Biomedical subjects

G Kapetanos

Publications and source records attributed to G Kapetanos.

12 recordsLinked to original sources

PubMed2006

The role of the dorsal vertebral cortex in the stability of transpedicular screws. A biomechanical study in human cadaveric vertebrae.

The aim of this biomechanical study was to investigate the role of the dorsal vertebral cortex in transpedicular screw fixation. Moss transpedicular screws were introduced into both pedicles of each vertebra in 25 human cadaver vertebrae. The dorsal vertebral cortex and subcortical bone corresponding to the entrance site of the screw were removed on one side and preserved on the other. Biomechanical testing showed that the mean peak pull-out strength for the inserted screws, following removal of the dorsal cortex, was 956.16 N. If the dorsal cortex was preserved, the mean peak pullout strength was 1295.64 N. The mean increase was 339.48 N (26.13%; p = 0.033). The bone mineral density correlated positively with peak pull-out strength. Preservation of the dorsal vertebral cortex at the site of insertion of the screw offers a significant increase in peak pull-out strength. This may result from engagement by the final screw threads in the denser bone of the dorsal cortex and the underlying subcortical area. Every effort should be made to preserve the dorsal vertebral cortex during insertion of transpedicular screws.

Adolescent↗

PubMed2004

Loading simulation of lumbar spine vertebrae during a compression test using the finite elements method and trabecular bone strength properties, determined by means of nanoindentations.

The mechanical strength properties of lumbar spine vertebrae are of great importance in a wide range of applications. Herein, through nanoindentations and appropriate evaluation of the corresponding results, trabecular bone struts stress-strain characteristics can be determined. In the frame of the present paper, an L2 fresh cadaveric vertebra, from which posterior elements were removed, was subjected to compression. With the aid of developed finite elements method based algorithms, the cortical shell and the cancellous core bulk elasticity moduli and stresses were determined, whereas the tested vertebra geometrical model used in these algorithms was considered as having a compound structure, consisting of the cancellous bone surrounded by the cortical shell. Moreover nanoindentations were conducted and an appropriate evaluation method of the obtained results was applied to extract stress-strain curves of individual lumbar spine vertebra trabecular bone struts. These data were used in the mathematical description of the vertebrae compression test. The vertebral cancellous bone structure was simulated by a beam elements network, possessing an equivalent porosity and different stiffnesses in vertical and horizontal direction. Thus, the measured course of the compression load versus the occurring specimen deformation was verified.

Algorithms↗

PubMed2002

Is the labyrinthine dysfunction a causative factor in idiopathic scoliosis?

The cause of idiopathic scoliosis remains unknown, although research has possibly eliminated some hypothetical causes. Recent reports associating scoliosis convexity with equilibrium control central processing and motor lateralization have suggested that idiopathic scoliosis is connected causally with the motor cortex. In order to analyze these factors a study of labyrinthine function was carried out. This study included seventeen female patients 12 to 14 years old (mean age= 13.36y) with right thoracic idiopathic scoliosis and twelve normal control females 12 to 14 years old (mean age =13.1y). An electro-nystagmographic study of labyrinthine function (potential nystagmus) was performed in all the patients of the study with caloric tests. The nystagmus was recorded with the electronystagmographic technique (ENG) using Hartmann device. We evaluate these parameters: Slow phase velocity (SPV), Total amplitude (Tamp), Frequency of nystagmus (Freq). No children of the study presented spontaneous nystagmus. No correlation was found between the convexity of the curvature and the direction of nystagmus in posture tests. There were no significant differences between left- and right- beating nystagmus. The results are discussed with special reference to aetiology in idiopathic scoliosis.

Adolescent↗

PubMed2002

Is the central nervous system a causative factor in idiopathic scoliosis?

