WO2020193004A1

WO2020193004A1 - Adjustable trial femoral neck assembly

Info

Publication number: WO2020193004A1
Application number: PCT/EP2020/053887
Authority: WO
Inventors: Jamie ATKIN; Graeme Dutton
Original assignee: DePuy Ireland ULC
Current assignee: DePuy Ireland ULC
Priority date: 2019-03-26
Filing date: 2020-02-14
Publication date: 2020-10-01
Anticipated expiration: 2021-09-26
Also published as: GB201904146D0

Abstract

The invention provides a kit in which progressive neck length is accommodated within the broach. This is achieved by the provision of a neck connection element (10) on each size of broach that allows the neck length to be varied on the broach side of a broach/trial femoral neck assembly. This prevents the need for a different trial femoral neck component for each broach size. The inventory of trial femoral neck components within the instrument tray may therefore be reduced to one trial standard offset femoral neck component and/or one trial high offset femoral neck component.

Description

ADJUSTABLE TRIAL FEMORAL NECK ASSEMBLY

FIELD OF THE INVENTION

The present invention relates generally to the field of orthopedics, and more particularly to trial femoral neck assembles, kits and methods for use in intraoperative trialling of hip prostheses to determine an appropriate length for the definitive femoral neck component of a prosthetic hip joint.

BACKGROUND TO THE INVENTION

Optimal hip mechanics in hip arthroplasty is achieved through the selection of an appropriate neck length and head offset in the femoral component of the prosthetic hip implant.

The distance between the femoral stem component and the femoral head component, provided by the length of the neck of the femoral component, establishes the requisite head offset and neck length which in turn contributes to the desired range of motion, leg length, and tension in the soft tissue at the implant site. In order to optimize hip mechanics, it is desirable to select the leg length with precision. Femoral offset is an important clinical requirement. When offset is not restored, medialization of the femur can occur which results in impingement and possible instability. Additionally, if offset is not restored at the time of surgery, laxity of tissues can occur resulting in weakness and possible dislocation.

Conventionally, femoral stem components are offered in standard offset and high offset configurations to provide proper joint tension without affecting leg length or surgical technique.

Traditional implant stem geometry with a progressive neck length requires a different neck trial for each stem size and each offset variation. Trial femoral neck components are usually designed to work with the corresponding size of broach. This requires a large inventory of trial neck components within an instrument tray. In order to reduce the inventory, it would be desirable to reduce the number of trial femoral neck components required.

Advantageously, the instrument tray would include a set of broaches of varying sizes, one trial standard offset trial femoral neck assembly and one trial high offset femoral neck assembly.

SUMMARY OF THE INVENTION

The invention provides a kit in which progressive neck length is accommodated within the broach. This is achieved by the provision of a neck connection element on each size of broach that allows the neck length to be varied on the broach side of a broach/trial femoral neck assembly. This prevents the need for a different trial femoral neck component for each broach size. The inventory of trial femoral neck components within the instrument tray may therefore be reduced to one trial standard offset femoral neck component and/or one trial high offset femoral neck component.

Therefore, according to an aspect of the invention there is provided an adjustable trial femoral neck assembly comprising:

a broach attachment part comprising:

a proximally facing surface, and

a broach facing surface from which a broach connection element extends distally;

a femoral head attachment part comprising:

a proximal portion configured for removable attachment to a trial femoral head, and

a distal portion having a detent,

wherein a channel is formed within the broach attachment part and extends from the proximally facing surface and along at least a portion of the broach connection element, the channel being dimensioned for telescopic receipt of the distal portion of the femoral head attachment part, wherein the channel defines a groove extending through a side wall of the broach connection element such that the detent protrudes outwardly beyond the side wall of the broach connection element for receipt within a recess provided within the broach, said recess being at a depth beneath a femoral neck facing surface of the broach such that when the broach attachment part is attached to the broach the receipt of the detent within the recess sets the distance between the proximal facing surface of the broach attachment part and a proximal end of the proximal portion of the femoral head attachment part.

Optionally, the groove is provided on at least one of a lateral aspect or a medial aspect of the broach connection element.

In some constructions, the femoral head attachment part is spring loaded such that the assembly is always in the smallest, most retracted position. This ensures that the spring is not under compression during trial reduction. Accordingly, the broach attachment part of the trial femoral neck assembly comprises a biasing means to bias the femoral head attachment part towards the broach attachment part. The biasing means may be a helical spring or a compression spring.

Optionally the trial femoral neck assembly is provided a standard offset femoral neck trial assembly or a high offset femoral neck trial assembly.

In some constructions, the trial femoral neck assembly is provided with a retaining feature that retains the neck assembly on the broach during trialling. This prevents disassociation of the neck from the broach. This retaining feature also prevents any inadvertent rotation of the neck assembly relative to the broach. An example of a suitable retaining feature is a live spring.

