Length/offset reproducing device for total hip arthroplasty

A guide device for assessing the length and offset of a hip of a patient is disclosed. The guide device includes an overlay portion and an alignment portion. The overlay portion is configured to enable assessment of the relative location of the guide device to the original femoral head of a patient using a marking on the overlay portion. Reference points for positioning the guide device are created on the femur. When the guide device is positioned at the reference points it can be used to position a replacement femoral head in the same position as the patient's original femoral head by aligning the replacement femoral head with the marking on the overlay portion.

BACKGROUND

Total hip arthroplasty (hip replacement surgery) involves replacement of both the ball and the socket sides of the hip joint. The ball portion of the patient's hip, the femoral head, is replaced with an artificial ball. The patient's socket, the acetabulum, is covered with an artificial socket liner. When replacing the hip, it is important for the surgeon to be able to judge the length and offset of the original femoral head and match the position of the artificial femoral head to the position of the original. Creating the correct offset and length with the replacement femoral head is important for avoiding leg length discrepancy and for hip stability and strength.

Some measurement devices attempt to measure the length and offset of the hip from a fixed position on the pelvis. This process usually involves driving a metal pin into the pelvis bone as a point of reference for measurements comparing the original hip to the replacement. However, these measurement techniques can be time consuming and difficult to keep accurate. Also, there is a risk of injury when inserting the pin into the pelvis. It would be desirable to provide a device that can accurately measure the offset and length of a patient's hip that is quick and easy to use and that also does not include an additional risk of injury.

Thus, there is a need for improvement in this field.

SUMMARY

The claims and only the claims recite the invention. In summary, it may include a guide device for assessing the length and offset of a hip of a patient. The guide device may have an overlay portion configured to enable assessment of the relative location of the guide device to the original femoral head of a patient. The relative location is indicated by a marking on the overlay portion. The guide device also includes an alignment portion including a contact surface. The contact surface is configured to contact the femur of a patient and create at least two reference points for positioning the guide device on the femur. When the contact surface of the alignment portion is positioned at the reference points, the guide device can be used to position a replacement femoral head in the same position as the original femoral head by aligning the replacement femoral head with the marking on the overlay portion.

In some embodiments, the guide device may include an overlay portion with a line system that may be used to determine the relative location of the original femoral head of the patient. The guide device has an alignment portion configured to physically engage a portion of the femur of the patient. The alignment portion includes at least one contact surface that extends obliquely from the alignment portion. The contact surface is configured to be inserted into a groove cut into the femur to create a reference point for positioning the guide device. The guide device can be used to position an artificial femoral head in the same relative position as the original femoral head by positioning the contact surface at the same reference points on the femur and aligning the artificial femoral head with the marking on the overlay portion.

Some embodiments may include a method for assessing the length and offset of the hip of a patient. The method may include placing a guide device including an overlay portion and an alignment portion with at least one contact surface into contact with the femur of a patient. At least two reference points are created at positions at which the contact surface contacts the femur of the patient.

The relative location of the guide device is assessed in comparison to the position of the original femoral head of the patient by marking the overlay portion at a reference point corresponding to the position of the original femoral head. Then, the original femoral head of the patient is removed.

The guide device is positioned on the femur of the patient so the contact surface is aligned on the femur at the previously created reference points. A replacement femoral head is positioned on the femur of the patient so the replacement femoral head aligns with the marking on the overlay portion made at the reference point that corresponds to the position of the original femoral head.

DESCRIPTION OF THE SELECTED EMBODIMENTS

With reference to the drawing Figures, for exampleFIGS. 1-9, a guide device100,200,300for assessing the length and offset of the hip of a patient is shown. As shown inFIGS. 1, 4, and 7, guide device100,200,300includes an overlay portion110,210,310configured to enable assessment of the relative location of the guide device100,200,300to the original femoral head20of a patient (seeFIGS. 2, 5 and 8). As an example, the relative location of the guide device to the original femoral head20may be determined from the center22of the femoral head20. The relative location of the femoral head20may be indicated by a marking120,220,320on the overlay portion110,210,310.

The guide device also includes an alignment portion125, including at least one contact surface134, wherein said contact surface134is configured to contact the femur of a patient to create at least two reference points A, B for positioning the guide device100on the femur10.

When the contact surface134of alignment portion125is positioned at the reference points A, B, the guide device100can be used to position a replacement femoral head40in the same position as the original femoral head20by aligning the replacement femoral head with the marking120on the overlay portion110(seeFIG. 3). As an example, the marking120on the overlay portion110may be aligned with the center42of the replacement femoral head.

As shown inFIGS. 4-6, one feature that is optional, but not required, may be that guide device200includes an alignment portion225with two legs230,240. Leg230has a corresponding contact surface232and leg240has a corresponding contact surface242. Each contact surface232,242sits on the femur10when the guide device200is in use to create reference points A, B.

In another optional embodiment, shown inFIGS. 7-9, guide device300includes an alignment portion325with two legs330,340. Each leg has a corresponding contact surface332,342that makes contact with the femur10when guide device300is in use. The point at which the contact surfaces332,342contact the femur10creates reference points A, B. In this embodiment, leg342may be configured to wrap around the lesser trochanter38instead of resting on top of the lesser trochanter.

