In the setting of revision total hip arthroplasty (THA), the use of electrocautery—and contact between the thermal device and retained components—cannot always be avoided. In the May 15, 2019 issue of The Journal of Bone & Joint Surgery, Sonntag et al. perform two implant-retrieval analyses and a separate in vitro investigation to determine what kinds of damage take place when electrocautery energy meets titanium femoral stems.
The components for retrieval analyses were removed from patients who experienced a fracture of the femoral stem or femoral neck after revision THA. The authors found superficial discoloration and melting marks on the retrieved components, and elemental analysis indicated that material had been transferred from the electrocautery tip. During in vitro testing of 6 titanium alloy femoral stems, the authors found that electrocautery surface damage reduced load-to-failure by up to 47% when compared to undamaged femoral neck specimens. Microscopic analysis revealed notable changes in metal microstructure in electrocautery-exposed components, whereby certain zones exhibited higher strength than others, which, the authors speculate, might result in lower overall fatigue resistance.
Both the retrieval and in vitro analyses showed that electrocautery damage to femoral implants, particularly in the anterolateral region at the base of the neck, reduced implant fatigue resistance. However, the authors say their results need to “be carefully interpreted,” because they are based on only 2 retrievals and a limited number of test specimens. Nevertheless, they conclude that “electrocautery device contact [with femoral implants] should be avoided and the use of conventional scalpels is recommended, where reasonable.”
Despite what seems like a new, high-quality study being published on the topic every week or so, orthopaedic surgeons still have an extremely hard time determining whether a prosthetic hip or knee is infected or not. We have an array of available tests and the relatively easy-to-follow criteria for a periprosthetic joint infection (PJI) from the Musculoskeletal Infection Society (MSIS), but a large number of these patients still fall into the gray zone of “possibly infected.” This predicament is especially thorny in patients who received antibiotics just prior to the diagnostic workup, which interferes with the accuracy of many tests for PJI.
In the April 17, 2019 issue of The Journal, Shahi et al. remind orthopaedic surgeons about a valuable tool that can be used in this scenario. Their retrospective study looked at 121 patients who had undergone revision hip or knee arthroplasty due to an MSIS criteria-confirmed periprosthetic infection. Shahi et al. sought to determine which diagnostic tests were least affected by prior antibiotic administration. The authors found that erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) level, synovial white blood cell (WBC) count, and polymorphonuclear neutrophil (PMN) percentage were all significantly lower in the 32% of patients who had received antibiotics within 2 weeks of those tests, compared with the 68% who did not receive antibiotics. The only test that was found not to be significantly affected by the prior admission of antibiotics was the urine-based leukocyte esterase strip test.
Considering the ease and rapidity with which a leukocyte esterase test can be performed and evaluated (at a patient’s bedside, with immediate results), its low cost, and the fact that it is included in the MSIS criteria, these findings are very important and useful. While we would prefer that patients with a possibly infected total hip or knee not receive antibiotics prior to their diagnostic workup, previous antibiotic exposure remains a relatively common scenario. The findings from this study can assist us in those difficult cases, and they add further evidence to support the value and reliability of the easy-to-perform leukocyte esterase test.
Chad A. Krueger, MD
JBJS Deputy Editor for Social Media
The indications for treating total hip arthroplasty (THA) dislocations by cementing a constrained polyethylene liner into a well-fixed, retained acetabular component at the time of revision are narrow. That’s largely due to concerns about the durability of the resulting acetabular construct. Now, thanks to a study by Brown et al. in the April 3, 2019 issue of JBJS, hip surgeons have some hard data about the long-term outcomes of this approach.
After reviewing 125 cases in which a constrained liner was cemented into a retained, osseointegrated acetabular component during revision THA, with a mean follow-up of 7 years, the authors found that:
- Survivorship free from revision for instability was 86% at 5 years and 81% at 10 years. The cumulative incidence of instability at 7 years was 18%.
- Survivorship free from aseptic acetabular component revision was 78% at 5 years and 65% at 10 years. The most common failure mechanism was dissociation of the constrained liner from the retained component.
- Harris hip scores (HHS) did not improve significantly after revision. This finding is consistent with prior research that shows better post-revision HHS scores in patients whose revisions include the entire acetabular component.
- Position of the retained cup did not affect implant survivorship or risk of dislocation.
The authors mention alternative strategies for reducing the risk of dislocation after revision THA, such as the use of large-diameter heads and dual-mobility constructs. Still, they conclude that this constrained-liner approach, in the setting of a relatively well-positioned acetabular component, is a viable and durable THA revision option, especially for those “with a compromised abductor mechanism, recurrent instability, [and] a well-fixed and well-positioned acetabular component, for whom an acetabular revision would not be tolerated.”
