arthroplasty were identified. 39 patients were identified to have undergone at least one hip arthroscopy on the affected hip prior to arthroplasty. There were 21 female and 18 male patients. The mean age of patients at the time of hip arthroscopy was 45.9 years. Data regarding demographics, comorbidities, preoperative diagnosis, number of previous procedures, and the details of the surgical procedure were compiled. Radiographs were evaluated.

Results: The median time from arthroscopy to arthroplasty was 14.8 months (range 2.2 months to 7 years). Fourteen patients (35%) underwent THA within 12 months of a previous hip arthroscopy and in nine of these patients the indication for hip arthroscopy was labral tear debridement. These patients despite having none to minimal arthritis at the time of arthroscopy developed accelerated arthritis within a year that necessitated hip replacement.

Conclusion: Hip arthroscopy can cause accelerated degenerative arthritis of the hip in some patients. We believe the subset of our patients who developed arthritis so early after hip arthroscopy may have suffered chondrolysis and/or chondral injury during the arthroscopy that resulted in progressive and aggressive arthritis of the hip within 12 months. Hip arthroscopy should be reserved for a select group of patients. All measures to minimize the possibility of chondrolysis and/or chondral injury should be exercised.

Purpose: Femoroacetabular impingement (FAI) is recognized as an etiological risk factor for hip arthritis. The potential for joint preserving surgical techniques that may delay the progression to early arthritis and retard the possibility of arthroplasty at a young age is promising. This study presents the outcome of surgical treatment of FAI through a less invasive technique performed through a modified Smith-Peterson approach without hip dislocation, or arthroscopy.

Method: Using an institutional database, a total of 72 patients (80 hips) with radiographic and clinical diagnosis of FAI who underwent direct anterior femoroacetabular osteoplasty (FAO) were identified. Preoperative and postoperative functional evaluation was performed on these patients. The operative findings were recorded in detail and evaluated with regard to outcome.

Results: Intraoperative diagnosis of labral tear and osteochondral lesions in the anterosuperior acetabulum was confirmed in all cases. The surgical approach provided adequate access to allow labral repair and osteoplasty of the femoral neck and the acetabulum, whenever needed. There were no intraoperative complications. All patients experienced a significant improvement in function as measured by modified Harris hip and SUSHI scores. Majority (85%) of the patients were satisfied with the outcome of the surgery. In addition, Health Survey SF-36 showed most patients felt their health had improved significantly. The predictors of poor outcome were previous hip scope, lack of labrum for repair, large chondral lesions, and workman’s compensation status.

Conclusion: This study presents the early results of a less invasive surgical treatment for femoroacetabular impingement. This ongoing study shows that the described technique seems to be a viable approach for treatment of this painful condition in the young.

Purpose: The purpose of our study is to compare hips to knees in regards to the cost per increase in function, to determine the relationship of economic investment to improved quality of life.

Method: During the year 2005, a total of 23 TKA and 41 THA revisions were performed for aseptic mechanical failure. Patients were enrolled prospectively and quality of life questionnaires including the SF-36, WOMAC, Harris Hip Score (HHS), and Knee Society Score (KSS) were collected prior to and following their procedure at two year follow-up. The total cost of the procedure including the hospital, implant, and surgeon fee were implemented in a cost effectiveness model to calculate the mean cost per SF-36, WOMAC, and HHS or KSS point gained. Demographical variables and co-morbidities were collected to determine risk factors for low cost-effectiveness.

Results: The majority of patients had significant improvement in SF-36, WOMAC, HHS and KSS scales. Patients with THA revisions experience a cost per point increase for HHS of $3,000, and $500 per point SF-36 compared to knee patients who experienced a cost per point increase for KSS of $2,000, and $2,800 per point SF-36. The WOMAC exhibited similar cost effectiveness in the subscales of pain, stiffness and functioning.

Conclusion: There are few studies that have compared the cost effectiveness of total joint arthroplasty revision procedures. Given the increasing cost of health care expenditures, prioritization of funding for the different health practices will become necessary. This study demonstrates that revision THA and TKA are relatively cost effective procedures compared to other non-orthopaedic interventions.

