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More Data on Periprosthetic Hip Infections

Among >100,000 total hip arthroplasty (THA) patients ≥55 years of age whose data resides in a Canadian arthroplasty database, the 15-year cumulative incidence of periprosthetic joint infection (PJI) was 1.44%, according to a study by the McMaster Arthroplasty Collaborative in the March 18, 2020 issue of JBJS.

In addition to finding that the overall risk of developing PJI after THA has not changed over the last 15 years in this cohort, the authors found the following factors associated with increased risk of developing a PJI:

  • Male sex (absolute increased risk of 0.48% at 10 years)
  • Type 2 diabetes (absolute increased risk of 0.64% at 10 years)
  • Discharge to a convalescent-care facility (absolute increased risk of 0.46% at 10 years)

The authors view the third bulleted item above as “a surrogate marker of frailty and poorer general health.”

Patient age, surgical approach, surgical setting (academic versus rural), use of cement, and patient income were not associated with an increased risk of PJI. Nearly two-thirds of PJI cases occurred within 2 years after surgery, and 98% occurred within 10 years postoperatively.

The authors conclude that these and other substantiated findings about PJI risk factors “should be reviewed with the patient during preoperative risk counseling.”

COVID-19 Rallies the Orthopaedic Community: Singapore’s Experience

The mind and heart of almost everyone on the planet are now focused to some extent on COVID-19. In the first of what will be a series of fast-tracked JBJS articles about how orthopaedic surgeons are helping mitigate the pandemic, Liang et al. describe orthopaedists’ early experiences in Singapore, where the first case of COVID-19 was confirmed in a tourist from Wuhan, China on January 23, 2020.

Singapore has had a nationwide outbreak-response system (called DORSCON, for Disease Outbreak Response System Condition) since the SARS crisis of 2003 (see Figure). Immediately after the first evidence of community spread of the virus on the island, on February 7, 2020, the Ministry of Health raised the DORSCON status to Orange, which triggered the following outbreak-control measures:

  • Ramping up of contact tracing
  • Mandatory 14-day quarantining of those in close contact with people who had confirmed infections
  • A 2-week mandatory leave of absence for healthcare workers with recent travel histories to China
  • Compulsory, twice-daily temperature screenings of all healthcare workers

The COVID-19-driven changes in orthopaedic practice revolved around 2 strategies:

  • Clinical Urgency
    • Musculoskeletal trauma and tumor patients were operated on as scheduled, but elective surgical cases were postponed to free up beds for confirmed or suspected COVID-19 patients.
    • Orthopaedists were encouraged to consider temporary pain-relieving measures (such as corticosteroid injections or nerve-root blocks) for patients with severe pain whose surgeries were postponed.
  • Patient and Healthcare-Worker Protection
    • Clinicians have been advised to prolong the duration between nonurgent follow-up appointments. All patients attending outpatient clinics are screened for risk factors and have their temperatures checked. Febrile patients are moved to the emergency department for further evaluation.
    • Orthopaedic teams wear surgical masks for all patient encounters and practice strict hand-hygiene practices.
    • When evaluating orthopaedic patients suspected of or diagnosed with COVID-19, all staff wear full personal protective equipment. Whenever possible, such evaluations take place in pressure-negative isolation units, and these patients are co-managed with infectious-disease colleagues.
    • If surgery on a suspected or confirmed COVID-19 patient is needed, it is performed by a dedicated orthopaedic contamination team; these teams are segregated from the rest of the staff to minimize the risk of cross-contamination.

Technology Tools for Training
Telemedicine and telerehabilitation have helped ensure the quality of patient care in Singapore, and technology is also being used to keep orthopaedic training going. Because all interhospital rotations and in-person combined teaching programs have been suspended, residency training programs are relying on videoconferencing platforms for scheduled teaching sessions. For trainees who engage with instructional videos or webinars, faculty members follow up with online discussions.

As residents take shifts in the emergency department to assist with COVID-19 screening, they learn important lessons in management of limited resources and “softer” skills such as empathy and teamwork.

Liang et al. conclude with this admonition to orthopaedic surgeons everywhere: “Stay vigilant even when reviewing low-risk elective patients; be champions of good hygiene practices, and be open-minded in the adoption of novel workplace technologies.”

