Role of the NeuroCuple™ Device for the Postoperative Pain Management of Patients Undergoing Unilateral Primary Total Knee and Hip Arthroplasty: A Pilot Prospective, Randomized, Open-Label Study.

BACKGROUND: The potential effectiveness of the non-pharmacological and nanotechnology-based NeuroCuple™ device in reducing postoperative surgical pain and opioid consumption remains unknown. METHODS: This randomized controlled open-label study was conducted in patients undergoing a primary unilateral total knee or total hip arthroplasty. In the recovery room, patients were randomized to receive either standard of care (control group) or standard of care plus two NeuroCuple™ devices. The outcome variables included pain and opioid consumption (oral morphine equivalent, OME in milligrams). RESULTS: A total of 69 patients were randomized to either the NeuroCuple™ group (n = 38) or the control group (n = 31). Use of the NeuroCuple™ devices was associated with a significant 34% reduction in pain at rest (means of area under the curve: 6.3 vs. 9.5; p = 0.018) during postoperative days 1-3. Opioid consumption was reduced by 9%. More importantly, use of the NeuroCuple™ devices reduced the number of patients requesting an opioid prescription following discharge from the hospital by 52% (26% vs. 55%, p = 0.016). CONCLUSIONS: Our data suggest that the NeuroCuple™ device may be an effective non-pharmacological alternative to opioids to manage postoperative pain following unilateral arthroplasty due to its ability to reduce postoperative opioid use.

Reasons and Risk Factors for Failed Same-Day Discharge After Total Joint Arthroplasty.

BACKGROUND: A shift toward same-day discharge (SDD) in primary elective total knee arthroplasty (TKA) and total hip arthroplasty (THA) has created a need to optimize patient selection and improve same-day recovery pathways. The objectives of this study were (1) to identify our institution's most common causes for failed SDD, and (2) to evaluate risk factors associated with failed SDD. METHODS: A retrospective review of SDD patients undergoing primary TKA or THA from January 2021 to September 2022 was conducted. Reasons for SDD failure were recorded and differences between successful and failed SDD cases were assessed via a multivariate logistic regression. RESULTS: Overall, 85.3% (651 of 753) of patients included were successful SDDs. Failed SDD occurred in 16.8% (74 of 441) of TKA and 11.8% (38 of 322) of THA cases. Primary reasons included failure to clear physical therapy (33.0%, 37 of 112), postoperative hypotension (20.5%, 23 of 112), and urinary retention (16.9%, 19 of 112). Analysis revealed that overall failed SDD cases were more likely to have had prior opioid use and a longer surgical time. Failed TKA SDD cases were more likely to have had a longer surgical time and not have receive a preoperative nerve block, while failed THA SDD cases were more likely to be older. CONCLUSIONS: The SDD selection criteria and pathways continue to evolve, with multiple factors contributing to failed SDD. Improving patient selection algorithms and optimizing post-operative pathways can enhance the ability to successfully choose SDD candidates. LEVEL OF EVIDENCE: III.

SuRxgWell: study protocol for a randomized controlled trial of telemedicine-based digital cognitive behavioral intervention for high anxiety and depression among patients undergoing elective hip and knee arthroplasty surgery.

