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Biomedical subjects

P Christel

Publications and source records attributed to P Christel.

At least 73 records · Page 4Linked to original sources
PubMed1985

Treatment of chronic anterior knee instabilities with combined intra- and extra-articular transfer augmented with carbon-PLA fibers.

In the treatment of old chronic anterior knee instabilities by anterior cruciate ligament (ACL) insufficiency, isolated reconstruction of the ACL is insufficient because of an associated stretching of the lateral capsule and lateral collateral ligament. A combined intra- and extra-articular transfer (consisting of the central one-third of the patellar tendon, the prepatellar tissue, and the central one-third of the quadriceps tendon) is necessary to repair ACL instability. Augmentation of the autogenous transfer with polylactic acid-coated carbon fibers has several advantages. It improves the transfer's strength by reinforcing its weak zones; gives initial strength during graft remodeling and vascularization, thus avoiding cast immobilization; and allows early active rehabilitation and possibly return to sports activity. The surgical technique is based on biomechanical and biologic principles. The transfer remains attached to the tibial tubercle, passing through a tibial tunnel, through the intercondylar notch, behind the lateral femoral condyle in a bony groove, then on the lateral aspect of the condyle, beneath the lateral collateral ligament, and ending close to Gerdy's tubercle. The preliminary results in 30 patients are encouraging. The subjective and objective results are similar to those previously obtained with nonreinforced methods of repair, except that there is an early return to normal activities.

Carbon↗
PubMed1984

Callus characteristics following intramedullary nailing with stainless steel or epoxy-carbon nails.

Biological mechanical improvements of osteosynthesis make intramedullary nailing an attractive alternative to bone plate fixation. However, little is known about stress shielding induced by intramedullary implantation of a nail. To evaluate the effect of the nail rigidity on bone healing, mid-metatarsal osteotomies were performed in sheep and fixed with either stainless steel or epoxy-carbon composite V-shaped nails. Mechanical and histomorphometric features of the callus were evaluated 4 months postoperatively. No statistical difference between the two groups were demonstrated for either mechanical or microstructural characteristics. The presence of a fibrous membrane filling the bone/nail interface and allowing sliding micromotions of the implants and the much smaller effect of nail rigidity, as compared to bone plate after implantation, were assumed to be the main reason for this uniformity. At this stage of healing, bone characteristics were more related to a nonspecific (vascular) bone remodeling phenomenon than to a stress-shielding effect.

Animals↗
PubMed1984

The effects of remodeling on the elastic properties of bone.

Cortical bone can be modeled as a complex hierarchical composite interrelating both structure and material properties on four levels of structural organization: molecular, ultrastructural, microscopic, and macroscopic. In young animals, the microstructural systems are long parallel lamellar units, plexiform bone, which in older or more mature animals converts by internal remodeling into multiple concentric lamellar units, secondary osteons, forming haversian bone. Ultrasonic wave propagation measurements performed on both plexiform and haversian bone clearly show a definitive relationship with microstructure; haversian bone can be described as a transversely symmetric material whereas plexiform bone appears to be orthotropic in nature. The anisotropy of the elastic constants are found to reflect the tissue symmetry; moreover, plexiform bone is stiffer and more rigid in all directions than is haversian bone. Similar experiments were performed on osteoporotic and osteopetrotic bone. While the results for osteoporotic bone are understandable in terms of the increased porosity, the results for the osteopetrotic bone are anomalous with respect to its density. Since Wolff, the remodeling of bone has been interpreted as a way of altering the mechanical properties to suit some need. For haversian remodeling from plexiform bone, the argument that adaptation occurs to optimize properties requires additional clarification since haversian bone appears to have inferior mechanical properties to plexiform bone.

Animals↗
PubMed1983

[Analysis of the mechanical function of the cruciate ligaments in antero-posterior knee laxity. An in vitro study].

In order to evaluate the contribution of both anterior (ACL) and posterior cruciate ligaments (PCL) in antero-posterior knee laxity, mechanical tests were performed on 31 fresh-cadaver-knees ranging from 20 to 68 years old. The joints flexed at 90 degrees in a mounting apparatus were placed in a testing machine with the tibia fixed in neutral rotation. The load-displacement curves were then analyzed. The results showed that the tensile strength of the ACL decreased greatly with age whereas its stiffness measured during anterior drawer test remained independent of age and sex. Successive resection of the antero-medial (AM) and postero-lateral (PL) bundles of the ACL demonstrated the AM bundle to be the major structure involved in the limitation of tibial displacement in the anterior drawer test. The amount of tibial shift during the anterior drawer test did not reflect the condition of the ACL, while its resection always induced a strong and significant drop in anterior knee stiffness. Dissection of the PCL was always followed by significant posterior tibial displacement during the posterior drawer test of over 10 mm, which did not permit the experimental apparatus to quantify the posterior load displacement relationship.

Adult↗
PubMed1981

[Acceleration of repair of non-unions by electromagnetic fields (author's transl)].

This work deals with the results obtained by four French orthopaedic departments using the electromagnetic field stimulation for non union treatment. This is the method established by A. Bassett. 37 cases are studied, the results are known for 35 of them with 6 failures and 29 successes. The failures can be explained for four of them by a bad application of the device. Concerning the 29 successful cases, the role of the stimulation is discussed. Discarding those who have been treated a short time after a surgical procedure, those who have been immobilized more than 6 months and those where the non union could have been a delayed union, it remains 14 successful cases apparently undisputable. For them the role of the electromagnetic field stimulation seems real.

Adolescent↗
PubMed1980

Comparison of the effects of intramedullary nailing or plating on the mechanical properties of fracture callus.

Twelve metatarsal sheep bones were osteotomized and fixed either with an intramedullary nail or with a standard plate without compression. The mechanical properties of the callus were assessed three months post-operatively using a bending test. Ultimate bending strength, tangential stress, energy to tailure, stiffness and moment of inertia were measured or computed with the recorded data. It was concluded that the nailing technique improved callus properties more than plating. For the 12 weeks of consolidation, the mechanical properties of the callus at this stage have been ascribed to the degree of mineralization.

Animals↗