According to a second aspect of the invention, there is provided a kit for use in trialling of a femoral head, said kit comprising a trial femoral neck assembly as herein described, and further comprising:

a first broach having a recess for receipt of the detent located at a first depth beneath a femoral neck facing surface of the broach, such that when the broach attachment part of the adjustable femoral neck assembly is attached to the first broach the receipt of the detent within the recess sets a first distance between the proximal facing surface of the broach attachment part and a proximal end of the proximal portion of the femoral head attachment part, and

a second broach having a recess for receipt of the detent located at a second depth beneath a femoral neck facing surface of the broach, such that when the broach attachment part of the adjustable femoral neck assembly is attached to the second broach the receipt of the detent within the recess sets a second distance between the proximal facing surface of the broach attachment part and a proximal end of the proximal portion of the femoral head attachment part, wherein said second distance is different to the first distance.

In some constructions, the second broach is larger than the first broach. The recess in the first broach is provided at a first depth from the femoral neck facing surface of the broach, and the recess in the second broach is located at a second depth from the femoral neck facing surface of the broach, the first depth being greater than said second depth. As a result when the trial femoral neck assembly is assembled onto the second broach the trial femoral neck assembly has a longer neck length.

The kit includes at least one of a standard offset femoral neck trial assembly or a high offset femoral neck trial assembly.

According to a third aspect of the invention there is provided a method of selecting a femoral neck component for use in an orthopaedic joint prosthesis, the method comprising the steps of:

(i) using a kit comprising:

an adjustable trial femoral neck assembly comprising:

a broach attachment part comprising:

a proximally facing surface, and

a femoral head attachment part comprising:

a proximal portion configured for removable attachment to a trial femoral head, and a distal portion having a detent,

wherein a channel is formed within the broach attachment part and extends from the proximally facing surface and along at least a portion of the broach connection element, the channel being dimensioned for telescopic receipt of the distal portion of the femoral head attachment part, wherein the channel defines a groove extending through a side wall of the broach connection element such that the detent protrudes outwardly beyond the side wall of the broach connection element for receipt within a recess provided within the broach, said recess being at a depth beneath a femoral neck facing surface of the broach such that when the broach attachment part is attached to the broach the receipt of the detent within the recess sets the distance between the proximal facing surface of the broach attachment part and a proximal end of the proximal portion of the femoral head attachment part;

a second broach having a recess for receipt of the detent located at a second depth beneath a femoral neck facing surface of the broach, such that when the broach attachment part of the adjustable femoral neck assembly is attached to the second broach the receipt of the detent within the recess sets a second distance between the proximal facing surface of the broach attachment part and a proximal end of the proximal portion of the femoral head attachment part, wherein said second distance is different to the first distance;

(ii) broaching a patient’s femur using at least one of the first broach or the second broach;

(iii) retaining the broach within the patient’s femur;

(iv) connecting the trial femoral neck assembly to the first broach or to the second broach;

(v) connecting a trial femoral head component to the trial femoral neck

assembly; and (vi) performing a trial reduction.

In some examples of the method, the trial femoral neck assembly that is connected to the first broach or second broach is a standard offset femoral neck trial assembly or a high offset femoral neck trial assembly.

DETAILED DESCRIPTION OF THE INVENTION

The invention will now be described, by way of example only, with reference to the following drawings, in which:

FIG. 1 shows a trial femoral neck assembly according to the invention in an extended (Figure la) and retracted position (Figure lb);

FIG. 2 shows a cross section of the trial femoral neck assembly of Figure 1 ;

FIG. 3 shows a trial femoral neck assembly of Figure 1 and 2 having a broach retaining element.

FIG.l shows the trial femoral neck assembly 10 in the fully extended position (FIG. la) and in the retracted position (FIG. lb). As shown, in the extended position the trial femoral neck assembly has a greater neck length than in the retracted position as described below. The trial femoral neck assembly includes a broach attachment part 12 that is in a telescopic relationship with a femoral head attachment part 14.

The broach attachment part 12 has a proximal facing surface 16, and a distally located broach facing surface 18. A broach connection element 20 is associated with the distally located broach facing surface. In the construction shown, the broach connection element is a female connection element, here shown in the form of a post. This male connection element mates with a complementary female connection element provided on the broach.

As shown in FIG. 2, a channel 22 is formed within the broach attachment part 12. The channel extends from the proximally facing surface 16 and along at least a portion of the broach connection element 20. The channel is dimensioned for telescopic receipt of a distal portion of the femoral head attachment part 14, as described below. The channel defines a groove 24 extending through a side wall 26 of the broach connection element. In the construction shown, the groove extends along the medial aspect of the side wall. It is however envisaged that in other constructions the groove may extend along the lateral aspect of the side wall. In still further constructions, the groove may extend along the medial aspect and the lateral aspect of the side wall. The groove is dimensioned such when a distal portion of the femoral head attachment part is slidably received within the broach connection element, a detent (described below) on the femoral head attachment part protrudes outwardly beyond the side wall of the broach connection element, and is postioned for receipt within a recess provided within the broach.