BACKGROUND: Mood disorders (anxiety, depression), sleep disorders, and catastrophizing lead to increased post-operative pain perception, increase in postoperative opioid consumption, decreased engagement with physical activity, and increased resource utilization in surgical patients. Psychosocial disorders significantly affect postoperative outcome. Unfortunately, studies focused on perioperative psychological assessment and treatment are scarce. We propose to test whether digital cognitive behavioral intervention (dCBI) can help surgical patients. dCBI such as RxWell™ is a proven treatment for mood disorders in medical patients such as reducing depression in patients with inflammatory bowel disease. We hypothesize that RxWell™ will also be effective in surgical patients. This study aims to test whether RxWell™ can improve preoperative mood disorders and subsequently reduce postoperative pain and opioid requirement in patients scheduled for primary total hip and knee arthroplasty (THA, TKA). We named the trial as the SuRxgWell trial. METHODS: This is a randomized, controlled trial that will enroll primary and unilateral THA or TKA patients with anxiety and/or depression symptoms before surgery to receive the SuRxgWell dCBI program and investigate its impact on postoperative outcomes including postoperative pain, anxiety, depression, sleep disorder, and catastrophizing. After signing an informed consent, subjects will be screened using the PROMIS questionnaires, and subjects with a T-score of ≥ 60 on the short Patient-Reported Outcomes Measurement Information System (PROMIS) 4a Anxiety and/or short PROMIS 4a Depression questionnaires will be randomized to either usual care (control group) or the cognitive behavioral intervention, RxWell™, plus usual care (intervention group). The control group will receive information on how to locate tools to address anxiety and depression, whereas the intervention group will have access to SuRxgWell 1 month prior to surgery and up to 3 months after surgery. The allocation will be 3:1 (intervention to control). Investigators will be blinded, but research coordinators approaching patients and research subjects will not. The primary outcome will be day of surgery anxiety or depression symptoms measured with the PROMIS Short Form v1.0 -Anxiety 4a/Depression and Generalized Anxiety Disorder Measure (GAD-7) and Patient Health Questionnaire (PHQ-8). Secondary end points include measuring other health-related quality of life outcomes including sleep disturbance, fatigue, ability to participate in social roles, pain interference, cognitive function, pain catastrophizing, and physical function. Other secondary outcomes include collecting data about preoperative and postoperative pain scores, and pain medication usage, and orthopedic functional recovery at baseline, day of surgery, and 1, 2, and 3 months after the surgery with the Pain Catastrophizing Scale, the Knee injury and Osteoarthritis Outcome Score (KOOS), and Hip injury and Osteoarthritis Outcome Score (HOOS). In addition, subjects will be asked to complete a GAD-7 and PHQ-8 questionnaires bi-weekly (via the RxWell™ app for the interventional group or REDCAP for the control group). Data about postsurgical complications, and resource utilization will also be recorded. We will also receive monthly reports measuring the usage and engagement of RxWell use for each participant randomized to that arm. The primary hypotheses will be assessed with intention-to-treat estimates, and differences in primary outcome will be tested using independent two sample t-tests. This trial is registered to the ClinicalTrials.gov database (NCT05658796) and supported by the DAPM, UPMC Health Plan, and the NIH. DISCUSSION: Our trial will evaluate the feasibility of digital cognitive behavioral intervention as a perioperative tool to improve anxiety and depression before and after major orthopedic surgery in comparison to education. If digital cognitive behavioral intervention proves to be effective, this might have important clinical implications, reducing the incidence of chronic postsurgical pain and improving outcomes.

The Microbiome of Osteoarthritic Hip and Knee Joints: A Prospective Multicenter Investigation.

BACKGROUND: Recent advances in high-throughput DNA sequencing technologies have made it possible to characterize the microbial profile in anatomical sites previously assumed to be sterile. We used this approach to explore the microbial composition within joints of osteoarthritic patients. METHODS: This prospective multicenter study recruited 113 patients undergoing hip or knee arthroplasty between 2017 and 2019. Demographics and prior intra-articular injections were noted. Matched synovial fluid, tissue, and swab specimens were obtained and shipped to a centralized laboratory for testing. Following DNA extraction, microbial 16S-rRNA sequencing was performed. RESULTS: Comparisons of paired specimens indicated that each was a comparable measure for microbiological sampling of the joint. Swab specimens were modestly different in bacterial composition from synovial fluid and tissue. The 5 most abundant genera were Escherichia, Cutibacterium, Staphylococcus, Acinetobacter, and Pseudomonas. Although sample size varied, the hospital of origin explained a significant portion (18.5%) of the variance in the microbial composition of the joint, and corticosteroid injection within 6 months before arthroplasty was associated with elevated abundance of several lineages. CONCLUSIONS: The findings revealed that prior intra-articular injection and the operative hospital environment may influence the microbial composition of the joint. Furthermore, the most common species observed in this study were not among the most common in previous skin microbiome studies, suggesting that the microbial profiles detected are not likely explained solely by skin contamination. Further research is needed to determine the relationship between the hospital and a "closed" microbiome environment. These findings contribute to establishing the baseline microbial signal and identifying contributing variables in the osteoarthritic joint, which will be valuable as a comparator in the contexts of infection and long-term arthroplasty success. LEVEL OF EVIDENCE: Diagnostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Dynamic Changes in Lumbar Spine Kinematics During Gait May Explain Improvement in Back Pain and Disability in Patients With Hip-Spine Syndrome.

