Locator for positioning the original hip joint center during hip replacement surgery

Abstract

A locator for positioning the original hip joint center during hip replacement surgery. A bar-shaped arm is a fixed arm. One end of the fixed arm is hinged to the fixed end of the first movable arm through a first hinge stud, and the other end of the fixed arm is hinged to the fixed end of the second movable arm through a second hinge stud. The distance between the hinge points at both ends of the fixed arm is 45 - 55 mm. Bar-shaped guide holes extending towards the free ends are provided on both the first and second movable arms. The free ends of the two movable arms overlap staggeredly and are hinged by passing a third hinge stud through the bar-shaped guide holes. All three hinge studs are threadedly fitted with locking nuts, and axial through holes are provided on each hinge stud. The through holes on the first and second hinge studs are used for fixing screws to pass through and fix to the femur, and the through hole of the third hinge stud is used for a positioning screw to pass through and drill a hole at the center of rotation of the femoral head to make a mark. It can determine the patient's own original hip joint center, guide the selection of femoral prostheses, and avoid subjective errors caused by human eye observation.

Description

Technical Field

[0001] The present invention relates to a medical device, in particular to a locator for positioning the original hip joint center during hip joint replacement surgery. Background Art

[0002] Anatomical parameters of the proximal femur of the human body: the diameter of the femoral head is (46.69±3.73) mm; the longitudinal length of the femoral head is (39.22±4.17) mm; the length of the femoral neck axis is (95.45±8.16) mm; the length of the upper edge of the femoral neck axis is (84.02±7.11) mm. The length of the lower edge of the femoral neck axis is (99.95±9.34) mm; the anteroposterior diameter of the femoral neck is (26.27±3.15) mm; the longitudinal diameter of the femoral neck is (32.24±3.31) mm; the femoral neck shaft angle is 126.21°±7.13°; the angle between the greater trochanter and the upward extension line of the lateral femoral cortex (greater trochanter angle) is 16.38°±4.04°; the transverse diameter of the femoral shaft at the level of the lesser trochanter is (31.05±3.57) mm; the anteroposterior diameter of the femoral shaft at the level of the lesser trochanter is (27.63±2.96) mm; the transverse diameter of the femoral shaft 5 cm below the lesser trochanter is (26.36±3.22) mm; the anteroposterior diameter of the femoral shaft 5 cm below the lesser trochanter is (25.59±2.75) mm. The horizontal distances from the apex of the bilateral greater trochanters to the rotation center of the femoral head were measured using the standard pelvic anteroposterior radiographs of 100 normal adults, indicating that 95% of the greater trochanter apices were higher than the femoral head center, 3% were lower than the femoral head center, and only 2% were flush with the femoral head center. Among them, those greater than 5 mm accounted for 83%, and more than 47% of the hip joints were greater than 10 mm. According to the literature, the distance from the apex of the greater trochanter to the femoral head center is 47.4 mm (42.5 - 56.6 mm), the average femoral neck shaft angle is 129.5° (120° - 140°), the distance between the greater and lesser trochanters is 59.2 (58.2 - 63.4 mm), and the average femoral offset is 37.2 (32.6 - 45.7 mm).

[0003] Femoral offset refers to the perpendicular distance from the rotation center of the femoral head to the long axis of the femur, which reflects the abductor muscle lever arm of the hip and is considered an important reference index for reconstructing the biomechanics of the hip joint. The reconstruction of femoral offset during total hip arthroplasty is related to abductor muscle tension, joint stability and mobility, and also plays an important role in prosthesis wear, loosening, the magnitude of proximal femoral stress, and balancing the lengths of the lower limbs. And whether the reconstruction of femoral offset is ideal depends to a large extent on whether the hip joint center is positioned reasonably.

[0004] In existing surgical procedures, the following methods are mainly used to determine whether the center positioning of the hip joint is reasonable. One is to roughly estimate whether the prosthesis is suitable based on the femoral anatomical landmarks during the operation, such as by visual inspection or using simple tools to roughly compare the distance and angle between the greater trochanter and the femoral head. This method is affected by the subjective error of the surgeon and the patient's position, which can easily lead to large deviations in positioning. Another method is to analyze the position parameters of the prosthesis through X-ray transmission during the operation, including acetabular abduction angle, acetabular anteversion angle, femoral head rotation center, femoral vertical offset, femoral eccentricity, femoral stem varus and valgus, neck-shaft angle, etc. However, this method is greatly affected by the patient's position during the operation, and often requires repeated transmission, which will increase the radiation dose received by the patient.

