Hemodynamics of the juvenile knee

Adrenergic responses in human small arteries isolated from the femoral neck

Many pathological bone conditions are accompanied by changes in bone perfusion. However, no method has yet allowed investigation of vascular reactivity in human bone tissue. In the present study, arterial segments (diameter approximately 0.25 mm) were isolated from human bone biopsies and mounted as ring preparations in vitro. The viability of the arteries and the effects of adrenoceptor stimulations were investigated. Combined alpha- and beta-adrenoceptor stimulation (noradrenaline 10(-8)-10(-5) M) and specific alpha1-adrenoceptor stimulation (phenylephrine, 10(-8)-10(-4.5) M) induced concentration-dependent contractions in all arteries. Selective stimulation of alpha2-receptors (B-HT 933, 10(-8)-10(-3.5) M) only induced contraction in three of eight arteries. Stimulation of beta-receptors with isoprenaline (10(-6) M) resulted in vasorelaxation in 3 of 10 arteries. In all arteries, acetylcholine (10(-10)-10(-5) M) induced vasorelaxation, demonstrating preserved function of the endothelium. The results suggest that primarily alpha1-receptors are responsible for adrenoceptor induced vasoconstriction in human bone while functional alpha2- and beta-receptors may not be consistently expressed. The model is the first to allow investigations on vascular reactivity in human bone tissue and may become valuable for assessment of both normal and pathological bone physiology.

Spinal cord and nerve root blood flow in acute double level spinal stenosis

STUDY DESIGN

Twenty-four pigs were randomized into three groups of eight pigs; a control group with 0% stenosis, a 25% stenosis group, and a 50% stenosis group. A fourth 75% stenosis group was added when results of the randomized experiment had been analyzed. Blood flow of the spinal cord and nerve roots and spinal evoked potentials were determined before and 1 hour after induction of the spinal stenoses.

OBJECTIVES

To study the acute effects of different degrees of spinal stenosis on neural tissue blood flow and spinal evoked potentials.

SUMMARY OF BACKGROUND DATA

Spinal cord dysfunction may be caused by vascular impairment or mechanical injury to neural tissue. Experimental double level compression of the cauda equina causes reversible nerve root edema, stasis, blood flow decrease, and compromised neural function. The vascular pathophysiology after spinal cord trauma was studied previously, and both increased and decreased neural tissue blood flow have been reported.

METHODS

Two level spinal stenosis was introduced by placement of stenosing bands around the dural sac at L4 and L6. Neurologic function was monitored by sensory and motor evoked potentials. Regional blood flow (RBF) was measured in the stenotic segments between the bands and other regions of neural tissue by radioactive microspheres before and after induction of stenosis.

RESULTS

Regional blood flow increased in the stenotic segments after 0% sham stenosis. Analysis of variance revealed no differences in RBF between the three randomized groups under comparable conditions of 0% stenosis. However, the RBF level of the added 75% group was lower than that of the other three groups. By comparison of RBF within groups before and after stenosis, no decrease in RBF was found between the stenosing bands in any of the groups. Fifty percent stenosis changed the amplitude of evoked potentials in half of the animals. Seventy-five percent stenosis caused severe changes in evoked potentials in 7 of 8 animals.

CONCLUSIONS

Blood supply of the spinal cord and nerve roots in the segments between two central stenoses is preserved immediately after stenosis introduction by way of the segmental nerve pathway, even if nerve conduction is impaired.

Method for assessment of vascular reactivity in bone: in vitro studies on resistance arteries isolated from porcine cancellous bone

Knowledge about vascular regulation in bone is central to the understanding of both normal and pathological bone physiology. This article describes a new method for direct assessment of the reactivity of bone blood vessels. Resistance arteries (diameter approximately 250 microns) were isolated from epiphyseal cancellous bone (porcine femoral condyle). Arterial segments (2 mm long) were mounted as ring preparations on a myograph, and isometric force development was measured continuously. Fifty-nine vessels from 31 pigs were investigated. The active force development was maximal at 0.9 x L100 in nine of 12 investigated arteries (L100 corresponds to the circumference the vessel would have if relaxed and exposed to a luminal pressure of 100 mm Hg [13.3 kPa]). In all subsequent experiments, the vessels were stretched to 0.9 x L100. Noradrenaline (2 x 10(-8) to 10(-5) M) induced a concentration-dependent vasoconstriction; mean maximal tension development was 3.69 N/m. This force development would enable the arteries to contract against a pressure of more than 22 kPa (165 mm Hg), indicating preserved function of the media smooth muscle. Response to acetylcholine (10(-7) to 10(-5) M) was observed in only two of 12 arteries. Bradykinin (10(-11) to 10(-6) M) induced a concentration-dependent and reproducible relaxation in all vessels; the relaxation was endothelium-dependent, since no effect of bradykinin was detected after mechanical removal of the endothelium. Sodium nitroprusside (10(-4) M) induced a reproducible and endothelium-independent vasorelaxation. The results demonstrate preserved function of both smooth muscle and endothelium in this preparation. The model allows pharmacological investigations of bone arteries under well defined conditions and enables studies on focal bone lesions and human bone tissue.