STUDY DESIGN: Prospective cohort. OBJECTIVE: Determine if total hip arthroplasty (THA) changes lumbar spine kinematics during gait in a manner that explains the improvements in back pain seen in patients with hip-spine syndrome. SUMMARY OF BACKGROUND DATA: For patients with hip-spine syndrome, improvements in both hip and back pain have been demonstrated after THA; however, the exact mechanism of improvement in back pain remains unknown, as no corresponding changes in lumbar spine static radiographic parameters have been identified. METHODS: Thirteen patients with severe, unilateral hip osteoarthritis scheduled to undergo THA with concomitant back pain and disability were tested at baseline and 6 months after THA. Harris Hip Score (HHS) and Oswestry Disability Index questionnaires were completed; the static orientation of the spine and pelvis were measured on standing radiographs, and lumbar spine kinematics were measured during treadmill walking using a validated measurement system that matched subject-specific bone models created from CT scans to dynamic biplane radiographs. RESULTS: After THA, both the Oswestry Disability Index (36.3-11.3, P <0.001) and Harris Hip Score (55.7-77.9, P <0.001) improved; however, there were no changes in static intervertebral or pelvis orientation. During gait after THA, the overall lumbar spine (L1 to L5) was less lordotic from heel strike to contralateral toe off ( P <0.001), the L4 and L5 vertebra were less anteriorly tilted by 3.9° ( P =0.038) from midstance to contralateral heel strike and by 3.9° ( P =0.001) during stance, respectively. CONCLUSION: The decreased anterior tilt of the 2 lowest lumbar vertebrae and the corresponding loss of lumbar lordosis may reduce facet loading during the stance phase of gait after THA. This change in lumbar spine kinematics during gait is a potential mechanism to explain the observed improvements in back pain and disability after THA. LEVEL OF EVIDENCE: 4.

An Enhanced Understanding of Culture-Negative Periprosthetic Joint Infection with Next-Generation Sequencing: A Multicenter Study.

BACKGROUND: The challenges of culture-negative periprosthetic joint infection (PJI) have led to the emergence of molecular methods of pathogen identification, including next-generation sequencing (NGS). While its increased sensitivity compared with traditional culture techniques is well documented, it is not fully known which organisms could be expected to be detected with use of NGS. The aim of this study was to describe the NGS profile of culture-negative PJI. METHODS: Patients undergoing revision hip or knee arthroplasty from June 2016 to August 2020 at 14 institutions were prospectively recruited. Patients meeting International Consensus Meeting (ICM) criteria for PJI were included in this study. Intraoperative samples were obtained and concurrently sent for both routine culture and NGS. Patients for whom NGS was positive and standard culture was negative were included in our analysis. RESULTS: The overall cohort included 301 patients who met the ICM criteria for PJI. Of these patients, 85 (28.2%) were culture-negative. A pathogen could be identified by NGS in 56 (65.9%) of these culture-negative patients. Seventeen species were identified as common based on a study-wide incidence threshold of 5%. NGS revealed a polymicrobial infection in 91.1% of culture-negative PJI cases, with the set of common species contributing to 82.4% of polymicrobial profiles. Escherichia coli, Cutibacterium acnes, Staphylococcus epidermidis, and Staphylococcus aureus ranked highest in terms of incidence and study-wide mean relative abundance and were most frequently the dominant organism when occurring in polymicrobial infections. CONCLUSIONS: NGS provides a more comprehensive picture of the microbial profile of infection that is often missed by traditional culture. Examining the profile of PJI in a multicenter cohort using NGS, this study demonstrated that approximately two-thirds of culture-negative PJIs had identifiable opportunistically pathogenic organisms, and furthermore, the majority of infections were polymicrobial. LEVEL OF EVIDENCE: Diagnostic Level II . See Instructions for Authors for a complete description of levels of evidence.

