Biomedical subjects

S Larsson

Publications and source records attributed to S Larsson.

At least 55 records · Page 3Linked to original sources

PubMed2001

Torsional testing and peripheral quantitative computed tomography in rat humerus.

Peripheral quantitative computed tomography (pQCT) is a noninvasive method mainly used to evaluate the densitometric and geometric properties of bone. In the present study, we evaluate the different variables provided by pQCT examination and their ability to predict the mechanical strength properties of the rat humerus. Humeri from 68 female rats were utilized. These humeri represented bone with a wide range of mechanical and densitometric properties as well as geometric dimensions. Various characteristics, such as volumetric cortical density, total mineral content, cortical thickness, total cross-sectional area, cortical area, and polar strength strain index (SSI), were measured by pQCT. The reproducibility of these measurements was good, with a coefficient of variation (CV) ranging from 0.8% to 4.9%. Bone composition (e.g., ash weight, water content, and inorganic content) and bone dimensions (e.g., length, waist, and volume) were also determined. The mechanical properties (maximum torque, torsion at failure, and stiffness) were measured by torsional testing. Stepwise multiple linear regression was performed to identify the best explanatory variables for each mechanical parameter. Total cross-sectional area and polar SSI were equally well correlated to stiffness (r = 0.57, p < 0.001), whereas ash weight was superior to the pQCT variables to explain maximum torque (r = 0.42, p < 0.001). No other independent pQCT variable entered the two models in the stepwise regression analysis. It was found to be feasible to measure properties of the rat humerus with pQCT. Cross-sectional area and the polar SSI were shown to be the best explanatory variables for stiffness, whereas ash weight was the best predictor for maximum torque.

Animals↗

PubMed2001

Evaluation of a whole-blood WBC-reduction filter that saves platelets: in vitro studies.

BACKGROUND: In this study, a new WBC-reduction in-line filter that removes WBCs but not platelets was evaluated. Three WBC-reduced blood components were prepared: RBCs, plasma, and platelet concentrates (PCs). STUDY DESIGN AND METHODS: Whole-blood components (n = 30) were filtered within 2 to 4 hours after collection and then were centrifuged and separated into RBCs, plasma, and WBC-reduced buffy coat. Saline-adenine-glucose-mannitol solution was added to the RBCS: The WBC-reduced buffy coats were stored overnight; on the following day, PCs were prepared from pooled WBC-reduced buffy coats and stored in a medium composed of approximately 35 percent CPD plasma and 65 percent platelet additive solution (T-Sol, Baxter). The WBC-reduction capacity of the filter, the recovery of cells after filtration, and the in vitro storage of RBCs (n = 10) and platelets (n = 6) were evaluated. RESULTS: Mean and maximum WBC counts after filtration were 0.08 x 10(6) and 0.3 x 10(6), respectively, per filtered whole-blood unit. Recovery of RBCs (mean values) after filtration was 90 percent in whole-blood components and 73 percent in RBCS: Recovery of platelets (mean values) was 81 percent after filtration and 66 percent in PCS: The in vitro storage study of RBCs showed results comparable with previously published data, except for a lower degree of hemolysis. In the in vitro platelet storage study, results were compared with those of standard preparations. In all essentials, similar results were found. CONCLUSION: The results of the present study suggest that effective WBC reduction meets current standards and satisfactory recovery after filtration. The storage characteristics for RBCs and PCs are similar to those of standard preparations. Use of a whole-blood in-line filter to save platelets is a new option for whole-blood processing, which may simplify WBC reduction and blood component preparation, as well as reduce costs in the future.

Blood Component Removal↗

PubMed2001

Extramedullary fixation of 569 unstable intertrochanteric fractures: a randomized multicenter trial of the Medoff sliding plate versus three other screw-plate systems.