Introduction: Clinical experience has shown that addressing variations in bone morphology is important in the development of successful hip implant designs. Numerous studies of femoral bone morphology have been published utilizing various techniques. This study has developed a method which consistently measures large quantities of 3-dimensional digital femura geometry segmented from computed tomography (CT) scans and can accurately make anatomical measurements from these images

Methods: CT images of left femora on five hundred fifty six left femura (57% male, 43% female), consisting of 69% Caucasian, 16% Asian and 14% unknown were analyzed. The average age was 66 years, ranging from 40 to 93 years. Segmentation of the outer cortical, inner cortical, and marrow boundaries were consistently performed over all CT scans. The positions identified on the reference bone are transformed to the equivalent position on the clinical bone images, from which the dimensional data is extracted and stored. The mediolateral width (MLW), medial offset (MO) and lateral offset (LO) were measured in 10mm increments, ranging from 20mm above the lesser trochanter (LT) to 130mm below the lesser trochanter. The canal flare index was defined as a ratio of the mediolateral width at a section 20mm above the lesser trochanter to the mediolateral width at the isthmus level.

Results: The mean mediolateral width at 20mm above the lesser trochanter was 47.0 ± 4.5 (35.1–61.8; n=556). Noble reported 45.4 ± 5.3 (31.0–60.0; n=200), Husmann reported in a neck oriented study 46.3 ± 6.9 (27.6–63.6; n=310) and Laine reported 47.1 ± 4.9 (n=50). The mean medial offset at a section 20mm above the lesser trochanter was 25.1 ± 2.9 (16.7–33.4). In the study by Husmann, a mean of 25.0 ± 5.2 (9.4–45.5) was reported. The mean canal flare index was 4.49 ±.8. Noble reported a mean canal flare index of 3.80 ±.074, Husmann 3.81 ±.83 and Laine 4.3 ±.93.

Discussion: In general, the study showed minor differences to published data of proximal bone morphology. However, this more powerful study has shown that there is a higher mean canal flare index than determined by Noble and a similar mean canal flare index as determined by Laine. As reported by Laine, the canal flare index varies significantly with the placement of measurements in the canal. In this study the measurements were performed in a plane oriented by the femoral neck as a hip stem would be placed. The CFI over the isthmus width showed a greater correlation than previously shown by Noble. The novel software tool allows for anatomical measurements that can be applied to an unlimited population size enabling further applications and studies.

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.

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.

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

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.

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.

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.

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.

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.

Introduction: Pulmonary embolism (PE) is a potentially fatal complication of total joint arthroplasty (TJA). Therefore, reliable means for diagnosis and evaluation of severity is essential. This study evaluates the reliability of common clinical signs and symptoms in the diagnosis of PE. In addition, clinical presentation is correlated with size and location of emboli within the pulmonary vasculature (segmental, lobar, or main).

Methods: The clinical and imaging records of all patients with confirmed diagnosis of PE following TJA performed between 2000 and 2004 were reviewed in detail. The mode of presentation and the subsequent imaging findings were noted.

Results: A total of 132 confirmed PE cases were studied. Clinical presentation included dyspnea (19.7%), chest pain (7.6%), change of mental status (6.8%0, hypotension (6.1%), and diaphoresis (3.8%). Mean room air pulse-oximetry was 85.5%. Arterial sampling showed mean O2 saturation of 88.1% and pO2 of 58.7. There was not a direct correlation between the size of the PE and the clinical presentation. However, there was a correlation between the severity of oxygen desaturation and the size and location of the embolus.

Conclusions: The presentation of PE can be non-specific and highly variable ranging from mild dyspnea to catastrophic hemodynamic collapse. Common clinical signs have a low sensitivity for diagnosis and do not correlate with severity of disease. The only correlation seemed to be measured arterial O2 saturation and pressure. Thresholds for the diagnosis of clinically significant pulmonary embolisms need to be established to improve management of this important condition.

Introduction: The use of coumadin for prophylaxis against thromboembolism (TE) following total joint arthroplasty is the standard of care. In light of recent publication of the American College of Chest Physicians (ACCP), we altered our anticoagulation protocol to be compliant with the recommendations. This study evaluates the incidence of TE and bleeding complications following TJA when low dose coumadin vs. regular dose coumadin was administered.

