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Biomedical subjects

T Kiaer

Publications and source records attributed to T Kiaer.

At least 19 recordsLinked to original sources
PubMed2003

Shock absorption in lumbar disc prosthesis: a preliminary mechanical study.

Lumbar disc prostheses have been used in treating symptomatic degenerative disc diseases. A few prostheses of the ball-socket design are currently available for clinical use, the joint mechanism being materialized either with a hard polymer core or a metal-to-metal couple. Other prostheses of "shock absorber" design were not available at the time of the study. The objective of this work was to establish whether there was a difference in the shock absorption capacity between a device having an ultra-high-molecular-weight polyethylene center core and a device having a metal-on-metal bearing. Vibration and shock loading were applied to two lumbar total disc prostheses: PRODISC, manufactured by Spine Solutions, and MAVERICK Total Disc Replacement, manufactured by Medtronic Sofamor Danek. The shock absorption capacity of the device was evaluated by comparing the input and the output force measurements. The disc prosthesis was mounted onto a test apparatus. Each side of the device was equipped with a force sensor. The input shock load and the output resulting forces were simultaneously measured and recorded. The loading force pattern included 1). a static preload of 350 N plus an oscillating vibration of 100 N with frequency sweeping from 0 to 100 Hz and 2). a sudden shock load of 250 N applied over a 0.1-second interval. Both input and output signal data were processed and were transformed into their frequency spectrums. The vibration and shock transmissibility of the device, defined as the ratio of the output spectrum over the input spectrum, were calculated in sweeping the frequency from 0 to 100 Hz. The phase deviation was calculated to characterize the shock absorber effects. For both tested devices under vibration and shock loading, the phase angle displacement between the input and the output signals was 10 degrees. Under oscillating vibration loading, both tested devices had a transmission ratio higher than 99.8%. Over the frequency interval 1-100 Hz, the difference in transmission ratio between the two devices was <0.3%. Under sudden shock loading, both tested devices had a transmission ratio higher than 98%. The difference between the two devices was <0.8%. Both tested devices have identical vibration and shock transmissibility.

Arthroplasty, Replacement↗
PubMed2001

Gc-globulin is an acute phase reactant and an indicator of muscle injury after spinal surgery.

OBJECTIVES AND DESIGN: Actin is the dominating protein in mammalian cells, including muscle cells, and is released into the circulation after tissue injury. Gc-globulin, one of the proteins in the Extracellular Actin Scavenger System (EASS) is responsible for the clearance of actin from the circulation. Clinical studies show that plasma levels of Gc-globulin are reduced in situations with tissue death, and that the degree of reduction correlates with development of organ dysfunction and survival. The purpose of the present study was to describe the serial changes in Gc-globulin after a standardized surgical procedure resulting in major muscle injury, comparing changes in Gc-globulin with changes in other acute phase proteins. MATERIAL AND METHODS: Twelve patients who underwent posterolateral lumbar fusion from L4 or L5 to sacrum were included in the study. Peripheral venous blood samples were obtained before surgery and on day 1, 3, 5, 12, 21, and 28 after surgery. Serum samples were analyzed for total Gc-globulin (Gc(total)), percentage of Gc-globulin complexed with actin (GC(complexed)), albumin, orosomucoid, haptoglobin, transferrin and creatin phosphokinase (CK). RESULTS: Gc(total) decreased to 87% of pre-operative values on day one. Thereafter the levels increased to a maximum of 135% of pre-operative values on day five, approaching baseline values towards the end of the observation period. Compared to this, changes in GC(complexed) displayed a mirror-like time-course, with levels of Gc(total) and GC(complexed) being significantly inversely correlated on day one (P < 0.05). Levels of albumin remained below pre-operative values the first three weeks post-operatively, reaching baseline at the end of the observation period (P < 0.05). CONCLUSION: The initial changes in Gc-globulin can be explained by increased release of actin from injured muscle tissue. Subsequently Gc-globulin displays characteristics of a so-called positive acute phase reactant, supporting previous in vitro studies, and clinical studies after minor surgery. In spite of genetic linkage and structural homology Gc-globulin and albumin are regulated differently after surgical trauma.

Actins↗
PubMed2001

Trauma stimulates the synthesis of Gc-globulin.