We compared the efficacy of the Medoff sliding plate (MSP) with 3 other screw-plate systems for fixation of unstable intertrochanteric fractures in a randomized multicenter trial of 569 elderly patients. The MSP has biaxial dynamic capacity along both the neck and the shaft of the femur unlike the other systems, which lack dynamic capacity along the shaft. 268 fractures were operated on with the MSP, and 301 with the dynamic hip screw (DHS), with or without a trochanteric stabilizing plate (DHS/TSP) or with the dynamic condylar screw (DCS). The MSP had recently been shown to the surgeons. The patients in the groups were similar as regards age, domestic situation, preinjury walking ability and type of fracture. We followed the patients clinically and radiographically for at least 1 year. There was no significant difference in walking ability at follow-up or rate of return to home. Fixation failure occurred in 18/268 fractures operated on with the MSP, in 8/238 with the DHS, in 3/49 with the DHS/TSP and in 1/14 with the DCS. The difference in the rate of fixation failure was not statistically significant when the MSP group was compared to the 3 other groups. In 14 of the 18 fixation failures in the MSP group, the biaxial dynamic capacity of the MSP had not been used due to technical errors by surgeons, unfamiliar with the new method. No selection bias was found regarding fracture types in the 2 subgroups of patients with correct or inadequate biaxial dynamization. Extramedullary fixation of unstable intertrochanteric fractures with these implants showed a low failure rate. When using the MSP, biaxial dynamization must be correctly performed.

Adult↗

PubMed2001

Effect of early axial dynamization on tibial bone healing: a study in dogs.

Early axial dynamization and its effect on experimental tibial bone healing was compared with healing under rigid fixation in a time-sequenced manner using dogs. An external fixator that could be rigidly locked or set to allow free axial movement while preventing bending and shear was used. Both tibias were osteotomized and externally fixed, leaving a gap between bone ends of 2 mm. At 1 week, one side was dynamized, whereas the other side was kept rigidly locked as a control. Dogs were euthanized at 1 day and 1, 3, 5, 8, and 11 weeks after dynamization. The outcome measures were static and dynamic load-bearing, periosteal callus development, new bone formation, callus tissue composition, and mechanical strength. Load bearing was higher on the dynamized limbs during standing for the first 5 weeks and during gait for the first 3 weeks after dynamization compared with the controls. Maximum periosteal callus size was reached faster and was distributed more symmetrically on the dynamized side. The periosteal callus area decreased at 12 weeks on the dynamized sides, but there was no significant change in the area on the control sides. Endosteal new bone formation and bone density decreased between 9 and 12 weeks only on the dynamized sides. The dynamized side showed a significantly higher torsional stiffness at 6 weeks than did the controls. There were no significant differences between dynamized and control tibias at other times. Maximum torque also tended to be higher on the dynamized sides at the same time. Early axial dynamization appeared to accelerate callus formation and remodeling and to provide higher mechanical stiffness during early stages of bone healing.

Animals↗

PubMed2001

Limited bone loss in the hip and heel after reamed intramedullary fixation and early weight-bearing of tibial fractures.

OBJECTIVE: To determine changes in bone mineral density at the hip and calcaneus in the injured and uninjured sides after surgery for tibial fractures. DESIGN: Prospective, longitudinal study. SETTING: University hospital. PATIENTS AND METHODS: Twenty-six patients with a tibial fracture were treated with a reamed and statically locked intramedullary nail with early weight-bearing. Dual-energy x-ray absorptiometry at the proximal femur and quantitative ultrasonography at the calcaneus were performed bilaterally after surgery and after three, six, and twelve months. RESULTS: At three months, the bone mineral density in the trochanteric region in the injured limb had decreased almost 4 percent (p < 0.007), a reduction still present at twelve months, whereas in the femoral neck, the reduction was approximately 2.5 percent at twelve months (p < 0.03). The stiffness index and speed of sound at the calcaneus on the injured side decreased (p < 0.03 and p < 0.008, respectively) during the first three months, whereas at twelve months, there was no significant difference when compared with those measured directly after surgery. There were no significant changes at any time in the proximal femur or calcaneus of the uninjured limb. CONCLUSION: Treatment with a reamed statically locked intramedullary nail and early weight-bearing resulted in limited bone loss in the proximal femur and calcaneus of the injured limb. After twelve months, the bone properties at the heel were restored, whereas there was still a small reduction at the hip. Compared with previous studies of patients with similar fractures treated with casts and restricted weight-bearing, the loss in bone mineral density was less and not as longstanding.

