Biomedical subjects

P Buma

Publications and source records attributed to P Buma.

At least 19 recordsLinked to original sources

PubMed2007

Biological activity of tri-calciumphosphate/hydroxyl-apatite granules mixed with impacted morsellized bone graft. A study in rabbits.

Reconstruction of bone defects with impacted morsellized cancellous bone grafts (MCB) is a popular method. Because of a shortage of human bone, mixing with biomaterials may be attractive. Ceramics may be used as bone graft extenders. In this study, various volume mixtures of biphasic tri-calciumphosphate/hydroxyl-apatite (TCP-HA) granules (1.5-2 mm) with MCB were examined in a non-loaded defect model in rabbits. Direct post-operatively, many 10-150 microm TCP-HA particles were present due to impaction. Irrespective to the group, after 8 weeks, virtually all MCB was resorbed and most TCP-HA granules were osseous-integrated with newly formed bone. The cross-sectional areas of TCP-HA after 8 weeks was generally smaller compared with direct post-operatively and the number of small 10-150 microm TCP-HA particles seemed reduced. Macrophages and giant cells were sparse after 8 weeks. In conclusion, the osteoconductivity of various mixtures of MCB and TCP-HA granules is not dependent on the ratio of TCP-HA over MCB. The reduced number of the 10-150microm TCP-HA particles after 8 weeks, may suggest that a cellular mediated resorption process of TCP-HA granules took place. Based on these favorable biological findings subsequent in-vivo experiments are warranted in load-bearing conditions to investigate whether these findings hold for joint reconstruction purposes.

Animals↗

PubMed2006

Meniscal replacement in dogs. Tissue regeneration in two different materials with similar properties.

In earlier studies, meniscal replacement with a porous polymer implant led to regeneration of neo-meniscal tissue. To evaluate the influence of the chemical properties on the tissue regeneration in the implant, in the present study, the meniscus in the dog's knee was replaced with either an aromatic 4,4-diphenylmethanediisocyanate based polyesterurethane implant (Estane) (n = 6) or with an aliphatic 1,4-butanediisocyanate based polyesterurethane implant (PCLPU) (n = 6). After 6 months, the knee joints were resected and the tissue behavior in the two different prostheses was evaluated microscopically. In both prostheses, a meniscus-like distribution of the tissue phenotype was found with collagen type I in the peripheral fibrous zones and collagen type II in the central, more cartilaginous zones. The compression-stress behavior of the implant-tissue construct remained in between the stiffness of the polymer material and that of the native meniscus. The PCLPU implant seemed to provoke less synovial tissue reaction. After meniscectomy solely, in 5 out of 6 cases, a meniscus-like regenerate was formed. Furthermore, the articular cartilage degeneration after placing a PCLPU implant did also not exceed the degeneration after the Estane implant or after meniscectomy. The differences between these two implants did not seem to influence the tissue regeneration in the implant. However, PCLPU seemed to evoke less tissue reaction and, therefore, is thought to be less or even nontoxic as compared with the Estane implant. Therefore, for studies in the future, the authors prefer the PCLPU prostheses for replacement of the meniscus.

Animals↗

PubMed2006

Cortical bone development under the growth plate is regulated by mechanical load transfer.

Longitudinal growth of long bones takes place at the growth plates. The growth plate produces new bone trabeculae, which are later resorbed or merged into the cortical shell. This process implies transition of trabecular metaphyseal sections into diaphyseal sections. We hypothesize that the development of cortical bone is governed by mechanical stimuli. We also hypothesize that trabecular and cortical bone share the same regulatory mechanisms for adaptation to mechanical loads. To test these hypotheses, we monitored the development of the tibial cortex in growing pigs, using micro-computer tomography and histology. We then tested the concept that regulatory mechanisms for trabecular bone adaptation can also explain cortical bone development using our mechanical stimulation theory, which could explain trabecular bone (re)modelling. The main results showed that, from the growth plate towards the diaphysis, the pores of the trabecular structure were gradually filled in with bone, which resulted in increased density and cortical bone. The computer model largely predicted this morphological development. We conclude that merging of metaphyseal trabeculae into cortex is likely to be governed by mechanical stimuli. Furthermore, cortex development of growing long bones can be explained as a form of trabecular bone adaptation, without the need for different regulatory mechanisms for cortical and trabecular bone.

