The Infected Polypropylene Mesh: When Does Biofilm Form and Which Antiseptic Solution Most Effectively Removes It?

BACKGROUND

Polypropylene (PPE) mesh is commonly utilized to reconstruct catastrophic extensor mechanism disruptions in revision total knee arthroplasty. Unfortunately, these procedures are associated with a high rate of periprosthetic joint infection. The purpose of the current study was to: 1) visualize and quantify the progression of bacterial biofilm growth on PPE-mesh; and 2) determine which antiseptic solutions effectively remove viable bacteria.

METHODS

Knitted PPE mesh samples were cultured with either methicillin-sensitive Staphylococcus aureus (MSSA) or Escherichia coli (E. coli) for 7 days, with regular quantification of colony forming units (CFUs) and visualization using scanning electron microscopy to identify maturity. Immature (24 hour) and mature (72 hour) biofilm was treated with one of 5 commercial antiseptics for 3 minutes. A 0.05% chlorhexidine gluconate, a surfactant-based formulation of ethanol, acetic acid, sodium acetate, benzalkonium chloride, diluted povidone-iodine (0.35%), undiluted (10%) povidone-iodine, and 1:1 combination of 10% povidone-iodine and 3% hydrogen peroxide. A 3-log reduction in CFUs compared to saline was considered clinically meaningful.

RESULTS

The CFU counts plateaued, indicating maturity, at 72 hours for both MSSA and E. coli. The scanning electron microscopy confirmed confluent biofilm formation after 72 hours. The 10% povidone-iodine was clinically effective against all MSSA biofilms and immature E. coli biofilms. The 10% povidone-iodine with hydrogen peroxide was effective in all conditions. Only 10% povidone iodine formulations produced significantly (P < .0083) reduced CFU counts against mature biofilms.

CONCLUSIONS

Bacteria rapidly form biofilm on PPE mesh. Mesh contamination can be catastrophic, and clinicians should consider utilizing an antiseptic solution at the conclusion of mesh implantation. Undiluted povidone-iodine with hydrogen peroxide should be considered when attempting to salvage infected PPE mesh.

Perioperative Cefazolin for Total Joint Arthroplasty Patients Who Have a Penicillin Allergy: Is It Safe?

BACKGROUND

Cefazolin is the standard of care for perioperative antibiotic prophylaxis in total joint arthroplasty (TJA) in the United States. The potential allergic cross-reactivity between cefazolin and penicillin causes uncertainty regarding optimal antibiotic choice in patients who have a reported penicillin allergy (rPCNA). The purpose of this study was to determine the safety of perioperative cefazolin in PCNA patients undergoing primary TJA.

METHODS

We identified all patients (n = 49,842) undergoing primary total hip arthroplasty (n = 25,659) or total knee arthroplasty (n = 24,183) from 2016 to 2022 who received perioperative intravenous antibiotic prophylaxis. Patients who had an rPCNA (n = 5,508) who received cefazolin (n = 4,938, 89.7%) were compared to rPCNA patients who did not (n = 570, 10.3%), and to patients who did not have an rPCNA (n = 43,359). The primary outcome was the rate of allergic reactions within 72 hours postoperatively. Secondary outcomes included the rates of superficial infections, deep infections, and Clostridioides difficile infections within 90 days.

RESULTS

The rate of allergic reactions was 0.1% (n = 5) in rPCNA patients who received cefazolin, compared to 0.2% (n = 1) in rPCNA patients who did not (P = .48) and 0.02% (n = 11) in patients who have no rPCNA (P = .02). Allergic reactions were mild in all 5 rPCNA patients who received cefazolin and were characterized by cutaneous symptoms (n = 4) or dyspnea in the absence of respiratory distress (n = 1) that resolved promptly with antibiotic discontinuation and administration of antihistamines and/or corticosteroids. We observed no differences in the rates of superficial infections (0.1 versus 0.2%, P = .58), deep infections (0.3 versus 0.4%, P = .68), or C difficile infections (0.04% versus 0%, P = .99) within 90 days in rPCNA patients who received cefazolin versus alternative perioperative antibiotics.

CONCLUSIONS

In this series of more than 5,500 patients who had an rPCNA undergoing primary TJA, perioperative prophylaxis with cefazolin resulted in a 0.1% incidence of allergic reactions that were clinically indolent. Cefazolin can be safely administered to most patients, independent of rPCNA severity.

LEVEL OF EVIDENCE

III.

Robotics and Navigation Do Not Affect the Risk of Periprosthetic Joint Infection Following Primary Total Hip Arthroplasty: A Propensity Score-Matched Cohort Analysis

BACKGROUND

The use of computer navigation or robotic assistance during primary total hip arthroplasty (THA) has yielded numerous benefits due to more accurate component positioning. The utilization of these tools is generally associated with longer operative times and also necessitates additional surgical equipment and personnel in the operating room. Thus, the aim of this study was to evaluate the impact of technology assistance on periprosthetic joint infection (PJI) after primary THA.

METHODS

We retrospectively reviewed the records for 12,726 patients who had undergone primary THA at a single high-volume institution between 2018 and 2021. Patients were stratified by surgical technique (conventional THA, computer-navigated THA [CN-THA], or robotic-assisted THA [RA-THA]) and were matched 1:1 with use of propensity score matching. Univariate and logistic regression analyses were performed to compare the rates of PJI within 90 days postoperatively between the cohorts.

RESULTS

After propensity score matching, there were 4,006 patients in the THA versus RA-THA analysis (2,003 in each group) and 5,288 patients in the THA versus CN-THA analysis (2,644 in each group). CN-THA (p < 0.001) and RA-THA (p < 0.001) were associated with longer operative times compared with conventional THA by 3 and 11 minutes, respectively. The rates of PJI after conventional THA (0.2% to 0.4%) were similar to those after CN-THA (0.4%) and RA-THA (0.4%). On the basis of logistic regression, the development of PJI was not associated with the use of computer navigation (odds ratio [OR], 1.8 [95% confidence interval (CI), 0.7 to 5.3]; p = 0.232) or robotic assistance (OR, 0.9 [95% CI, 0.3 to 2.3]; p = 0.808).

CONCLUSIONS

Despite longer operative times associated with the use of computer navigation and robotic assistance, the use of these tools was not associated with an increased risk of PJI within 90 days after surgery.

LEVEL OF EVIDENCE

Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.

When to lavage in the absence of a sonographically visible joint effusion in painful total knee arthroplasty: a retrospective longitudinal study

OBJECTIVE

To determine if knee arthroplasty without sonographically visible effusion needs to undergo lavage to rule out infection.

METHODS

Patients were accrued by a retrospective search of a longitudinally maintained radiology database looking for patients referred for ultrasound guided aspiration of suspected TKA infection. Clinical presentations, laboratory tests, intraoperative findings, and follow-up were reviewed.

RESULTS

Four hundred sixty-nine patients were included (mean age of 67 years (range, 36-91)) including 251 females. Four hundred three patients had effusions, of which 57 were infected based on ultrasound-guided and surgical aspirates. Sixty-four patients lacked effusions, of which 47 underwent lavage at the clinicians' request, with 6/47 infected. Nineteen patients without effusion were not lavaged at the clinicians' request due to low suspicion, and none were infected. Patients with positive lavage cultures all had clinical risk factors. Infection rates were significantly higher in patients with joint effusion and clinical suspicion for infection compared to absent joint effusion and absent clinical suspicion. A significantly higher proportion of patients with hyperemia or moderate-severe synovial thickening on ultrasound were symptomatic and had joint effusion and positive joint cultures. Aspiration of native fluid had 85% sensitivity and 100% specificity while lavage had a sensitivity of 57% and specificity of 100%. Negative predictive value for native aspirates was 94% compared to 86% for lavage.

CONCLUSION

A TKA with low clinical suspicion of infection does not need to undergo lavage in the absence of a sonographically visible effusion.

Outcomes after débridement, antibiotics, and implant retention for prosthetic joint infection in shoulder arthroplasty

BACKGROUND

Patients who undergo total shoulder arthroplasty usually have excellent long-term outcomes. However, a subset of patients is diagnosed with a prosthetic joint infection (PJI) requiring revision procedures and prolonged recovery. The purpose of this study was to evaluate rates of recurrent shoulder PJI in patients undergoing débridement, antibiotics, and implant retention (DAIR), single-stage revision, and 2-stage revision. We also sought to compare outcomes and complications across procedures.

METHODS

Retrospective chart review was conducted for patients diagnosed with PJI after primary shoulder arthroplasty between January 2010 and August 2021. Patients were included if they underwent treatment with DAIR, single-stage revision, or 2-stage revision. Demographic information, surgical details, complications, laboratory data, postoperative antibiotic regimen, and infectious pathogen were collected. Postoperative patient-reported outcomes were collected: American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form, Single Assessment Numeric Evaluation, Shoulder Activity Scale, and PROMIS Upper Extremity. Chi-square, t test, and 1-way analysis of variance were used as appropriate to evaluate each factor.

RESULTS

Sixty-five patients were included in the study, 26% treated with DAIR, 9% treated with single-stage revision, and 65% treated with 2-stage revision. There were no significant differences in patient comorbidities. Patients undergoing DAIR were diagnosed significantly earlier than those undergoing single- and 2-stage revision procedures (12.6 ± 22.9 months vs. 49.6 ± 48.4 vs. 25.0 ± 26.6, P = .010). Recurrent PJI was noted in 23.1% of patients: 29.4% of DAIR patients, no single-stage patients, and 23.8% of 2-stage patients (P = .330). Patients undergoing 2-stage revision with treatment failure had a significantly higher Elixhauser Comorbidity Index (0.2 ± 3.7 vs. 3.7 ± 3.9, P = .027). There was no significant difference in patient-reported outcomes across groups.

CONCLUSION

Patients undergoing treatment of shoulder PJI with DAIR did not have an increased rate of reinfection compared with single-stage and 2-stage revision procedures. Patients treated with DAIR were diagnosed with PJI significantly earlier than those undergoing single-stage and 2-stage revision procedures. There was no difference in complication rates between groups. This information adds to the body of work detailing outcomes after DAIR for shoulder PJI and provides encouraging data for use in this patient population. Future studies with a larger sample size may be conducted to further investigate specific pathogens, infection timelines, and antibiotic regimens that reduce the risk of treatment failure.

Does Computer Navigation or Robotic Assistance Affect the Risk of Periprosthetic Joint Infection in Primary Total Knee Arthroplasty? A Propensity Score-Matched Cohort Analysis

BACKGROUND

The use of technology during total knee arthroplasty (TKA) has been associated with more accurate component position and less blood loss. Yet to date, the risk of developing prosthetic joint infection (PJI) associated with computer navigation (CN) or robotic assistance (RA) has not been thoroughly evaluated. This study used propensity score-matching (PSM) in a large cohort of primary TKA patients to compare the rate of PJI following conventional TKA (TKA) versus CN-TKA and RA-TKA.