Adolescent↗

PubMed2001

Development of a Saccharomyces cerevisiae strain with enhanced resistance to phenolic fermentation inhibitors in lignocellulose hydrolysates by heterologous expression of laccase.

To improve production of fuel ethanol from renewable raw materials, laccase from the white rot fungus Trametes versicolor was expressed under control of the PGK1 promoter in Saccharomyces cerevisiae to increase its resistance to phenolic inhibitors in lignocellulose hydrolysates. It was found that the laccase activity could be enhanced twofold by simultaneous overexpression of the homologous t-SNARE Sso2p. The factors affecting the level of active laccase obtained, besides the cultivation temperature, included pH and aeration. Laccase-expressing and Sso2p-overexpressing S. cerevisiae was cultivated in the presence of coniferyl aldehyde to examine resistance to lignocellulose-derived phenolic fermentation inhibitors. The laccase-producing transformant had the ability to convert coniferyl aldehyde at a faster rate than a control transformant not expressing laccase, which enabled faster growth and ethanol formation. The laccase-producing transformant was also able to ferment a dilute acid spruce hydrolysate at a faster rate than the control transformant. A decrease in the content of low-molecular-mass aromatic compounds, accompanied by an increase in the content of high-molecular-mass compounds, was observed during fermentation with the laccase-expressing strain, illustrating that laccase was active even at the very low levels of oxygen supplied. Our results demonstrate the importance of phenolic compounds as fermentation inhibitors and the advantage of using laccase-expressing yeast strains for producing ethanol from lignocellulose.

Basidiomycota↗

PubMed2001

IgG subclasses in smokers with chronic bronchitis and recurrent exacerbations.

BACKGROUND: Tobacco smokers have lower serum levels of IgG than non-smokers. IgG subclass deficiency is common in patients with recurrent respiratory infections. Recurrent bronchial infections are common in smokers with chronic bronchitis (CB). We have investigated whether susceptibility to recurrent exacerbations in smokers with CB is associated with altered IgG subclass levels or IgG subclass deficiency. METHODS: Serum levels of IgG, IgA, IgM, and IgG subclasses 1-4 were determined by radial immunodiffusion in 100 subjects: 33 smokers with stable CB and recurrent exacerbations, 24 asymptomatic smokers, and 43 healthy never smokers. Systemic tobacco exposure was verified and excluded using a serum cotinine ELISA. Immunoglobulin data were log transformed to enable use of parametric statistical methods. RESULTS: Compared with never smokers, both patients with CB and asymptomatic smokers had significantly lower levels of IgG (median 9.7 g/l (range 5.6-15.2) and 9.9 (6.1-12.1) g/l v 12.0 (6.9-18.5) g/l) and IgG2 (2.8 (0.9-5.9) g/l and 2.5 (1.0-6.3) g/l v 4.0 (1.7-10.2) g/l). The estimated ratio of median values between the patients with CB and never smokers was 0.78 (95% confidence interval (CI) 0.69 to 0.89) for IgG and 0.65 (95% CI 0.50 to 0.83) for IgG2. The corresponding ratios between asymptomatic smokers and never smokers were 0.79 (95% CI 0.69 to 0.91) and 0.60 (95% CI 0.50 to 0.83), respectively. There were no significant differences between the smoking groups. CONCLUSIONS: Susceptibility to recurrent exacerbations in smokers with CB is not associated with lower levels of IgG subclasses than can be accounted for by smoking per se.

