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Biomedical subjects

P Merloz

Publications and source records attributed to P Merloz.

17 recordsLinked to original sources
PubMed1997

Computer assisted spine surgery.

When inserting screws into a vertebral pedicle, the surgeon usually exposes the back part of the vertebra and uses his or her anatomic knowledge to align the drill in the proper direction. A slight error in direction may result in an important error in the position of the tip of the screw. This is done with no direct visibility of crucial structures (spinal cord, pleura, vessels). Statistical analysis of a series of surgical procedures has shown that 10% to 40% of the screws are not installed correctly. To reduce the risk of complication, a computer assisted method is proposed that enables the surgeon to place a screw at a position preoperatively defined in 3 dimensions using computed tomography images. This allows the surgeon to align a standard surgical drill with the optimal position and direction. The depth of the pilot hole during drilling also is monitored by the system to prevent penetration of the anterior cortex of the vertebral body. Using this procedure, in vitro tests were performed and showed that an accuracy of less than 1 mm can be obtained. Clinical trials were done in 10 patients who suffered severe scoliosis or spondylolisthesis. The trajectory of the holes drilled in L2, L3, L4, and L5 vertebrae were checked for all clinical tests. Postoperative radiographs and computed tomography scans showed that the screws were well inserted in each plane for each pedicle. This technique also can be used to perform osteosynthesis at the thoracic and cervical levels.

Adult↗
PubMed1997

[Proximal femoral fractures in patients over 75 years. Vital and functional prognosis of a cohort of 78 patients followed during 2.5 years].

PURPOSE OF THE STUDY: The purpose of this study was to highlight factors influencing vital and functional prognosis at 2.5 years of elderly people being treated for a proximal femoral fracture. MATERIAL: The study was based on 78 patients more than 75 years old admitted to the orthopedic department for emergency treatment. After post-operative care, patients were transferred to a geriatric readaptation unit. The average patient age at the time of surgery was 85 years. METHODS: This was a retrospective study. Survival graphs were established for the entire population as well as for the sub-populations characterized by a studied parameter. Mortality factors were compared via a univariable analysis. A multivariable logistical regression analysis isolated the factors explaining mortality at 12, 18, and 30 months and survival at 30 months, as well as factors explaining functional prognosis at 1 year. RESULTS: The overall mortality rate was 41 per cent, 48.5 per cent of deaths occur within the first year. Factors which are harmful for vital prognosis are the following: high degree of dependence before the fracture, the existence of a neuropsychiatric pathology, and age factor (more than 85 years). 61.5 per cent of surviving patients were independent for daily activities. 77 per cent of surviving patients lived in their usual place of residence. Factors which were harmful for functional prognosis were the following: type of the fall, symptomatic of an underlying pathological state, and existence of a neuropsychiatric pathology. Nutrition was also a predictive factor concerning the patient's out come. DISCUSSION: The average age of the studied population was higher than in most studies in literature. The treatment is mainly based on hip arthroplasty. The group of patients of over 85 have the highest mortality rate. However, a better survival rate at 18 months has been observed for patients older than 90 years. The delay before surgical care was significantly negative if longer than 6 days. However, a delay of 3 to 6 days was not significantly harmful for survival. Within the studied population, the maximum autonomy gain was observed during the first 6 months. The type of non-accidental fall, symptomatic of an associated pathology, was a factor for functional prognosis which has not been often mentioned. So was the biological deficit of nutrition. Social status acted as an indicator of functional status evolution. CONCLUSION: Therapeutic choices can only be guided by assessments of patients' vital and functional prognosis. A sophisticated or even expensive device should be demanded for patients with favorable prognosis. For patients with precarious functional and vital prognosis, priority should be given to less invasive techniques with immediate walking. The cost of the device should be correlated with patient's functional investment.

Age Factors↗
PubMed1995

Computer-assisted spine surgery: a technique for accurate transpedicular screw fixation using CT data and a 3-D optical localizer.

The computer-assisted spine surgery system presented in this paper follows the basic ideas which have been developed for computer-assisted medical interventions (CAMI) in our lab since 1985. There are three steps to insert a linear tool inside vertebral pedicles. First, the surgeon defines an optimal trajectory on pre-operative computed tomography. Second, this trajectory is reported in the operating room coordinate system using an intra-operative sensor and a registration algorithm. Third, a guiding system helps the surgeon follow the selected trajectory. In this paper, we present an implementation of this method that uses only a 3-dimensional optical localizer. Results on cadaver specimens and on the first seven patients are presented.

Bone Screws↗
PubMed1995

[In vitro study of the properties of bioresorbable lactic acid polymer materials].

