Apparatus and method for forming custom cement-on-cement joint-type hip spacers
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- CEDARS SINAI MEDICAL CENT
- Filing Date
- 2025-05-23
- Publication Date
- 2026-08-05
Smart Images
Figure 0007900890000001 
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Abstract
Description
Technical Field
[0001] Cross - Reference to Related Applications This application claims the priority and benefit of U.S. Provisional Patent Application No. 62 / 898,691, filed on September 11, 2019, which is hereby incorporated by reference in its entirety.
[0002] Technical Field The present disclosure relates to devices for assisting in orthopedic surgery. Specifically, the present disclosure relates to devices for creating a custom cement - on - cement articulating hip joint spacer during surgery.
Background Art
[0003] Background In the United States, a total of 500,000 hip arthroplasties are performed each year. With the aging of the population, that number is expected to exceed 1 million. Busy orthopedic surgeons perform 10 surgeries a day. However, the overall infection rate of hip arthroplasty is usually 5%. Infections are disease - causing, life - threatening, and costly. Infections can occur due to the growth of biofilms on metal implants. The second surgery after infection is high - risk and usually more complex.
Summary of the Invention
[0004] Summary The standard treatment for chronically infected total hip replacements is to remove all implants and place a spacer made of bone cement mixed with antibiotics for a certain period. The cement spacer is a cast made from the mold of the spherical head of the femoral stem. The cement spacer is implanted and articulates with the raw surface of the patient's acetabulum, which can be very painful. Compared to off - the - shelf antibiotic acetabular and femoral components, this technology enables a custom - made cement for articulating the hip joint spacer during surgery.
[0005] Aspects of this disclosure include a device for forming a custom cement cast of a patient acetabular implant. The device includes an elongated handle and a head coupled to the proximal end of the elongated handle. The head includes a body, a circumferential lip, and a nipple. The body of the head is shaped as a spherical crown and includes a circular base and apex. The circumferential lip extends radially outward from the circular base of the body. The nipple extends perpendicularly to the circular base from the apex of the body.
[0006] In some embodiments, the head body is shaped as a hemisphere. In some embodiments, the head body is shaped to fit a prosthetic femoral head fitted to the patient. In some embodiments, the radius of the body is sized to fit the patient's acetabular defect (e.g., to be modifiable based on it). The radius of the body is the radius of the sphere on which the crown is based. In some embodiments, the apex is at the pole of the crown. In some embodiments, the circumferential lip extends generally along the same plane as the circular base. In some embodiments, the nipple is the center of rotation of the device.
[0007] In some examples, the device measurements may include any of the following: the radius of the body is 27.5 mm; the height of the body is 27.5 mm; the radius of the circular base is 55 mm; the circumferential lip extends 5 mm radially outward from the circular base; the thickness of the circumferential lip is 5 mm; and the height of the nipple is 5 mm.
[0008] In some embodiments, the nipple is sized to contact both the patient's cement and acetabulum, thereby forming a custom cement cast. In some examples, the head is rotatable coaxially around the nipple without damaging the cement while it hardens. In some examples, the thickness of the custom cement cast is the same as the height of the nipple. In some examples, the length of the nipple is sized based on the intended thickness of the custom cement cast.
[0009] Additional aspects of this disclosure include a method for treating a patient's infected total hip replacement. This method includes removing implants associated with the patient's infected total hip replacement. Cement is placed in the patient's acetabulum. A device is pressed into the cement, thereby forming a concave cemented acetabular cast. The device advances toward the patient's acetabulum. The device includes an elongated handle and a head coupled to the proximal end of the elongated handle. The head includes a body, a circumferential lip, and a nipple. The body is spherical in shape. The circumferential lip extends radially outward from the base of the body. The nipple extends perpendicularly to the base from the apex of the body. The device is advanced until the nipple of the head contacts the acetabulum, thereby ensuring an appropriate thickness of the cemented acetabular cast.
[0010] In some embodiments, the method further includes placing mineral oil between the cement and the device, thereby preventing the device from adhering to the cement. In some embodiments, the method further includes shaping the body of the head to conform to the prosthetic femoral head fitted to the patient.
