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Study Supports Routine Patellar Resurfacing during TKA

The July 17, 2019 issue of The Journal features another investigation evaluating patellar resurfacing. Despite much research (see related OrthoBuzz post), this topic remains controversial among many total knee arthroplasty (TKA) surgeons. This study, by Vertullo et al., analyzed data from the Australian Orthopaedic Association National Joint Replacement Registry. The findings suggest that routine resurfacing of the patella reduces the risk of revision surgery for TKA patients.

The authors evaluated more than 136,000 TKA procedures after placing the cases into three groups based on the surgeon’s patellar-resurfacing preference: infrequent (<10% of the time), selective (10% to 90% of the time), or routine (≥90% of the time). All of the cases evaluated utilized minimally stabilized components and cemented or hybrid fixation techniques, and they all were performed by surgeons who completed at least 50 TKAs per year.

The authors found that patients in the infrequent-resurfacing cohort had a nearly 500% increased risk of undergoing subsequent patellar revision during the first 1.5 years after TKA, compared to those in the routine-resurfacing cohort. Even more surprising to me was the finding that patients in the selective-resurfacing cohort had a >300% increased risk of needing a patellar revision within the first 1.5 years, compared to those in the routine-resurfacing cohort. In addition, the risk of all-cause revision was 20% higher in the selective cohort compared to the routine cohort.

What struck me most about this study were the differences between the selective and routine cohorts. One of the arguments against routine resurfacing of the patella is that surgeons should decide intra-operatively, on a patient-by-patient basis, whether the osteochondral health and biomechanics of the native patella warrant resurfacing. The findings of Vertullo et al. seem to call that reasoning into question. Although the results of this study add to the evidence supporting the routine resurfacing of the patella during TKA, I would like to reiterate a proviso from my earlier post on this topic: resurfacing is associated with added costs and an increased risk of potential complications.

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

With or Without Cement, Results with Triathlon TKA Are Same after 2 Years

With the increasing frequency of total knee arthroplasty (TKA) surgeries and the ever-increasing implant options available to orthopaedists for these cases, it is important that we carefully analyze new devices and technologies. We have already seen too many instances in which the enthusiasm for (and use of) a new implant outpaced the evidence for its efficacy and safety, leading to problems for patients, surgeons, and manufacturers alike.

The results of the randomized trial by Nam et al. in the July 3, 2019 issue of The Journal start to tackle this issue. The authors compared operative times, patient outcomes, and radiographic measures between patients who received either a recently introduced cementless or traditionally cemented cruciate-retaining TKA implant of the same design (the Triathlon TKA implant from Stryker). They found no clinically meaningful or statistically significant differences between the two groups in terms of Oxford Knee Score or Knee Society Score at any point during the average 2-year follow-up. In addition, nearly equal percentages of patients in each group reported being “extremely” or “very” satisfied with their functional outcome at 2 years, and radiographically, the researchers found no significant difference between the groups in terms of radiolucency behind the tibial or femoral implants. The one notable between-group difference was operative time, with the cementless cohort having a mean surgical time roughly 11 minutes less than that of the cemented cohort.

These results are encouraging in that they show improved operative efficiency with none of the aseptic loosening that has historically been a concern with cementless knee implants. Still, the authors make it clear that “the burden of proof remains with cementless fixation,” largely because cementless implants cost more than their cemented counterparts. Those higher costs need to be justified by improved outcomes (including implant survivorship), decreased complications, or both in order for cementless implants to displace cemented ones as the “standard of care.”

We are not there yet,  but the findings from Nam et al. justify further surveillance of this cementless device. Future high-quality studies incorporating joint registry data and longer patient follow-up will hopefully provide the supporting evidence with which the joint-arthroplasty community can decide whether this relatively new cementless technology should be the implant of choice for certain  patient populations.

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

Placenta-Derived Cells Give Short-term Boost to Tendon Repair

From journal articles to nightly news segments, it’s hard to avoid the barrage of information related to the use of cell-based therapies for musculoskeletal problems. While these approaches may turn out to be enthusiasm outpacing science (see related OrthoBuzz post, “Stemming the Tide of Stem Cell Hype”), one reason for the excitement is rooted in a very simple fact: it is really hard to get many soft tissues to heal, especially in certain patient populations. Moreover, failure of initial repair usually leads to even more biologically inhospitable repair environments. This clinical challenge has led to the zealous investigation of various cell-based compounds to see which ones might assist native soft-tissue cells with the formidable task of quick healing.

