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Biomedical subjects

K H Kraus

Publications and source records attributed to K H Kraus.

At least 19 recordsLinked to original sources
PubMed2005

In vivo axial dynamization of canine tibial fractures using the Securos external skeletal fixation system.

Bilateral transverse mid-shaft tibial osteotomies, with a 4-mm gap, were performed in purpose-bred research dogs and stabilized using a Securos Type 2 external skeletal fixotor (ESF). Full (100%) axial dynamization of one randomly selected ESF in each dog was performed at 31 days postoperatively. Caudo-cranial radiographs were obtained at weekly intervals, which were qualitatively and quantitatively evaluated (densitometry and ImageJ analysis). The dogs were euthanatized 13 weeks postoperatively, at which time dual energy x-ray absorptiometry (DEXA), peripheral quantitative computed tomography (pQCT), mechanical testing in torsion, and qualitative histological analysis were performed. A two-tailed paired Student's t-test was performed for statistical analysis of all parameters of interest, with significance set at p < 0.05. Three of five dynamized bones bridged quicker, and four of five dynamized bones appeared to have greater callus formation, however, statistically significant differences could not be definitively determined. Statistically significant differences were not found with densitometry (any time frame), DEXA, pQCT, torsional stiffness or maximum torque. Despite the lack of statistically relevant data, trends were observed with larger callus size and density in the dynamized tibiae. The dynamized tibiae appeared to fracture more consistently outside of the area of the healing callus as compared to the control tibiae. Histological evaluation showed greater remodelling in four of five control limbs when compared to the dynamized limb. Dynamization at 31 days post-operatively may delay bone remodelling, despite a trend towards a larger callus size. The results of this study failed to show a definitive role for early full axial dynamization.

Animals↗
PubMed1998

Type-II external fixation, using new clamps and positive-profile threaded pins, for treatment of fractures of the radius and tibia in dogs.

A new external fixation system for repair of fractures of the radius and tibia was developed that uses positive-profile threaded pins. This system allows for addition of a fixation clamp between 2 installed clamps, predrilling of pin holes through a drill sleeve, use of positive-profile threaded pins in all locations, and easier application of full pins. Type-II external fixators were applied, using this system, to fractures in 10 client-owned dogs, and outcome was evaluated. All fractures healed without complications. Duration of surgery, mean time until radiographic evidence of a bridging callus, and mean time until removal of the external fixator were shorter, and frequency of pin loosening were less than with other techniques. Pin loosening was uncommon. This system provides an important improvement in external skeletal fixation.

Animals↗
PubMed1998

Mesenchymal stem cells in osteobiology and applied bone regeneration.

Bone marrow contains a population of rare progenitor cells capable of differentiating into bone, cartilage, muscle, tendon, and other connective tissues. These cells, referred to as MSCs, can be purified and culture expanded from animals and humans. This review summarizes recent experimentation focused on characterizing the cellular aspects of osteogenic differentiation, and exploration of the potential for using autologous stem cell therapy to augment bone repair and regeneration. The authors have completed an array of preclinical studies showing the feasibility and efficacy of MSC based implants to heal large osseous defects. After confirming that syngeneic rat MSCs could heal a critical size segmental defect in the femur, it was established that human MSCs form bone of considerable mechanical integrity when implanted in an osseous defect in an immunocompromised animal. Furthermore, bone repair studies in dogs verify that the technology is transferable to large animals, and that the application of this technology to patients at geographically remote sites is feasible. These studies suggest that by combining MSCs with an appropriate delivery vehicle, it may be possible to offer patients new therapeutic options.

Animals↗
PubMed1998

The effect of implants loaded with autologous mesenchymal stem cells on the healing of canine segmental bone defects.

