Surgery – Instruments – Orthopedic instrumentation
Patent
1991-07-28
1993-03-23
Hafer, Robert A.
Surgery
Instruments
Orthopedic instrumentation
A61F 504
Patent
active
051960133
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a pedicel screw which may be employed in particular in combination with a correcting and supporting apparatus for a spinal column, and to a correcting and supporting apparatus for a spinal column in combination with such pedicel screw.
UNFALLCHIRURGIE, Vol. 12 (1986), pages 68-79 discloses the mechanical principle for the dorsal stabilisation of the pectoral and lumbar spinal column by means of a correction and supporting apparatus. The brochure "Fixateur Interne fur die Wirbelsaule, Original-Instrumente und -Implantate der Schweizerischen Arbeitsgemeinschaft fur Osteosynthesefragen-AO" discloses a fixateur interne or internal fixation device. This device comprises two paris of so-called Schanz screws. A first pair thereof is screwed into the first vertebra through the arc roots (pediculus) on both sides and a second pair thereof is screwed into a second vertebra through the arc roots (pediculus) on both sides. The Schanz screws then have a shaft of a length of about 10 cm projecting from the vertebra. After mounting the four Schanz screws a parital reposition of the vertebra is already manually possible by means of the long projecting screw ends. Thereafter threaded rods are slipped into respective two Schanz screws lying on the same side of the superposed vertebra. Thereupon the projecting free ends of the Schanz screws are again operated and the threaded rods are arrested. Finally those parts of the Schanz screws which project beyond the threaded rods are cut off. Threrafter the fixateur is covered with the muscles and the skin and the cut is closed. Whenever the surgeon will discover the next day that an adjustment of the angular position of the vertebra would be required, such an adjustment is no longer possible, because the projecting parts of the Schanz screws which are necessary for adjusting the angular position have already been removed. Moreover, the rotational flexibility of the apparatus is low.
The DE 36 39 810 Al discloses an implant for correction and/or stabilization of the spinal column. The implant comprises screws having a threaded shaft part and a receiving part which is rigidly connected with the threaded shaft part and turned away therefrom. A respective pair of screws has the end thereof rigidly connected with a tie rod through the corresponding receiving part. Moreover, the pair of screws is additionally connected through a tension rod at a point in a distance from the connection between the receiving part and the tie rod. In order to allow an adjustment of the axial direction of the screws and the vertebra receiving the screws in a direction deviating from the parallel position, the connection between the tension rod and both screws is adjusted such that a flexion or bending strain is exerted onto the tie rod or the tension rod. This results in an uncontrollable material stress which may, in course of time, lead to a destruction of the tension rod and/or the tie rod. This may result in unpredictable problems in the interior of the body.
It has been found that while adjoining vertebrae are expanded by such correcting and supporting device, the vertebra which is positioned between the vertebrae into which the screws of the device engage, is shifted into the direction where the expanded vertebrae are close to each other, which constitutes an unwanted effect.
It is an object of the invention to provide a pedicel screw to compensate this effect in combination with a correction and supporting apparatus for the spinal region, and to provide a correcting and supporting apparatus in particular for the spinal column employing such pedicel screw, which prevents or compensates for the shifting of a vertebra transverse to the spinal column apparatus when such correcting and supporting apparatus is employed.
A correcting and supporting device to solve this problem is indicated in claim 1.
Additional embodiments are indicated in the subclaims.
Further features and advantages will become apparent from the description of the embodiments and the figures, in which:
FIG. 1 is
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Biedermann Lutz
Harms Jurgen
Brown Donald
Hafer Robert A.
Hanlon Brian E.
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