METHODS

We retrospectively reviewed 13,015 knees in 11,727 patients who underwent primary TKA at a single institution from 2018 to 2021. The cohort was stratified into TKA, CN-TKA, and RA-TKA groups. 1:1 PSM was applied to 11,834 patients. Propensity score-matching was performed using logistic regression accounting for age, sex, body mass index, Charlson Comorbidity Index (CCI) score, CCI components, and smoking status. Univariate and multivariable analyses were performed to evaluate differences in surgical time and PJI rate.

RESULTS

Significantly longer median operating times were noted in the RA-TKA group (14 minutes) compared to TKA (P < .001). The PJI rates among matched cohorts were similar among RA-TKA (0.3%), CN-TKA (0.3%), and conventional TKA (0.5%). Multivariable logistic regressions demonstrated that the use of robotic assistance (odds ratio (OR) = 0.5, P = .423) or computer navigation (OR = 0.61, P = .128) was not associated with increased risk of PJI when compared to conventional TKA.

CONCLUSIONS

Use of computer navigation and robotic assistance during primary TKA are associated with longer surgical times, but no difference in PJI frequency within 90 days of surgery.

Development of Diagnostic Quality Metrics for Prosthetic Joint Infection

ABSTRACT

Although well-accepted clinical practice guidelines exist for the diagnosis of prosthetic joint infection (PJI), little is known about the quality of diagnosis for PJI. The identification of quality gaps in the diagnosis of PJI would facilitate the development of care structures and processes to shorten time to diagnosis and reduce the significant morbidity, mortality, and economic burden associated with this condition. Hence, we sought to develop valid clinical quality measures to improve the timeliness and accuracy of PJI diagnosis. We convened a nine-member multidisciplinary national panel of PJI experts including orthopedic surgeons, infectious disease specialists, an emergency medicine physician, and a patient previously treated for PJI to review, discuss, and rate the validity of proposed measures using a modification of the RAND-UCLA appropriateness method. In total, 57 permutations of six proposed measures were rated. Populations considered to be at high enough risk for PJI that certain care processes should always be performed were identified by the panel. Among the proposed quality measures, the panel rated five as valid. These novel clinical quality measures could provide insight into care gaps in the diagnosis of PJI.

Clinical and Biomechanical Characteristics of Posterior-Stabilized Polyethylene Post Fractures in Total Knee Arthroplasty: A Retrieval Analysis

BACKGROUND

Fractures of the polyethylene post are a rare but known complication after posterior-stabilized (PS) total knee arthroplasty (TKA). We evaluated the polyethylene and patient characteristics for 33 primary PS polyethylene components that were revised with fractured posts.

METHODS

We identified 33 PS inserts revised between 2015 and 2022. Patient characteristics collected included age at index TKA, sex, body mass index, length of implantation (LOI), and patient-reported details on events surrounding the post fracture. Implant characteristics recorded were manufacturer, cross-linking properties (highly cross-linked polyethylene [XLPE] versus ultra-high molecular weight polyethylene [UHMWPE]), wear characteristics based on subjective scoring of the articular surfaces and scanning electron microscopy (SEM) of fracture surfaces. Mean age at index surgery was 55 years (range, 35 to 69), mean body mass index was 29.5 (range, 18.5 to 37.2), and mean LOI was 10.0 (range, 4 to 26).

RESULTS

Total surface damage scores were significantly higher in the UHMWPE group versus the XLPE group (57.3 versus 44.2, P = .003). SEM demonstrated fracture initiation at the posterior edge of the post in 10 of 13 cases. UHMWPE fracture surfaces posts had more tufted, irregularly clamshell features, while XLPE posts had more precise clamshell marking and a diamond pattern in the region of acute, final fracture.

CONCLUSION

Characteristics of PS post fracture differed between XLPE and UHMWPE implants, with fractures occurring in the XLPE with less generalized surface damage, after a shorter LOI, and with SEM evaluation indicative of a more brittle fracture pattern.

No Difference in the Rate of Periprosthetic Joint Infection in Patients Undergoing the Posterolateral Compared to the Direct Anterior Approach

BACKGROUND

There remains inconsistent data about the association of surgical approach and periprosthetic joint infection (PJI). We sought to evaluate the risk of reoperation for superficial infection and PJI after primary total hip arthroplasty (THA) in a multivariate model.

METHODS

We reviewed 16,500 primary THAs, collecting data on surgical approach and all reoperations within 1 year for superficial infection (n = 36) or PJI (n = 70). Considering superficial infection and PJI separately, we used Kaplan-Meier survivorship to assess survival free from reoperation and a Cox Proportional Hazards multivariate models to assess risk factors for reoperation.

RESULTS

Between direct anterior approach (DAA) (N = 3,351) and PLA (N = 13,149) cohorts, rates of superficial infection (0.4 versus 0.2%) and PJI (0.3 versus 0.5%) were low and survivorship free from reoperation for superficial infection (99.6 versus 99.8%) and PJI (99.4 versus 99.7%) were excellent at both 1 and 2 years. The risk of developing superficial infection increased with high body mass index (BMI) (hazard ratio [HR] = 1.1 per unit increase, P = .003), DAA (HR = 2.7, P = .01), and smoking status (HR = 2.9, P = .03). The risk of developing PJI increased with the high BMI (HR = 1.04, P = .03), but not surgical approach (HR = 0.68, P = .3).

CONCLUSION

In this study of 16,500 primary THAs, DAA was independently associated with an elevated risk of superficial infection reoperation compared to the PLA, but there was no association between surgical approach and PJI. An elevated patient BMI was the strongest risk factor for superficial infection and PJI in our cohort.

LEVEL OF EVIDENCE

III, retrospective cohort study.

Which Combination is Best? A Comparison of the Predictive Potential of Serum Biomarker Combinations to Diagnose Periprosthetic Joint Infection

BACKGROUND

Without a gold standard test, recent periprosthetic joint infections (PJI) literature has explored the utility of combining serological results, with promising findings. However, previous studies evaluated fewer than 200 patients and often studied only 1 to 2 test combinations. The purpose of this study was to accumulate a large single institution cohort of revision total joint arthroplasty (rTJA) patients to determine the diagnostic utility of combination serum biomarkers to identify PJI.

METHODS

A single institution longitudinal database was assessed to identify all patients who underwent rTJA from 2017 to 2020. There were 1,363 rTJA patients (715 rTKA patients and 648 rTHA patients) including 273 PJI cases (20%) analyzed. The PJI was diagnosed post-rTJA utilizing 2011 Musculoskeletal Infection Society (MSIS) criteria. Erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), D-dimer, and interleukin 6 (IL-6) were systematically collected for all patients.

RESULTS

The rTKA combination markers of CRP+ESR (sensitivity: 78.3%, specificity: 88.8%, positive predictive value (PPV): 70.0%, negative predictive value (NPV): 92.5%), CRP+D-dimer (sensitivity: 60.5%, specificity: 92.6%, PPV: 63.4%, NPV: 91.7%), and CRP+IL-6 (sensitivity: 38.5%, specificity: 100.0%, PPV: 100.0%, NPV: 92.9%) all yielded higher specificity than CRP alone (sensitivity: 94.4%, specificity: 75.0%, PPV: 55.5%, NPV: 97.6%). Similarly, the rTHA combination markers of CRP+ESR (sensitivity: 70.1%, specificity: 88.8%, PPV: 58.1%, NPV: 93.1%), CRP+D-dimer (sensitivity: 57.1%, specificity: 90.1%, PPV: 43.2%, NPV: 94.1%), and CRP+IL-6 (sensitivity: 21.4%, specificity: 98.4%, PPV: 60.0%, NPV: 91.7%) all yielded higher specificity than CRP alone (sensitivity: 84.7%, specificity: 77.5%, PPV: 45.4%, NPV: 95.8%).

CONCLUSIONS

Overall, in diagnosing PJI for both rTKA and rTHA, two marker combinations yielded higher specificity, while three marker combinations yielded higher sensitivity compared to CRP alone. However, compared to all two and three marker combinations, CRP demonstrated superior overall diagnostic utility. These findings suggest that routine combination testing of markers for PJI diagnosis may be excessive and an unnecessary use of resources, especially in resource-limited situations.

The Risk Assessment and Prediction Tool (RAPT) Score Predicts Discharge Destination, Length of Stay, and Postoperative Mobility after Total Joint Arthroplasty

INTRODUCTION

Predicting an arthroplasty patient's discharge disposition, length of stay, and physical function is helpful because it allows for preoperative patient optimization, expectation management, and discharge planning. The goal of this study was to evaluate the ability of the Risk Assessment and Prediction Tool (RAPT) score to predict discharge destination, length of stay, and postoperative mobility in patients undergoing primary total knee arthroplasty (TKA) and total hip arthroplasty (THA).

METHODS

Primary unilateral TKAs (n=9,064) and THAs (n=8,649) performed for primary osteoarthritis at our institution from 2018 to 2021 (excluding March to June 2020) were identified using a prospectively maintained institutional registry. We evaluated the associations between preoperative RAPT score and (1) discharge destination, (2) length of stay, and postoperative mobility as measured by (3) successful ambulation on the day of surgery and (4) Activity Measure for Post-Acute Care (AM-PAC) "6-Clicks" score.

RESULTS

On multivariable analyses adjusting for multiple covariates, every one-point increase in RAPT score among TKA patients was associated with a 1.82-fold increased odds of home discharge (P<0.001), 0.22 days shorter length of stay (P<0.001), 1.13-fold increased odds of ambulating on postoperative day 0 (P<0.001), and 0.25-point higher AM-PAC score (P<0.001). Similar findings were seen among THAs. A RAPT score of 8 or higher was the most sensitive and specific cutoff to predict home discharge.

CONCLUSION

Among nearly 18,000 TKA and THA patients, RAPT score was predictive of discharge disposition, length of stay, and postoperative mobility. A RAPT score of 8 or higher was the most sensitive and specific cutoff to predict discharge to home. In contrast to prior studies of the RAPT score which have grouped TKAs and THAs together, this study ran separate analyses for TKAs and THAs and found that THA patients seemed to perform better than TKA patients with equal RAPT scores, suggesting that RAPT may behave differently between TKAs and THAs, particularly in the intermediate risk RAPT range.

