Biomedical subjects

Nico Verdonschot

Publications and source records attributed to Nico Verdonschot.

30 records · Page 2Linked to original sources

PubMed2005

Philosophies of stem designs in cemented total hip replacement.

Stem designs, which have different design features, may produce similar clinical survival curves. Alteratively, some designs that are considered to be similar in design produce different survival rates. In this paper, design aspects of cemented femoral total hip replacement stems, how they can be grouped to design philosophies, and how they may affect the failure process are discussed. In addition, explanations of unsuccessful designs are posed to learn from previous mistakes and improve understanding of design aspects that affect the longevity of cemented femoral stem designs.

Arthroplasty, Replacement, Hip↗

PubMed2004

The initial stability of an exeter femoral stem after impaction bone grafting in combination with segmental defect reconstruction.

Bone impaction grafting of the femur is associated with more complications when segmental defects are present. The effect of segmental defect repair on initial stem stability was studied in an in vitro study with fresh-frozen goat femora. A standardized medial segmental defect was reconstructed using a cortical strut or a metal mesh. As controls, we used intact femora and femora with a nonreconstructed defect. In all 4 groups, impacted bone grafting was performed in combination with a cemented Exeter stem. Each group contained 5 femora. Reconstructions were dynamically loaded up to 1,500 N. Migration was measured with Roentgen stereophotogrammetric analysis. All cases with a nonreconstructed segmental defect failed into excessive varus rotation. None of the femora with a reconstructed defect failed. Cortical struts and metal meshes were equally effective in creating a stable stem construction (varus rotation, 2.89 +/- 2.27 and 2.27 +/- 0.57, respectively). Reconstructions with a metal mesh were more reproducible, although the obtained stability was significantly lower (P<.01) when compared with impaction grafting in an intact femur (varus rotation, 0.58 +/- 0.36).

Animals↗

PubMed2004

Skeletal tissue engineering-from in vitro studies to large animal models.

Bone is a tissue with a strong regenerative potential. New strategies for tissue engineering of bone should therefore only focus on defects with a certain size that will not heal spontaneously. In the development of tissue-engineered constructs many variables may play a role, e.g. the source of the cells used, the design and mechanical properties of the scaffold and the concentration and mode of application of growth factor(s). Models for studying new strategies for tissue engineering of bone should be based on the target tissue to be restored. However, in light of the many potential variables, which may also interact if used in combination(s), there is also a large need for relatively simple models in which variables can be tested in a limited number of animals. Moreover, in compromised bone there may be a problem with the load-bearing capacity of the remaining healthy bone. In this light, an important prerequisite for tissue-engineering constructs is that they can be tested in loaded conditions. Particularly, this latter prerequisite is very difficult to achieve. Therefore, in vitro tests for mechanical stability are very useful for evaluating the mechanical consequences of a particular reconstruction procedure prior to the animal experiment. Before a tissue-engineered construct can be introduced into a clinical trial, a final test should be available in a large animal model that is as close and relevant to a particular problematic clinical situation as possible.In the past, a series of models were developed in our laboratory that are very useful for testing tissue-engineered constructs. In this paper, we focus on the use of relatively new simple in vitro and in vivo models for hip revision surgery, segmental bone defect restoration and tumour surgery.

Animals↗

PubMed2004

Wire mesh allows more revascularization than a strut in impaction bone grafting: an animal study in goats.

Segmental defects can be reconstructed with a cortical strut or a metal wire mesh when using bone impaction grafting in the femur. We hypothesized that structural grafts would negatively influence revascularization of the underlying impacted grafts compared with an open wire mesh. A standardized large medial wall defect was reconstructed with a strut or a mesh in six goats per group. In all femurs impaction grafting was done in combination with a cemented collarless double-tapered highly polished Exeter stem. After 6 weeks the femurs were harvested. A high rate of periprosthetic fractures was observed (three of seven and two of six for the strut and mesh groups, respectively). Histologic analysis showed different revascularization and tissue ingrowth patterns for both reconstruction techniques. In the strut group, fibrous tissue ingrowth was limited to the edges of the defect. Medially behind the strut no or limited fibrous tissue ingrowth was found. In the mesh group, fibrous tissue and blood vessels penetrated the mesh and a superficial zone of revascularized grafts was observed. Although revascularization, concomitant graft resorption and bone incorporation may compromise the short-term stability of the stem after surgery, the long-term stability of the stem probably is best guaranteed by graft incorporation.

Animals↗

PubMed2004

Acetabular reconstruction with impaction bone-grafting and a cemented cup in patients younger than fifty years old.

