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Highly Cross-Linked Poly Adds No Benefit to Most TKAs

The preponderance of published orthopaedic evidence supports the use of highly cross-linked polyethylene (HXLPE) in acetabular components for patients undergoing total hip arthroplasty (THA). (See related OrthoBuzz post.) But the literature is filled with conflicting findings about the benefits of HXLPE for those undergoing total knee arthroplasty (TKA). Seeking clarity, in the January 15, 2020 issue of The Journal of Bone & Joint Surgery, Partridge et al. report findings from a registry-based cohort analysis of more than a half-million TKAs, comparing revision rates among those using conventional polyethylene (CPE) with those using HXLPE.

The authors analyzed TKA data captured by the National Joint Registry for England, Wales, and Northern Ireland during the period from 2003 to 2014. Of the >550,000 procedures examined, only about 10% utilized HXLPE. When the authors compared adjusted aseptic revision rates per 100 years observed within the three most common TKA systems in the database (NexGen by Zimmer, PFC Sigma by DePuy, and Triathlon by Stryker), they found no significant differences between HXLPE and CPE after a maximum follow-up of 12 years.

The only notable difference between the two polyethylene types was found in patients <60 years old and/or those with BMI >35 kg/m2, in whom the second-generation Stryker X3 HXLPE showed significantly better survival than its CPE counterpart. In explaining why the benefits of HXLPE seen in THA might not translate to TKA, Partridge et al. contrast the “ball and socket” hip joint with the wear mechanisms in TKA, which involve “rolling, sliding, and rotational motion that potentially put the polyethylene insert at greater risk of wear by delamination, pitting, and fatigue failure.”

The authors conclude that the extra costs of HXLPE bearings for TKA may not be justified for most TKA patients in the intermediate term, but commentator Remy Simon Nizard, MD notes that “other uncontrolled or insufficiently controlled parameters [such as quality of component positioning] may have had an influence on the results.”  While Partridge et al. call for “additional follow-up,” Dr. Nizard questions whether full-blown clinical trials investigating alternative bearings in TKA are justified, “given the emerging subject of the burden of research waste.”

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Curb Your Enthusiasm about Stem Cells for Knee OA

Mark Miller, MD is a professor of orthopaedic surgery at the University of Virginia, founder and co-director of the Miller Review Courses, and former deputy editor for sports medicine at JBJS. In a piece he authored recently for The Conversation, Dr. Miller labeled stem-cell treatments for knee osteoarthritis (OA) “unproven, expensive, and potentially dangerous.”

About 2 years ago, Dr. Miller himself underwent bilateral knee replacements for severe knee arthritis. He understands why patients may fall prey to misleading marketing hype that claims stem cell treatments can help people postpone or entirely avoid knee replacement. (See related OrthoBuzz post.) “My mission,” he writes, is to “try to keep the enthusiasm regarding new cutting-edge options in check,” adding that “the excitement about stem cells has outpaced the science,” especially when it comes to knee OA.

Although stem cell injections have been promoted as a way to regenerate cartilage in arthritic joints, Dr. Miller echoes the American Association of Hip and Knee Surgeons when he says that “there are no proven…therapies that can delay or reverse the progressive joint destruction that occurs with osteoarthritis.” Moreover, the do-no-harm part of the Hippocratic oath requires doctors to give their patients “a clear picture of the potential benefits and side effects of their treatment options,” writes Dr. Miller, who cited a December 20, 2018 New York Times article describing 12 patients who were hospitalized for serious infections after receiving stem cell injections into their knees, shoulders, or spines.

For their part, Dr. Miller says patients should employ the “buyer beware” concept because stem cell therapy for osteoarthritis is not only unproven but also expensive—and usually not covered by medical insurance. The best approach to knee OA, says Dr. Miller, is what is nowadays called shared decision making: “Physicians need to work closely with patients to help them understand their options and which choice may be best for them.”

What’s Really Important to You?

The two most recent JBJS “What’s Important” articles (“Learning Names” by J. Lawrence Marsh in the December 4, 2019 issue and “Not Becoming a Robot” by Ramon B. Gustilo in the January 2, 2020 issue) typify the variety of topics and individuality these personal essays are known for.

Dr. Marsh’s piece is about leadership, with the focal point being golf great Arnold Palmer. “I will never forget that he knew each of our names…and wanted to know our stories,” Dr. Marsh writes, recalling the day he and 4 friends played 9 holes with Arnie during a charity golf tournament. “We had the impression that he would not want to be anyplace else in the world other than playing golf with us,…a foursome of nobodies.” From that day on, Dr. Marsh has practiced leadership that entails much more than strategic thinking and motivational rhetoric: “With a smile, a pleasantry, a handshake, or an offer to help, a leader can leave a positive impression,” he writes.

Dr. Gustilo’s “What’s Important” essay is clinically focused on orthopaedics, but he too emphasizes the human component. Echoing the experiences and message of an earlier “What’s Important” author, Jack W. Crosland, Dr. Gustilo laments the “industrialization of medicine.” Citing one of several examples, he writes that the overuse of advanced imaging such as CT and MRI “leads to the deterioration of the practice of history-taking and physical examination of the patient.”

