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Biomedical subjects

P Y Zambelli

Publications and source records attributed to P Y Zambelli.

11 recordsLinked to original sources
PubMed2006

[Gait disorders and lower leg deformities in children].

Gait disorders and lower legs deformities in children are frequent causes of parental concern and of medical advice. These deformities should be analysed systematically as well as their consequences for daily activities. We should define precisely type, localisation and importance of the deformity: femoral or tibial torsion, knock knees, bow legs. The evaluation should always be done according to age of the child because these deformities are most often a step toward adult morphotype. Sometimes they could be the manifestation of some generalised or localised pathology that should be investigated and treated. Nevertheless patience and explanations, regular follow-up allow to reassure the parents. There is in the great majority of case no place for any conservatrice and especially surgical treatment for theses disorders spontaneously healing in 95% of cases.

Child↗
PubMed2005

How plate positioning impacts the biomechanics of the open wedge tibial osteotomy; a finite element analysis.

A numerical model of the medial open wedge tibial osteotomy based on the finite element method was developed. Two plate positions were tested numerically. In a configuration, (a), the plate was fixed in a medial position and (b) in an anteromedial position. The simulation took into account soft tissues preload, muscular tonus and maximal gait load.The maximal stresses observed in the four structural elements (bone, plate, wedge, screws) of an osteotomy with plate in medial position were substantially higher (1.13-2.8 times more) than those observed in osteotomy with an anteromedial plate configuration. An important increase (1.71 times more) of the relative micromotions between the wedge and the bone was also observed. In order to avoid formation of fibrous tissue at the bone wedge interface, the osteotomy should be loaded under 18.8% (approximately 50 kg) of the normal gait load until the osteotomy interfaces union is achieved.

Arthroplasty, Replacement, Knee↗
PubMed2004

Peri-implant bone remodeling after total hip replacement combined with systemic alendronate treatment: a finite element analysis.

In order to decrease the peri-implant bone loss during the life-time of the implant, oral use of anti-osteoporosis drugs (like bisphosphonates) has been suggested. In this study, bone remodeling parameters identified from clinical trials of alendronate were used to simulate the effect of those drugs used after total hip arthroplasty on the peri-implant bone density. Results of the simulation show that the oral administrated drugs increase bone density around the implant and decreases, at the same time, the micromovements between the implant and the surrounding bone tissue. Incorporation of drug effect in numerical studies of bone remodeling is a promising tool especially to predetermine safe bisphosphonate doses that could be used with orthopedic implants.

Administration, Oral↗
PubMed1999

Simplified 3D-evaluation of periacetabular osteotomy.

Reorientation osteotomies are widely used for the treatment of residual dysplasia of the hip. Preoperative planning is mandatory, and 3D-evaluation is of utmost importance for precise definition of direction and magnitude of displacement of the acetabulum. Instead of a 3D-CT scan reconstruction which needs multiple slices, we developed a 3D-reconstruction from a single AP pelvic view. This method is applicable if we accept that the femoral head and acetabulum are quite spherical. Appropriate software and a PC are used for this reconstruction that we compared with 3D CT-scan reconstruction and pelvic anatomical preparations. Twenty-two patients, 17 female, 5 male, with hip dysplasia, were treated by periacetabular osteotomy according to Ganz. The mean age was 27 years (14-40 years); the mean follow-up, 4.8 years (2-7 years). Four patients were treated conservatively in infancy for DDH, one patient had snapping hips associated with hip dysplasia, and two patients had slight sequellae of cerebral palsy. All patients were symptomatic mainly during daily activities or sports. The clinical evaluation was done using the Charnley scoring system. The Charnley score for pain improved from 3.6 (2-3.5) to 5.8 (5-6) at follow-up. No restriction of mobility or of walking capacity was observed after operation. The computer-assisted method also permits appreciation of the evolution of classical coxometry; i.e. Wiberg and Lequesne angles. The improvement after Ganz osteotomy was respectively 141% and 161% for Wiberg and Lequesne angles without any posterior uncoverage. The 3D-evaluation showed an improvement of 28% of the vertical projection area of the acetabulum on the femoral head. The anterolateral coverage improved from 20.3 to 50.1%. The Ganz osteotomy is really a 3D-reorientation osteotomy. With our simplified method it is possible to predict and control the amount of displacement to be done. However, we have to keep in mind that the articular cartilage is a limited crescent in the acetabulum; this method cannot replicate exactly the form and shape of articular cartilage. At this time it allows us to better control the amount of displacement during operation to avoid too large a displacement or lateralization.