[0005] Therefore, it is of great significance to find a simple and intuitive tool to locate the center of the hip joint. Summary of the invention

[0006] The purpose of the present invention is to address the deficiencies of the prior art and to provide a locator for locating the original hip joint center during hip replacement surgery, which can determine the patient's own original hip joint center, guide the selection of femoral prosthesis, avoid subjective errors caused by human visual observation, and shorten the operation time.

[0007] The technical solution of the present invention is: a hip joint center locator for hip replacement, comprising a movable frame formed by hinged connection of three bar arms, two fixing screws and one positioning screw, wherein one of the bar arms is a fixed arm, one end of the fixed arm is hinged to the fixed end of the first movable arm through a first hinge stud, and the other end of the fixed arm is hinged to the fixed end of the second movable arm through a second hinge stud, the distance between the hinge points at both ends of the fixed arm is 45~55mm, the first movable arm and the second movable arm are both provided with a bar guide hole extending to the free end, the free ends of the two movable arms are staggered and overlapped, and a hinge is formed by passing the third hinge stud through the bar guide hole, the first, second and third hinge studs are all threadedly matched with locking nuts, and each hinge stud is provided with an axially penetrating axial hole, wherein the axial holes on the first and second hinge studs are used for fixing screws to pass through and fix to the femur, and the axial hole of the third hinge stud is used for the positioning screw to pass through and drill a hole in the rotation center of the femoral head to make a mark.

[0008] Furthermore, mounting grooves extending toward the end are respectively arranged at both ends of the fixed arm, and the two mounting grooves are arranged in opposite directions on the upper and lower end surfaces of the fixed arm, so that the free end of the second movable arm overlaps the free end of the first movable arm in an alternating manner.

[0009] Furthermore, the thickness of the fixed arm is 4 mm, the depth of the mounting groove is 2 mm, and the thickness of the first movable arm and the second movable arm are both 2 mm.

[0010] Further, the first articulated stud and the third articulated stud are "T"-shaped studs, and a limiting flange is provided at the lower end of the first articulated stud and the third articulated stud.

[0011] Further, a wedge-shaped flange is provided at the lower end of the second articulated stud, and the wedge-shaped surface of the wedge-shaped flange fits the convex inclined surface of the lesser trochanter.

[0012] Further, the wedge-shaped surface of the wedge-shaped flange is an arc surface.

[0013] Further, the width of the strip-shaped guide hole is 6-7 mm, and the length of the strip-shaped guide hole is less than the distance between the free end and the fixed end of the movable arm.

[0014] Further, the widths of the fixed arm, the first movable arm, and the second movable arm are all 12-14 mm.

[0015] Further, the maximum distance between the hinge point of the free end and the hinge point of the fixed end of the first movable arm is 60 mm.

[0016] Further, the maximum distance between the hinge point of the free end and the hinge point of the fixed end of the second movable arm is 80 mm.

[0017] Adopting the above technical solution: When this positioner is in use, the hinge point of the fixed arm and the first movable arm is positioned at a position 1 / 3 of the distance from the greater trochanter to the lesser trochanter near the greater trochanter end of the line connecting the greater trochanter and the lesser trochanter, and the hinge point is fixed at this position by a fixing screw; the hinge point of the fixed arm and the second movable arm is positioned at the intersection point between the extension line of the lower edge of the lesser trochanter and the axis of the femoral shaft, and the hinge point is fixed at this position by a fixing screw; move the first movable arm and the second movable arm, let the third hinge stud slide along the strip-shaped guide hole, so that the hinge point between the first movable arm and the second movable arm is positioned at the center of rotation of the femoral head, use a positioning screw to pass through the shaft hole of the third hinge stud to mark the center of rotation of the femoral head on the femur, and then lock each hinge point through a lock nut respectively, so that the fixed arm, the first movable arm, and the second movable arm form a fixed triangular bracket, and the triangular bracket can be removed by loosening the fixing screw and the positioning screw. After the surgeon completes the femoral neck osteotomy, the shaped positioner can be compared with the femoral prosthesis to help select a femoral prosthesis with a suitable size and model, or after the femoral prosthesis is placed, the positioner can be placed on the femur according to the marks made on the femur in advance to verify whether the center of rotation of the hip joint prosthesis coincides with the hinge point between the first movable arm and the second movable arm, so as to ensure that the center of rotation of the hip joint prosthesis coincides with the center of rotation of the patient's own hip joint, improving the success rate of the operation. This positioner has a simple structure and convenient operation, can ensure that the center of rotation of the femoral prosthesis is consistent with the center of the patient's hip joint, avoid subjective errors caused by human eye observation, improve the success rate of the operation, does not require repeated trial fitting, can avoid the risk of fracture caused by repeated trial fitting, and can shorten the operation time and reduce the surgical risk of the patient.