More Work, Less Pay for Revision TKAs

Time is a valuable commodity for everyone. Most physicians have spent long hours in the clinic or hospital, away from our families, sometimes missing important life events. We accept those aspects of our chosen profession. But everyone, including surgeons, wants to be appropriately reimbursed for their time. It’s logical that more complex surgical cases take more time to perform correctly and safely. But does Medicare (and the private insurers who base their physician payments on Medicare rates) adequately reimburse for that extra time?

The short answer is “no,” at least in terms of revision surgery for infected total knee arthroplasties (TKAs). Samuel et al. tackle that topic in the February 5, 2020 issue of The Journal. The authors reviewed records from the NSQIP database to identify cases of aseptic revision TKA, 1-stage septic revision TKA, and 2-stage septic revision TKA. Using propensity-score matching that controlled for age, sex, race, BMI, and ASA classification, the authors established 4 cohorts that allowed for comparison of the following types of revision TKA:

  • 1-stage, 2-component aseptic revisions (n=1,096)
  • 1 stage, 2-component septic revisions (n=274)
  • First stage of a 2-stage septic revision (n=274)
  • Second stage of a 2-stage septic revision (n=274)

The authors then compared the relative value units (RVUs) for each type of revision TKA. (Medicare uses RVU-based algorithms to reimburse physicians for their services.) The authors also identified operative times for the surgery types and made RVU-per-minute and dollars-per-minute calculations.

The mean operative times were statistically different between each cohort (149 minutes for the aseptic group, 160 minutes for the 1-stage septic group, 138 minutes for the first-stage of the 2-stage septic group, and 170 minutes for the second-stage of the 2-stage septic group). The dollar-per-minute calculation in the “easiest case” of aseptic revision was $7.74 per minute, while in the “hardest case” of a 2-stage septic revision, reimbursement was $5.66 per minute for the first stage and $5.19 per minute for the second stage.

The fact that Medicare’s current reimbursement system does not account for the complexity of treating an infected TKA harms not only surgeons. Financially discouraging physicians from taking complex cases could lead to patients having a difficult time finding a doctor to treat their infected knee replacement. This entire predicament warrants further investigation, possible adjustments to the RVU system, and more realistic valuations of time in the OR.

Matthew R. Schmitz, MD
JBJS Deputy Editor for Social Media

Vancomycin-Soaked ACL Grafts Cut Already-Low Infection Rates

The word “infection” contains 9 letters, but it’s a four-letter word for orthopaedic surgeons. Postoperative infections are complications that we all deal with, but we try hard to avoid them. Infections after elective sports surgeries can have especially devastating long-term consequences. Thankfully, scientific advances such as  improved sterile techniques and more powerful prophylactic antibiotics have helped us decrease the rates of perioperative infections. But more can always be done in this arena.

Baron et al. discuss one additional infection-fighting approach in the December 18, 2019 issue of JBJS, where they report on findings from a retrospective cohort study that looked at 90-day infection rates after >1,600 anterior cruciate ligament (ACL) reconstructions. Specifically, they investigated whether the rates of infection differed when the ACL grafts were prepared with or without a vancomycin irrigant. The average patient age was 27 years old, and all the surgeries (84.1% of which were primary reconstructions) were performed by 1 of 6 fellowship-trained surgeons. The graft was soaked in vancomycin solution in 798 cases (48.7%), while the remaining 51.3% did not use vancomycin.

Baron et al. found that 11 of the reconstructions were complicated by infection within 90 days, but only 1 of those 11 infections occurred in the vancomycin group (p=0.032). After controlling for various confounding factors, the authors found that increased body mass index and increased operative time were also significantly associated with postoperative infection, while age, sex, smoking, surgeon, and insurance type were not.

These results reveal an 89.4% relative risk reduction in postoperative infections after ACL reconstructions when grafts are bathed in vancomycin solution, although the absolute rate of infection among non-soaked grafts (1.2%) was still quite low. Time and more rigorous study designs will tell us whether this is a big step forward in the evolution of infection prevention, but these results should at least prompt further investigation.