Bone marrow has been shown to contain a population of rare mesenchymal stem cells that are capable of forming bone, cartilage, and other connective tissues. We examined the effect of cultured autologous mesenchymal stem cells on the healing of critical-sized (twenty-one-millimeter-long) segmental defects in the femora of adult female dogs. Autologous mesenchymal stem cells were isolated from bone marrow, grown in culture, and loaded onto porous ceramic cylinders consisting of hydroxyapatite (65 per cent) and beta-tricalcium phosphate ceramic (35 per cent). The animals were randomly assigned to one of three groups. In Group A (six dogs), a porous ceramic cylinder that had been loaded with autologous mesenchymal stem cells was implanted in the defect. In Group B (six dogs), a ceramic cylinder that had not been loaded with cells was placed in the defect. In Group C (three dogs), the defect was left untreated (no ceramic cylinder was implanted). Radiographs were made immediately after the operation and at four-week intervals. At sixteen weeks, the animals were killed, the involved femora were removed, and undecalcified histological sections from the defects and adjacent bone were prepared. Histological and histomorphometric studies were carried out to examine the healing of the defects and the formation of bone in and around the ceramic implants. Atrophic non-union occurred in all of the femora that had untreated defects, and only a small amount of trabecular bone formed at the cut ends of the cortex of the host bone in this group. In contrast, radiographic union was established rapidly at the interface between the host bone and the implants that had been loaded with mesenchymal stem cells. Numerous fractures, which became more pronounced with time, developed in the implants that had not been loaded with cells. Histological and morphometric analyses demonstrated that both woven and lamellar bone had filled the pores of the implants that had been loaded with mesenchymal stem cells; the amount of bone was significantly greater (p < 0.05) than that found in the pores of the implants that had not been loaded with cells. In addition, a large collar of bone (mean maximum thickness, 3.14 millimeters) formed around the implants that had been loaded with cells; this collar became integrated and contiguous with callus that formed in the region of the periosteum of the host bone. The collar of bone remodeled during the sixteen-week period of study, resulting in a size and shape that were comparable with those of the segment of bone that had been resected. Callus did not develop around the cortex of the host bone or around the defect in any of the specimens in the other two groups.

Animals↗
PubMed1997

Partial regeneration of the sciatic nerve in rats enhances motor excitability to magnetic stimulation.

Motor-evoked potentials elicited from transcranial magnetic stimulation were recorded from both cranial tibial muscles of 10 Lewis rats. One sciatic nerve was then transected and surgically reanastomosed and allowed to regenerate for 6 weeks. Walking function was tested weekly using a footprint test giving a functional sciatic nerve index. At the end of the study motor-evoked potentials were again performed, as were nerve conduction velocities and supramaximal stimulation of operated and unoperated sciatic nerves. The nerve was evaluated for myelinated axon numbers. Functional sciatic index, numbers of myelinated axons, nerve conduction velocities, and supramaximal stimulation demonstrated the regenerated nerve to be functional, but to a lesser extent than the unoperated nerve. In all cases the amplitude of the compound muscle action potential evoked from transcranial magnetic stimulation of the motor cortex was greater in the operated motor pathway. This finding demonstrates hyperexcitability of the motor pathway to magnetic stimulation during peripheral nerve regeneration.

Animals↗
PubMed1997

Effect of combined administration of insulin-like growth factor and platelet-derived growth factor on the regeneration of transected and anastomosed sciatic nerve in rats.

OBJECTIVE: To evaluate the efficacy of combined administration of platelet-derived growth factor (PDGF) and insulin-like growth factor (IGF-I) on the regeneration of transected and anastomosed sciatic nerves. ANIMALS: 25 male Lewis rats. PROCEDURE: Transection and anastomosis was performed of the left sciatic nerve of all rats. At the time of surgery, treatment group rats received a combination of PDGF (0.75 microgram) and IGF-I (1.5 micrograms) along with vehicle (2% methyl cellulose gel) at the anastomosis site. Control rats received vehicle alone. Evaluation consisted of motor evoked potentials and nerve conduction velocity, quantitative histologic examination, sciatic functional index, and visual assessment of repair organization (lesion scores). RESULTS: Significant differences in motor evoked potential latency, nerve conduction velocity, axon number, sciatic functional index, or lesion scores were not found between groups. CONCLUSIONS: Combined administration of PDGF and IGF-I did not enhance peripheral nerve regeneration in a transection and anastomosis model as determined 6 weeks after surgery. CLINICAL RELEVANCE: These findings support the assumption that mechanical, versus trophic, effects predominate when nerve ends are closely apposed.

Anastomosis, Surgical↗
PubMed1996

Modified distraction-stabilization technique using an interbody polymethyl methacrylate plug in dogs with caudal cervical spondylomyelopathy.

