Femoral insert for total hip prosthesis

Abstract: The insert -1- lacks any widening on the trochantereal part and the internal longitudinal hollow -2- has constant diameter throughout its length. A version with a rib -5- of scant relief on the trochantereal part has been envisaged. The insert has elasticity and power of recovery when it is pressed laterally in the direction of closing the slot -2a-. It requires a simpler and less traumatic operaion for the patient.

Description: The present invention refers to a femoral insert for total hip prosthesis, thanks to which notable improvements are achieved in relation to the inserts of this type known to date. Said improvements involve simplification of the operation which has to be carried out on the patient in order to implant the insert and also of the fitting of a pin inside the insert in the event of a hypothetical fracture of the femur once the insert has been fitted. BACKGROUND OF THE INVENTION Known in the art of prostheses are femoral inserts for total hip prosthesis, which inserts present great difficulty when it comes to extraction thereof, due to the special characteristics of their mechanism for anchorage in the bone and due also to their solid configuration, which prevents reduction of their diametral width. In order to avoid the disadvantages of this type of insert, the holder of the present invention, Dr. Enrique Pelegrín Solá, made a new insert, which is the object of Spanish Utility Model U 8600323, whose fundamental characteristics are as follows: the presence of external longitudinal ribs; the hollow configuration of the insert, due to the fact that it possesses a cavity running along its entire length; and the presence of a trochantereal part which is notably thicker than the rest, provided with notches for the coupling of a mechanical compressor device for reduction of the cross-section of the entire insert in order to facilitate the extraction thereof. FR-A-2627380 discloses a femoral insert for total hip prosthesis, of the type which is of a hollow configuration, with a hollow running throughout its length which communicates with the exterior by means of a longitudinal slot placed on the back side of the insert, the insert being provided on the tronchatereal part with notches near the edges of the slot. In addition, FR-A-2627380 discloses that the upper part of the insert, corresponding to the trochantereal zone, lacks pronounced thicker sections. Utility Model ES-8600323 (Publication No. 1000105) discloses a femoral insert which has a longitudinal hollow along its length for the implantation of a pin, which hollow is conically decreasing towards its end. Experience has nevertheless shown that it is possible to improve the characteristics of the insert object of said Spanish Utility Model U 8600323, and in consequence a new insert has been designed, the characteristics of which are the object of the present invention. DESCRIPTION OF THE INVENTION The femoral insert for total hip prothesis is of hollow configuration, with a hollow running throughout its length which communicates with the exterior by means of a longitudinal slot placed on the lateral side of the insert, provided on the trochantereal part with notches near the edges of the slot, the tronchantereal zone lacking pronounced thicker sections, the insert is characterized in that the longitudinal hollow has a circular cross-section with a uniform diameter throughout its entire length. In an optional embodiment, the insert presents around the trochantereal part an outcrop in the form of a rib in inclined position with respect to the longitudinal axis of the insert. This outcrop projects very little in relation to the lateral surface of the insert and rather more in relation to the front part of same. The external surface of the insert presents longitudinal slots which run along approximately the upper half of the height of the insert. The insert presents sufficient elasticity to allow it to deform temporarily by means of lateral pressure in the direction of closing the longitudinal slot of the hollow and to recover its position again when said lateral pressure ceases. BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of all that is described in the present specification, some drawings are attached in which, solely by way of example, a practical case of embodiment of the femoral insert is shown. In said drawings figure 1 is a side elevation view of the insert without a rib on the trochantereal part; figure 2 is a longitudinal section view of the insert provided with an inclined rib around the trochantereal part, constituting a calcar support once the insert has been placed inside the bone; figure 3 is an elevation view of the side on which the groove is open on an insert; figure 4 is a side elevation view of the same insert; figure 5 is an elevation view of the same insert, seen from the opposite side with respect to the view of figure 3; and