Temporal subsidence patterns of cemented polished taper-slip stems: a systematic review

Use of Cemented Hemiarthroplasty for Femoral Neck Fractures

Geriatric femoral neck fractures are common orthopaedic injuries, which are associated with a high morbidity and mortality. Arthroplasty is the optimum treatment for many of these injuries, but debate exists regarding optimal surgical strategy. Multiple recent investigations have demonstrated strong superiority for cemented stems as compared with noncemented fixation with a decreased risk of periprosthetic fracture, shorter length of stay, lower cost, and decreased rate for revision surgery. The main purpose of this article is to refamiliarize the resident or practicing surgeon with cemented arthroplasty by reviewing the basic science of cement, common cementing concerns, and outcomes, as well as by providing tips on cementing technique to ensure safe, simple, and reproducible results.

Periprosthetic Femoral Fractures-Beyond B2

The proliferation of hip arthroplasty has seen concomitant increases in periprosthetic femoral fractures (PFFs). The most common pattern involves fracture at the level of a loose prosthesis (B2). B2 PFFs have a unique mechanopathogenesis linked to the tendency of polished taper-slip cemented stems to subside in the cement. Such stems carry a much higher PFF risk than other cemented designs. Mega-data, consistent across national registries, suggest that increasing application of the taper-slip principle has resulted in the emergence of highly polished, very low friction cemented prostheses. These have the propensity to migrate within the cement, increasing B2 PFF risk. This would explain the strong association between cobalt-chromium stems and PFF. Is PFF the mode of failure of polished taper-slip stems rather than aseptic loosening? Established wisdom teaches that B2 PFFs should be managed with revision surgery. There is a large body of new evidence that, in certain instances, fixation results in outcomes at least equivalent to revision arthroplasty, with shorter surgical time, decreased transfusion requirements, and lower dislocation risk. This is so in B2 PFFs around cemented polished taper-slip stems with an intact bone-cement interface. We outline advances in understanding of B2 PFF with special reference to mechanopathogenesis and indications for fixation.

Cemented Stem Design in Total Hip Arthroplasty: Fixation Philosophies, Biomechanics, and an Updated Classification System

There is renewed interest in cemented femoral fixation in total hip arthroplasty in the United States, and to fully appreciate the evolution of cemented femoral stem designs, an understanding of their history and design rationale is essential. To adequately study the outcomes of modern-day designs, a comprehensive classification system is also necessary. The biomechanical principles, failure mechanisms, and clinical outcomes associated with various cemented femoral stems are described in this comprehensive review. In addition, an updated version of an existing classification system is described that incorporates the primary design characteristics which differentiate implants currently in use. In this classification, implants are categorized as taper-slip (Type I), which are subdivided by Anatomic (IA), Double-Taper (IB), and Triple-Taper (IC) with subclassification for Traditional and Line-to-Line implants. Composite beam (Type II) implants are similarly divided into Anatomic (IIA), Straight (IIB), and Wedge (IIC) with subclassification for Polished, Satin, or Roughened finish. This classification system provides a basis for comparing cemented femoral stems, thereby improving our understanding of the effect of design characteristics on survivorship to guide future advancements and improve clinical outcomes.

Femoral stem taper geometry and porous coating in cementless direct anterior primary total hip arthroplasty

Objective

This study aims to compare the clinical outcomes and complications between a fully coated, dual-tapered hip stem versus a proximally coated, triple-tapered hip stem in patients undergoing cementless direct anterior (DA) primary total hip arthroplasty (THA).

Methods

A retrospective analysis was conducted on patients who underwent primary THA with either a fully coated, dual-tapered hip stem or a proximally coated, triple-tapered stem with at least a 1-year follow up. Exclusion criteria included any patients that did not receive either femoral stem, those undergoing bilateral THA, those with a surgical approach other than DA, those with an indication other than osteoarthritis, avascular necrosis (AVN), or femoral neck fracture, and those that had a cemented femoral component. Complications and clinical outcomes were assessed. Statistical analyses were conducted to identify significant differences between the groups.