[0018] Installation grooves extending towards the ends are respectively arranged at both ends of the fixed arm, and the two installation grooves are arranged in a reverse manner on the upper and lower two end faces of the fixed arm, so that the free end of the second movable arm overlaps the free end of the first movable arm in a staggered manner, enabling the fixed arm, the first movable arm, and the second movable arm to overlap each other flatly and staggeredly, avoiding the upward warping of the second movable arm, thereby ensuring that the positioning screw can drill and mark perpendicular to the bone surface, avoiding the skew of the positioning screw, and ensuring the accuracy of positioning.

[0019] The thickness of the fixed arm is 4 mm, the depth of the installation groove is 2 mm, and the thicknesses of both the first movable arm and the second movable arm are 2 mm, so that the end faces of the first movable arm, the second movable arm, and the fixed arm are on the same plane.

[0020] The lower end of the second articulated stud is provided with a wedge-shaped flange, and the wedge-shaped surface of the wedge-shaped flange fits the raised inclined surface of the lower edge of the lesser trochanter. The height difference between the lesser trochanter and the greater trochanter is compensated by the wedge-shaped flange to prevent the second movable arm from tilting, so that the whole positioner remains straight during the positioning process, ensuring that both the fixing screw and the positioning screw can drill and mark perpendicular to the bone surface, and improving the positioning accuracy. The wedge-shaped surface of the wedge-shaped flange is an arc surface, making the wedge-shaped flange fit the femoral surface better.

[0021] The present invention will be further described below in conjunction with the accompanying drawings of the specification and specific embodiments. Brief Description of the Drawings

[0022] Figure 1 is a schematic structural diagram of the present invention;

[0023] Figure 2 is a schematic diagram of the articulated cooperation between the fixed arm and the two movable arms of the present invention. Detailed Embodiments

[0024] See Figures 1 to 2, A locator for positioning the original hip joint center during hip replacement surgery, comprising a movable frame formed by hinging three bar-shaped arms, and two fixing screws 9 and a positioning screw 10. One of the bar-shaped arms is a fixed arm 1. One end of the fixed arm 1 is hinged to the fixed end of the first movable arm 2 through a first hinge stud 4, and the other end of the fixed arm 1 is hinged to the fixed end of the second movable arm 3 through a second hinge stud 5. The widths of the fixed arm 1, the first movable arm 2, and the second movable arm 3 are all 12 - 14 mm. The hinge point between the fixed arm 1 and the first movable arm 2 is used to be positioned at the position of 1 / 3 distance from the greater trochanter end of the line connecting the greater trochanter and the lesser trochanter, and the hinge point between the fixed arm 1 and the second movable arm 3 is used to be positioned at the intersection point between the extension line of the lower edge of the lesser trochanter and the axis of the femoral shaft. Since the anatomical structures of the greater trochanter and the lesser trochanter of the femur are obvious, the distance between the two hinge points at both ends of the fixed arm 1 is set to be 45 - 55 mm according to the distance between the greater and lesser trochanters, which conforms to the anatomical parameters of the proximal femur of the human body, and two positioning base points can be determined on the femur. Bar-shaped guide holes 6 extending towards the free ends are provided on both the first movable arm 2 and the second movable arm 3. The free ends of the two movable arms overlap staggeredly, and are hinged through a third hinge stud 7 passing through the bar-shaped guide holes 6, so that the first movable arm 2 and the second movable arm 3 can slide along the bar-shaped guide holes 6 respectively, and the hinge point between the two movable arms moves along the bar-shaped guide holes 6 at the same time. By moving the first movable arm 2 and the second movable arm 3 to find the center of rotation of the femoral head, the hinge point between the two movable arms can be positioned at the center of rotation of the femoral head of the patient himself, and this center of rotation of the femoral head is the hip joint center. Since the distance between the hinge point at the free end and the hinge point at the fixed end of the first movable arm 2, and the distance between the hinge point at the free end and the hinge point at the fixed end of the second movable arm 3 are both adjustable, in this embodiment, the maximum distance between the hinge point at the free end and the hinge point at the fixed end of the first movable arm 2 is set to be 60 mm, and the maximum distance between the hinge point at the free end and the hinge point at the fixed end of the second movable arm 3 is set to be 80 mm, which can meet the surgical requirements of most hip replacement surgeries. The width of the bar-shaped guide hole 6 is 6 - 7 mm, so that the bar-shaped guide hole 6 leaves enough installation space for the third hinge stud 7. The length of the bar-shaped guide hole 6 is less than the distance between the free end and the fixed end of the movable arm, so that the bar-shaped guide hole 6 does not penetrate the entire free end of the movable arm, ensuring the strength of the two movable arms. The first, second, and third hinge studs are all threadedly fitted with locking nuts 8. By tightening the locking nuts 8, the fixed arm 1, the first movable arm 2, and the second movable arm 3 can be locked to each other, so that the three bar-shaped arms form a fixed tripod. Axially penetrating shaft holes are provided on each hinge stud. The shaft holes on the first and second hinge studs are used for the fixing screws 9 to pass through and be fixed to the femur, so that the two hinge points on the fixed arm 1 are fixed on the femur. The shaft hole of the third hinge stud 7 is used for the positioning screw 10 to pass through and make a mark by drilling a hole at the center of rotation of the femoral head, so that the hinge point between the first movable arm 2 and the second movable arm 3 is fixed on the femoral head.