[0011] In some embodiments, the cement comprises antibiotic bone cement. In some embodiments, the body of the head is shaped as a hemisphere and includes a circular base. In some embodiments, the radius of the body is modifiable based on the patient's acetabular defect. The radius of the body is the radius of the sphere on which the corona is based. In some embodiments, the nipple of the head is the center of rotation of the device. In some embodiments, the length of the nipple is modifiable based on the appropriate thickness of the cemented acetabular cast. In some embodiments, the head is rotatable coaxially around the nipple without breaking the cement while the cement hardens.
[0012] The above summary is not intended to represent any or all embodiments of the present disclosure. Rather, the above summary merely provides examples of some novel embodiments and features described herein. The above features and advantages, as well as other features and advantages of the present disclosure, will be readily apparent from the following detailed description of representative embodiments and styles for carrying out the invention, when taken in connection with the accompanying drawings and the accompanying claims. [Invention 1001] A device for forming custom cemented casts for patient acetabular implants, With a long, slender handle, A head attached to the proximal end of the elongated handle, A body formed as a spherical crown, including a circular base and a apex. A circumferential lip extending radially outward from the circular base of the main body, and A nipple extending from the top of the main body in a direction perpendicular to the circular base. Including the head and The device, including the device. [Invention 1002] The device of the present invention 1001, wherein the main body of the head is shaped as a hemisphere. [Invention 1003] A device according to any one of the present invention 1001 to 1002, wherein the radius of the main body is sized to fit the acetabular defect of the patient, and the radius of the main body is the radius of the sphere that forms the base of the crown. [Invention 1004] The device of the present invention 1003, wherein the radius of the main body is 27.5 mm. [Invention 1005] A device according to any of the present invention 1001 to 1004, wherein the height of the main body is 27.5 mm. [Invention 1006] A device according to any one of the present invention 1001 to 1005, wherein the radius of the circular base is 55 mm. [Invention 1007] A device according to any one of the present invention 1001 to 1006, wherein the apex is located at the pole of the spherical cap. [Invention 1008] A device according to any one of the present invention 1001 to 1007, wherein the circumferential lip extends generally along the same plane as the circular base. [Invention 1009] A device according to any one of the present invention 1001 to 1008, wherein the circumferential lip extends 5 mm radially outward from the circular base. [Invention 1010] A device according to any one of the present invention 1001 to 1009, wherein the thickness of the circumferential lip is 5 mm. [Invention 1011] A device according to any one of the present invention 1001 to 1010, wherein the height of the nipple is 5 mm. [Invention 1012] A device according to any one of the inventions 1001 to 1011, wherein the nipple is sized to contact both the cement and the patient's acetabulum, thereby forming the custom cement cast. [Invention 1013] The device of the present invention 1012, wherein the head is rotatable coaxially around the nipple without damaging the cement while the cement hardens. [Invention 1014] A device according to any one of the inventions 1012 to 1013, wherein the thickness of the custom cement cast is the same as the height of the nipple. [Invention 1015] A device according to any one of the inventions 1012 to 1014, wherein the length of the nipple is sized based on the intended thickness of the custom cement cast. [Invention 1016] A device according to any one of the present invention 1001 to 1015, wherein the head of the main body is shaped to fit a prosthetic femoral head attached to the patient. [Invention 1017] A device according to any one of the present invention 1001 to 1016, wherein the nipple is the center of rotation of the device. [The present invention 1018] A method for treating an infected total hip replacement in a patient, comprising: Removing an implant associated with the infected total hip replacement in the patient; Placing cement in the acetabulum of the patient; An elongated handle, and A head coupled to the proximal end of the elongated handle, the head including a body formed as a spherical cap, a circumferential lip extending radially outward from a base of the body, and a nipple extending in a direction perpendicular to the base from a top of the body, and Pushing a device including the above into the cement, thereby forming a concave cement acetabular cast; Advancing the device toward the acetabular bone of the