Acetabulum↗
PubMed1997

Gentamicin-loaded hydraulic calcium phosphate bone cement as antibiotic delivery system.

A hydraulic calcium phosphate cement made of beta-tricalcium phosphate [beta-Ca3(PO4)2], monocalcium phosphate monohydrate [Ca(H2PO4)2-H2O], and water was used as a delivery system for the antibiotic gentamicin sulfate (GS). GS, added as powder or as aqueous solution, was very beneficial to the physicochemical properties of the cement. The setting time increased from 2 to 4.5 min with 3% (w/w) GS and then slowly decreased to 3.75 min with 16% (w/w) GS. The tensile strength increased from 0.4 to 1.6 MPa with 16% (w/w) GS. These effects were attributed to the presence of sulfate ions in GS. The release of GS from the cement was measured in a pH 7.4 phosphate-buffered saline solution at 37 degrees C by USP paddle method. Factors such as cement porosity, GS content and presence of sulfate ions or polymeric additives were investigated. The amount of GS released was roughly proportional to the square root of time up to approximately 50% release. Afterwards, the release rate markedly slowed down to zero. In all but two cement formulations, the total dose of GS was released within 7 days, indicating that no irreversible binding occurred between the cement paste and the antibiotic. When small amounts of hydroxypropylcellulose or poly(acrylic acid) were added to the cement, the maximum fraction released was a few percent lower than the total GS dose, suggesting some binding between the polymer and GS. The GS release rate was strongly influenced by the presence of sulfate ions in the cement paste and by the cement porosity. The higher the sulfate ion content of the cement paste, the lowe the GS release rate. This influence was attributed to the finer cement micro-structure induced by the presence of sulfate ions. Furthermore, when the initial cement porosity was increased from 38 to 69%, the release rate almost tripled (0.16 to 0.45 h-1/2). Finally, the biological activity of GS in the cement was maintained, as measured by assaying the release medium.

Anti-Bacterial Agents↗
PubMed1996

[Knee joint endoprostheses].

The story of the total knee arthroplasty begins in the last century. But in 1971, Gunston shows the way of the modern knee arthroplasty and creates the concept of unconstrained arthroplasty. The indication of the total knee arthroplasty should be precise and rigorous. It's not possible to describe all the situations, where a total knee arthroplasty is indicated or not, but the clinical signs could be summarized in pain, stiffness, deformation with or without instability. We observed 10% of postoperative complications; most of them are secondary, but the infections and loosening remain the principal problem in 2% and in 5% of cases, respectively. If the results are now quite the same to those of total hip arthroscopy by survivorship analysis, the indication and the choice of the total knee prosthesis should be passed on a reflection, where the clinical and functional evaluation are the most important.

Aged↗
PubMed1995

[Clinical evaluation of total knee prosthesis: comparative analysis of scores].

PURPOSE OF THE STUDY: Numerous scoring systems have been described for the evaluation of total knee arthroplasty. The aim of this study was to analyze the reality of the results and the differences between clinical evaluation scores. MATERIAL AND METHOD: We calculated the mean overall scores (Hungerford, Laskin, Hospital Special Surgery and Mansat) in a series of 89 PCA total knee arthroplasties with a mean follow-up of 4.5 years. We compared postoperative score values considered as borderline between poor and good results with survival curves. RESULTS: The mean values of the postoperative scores were very similar and showed no significant differences: Hungerford: 83 pts; Laskin: 80 pts; HSS: 80 pts; and Mansat: 86 pts. The comparison between the four survival curves was statistically significant: the Hungerford curve was the most optimistic (62 per cent success at 8 years) when compared to the Laskin score (16 per cent success at 8 years). DISCUSSION: The scores do not express the same reality. For mean values close or identical to the scores, the quality of the results may be different. Our analytic method reveals considerable differences explained by the juxtaposition of clinical and functional parameters in the scores. The Hungerford and Mansat scores are principally based on clinical criteria while the Laskin score is more functionally orientated. The HSS score is more even handed. CONCLUSION: It is incorrect to appreciate the value of survival curves if the scores are based on functional criteria as these parameters will naturally deteriorate over time and therefore these scores do not reflect the real quality of the arthroplasty. The Knee Society Score is probably the most interesting system since functional and clinical parameters are separated.

