WO2010046634A1

WO2010046634A1 - A surgical instrument

Info

Publication number: WO2010046634A1
Application number: PCT/GB2009/002493
Authority: WO
Inventors: Alec Birkbeck; James Brooks
Original assignee: Depuy International Limited
Priority date: 2008-10-23
Filing date: 2009-10-20
Publication date: 2010-04-29
Also published as: GB0819380D0

Abstract

An elongate surgical instrument (30) has a handle (60) towards a first end and functional features for use in a surgical procedure towards a second end. The instrument has a rest portion (66) which contacts a surface when the instrument is placed on that surface and which is rounded when the instrument is viewed along its length. The handle comprises a core (62), and a sheath (64) which fits over the core and defines the longitudinal axis of the handle. The centre of mass of the handle is offset relative to its axis.

Description

A SURGICAL INSTRUMENT

This invention relates to a surgical instrument.

Surgical instruments are required to be capable of being held comfortably by a surgeon. An instrument will frequently have a handle by which it is held by the surgeon. The handle can be circular when viewed in cross-section along its length.

A surgeon might pick up an instrument for use from a flat surface on which it has been placed. An instrument whose shape is circular when viewed in cross-section along its length can roll on that surface. Examples of instruments which might be circular when viewed in cross-section along their lengths might include certain hammers (known as slap- hammers) which might be used to apply an impaction force to a component of an orthopaedic joint prosthesis or a corresponding trial component, and introducer instruments which might be used to grip a component of an orthopaedic joint prosthesis or a corresponding trial component to enable the component to be manipulated and positioned.

It can be inconvenient if an instrument can tend to roll when placed on a flat surface. For example, the instrument might roll out of the convenient reach of the surgeon. It might roll beyond the sterile region within the operating theatre, for example falling off the surface on to the floor.

The present invention provides a surgical instrument having a rest portion which contacts a surface when the instrument is placed on that surface and is generally rounded in outline when viewed along its length, in which a handle comprises a core and an overlying sheath, in which the centre of mass of the core is offset relative to the axis of the handle.

Accordingly, in one aspect, the invention provides a surgical instrument having a handle towards a first end and functional features for use in a surgical procedure towards a second end, in which the instrument is elongate and has a rest portion which contacts a surface when the instrument is placed on that surface, in which the rest portion is rounded when the instrument is viewed along its length, and in which the handle comprises a core and a sheath which fits over the core and defines the longitudinal axis of the handle in which the centre of mass of the handle is offset relative to its axis.

The instrument of the invention has the advantage that its tendency to roll across a flat surface is reduced compared with an instrument with the same rounded (especially circular) 5 cross-section. If a force is applied to the instrument of the invention which might otherwise cause it to roll, the instrument will tend then to roll back towards its original position. The instrument might tend to roll back and forth in a rocking type motion. This can help to ensure that the instrument remains in position on a surface when placed there for use by a surgeon. In particular, it can reduce the risk of the sterility of the instrument 10 being compromised as a result of it rolling across a surface.

It can be preferred that the rest portion is generally rounded when the instrument is viewed along its length. It can be preferred that the rest portion is circular when the instrument is viewed along its length. It can however be polygonal, for example with at least six sides, preferably at least eight sides, for example at least ten sides or at least twelve sides. The

15 vertices between adjacent sides of a polygonal rest portion can be rounded. The rest portion can be rounded with a radius which varies around the instrument. For example, the rest portion can have an oval shape when the instrument is viewed along its length. When the rest portion is not circular when viewed along the length of the instrument, it can be preferred that the ratio of the maximum radius to the minimum radius is not more than

!0 about 1.2, more preferably not more than about 1.1 , for example not more than about 1.05.

The rest portion can be provided by the instrument handle so that the handle contacts a surface when the instrument is placed on that surface.

It can be preferred that the handle is generally rounded when the instrument is viewed along its length. It can be preferred that the handle is circular when the instrument is .5 viewed along its length. It can however be polygonal, for example with at least six sides, preferably at least eight sides, for example at least ten sides or at least twelve sides. The vertices between adjacent sides of a polygonal rest portion can be rounded. The handle can be rounded with a radius which varies around the instrument. For example, the handle can have an oval shape when the instrument is viewed along its length. When the handle is not circular when viewed along the length of the instrument, it can be preferred that the ratio of the maximum radius to the minimum radius is not more than about 1.2, more preferably not more than about 1.1 , for example not more than about 1.05.

5 The longitudinal axis of the handle is defined by the sheath. The sheath will generally have an axis of symmetry and its longitudinal axis will then coincide with the axis of symmetry. For example, when the handle has a circular cross-section, the longitudinal axis of the handle will extend along the centre of the handle.

