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Biomedical subjects

L M Jonck

Publications and source records attributed to L M Jonck.

At least 19 recordsLinked to original sources
PubMed1993

Ionogran--an ionomeric micro implant in bone tumour reconstruction. A clinical evaluation.

A new implant material, Ionogran (Ionos, Medizinische Produkte GmbH & Co. K.G., Germany), is evaluated in a series of 60 cases requiring augmented bone grafting for major bone defects. The material, an ionomeric porous micro implant (IMI), is stable, non-degradable, osteoconductive and biocompatible. It promotes the formation of osteoid and displays a dynamic surface activity which stimulates the process of repair. In the compromised situation of a large cavity following curettage and cryotherapy, Ionogran when mixed with a mulch of autogenous cancellous bone is a valuable filler, providing a direct osteoid bond with host bone, and a permanent scaffold which maintains shape, length and form of the affected part. It replaces allogenic bone grafts and the problems associated with that technique.

Adolescent↗
PubMed1992

Bone cell interactions with a granular glass-ionomer bone substitute material: in vivo and in vitro culture models.

The interface between bone and a synthetic bone substitute constructed from glass-ionomer cement (ionomeric microimplant) was studied in diffusion chambers implanted in a primate baboon model (Papio ursinus) and in in vitro primary bone organ cultures derived from neonate rat calvaria. In both models osteoblast-like cells colonized the surface of the implant producing a collagenous extracellular matrix. An electron-dense bonding zone similar to that reported for hydroxyapatite and titanium was seen in both models but was a more constant feature of the tissue/implant interface in calvarial culture.

Animals↗
PubMed1992

A glass ionomer for reconstructive surgery. Ionogran--an ionomeric micro implant. A biological evaluation.

A porous glass-ionomer (Ionogran) was evaluated and compared to hydroxyapatite Interpore 200. In an in-vivo screening test procedure, microfilter diffusion chambers embedded on the tibial surfaces of adult baboons were used to evaluate cell survival, cell regeneration and cell differentiation. In a bulk testing procedure a standardized bone core was removed from the tibia through the knee joint and the material exposed to the defense mechanisms of the system. Both materials were found to be biocompatible, non-toxic and did not inhibit cell proliferation in the enclosed environment of diffusion chambers. Histological response and cell arrangement within the chambers containing Ionogran were similar to that of the controls with cancellous bone only. Highly specialized haemopoietic tissues were in direct contact with the Ionogran. In the presence of hydroxyapatite new bone was actively formed. Haemopoietic elements were never found in contact with the hydroxyapatite. In the bulk testing procedure, the general histological appearance was that of a reactive tissue response to a low grade persistent stimulation coupled to surface degradation products. The Ionogran was found to be stable, osteo-conductive and promoted osteoid formation when in contact with bone. From a clinical point of view the material could serve as a permanent scaffold, maintaining form, and will be of value in bone reconstructive procedures.

Animals↗
PubMed1991

Tendon response to trauma and its possible clinical application. An experimental study in primates.

A study was undertaken to determine the response of tendon to trauma, and to establish the precise role of the intrinsic tendon cells vis-à-vis the paratendinous tissues in the healing process. It was found that tendon collagen has the ability to resist gross trauma and that tendons possess an inherent ability to regenerate and heal. The high rate of proliferation of synovial cells and the initial much lower rate of activity of intrinsic tendon cells have a direct bearing on the end result of the repair process. The principle of pre-stimulation of the tendon to improve the intrinsic vasculature and hence the rate and the quality of the healing process has been applied with promising, indeed striking, effect.

Animals↗
PubMed1990

Ionos bone cement (glass-ionomer): an experimental and clinical evaluation in joint replacement.

Ionos bone cement (glass-ionomer) was evaluated in total joint replacement procedures, initially in a baboon model, and finally in a highly selected group of patients in whom polymethyl methacrylate cement was contra-indicated. It was found that the cement has no inhibitory effect on bone tissue development. It is effectively incorporated into the bone, both structurally and functionally without the interposition of fibrous tissue. Under the functional stress situation in baboon hip and knee arthroplasties, the bone and marrow in direct contact with the cement responded favourably. A direct bone bond was demonstrated. The clinical results achieved were satisfactory, notwithstanding the complexity of the clinical problems included in the series. The continued clinical evaluation on a controlled basis has been shown to be well-justified.