Adaptation, Physiological↗

PubMed2005

Sugioka's osteotomy for femoral-head necrosis in young Caucasians.

The transtrochanteric rotational osteotomy described by Sugioka is used to preserve the femoral head and to prevent secondary osteoarthritis in young patients with osteonecrosis of the femoral head. Several Japanese studies have shown favourable results, but European and American studies were disappointing. An explanation for these outcomes may be that the original protocol was not followed exactly. The objective of our study was to investigate this trans-trochanteric rotational osteotomy in Caucasian patients with osteonecrosis in which we followed the original method of Sugioka as closely as possible, including a 6-month period of non-weight bearing. We included 26 hips in 22 consecutive patients who were followed up for 8.7 (range 6.6-10) years. At review, 17 hips had been converted to total hip arthroplasty. The clinical survival rate was 56% after 7 years (95% CI 36-76%). The radiological survival rate was 54% after one year (95% CI 35-73%). Even after excluding the failures due to problems with osteosynthesis and infection, the results were not satisfactory and the osteoarthritic process was not delayed. Based on our results, we cannot recommend this technique as an alternative for total hip arthroplasty in Caucasians.

Adult↗

PubMed2005

Cemented cup stability during lever-out testing after acetabular bone impaction grafting with bone graft substitutes mixes containing morselized cancellous bone and tricalcium phosphate--hydroxyapatite granules.

Bone defects after failed total hip arthroplasty can be reconstructed with impacted morselized bone grafts and a cemented cup. In the near future the amount of bone grafts available for surgical purposes will be insufficient. Ceramic calcium phosphates [tricalcium phosphate (TCP) and hydroxyapatite (HA)] have been widely considered as potential bone graft substitutes or bone graft extenders. In the past, mechanical experiments have been performed to determine implant stability of bone grafts and ceramic TCP-HA granules mixes under a compressive load. However, in-vivo migration studies suggest that shear loading may be equally important. This in-vitro study investigated the initial stability of cups reconstructed with various mixes of bone grafts and ceramic TCP-HA granules in a lever-out situation, where shearing is the predominant loading mode. It was found that the cups reconstructed with mixes of bone graft and TCP-HA granules exhibited greater mechanical stability than the cups reconstructed with bone grafts only. It is concluded that from a mechanical standpoint, when considering shear force resistance, 50-50 per cent volume mix and 25-75 per cent volume mix of morselized cancellous bone graft and TCP-HA granules both provide adequate initial cup stability and can be used for acetabular reconstructions with the bone impaction grafting technique.

Acetabulum↗

PubMed2004

Is hydroxyapatite cement an alternative for allograft bone chips in bone grafting procedures? A mechanical and histological study in a rabbit cancellous bone defect model.

To evaluate in vivo performance of hydroxyapatite cement (HAC) as a porous bone graft substitute, HAC was mixed (1:1 ratio) with either porous calcium-phosphate granules (80% tricalcium phosphate, 20% hydroxyapatite) or defatted morsellized cancellous bone (MCB) allograft and implanted bilaterally in cylindrical drill holes in distal femurs of rabbits. Groups with empty defects and impacted MCB were used for reference. After 8 weeks, one femur from each pair was examined histologically. All contralateral specimens and Time-0 specimens were used for mechanical indentation tests. Histology showed that some empty defects were filled with newly formed osteopenic bone after 8 weeks. The impacted MCB showed remodeling into new vital bone. Incorporation of the HAC/MCB composite was incomplete, whereas minimal new bone ingrowth was found in the HAC/granule composites. Though not different from each other, both composites were significantly stronger than empty defects, incorporated impacted MCB, and intact cancellous bone. At Time 0, the mechanical behavior of impacted MCB was similar to both HAC composites. In conclusion, composites of HAC and porous biomaterials can maintain relatively high strength over 8 weeks in vivo, but their incorporation into a new bony structure is slower than impacted MCB. The HAC/MCB composite showed favorable incorporation behavior.