BACKGROUND: Acetabular bone deficiency can present a challenge during total hip arthroplasty, especially in young patients. The purpose of the present study was to evaluate the long-term clinical and radiographic outcomes of primary and revision acetabular reconstruction with use of an impaction bone-grafting technique and a cemented polyethylene cup in young patients who had preexisting acetabular bone deficiency. METHODS: Forty-two consecutive acetabular reconstructions were performed in thirty-seven patients who were younger than fifty years old (average, 37.2 years old). The impaction bone-grafting technique was used for twenty-three primary and nineteen revision acetabular reconstructions. Twenty-eight patients (thirty-one hips) were available for review after a minimum duration of follow-up of fifteen years. Clinical and radiographic results were assessed, and survivorship analysis was performed with the Kaplan-Meier method. RESULTS: Eight hips were revised at a mean of twelve years (range, three to twenty-one years) after a primary reconstruction (four hips) or revision reconstruction (four hips). The revision was performed because of aseptic loosening of the acetabular component in four hips and because of culture-proven septic loosening in two. Two additional cups (both in hips that had had a revision reconstruction) were revised, during revision of the femoral stem, because of wear (one hip) or because of persistent intraoperative instability (one hip). Twenty-eight hips (in twenty-five patients) had retention of the acetabular component for a minimum of fifteen years. The mean Harris hip score for that group was 89 points. Twenty-six of these twenty-eight hips had no or slight pain. Kaplan-Meier analysis revealed a twenty-year survival rate of 80% (95% confidence interval, 67% to 94%) with acetabular revision for any reason as the end point and of 91% (95% confidence interval, 80% to 100%) with acetabular revision because of aseptic loosening as the end point. CONCLUSIONS: Acetabular reconstruction with use of impaction bone-grafting and a cemented polyethylene cup is a reliable and durable technique that is associated with good long-term results in young patients with acetabular bone-stock defects.

Acetabulum↗

PubMed2004

How close does an uncemented hip stem match the final rasp position?

During total hip arthroplasty the final clinical position of the cementless CLS stem (Centerpulse) is not always identical to the position of the final rasp with which a successful trial reduction was performed. Therefore, the rasp-stem correspondence of CLS system (Centerpulse) was investigated in a laboratory study and compared to the CBC-T system (Mathys). Both systems showed an average rasp-stem mismatch below 2 mm in three orthogonal directions. It was found that this mismatch related to geometric differences at the corners between rasp and stem. The measured mismatch is not expected to have adverse clinical consequences.

Arthroplasty, Replacement, Hip↗

PubMed2003

Particle size of bone graft and method of impaction affect initial stability of cemented cups: human cadaveric and synthetic pelvic specimen studies.

We determined the effect of bone graft particle size and impaction technique on the initial stability of cemented acetabular cups. First, acetabular reconstructions were performed in human cadaveric pelvic bones in which type 2 AAOS cavitary defects were created. Reconstructions were made with small bone grafts (average 2 mm) produced by a bone mill or large bone grafts (average 9 mm) produced by hand with a rongeur. All chips were made from freshly-frozen femoral heads. Impaction was done using acetabular impactors and a hammer. We did a loading experiment with a gradually increasing dynamic load up to 3000 N. We used radiostereometric analysis (RSA) to determine cup stability. The cups were more stable when large bone grafts were used. Because of limitations of the cadaver model, we developed a synthetic acetabular model. For validation of this model, we repeated the experiments using small and large bone grafts. The results with both models were similar. In the synthetic model, we compared impaction with hammer and impactors with the reversed reaming technique using manual compression on the reamer. The latter method resulted in more migration. We recommend firm impaction with a hammer of large bone grafts for optimal stability of the cup.

Acetabulum↗

PubMed2003

Can finite element models detect clinically inferior cemented hip implants?

Rigorous preclinical testing of cemented hip prostheses against the damage accumulation failure scenario will reduce the incidence of aseptic loosening. For that purpose, a finite element simulation is proposed that predicts damage accumulation in the cement mantle and prosthetic migration. If the simulation is to become a convincing preclinical test, it should be able to distinguish between implants in a clinically relevant way, based on accurate predictions of long-term failure mechanisms of cemented hip prostheses. The algorithm was used to simulate long-term fatigue experiments on femoral reconstructions with Mueller Curved and Lubinus SPII stems. Clinically, the Mueller Curved system performs inferior to the Lubinus SPII system. The finite element simulation predicted much more cement damage around the Mueller Curved stem and showed that the entire cement mantle was involved in the failure process, which was not the case around the Lubinus SPII stem. In addition, the Mueller Curved stem was predicted to migrate more than the Lubinus SPII. The predictions showed excellent agreement with the experimental findings: similar damage locations in the cement, more damage for the Mueller Curved, similar prosthetic migration directions, and more migration for the Mueller Curved stem. This is the first time that a finite element simulation is able to differentiate between a clinically superior and an inferior implant, based on accurate simulation of the long-term failure mechanisms in a cemented reconstruction. Its use for preclinical testing purposes is corroborated.

Cementation↗

PubMed2002

Stemmed femoral knee prostheses: effects of prosthetic design and fixation on bone loss.