The presence of a draining sinus is associated with failure of re-implantation during two-stage exchange arthroplasty.

Background: Reinfection rates after two-stage exchange arthroplasty for prosthetic joint infection (PJI) have been reported as high as 33 % in the literature. Understanding risk factors for treatment failure will help to preoperatively counsel patients on the likelihood of successful treatment and possibly influence the surgeon's treatment algorithm. This study aimed to delineate whether the presence of a draining sinus tract is associated with risk of failure of two-stage exchange arthroplasty. Methods: We performed a single institution, multi-center retrospective chart review of outcomes of patients treated for PJI with two-stage exchange arthroplasty between June 2006 and May 2016. For patients treated prior to 2011, PJI was defined based on the preoperative work-up and intraoperative findings as determined by the attending surgeon. After 2011, PJI was defined using MSIS consensus criteria. All patients had a minimum of follow-up of 2 years or treatment failure prior to 2 years. Treatment failure was defined as reinfection or failure to complete two-stage exchange secondary to persistent infection or other host factors. Operative reports and clinical notes were reviewed to assess for presence of a draining sinus tract. Results: 240 patients were treated for PJI with intended two-stage exchange arthroplasty. The overall rate of treatment failure was 29.6 % ( 71 / 240 ), while the overall rate of reinfection was 13.3 % ( 32 / 240 ). A total of 39 patients did not complete second stage revision; final treatment for these patients was amputation, fusion, or chronic antibiotic suppression. A total of 52 of 240 patients (21.7 %) had a draining sinus tract at presentation. Patients with a sinus tract were significantly less likely to be replanted compared to those without a sinus tract at presentation (13.3 % vs. 26.9 %, p = 0.02 ). However, when accounting for all mechanisms of treatment failure, including reinfection following replantation, there was no statistically significant difference detected between the sinus and no-sinus groups (27.7 % vs. 36.5 %, p = 0.22 ). Discussion: A draining sinus tract represents a chronic, deep infectious process with ultimate compromise of overlying soft tissues. Thus we hypothesized it would be associated with failure in a two-stage exchange arthroplasty. These data demonstrate that patients with a draining sinus are significantly less likely to undergo re-implantation. This provides evidence to the paucity of data surrounding draining sinuses and two-stage PJI treatment.

Perioperative Blood Management in Total Joint Arthroplasty.

Preoperative anemia is an established risk factor for complications following total joint arthroplasty. Postoperative anemia can be managed with allogeneic blood transfusion, but this has inherent risks. A thorough preoperative workup can help to diagnose anemia and optimize these patients for surgery to minimize the need for postoperative transfusion. Perioperatively, the amount of blood loss can be minimized by using hypotensive anesthetic techniques and administering antifibrinolytic agents. Last, in the event that allogeneic blood transfusion is still required, strict transfusion guidelines should be followed. Evidence-based interventions for preoperative, perioperative, and postoperative blood management in total joint arthroplasty will be reviewed.

Administration of Tranexamic Acid Improves Long-Term Outcomes in Total Knee Arthroplasty.

