Systematic Review of Clinical Outcome using Titanium Fiber Mesh Porous Ingrowth Surfaces Timothy L. Tan, BS 1, Brenna C. Moeljadi, BS 2, Edward Ebramzadeh, PhD 3, Patricia Campbell, PhD 3, Sophia Nicole Sangiorgio, PhD 3. 1 UCLA, Los Angeles, CA, USA, 2 Orthopaedic Hospital, Los Angeles, CA, USA, 3 Orthopaedic Hospital/UCLA, Los Angeles, CA, USA. Disclosures: T.L. Tan: None. B.C. Moeljadi: None. E. Ebramzadeh: None. P. Campbell: None. S.N. Sangiorgio: None. Introduction: Uncemented acetabular components, utilizing a wide selection of available porous ingrowth surfaces, have emerged as the standard for total hip arthroplasty. Many recent porous ingrowth technologies, such as roughened plasma sprayed titanium, hydroxyapatite-coated beads and porous tantalum surfaces, have been developed to potentially improve ingrowth and biologic fixation. However, a recent registry comparison of porous technologies revealed that not all porous surfaces are producing equivalent outcomes. Furthermore, the study questioned whether recent technologies are in fact producing better cup survivorship or lower loosening rates than ingrowth technologies developed in the 1980 s, such as titanium fiber mesh. One of the original porous ingrowth surfaces, titanium fiber mesh, has historically resulted in low rates of acetabular loosening. By and large, the most documented use of fiber mesh was with the Harris-Galante I and II (HG) (Zimmer Inc., Warsaw, IN) implants. Studies of HG I and II reported long-lasting ingrowth and low rates of aseptic loosening; however, this success was overshadowed by failure modes other than cup fixation. We investigated the literature to answer the following: 1) What were the HG I and HG II modes of failure, and to what extent are they related to the cup fixation surface? 2) How do loosening rates of HG I and II acetabular cups compare to representative long-term studies of other more recent acetabular cups? Finally, 3) How do the overall revision and cup survivorship rates of HG I and II compare to more recent ingrowth technologies and current fiber mesh surfaces? Methods: A MedLine search was performed in the National Library of Medicine catalog using the search term Harris Galante follow up OR Harris Galante. The abstracts were then screened for studies with HG I and HG II follow-up (F/U) greater than 10 years that report either survivorship or modes of failure. Another MedLine search was performed to obtain the failure rates and survivorship of the acetabular component in hip arthroplasty and hip resurfacing. Two representative long-term studies were chosen using each of the following surfaces: Ti beaded, CoCr beaded, tantalum, titanium mesh, plasma-sprayed components, and ingrowth surfaces with hydroxyapatite coatings for a total of 12 studies. Importantly, when multiple studies of the same patient cohort existed, only the most recent study was included. Data was collected from each article for the following: cup survivorship rates, overall survivorship rates, and the modes of failure including loosening rates if reported. Results: The search query for long term HG cups resulted in 170 studies. Of these studies, 9 articles were identified, with F/U ranging from 10.8-23.3 years. Q1) The common modes of failure resulting in revision were osteolysis, liner wear, femoral loosening, and locking mechanism failure (Table 1). Locking mechanism failures were frequently found in both HG I and HG II implants. Rates of acetabular loosening ranged from 0-33%, which was generally lower than reported rates for femoral loosening, which ranged from 25-64%. Q2) 12 representative studies of hip replacement implants with six different ingrowth surfaces were selected for comparison purposes (Table 2). The 5-yr and 10-yr survivorship rates, with the endpoint as revision for any reason, were comparable among implants coated with cobalt-chrome beads (99.6%, 92.0-98.3%), titanium beads (99.5%, 99.5%), hydroxyapatite-coated (95.6%), and titanium fiber mesh (98.7%, 93.5%). While 5-yr and 10-yr survivorship of tantalum coated implants is unknown, the 3-yr survivorship of tantalum was similar (98.0%-98.8%) to the other ingrowth surfaces. Acetabular loosening rates ranged from 0-4% for those coated with CoCr beads (follow up 5.6-10.4 years), 0% for titanium beads (F/U 7 years), 1% for hydroxyapatite coated (F/U 8-8.4 years), 0-1% for current fiber mesh (F/U 9.7 years), and 1-10% for plasma-sprayed (F/U 5-13 years). Q3) The overall survivorship of HG hip replacements ranged from 60.0-88.0% between 12 to 27.5 years. In contrast, the survivorship of the cup alone was much higher. With revision of the acetabular component as an endpoint, the cup survivorship ranged from 73.0-98.0% between 10 and 22.5 years. At longer periods of F/U, the loosening rates and acetabular component survivorship of HG I and II were comparable to those with more recent ingrowth surfaces. Recent implant designs utilizing a fiber mesh coating have also demonstrated excellent survivorship results. Discussion: This review suggests that the HG acetabular cups failed primarily due to factors unrelated to cup fixation surface. Furthermore, it is widely documented that high rates of polyethylene wear debris, particularly of older generation polyethylene, from both the articular surface and the liner backside, contributed to osteolysis. Despite these high rates of wear debris, the
loosening rates of the HG acetabular cups were low, comparable to recent designs. With more recent porous ingrowth technologies, the acetabular survivorship rates of HG I and II were similar. The cup survivorship rates of HG I and II were also comparable to the short-term results for the recently developed tantalum ingrowth surface, 98.0% at 3 years. Despite longer F/U for the HG I and II, their survivorship and loosening rates were comparable to those studies with shorter F/U of implants with recent ingrowth technologies. In addition, excellent acetabular survivorship and low loosening rates were also demonstrated in modern implants sharing the fiber mesh ingrowth surface. In this review, consistent with other clinical studies, acetabular cups coated with titanium fiber mesh demonstrated excellent cup survivorship. In a study comparing the clinical success of multiple ingrowth surfaces at the same institution, Kremers et al. found that the cup survivorship of implants with fiber mesh were superior to beaded and hydroxyapatite-coated implant surfaces. Additionally, Kremers found that the short-term F/U of the more recent technologies, roughened and tantalum surfaces, have thus far demonstrated excellent fixation. However, a limitation of these studies is that a direct comparison between titanium fiber mesh and more recent implant technologies, e.g. tantalum and roughened titanium, is limited because long term studies of recent technologies are unavailable. In addition to the clinical findings, in-vitro studies have suggested the efficacy of titanium fiber mesh over newer ingrowth technologies. In a canine retrieval study comparing CoCr beaded implants with titanium fiber mesh acetabular components of the same design, Jasty et al. found superior ingrowth in fiber mesh cups despite the fiber mesh beads having less porosity. This stresses that increased porosity does not necessarily result in better bone ingrowth; a concept that is frequently forgotten, with industry often focusing solely on achieving increased porosity. Furthermore, Baad-Hansen et al. reported that the clinical results of newer trabecular metal cups are similar to that of fiber mesh. In this study comparing a recent fiber mesh cup and a tantalum cup with migration as an endpoint, both cups showed excellent fixation with no difference in translation or rotation except for transverse rotation. Significance: This review suggests that fixation of fiber mesh coated HG I and II acetabular components was perhaps more successful than some of the more recent fixation surfaces, and that failures were unrelated to the ingrowth surface. The fiber mesh ingrowth surface in both historic and current implant designs demonstrated comparable results to other recent ingrowth technologies, even with periods of longer follow-up. Acknowledgments: None. References:
ORS 2014 Annual Meeting Poster No: 0914