FR2682288A1 - Surgical acetabular drilling device comprising a depth index - Google Patents

Abstract

The invention relates to an arrangement which makes it possible to drill the acetabulum of the pelvis in a perfectly hemispherical manner, and to know the thickness of bone removed during the drilling. The device, fitted with a hemispherical drill (1) comprises, within the drive shaft (2), a feeler (3) with a spring (4), provided with an index (5) which can be seen in a slot (6). The device according to the invention is particularly intended for fitting cementless total hip prostheses.

Description

 The present invention relates to a surgical milling device, comprising a depth index in order to safely bore the acetabular cavity of the coxofemoral joint. There is nothing to prevent the device from being adopted for other interventions on other joints, the scapulo-humeral cavity for example.

 The recent progress made in the area of ablation of the coxofemoral joint, and of its replacement by a PTH, lead to the installation on the pelvis of a prosthetic acetabulum semi hemispherical.

 In the case of "cementless" THA where the mechanical connection between pelvis and prosthesis is ensured in the long term by bone regrowth, the surgeon must mill all or part of the cortical bone which lines the acetabular cavity. This operation is suitably successful when the poles of the cavity and the prosthesis are in contact.

In addition, if it is necessary to mill the cavity to reach the cancellous bone, and thus promote bone regrowth, the practitioner must be able to know at all times the thickness of bone that he has just removed.

 Current burs, without index, do not allow this thickness to be measured in situ, and the surgeon therefore works without direct information. He must regularly remove the cutter, observe the marks on the tool, and only his skill allows him to stop milling when he deems it appropriate.

 In addition to wasting time observing the marks on the tool, the practitioner is faced with permanent operating risks, if the permitted depths are exceeded.

 To carry out such milling under excellent conditions, it is desirable to constantly know the distance separating the cutter from the polar bottom of the acetabular cavity.

 This result is achieved in accordance with the invention by the fact that the device comprises a central rod in the polar drive axis of the cutter. This central rod which acts as a feeler, initially comes out of the cutter, extends inside the drill cutter connecting shaft and has a positioning index.

 Other characteristics and advantages of the invention will become apparent from the description and the appended drawings, which show a preferred embodiment of the invention.

 Figure 1 is a sectional view in a meridian plane of the device, and of the acetabular cavity before milling.

 Figure 2 is a sectional view of the same device during milling.

 Figure 3 is a sectional view at the end of wise milling.

 FIG. 4 represents a complete view of the device.

 FIG. 5 represents a variant of the previous device. The central rod can be removable, and its end is provided with a front point.

 FIG. 6 represents another variant with a hollow rod which can thus slide on a guide pin.

 FIG. 7 shows a last variant with a rod provided with a front point. This figure also shows the possibility of interchanging on the tree, the spheroidal cutters. These cutters are further surmounted by an annular suction system.

 The device seen in section in FIG. 1 comprises a central rod or feeler (3) sliding inside the drive shaft (2) of the cutter (1).

 In FIG. 2, the polar axes of the cutter and the acetabular cavity (11) are generally merged during milling, which will progress along this axis. The circular internal rod, provided with a ball stop (14), if necessary, will not be driven during the rotation of the tool; on the other hand, by means of a welded ring, surmounted by the ball stop, this rod will be pressed by a spring (4) on the acetabular pole.

As the tool goes deep, the stem seems to go up inside the tree. One or more windows placed on this tree make it possible to observe this rise equivalent to penetration and quantified by an index (5) meeting graduations.

A screw (10) placed at the end of the shaft allows easy access and disassembly of all internal parts if necessary.

 At all times, the surgeon appreciates his work to the millimeter. He will thus know perfectly when he has reached the polar cortex; at this instant the pole of the cutter, and the end of the stem are concomitant.

 He can then (Figure 3) continue milling if he wishes to remove the polar cortex. On the condition of maintaining his drill along the polar axis of reference, he will assess by the same technique the thickness of cortical removed. In fact, the cortex under the index finger will not be attacked by the tool and will therefore end up inside the cutter acting as a reference stud (15).

 Maintaining the tool along the polar axis can tolerate a slight movement of about one centimeter. This movement is reflected at the level of the rod only by a slight lateral movement of one or two millimeters which cannot destroy the stud if it has for example a diameter of five millimeters like the rod which it supports.

 When the practitioner judges the required depth reached, he can then deliberately tilt the shaft of the hemispherical bur, which then makes it possible to cut the previous stud, and to perfect the spheroidal bore of the cavity.

 The embodiment which has just been described constitutes a preferred and nonlimiting example of the invention.

 Various variants are possible, and do not depart from the scope of the invention.

 Thus (FIG. 5), it is possible to make the central rod (8) removable. The latter can then serve as a spindle guide to the cutter at the same time as it will serve as a depth index. The forefront with which it is provided is previously fixed in the polar cortex. The stop flat (16) placed on the bone ensures the zero setting of the device.

 Figure 6 shows a hollow rod (12); in this case, we can first put an ordinary spindle guide (13) on which the indexed hollow rod will slide.

 Figure 7 shows a rod provided with a small lug (17) whose role is to avoid any parasitic sliding, and to ensure a better maintenance of the tool by the practitioner. We can also see a thread (7) inside the cutter, corresponding to the end of the drive shaft (2). This makes it possible to reduce the milling material, with a single shaft rod device, on which the required cutter is screwed according to the diameter to be bored chosen.

 This is how it is possible to replace the spring with a comparator integrated in the shaft.

 Thus it is possible to replace the index visible through the windows of the drive shaft by another conventional indexing means, such as an electrical contact or the appearance of any mark.

Claims (5)

1) Device for milling the acetabular cavities with  by means of a hemispherical bur (1) and characterized by  what it includes within its drive tree  (2) a spring-loaded probe (3) (4) provided with a  index (5) appearing in a lumen (6), when  the poles of the cavity and the strawberry arrive in  contact. 2) Device according to claim 1 characterized in that  the hemispherical bur is screwed (7) onto the shaft  training 3) Device according to one of claims 1 or 2 charac  terized in that the shape of the strawberry is arbitrary. 4) Device according to one of claims 1 to 3 charac  terized in that the displacement of the index finger (5) is  secured to an electrical or mechanical measuring device  Annex.  guide (13).  hollow (12) which can slide along a spindle  characterized in that the probe is a rod 5) Device according to one of claims 1 to 4 and 5) Device according to one of claims 1 to 5 charac  terrified in that it adds an aspi system  ration (9) for removing debris.