GB2495090A - Bone reamer - Google Patents

Abstract

A bone reamer is disclosed comprising a domed head 19 and a handle connected to the domed head 19. The domed head 19 comprises a plurality of curved segments 5, each with a curved outer face 6 defined by first and second curved edges. The curved outer face of each segment 5 partially defines the surface of the domed head. A cutting blade 13 is attached to the first curved edge of at least one of the segments 5. Preferably each of the segments 5 has a cutting blade 13 and the blades are sandwiched between the segments 5. Preferably, each cutting blade 13 comprises a support arm 17 extending from the domed head 19 to the support handle, and a retention band 20 that is attached to each of the support arms 17. The reamer optionally further comprises at least one annular clip. Preferably the handle comprises a driver rod which can engage with at least one cutting blade 13 and/or support arm 17. The reamer is preferably an acetabular or femoral reamer.

Description

A BONE REAMER

The present invention relates to a bone reamer. More particularly, but not exclusively, the present invention relates to a bone reamer having a domed head made up of a plurality of curved segments, at least one of the curved segments having a cutting blade connected to a curved edge of one of the segments.

Bone reamers are known. Typically the bone reamer comprises a domed head.

Upstanding from the domed head are a plurality of reaming edges for reaming the bone. The reaming edges are typically arranged in a cheese grater' type pattern.

Usually the domed head and reaming edges are manufactured from a single metal sheet. This can be expensive. In an alternative method of manufacture the domed head is a plastics material. At least one curved cutting blade comprising the reaming edges is mouided into position in the domed head. Again, such a reamer is expensive to manufacture. There is also a problem of over-moulding where the plastics material at least partially extends over the cutting blade.

Because bone reamers are expensive devices to manufacture it is required that they are used several times before they are disposed of. The bone reamer must be cleaned between uses which can take several days. If a hospital has only a small number of bone reamers this can reduce the rate at which patients can be treated as the surgeon must wait for the reamer to be returned from cleaning before the next patient can be treated.

The bone reamer according to the invention is significantly less expensive to manufacture than known bone reamers. The bone reamer can therefore be used as a single use surgical device. This eliminates the long cleaning process so enabling a much greater throughput of patients.

Accordingly, the present invention provides a bone reamer comprising a domed head; and a handle connected to the domed head; the domed head comprising a plurality of curved segments each having a curved outer face defined by first and second curved edges, the curved outer face of each segment partially defining the surface of the domed head; the reamer further comprising a cutting blade attached to the first curved edge of a curved segment.

The domed head of the bone reamer is made up of a plurality of curved segments. A cutting blade is attached to a curved edge of at least one of the segments. The segments are then connected together to define the domed head. It is far less expensive to manufacture curved segments than a dome, so enabling the device to be used as a single use surgical device. In addition, because the cutting blade is attached to the edge of a curved segment the problem of over-moulding is eliminated.

Preferably a plurality of segments, preferably each segment, has a cutting blade attached to its first curved edge.

Preferably each segment is connected to the adjacent segment such that the at least one cutting blade, preferably each cutting blade, is sandwiched between adjacent segments.

Preferably, each cutting blade comprises a plurality of spaced apart reaming edges, defining blade recesses therebetween.

Preferably, the reaming edges of one cutting blade at least partially overlap the blade recesses of the adjacent cuffing blade in the direction from one blade to the next.

At least a portion of the cutting blade can be raised from the surface of the domed head.

The bone reamer can be an acetabular reamer.

Each cutting blade can comprise a support arm extending from the domed head towards the handle, the reamer further comprising at least one retention band attached to each of the support arms retaining the segments in place.

At least a portion of the at least one cutting blade can extend inwardly from the domed head.

The bone reamer can be a femoral reamer.

The bone reamer can further comprise at least one annular clip extending around the outside of the domed head retaining the segments in place.

The handle can comprise a driver rod, the driver rod being adapted to engage with at least one cuffing blade.

Preferably, the driver rod engages with the support arm of at least one cutting blade.

The driver rod can comprise at least one protrusion which engages with the support arm.

The reamer can further comprise a collar which engages with the driver rod and abuts the head, fixing the rod in place with respect to the head.

The collar can comprise a thread adapted to be threaded into engagement with a corresponding thread on the outer surface of the driver rod.

The present invention will now be described by way of example only and not in any limitative sense with reference to the accompanying drawings in which Figure 1 shows a known bone reamer in perspective view; Figure 2 shows a curved segment of a domed head of a bone reamer according to the invention in perspective view; Figure 3 shows the curved segment of figure 2 in combination with a cutting blade; Figure 4 shows a plurality of segments and cutting blades connected together to form a domed head of a bone reamer according to the invention; Figure 5 shows the domed head of figure 4 in combination with a driver rod; Figure 6 shows an acetabular reamer according to the invention; Figure 7(a) shows a portion of the domed head of a further embodiment of a bone reamer according to the invention in perspective view; and, Figure 7(b) shows the embodiment of figure 7(a) in cross section.