BACKGROUND: Blood transfusion in total knee arthroplasty (TKA) is associated with increased morbidity, including periprosthetic joint infection (PJI). Tranexamic acid (TXA) reduces blood transfusion rates, but there is limited evidence demonstrating improved outcomes in TKA resulting from TXA administration. The objectives of this study are determining whether TXA is associated with decreased rate of PJI, decreased rate of outcomes associated with PJI, and whether there are differences in rates of adverse events. METHODS: A multicenter cohort study comprising 23,421 TKA compared 4423 patients receiving TXA to 18,998 patients not receiving TXA. Primary outcome was PJI within 2 years of TKA. Secondary outcomes included revision surgery, irrigation and debridement, transfusion, and length of stay. Adverse events included readmission, deep vein thrombosis, pulmonary emboli, myocardial infarction, or stroke. Adjusted odds ratios were determined using linear mixed models controlling for age, sex, thromboembolic prophylaxis, Charlson comorbidity index, year of TKA, and surgeon. RESULTS: TXA administration reduced incidence of PJI by approximately 50% (odds ratio [OR], 0.55; P = .03). Additionally, there was decreased incidence of revision surgery at 2 years (OR, 0.66; P = .02). Patients receiving TXA had reductions in transfusion rate (OR, 0.15; P < .0001) and length of stay (P < .0001). There was no difference in the rate of pulmonary emboli (OR, 1.20; P = .39), myocardial infarction (OR, 0.78; P = .55), or stroke (OR, 1.17; P = .77). CONCLUSION: Administration of TXA in TKA resulted in reduced rate of PJI and overall revision surgery. No difference in thromboembolic events were observed. The use of TXA is safe and improves outcomes in TKA. LEVEL OF EVIDENCE: Level III, Observational Cohort Study.

Musculoskeletal Infection Society (MSIS) Update on Infection in Arthroplasty.

Periprosthetic joint infection (PJI) continues to be a devastating problem in the field of total joint arthroplasty, and recent literature can be used to make the preoperative diagnosis of PJI, guide nonsurgical and surgical treatment, and provide postoperative antimicrobial management of PJI patients. The diagnosis of PJI relies on traditional serum and synovial fluid tests, with newer biomarkers and molecular tests. Surgical treatment depends on the duration of infection, host qualities, and surgeon factors, and procedures include débridement, antibiotics, and implant retention, one-stage exchange arthroplasty, two-stage exchange arthroplasty, resection arthroplasty, fusion, or amputation. Appropriate management of PJI involves coordination with infectious disease consultants, internal medicine physicians, and orthopaedic surgeons. Antimicrobial management is guided by the organisms involved, whether it is a new or persistent infection, and antibiotic suppression should be administered on an individual case basis. The goals of this instructional course lecture are to review the most relevant recent literature and provide treating physicians and surgeons with the most up-to-date armamentarium to reduce the recurrence of PJI.

Do Culture Negative Periprosthetic Joint Infections Remain Culture Negative?

BACKGROUND: Diagnosis and treatment of culture negative total knee arthroplasty (TKA) periprosthetic joint infection (PJI) is challenging. There is debate over whether culture negative PJI confers increased risk of failure and which organisms are responsible. It is also unclear as to what factors predict conversion from culture negative to culture positivity. To address these issues, we performed an observational study to detect factors associated with transition from culture negative to culture positive TKA PJI in those patients that failed irrigation and debridement (I&D), determine the incidence of this transition, and identify those organisms that were associated with treatment failure. METHODS: A multicenter observational cohort study was performed on patients with TKA PJI as defined by Musculoskeletal Infection Society criteria without cultured organisms and treated with I&D. Primary outcome was failure defined as any subsequent surgical procedure. Secondary outcome included cultured organism within 2 years of initial I&D. RESULTS: Two hundred sixteen TKA I&D procedures were performed for PJI, and 36 met inclusion criteria. The observed treatment failure rate for culture negative PJI treated with I&D was 41.67%. Of those culture negative I&Ds that failed, 53.33% became culture positive after failure. Of those that converted to culture positive, 62.5% were Staphylococcus species. The odds ratio associated with becoming culture positive following culture negative treatment failure in the setting of antibiotic administration prior to the initial I&D procedure was 0.69 (95% confidence interval 0.14-3.47, P = .65). CONCLUSION: Many cases of culture negative TKA PJI treated with I&D eventually fail and become culture positive. Staphylococci are common organisms identified after culture negative PJI.

Effectiveness of Later-Stage Exercise Programs vs Usual Medical Care on Physical Function and Activity After Total Knee Replacement: A Randomized Clinical Trial.