[0025] Both ends of the fixed arm 1 are respectively provided with mounting grooves 11 extending towards the ends. The two mounting grooves 11 are arranged in opposite directions on the upper and lower end faces of the fixed arm 1, so that the free ends of the second movable arm 3 stagger and overlap on the free ends of the first movable arm 2, avoiding the upward warping of the second movable arm 3, and enabling the fixed arm 1, the first movable arm 2, and the second movable arm 3 to stagger and overlap with each other flatly. Thus, it is ensured that the positioning screw 10 can drill and mark perpendicular to the bone surface, avoiding the skew of the positioning screw 10 and ensuring the accuracy of positioning. The thickness of the fixed arm 1 is 4 mm, the depth of the mounting groove 11 is 2 mm, and the thicknesses of both the first movable arm 2 and the second movable arm 3 are 2 mm, so that the end faces of the first movable arm 2, the second movable arm 3, and the fixed arm 1 are in one plane, ensuring the positioning accuracy of the fixing screw 9 and the positioning screw 10.

[0026] The first hinge stud 4 and the third hinge stud 7 are "T"-shaped studs. The lower ends of the first hinge stud 4 and the third hinge stud 7 are provided with limiting flanges 12, so that the lower ends of the first hinge stud 4 and the third hinge stud 7 are limited by the limiting flanges 12, and the upper ends are limited by the locking nuts 8.

[0027] The lower end of the second hinge stud 5 is provided with a wedge-shaped flange 13. The wedge-shaped surface of the wedge-shaped flange 13 fits the raised inclined surface at the lower edge of the lesser trochanter. By means of the wedge-shaped flange 13, the height difference between the lesser trochanter and the greater trochanter is compensated, avoiding the skew of the second movable arm 3, keeping the whole positioner flat during the positioning process, ensuring that both the fixing screw 9 and the positioning screw 10 can drill and mark perpendicular to the bone surface, and improving the positioning accuracy. The wedge-shaped surface of the wedge-shaped flange 13 is an arc surface, making the wedge-shaped flange 13 fit the femoral surface better.

[0028] The using method of this positioner is as follows:

[0029] 1) Prompt the patient to lie on the side, layer by layer incise the skin, subcutaneous tissue, and fascia to expose the hip joint, incise the joint capsule, and then externally rotate the hip joint to dislocate.

[0030] 2) Position the hinge point between the fixed arm 1 and the first movable arm 2 of this positioner at the position of 1 / 3 distance from the greater trochanter end of the connection line between the greater trochanter and the lesser trochanter, and position the hinge point between the fixed arm 1 and the second movable arm 3 at the intersection point between the extension line of the lower edge of the lesser trochanter and the femoral shaft axis. Then, through the fixing screw 9, fix the above two hinge points at the corresponding femoral positions for marking respectively.

[0031] 3) Move the first movable arm 2 and the second movable arm 3 to slide the third hinge stud 7 along the strip-shaped guide hole 6, position the hinge point between the first movable arm 2 and the second movable arm 3 at the center of rotation of the femoral head, fix the hinge point at the center of rotation of the femoral head with the positioning screw 10 passing through the third hinge stud 7, and then tighten each locking nut 8 to lock each hinge point. At this time, the fixed arm 1, the first movable arm 2, and the second movable arm 3 form a fixed triangular bracket, and the positional relationship of the three hinge points is locked and cannot be moved anymore.

[0032] 4) Loosen the fixing screw 9 and the positioning screw 10, remove the positioner, and complete the femoral neck osteotomy.