patient until the nipple of the head contacts the acetabular bone, thereby ensuring an appropriate thickness of the cement acetabular cast The method comprising the above. [The present invention 1019] The method of the present invention 1018, wherein the body of the head is shaped as a hemisphere and includes a circular base. [The present invention 1020] The method according to any one of the present inventions 1018 to 1019, wherein the radius of the body is changeable based on the acetabular defect of the patient, and the radius of the body is the radius of the sphere that forms the base of the spherical cap. [The present invention 1021] The method according to any one of the present inventions 1018 to 1020, wherein the nipple of the head is the center of rotation of the device. [The present invention 1022] The method of the present invention 1021, wherein the head is rotatable coaxially around the nipple without destroying the cement while the cement cures. [The present invention 1023] The method according to any one of the present inventions 1018 to 1022, wherein the length of the nipple is changeable based on the appropriate thickness of the cement acetabular cast. [The present invention 1024] Any method of the present invention 1018 to 1023 further comprises placing mineral oil between the cement and the device to prevent the device from adhering to the cement. [Invention 1025] A method according to any one of the present invention 1018 to 1024, wherein the cement comprises antibiotic bone cement. [Invention 1026] A method of the present invention, any one of items 1018 to 1025, further comprising shaping the body of the head to fit the prosthetic femoral head fitted to the patient.
[0013] The aforementioned and other advantages of this disclosure will become apparent upon reading the following detailed description and referring to the drawings. [Brief explanation of the drawing]
[0014] [Figure 1] Anterior views of exemplary implants in total hip replacement according to several embodiments of this disclosure are shown. [Figure 2] Figure 1 shows an exploded view of the implant. [Figure 3] Figure 1 shows a forward-facing view of the implant fitted in a patient's hip joint according to several embodiments of the present disclosure. [Figure 4] The images show side views of devices for forming custom cemented casts for acetabular implants for patients, according to several embodiments of the present disclosure. [Figure 5] Figure 4 shows a first perspective side view of the device. [Figure 6] Figure 4 shows a second perspective side view of the device. [Figure 7] The images show the pelvic bone of a patient before placement of a custom cemented cast for an acetabular implant, according to several embodiments of this disclosure. [Figure 8] Figure 7 shows bone cement placed in the acetabulum of the pelvic bone according to several embodiments of the present disclosure. [Figure 9]Figure 8 shows a bone cement-embedded device for forming a custom cement cast, according to some embodiments of the present disclosure. [Figure 10] The present disclosure shows a device pressed into the acetabulum of the pelvic bone without bone cement, according to several embodiments of this disclosure. [Figure 11] The bone cement obtained after the device shown in Figure 9 is removed, according to some embodiments of the present disclosure. [Modes for carrying out the invention]
[0015] This disclosure is subject to various modifications and alternative forms, although certain embodiments have been shown in the drawings as examples and are described in detail herein. However, it should be understood that this disclosure is not intended to be limited to any particular form disclosed. Rather, this disclosure covers all modifications, equivalents, and alternatives that fall within the spirit and scope of this disclosure as defined by the appended claims.
[0016] Detailed explanation The present invention is described with reference to the accompanying drawings, and similar reference numerals are used throughout the drawings to indicate similar or equivalent elements. The drawings are not drawn to scale and are provided solely for illustrative purposes. Some aspects of the present invention are described below with reference to illustrative use. It should be understood that a number of specific details, relationships, and methods are shown to bring about a full understanding of the present invention. However, those skilled in the art will readily recognize that the present invention can be carried out without one or more specific details or in other ways. In other examples, well-known structures or operations are not shown in detail to avoid obscuring the present invention. The present invention is not limited by the illustrated order of actions or events, as some actions may occur in different orders and / or simultaneously with other actions or events. Furthermore, not all illustrated actions or events are required to carry out the methodology according to the present invention.