One feature that is optional, but not required, may be that one of the reference points A, B is located at the lesser trochanter38of the patient. Alternatively, one of the reference points A, B may be located at the greater trochanter36of the patient. In some embodiments, one of the reference points is located at the lesser trochanter38of the patient and the other reference point is located at the greater trochanter36of the patient.

One feature that is optional, but not required, may be that the overlay portion110,210,310is made of plastic. Also, in some embodiments, the overlay portion may be transparent.

One feature that is optional, but not required, may be that a support piece140is included on one or both of the sides of the alignment portion that may help keep guide device100positioned on femur10. A bottom surface142of support piece140may contact the femur10.

One feature that is optional, but not required, may be that the marking made on the overlay portion110,210,310indicating the relative position of the femoral head20is located at a position on the overlay portion corresponding to the center22of the original femoral head20. In some embodiments, the marking on the overlay portion may be created manually, for example, using a marker or by creating an indentation on overlay portion110,210,310. Alternatively, in other embodiments, the marking on the overlay portion may be a line system122,322(seeFIGS. 1 and 7) which may be used to assess the location of a desired point of the femoral head. Some embodiments may include multiple markings. For example, a device may include a line system122,322on the surface of the overlay portion and a manually created mark120,320within the line system122,132for determining the relative location of a point of the femoral head.

One feature that is optional, but not required, may be that the overlay portion110,210,310is configured to allow a user to assess the location of a femoral head20of a patient when the overlay portion is positioned between the femoral head20and the user (seeFIG. 2, 5, or8).

One feature that is optional, but not required, may be that the guide device100includes an extension150that is used to determine the center of the femoral head20. An opening155is defined through the center of extension150. Extension150may be aligned with femoral head20so opening155is positioned at the center of femoral head20. A user may make a mark on at the center22of femoral head20through opening155. This mark may then be used as a reference point when aligning overlay portion110with femoral head20.

In some embodiments of guide device100(seeFIGS. 1-3), the alignment portion125includes a contact surface134that extends obliquely from the alignment portion125and is configured to be inserted into a groove24cut into the femur to create a reference point for positioning the guide device100. Groove24is later deepened to completely remove the original femoral head20. The guide device100can be used to position an artificial femoral head in the same relative position as the original femoral head20by positioning contact surface134at reference points A, B on the femur at groove24and aligning the artificial femoral head with a marking120on overlay portion110.

One feature that is optional, but not required, may be a second contact surface136that extends from alignment portion125. The symmetric design of second contact surface136with respect to first contact surface134allows guide device100to be used on either the left hip or the right hip. In some embodiments, second contact surface136may be inserted into groove24and be positioned at reference points on the femur.

A method for assessing the length and offset of a hip of a patient is provided (seeFIG. 10). This method400may comprise the acts of placing410a guide device including an overlay portion and an alignment portion with at least one contact surface into contact with the femur of a patient. At least two reference points are created 420 along the contact surface(s). The relative location of the guide device is assessed430in comparison to the position of the original femoral head of a patient. The overlay portion is marked440at a reference point corresponding to the position of the original femoral head.

After marking the position of the original femoral head, the femoral head is removed450. Then the guide device is positioned460on the femur of the patient so the contact surface(s) contacts the femur at the reference points. A replacement femoral head is positioned470on the femur of the patient so the replacement femoral head aligns with the marking of the reference point on the overlay portion that corresponds to the position of the original femoral head.

One feature that is optional, but not required, is that the position of the original femoral head is assessed using an extension on the guide device. The extension is aligned with the original femoral head and an opening defined through the center of the extension is aligned with the center of the original femoral head. A mark may be made through the opening directly on the original femoral head to assist in aligning the overlay portion with the original femoral head.

One feature that is optional, but not required, may be that one of the reference points is located at the lesser trochanter of the patient, or, optionally, one of the reference points may be located at the greater trochanter of the patient. In some embodiments, one of the reference points is located at the lesser trochanter and the other reference point is located at the greater trochanter of the patient.

One feature that is optional, but not required, may be that there are two distinct contact surfaces. Each of the contact surfaces is placed on the femur at a separate location. Each contact surface may be used to create one of the reference points used to position the replacement femoral head.

One feature that is optional, but not required, may be that one of the reference points is located at the femoral neck near the lesser trochanter of the patient and one of the reference points is located at the femoral neck near the greater trochanter of the patient.

In terms of the meaning of words or terms or phrases herein, literal differences therein are not superfluous and have different meaning, and are not to be synonymous with words or terms or phrases in the same or other claims. As used here (claims, specification, and other definitions) the following terms have the following meaning:

Articles and phases such as, “the”, “a”, “an”, “at least one”, and “a first”, “comprising”, “having” and “including” here are not limited to mean only one, but rather are inclusive and open ended to also include, optionally, two or more of such elements and/or other elements. In terms of the meaning of words or terms or phrases herein, literal differences therein are not superfluous and have different meaning, and are not to be synonymous with words or terms or phrases in the same or other claims.