The broach attachment part also includes a compression spring channel 28 in which a compression spring (not shown) is received.

The femoral head attachment part 14 has a proximal portion that includes a femoral head receiving portion 30. The femoral head receiving portion is configured for removable receipt of a trial femoral head (not shown). An elongate portion 32 extends distally from the femoral head receiving portion 30. This elongate portion 32 is dimensioned for slidable receipt within the channel 22 of the broach attachment portion.

A detent 34 is provided along the length of the elongate portion 32. The detent is positioned such that the detent extends outwardly from the groove 24 within the broach connection element. Accordingly, the detent can be reversibly retained within a complementary recess within a broach. In the construction shown, the detent is provided at the distal terminus of the elongate portion. The retention of the detent within the recess of the broach sets the neck length.

Broaches are used during hip arthroplasty to replicate the definitive femoral stem.

Each incremental size of broach that is used in conjunction with the inventive trial femoral neck assembly as herein described includes a recess located at a predetermined depth below the proximal-most surface, also referred to as the femoral neck facing surface. With each increasing size of broach, the location of the recess is located nearer to the femoral neck facing surface. This results in a variation in neck length when the trial femoral neck assembly is connected to the broach. The length of the broach connection element 20, and its associated groove 24 can be chosen in accordance with a desired range of neck lengths. The positions of the recess within the broach can be chosen to coincide with a position along the groove when the broach connection element is inserted, in accordance with the broach size and the desired neck length.

FIG. 1 a shows the configuration of the trial femoral neck assembly as it would be when it is connected to a first broach (not shown). FIG. lb shows the configuration of the trial femoral neck assembly as it would be when it is connected to a second, smaller, broach (not shown). As the first broach is of a larger size than the second broach, the recess in the first broach is located nearer to the femoral neck facing surface.

Accordingly, when the detent 34 is retained in the recess of the first broach it is located in a more proximal position along the groove 24 of the broach connection element than when the detent 34 is retained in the recess of the second broach.

In FIG. la, the detent 34 is positioned at the proximal limit of the groove 24, and the trial femoral neck assembly is in a fully extended position. The neck length, which is defined as the distance between the proximal facing surface of the broach attachment part 16 and the proximal end of the proximal portion of the femoral head attachment part 14 is Ni.

In FIG. lb, the detent is shown at the distal limit of the groove 24, and the trial femoral neck assembly is in a fully retracted position. The neck length is N2, which is less than Ni.

It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this disclosure is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present disclosure as defined by the claims.

Claims

1. An adjustable trial femoral neck assembly comprising a broach attachment part comprising:

a proximally facing surface, and

a femoral head attachment part comprising:

a distal portion having a detent,

2. The trial femoral neck assembly according to claim 1 , wherein the groove is

provided on at least one of a lateral aspect or a medial aspect of the broach connection element.

3. The trial femoral neck assembly according to claim 1 or 2, wherein the broach

attachment part comprises a biasing means to bias the femoral head attachment part towards the broach attachment part.

4. The trial femoral neck assembly according to claim 3, wherein the biasing means is a helical spring.

5. The trial femoral neck assembly according to any of claims 1 to 4, wherein the trial femoral neck assembly is a standard offset femoral neck trial assembly or a high offset femoral neck trial assembly.

6. A kit for use in trialling of a femoral head, said kit comprising:

a trial femoral neck assembly according to any of claims 1 to 5, a first broach having a recess for receipt of the detent located at a first depth beneath a femoral neck facing surface of the broach, such that when the broach attachment part of the adjustable femoral neck assembly is attached to the first broach the receipt of the detent within the recess sets a first distance between the proximal facing surface of the broach attachment part and a proximal end of the proximal portion of the femoral head attachment part, and

7. The kit according to claim 6, wherein the first broach is larger than the second broach and wherein the recess in the first broach is provided at a first depth from the femoral neck facing surface of the broach, and the recess in the second broach is located at a second depth from the femoral neck facing surface of the broach, said first depth being less than said second depth, such that when the trial femoral neck assembly is assembled onto the first broach the trial femoral neck assembly has a longer neck length.

8. The kit according to claim 6 or 7, wherein the kit includes a standard offset femoral neck trial assembly and a high offset femoral neck trial assembly.

9. A method of selecting a femoral neck component for use in an orthopaedic joint prosthesis, the method comprising the steps of:

(i) using a kit comprising:

an adjustable trial femoral neck assembly comprising:

a broach attachment part comprising:

a proximally facing surface, and

a femoral head attachment part comprising:

a distal portion having a detent,

(ii) broaching a patient’s femur using at least one of the first or second broaches;

(iii) retaining the broach within the patient’s femur;

(v) connecting a trial femoral head component to the trial femoral neck assembly; and

(vi) performing a trial reduction.

10. The method according to claim 9, in which the trial femoral neck assembly connected to the first broach or the second broach is a standard offset femoral neck trial assembly or a high offset femoral neck trial assembly.