[Treatment of symptomatic degenerative lumbar spinal stenosis by a percutaneous stand-alone lumbar interspinous implant. Preliminary experience with the Aperius device]. / Traitement de la sténose lombaire dégénérative symptomatique par mise en place percutanée d'implant interépineux. Expérience préliminaire avec l'implant Aperius.

BACKGROUND AND PURPOSE: Surgery for degenerative spinal stenosis classically involves decompression by laminectomy or foraminotomy. The use of interspinous process devices has been described for these indications in recent years. This study evaluates the efficacy and morbidity of a percutaneous interspinous device to define whether this technique would be a suitable alternative to classical surgery. METHOD: Twenty-two patients with degenerative lumbar spinal stenosis were studied prospectively. Pre- and postoperative symptoms were assessed using the Visual Analogic Score (VAS), the Zurich Claudication Questionnaire (ZCQ), physical activity, and patient satisfaction. The implant was positioned under biplanar fluoroscopic control after progressive distraction of the interspinous space using trocars. The patients were reviewed after 7 days, 6 weeks, and 6 months. RESULTS: All patients showed improved gait perimeter: 90 % could walk more than 1000 m 6 months after surgery, whereas only 50 % could walk this distance preoperatively. The mean symptom severity scores of 2.71 and physical activity scores of 2.38 improved to 1.87 (p=0.0003) and 1.53 (p<0.0001), respectively, after 6 months. The VAS decreased 3.5 points (p=0.0008) 6 months after surgery for leg pain. Ninety-one percent of the patients declared they were satisfied with the operation. CONCLUSION: The Aperius stand-alone and percutaneous interspinous device proved to be effective and safe in treating symptomatic lumbar spinal stenosis. This could be a good alternative to classic decompression surgery, but long-term follow-up studies are needed as well as subgroup analysis to define which patients could benefit from this technique.

[Balloon kyphoplasty for treatment of vertebral osteoporotic compression fractures]. / Traitement des fractures vertébrales ostéoporotiques avec kyphoplastie par ballonnet.

Kyphoplasty, the newest of the tools treating vertebral osteoporotic compression fractures (VOCF) is the evolution of vertebroplasty, allowing not only pain control and strengthening of the fractured vertebra, but also offering the possibility to restore vertebral height with a lower risk of complications. We present our series of 41 consecutive VOCF treated by kyphoplasty in 30 patients between October 2003 and March 2006. Systematic spinal X rays and CT scan have be performed, occasionally followed by bone scintigraphy or spinal MRI. The mean preoperative duration of symptoms before surgery was 52 days. Pain control after the operation was considered excellent in all cases and all patients were mobilized the day after surgery. Kyphoplasty allowed a 50% restoration of vertebral height in 66% of the treated vertebras. The results were better when surgery was performed within the first three months after the fracture. The mean vertebral deformity correction by comparison of the pre- and postoperative Cobb angles was 9.7 degrees. One patient showed cement leakage in the spinal canal without neurological deterioration. The mean postoperative stay was 2.5 days. We found kyphoplasty to be a safe technique allowing immediate pain control after VOCF, with minimal risks of cement leakage or pulmonary embolism. Vertebral height and deformity correction are best achieved with early surgery, but pain control is always excellent even with a delayed procedure.

Nature of perceptual encoding of hand positions according to subjects' perceptuomotor expertise.

We investigated whether the nature of the perceptual information encoded for the memorization of successive hand positions varied according to subjects' perceptuomotor expertise. The experimental task used perceptual conflicts, induced by prisms, between visual and proprioceptive afferences during the encoding of various static hand positions. Control subjects were compared with skilled fencers, whose expertise was derived from the optimization. required and developed with practice, of the perceptuomotor processes involved in movement control. The analysis of spatial errors observed in a remembered target location test indicated that control subjects were dependent on the use of static visual information for the encoding of hand positions, whereas skilled fencers were not. Results are discussed in the light of the role of expertise in sensory integration and perceptual dominance.

Comparison of the pharmacokinetic profiles of three low molecular mass heparins--dalteparin, enoxaparin and nadroparin--administered subcutaneously in healthy volunteers (doses for prevention of thromboembolism).