The term “means for” in a claim invokes 35 U.S.C. § 112(f), literally encompassing the recited function and corresponding structure and equivalents thereto. Its absence does not, unless there otherwise is insufficient structure recited for that claim element. Nothing herein or elsewhere restricts the doctrine of equivalents available to the patentee.

The term “and/or” is inclusive here, meaning “and” as well as “or”. For example, “P and/or Q” encompasses, P, Q, and P with Q; and, such “P and/or Q” may include other elements as well.

The term “alignment portion” means here the part of the guide device that is connected to and extends from the overlay portion to engage the femur of the patient.

The term “center of the femoral head” means here the middle point of a patient's femoral head.

The term “contact surface” means here a portion of the guide device that touches the patient's bone when the guide device is in use. A contact surface may be a portion of the guide device that is inserted into a groove, a cut made into the bone, or may be a portion of the guide device that rests on the bone.

The term “extension” means here a portion of the guide device that extends past the overlay portion that may be used to determine the location of the original femoral head and make reference marks at the center of the original femoral head.

The term “femoral head” means here the rounded, articulating portion of the femur. The femoral head is the ball portion of the ball and socket joint that makes up the hip.

The term “femur” means here the thigh bone. The term femur as used includes all portions of the femur, including the femoral head, the neck of the femur, the lesser and greater trochanters, and the body of the femur.

The term “greater trochanter” means here the quadrilateral eminence located at the proximal and lateral portion of the shaft of the femur that provides an attachment point to the gluteus medius and minimus muscles, the piriform muscle, the internal and external obturator muscles, and the gemelli muscles.

The term “groove” means here a narrow cut or depression. A groove may be any man-made cut or naturally occurring opening in the bone that is meant to receive a portion of the guide device to aid in positioning.

The term “leg” means here a part of the alignment portion that includes a surface for contacting the femur. A leg may have any desired length or width and may be any shape that allows the leg to contact the patient's femur.

The term “lesser trochanter” means here a projection from the base of the neck of the femur that receives the insertion of the psoas major and the iliacus muscles.

The term “line system” means here a framework of lines that enable determination of a location. The framework of lines may be parallel lines or may include both parallel and perpendicular lines to form a grid. A line system may be placed on the overlay portion to determine the position of the guide device relative to the femoral head. The line system may be printed on, etched into, or engraved into the overlay portion, or included on the overlay portion by any other suitable method.

The term “manually” means here to be done by a person. As applied to making a marking, the term manually can mean making a marking with a writing utensil such as a marker, making a marking by creating an indentation on the surface of the overlay portion of the guide device, or by any other method a person may perform which makes a visible feature on the overlay portion to indicate a reference position.

The term “marking” means here a visual indication on the overlay portion of the guide device that indicates the position of the femoral head. For example, a marking could be a mark made by a marker at a certain location, such as the center of the femoral head, or could trace the entire femoral head to show its location. The marking could be an indentation or scratch made on the overlay portion. The marking could also be pre-formed, such as a line pattern formed on the overlay portion that shows the position of the femoral head. For example, the user may determine the position of the center of the original femoral head with respect to the line system and align the center of the replacement femoral head with the correct location on the line system.

The term “obliquely” means here positioned at an angle that is neither parallel nor perpendicular.

The term “original femoral head” means here the actual bone of the patient that forms the femoral head before being removed during an arthroplasty procedure.

The term “overlay portion” means here the portion of the guide device that covers the femoral head when the guide device is positioned on the femur. The overlay portion and alignment portion of the guide device may be monolithic or may be separate pieces that are connected. The overlay portion may be made from a different material than the alignment portion. For example, the overlay portion may be made from a clear plastic while the alignment portion is made from steel. The size and shape of the overlay portion may be different for different embodiments. In some embodiments, the overlay portion may be circular, but in other embodiments, the overlay portion may be square, rectangular, or any other desired shape. The overlay portion may be larger than the femoral head of the patient or, in some embodiments, may be smaller than the femoral head of the patient.

The term “physically engage” means here to make contact so the surfaces of the two objects are touching.

The term “reference point” means here a fixed location or a set of fixed locations that are used as the basis for measurement or assessment of the location of another object. As an example, reference points may be located at the positions at which the guide device contacts the portion of the patient's femur that is not removed during the removal procedure. A reference point may also be created on the overlay portion of the guide device.

The term “replacement femoral head” means here a prosthetic femoral head that is attached to the femur during an arthroplasty procedure to replace the original femoral head.

The term “transparent” means here to be clear or to have the property of allowing light to pass through to allow object behind to be distinctly seen.

The invention may include any one or more articles or devices made by any of the claimed methods and/or may by different methods but with a claimed composition.

The language used in the claims and the written description and in the above definitions is to only have its plain and ordinary meaning, except for terms explicitly defined above. Such plain and ordinary meaning is defined here as inclusive of all consistent dictionary definitions from the most recently published (on the filing date of this document) general purpose Webster's dictionaries and Random House dictionaries.