Hemostatic Agents in Orthopedic Surgery

Controlling blood loss is a crucial aspect of orthopedic surgery. Hemostatic agents can be used intraoperatively in combination with antifibrinolytics as part of an overall strategy to limit blood loss. Several new hemostatic agents have recently come to the market designed specifically for vascular surgery but have found uses in other surgical fields, including orthopedics. This article reviews the mechanisms of action and best uses of various mechanical hemostats, active hemostats, flowable hemostats, and fibrin sealants for achieving hemostasis in orthopedic surgery. Mechanical and active hemostats have been reported to successfully decrease blood loss from cancellous bone, capillaries, and venules. Flowable hemostats are generally favorable for use in small spaces where the swelling capabilities of mechanical and active hemostats can be detrimental to surrounding structures. Sealants are best used for closing defects in tissues.

Taking a Deeper Dive into Malnutrition and Revision Arthroplasty: When do Nutritionists Get Involved?

BACKGROUND

Perioperative malnutrition is associated with increased complications and mortality following revision total joint arthroplasty (TJA). Nutritional consultations are useful in characterizing patient nutritional status, but are inconsistently utilized post-revision TJA. We sought to describe 1) the prevalence of nutritional consultations post revision TJA, 2) determine if septic revision TJA patients needed consultations more often, and if 3) a diagnosis of 'malnutrition' from the nutritionist conferred increased readmission rates.

METHODS

A retrospective study of 2,697 rTJAs performed in a single institution over a 4-year period was performed. Patient demographics, reasons for revision TJA, occurrences of nutritional consultation (indicated if body mass index (BMI)<20, Malnutrition Screening Tool (MST) score > 2, or poor oral intake postoperatively), specific nutritional diagnosis (according to 2020 Electronic Nutrition Care Process Terminology (eNCPT) and 90-day readmission rates were recorded and analyzed. Rates of consultations and adjusted logistic regressions were calculated.

RESULTS

There were 501 patients (18.6%) who required nutritional consultations, with 55 (11.0%) of these patients receiving a 'malnutrition' diagnosis. Septic rTJA patients required significantly more nutritional consultations (P<0.01) and were significantly more likely to have 'malnutrition' (P=0.49). A diagnosis of malnutrition was associated with highest odds of all-cause readmission (Odds Ratio (OR)=3.89, P=0.01), which was even higher than undergoing a septic revision TJA.

CONCLUSION

Nutritional consultations occur frequently following revision TJA. Patients who receive a diagnosis of 'malnutrition' through consultation are at significantly higher risk for re-admission and require close follow-up. Future efforts are needed to further characterize these patients in order to identify as well as optimize them preoperatively.

Early Femoral Insufficiency Fractures After Primary Total Knee Arthroplasty

Background

Periprosthetic femur fracture following total knee arthroplasty (TKA) is a devastating complication. Although trauma-related periprosthetic femur fractures have been well studied, early atraumatic insufficiency periprosthetic fractures (IPFs) are gaining attention. We present the largest IPF series to date to better understand and prevent this complication.

Methods

A retrospective study of all patients who underwent a revision surgery for periprosthetic fracture within 6 months of primary TKA between 2007 and 2020 was performed. Patient demographics, preoperative radiographs, implant details, and fracture radiographs were reviewed. Alignment measurements and fracture characteristics were assessed.

Results

Sixteen patients met criteria (rate 0.05%), and 11 had posterior-stabilized TKAs. The mean age was 79 years, mean body mass index was 31 kg/m², and 94% (15/16) were female. Seven (47%) patients had a confirmed history of osteoporosis. IPF occurred on average 4 weeks (range, 4 days-13 weeks) after the index TKA. Overall, 12 of 16 (73%) had preoperative valgus deformities, and 11 patients (10 valgus, 1 varus) had preoperative deformities >10 degrees. A characteristic radiographic appearance of femoral condylar impaction and collapse was noted in 12 of 16 cases (75%); 11 of these 12 fractures (92%) involved the unloaded compartment based on preoperative varus/valgus deformity.

Conclusions

Patients who developed IPFs were most commonly elderly, obese women with osteoporosis and severe preoperative valgus deformities. The apparent mechanism of failure was overloading of previously unloaded osteopenic femoral condyle. In high-risk patients, the use of a cruciate-retaining femoral component or a femoral stem for a posterior-stabilized femur may be considered to help avoid this catastrophic complication.

Identifying alternative antibiotics that elute from calcium sulfate beads for treatment of orthopedic infections

There has been increasing interest in the use of a synthetic absorbable calcium sulfate (CaSO₄ ) for local antibiotic delivery in orthopaedic infections. The purpose of this study was to quantify elution kinetics of six antibiotics (amikacin, meropenem, fosfomycin, minocycline, cefazolin, and dalbavancin) from a clinically relevant CaSO₄ bead model and compare elution and antimicrobial activity to the current clinical gold standards: vancomycin and tobramycin. Antibiotic-loaded synthetic CaSO₄ beads were immersed in phosphate buffered saline and incubated at 37°C. Eluent was harvested at eight time points over 28 days. Antibiotic concentrations were measured by high performance liquid chromatography to quantify elution rates. CaSO₄ beads demonstrated burst release kinetics. Dalbavancin, cefazolin, and minocycline all demonstrated similar elution profiles to vancomycin. Amikacin and meropenem demonstrated favorable elution profiles and durations of above-minimum inhibitory concentration when compared to tobramycin. Clinical Significance: This study provides important novel data regarding the utility of amikacin, meropenem and dalbavancin as alternative choices to place in CaSO₄ carriers when treating orthopaedic infections.

Immune Response to Persistent Staphyloccocus Aureus Periprosthetic Joint Infection in a Mouse Tibial Implant Model

Staphyloccocus aureus is one of the major pathogens in orthopedic periprosthetic joint infection (PJI), a devastating complication of total joint arthroplasty that often results in chronic and persistent infections that are refractory to antibiotics and require surgical interventions. Biofilm formation has been extensively investigated as a reason for persistent infection. The cellular composition, activation status, cytokine profile, and role of the immune response during persistent S. aureus PJI are incompletely understood. In this study, we used histology, multiparametric flow cytometry, and gene expression analysis to characterize the immune response in a clinically relevant orthopedic PJI model. We tested the hypothesis that persistent S. aureus infection induces feedback mechanisms that suppress immune cell activation, thereby affecting the course of infection. Surprisingly, persistent infection was characterized by strikingly high cytokine gene expression indicative of robust activation of multiple components of innate and adaptive immunity, along with ongoing severe neutrophil-dominated inflammation, in infected joint and bone tissues. Activation and expansion of draining lymph nodes and a bone marrow stress granulopoiesis reaction were also maintained during late phase infection. In parallel, feedback mechanisms involving T-cell inhibitory receptors and exhaustion markers, suppressive cytokines, and regulatory T cells were activated and associated with decreased T-cell proliferation and tissue infiltration during the persistent phase of infection. These results identify the cellular and molecular components of the mouse immune response to persistent S. aureus PJI and indicate that neutrophil infiltration, inflammatory cytokine responses, and ongoing lymph node and bone marrow reactions are insufficient to clear infection and that immune effector mechanisms are suppressed by feedback inhibitory pathways. These immune-suppressive mechanisms are associated with diminished T-cell proliferation and tissue infiltration and can be targeted as part of adjuvant immunotherapeutic strategies in combination with debridement of biofilm, antibiotics, and other therapeutic modalities to promote eradication of infection. © 2021 American Society for Bone and Mineral Research (ASBMR).

Radiographic assessment of the dynasty biofoam acetabular component with a minimum 2 years follow-up

INTRODUCTION

Acetabular components utilising novel ultraporous metal matrices have been recently introduced into clinical practice with improved interference fit, decreased stress shielding, and hope for more reliable osseointegration. 1 such example is the Dynasty Biofoam cup, which has been in clinical use for over a decade but has few reports documenting its clinical and radiographic performance.

METHODS

A single-centre retrospective study was performed evaluating 96 Dynasty Biofoam acetabular components implanted between March 2010 and August 2014 with minimum 2-year radiographic follow-up. Patients that received components for revision surgery or that had early complications postoperatively (femur fracture, prosthetic infection) were excluded. Biofoam patients were compared to 96 patients that received the Trident PSL acetabular component and were matched for age, gender, and BMI. Patient reported outcomes, component position and radiographic features of cup loosening, including radiolucent lines and sclerosis were compared among groups.

RESULTS

Patient-reported outcomes at 2 years were similar among groups. Cup anteversion was similar but inclination was significantly greater in the Biofoam group (p = 0.006). A significantly greater number of Biofoam components exhibited 2-zone (27.2%) and 3-zone (12.0%) radiolucencies compared to 0% of the Trident shells (p < 0.05). 2 Biofoam cups were revised for aseptic loosening compared to no Trident cups (p = 0.49).

DISCUSSION

Despite adequate implant survivorship, over a quarter of Biofoam cups had 2 or more radiolucent zones in early follow-up. Longer follow-up is needed to determine if the aseptic revision rate for this cup will increase.

255. Utility of Magnetic Resonance Imaging in Predicting Failure of DAIR (Debridement, Antibiotics, and Implant Retention) for Treatment of Periprosthetic Joint Infection

Background

Debridement, antibiotics, and implant retention (DAIR) is commonly utilized to treat acute periprosthetic joint infection (PJI) where thorough debridement of affected tissues is considered essential. Small case series describe occurrences where PJI spreads into adjacent tissues (iliopsoas recess in hips; neurovascular bundle in knees) and bone (osteomyelitis). Surgeons often cite adjacent tissue/bone infiltration as a poor predictor for DAIR. We sought to evaluate if the presence of adjacent tissue/bony lesions on preoperative magnetic resonance imaging (MRI) was associated with poorer DAIR outcomes.

Methods

MSIS criteria-positive hip (n=22) and knee (n=12) PJI cases in our institution from 2010-2020, with preoperative MRI prior to DAIR treatment, were evaluated. Demographics, microbiology, chronicity, and host grade were recorded. MRIs were assessed by two board-certified radiologists blinded to treatment outcomes, scoring images based on the presence of 18 distinct findings. Inter-rater reliability was calculated using bias adjusted Kappa scores. Failure was defined as repeat surgery for PJI. Univariate analysis and logistic regression were used to determine predictors of DAIR success at 90 days and 2 years.

Results

When comparing successful and non-successful hip PJI cases, the presence of a psoas recess fluid collection on MRI was significantly predictive of a higher rate of treatment failure at 2 years (odds ratio=0.12; p = 0.045), with a moderate adjusted kappa score of 0.5. With regard to knee PJI cases, capsular disruption (40% [2/5] vs 100% [7/7], p= 0.046) and patellar tendon disruption (25% [1/4] vs 100% [8/8], p = 0.018) were independently associated with higher 90-day failure. However, knee MRI findings were not predictive of failure using regression.

Conclusion

In this preliminary study, preoperative MRI findings anecdotally linked with PJI treatment failure could be reliably identified. However, few predicted DAIR failure. Further studies are needed to clarify the role of MRI in predicting PJI treatment success.