Although the revision rates for modern knee prostheses have decreased drastically, the total number of revisions a year is increasing because many more primary knee replacements are being done. At the time of revision, bone loss is common, which compromises prosthetic stability. To improve stability, intramedullary stems are often used. The aim of this study was to estimate the effects of a stem, its diameter and the interface bonding conditions on patterns of the bone remodeling in the distal femur. We created finite element models of the distal half of a femur in which 4 types of knee prostheses were placed. The bone remodeling process was simulated using a strain-adaptive bone remodeling theory. The amount of such remodeling was determined by calculating the changes in bone mineral density in 9 regions of interest from simulated DEXA scans. The computer simulation model showed that revision prostheses tend to cause more bone resorption than primary ones, especially in the most distal regions. Predicted long-term bone loss due to a revision prosthesis with a thin stem equalled that around a prosthesis with an intercondylar box. However, strong regional differences were found--the stemmed prostheses having more bone loss in the most distal areas and some bone gain in the more proximal ones. A prosthesis with a thick stem led to an increase in bone loss. When the prosthesis-cement interface was bonded, more bone loss was predicted than with an unbonded interface. These results suggest that a stem which increases stability initially may reduce stability in the long term. This is due to an increase in stress shielding and bone resorption.

Bone Remodeling↗

PubMed2002

Stair climbing is more detrimental to the cement in hip replacement than walking.

Stair climbing may be detrimental to cemented total hip arthroplasties, because it subjects the reconstruction to high torsional loads. The current study investigated how stair climbing contributes to damage accumulation in the cement around a femoral stem compared with walking, taking into account the different frequencies of these activities during patient functioning. In finite element analyses, the damage accumulation process in the cement mantle around a Lubinus SPII stem was simulated for three different loading histories: (1) isolated walking, representative for patients who climb no stairs; (2) isolated stair climbing; (3) alternating walking and stair climbing in a ratio of nine to one cycles, representative for patients who climb many stairs. Relative to isolated walking, isolated stair climbing increased the amount of cement damage by a factor of 6. Inclusion of 10% stair climbing cycles in the loading history increased the amount of damage by 47% relative to isolated walking. Stair climbing produced damage along the entire stem, whereas isolated walking produced damage proximomedially and around the tip only. This study confirmed that stair climbing is more risky for failure of cemented femoral stems than walking. A few stair climbing cycles during daily patient functioning increases the amount of cement damage dramatically.

Biomechanical Phenomena↗

PubMed2002

Soft tissue movement and stress shielding do not affect bone ingrowth in the bone conduction chamber.

A variety of bone chambers are used in orthopedic research to study bone and tissue ingrowth in small and large animals. If different bone chambers are placed in one species, differences in bone ingrowth are observed. For instance, bone ingrowth in the bone conduction chamber (BCC) is high, but is low or absent in the repeated sampling bone chamber (RSBC). This difference may be explained by the design and fixation of these chambers. It is known that stress shielding and micromovement can influence bone formation. The objective of the study reported here was to determine whether stress shielding or soft tissue movement affected bone ingrowth in the BCC in the goat. Two types of caps were made, with fixation similar to that of the fixation plate of the RSBC. By placing the caps over the BCCs and fixating the caps directly to the tibial bone, the effect of stress shielding was studied. One cap was in direct contact with the bone chamber underneath, the other cap did not touch the chamber. This difference was used to observe whether movement of the soft tissue on top of the chamber and cap would affect bone ingrowth. Each limb received one control chamber without a cap and a chamber with a cap, either with or without contacting the BCC, yielding four implants per goat. After 12 weeks, bone and total tissue ingrowths were measured. Bone ingrowth was seen in 38 of 40 chambers. Total tissue and bone ingrowths were comparable between control chambers and BCCs with a cap, irrespective of type. Neither stress shielding, nor lack of movement of soft tissue affected bone ingrowth. Other factors in the design of the chambers were responsible for the difference in bone ingrowth between the BCC and the RSBC.

Animals↗

PubMedDate not supplied

Fatigue resistance of teeth restored with cuspal-coverage composite restorations.

PURPOSE: This study assessed the influence of palatal cuspal coverage on the in vitro fatigue resistance and failure mode of Class II resin composite restorations including replacement of the buccal cusp in premolars. MATERIALS AND METHODS: A master model was made of a maxillary premolar with an MOD amalgam cavity and a simulated fracture of the buccal cusp from the isthmus floor to the CEJ. Using a copy-milling machine, this preparation was copied to 20 extracted human maxillary premolars (group A). Subsequently, the palatal cusp was reduced by 1.5 mm; this modified preparation was copied to 20 additional maxillary premolars (group B). Direct resin composite restorations were made in all teeth. Cyclic load (5 Hz) was applied, starting with a load of 200 N (10,000 cycles), followed by stages of 400, 600, 800, and 1,000 N at a maximum of 50,000 cycles each. Samples were loaded until fracture or to a maximum of 210,000 cycles. RESULTS: Of the restored premolars of group A, 20% withstood all 210,000 loading cycles; in group B, this figure was 55%. In group A, 19% of the fractures ended below the CEJ; in group B, 78% did. CONCLUSION: Palatal cuspal coverage increased the fatigue resistance of Class II resin composite restorations with replacement of the buccal cusp in premolars. However, fractures of restorations with cuspal coverage led to more dramatic failures that made restoration virtually impossible. This suggests caution in lowering remaining cusps for these adhesive restorations in the clinical situation.

Bicuspid↗