Search PubMed⌕ Search

Biomedical subjects

P A Simkin

Publications and source records attributed to P A Simkin.

At least 55 records · Page 3Linked to original sources
PubMed1988

Apophyseal arthritis limits lumbar motion in patients with ankylosing spondylitis.

Ankylosing spondylitis patients who develop progressive spinal flexion may assume this posture to alleviate the pain of apophyseal arthritis. To examine this relationship, we scored injury to L4-L5 and L5-S1 apophyseal joints, as assessed by computed tomography, in 10 men with early ankylosing spondylitis. Both by the modified Schober test and by radiography of the lateral spine, impaired spinal motion correlated highly with evidence of apophyseal injury.

Adolescent↗
PubMed1988

Hydraulic resistance: a measure of vascular outflow obstruction in osteonecrosis.

This study introduces hydraulic resistance (HR) as a new method to measure intraosseous vascular outflow resistance in the human proximal femur. HR is the standard measure of resistance to fluid flow in porous matrices and is derived from serial pressure/flow determinations. Eighteen hips were studied in 11 patients taken to surgery for core decompression therapy of presumable atraumatic osteonecrosis of the femoral head. HR was much higher in osteonecrotic (174 +/- 29 mm Hg min/ml, SE) than in normal human cadaveric femora (14 +/- 6) and was also higher in subcapital (253 +/- 39) than intertrochanteric sites (78 +/- 17). HR correlated highly with baseline intraosseous pressure (r = 0.74, p less than 0.001). HR testing is a simple, practical method which quantifies outflow obstruction of the intraosseous circulation. We believe this test will be helpful in the diagnosis of atraumatic osteonecrosis and in the understanding of its underlying pathophysiology.

Adult↗
PubMed1988

Concentration-effect relationships of NSAID.

For the most part, plasma concentrations of nonsteroidal antiinflammatory drugs (NSAID) have not correlated well with assessments of therapeutic response. This disappointing record may largely reflect weaknesses in experimental design. It may also be, however, that concentrations in plasma bear only a distant relationship to those in the inflamed tissues where NSAID presumably act. Elimination kinetics, protein binding, fat solubility, tissue blood flow, and uptake by cells may be determinants of concentration and response in target tissues. These factors are considered as they relate to NSAID concentrations in synovial effusions.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1988

The effect of compressive loading on intraosseous pressure in the femoral head in vitro.

We measured intraosseous pressures in twenty human hips from cadavera during progressive serial applications of load using a materials-testing machine. Pressure rose in strict proportion to load at each of four different testing sites. In the femoral head, the mean response to loads applied over 0.1 second was 55 +/- 66 millimeters of mercury per 980 newtons. This value was 3.6 times higher than the mean response in a region cephalad to the acetabulum and 2.6 and 2.8 times higher than the mean response in the femoral neck and intertrochanteric regions. In further studies within the femoral head, pressures were accentuated and reduced by factors of 1.7 and 0.4, respectively, at faster (0.03 second) and slower (1.0 second) loading times.

Biomechanical Phenomena↗
PubMed1987

Protein traffic in human synovial effusions.

Concentrations of 5 marker proteins were measured in synovial fluid and serum samples from knee effusions of 11 patients with rheumatoid arthritis and 9 with osteoarthritis. Indirect determinations of synovial plasma flow and lymphatic drainage were obtained by measuring iodide clearance (ml/minute) and radio-albumin clearance (ml/minute). Together with protein concentrations, these determinations allowed us to calculate: the flux of each marker protein through synovial tissues (mg/minute); the volume of plasma cleared by synovium per unit time (ml/minute); and the fractional extraction per passage through the synovial microcirculation (protein permeance). These measures differed substantially between rheumatoid arthritis and osteoarthritis patient populations and quantified the severity of the microvascular lesion in rheumatoid synovitis.

Arthritis, Rheumatoid↗
PubMed1985

Intraarticular volume and clearance in human synovial effusions.