Animals↗

PubMed2004

Displacement of the medial meniscus within the passive motion characteristics of the human knee joint: an RSA study in human cadaver knees.

The objective of this study was to validate an in vitro human cadaver knee-joint model for the evaluation of the meniscal movement during knee-joint flexion. The question was whether our model showed comparable meniscal displacements to those found in earlier meniscal movement studies in vivo. Furthermore, we determined the influence of tibial torque on the meniscal displacement during knee-joint flexion. Three tantalum beads were inserted in the medial meniscus of six human-cadaver joints. The knee joints were placed and loaded in a loading apparatus, and the movements of the beads were determined by means of RSA during knee-joint flexion and extension with and without internal tibial (IT) and external tibial (ET) torque. During flexion without tibial torque, all menisci moved in posterior and lateral direction. The anterior horn showed significantly greater excursions than the posterior horn in both posterior and lateral direction. Internal tibial torque caused an anterior displacement of the pathway on the tibial plateau. External tibial torque caused a posterior displacement of the pathway. External tibial torque restricted the meniscal displacement during the first 30 degrees of knee-joint flexion. The displacements of the meniscus in this experiment were similar to the displacements described in the in vivo MRI studies. Furthermore, the application of tibial torque confirmed the relative immobility of the posterior horn of the meniscus. During external tibial torque, the posterior displacement of the pathway on the tibial plateau during the first 30 degrees of flexion might be restricted by the attached knee-joint capsule or the femoral condyle. This model revealed representative meniscal displacements during simple knee-joint flexion and also during the outer limits of passive knee-joint motion.

Aged↗

PubMed2004

Prosthetic replacement of the medial meniscus in cadaveric knees: does the prosthesis mimic the functional behavior of the native meniscus?

UNLABELLED: Meniscus replacement by a polymer meniscus prosthesis in dogs resulted in generation of new meniscal tissue. HYPOTHESIS: Optimal functioning of the prosthesis would involve realistic deformation and motion patterns of the prosthesis during knee joint motion. STUDY DESIGN: Controlled laboratory study. METHODS: The movements of the meniscus were determined during knee joint flexion and extension with and without internal and external tibial torque by means of roentgen stereophotogrammetric analysis. Subsequently, the meniscus in 6 human cadaveric knee joints was replaced by a meniscus prosthesis. RESULTS: All different parts of the meniscus showed a posterior displacement during knee joint flexion. The anterior horn was more mobile than the posterior horn. The prosthesis mimicked the movements of the meniscus. However, the excursions of the prosthesis on the tibial plateau were less. The knee joint laxity was not significantly higher after replacement with the meniscus prosthesis. CONCLUSIONS: The prosthesis approximated the behavior of the native meniscus. Improvement in both the gliding characteristics of the prosthetic material and the fixation of the prosthesis may improve the function. CLINICAL RELEVANCE: The meniscus prosthesis needs to be optimized to achieve a better initial function in the knee joint.

Aged↗

PubMed2004

Tissue engineering of the meniscus.

