Biomedical subjects

P Y Descamps

Publications and source records attributed to P Y Descamps.

11 recordsLinked to original sources

PubMed2001

[Shock absorption by intermediate hip prostheses].

PURPOSE OF THE STUDY: The bipolar prosthesis was developed in an attempt to alleviate acetabular wear of conventional metallic endoprostheses. The prosthesis was designed to achieve low-friction metal-on-polyethylene inner bearing motion while decreasing shear stress across the acetabular cartilage. Although good clinical results were obtained, the principle of a persistent inner mobility was contested and some authors have assigned the delay of cartilage erosion to the shock absorption capacity of the polyethylene. The present study was focused on assessing the vibration and shock damping effect of metal monoblock and bipolar head prostheses. MATERIAL AND METHODS: The transmission of the shock wave through these two types of prostheses was studied in vitro. The two heads were first tested in a rigid environment to eliminate all external parasite frequencies. The impact excitation was applied with a hammer connected to an oscillometer. A second accelerometer was connected to the prosthesis stem. Shock wave transmission was analyzed. Secondly, the head was tested with a system vibrating in the same order of frequencies as the skeleton, with and without pre-constraint. The frequency response functions were analyzed. RESULTS: For the metallic prosthesis, the frequency of vibration recorded on the femoral stems was in a large frequency range from 0 Hz to 10 KHz. For the bipolar prosthesis, all the high frequencies of the shock wave were eliminated and only shock wave frequencies from 0 to 500 Hz were recorded. In an environmental system vibrating below 100 Hz, the metallic head did not express high frequencies of vibration. The coefficient of shock absorption was not significantly different for the two heads. DISCUSSION: In the first rigid environment, the metallic head did not filter the high frequency components of the shock wave and the bipolar head tended to eliminate high frequency components due to the flattening effect of the impulse load by the polymer. But, the lower leg is not a rigid structure and the musculo-skeletal system vibrates in frequencies below 100 Hz. In similar conditions, the increased shock-absorbing effect of the polyethylene is far more difficult to observe. For the metallic prosthesis, the recorded frequency of vibration also belongs to a small domain of frequency, from 0 Hz to 100 Hz. The range of frequency is similar for the two types of prostheses. CONCLUSION: Even though polyethylene is characterized by a more pronounced damping capacity than metallic materials, in experimental conditions simulating the vibratory characteristics of the human body, the introduction of a high-density polyethylene liner does not afford any additional shock-absorbing effect compared with a metallic head. It cannot explain cartilaginous sparing.

Equipment Failure Analysis↗

PubMed2001

Biomechanical evaluation of Hackethal's intramedullary bundle pin fixation of humeral neck fractures.

Humeral neck fractures can be stabilized using a bundle of intramedullary pins as described by Hackethal. In order to decrease the risk of pin migration, packing of the medullary cavity with as many pins as possible is sometimes recommended, but others believe that stability can be decreased by destruction of cancellous bone in the humeral head by a large bundle of pins. A surgical neck fracture was created with a saw in 30 frozen cadaveric humeri. Bone quality was evaluated by radiography and densitometry. Fractures were stabilized using Hackethal's technique of retrograde intramedullary pinning with varying numbers of 2.5-mm diameter pins; increasing torsion or bending moments of force were then applied to the bones studied. Stability was found to improve with an increasing number of pins and with higher humeral head density. Based upon these findings, the use of a large number of pins is recommended to reduce the risk of pin migration. Up to eight pins, the risk of destruction of cancellous bone in the humeral head appears very low.

Biomechanical Phenomena↗

PubMed1999

Histopathology of a well-functioning hydroxyapatite-coated femoral prosthesis after 52 months.