OBJECTIVE: Actin is the dominating intracellular protein and is released to the circulation after tissue injury. Gc-globulin is one of the plasma proteins responsible for removal of actin from the circulation. Recent studies have shown that the level of Gc-globulin is reduced shortly after trauma. Serial changes in Gc-globulin after severe injury have not been studied so far and could provide additional information about the role of Gc-globulin in the pathophysiological response to trauma. DESIGN: Prospective, observational. SETTING: Surgical intensive care unit in a university hospital. PATIENTS: Thirty-eight patients were included in the study: 12 women and 26 men with a median age of 38 years (range 19-86) and a median Injury Severity Score (ISS) of 18 (range 6-45). Seven patients died, on day 5, 8, 8, 10, 10, 13 and 21, respectively. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The serum concentration of Gc-globulin (Gctotal) and the percentage of Gc-globulin bound to actin (Gc%complexed) were measured daily for 1 week using rocket immunoelectrophoresis. Concentrations of free Gc-globulin (Gcfree) and Gc-globulin bound to actin (Gcbound) were calculated from these analytical results. The concentration of Gctotal and Gccomplexed correlated significantly (r = -0.99, p < 0.001) throughout the time period. After day 3 levels of Gc%complexed normalised, whereas levels of Gctotal continued to increase above control values. The concentrations of Gctotal and Gcfree were significantly lower in non-survivors compared to survivors; p = 0.005 and p = 0.03, respectively. This was combined with an inverse correlation of Gcbound between these two groups (r = -0.73; p = 0.04). CONCLUSIONS: Severe injury results in a prolonged load on the extracellular actin scavenger system; more pronounced in patients who do not survive. Gc-globulin displays characteristics of an acute phase reactant, with supra-normal serum levels 1 week after severe injury. Serial measurements of Gc-globulin after trauma could prove to be a method of early identification of patients with increased risk of mortality.

Actins↗
PubMed2001

Nonorganic pain drawings are associated with low psychological scores on the preoperative SF-36 questionnaire in patients with chronic low back pain.

The Short Form 36 questionnaire (SF-36) measures general health and well-being. Within the last 5 years it has been used increasingly to characterise patients in the medical literature. Relatively few studies have used the SF-36 on patients with chronic low back pain undergoing preoperative evaluation, but results suggest that it may be predictive of surgical outcome. Pain drawings are a routine part of evaluation prior to spinal surgery in several centres, since their classification of organic or nonorganic has been shown in some studies to correlate well with psychological characteristics predicting poor outcome. The purpose of the present study was to assess possible correlations between nonorganic pain drawings and the psychological scales in the SF-36. We included 128 patients in the study, all of them referred from other hospitals. Previous spinal surgery had been undergone by 25%, and 59% required daily medication because of low back pain. All patients completed pain drawings using predefined symbols These pain drawings were scored dichotomously as organic or nonorganic based on a brief description of a typical nonorganic characteristics. Patients also completed the Danish version of the SF-36 questionnaire. Statistical analysis was performed using logistic regression analysis. The pain drawing classification was used as the dependent variable and scores on the eight scales of the SF-36 as independent variables. P values of <0.05 were considered significant. The mean scores of the patient population on all eight scales were significantly lower than Danish norms. The only scales that correlated with the presence of nonorganic pain drawings were emotional role (RE) and mental health (MH), both measuring psychological health. The odds ratio (OR) of receiving a nonorganic pain drawing was 22 (95% confidence interval, or CI, 7-65) if the scores on RE and MH were more than 2 standard deviations (SD) below the Danish norm. This is the first study providing evidence that pain drawing ratings are influenced by the psychological scales of the SF-36. The clinical relevance of this observation regarding prediction of outcome after spinal surgery should be assessed in future studies.

Adolescent↗
PubMed1999

Admission level of Gc-globulin predicts outcome after multiple trauma.

BACKGROUND: Actin is the dominating protein in mammalian cells. Release of excessive amounts of actin into the circulation may result in a condition resembling multiple organ failure. The purpose of this study was to determine if admission levels of Gc-globulin can predict survival after multiple trauma. Also, we wanted to compare the predictive ability of Gc-globulin with that of the TRISS-Like scoring system. METHODS: Fifty-seven patients with a median ISS 18 (16-75) were included. All patients had a blood sample taken median 42 min after the injury (19-110 min). Serum Gc-globulin was measured by rocket immunoelectrophoresis. RESULTS: On admission, all patients had significantly reduced levels of Gc-globulin compared with normal controls. Gc-globulin was significantly higher in the group of survivors (n = 41), compared with non-survivors (n = 16). Median 237 mg/l vs. 188 mg/l (P < 0.01). The predictive ability of Gc-globulin regarding death was similar to that of TRISS-Like with positive predictive values of 69%, a negative predictive value of 84%, a sensitivity of 56% and a specificity of 90%. CONCLUSIONS: The predictive value of Gc-globulin regarding survival was similar to that of an established scoring system. Gc-globulin, alone or in combination with other parameters, may serve as a routine tool for early identification of patients at risk after severe injury, increasing the possibility of early intervention.

Adolescent↗
PubMed1998

[Percutaneous fixation of sacral fractures. Primary experiences with a new technique].