Matthew R. Schmitz, MD
JBJS Deputy Editor for Social Media

Vancomycin Powder May Thwart Spinal Fusion

Prompted by relatively high infection rates associated with surgical treatment of pediatric spinal conditions such as scoliosis and spinal-deformity surgery in immunocompromised adults, spine surgeons have led “deep dive” clinical research into the possible benefits of local, intrawound antibiotic therapy. Consequently, the administration of antibiotic powder around the spine’s posterior elements and internal-fixation devices has become fairly widespread. But are there possible downsides to this approach that can impact patient outcomes?

This important question is addressed in the basic-science study by Ishida et al. in the October 2, 2019 issue of The Journal. The authors analyzed the fusion-specific impact of varying concentrations of intrawound vancomycin and tobramycin in a well-characterized rat model of posterolateral fusion performed with syngeneic iliac-crest allograft plus clinical bone-graft substitute. Ishida et al. found that a high dose of vancomycin (71.5 mg/kg, about 5 times higher than spine surgeons typically use) but not tobramycin had detrimental effects on fusion-mass formation in this model, as demonstrated by micro-computed tomography and histological analysis.

We now need further clinical research from the spine community to determine the optimal doses and types of intrawound antibiotics in this setting. Based on the currently available data, power calculations should be performed when designing future trials focused on this question. There seems to be little remaining doubt that locally delivered antibiotics help limit surgical-site and deep infections in spinal surgery. The impact of antibiotics on fusion rates must now be investigated further.

Marc Swiontkowski, MD
JBJS Editor-in-Chief

Stop Adding Antibiotics to Irrigation Solutions

The rate of adoption of knowledge gleaned from multiple well-done randomized clinical trials into medical practice is disappointingly slow. This has been well-documented in cardiovascular medicine, and the examples in orthopaedic surgery are embarrassingly similar. A corollary phenomenon exists with the slow rate of transfer of information from basic science studies to orthopaedic clinical practice.

These “disconnects” occur largely because we tend to adopt the practices of our residency faculty, often without any rational inquiry. Having been an oral examiner for the Part II ABOS Oral Boards, I frequently asked, “Why did you decide on that approach to the patient’s problem?” And I often heard in response, “That’s the way it was done in my residency.”

In the September 18, 2019 issue of The Journal, Goswami et al,. report findings from a well-designed in vitro study demonstrating that the common practice of adding the antibiotics polymyxin and bacitracin to irrigation solution to lower the risk of infection is not based on sound evidence. While adding antibiotics might make intuitive sense, according to these authors, it is “a futile exercise.”

After testing 8 different irrigation solutions for efficacy against S. aureus and E. coli and for toxicity to musculoskeletal cells, Goswami et al. concluded that “our results provide further support for the use of dilute povidone-iodine because of its bactericidal properties, relatively limited toxicity,… and modest cost.” They go on to say that their findings bring into question the widespread usage of polymyxin-bacitracin.

Certainly, we need to assemble more evidence from additional research to identify the optimal irrigation solution for orthopaedic surgery, but in the interim, we should probably stop using polymyxin-bacitracin. Doing so would have the added benefits of lowering costs and not exacerbating the serious problem of antimicrobial resistance. There are many areas of clinical practice where we have no evidence either for against a particular approach. But when we do have solid evidence, even if it’s from an in vitro study, we should work together to improve the rates of adoption into clinical practice.

Marc Swiontkowski, MD
JBJS Editor-in-Chief

What’s New in Musculoskeletal Infection 2019

Every month, JBJS publishes a review of the most pertinent and impactful studies published in the orthopaedic literature during the previous year in 13 subspecialties. Click here for a collection of all OrthoBuzz Specialty Update summaries.

This month, Thomas K. Fehring, MD, co-author of the July 17, 2019 What’s New in Musculoskeletal Infection,” selected the five most clinically compelling findings—all focused on periprosthetic joint infection (PJI)—from among the more than 90 noteworthy studies summarized in the article.

Preventive Irrigation Solutions
–An in vitro study by Campbell et al.1 found that the chlorine-based Dakin solution forms potentially toxic precipitates when mixed with hydrogen peroxide and chlorhexidine. The authors recommend that surgeons not mix irrigation solutions in wounds during surgery.

