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Wolfram Mittelmeier - One of the best experts on this subject based on the ideXlab platform.

  • Primary stability of a cementless modular revision Hip Stem in relation with the femoral defect size: A biomechanical study:
    Journal of Orthopaedic Surgery, 2020
    Co-Authors: Martin Ellenrieder, Wolfram Mittelmeier, Daniel Kluess, Robert Souffrant, Christian Schulze, Rainer Bader
    Abstract:

    Purpose:Cementless modular fluted Hip Stems are commonly used in revision arthroplasty. Nevertheless, there is a wide spectrum of recommendations concerning the minimum bone stock required to enabl...

  • Supplementary finite element analysis in experimental testing of total Hip Stems
    Materials Testing, 2018
    Co-Authors: Daniel Kluess, Wolfram Mittelmeier, Hans-e. Lange, Horst Heyer, Manuela Sander, Rainer Bader
    Abstract:

    Abstract Before an implantable medical device passes market clearance, a number of mechanical tests need to be conducted in order to verify the mechanical safety of the product. With regard to total Hip replacement Stems, these are subject to fatigue tests both in the proximal region of the neck as well as in the distal region of the shaft. Despite these tests, we experienced two clinical fractures of the same product in our clinic. It was shown that these fractures were initiated by a laser engraving of the manufacturer with subsequent crack growth. The basic question raised in the present work was to find out why fracture may not have occurred during experimental preclinical testing. Hence, a supplementary finite element analysis was conducted considering the same Hip Stem under the prescribed conditions of the test standard in different variations. It was found that the choice of orientation and side (left or right leg) strongly influences stress in the Hip Stem which has not yet been prescribed in tes...

  • How stiffness and distal interlocking of revision Hip Stems influence the femoral cortical strain pattern
    Journal of Orthopaedic Science, 2012
    Co-Authors: Martin Ellenrieder, Erwin Steinhauser, Rainer Bader, Wolfram Mittelmeier
    Abstract:

    BackgroundStress shielding and nonphysiological load transfer after primary or revision total Hip replacement (THR) prepare the ground for resorptive bone remodeling. The quality of the bone stock influences the risk of periprosthetic fractures and the severity of future revision surgeries. The question of whether or not bending stiffness and distal screw interlocking influence load transfer of a modular revision Hip Stem with a solid, hollow, and hollow-slotted Stem extension led to the conception of this experimental study. The results were compared with a standard Hip Stem for primary THR.MethodsRevision Stems were implanted in photoelastically coated composite femora. Cortical strain mapping was conducted before and after insertion of the implants under standardized loading conditions, considering the relevant muscle forces. Statistical analysis was based on a 95% confidence interval and a variance analysis for repeated measurements.ResultsSignificant stress shielding was observed after insertion of all types of Hip Stems compared with the intact femora. There was also a marked difference between strain alterations induced by standard and revision Hip Stems. With revision Stems, the most distinct stress shielding effects were registered with the solid Stem extension, particularly in the femoral diaphysis. Distal interlocking screws only had a local action on strain pattern and tended to enhance stress shielding at the midStem area when using the more flexible components.ConclusionMore flexible revision Stems provide a cortical strain pattern of the femur closer to the preoperative status. This may reduce resorptive bone remodeling in the long term. However, any type of revision Stem tested in this study caused higher stress shielding than the Hip Stem for primary THR, especially in the diaphyseal region medially and laterally. With sufficient proximal anchorage, the influence of distal interlocking screws on the femoral strain pattern was localized.

  • How stiffness and distal interlocking of revision Hip Stems influence the femoral cortical strain pattern
    Journal of Orthopaedic Science, 2012
    Co-Authors: Martin Ellenrieder, Erwin Steinhauser, Rainer Bader, Wolfram Mittelmeier
    Abstract:

    Background Stress shielding and nonphysiological load transfer after primary or revision total Hip replacement (THR) prepare the ground for resorptive bone remodeling. The quality of the bone stock influences the risk of periprosthetic fractures and the severity of future revision surgeries. The question of whether or not bending stiffness and distal screw interlocking influence load transfer of a modular revision Hip Stem with a solid, hollow, and hollow-slotted Stem extension led to the conception of this experimental study. The results were compared with a standard Hip Stem for primary THR.

