CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Stage Application filed Under 35 U.S.C. § 371 of International Application No. PCT/EP2019/060894 filed Apr. 29, 2019, which claims priority to GB1810480.2 flied Jun. 26, 2018 and GB1904257.1 filed Mar. 27, 2019, all of which are hereby incorporated by reference in their entireties.

FIELD OF THE INVENTION

This invention relates to a surgical kit and method for performing a controlled resection of the neck of a femur during a hip replacement procedure.

BACKGROUND OF THE INVENTION

Hip replacement is a surgical procedure in which the hip joint is replaced by a prosthetic implant. Total replacement of the hip joint involves installing an acetabular cup implant in the acetabulum of a patient and installing another implant in the femur of the patient. In partial hip replacement, an implant is installed in the femur of the patient, but an acetabular cup is not installed in the acetabulum. In either type of procedure, the implant that is installed in the femur typically includes a stem, which is received in the intramedullary canal, and a head having a bearing surface which is received in the acetabulum or acetabular cup implant. The implant typically also includes a neck, which extends between a proximal end of the stem and the head.

In a conventional procedure, in order to install the implant in the intramedullary canal, the neck of the femur is first resected. The resection of the femoral neck provides access to the intramedullary canal, which can then be prepared to receive the stem of the implant using broaches and reamers. During a hip replacement procedure, restoration of leg length is generally a product of good planning and experience and may generally be controlled by pre-operative planning. The neck resection may generally be a freehand cut and. A seating position of the implant, once the stem has been installed within intramedullary canal, may generally depend upon the location of the cut. If the cut is not correctly positioned, this can lead to an incorrect seating position for the implant. This can in turn adversely affect the resulting leg length of the femur with its femoral implant.

U.S. Pat. No. 6,503,255 B1 describes a cutting guide instrument and method for enabling high-precision resection of the head of the neck of a human femur at a predetermined cutting angle to the femoral shaft and on a predetermined cutting level with respect to the proximal end of the caput. A support part is fixed to the femur during the resection. A longitudinal guide carrier is supported by the support part and is aligned along the femoral collum at said predetermined cutting angle to the femoral shaft. A cutting guide is supported by and movable along the axis of the guide carrier to a cutting position corresponding to the predetermined cutting level.

WO 2002/026145 A1 describes a guiding instrument for the resection of a femoral neck in connection with total hip replacement, said guiding instrument comprising an instrument body having means for receiving a shank or the like that is mounted in the medullary canal of the femoral neck, said shank having a longitudinal centre axis the instrument body being displacable along said shank, and a guiding means having a guiding arrangement for the means that perform cutting of the femoral neck. At least a rotation ruler is attached to the instrument body, said rotation ruler being intended to cooperate with the existing femoral head of the femur.

U.S. Pat. No. 5,578,037 A describes a surgical resection guide that enables a surgeon to resect a femoral neck, during a hip arthroplasty procedure, such that a femoral prosthesis can be implanted within a patient to preserve or closely approximate the anatomic center of rotation of the hip. The guide is able to be used for left or right hip arthroplasty procedures, with either anterior or posterior surgical approaches.

U.S. Pat. No. 8,246,621 B2 describes an instrument kit is provided for reaming bone around a head of a bone, the bone including an implanted epiphysis component. The instrument kit includes a reaming guide and a reamer. The reaming guide is couplable to the epiphysis component and has a first reamer support feature and a second reamer support feature. The reamer is couplable to one of the first reamer support feature and the second support feature to ream bone around the epiphysis component.

U.S. Pat. No. 7,601,155 B2 describes an intramedullary femoral broach that aligns two instruments. A femoral neck resector guide slides over the broach and centers on the patient's femoral head to determine the height and angular rotation of resection. A circular ring of the head and cutting anus assure the system will fit any femur. A template is applied to the femoral broach and seats itself against the buttress of the broach locking it into place. The broach is then reinserted into the intramedullary canal. When the template reaches the greater trochanter the sizer is adjusted to the rotational anteversion of the canal. The handle of the femoral broach is struck with a mallet until the template is imbedded into the proximal femoral neck intramedullary bone. A retractor facilitates reaming of the acetabulum through a small anterior incision. A proximal portion digs into the bone of the superior acetabulum to allow for retraction of soft tissues.

U.S. Pat. No. 4,959,066 A describes an osteotomy guide assembly for femoral neck osteotomy includes a saddle locator assembly and a saw guide attachment. The saddle locator assembly includes a barrel-shaped locating device that locates the saddle region of the proximal femur. The barrel further includes a transverse support bar extending from the barrel. The barrel is positioned over an intramedullary shaft which is temporarily positioned in and extends from the medullary canal of the femur. A saw guide is used in conjunction with the saddle locator assembly. The saw guide is attached to the support bar by a single locking means which provides for positional adjustment of the saw guide relative to the support bar in two directions, including adjustment in the anterior-posterior direction along the transverse support bar and axially along the femur via a post which extends from the saw guide.