A fully hydroxyapatite-coated femoral implant was retrieved during autopsy. This component, provided with a bipolar femoral head, had been inserted for a displaced fracture of the femoral neck 52 months before. Osseointegration of the implant was evident, without any formation of fibrous tissue :39.9% of the perimeter of the prosthesis at the level of its proximal third was interfaced with bone (62.8% at the mid-third and 65.2% at the distal third). Remodeling of bone had ensued. Deposition of bone was most prominent in the calcar zone, along the medial and lateral aspects and around the tip. Proximally, cortical porosity was found to be increased by 73%, whereas medullary bone porosity was increased by a factor of 2. Cell-mediated resorption of the coating was systematically present in these bone remodeling areas. The average thickness of the coating was respectively 10.8, 50.2 and 151.2 microns in the proximal, mid- and distal thirds of the implant. Formation of new bone was often coupled with resorption. No debris from the coating was found in the joint tissues or in the articulating surface of the polyethylene insert. These overall histopathological features support mechanical stability of the implant and active remodelling of bone along with focal removal of HA coating associated with osteoclastic activity. No side effects from coating degradation could be demonstrated.

Aged↗

PubMed1999

[Analysis of the acetabulum anterior cover].

PURPOSE: The false profile X-Ray view as described by Lequesne, allowing the measurement of the anterior cover of the acetabulum, is a slantwise view obtained by a 65 degrees inclination of the pelvis on the radiographic plate. The errors introduced by this radiological measurement of the anterior cover are evaluated. MATERIALS AND METHODS: An anatomical and radiological analysis is conducted on 20 acetabula. The anterior cover is measured on the bone and the A point, the anterior extremity of the acetabular roof, is plumbed. Each pelvis is imaged following the Lequesne method. The VCA angle is measured with the radiological point A described by Lequesne and with the metallic point A as reference. RESULTS: The difference between the anatomical and radiological values of the anterior cover is an average by 11 degrees and undervalues the anatomical value. The deviation is reduced by the application of a trigonometrical formula. A difference between the radiological localisation of A point described by Lequesne and the metallic marker is pointed out. This difference increases when the acetabulum becomes dysplasic. CONCLUSION: The acetabular anterior cover measured with the radiological incidence described by Lequesne undervalues the real value. Moreover, the error increases when the acetabulum is dysplasic.

Acetabulum↗

PubMed1999

A method to measure acetabular cup anteversion after total hip replacement.

The authors propose a simple and practical method to measure radiologically the angle of ante- or retroversion of the acetabular cup using a goniometer. It only necessitates an anteroposterior radiograph centered on the femoral head and another one centered on the public symphysis. Special x ray equipment, compass, conversion table, mathematical formulas, or a pocket calculator are not required. The opening of the prosthetic cup is projected on the film as an ellipse. According to the rules of descriptive geometry, the true size of the angle of anteversion is easily obtained. The geometric constructions consist in drawing four lines. The adequate positioning on a hip radiograph of the protractor, drawn on the goniometer, permits the direct reading of the true and planar anteversion angles of the cup.

Acetabulum↗

PubMed1998

Use of an intramedullary hip-screw compared with a compression hip-screw with a plate for intertrochanteric femoral fractures. A prospective, randomized study of one hundred patients.

One hundred elderly patients who had an intertrochanteric femoral fracture were randomized to treatment with a compression hip-screw with a plate (fifty patients) or a new intramedullary device, the intramedullary hip-screw (fifty patients). All patients were followed prospectively for one year or until death. A detailed assessment of the functional status and the plain radiographs of the hip was performed one, three, six, and twelve months postoperatively. The two treatment groups were strictly comparable. The operative time needed to insert the intramedullary hip-screw was significantly greater than that needed to insert the compression hip-screw with the plate (p = 0.02), but use of the intramedullary hip-screw was associated with less estimated intraoperative blood loss (p = 0.011). The prevalence of perioperative complications, such as bronchopneumonia, cardiac failure, and urinary tract infection, was comparable in the two treatment groups. There were one intraoperative fracture of the femoral shaft and two intraoperative fractures of the greater trochanter in the group managed with the intramedullary hip-screw. One patient had pulling-out of the compression hip-screw on the seventh postoperative day. Four patients had a trochanteric wound hematoma, without infection, after insertion of an intramedullary hip-screw. All but one of the fractures healed. The one non-union, which was in a patient who had a compression hip-screw, was treated with a hemiarthroplasty. The mortality rate was similar in the two treatment groups. The patients who had an intramedullary hip-screw had, on the average, significantly better mobility at one (p < 0.0001) and three months (p = 0.0013) postoperatively. This difference was no longer seen at six and twelve months, although the patients who had an intramedullary hip-screw still had significantly better walking ability outside the home at those time-periods (p = 0.05). The compression hip-screw was removed from two patients because of pain in the mid-portion of the thigh, which had begun after consolidation of the fracture. Fourteen patients who had an intramedullary hip-screw had cortical hypertrophy at the level of the tip of the nail at twelve months postoperatively. Cortical hypertrophy was significantly related to the use of two interlocking screws (p = 0.02). Six of these patients also had pain in the mid-portion of the thigh, and the nail had been locked with two screws in five of them. Three of the six patients had the hardware removed because of the pain, and the symptoms resolved. A seventh patient had pain without cortical hypertrophy. The intramedullary hip-screw device was associated with significantly less sliding of the lag-screw and subsequent shortening of the limb in the region of the thigh (p = 0.012 and 0.019, respectively); these differences were more pronounced when the unstable fractures in the two treatment groups were compared (p < 0.001).