Results

A total of 95 patients were included in the study. The average ages for the dual-tapered and triple-tapered stem cohorts were 63.6 and 59.5, respectively (p = 0.168). At 1-year follow-up, no significant differences were seen between the groups in terms of ambulatory status, ROM, and patient satisfaction (p = 0.414, p = 0.106, and p = 0.126). 6 (18 %) of the patients receiving the dual-tapered, fully coated hip stem had at least one complication while 8 (13 %) of the triple-tapered, proximally coated hip stem patients did (p = 0.550).

Conclusion

Both hip stem cohorts demonstrated comparable clinical outcomes and complication rates in patients undergoing primary DA THA and we believe that either hip stem may be a reasonable choice for patients. Future studies with larger sample sizes and longer follow-up periods are warranted to validate these findings.

Collarless Polished Tapered Stems of Identical Shape Provide Differing Outcomes for Stainless Steel and Cobalt Chrome: A Biomechanical Study

Cemented polished tapered femoral stems (PTS) made of cobalt-chrome alloy (CoCr) are a known risk factor for periprosthetic fracture (PPF). The mechanical differences between CoCr-PTS and stainless-steel (SUS) PTS were investigated. CoCr stems having the same shape and surface roughness as the SUS Exeter^® stem were manufactured and dynamic loading tests were performed on three each. Stem subsidence and the compressive force at the bone-cement interface were recorded. Tantalum balls were injected into the cement, and their movement was tracked to indicate cement movement. Stem motions in the cement were greater for the CoCr stems than for the SUS stems. In addition, although we found a significant positive correlation between stem subsidence and compressive force in all stems, CoCr stems generated a compressive force over three times higher than SUS stems at the bone-cement interface with the same stem subsidence (p < 0.01). The final stem subsidence amount and final force were greater in the CoCr group (p < 0.01), and the ratio of tantalum ball vertical distance to stem subsidence was significantly smaller for CoCr than for SUS (p < 0.01). CoCr stems appear to move more easily in cement than SUS stems, which might contribute to the increased occurrence of PPF with the use of CoCr-PTS.

The influence of calcar collar and surface finish in the cemented femoral component on the incidence of postoperative periprosthetic femoral fracture at a minimum of five years after primary total hip arthroplasty

INTRODUCTION

Cemented femoral component design including its mechanical behavior in total hip arthroplasty (THA) has influenced the occurrence of postoperative periprosthetic femoral fracture (PPFF). The main aim of this study was to investigate the influence of the calcar collar and surface finish in the cemented femoral component on the risk of PPFF.

MATERIALS AND METHODS

This retrospective review was undertaken of 1082 primary THAs in 912 patients using cemented femoral components followed for a minimum of five years (mean, 9.4 years; range, 5-24 years). The incidence of PPFF, patients' demographics and surgical details were evaluated. Kaplan-Meier survivorship analysis was performed for four different outcomes: any PPFF, revision of the femoral component for PPFF, aseptic loosening, and for any reason.

RESULTS

The overall incidence of PPFFs was 1.0% (n = 11): 1.4% (n = 10) in the collarless polished (CLP) group, none in the collared polished (CP) group and 0.6% (n = 1) in the collared non-polished (CNP) group (p > 0.05). Kaplan-Meier survival analysis for the femoral component at 12 years with PPFF as the end point was 97.4% (95% confidence interval [CI], 94.9 to 99.8) in the collarless group and 99.7% (95% CI, 99.1 to 100) in the collared group (p = 0.048). With revision of the femoral component for aseptic loosening as the end point, survivorship was 100.0% in the CLP and CP groups, and 98.1% (95% CI, 95.9 to 100) in the CNP group (CLP vs CP, p > 0.999; CLP vs CNP, p = 0.001; CP vs CNP, p = 0.112).

CONCLUSION

This study demonstrated that the calcar collar in the cemented femoral component could play an important role to reduce the incidence of PPFF. The surface finish in the cemented femoral components influenced the incidence of femoral component revision for aseptic loosening over 5-12 years. Surgeons should consider not only the geometry and the mechanical function of the femoral components based on different design philosophies, but also potential complications associated with different designs that may require revision arthroplasty.