Biomedical subjects

J B Volpon

Publications and source records attributed to J B Volpon.

9 recordsLinked to original sources

PubMed1997

Mechanical testing of the tension band wire fixation in the proximal femur.

The mechanical stability of proximal femoral osteotomies fixed by the tension band wire technique was studied in flexion-compression and torsion tests. The fixation consisted in crossing the section with two Kirschner wires and with a wire cerclage applied to the tension surface. The study was conducted in three steps. First, cyclinders of wood were cut either transversely or at 30 degrees of inclination in relation to the long axis of the specimen, and fixed with two Kirschner wires and a wire cerclage. We concluded that the inclination of the plane of section significantly increased the stability of fixation. No significant difference was observed when oblique sections were made in the reverse orientation. Second, 30 degrees subtrochanteric varus osteotomies were performed in dog femurs, so that the section plane was transverse in one group and oblique in another, after closing the osteotomy. In both groups the fixation was achieved by two Kirschner wires that crossed the osteotomy and a wire cerclage placed on the lateral cortex (tension surface). We concluded that inclination of the osteotomy plane increased the stability of osteosynthesis in bone specimens, as already seen with the wood pieces. Third, the stability of tension band wire fixation was compared with that provided by the AO/ASIF paediatric angled plate. Varus osteotomies (30 degrees) were created at the subtrochanteric level of paired dog femurs. On one side, the femur was fixed with Kirschner wires and a wire cerclage as described previously. For the other femur, the osteotomy was fixed with the angled plate. We found that both types of fixation presented the same stability in flexion-compression tests. However, under torsion the tension band wire fixation was 30%-50% less stable than the plate fixation.

Animals↗

PubMed1997

Idiopathic genu valgum treated by epiphyseodesis in adolescence.

Twenty-three patients (13 boys and 10 girls) with the adolescent type of genu valgum were treated by temporary medial epiphyseodesis of both distal femurs with Blount staples (46 knees); 5 also underwent stapling of the proximal tibia. Evaluation before the operation and during the follow up was based on growth charts, photographs and measurement of the intermalleolar distance. The indication for operation was increasing genu valgum with 10 cm or more of intermalleolar separation; the median distance before operation was 13 cm for boys and 12 cm for girls. The staples were removed after a median time of 11 months. At skeletal maturity the median intermalleolar separation was 3 cm for boys and 2 cm for girls. The median frontal angle before operation was 14 degrees for boys and 6 degrees at follow up, the corresponding figures for girls being 14 degrees and 4 degrees. In 2 cases the deformity recurred because the staples were removed too early. In another case a bony bridge formed after the staple was removed and a varus deformity developed; the bridge was resected and the knees became valgus again, but 1 cm of shortening remained on one side. There were no other complications.

Adolescent↗

PubMed1994

Nonunion using a canine model.

The investigation involved a search for a model of atrophic nonunion. Fifty-two mature, adult, mongrel dogs were used to study the repair after creating a 0.5-cm bone defect in the mid-diaphysis of the radius. In addition, a 2-cm wide strip of periosteum was circumferentially resected from each osteotomy extremity. No immobilization was used thereafter. The reparative process was assessed by X-rays, histology, vascular injection, and scintigraphy. The dogs we distributed into three groups according to the time of follow-up (1, 3, and 6 months). Two kinds of repair were recognized after 3 months and were well-established after 6 months: disturbed healing with much callus (54%) and disturbed healing with absent or scanty callus (46%). In the first instance, the periosteum had regenerated and produced the external callus. The bone ends were capped with fibrocartilage; the vascularization around the defect was increased and displayed a well-defined vascular picture. In the healing pattern with absent external callus (atrophic nonunion), the bone defect was enlarged and filled with fibrous tissue, but there was no deficient vascularization in and around the osteotomy. Radioactivity counting showed an increased uptake around the osteotomy site in both types of repair, which persisted over time but was higher in the 1-month group. It was concluded that the present model yields a consistent pattern of a disturbed reparative process that mimics human cases of atrophic or hypertrophic nonunion. The differences between the two kinds of repair seemed to be related to the periosteal capacity of regeneration.

Animals↗

PubMed1993

Experimental physeal fracture-separations treated with rigid internal fixation.

Salter-Harris Type-III and Type-IV epiphyseal injuries were created in the distal aspect of the femur in growing rabbits, and the healing process was analyzed both in the absence of any treatment and after treatment with anatomical reduction and fixation with compression with use of a cortical screw. A sham operation was performed on the left knee, to create a control group. Untreated Type-III injuries led to an angular deformity of the femur that became more severe with time. In the group that had an untreated Type-IV injury, a step-off developed on the articular surface and increased with time. Early vascular anastomoses between the epiphysis and the metaphysis preceded the formation of osseous bridges in these lesions. The healing process in the animals that were treated with anatomical reduction and rigid internal fixation occurred without the formation of osseous callus, and no marked abnormalities were discernible in the physis.

