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    Current Controversies in Stem Fixation for Total Hip Arthroplasty

    Cementless fixation has become the most common form of femoral fixation in the US. However, cemented fixation with modern techniques has demonstrated excellent outcomes and may be particularly advantageous in older adults with osteoporotic bone. In this article, surgeons from NYU Langone Health review the literature on cemented and cementless femoral stem fixation in total hip arthroplasty patients.

    Authors

    Noah Kirschner, MD; Charles Lin, MD, MS; Tyler Luthringer, MD; Nury Yim, MD; James Slover, MD, MS; and Ran Schwarzkopf, MD, MSc

    Introduction

    Sir John Charnley had early success with a low-friction total hip arthroplasty (THA) utilizing a stainless steel femoral component that was cemented in place with first-generation cementing technique. Although Charnley had excellent long-term results, other series with cemented stems raised concerns about early loosening. [1]

    These concerns, combined with the recognition of osteolysis – which was thought to originate from the use of bone cement and was mistakenly given the moniker “cement disease” – paved the way for the rise of cementless fixation in THA. [2] Implant surfaces were developed that promoted bone in-growth or on-growth, allowing for alternative forms of rigid fixation comparable to the grout properties of polymethylmethacrylate (PMMA). [3]

    In the US, cementless fixation has become the most common form of femoral fixation: Approximately 93% of THAs in 2012 were cementless. [4] Despite this, cemented fixation with modern techniques has demonstrated excellent outcomes and may be particularly advantageous in older adults with osteoporotic bone.

    Fixation of Cemented and Uncemented Stem 

    Cemented stems rely on PMMA to act as a grout between the stem and bone. Cement fills the canal and interdigitates with the cancellous bone to form a rigid mantle. 

    There are 2 categories of cemented stem designs. Taper-slip (“force-closed”) designs are collarless with highly polished surfaces. They rely on controlled subsidence of the stem into the cement mantle to generate radial stress, resulting in compression at the prosthesis-cement and bone-cement interfaces. [5] In contrast, composite beam (“shape closed”) designs rely on direct bonds at the implant-cement interface and cement-bone interface to rigidly hold the stem in place. [5] The 2 designs have demonstrated relatively similar outcomes; however, registry analyses have shown lower rates of revision with the taper-slip design. [6]

    Cementing technique has undergone crucial changes since the first-generation, finger-packed cementation. [7] Current fourth-generation cementation technique emphasizes: [8]

    • The use of a canal restrictor
    • Rigorous cleaning of the canal to remove loose bone and medullary canal debris
    • Retrograde fill of the canal with pressurization
    • Centralization of the implant with a centralizer
    • Late insertion of the implant into viscous cement

    Outcomes using modern cementation technique have been excellent, appearing to have largely overcome the loosening associated with the first-generation technique. Furthermore, certain patient factors, such as increased bone porosity, allow for greater cement penetration and greater cement fracture toughness. [9]

    Cementless stems rely on different fixation mechanisms. They achieve early fixation through press-fit into metaphyseal or diaphyseal bone. In the long term, stem fixation relies on osseointegration through bone in-growth and on-growth into roughened implant surfaces, often with osteoinductive coatings. To optimize osseointegration, micromotion at the bone-implant interface should be minimized, as implant motion stimulates a fibrous membrane formation around the implant and inhibits long-term bonding between the implant and bone. [10]

    Outcomes of Cemented Fixation

    Early outcomes of Charnley’s cemented THAs were impressive, with only 4.9% aseptic loosening of the femoral component at mean follow-up of 15 years. [1] Other early adopters of cemented stems, however, were unable to replicate this success. Mayo Clinic’s series of Charnley low-friction THAs demonstrated a 29.9% incidence of radiographic loosening at 10 years. [11] Sutherland et al. [12] reported a 40% rate of femoral component loosening using the cemented Mueller curved-stem prosthesis.

    After adoption of improved cementing technique, rates of aseptic loosening of the femoral components dropped. Barrack et al. [7] demonstrated in 44 patients under age 50 that femoral aseptic loosening decreased with the use of a cement gun and femoral medullary plug. None of these patients required femoral revision for aseptic loosening, and only 2% had evidence of loosening at 12-year follow-up. [7] Similarly, Buckwalter et al. [13] reported only a 10% revision rate for aseptic loosening of the femoral component at 25-year follow up with third-generation cementing technique.

    Evolution of Outcomes of Cementless Fixation

    Early outcomes of cementless fixation were also less than ideal. In 1956, McKee and Watson-Farrar [14] trialed uncemented fixation and found that only 51% of patients had “good” or “fair” results.

    Despite modest beginnings, cementless fixation has continued to evolve, with a more modern series demonstrating 87% survivorship for all-purpose revision at 25-year follow-up. [15] Morrey et al. [16] similarly demonstrated excellent outcomes with cementless fixation, reporting 91% survival without osteolysis at 10-year follow-up.