PURPOSE OF THE STUDY: The potential applications of biodegradable osteosynthesis implants present many advantages over conventional metallic devices. Polyesters of the poly and hydroxy-acid type were recognized early as serious candidates. These polymers have demonstrated a very good biocompatibility and are biodegradable in vivo. After biological and chemical testing poly L. lactic acid 98 (PLA 98) was selected as a candidate. We used a static and dynamic investigation in vitro to assess firstly the material properties of PLA 98 and secondly how its characteristics could be modified within a physiological environment. MATERIAL: Michel Vert and colleagues have shown that polymers of lactic acid have a similar time to resorption providing they contain 98 per cent of the "L" form of the polymer. In vitro studies were assessed on bars made in PLA 98. METHODS: In a first time in vitro studies in traction and flexion on bars allowed an assessment of mechanical properties of PLA 98. In a second time stresses were applied on bars using a physiological environment (Haemacel - 37 degrees C). In a third time we assessed the mechanical properties at the temperature of 37 degrees C with dynamic tests on bars in traction and flexion. RESULTS: The stress-strain curves on bars showed that the material is fragile. Sterilisation with ethylene-oxide did not affect the mechanical properties. When bars were placed in a thermostatically controlled (37 degrees C) physiological environment, the stress-strain curve showed that the material became ductile. With a temperature of 37 degrees C and with a frequency better than one hertz, the dynamic tests on bars showed that the material endurance is good up to 20,000 cycles. At 37 degrees C and at the end of one month, the Young modulus and the maximal strain before breaking lose 50 per cent of their initial value. DISCUSSION: All things considered and as the digital value showed, the PLA 98 appear to be ten times less strong than steel. In a physiological environment the mechanical properties improved due to hydratation of the polymer. The material become quickly ductile or malleable. This allowed transient loading without causing breakage. CONCLUSION: The mechanical properties of bioresorbable materials are very different from those of stainless steel and there is a learning curve in their utilisation. The PLA 98 polymer has demonstrated a very good biocompatibility and is totally biodegradable in vivo. With these results we think that PLA 98 can be used in clinical practice. Indications and clinical use should remain limited to bones regions with low applied stresses.

Biocompatible Materials↗
PubMed1991

[Three-dimensional rigidity of the Ilizarov external fixator (original and modified) implanted at the femur. Experimental study and clinical deductions].

The application of the Ilizarov device to the femur creates several problems: anatomical (transfixion of the thigh), mechanical (asymetrical assembly) and clinical (patient acceptability and duration of treatment). Geometric modifications of the original fixator are proposed. These comprise the use of threaded pins proximally and special connecting pieces. Two large fixators were tested under load and after the introduction of certain variables led the authors to experiment with 18 different assemblies. Four loads were used (compression, flexion in the sagittal and coronal planes and torsion) and stiffness calculated in three dimensions. Three linear and three angular displacements were defined for each type and magnitude of external load. The following sequence of analysis was followed to select the best type of assembly; increased ridigity in torsion; moderate displacement in flexion and axial elasticity. These considerations also apply to the mechanics of fracture healing. After testing under load it was concluded that the original assembly gave the best compromise. The modified assemblies gave a slightly inferior mechanical performance but their geometrical configuration should give better patient tolerance if the following items are used: a proximal arc of 120 degrees, 5 mm diameter threaded pins for the adult and 4 mm diameter for the child.

Biomechanical Phenomena↗
PubMed1990

[Congenital bowing and pseudoarthrosis of the tibia in children].

Congenital pseudarthrosis of the tibia is nearly always the result of a congenital bowing of the tibia when it is unilateral and with an antero-external angle. There is no possible spontaneous consolidation and there may be several associated sequellae (shortening and trophic disorders of the limb). The etiological and therapeutic aspects of the affection are reviewed.

Bone Diseases↗
PubMed1990

[Value of Illizarov's method in the treatment of long bone pseudarthrosis. Apropos of a A.S.A.M.I.F series of 87 cases].

This study is the outcome of multicenter endeavour compiling 87 cases of pseudoarthrosis managed according to principles set forth by G.A. Ilizarov. All clinical forms are described: simple pseudoarthrosis (non-infected and without loss of substance); septic pseudoarthrosis; pseudoarthrosis with loss of bone substance, both septic and aseptic. This method is used in the majority of cases. This method is used in the majority of cases after several consecutive unavailing attempts with conventional therapeutical procedures. Considering all situations, the lesions heal in over 90% of cases and the infection subsides with an equal rate of success. Such results are achieved within a period of 5 months. Sequelae or complications imputable to the method are few. Indications are specified, which depend upon the clinical form of the treated pseudoarthrosis, as well as upon the surgeon's personal skill.