Disclosures

All Authors: No reported disclosures

239. Sex Differences in Prosthetic Joint Infection

Background

Male sex has been demonstrated to be a non-modifiable risk factor for prosthetic joint infection (PJI) incidence in multiple studies. Given the known anatomical, genetic, and immunological differences between sexes, we compared the clinical characteristics of PJI among men and women.

Methods

A retrospective cohort of total hip and knee arthroplasty PJIs from 2009 to 2019 were identified using a single institution PJI database. Included cases met the 2013 MSIS criteria. Microbiology, acuity (defined by implant age and symptom days), and surgical outcomes were collected. Success was defined as no further PJI surgery at two years. Continuous variables were tested with either Student’s t test or Mann-Whitney U test. Categorical variables were tested with either Chi-squared test or Fisher’s exact test.

Results

We identified 1052 PJI patients, of whom 463 (44.0%) were women. In univariate analysis of the total cohort, women were younger (68.1 ± 11.2 vs 66.1 ± 11.8 years, p=0.01), had higher BMI (30.8 ± 7.78 vs 29.8 ± 6.0, p=0.04), and had a higher culture-negative rate (14.5% vs 9.0%, p < 0.01) than men, but no difference was noted in Charlson Comorbidity Index (Table 1). Among hip PJIs, women were likelier than men to present with acute PJI (15.9% vs 8.7%, p=0.03). There were no differences in debridement, antibiotics, and implant retention (DAIR) utilization (48.2% vs 44.1%, p=0.067), and overall treatment success (72.1% vs 71.6%, p=0.9), nor in any subanalysis of acute, hip, or knee PJIs.

Conclusion

Although females may present differently when diagnosed with PJI, overall outcomes and outcomes with respect to acuity and type of septic revision did not clearly differ in this single-center cohort. Further research in larger cohorts, including additional biomarkers and socioeconomic variables, may further elucidate relationships between sex and PJI characteristics including culture-negativity and symptom acuity.

Disclosures

All Authors: No reported disclosures

Irrigation and Debridement With Implant Retention: Does Chronicity of Symptoms Matter?

BACKGROUND

Periprosthetic joint infection (PJI) remains a rare, yet devastating complication of total joint arthroplasty (TJA). Chronic infection is generally considered a contraindication to debridement, antibiotics, and implant retention (DAIR); however, outcomes stratified by chronicity have not been well documented.

METHODS

A retrospective review of all DAIR cases performed at a single institution from 2008 to 2015 was performed. Chronicity of PJI was categorized as acute postoperative, chronic, or acute hematogenous. Failure after DAIR, defined as re-revision for infection recurrence with the same organism, was evaluated between the 3 chronicity groups at 90 days as well as at a minimum 2-year follow-up.

RESULTS

Overall, 248 patients undergoing DAIR for total hip arthroplasty or total knee arthroplasty PJI were included. Categorization of PJI was acute (acute postoperative) in 59 cases (24%), chronic in 54 (22%), and acute hematogenous in 135 (54%). DAIR survivorship was 47% (range 0.3-10 years). Overall, there were 118 (47.6%) treatment failures after DAIR with a minimum of 2-year follow-up. There was no difference in failure rate between total hip or total knee arthroplasty patients (P = .07). Patients infected with Staphylococcus conferred a higher risk of failure for all DAIR procedures regardless of chronicity category.

CONCLUSION

Identification of microbial species prior to undertaking DAIR may be more clinically relevant than stratification according to chronicity category when considering treatment options.

Sequencing of Circulating Microbial Cell-Free DNA Can Identify Pathogens in Periprosthetic Joint Infections

BACKGROUND

Over 1 million Americans undergo joint replacement each year, and approximately 1 in 75 will incur a periprosthetic joint infection. Effective treatment necessitates pathogen identification, yet standard-of-care cultures fail to detect organisms in 10% to 20% of cases and require invasive sampling. We hypothesized that cell-free DNA (cfDNA) fragments from microorganisms in a periprosthetic joint infection can be found in the bloodstream and utilized to accurately identify pathogens via next-generation sequencing.

METHODS

In this prospective observational study performed at a musculoskeletal specialty hospital in the U.S., we enrolled 53 adults with validated hip or knee periprosthetic joint infections. Participants had peripheral blood drawn immediately prior to surgical treatment. Microbial cfDNA from plasma was sequenced and aligned to a genome database with >1,000 microbial species. Intraoperative tissue and synovial fluid cultures were performed per the standard of care. The primary outcome was accuracy in organism identification with use of blood cfDNA sequencing, as measured by agreement with tissue-culture results.

RESULTS

Intraoperative and preoperative joint cultures identified an organism in 46 (87%) of 53 patients. Microbial cfDNA sequencing identified the joint pathogen in 35 cases, including 4 of 7 culture-negative cases (57%). Thus, as an adjunct to cultures, cfDNA sequencing increased pathogen detection from 87% to 94%. The median time to species identification for cases with genus-only culture results was 3 days less than standard-of-care methods. Circulating cfDNA sequencing in 14 cases detected additional microorganisms not grown in cultures. At postoperative encounters, cfDNA sequencing demonstrated no detection or reduced levels of the infectious pathogen.

CONCLUSIONS

Microbial cfDNA from pathogens causing local periprosthetic joint infections can be detected in peripheral blood. These circulating biomarkers can be sequenced from noninvasive venipuncture, providing a novel source for joint pathogen identification. Further development as an adjunct to tissue cultures holds promise to increase the number of cases with accurate pathogen identification and improve time-to-speciation. This test may also offer a novel method to monitor infection clearance during the treatment period.

LEVEL OF EVIDENCE

Diagnostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Thermal Stability and in Vitro Elution Kinetics of Alternative Antibiotics in Polymethylmethacrylate (PMMA) Bone Cement

BACKGROUND

Amikacin, meropenem, minocycline, and fosfomycin have potential clinical utility for orthopaedic infections; however, their suitability for use in polymethylmethacrylate (PMMA) is poorly understood. The purpose of this study was (1) to quantify the thermal stability of these antibiotics at clinically relevant temperatures and (2) to determine the elution pharmacodynamics of these alternative antibiotics in vitro from PMMA beads of different sizes.

METHODS

Polymerization temperatures of 10-mm PMMA beads were measured over time to generate a simulated heating curve. Aqueous solutions of tobramycin, amikacin, meropenem, minocycline, and fosfomycin were subjected to the temperature curves, followed by incubation at 37°C. Minimum inhibitory concentrations of each antibiotic were evaluated against Staphylococcus aureus, Escherichia coli, and Acinetobacter baumannii. High-dose 4.5-mm, 6-mm, and 10-mm antibiotic-laden PMMA beads (10% antibiotic by weight) were submerged individually in a phosphate-buffered saline solution and incubated at 37°C. Antibiotic elution was determined with use of high-performance liquid chromatography with mass spectrometry.

RESULTS

Tobramycin, amikacin, and fosfomycin demonstrated thermal stability and maintained antimicrobial activity for 28 days. Minocycline and meropenem lost antimicrobial activity against all 3 organisms after 48 hours and 7 days, respectively. Elution concentrations, rates, and cumulative drug mass for tobramycin, amikacin, and meropenem were orders of magnitude higher than minocycline and fosfomycin at each time point.

CONCLUSIONS

This study identified notable differences in thermal stability and elution among antibiotics used to treat infections. Amikacin exhibited activity similarly to tobramycin. Meropenem demonstrated favorable elution kinetics and thermal stability in the initial 7-day period.

CLINICAL RELEVANCE

Amikacin and meropenem show pharmacologic promise as potential acceptable alternatives for local delivery in PMMA for treatment of orthopaedic infections. Further work to establish clinical relevance and utility is needed.

Unicompartmental Knee Arthroplasty Is Associated With a Lower Rate of Periprosthetic Joint Infection Compared to Total Knee Arthroplasty

Background

Several studies have reported lower perioperative complications with unicompartmental knee arthroplasty (UKA) than with total knee arthroplasty (TKA). However, there is a paucity of data analyzing the incidence of periprosthetic joint infection (PJI) in similar patients undergoing UKA and TKA. As such, we sought to analyze the incidence of UKA and TKA PJI in a large matched population.

Material and Methods

The Mariner data set of the PearlDiver database was queried for all patients undergoing UKA or TKA during 2010-2017. Included patients were required to have at least 2 years of database inclusion after surgery. Patients were then matched at a 1:3 ratio (UKA:TKA) on age, gender, Elixhauser Comorbidity Index, tobacco use, and obesity. Rates of PJI requiring operative intervention within 90 days and 1 year were calculated.

Results

In total, 5636 patients having undergone UKA were matched to 16,890 patients having undergone TKA. Fifteen (0.27%) after UKA and 79 (0.47%) after TKA had a PJI surgically managed within 90 days (risk ratio = 0.57, 95% confidence interval = 0.33-0.99, P = .04). Thirty (0.53%) after UKA and 136 (0.81%) after TKA had a PJI surgically managed within 1 year (risk ratio = 0.66, 95% confidence interval = 0.45-0.98, P = .04).

Conclusions

In a large group of rigorously matched patients, UKA was associated with a significantly lower rate of surgically managed PJI than TKA at 90 days and 1 year; however, the rate of PJI in both groups remained low at <1% at 90 days and 1 year.

The James A. Rand Young Investigator's Award: Are Intraoperative Cultures Necessary If the Aspiration Culture Is Positive? A Concordance Study in Periprosthetic Joint Infection

BACKGROUND

The concordance between preoperative synovial fluid culture and multiple intraoperative tissue cultures for identifying pathogenic microorganisms in periprosthetic joint infection (PJI) remains unknown. Our aim is to determine the diagnostic performance of synovial fluid culture for early organism identification.

METHODS

A total of 363 patients who met Musculoskeletal Infection Society criteria for PJI following primary total joint arthroplasty were identified from a retrospective joint infection database. Inclusion criteria required a positive preoperative intra-articular synovial fluid sample within 90 days of intraoperative tissue culture(s) at revision surgery. Concordance was defined as matching organism(s) in aspirate and intraoperative specimens.

RESULTS

Concordance was identified in 279 (76.8%) patients with similar rates among total hip arthroplasties (77.2%) and total knee arthroplasties (76.4%, P = .86). Culture discordance occurred in 84 (23.1%) patients; 37 (10.2%) had no intraoperative culture growth and 33 (90.1%) were polymicrobial. Monomicrobial Staphylococcal PJI cases had high sensitivity (0.96, 95% confidence interval [CI] 0.92-0.98) and specificity (0.85, 95% CI 0.80-0.90). Polymicrobial infections had the lowest sensitivity (0.06, 95% CI 0.01-0.19).