Adult↗

PubMed2001

Role of us in the preoperative evaluation of patients with anterior shoulder instability.

PURPOSE: To assess the value of ultrasonography (US) in the preoperative evaluation of patients with anterior shoulder instability. MATERIALS AND METHODS: Twenty-two patients with one-sided anterior shoulder instability were examined with US by using three dynamic scanning approaches: two frontal and one axillary. The anterior labrum, the anterior ligamental-capsular complex, and the presence of humeral head and glenoid rim fractures were evaluated. Arthroscopy or arthrotomy was subsequently performed in all patients and was considered the standard. RESULTS: US correctly depicted the presence (n = 20) or absence (n = 1) of humeral head fractures and the presence (n = 10) or absence (n = 9) of glenoid rim fractures. All 22 patients had anterior labral tears; 21 tears were correctly depicted with US. The labral tear was seen as a hypoechoic zone larger than 2 mm (n = 15), labral movement (n = 10), a degenerated labrum (n = 6), or a vacuum phenomenon (n = 3). The anterior ligamental-capsular complex was correctly evaluated in 14 patients. The use of multiple approaches helped to prevent misinterpretation, but there were no substantial differences among the approaches in the depiction of the anterior shoulder structures. CONCLUSION: The high accuracy in the depiction of labral tears and associated fractures indicates that US can provide useful preoperative information in patients with anterior shoulder instability.

Adult↗

PubMed2001

Health-related quality of life in COPD: why both disease-specific and generic measures should be used.

Although research has consistently demonstrated that chronic obstructive pulmonary disease (COPD) impairs health-related quality of life (HRQL), little agreement has been evidenced regarding the factors identified as contributing to impaired HRQL. The aim was to study such factors using well established generic and specific HRQL instruments. The patients (n=68) were stratified by forced expiratory volume in one second (FEV1) to represent a wide range of disease severity. Pulmonary function, blood gases and 6-min walking distance test (6MWD) were assessed. HRQL instruments included: St George's Respiratory Questionnaire (SGRQ), Sickness Impact Profile (SIP), Hospital Anxiety and Depression Scale and Mood Adjective Check List. The strength of the impact of COPD on HRQL was represented along a continuum ranging from lung function, functional status (physical and psychosocial) to wellbeing. Although correlations between FEV1 versus SGRQ total and SIP overall scores (r=-0.42 and -0.32) were stronger than previously reported, multiple regression analyses showed that lung function contributed little to the variance when dyspnoea-related limitation, depression scores and 6MWD were included in the models. These three factors were important to varying degrees along the whole range of HRQL. Physiological, functional and psychosocial consequences of chronic obstructive pulmonary disease are only poorly to moderately related to each other. The present study concludes that a comprehensive assessment of the effects of chronic obstructive pulmonary disease requires a battery of instruments that not only tap the disease-specific effects, but also the overall burden of the disease on everyday functioning and emotional wellbeing.

Activities of Daily Living↗

PubMed2001

Detoxification of lignocellulose hydrolysates with ion-exchange resins.

Lignocellulose hydrolysates contain fermentation inhibitors causing decreased ethanol production. The inhibitors include phenolic compounds, furan aldehydes, and aliphatic acids. One of the most efficient methods for removing inhibiting compounds prior to fermentation is treatment of the hydrolysate with ion-exchange resins. The performance and detoxification mechanism of three different resins were examined: an anion exchanger, a cation exchanger, and a resin without charged groups (XAD-8). A dilute acid hydrolysate of spruce was treated with the resins at pH 5.5 and 10.0 prior to ethanolic fermentation with Saccharomyces cerevisiae. In addition to the experiments with hydrolysate, the effect of the resins on selected model compounds, three phenolics (vanillin, guaiacol, and coniferyl aldehyde) and two furan aldehydes (furfural and hydroxymethyl furfural), was determined. The cation exchanger increased ethanol production, but to a lesser extent than XAD-8, which in turn was less effective than the anion exchanger. Treatment at pH 10.0 was more effective than at pH 5.5. At pH 10.0, the anion exchanger efficiently removed both anionic and uncharged inhibitors, the latter by hydrophobic interactions. The importance of hydrophobic interactions was further indicated by a substantial decrease in the concentration of model compounds, such as guaiacol and furfural, after treatment with XAD-8.