Aged↗

PubMed1998

[Study of cotyloid anteversion by coxometric measurement].

A coxometric evaluation is helpful for the diagnosis and the prognosis of hip dysplasia. These measurements also given an intrinsic guide to the surgeon for total hip arthroplasty. A coxometric protractor is drawn on the majority of the goniometers and allows the measurement of the angle of internal and external roof, the angle of the acetabular roof obliquity and the femoral neck-shaft angle on a hip AP X-ray. The purpose of this report is to demonstrate that on the same X-ray, the adequate placement of the coxometric protractor allows to calculate the inclination angle, the acetabular anteversion angles and the anterior roof angle.

Acetabulum↗

PubMed1998

The femoral supracondylar nail: preliminary experience.

The treatment of supracondylar fractures of the femur with an intramedullary nail presents some theoretical advantages. Compared to plate osteosynthesis, intramedullary fixation requires less extensive dissection and is biomechanically more favorable. In the elderly patient, these characteristics seem important since bone quality, extensive procedures and bone grafting remain problematic. Since August 1994 we have treated 16 consecutive closed fractures of the distal femur (A.O. type: 7 A.1, 2 A.3, 4 C.1, and 3 C.2) with the Green-Seligson-Henry intramedullary retrograde supracondylar nail. Twelve elderly and osteoporotic patients had suffered low-energy trauma, three young patients had been involved in a traffic accident and one other young patient had attempted suicide. The operative technique, complications and results are described. All fractures healed within a few months (2 to 7) without bone grafting. No failure of the fixation material and no deep infection were encountered. With most elderly patients the functional result was judged satisfactory, considering the population studied. Intraoperative determination of alignment and avoiding shortening were the major difficulties, especially with long oblique or comminuted fractures. Two major complications were encountered in the young population. In one instance nail protrusion in the intercondylar notch caused a deep patellar cartilage erosion and sympathetic distrophy leading to a 15 degrees flexion deformity. Another young patient needed a quadriceps release at the fracture site and subsequently a femoral valgus osteotomy in order to achieve an acceptable final result. In elderly osteoporotic patients presenting an isolated supracondylar fracture, antegrade nailing remains the "safest" technique by avoiding an unnecessary arthrotomy. When previous hip or knee surgery precludes the use of antegrade nailing techniques or when the fracture extends into the intercondylar region, retrograde supracondylar nailing offers some advantages compared to conservative treatment or plate osteosynthesis. On the other hand in young patients, anatomic reduction and alignment should be the goal, and open reduction with plate osteosynthesis, supplemented by bone grafting if needed, should remain the gold standard. When this seems technically impossible, the antegrade or retrograde insertion of an intramedullary nail with intraoperative assessment of length and fracture alignment is an interesting alternative.

Adult↗

PubMed1994

[Contribution to the study of pelvic stress during weight-bearing. Role of the pubic branch and trabecular bone].