Methods: 987 consecutive patients undergoing total joint arthroplasty by a single surgeon between the years of 2004–2005 were included. 446 patients operated on during the 2004 received low dose coumadin (intended INR 1.5–1.7) whilst 541 patients undergoing TJA during 2005 were given regular dose coumadin (intended INR 2–2.5).

Results: The mean INR for patients operated during the year 2005 was significantly higher than the INR for patients receiving TJA in 2004. There were more complications in 2005. There were 13 PE, 44 wound drainage, 4 DVT, and 11 hematoma formation (requiring surgical evacuation) during the year 2005 compared to 10 PE, 26 wound drainage, 6 DVT, and 5 hematoma formation in 2004. The difference for all complications except DVT was significant.

Conclusion: This study confirms the commonly held belief that aggressive anticoagulation does carry a higher incidence of complications such as wound drainage and bleeding. It appears that administering higher dose coumadin increased the bleeding complications without conferring additional protection against thromboembolic disease.

Background: Vascular injuries associated with total joint arthroplasty are the most feared complication. The arterial and venous injury can occur due to direct or indirect trauma. A high index of suspicion, recognition of the injury and prompt treatment, with the immediate availability of a vascular surgeon is vital for good outcome.

Methods: Using prospectively collected data on 13624 patients undergoing total joint arthroplasty at our institution, all incidences of vascular injury were identified. Detailed data regarding the mode of presentation, the type and the outcome of intervention delivered, and the eventual functional outcome of the total joint arthroplasty were determined.

Results: There were a total of 17 vascular injuries (0.1%). Majority (16/17) of these vascular injuries were detected in the postoperative recovery area. 9 injuries occurred after TKA and 8 occurred after THA. Indirect injury was the mechanism in TKA patients with popliteal artery thrombosis being the mechanism. In contrast direct injury was the mechanism in THA patients. Fasciotomy was performed in all TKA patients and none were needed in the THA patients. One patient died of complications related to vascular injury. 12 of 17 patients (70%) had launched a legal suit against the operating surgeon.

Conclusions: After more than 80 years of accumulated experience and more than 35000 joint replacements performed by 5 surgeons in our center, the vascular complication still continues to occur. Patient awareness regarding this real problem may play a role in defraying the extremely high likelihood of legal suits associated with this complication.

INTRODUCTION: We have previously demonstrated the efficacy of a modified Ti-surface tethered with antibiotics in preventing bacterial colonization. It is not known if coverage of this surface with serum or other physiological material may hinder the bactericidal properties of such a surface.. The in vitro activity and efficacy of such a surface against S. aureus and S. epidermidis was tested following coverage of the surface with serum.

METHODS: Vancomycin was coupled to Ti6Al4V pins by aminopropylation, linker addition, and vancomycin coupling (VancTi). Bactericidal activity was tested in solutions of bacteria (Ci=1×104cfu/ml) incubated with pins±pre-incubation with fetal bovine serum (FBS). Anti fibronectin and anti-vancomycin antibodies were used to detect surface coating or modification. Bacteria were detected by fluorescent labeling (Syto9) or by direct counting after solubilization.

RESULTS: By immunofluorescence, pins were extensively covered with serum fibronectin which did not interfere with the diffuse, intense vancomycin staining. When incubated with S. epidermidis or S. aureus, VancTi showed little colonization compared to control pins (> 95% reduction in cfu).

DISCUSSION: In a physiological environment, implants will be coated with serum proteins. Activity of the VancTi was unaffected by this coating and maintained potent inhibition of bacterial colonization. We have described a surface modification that allows Ti implants to resist colonization and subsequent periprosthetic infection. Such surfaces hold great promise for the prevention and treatment of periprosthetic infections.

Introduction: Many patients with DJD of the hip may have co-existent spinal arthritis. This prospective study sought to determine: how hip arthritis commonly presents, the incidence of low back pain- as identified by patients- before and after THA and the correlation between LBP and hip arthritis.

Methods: 344 consecutive patients undergoing THA were recruited prospectively at a single institution. A detailed questionnaire containing diagrams on which the patient could draw out the site of their pain was administered to all patients preoperatively and postoperatively. Detailed clinical, radiographic, and cross sectional imaging of all the patients were reviewed in detail by a hip surgeon, a spine surgeon, and a neurologist.

