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K Schaser

Publications and source records attributed to K Schaser.

7 recordsLinked to original sources
PubMed2006

[Percutaneous reduction and stabilization of a dislocated acetabular fracture. Case report].

In the treatment of acetabular fractures, anatomic reconstruction of the joint is the primary aim. To achieve this, rather large approaches with approach-related morbidity are needed. Percutaneous stabilizations are still limited to nondisplaced or minimally displaced fractures. For displaced acetabular fractures there are percutaneous procedures described with intraoperative CT control, requiring that CT be available in the OR and posing a logistic challenge. The fluoroscope Siremobil Iso-C3D offers the possibility of displaying osseous structures with CT-like quality using a fluoroscopy technique. The case of a minimally displaced acetabular T-type fracture with a clear articular step in the weight-bearing area is presented. The percutaneous reduction and stabilization after intraoperative control of the reduction quality with the Siremobil Iso-C3D is demonstrated. Using the enhanced fluoroscopy technology with the ability to generate axial cuts and reconstructions comparable to CT clearly improves the reduction control also in acetabular surgery. Thus even displaced acetabular fractures can be reduced and stabilized percutaneously. Anatomic reconstruction of the joint remains the primary aim.

Acetabulum↗
PubMed2004

Locked internal fixator: sensitivity of screw/plate stability to the correct insertion angle of the screw.

OBJECTIVE: Internal fixators with angular stability have been developed to provide high stability without compression of the plate on to the bone. Angular and axial stability of a plate-screw construct can be achieved using a conically threaded screw head undersurface and a corresponding conically threaded plate hole. Furthermore, the insertion angle of the screw must correspond precisely to the axis of the screw hole. This is not always achieved in clinical practice and may result in screw loosening. The objective of this study was to examine the relationship between the stability of the locked screw-plate on the insertion angle of the screw. METHODS: Locking screws were inserted in an isolated (Point Contact Fixator, PC-Fix) or combined (Locking Compression Plate, LCP 4.5) locking hole with the use of an aiming device. The optimal insertion angle for these plates is perpendicular to the plate surface. The screws were inserted with an axis deviation of 0 degrees (optimal condition), 5 degrees , and 10 degrees respective to the optimal angle (variance +/- 1 degrees ). The samples were tested under shear or axial (push out) loading conditions until failure occurred. An Instron materials testing machine was used. RESULTS: Locking screws inserted in the isolated locking hole (PC-Fix) showed a significant decrease of failure load if inserted at 5 degrees and 10 degrees angle. Using an optimal insertion angle (0 degrees ), failure load was 1480 +/- 390 N, with 5 degrees axis deviation 780 +/- 160 N, P = 0.0001, and with 10 degrees axis deviation 550 +/- 110 N, P = 0.0001. Screws inserted in the combined locking hole (LCP) also showed a significant decrease of push-out force of 77% (4960 +/- 1000 N versus 1120 +/- 400 N) with 10 degrees axis deviation. Compared to optimal insertion angle (0 degrees ), bending load to failure did decrease up to 69% (1240 +/- 210 N vs. 390 +/- 100 N) with 10 degrees axis deviation. CONCLUSION: A locking head screw exhibits high stability with a moderate axis deviation in the angle of insertion of up to 5 degrees . However, there is a significant decrease in stability with increasing axis deviation (>5 degrees ). An aiming device is recommended to provide optimal fixation with angular stability.

Bone Screws↗
PubMed2003

[CT and fluoroscopy based navigation in pelvic surgery].

Navigation procedures based upon CT data were introduced into spine surgery in 1994. Since then the method has been used in other areas, such as joint replacement, reconstructive surgery and tumor surgery, because of its high precision and reduced radiation exposure. The original CT-based spine module can be adapted for pelvic surgery with the prerequisite, that the positioning of the fragments is identical in CT and at operation; otherwise, a new data set has to be acquired. The experience with CT-based navigation in pelvic surgery will be explained in the context of five percutaneous screw fixations and three tumor resections. The technique will be described. The fluoroscopy-based navigation has been used in trauma surgery since the late 1990 s. Since than the method has gained wide acceptance in the field of joint replacement and reconstructive surgery as well. Between June 2000 and December 2002 we performed 36 percutaneous screw fixations in the pelvis with postoperative X-ray and CT control. Thirty five of the 36 screws were placed correctly. In one screw an anterior cortex perforation of the sacrum was seen on CT, but without neurological consequences. Based upon our clinical experience we believe that CT-based navigation is indicated in screw fixations for minimally displaced pelvic injuries or dysplasia and, with increasing importance, in tumor surgery. Fluoroscopy based navigation with adequate image quality is the method of choice for SI screw fixations in traumatic or degenerative instabilities, especially if an update of the images is needed.