figure 6 is a plan view from the lower end of the insert. DESCRIPTION OF A PREFERRED EMBODIMENT The femoral insert in question comprises a piece -1- of a hard biocompatible material, whether plastic or metal. The external surface of the piece -1- may be provided with a rough coating of granular, filamentary or any other nature, in order to facilitate regeneration of tissues involved, basically osseous tissue. The piece -1-is provided with a longitudinal hollow -2-, in communication with the exterior by means of a longitudinal slot -2a-, opened in its lateral side, running from the trochantereal zone -3- to the lower end -4- of the insert. The piece -1- diminishes progressively in width towards its lower end. A description has been provided so far of already known aspects of the femoral insert. The essential characteristics of the femoral insert consist in the absence of thick outcrops on the trochantereal part -3- (figure 1), or, at most, in the presence of an inclined rib -5- around it - figures 2, 3, 4 and 5 - which projects slightly with respect to the surface of the side walls of the zone -3- and which at the medial part forms a more pronounced outcrop -5a-. Another notable characteristic of the femoral insert consists in the hollow -2- having a uniform diameter throughout its entire length (figure 2). On the exterior surface of the insert -1- there are longitudinal slots -6- which take in only the upper half of the total height of the insert. In the zone -3- there are two lateral depressions -7- near to the slot -2a-, or in any other appropriate zone, for the placing of an instrument intended to apply pressure on the zone -3- in a direction which brings together the edges of the slot in order to facilitate driving of the insert into the bone. From all that has been set forth and through observation of the drawings, the advantages presented by the insert in question compared to other preceding embodiments may be appreciated. In the first place, the absence of a wide head at the upper or trochantereal part should be stressed. Thanks to this, fitting of the insert requires a surgical operation through the lateral part of the limb, instead of an operation through the rear part. This surgical operation through the lateral part is less traumatic and easier to perform. Furthermore, the absence of the aforesaid head permits elimination of a smaller zone of the affected bone, thus simplifying the intervention and facilitating recovery of the affected limb. In the version illustrated in figures 2 to 5, in which the insert presents a rib -5- which projects very little on the anterior and posterior sides, surgical intervention is also viable by lateral access, thanks to the scant relief of the rib in question. This rib provides a calcar support on the bone, cut in an inclined manner, as illustrated in figure 2. When the insert lacks a calcar support (figure 1), the insert is fitted by pressing on it laterally in a direction which brings together the edges of the slot -2a-so that, once placed inside the bone, it recovers its position on ceasing of the lateral pressure, thus allowing the insert to be perfectly secured inside the bone. Thanks to the uniformity of the diameter of the hollow -2- throughout its entire length, when it is necessary to fit a pin inside the insert, due to breakage of the bone arising once the insert has been fitted, the pin is perfectly tight throughout its length, with no lateral displacements of same occurring. Independent of the object of the invention shall be the materials used in manufacturing of the femoral insert, shapes and dimensions of same and all accessory details which might be presented, as long as they do not affect its essential nature.

Claims: Femoral insert for total hip prothesis, which is of hollow configuration, with a hollow (2) running throughout its length which communicates with the exterior by means of a longitudinal slot (2a) placed on the lateral side of the insert, provided on the trochantereal part (3) with notches near the edges of the slot (2a), the tronchantereal zone (3) lacking pronounced thicker sections, characterized in that the longitudinal hollow (2) has a circular cross-section with a uniform diameter throughout its entire length. Femoral insert for total hip prosthesis, as claimed in claim 1, characterized in that its external surface presents longitudinal slots (6), which take in approximately the upper half of the height of the insert. Femoral insert for total hip prosthesis, as claimed in claim 1, characterized in that it presents sufficient elasticity to permit it to be deformed temporarily by means of lateral pressure in a direction to close the longitudinal slot (2a) of the hollow, and to recover its position again when said lateral pressure ceases.

Inventors: PELEGRIN SOLA ENRIQUE, PELEGRIN SOLA, ENRIQUE
Applicants: TRAIBER S A, TRAIBER, S.A.
Application year: 1991
Main classification: A61F2
IPC codes: A61F2