CONCLUSION

Aspiration culture has favorable sensitivity and specificity when compared to tissue culture for identifying the majority of PJI organisms. Clinicians can guide surgical treatment and postoperative antibiotics based on monomicrobial aspiration results, but they should strongly consider collecting multiple tissue cultures to maximize the chance of identifying an underlying polymicrobial PJI.

LEVEL OF EVIDENCE

Level III.

Accuracy of Predictive Algorithms in Total Hip and Knee Arthroplasty Acute Periprosthetic Joint Infections Treated With Debridement, Antibiotics, and Implant Retention (DAIR)

BACKGROUND

Debridement, antibiotics, and implant retention (DAIR) failure remains high for total hip and knee arthroplasty periprosthetic joint infection (PJI). We sought to determine the predictive value of the CRIME80 and KLIC for failure of DAIR in acute hematogenous (AH) and acute postoperative (AP) PJIs, respectively.

METHODS

We identified 134 patients who underwent DAIR for AH PJI with <4 weeks of symptoms after index arthroplasty and 122 patients who underwent DAIR for AP PJI <90 days from index. In the AH group, 15 patients (11%) failed at 90 days and overall, 33 (25%) had failed by 2 years. In the AP group, 39 (32%) failed at 90 days and overall, 52 (43%) failed by 2 years. Logistic regression models were used to determine the area under the curve (AUC) to establish thresholds using the Youden index.

RESULTS

For the AP cohort, AUCs were below 0.66 for KLIC, Charlson comorbidity index, Elixhauser comorbidity index, and McPherson host grade. For the AH cohort, 90-day AUCs were 0.70 for CRIME80 and below 0.66 for Charlson comorbidity index, Elixhauser comorbidity index, and McPherson host grade. In multivariate analysis controlling for age, sex, and body mass index, the CRIME80 AUC improved to 0.77 at 90 days.

CONCLUSION

To the authors' knowledge, this study represents the first external validation of the KLIC and CRIME80 for predicting DAIR failure in a North American population. The results indicate that alternative methods for predicting DAIR failure at 90 days and 2 years for acute PJI are needed.

LEVEL OF EVIDENCE

Prognostic III.

The AAHKS Best Podium Presentation Research Award: Comparing the Efficacy of Irrigation Solutions on Staphylococcal Biofilm Formed on Arthroplasty Surfaces

BACKGROUND

A diverse array of antibacterial solutions is utilized by orthopedic surgeons in an attempt to disperse bacterial biofilm. Few studies compare these agents against biofilm grown on clinically relevant orthopedic biomaterials, such as plastic, acrylic cement, and porous titanium.

METHODS

MSSA biofilm was grown on plastic 48-well plates, polymethylmethacrylate cement beads and porous Ti-6Al-4V acetabular screw caps. Antibacterial solutions were tested according to manufacturer guidance and included: isotonic saline, vancomycin (1 mg/mL), polymyxin-bacitracin (500,000 U/L-50,000 U/L), povidone-iodine 0.3%, povidone-iodine 10%, a 1:1 combination of povidone-iodine 10% & 4% hydrogen peroxide, polyhexamethylene biguanide (PHMB) and betaine 0.04%, a commercial solution containing chlorhexidine gluconate (CHG) 0.05%, and a commercial solution containing benzalkonium chloride and ethanol. Twenty four and 72-hour biofilms were exposed to solutions for 3 minutes to reproduce intraoperative conditions. Solution efficacy was measured through sonication of treated surfaces followed by counting colony forming units and validated with a resazurin assay to assess cell viability. Experiments were performed in triplicate and repeated at least once. A three-fold log reduction in CFU counts versus controls was considered as a measure of solution efficacy.

RESULTS

Saline, vancomycin and polymyxin-bacitracin were ineffective compared to other solutions against planktonic MSSA. Povidone-iodine 10% and a 1:1 solution of povidone-iodine 10% and 4% hydrogen peroxide were the only effective solutions against biofilm across all three surfaces and time points.

CONCLUSION

Commercial antibacterial solutions vary significantly in their efficacy against MSSA biofilm. Efficacy globally decreased as biofilm maturity increased. Increased solution cost did not confer increased efficacy.

Sister, Sister! Siblings With Simultaneous Early Femoral Insufficiency Fractures After Total Knee Arthroplasty

Early periprosthetic fractures after total knee arthroplasty are rare but devastating complications which require revision surgery and lead to poor patient satisfaction. We present 2 siblings who underwent primary total knee arthroplasty on the same day and then both presented 2 weeks after surgery with atraumatic periprosthetic femur fractures. The first patient underwent revision for a cemented distal femoral replacement with stemmed tibial fixation. The second patient underwent an isolated femoral component revision with a stemmed femoral component and distal augment. Histological evaluation identified significant peri-implant osteoporosis. The variation in complexity associated with early periprosthetic femoral insufficiency fractures is highlighted by these 2 cases. Surgeons may consider using stemmed femoral components in similar patients if poor distal femoral bone stock is encountered intraoperatively.

Combination Tests in the Diagnosis of Chronic Periprosthetic Joint Infection: Systematic Review and Development of a Stepwise Clinical Decision-Making Tool

BACKGROUND

Our objective was to identify combination tests used to diagnose chronic periprosthetic joint infection (PJI) and develop a stepwise decision-making tool to facilitate diagnosis.

METHODS

We conducted a systematic review of existing combinations of serum, synovial, and tissue-based tests for diagnosing chronic PJI after hip or knee replacement. This work is an extension of our systematic review of single tests, from which we chose eligible studies that also described the diagnostic performance of combination tests.

RESULTS

Thirty-seven eligible articles described the performance of 56 combination tests, of which 8 combinations had at least 2 studies informing both sensitivity and specificity. We also identified 5 types of combination tests: (1) a type-I Boolean combination, which uses Boolean logic (AND, OR) and usually increases specificity at the cost of sensitivity; (2) a type-II Boolean combination, which usually increases sensitivity at the cost of specificity; (3) a triage-conditional rule, in which the value of 1 test serves to triage the use of another test; (4) an arithmetic operation on the values of 2 tests; and (5) a model-based prediction rule based on a fitted model applied to biomarker values.

CONCLUSIONS

Clinicians can initiate their diagnostic process with a type-II Boolean combination of serum C-reactive protein (CRP) and interleukin-6 (IL-6). False negatives of the combination can be minimized when the threshold is chosen to reach 90% to 95% sensitivity for each test. Once a joint infection is suspected on the basis of serum testing, joint aspiration should be performed. If joint aspiration yields a wet tap, a leukocyte esterase (LER) strip is highly recommended for point-of-care testing, with a reading of ++ or greater indicating PJI; a reading below ++ should be followed by one of the laboratory-based synovial tests. If joint aspiration yields a dry tap, clinicians should rely on preoperative tissue culture and histological analysis for diagnosis. Combinations based on triage-conditional, arithmetic, and model-based prediction rules require further research.

LEVEL OF EVIDENCE

Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Treatment and Outcome of Periprosthetic Joint Infection in Unicompartmental Knee Arthroplasty

BACKGROUND

Periprosthetic joint infection (PJI) after unicompartmental knee arthroplasty (UKA) is a devastating but poorly understood complication, with a paucity of published data regarding treatment and outcomes. This study analyzes the largest cohort of UKA PJIs to date comparing treatment outcome, septic and aseptic reoperation rates, and risk factors for treatment failure.

METHODS

Twenty-one UKAs in 21 patients treated for PJI, as defined by Musculoskeletal Infection Society criteria, were retrospectively reviewed. Minimum and mean follow-up was 1 and 3.5 years, respectively. Fourteen (67%) patients had acute postoperative PJIs. Surgical treatment included 16 debridement, antibiotics, and implant retentions (DAIRs) (76%), 4 two-stage revisions (19%), and 1 one-stage revision (5%). Twenty (95%) PJIs were culture positive with Staphylococcus species identified in 15 cases (71%).

RESULTS

Survivorship free from reoperation for infection at 1 year was 76% (95% confidence interval, 58%-93%). Overall survival from all-cause reoperation was 57% (95% confidence interval, 27%-87%) at 5 years. Two additional patients (10%) underwent aseptic revision total knee arthroplasty for lateral compartment degeneration 1 year after DAIR and tibial aseptic loosening 2.5 years after 2-stage revision. All patients who initially failed PJI UKA treatment presented with acute postoperative PJIs (5 of 14; 36%).

CONCLUSION

Survivorship free from persistent PJI at 1 year is low at 76% but is consistent with similar reports of DAIRs for total knee arthroplasties. Furthermore, there is low survivorship free from all-cause reoperation of 71% and 57% at 2 and 5 years, respectively. Surgeons should be aware of these poorer outcomes and consider treating UKA PJI early and aggressively.

Long-term performance of oxidized zirconium on conventional and highly cross-linked polyethylene in total hip arthroplasty

Introduction: Polyethylene wear and subsequent osteolysis remain obstacles to the long-term survivorship of total hip arthroplasty (THA). Highly cross-linked polyethylene (XLPE) with radical quenching represents a massive leap forward with dramatically improved wear rates compared to ultra-high molecular weight polyethylene (UHMWPE). In this study we evaluate the wear of UHMWPE and XLPE coupled with oxidized zirconium (OxZr) femoral heads. Methods: A longitudinal, retrospective analysis was performed identifying consecutive patients who received a 28-mm OxZr-on-polyethylene primary THA from 2003 to 2004 by a single, high-volume arthroplasty surgeon. Patients were divided into two groups: those that received (1) UHMWPE liner and (2) a highly XLPE liner. Patients were included if clinical follow-up was complete to 2014 or later. Radiographic analysis was performed by two blinded observers. Measures included cup position, annual linear wear rate, and presence of osteolysis. Pairwise comparisons, correlations, and inter-rater reliability were calculated. Results: Eighty patients were in the UHMWPE group with an average follow-up of 10 ± 1.23 years and 88 patients in the XLPE group with an average of 10 ± 1.03-year follow-up. Average age (68) was similar between groups (p = 0.288). Observer reliability was excellent for cup abduction (ICC = 0.940), anteversion (ICC = 0.942), and detection of osteolysis (ICC = 0.811). Annual linear wear rates were significantly higher (p = 1 × 10⁻¹⁹) with UHMWPE (0.21 ± 0.12 mm/year) compared to XLPE (0.05 ± 0.03 mm/year). Linear wear rate was significantly correlated to decreasing acetabular abduction (p = 0.035). Osteolysis was noted only in the UHMWPE group, with 17 patients (21.2%) exhibiting acetabular osteolysis and 37 (46.3%) patients exhibiting femoral osteolysis. Conclusions: OxZr coupled with XLPE showed minimal wear and no osteolysis at 10-year follow up. The yearly linear penetration rate is similar to that seen in other studies of XLPE THA. A careful longitudinal follow-up will be required to determine if advanced bearings such as OxZr or ceramic can show improved performance in the second decade of implantation.