Cellulose↗

PubMed2001

A prospective comparison between external fixation and plates for treatment of midshaft nonunions of the clavicle.

BACKGROUND AND AIMS: Several surgical techniques have been used to treat clavicular nonunions. The aim with this prospective study was to compare treatment of symptomatic midshaft clavicular nonunions with either external fixation or plating. PATIENTS AND METHODS: The study included two consecutive series where the first 11 patients (8 men and 3 women) were treated with external fixation (EF) while the following 13 patients (5 men and 8 women) were treated with internal fixation using a 3.5 mm reconstruction plate (RP). All patients had autologous cancellous bone graft. After on average 8.6 years (EF) and 5.4 years (RP), respectively, an independent observer evaluated the patients. RESULTS: In the EF-group 8/11 healed within 12 months while 3/11 healed after reoperation with a reconstruction plate and new bone grafting at 6-9 months. In the RP-group 12/13 healed within six months while 1/13 healed after two additional bone transplants. There was no hardware breakage. The healing time for the RP group was significant shorter when compared with the EF group even if the fractures that did not heal after the first operation were excluded. In 4 patients the plate was removed following healing. There was no significant difference in functional outcome between groups at follow up. CONCLUSION: The reconstruction plate was a better alternative than external fixation due to faster and more reliable healing. Patients commonly considered the external frame cumbersome.

Adolescent↗

PubMed2000

Biomechanical comparison of five different atlantoaxial posterior fixation techniques.

STUDY DESIGN: Five different reconstructions of the atlantoaxial complex were biomechanically compared in vitro in a nondestructive test. OBJECTIVES: To determine whether non-bone graft-dependent one-point fixation affords stability levels equivalent to three-point reconstructions. SUMMARY OF BACKGROUND DATA: Previous investigations have demonstrated that three-point fixation, using bilateral transarticular screws in combination with posterior wiring, provide the most effective resistance to minimize motion around C1-C2. However, placement of transarticular screws is technically demanding. Posterior wiring techniques affording one-point fixation have failure rates of approximately 15%, with failure considered to be secondary to structural bone graft failures. One-point, non-bone graft-dependent fixations have not been tested. METHODS: Eight human cervical specimens, C0-C3 were loaded nondestructively. Unconstrained three-dimensional segmental motion was measured. The reconstructions tested were two one-point fixations, one two-point fixation, and two three-point fixations. RESULTS: Under axial rotation two and three-point reconstructions provided better stiffness than the one-point reconstructions (P < 0.05). During flexion-extension, higher stiffness levels were observed in one- and three-point fixations when compared with the intact spine (P < 0.05). In lateral bending no significant differences were observed among the six groups, although the trend was that reconstructions including transarticular screws provided greater stability than one-point fixations. CONCLUSION: The current findings substantiate the use of three-point fixation as the treatment of choice for C1-C2 instability. [l: atlantoaxial fixation, biomechanics, cervical spine, instability, spinal instrumentation, transarticular screws]

Aged↗

PubMed2000

Risk for gastric cancer after antibiotic prophylaxis in patients undergoing hip replacement.

