Surgery – Instruments – Orthopedic instrumentation
Patent
1994-05-09
1996-12-17
Graysay, Tamara L.
Surgery
Instruments
Orthopedic instrumentation
A61B 1770
Patent
active
055848320
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a hook for correction of spinal deformities.
It is often necessary to treat thoracic vertebral column deformities surgically. The anatomy of the vertebral column must be restored and maintained. For this, fixation systems are used either dorsally or ventrally. Dorsal systems generally consist of at least one longitudinal support, but most have a left and a right support, and individual anchoring elements. The latter form a load-transferring connection between the vertebral column and the longitudinal support.
Currently there are three possibilities known for connecting the longitudinal support to the vertebral column: wire cerclages, pedicular screws and vertebral column hooks.
The wire cerclages are placed along the lamina and the spinous processes of the spinal vertebrae. There is a certain risk connected with the attachment of wire cerclages for the patient, since they may injure the spinal cord. In addition, the wires may, over time, cut through the bones (high local tension peaks cause resorption of the bones under the wire) or may simply break.
Pedicular screws are generally screwed through the pediculus into the vertebra. The pediculi are very narrow in the upper thoracic vertebral column and difficult to locate due to the deformity. The use of pedicular screws in this area therefore poses a high risk. In addition, many surgeons generally avoid using pedicular screws in the area of the thoracic vertebral column.
Vertebral column hooks are currently the elements most often used. Depending on the situation, they are placed on the lamina, the pediculus or the transverse process of the vertebrae. In contrast to the wire cerclages, they offer the advantage that the stress is transferred to a relatively large area of the bone and accordingly there is hardly any bone resorption at the point of contact between bone and hook. The hooks have, however, in contrast to the pedicular screws, the major disadvantage that they can transfer stress to the longitudinal support only when they are pressed firmly against the bone. With current systems such an initial load can be applied only through the longitudinal support. This makes it very difficult to manipulate the vertebrae in the area of the deformity with currently known hooks. The invention is intended to create remedial measures here. The invention is based on the task of creating a hook firmly and stably connected to the vertebra.
These difficulties are overcome or ameliorated by means of a hook comprising a shaft portion having a longitudinal axis, receiving means for seating a support rod positioned transversely to the axis and a curved hook body having a first end connected to said shaft portion, a second free end, and a curved section connecting said first and second ends forming a bight between the first end and the second end, and a hole in the curved section of the curved hook body adjacent the first end, the hole having a central longitudinal axis extending into the bight at an angle to the longitudinal axis.
Pedicular hooks pursuant to the invention are suitable, in particular, for thoracic application. Due to the additional screws insertable through the hook shaft, the pedicular hook can be pressed firmly into the osseous seat. The screw here is introduced from the caudal to the cranial (at an angle of approximately 120.degree.-125.degree. to the longitudinal axis of the pedicular hook) through the hook shaft into the main mass of the facet joint or to the corresponding vertebra. Thus, the pedicular hook can transfer forces and torque like a pedicular screw without slipping out from its osseous anchorage, which forms the precondition for the execution of a segmental correction.
There are many other advantages to the invention: invention with the vertebra, the hook can be manipulated individually; from the less deformed side; insertion of pedicular screws, since the hooks serve simultaneously as the drilling guides for the bone screws; position of the bone screws.
The fastening of the hook pursuant to the invention to the lon
REFERENCES:
patent: 5000165 (1991-03-01), Watanabe
patent: 5263954 (1993-11-01), Schlapfer et al.
J. Dubousset & Y. Cotrel, "Die CD-Instrumentation in der Behandlung von Wirbelsaulendeformitaten", Orthopade (1989) 18:118-127.
Graysay Tamara L.
Synthes (U.S.A.)
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