A modified technique for distraction-stabilization that used an interbody polymethyl methacrylate plug was performed in 22 dogs with confirmed caudal cervical spondylomyelopathy. Myelographically, all compressive lesions were dynamic and predominantly located ventral to the spinal cord. Nineteen of 21 (90%) dogs for which success/failure could be determined had a successful outcome, and 11 of 22 (50%) dogs attained normal neurologic status. The 2 cases that were considered failures involved dogs that were nonambulatory tetraparetic prior to surgery and failed to improve to a functional status. Complications were self-limiting and included ventral displacement of the cement without loss of distraction in 1 dog and diskosponsylitis at an adjacent disk space in another dog. Evidence of fusion of the affected vertebrae, in the distracted position, was radiographically evident in all dogs. Use of the interbody polymethyl methacrylate plug appears to be a viable surgical treatment of caudal cervical spondylomyelopathy in dogs.

Animals↗
PubMed1996

The pathophysiology of spinal cord injury and its clinical implications.

The pathophysiology of spinal cord injury can be categorized as acute impact or compression. Acute impact injury is a concussion of the spinal cord. This type of injury initiates a cascade of events focused in the gray matter, and results in hemorrhagic necrosis. The initiating event is a hypoperfusion of the gray matter. Increases in intracellular calcium and reperfusion injury play key roles in cellular injury, and occur early after injury. The extent of necrosis is contingent on the amount of initial force of trauma, but also involves concomitant compression, perfusion pressures and blood flow, and administration of pharmacological agents. Preventing or quelling this cascade of events must involve mechanisms occurring in the initial stages. Spinal cord compression occurs when a mass impinges on the spinal cord causing increased parenchymal pressure. The tissue response is gliosis, demyelination, and axonal loss. This occurs in the white matter, whereas gray matter structures are preserved. Rapid or a critical degree of compression will result in collapse of the venous side of the microvasculature, resulting in vasogenic edema. Vasogenic edema exacerbates parenchymal pressure, and may lead to rapid progression of disfunction. Treatment of compression should focus on removal of the offending mass.

Animal Diseases↗
PubMed1996

Identification and management of brain tumors.

Brain tumors occur commonly in small animals. The clinical history and physical examination findings can strongly suggest their presence. Specifically, an older dog with onset of seizures and behavioral changes, or an older cat with behavioural changes and weakness, should be further evaluated for the presence of a brain tumor. A thorough neurological examination should be performed to localize the lesion(s). Groups of neurological signs will suggest the tumor to be cerebral, cerebellar, or brainstem. Cerebral tumors without brainstem signs carry the best prognosis, especially for cats. Patients suspected of having brain tumors should be imaged with computed tomography, or magnetic resonance imaging. Initial medical therapy includes anticonvulsants and glucocorticosteroids. Cerebral tumors not located on the floor of the calvarium can be successfully excised. These and other tumors can also be treated with radiation therapy.

Adrenal Cortex Hormones↗
PubMed1995

Partial scapulectomy for management of sarcomas in three dogs and two cats.

Three dogs and 2 cats were treated by partial scapulectomy for management of sarcomas of the proximal aspect of the scapula. Surgical margins were considered complete in all cases. In 3 animals, limb function was excellent for 8, 18, and 24 months, respectively, after surgery. Poor limb function persisted in 1 dog that developed local metastatic disease to the affected forelimb. One dog had good limb function for 3 months after surgery and underwent force-plate analysis, which determined a reduction in peak vertical force, decelerating force, and stride time for the affected limb, compared with that for the forelimb that was not subjected to surgery. Tumor recurrence associated with fibrosarcomas was detected in 2 animals. In selected cases, partial scapulectomy can preserve limb function and may be considered a viable alternative to limb amputation.

Animals↗
PubMed1995

Comparative viability of peninsular and island axial pattern flaps incorporating the cranial superficial epigastric artery in dogs.

Experimental island and peninsular axial pattern flaps that incorporated the cranial superficial epigastric artery and vein were developed in 6 Beagles. Mean percentage of flap area that survived, for both flaps, was 87%, and percentage of surviving flap area was not significantly different for island versus peninsular flaps. In 1 dog, ligation of an aberrant, perforating branch of the cranial epigastric artery resulted in necrosis of 53% of the flap area. The cranial superficial epigastric axial pattern flaps have potential application for closure of skin defects within their arc of rotation and may be particularly useful for closure of large defects on the ventral aspect of the thorax. A peninsular flap was used to close a defect of the ventral portion of the thoracic wall in a clinical case.