Despite strong evidence of an association between Helicobacter pylori and gastric cancer, the benefit of eradicating H. pylori infection is unknown. Our aim was to test the hypothesis that exposure to high doses of antibiotics reduces risk for gastric cancer via possible eradication of H. pylori We conducted a nationwide case-control study nested in a cohort of 39,154 patients who underwent hip replacement surgery between 1965 and 1983. Such patients frequently receive prophylactic antibiotic treatment. During follow-up through 1989, we identified 189 incident cases of gastric cancer. For each case, three controls were selected from the cohort. Exposure data were abstracted from hospital records. Blood samples from a separate cohort undergoing hip replacement surgery were analyzed for anti-H. pylori IgG before and after surgery. Both long-term antibiotic treatment before surgery [odds ratio (OR), 0.3; 95% confidence interval (CI), 0.1-0.7] and prophylactic antibiotic treatment (OR, 0.7; 95% CI, 0.5-1.1) conferred a reduction in gastric cancer risk. The reduction appeared stronger after 5 years (OR, 0.6; 95% CI, 0.3-1.2) than during shorter follow-up after hip replacement (OR, 0.8; 95% CI, 0.4-1.7). There was an apparent decrease in risk with increasing body weight-adjusted doses of antibiotics (P = 0.13). However, the rate of H. pylori antibody disappearance was not strikingly higher in the cohort of patients undergoing hip replacement than in a control cohort. Our findings provide indirect support for the hypothesis that treatment with antibiotics at a relatively advanced age reduces the risk of gastric cancer.

Adult↗

PubMed2000

Bone tissue composition, dimensions and strength in female rats given an increased dietary level of vitamin A or exposed to 3,3',4, 4',5-pentachlorobiphenyl (PCB126) alone or in combination with vitamin C.

In previous studies we have described structural and functional changes in rat bone tissue caused by 3,3',4,4',5-pentachlorobiphenyl (PCB126). Some of the effects caused by PCB126 resemble those found in vitamin C-deficient rats, as well as those found in rats with a high dietary intake of vitamin A. The present investigation was designed to determine if these PCB126-induced changes could be inhibited by addition of vitamin C to the drinking water and if they could be evoked by vitamin A administration. Five groups of female rats were used in this study, which lasted for 12 weeks. Three of the groups were exposed to PCB126 (total dose 320 microgram/kg, bw), either alone or in combination with vitamin C added to the drinking water (1 and 10 g/l, respectively). One group was given feed with increased level of vitamin A (600000 U/kg pellet) and the fifth group served as controls. Using peripheral quantitative computed tomography (pQCT), it was found that PCB126 increased trabecular density and cortical thickness, but reduced the trabecular area. Furthermore, maximum torque and stiffness of the humerus during torsional testing and serum osteocalcin levels were reduced by PCB126. Of the PCB126 induced effects observed, addition of vitamin C only inhibited the reduction of serum osteocalcin. Like PCB126 vitamin A supplementation increased the inorganic content and the bone density and also reduced the trabecular area and polar moment of inertia but did not increase the cortical thickness or reduce maximum torque, stiffness or serum osteocalcin level. Apparently, the effects induced by PCB126 are not mediated either via decreased vitamin C level or increased vitamin A level.

Animals↗

PubMed2000

Change of bone tissue composition and impaired bone strength in rats exposed to 3,3',4,4',5-pentachlorobiphenyl (PCB126).

The aim of this study was to compare effects of estrogen depletion (ovariectomy) and exposure to 3,3',4,4',5-pentachlorobiphenyl (PCB126) on bone strength and bone tissue composition in the rat. Half of the rats were ovariectomized (n=20) and the remainder were sham-operated. Ten of the ovariectomized rats and ten of the sham operated were exposed to PCB126 (ip injections) for 3 months (total dose, 384 microgram/kg bodyweight), while those remaining received the vehicle. The humerus and femur were used for analysis of torsional strength and biochemical studies, respectively. Both sham-operated and ovariectomized animals showed a significantly shorter bone length, lower water content and a decreased torsional stiffness when exposed to PCB126. Sham-operated rats exposed to PCB126 had lower maximum torque when compared with sham operated controls. The PCB126-exposed rats also exhibited a significantly lower collagen concentration, but showed a higher pyridinoline concentration of cortical bone. PCB126 exposure decreased the hepatic level of vitamin A but increased vitamin A levels in serum and kidneys. Ovariectomy per se increased bone length and organic content and decreased the inorganic content significantly, but did not affect any of the tested biomechanical parameters. In conclusion, this study showed that the common environmental pollutant PCB126 impaired bone strength and altered bone composition. It is hypothesized that these effects might partly be explained by PCB-induced retinoid disturbances.