In the July 3, 2019 issue of The Journal, Ma et al. investigate the potential for human placenta-derived cells to augment the healing of chemically induced patellar tendon ruptures in rats. The injected placental cells introduced a transitory inflammatory response that led to increased load to failure at the 2-week mark, compared to biomechanical results in control rat tendons injected with saline solution. However, the addition of placenta-derived cells did not increase tendon load to failure beyond 2 weeks, and at no time point were differences seen between the control and experimental groups in tendon strength, stiffness, collagen organization, or cellularity.

While the positive results of this study were short-lived, they are important nonetheless. The animal model used is well thought-out and reproducible, allowing an easy path for future investigators to compare and contrast these results. Placenta-derived cell populations are widely available, and the authors clearly explained how the cells were processed, preserved, and delivered. With the increasing incidence of acute and chronic tendon injuries, and with the results of studies using other cell types being equivocal at best, these findings from Ma et al. are noteworthy.

Marc Swiontkowski, MD
JBJS Editor-in-Chief

New Minute-Commentary Video

Here’s what JBJS Deputy Editor for Social Media Chad Krueger, MD concludes after reading a prospective cohort study from the Cleveland Clinic Orthopaedic Arthroplasty Group examining the main predictors of length of hospital stay after knee replacement:

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

Sarcopenia’s Role in Knee OA Progression

OrthoBuzz occasionally receives posts from guest bloggers. This guest post comes from Jeffrey Stambough, MD, in response to a recent study in Arthritis & Rheumatology.

The incidence of total knee arthroplasty to treat end-stage knee osteoarthritis (OA) continues to rise even in the face of patient risk-stratification tools and alternative payment models. Consequently, payers, patients, and their doctors are placing a premium on methods to prolong the native knee joint and delay or avoid surgery. This partly explains the explosion of interest in biologics and the subsequent checkreins being put in place regarding their use.

As the AAOS clinical practice guidelines for the management of knee arthritis clearly state, the best management for symptoms of knee arthritis remains weight loss and self-directed physical activity. However, there is uncertainty regarding which subtypes of patients are likely to achieve OA symptom benefits with different weight-loss strategies.

A recent large, multicenter cohort study published in Arthritis & Rheumatology attempted to further characterize patient body composition and its association with knee OA.  Using whole-body dual x-ray absorptiometry (DXA) measures of fat and muscle mass, researchers classified patients into one of four categories: nonobese nonsarcopenic, sarcopenenic nonobese, nonsarcopenic obese, or sarcopenic obese. Sarcopenia is the general loss of muscle mass associated with aging. If orthopaedic surgeons better understand how fat and muscle metabolism change with time and affect inflammation and chronic disease, they may be able to provide patients with additional insight into preventive measures.

Using DXA-derived calculations, the authors observed that among older adults, the relative risk of developing clinically significant knee osteoarthritis (Kellgren-Lawrence grade ≥2) at 5 years was about 2 times greater in both sarcopenic and nonsarcopenic obese male and female patients compared to nonobese, nonsarcopenic patients.  Sarcopenia alone was not associated with risk of knee OA in women or men. In a sensitivity analysis focusing on BMI, men showed a 3-fold greater risk of knee OA if they were sarcopenic and obese, relative to nonobese nonsarcopenic patients.

The takeaway from this study is that focusing solely on fat/weight loss may overlook a valuable opportunity to slow the progression of knee arthritis in some patients.  Further studies are needed to validate the contribution of low muscle mass to the development and progression of symptomatic knee arthritis.

Read this related OrthoBuzz post about sarcopenia’s relationship to mortality in elderly patients with acetabular fractures.

Jeffrey B. Stambough, MD is an orthopaedic hip and knee surgeon, an assistant professor of orthopaedic surgery at University of Arkansas for Medical Sciences, and a member of the JBJS Social Media Advisory Board.

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.

Meniscal Extrusions: Imaging and Repair

This post comes from Fred Nelson, MD, an orthopaedic surgeon in the Department of Orthopedics at Henry Ford Hospital and a clinical associate professor at Wayne State Medical School. Some of Dr. Nelson’s tips go out weekly to more than 3,000 members of the Orthopaedic Research Society (ORS), and all are distributed to more than 30 orthopaedic residency programs. Those not sent to the ORS are periodically reposted in OrthoBuzz with the permission of Dr. Nelson.

