Biomedical subjects

J Kahrs

Publications and source records attributed to J Kahrs.

6 recordsLinked to original sources

PubMed2000

[Autologous meniscus replacement with rib perichondrium. Experimental results].

The purpose of our study was to examine the potential of autologous perichondrial tissue to form meniscal replacements. Eighteen mature sheep were used. In 12 animals a complete meniscal resection was performed; replacement was formed using strips of autologous perichondrial tissue explanted from the lower rib; six animals with a complete meniscal resection but without any replacement served as controls. In all animals restriction from weight-bearing was achieved by means of transsection and partial achillestendon resection. Six animals each, 4 of group T and 2 of group C, were sacrificed after 3, 6 and 12 months. Perichondrial grafts and the underlying articular cartilage were removed and investigated by gross macroscopic examination, by means of light and scanning electron microscopy, polarized light examination, and biomechanical tests evaluating the failure stress and tensile modulus. In all transplanted animals a new perichondrial meniscus developed. After 3 months the transplants resembled in size and thickness normal menisci, while in the control animals only small rims of spontaneously grown tissue were detectable. Microscopically, the perichondrial menisci exhibited similarity to normal collagen fiber orientation and cellular characteristics, but, in their central region, areas of calcification disturbed the regular tissue differentiation. In contrast, spontaneously grown tissue in control animals lacked normal fiber orientation and cellularity. Scanning electron-microscopy of perichondrial menisci revealed surface characteristics similar to normal sheep menisci without fissures and lacerations, while the control specimens exhibited such defects. The femoral and tibial cartilage being in contact with the new menisci showed normal surface characteristics apart from one animal with slight surface irregularities. Control animals showed superficial lesions after 3 months, and the extent increased from 6 to 12 months postoperatively. Exemplary microangiographies of the newly grown tissue exhibited a less intense vascularisation after three months when compared to normal menisci with an improving tendency after 6 and 12 months. Biomechanically, values of the failure stress as well as of the tensile modulus of perichondrial menisci were significantly lower than those of normal contralateral menisci. But, spontaneously regenerated tissue in meniscectomized animals exhibited even smaller values also with significant differences towards original menisci. There were no significant differences in values of newly grown perichondrial menisci and spontaneously grown tissue.

Animals↗

PubMed2000

Achilles tendon rupture: experimental results on spontaneous repair in a sheep-model.

We studied the course of spontaneous healing of Achilles tendons in a sheep model after transection and partial resection of the tendon by means of histological and biomechanical analyses. In 18 sheep used for another animal study the operated knee had to be excluded from weight-bearing; therefore the Achilles tendons were transected and for 1.5 cm partially resected in the middle substance of the tendon. For evaluation these spontaneously healed tendons (n = 18) were compared with the contralateral noninvolved tendons (n = 18). Specimens were analyzed 3, 6, and 12 months postoperatively by means of histology, polarized light, angiography, and mechanically analyzing the specific tensile strength and absolute tensile strength. We found that in all animals the resected tendon healed spontaneously. All animals exhibited a normal gait pattern at least 6 weeks postoperatively. Histologically, the tendinous area of healing demonstrated after 3 months a fibrous collagenous tissue with a loose fiber orientation. The cross-sectional area had at 3 months increased to maximum but decreased later. Concomitantly the fiber orientation improved with time and 12 months after transection the specimens showed a nearly normal histological structure of the healed tendon. Biomechanically the specimens exhibited a rather low specific rupture force after 3 months (28.8% of normal tendons) and 6 months (30.2%) but increased after 12 months (56.7%). In regard to the resulting total rupture force the decrease in the spontaneously healed tendons was less (75.6% after 3 months, 56.1% after 6 months, 81.18% after 12 months), because the cross-sectional area of the healing tendon had significantly (P < 0.05) increased to maximum after 3 and 6 months. Sheep Achilles tendons thus healed spontaneously without any immobilization. The initial healing mechanism is thickening of the scar tissue with improvement of the fiber orientation towards a tendonlike structure within 1 year. Parallel to this, the specific rupture force increased and the thickness of the newly tendonlike area decreased.

Achilles Tendon↗

PubMed1998

Autologous perichondral tissue for meniscal replacement.