[0017] The standard treatment for chronically infected total hip replacement involves removing all implants and placing a spacer made of bone cement (e.g., polymethyl methacrylate) mixed with antibiotics for a period of time (e.g., at least six weeks). The cement spacer is a cast made from a mold of the spherical head of the femoral stem. The cement spacer is implanted and articulates with the raw surface of the acetabulum. Implantation and articulation can be very painful. Compared to off-the-shelf antibiotic acetabular and femoral components, this technique allows for custom-made, low-cost cement articulated hip spacers during surgery. In some cases, the articulated hip spacer is an antibiotic hip spacer.
[0018] In total hip replacement (e.g., total hip replacement), damaged bone and cartilage are removed and replaced with prosthetic components such as an implant 100. Referring generally to Figures 1 and 2, the implant 100 includes a prosthetic cup 110, a liner 120, a prosthetic femoral head 130, and a prosthetic femoral stem 140. In some examples, the prosthetic cup 110, the prosthetic femoral head 130, and the prosthetic femoral stem 140 are made of metal, ceramic, etc. In some examples, the material used for the implant can also be any kind that can be incorporated into the bone and is likely to stimulate bone growth on the implant.
[0019] Referring here to Figure 3, the patient's damaged femoral head is removed and replaced with a prosthetic femoral stem 140 inserted into the recessed center of the femur 35. The prosthetic femoral stem 140 may be cemented into the bone of the femur 35 or "press-fitted". The prosthetic femoral head 130 is placed on top of the prosthetic femoral stem 140. In some cases, the prosthetic femoral head 130 is ball-shaped and made of metal or ceramic. The prosthetic femoral head 130 replaces the removed damaged femoral head. The damaged cartilage surface of the acetabulum 15 (e.g., the socket in the patient's pelvis) is removed and replaced with a prosthetic cup 110. The prosthetic cup 110 is held in place and in contact with the bone of the acetabulum 15, secured with screws, or rarely with cement, without screws. The liner is inserted between the prosthetic femoral head 130 and the prosthetic cup 110 to allow for a smooth gliding surface. In some cases, the liner is made of plastic, ceramic, metal, or the like.
[0020] However, the infection rate after total hip replacement is typically 5%. Infections are disease-related, life-threatening, and costly. Infections can occur due to the growth of biofilm on metal implants. A second surgery after infection carries higher risks and is usually more complex. If an infection occurs and is treated in its early stages (usually within 6 weeks of the initial procedure), treatment includes irrigation and debridement, followed by replacement of the liner 120 and prosthetic femoral head 130. Such early treatment is effective in 50% to 80% of cases. If the infection recurs or is treated more than 6 weeks later (e.g., chronic infection), the standard care for treatment in many countries (such as the United States) is the removal of all components and placement of an antibiotic cement spacer.
[0021] The current common spacer options are one of two: (1) removing all components and placing them in an antibiotic cement mold of the femoral head and femoral stem, and (2) placing a new femoral implant with antibiotic cement around the femoral stem and a new liner with antibiotic cement in the acetabulum. The second option can be a waste of money because the new implant is expensive and needs to be removed once the infection is gone.
[0022] Furthermore, treatment for chronically infected hip replacements may be performed in one or two stages. In one-stage treatment, the infected hip replacement implant is removed and a new hip replacement implant is placed. The new hip replacement implant often contains antibiotic bone cement. The drawback of one-stage treatment is the high rate of reinfection, which means that expensive components are placed with the risk of reinfection. In two-stage treatment, the infected hip replacement implant is removed, an antibiotic spacer is placed, and after a waiting period, a new hip replacement implant is placed. Two-stage treatment is standard care in many countries (including the United States) and requires two separate procedures. This can be difficult for already unhealthy patient populations. Therefore, the effective and low-cost antibiotic cement spacer disclosed herein would greatly benefit these patients, especially in the first stage.