Adult↗
PubMed1989

Thermotoxicity of palacos cement. Clinical observation.

In total hip joint replacement with cemented prostheses, Palacos (polymethyl methacrylate, PMMA) involves a high perioperative risk for the patient, on account of the effects on both the systemic and the pulmonary circulation. Data were assembled retrospectively from the records of 203 patients who underwent hip joint operation with Palacos implantation in the Inner City Surgical Clinic and the Surgical Polyclinic of the University of Munich from 1982 to 1986. In the hemiarthroplasty series, hemiarthroplasty was performed in 61% of patients in risk group III, whereas in the risk groups I and II it was done in 31% of cases. The mortality following hemiarthroplasty was greater than that following implantation of total prostheses in risk groups I and II. In risk groups II and III the mortality was 17% with surgery on the day of injury, lower, at only 10%, when the operation was performed on the day after injury, and markedly higher, at 31% and 38%, respectively, when surgery was postponed to the 2nd or 3rd day. It has been shown in burn research that the prostanoid levels in the plasma of untreated animals show a typical curve with two peaks, the first on the day of the injury and the second on the 3rd day after injury. Our observations support the assumption that the effect of trauma and surgical treatment are complementary.

Aged↗
PubMed1982

Primary tendon healing. An experimental study.

The management of a severed tendon within the digital sheath continues to present a formidable challenge. The major problem is one of excessive scar tissue formation. It was found experimentally in severed and partially divided tendons that the source of the blood supply, i.e. the vasculature in the tendon proper, will promote healing through the primary tissue (tenoblast) of the tendon itself, whereas the blood supply and granulation tissue from the damaged area of the flexor sheath leads to fibrous (scar) tissue formation. In this study of tendon repair special attention was paid to a suturing procedure which would have the least effect on the intrinsic blood supply to the severed ends. It was found that the basic requirement in successful tendon repair was to approximate and not to strangulate, and to minimize trauma to the flexor sheath which is the main source of scar tissue.

Animals↗
PubMed1981

Allogenic bone transplantation. Part II. A histological and radiographic study of freeze-dried bone allo-implants in primates.

A histological and radiographic study was undertaken to evaluate freeze-dried bone as an alternative to the autogenous transplant. The source of the blood supply from the surrounding soft tissues or from the host bone bed can be the determining factor in the incorporation of the implant/transplant. The testing of the osteogenic potential in non-orthotopic sites in primates is an inappropriate method. Freeze-dried allograft bone is an inert, rapidly immobilized biodegradable implant which can also serve a structural function.

Animals↗
PubMed1981

Allogenic bone transplantation. Part I. A review of the status of allogenic bone banks.

The various methods of preserving bone for implantation are reviewed. Biological assay systems to determine the physiological and osteogenic potential of the implant are discussed. Sterilization remains the major problem. The influence of high-energy irradiation of freeze-dried bone is still uncertain. Experimentally and clinically it was found that the immunological status of the freeze-dried allo-implant is biocompatible.

Animals↗
PubMed1981

Condylar hyperplasia. A case for early treatment.

Clinical experience indicates that the condylar growth centre is an important factor in the dimensional changes of the face up to the 10th year. Thereafter muscular and functional occlusion determine the ultimate facial form. condylar hyperplasia should be recognised at a very early age. To achieve an acceptable result early treatment of facial asymmetry related to condylar hyperplasia should be considered in the most active growth phase of the mandible (6-8 years).

Age Factors↗
PubMed1978

Ear symptoms in temporomandibular joint disturbances.

The symptoms related to temporomandibular joint disturbances in 530 cases are reviewed. A possible anatomical explanation for the middle ear symptoms related to disturbance of the temporomandibular joint is presented.

Headache↗