Animals↗
PubMed1995

Comparison of the holding power of 3.5-mm cortical versus 4.0-mm cancellous orthopedic screws in the pelvis of immature dogs (cadavers).

A 3.5-mm cortical orthopedic screw was compared with a 4.0-mm cancellous screw for maximal load to failure in the pelvis of immature dogs. The pelvis from young cadavers (7 to 13 months old) was divided into hemipelves and used for testing of the 2 screw types. Two sites in each hemipelvis were used, mid-shaft of the ilium and mid-sacrum, including the wing of the ilium. The screws were extracted, and maximal load to failure and mode of failure were recorded. Maximal load to failure per millimeter of engaged thread was calculated. In either pelvic site, the 4.0-mm cancellous screw required a significantly (P < 0.05) higher pullout force per millimeter of engaged screw threads than did the 3.5-mm cortical bone screw.

Animals↗
PubMed1993

The use of a cap-shaped coil for transcranial magnetic stimulation of the motor cortex.

A cap-shaped coil is introduced as a superior design for inducing transcranial magnetic motor evoked potentials for spinal cord monitoring. Evaluation of the magnetic characteristics of the cap coil showed higher induced electrical fields at and below the depth of the cortical surface, compared to a 9-cm, butterfly-shaped coil. Twenty normal adults were stimulated with the cap coil and a 9-cm round coil in three positions. Compound muscle action potentials were recorded from the left and right abductor digiti minimi and anterior tibialis muscles. The cap coil induced potentials with higher intensities and lower variability between consecutive stimuli. The cap coil was also more able to simultaneously induce motor evoked potentials from the four muscles studied. This coil design should provide superior means of inducing transcranial magnetic motor evoked potentials in multiple muscles.

Arm↗
PubMed1990

Evoked potentials induced by transcranial stimulation in dogs.

Evoked potentials were induced by transcranial stimulation and recovered from the spinal cord, and the radial and sciatic nerves in six dogs. Stimulation was accomplished with an anode placed on the skin over the area of the motor cortex. Evoked potentials were recovered from the thoracic and lumbar spinal cord by electrodes placed transcutaneously in the ligamentum flavum. Evoked potentials were recovered from the radial and sciatic nerves by surgical exposure and electrodes placed in the perineurium. Signals from 100 repetitive stimuli were averaged and analyzed. Waveforms were analyzed for amplitude and latency. Conduction velocities were estimated from wave latencies and distance traveled. The technique allowed recovery of evoked potentials that had similar characteristics among all dogs. Conduction velocities of potentials recovered from the radial and sciatic nerves suggested stimulation of motor pathways; however, the exact origin and pathway of these waves is unknown.

Animals↗
PubMed1989

Paraparesis caused by epidural granuloma in a cat.

Caudal paraparesis in a cat was determined to be caused by an epidural mass. Surgical decompression was performed, and the mass was determined to be a granuloma. Fusobacterium and Bacteroides spp were isolated from the granuloma. Epidural granulomas are seldom reported in dogs and cats. Decompression and administration of antibiotics led to recovery of this cat even though in human beings an unfavorable prognosis is given if neurologic deficits have developed.

Amoxicillin↗
PubMed1988

Eosinophilic granuloma of the nasal skin in a dog.

A recurrent mass removed surgically from the dorsocaudal aspect of the planum nasale in a 12-year-old dog was identified histologically as eosinophilic granuloma. The dog was treated orally with prednisone for 15 days, and the granuloma has not recurred.

Animals↗
PubMed1988

Canine von Willebrand's disease. A heterogeneous group of bleeding disorders.

The term "von Willebrand's disease," refers to a group of inherited bleeding disorders, all of which are caused by a deficiency of the multimeric plasma glycoprotein, von Willebrand factor. The various forms of canine von Willebrand's disease can be categorized into one of three major types: in type I canine von Willebrand's disease, all sizes of von Willebrand factor multimers can be detected in the plasma; in type II canine von Willebrand's disease, only the smaller von Willebrand factor multimers are found in the plasma (larger multimers are absent); and in type III canine von Willebrand's disease, von Willebrand factor is completely absent from the plasma or present in only trace amounts. Von Willebrand's disease is common in dogs, but some forms of the disease are so mild that they are of questionable clinical significance.

Animals↗