1. Field of the Invention
The present invention generally relates to an anti-subsidence dynamic hip screw, and more particularly to an anti-subsidence dynamic hip screw capable of decreasing the subsidence of the femoral head when using for reconstructing and resetting femoral fractures.
2. Description of the Related Art
Clinically, the proximal femoral fracture is one of the common diseases and occurred in the eldly and the population of the osteoporosis. Because the osteoporosis results in the fractures of the femoral neck or greater trochanter of the hip joint, it is usually used the dynamic hip screw or compression hip screw to reconstruct and reset the fracture.
The design of conventional compression hip screw emphasizes on enhancing the lock of the screw (disclosed by U.S. Pat. No. 4,973,333 and U.S. Pat. No. 5,041,116), preventing the rotation of the femoral head (disclosed by U.S. Pat. No. 4,657,001), or providing the better fixing way of the screw (disclosed by U.S. Pat. No. 6,511,481 and U.S. Pat. No. 7,118,572).
However, when the screws of above patents disclosed is used in the osteoporosis patients, the bone mass of the femoral head is too low and results in the femoral head collapsing excessively so that the contact area between the lag screw locked in the femoral head and the bone is too small and further results in the complications of superior cut-out of the lag screw
Although U.S. Pat. No. 7,118,572 provides a lag screw assembly with better fixing function which the lag screw is disposed four tang legs and spreads out after the lag screw anchors into the femoral head so as to enhance the fixing effect. However, the contact area between the tang legs and the femur is not large enough, and then it is not obvious to fix the lag screw to the femoral head when encountering the situation of above mentioned that the femoral head collapses excessively because the bone mass is too low.
The U.S. Pat. No. 4,657,001 provides an anti-rotational hip screw capable of increasing the contact area with the femur, which achieves the objective of increasing contact area by the four aligned grooves disposed at the edges of the screw and four pins implanted into the femoral neck. However, the depth of each pin implanting into the femur is limited. Therefore, the effect of the subsidence relative to the femoral head is limited, too.
An anti-subsidence dynamic hip screw of the present invention is comprising: a barrel having a connection portion and an extending portion connecting with an upper end of the connection portion by an outside end of the extending portion, and there is a predetermined angle between the connection portion and the extending portion so as to become a bending form, at least one first long groove disposed at a predetermined position of the extending portion and axially extended between an inside end and an outside end of the first groove, a stop portion disposed at the predetermined position; a lag screw having an inside end with threading screw at the outer edge of the inside end and an outside end with a predetermined length to combine with the extending portion by the way of reciprocation, at least one second long groove disposed at an outer edge of the lag screw and axially extending a predetermined length; a blade piece having a predetermined length and a predetermined width and simultaneously passed through the first long groove and the second long groove corresponding to each other; and a compressing screw having an inside end screwed with the outside of the lag screw, and an outside end limited by the stop portion to retain in the outside end of the extending portion.
According to above structure, it is not only easy to assembly, especially for the effect of decreasing the subsidence of the femoral head, but also makes the effect more obvious when using for the hip fracture of the osteoporosis body.
Further features and advantages of the present invention will become apparent to those of skill in the art in view of the detailed description of preferred embodiments which follows, when considered together with the attached drawings and claims.
All the objects, advantages, and novel features of the invention will become more apparent from the following detailed descriptions when taken in conjunction with the accompanying drawings.
Referring now to the drawings where like characteristics and features among the various figures are denoted by like reference characters. The present invention is disclosed a dynamic hip combination structure used for reconstructing the femoral head fractures, which mainly comprises of a barrel 1, a lag screw 2, two blade piece 3 and a compressing screw 4.
The barrel 1, as shown in
The lag screw 2, as shown in
The two blade pieces 3, as shown in
The inside end of the compressing screw 4, as shown in
When operating, the lag screw 2 is screwed into the fracture of the femoral head first, the extending portion 14 of the barrel I is put onto the outside end of the lag screw 2 and each first limit portion 144 and second limit portion 24 are disposed relatively each other to prevent the lag screw 2 from rotating therein, and then the connection portion 12 of the barrel 1 is fixed to the femur through the through hole 120 by four fixation bolts (not shown).
Subsequently, the two blade pieces 3 are wedged in each first long groove 146 and second long groove 26 against each other, as shown in
Finally, rotate the compressing screw 4 after the compressing screw 4 is inserted from the outside end of the extending portion 14 and screwed with the outside end of the lag screw 4. Since the outside end of the compressing screw 4 is stopped by the stop portion 142 of the extending portion 14 and each first limit portion 144 is set against each related second limit portion 24, operator rotates the compressing screw 4 through the barrel 1 and the lag screw 4 to tow two relative fracture position to reset.
In the embodiment, it is effectively increasing the contact area between the cross-lock combination structure and the femoral head by the two wing-type blade pieces 3, as shown in
Due to the inside ends of the above mentioned blade pieces 3 are protruded an adaptive length out of the extending portion 14, in practical operation, operator is able to drill a strip hole (not shown) in the femoral head adjacent to the outsides of the two second long grooves 26 so that the insides of the two blade pieces 3 extend to the inside of the femoral head.
In above mentioned embodiment, the quantity and the position of each blade piece 3 is a best implementation. In practical application, the quantity is not only able to adjust considerably, but also the each related long groove 146, 26 is able to be disposed at another non-planar positions excluding each first limit portion 144 or second limit portion 24.
Although the invention has been explained in relation to its preferred embodiment, it is not used to limit the invention. It is to be understood that many other possible modifications and variations can be made by those skilled in the art without departing from the spirit and scope of the invention as hereinafter claimed.
Number | Date | Country | Kind |
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098105867 | Feb 2009 | TW | national |