Surgery – Truss – Perineal
Patent
1980-05-09
1984-05-08
Rosenbaum, C. Fred
Surgery
Truss
Perineal
128 92BA, A61F 504
Patent
active
044468571
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a medullary nail for the fixation of fractures and which consists of an approximately tubular body provided with longitudinal grooves in the outer surface and having a circular cutting surface at one end, and, as well, to a process for making the same.
At the present, standardized medullary nails according to Kuntscher are used predominantly in bone surgery. The nails have a slotted tubular form of cloverleaf cross-section or V-shaped cross-section and are provided with a ring-shaped cutter at one end. A slot-type eye at the opposite end of the nail provides the means to attach an extraction hook thereto, thus permitting the nail to be pulled out of the bone. A certain spring action is known to be achieved by the longitudinal slits in the nail, whereby the driven nail is pressed laterally against the bone tissue. However, the mechanical hold or grip in the bone marrow, and, in particular, the rotation stability, is insufficient where such medullary nails are employed.
A number of other prior publications are known which show other forms of medullary nails. Thus, DT-PS No. 913,228 describes longitudinally slotted medullary nails which have a variety of cross-sections. The strength of such nails has, in part, been increased by "embossing" of individual wall regions or portions. A medullary nail according to French Patent Application No. 2,288,506 is a solid round rod provided with longitudinal grooves which are semicurcular in profile. A medullary nail described in French Patent Application No. 2,342,710 for the retention of a bone plate has a tubular form and is provided on the outer surface with longitudinal grooves having a rounded profile milled therein.
In DT-AS No. 2,361,933 there is disclosed a tubular medullary nail which has longitudinal elevations on its outer surface, terminating in the cutting surface at one end of the tube. The elevations taper outwardly, sharply forming tips and bone material is cut out by these tips as the medullary nail is being driven into the bone and is deposited in the cavities between adjacent tips. An advantage of this form of medullary nail over the Kuntscher nail, for instance, is the better hold or grip and the greater rotation stability in the bone. It is regarded as a disadvantage that in driving in or inserting such a nail considerable amounts of bone material are cut out and in the region of the pointed longitudinal elevations an adversely high pressure is exerted by the nail on the bone material, thereby increasing the danger of splintering and fissuring. The nail has an extraction slit at one end, or alternatively, a female thread into which a corresponding extraction tool is screwed.
Medullary nails must be made of materials of high tensile and bending strength, sufficient elongation and the highest possible corrosion stability, as well as tissue compatibility. To this day, they are made, as a rule, of chromium, molybdenum, and nickel alloyed steels. Although such materials must be considered as being among the stainless steels, when used in the living body, there occur therewith most undesirable chemical corrosion reactions, e.g. stress corrosion, cracking and pitting. Consequently, the implants are damaged and become useless. In addition, due to the reactions between the implant material and organic tissue the tissue per se is damaged and healing of the fracture is made difficult or impossible. Such phenomena are known as metallosis.
Many attempts have, therefore, been made to get away from the mentioned steel grades of materials for the making of medullary nails and to use in their stead, for example, alloys of cobalt or titanium. It has been proposed also to improve the mentioned materials superficially by oxidizing, nitriding or carbonizing them or by applying ceramic coating or layers thereon.
In connection with the metallosis phenomena, occasionally tantalum has been mentioned in the past, because of its high tissue compatibility. The prevailing opinion is, however, that because of its low strength tantalum can be used only wher
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"The Metal Tantalum", 1939, Fansteel Metallurgical Corp., North Chicago, Ill.
Otte Heinz
Otte Wolf-Dieter
Schider Siegfried
Wiesner Otto
Rosenbaum C. Fred
Schwarzkopf Development Corporation
Shedd C. W.
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