The present study was designed to investigate the involvement of central nervous system (CNS) in the pathogenesis of idiopathic scoliosis. Seventeen female patients with right thoracic idiopathic scoliosis (mean age = 13.36y) and ten normal controls (mean age =12.6y) entered the study. Magnetic stimulation of the brain was performed. Threshold measurements included upper (UT) and lower threshold (LT). Cortical latencies of MEPs during muscle activation were also measured.

Adolescent↗

PubMed2001

Comparative study between Wilson and Mitchell metatarsal osteotomies for the treatment of hallux valgus in adults.

Although Mitchell osteotomy and Wilson osteotomy are two popular methods for the treatment of hallux valgus, there are no studies directly comparing their results. Fifty-six patients (73 feet) who underwent a Wilson osteotomy and 30 patients (34 feet) who had a Mitchell osteotomy were followed for a mean period of 33.7 and 38.9 months, respectively. The results were comparable in terms of hallux valgus angle correction and first intermetatarsal angle correction, although symptomatic improvement was higher in the Mitchell group. Moreover, the incidence of postoperative metatarsalgia was significantly lower in the Mitchell group as compared to the Wilson group (11.8% vs 32.9%), while less time was required for the patients who underwent Mitchell osteotomy to return to work or normal activities postoperatively. The difference in symptomatic improvement, incidence of postoperative metatarsalgia and rehabilitation time was even more clearly in favor of the Mitchell group in patients over 55. The increased stability at the osteotomy site offered by the Mitchell osteotomy compared to Wilson osteotomy could be the reason why patients had a lower incidence of postoperative metatarsalgia and returned to their normal activities faster, thus giving a higher satisfaction rate.

Adolescent↗

PubMed1997

Replacement of deficient acetabulum using Burch-Schneider cages. 22 patients followed for 2-10 years.

The absence of good bone stock with massive acetabular deficiency has been a major problem in both revision hip arthroplasty and in primary arthroplasty for congenital dislocation of the hip (CDH). 22 patients (24 hips; 21 revision and 3 primary replacements: mean age 58 years) with substantial bone loss underwent acetabular reinforcement with Burch-Schneider cages. Classification of acetabular deficiency was made according to the AAOS system. The surgical procedure involved preparation of acetabulum, filling the defect with bone autografts, placement of the cage with its flanges, fixation with screws on the lateral wall only and placement of a cement and plastic cup. Radiographic loosening with breakage of the screws was observed in only 1 patient. After a mean follow-up of 8 (2-10) years, good stability was achieved in all patients and no mechanical failure was observed. Satisfactory results were observed in all but one of the cases, indicating that effective support of the acetabulum can be achieved using Burch-Schneider cages.

Acetabulum↗

PubMed1997

A double blind study of intranasal calcitonin for established postmenopausal osteoporosis.

Intranasal administration of calcitonin (CT) avoids the problem of daily injections in the long-term treatment of osteoporosis. We examined the effect of nasal CT on bone and calcium metabolism in postmenopausal osteoporotic women in a double-blind design. 46 women, 55-75 years in age, and in good general health were included in the study. All patients were at least 6 months postmenopausal and had at least 1 vertebra fracture, bone mineral density (BMD; g/cm2) lower than 0.850 in L2-L4 in a dual energy x-ray absorptiometry (DEXA) AP view of the spine and showed biochemical indications of a fast bone loser. The patients were randomly treated with either nasal CT 200 IU per day, divided in 2 doses (n = 23) or placebo (n = 23) for 1 year. All participants received a daily calcium supplement of 1 g. Clinical and laboratory follow-up every 3 and 6 months, respectively, assessed the clinical picture, bone mineral density measured by DEXA, serum alkaline phosphatase, fasting urinary calcium, creatinine and hydroxyproline. BMD was measured in 4 sites (spine and cervical, Ward's triangle, and the trochanteric area of the hip) before treatment and after 6 and 12 months of treatment. In the placebo group, mean values at the 4 sites showed a 3.3% decrease in BMD after 6 months and a 5.0% decrease after 12 months. In contrast, the calcitonin group showed a 6.8% increase in BMD after 6 months and 11% increase after 12 months (p < or = 0.005). No patient experienced side-effects and there were no complaints of local irritation. We conclude that nasal administration of 200 IU calcitonin daily, continuously for 1 year had a positive effect on the bone mass density in osteoporotic postmenopausal women.