Shown in figure 1 is a typical known acetabular reamer 1, as disclosed in GB0616129.3. The reamer 1 comprises a curved shim 2. A hemispherical plastics substrate 3 is over-moulded onto the shim 2. Apertures 4 are then made in the substrate 3 proximate to the cutting edges of the shim 2 to allow the exit of bone fragments during use of the reamer 1.

Such a reamer 1 has a number of drawbacks. Firstly it is relatively expensive to manufacture, requiring the production of a domed substrate 3 and use of an over-moulding process. Secondly, over-moulding can be difficult to control with the plastic material covering unanticipated portions of the shim 2. With over-moulding it can also be difficult to control the bond strength between shim 2 and substrate 3, introducing a reliability problem.

Shown in figure 2 is a curved segment 5 of a domed head of a bone reamer according to the invention. The curved segment 5 comprises a curved outer face 6 defined by first and second curved edges 7,8. At one end the two curved edges 7,8 meet at a vertex 9. At the other end a curved rim edge 10 extends between the two curved edges 7,8. The curved outer face 6 substantially defines a portion of a hemisphere. Close to one of the edges 7 of the curved face 6 the curved face 6 dips inwards slightly towards the centre of the hemisphere defining a surface recess 11 for receiving bone fragments. This is described in more detail below.

Each of the first and second curved edges 7,8 comprises connection means 12 for connecting the segment 5 to adjacent segments 5. In this embodiment one of the curved edges 7 comprises a plurality of location holes 12. The other curved edge 8 comprises location protrusions 12. In use the location protrusions 12 of one segment are received in the location holes 12 of the adjacent segment 5 so fixing the segments 5 together.

In this embodiment the curved segment 5 is a plastics material.

Shown in figure 3 is the first step in the assembly of the bone reamer according to the invention. In this first step a curved cutting blade 13 is arranged proximate to one of the sides 8 of the curved segment 5. The curved cutting blade 13 comprises a plurality of blade location holes 14. The location protrusions 12 of the curved segment 5 are passed through the blade location holes 14 so arranging the curved cutting blade 13 in the correct position with respect to the curved segment 5.

The cutting blade 13 comprises a plurality of spaced apart reaming edges 15. The reaming edges 15 ream the bone in use as is described in more detail below. Blade recesses 16 extend between the reaming edges 15.

The reaming edge positions are accurately defined because the position of the edges is the product of a cutting (machining/stamping) operation, rather than a forming operation.

The cutting blade 13 further comprises a support arm 17 which extends from proximate to the curved surface 6 of the segment 5 towards the center of the domed head. The support arm 17 is arranged proximate to the rim edge 10. The support arm 17 comprises a plurality of band retention grooves 18.

Shown in figure 4 is the next step in the assembly of the bone reamer according to the invention. In this step a plurality of segments 5 and associated blades 13 are connected together to form the domed reamer head 19 as shown. The location protrusions 12 of one segment 5 pass through the location holes 14 in the associated cutting blade 13 and then into the location holes 12 of the adjacent segment 5. Retention bands 20 are arranged in the band retention grooves 18 as shown, retaining the segments 5 in place.

In this assembled configuration the cutting blades 13 are sandwiched between adjacent curved segments 5 and are held in place by the location protrusions 12.

In this embodiment each segment 5 has an associated cutting blade 13. In alternative embodiments a different number of cutting blades 13 is possible. As an example, in an alternative embodiment the domed head 19 has only two blades 13 on opposite sides of the head 19.

In the embodiment shown in figure 4 each blade 13 is arranged such that it is proximate to the recess 11 for receiving bone fragments of the adjacent segment 5.

As can be seen in the figure in this embodiment two slightly different types of curved cutting blade 13 are used which alternate around the domed head 19. The reaming edges 15 of one curved blade 13 overlap with the blade recesses 16 of the adjacent cutting blades 13 in a direction around the head 19, giving a cheese grater' type of arrangement of reaming edges 15 around the domed head 19. Also, as can be seen the support arms 17 of one of the types of blade 13 is longer than the other.

Shown in figure 5 is the next step in the assembly of the bone reamer according to the invention. In this step the end of a driver rod 21 is inserted into the head 19 of the bone reamer. The driver rod 21 comprises a plurality of protrusions 22 on its outer face proximate to the end inserted into the head 19. When inserting the driver rod 21 into the head 19 the protrusions 22 are arranged to pass between the support arms 17 of the blades 13. Once in position the driver rod 21 is rotated so that the protrusions 22 hook underneath the support arms 17 as shown.

The driver rod 21 has a thread 23 on its outer surface. In a final step a collar 24 having a threaded aperture passing therethrough is threaded along the driver rod 21 until it abuts the support arms 17, so fixing the driver rod 21 in position. This is shown in figure 6.