Adolescent↗
PubMed1990

[Axial correction of the legs of children using the Ilizarov method. Apropos fo 22 cases].

22 axial corrections of limbs in children were performed using the Ilizarov technique between 1984 and 1986. This prospective study has been performed under the auspices of the Association pour l'Etude Systémique et l'Application de la Méthode d'Ilizarov en France (ASAMIF). Total correction of deformity was achieved in 20 cases. A minimal angulation (less than 5 degrees) was observed in two cases. In 9 cases tibia or femoral lengthening was performed simultaneously. After corticotomy and placement of the stimulant effect of limb distraction. The mean lengthenings achieved was 30 mm. Serious complications were are: there was one case of fracture of the regenerating bone. We deplore only two superficial pin track infections, two cases of rarefaction of bone. The bone consolidation was obtained on an average of two months. If inequality was associated (more than 40 mm) technique of double corticotomy was performed. The best and more results were certainly performed in great deformities. On the other hand the Ilizarov method addresses all inequalities of leg length, whatever the aetiology, who are associated with common deformity.

Bone Diseases↗
PubMed1988

[A hip prosthesis with a non-rigid femoral implant. The Butel iso-elastic prosthesis].

A new type of femoral prosthesis is described by the authors. This non-rigid implant respects the natural elasticity of bone and, because of this, avoids excessive stress protection of the bone. In addition, bone atrophy caused by rigid components and osteolysis provoked by cement are eliminated. Experimental studies and the clinical and radiological results five years after insertion seem to confirm the value of this concept.

Adolescent↗
PubMed1987

The anatomical basis for transfixion of the thigh.

Serial cross-sections of the thigh have been used to indicate where osseous transfixion is possible without damaging neuro-vascular structures or major tendons or penetrating a joint. Safe areas for transfixion using fine wires and their corresponding cutaneous zones are indicated. Two cutaneous zones each representing a quarter of the circumference of the thigh form safe zones for transfixion. The first begins on the ventral surface of the hip and ends on the medial aspect of the knee, while the second begins on the posterior aspect of the buttock and ends on the lateral aspect of the knee.

Humans↗
PubMed1986

[Butel's hip screw-plate in osteosynthesis of fractures of the upper end of the femur. Apropos of 241 osteosyntheses (100 true cervical fractures and 141 fractures of the trochanter)].

Butel's hip plate was used for osteosynthesis of 241 fractures of upper end of femur (100 true cervical - 141 trochanteric and subtrochanteric fractures). Results for true cervical fractures were assessed as satisfactory in 89.5% of cases, with only 3 pseudarthroses and 4 cases of femoral head necrosis (2 septic, 2 aseptic), a total complication rate of 7.5%. These clinical results confirm the value of screw fixation at several cephalic anchorage sites (demonstrated biomechanically) in true cervical fractures. Results in trochanteric and subtrochanteric fractures were rated as satisfactory in 86.9% of cases, complications including 2 ruptures of plate, 1 sepsis and 4 early loosening of plate. The latter sequela was avoided by an improved choice of indication for the procedure and by substitution of this compound material (screw-plate) for a monobloc piece ("anti-loosening cervicocephalic screw apparatus"), in compound fractures of trochanter.

Adult↗
PubMed1982

Segmental shortening of the ulna in some malunions of the distal radius.

In patients who have a malunion of the distal part of the radius with a shortened radius, the ulna is too long. A discrepancy between the ulna and the lower radius, and between the ulna and the carpal bones occurs, compromising the mobility and appearance of the wrist. We reviewed ten such patients in whom the ulna was shortened by performing a resection of a diaphysar cylinder followed by a plate osteosynthesis. This method restored the normal anatomy of the distal radio-ulnar joint, markedly reduced the patient's pain and improved pronation and supination. When performed in young patients, when the radial deformity is not very important, this procedure has most satisfying functional results.

Adolescent↗
PubMedDate not supplied

[Posterior dislocation of the hip associated with fracture of the neck of the femur. Apropos of 3 cases].

Three patients with posterior dislocation of hip associated with fracture of neck of femur were treated by early sanguineous reduction and osteosynthesis. This therapy was very effective since necrosis did not develop either in the short or long-term follow up (1, 3 and 4 years). These findings combined with documented data are in favor of anatomic reconstruction of upper end of femur by stable and solid osteosynthesis, at least in young adults. Early operation, an irreproachable operating tactic (orthopedic table, ventral decubitus, posterior approach), an immediate stable and solid synthesis and a deferred load bearing (beyond 6 months) should reduce the risk of femoral head necrosis to a minimum.

Adult↗