PJI Diagnosis
–A clinical evaluation by Stone et al. showed that alpha-defensin levels in combination with synovial C-reactive protein had high sensitivity for PJI diagnosis, but the alpha-defensin biomarker can lead to false-positive results in the presence of metallosis and false-negative results in the presence of low-virulence organisms.

–In an investigation of next-generation molecular sequencing for diagnosis of PJI in synovial fluid and tissue, Tarabichi et al. found that in 28 revision cases considered to be infected, cultures were positive in only 61%, while next-generation sequencing was positive in 89%. However, next-generation sequencing also identified microbes in 25% of aseptic revisions that had negative cultures and in 35% of primary total joint arthroplasties. Identification of pathogens in cases considered to be aseptic is concerning and requires further research.

Treating PJI
–A multicenter study found that irrigation and debridement with component retention to treat PJI after total knee arthroplasty had a failure rate of 57% at 4 years.2

–Findings from an 80-patient study by Ford et al.3 challenge the assumption that 2-stage exchanges are highly successful. Fourteen (17.5%) of the patients in the study never underwent reimplantation, 30% had a serious complication, and of the 66 patients with a successful reimplantation, only 73% remained infection-free. Additionally 11% of the patients required a spacer exchange for persistent infection.

References

  1. Campbell ST, Goodnough LH, Bennett CG, Giori NJ. Antiseptics commonly used in total joint arthroplasty interact and may form toxic products. J Arthroplasty.2018 Mar;33(3):844-6. Epub 2017 Nov 11.
  2. Urish KL, Bullock AG, Kreger AM, Shah NB, Jeong K, Rothenberger SD; Infected Implant Consortium. A multicenter study of irrigation and debridement in total knee arthroplasty periprosthetic joint infection: treatment failure is high. J Arthroplasty.2018 Apr;33(4):1154-9. Epub 2017 Nov 21.
  3. Ford AN, Holzmeister AM, Rees HW, Belich PD. Characterization of outcomes of 2-stage exchange arthroplasty in the treatment of prosthetic joint infections. J Arthroplasty.2018 Jul;33(7S):S224-7. Epub 2018 Feb 17.

Failure Factors after 1-Stage Exchange TKA

Prior to performing a primary total joint arthroplasty, patient optimization is both possible and recommended. However, when a patient with a periprosthetic joint infection (PJI) comes in to your office, opportunities for patient optimization are limited. At that point, the patient’s BMI, kidney/liver values, and HgbA1c/fructosamine levels are not going to be dramatically improved prior to any procedure to eradicate the infection and/or salvage the implant. Still, for the purposes of care optimization and prognostic guidance, it is important to identify specific patient or wound characteristics that may help us flag patients who are at increased risk for failure after treatment of a PJI.

That was the goal of the case-control study by Citak et al. in the June 19, 2019 edition of The Journal. The authors compared 91 patients who experienced a failed 1-stage revision total knee arthroplasty that was performed to treat a PJI to a matched cohort who had a successful 1-stage revision to treat a PJI. (The authors defined “failure” as any subsequent surgical procedure regardless of reason.)

A bivariate logistic analysis revealed that patients who had a history of a previous 1-stage (OR 29.3; p< 0.001) or 2-stage (OR 5.8; p <0.001) exchange due to PJI, or who had Streptococcus (OR 6.0; p = 0.013) or Enterococcus (OR 17.3; p = 0.023) isolated from their wound were at increased risk of reinfection compared to the control group. Just as important, the authors found that patient body weight of 100 kg or above and history of deep vein thrombosis (DVT) were the only patient comorbidities related to an increased risk of a failed revision.

While these findings may not be surprising in light of previous data on this topic, they are important in aggregate. Patients whose wounds contain isolated enterococci or streptococci may not be ideal candidates for 1-stage PJI revision surgery. Additionally, the authors highlight that patients who have failed two or more attempts at a 1-stage revision should be considered for a 2-stage protocol.