INTRODUCTION: Several authors have reported evidence of loosening of the acetabular component in 14 per cent of cases at 10 years follow-up. To understand this phenomena, parametric studies of the acetabulum have involved finite element analysis, photo elastic models or strain gauges. The differing and sometimes contradictory results were due to the way the model was solicited. If the classic "Resultant" is accurate for the study of the forces on the hip, Pauwels described other forces on the pelvis during the gait. The effect of the application of these other forces on the acetabulum are the object of this study. MATERIALS AND METHOD: Four pelvises were loaded with different forces. Nine strain gauges were pasted around the acetabulum. The pelvis was loaded up to 140 Kg and a compressive force was applied to the pubis by 10 Kg increments up to 40 Kg. The stress data with and without the second force were recorded. A cortical window was bored on the anterior inferior iliac spine. Through this patch, the trabecular bone of the acetabular roof was cut up to disturb its mechanical properties. The load was once again applied to the pelvis and the stress data recorded. RESULTS: The compressive force applied to the symphyseal surface decreases the deformation of the posterior acetabular rim and increases deformation in the proximity of the ischio-iliac and iliopubic junctions. The disruption of trabecular bone generates an increase in deformation mainly perpendicularly to the acetabular rim. DISCUSSION: The decrease of the stress on the posterior acetabular rim is interpreted as a reduction of the solicitations on a fragile zone and its increase on the iliopubic and ischio iliac junctions expresses the application of the acetabular horn on the femoral head permitting better settling of the hip during the gait. The constatation of a stress increase around the acetabulum after disruption of the traecbular bone is interesting. The bone behavior with different acetabular cup models on different pelvis may be studied by strain gauges pasted on the cortical bone. The variable quality of the trabecular bone may introduce an error factor in the measurement. CONCLUSION: The deformation of the acetabulum during gait has to be studied following the different forces described by Pauwels. The compressive force on the pubic symphysis during one leg stance permits a decrease of the stress on the acetabular rim and an increase in the setting of the femoral head. Different qualities of trabecular bone change the deformation of the cortical bone for an equivalent load. This incites us, in comparative studies, to be careful in the deduction of the acetabular roof stresses from the recorded cortical bone deformations.

Aged↗

PubMedDate not supplied

Different aspects of the cyclops lesion following anterior cruciate ligament reconstruction: a multifactorial etiopathogenesis.

After anterior cruciate ligament (ACL) reconstruction using a patellar-tendon autograft, 65 patients underwent second-look arthroscopy in conjunction with hardware removal. In 23 patients, hypertrophic tissue was found in the anterior part of the knee. This tissue presented different aspects, from a well-synovialized nodule to a more disorganized fibrous tissue according to patients' complaints. Endoscopic resection of this offending tissue was generally sufficient to obtain a satisfactory result. In patients presenting a loss of extension, the notch frequently had to be enlarged. We have found a multifactorial pathogenesis to be likely: the nodule is a natural fibroproliferative tissue process originating either from drilling debris from the tibial tunnel or from remnants of the ACL stump and, more rarely, from broken graft fibers. Sometimes, when the graft is malpositioned, the scar tissue can result from repeated graft impingement on the notch at terminal extension. Formation of this aberrant tissue should be prevented by proper positioning of the graft, by enlargement of the narrowed notch in chronic cases, by using drills of increasing diameters to avoid production of osteocartilaginous fragments, by meticulous resection of all drilling debris and ACL remnants around the tibial tunnel, and by enlarging the notch roof if any contact with the graft is present when the knee is fully extended intraoperatively.

Adult↗

PubMedDate not supplied

Computed tomography measurement of humeral head retroversion: influence of patient positioning.

For accurate humeral head arthroplasty, the surgeon needs to know some geometric data, such as, for example, the retroversion angle of the humeral head. Only a few reports have described and evaluated the use of computed tomography (CT) to measure humeral head retroversion. The humerus position relative to the roentgen beam is variable from one subject to another depending on the patients' morphology. It could influence the retroversion measurement and has not been investigated previously. This study analyzes in 9 cadaver humeri the variability of retroversion angle measurements with different humerus positioning relative to the roentgen beam during CT examination. The truest retroversion angle can be obtained when true axial slices, perpendicular to the humeral diaphysis, are obtained. Our study tries to clarify technical problems that occur during CT examination. Geometric considerations that can modify the measurements are presented. A reliable method of humeral head retroversion angle measurement is recommended, which could be useful to the shoulder surgeon.

Arthroplasty, Replacement↗