The recent orthopaedic literature, including a 2017 JBJS study, provides substantial evidence that oral and intravenous tranexamic acid (TXA) are equivalent in their effectiveness at reducing blood loss after total hip arthroplasty (THA)—with oral administration being less expensive and more convenient. But what are the optimal doses and timing of oral TXA in the setting of THA?
The findings of a randomized controlled trial by Wang et al. in the March 6, 2019 issue of JBJS go a long way toward answering that question. The authors randomized 200 patients undergoing primary THA to 1 of 4 groups, with all patients receiving an intraoperative topical dose of 1.0 g of TXA and a single dose of 2.0 g of TXA orally at 2 hours postoperatively. In addition,:
- Group A received 1.0 g of oral placebo at 3, 9, and 15 hours postoperatively
- Group B received 1.0 g of oral TXA at 3 hours postoperatively and 1.0 g of placebo at 9 and 15 hours postoperatively
- Group C received 1.0 g of oral TXA at 3 and 9 hours postoperatively and 1.0 g of placebo at 15 hours postoperatively
- Group D received 1.0 g of TXA at 3, 9, and 15 hours postoperatively
The mean total blood loss during hospitalization was significantly less in Groups B, C, and D (792, 631, and 553 mL, respectively) than in Group A (984 mL). Groups C and D had lower mean reductions in hemoglobin than did Groups A and B. No significant between-group differences were observed regarding 90-day thromboembolic complications (there were none) or transfusions (there was only 1, in Group A), but the authors said “this study was likely underpowered for establishing meaningful comparisons concerning [those 2] outcomes.”
Although this study documented significantly lower total blood losses in patients who were managed with multiple doses of oral TXA postoperatively, additional studies are required to determine whether the 3-dose regimen is superior to the 2-dose regimen.
When Medicare’s Comprehensive Care for Joint Replacement (CJR) program was implemented in 2016, the health care community—especially orthopaedic surgeons— had 2 major concerns. First, would the program actually demonstrate the ability to decrease the costs of total joint replacements while maintaining the same, or improved, outcomes? Second, would CJR promote the unintended consequence of participating hospitals and surgeons ”cherry picking” lower-risk patients and steering clear of higher-risk (and presumably higher cost) patients? Both of these questions were at the heart of the study by Barnett et al. in a recent issue of the New England Journal of Medicine.
The authors evaluated hip and knee replacements at 75 metropolitan centers that were mandated to participate in the CJR program and compared the costs, complication rates, and patient demographics to similar procedures at 121 control centers that did not participate in CJR. The authors found significantly greater decreases in institutional spending per joint-replacement episode in institutions participating in the CJR compared to those that did not. Most of these savings appeared to come from CJR-participating institutions sending fewer patients to post-acute care facilities after surgery. Furthermore, the authors did not find differences between centers participating in the CJR and control centers in terms of composite complication rate or the percentage of procedures that were performed on high-risk patients.
While this 2-year evaluation does not provide the level of detail necessary to make far-reaching conclusions, it does address two of the biggest concerns related to CJR implementation from a health-systems perspective. There may be individual CJR-participating centers that are not saving Medicare money or that are cherry picking lower-risk patients, but overall the program appears to be doing what it set out to do—successfully motivating participating hospitals and healthcare facilities to look critically at what they can do to decrease the costs of a joint-replacement episode while simultaneously maintaining a high level of patient care. The Trump administration shifted CJR to a partly voluntary model in March 2018, and I hope policymakers consider these findings if further changes to the CJR model are planned.
Chad A. Krueger, MD
JBJS Deputy Editor for Social Media
Periprosthetic joint infections (PJIs) create a significant burden for patients, surgeons, and healthcare systems. That is why so much research has gone into how best to optimize certain patients preoperatively—such as those with obesity, diabetes, or kidney disease—to decrease the risk of these potentially catastrophic complications. Still, it is not always possible or feasible to optimize every “high-risk” patient who would benefit from a total hip or knee replacement, and therefore many such patients undergo surgery with an increased risk of infection. In such cases, surgeons need additional strategies to decrease PJI risk.
In the December 19, 2018 issue of JBJS, Inabathula et al. investigate whether providing high-risk total joint arthroplasty (TJA) patients with extended postoperative oral antibiotics decreased the risk of PJI within the first 90 days after surgery. In their retrospective cohort study, the authors examined >2,100 total hip and knee replacements performed at a single suburban academic hospital. The patients in 68% of these cases had at least one risk factor for infection. Among those high-risk patients, about half received 7 days of an oral postoperative antibiotic, while the others received only the standard 24 hours of postoperative intravenous (IV) antibiotics.
