Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Patent
1998-04-17
2000-01-18
Yu, Mickey
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
623 16, A61F 202, A61F 228, A61F 244
Patent
active
060154365
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to an implant for insertion between vertebral bodies as a replacement, consisting of two end implant parts to be positioned on the two adjacent vertebrae, and between them a center implant part which is connected by a thread to one of the end parts of the implant, whereby the three implant parts and the threading are arranged coaxially in the longitudinal direction of the spinal column and, by a rotation of the center implant part, the overall length of the implant can be adjusted and whereby end parts of the implant form tubular sleeves whose sleeve walls are perforated by openings.
BACKGROUND OF THE INVENTION
Implants of this kind are known from DE 44 23 527 A1 and serve as replacements for vertebrae or vertebral parts ablated from the spinal column. The implants make possible a distraction of the spinal column region containing the implant by twisting the center part of the implant. Each of the two end parts of the implant can be connected with the center implant part by its own screw thread, whereby the two threads are arranged coaxially in the longitudinal direction of the spinal column and run in opposite directions with respect to each other. If desired, through the openings in the implant parts it is possible to introduce a material to be put inside tubular elements, such as bone cement or bone fragments, to achieve a quicker attachment of the implant. Therefore the implant is well suited for the induction of bone formation and stimulation of bone growth and after implantation can grow easily and quickly into the bone. In any case in these implants the total axial length is at least equal to the total length of two oppositely working threads, which is a limitation of the minimal implant length, so that these known implants can not be used as intervertebral spacers or as intervertebral disk replacements.
OBJECT OF THE INVENTION
It is an object of the invention to provide an improved implant of the aforementioned kind, so that it can be adjusted to a minimal length, making possible its use not only as a complete replacement of a vertebral body, particularly in the area of the cervical vertebrae, but also as an intervertebral spacer for the replacement of an intervertebral disk, especially in the lumbar region.
SUMMARY OF THE INVENTION
According to the invention this object is attained in an implant in which the two end implant parts interengage axially with their sleeves and are guided at the sleeve walls axially slidably with respect to each other, and are secured against mutual pivoting about the sleeve axis. The thread between the center implant part and the end part which is connected therewith by the thread is provided on its sleeve. The center implant which can be rotated in the thread of this sleeve and is designed as an axial stop for the other end part of the implant.
Since the implant of the invention has only one screw thread the minimal length to which the implant can be shortened is determined only by the length of this single thread, since the two end parts of the implant can be practically completely threaded into each other over the entire length of their tubular sleeves, which altogether results in an axially very low construction, thereby making possible the use of the implant as a replacement for intervertebral disks. Nevertheless the distraction capability of the implant during surgery is fully maintained, since only the center implant part has to be correspondingly pivoted in the thread for the desired length of the implant to be set.
An embodiment of the implant of the invention, which is particularly simple and advantageous from the manufacturing, assembly and handling point of view, has the sleeve of the end implant part connected by the screw thread to the center implant part with its thread on its outer periphery, and is radially surrounded on the outside by the center implant part as well as by the sleeve of the other end part of the implant. In this way the center implant part is easily accessible for turning and the t
REFERENCES:
patent: 5336223 (1994-08-01), Rogers
patent: 5358524 (1994-10-01), Richelsoph
patent: 5702455 (1997-12-01), Saggar
Dubno Herbert
Heinrich Ulrich
Stewart Alvin
Yu Mickey
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