What’s really important to you? If you would like JBJS to consider your “What’s Important” story for publication, please submit a manuscript via Editorial Manager. When asked to select an artic le type, please choose Orthopaedic Forum and include “What’s Important:” at the beginning in the title field.

Because they are personal in nature, “What’s Important” submissions are not subject to the usual stringent JBJS peer-review process. Instead, they are reviewed by the Editor-in-Chief, who will correspond with the author if revisions are necessary and make the final decision regarding acceptance.

Revisiting INR Targets Prior to THA

In March 2019, OrthoBuzz covered a JBJS study by Rudasill et al. that found a progressively increasing risk of bleeding requiring transfusion among total knee arthroplasty (TKA) patients who had a preoperative International Normalized Ratio (INR) >1. (INR is a standardized measure of how long it takes blood to clot—the higher the number, the longer the clotting time.) These authors also found a significantly increased risk of infection in TKA patients with INR >1.5. and an increased risk of mortality within 30 days of surgery among those with an INR >1.25 to 1.5.

In the January 2, 2020 issue of JBJS, the same team of researchers report findings from a similarly designed NSQIP-based study of patients undergoing total hip arthroplasty (THA). The authors evaluated data from >17,500 patients who underwent a primary THA between 2005 and 2016 and who also had an INR value documented within 2 days prior to joint replacement. Rudasill et al. stratified these patients into 4 groups based on preoperative INRs: ≤1, >1 to <1.25, 1.25 to <1.5, and ≥1.5).

After adjustment, the authors found a significant, independent effect between increased preoperative INR and increased bleeding requiring transfusion and mortality. Specifically, bleeding risk became evident at INR ≥1.25, and patients with INR ≥1.5 were at a significantly increased risk of mortality. The length of hospital stay also increased significantly as INR class increased.

The authors suggest that “current INR targeting [INR <1.5 for elective orthopaedic surgery] may not be strict enough to minimize adverse outcomes for patients undergoing primary total hip arthroplasty.” While admitting that these findings are not likely to change the day-to-day practice of orthopaedic surgeons, the authors say they “may influence preoperative risk stratification for those patients with elevated INR.”

Predicting ‘Fast,’ ‘Slow Starters’ and ‘Late Dippers’ after THA

Based on ample published data and experience, today’s hip surgeons can give patients who are considering total hip arthroplasty (THA) a good general idea of outcomes to expect. But what if orthopaedists could provide more tailored predictions of THA outcome, and thus help patients more realistically manage expectations?

That is essentially what Hesseling et al. set out to do in their database analysis of 6,030 THA patients gleaned from the Dutch Arthroplasty Register; the findings appear in the December 18, 2019 issue of JBJS. Using the patients’ Oxford Hip Scores (OHS) collected up to 1 year postoperatively and a sophisticated statistical technique called latent class growth modeling, the authors categorized outcome trajectories into 3 categories:

  1. Fast Starters (n = 5,290)—steep improvement in OHS during the first 3 postoperative months, after which the OHS leveled out
  2. Late Dippers (n = 463)—more modest improvement in OHS initially, followed by subsequent decline toward the 1-year mark
  3. Slow Starters (n = 277)—virtually no change at the 3-month mark, followed by an improvement in OHS at 1 year postoperatively

Although the authors were unable to tease out factors that clearly distinguished between late dippers and slow starters, they did identify several factors associated with less-than-fast-starter outcomes:

  • Female sex
  • Smoking
  • Age >75 years
  • Obesity
  • Anxiety and depression
  • American Society of Anesthesiologist (ASA) grade III or IV
  • Hybrid fixation (cemented acetabular implant)
  • Direct lateral surgical approach

Emphasizing that all 3 subgroups experienced functional improvement after THA, Hesseling et al. nevertheless provide useful information that can help surgeons more accurately estimate which patients might be at risk of a less favorable recovery.

3 Reference Axes Help Ensure Rotational Alignment During TKA

Rotational malalignment of the femoral component during total knee arthroplasty (TKA) is associated with poor outcomes, but how best to assess femoral component rotation intraoperatively remains an unanswered question for arthroplasty surgeons. Now, in the largest study of its kind, Jang et al. conclude in the December 4, 2019 issue of JBJS that combining 3 reference axes is the optimal strategy for ensuring accurate femoral component positioning, sex/ethnic generalizability, and intraoperative efficiency.

The authors compared 5 reference axes commonly used for intraoperative assessment of femoral component rotation by mapping them to >2,100 entire-femur CT scans from patients with nonarthritic knees. Using the surgical transepicondylar axis (sTEA) as the gold-standard reference, Jang et al. found that no single other axis was both highly accurate and relatively immune to ethnic and sex variability. Based on their findings, they instead recommend using a combination of 3 axes—posterior condylar axis externally rotated 3° (PCA + 3° ER), the Whiteside or sulcus line, and the anatomical transepicondylar axis (aTEA)—to ensure rotational alignment.