A number of techniques have been introduced to obtain reduction and fixation of rotational and vertical unstable sacral fractures and sacro-iliac (SI) joint disruptions. The purpose of this study is to report our primary experience with percutaneous cannulated screw fixation across the joint or fracture line. Fifteen consecutive patients, seven males and eight females, were operated. Six patients had isolated sacral fractures or SI joint disruption. All patients had a type C pelvic fracture according to Tile's classification. Percutaneous fixation of sacral fractures and sacro-iliac joint disruptions allows a short operating time, minimal bleeding and soft tissue damage, and immediate non-weight bearing mobilisation. No non-unions were seen and there were no cases of infection. In two patients the material had to be removed. The method gives adequate fixation of unstable posterior pelvic-ring fractures, but is technically difficult as malposition of the screws might cause serious perioperative complications.

Acetabulum↗
PubMed1998

Serum Gc-globulin in the early course of multiple trauma.

OBJECTIVES: In patients with multiple trauma, actin released from damaged cells may cause severe circulatory disturbance due to thrombi formation. The aim of this study was to evaluate serum concentrations of the actin scavenger, Gc-globulin, in relation to the severity of injury and outcome. DESIGN: Prospective, longitudinal, observational study. SETTING: Trauma center at a university hospital. PATIENTS: Twelve patients with multiple trauma, consecutively included, according to defined criteria. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Serum Gc-globulin concentrations were measured at the time of admission and daily thereafter for 1 wk or until death. In all patients, the Gc-globulin concentration was significantly low (p < .0001), and the proportion of Gc-globulin bound to actin was already increased compared with normal values (p < .0001) by the time of hospital arrival. There was an inverse correlation between the mean concentration of serum Gc-globulin in the first week after trauma and the Injury Severity Score (r = -0.72, p < .05). Surviving patients had a significantly (p < .05) higher concentration of serum Gc-globulin in the first week after trauma compared with nonsurvivors. CONCLUSIONS: Serum concentrations of Gc-globulin were significantly low in trauma patients. The reduction took place within 60 mins after injury. Because the normal half-life of Gc-globulin is almost 48 hrs, our observations suggest a marked consumption of Gc-globulin immediately after the trauma. This finding could be the first clinical evidence that Gc-globulin plays a role in the systemic inflammatory response syndrome after trauma. This result is supported by the finding that lack of Gc-globulin was related to nonsurvival and the severity of the trauma.

Actins↗
PubMed1997

Clinical outcome after spinal fusion with a rigid versus a semi-rigid pedicle screw system.

Several biomechanical studies have evaluated the quality of fusion obtained with a rigid versus a semi-rigid pedicle screw implant. Some studies indicate that increased rigidity of the implant system results in an increased strength of the fusion mass. Other reports have underlined the risk of stress shielding due to rigid implant systems. Based on these findings some authors have recommended the use of a semi-rigid system. There are, however, few studies focusing on any possible difference in clinical outcome between the two different types of implant systems. Questionnaires were sent to 89 patients who had undergone primary spinal fusion with either a rigid or a semi-rigid pedicle-screw-based implant system. In every case the diagnosis was spondylolisthesis or degenerative lumbar disease. The questionnaires were analysed using forward stepwise logistic regression analysis. Eighty (90%) of the questionnaires were returned. There was a mean follow-up of 4 years (range 2-8 years). It was not possible to demonstrate any difference in clinical outcome between patients undergoing lumbar fusion with a rigid implant system and those given a semi-rigid system. The overall patient satisfaction rate was 69%, with no difference between the two types of implant. No difference in clinical outcome between the two types of implant was found. Considering the fact that the primary goal of spinal fusion procedure is to obtain a solid fusion mass, biomechanical tests favour the used of a rigid pedicle screw system. This fact combined with the fact that early mobilisation is possible with rigid implants justifies the use of rigid implant systems, although no difference in clinical outcome could be demonstrated in this study.

Adolescent↗
PubMed1996

[Traumatology. Scoring systems and their use].

Centralized trauma care is developing in Denmark, and is producing an increasing interest in the scoring systems used in traumatology. A large number of scoring systems have been developed within the trauma field. After reviewing the literature, we recommend the Revised Trauma Score at strategic intervals during admission, and scoring of the Abbreviated Injury Scale (AIS) according to the 1990 revision at discharge or by autopsy. This will allow calculation of the Injury Severity Scale (ISS) and The Trauma Score--Injury Severity Score (TRISS) making scientific studies in accordance with international standards possible.

Abbreviated Injury Scale↗
PubMed1994

The Cotrel-Dubousset instrumentation for unstable sacral fractures. Report of 3 patients.

We present a new operative procedure using the Cotrel-Dubousset (C-D) instrumentation in unstable sacral fractures, where the vertebral column is dissociated from the pelvis. This technique is based on screw fixation in the ileum and in the first sacral and the fifth lumbar vertebrae or the fifth and fourth lumbar vertebrae, with help of interconnecting rods. 3 patients were successfully treated.