Relative to those who received IV antibiotics only, those who received extended oral antibiotics experienced an 81% reduction in infection for total knee arthroplasties and a 74% reduction in infection for total hip arthroplasties. I was stunned by such large reductions in infection rates obtained simply by adding an oral antibiotic twice a day for 7 days. Most arthroplasty surgeons go to great lengths to decrease the risk of joint infection by percentages much less than that.
While further investigations are needed and legitimate concerns exist regarding the propagation of antimicrobial-resistant organisms from medical antibiotic misuse, these data are very exciting. I agree with Monti Khatod, MD, who, in his commentary on this study, says that “care pathways that aim to improve modifiable risk factors should not be seen as obsolete based on the findings of this paper.” Furthermore, the study itself is at risk for treatment and selection biases that could greatly influence its outcomes. Nevertheless, getting a successful result in these patients is challenging and, if validated with further data, this research may help surgeons obtain better outcomes when treating high-risk patients in need of hip or knee replacements.
Chad A. Krueger, MD
JBJS Deputy Editor for Social Media
The adult joint-reconstruction community has made great strides in the last 2 decades in understanding what causes aseptic loosening of arthroplasty components. For example, revelations about polyethylene particulate debris has led to the production of highly cross-linked polyethylene, which in turn has lowered wear rates, decreased revision rates, and increased the survivorship of total hip implants (see related OrthoBuzz post). Still, polyethylene debris is only one factor that can lead to aseptic loosening. Another important, yet often overlooked, factor is friction between the impacted acetabular shell and the host bone.
In the October 3, 2018 issue of The Journal, Bergmann et al. report data that help us better understand the “friction factor” in aseptic loosening. The authors implanted specially designed, instrumented acetabular components that measured in vivo friction moments among nine patients while they engaged in >1,400 different activities. The authors found that 124 of those activities led to friction moments >4 Nm—which appears to be the upper limit for facilitating a firm union between the acetabular component and the native socket.
Movements such as muscle stretching in the lunge position, the breaststroke in swimming, 2-legged standing with muscles contracted, and a single-legged stance while moving the contralateral leg were among those that created the highest friction between the implant and the host bone—and that could impede bone ingrowth into the acetabular component and thus contribute to aseptic loosening. The study also highlights the importance of periodic unloading of the prosthetic joint to allow proper synovial lubrication, which helps minimize the effects of high-friction moments. The good news is that the vast majority of activities studied do not appear to result in friction forces above the 4 Nm threshold.
Although these data should be confirmed with other in-vivo instrumented prostheses (assuming there are more patients willing to receive acetabular components capable of delivering telemetric data), they provide practical insight into the real-world forces placed on total hip prostheses after implantation. Such information can be used to counsel patients regarding high-friction and sustained-loading activities to be avoided, and it can help physical therapists and surgeons tailor postoperative regimens that optimize patient recovery while minimizing the risk to implanted prostheses.
Marc Swiontkowski, MD
Every month, JBJS publishes a Specialty Update—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, Mengnai Li, MD, co-author of the September 19, 2018 Specialty Update on Hip Replacement, selected the five most clinically compelling findings from among the more than 100 studies covered in the Specialty Update.
The Benefits of HXLPE
–A double-blinded study that randomized patients to receive either a conventional polyethylene liner or one made from highly cross-linked polyethylene (HXLPE) found that, after a minimum of 10 years, the HXLPE group had significantly lower wear rates, lower prevalence of osteolysis, and lower revision rates than the conventional-liner group.
Outcomes for Hip Fracture vs OA
–A propensity score-matched cohort analysis of NSQIP data found that total hip arthroplasty (THA) undertaken to treat hip fractures among Medicare beneficiaries was significantly associated with an increased risk of CMS-reportable complications, non-homebound discharge, and readmission, relative to THA undertaken to treat osteoarthritis.1
Infection Risk Factors
–A multicenter retrospective study found that a threshold of 7.7% for hemoglobin A1c was more predictive of periprosthetic joint infection than the commonly used 7%, and the authors suggest that 7.7% should be considered the goal in preoperative patient optimization.2
THA in Patients with RA
–Recently published guidelines from the American College of Rheumatology and AAHKS regarding antirheumatic medication use in patients with rheumatic diseases who are undergoing THA suggest the following:
- Continuing nonbiologic disease-modifying antirheumatic drugs (DMARDs)
- Continuing the same daily dose of corticosteroids
- Withholding biologic agents prior to surgery
- Planning surgery for the end of the biologic dosing cycle.
All recommendations are conditional due to the low or moderate-quality evidence on which they were based.3
–A double-blinded, randomized trial found that oral tranexamic acid (TXA) provided equivalent reductions in blood loss in the setting of primary THA, at greatly reduced cost, compared with intravenous TXA.
