Surgery – Instruments – Orthopedic instrumentation
Reissue Patent
1993-10-12
2001-06-26
Brown, Michael A. (Department: 3301)
Surgery
Instruments
Orthopedic instrumentation
C606S070000
Reissue Patent
active
RE037249
ABSTRACT:
In neurosurgical, plastic and craniofacial operations on or through the vault of the human skull, after detachment of the soft parts covering the cranial vault frequently large-area bone segments of the skull cap are detached and secured again at the same point of the skull cap or in a different position at the end of the surgical operation (refixed).
In the surgical treatment of craniofacial abnormalities, frequently one or more bone segments of the skull cap are removed and after modeling corresponding to the desired cosmetic result refixed again in a displaced position. Such operations, which are frequently carried out in infancy, serve the purpose of correcting bone malformations of the skull cap in order to permit unobstructed growth of the brain and at the same time also to improve the cosmetic appearance of the patient.
In neurosurgical operations bone covers of the skull are lifted off in various regions and sizes to permit access to the brain. As a rule, the bone segments removed in this manner (hereinafter referred to as cranial bone covers) are refixed in the original position after completion of the socalled soft part operation (i.e. the operation on the brain).
The operating technique employed in such operations frequently includes a socalled bow incision (from ear to ear over the highest point of the skull cap) through the soft parts, whereafter a subpereosteal undermining is carried out and the largest soft part lobes are folded forwardly or rearwardly.
Depending on the size, location and geometrical form of the bone cover to be lifted off, several holes are drilled through the cranial vault. If the bone cover to be removed is for example a triangular skull cap segment, as a rule three holes are drilled at the corner points of the bone cover. Thereafter, by means of a saw (which is provided with a guide nose in order to avoid dura mater injuries) the socalled connecting osteotomies are made between the drill holes; with a triangular form of the bone cover to be lifted off the connecting osteotomies are thus the sides of a spherically curved triangle. Thereafter the bone cover can be lifted off to carry out the further operation.
After completion of the operation the previously removed bone covers have to be refixed again, i.e. secured again at the desired location. Various aids are known in the prior art for this refixation of the bone cover. EP 0 290 138 A2 and EP 0 291 632 A1 describe for this purpose socalled small bone plates of body-compatible material, for example titanium or a chromium-cobalt-molybdenum alloy, which are made strip-like and at intervals are provided with holes for receiving bone screws. These elongated plates are so designed that they can be deformed by the surgeon to adapt them to the bone in the area to be treated.
EP 0 347 658 A1 described a bone plate for osteosynthesis having holes to receive bone screws and a gear mechanism between the plate parts for adjusting the relative position of the plate parts.
German utility models DE 85 28 003 U1 and DE 87 06 912 U1 describe bone plates employed for fixing a cranial bone cover.
The elder application published as DE 40 28 021 C1 describes an osteosynthesis grid with holes for receiving bone screws (i.e. securing screws which are screwed into the bone).
Another implant is the socalled mesh systems, in particular according to Dumbach. Here, relatively large-area perforated discs (for example of titanium) which are flexible in order to be exactly fitted by the surgeon are used as implant for bone fixation, primarily in the jaw region. The aforementioned drill holes made at the start of a trephination present particular problems. For several reasons, among others for protecting the brain covered postoperatively only by the soft parts and for improving the cosmetic result, the drill holes should also be closed after the operation. When the drill holes are made using conventional drills or trephines, as a rule however no bone plug is formed which could be refixed; on the contrary, due to the cutting action of the rotating instrument only bone meal is formed. In the prior art, the following attempts are made to solve the problem of the drill holes.
The drill holes remain unclosed. However, after the healing phase this gives a mostly unsatisfactory cosmetic result because, in particular in the region of the forehead, visible “dents” result beneath which frequently the pulsation of the brain is even visible. The covering of the drill holes simply by means of the soft parts does not provide adequate protection of the brain from injuries.
The bone meal forming when making the drill holes can be partially collected and used for covering the perforation. However, with this method adequate stability of the bone and a predictable positive cosmetic result cannot be ensured. Also, no immediate protection of the brain is obtained.
It is further known to use alloplastic materials, such as bone waxes, bone cement, etc. However, these materials do not provide reliable protection of the brain either and in addition as a rule they are exogenous implantation materials which remain in place and are not surrounded naturally in the course of time so that infections or other undesired reactions of the body can occur.
Finally, it is further known in the prior art to use plastic covers which project over the edge of the drill hole and are clamped in the drill hole itself. With this method as well no cosmetically satisfactory result is ensured (the plastic covers can project over the contour of the bone). Furthermore, due to its softness plastic does not offer reliable protection against puncture wounds. The invention is based on the problem of providing means for solving the problems explained above and permitting refixation of cranial bone covers which ensures both a reliable protection against injury and a cosmetically predictable and desired result.
This problem is solved in a plate of the type mentioned at the beginning by a plurality of vanes which extend racially with respect to a centre and which are separated from each other by slots, and of which at least some comprise at their outer peripheral portions in each case a hole for receiving a bone screw.
The plate according to the invention covers the drill hole and its outer contour is preferably substantially round, in particular circular, or polygonal. The preferably slightly concavely formed cover plate is made available in various sizes and arranged by the surgeon concentrically over the drill hole and can then be anchored securely to the cranial bone by means of bone screws.
The bone screws are led through holes in the plates according to the invention which are arranged at the outer peripheral portions of the vanes, i.e. readily adjacent (inside or outside) said portions. This optimizes the mechanical stability of the refixation.
Preferably, the holes for receiving a respective bone screw are arranged on a circle of which the centre point coincides with the centre of the plate.
Along the periphery of the plate according to the invention the holes for receiving the bone screws are preferably arranged at regular intervals, at least three holes for receiving screws being necessary and provided, in order to achieve a fixation-stable three-point anchoring. Additional holes for receiving screws increase the anchoring possibilities of the plate.
The vanes of the plate according to the invention are joined together in the interior of the plate. The entire plate is made integrally from a single material, such as titanium, niobium, etc.
The individual vanes of the plate according to the invention are separated from each other by radially extending slots. The slots extend however preferably only over a portion of the radius of the plate in order to achieve good stability in the refixation. Preferably, the slot length corresponds to approximately half the radius of the plate with an allowed deviation of ±30%, the radius being related to the solid part of the plate, i.e. without any possibly provided additional rings at the exterior of the plate for accommodating
Leibinger Franz
Leibinger Karl
Akers Lawrence C.
Augustin Raymond W.
Brown Michael A.
Oswald Leibinger GmbH
Richardson Peter C.
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