Bone Neoplasms↗
PubMed2002

Cortical hypoperfusion precedes hyperperfusion following controlled cortical impact injury.

Impaired cerebral perfusion contributes to tissue damage following traumatic brain injury. In this longitudinal study persistence of reduced cortical perfusion employing laser doppler flowmetry was investigated following controlled cortical impact injury (CCII). Before, 30 minutes, 6, 24, and 48 hours after CCII, perfusion in pericontusional cortex was determined by moving a laser doppler probe in 50 x 0.2 mm steps over the traumatized hemisphere in 5 rats. Arterial blood gases and mean arterial blood pressure were monitored. Mean arterial blood pressure and arterial blood gases remained stable during the entire experiments. At 30 minutes and 6 hours following CCII, cortical perfusion was significantly diminished by 24% and 43% (p < 0.05), respectively compared to pre-trauma levels. At 24 and 48 hours after CCII, pericontusional blood flow was significantly increased by 64% and 123%. Cortical hypoperfusion found within the early phase following trauma is reversible and precedes a long lasting phase of hyperperfusion. Changes in tissue mediators (endothelin, acidosis, NO) could account for these findings.

Animals↗
PubMed2001

Chondrocyte death precedes structural damage in blunt impact trauma.

Joint impact trauma has been shown to cause fissures, fibrillation, and other structural damage of the cartilage or subchondral bone. Previous studies used impact energies sufficient to fracture the underlying bone. Under these circumstances, the initial influence of impact trauma on cellular components and cartilage structure is unknown. The goal of this study was to determine whether an impact trauma first causes cellular or structural damage to a cartilage layer. Such damage might be the starting point of degenerative changes found in osteoarthrosis. Porcine patellas (n = 12) were subjected to standardized low-impact loading of three magnitudes with a spherical impactor attached to a drop tower device (0.06, 0.1, and 0.2 J). India ink staining and scanning electron microscopic analysis were used for analysis and showed no evidence of gross structural disruption. Chondrocyte viability assessed with thiazole blue staining and propidium iodide counterstaining was reduced significantly in the tangential and middle zones with increasing impact energy. These results indicate that chondrocyte death may precede excessive structural damage reported in earlier studies and might be a crucial factor in posttraumatic osteoarthrosis.

Animals↗
PubMed1996

[Proliferation of T-cells, macrophages, neutrophilic granulocytes and fibroblast-like cells in the synovial membrane of patients with rheumatoid arthritis].

The aim of this study was to determine the proliferation rates within the lining layer of the rheumatoid arthritis (RA) synovial membrane (SM) as opposed to the SM of other degenerative and neoplastic joint diseases and to characterize the proliferating cells. 13 RA, 23 osteoarthritis (OA), 21 joint trauma (JT), and 9 synovial sarcoma (SS) specimens were immunostained for Ki-67 and PCNA, silver-stained for nucleolar organizer regions (AgNORs), and double stained with either T-cell- (CD3), macrophage- (CD68), or polymorphonuclear neutrophilic leucocytes (PMN)-markers (CD15). The frequency of PCNA positive synovial lining cells (SLCs) varied from 15.7 +/- 8.7% in RA (mean +/- SEM), 30.97 +/- 4.13% in JT, and 48.55 +/- 3.66% in OA to more than half of all cells in SS (67.2 +/- 3.1%). MIB-1 labeling was observed in 20.0 +/- 8.4% of SS cells., but only in 0.6 +/- 0.2% RA or < or = 1.1% in JT and OA SLCs. Mean AgNOR number per cell ranged from 2.9 +/- 0.1 in JT, 3.6 +/- 0.05 in OA and 4.3 +/- 0.3 in RA to 7.3 +/- 0.3 in SS. Significant differences were observed for Ki-67 and AgNORs, between SS and all other diseases and also between RA and OA (p < 0.01, U-test). In RA, Ki-67 was solely expressed in lymphocytes of germinal centres, but not in macrophages or PMN; in the lining layer expression of Ki-67 was only found in fibroblast-like cells. Our study confirms that T-cell or macrophage proliferation is rare in the RA SM. Also, the proliferation rates of fibroblast-like cells in the RA lining layer are rather low, in particular when compared to a sarcoma in the same anatomical location.

Arthritis, Rheumatoid↗