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Biomedical subjects

Chaim Zinman

Publications and source records attributed to Chaim Zinman.

6 recordsLinked to original sources
PubMed2007

A novel poly(ethylene glycol)-fibrinogen hydrogel for tibial segmental defect repair in a rat model.

The aim of this study is to investigate regeneration in a segmental bone defect using a novel fibrinogen-based hydrogel material. The use of hydrogels made from poly(ethylene glycol) (PEG) conjugated to fibrinogen for this purpose may be better to conventional fibrin-based materials as it offers an additional degree of control over the structural characteristics and biodegradation of the material. At the same time, it maintains some of the inherent biofunctionality of the fibrinogen molecule. PEGylated fibrinogen hydrogels with various degrees of proteolytic resistance based on PEG and fibrinogen composition were designed for slow, intermediate, and fast biodegradation. The hydrogels were implanted into 7-mm segmental rat tibial defects without additional osteoinductive factors with the rationale that the ingrowth matrix will displace the normal fibrin clot while sustaining a similar healing effect for a longer duration. Histological and X-ray results confirmed that the extent and distribution of newly formed bone in the defect after 5 weeks strongly parallels the biodegradation pattern of the implanted material. When compared to nonunions in animals treated with the fast-degrading implants and untreated control animals, the rats implanted with the intermediate-degrading material exhibited osteoneogenesis. This data supports the hypothesis that the perseverance of the PEGylated fibrinogen material can be synchronized with the optimal healing characteristics of a segmental osseous defect and that the consequent sustained release of fibrinogen fragments facilitates the osteogenic response at the injury site. The PEGylated fibrinogen material may, therefore, be a highly efficacious material for promoting the healing of bone defects and especially nonunion fractures.

Absorbable Implants↗
PubMed2006

Vasculature deprivation-induced osteonecrosis of rats' femoral heads associated with the formation of deep surface depressions.

BACKGROUND: Shallow or deep bowl-shaped depressions often develop after drilling an intraosseous conduit in the necrotic, avascular femoral head of rats. The etiopathogenesis of tissue loss at the articulation surface after a drilling procedure was elaborated in the authors' previous reports. GOALS: To scrutinize a large collection of femoral heads of rats in order to search for similar changes in cases in which no drilling procedure was carried out. STUDY: This retrospective study comprised the specimens of 386 rats with vessels-deprived osteonecrosis of the femoral heads, none of the animals having undergone a drilling procedure. RESULTS: Shallow or deep bowl-shaped depressions were encountered at an incidence as low as 2.8% of the femoral heads of the above mentioned 386 rats. It is not feasible to distinguish histologically the "spontaneously" arising from and drilling-related depressions. CONCLUSIONS: No assured explanation can be offered for the evolving depressions of the surface of femoral heads of rats, which have not undergone a drilling procedure. It is hypothesized that the synovial fluid forces its way via slits in the articulation surface and bores cavities in the substance of femoral heads, which display a postosteonecrotic osteoarthritis-like disorder. The rising pressure in the arthritic joints results, firstly, in an enlargement of these cavities and, secondly, loss of fibro-cartilaginous tissue such that the cavities come to communicate with the articular space.

Animals↗
PubMed2005

Arthroscopic subacromial decompression performed under local anesthesia.

Shoulder arthroscopy is usually performed under general anesthesia or interscalene block. General anesthesia may be contraindicated and interscalene block sometimes fails. We had 8 patients who were at high-risk and, therefore, shoulder arthroscopy and decompression were performed under local anesthesia in the beach-chair position. We used 50 mL of 1% lidocaine; 30 mL were infiltrated into the skin and underlying tissues and into the glenohumeral joint, and the rest was infiltrated into the subacromial joint. Before the infiltration, all patients were given 5 mg midazolam and 0.1 mg fentanyl intravenously. All 8 patients were satisfied with the analgesia provided by the anesthesia. We conclude that arthroscopy and subacromial decompression can be readily performed under local anesthesia in combination with efficient sedation.

Anesthesia, Local↗
PubMed2004

Pyogenic granuloma-like reaction in the necrotic, vessels-deprived femoral head of the rat.

Osteonecrosis of the femoral head was produced in rats by cutting the ligamentum teres and incising the cervical periosteum. As of the second postoperative week, fibrous tissue pervaded the necrotic epiphyses, macrophages and osteoclasts removed the debris, osteoblasts deposited lamellar-fibred and woven-fibred intramembranous bone, and remodeling began. In 16% of the rats killed during the 2nd postoperative week, the epiphyses contained big fragments of necrotic bone enclosed by densely packed, capillary-sized vessels. Ingrowth of this hypervascularized, pyogenic granuloma-like tissue is presumably due to the presence of excessive growth factors, reflecting an exaggerated pathophysiological reaction within the framework of organization of the necrotic epiphyses.

Animals↗
PubMed2002

The effects of enoxaparin on the reparative processes in experimental osteonecrosis of the femoral head of the rat.

The blood supply of one femoral head of 6-month-old rats was severed by incising the periosteum of the neck and cutting the ligamentum teres. The rats were killed on the 30th postoperative day and the femoral bones were obtained for semiquantification of the reparative processes in the necrotic heads. Fourteen rats were treated with enoxaparin and 14 untreated animals served as controls. Statistically, the amounts of necrotic bone in the epiphysis were less, the extent of remodeling of the femoral heads was milder, and the articular cartilage degeneration was slighter in the enoxaparin-treated than untreated rats. There was no significant difference in the quantities of newly formed bone in femoral heads of treated and untreated rats. These findings are in agreement with the known effects of unfractionated and low-molecular-weight heparins which enhance osteoclastic bone resorption and angiogenesis and decrease osteoblastic bone formation. The former activities, operative in minimizing the structural distortion of the femoral head, oppose the crucial event in the pathogenesis of post-osteonecrotic osteoarthritis.

Animals↗