Meniscus lesions are among the most frequent injuries in orthopaedic practice and they will inevitably lead to degeneration of the knee articular cartilage. The fibro-cartilage-like tissue of the meniscus is notorious for its limited regenerative capacity. Tissue engineering could offer new treatment modalities for repair of meniscus tears and eventually will enable the replacement of a whole meniscus by a tissue-engineered construct. Many questions remain to be answered before the final goal, a tissue-engineered meniscus is available for clinical implementation. These questions are related to the selection of an optimal cell type, the source of the cells, the need to use growth factor(s) and the type of scaffold that can be used for stimulation of differentiation of cells into tissues with optimal phenotypes. Particularly in a loaded, highly complex environment of the knee, optimal mechanical properties of such a scaffold seem to be of utmost importance. With respect to cells, autologous meniscus cells seems the optimal cell source for tissue engineering of meniscus tissue, but their availability is limited. Therefore research should be stimulated to investigate the suitability of other cell sources for the creation of meniscus tissue. Bone marrow stroma cells could be useful since it is well known that they can differentiate into bone and cartilage cells. With respect to growth factors, TGF-beta could be a suitable growth factor to stimulate cells into a fibroblastic phenotype but the problems of TGF-beta introduced into a joint environment should then be solved. Polyurethane scaffolds with optimal mechanical properties and with optimal interconnective macro-porosity have been shown to facilitate ingrowth and differentiation of tissue into fibro-cartilage. However, even these materials cannot prevent cartilage degeneration in animal models. Surface modification and/or seeding of cells into the scaffolds before implantation may offer a solution for this problem in the future.This review focuses on a number of specific questions; what is the status of the development of procedures for lesion healing and how far are we from replacing the entire meniscus by a (tissue-engineered) prosthesis. Subquestions related to the type of scaffold used are: is the degree of tissue ingrowth and differentiation related to the initial mechanical properties and if so, what is the influence of those properties on the subsequent remodelling of the tissue into fibro-cartilage; what is the ideal pore geometry and what is the optimal degradation period to allow biological remodelling of the tissue in the scaffold. Finally, we will finish with our latest results of the effect of tear reconstruction and the insertion of prostheses on articular cartilage degradation.

Animals↗

PubMed2004

Design, synthesis and properties of a degradable polyurethane scaffold for meniscus regeneration.

Longitudinal lesions in menisci are among the most frequent orthopedic problems of the knee. Repair by simple techniques is only limited to the vascular part of the meniscus. For repair of the avascular part of the meniscus a scaffold, which will assist the body in the formation of new meniscus cell tissue, might be applicable. In this study a biomedical segmented polyurethane with poly(epsilon-caprolactone) as soft segment and 1,4-butanediisocyanate and 1,4-butanediol as uniform hard segments has been synthesised. The material has a micro phase separated morphology and excellent mechanical properties. A porous scaffold was prepared via a combination of liquid-liquid phase separation and salt leaching. The foams prepared combined a very high interconnectivity and porosity with the desired compression modulus. After six months of implantation in the knees of beagles full ingrowth with cells was obtained and it was found that meniscus like tissue had been formed in the scaffold. Moreover, compression behaviour appeared to be comparable to native meniscus tissue.

Absorbable Implants↗

PubMed2003

Augmentation in anterior cruciate ligament reconstruction-a histological and biomechanical study on goats.

We studied reconstruction of the anterior cruciate ligament (ACL) in skeletally mature goats. In one group, the autogenous tissue was augmented with polydioxanone (PDS), the other group had no augmentation. Histological complete incorporation and remodeling of the transplant was found in both groups. The newly formed connective tissues gradually assumed the microscopic properties of the normal ligament. The augmented group showed a delay in remodeling and maturation of the fiber bundles. Mechanically, the PDS-augmented transplants were stronger than the nonaugmented transplants immediately after surgery. During the first 6 weeks, a rapid decrease in strength of the augmented transplants was found, whereas the strength of the nonaugmented group gradually increased. The results of our experiment do not favor augmentation of autografts in reconstruction of the ACL.

Animals↗

PubMed2003

Potential healing benefit of an osteoperiosteal bone plug from the proximal tibia on a mosaicplasty donor-site defect in the knee. An experimental study in the goat.

INTRODUCTION: Autologous osteochondral transplantation is a popular treatment for articular cartilage lesions in the knee joint. The donor defect is commonly left empty and remains a matter of concern. MATERIALS AND METHODS: In 20 knees of 10 goats, we created a standardised donor defect in the knee. In the control group the defects were left empty, whereas in two other groups a bone plug from the proximal tibia was press-fitted into the defect with or without a covering periosteal layer. RESULTS: Histological evaluation after 8 and 16 weeks showed that relatively rapid osteoclastic resorption of the bone plug occurred. Defects were mainly filled with fibrous tissue, and collapse of the adjacent bone and cartilage was visible, especially when the defects were left empty. Occasionally, some consolidation of the graft to the host bone could be detected, and in some samples periosteal chondrogenesis was present. CONCLUSION: Our findings suggest that transplantation of a tibial bone plug with covering periosteum to the donor defect in a cartilage transplantation procedure does not have any additional value in an attempt to minimise the damage at the donor site. The observed resorption of the bone plug and the collapse of the adjacent joint margin remain a matter of concern with this technique.