Assessing the Role of Daptomycin as Antibiotic Therapy for Staphylococcal Prosthetic Joint Infection

Background: The role of daptomycin, a potent, safe, convenient anti-staphylococcal antibiotic, in treatment of prosthetic joint infection (PJI) is unclear. We evaluated our experience with the largest cohort of patients with staphylococcal PJI managed with daptomycin. Methods: A cohort of staphylococcal hip and knee PJI treated with daptomycin was identified by hospital records from 2009 to 2016. All cases met Musculoskeletal Infection Society International Consensus criteria for PJI. The primary endpoint was 2 year prosthesis retention. Univariate analyses and regression statistics were calculated. Results: 341 patients with staphylococcal PJI were analyzed. 154 two-stages (77%) and 74 DAIR procedures (52%) met criteria for treatment success at 2 years. 77 patients were treated with daptomycin, of which 34 two-stages (68%) and 15 DAIRs (56%) achieved treatment success. Pairwise and regression analysis found no association between treatment success and daptomycin use. Organism (DAIR only) and Charlson Comorbidity Index scores (DAIR and two-stage) were significantly associated with treatment outcome. Six daptomycin patients (7.8%) had adverse side effects. Discussion: Daptomycin fared no better or worse than comparable antibiotics in a retrospective cohort of staphylococcal hip and knee PJI patients, regardless of surgical strategy. Conclusion: The convenient dosing, safety, and potency of daptomycin make it an attractive antibiotic for staphylococcal PJI. However, these advantages must be weighed against higher costs and rare, but serious side effects.

Single 3° tapered fluted femoral stems demonstrate low subsidence at mid-term follow-up in severe bony deficiency

Background

Tapered femoral stems have become popular in revision total hip arthroplasty (rTHA). Increasing the distal taper angle may mitigate subsidence. This study reports osseointegration of a new 3 degree distal taper revision stem at minimum 4 years post-operatively.

Methods

Indication for surgery, pre-operative bony deficiency and latest clinical, tribological and radiological follow-up were analysed. Radiographs were assessed by two blinded observers for preoperative femoral bone stock according to Paprosky, postoperative subsidence according to Callaghan and restoration of femoral bone stock over time according to Kolstad. Stem integration was determined using the Rodriguez classification.

Results

Twenty-three cases were analyzed at 5.9±1.0 years. All patients presented with Paprosky III defects. All stems met the criteria for osseointegration. Spot welds occurred distal to the proximal modular junction and at the tip. Two femora with severe proximal femoral bone loss recovered bone stock by final follow-up but two demonstrated stress shielding. No intraoperative fractures occurred. One stem subsided early but remained stable and osseointegrated at final follow up. There were no stem failures due to taper corrosion or modular junctional failure.

Conclusions

This study reports good osseointegration and low subsidence with a novel fluted, 3-degree tapered femoral stem demonstrates at medium-term follow-up in cases with severe femoral bone deficiency.

390. Treatment and Outcome of Methicillin-Resistant Staphylococcus aureus Hip and Knee Prosthetic Joint Infection

Background

Methicillin-resistant Staphylococcus aureus (MRSA) total hip and knee prosthetic joint infections (PJI) can be highly morbid and difficult to treat. Other clinical factors notwithstanding, explantation is usually recommended, although comparative treatment data are lacking. We sought to compare the success of implant retention to two-stage exchange in MRSA-infected PJI to better understand treatment options in this difficult cohort.

Methods

A retrospective cohort of hip and knee PJIs from 2009 to 2016 were identified by ICD code and surgical treatment. All cases met MSIS criteria for PJI, and had culture-confirmed MRSA from synovial or intra-articular tissue culture. PJIs were either treated with exchange arthroplasty or debridement with antibiotic and implant retention (DAIR). Success was defined as no further surgical treatment for infection at two years. Kaplan–Meier estimates were used to calculate the 2-year survival rate free from treatment failure. Univariate logistic regression was performed to identify risk factors associated with treatment failure.

Results

65 MRSA PJIs were identified with 42 undergoing explantation and 23 undergoing DAIR. Demographics, Charlson comorbidities, infection type (early post-operative, hematogenous or late chronic), and history of prior PJI were not significantly different between treatment groups. Survivorship at two years was 75% (95% confidence interval [CI] 61–88%) for exchange compared with 29% (95% CI 10–48%) for DAIR, P = 0.0002. Within the exchange group, knee PJIs were more likely to fail than hip PJI (odds ratio [OR] 7.1, CI 1.3–38, P = 0.02), and patients with diabetes were more likely to fail (OR 17, CI 1.6–178, P = 0.02).

Conclusion

MRSA PJIs treated with DAIR have worse outcomes than those treated with prosthesis exchange. Further investigation is needed to identify predictors of DAIR success, to optimize surgical treatment choice, and to improve outcomes of these difficult infections.

Disclosures

All authors: No reported disclosures.

399. Treatment and Outcome of Prosthetic Joint Infection in Unicompartmental Knee Arthroplasty

Background

Unicompartmental knee arthroplasty (UKA) is an increasingly popular alternative to total knee replacement due to easier recovery and greater satisfaction. However, limited evidence guides the management of periprosthetic joint infection (PJI) in UKA specifically. We retrospectively reviewed the largest cohort of UKA PJI to date, providing our experience in a high volume tertiary institution.

Methods

An institutional PJI database was queried from 2008 to 2016 to identify all PJI cases with an index procedure of UKA. Treatment, diagnostic criteria, Charlson Comorbidity Index (CCI) and microbiology data were collected. Success was defined as no further surgical treatment for infection at 2 years. A chi-square test or Fisher’s exact test was used for comparisons between treatment success and failure groups. Survival probability was calculated using the Kaplan–Meier method.

Results

A total of 24 UKA PJIs were identified with 22 meeting MSIS criteria. Median age at infection was 65.9 years (range, 50.8–87.4), median BMI was 26.7 kg/m² (range, 21.2–49.5), 75% male (18/24).The average follow-up time was 2.83 years. 9 patients presented with early (4 weeks of symptoms). 63% (15/24) of PJI cases were staphylococcal and 8.3% (2/24) were culture negative. Patients were either treated with 1 stage exchange (n = 3, 100% success), two-stage exchange (n = 5, 80% success) or implant retention (n = 16, 75% success). Overall survivorship was 79% at 2 years (95% confidence interval [CI], 63%–95%). Overall there was no significant association between success and CCI (P = 0.46), infection type (P = 0.29), surgical therapy (P = 0.62), and microorganism (P = 0.05).

Conclusion

In this series, UKA PJIs tended to present more often as early post-operative or hematogenous infections. We observed no significant benefit with revision surgery and therefore conclude that implant retention should be considered as first-line surgical treatment. Outcomes of UKA PJI appear comparable to those in TKA PJIs.

Disclosures

All authors: No reported disclosures.

Different clinical outcomes on the second side after staged total knee replacement. A systematic review

BACKGROUND

The clinical outcomes of the contralateral side in staged bilateral total knee arthroplasty (BTKA) are relatively unknown. The purpose of this study was to answer: 1) Does the second-operated knee in a staged BTKA result in inferior clinical and functional outcomes? 2) Is the duration of time between the first- and the second-operated knee defined in a consistent fashion in the literature? 3) Does the time interval between TKAs influence clinical outcomes?

METHODS

Two reviewers independently conducted a systematic search of the literature using different databases according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines.

RESULTS

Five of the seven included studies reported significantly inferior postoperative clinical outcomes for the second-operated knee compared with the first-operated knee. There was no difference in the overall major complication rate between first- and second-operated TKA (2.4% and 1.2% respectively). Based on the literature reviewed, there is no consensus on the optimal time interval between the stages. Most studies, which investigated the impact of different intervals on the outcomes of the second-operated knee, concluded that the differences in outcomes with different intervals were not significant.

CONCLUSIONS

Current literature suggests that the second-operated knee, in patients undergoing staged BTKAs, might have inferior clinical outcomes when compared with the first-operated knee.

Diagnostic Accuracy of Serum, Synovial, and Tissue Testing for Chronic Periprosthetic Joint Infection After Hip and Knee Replacements: A Systematic Review

BACKGROUND

Chronic periprosthetic joint infection (PJI) is a devastating complication that can occur following total joint replacement. Patients with chronic PJI report a substantially lower quality of life and face a higher risk of short-term mortality. Establishing a diagnosis of chronic PJI is challenging because of conflicting guidelines, numerous tests, and limited evidence. Delays in diagnosing PJI are associated with poorer outcomes and morbid revision surgery. The purpose of this systematic review was to compare the diagnostic accuracy of serum, synovial, and tissue-based tests for chronic PJI.

METHODS

This review adheres to the Cochrane Collaboration's diagnostic test accuracy methods for evidence searching and syntheses. A detailed search of MEDLINE, Embase, the Cochrane Library, and the grey literature was performed to identify studies involving the diagnosis of chronic PJI in patients with hip or knee replacement. Eligible studies were assessed for quality and bias using the Quality Assessment of Diagnostic Accuracy Studies-2 (QUADAS-2) tool. Meta-analyses were performed on tests with sufficient data points. Summary estimates and hierarchical summary receiver operating characteristic (HSROC) curves were obtained using a bivariate model.

RESULTS

A total of 12,616 citations were identified, and 203 studies met the inclusion criteria. Of these 203 studies, 170 had a high risk of bias. Eighty-three unique PJI diagnostic tests were identified, and 17 underwent meta-analyses. Laboratory-based synovial alpha-defensin tests and leukocyte esterase reagent (LER) strips (2+) had the best performance, followed by white blood-cell (WBC) count, measurement of synovial C-reactive protein (CRP) level, measurement of the polymorphonuclear neutrophil percentage (PMN%), and the alpha-defensin lateral flow test kit (Youden index ranging from 0.78 to 0.94). Tissue-based tests and 3 serum tests (measurement of interleukin-6 [IL-6] level, CRP level, and erythrocyte sedimentation rate [ESR]) had a Youden index between 0.61 to 0.75 but exhibited poorer performance compared with the synovial tests mentioned above.

CONCLUSIONS

The quality of the literature pertaining to chronic PJI diagnostic tests is heterogeneous, and the studies are at a high risk for bias. We believe that greater transparency and more complete reporting in studies of diagnostic test results should be mandated by peer-reviewed journals. The available literature suggests that several synovial fluid-based tests perform well for diagnosing chronic PJI and their use is recommended in the work-up of any suspected case of chronic PJI.