- Qin CD, Helfrich MM, Fitz DW, Hardt KD, Beal MD, Manning DW. The Lawrence D. Dorr Surgical Techniques & Technologies Award: differences in postoperative outcomes between total hip arthroplasty for fracture vs osteoarthritis. J Arthroplasty. 2017 Sep;32(9S):S3-7. Epub 2017 Feb 6.
- Tarabichi M, Shohat N, Kheir MM, Adelani M, Brigati D, Kearns SM, Patel P, Clohisy JC, Higuera CA, Levine BR, Schwarzkopf R, Parvizi J, Jiranek WA. Determining the threshold for HbA1c as a predictor for adverse outcomes after total joint arthroplasty: a multicenter, retrospective study. J Arthroplasty. 2017 Sep;32(9S): S263-7: 267.e1. Epub 2017 May 11.
- Goodman SM, Springer B, Guyatt G, Abdel MP, Dasa V, George M, Gewurz- Singer O, Giles JT, Johnson B, Lee S, Mandl LA, Mont MA, Sculco P, Sporer S, Stryker L, Turgunbaev M, Brause B, Chen AF, Gililland J, Goodman M, Hurley-Rosenblatt A, Kirou K, Losina E, MacKenzie R, Michaud K, Mikuls T, Russell L, Sah A, Miller AS, Singh JA, Yates A. 2017 American College of Rheumatology/American Association of Hip and Knee Surgeons guideline for the perioperative management of antirheumatic medication in patients with rheumatic diseases undergoing elective total hip or total knee arthroplasty. J Arthroplasty. 2017 Sep;32(9):2628-38. Epub 2017 Jun 16.
Annual volume projections for total joint arthroplasty (TJA) have been cited frequently and applied broadly, often to estimate future costs. But with a slowdown in the growth of the annual incidence of total knee arthroplasty (TKA), updated projections are needed, and that’s what Sloan et al. provide in the September 5, 2018 issue of JBJS.
Using the National Inpatient Sample to obtain TJA incidence data, the authors first analyzed the volume of primary TJA procedures performed from 2000 to 2014. They then performed regression analyses to project future volumes of TJA procedures. Here are the numbers based on the 2000-to-2014 data:
- Primary total hip arthroplasty (THA) is projected to grow 71%, to 635,000 annual procedures by 2030.
- Primary TKA is projected to grow 85%, to 1.26 million annual procedures by 2030.
However, the TKA procedure growth rate has slowed in recent years, and models based on 2008-to-2014 data project growth to only 935,000 annual TKAs by 2030—325,000 fewer procedures relative to the 2000-to-2014 models.
Earlier studies, notably one by Kurtz et al. in 2007, obviously could not account for the reduced growth rate in TKA after 2008. A 2008 analysis by Wilson et al., based on the Kurtz et al. data, estimated that annual Medicare expenditures on TJA procedures would climb from $5 billion in 2006 to $50 billion in 2030. “Using our projections,” say Sloan et al., “we predict that Medicare expenditures on these procedures in 2030 will be less than half of that predicted by Wilson et al.”
These findings lend credence to the authors’ observation that “it is imperative that projections of orthopaedic procedures be regularly evaluated and updated to reflect current rates.”
Allograft bone is used often in orthopaedic surgery. However, the use of structural allografts to address large acetabular defects in total hip arthroplasty (THA) is not common. But it may become more so in light of the study by Butscheidt et al. in the August 15, 2018 issue of JBJS. The authors add to our knowledge about these relatively rare procedures by evaluating the incorporation of structural acetabular allografts into host bone among 13 complete pelvic explants containing allograft that had been in place for a mean of 13 years.
Using sophisticated imaging and histological techniques, the authors found that in 10 out of the 13 specimens retrieved, 100% of the interface was characterized by direct contact and additional overlap of the allograft bone and the host bone. The remaining 3 allografts showed direct contact along 25% to 80% of the interface. The authors found no correlation between ingrowth of the host bone into the allograft and the amount of time the allograft had spent in situ, leading them to surmise that “a large proportion of the incorporation process may be completed within the first weeks.”
Large, structural allografts are not commonly used for acetabular reconstructions, as most surgeons seem to favor other options. (See the JBJS Clinical Summary on “Managing Acetabular Defects in Hip Arthroplasty.”) While a postmortem study of 13 cases may not be “practice-changing,“ the Butscheidt et al. analysis does provide some detailed clarity as to what surgeons can expect from these large allograft reconstructions in terms of incorporation with host bone. Obviously, one limitation of this study is that structural allografts that never incorporated with the host bone probably failed early and would not be available for analysis in a long-follow-up retrieval study.
Chad A. Krueger, MD
JBJS Deputy Editor for Social Media