Time-dependent Viscoelastic Response of Acetabular Bone and Implant Seating during Dynamic Implantation of Press-fit Cups

Abstract Background Bone stock preservation in total hip replacement is essential to allow for later revisions in an increasingly younger and fitter index patient population. While contemporary modular press-fit acetabular cups lead to rigid fixation with equatorial stress and central osteolysis, more elastic fixation may cause different peri-acetabular bone remodelling. The purpose of this study was to investigate changes in peri-acetabular bone mineral density (BMD) in uncemented elastic fixation with monoblock press-fit cups. Methods This prospective observational study included 45 patients with monoblock cups. We evaluated peri-acetabular BMD using dual-energy X-ray absorptiometry and reported functional outcomes and complications. Results At a mean follow-up of 24.2 ± 2.2 months, we found that BMD stabilised in DeLee and Charnley zones I and III and recovered to baseline value in zone II. The mean Harris Hip Scores improved significantly from 56.9 ± 20.0 to 97.2 ± 4.0 (p < 0001). Other than one peri-operative dislocation, we saw no post-operative complications. Conclusions We found favourable adaptive bone changes with BMD stabilisation in the equatorial zones and recovery to pre-operative values in the central zone. Additionally, excellent clinical outcomes and few prosthesis-related complications strengthened the favourable results of monoblock acetabular cups. Trial registration Registration number DRKS00017076.

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Thermal wrinkling behavior of formable decorative film laminates

Journal of Plastic Film & Sheeting ◽

10.1177/8756087916663031 ◽

2016 ◽

Vol 33 (3) ◽

pp. 290-308 ◽

Cited By ~ 1

Author(s):

G Prasath Balamurugan ◽

Rohan N Pukadyil ◽

Mahdy M Malayery ◽

Michael R Thompson ◽

John Vlachopoulos ◽

...

Keyword(s):

Heating Rate ◽

Thermal Stresses ◽

Metal Substrate ◽

Rate Effect ◽

Time Dependent ◽

Threshold Temperature ◽

Viscoelastic Response ◽

Final Temperature ◽

Rate Effects ◽

Compliant Layer

This paper focuses on wrinkle development in decorative film laminates during heating operations with the goal to understand their driving factors and develop strategies to overcome such defects. The study looked at temperature and heating rate effects on the wrinkling behavior of a commercial black-out film laminated onto a metal substrate. The 135℃ threshold temperature identified for our film under which no wrinkles formed, related to the stiffness of its different construction layers. Heating rate was also noted by this study to be an important parameter in wrinkling; values between 1℃ and 350℃/min were tested. It was possible to exceed the threshold temperature stated above without wrinkling when the heating rate was sufficiently low (closer to 1℃/min, though less than 50℃/min was often sufficient depending on the final temperature). The heating rate effect is believed to be related to the time-dependent viscoelastic response of the compliant layer in relation to building thermal stresses.

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Optimizing Acetabular Component Bone Ingrowth: The Wedge-Fit Bone Preparation Method

Advances in Orthopedics ◽

10.1155/2019/9315104 ◽

2019 ◽

Vol 2019 ◽

pp. 1-6

Author(s):

Dani M. Gaillard-Campbell ◽

Thomas P. Gross

Keyword(s):