The offset weight feature of the instrument of the invention allows an instrument to be ) made in which the handle is circular, or otherwise rotationally symmetrical (for example with at least six or at least eight or at least ten sides), in cross-section, but which does not roll across a surface as might otherwise happen with an instrument having that cross- sectional shape. The invention can avoid the need to introduce shape features into the handle in order to reduce the tendency of the instrument to roll.

5 The core of the handle will generally be made from a material which has a density which is higher than of the sheath. The core can include a material which is the same as that from which at least some of the functional features of the instrument is made. For example, the instrument can include a shaft which extends from the handle and at least part of the core can be formed as one piece with the shaft.

D It will generally be preferred that the core is made from a metal. An example of a suitable metal for the core is a stainless steel. Stainless steels which are suitable for use in the instrument of the invention are known and commonly used in the manufacture of surgical instruments.

The core of the handle can comprise a core shaft which defines a shaft axis and at least one S core weight which is fixed to the shaft with the centre of mass of the weight offset relative to the shaft axis. For example, the core shaft might have at least one bore formed in it, at which a core weight can be fixed to the core shaft. For example, a core weight might comprise a pin which can be inserted in the bore in the core shaft. The core shaft might have a plurality of bores formed in it, and the core weight might comprise a plurality of pins which are inserted into respective ones of the bores.

The core of the handle can comprise a core shaft which is bent along the portion of its length in which the sheath overlies the shaft so that the centre of mass of the handle becomes offset relative to the axis of the instrument.

The core of the handle can have material removed from it selectively on one side, so that the centre of mass of the handle becomes offset relative to the axis of the instrument.

The sheath can be applied to the core of the handle by overmoulding.

The sheath can be applied to the core of the handle as a result of being shrunk on to the core. For example, a sheath can be made from a polymeric material which has been treated so that the sheath will shrink when heat is applied to it. This can be achieved, for example, by moulding the sheath in a desired configuration from a crosslinkable thermoplastic polymer, crosslinking the polymer, applying heat to the polymer so that it softens, expanding the sheath, and cooling the polymer so that its expanded shape becomes fixed temporarily. Subsequent application of heat to the polymer can cause the sheath to shrink back towards its as-moulded shape.

Polymers which can be used in the sheath part of the handle include polyolefins such as polyethylene and polypropylene, polyamides, polyesters and so on. Elastomeric materials which can be used in the sheath part of the handle include silicone rubbers. Mixtures of polymeric materials can be used.

The rest portion can be provided by a flange which is wider when the instrument is viewed along its length than the handle. The flange can be provided at an end of the handle. The rest portion can be provided between the portion of the instrument which is to be gripped by the user and the functional features of the instrument. When the flange is provided at the end of the handle which is adjacent to the functional features of the instrument, it can also function as a guard so that a user's fingers are kept away from the functional features of the instrument, which might be sharp or otherwise cause danger for the user.

The rest portion can be provided as a part of the handle or it can be provided as a part of the instrument which is separate from the handle. Preferably, the handle contacts a surface when the instrument is placed on that surface so that the rest portion is provided by the instrument. Preferably, the handle is circular when the instrument is viewed along its length.

Preferably, the instrument has features for gripping a component of an orthopaedic joint prosthesis or a trial component. For example, the instrument can have features for gripping the cup part of an acetabular component of a hip joint prosthesis. Known cup inserter instruments can grip the cup at its rim, on the external surface of the cup or on the internal surface or on a combination of the two. The instrument can have features for gripping the femoral component of a hip joint prosthesis. Known femoral component inserter instruments can engage the femoral component at the lateral and medial edges of the component. Such instruments can be used to manipulate the component so that it can be positioned appropriately relative to a patient's bone. An instrument can have a force applied to it to implant the component on to a patient's bone. Instruments for use in such applications are well known.

The instrument might be a slap hammer as is known in orthopaedic procedures for applying implantation forces to a component of an orthopaedic joint prosthesis.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings, in which:

Figure 1 is a side view, partially in section, of an acetabular cup inserter instrument showing hidden internal details of the handle. ^■

Figure 2 is a side view of a handle of an alternative embodiment of instrument. Figure 3 is a side view of a handle of a further embodiment of instrument.