The authors also suggest a straightforward intraoperative process for using these 3 axes:

  1. Start with the PCA + 3° ER, which most accurately approximates the gold-standard sTEA.
  2. Then use the Whiteside or sulcus line, neither of which is significantly affected by sex or ethnicity.
  3. Finally, palpate for the aTEA to narrow the margin of error.

Citing a limitation to this CT-based study of nonarthritic knees, the authors note that “we could not account for the effects of cartilage wear or other changes caused by degenerative arthritis.”

Factors Affecting Union after Capanna Reconstruction

Resection of long-bone tumors often leaves large skeletal defects. Since the late 1980s, surgeons have used the “hybrid” Capanna technique—a vascularized fibular graft inlaid in a massive bone allograft—to fill those voids, with good functional outcomes reported. In the November 20, 2019 issue of The Journal of Bone & Joint Surgery, Li et al. report on factors influencing union after the Capanna technique.

The authors radiographically evaluated Capanna-technique reconstructions in 60 patients (10 humeral, 33 femoral, and 17 tibial) and correlated allograft-host union time to the following variables:

  • Patient age
  • Tumor site
  • Adjuvant treatment (e.g., chemotherapy)
  • Previous surgical procedures
  • Defect length
  • Fixation method
  • Fibular viability (assessed with a bone scan 10 days after reconstruction)

They also histologically analyzed a retrieved specimen from one patient.

Among these 60 reconstructions, the mean defect length was 16 cm, and the mean time to union of the constructs was 13 months. The overall survival rate of the constructs was 93% at the latest follow-up.

Multivariate linear regression revealed no correlation between allograft-host osseous union time and patient age, defect length, tumor site, or fixation method. Conversely, devitalization of the transplanted fibular graft, chemotherapy administration, and a previous surgical procedure were associated with a prolonged union time. Histologically, the allograft-host cortical junction was united by callus from periosteum of both the host bone and the fibular graft.

Li et al. conclude that “ensuring patent vascular anastomoses of the transplanted fibula is crucial to prevent delayed or nonunion.” They also suggest that Capanna-technique patients who have any of the 3 “adverse factors” noted above should be treated with extended postoperative immobilization and delayed weight-bearing.

Subtalar Joint’s Middle Facet Yields Insight into Flatfoot

Many foot and ankle surgeons would relish a simple measurement made from a readily available imaging modality to help detect whether patients with adult acquired flatfoot deformity (AAFD) are at high risk for progressive collapse—and to help them with surgical planning. According to the findings from a case-control study by de Cesar Netto et al. in the October 16, 2019 issue of The Journal of Bone & Joint Surgery, that wish may soon be realized.

The authors made standing, weight-bearing computed tomography (CT) scans of 30 patients with stage-II AAFD (mean age of 57.4 years) and 30 matched controls (mean age of 51.8 years). From those images, 2 fellowship-trained surgeons, who were blinded regarding the patient cohorts, measured the amount of subluxation (percentage of uncoverage) and the incongruence angle of the middle facet of the subtalar joint in the coronal plane. The authors found substantial to almost perfect intraobserver and interobserver reliability for both measurements.

Based on these middle-facet measurements, the mean value for joint uncoverage in patients with AAFD was 45.3% compared with 4.8% in controls. Similarly, the mean incongruence angle in the AAFD group was 17.3° in the AAFD group and 0.3° in controls. Further analysis led the authors to conclude that “an incongruence angle of >8.4° and an uncoverage percentage of 17.9% were found to be highly diagnostic for symptomatic stage-II AAFD.”

De Cesar Netto et al. say the biomechanics of the subtalar joint made focusing on the middle facet a sensible approach, and they attributed the high reliability of the measurements to the relatively simple anatomy of the middle facet. Still, because clinical outcomes were not assessed in this study, the role of the middle facet as a marker of peritalar subluxation and a tool for deformity correction in AAFD patients needs further investigation in prospective, longitudinal studies.

Association ≠ Causation: Are Steroid Injections for OA Risky?

A recent report in Radiology citing possible complications from injecting steroids into painful joints with osteoarthritis (OA) has received lots of attention in the mainstream media. Radiologists from Boston, Germany, and France reviewed the existing literature and found an association between intra-articular steroid injections and a small increased risk of four adverse joint findings: accelerated OA progression, subchondral insufficiency fracture, complications from osteonecrosis, and bone loss. However, the study did not include a control group that did not receive injections, and therefore it cannot be used to assess whether injections are associated causally with the adverse joint findings.

In an interview with Boston radio station WBUR, lead author Ali Guermazi, MD stressed the point that readers should not conclude from this report that steroid injections cause these complications, adding that additional research in this area is “urgently needed.” In the same radio coverage, Jeffrey Katz, MD, a professor of orthopaedic surgery at Boston’s Brigham & Women’s Hospital and a Deputy Editor at JBJS, said patients who have received such injections or plan to should not be overly worried. However, he added that “for clinicians and patients who’ve been doing injections for several years, it’s worth it to pause and say, ‘Do we want to discuss [again] what we think are the benefits and risks of this.’”