Animals↗

PubMed2000

Interaction between hammerhead ribozyme and RNA substrates measured by a surface plasmon resonance biosensor.

Dynamic interactions between hammerhead ribozymes and RNA substrates were measured using the surface plasmon resonance (SPR) technology. Two in vitro transcribed substrates (non-cleavable and cleavable) were immobilised on streptavidin-coated dextran matrices and subsequently challenged with non-related yeast tRNA or two hammerhead ribozymes, both of which had previously been shown to exhibit functional binding and cleavage of complementary target RNAs. The target-binding domain of one of the ribozymes was fully complementary to a 16-ribonucleotide stretch on the immobilised substrates, while the other ribozyme had a nine-ribonucleotide complementarity. The two ribozymes could readily be differentiated with regard to affinity. Cleavage could be measured, using the ribozyme with full target complementarity to the cleavable substrate. In contrast, the ribozyme with lower affinity lacked cleavage activity. We suggest that SPR will be useful for investigations of ribozyme-substrate interactions.

Base Pairing↗

PubMed2000

Arthroscopic lavage speeds reduction in effusion in the glenohumeral joint after primary anterior shoulder dislocation: a controlled randomized ultrasound study.

Recent studies have shown that arthroscopic lavage of the glenohumeral joint within 10 days following a primary anterior dislocation significantly lowers the recurrence rate when compared with a nonoperative regime. We hypothesize that the lavage reduces distension in the joint and thereby facilitates adaptation and healing of the soft tissue lesion. Using ultrasound, we assessed the hemarthrosis in the glenohumeral joint weekly in 16 consecutive patients after traumatic primary anterior shoulder dislocation. The patients were randomized into two groups for treatment with either arthroscopic lavage or a nonoperative regime. Except for the lavage the two groups followed an identical rehabilitation program. Transversal dorsal ultrasound of the glenohumeral joint was performed, in which the joint effusion was assessed as the distance between the humeral head and the glenoid. Prior to the lavage the two groups had a similar amount of excessive joint effusion. The effusion declined to a steady state level within 3-7 weeks. The joint effusion decreased more rapidly (33%) in the group treated with arthroscopic lavage (P = 0.02) than in the nonoperated group.

Adolescent↗

PubMed2000

Improved extraction torque of hydroxyapatite-coated pedicle screws.

Loosening of the screws is a problem in instrumentation with pedicle screws. Coating with hydroxyapatite improves the holding characteristics for metal implants, but the possible effects on the anchorage of pedicle screws have not been described. In this study, seven patients were operated on with spinal instrumentation using four stainless steel pedicle screws. Hydroxyapatite-coated screws were used in either the upper or the lower of the instrumented levels. The insertion torque was measured. In four cases the screws were removed after 10-22 months and the extraction torque was measured. The mean insertion torque was found to be significantly greater in the hydroxyapatite-coated screws (107 Ncm) than in the standard screws (76 Ncm). In three cases, the extraction torque for the hydroxyapatite-coated screws exceeded the range for the torque wrench (600 Ncm), while the conventional screws were loose (< 5 Ncm). In one case, the extraction torque was 475 and 550 Ncm for the coated screws, and 5 and 25 Ncm for the conventional screws. The difference in extraction torque was significant. Hydroxyapatite coating was shown to have improved the purchase of pedicle screws very effectively. By using fully coated screws, as in the present study, extraction was extremely difficult compared to extraction of conventional stainless steel screws, which were regularly loose. By reducing the area of the screws that is coated, it may be possible to achieve an enhanced purchase while extraction will be easier when compared to fully coated screws.

Adolescent↗