  • Influence of cementless Hip Stems on femoral cortical strain pattern depending on their extent of porous coating.
    Biomedizinische Technik Biomedical Engineering, 2012
    Co-Authors: Martin Ellenrieder, Erwin Steinhauser, Rainer Bader, Wolfram Mittelmeier
    Abstract:

    The extent of porous coating of cementless total Hip Stems is held responsible for radiological periprosthetic changes, the rate of thigh pain, and even its long-term success. However, there is only sparse knowledge on how the biomechanical loading conditions of the femur are influenced by the extent of porous coating in the early phase after implantation of a cementless Hip Stem. Aiming to evaluate the effect of surface structuring on the strain pattern of the femur, we implanted three anatomic Hip Stems with different extents of porous coating (full, two-thirds proximal, and penguin type) in second-generation composite femora coated with a photoelastic layer. A cortical strain mapping was conducted before and after insertion of the implants under standardized loading conditions considering relevant muscle forces. The results of the statistical analysis of three different implantation sequences proved that composite femora are suitable for repeated measurements within the applied experimental setup. Cortical strain changes including stress-shielding effects medially (-60%) and laterally (-50%) were validated with a cadaver femur. The extent of porous coating had no significant influence on the surface strain pattern for an immediate postoperative situation.

Bernd Ishaque - One of the best experts on this subject based on the ideXlab platform.

  • Age-related osseointegration of a short Hip Stem: a clinical and radiological 24 months follow-up.
    Archives of Orthopaedic and Trauma Surgery, 2018
    Co-Authors: Sarah Boller, Alexander Jahnke, Laura Augustin, Gafar Adam Ahmed, Markus Rickert, Bernd Ishaque
    Abstract:

    The purpose of this study was to examine potential differences between patients under and over 60 years who underwent a total short Hip Stem arthroplasty in a 24-month follow-up in a clinical setting. Sixty seven patients were included in this prospective study and divided in two groups. In the younger cohort 39 patients ≤ 59 years and in the older cohort 28 patients ≥ 60 years were included. Clinical and radiological examinations of the patients took place preoperatively, postoperatively and after 3, 6, 12 and 24 months. The Harris Hip Score (HHS) was raised as clinical examination. Changes of bone mass density (BMD), stress shielding, reactive lines, spot welds and sclerosing were examined as radiological analysis. The HHS improved from 53.6 ± 8.2 preoperative to 93.2 ± 9.6 in the younger cohort and for the older cohort from 57.6 ± 14.8 to 94.1 ± 7.6 after 24 months. BMD growth was detectable in regions of interest (ROI) 3 and 6 for both groups. Different results between the cohorts could only be detected in ROIs 4 and 5. The older cohort showed a loss of BMD of 5.95% in ROI 4 and 3.17% in ROI 5 after 24 months, whereas the younger cohort showed no loss of BMD in both ROIs. No significant differences or any influences of osseointegration and clinical outcome of the short Hip Stem for both groups were detectable. Lower losses (ROIs 1 and 2) and higher growths (ROIs 3, 4, 5) were discovered in younger patients and the HHS improved in both groups. Reasons for this result could be age, sex or the level of activity of the patients, but in both groups the short Hip Stem shows comparable results in clinical as well as in radiological examination. We conclude that the short Hip Stem seems to be an adequate treatment also for older patients.