[0023] In some cases of antibiotic spacers, metal-on-polyethylene implants are used. This is done by placing cement in the acetabulum and then placing a polyethylene component within the cement. Next, instead of a cement spacer, a regular metal femoral head and femoral stem are implanted and held in place with antibiotic cement. This technique has at least two drawbacks. Firstly, the new implants significantly increase the cost of the procedure. Secondly, the metal and polyethylene implants are a new heterogeneous surface for bacteria to form a biofilm (sugar-coated film), allowing the bacteria to evade antibiotics and the immune system. In some cases, surgeons can purchase ready-made cemented antibiotic acetabular and femoral components that enable cement-on-cement jointing. The drawback is that the cost of prefabricating such implants can be higher compared to fabricating custom cement-on-cement implants during surgery. The reason these options exist is to find a way to protect the acetabulum and / or prevent pain from the cement occluding with the bone.
[0024] This disclosure enables surgeons to fabricate low-cost, custom cement-on-cement articular antibiotic hip spacers. This disclosure has several advantages over other solutions. Compared to metal-on-polyethylene articular hip spacers, this disclosure enables articular hip spacers without the use of metal or polyethylene implants. Such metal or polyethylene implants increase the cost of surgery and leave foreign bodies in infected wounds due to potential biofilm formation. Compared to off-the-shelf antibiotic acetabular and femoral components, this disclosure enables a custom-made, low-cost solution instead of paying for off-the-shelf implants. Furthermore, in some embodiments, this disclosure also enables surgeons to determine and / or customize the type and / or dosage of antibiotics in the bone cement, which may often be unsuitable with off-the-shelf cement components.
[0025] As discussed herein, typical implant cement spacers can be painful for patients. This disclosure enables surgeons to mold cement-on-cement spacers for the treatment of infected total hip replacement. This disclosure enables the formation of a cement cast from a mold of the acetabular implant and a cement-on-cement articular spacer, thus eliminating the pain of cement articulating with the natural acetabulum. This disclosure includes an inexpensive device that helps reduce patient pain associated with the spacer. In some embodiments, the device is a medical device used to fabricate a custom cement-on-cement articular antibiotic hip spacer during surgery. In some embodiments, the device is used for the treatment of infected total hip replacement. The device is a tool and is not implanted in the body during surgery. It is sterile and reusable. The device can be molded in various sizes and is customizable to the patient. The hemispherical head of the device is important for obtaining the correct shape of the resulting spacer, and its nipple is important for obtaining the correct thickness of the resulting spacer.
[0026] Referring generally to Figures 4 to 6, a device 200 for forming a custom cement cast of an acetabular implant for a patient is disclosed herein. The device 200 includes an elongated handle 210 and a head 250 coupled to the proximal end 215 of the elongated handle 210. The head 250 includes a body 220, a circumferential lip 230, and a nipple 240. The body 220 of the head 250 is shaped as a spherical crown and includes a circular base 252 and a apex 254. The circumferential lip 230 extends radially outward from the circular base 252 of the body 220. The nipple 240 extends perpendicularly to the circular base 252 from the apex 254 of the body 220.
[0027] In some embodiments, the body 220 of the head 250 is shaped as a hemisphere. In some embodiments, the body 220 of the head 250 is shaped to fit a prosthetic femoral head fitted to the patient. In some embodiments, the radius of the body 220 is sized to fit the patient's acetabular defect (e.g., to be modifiable based on it). The radius of the body 220 is the radius of the sphere on which the crown is based. In some embodiments, the apex 254 is at the pole of the crown. In some embodiments, the circumferential lip 230 generally extends along the same plane as the circular base 252. In some embodiments, the nipple 240 is the center of rotation of the device 200.
[0028] Referring to Figure 4, the diameter or width 212 of the handle 210 is 20 mm. The body 220 includes a diameter (or width) 222 of 55 mm and a height 224 of 27.5 mm. In the illustrated example where the body 220 is shaped as a special type of spherical crown (hemispheric), the diameter 222 of the circular base 252 is the same as the diameter 222 of the body 220 (for example, the diameter of the base sphere). However, in other examples, the body 220 is also intended to be shaped as another type of spherical crown, where the diameter of the base sphere is different from the diameter of the circular base.