High hydrostatic pressures in traumatic joints require elevated synovial capillary pressure probably associated with arteriolar vasodilatation

Three out of the four Starling pressures were determined at arthroscopy of traumatic effusions of the knee. The range of the joint fluid hydrostatic pressure Pjoint was 5-83 cmH2O (0.5-8.1 kPa, 4-61 mmHg), that of the colloid osmotic pressure difference COPplasma-COPjoint 0-21.7 cmH2O. In 11 of 15 cases the sum Pjoint+COP difference exceeded 32.6 cmH2O (3.19 kPa, 24 mmHg), a high estimate of average capillary pressure at the level of the heart. The number of 'exceeding' cases was 8/15 if only 80% of the COP difference was considered effective. Pjoint and the COP difference oppose filtration of fluid from plasma into joints, indicating that mean capillary pressure, the only Starling pressure not determined, was elevated unless the effusions were being resorbed back into the blood. The findings can be explained by tamponade compensated by arteriolar vasodilatation, suspected to be metabolically mediated.

[99mTc]diphosphonate uptake and hemodynamics in experimental arthritis: effect of naproxen in the canine carrageenan injection model

The impact of naproxen treatment on juxta-articular hemodynamics and bone metabolism in experimental juvenile arthritis was studied in the articular carrageenan injection model. Unilateral gonarthritis was induced for 12 weeks in eight dogs receiving naproxen (dosage, 2 mg/kg) and eight controls. Regional blood flow was assessed by the microsphere method, plasma volume by the distribution space of [125I]fibrinogen, and bone metabolism by the 2-h uptake of [99mTc]diphosphonate ([99mTc]DPD). Synovial effusion was less prominent with naproxen treatment as judged by joint fluid volume and pressure. Naproxen reduced the arthritic capsular hyperemia, almost normalized a severe blood flow increase in patella and both juxta-articular epiphyses, ameliorated an expansion of plasma volume in the patella and the distal femoral epiphysis, and normalized an increased [99mTc]DPD uptake in subchondral femoral bone and the tibial cortex. Significantly increased arteriovenous shunting in the arthritic extremity was unaffected by naproxen. The study suggests that long-term cyclooxygenase inhibition offers protection against hemodynamic and metabolic changes in juxta-articular bone secondary to synovial inflammation.

Early hemodynamic response to tibial osteotomy in rabbits: influence of indomethacin and prostaglandin E2

The hemodynamic role of prostaglandins in the inflammatory phase of bone healing was studied on day 4 after creation of a nailed midtibial osteotomy in 40 rabbits, divided into groups of 10, treated with either indomethacin (oral dosage 10 mg/kg), subcutaneous (s.c.) prostaglandin E2 (PGE2) (dosage 1 mg/kg), or PGE2 infusion into the abdominal aorta (rate 20 ng/kg/min) for a 20-min period immediately before the animals were killed. The last group served as controls. Regional blood flow was measured by means of radioactive microspheres, and plasma volume was assessed by distribution of circulating [125I]fibrinogen. Neither indomethacin nor s.c. PGE2 treatment had any hemodynamic effects in the osteotomy area. PGE2 infusion caused increased blood flow in bone, bone marrow, and muscle of the lower limbs except in the osteotomy area. Thus, the influence of prostaglandins and indomethacin on bone healing of a rabbit midtibial osteotomy does not appear to be a direct vascular effect in the early healing phase.