  • Development of periprosthetic bone mass density around the cementless Metha® short Hip Stem during three year follow up-a prospective radiological and clinical study.
    International Orthopaedics, 2018
    Co-Authors: Laura Augustin, Sarah Boller, Alexander Jahnke, Gafar Adam Ahmed, Markus Rickert, Cathrein Bobach, Bernd Ishaque
    Abstract:

    PURPOSE The purpose of this study was to check the concept of the cementless Metha® short Hip Stem in order to find out whether proximal physiological load transfer can be achieved. METHODS Fourty-three patients were included. Epidemiological factors were established. The Harris Hip Score was determined and measurement of bone mass density as well as osteodensitometric and radiological measurements was carried out pre-operatively, post-operatively, and after six, 12, 24, and 36 months. RESULTS Harris Hip Score improved from 55.9 ± 12.4 pre-operatively to 94.8 ± 8.2 after 36 months (p 

  • Length of clinically proven cemented Hip Stems: State of the art or subject to improvement?
    International Orthopaedics, 2014
    Co-Authors: Moussa Hamadouche, Alexander Jahnke, Markus Rickert, Bernd Ishaque, Caroline Scemama, L. Kerboull, Eike Jakubowitz
    Abstract:

    Purpose The purpose of this study was to identify the shortest possible length of an established cemented Hip Stem in order to reduce stress shielding and optimise its bending behaviour.

  • changes of periprosthetic bone density after a cementless short Hip Stem a clinical and radiological analysis
    International Orthopaedics, 2014
    Co-Authors: Alexander Jahnke, Markus Rickert, Eike Jakubowitz, Jörn Bengt Seeger, Sandra Engl, Corinna Altmeyer, Bernd Ishaque
    Abstract:

    Purpose The purpose of this study was to examine the concept of proximal load initiation of a total short-Stemmed Hip arthroplasty (Metha® BBraun, Aesculap, Tuttlingen, Germany) on the basis of bone variations by means of osteodensitometric dual energy X-ray absorptiometry and radiologic measurements.

Eike Jakubowitz - One of the best experts on this subject based on the ideXlab platform.

  • Length of clinically proven cemented Hip Stems: State of the art or subject to improvement?
    International Orthopaedics, 2015
    Co-Authors: Moussa Hamadouche, Alexander Jahnke, Markus Rickert, Caroline Scemama, L. Kerboull, Bernd Alexander Ishaque, Eike Jakubowitz
    Abstract:

    Purpose The purpose of this study was to identify the shortest possible length of an established cemented Hip Stem in order to reduce stress shielding and optimise its bending behaviour. Methods Twenty-five prototypes from the same batch (five for each Stem length) were included. Lengths resulted from the original length (100 %) and four distal shortenings to 94, 88, 83 and 78 % of original length. For standardised implantations, synthetic femurs were prepared. Relative movements under axial torque and Stem bending under varus–valgus torque applications were investigated consecutively. Analyses of variance (ANOVA) were applied to detect differences between lengths. Results The maximum torque transfer occurred at the level of the lesser trochanter ( p  

  • Length of clinically proven cemented Hip Stems: State of the art or subject to improvement?
    International Orthopaedics, 2014
    Co-Authors: Moussa Hamadouche, Alexander Jahnke, Markus Rickert, Bernd Ishaque, Caroline Scemama, L. Kerboull, Eike Jakubowitz
    Abstract:

    Purpose The purpose of this study was to identify the shortest possible length of an established cemented Hip Stem in order to reduce stress shielding and optimise its bending behaviour.

  • changes of periprosthetic bone density after a cementless short Hip Stem a clinical and radiological analysis
    International Orthopaedics, 2014
    Co-Authors: Alexander Jahnke, Markus Rickert, Eike Jakubowitz, Jörn Bengt Seeger, Sandra Engl, Corinna Altmeyer, Bernd Ishaque
    Abstract:

    Purpose The purpose of this study was to examine the concept of proximal load initiation of a total short-Stemmed Hip arthroplasty (Metha® BBraun, Aesculap, Tuttlingen, Germany) on the basis of bone variations by means of osteodensitometric dual energy X-ray absorptiometry and radiologic measurements.