Acetabular Component ◽

Preparation Method ◽

Bone Ingrowth ◽

Hip Resurfacing ◽

Outer Diameter ◽

Preparation Technique ◽

Acetabular Bone ◽

Press Fit ◽

Unexplained Pain ◽

Clinical Problems

We investigate the efficacy of a modified acetabular bone-preparation technique in reducing the incidence of two clinical problems identified in hip resurfacing arthroplasty. The first issue is failure due to lack of bone ingrowth into the acetabular component. The second is a newly recognized phenomenon of early cup shift. We hypothesize that these issues might be resolved by using a “wedge-fit method”, in which the component wedges into the peripheral acetabular bone rather than bottoming out and potentially toggling on the apex of the cup. Prior to November 2011, all acetabula were reamed 1 mm under and prepared with a press-fit of the porous coated acetabular component. After November 2011, we adjusted reaming by bone density. In “soft bone” (T-score <-1.0), we underreamed acetabula by 1 mm less than the outer diameter of the cup, as was previously done in all cases. For T-scores greater than -1.0, we reamed line-to-line. Additionally, we began performing an “apex relief” starting June 2012 in all cases by removing 2 mm of apex bone with a small reamer after using the largest reamer. Failure of acetabular ingrowth occurred in 0.5% of cases before the wedge-fit method and <0.1% after. Rate of cup shift was reduced from 1.1% to 0.4%. The rate of unexplained pain between 2 and 4 years postoperatively also declined significantly from 2.6% to 1.3%. Our evidence suggests that wedge-fit acetabular preparation improves initial implant stability, leading to fewer cases of early cup shift, unexplained pain, and acetabular ingrowth failure.

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Peri-acetabular bone remodelling after uncemented total hip arthroplasty with monoblock press-fit cups: an observational study

10.21203/rs.3.rs-19063/v3 ◽

2020 ◽

Author(s):

Conrad Anderl ◽

Georg Mattiassich ◽

Reinhold Ortmaier ◽

Martin Steinmair ◽

Josef Hochreiter

Keyword(s):

Observational Study ◽

Bone Remodelling ◽

Central Zone ◽

Rigid Fixation ◽

Mineral Density ◽

Acetabular Bone ◽

Total Hip ◽

Press Fit ◽

Uncemented Total Hip Arthroplasty ◽

Elastic Fixation

Abstract Background: Bone stock preservation in total hip replacement is essential to allow for later revisions in an increasingly younger and fitter index patient population. While contemporary modular press-fit acetabular cups lead to rigid fixation with equatorial stress and central osteolysis, more elastic fixation may cause different peri-acetabular bone remodelling. The purpose of this study was to investigate changes in peri-acetabular bone mineral density (BMD) in uncemented elastic fixation with monoblock press-fit cups.Methods: This prospective observational study included 45 patients with monoblock cups. We evaluated peri-acetabular BMD using dual-energy X-ray absorptiometry and reported functional outcomes and complications.Results: At a mean follow-up of 24.2 ± 2.2 months, we found that BMD stabilised in DeLee and Charnley zones I and III and recovered to baseline value in zone II. The mean Harris Hip Scores improved significantly from 56.9 ± 20.0 to 97.2 ± 4.0 (p < 0001). Other than one peri-operative dislocation, we saw no post-operative complications.Conclusions: We found favourable adaptive bone changes with BMD stabilisation in the equatorial zones and recovery to pre-operative values in the central zone. Additionally, excellent clinical outcomes and few prosthesis-related complications strengthened the favourable results of monoblock acetabular cups.Trial registration: Registration number DRKS00017076.

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Peri-acetabular bone remodelling after uncemented total hip arthroplasty with monoblock press-fit cups: an observational study

10.21203/rs.3.rs-19063/v1 ◽

2020 ◽

Author(s):

Conrad Anderl ◽

Georg Mattiassich New ◽

Reinhold Ortmaier New ◽

Martin Steinmair New ◽

Josef Hochreiter New

Keyword(s):

Observational Study ◽

Bone Remodelling ◽

Central Zone ◽

Rigid Fixation ◽

Mineral Density ◽

Acetabular Bone ◽

Total Hip ◽

Press Fit ◽

Uncemented Total Hip Arthroplasty ◽

Elastic Fixation

Abstract Background: Bone stock preservation in total hip replacement is essential to allow for later revisions in an increasingly younger and fitter index patient population. While contemporary modular press-fit acetabular cups lead to rigid fixation with equatorial stress and central osteolysis, more elastic fixation may cause different peri-acetabular bone remodelling. The purpose of this study was to investigate changes in peri-acetabular bone mineral density (BMD) in uncemented elastic fixation with monoblock press-fit cups.Methods: This prospective observational study included 45 patients with monoblock cups. We evaluated peri-acetabular BMD using dual-energy X-ray absorptiometry and reported functional outcomes and complications.Results: At a mean follow-up of 24.2 ± 2.2 months, we found that BMD stabilised in DeLee and Charnley zones I and III and recovered to baseline value in zone II. The mean Harris Hip Scores improved significantly from 56.9 ± 20.0 to 97.2 ± 4.0 (p < 0001). Other than one peri-operative dislocation, we saw no post-operative complications.Conclusions: We confirmed favourable adaptive bone changes with BMD stabilisation in the equatorial zones and recovery to pre-operative values in the central zone. Additionally, excellent clinical outcomes and few prosthesis-related complications confirmed the favourable results of monoblock acetabular cups.