Results: 170 patients (49.4%) had true LBP which resolved in 63 patients (37%). Of the remaining 107 patients the back pain was of the same intensity following THA in 33 patients (30%) and had decreased in 74 (70%) patients. 22 of the 33 patients with continued LBP were known to have spine pathology. 35 patients developed LBP after THA.18 patients in the latter group were investigated further and 12 were found to have severe previously unrecognized spine pathology.

Discussion: Hip and spine arthritis often co-exist. Majority of patients with ‘back’ pain experience a complete resolution of their pain following THA so long as prior spine pathology did not exist. THA seems to be beneficial in reducing the symptoms even for those with a pre-existent LBP and spine pathology. A number of patients may develop LBP following THA that may relate to unidentified spine pathology. Patients with true LBP may benefit form evaluation of their spine prior to THA.

Introduction: The potential benefits of Minimally invasive total hip arthroplasty (MIS THA) continues to be heavily debated. We hypothesized that the potential benefits of MIS THA may relate to factors such as patient selection, patient preconditioning, improvements in anesthesia technique, pain management, and not the incision size. This randomized, prospective study was designed to investigate the role of these confounding factors in general and aggressive rehabilitation in particular on the outcome of THA.

Methods: 100 patients undergoing THA at our institution were randomized into one of four groups. Group A was patients who had standard THA (incision length> 10 cm) and received standard preoperative and postoperative care. Group B patients had THA using small incision (< 10 cm) and standard protocols. Group C patients had regular incision THA, but received aggressive rehabilitation and pain control regimen. Group D patients had THA through small incision and received aggressive regimen.

Results: The demographic distribution amongst all the groups was similar. There was a significant improvement in function as measured by Harris Hip Score, LASA (validated rehabilitation score), SF-36, and lower extremity function test in all groups. The extent of functional improvement, home discharge, patient satisfaction, and analgesia requirement was better in patients who received aggressive preoperative and postoperative care regimen regardless of the size of their incision. There was no difference in estimated blood loss, mean operative time, transfusion needs, and complications between the groups.

Discussion: This study highlights the importance of family education, patient conditioning, pre-emptive analgesia, and aggressive preoperative and postoperative rehabilitation in influencing the outcome of THA. The aforementioned factors, and perhaps not the surgical technique per se, may play a major role in imparting advantageous outcome to MIS THA that is reported by various investigators.

Purpose: Periprosthetic infection (PPI) is a devastating complication. Surgical intervention to treat PPI is often required. The objective of this prospective study is to determine if there is any difference in functional improvement following revision TKA in patients with infected and non-infected failures.

Methods: 123 consecutive patients undergoing revision TKA at our institution were prospectively recruited into this study. The indication for revision TKA was PPI in 37 cases and aseptic failure in 86 cases. Detailed patient demographics and functional outcome using SF-36, KSS, Womac, lower extremity functional outcome score were collected at base line and at various time points after revision TKA. The baseline and two year follow up functional scores were calculated and compared. The functional score at the time of diagnosis of PPI (prosthesis in place) were used for baseline comparisons

Results: All baseline functional scores, and their individual elements, for the infected cases were worse than the non-infected cases. The functional scores at the two-year follow-up were not different between the infected and non-infected cases. Hence, there was a more impressive improvement (Δ) in functional outcome for the infected cases following revision TKA compared to non-infected cases. However, the general health perception as determined by the patients themselves appeared to deteriorate after revision TKA in both groups.

Discussion: It appears that patients with PPI are markedly more disabled at base line than the non-infected cases. These patients, however, benefit the most from surgical intervention compared to the non-infected cases. It appears that the patients’ perception of improvement in functional scores is less optimistic than physician measured parameters.

Introduction: Intraoperative tissue culture remains the “gold standard” in diagnosing periprosthetic infection (PPI). However, an organism is not always cultured and this has been attributed to the fact that preoperative antibiotics were administered. This study intends to examine if preoperative antibiotics prevent isolation of intraoperative organisms.