  • Do short-Stemmed-prostheses induce periprosthetic fractures earlier than standard Hip Stems? A biomechanical ex-vivo study of two different Stem designs
    Archives of Orthopaedic and Trauma Surgery, 2008
    Co-Authors: Eike Jakubowitz, Jörn Bengt Seeger, C. Lee, Christian Heisel, Jan Philippe Kretzer, M. Thomsen
    Abstract:

    Introduction The causes of periprosthetic fractures of the femur due to the design of the prosthesis and the individual parameters of the patient are unexplored. By diVerent anchorage techniques in cementless total Hip arthroplasties, it is assumed that there are various load limits of the implant’s bearing femur. Materials and methods In the present study, we compared a standard Hip Stem (cementless Spotorno ® ) and a shortStemmed design (Mayo ® ) by an artiWcial reproduction of periprosthetic fractures in 20 femur specimens. Results The measured fracture loads showed an extensive range, with higher maximum loads in the standard Stem group. The bone mineral density and the subsiding pattern of the standard Stems showed a signiWcant correlation to the incidence of the periprosthetic fractures. In the experimental setup, a slightly lower fracture resistance was shown for the short-Stemmed prosthesis. Additionally, it was shown that donors with a higher body mass index had a signiWcantly increased fracture risk. Conclusions Short-Stemmed prostheses, especially the Mayo ® Hip, do not constitute a higher fracture risk. In general, an increased body mass index among patients with a cementless Hip Stem is associated with an increased fracture risk, particularly at high load values, i.e., resulting from a step during stumbling. Taking into account the ascertained results, the danger of provoking a femoral periprosthetic fracture can be reduced.

Alexander Jahnke - One of the best experts on this subject based on the ideXlab platform.

  • Age-related osseointegration of a short Hip Stem: a clinical and radiological 24 months follow-up.
    Archives of Orthopaedic and Trauma Surgery, 2018
    Co-Authors: Sarah Boller, Alexander Jahnke, Laura Augustin, Gafar Adam Ahmed, Markus Rickert, Bernd Ishaque
    Abstract:

    The purpose of this study was to examine potential differences between patients under and over 60 years who underwent a total short Hip Stem arthroplasty in a 24-month follow-up in a clinical setting. Sixty seven patients were included in this prospective study and divided in two groups. In the younger cohort 39 patients ≤ 59 years and in the older cohort 28 patients ≥ 60 years were included. Clinical and radiological examinations of the patients took place preoperatively, postoperatively and after 3, 6, 12 and 24 months. The Harris Hip Score (HHS) was raised as clinical examination. Changes of bone mass density (BMD), stress shielding, reactive lines, spot welds and sclerosing were examined as radiological analysis. The HHS improved from 53.6 ± 8.2 preoperative to 93.2 ± 9.6 in the younger cohort and for the older cohort from 57.6 ± 14.8 to 94.1 ± 7.6 after 24 months. BMD growth was detectable in regions of interest (ROI) 3 and 6 for both groups. Different results between the cohorts could only be detected in ROIs 4 and 5. The older cohort showed a loss of BMD of 5.95% in ROI 4 and 3.17% in ROI 5 after 24 months, whereas the younger cohort showed no loss of BMD in both ROIs. No significant differences or any influences of osseointegration and clinical outcome of the short Hip Stem for both groups were detectable. Lower losses (ROIs 1 and 2) and higher growths (ROIs 3, 4, 5) were discovered in younger patients and the HHS improved in both groups. Reasons for this result could be age, sex or the level of activity of the patients, but in both groups the short Hip Stem shows comparable results in clinical as well as in radiological examination. We conclude that the short Hip Stem seems to be an adequate treatment also for older patients.