Intraarticular volumes were measured by radiolabeled albumin (RISA) distribution in chronic knee effusions from 11 rheumatoid arthritis patients and 9 osteoarthritis patients. Volumes of synovial fluid obtained at joint aspiration were substantially less than those found by RISA dilution. Up to 24 hours was needed for full distribution of RISA throughout the intraarticular compartment. Measured 123I and RISA radioactivity over the knee described monoexponential rate constants, lambda (minute-1). The clearance of 123I and RISA from synovial effusions was derived by the formulation volume (ml) X lambda (minute-1) = clearance (ml/minute). RISA clearance in rheumatoid effusions was significantly greater than that found in osteoarthritis effusions. Intraarticular volume and isotope clearance were easily quantified and provide measures for further evaluating the microvascular physiology of synovial effusions.

Adult↗
PubMed1985

Low synovial clearance of iodide provides evidence of hypoperfusion in chronic rheumatoid synovitis.

Iodide clearance was measured in the chronic knee effusions of 11 patients with rheumatoid arthritis and 9 patients with osteoarthritis. The mean (+/- SE) iodide clearance of 1.92 +/- 0.30 ml/minute in rheumatoid arthritis effusions did not differ significantly from the 2.19 +/- 0.52 ml/minute found in osteoarthritis effusions. Clearance values in rheumatoid arthritis patients ranged widely (0.79-3.22 ml/minute). Iodide clearance in these patients correlated directly with synovial fluid (SF) pH (r = 0.731, P = 0.005), SF glucose:serum glucose ratio (r = 0.746, P = 0.004), and SF temperature (r = 0.878, P = 0.001), and directly with SF lactate (r = -0.782, P = 0.002) and percentage of SF neutrophils (r = -0.581, P = 0.03). These relationships support the hypothesis that rheumatoid synovitis is often marked by tissue hypoperfusion, and that the "sickest" rheumatoid joints (as defined by physiologic indices) are the most ischemic.

Arthritis, Rheumatoid↗
PubMed1985

Hydraulic resistance in bones of the canine shoulder.

The hydraulic properties of trabecular bone were explored in both sides of normal canine shoulders by following the hydrostatic pressure response to transchondral injections of saline. In a series of isovolumetric injections at sites 9 mm beneath either joint surface, the pressure consistently rose higher and lasted longer in the humerus than it did in the scapula. Hydraulic resistance, the linear function of pressure per unit flow, averaged 8.8 times higher within the humerus than in the scapula in a second series of experiments. Hydraulic resistance fell by average factors of 9.6 in the humerus and 4.3 in the scapula when the surrounding bone was cut away to leave the injection site centered within a 1 cm 'cube' of trabecular bone. Direct determinations of hydraulic resistance provide a useful tool for the study of normal and abnormal physiology in trabecular bone.

Animals↗
PubMed1985

Compliance and viscoelasticity of canine shoulders loaded in vitro.

Humeral and scapular components of normal canine shoulders were used to load each other in a special testing jig permitting measurement of subchondral plate deflection on each side of the joint. In eleven shoulders, at three loading rates, the humeral compliance (mu deflection kg load-1) was always greater than that of the glenoid fossa (geometric mean ratio = 6.0). On sustained compression, there was prominent stress relaxation most suggestive of intraosseous hydraulic flow.

Animals↗
PubMed1984

Management of gout and hyperuricemia.

The medical management of gout follows a logical course in eventually controlling the underlying hyperuricemia. Approached properly, it is one of the most gratifying rheumatic diseases for a physician to treat.

Allopurinol↗
PubMed1984

Interarticular differences in oncotic pressure of canine synovial fluid.

The colloid osmotic pressure of synovial fluid from canine shoulders, elbows, wrists, hips, and knees varied significantly from one joint to the next with the lowest values regularly present in wrists. These differences imply a corresponding, regular variation in microvascular function which may contribute to the distribution patterns of specific rheumatic diseases.

Animals↗
PubMed1983

Free fatty acids in the pancreatitic arthritis syndrome.

Fat necrosis and arthritis occur in some individuals with pancreatitis. The intraarticular free fatty acid concentration was found to be markedly elevated in 2 patients with this pancreatitic arthritis syndrome. Injection of free fatty acids into rabbit knees reproduced the inflammatory synovial response including intracellular fat globules within leukocytes. Free fatty acids exceeding the available binding sites of albumin appear to mediate the extrapancreatic inflammatory manifestations of this syndrome.

Aged↗