Methods: 91 total joint arthroplasty patients diagnosed with PPI during (1999–2005) and who had positive aspiration culture were included in the study. All intravenous antibiotics that were given to the patient within seven days of surgery were documented. The total number of positive intraoperative fluid and tissue samples of patients who did and did not receive antibiotics was calculated. Susceptibility of the organism(s) to antibiotics was determined by antibiogram of the preoperative and intraoperative culture.

Results: 60 out of 91 patients received preoperative antibiotics within seven days of surgery. Antibiotics prevented isolation of an intraoperative organism in 6 out of the 60 (10%) cases. All of the 31 patients who did not receive any preoperative antibiotics had positive intraoperative cultures. Chi-square analysis revealed no significant difference between giving preoperative antibiotics within 7 days and isolating an intraoperative organism (p=0.068). Giving antibiotics that specifically targets the culprit organism did not significantly affect the fluid (p=0.585) or tissue culture yield (p=0.152) either.

Discussion: Although, giving preoperative antibiotics can prevent isolation of intraoperative organisms in 10% of cases, this is not statistically or clinically significant in patients with positive aspiration cultures because the organism is known beforehand. However, it is clinically and medicolegally relevant to withhold antibiotics in patients with negative aspiration cultures since the postoperative treatment antibiotic is tailored according to the organism cultured.

INTRODUCTION: Range of motion following TKA is a commonly assessed and important outcome parameter. The reported knee ROM is often measured using manual goniometers. The accuracy of goniometer in measuring ROM of the knee is not known. We compared the knee ROM measured with a manual goniometer and compared that to measurements obtained from computer assisted navigation system.

METHODS: This prospective ongoing study has so far recruited 60 patients (71 knees) undergoing TKA by a single surgeon. Measurements of the ROM were performed intraoperatively using a 14 inch 360° Nexgen Baseline® goniometer, validated by physical therapists, and the Stryker knee navigation system^™. Consistent anatomical landmarks were used to obtain flexion and extension measurements. Each goniometer and navigation measurement was performed twice by the same reader.

RESULTS: Goniometer was more inaccurate in measuring the knee ROM than the navigation. There was a 5.07° difference between two measurements obtained with the goniometer compared to a mean discrepancy of 1.15° using the navigation system. Further, the ROM measured by navigation was on average 13.9° larger than that measured by the goniometer. BMI affected the ROM recording obtained by both the goniometer and the navigation system.

DISCUSSION AND CONCLUSION: This study indicates that goniometer is not an accurate tool for measurements of knee ROM as there is a marked discrepancy between two goniometer readings. The navigation system seemed to produce more consistent, but markedly higher, readings than a manual goniometer. Reported results on knee ROM in the literature need to be interpreted with caution and scrutinized for potential inaccuracy of the measuring tool.

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.

Methods: A computerized 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 randomized, prospective studies reporting the outcome of BTKA were included. Details of any reported data were extracted and extensive analysis of relevant variables carried out.

Results: 150 published articles pertaining to BTKA were identified of which 18 papers on 27,807 patients (44,684 knees) were included in the meta-analysis.10,734 cases were unilateral TKA, 16,378 were simultaneous BTKA and 458 were staged bilateral TKA with at least 3 months time duration between the surgical procedures. The complications analyzed were DVT, PE, cardiac events and mortality. The incidence of PE (OR=1.8), cardiac complications (OR=2.4), and mortality (OR=2.24) were higher after simultaneous BTKA. The incidence of DVT was LOWER in the group with simultaneous BTKA.

Discussion: Based on the findings of this meta-analysis, simultanous BTKA seems to carry a higher risk of serious cardiac complications, pulmonary complications, and mortality. This procedure should be reserved for the healthy and young patients.

Introduction: A small, yet not uncommon, problem following total joint arthroplasty (TJA) is post-operative ileus (POI). The purpose of this study was two-fold. First the study sought to determine the incidence of POI after TJA in a consecutive series of patients receiving regional anesthesia and an aggressive postoperative rehabilitation protocol. Second, the influence of narcotic medications, including intrathecal medications, in the incidence of POI was examined.

Methods: 5,262 patients underwent total joint replacements, including primary and revision surgery, at our institution from 2004 to 2005. All surgeries were performed at a university-affiliated institution where complications, if any, are prospectively recorded in a comprehensive database. Demographic, clinical, surgical, and radiographic details were obtained and examined.