Animals↗

PubMed2003

A porous polymer scaffold for meniscal lesion repair--a study in dogs.

Meniscal lesions often occur in the avascular area of the meniscus with little chance of spontaneous repair. An access channel in the meniscal tissue can function as an entrance for ingrowing repair tissue from the vascular periphery of the meniscus to the lesion in the avascular zone which again induced healing of the lesion. Implantation of a porous polymer in a full-thickness access channel induced healing. However, a better integration between meniscal tissue and the implant might be achieved with the combination of the newly developed porous polymers and a modified surgical technique. This might improve meniscal lesion healing and the repair of the access channel with neo-meniscal tissue. Longitudinal lesions were created in the avascular part of 24 canine lateral menisci and a partial-thickness access channel was formed to connect the lesion with the meniscal periphery. In 12 menisci, the access channel was left empty (control group), while in the remaining 12 menisci the polymer implant was sutured into the access channel. Repair of the longitudinal lesions was achieved with and without polymer implantation in the partial-thickness access channel. Polymer implants induced fibrous ingrowth with cartilaginous areas, which resembled neo-meniscal tissue. Implantation did not prevent articular cartilage degeneration.

Animals↗

PubMed2003

The initial stability of cemented acetabular cups can be augmented by mixing morsellized bone grafts with tricalciumphosphate/hydroxyapatite particles in bone impaction grafting.

Tricalciumphosphate (TCP) and hydroxyapatite (HA) have been suggested as bone graft substitutes in a wide range of applications. In this study, the initial stability of cemented acetabular cups was determined after reconstructing a combined cavitary and segmental defect in a realistic acetabular revision surgery model. The defects were reconstructed with mixes of TCP/HA particles and human bone grafts using the bone impaction grafting technique. In comparison with defect reconstruction with human bone grafts only, cup translation and tilt decreased by 27% when mixes of bone grafts and porous TCP/HA particles were used and by 55% when mixing the bone grafts with solid TCP/HA particles. Increasing the TCP/HA ratio within the mix significantly decreased cup translation. From a biomechanical perspective, mixes of TCP/HA particles and bone grafts are an attractive alternative for morsellized bone grafts when using the bone impaction grafting technique in the reconstruction of large defects of the acetabulum.

Acetabulum↗

PubMed2003

Presence and mechanism of knee articular cartilage degeneration after meniscal reconstruction in dogs.

OBJECTIVE: Partial meniscectomy is the golden standard for treating a bucket-handle tear in the meniscus of the knee, but it inevitably leads to articular cartilage degeneration. Surgical creation of an access channel between the lesion and the vascularized synovial lining is intended to induce ingrowth of repair tissue and thus avoid degeneration of articular cartilage. DESIGN: The presence and mechanism of cartilage degeneration were evaluated in 24 canine menisci after a longitudinal lesion and access channel had been created in the avascular part of the meniscus. In 12 menisci the channel was implanted with a porous polymer scaffold, while the remaining 12 were left empty. Evaluation was performed using routine histology and antibodies directed against denatured type II collagen (Col2-3/4M). RESULTS: Articular degeneration was apparent in the polymer implant group and the empty channel group. This consisted of fibrillation, loss of chondrocytes and decreased proteoglycan content. Areas of fibrillated cartilage always showed positive labeling with the collagen degradation antibody Col2-3/4M. Collagen degradation was also visible in non-fibrillated areas. The upper zone of the cartilage showed swelling especially in the implant group, with empty cell lacunae and moderate levels of Col2-3/4M antibody labeling. DISCUSSION: This reconstruction technique cannot be considered superior to partial meniscectomy. We propose that degradation of the collagen type II network is a result of cartilage fibrillation and vice versa.

Animals↗

PubMed2002

Effect of load on the early incorporation of impacted morsellized allografts.