[0033] 5) When installing the femoral side prosthesis of the hip joint, place the fixed-positioner in accordance with the marked position on the femur, compare the femoral prosthesis with the positioner to help select a suitable femoral prosthesis, or after placing the femoral side prosthesis according to experience, place each hinge point of the positioner on the femur according to the marks to verify whether the center of rotation of the hip joint prosthesis coincides with the hinge point between the first movable arm 2 and the second movable arm 3.

[0034] 6) Complete the positioning and remove the positioner.

[0035] This positioner has a simple structure and is convenient to operate. Through this positioner, it is possible to verify the deviation of the center of rotation of the femoral head prosthesis from the hip joint center of the patient himself, thereby guiding the selection and position adjustment of the femoral head prosthesis, so as to ensure that the center of rotation of the hip joint prosthesis coincides with the original hip joint rotation center of the patient himself, and further help the artificial hip joint achieve "anatomical replacement" during the operation, improving the success rate of the operation. Moreover, this positioner can ensure that the hip joint rotation center before and after the hip joint replacement is consistent, avoid the subjective error caused by human eye observation, does not require repeated trial molds, can avoid the risk of fracture caused by repeated trial molds, can shorten the operation time, reduce the number of intraoperative fluoroscopies, reduce the number of times the patient is exposed to the radioactive environment, and reduce the surgical risk of the patient. In addition, the entire positioner is made smooth to avoid scratching the patient during the operation.

Claims

1. A locator for positioning the original hip joint center during hip replacement surgery, characterized in that: It includes a movable frame formed by hinging three bar-shaped arms, as well as two fixing screws (9) and a positioning screw (10). One of the bar-shaped arms is a fixed arm (1). One end of the fixed arm (1) is hinged to the fixed end of the first movable arm (2) through a first hinge stud (4), and the other end of the fixed arm (1) is hinged to the fixed end of the second movable arm (3) through a second hinge stud (5). Installation grooves (11) extending towards the ends are respectively arranged at both ends of the fixed arm (1). The two installation grooves (11) are arranged in opposite directions on the upper and lower end faces of the fixed arm (1), so that the free end of the second movable arm (3) overlaps staggeredly on the free end of the first movable arm (2). The thickness of the fixed arm (1) is 4 mm, the depth of the installation groove (11) is 2 mm, the thicknesses of the first movable arm (2) and the second movable arm (3) are both 2 mm. The distance between the hinge points at both ends of the fixed arm (1) is 45 - 55 mm. Bar-shaped guide holes (6) extending towards the free ends are provided on both the first movable arm (2) and the second movable arm (3). The free ends of the two movable arms overlap staggeredly and are hinged through a third hinge stud (7) passing through the bar-shaped guide hole (6). The first, second, and third hinge studs are all threadedly fitted with locking nuts (8). Axially penetrating shaft holes are provided on each hinge stud. The shaft holes on the first and second hinge studs are for the fixing screw (9) to pass through and fix to the femur, and the shaft hole of the third hinge stud (7) is for the positioning screw (10) to pass through and mark by drilling at the center of rotation of the femoral head. A wedge-shaped flange (13) is provided at the lower end of the second hinge stud (5), and the wedge-shaped surface of the wedge-shaped flange (13) fits with the raised inclined surface at the lower edge of the lesser trochanter.

2. The locator for positioning the original hip joint center during hip replacement surgery according to claim 1, characterized in that: The first hinge stud (4) and the third hinge stud (7) are "T"-shaped studs, and limiting flanges (12) are provided at the lower ends of the first hinge stud (4) and the third hinge stud (7).

3. The locator for positioning the original hip joint center during hip replacement surgery according to claim 1, characterized in that: The wedge-shaped surface of the wedge-shaped flange (13) is an arc surface.

4. The locator for positioning the original hip joint center during hip replacement surgery according to claim 1, characterized in that: The width of the bar-shaped guide hole (6) is 6 - 7 mm, and the length of the bar-shaped guide hole (6) is less than the distance between the free end and the fixed end of the movable arm.

5. The locator for positioning the original hip joint center during hip replacement surgery according to claim 1, wherein: The widths of the fixed arm (1), the first movable arm (2), and the second movable arm (3) are all 12 - 14 mm.

6. The locator for positioning the original hip joint center during hip replacement surgery according to claim 1, characterized in that: The maximum distance between the hinge point at the free end and the hinge point at the fixed end of the first movable arm (2) is 60 mm.

7. The locator for positioning the original hip joint center in hip joint replacement surgery according to claim 1, characterized in that: The maximum distance between the hinge point at the free end and the hinge point at the fixed end of the second movable arm (3) is 80 mm.

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