The present trial was designed to comparatively investigate the pharmacokinetic profile and evaluate the apparent bioavailability pattern of three already marketed low molecular mass heparins (LMMHs): dalteparin (Fragmin), nadroparin (Fraxiparin), and enoxaparin (Lovenox) given by subcutaneous route. The study was carried out in 20 healthy young volunteers given, according to a cross over design, a single subcutaneous injection of the doses recommended for the prophylaxis of deep vein thrombosis (commercial preparations, prefilled syringes): dalteparin 2,500 IU (= 2,500 IU anti-Xa), nadroparin 7,500 ICU (= 3,075 IU anti-Xa), enoxaparin 20 mg (= 2,000 IU anti-Xa) and enoxaparin 40 mg (= 4,000 IU anti-Xa). Of the markers used, activated partial thromboplastin time (APTT), thrombin clotting time (TCT), Heptest, anti-thrombin (aIIa) activity and anti-Xa (aXa) activity, the most pertinent parameter (from a biodynamic viewpoint) is plasma aXa activity. We demonstrated that dalteparin, nadroparin and enoxaparin exhibit statistically significantly different pharmacokinetic and overall disposition patterns. Normalized to the same injected dose (1,000 IU aXa), the relative actual amount of plasma anti-Xa activity generated by enoxaparin is 1.48 times greater (p < 0.001) than that of nadroparin and 2.28 times greater (p < 0.001) than that of dalteparin while the plasma amount induced by nadroparin is 1.54 times greater (p < 0.001) than that of dalteparin. The apparent total body clearance of enoxaparin doses (CL/F = 16.7 +/- 5.5 and 13.8 +/- 3.2 ml/min) is significantly smaller than those of nadroparin (CL/F = 21.4 +/- 7.0 ml/min; p < 0.01) and dalteparin (CL/F = 33.3 +/- 11.8 ml/min; p < 0.001) while dalteparin apparent clearance is about 1.5-fold greater (p < 0.001) than that of nadroparin. These LMMHs also differ by their renal excretion pattern: more fragments exhibiting an anti-Xa activity are recovered in urine following enoxaparin doses (6.4 and 8.7% of the dose, respectively) than following nadroparin (3.9%) and dalteparin (3.4%) injection. These differences in the disposition profiles explain why the apparent elimination half life t1/2 values of the LMMHs compared here are different: dalteparin: 2.8 h; nadroparin: 3.7 h; and enoxaparin: 4.1 h. Whether or not these differences may contribute to explain the different safety/efficacy balance of each of these antithrombotic medications remains to be discussed and needs further studies.

Comparative effects of enoxaparin and unfractionated heparin in healthy volunteers on prothrombin consumption in whole blood during coagulation, and release of tissue factor pathway inhibitor.

In a randomized crossover study twelve healthy male volunteers (23.5 +/- of 4.8 years, 73.0 +/- 6.4 kg, 180.8 +/- 5.7 cm) received one subcutaneous injection of either enoxaparin (EN) at 40 mg or 1 mg kg-1, or unfractionated heparin (UH) at 5,000 IU at one week intervals. Area under curves (AUC) of Anti-Xa and Anti-IIa activities correlated with EN dose. The relative effectiveness of EN versus UH 5,000 U as assessed by AUC ratio (EN/UH) was 7 and 15 for Anti-Xa activity, 1.3 and 3.1 for Anti-IIa activity after sc injection of EN 40 mg (4,000 Anti-Xa IU and 1,200 Anti-IIa U) and 1 mg kg-1 (7,300 +/- 640 Anti-Xa IU and 2,190 +/- 290 Anti-IIa IU) respectively. In volunteers receiving EN, a dose dependent inhibition of thrombin generation rate in platelet depleted plasma (PDP), measured with a new and simple chromogenic thrombin generation assay, was observed when compared with baseline values. Similarly, intrinsic prothrombin activation in whole blood, evidenced by measuring residual factor II in serum 2 hours after clotting (prothrombin consumption test: PC), was inhibited in a dose dependent manner. In UH treated volunteers, although the inhibition of thrombin generation rate in PDP was similar to that observed with EN 40 mg, prothrombin consumption in whole blood was not significantly modified. Tissue factor pathway inhibitor (TFPI) activity release was increased similarly for UH and EN 40 (1.4 fold increase above baseline values) and 1.9 fold for the higher dose of EN. The discrepancy between prothrombin consumption in whole blood and inhibition of thrombin generation rate in PDP in the UH and not in the EN group strongly suggests that UH and not EN is influenced by the presence of a platelet component. This could be formed during thrombin induced platelet activation. Platelet factor 4 is a possible candidate. Another hypothesis involves the role of TFPI-UH complex anticoagulant activity which might be inhibited more during whole blood coagulation than the TFPI-EN complex.

Highly sensitive and specific radioimmunoassays for dihydroergotoxine components in plasma.

The development of three analogous radioimmunoassay (RIA) procedures for dihydroergotoxine components is described. The antisera were produced by immunization of rabbits with immunogens obtained by coupling egg albumin to the indole group of each ergot alkaloid derivative. In each radioimmunoassay, antibodies do not cross-react more than 5% with the two other derivatives. The tracers iodinated with iodine 125 were prepared by the chloramine-T method and purified by thin layer chromatography. Both antibody affinity and high specific radioactivity of tracers allow a sensitive assay (detection limit less than 20 pg/ml) in human plasma. After high performance liquid chromatography of extracted plasma, immunoreactive materials other than those corresponding to the elution of the three dihydroergotoxine components were not detected. Two preliminary pharmacokinetic profiles obtained in dog and human for each derivative are shown.