  • Development of periprosthetic bone mass density around the cementless Metha® short Hip Stem during three year follow up-a prospective radiological and clinical study.
    International Orthopaedics, 2018
    Co-Authors: Laura Augustin, Sarah Boller, Alexander Jahnke, Gafar Adam Ahmed, Markus Rickert, Cathrein Bobach, Bernd Ishaque
    Abstract:

    PURPOSE The purpose of this study was to check the concept of the cementless Metha® short Hip Stem in order to find out whether proximal physiological load transfer can be achieved. METHODS Fourty-three patients were included. Epidemiological factors were established. The Harris Hip Score was determined and measurement of bone mass density as well as osteodensitometric and radiological measurements was carried out pre-operatively, post-operatively, and after six, 12, 24, and 36 months. RESULTS Harris Hip Score improved from 55.9 ± 12.4 pre-operatively to 94.8 ± 8.2 after 36 months (p 

  • Length of clinically proven cemented Hip Stems: State of the art or subject to improvement?
    International Orthopaedics, 2015
    Co-Authors: Moussa Hamadouche, Alexander Jahnke, Markus Rickert, Caroline Scemama, L. Kerboull, Bernd Alexander Ishaque, Eike Jakubowitz
    Abstract:

    Purpose The purpose of this study was to identify the shortest possible length of an established cemented Hip Stem in order to reduce stress shielding and optimise its bending behaviour. Methods Twenty-five prototypes from the same batch (five for each Stem length) were included. Lengths resulted from the original length (100 %) and four distal shortenings to 94, 88, 83 and 78 % of original length. For standardised implantations, synthetic femurs were prepared. Relative movements under axial torque and Stem bending under varus–valgus torque applications were investigated consecutively. Analyses of variance (ANOVA) were applied to detect differences between lengths. Results The maximum torque transfer occurred at the level of the lesser trochanter ( p  

  • Length of clinically proven cemented Hip Stems: State of the art or subject to improvement?
    International Orthopaedics, 2014
    Co-Authors: Moussa Hamadouche, Alexander Jahnke, Markus Rickert, Bernd Ishaque, Caroline Scemama, L. Kerboull, Eike Jakubowitz
    Abstract:

    Purpose The purpose of this study was to identify the shortest possible length of an established cemented Hip Stem in order to reduce stress shielding and optimise its bending behaviour.

  • changes of periprosthetic bone density after a cementless short Hip Stem a clinical and radiological analysis
    International Orthopaedics, 2014
    Co-Authors: Alexander Jahnke, Markus Rickert, Eike Jakubowitz, Jörn Bengt Seeger, Sandra Engl, Corinna Altmeyer, Bernd Ishaque
    Abstract:

    Purpose The purpose of this study was to examine the concept of proximal load initiation of a total short-Stemmed Hip arthroplasty (Metha® BBraun, Aesculap, Tuttlingen, Germany) on the basis of bone variations by means of osteodensitometric dual energy X-ray absorptiometry and radiologic measurements.

Gunnar Flivik - One of the best experts on this subject based on the ideXlab platform.

  • fatigue fracture in dual modular revision total Hip arthroplasty Stems failure analysis and computed tomography diagnostics in two cases
    Journal of Arthroplasty, 2014
    Co-Authors: Pontus Norman, Srinivasan Iyengar, Ingrid Svensson, Gunnar Flivik
    Abstract:

    We report on two patients with fracture of a modular, tapered and distally fixed, uncemented titanium revision Hip Stem, not previously described. A failure analysis revealed that the cause of the fractures was the development of fatigue cracks in the mid-Stem cobalt-chromium modular junction ending in corrosion-fatigue failure. No material defects or stress risers were found in any of the implants. The diameter of the mid-Stem modular junction might be undersized for use in heavy and active patients. We also report a new way of detecting an undisplaced fracture at the modular junction, using the scout image from a computed tomography (CT) scan; a technique that can be used when plain radiographs are inconclusive.