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D'Antonio J.A.,Greater Pittsburgh Orthopaedics Association | Capello W.N.,Indiana University | Ramakrishnan R.,Stryker Orthopaedics
Clinical Orthopaedics and Related Research | Year: 2012

Background Compared with conventional polyethylene, first-generation highly cross-linked polyethylenes have low wear, but controversy exists regarding their reduced mechanical strength and/or retained free radicals. Secondgeneration highly cross-linked polyethylenes have been developed to reduce wear, maintain mechanical strength, and have oxidative resistance, but it is unclear whether they do so. Questions/purposes The primary objective of this study therefore was to determine if a second-generation annealed material has low linear wear at 5 years followup. Secondary objectives were to evaluate for overall survivorship, implant fixation, osteolysis, and effect of socket inclination on wear. Methods In a multicenter prospective study, we radiographically evaluated 155 patients (167 hips) at 3 years, 124 patients (132 hips) at 4 years, and 46 patients (51 hips) at 5 years. The linear head penetration rate was measured at 6 weeks, 1 year, and yearly through 5 years. Results The head penetration per year after the first year of bedding-in was 0.024 mm per year at 3 years, 0.020 mm per year at 4 years, and 0.008 mm per year at 5 years. The average wear rate over 5 years was 0.015 mm per year and represents a 58% improvement over a first-generation annealed highly cross-linked polyethylene. The Kaplan- Meier survivorship (revision for any reason) was 97.8%. We revised no hip for bearing surface failure and observed no osteolysis. Socket inclination did not affect linear wear. Conclusions These data suggest the linear wear rate for a second-generation annealed highly cross-linked polyethylene is no greater than that for historic controls of first-generation highly cross-linked polyethylenes, and no untoward complications were encountered with this new material. © The Association of Bone and Joint Surgeons® 2012.

Race A.,SUNY Upstate Medical University | Heffernan C.D.,Stryker Orthopaedics | Sharkey P.F.,Rothman Institute
Journal of Arthroplasty | Year: 2011

Nonbiologic and mechanical effects of hydroxyapatite coatings have received little evaluation. Hydroxyapatite coatings give porous metal the appearance of decreased roughness. We hypothesized that this apparent decrease in surface roughness would result in diminished initial implant stability. We measured the initial stability of titanium plasma sprayed press-fit femoral stems with and without HA. Stems were implanted into cadaver and synthetic femora and subjected to aggressive stair-climbing loads. Migrations (retroversion and subsidence) and cyclic motions were recorded. Hydroxyapatite coating significantly reduced retroversion (P = .0007) and cyclic subsidence (P = .0086). Scanning electron microscopy imaging revealed that HA coating appeared to have reduced roughness on a millimeter scale but increased roughness on a micrometer scale. We concluded that HA coating improves initial stability through mechanical means, before biological action. © 2011 Elsevier Inc.

Capello W.N.,Indiana University | D'Antonio J.A.,Greater Pittsburgh Orthopaedics Association | Naughton M.,Stryker Orthopaedics
Clinical Orthopaedics and Related Research | Year: 2014

Background: Periprosthetic fractures can occur both intraoperatively and postoperatively with implantation of cementless tapered stems. Questions/purposes: In a large cohort of patients receiving cementless, proximally hydroxyapatite-coated femoral implants, we answered the following questions: What was the incidence of intraoperative and postoperative fractures associated with the implant? What were the fracture patterns as classified by the Vancouver classification system? Did the Vancouver classification represent the fracture patterns found? How were the fractures treated and what were the treatment outcomes; that is, how many fractures healed and did the stems osseointegrate? Methods: We evaluated 1039 hips (932 patients) from three prospective studies. The hips were divided into three groups: no fractures, intraoperative fractures, and postoperative fractures. Demographic differences among the groups were noted. Postoperative fractures were classified using the Vancouver classification system. We judged stem stability using Engh's criteria and fracture union was determined by the treating surgeon and confirmed by the authors. Results: We identified 58 periprosthetic fractures in the 1039 hips (5.6%): 38 intraoperative (3.7%) and 20 postoperative (1.9%). Eleven of the postoperative fractures were classifiable by the original Vancouver classification system and nine were of the newly described "clamshell" variety, not classifiable by this system. No intraoperative fractures extended below the lesser trochanter. Twenty-five of these fractures were treated with a single cable or cerclage wire. The remaining received no specific treatment. Of the 20 postoperative fractures, five were treated nonoperatively. All stems osseointegrated. Conclusions: Both intraoperative and postoperative fractures can be managed with success when the stem is stabilized or found to be osseointegrated. An adjustment to the Vancouver classification is suggested to include the clamshell fracture, which has not been previously described. Level of Evidence: Level IV, therapeutic study. See Instructions for Authors for a complete description of levels of evidence. © 2013 The Association of Bone and Joint Surgeons®.

Bhimji S.,Stryker Orthopaedics | Meneghini R.M.,Indiana University School of Medicine - Terre Haute
Journal of Arthroplasty | Year: 2014

Initial implant stability is crucial to cementless knee arthroplasty fixation. The objective of this study was to evaluate the stability of two baseplates with different fixation features: a monoblock porous tantalum baseplate featuring two hexagonal pegs alone, and a modular design featuring a keel with four adjuvant cruciform pegs. A physiologically relevant test method previously described was used to evaluate compression and liftoff of the baseplates during stair descent. The porous tantalum baseplate with dual-hex peg fixation experienced greater rocking motions and liftoff compared to the baseplate with a keel and adjuvant pegs. Liftoff and displacement motion is likely deleterious and may inhibit biological fixation due to the physical separation of the baseplate from the bone. © 2014 Elsevier Inc.

D'Antonio J.A.,Greater Pittsburgh Orthopaedics Association | Capello W.N.,Indiana University | Naughton M.,Stryker Orthopaedics
Clinical Orthopaedics and Related Research | Year: 2012

Background: Ceramic bearings were introduced to reduce wear and increase long-term survivorship of total hip arthroplasty. In a previous study comparing ceramic with metal-on-polyethylene at 5 to 8 years, we found higher survivorship and no osteolysis for the ceramic bearings. Questions/Purposes: We asked whether ceramic bearings have equal or superior survivorship compared with that for metal-on-polyethylene at longer followup; we also determined survivorship of the implant systems, the presence or absence of radiographic osteolysis, and incidence of device squeaking. Methods: Five surgeons at five sites have followed 189 patients (216 hips) for a minimum of 10 years and average of 10.3 years (range, 10-12.4 years) comparing alumina ceramic bearings (144 hips) with cobalt chrome-on-polyethylene bearings (72 hips). We determined Kaplan-Meier survivorship of the bearing surface and implant systems and collected radiographic and clinical data. Results: We observed no difference between the control metal-on-polyethylene and the alumina-bearing couple cohorts with regard to bearing-related failures (98.9% versus 99.1%). Revisions for any reason occurred in 10.5% of the control patients and 3.1% of the patients with alumina bearings. All femoral implants remain well fixed (100%), whereas one acetabular component (1%) is unstable in the control group. Osteolysis occurred in 26% of the control patients and in none of the patients with alumina bearings. Squeaking occurred in two of 144 hips (1.4%) of the patients with ceramic bearings. Conclusions: Patients receiving the ceramic-on-ceramic bearings had fewer revisions for any reason and less osteolysis than the control metal-on-polyethylene at 10 years. Our data suggest ceramic bearings continue to provide an option for the young and more active patient and provide for a measure to compare other new alternative bearings that are currently available. Level of Evidence: Level I, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence. © 2011 The Association of Bone and Joint Surgeons®.

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