U.S. Pat. No. 7,833,275 B2 describes a method and apparatus for performing a minimally invasive total hip arthroplasty. An approximately 3.75-5 centimeter (1.5-2 inch) anterior incision is made in line with the femoral neck. The femoral neck is severed from the femoral shaft and removed through the anterior incision. The acetabulum is prepared for receiving an acetabular cup through the anterior incision, and the acetabular cup is placed into the acetabulum through the anterior incision. A posterior incision of approximately 2-3 centimetres (0.8-1.2 inches) is generally aligned with the axis of the femoral shaft and provides access to the femoral shaft. Preparation of the femoral shaft including the reaming and rasping thereof is performed through the posterior incision, and the femoral stem is inserted through the posterior incision for implantation in the femur. A variety of novel instruments including an osteotomy guide; an awl for locating a posterior incision aligned with the axis of the femoral shaft; a tubular posterior retractor; a selectively lockable rasp handle with an engagement guide; and a selectively lockable provisional neck are utilized to perform the total hip arthroplasty.

U.S. Pat. No. 5,607,431 A describes a surgical instrument system for preparing the medullary canal of the femur for implanting a prosthetic femoral component includes a template to be used in determining osteotomy position from an x-ray. A gauge is provided to locate and mark this position on the anterior femur. A distal reamer having an elongated drive shaft is used to form the canal to receive the distal stem of the femoral component. A metaphyseal template is used to determine the proper anteversion/retroversion and a chisel is used to cut the lateral area of the femur, both of which are guided by the elongated reamer shaft. A proximal broach also guided by the reamer shaft is used to shape the proximal medullary canal.

U.S. Pat. No. 7,582,091 B2 describes an osteotomy guide for indicating the femoral neck resection on a femur and its method of use are presented. The osteotomy guide includes an indexing feature for aligning the guide with an anatomic landmark and a resection guide for indicating the resection relative to the indexing feature.

U.S. Pat. No. 4,621,630 A describes a guide for femoral neck osteotomy that comprises a longitudinal rod having attaching structure at the lower end thereof for securing the rod to a femur at the greater trochanter. A transversely extending support arm is secured to the rod adjacent the lower end thereof, and a guide bar is connected to the support arm. The guide bar has at least one elongate planar surface disposed at an angle of 45 DEG to the axis of the rod. In use, the rod is aligned with the long shaft axis of the femur and attached to the femur at the greater trochanter. The rod is manipulated until the support arm and the long shaft axis of the tibia are disposed in the same plane. This procedure properly positions the elongate planar surface of the guide bar whereby an instrument in engagement with that surface traverses the femoral neck at an angle of 45 DEG to the long shaft axis of the femur.

SUMMARY OF THE INVENTION

Aspects of the invention are set out in the accompanying independent and dependent claims. Combinations of features from the dependent claims may be combined with features of the independent claims as appropriate and not merely as explicitly set out in the claims.

According to an aspect of the invention, there is provided a surgical kit for performing a controlled resection of the neck of a femur during a hip replacement procedure, the surgical kit comprising:

a mounting portion, wherein the mounting portion includes at least two guide holes for inserting guide pins into the femoral head while the mounting portion is located on an anterior aspect of the femoral head;

a body portion connected to the mounting portion, wherein the body portion includes an opening for mounting the body portion on an intramedullary pin located in an intramedullary canal of the femur; and

a resection guide including at least two guide holes having the same layout as the guide holes of the mounting portion, to allow the resection guide to be mounted on the anterior aspect of the femoral head with said guide pins inserted into the femoral head for positioning a resection plane indicator of the resection guide with respect to the neck of the femur.

A kit according to embodiments of this invention can aid in indicating a correct position of the neck resection plane, for restoring the leg length in a hip replacement procedure. Embodiments of this invention achieve this by providing a body portion that can be mounted on the femur using an intramedullary pin (such as an initiation rod or reamer) located in the intramedullary canal of the femur to create an extramedullary reference to the intramedullary axis and a mounting portion that can be used to reference the femoral head center while inserting guide pins into the femoral head, and a resection guide having corresponding guide holes for mounting the resection guide on the guide pins such the correct resection plane is then indicated on the neck of the femur at a position relative to the femoral head center.

The resection plane indicator can, for instance, indicate a position of two resection planes. This can allow a neck resection using two angled cuts to be implemented. The two resection planes can be oriented at an angle of about 127°, 129° or 135° with respect to each other.

The resection plane indicator can comprise a guide slot or a guide surface.

The guide slot or guide surface can be a cutting slot or a cutting guide surface for receiving a blade of a cutting device during said resection of the neck.

