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FEMORAL HEAD CALCAR LOADING PROSTHESIS - …

The achievability of calcar loading with a titanium prosthesis was demonstrated in in vitro strain-gauge tests

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Depuy Inc. AML Calcar Femoral Prosthesis - …

T1 - The influence of prosthetic stem stiffness and of a calcar collar on stresses in the proximal end of the femur with a cemented femoral component

At this point, a trial prosthesis size 3 with 45 mm calcar body was inserted.

N2 - We used three-dimensional finite-element models of the proximal end of the femur to examine the influence of stem material, stem geometry, and the use of a calcar collar on the stresses in and around implanted total hip replacement femoral components. Anatomical bone geometries and realistic prosthetic geometries were considered. A slender titanium-alloy stem with a collar allows creation of calcar stresses of approximately 80% of the anticipated normal levels. A similar stem of cobalt-chromium alloy creates calcar stresses of 67% of these normal values. Stem designs without a collar were shown to generate no more than 40% of normal values while larger, stiffer stems were seen to create less than 30% of normal values, with or without a collar. Proximal cement stresses were increased by the use of titanium-alloy stems, but were reduced to low levels by a functioning collar. The highest cement stresses in the system were found near the tip of the stem, where titanium-alloy stems create lower stresses than do corresponding cobalt-chromium-alloy stems. The achievability of calcar loading with a titanium prosthesis was demonstrated in in vitro strain-gauge tests. Clinical relevance: Loosening of the femoral stem and calcar resorption are problems that are seen in many long-term clinical series of total hip prostheses. In order to reduce the incidence of these problems, the goal of the designer of a prosthesis is to reduce cement and cement interface stresses around the femoral stem and to create stress distributions in the bone that will prevent resorption. We have demonstrated that, in a well bonded system, properly designed titanium-alloy stems with functioning collars create higher calcar bone stresses (nearer their normal values) and lower cement stresses than do equivalent cobalt-chromium-alloy stems. The ability to achieve calcar-collar contact and loading was demonstrated; however, the long-term effectiveness of the collar is unknown.

Femoral Head Calcar Loading Prosthesis - …

AB - We used three-dimensional finite-element models of the proximal end of the femur to examine the influence of stem material, stem geometry, and the use of a calcar collar on the stresses in and around implanted total hip replacement femoral components. Anatomical bone geometries and realistic prosthetic geometries were considered. A slender titanium-alloy stem with a collar allows creation of calcar stresses of approximately 80% of the anticipated normal levels. A similar stem of cobalt-chromium alloy creates calcar stresses of 67% of these normal values. Stem designs without a collar were shown to generate no more than 40% of normal values while larger, stiffer stems were seen to create less than 30% of normal values, with or without a collar. Proximal cement stresses were increased by the use of titanium-alloy stems, but were reduced to low levels by a functioning collar. The highest cement stresses in the system were found near the tip of the stem, where titanium-alloy stems create lower stresses than do corresponding cobalt-chromium-alloy stems. The achievability of calcar loading with a titanium prosthesis was demonstrated in in vitro strain-gauge tests. Clinical relevance: Loosening of the femoral stem and calcar resorption are problems that are seen in many long-term clinical series of total hip prostheses. In order to reduce the incidence of these problems, the goal of the designer of a prosthesis is to reduce cement and cement interface stresses around the femoral stem and to create stress distributions in the bone that will prevent resorption. We have demonstrated that, in a well bonded system, properly designed titanium-alloy stems with functioning collars create higher calcar bone stresses (nearer their normal values) and lower cement stresses than do equivalent cobalt-chromium-alloy stems. The ability to achieve calcar-collar contact and loading was demonstrated; however, the long-term effectiveness of the collar is unknown.

We used three-dimensional finite-element models of the proximal end of the femur to examine the influence of stem material, stem geometry, and the use of a calcar collar on the stresses in and around implanted total hip replacement femoral components. Anatomical bone geometries and realistic prosthetic geometries were considered. A slender titanium-alloy stem with a collar allows creation of calcar stresses of approximately 80% of the anticipated normal levels. A similar stem of cobalt-chromium alloy creates calcar stresses of 67% of these normal values. Stem designs without a collar were shown to generate no more than 40% of normal values while larger, stiffer stems were seen to create less than 30% of normal values, with or without a collar. Proximal cement stresses were increased by the use of titanium-alloy stems, but were reduced to low levels by a functioning collar. The highest cement stresses in the system were found near the tip of the stem, where titanium-alloy stems create lower stresses than do corresponding cobalt-chromium-alloy stems. The achievability of calcar loading with a titanium prosthesis was demonstrated in in vitro strain-gauge tests. Clinical relevance: Loosening of the femoral stem and calcar resorption are problems that are seen in many long-term clinical series of total hip prostheses. In order to reduce the incidence of these problems, the goal of the designer of a prosthesis is to reduce cement and cement interface stresses around the femoral stem and to create stress distributions in the bone that will prevent resorption. We have demonstrated that, in a well bonded system, properly designed titanium-alloy stems with functioning collars create higher calcar bone stresses (nearer their normal values) and lower cement stresses than do equivalent cobalt-chromium-alloy stems. The ability to achieve calcar-collar contact and loading was demonstrated; however, the long-term effectiveness of the collar is unknown.

Radiology, News, Education, Service

Used for hip arthroplasty in cases of hip fractures when collapse of the neck stucture has occured and revision arthroplasty where there is significant loss of bone stock in the region of the calcar. Specially for large deficits in the calcar region and severe proximal bone loss, the calcar replacement femoral stem allows customization via its proximal segments. The calcar series offers 38-48 and 58 mm resection levels to compensate for bone deficiencies in the proximal/medial portion of the femur. In adittion to the three resection levels, the stems are offered in three different diameters 8-10-12 mm. Diameter 8 mm component has standard 140 mm stem length, other stem diameters 10-12 mm offered with 150 mm stem length. These components are specifically designed to conform and match with the patient’s anatomy. The keel, located below the medial collar provides the additional rotational stability that has been reduced due to medial bone loss. Three dimensional Interlock grit blast all over on the stem surface provides increased fixation at the prosthesis/cement interface compared with that of traditional smooth surface implants. The angle of the neck is 135º for all size, while neck length increases in line with the prosthesis diameter. Also prosthesis has a cone 12/14 taper 5º 38’.
Material
It is manufactured from casting CoCrMo alloy according to ASTM F 75 – ISO 5832/4.

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