LEVEL OF EVIDENCE

Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Patients Discharged to Inpatient Rehabilitation Facilities Undergo More Diagnostic Interventions With No Improvement in Outcomes

The purpose of this study was to determine if there is a difference in the number of diagnostic tests and interventions, pain and function scores, or satisfaction of patients discharged to inpatient rehabilitation facilities vs to home. From February to May 2015, 171 consecutive patients were prospectively recruited following primary total knee arthroplasty. Six weeks postoperatively, based on the patients' recollections, the number and types of diagnostic imaging tests, number of blood transfusions, and overall satisfaction whether discharged to inpatient rehabilitation facilities (n=85) or to home (n=86) were assessed. A significantly greater proportion of patients discharged to inpatient rehabilitation facilities reported undergoing at least 1 diagnostic imaging test compared with patients discharged to home (25.9% vs 8.1%; P=.013). Multivariate logistic regressions revealed that patients discharged to an inpatient rehabilitation facility were more likely to have a greater number of diagnostic tests (odds ratio, 5.01; 95% confidence interval, 1.69-14.92; P=.004) and radiographs (odds ratio, 16.10; 95% confidence interval, 1.54-169.70; P=.020) performed. There was no significant difference in readmission rates for patients discharged to home (2.3%) vs to an inpatient rehabilitation facility (0%) (P=.246). No significant differences were observed in postoperative Knee Society pain or function scores (P=.083 and P=.057, respectively) or visual analog scale satisfaction scores (P=.206). Twenty-nine (34.1%) patients were discharged under the care of the visiting nurse service after leaving the rehabilitation facility. Patients discharged to an inpatient rehabilitation facility underwent more diagnostic testing, especially radiographs, than patients discharged to home. There were no clinically relevant differences in Knee Society pain or function scores or patient satisfaction. [Orthopedics. 2018; 41(6):e841-e847.].

Variation in Use of Postoperative Precautions and Equipment Following Total Hip Arthroplasty: A Survey of the AAHKS and CAS Membership

BACKGROUND

A traditional method to reduce dislocation risk following total hip arthroplasty involves prescribing postoperative precautions and ambulatory equipment to patients. The purpose of this study was to determine the prevalence of postoperative precaution and equipment use among North American arthroplasty surgeons for patients undergoing primary total hip arthroplasty.

METHODS

We conducted a survey of American Association of Hip and Knee Surgeons and Canadian Arthroplasty Society members using an electronic questionnaire format to determine how often precautions and equipment were prescribed, and whether their use was associated with surgical approach and other surgeon demographics.

RESULTS

Of the respondents, 44% universally prescribed precautions while 33% never prescribed precautions. Use of the posterolateral approach, surgeon experience, and larger head size use were significantly associated (P < .01) with precaution and equipment use. Direct anterior approach surgeons were significantly less likely to prescribe precautions (P < .0001) and significantly less likely to prescribe equipment (P < .0001).

CONCLUSION

Although postoperative precautions continue to be used to some degree by the majority of members, their consumption of healthcare resources through utilization of additional care providers and purchasing of equipment, known association with reduced patient satisfaction, and lack of supporting evidence make them a target for future scrutiny.

Periprosthetic Joint Infection in Patients with Inflammatory Joint Disease: Prevention and Diagnosis

PURPOSE OF REVIEW

Periprosthetic joint infection (PJI) is a devastating complication that can occur following total joint arthroplasty (TJA), causing significant morbidity and often requiring revision surgery. This goal of this manuscript is to review the current evidence for the prevention and diagnosis of PJI in patients with inflammatory arthritis.

RECENT FINDINGS

Patients with inflammatory arthritis have a higher risk of PJI after TJA; however, there are several preventive, diagnostic, and therapeutic measures that can be optimized to lower the burden of PJI in this population. This manuscript will review the current evidence and clinical practice recommendations that support specific features of preoperative evaluation, perioperative medication management, and surgical planning in inflammatory arthritis patients undergoing TJA. Evidence and recommendations for the diagnosis of PJI in this patient population will also be reviewed. Despite increased research efforts directed towards PJI, specific approaches directed at the inflammatory arthritis patient population remain surprisingly limited. Optimization strategies such as adequately managing disease-modifying medications, treating preoperative anemia, encouraging smoking cessation, and improving weight management are strongly encouraged before entering the perioperative period. If PJI does occur in the inflammatory arthritis patient, establishing the diagnosis is challenging, since guidelines were created from investigations of PJI in primarily patients without inflammatory arthritis. Future prospective research is required to better guide clinicians in preventing and diagnosing PJI in inflammatory arthritis patients undergoing TJA.

New Innovations in the Treatment of PJI and Biofilms-Clinical and Preclinical Topics

PURPOSE OF REVIEW

Periprosthetic joint infection (PJI) is a devastating complication after total joint replacement. A main source for antibiotic tolerance and treatment failure is bacterial production of biofilm-a resilient barrier against antibiotics, immune system, and mechanical debridement. The purpose of this review is to explore some novel approaches to treat PJI and biofilm-related infections.

RECENT FINDINGS

Innovative treatment strategies of bacterial and biofilm infections revolve around (a) augmenting current therapies, such as improving the delivery and efficiency of conventional antibiotics and enhancing the efficacy of antiseptics and (b) administrating completely new therapeutic modalities, such as using immunotherapy, nanoparticles, lytic bacteriophages, photodynamic therapy, novel antibiotics, and antimicrobial peptides. Several promising treatment strategies for PJI are available to be tested further. The next requirement for most of the novel treatments is reproducing their effects in clinically representative animal models of PJI against clinical isolates of relevant bacteria.

Vancomycin-Loaded Polymethylmethacrylate Spacers Fail to Eradicate Periprosthetic Joint Infection in a Clinically Representative Mouse Model

BACKGROUND

Periprosthetic joint infection (PJI) remains a devastating complication following total joint arthroplasty. Current animal models of PJI do not effectively recreate the clinical condition and thus provide limited help in understanding why treatments fail. We developed a mouse model of the first-stage surgery of a 2-stage revision for PJI involving a 3-dimensionally printed Ti-6Al-4V implant and a mouse-sized cement spacer that elutes vancomycin.

METHODS

Vancomycin was mixed with polymethylmethacrylate (PMMA) cement and inserted into custom-made mouse-sized spacer molds. Twenty C57BL/6 mice received a proximal tibial implant and an intra-articular injection of 3 × 10 colony-forming units of Staphylococcus aureus Xen36. At 2 weeks, 9 mice underwent irrigation and debridement of the leg with revision of the implant to an articulating vancomycin-loaded PMMA spacer. Postoperatively, mice underwent radiography and serum inflammatory-marker measurements. Following euthanasia of the mice at 6 weeks, bone and soft tissues were homogenized to quantify bacteria within periprosthetic tissues. Implants and articulating spacers were either sonicated to quantify adherent bacteria or examined under scanning electron microscopy (SEM) to characterize the biofilm.

RESULTS

Vancomycin-loaded PMMA spacers eluted vancomycin for ≤144 hours and retained antimicrobial activity. Control mice had elevated levels of inflammatory markers, radiographic evidence of septic loosening of the implant, and osseous destruction. Mice treated with a vancomycin-loaded PMMA spacer had significantly lower levels of inflammatory markers (p < 0.01), preserved tibial bone, and no intra-articular purulence. Retrieved vancomycin-loaded spacers exhibited significantly lower bacterial counts compared with implants (p < 0.001). However, bacterial counts in periprosthetic tissue did not significantly differ between the groups. SEM identified S. aureus encased within biofilm on control implants, while vancomycin-loaded spacers contained no bacteria.

CONCLUSIONS

This animal model is a clinically representative model of PJI treatment. The results suggest that the antimicrobial effects of PMMA spacers are tightly confined to the articular space and must be utilized in conjunction with thorough tissue debridement and systemic antibiotics.

CLINICAL RELEVANCE

These data provide what we believe to be the first insight into the effect of antibiotic-loaded cement spacers in a clinically relevant animal model and justify the adjunctive use of intravenous antibiotics when performing a 2-stage revision for PJI.

Selected Heat-Sensitive Antibiotics Are Not Inactivated During Polymethylmethacrylate Curing and Can Be Used in Cement Spacers for Periprosthetic Joint Infection

BACKGROUND

Antibiotic use in polymethylmethacrylate (PMMA) spacers has historically been limited to those which are "heat-stable" and thus retain their antimicrobial properties after exposure to the high temperatures which occur during PMMA curing.

METHODS

This study examines the requirement of "heat stability" by measuring temperatures of Palacos and Simplex PMMA as they cure inside commercial silicone molds of the distal femur and proximal tibia. Temperature probes attached to thermocouples were placed at various depths inside the molds and temperatures were recorded for 20 minutes after PMMA introduced and a temperature curve for each PMMA product was determined. A "heat-stable" antibiotic, vancomycin, and a "heat-sensitive" antibiotic, ceftazidime, were placed in a programmable thermocycler and exposed to the same profile of PMMA curing temperatures. Antimicrobial activity against Staphylococcus aureus was compared for heat-treated antibiotics vs room temperature controls.

RESULTS

Peak PMMA temperatures were significantly higher in tibial (115.2°C) vs femoral (85.1°C; P < .001) spacers. In the hottest spacers, temperatures exceeded 100°C for 3 minutes. Simplex PMMA produced significantly higher temperatures (P < .05) compared with Palacos. Vancomycin bioactivity did not change against S aureus with heat exposure. Ceftazidime bioactivity did not change when exposed to femoral temperature profiles and was reduced only 2-fold with tibial profiles.

CONCLUSION

The curing temperatures of PMMA in knee spacers are not high enough or maintained long enough to significantly affect the antimicrobial efficacy of ceftazidime, a known "heat-sensitive" antibiotic. Future studies should investigate if more "heat-sensitive" antibiotics could be used clinically in PMMA spacers.

Current Options and Emerging Biomaterials for Periprosthetic Joint Infection

PURPOSE OF REVIEW

Infection in the setting of total joint arthroplasty, referred to as periprosthetic joint infection (PJI), is a devastating complication requiring prolonged and costly treatment. The unique environment around an artificial joint and ability of surrounding tissues to sequester bacteria collectively make prevention, diagnosis, and treatment of this condition challenging. In light of the unique pathogenesis of PJI, this review explores the limitations of contemporary treatments and discusses novel treatment options.

RECENT FINDINGS

Recent advancements in local antibiotic delivery platforms for preventing and treating PJI include titanium nanotube arrays, synthetic polymers, resorbable hydrogels, and cyclodextrin-based drug delivery options. In particular, cyclodextrins have facilitated great advancements in other clinical disorders and have demonstrated early promise as a future option in the arena of PJI. Novel treatment modalities for PJI optimize the implant surfaces to prevent bacterial biofilm formation or provide prolonged intra-articular antibiotic dosing to eradicate bacteria.