Impacted morsellized bone grafts are clinically successful to restore bony defects after failed total hip arthroplasties. The incorporation process seems to be dependent on the location where the reconstruction is performed, which suggests that load could play a role. In this study, we hypothesised that, as in fracture healing, physiological loading has a stimulatory effect on the process of early bone graft incorporation. To test this hypothesis we created a standardised defect in the distal femur of twelve goats. Allograft bone chips were impacted into the defect and a subcutaneous pressure implant was screwed in. With this implant the graft can be loaded under controlled circumstances. Six goats were subjected to a daily loading regime of 3 MPa, the other six were non-loaded. After five weeks the bone mineral density was measured with peripheral quantitative computer tomography. Thereafter, routine histology and histomorphometry were carried out. Bone mineral density was not affected by load. Histology revealed microscopic evidence of bone graft incorporation, which proceeded in a similar way in both loaded and non-loaded specimens. New bone was formed free in the stroma or on graft remnants after osteoclastic resorption of the graft. Only the area of active incorporating bone graft was higher under load. In conclusion, the formation of a new bony structure was not affected by load after five weeks. However, load resulted in a larger area of active graft incorporation at this early stage. Possibly biological and immunological factors govern the early incorporation process independent of the local loading regime.

Animals↗

PubMed2002

Acetabular defect reconstruction with impacted morsellized bone grafts or TCP/HA particles. A study on the mechanical stability of cemented cups in an artificial acetabulum model.

In revision surgery of the acetabulum bone defects can be filled with impacted human morsellized bone grafts. Because of a worldwide limited availability of human bone, alternatives are being considered. In this study we compared the initial stability of acetabular cups after reconstructing a cavitary defect with various compositions of impacted tricalciumphosphate-hydroxyapatite (TCP/HA) particles and mixes of TCP/HA particles and human grafts in a realistic acetabulum model. Primary cemented cups and reconstructions with impacted human cancellous grafts were used as reference. A dynamic load displaced the acetabular cups superomedially. The primary cemented cups showed the highest stability. The cups with impacted human grafts produced the most displacement. All reconstructions with the TCP/HA particles showed a high stability of the cups. However, especially when using large TCP/HA particles this was probably due to a large amount of cement penetration. Mixing TCP/HA particles with human grafts seemed to decrease cement penetration. although still a high stability was obtained. In this perspective, we concluded that TCP/HA particles might be useful as a bone graft extender in the reconstruction of acetabular bone defects.

Acetabulum↗

PubMed2002

Crosslinked type II collagen matrices: preparation, characterization, and potential for cartilage engineering.

The limited intrinsic repair capacity of articular cartilage has stimulated continuing efforts to develop tissue engineered analogues. Matrices composed of type II collagen and chondroitin sulfate (CS), the major constituents of hyaline cartilage, may create an appropriate environment for the generation of cartilage-like tissue. In this study, we prepared, characterized, and evaluated type 11 collagen matrices with and without CS. Type II collagen matrices were prepared using purified, pepsin-treated, type II collagen. Techniques applied to prepare type I collagen matrices were found unsuitable for type II collagen. Crosslinking of collagen and covalent attachment of CS was performed using 1-ethyl-3-(3-dimethyl aminopropyl)carbodiimide. Porous matrices were prepared by freezing and lyophilization, and their physico-chemical characteristics (degree of crosslinking, denaturing temperature, collagenase-resistance, amount of CS incorporated) established. Matrices were evaluated for their capacity to sustain chondrocyte proliferation and differentiation in vitro. After 7 d of culture, chondrocytes were mainly located at the periphery of the matrices. In contrast to type I collagen, type II collagen supported the distribution of cells throughout the matrix. After 14 d of culture, matrices were surfaced with a cartilagenous-like layer, and occasionally clusters of chondrocytes were present inside the matrix. Chondrocytes proliferated and differentiated as indicated by biochemical analyses, ultrastructural observations, and reverse transcriptase PCR for collagen types I, II and X. No major differences were observed with respect to the presence or absence of CS in the matrices.

Biocompatible Materials↗