Surgery – Instruments – Orthopedic instrumentation
Patent
1997-01-10
1998-04-07
Buiz, Michael
Surgery
Instruments
Orthopedic instrumentation
606 72, 606 73, A61F 500
Patent
active
057358524
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to a clamp for a spinal affixation device.
BACKGROUND ART
Such a clamp is known for instance from European patent Application No. A 0,553,424. It is used to affix the individual intravertebral body in a mutually defined position, a number of bone screws implanted into the intravertebral bodies being fastened by such clamps onto a longitudinal support running in the direction of the spine.
The known clamp disclosed in ,the European patent Application No. A 0,553,424 is in three parts in order to allow adjusting both the distance and the angular position between the bone screw and the longitudinal support. It is precisely this high adaptability which substantially hampers surgery. The angle and distance between the bone screw and the longitudinal support must be adjusted in-situ. This constraint entails simultaneously setting the clamp and the longitudinal support on one hand and on the other hand fastening the affixation screw to achieve the desired configuration. Thereby a spanner wrench must be used to apply a torque opposing the tightening torque of the affixation screw to prevent the assembly as a whole from rotating while this affixation screw is being tightened. Mounting several such assemblies within the confines of the cervical spine is exceedingly laborious because the parts to be assembled are not easily seen and because the surgeons hamper one another when lining up and affixing the individual components.
SUMMARY OF THE INVENTION
The object of the invention is palliation. It addresses the task of creating an easily and economically manufactured clamp making superfluous intra-surgery adjustment of the mutual distances and angles of the structures held by the clamp and thereby reducing surgery time while increasing reliability.
The object of the invention is solved by a clamp having a base body (1) crossed by a duct (2) with longitudinal axis (3) receiving a longitudinal support (15), the duct (2) being fitted with means allowing to rotationally and longitudinally lock in place the inserted longitudinal support, an extension (4) continuing the base body (1) and crossed by a screw hole (5) evincing a center axis (6) and receiving a bone screw (16). The longitudinal axis (3) and the center axis (6) define skewed straight lines. The extension (4) is mounted at an angle of 0.degree. to 45.degree. with regard to the plane of projection (11), and the plane of projection (11) is formed by the longitudinal axis (3) and the orthogonal line (10) which is perpendicular to the longitudinal axis (3) as well as to the longitudinal axis (9). In this device, the spacing (7) between the longitudinal axis (3) and the center axis (6) is constant and within the range of 4-10 mm; and the extension (4) is substantially tabular.
Preferably, the spacing (7) is within the range of 5-8 mm, and more preferably is from 5.8 to 6.7 mm. Also, the length of the duct (2) measured in the axial direction is from 5 to 7 mm, and more preferably from 5.7 to 6.3 mm. Furthermore, the duct (2) evinces a diameter in the range of 3.0 to 4.5 mm, and preferably from 3.2 to 3.8 mm.
Advantageously, the means locking a longitudinal support inserted into the duct (2) include, inside the base body (1), a threaded borehole (8) having a longitudinal axis (9) orthogonal to the plane (11), and an adjusting screw (17) being insertable into said borehole (8). The screw hole (5) is concave, preferably spherical, in the seating zone for the head of a bone screw inserted into the hole (5).
In a most preferred arrangement, the clamp is integral.
The clamp may have an azimuth angle (12), subtended by the longitudinal axis (6) and the longitudinal axis (3) in the plane of projection (11) formed by the longitudinal axis (3) and the orthogonal line (10), which is within the range of +20.degree. to 30.degree.. The clamp may also have an azimuth angle (12) which is within the range of -5.degree. to +5.degree. C., and a cranial angle (13), subtended by the center axis (6) and the longitudinal axis (3) in the plane of pr
REFERENCES:
patent: 5133717 (1992-07-01), Chopin
patent: 5147360 (1992-09-01), Dubousset
patent: 5403314 (1995-04-01), Currier
Amrein Thomas
Jeanneret Bernhard
Tagwerker Konrad
Buiz Michael
Synthes (U.S.A.)
Woo Julian W.
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