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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Let’s Continue Improving Hip-Implant Longevity
In October 2017, JBJS published results from a 10-year randomized controlled trial by Devane et al. documenting the dramatic reduction in polyethylene wear in total hip arthroplasties (THAs) using highly cross-linked polyethylene (HXLPE). This followed decades of research documenting that wear debris was implicated in macrophage activity that was ultimately responsible for implant loosening. In the September 4, 2019 issue of The Journal, Hart and colleagues produce further evidence of the improved performance of HXLPE, this time showing revision rates among THA patients with osteonecrosis that rival the rates among patients with osteoarthritis.
In this matched cohort of 922 THAs performed from 1999 to 2007 that used an HXLPE bearing, the 15-year cumulative rate of revision was 6.6% among patients treated for osteonecrosis and 4.5% among patients treated for osteoarthritis (p = 0.09). There were no radiographic signs of component loosening in the entire cohort, and, despite a lower median preoperative Harris hip score (HHS) among patients with osteonecrosis, both groups had marked improvements in HHS score. These findings are especially noteworthy because patients with osteonecrosis typically undergo THA at an earlier age and have much higher functional demands than the typical 70- or 80-year-old osteoarthritis patient.
However, the 15-year revision rate—even with HXLPE—remains at 4.5% for osteoarthritis patients, which should provide impetus to continue our work identifying all possible factors and mechanisms that lead to THA revision. A partial list would include bearing-surface wear, reliability of implantation, biomechanics, biomaterials, and patient perception of postoperative pain. Also, in a subgroup analysis, Hart et al. found that the 15-year rate of any reoperation among osteonecrosis patients ranged from 0% for hips with radiation-induced osteonecrosis to 25% for hips with idiopathic osteonecrosis. These findings add to the list of factors for THA success that need further investigation.
The work list for improvements in THA will remain substantive for at least the next few decades, and we may never get to 0% revisions for all patients. But we have certainly demonstrated that our research can produce very worthwhile results.
Marc Swiontkowski, MD
JBJS Editor-in-Chief
What’s New in Hip Replacement 2018
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
Blood Management
–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.
References
- 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.
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