Animals↗

PubMed1988

Traumatic separation of epiphyses. An experimental study in rats.

Four types of physeal fracture-separations, defined by the Salter-Harris classification, were created experimentally in the proximal physis of the right tibia of immature rats. The four types are: Type I, pure epiphyseal separation; Type II, separation of the epiphysis with a metaphyseal fracture; Type III, partial epiphyseal separation with a vertical fracture of the epiphysis; and Type IV, vertical epiphyseal and metaphyseal fractures. A sham operation performed on the left tibia served as the control. The animals were killed at various intervals up to 25 days after the operation. The findings were assessed by roentgenographic, histologic, and vessel injection methods. For Types I and II morphometric analyses were also performed. The influence of various types of lesions on the growth rate and the healing process was documented. For Types I and II lesions there was a transitory growth arrest and an increased thickening of the zone of hypertrophic cells. The alterations regressed after Day 15, and by day 25, a nearly normal plate was seen. For Type III lesions an angular deformity of the tibia occurred that increased with time. For Type IV lesions, a step-off developed on the articular surface that became more severe with time. Early vascular anastomoses between the epiphysis and the metaphysis led to the formation of bone bridges in Type III and Type IV lesions.

Animals↗

PubMed1982

The use of decalcified granulated homologous cortical bone matrix in the correction of diaphyseal bone defect. An experimental study in rabbits.

In order to investigate an alternative way to correct diaphysial bone defects, granulated decalcified homologous cortical bone was used as a graft. Because of the suitable anatomic arrangement, the forearm of rabbits was chosen as an experimental model of bone defect. A 2 cm long bone cylinder was removed from the diaphysis of both radii preserving the periosteum. The artificial bone defect was filled with granular decalcified bone on the right side. The left side was used as control and kept empty or filled with undecalcified granular bone. The 18 animals were sacrificed in batches, 3,6, and 9 weeks after the operation. New bone formation was followed by X-rays, routine histology and incorporation of calcein blue, xylenol orange and tetracycline. In the decalcified granular bone grafts new bone formation was already detected at the first week and 9 weeks after the graft operation there was a well developed cylindric ossicle, in 89% of the cases. In some cases a medullary canal was present. No bone formation was found neither in the empty defects nor in the ones filled with undecalcified granular bone grafts.

Animals↗

PubMedDate not supplied

Footprint analysis during the growth period.

Static footprints were obtained from 672 healthy white subjects ranging in age from newborn to 15 years. The length of the footprint was measured and the medial longitudinal arch was evaluated. The findings showed that the feet grew most rapidly up to 3 years of age. From age 3 onward, the feet maintained an almost constant growth rate, which was the same for both sexes until age 12 years, when girls' feet stopped growing, but boys' feet exhibited further growth. From birth up to 2 years of age, there was a higher incidence of flat feet. Rapid progression of plantar arch development was observed between 2 and 6 years of age.

Adolescent↗

PubMedDate not supplied

Experimental nonunion in dogs.

A consistently reproducible nonunion was produced in mongrel dogs by resecting 3 mm of bone and 1 cm of periosteum at the diaphyseal-metaphyseal junction in the radius. Bone wax was used to seal the cut surfaces. No external or internal immobilization was necessary. The animals were sacrificed at various intervals up to one year after the operation. In one subgroup the events were assessed by radiologic and histologic techniques, and in another the limb was examined by microvascular and bone scintigraphic methods. Nonunion of the hypertrophic type occurred in 85% of cases and of the oligotrophic type in 15% of cases. Pseudarthrosis (with persistent mobility, neocapsule, synovial-like fluid, and well-differentiated cartilaginous tissue capping the bone ends) was established by the 28th week.

Animals↗

PubMedDate not supplied

Inherited risk factors for thrombophilia among children with Legg-Calvé-Perthes disease.

An inherited tendency to hypercoagulability has been suggested as a cause of vascular thrombosis resulting in Legg-Calvé-Perthes disease (LCPD). Here we carried out an investigation of the most common inherited risk factors for hypercoagulability including the mutation in the factor V gene (factor V Leiden), the transition 20.210G-->A in the prothrombin gene, and also the homozygosity for the 677C-->T transition in the methylenetetrahydrofolate reductase gene (MTHFR). The investigation was carried out among 61 Brazilian children with LCPD, who were compared with 296 individuals from the general population. The prevalence of the factor V Leiden mutation was higher in LCPD patients than in the controls (4.9 vs. 0.7%; p = 0.03). However, no patient had the prothrombin gene variant, and no difference was found between patients and controls when homozygosity for MTHFR-T (3.2 vs. 2.6%: p = 0.64) was determined. These data suggest that in our population, the heterozygosity for factor V Leiden was the only inherited risk factor associated with the development of LCPD.

Adolescent↗