    Although surgeons who initially adopted cementless fixation reported poor outcomes, the technique has evolved to become a reliable option for femoral stem fixation. It is now the predominant fixation method used throughout North America. [17]

    Comparisons of Cemented and Cementless Fixation

    Multiple direct comparisons of cemented and cementless fixation have been made. Jamsen et al. [18] evaluated the effects of fixation methods on survival in primary THA, reviewing data on 4777 patients in the Finnish Arthroplasty Register. They found that cementless fixation was associated with increased revision rates within the first year. [18] 

    Medding et al. [19] compared cemented and uncemented THA using the same femoral component. At 20-year follow-up, they found higher rates of aseptic loosening in cemented total hips (1.2%) than in cementless total hips (0.4%). Overall survivorship showed no significant difference. [19]

    In an analysis of THA patients over age 80, Stihsen et al. [20] found no significant difference in the revision rate between cementless and cemented fixation at 10-year follow-up, which contradicts the findings of Jamsen et al. [18]. As an explanation for the difference in their results, Stihsen et al. postulated that the surgeons in their cohort were more familiar with cementless implantation techniques than those in the Finnish cohort. [20]

    Stihsen et al. also found a trend toward more complications in THA patients with osteoporosis, which is more common in the octogenarian population. [20] Gkagkalis et al. [21] compared outcomes of patients over age 75 with those of patients under age 60 who received cementless stems. They found clinical and radiologic outcomes to be similar in both groups. In their analysis, they noted that patients with Dorr C femur morphology had an increased rate of postoperative periprosthetic femur fractures, 22.2% for Dorr C femurs compared with 2.1% and 0% in Dorr B and Dorr A femurs, respectively. [21] Springer et al. [22] similarly found that patients with cementless stems were 2.6 times more likely to have a periprosthetic femur fracture than patients with cemented fixation.

    Registry data appear to support the risk of periprosthetic fractures with cementless fixation, with increased risk in the older adult population. Cementless fixation accounted for 93% of periprosthetic fractures in 10,277 patients in the American Joint Replacement Registry. [22] Using data from the Danish Hip Arthroplasty Registry, Lindberg-Larsen et al. [23] demonstrated that use of uncemented femoral stems was associated with an increased relative risk of 4.1 for periprosthetic femoral fractures when compared with cemented stems. However, they also found that medically treated osteoporosis, female gender, and age were associated with increased risks of periprosthetic fracture. [23]

    Cost Considerations

    In cohorts with similar outcomes for cemented and cementless stems, cost can be a differentiating factor. Cementless stems are considerably more expensive than cemented stems; however, costs associated with cemented techniques are not applicable for cementless fixation. Tripuraneni et al. [24] found that despite differences in actual implant costs, cemented hemiarthroplasty is more expensive than cementless hemiarthroplasty due to the cost of the cement, cement mixer, centralizer, and pressurizer.

    Pennington et al. [25] compared the cost-effectiveness of cemented, cementless, and hybrid prostheses in THA. In contrast to Tripuraneni et al., [24] they found that based on lifetime costs, cemented stems were the least costly, with cementless stems failing to show significantly improved health outcomes to justify their increased cost. [25] Similarly, Oh et al. [26] found that patients in the Medicare population with cemented femoral fixation had improved discharge disposition and trended toward superiority in length of stay, readmission, cost of care, and reoperations.

    Physiologic Risks of Cementing

    Detractors of femur cementation contend that it is technically more demanding, increases operative time, and requires meticulous technique to achieve a proper cement mantle. [27] Furthermore, cementation has been associated with a rare but catastrophic complication known as bone cement implantation syndrome (BCIS). This phenomenon is characterized by hypoxia and/or hypotension during the process of implant fixation with bone cement and can result in intraoperative mortality, with an estimated incidence of 0.11%. [28]

    Mechanisms behind this phenomenon are poorly understood and continue to be debated. Previous theories have suggested that cement monomers in circulation trigger vasodilation. [29, 30] Competing theories have proposed that high intramedullary pressures that develop during the cementation process result in an embolic shower of air and medullary contents. [31, 32] Regardless of mechanism, the results of BCIS can be potentially catastrophic and should be considered as a potential risk of cement use.

    Conclusion

    Early successes in THA were achieved with cemented femoral components. However, concerns over loosening led to the adoption of cementless fixation as the most commonly used technique for femoral fixation in the US today.

    As cemented and cementless fixation have evolved, both appear to be associated with excellent outcomes. However, concerns regarding periprosthetic fracture remain when selecting the most appropriate form of fixation, particularly with cementless fixation in older adults with osteoporotic bone. Despite possible increased costs and the remote possibility of BCIS, cemented fixation can be beneficial for this population. Therefore, surgeons should be well versed in cemented and cementless techniques.

    Author Information

    Noah Kirschner, MD; Charles Lin, MD, MS; Tyler Luthringer, MD; Nury Yim, MD; James Slover, MD, MS; and Ran Schwarzkopf, MD, MSc, are from NYU Langone Orthopedic Hospital, NYU Langone Health, New York, NY.

    Disclosures: The authors have no disclosures relevant to this article.

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