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Comparison of Test Setups for the Experimental Evaluation of the Primary Fixation Stability of Acetabular Cups

Materials ◽

10.3390/ma13183982 ◽

2020 ◽

Vol 13 (18) ◽

pp. 3982

Author(s):

Christian Schulze ◽

Danny Vogel ◽

Sina Mallow ◽

Rainer Bader

Keyword(s):

Test Methods ◽

Load Test ◽

Test Method ◽

Artificial Bone ◽

Acetabular Cup ◽

Acetabular Bone ◽

Press Fit ◽

Orthopedic Surgeons ◽

Fixation Stability

Sufficient primary fixation stability is the basis for the osseointegration of cementless acetabular cups. Several test methods have been established for determining the tilting moment of acetabular press-fit cups, which is a measure for their primary fixation stability. The central aim of this experimental study was to show the differences between the commonly used lever-out test method (Method 1) and the edge-load test method (Method 2) in which the cup insert is axially loaded (1 kN) during the tilting process with respect to the parameters, tilting moment, and interface stiffness. Therefore, using a biomechanical cup block model, a press-fit cup design with a macro-structured surface was pushed into three cavity types (intact, moderate superior defect, and two-point-pinching cavity) made of 15 pcf and 30 pcf polyurethane foam blocks (n = 3 per cavity and foam density combination), respectively. Subsequently, the acetabular cup was disassembled from the three artificial bone cavities using the lever-out and the edge-load test method. Tilting moments determined with Method 1 ranged from 2.72 ± 0.29 Nm to 49.08 ± 1.50 Nm, and with Method 2, they ranged from 41.40 ± 1.05 Nm to 112.86 ± 5.29 Nm. In Method 2, larger areas of abrasion were observed in the artificial bone cavity compared to Method 1. This indicates increased shear forces at the implant–bone interface in the former method. In conclusion, Method 1 simulates the technique used by orthopedic surgeons to assess the correct fit of the trial cup, while Method 2 simulates the tilting of the cup in the acetabular bone cavity under in situ loading with the hip resultant force.

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Cortical Bone Viscoelasticity and Fixation Strength of Press-Fit Femoral Stems: An In-Vitro Model

Journal of Biomechanical Engineering ◽

10.1115/1.2133766 ◽

2005 ◽

Vol 128 (1) ◽

pp. 13-17 ◽

Cited By ~ 16

Author(s):

T. L. Norman ◽

E. S. Ackerman ◽

T. S. Smith ◽

T. A. Gruen ◽

A. J. Yates ◽

...

Keyword(s):

Cortical Bone ◽

Viscoelastic Behavior ◽

Fixation Strength ◽

Viscoelastic Response ◽

Press Fit ◽

Initial Stability ◽

Vitro Model ◽

Stem Stability ◽

Push Out

Cementless total hip femoral components rely on press-fit for initial stability and bone healing and remodeling for secondary fixation. However, the determinants of satisfactory press-fit are not well understood. In previous studies, human cortical bone loaded circumferentially to simulate press-fit exhibited viscoelastic, or time dependent, behavior. The effect of bone viscoelastic behavior on the initial stability of press-fit stems is not known. Therefore, in the current study, push-out loads of cylindrical stems press-fit into reamed cadaver diaphyseal femoral specimens were measured immediately after assembly and 24h with stem-bone diametral interference and stem surface treatment as independent variables. It was hypothesized that stem-bone interference would result in a viscoelastic response of bone that would decrease push-out load thereby impairing initial press-fit stability. Results showed that push-out load significantly decreased over a 24h period due to bone viscoelasticity. It was also found that high and low push-out loads occurred at relatively small amounts of stem-bone interference, but a relationship between stem-bone interference and push-out load could not be determined due to variability among specimens. On the basis of this model, it was concluded that press-fit fixation can occur at relatively low levels of diametral interference and that stem-bone interference elicits viscoelastic response that reduces stem stability over time. From a clinical perspective, these results suggest that there could be large variations in initial press-fit fixation among patients.