Tertiary care centre adherence to unified guidelines for management of periprosthetic joint infections: a gap analysis

BACKGROUND

The success rate of surgical treatment for periprosthetic joint infection (PJI) remains inconsistent in the literature. Variability in PJI clinical guidelines and surgeon adherence to guidelines could affect treatment success. The objectives of this study were to appraise current recommendations for PJI management and develop a unified clinical standard of care, to perform a gap analysis of PJI cases in a tertiary institution to determine the rate of guideline adherence, and to determine if adherence to unified PJI guidelines affected 2-year treatment outcomes.

METHODS

We appraised the PJI guidelines from 3 academic medical societies, and consistent statements were aggregated. We retrospectively reviewed all PJI cases in a tertiary care institution. We defined PJI based on Musculoskeletal Infection Society PJI criteria. Surgeon adherence to preoperative, intraoperative, surgical and medical management guidelines was calculated, and we evaluated the association between guideline adherence and 2-year treatment outcomes.

RESULTS

The institutional rate of PJI was 1.13% (38 of 3368). Treatment success was 57.8% at 2 years. Unified guideline adherence percentages varied substantially: 92% of patients had preoperative erythrocyte sedimentation rate and C-reactive protein, 97% had intraoperative tissue cultures, 42% had appropriate preoperative arthrocentesis, and 74% underwent guideline-appropriate surgery. Performing appropriate preoperative arthrocentesis significantly correlated with positive treatment outcomes at 2 years (p = 0.028).

CONCLUSION

Adherence to PJI guidelines varies considerably, indicating that clinicians are either unaware of them or do not recognize their value for PJI treatment. This study shows the need for institution-based PJI treatment pathways that are consistent with published guidelines and the need to monitor adherence.

Using a non-invasive secure skin closure following total knee arthroplasty leads to fewer wound complications and no patient home care visits compared to surgical staples

BACKGROUND

Superficial wound complications occur in up to 10% of total knee arthroplasty (TKA) procedures and have been associated with periprosthetic joint infection. The ideal material for TKA closure should offer: 1) fast intraoperative application, 2) minimal wound complications and 3) removable by patients without assistance. We evaluated a novel, non-invasive, removable skin closure system for TKA to determine its effect on wound complications.

METHODS

We prospectively evaluated 221 consecutive TKA patients who received skin closure using a non-invasive zipper-like system ('Zip'; Zip 16 Surgical Skin Closure System; Zipline Medical). All procedures were performed by a single surgeon using the mini-midvastus approach. Patients received two weeks of rivaroxaban postoperatively. Demographics, comorbidities, in-hospital complications and six-week wound evaluation were recorded. Data was compared to a cohort of 1001 patients from the same surgeon who received staples for closure and coumadin for thromboprophylaxis.

RESULTS

Zip patients had a significantly higher BMI (p=0.001), incidence of diabetes (p=0.035) and smoking (p=0.005). Zip patients removed dressings themselves and did not report problems with dressing care. Rate of readmission for wound-related complications was significantly lower in the Zip closure group (p=0.045). Overall readmission rates were similar between groups.

CONCLUSIONS

In our experience, the Zip 16 Surgical Skin Closure System is easy to apply, avoids home care and has produced fewer wound complications compared to staples. Results have been positive despite the study cohort having a higher number of diabetic patients and using an anticoagulant associated with a higher risk of wound complications.

Substrain-specific differences in bone parameters, alpha-2-macroglobulin circulating levels, and osteonecrosis incidence in a rat model

Osteonecrosis of the femoral head (ONFH) is a potentially devastating complication that occurs in up to 40% of young adults receiving chronic glucocorticoid (GC) therapy. Through a validated GC therapy rat model, we have previously shown that Wistar Kyoto (WK) rats exhibit a genetic susceptibility to GC-induced ONFH compared to Sasco Fischer (F344) rats. We have undertaken this study in order to investigate differences between these two strains for their bone parameters, alpha-2-macroglobulin (A2M) circulating levels and incidence of GC-induced osteonecrosis of the femoral head. WK and F344 rats were treated either with 1.5 mg/kg/day of prednisone or placebo for 6 months. Blood was taken every month. The femoral heads were harvested for histological examination to detect ONFH and analyzed with micro-computed tomography. After 3 months of GC-therapy, plasma A2M was elevated in treated rats only. GC-treated WK rats exhibited histological evidence of early ONFH through higher rates of cellular apoptosis and empty osteocyte lacunae in the subchondral bone compared to placebos and to F344 rats. Furthermore, micro-CT analysis exhibited femoral head collapse only in GC-treated WK rats. Interestingly, GC-treated F344 rats exhibited significant micro-CT changes, but such changes were less concentrated in the articular region and were accompanied histologically with increased marrow fat. These µCT and histological findings suggest that elevated A2M serum level is not predictive and suitable as an indicative biomarker for early GC-induced ONFH in rodents. Elevated A2M levels observed during GC treatment suggests that it plays role in the host reparative response to GC-associated effects. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1183-1194, 2017.

Quantification of Peri-Implant Bacterial Load and in Vivo Biofilm Formation in an Innovative, Clinically Representative Mouse Model of Periprosthetic Joint Infection

BACKGROUND

Periprosthetic joint infection (PJI) is a devastating complication following total joint arthroplasty. Current animal models of PJI are limited because of a lack of quantitative methods and failure to effectively recreate the periprosthetic space. We therefore developed a murine PJI model involving a 3-dimensionally printed Ti-6Al-4V implant capable of bearing weight and permitting quantitative analysis of periprosthetic bacterial load and evaluation of biofilm.

METHODS

Twenty-five 12-week-old C57BL/6 mice received a unilateral proximal tibial implant and intra-articular injection of either 3 × 10 colony forming units (CFUs) of Staphylococcus aureus Xen 36 or saline solution. Postoperatively, mice underwent gait analysis, knee radiographs, and serum inflammatory marker measurements. Following euthanasia at 2 or 6 weeks, bone and soft tissues were homogenized to quantify bacteria within periprosthetic tissues. Implants were either sonicated to quantify adherent bacteria or examined under scanning electron microscopy (SEM) to characterize biofilm.

RESULTS

All mice survived surgery and were not systemically septic. The control mice immediately tolerated weight-bearing and had normal inflammatory markers and radiographic signs of osseointegration. Infected mice had difficulty walking over time, exhibited radiographic findings of septic implant loosening, and had significantly elevated inflammatory markers. Periprosthetic tissues of the infected animals displayed a mean of 4.46 × 10 CFUs of S. aureus at 2 weeks and 2.53 × 10 CFUs at 6 weeks. Viable S. aureus was quantified on retrieved implant surfaces. SEM demonstrated S. aureus cocci in clusters encased within biofilm.

CONCLUSIONS

This animal model is, to our knowledge, the most clinically representative PJI replication to date. It is the first that we know of to produce infection through the same method hypothesized to occur clinically, utilize a weight-bearing implant that can osseointegrate, and provide quantitative data on 8 aspects of PJI, including radiographic features, inflammatory markers, and bacterial loads.

CLINICAL RELEVANCE

This novel animal model is, to our knowledge, the first to provide a load-bearing translational representation of clinical PJI that effectively recreates the periprosthetic space.

Periprosthetic femoral fractures and trying to avoid them: what is the contribution of femoral component design to the increased risk of periprosthetic femoral fracture?

AIMS

Periprosthetic femoral fractures (PFF) following total hip arthroplasty (THA) are devastating complications that are associated with functional limitations and increased overall mortality. Although cementless implants have been associated with an increased risk of PFF, the precise contribution of implant geometry and design on the risk of both intra-operative and post-operative PFF remains poorly investigated. A systematic review was performed to aggregate all of the PFF literature with specific attention to the femoral implant used.

PATIENTS AND METHODS

A systematic search strategy of several journal databases and recent proceedings from the American Academy of Orthopaedic Surgeons was performed. Clinical articles were included for analysis if sufficient implant description was provided. All articles were reviewed by two reviewers. A review of fundamental investigations of implant load-to-failure was performed, with the intent of identifying similar conclusions from the clinical and fundamental literature.

RESULTS

In total 596 articles were initially identified, with 34 being eligible for analysis. Aggregate analysis of 1691 PFFs in 342 719 primary THAs revealed a significantly higher number of PFFs with cementless femoral implants (p < 0.001). Single-wedge and double-wedge (fit-and-fill) femoral implants were associated with a threefold increase in PFF rates (p < 0.001) compared with anatomical, fully coated and tapered/rounded stems. Within cemented stems, loaded-taper (Exeter) stems were associated with more PFFs than composite-beam (Charnley) stems (p = 0.004). Review of the fundamental literature revealed very few studies comparing cementless component designs.

CONCLUSION

Very few studies within the PFF literature provide detailed implant information. Cementless implants, specifically those of single-wedge and double-wedge, have the highest PFF rates in the literature, with most investigations recommending against their use in older patients with osteoporotic bone. This review illustrates the need for registries and future PFF studies to record implant name and information for future analysis. Furthermore, future biomechanical investigations comparing modern implants are needed to clarify the precise contribution of implant design to PFF risk. Cite this article: Bone Joint J 2017;99-B(1 Supple A):50-9.

Short to Midterm Follow-Up of the Tritanium Primary Acetabular Component: A Cause for Concern

BACKGROUND

Several acetabular components utilizing novel ultraporous metal substrates have been introduced over the past decade. Collectively by design, they have a lower modulus of elasticity to reduce stress shielding, a higher coefficient of friction to enhance interference fit, and ultraporous surfaces to enhance osseointegration. However, little literature exists regarding their clinical performance.

METHODS

This study compared the clinical and radiographic results of 109 hips in 95 patients using a Tritanium primary cup (Stryker, Mahwah, NJ) to an age, body mass index, and gender-matched cohort of 100 patients that received a contemporary cup (Stryker Trident PSL HA).

RESULTS

At an average 4.24 + 1.49 years, implant survivorship of the Tritanium primary cup was 98.2%, with 2 cups revised for failure of osseointegration. One-year radiographs revealed radiolucent and radiosclerotic lines in 2 or more DeLee zones in 30.3% of cups and 3 zone involvement in 8.2%. These proportions increased (40.0% and 17.1%, respectively) at minimum 5-year follow-up. A comparison of 1 year and last follow-up radiographs revealed progression in 13.8%. Tritanium primary components with radiolucency in 2 or more zones exhibited significantly lower HHS at 2 years compared to all Trident peripheral self-locking (PSL) components (P < .0001) and Tritanium primary components with 1 zone or no radiolucency (P = .026). Scanning electron microscopy of a retrieved cup revealed local inflammatory reaction and no evidence of osseointegration.

CONCLUSION

Despite adequate implant survivorship, over one third of Tritanium primary cups had 2 or more zone radiolucency at minimum 5-year follow-up with associated lower Harris hip scores.