Referring to the drawings, Figure 1 shows an acetabular cup instrument 30 of the kind which is disclosed in WO-A-2004/069107. It comprises a shaft 32 with a flange 34 towards an end 35 of the shaft. The flange 34 extends transversely from the shaft and can be retracted from an in-use position in which the flange can be received in a groove in the internal surface of a cup component to a retracted position in which the flange is withdrawn towards the axis of the shaft from the in-use position. Retraction of the flange allows the cup component to be released from the instrument. The flange is provided by a plurality of flange portions 36 which are spaced apart around the axis of the instrument. The flange portions are biassed towards their in-use position by means of a deformable O-ring 39 which acts against an upstand 42 on each flange portion. They can be displaced inwardly towards the retracted position by means of a collar 44 which carries a plurality of pins 45. The pins are tapered towards their tips and can be received in holes in the flange portions. The collar can slide on the shaft to move the pins into and/or out of the holes in the flange portions.

Metal components of the instrument such as the shaft and the flange can be made from a metal. Metals which are suitable for use in the manufacture of surgical instruments are known. Preferred materials include certain stainless steels.

The instrument includes a handle 60 which comprises a central core 62 which is continuous with the shaft 32. It includes an overmoulded sheath 64 which is circular in cross-section, and is shaped along its length to facilitate comfortable gripping by a user. The sheath is widest at a point 66 which is towards the end of the handle which is remote from the part of the instrument which engages the cup component. The sheath provides a flange 68 at its end which is closer to the part of the instrument which engages the cup component. When the instrument is placed on a surface, the handle contacts the surface at the widest point 66.

The core has a series of bores 70 extending through it. Each of the bores has a pin 72 fixed in it which protrudes from its bore on one side of the instrument. The length of the pins beyond the core varies depending on the width of the handle at that point along the length of the core. Preferably, the pins are made from a material which is similar to or more preferably the same as the material of the core 62. Preferably, the pins are made from stainless steel. The pins can be fastened in their respective bores by techniques such as force fitting (for example when the pins are tapered along a portion of their length), or interengaging threads, or an adhesive, or spot welding.

The sheath can be formed on the core and the pins by an overmoulding process. It can be formed from a polymeric material, for example from a polyolefm such as polyethylene or polypropylene, or from a polyamide or from a polyester. Suitable materials for use in the manufacture of surgical instruments, especially handle parts thereof, are well known. The sheath has a circular cross-section and the longitudinal axis of the handle coincides with the axis which extends along the centre of the sheath.

Figure 2 is a side view of the handle portion 80 of an instrument. The handle portion comprises a shaft 81 and a handle 82. The handle comprises a core 83 and an overmoulded sheath 84. The core and the shaft can be formed as a single piece, for example by a moulding or casting process. Alternatively, the core and the shaft might be formed as two pieces which can be joined together, for example permanently such as by means of a bonding agent (for example an adhesive) or by welding, or temporarily such as by means of a threaded connection. The shaft and the core can be formed from different materials or from the same material. Preferred materials include metals, for example stainless steels or another metals such as are commonly used in the manufacture of surgical instruments.

The handle core 83 as a cavity 85 defined within it on one side. On the opposite side, the material of the core has a plurality of grooves 86 formed in it. The grooves can be formed directly during a casting step. The grooves can be formed by a machining step, for example by milling.

The sheath 84 fills the cavity 85 on one side of the core and the grooves 86 on the other side of the core. Figure 3 is a side view of the handle portion 90 of an instrument. The handle portion comprises a shaft 91 and a handle 92. The handle comprises a core 93 and an overmoulded sheath 94. The core and the shaft are formed as a single piece from a rod.

The core within the handle is curved along its length, away from the axis of the instrument as defined by the shaft and the overmoulded sheath.

Claims

CLAIMS:

1. A surgical instrument having a handle towards a first end and functional features for use in a surgical procedure towards a second end, in which the instrument is elongate and has a rest portion which contacts a surface when the instrument is placed on that surface, in which the rest portion is rounded when the instrument is viewed along its length, and in which the handle comprises a core and a sheath which fits over the core and defines the longitudinal axis of the handle in which the centre of mass of the handle is offset relative to its axis.

2. An instrument as claimed in claim 1, in which the core of the handle is made from a metal and the sheath is made from a polymeric material.

3. An instrument as claimed in claim 1, in which the core comprises a shaft which defines a shaft axis and at least one weight which is fixed to the shaft with the centre of mass of the weight offset relative to the shaft axis.

4. An instrument as claimed in claim 1, in which the sheath is made from a polymeric material which is applied to the core by an overmoulding process.

5. An instrument as claimed in claim 1, in which the rest portion is provided by a flange which is wider when the instrument is viewed along its length than the handle.

6. An instrument as claimed in claim 1, in which the rest portion is provided by the handle.

7. An instrument as claimed in claim 1, which has features for gripping a component of an orthopaedic joint prosthesis or a trial component to enable the component to be manipulated and positioned, or which is a hammer.