Bone Screws↗
PubMed1993

[Lumbosacral spondylolisthesis. Occurrence and therapeutic possibilities].

The incidence of lumbosacral spondylolisthesis is 5%, and 25% of the patients will develop symptoms. The debut of the symptoms typically occurs during the teenage years, and is not always related to the degree of spondylolisthesis. The principles of conservative treatment include symptomatic relief and reduction of the lumbar lordosis using a brace. Conservative treatment often results in temporary improvement, but symptoms often come back. In case of ineffective conservative treatment, progressive neurologic symptoms and disability surgery is indicated. New techniques make it possible to reduce the spondylolisthesis and the lumbosacral kyphosis using metal implants and spondylodesis involving the transverse processes, facet joints and pedicles.

Adolescent↗
PubMed1993

The relationship between inert gas wash-out and radioactive tracer microspheres in measurement of bone blood flow: effect of decreased arterial supply and venous congestion on bone blood flow in an animal model.

Several methods have been employed in the study of bone perfusion. We used a method of determining inert gas wash-out by mass spectrometry in the study of blood flow rates in pigs. The method was validated by comparison of the result obtained with inert gas wash-out to that with measurement by microspheres. Furthermore, the effect of decreased inlet flow and venous congestion on the bone perfusion data was tested. The undisturbed bone blood flow was not significantly different when measured with wash-out of inert gas (7 +/- 0.7 ml/min/100 g) or with microspheres (9 +/- 2.9 ml/min/100 g), and the methods were correlated. Perfusion was reduced significantly, to 20% of the original value, after arterial occlusion. The changes in wash-out curves and accumulation of radioactive tracer provided substantial evidence for impaired intraosseous circulation following venous obstruction also. In conclusion, the study showed that this method of determining inert gas wash-out is feasible for studies of local perfusion rates in bone. The flow rates obtained by wash-out correlated well with the results of microsphere studies. In this animal model, both methods detected a fivefold reduction in flow rate after clamping of the arterial inflow. Obstruction of the venous outflow also impaired blood flow and lowered the cellular supply.

Animals↗
PubMed1993

Laser Doppler flowmetry for estimation of bone blood flow: studies of reproducibility and correlation with microsphere technique.

The blood flow in the femoral condyles of six pigs was measured by the microsphere technique and by laser Doppler flowmetry (LDF) before and after clamping of the external iliac artery. A significant decrease in the bone blood flow was found with both microsphere and LDF measurements, and a high correlation was found between the two methods. After release of the arterial clamp, the LDF values rapidly returned to approximately the same values as before clamping. In a second part of the study, the LDF output signal was studied in the intertrochanteric area of eight patients. The reproducibility of two LDF measurements at the same location was within 15%. The temporal variability of the LDF signal during 10 min of recording showed only slight variations. It is concluded that LDF is relative in nature and that the mean LDF output signal is suitable for monitoring dynamic responses of the bone blood flow to various stimuli. Several consecutive measurements have to be performed if the blood flow at different locations of a specific bone are to be compared with each other.

Animals↗
PubMed1992

Partial pressures of oxygen and carbon dioxide in bone and their correlation with bone-blood flow: effect of decreased arterial supply and venous congestion on intraosseous oxygen and carbon dioxide in an animal model.

Pathological changes in bone have been related to a preceding impediment of the arterial or venous bone circulation and hypoxia. In this study, we analyzed the feasibility of mass spectrometry in measuring intraosseous oxygen and carbon dioxide. The partial pressures were also measured in intraosseous blood samples, and blood flow in bone was measured with the radioactive microspheres technique. The average partial pressure of oxygen in the lateral femoral condyle was 34 +/- 1.6 mm Hg when measured in intraosseous blood samples and 36.3 +/- 2.3 mm Hg when measured with the on-line mass spectrometer, with significant correlation between the methods. The absolute value of the partial pressure of carbon dioxide measured in situ with mass spectrometry was correlated with the value in the withdrawn blood. There was no significant difference in partial pressures of oxygen and carbon dioxide between the two sides or between repetitive measurements. Arterial occlusion resulted in severe hypoxia, whereas more moderate changes followed venous occlusion.

Animals↗
PubMed1992

Measurement of bone cell metabolism in vitro using mass spectrometry.

The metabolism of bone cells can be monitored directly and continuously 'in vitro' by a new technique, based on mass spectrometry. The consumption of oxygen and production of carbon dioxide were measured in 6 different cultures of human bone cells. The method was feasible for measurement of bone cell metabolism and was also tested in suspensions of hepatocytes. The data obtained with these cells were comparable to results obtained with traditional techniques, and a relation to cellular concentration was demonstrated.

Bone and Bones↗