While many of the patients in this study who failed the 1-stage revision may have also failed a 2-stage revision, ongoing research comparing the two protocols should help further clarify whether certain infections are more amenable to successful treatment with one protocol or the other. In the meantime, studies such as this add valuable data that surgeons can use to guide patient care and provide meaningful patient education for shared decision-making about how to treat these difficult infections.

Chad A. Krueger, MD
JBJS Deputy Editor for Social Media

Diagnosing Infection in “Dry” Prosthetic Joints

Despite a bevy of research and intense clinical focus, definitively diagnosing periprosthetic joint infections (PJIs) remains a major challenge in many patients. There is no single test that can confirm a PJI diagnosis with absolute accuracy, and surgeons often encounter clinical factors that make the diagnostic challenge even more complex. One such scenario is when a surgeon cannot aspirate enough fluid for culture from the affected joint of a patient who may have a PJI. In such situations, important microbiological data that would come from culturing synovial fluid are unavailable, leaving treating surgeons information-poor.

In the June 5, 2019 issue of The Journal, Li et al. provide surgeons with data about a controversial solution to this so-called “dry-tap” problem. The lead author performed aspirations on nearly 300 joints that were suspicious for periprosthetic infection. Eighty-two of those aspirations (29%) yielded ≤1.0 mL of synovial fluid. In those “dry-tap” cases, 10 mL of saline solution was injected into the joint, which was then reaspirated.

When comparing cultures from the aspirates that were the result of a saline lavage to those in which no lavage was performed, the authors found overlapping 95% confidence intervals in sensitivity, specificity, positive predictive value (PPV), and negative predictive value. However, the specificity (0.991 vs 0.857) and PPV (0.987 vs 0.889) were higher in the nonlavage cohort, even if those differences did not reach statistical significance. In addition, no significant differences were found between the groups in terms of relative frequencies of specific pathogen types.

Although the authors conclude that this lavage-and-reaspiration technique “is not necessarily inappropriate,” it is important to note that no post-hoc power analysis was performed, and therefore type II error needs to be considered because the study was probably underpowered. In addition, the International Consensus Meeting (ICM) recommends against lavaging a “dry” joint to obtain fluid for culture, largely because the injected saline will dilute results if a leukocyte esterase strip test or cell count is subsequently performed as part of the PJI-diagnosis process. Still, the authors point out that the data supporting the ICM’s recommendations against this practice are relatively weak, and the specificity and sensitivity data from this study are quite satisfactory.

So does this give us another option for determining whether a periprosthetic joint infection is present in patients from whom little or no synovial fluid can be obtained? Maybe. But this technique requires further investigation before it becomes widely implemented in practice. Without validation, it risks becoming just one more variable that could reinforce our own confirmation biases in these challenging cases. With further validation, however, it could allow pre-revision collection of valuable and accurate culture information from “dry” joints.

Chad A. Krueger, MD
JBJS Deputy Editor for Social Media

FDA Approves Rapid Alpha-Defensin Test for PJI

The US FDA has approved the Synovasure Alpha Defensin Lateral Flow Test Kit for helping detect periprosthetic joint infection (PJI) in the synovial fluid of patients being evaluated for revision joint replacement.

Alpha defensins are proteins released by neutrophils in early response to infection. OrthoBuzz previously summarized a 2018 JBJS study that found this rapid alpha defensin test to have 96.9% overall accuracy.

In the FDA news release about the approval, Tim Stenzel, MD, director of the FDA’s Office of In Vitro Diagnostics and Radiological Health, said the test provides health care professionals with additional information that “could potentially reduce patient risk by avoiding unnecessary revision operations for replacement joints.”

In a Commentary on the 2018 JBJS study, Garth Ehrlich, PhD and Michael Palmer, MD said the device is a “substantive advance,” but not “a panacea.” For one thing, metallosis would still need to be ruled out with MRI, because that noninfectious etiology triggers a false-positive result with this rapid test. Synovasure is also likely to miss detection of slow-growing, chronic bacterial pathogens such as Proprionibacterium acnes, the commentators said.

The Synovasure test kit received approval through the FDA’s de novo premarket pathway, which is reserved for “low- to moderate-risk devices of a new type,” according to the agency.