The resection guide can include a plurality of sets of guide holes. Each set of guide holes can include at least two guide holes having the same layout as the guide holes of the mounting portion. The plurality of sets of guide holes can be respectively positioned in the resection guide to allow adjustment of the position of the resection plane indicator with respect to the neck of the femur by mounting the resection guide on the anterior aspect of the femoral head with the guide pins inserted into the guide holes of one of the sets of guide holes.

The mounting portion can include three guide holes. This can provide additional stability/accuracy in the mounting of the mounting portion and subsequently the resection guide.

The guide holes of the mounting portion can comprise:

a central guide hole for alignment with the femoral head center when the mounting portion is located on the anterior aspect of the femoral head; and

a lateral guide hole located on a first side of the central guide hole; and

a medial guide hole located on a second side of the central guide hole opposite the first side.

The surgical kit can further include a plurality of the guide pins.

The opening for mounting the body portion on the intramedullary pin can be adjustably positionable within the body portion according to a femoral offset of the femur.

The body portion can include markings for reading off the femoral offset of the femur according to the position of the opening for mounting the body portion on the intramedullary pin, while the mounting portion is mounted on the femoral head. The femoral offset value that is read off can be used to determine the type of neck/head combination that is used in the implant, for restoring the femoral offset.

The kit can include a plurality of the resection guides, each resection guide being of a different shape and/or size according to a respective implant geometry, for a positioning a resection plane indicator of a selected resection guide with respect to the neck of the femur. The implant geometries may, for instance, include standard, lateralised, short neck and/or, coxa vara geometries.

The mounting portion may include a substantially circular femoral head contacting surface.

The mounting portion may be referred to by those skilled in the art as a spherometer.

According to another aspect of the invention, there is provided a method for performing a controlled resection of the neck of a femur during a hip replacement procedure using a surgical kit comprising:

a mounting portion, wherein the mounting portion includes at least two guide holes for receiving pins;

a body portion connected to the mounting portion, the body portion having an opening; and

a resection guide, wherein the resection guide includes at least two guide holes having the same layout as the guide holes of the mounting portion, the method comprising:

mounting the body portion on an intramedullary pin located in an intramedullary canal of the femur by inserting the pin into the opening in the body portion;

placing the mounting portion on an anterior aspect of the femoral head;

inserting a respective guide pin through each guide hole of the mounting portion and into the femoral head;

removing the mounting portion from the femoral head;

mounting the resection guide on the anterior aspect of the femoral head with said guide pins inserted into the femoral head for positioning a resection plane indicator of the resection guide; and

using the resection plane indicator to either:mark the position of the resection plane on the neck of the femur; orguide a blade of a cutting device to resect the neck of the femur.

A method according to embodiments of this invention can aid in indicating a correct position of the neck resection plane, for restoring the leg length in a hip replacement procedure. Embodiments of this invention achieve this by using a body portion that can be mounted on the femur using an intramedullary pin (such as an initiation rod or reamer) located in the intramedullary canal of the femur to create an extramedullary reference to the intramedullary axis, using a mounting portion to reference the femoral head center while inserting guide pins into the femoral head, and using a resection guide having corresponding guide holes for mounting the resection guide on the guide pins such the correct resection plane is then indicated on the neck of the femur at a position relative to the femoral head center.

The resection guide can include a plurality of sets of guide holes. Each set of guide holes can include at least two guide holes having the same layout as the guide holes of the mounting portion. The plurality of sets of guide holes can be respectively positioned in the resection guide to allow adjustment of the position of the resection plane indicator with respect to the neck of the femur by mounting the resection guide on the anterior aspect of the femoral head with said guide pins inserted into the guide holes of one of said sets of guide holes. The method can include:

selecting a set of guide holes; and

mounting the resection guide on the anterior aspect of the femoral head with said guide pins inserted into the guide holes of one of the selected set of guide holes.

The method can include adjustably positioning the opening for mounting the body portion on the intramedullary pin with respect to a remainder of the body portion according to a femoral offset of the femur.

The method can include reading off the femoral offset of the femur according to the position of the opening for mounting the body portion on the intramedullary pin with respect to the remainder of the body portion according to a femoral offset of the femur, while the mounting portion is mounted on the femoral head.

The method can include using the femoral offset value to determine a femoral offset of a femoral implant to be installed in the hip replacement procedure.

The kit can include a plurality of the resection guides, each resection guide being of a different shape and/or size according to a respective implant geometry, for a positioning a resection plane indicator of a selected resection guide with respect to the neck of the femur. The method can further comprise: selecting one of the resection guides; and mounting the selected resection guide on the anterior aspect of the femoral head with said guide pins inserted into the femoral head. The implant geometries may, for instance, include standard, lateralised, short neck and/or, coxa vara geometries.

The method can include inserting the intramedullary pin into the intramedullary canal of the femur prior to mounting the body portion on the intramedullary pin.

The mounting portion may include a substantially circular femoral head contacting surface.

The mounting portion may be referred to by those skilled in the art as a spherometer.