Results: 26 (0.5%) patients developed ileus. There were 17 males and 9 female patients, who had a mean age of 67.7 years (range, 52.7 to 91.2 years). The mean BMI was 30.2 kg/m2. The index procedures included 15 primary hip, 4 primary knee, 4 revision hip, and 3 revision knee procedures. Of the patients who developed ileus, intrathecal narcotics were administered in 16 patients (62%).

Discussion: There is a very low incidence of postoperative ileus and gastrointenstinal hypomobility following joint arthroplasty. Early patient ambulation, a reduction in the use of postoperative narcotics, supplementation of analgesia with non-narcotic drugs, and reduced length of hospital stay may all have an important role in reducing this complication. Based on our findings, it seems unlikely that intrathecal narcotics have an adverse effect on gastrointestinal motility.

Introduction: Diabetes mellitus type 2 (DM II) affects 18.2 million Americans and can cause several chronic and morbid complications. Furthermore, 90% of Americans have radiographic evidence of osteoarthritis by age 40. Diabetes may be an important risk factor for symptomatic osteoarthritis later in life. The aim of our study is to determine if diabetic patients are predisposed to osteoarthritis.

Methods: We conducted a review of the all total knee arthroplasty (TKA) cases performed at our institute during the past two years for end stage osteoarthritis. We excluded TKAs performed for post-traumatic arthritis and patients with inflammatory diseases. Comorbidities and demographical information including age, gender, BMI, and family history were collected from our database. A cross sectional study was performed to analyze the prevalence of DM II in our population. This prevalence was compared to that of diabetics in the general population available from various sources including the National Center for Health Statistics.

Results: Our cohort included a total of 3421 patients (1972 females, 1449 males) who had undergone TKA for end stage osteoarthritis. The average age and BMI were 66 years (range: 39–92) and 32 (range: 21–65) respectively. The prevalence of diabetes mellitus type 2 in our cohort was 12%, while the prevalence of DM II in the general US population currently ranges from 6%–7%.

Discussion: Chronic diabetes causes multiorgan failure via microvascular and macrovascular damage and may possibly lead to degeneration of articular cartilage and eventual arthritis. Based on this study, diabetes appears to be a strong predisposing factor for arthritis. Our laboratory has launched an extensive series of experiments delinating the potential cellular mechanism for such association.

Introduction: We have previously described modification of Ti that renders the implant surface bactericidal and prevents bacterial colonization in vitro. This study evaluates the efficacy of the same surface in preventing periprosthetic infection in a small mammal model.

Methods: Control or VancTi rods were incubated with S. aureus (Ci=104CFU/mL) in TSB containing 0, 5×10-3, 4, or 100 μg/mL vancomycin at 37°C for 24h. Bacteria were detected by fluorescence (Live/Dead BacLight) and imaged by confocal microscopy. Resistance was tested by incubating control or VancTi rods with S. aureus for 0–8 weeks. Adherent bacteria were tested every 7 days on vancomycin screening agar (6μg/mL).

Results: Using a percutanous approach, the intercondylar region of the knee in rats were identified. The intrameduallry canal of the femur was retrograde reamed using an 18-gauge needle. Infection was induced by injection of 103 CFU S. aureus in 150uL of saline into the femoral canal followed by insertion of a 20 mm Ti implant. Animals were harvested at various time points. At harvest, animals were euthanized with CO2.. Detailed analysis including radiographic, micro-CT, histological, bacteriological, and clinical evaluation was performed.

Results: All animals showed signs of infection within the first few post-operative days with increased soft tissue swelling and limited mobility. At 1 week 75% of the animals showed radiographic signs of periprosthetic infection including periosteal reaction, abscess formation, widened canal, bone destruction, and formation of involucrum. PPI could be prevented in 92% of cases when modified Ti-Van was used. In one animal despite the use of antibiotic-tethered implant, PPI occurred partially due to the pin insertion penetrating the bone cortex.

Discussion: Biologically modified implants with bactericidal surface can have a promising role in management of periprosthetic infection. The modified implant described herein contains a nanoscale surface of covalently linked antibiotics that can potentially confer bactericidal properties throughout the life of the implant