Our aim was to examine the potential of autologous perichondral tissue to form a meniscal replacement. In 18 mature sheep we performed a complete medial meniscectomy. The animals were then divided into two groups: 12 had a meniscal replacement using strips of autologous perichondral tissue explanted from the lower rib (group G) and six (group C) served as a control group without a meniscal replacement. In all animals restriction from weight-bearing was achieved by means of transection and partial resection of tendo Achillis. Six animals (four from group G and two from group C) were each killed at 3, 6 and 12 months. The grafts and the underlying articular cartilage were removed and studied by gross macroscopic examination, light microscopy, SEM, polarised light examination, and by biomechanical tests. In all the transplanted animals a new perichondral meniscus developed. After three months the transplants resembled normal menisci in size and thickness, while in the control animals only small rims of spontaneously grown tissue were seen. Microscopically, the perichondral menisci showed a normal orientation of collagen fibres and normal cellular characteristics, but in the central region, areas of calcification disturbed the regular tissue differentiation. Healing tissue in control animals lacked the normal fibre orientation and cellularity. SEM of perichondral menisci showed surface characteristics similar to those of normal sheep menisci without fissures and lacerations; the control specimens had these defects. The femoral and tibial cartilage in contact with the new menisci had normal surface characteristics apart from one animal with slight surface irregularities. Control animals showed superficial lesions after three months which increased at six to 12 months postoperatively. Microangiography of the newly grown tissue demonstrated a less intense vascularisation after three months when compared with normal menisci. The failure stress and tensile modulus of perichondral menisci were significantly lower than those of normal contralateral menisci, and spontaneously regenerated tissue in meniscectomised animals had even lower values. There were no significant differences in values between newly grown perichondral menisci and spontaneously grown tissue.

Animals↗

PubMed1997

Language processing in aphasia: changes in lateralization patterns during recovery reflect cerebral plasticity in adults.

During single word processing the negative cortical DC-potential reveals a left frontal preponderance in normal right-handers as well as in patients with a history of transient aphasia. Lateralization of DC-negativity therefore provides a reliable and robust method for the assessment of language dominance. In 11 stroke patients with permanent aphasia this physiological pattern changed to bilateral activation reflecting an additional right-hemispheric involvement in compensatory mechanisms in aphasia. Along with complete clinical recovery the classical aphasic syndromes revealed specific differences in changes of their lateralization patterns. In Broca's aphasia the initial right-hemispheric preponderance changed to a left frontal lateralization while in Wernicke's aphasia a presumably permanent shift towards the right hemisphere occurred. Differences in lateralization patterns might reflect different mechanisms of recovery such as the initial disinhibition of homologous areas contralaterally and subsequent collateral sprouting and synaptic modulation. The assessment of changes in lateralization of the cortical DC-potential during language tasks in a non-invasive, safe method with excellent time resolution that might provide further insights in the neural basis of recovery from aphasia.

Action Potentials↗

PubMed1992

[Etiopathogenetic aspects of medial osteochondrosis dissecans tali].

In a cadaveric biostatic model the pressure distribution at the weightbearing ankle has been investigated under different joint positions and stages of artificial lateral ligament dissection mimicking a supination trauma. The location of the transduced contact area, the size of these areas and amount of pressure were evaluated after application of axial load. The results showed that the location, size of contact area and the maximum transduced pressure were depending on the joint position and stage of ligament dissection. Interestingly the peak pressure was located at the medial talar rim even without lateral ligament dissection. The transduced pressure areas were located at that locations were osteochondral lesions are mostly observed. In regard to these results the etiology and pathogenesis of osteochondritis dissecans tali is discussed. It is thought that supination traumas as well as other biomechanical factors such as overweight and lax ankle ligaments have an important influence on the development of osteochondritis dissecans at least at the medial rim of the talus.

Ankle Joint↗

PubMed1989

[Malignant lymphoma of the testis].

We review nine patients treated for malignant lymphoma at The Norwegian Radium Hospital. The median age was 67 years. All had non-Hodgkin's lymphoma, eight were high-grade malignant. Extragonadal manifestations were diagnosed in five patients. The treatment was orchidectomy and combination chemotherapy. Four patients with only gonadal affection survived, while all who had extragonadal affections died. Patients with only gonadal affection should be treated with adjuvant chemotherapy after orchidectomy. Patients with extragonadal affection are at high risk, and should receive intensive chemotherapy.

Aged↗