Arteriovenous shunting is not associated with venous congestion in bone. Knee tamponade studied with 15-microns and 50-microns microspheres in immature dogs

Blood flow in the hind-limb bones of 8 immature labrador dogs with unilateral knee joint tamponade at 75 percent of the mean arterial pressure was measured with 15-microns and 50-microns microspheres to determine whether or not arteriovenous shunting occurs in bone with venous congestion caused by increased outflow resistance. The intraosseous pressure was 43 percent of the mean arterial pressure in the experimental distal femoral epiphysis versus 14 percent in the control knee (P less than 0.001). No pressure changes were found in the distal femoral metaphysis. Regional blood flow with 15-microns microspheres decreased centrally in the distal femoral epiphysis and increased centrally in the proximal tibial epiphysis. Metaphyseal blood flow was largely unchanged. A net shift in the preferred embolization site of 50-microns microspheres relative to that of 15-microns microspheres from central to peripheral regions occurred within both juxtaarticular epiphyses, indicating arteriolar vasodilation, but the relation between the uptake of the two microsphere sizes was unchanged when the epiphyses and other bony flow compartments were viewed in toto. The result speaks against the hypothesis of arteriovenous shunting in intraosseous hypertension.

Physical bone changes in carragheenin-induced arthritis evaluated by quantitative computed tomography

Repeated non-invasive measurements were performed in dogs of trabecular bone density (TBD), low density bone area (LDBA), and high density bone area (HDBA) in chronic arthritis using quantitative computed tomography (QCT). Unilateral chronic arthritis of the knee had been induced by weekly instillation of 2 ml carragheenin into the right knee joint for 12 weeks with the left knee serving as a control. CT scanning of the distal femoral condyles was performed in 12 mature dogs with chronic arthritis. Another 6 dogs underwent a longitudinal CT study starting immediately prior to induction of arthritis. During induction of arthritis TBD decreased (P less than 0.01), LDBA increased (P less than 0.05) and HDBA decreased (P less than 0.01) in the arthritic bone. Opposite changes were found on the control side, i.e. TBD increased (P less than 0.01), LDBA decreased (P less than 0.01) and HDBA increased (P less than 0.01). The chronic arthropathic bone showed 20% lower TBD (P less than 0.0001), greater LDBA (P less than 0.0001) and lower HDBA (P less than 0.0001) as compared with the control bone. Reproducibility tests of TBD showed a coefficient of variation of 0.8%. Indentation tests and histomorphometric analyses confirmed the bone density changes as measured by CT.

[99mTc]diphosphonate uptake and hemodynamics in arthritis of the immature dog knee

The relationship between [99mTc]diphosphonate uptake and bone hemodynamics was studied in canine carrageenan-induced juvenile chronic arthritis. Blood flow was determined with microspheres, plasma and red cell volumes were measured by labeled fibrinogen and red cells, and the microvascular volume and mean transit time of blood were calculated. Normal femoral epiphyses had lower central and higher subchondral blood flow and diphosphonate uptake values. Epiphyseal vascular volume was uniform, resulting in a greater transit time of blood centrally. In arthritis, blood flow and diphosphonate uptake were increased subchondrally and unaffected centrally, while epiphyseal vascular volume was increased throughout, leading to prolonged transit time centrally. The normal metaphyses had low blood flow and diphosphonate uptake values in cancellous bone and very high values in growth plates, but a large vascular volume throughout. The mean transit time therefore was low in growth plates and high in adjacent cancellous bone. Arthritis caused decreased blood flow and diphosphonate uptake in growth plates but increased vascular volume and transit time of blood. Diphosphonate uptake correlated positively with blood flow and plasma volume and negatively with red cell volume in a nonlinear fashion. Thus, changes in diphosphonate uptake and microvascular hemodynamics occur in both epiphyseal and metaphyseal bone in chronic synovitis of the immature knee. The [99mTc]diphosphonate bone scan seems to reflect blood flow, plasma volume, and red cell volume of bone.

Microvascular hemodynamics in experimental arthritis: disparity between the distribution of microspheres and plasma flow in bone

The microcirculation in normal and arthritic juxtaarticular bone was studied in 16 young dogs with carragheenan-induced arthritis of one knee. The regional blood flow was determined by the tissue uptake of intracardially injected 15-microns 141Ce-labeled microspheres, and the microvascular plasma volume was determined by the distribution space of circulating 125I-fibrinogen. Disparities between the distribution of plasma flow and microspheres, introduced by plasma skimming or nonentrapment of spheres in the intraosseous circulation, were estimated by 59Fe-transferrin, a third intravascular tracer, injected as a bolus intracardially and trapped peripherally after 15 sec by prompt circulatory arrest. The tissue uptake of the plasma flow tracer was compared to that of microspheres by the ratio between observed and expected activity of 59Fe-transferrin, the expected activity being calculated from the microsphere distribution. The transferrin and microsphere uptake agreed well in patella, marginal epiphyseal bone, and cortical bone, whereas observed activity of transferrin was twice the expected in central epiphyseal bone, three times higher in marrow, and up to eightfold higher in metaphyses adjacent to growth plates. This discrepancy was significantly greater in arthritic bone when the metaphyses were examined in toto. The microsphere method thus appears to underestimate blood flow to cancellous bone and marrow due to uneven distribution of plasma and formed elements from profound plasma skimming and perhaps also by AV shunting.