Loss of hoop stress by either medial or lateral menisci can cause meniscal extrusion, which results in increased forces on articular cartilage. The degree of meniscal extrusion is typically measured as a 2-dimensional distance with MRI. However, investigators recently used 3-D MRI to analyze the relationship between medial meniscal extrusion (MME) and femoral cartilage change in patients with these tears.1

Fifteen males (mean age of 56 years) with a medial meniscal degenerative tear (grade 3 by the Mink classification) based on MRI were included. The cartilage area was reconstructed in 3-D, and the femoral cartilage was projected in 2-D by 3-D MRI analysis. The femoral cartilage of the femorotibial joint was divided into 4 segments, and the cartilage area ratio was defined as the ratio of cartilage with thickness ≥1.0 mm in each segment. The tibial MME area (mm2) and volume (cm3), excluding osteophytes, were measured by 3-D MRI.

The projected cartilage area ratio (cartilage thickness ≥1.0 mm) at the posteromedial segment was lower than the ratio at the other 3 segments. The cartilage area ratio at the posteromedial segment was not correlated with the MME distance measured by the 2-D MRI, but it was negatively correlated with MME area (r=-0.53, p=0.045) and MME volume (r=-0.62, p=0.016) as measured by 3-D MRI. Overall, the 3-D imaging more accurately reflected cartilage damage.

Both radial tears and posterior horn degeneration can lead to meniscal extrusion. When this injury is seen acutely in younger persons, repairs are often attempted. Recently efforts have been made to do repairs in older individuals. The use of cell-seeded nanofibrous scaffolds to repair radial tears and resulting hoop-structure injuries has been studied for prevention of articular cartilage degeneration using a rabbit model.2

Synovial mesenchymal stem cells were isolated and expanded into sheets that were then wrapped onto poly(e-caprolactone) scaffolds to create stable cell/scaffold tissue-engineered constructs (TECs). Scaffold-alone or TEC + scaffold constructs were then sutured into created radial meniscal defects (12 rabbits in each group).

The TEC-scaffold group maintained the structure of the hyaline cartilage with matrix staining with Safranin O up to 12 weeks after surgery. Although the cartilage coverage decreased in both groups, the TEC-scaffold group did not become significantly worse over time, suggesting stabilization of hoop structure integrity. Only the TEC-scaffold group showed repair tissue that exhibited positive Safranin O staining in the inner zone of the meniscus.

Future studies will be required to determine the role of tissue engineering in the preservation of meniscal coverage in the face of radial tears.

References

  1. Suzuki S, Ozeki N, Kohno Y, Mizuno M, Otabe K, Katano H, Tsuji K, Suzuki K, Itai Y, Masumoto J, Koga H, Sekiya I. Medial meniscus extrusion (MME) area and MME volume determined by 3D-MRI are more sensitive than MME distance determined by 2D-MRI for evaluating cartilage loss in knees with medial meniscus degenerative tears. ORS 2019 Annual Meeting Poster No. 0514.
  2. Shimomura K, Rothrauff BB, Hart DA, Hamamoto S,  Kobayashi M,  Yoshikawa H, Tuan RS, Nakamura N. Enhanced Repair of Meniscal Hoop Structure Injuries Using An Aligned Electrospun Nanofibrous Scaffold Combined with a Mesenchymal Stem Cell-derived Tissue Engineered Construct. ORS 2019 Annual Meeting Poster No. 0519.

NYT Cites Hype of Stem-Cell Treatments for Joint Problems

An active, 71-year old man who declined joint replacement in favor of stem-cell treatment is quoted in a recent New York Times article as saying, “They’re really quick to try to give you fake joints and make a bunch of money off you.” But the NYT article goes on to suggest that making money may be the main objective of some of the many hundreds of clinics that have sprung up around the US to offer cell-based injections to people with aging or damaged joints who want relief without surgery.

The article points out that the FDA has “taken an industry-friendly approach toward companies using unproven cell cocktails” and that the scant scientific evidence about these treatments, which include injections of platelet-rich plasma, is inconclusive.

For OrthoBuzz readers who want to dive more deeply into the scientific underpinnings (or lack thereof) related to cell therapies for joint problems, please peruse the following JBJS and JBJS Reviews articles, which have been made openly available for a limited period of time:

The main message running through all these articles is this: Effective clinical assessment and safe, optimized use of cell-based therapies demands greater attention to study methods; standards for cell harvesting, processing, and delivery; and standardized reporting of clinical and structural outcomes.