Administration, Intranasal↗

PubMed1997

Segmental spinal correction of idiopathic scoliosis. Luque rods and Hartshill rectangle in 30 patients followed for 2-6 years.

30 patients with idiopathic scoliosis were treated by posterior spinal arthrodesis using the Luque (8 patients) and Hartshill (22 patients) rodding systems with sublaminar segmental wiring. Patients were followed for 2 to 6 years. In most cases, postoperative correction exceeded safety correction limits (lateral bending film plus 10 degrees). Final correction was 55%, while derotation was not significant (average 3 degrees). No neurological deficit was noted. Postoperative bracing was not applied and there was 1 patient with broken rods (Luque trolley system without fusion) and 1 patient with broken wires in 4 segments. Allogenic blood transfusion was avoided in 19 patients by preoperative donation of autologous blood, in combination with salvage of intraoperative shed blood. We found segmental spinal wiring with either rods or rectangles to be a safe method for correction of scoliosis in experienced hands. It offered satisfactory stability and fusion rate with no need for external support.

Adolescent↗

PubMed1993

Chronic idiopathic hyperphosphatasemia. Case report.

Chronic idiopathic hyperphosphatasemia, or juvenile Paget disease is a very rare syndrome that is characterized by fragile bones, bowing deformities, shortness of stature, large head, premature loss of teeth, radiographic evidence of expanded osteoporotic long bones with coarse trabeculations, and widened bones of the skull. Increased levels of serum alkaline phosphatase and increased levels of urinary total hydroxyproline are notable. We present a case of juvenile Paget disease that was associated with a history of precocious puberty. The patient had odontogenic osteomyelitis of the mandible that was treated by drainage, surgical debridement and antibiotic therapy.

Absorptiometry, Photon↗

PubMed1991

Effect on atrial natriuretic peptide by bracing in scoliosis. Boston brace removal studied in 10 cases.

The immediate effect of Boston brace removal on plasma levels of atrial natriuretic peptide and arginine vasopressin was studied in 10 patients with idiopathic scoliosis ranging in age from 12 to 16 years. Blood samples were drawn via the antecubital vein in the supine position with the brace on and 10 min after brace removal. ANP and AVP plasma levels were measured by radioimmunoassay. Although no differences were found in the plasma concentrations of arginine vasopressin while on and after removal of the brace, atrial natriuretic peptide levels showed an approximately 80 percent increase 10 min after brace removal, presumably due to central volume redistribution. The changes of atrial natriuretic peptide plasma levels observed may be related to previously reported changes of the glomerular filtration rate and urinary sodium excretion following brace removal.

Adolescent↗

PubMed1983

Osteoid osteoma of the capitate.

Two cases of osteoid osteoma of the capitate bone are described. This lesion is rare in the capitate: only ten cases have been reported. Noctural pain was the most significant clinical feature, with characteristic relief by aspirin. The findings on routine x-rays, although not very typical, were sufficient to establish the diagnosis and to make the use of tomograms, bone scans and angiograms unnecessary. Resection "en bloc" through a dorsal approach led to complete cure.

Adolescent↗

PubMed1982

The effect of the local corticosteroids on the healing and biomechanical properties of the partially injured tendon.

The effects of repeated small doses of local corticosteroid into tendons on healing, formation of adhesions, and the biomechanical properties were investigated in 20 New Zealand rabbits. There were significant decreases in tendon weight (13%), amount of adhesions (66%), load to failure (29.8%), and energy to failure (67.16%) in the cortisone group compared to the saline group. There were no significant differences in healing and strain-elongation of the tendons in the two groups.

Achilles Tendon↗