Importance: Several functional limitations persist after total knee replacement (TKR). Intensive exercise programs could resolve these limitations but are not well tolerated by many patients until a later stage (>2 months) after surgery. Evidence for exercise at a later stage after TKR is limited. Objectives: To compare the effectiveness of later-stage exercise programs after TKR and to explore heterogeneity of treatment effects. Design, Setting, and Participants: Three-arm single-blind randomized clinical trial (January 7, 2015, to November 9, 2017) using an intent-to-treat approach with follow-ups at 3 months and 6 months. The setting was Allegheny County, Pennsylvania (an outpatient physical therapy clinic and 4 community centers). Participants had primary TKR performed more than 2 months previously, were 60 years or older, experienced moderate functional limitations, and were medically cleared to exercise. Interventions: Clinic-based physical therapy exercise (physical therapy arm), community-based group exercise (community arm), and usual care (control arm). The control arm continued their usual care, whereas the exercise arms participated in supervised exercise programs lasting 12 weeks. Main Outcomes and Measures: The primary outcome was arm differences in the Western Ontario and McMaster Universities Osteoarthritis Index-Physical Function (WOMAC-PF) at 3 months. The secondary outcomes included performance-based tests germane to knee replacement and additional surveys of physical function. Data were analyzed by linear mixed models and responder analysis. Results: A total of 240 participants (mean [SD] age, 70 [7] years; 61.7% female) were allocated to physical therapy (n = 96), community exercise (n = 96), or control (n = 48). All 3 arms demonstrated clinically important improvement. At 3 months, between-arm analyses for the WOMAC-PF demonstrated no differences between physical therapy and community (-2.2; 98.3% CI, -4.5 to 0.1), physical therapy and control (-2.1; 98.3% CI, -4.9 to 0.7), and community and control (0.1; 98.3% CI, -2.7 to 2.9). Performance-based tests demonstrated greater improvement in the physical therapy arm compared with both the community (0.1 z score units; 98.3% CI, 0.0-0.2) and control (0.3 z score units; 98.3% CI, 0.1-0.4) arms and the community arm compared with the control arm (0.2 z score units; 98.3% CI, 0.0-0.3). The physical therapy arm had more than 17.7% responders than the community arm and more than 19.0% responders than the control arm. There was no difference in responder rates between the community and control arms. Conclusions and Relevance: Based on the primary outcome, participation in late-stage exercise programs after TKR offered no benefit over usual care. The benefits of physical therapy identified by the secondary outcomes and responder analysis require confirmation. Trial Registration: ClinicalTrials.gov Identifier: NCT02237911.

Revision total knee arthroplasty with porous-coated metaphyseal sleeves provides radiographic ingrowth and stable fixation.

PURPOSE: Porous-coated metaphyseal sleeves are designed to fill bone defects and facilitate osseointegration when bone loss in encountered during revision total knee arthroplasty (TKA). The purpose of this study is to evaluate short-term results of porous-coated metaphyseal sleeves with regards to implant fixation and clinical outcomes. METHODS: A retrospective review was conducted on 50 patients (79 sleeves-49 tibial and 30 femoral) who had a press-fit metaphyseal sleeve with revision TKA. Tibial and femoral bone loss was classified according to the Anderson Orthopaedic Research Institute (AORI) bone defect classification. Post-operative complications of infection, revision surgery, and dislocation were assessed. Follow-up radiographs were evaluated for signs of loosening using the criteria developed by the Knee Society. The median follow-up was 58.8 months (range 25.8-93.0 months). RESULTS: The bone loss classifications were 1 type 1, 30 type 2a, 2 type 2b, and 17 type 3, and with regards to the femur, 5 were type 1, 8 type 2a, 31 type 2b, and 6 type 3. At final follow-up, 41/45 (91.1%) tibial and 28/29 (96.6%) femoral sleeves showed radiographic evidence of ingrowth. Of these 69 patients, all showed radiographic evidence of bony ingrowth. Three sleeves were revised for infection and two for loosening. The re-operation rate for loosening was 5/74 (6.8%) and for any reason was 14/74 (18.9%). CONCLUSIONS: Modular porous-coated press fit metaphyseal sleeves fill defects and provide evidence of radiographic ingrowth. Short-term stable fixation can be achieved with sleeves, which is helpful as more patients undergo revision total knee arthroplasty with greater bone loss. Longer duration studies are needed to ascertain the survival rate of these implants. LEVEL OF EVIDENCE: IV.

