Surgery – Instruments – Orthopedic instrumentation
Reexamination Certificate
2002-01-04
2003-04-08
Philogene, Pedro (Department: 3732)
Surgery
Instruments
Orthopedic instrumentation
C606S087000, C606S08600R, C606S064000
Reexamination Certificate
active
06544266
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and apparatus for delivering bio-active compounds to specified sites of action in the course of performing surgical procedures and particularly of performing surgical procedures requiring reconstructive orthopaedic intervention. It further relates to preferred constructions of such apparatus so that it is best adapted for use in the performance of surgical procedures requiring reconstructive orthopaedic intervention, especially high tibial osteotomies and mandibular, or other skull bone, reconstructions.
BACKGROUND ART
It is known that the delivery of bio-active substances, such as bone morphogenic protein, to surfaces of bone can encourage bone growth. It is also known that when other bio-active substances are delivered to injured body tissues, for example, those tissues injured in the course of performing invasive surgical procedures, they may catalyse the healing process or carry out other desirable actions including preventing bleeding or excessive healing.
There is a variation in devices which can be implanted into the body of a patient during surgical procedures requiring reconstructive orthopaedic intervention. In cases where it is preferred to deliver bio-active substances to a desired site of action, for example, to the cut surfaces of bone comprising a wedge osteotomy or to a cut surface of bone exposed during mandibular or other skull bone reconstruction, such bio-active substances can be delivered to those sites of action via means of conventional delivery devices. However, when using conventional deliver devices, the bio-active substances must be delivered during the operation and before closure of the incision.
In the case of skull bone reconstructions, it is known to use wire gutters as scaffolding along which, it is aimed, bone will grow. While the application of bio-active substances to surfaces of bone may encourage bone growth, a device which provided a means to ensure that bone was encouraged to row in a particular direction at a particular location would offer a considerable improvement to existing methods for achieving that result.
In the case of high tibial osteotomies, there are a number of additional issues which the present invention addresses and which require further comment.
High tibial osteotomy is an operation that is commonly used to straighten “bowed legs” or less commonly to correct “knock knees”. If a patient has either of these conditions the weight transmission through the knee is passed more to one side of the centre of the tibia than the other, resulting in excessive wear on that side of the patients knee. In the case of “bowed legs” the weight will be borne predominantly on the medial side of the knee and thus excessive wear will occur on that side of the patients knee. Often the wear will occur first, leading to bowing of the leg and then the wear accelerates. A positive feedback situation is thus created and the problem will be exacerbated with time unless there is surgical intervention.
Conventionally patients with this condition are given a number of choices of surgical intervention. In older patients it is usual to carry out a total knee replacement as the knee is often in a deteriorated state. In younger patients the choice is often to carry out a high tibial osteotomy. The best known procedure for this operation is to approach the upper end of the tibia from the lateral side and to fix the tibia in a more favourable alignment. This can be done either by removing a wedge of bone (referred to as a closing wedge) or by making a dome shaped cut, rotating the tibia and refixing the tibial plateau relative to the tibial shaft. In either of the above cases fixation of the “fracture” created by the saw cut during the osteotomy is required. This may be achieved using a plaster cast, staples, staple plates or plates and screws.
It is also known to approach the operation from the more worn side of the tibia and to provide an opening wedge. In this case a cut is made across the tibia and the worn side is elevated to give the tibial plateau a more favourable alignment.
There are a number of problems associated with the traditional approaches to carrying out high tibial osteotomy. The aim of the operation is to realign the tibia so that, in the case of “bowed legs”, the foot is swung outwardly and the weight is carried with an over correction of, typically, about 3° so that the lateral side of the joint gets more weight and the medial side can recover. This arrangement has been found preferable as compared with giving equal weighting to both sides of the joint.
Intra-operatively it is difficult to apply the correct angle of adjustment. In the closing wedge situation the correct thickness of wedge must be taken from the patient. If the second cut is not at the right angle it has been found very difficult to make a third cut to correct the angle. In the case of the domed osteotomy the actual angle of shift of the tibia is difficult to determine accurately. In either it is difficult to reliably set within 2° of the desired angle. It has been found a little easier to determine the right angle in the case of an opening wedge however this has substantial difficulties as will be explained in the following paragraph.
Fixation of the fracture created surgically is a problem in respect of all of the known methods of high tibial osteotomy however it is a particular problem in connection with the opening wedge operation. There is great force to close the wedge from gravity and from muscle forces. There is also the problem that bone requires some compression to heal so that a bone held open tends not to fill with bones The latter problem has been tackled by packing the open wedge with bone harvested from elsewhere on the patient The former problem has been approached by the use of a plate and screws to hold the gap open. These approaches have failed due to collapse of the bone graft before it has time to strengthen and heal, and failure of the plate to hold the bones apart. This latter failure occurs because there is only room for one screw above the osteotomy so that there is no rotational control of the plate which tends to collapse by twisting or shearing out of the bone. Even if two screws could be placed the forces are so great that screws can be ripped out of the bone.
In the case of surgical intervention on the lateral side of the knee there is a problem that the cut is near a major nerve and the incision is incompatible with subsequent incisions should a total knee replacement be required. Too many incisions in a limited area causes compromise of the blood supply to the skin and to underlying tissues creating a risk of these tissues failing to heal after surgery. Operations from the lateral side also have the problem that the fibula, which lies adjacent the lateral side of the tibia must also be cut and shortened.
Secondary alignment issues are also hard to control with the known methods of high tibial osteotomy. The osteotomy should be done exactly in the medial-lateral plane. There should be no posterior tilt, nor rotation about the axis of the tibia. If such misalignments are introduced by the operation other deformities are introduced into the long axis of the tibia. These problems are particularly severe in the case of the closing wedge operation as in that case two incisions have to be made in the bone rather than one in an opening wedge procedure. In addition the two cuts of the closing wedge osteotomy must meet exactly at the cortex of the bone on the side thereof opposite to the side on which the wedge is to be removed. As such, the cortex of the bone on that side will remain intact thereby acting as a stabilising means for the whole procedure. The absence of such stabilising means would considerably increase the risk of the procedure failing.
In order to overcome many of these problems Puddu (U.S. Pat. No. 5,749,875) designed a system for performing proximal tibial for femoral) osteotomies which includes a plurality of bone plates of various sizes, and a calibrated wedge too
Cross Mervin John
Roger Gregory James
Australian Surgical Design and Manufacture PTY, Ltd.
Hunton & Williams
Philogene Pedro
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