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Peri-acetabular bone remodelling after uncemented total hip arthroplasty with monoblock press-fit cups: an observational study

10.21203/rs.3.rs-19063/v2 ◽

2020 ◽

Author(s):

Conrad Anderl ◽

Georg Mattiassich ◽

Reinhold Ortmaier ◽

Martin Steinmair ◽

Josef Hochreiter

Keyword(s):

Observational Study ◽

Bone Remodelling ◽

Central Zone ◽

Rigid Fixation ◽

Mineral Density ◽

Acetabular Bone ◽

Total Hip ◽

Press Fit ◽

Uncemented Total Hip Arthroplasty ◽

Elastic Fixation

Abstract Background: Bone stock preservation in total hip replacement is essential to allow for later revisions in an increasingly younger and fitter index patient population. While contemporary modular press-fit acetabular cups lead to rigid fixation with equatorial stress and central osteolysis, more elastic fixation may cause different peri-acetabular bone remodelling. The purpose of this study was to investigate changes in peri-acetabular bone mineral density (BMD) in uncemented elastic fixation with monoblock press-fit cups.Methods: This prospective observational study included 45 patients with monoblock cups. We evaluated peri-acetabular BMD using dual-energy X-ray absorptiometry and reported functional outcomes and complications.Results: At a mean follow-up of 24.2 ± 2.2 months, we found that BMD stabilised in DeLee and Charnley zones I and III and recovered to baseline value in zone II. The mean Harris Hip Scores improved significantly from 56.9 ± 20.0 to 97.2 ± 4.0 (p < 0001). Other than one peri-operative dislocation, we saw no post-operative complications.Conclusions: We found favourable adaptive bone changes with BMD stabilisation in the equatorial zones and recovery to pre-operative values in the central zone. Additionally, excellent clinical outcomes and few prosthesis-related complications strengthened the favourable results of monoblock acetabular cups.Trial registration: Registration number DRKS00017076.

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VISCOELASTIC RESPONSES OF MDF KERF STRUCTURES

10.12783/asc36/35749 ◽

2021 ◽

Author(s):

ARYABHAT DARNAL ◽

ZARYAB SHAHID ◽

JIWAN HAN ◽

MICHAEL MORENO ◽

NASTASIA MULIANA

Keyword(s):

Epoxy Resin ◽

Medium Density Fiberboard ◽

Current Trend ◽

Time Dependent ◽

Viscoelastic Response ◽

Wood Fibers ◽

Creep Tests ◽

Viscoelastic Composite ◽

Dog Bone ◽

Complex Shapes

Medium-density fiberboard (MDF), comprised of chopped wood fibers and epoxy resin is commonly used in building construction. Given the current trend in freeform architecture, there is a need to generate complex geometric structures out of common construction materials. In this study, kerfing (relief cutting) method is used to create flexible and moldable shapes out of relatively rigid wood panels. The kerf panels can be easily formed into various complex shapes for outdoor facades and/or indoor paneling. The natural wood fibers and epoxy resin in MDF combine to produce a viscoelastic composite material that exhibits time-dependent changes in mechanical behavior, i.e., material stiffness/compliance. The work described herein comes from a study designed to develop a better understanding of the viscoelastic response of kerf unit cells and panels. Experimental creep tests were performed on dog-bone specimens under uniaxial loading conditions1in order to determine the viscoelastic response of the MDF. The experimental results were used to develop a model to be used in simulations. The simulations were carried out on a kerf unit cell, e.g., a square interlocked kerf, and kerf structures of complex geometries in order to investigate the time-dependent changes in the deformations of the kerf structures. From this study, a systematic design of kerf panels with complex shapes will be developed in order to minimize the time-dependent changes of kerf structures.

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