Data Interpretation, Statistical↗
PubMed1995

[Total knee prosthesis. Clinical and numerical study of micromovements of the tibial implant].

INTRODUCTION: The importance of the micromovements in the mechanism of aseptic loosening is clinically difficult to evaluate. To complete the analysis of a series of total knee arthroplasties (TKA), we used a tridimensional numerical model to study the micromovements of the tibial implant. MATERIAL AND METHODS: Fifty one patients (with 57 cemented Porous Coated Anatomic TKAs) were reviewed (mean follow-up 4.5 year). Radiolucency at the tibial bone-cement interface was sought on the AP radiographs and divided in 7 areas. The distribution of the radiolucency was then correlated with the axis of the lower limb as measured on the orthoradiograms. The tridimensional numerical model is based on the finite element method. It allowed the measurement of the cemented prosthetic tibial implant's displacements and the micromovements generated at bone-ciment interface. A total load (2000 Newton) was applied at first vertically and asymetrically on the tibial plateau, thereby simulating an axial deviation of the lower limbs. The vector's posterior inclination then permitted the addition of a tangential component to the axial load. This type of effort is generated by complex biomechanical phenomena such as knee flexion. RESULTS: 81 per cent of the 57 knees had a radiolucent line of at least 1 mm, at one or more of the tibial cement-epiphysis jonctional areas. The distribution of these lucent lines showed that they came out more frequently at the periphery of the implant. The lucent lines appeared most often under the unloaded margin of the tibial plateau, when axial deviation of lower limbs was present. Numerical simulations showed that asymetrical loading on the tibial plateau induced a subsidence of the loaded margin (0-100 microns) and lifting off at the opposite border (0-70 microns). The postero-anterior tangential component induced an anterior displacement of the tibial implant (160-220 microns), and horizontal micromovements with non homogenous distribution at the bone-ciment interface (28-54 microns). DISCUSSION: Comparison of clinical and numerical results showed a relation between the development of radiolucent lines and the unloading of the tibial implant's margin. The deleterious effect of lower limbs' axial deviation is thereby proven. The irregular distribution of lucent lines under the tibial plateau was similar of the micromovements' repartition at the bone-cement interface when tangential forces were present. A causative relation between the two phenomenaes could not however be established. Numerical simulation is a truly useful method of study; it permits to calculate micromovements which are relative, non homogenous and of very low amplitude. However, comparative clinical studies remain as essential to ensure the credibility of results.

Aged↗
PubMed1991

[Dorso-lumbar spinal compression fractures in the child. Follow-up at the termination of development].

Between 1970 and 1985, we count 32 children with compressive fractures of the vertebral column. None of them undergo a surgical procedure. We examine 24 of these 32 children with a mean delay of 10.5 years. Most of the fractures were referring to sporting activities and home games. The main localization was dorsal (T6) and upper-lumbar (12). The mean reduced height of the ventral portion of the vertebra was 27%. Some 10 years later, two third of the patients have some persistent pains and half of them daily. Most of the aches concerned children of more than 12 years when trauma occurred and those who developed a scoliosis during evolution. Wonder the global static of the rachis is little concerned in most of these children. Therefore compressive vertebral fracture of the youngster should be reduced and fixed by a corset. But the immobilization shouldn't be longer than 2 months, accompanied by appropriate gymnastics and followed by a quick renewal of the sporting activities.

Adolescent↗
PubMedDate not supplied

Osteoid osteoma or osteoblastoma of the cervical spine in relation to the vertebral artery.

Osteoid osteoma or osteoblastoma of the cervical spine require complex therapeutic solutions in cases in which there is proximity to the vertebral artery. We describe four such cases. Generally, resection was efficacious and without recurrence, but twice the vertebral artery had to be sacrificed. Although we did not find any serious neurological complication, we concluded that a simple sacrifice of one of the vertebral arteries is not acceptable, principally because of the importance and variability of the unknown radiculomedullary branches of the vertebral artery. We discuss the therapeutic strategies for treating these lesions, namely preoperative investigations, surgical approaches, and vascular control.

Adolescent↗