Proliferation of adherent synovial fluid cell cultures is modified by eicosanoids

Synovial fluid cells obtained from a carrageenan-induced chronic arthritis in the juvenile dog knee were allowed to adhere and proliferate in culture flasks. After twelve days secondary cultures were made and either 10(-8)M leukotriene B4 (LTB4), 25 microM 15-hydroxy-eicosatetraenoic acid (15-HETE), or both, were added and the cells were cultured for another 6 days. LTB4 is generated via the 5-lipoxygenase pathway of arachidonic acid metabolism and stimulates a number of phagocyte functions. Compared to control cells LTB4 increased proliferation in 9 out of 10 cell cultures (p less than 0.05). The 15-lipoxygenase product, 15-HETE, is not proinflammatory and is an endogenous inhibitor of 5-lipoxygenase. Addition of 15-HETE decreased proliferation of cell cultures by 23% (p less than 0.01). It is speculated that LTB4 in addition to its effect on phagocytes may play a role in synovial hyperproliferation observed in arthritis.

Synovitis reduced by inhibition of leukotriene B4. Carrageenan-induced gonarthritis studied in dogs

The pathophysiologic significance of leukotriene B4 (LTB4) in arthritis was studied in dogs by unilateral intraarticular deposition of 15-hydroxy-eicosatetraenoic acid (15-HETE), an endogenous inhibitor of the formation and the effects of LTB4, in bilateral carrageenan-induced gonarthritis. LTB4 in synovial fluid was selectively inhibited in 15-HETE treated joints, the formation of prostaglandin E2 (PGE2) being largely unaffected. The clinical symptoms, intraarticular pressure, and extractable synovial fluid volume were reduced in treated joints. No effect could be discerned regarding blood flow in the synovial membrane, capsule, or juxta-articular bone as measured by tracer microspheres; and no effect on bone metabolism was found as judged by 99mTc-diphosphonate uptake. Thus, inhibition of LTB4 reduces joint exudation, but does not seem to interfere with changes in juxta-articular hemodynamics or bone metabolism following synovial inflammation.

Hemodynamic effects of knee-joint tamponade. 99mTc-diphosphonate scintimetry in growing dogs

We studied the influence of joint effusion on juxtaarticular vascularity and bone metabolism of the immature knee in puppies by dynamic and static 99mTc-diphosphonate scintimetry. Unilateral joint tamponade of 10 KPa (75 mmHg), introduced by intraarticular dextran-70 infusion, resulted in quantitatively similar scintimetric changes in an angiographic Phase I (0-20 sec), a blood pool Phase II (20-256 sec), and a bone-uptake Phase III (2 h). The uptake was reduced by 20 percent in the distal femoral epiphysis, by 15 percent in the distal femoral growth plate in Phases II-III, and by 8 percent in the proximal tibial growth plate in Phase III. The main part of scintimetric changes during joint tamponade could be ascribed to altered epiphyseal and metaphyseal intraosseous hemodynamics.

99mTc-DPD uptake in juvenile hemarthrosis. Scintimetry and autoradiography of the knee in dogs

The pathogenesis of subchondral bone lesions and growth plate affection in hemophilic arthropathy was studied in puppies by means of repeated regional 99mTc-diphosphonate scintimetry and contact autoradiography. Unilateral hemarthrosis of the knee was induced by biweekly intraarticular injections of autologous blood for 12 weeks. Hemarthrosis caused an early (2 to 4 weeks) decrease in uptake of 99mTc-diphosphonate in the juxtaarticular growth plates (ratio 0.7) and a delayed (8 to 10 weeks) increase in epiphyseal uptake (ratio 1.5). In a recovery phase after hemarthrosis, growth plate uptake returned to normal, while the epiphyseal uptake remained elevated for 8 to 10 weeks. By contact autoradiography, the growth plate uptake was localized to the calcification layer at the metaphyseal aspect of the growth plates, while the epiphyseal uptake mainly was seen in the thin subchondral and subsynovial bone layer and around osteophytes. The changes in uptake of 99mTc-diphosphonate following hemarthrosis for 3 months were reversible and could be ascribed to the presence of synovial inflammation.