Are Sonication Cultures of Antibiotic Cement Spacers Useful During Second-stage Reimplantation Surgery for Prosthetic Joint Infection?

BACKGROUND: Organisms may persist on polymethylmethacrylate (PMMA) spacer surfaces, and subclinical infection is postulated to be a source of infection recurrence. Several small patient series have shown a high proportion of positive sonication cultures on PMMA spacers at the second stage of a two-stage revision. However, the association between a positive sonication culture and the risk for recurrence of infection after two-stage exchange is not fully elucidated. QUESTIONS/PURPOSES: Are cultures derived from sonication of antibiotic spacers associated with infection control or recurrence after two-stage revision for prosthetic joint infection (PJI)? METHODS: Between September 2013 and April 2016, we treated 67 patients with PJI with two-stage revisions. At the second stage, all cement spacers were explanted and sonicated. A total of`10 (15%) patients were lost to followup or failed to reach 1-year followup during the study period, and another 16 (24%) were excluded for prespecified reasons, leaving 41 patients for analysis in this study. Of the 41 patients included in this study, there were 25 TKAs, 15 THAs, and one distal femoral replacement. All patients met the Musculoskeletal Infection Society criteria for PJI at Stage 1 of the two-stage revision. The most common infecting organisms prompting two-stage revision were methicillin-sensitive Staphylococcus aureus and coagulase-negative staphylococci. PMMA spacers were most frequently loaded with gentamicin or gentamicin/vancomycin. Standard 6-week intravenous antibiotic courses were used for index infections and postreimplantation suppression was used for 3 months in all patients as determined by cultures and sensitivities. Patients were assessed for recurrence of infection at postoperative clinic visits completed at standard intervals. The average length of followup was 1.9 years with a range of 1 to 3.3 years. RESULTS: Sonication cultures that reached a threshold of 5 colony-forming units for positive culture had poor screening utility for subclinical persistent infection (sensitivity: 0%; confidence interval [CI], 0%-60%), but reasonable use for ruling in successful two-stage revision (specificity: 95%; 95% CI, 82%-99%). Positive sonication culture results in the two of 41 (4.9%) explanted spacers yielded coagulase-negative staphylococci, different from primary prosthesis cultures in both patients (Corynebacterium and Proteus mirabilis), and did not alter antibiotic choice. Neither of the patients has developed a reinfection at followup of 1.2 and 1.9 years. Of the 39 two-stage revisions with negative spacer sonication cultures, four developed reinfections. CONCLUSIONS: Positive sonication fluid culture of PMMA spacers during reimplantation surgery was not associated with persistent or recurrent infection at minimum followup of 1 year. We do not recommend routine sonication of explanted PMMA spacers in the absence of clinical evidence suggesting persistent infection. Multicenter, prospective studies with long-term followup are needed to determine if sonication of PMMA spacers can predict persistent or recurrent infection. LEVEL OF EVIDENCE: Level III, diagnostic study.

The influence of continuous versus interval walking exercise on knee joint loading and pain in patients with knee osteoarthritis.