[0029] Furthermore, the circumferential lip 230 includes an average thickness 234 of 5 mm, and extends 5 mm radially outward from the circular base 252. The circumferential lip 230 extends at a distance 236 from the first side of the body 220 and at a distance 238 from the opposite side of the body 220. In some examples, the circumferential lip 230 extends radially outward at a constant distance from the entire circumference, and therefore distances 236 and 238 are the same. In some such examples, the total diameter 232 of the disk (including the circular base 252 and the circumferential lip 230) is 65 mm.
[0030] In some examples, the nipple 240 is shaped as a short cylinder. The nipple 240 includes a height 242 of 5 mm and a diameter 244 of 5 mm. In some such examples, the resulting cement cast may have a thickness of approximately 5 mm due to the height 242 of the nipple.
[0031] The specific dimensions of the elements of the device 200 described herein are intended to be examples only. Other dimensions are intended according to the medical practice. In some embodiments, the diameter 222 of the body 220 is modifiable so that molds of different sizes of acetabular bones (e.g., acetabulum 15) can be fabricated. According to some embodiments of the present disclosure, a set of heads of various sizes (e.g., hemispheres) each includes a circumferential lip of the same size (e.g., 5 mm). Alternatively, a set of heads of various sizes includes a circumferential lip that is proportionally sized. For example, a head with a 55 mm body includes a 5 mm circumferential lip, and a head with a 66 mm body includes a 6 mm circumferential lip.
[0032] Each head set may have its own handle, or alternatively, they may be detachably attached to a single universal handle. In some examples, the diameter of pre-fabricated or intraoperatively molded cemented femoral heads ranges from 48 mm to 64 mm. Therefore, the diameter of the hemispheres disclosed herein ranges from 48 mm to 66 mm. The reason for the large dimensional variation is that the size of the acetabular defect depends on the patient's size, previous acetabular components, bone loss, or any combination thereof. Thus, acetabular defects among patients vary from small to large. Therefore, one size of device head is not suitable for all patients. Additionally or alternatively, the hemisphere selected for the acetabular mold has a diameter 1-2 mm larger than the diameter of the femoral head, allowing the femoral head to articulate smoothly within the acetabulum.
[0033] In some embodiments, the nipple 240 is sized to contact both the cement 45 and the patient's acetabulum, thereby forming a custom cement cast (Figure 9). In some examples, the head 250 is rotatable coaxially around the nipple 240 without damaging the cement 45 while the cement 45 hardens. In some embodiments, the thickness of the custom cement cast is the same as the height of the nipple 240. For example, if the height of the nipple is 5 mm, the resulting thickness of the custom cement cast will be approximately 5 mm. In some embodiments, the length of the nipple 240 is sized based on the intended thickness of the custom cement cast. In some examples, the length of the nipple 240 is sized based on the intended acetabular offset from the pelvis that the surgeon requires to achieve proper tension and / or stability of the hip joint.
[0034] Nipple 240 is also dimensionally adjustable. This allows surgeons to precisely dial in the required thickness of the cement mantle. Thickness is important for several reasons. First, the correct thickness is necessary to give the cement structure sufficient strength. Second, sufficient cement is necessary for proper antibiotic elution. Third, the correct thickness helps restore the offset of the hip joint's center of rotation. To elaborate on the third point, significant bone loss often occurs when the previous acetabular component is removed. Conventional antibiotic spacers, which articulate with raw bone, experience a significant reduction in offset because the acetabular component is gone. This reduction in offset leads to a decrease in the biomechanics of the spacer, which can then lead to spacer displacement. However, by creating a mold of the acetabular component, the offset can be restored, and this is where Nipple 240 comes in, allowing surgeons to dial in the required amount of offset.
[0035] According to some embodiments of this disclosure, the dimensions of the nipple 240 are further based on the patient's bone loss and / or natural hip joint structure. For example, the thickness of a standard metal cup (including a polyethylene liner) is approximately 10 mm at the top. Thus, the height of the nipple 240 to restore only the previous hardware is theoretically 10 mm, however, considering the offset described herein, nipples ranging in length from 5 mm to 20 mm should be available. In some examples, the nipple 240 is integral with the body 220. In some other examples, the nipple 240 is detachably attached to the body 220 and is therefore replaceable. With respect to the diameter of the nipple, 5 mm is preferred to form a relatively small defect in the acetabular shape.