15-Hydroxy-eicosatetraenoic acid (15-HETE) inhibits carrageenan-induced experimental arthritis and reduces synovial fluid leukotriene B4 (LTB4)

15-Hydroxy-eicosatetraenoic acid (15-HETE), a product of arachidonic acid, has no proinflammatory capacity, but can inhibit the formation and the chemotactic response of neutrophils to leukotriene B4 (LTB4), a potent mediator of inflammation. The purpose of the present study was to determine whether intraarticular administration of 15-HETE in carrageenan-induced acute arthritis might decrease the levels of LTB4 in synovial fluid and modify the arthritis. A bilateral acute knee joint arthritis was established in 7 dogs by intraarticular injections of carrageenan every third day. To the right joints, 15-HETE was administered both concomitantly with the carrageenan injections and continuously via an osmotic pump. In samples of synovial fluid obtained on day 0, 3 and 10 PGE2 and LTB4 were determined using reversed phase high performance liquid chromatography combined with radioimmunoassays and neutrophil chemokinesis. In the presence of 15-HETE the clinical severity of arthritis was significantly reduced and the volume of synovial effusate was decreased on an average by 42%. Furthermore, the relative number of neutrophils in histological sections of synovial tissue was decreased by 58%. Intraarticular caragheenan injections induced LTB4 formation, and maximum levels were obtained on day 3 (279.2 +/- 148.2 pg/joint). PGE2 was also present on day 3, but maximum levels were detected on day 10 (9.5 +/- 4.8 ng/joint). In joints injected with both carragheenan and 15-HETE the levels of LTB4 on days 3 and 10 were inhibited by 90% and 83%, respectively. For PGE2 a small but insignificant decrease was found on both day 3 and on day 10. These results show that LTB4 may be an important mediator of acute arthritis induced by carragheenan in dogs, and that intraarticular administration of 15-HETE can modify this arthritis by inhibiting LTB4 formation.

Three-phase [99mTc]diphosphonate scintimetry in septic and nonseptic arthritis of the immature knee: an experimental investigation in dogs

We compared the informative value of dynamic and static [99mTc]diphosphonate ([99mTc]DPD) scintimetry in early septic arthritis (SA) and chronic nonseptic arthritis (NSA) of the knee in puppies. SA (n = 10), induced by injection of Staphylococcus aureus into one knee, was examined after 48 h. NSA (n = 6) was induced by weekly intraarticular instillation of 1% carrageenan and examined at 2 and 12 weeks. Epiphyseal and metaphyseal count ratios (CRs) between experimental and control joint were calculated in an angiographic phase (0-20 s), a "blood pool" phase (20-256 s), and a bone uptake phase (2 hs). Control dogs (n = 4) had a CR of 1.0 in all regions and phases, the coefficients of variation being 0.06 and 0.03 in dynamic and static phases, respectively. In NSA, all scintimetric phases showed decreased metaphyseal uptake and largely unchanged epiphyseal uptake. Generally, SA exhibited vastly increased angiographic uptake in all regions and increased epiphyseal blood pool uptake, whereas delayed epiphyseal uptake varied and delayed metaphyseal uptake tended to decrease. Two septic joints had generalized reduction in dynamic uptake, probably owing to increased intraarticular pressure; in one of these, dynamic uptake in the distal femoral epiphysis (FE) was totally absent, suggesting temporary circulatory arrest during the dynamic scanning procedure. The use of regional dynamic and static [99mTc]DPD scintimetry increased the pathophysiologic and diagnostic value of joint scintigraphy, especially with respect to the early detection of SA and its avascular complications.

Carrageenan-induced coxitis in puppies

We studied the influence of chronic synovitis and joint effusion on the blood supply and growth of the immature femoral head in 12 puppies. Twelve weekly intraarticular injections of Carrageenan solution caused unilateral coxitis with caput magnum formation. Joint pressures in the neutral position were 0.9 kPa in the coxitis hips and -0.5 kPa in the contralateral hips. The joint capsule in coxitis showed hyperemia as measured by tracer microsphere technique. In nonmedicated, awake, standing dogs there was hyperemia of both the femoral head epiphysis and the joint capsule. In all the dogs, acetabular and proximal femoral metaphyseal blood flow was unchanged. In the control group, repeated cannulation and injection of normosaline did not change the hemodynamics, joint pressure, or femoral head size. We found no evidence of femoral head ischemia in coxitis with moderate chronic elevation of resting joint pressure.