OBJECTIVE: To evaluate whether knee contact force and knee pain are different between continuous and interval walking exercise in patients with knee osteoarthritis (OA). METHODS: Twenty seven patients with unilateral symptomatic knee OA completed two separate walking exercise sessions on a treadmill at 1.3m/s on two different days: 1) a continuous 45min walking exercise session, and 2) three 15min bouts of walking exercise separated by 1h rest periods for a total of 45min of exercise in an interval format. Estimated knee contact forces using the OpenSim software and knee pain were evaluated at baseline (1st minute of walking) and after every 15min between the continuous and interval walking conditions. RESULTS: A significant increase from baseline was observed in peak knee contact force during the weight-acceptance phase of gait after 30 and 45min of walking, irrespective of the walking exercise condition. Additionally, whereas continuous walking resulted in an increase in knee pain, interval walking did not lead to increased knee pain. CONCLUSION: Walking exercise durations of 30min or greater may lead to undesirable knee joint loading in patients with knee OA, while performing the same volume of exercise in multiple bouts as opposed to one continuous bout may be beneficial for limiting knee pain.

Sonication of Arthroplasty Implants Improves Accuracy of Periprosthetic Joint Infection Cultures.

BACKGROUND: There is evidence that sonication of explanted prosthetic hip and knee arthroplasty components with culture of the sonication fluid may enhance diagnostic sensitivity. Previous studies on the use of implant sonicate cultures have evaluated diagnostic thresholds but did not elaborate on the clinical importance of positive implant sonicate cultures in the setting of presumed aseptic revisions and did not utilize consensus statements on periprosthetic joint infection (PJI) diagnosis when defining their gold standard for infection. QUESTIONS/PURPOSES: (1) How do implant sonicate cultures compare with preoperative synovial fluid cultures and intraoperative tissue cultures in the diagnosis of PJI in both THA and TKA when compared against Musculoskeletal Infection Society (MSIS) criteria for PJI? (2) Utilizing implant sonicate cultures, what is the relative prevalence of bacterial species identified in PJIs? (3) What is the incidence of positive implant sonicate cultures in the setting of presumed aseptic revision hip and knee arthroplasty procedures, and what treatments did they receive? METHODS: Between 2012 and 2016 we performed implant sonicate fluid cultures on surgically removed implants from 565 revision THAs and TKAs. Exclusion criteria including insufficient data to determine Musculoskeletal Infection Society (MSIS) classification, fungal-only cultures, and absence of reported colony-forming units decreased the number of procedures to 503. Procedures represented each instance of revision surgery (sometimes multiple in the same patient). Of those, a definitive diagnosis of infection was made using the MSIS criteria in 178 of 503 (35%), whereas the others (325 of 503 [65%]) were diagnosed as without infection. A total of 53 of 325 (16%) were considered without infection based on MSIS criteria but had a positive implant sonicate culture. Twenty-five of 53 (47%) of these patients were followed for at least 2 years. The diagnosis of PJI was determined using the MSIS criteria. RESULTS: Sensitivity of implant sonicate culture was greater than synovial fluid culture and tissue culture (97% [89%-99%] versus 57% [44%-69%], p < 0.001; 97% [89%-99%] versus 70% [58%-80%], p < 0.001, respectively). The specificity of implant sonicate culture was not different from synovial fluid culture or tissue culture with the numbers available (90% [72%-97%] versus 100% [86%-100%], p = 0.833; 90% [72%-97%] versus 97% [81%-100%], p = 0.317, respectively). Coagulase-negative Staphylococcus was the most prevalent organism for both procedure types. In PJIs, the five most frequent bacteria identified by synovial fluid, tissue, and/or implant sonicate cultures were coagulase-negative Staphylococcus (26% [89 of 267]), methicillin-susceptible Staphylococcus aureus (19% [65 of 267]), methicillin-resistant S. aureus (12% [43 of 267]), α-hemolytic Streptococci (5% [19 of 267]), and Enterococcus faecalis (5% [19 of 267]). Fifty-three of 325 (16%) presumed aseptic revisions had a positive sonication culture. Thirty-four percent (18 of 53) of culture-positive aseptic revision patients received antibiotic treatment for infection and 8% (4 of 53) underwent a secondary revision. CONCLUSIONS: The routine use of implant sonicate cultures in arthroplasty revisions improves the diagnostic sensitivity for detecting the presence of bacteria in both clinical and occult infections. Future studies will need to refine colony-forming unit thresholds for determining clinical infection and indications for treatment. LEVEL OF EVIDENCE: Level III, diagnostic study.