The bone reamer 25 shown in figure 6 is an acetabular reamer according to the invention. The reaming edges 15 are raised slightly from the domed head 19 as can be seen in figure 6. In use the acetabular reamer 25 is placed against the acetabulum. The driver rod 21 is then rotated, so rotating the domed head 19. As the domed head 19 rotates the reaming edges 15 ream the bone forming the desired hemispherical recess. During reaming the reamed bone fragments are collected in the surface recess 11 in front of each blade 13. The fragments then fall through apertures in the blades 13 away from the domed head 19.

In the above embodiment the domed head 19 is designed to produce a hemispherical recess. In alternative embodiments other shapes of dome 19 are possible. The dome 19 for example may produce a recess which is a portion of an oblate or prolate spheroid. In a further alternative embodiment the domed head 19 may have a cylindrical portion with a curved or conical head.

Shown in figure 7(a) in perspective view is a portion of the domed head 19 of an alternative embodiment of a bone reamer 25 according to the invention. In this

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embodiment the dome 19 is on the inside of the segments 5 and cutting blades 6.

This reamer 25 is a femoral reamer. This embodiment is similar to that of figure 6 except the reaming edges 15 extend inwardly into the dome 19 as shown. The cutting blades 6 in this embodiment lack the support arms.

Figure 7(b) shows the embodiment of figure 7(a) in cross section. An annular clip 26 extends around the cutting blades 6 and segments 5, holding the blades 6 and segments 5 in position. The clip 26 is recessed in a groove 27 in the blades 6. The driver rod 21 in turn fastens over the clip 26.

In use the dome of the femoral reamer is placed over the end of a femur and rotated so reaming the end of the femur into a predetermined shape.

Claims (1)

1. <claim-text>CLAIMS1. A bone reamer comprising a domed head; and a handle connected to the domed head; the domed head comprising a plurality of curved segments each having a curved outer face defined by first and second curved edges, the curved outer face of each segment partially defining the surface of the domed head; the reamer further comprising a cutting blade attached to the first curved edge of a curved segment.</claim-text> <claim-text>2. A bone reamer as claimed in claim 1, wherein a plurality of segments, preferably each segment, has a cutting blade attached to its first curved edge.</claim-text> <claim-text>3. A bone reamer as claimed in either of claims 1 or 2, wherein each segment is connected to the adjacent segment such that the at least one cutting blade, preferably each cutting blade, is sandwiched between adjacent segments.</claim-text> <claim-text>4. A bone reamer as claimed in any one of claims 1 to 3, wherein each cutting blade comprises a plurality of spaced apart reaming edges, defining blade recesses therebetween.</claim-text> <claim-text>5. A bone reamer as claimed in claim 4, when dependent on claim 2, wherein the reaming edges of one cutting blade at least partially overlap the blade recesses of the adjacent cutting blade in the direction from one blade to the next.</claim-text> <claim-text>6. A bone reamer as claimed in any one of claims 1 to 5, wherein at least a portion of the cutting blade is raised from the surface of the domed head.</claim-text> <claim-text>7. A bone reamer as claimed in claim 6, wherein the bone reamer is an acetabular reamer.</claim-text> <claim-text>8. A bone reamer as claimed in either of claims 6 or 7, when dependent on claim 2, wherein each cutting blade comprises a support arm extending from the domed head towards the handle, the reamer further comprising at least one retention band attached to each of the support arms retaining the segments in place.</claim-text> <claim-text>9. A bone reamer as claimed in any one of claims 1 to 5, wherein at least a portion of the at least one cutting blade extends inwardly from the domed head.</claim-text> <claim-text>10. A bone reamer as claimed in claim 9, wherein the bone reamer is a femoral reamer.</claim-text> <claim-text>11. A bone reamer as claimed in either of claims 9 or 10, further comprising at least one annular clip extending around the outside of the domed head retaining the segments in place.</claim-text> <claim-text>12. A bone reamer as claimed in any one of claims 1 to 11, wherein the handle comprises a driver rod, the driver rod being adapted to engage with at least one cutting blade.</claim-text> <claim-text>13. A bone reamer as claimed in claim 12, when dependent on claim 8, wherein the driver rod engages with the support arm of at least one cutting blade.</claim-text> <claim-text>14. A bone reamer as claimed in claim 13, wherein the driver rod comprises at least one protrusion which engages with the support arm.</claim-text> <claim-text>15. A bone reamer as claimed in any one of claims 12 to 14, further comprising a collar which engages with the driver rod and abuts the head, fixing the rod in place with respect to the head.</claim-text> <claim-text>16. A bone reamer as claimed in claim 15, wherein the collar comprises a thread adapted to be threaded into engagement with a corresponding thread on the outer surface of the driver rod.</claim-text> <claim-text>17. A bone reamer substantially as hereinbefore described.</claim-text>