Surgery – Instruments – Orthopedic instrumentation
Reexamination Certificate
2000-11-13
2002-05-14
Philogene, Pedro (Department: 3732)
Surgery
Instruments
Orthopedic instrumentation
C606S08600R, C606S087000, C606S098000, C074S490070
Reexamination Certificate
active
06387100
ABSTRACT:
TECHNICAL FIELD
The present invention pertains to a method for aligning an arrangement for marking of directions for perforating together with a position determining arrangement, attached to a machine with a movable arm, in bone structures at surgery, and to said arrangements.
BACKGROUND ART
Present methods regarding, for example, hip fracture surgery involves a great deal of craftsmanship. A patient with an injured leg is placed supine on a fracture table and a reduction maneuver is carried out. The foot of an injured leg is firmly fixed in a specially built shoe. Traction and rotation are applied until the fracture is reduced.
A fixation of an injured leg is normally so firm that no movement will take place unless a substantial force is applied to the leg. A mobile X-ray apparatus, a “C-arm”, with two perpendicular radiographs, the anteroposterior (AP) and the lateral (Lat) projections, checks quality of reduction. The result of a reduction can only be judged through said at least two radiographs, and no correction for variations in hip rotation is possible.
Screws are inserted in order to fixate the fractured bone parts. The screws are introduced by a hand-held drill which opens up guide holes for the screws, whereby a surgeon has to judge the position of the drill from said two perpendicular radiographs and manually adjust the position of the drill in three dimensions, which is a very difficult task.
Unfortunately, the insertion of screws very often has to be repeated. Repeated trials of insertion destroy the bone structure in the femoral neck.
To be able to check the quality after a performed hip fracture surgery a method was developed for determining the post surgery position of a fixating means. It was introduced by the inventor of the present invention in his thesis “Internal Fixation of Femoral Neck Fractures”, Stockholm 1993, ISBN 91-628-0804-4. Nevertheless, the method has only been used for post-surgery quality checks and scientific statistics, and it has not occurred to or been obvious to any person skilled in the art to modify the method so it can be used in determining how and where to drill in a femoral bone fracture in order to attach fixating means and facilitate healing of said fracture in a best possible way.
Today, orthopedic surgery has promulgated towards sophisticated hi-tech implants being manually inserted through in-precise techniques. To manually insert implants is a task for a highly skilled orthopedic surgeon with, for example, 10 years of training in the present medical field.
For diagnosis groups, where a great number of injuries is accumulated, the result of performed surgery is less satisfactory than it could be. Hip fractures belong to such a group, hereby about 18,000 incidents/year occur in Sweden alone, 9.000 cervical and 9,000 pertrochanteric, to a cost of approximately SEK 1.4 billions.
Despite of the more than 100 different fixating methods developed for this kind of fractures, the result of performed surgery is relatively poor. As much as approximately 35% of all cervical fractures do not heal, and 20% of them have to be re-operated within a time period of 1-2 years. For pertrochanteric fractures the same rates are 10% and 4% respectively. Every re-surgery approximately costs SEK 185.000.
It is agreed with among surgeons and other experts that the main reason for the high percentage of re-surgery is an inadequately positioning of the fixating screws, which hold the fracture together during the following healing process, see “Fixation of femoral neck fractures: comparison of the Uppsala and Von Bahr screws.” By Rehnberg & Olerud, Acta Orthop Scand 60, 1989, p. 579-584.
Considering the costs of SEK 185.000 for one re-surgery, a decrease in the rate of such surgery with 50% would gain a save of SEK 160 millions in Sweden a year in surgery costs. A bigger Swedish Hospital would save approximately SEK 8 millions, not to say what is gained in relief for fractured patients.
A known arrangement to support surgery is the so-called ROBODOC™ Surgical Assistant System. The ROBODOC™ robot is able to precisely prepare a femoral channel for placement of a cementless prosthesis.
Due to the manual surgery technique involved in surgery relating to bone fractures and judgements made from said radiographs in real time during surgery/surgical treatment without any tools for performing analysis, the X-ray radiation will be unnecessary high for patients and personnel serving during surgery.
From U.S. Pat. No. 5,603,243 by Finley, an alignment apparatus for aligning X-ray images is known. The apparatus comprises two elongate members in an orthogonal configuration in relation to each other on a supporting framework. Within each member there are four predetermined axes with a plurality of balls mounted on each axis. The balls are preferably of different sizes or are designed to absorb different quantities of X-ray radiation, so that the images of the balls may be recognised individually on an X-ray plate. Since the orientation and spacing of the balls is known, it is possible to determine the precise position and precise orientation of parts of a patient present within an X-ray image through calculation.
The support frame and the elongated members with axes comprising balls provides a fairly complicated apparatus with a lot of calculations for alignment of X-ray images, thus an alignment method or apparatus of simpler construction would be appreciated.
It would be an advantage therefore, to provide a method and arrangements that can aid a surgeon in preparing and supporting orthopedic surgery. Such a method and arrangements are set forth through attached independent claims. Specific embodiments of the invention are introduced through the attached dependent claims. Hence, the method and arrangements of the present invention and details thereof provides such advantages.
SUMMARY OF THE DISCLOSED INVENTION
The present invention aims to solve problems related to determining positions, directions and distances in magnified X-ray images for bone structure surgery.
In order to solve said problems, the present invention sets forth a method for aligning a means for marking of directions for perforating together with position determining means, attached to a machine with a movable arm, in bone structures at surgery, comprising the following steps:
attaching a marking pin to said means for marking, activating said machine and move said means for marking to a defined start position;
assigning said machine a first operation position changing its co-ordinate system so that movement of the marking pin is, approximately, performed within the cross-section of a movable marking pin holder;
aligning said position determining means in relation to said means for marking, said position determining means having at least four round elements;
positioning said position determining means vertical to a reference surface, adjusted so that the marking pin points in a direction, which axis coincides with each round element when the machine moves a specified distance in a square pattern;
placing said position determining means adjacent to the part of the body where the perforation is to be made;
placing an X-ray machine adjusted so that, when radiographs are taken, two of said four round elements cover each other in two orthogonal projection planes;
determining a starting position, whereby said two covered round elements represent the starting position for the machine;
digitizing said radiographs and using the distances between said other non covered round elements in said radiographs, representing the magnification factor, which is calculated and displayed, whereby the magnification factor relates to the movement of the machine arm;
introducing said marking pin through skin and muscles to a position close to the bone structure which is to be perforated;
measuring the distance the marking pin holder has to be moved, thereby giving the machine a second operation position in accordance with the distance the marking pin holder has been moved, whereby the machine arm is able to move around this s
Medical Robotics i Stockholm AB
Philogene Pedro
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