Surgery – Instruments – Orthopedic instrumentation
Patent
1991-11-13
1993-11-16
Brown, Michael A.
Surgery
Instruments
Orthopedic instrumentation
606 72, A61B 1756
Patent
active
052619125
DESCRIPTION:
BRIEF SUMMARY
The invention refers to an implant for an osteosynthesis device, in particular for spinal column correction.
Various methods and osteosynthesis devices are known for the treatment of injuries to the spinal column.
EP-A1 0 128 058 COTREL describes the known method of anchoring hooks or screws at the back of the spinal column and connecting them with a longitudinal bar.
GB-A2 173 104 WEBB describes a pedicle screw with a slotted head designed to hold a longitudinal bar. The head is threaded on the outside so that the longitudinal bar placed in its slot can be clamped down by means of a screw-on cap and an additional loose holding piece.
FR-A 2 624 720 COTREL also describes a pedicle screw with a threaded head designed to hold a longitudinal bar. In this version of a pedicle screw implant the head is also threaded on the outside. The longitudinal bar is clamped in position primarily by the placement on it of two diametrically opposing edges of the screw-on cap. The screw-on cap, furthermore, contains a central opening, through which an additional pin can be screwed against the longitudinal bar, in theory creating a three-point hold.
Finally, EP-A1 0 348 272 LANOY describes a pedicle screw analogous to FR-A 2 624 720, where the two-armed head, however, is threaded on the inside, and these threads hold a grub screw against the longitudinal bar.
In all of the known state-of-the-art systems the connection of the anchoring elements (hooks or screws) to the longitudinal bar is fraught with severe problems, which have to do less with the mechanical solidity of the connection than the intraoperative manipulation of the connection mechanisms by the surgeon, their adaptability, reliability, and space requirements.
The system under GB-A 2 173 104 WEBB requires an additional loose holding element to clamp the longitudinal bar, complicating its use.
In the system under EP-A1 0 348 272 LANOY, both sides of the head are not secured and are spread apart further by the introduction of the grub screw.
The chief disadvantage of the system under FR-A 2 624 720 COTREL is that the screw-on cap cannot be positioned in a way that it locks itself in place. Nor can screwing in a pin through the screw-on cap prevent the connection with the longitudinal bar from loosening. To the contrary, the forced three-point hold produced thereby becomes overtightened, causing the bracing system to become unstable. A further disadvantage consists of the ring-like placement of the screw-on cap onto the longitudinal bar in this well-known system. This kind of placement is particularly disadvantageous if the longitudinal bar is bowed--as is most often the case. In such cases, the longitudinal bar must be left straight for a distance which at least equals the diameter of the screw-on cap. If this requirement is not met, the screw-on cap either cannot be screwed into place or the slightest bend in the longitudinal bar will cause the screw-on cap to be pinched against the longitudinal bar on one side. This one-sided pinch is extremely dangerous since the screw-on cap comes loose with the slightest tilt of the implant (pedicle screw or hook) and releases the longitudinal bar. This kind of implant tilting, caused by stresses on the patient's spinal column, is often observed.
Finally, the system under FR-A 2 624 720 COTREL exhibits a further disadvantage in intraoperative manipulation, namely that the outside threads, onto which the screw-on cap must be placed, are interrupted by the arms. If the screw-on cap is not placed on the implant absolutely coaxially, it becomes tilted during installation. This kind of tilt, because of the requirement of ring-like placement with this system, leads, in turn, to insufficient fixation, which the surgeon fails to notice because the opening in the body limits his view.
This is where the invention seeks to help. The invention seeks to provide an implant for an osteosynthesis device, in particular for spinal column correction, which is easy to use, can be installed securely, and saves space.
Because of the special design of
REFERENCES:
patent: 4611580 (1986-09-01), Wu
patent: 4641636 (1987-02-01), Cotrel
patent: 4658809 (1987-04-01), Ulrich
patent: 4776328 (1988-10-01), Frey
patent: 4790297 (1988-12-01), Lugue
patent: 4805602 (1979-02-01), Puno
patent: 4887596 (1989-12-01), Sherman
patent: 4946458 (1990-08-01), Harms
patent: 5092866 (1992-03-01), Breard
Brown Michael A.
Synthes (U.S.A.)
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