[0036] According to some embodiments of this disclosure, the nipple 240 is shaped cylindrically so as not to damage the cement mantle while the device is rotating on the nipple axis during cement hardening. Furthermore, shaping it cylindrically takes into account the diameter necessary to create an appropriate mold thickness and restore the offset, while simultaneously forming a minimal defect in the mold. Although the nipple 240 is intended to be of other shapes (e.g., rectangular), a cylindrical shape is generally preferred when the device is rotated as the cement hardens.
[0037] Additional aspects of the present disclosure include a method for treating an infected total hip replacement in a patient. The method can be illustrated by Figures 7 to 11 of the present disclosure. For example, Figure 7 shows the patient's pelvic bone 25 before placement of a custom cemented cast of an acetabular implant; Figure 8 shows bone cement 45 placed in the acetabulum of the patient's pelvic bone 25; Figure 9 shows a device 200 pressed into the bone cement 45 to form a custom cemented cast; Figure 10 shows the device 200 pressed into the acetabulum of the patient's pelvic bone 25 without the use of bone cement; and Figure 11 shows the bone cement 45 obtained after the device 200 has been removed.
[0038] This method involves removing an implant associated with an infected total hip replacement in a patient. Referring here to Figures 8-9 and 11, cement 45 (e.g., bone cement) is placed in the patient's acetabulum. A device 200 (such as device 200 in Figures 4-6) is pressed into the cement 45, thereby forming a concave cemented acetabular cast (Figure 11). The device 200 is advanced toward the patient's acetabulum. As shown herein with reference to Figures 4-6, the device 200 includes an elongated handle 210 and a head 250 coupled to the proximal end 215 of the elongated handle 210. The head 250 includes a body 220, a circumferential lip 230, and a nipple 240. The body 220 is shaped as a spherical cap. The circumferential lip 230 extends radially outward from the base 252 of the body 220. The nipple 240 extends from the top 254 of the main body 220 in a direction perpendicular to the base 252.
[0039] The device 200 is advanced until the nipple 240 of the head 250 contacts the acetabulum 55, thereby ensuring (i) the proper thickness of the cemented acetabular cast and / or (ii) the intended acetabular offset from the pelvis. Referring more specifically to Figure 11, after the device 200 has been removed, a concave cemented acetabular cast is formed, showing the negative indentation 440 of the nipple 240 (e.g., the shape of a recessed point) and the negative indentation 430 of the circumferential lip 230 (e.g., the shape of a recessed ring).
[0040] In some embodiments, the cement includes antibiotic bone cement. In some embodiments, the method further includes placing mineral oil between the cement 45 and the device 200 and thereby preventing the device from adhering to the cement 45. In some embodiments, the method further includes shaping the body 220 of the femoral head 250 to fit the prosthetic femoral head 250 fitted to the patient.
[0041] In some embodiments, the body 220 of the head 250 is shaped as a hemisphere and includes a circular base 252. In some embodiments, the radius of the body 220 is modifiable based on the patient's acetabular defect. The radius of the body 220 is the radius of the sphere on which the corona is based. In some embodiments, the nipple 240 of the head 250 is the center of rotation of the device 200. In some embodiments, the length of the nipple 240 is modifiable based on the appropriate thickness of the cemented acetabular cast. In some embodiments, the head 250 is rotatable coaxially around the nipple 240 without damaging the cement while the cement hardens.
[0042] In contrast to knee replacement surgery, measuring cement thickness within the knee is easier because the tibial plateau is exposed during surgery. However, in the buttocks, the acetabulum 15 is not visible once cement is inserted. Therefore, the nipple 240 of device 200 is important in measuring the thickness 234 of the cement mantle. Thus, while other methods of measuring depth exist in orthopedic surgery or other fields (e.g., using pins, depth gauges, or rulers), it is a specific and important fact in this disclosure that the nipple 240 is located at the very top 254 of the dome of device 200. By positioning the nipple 240 at the top 254 of the dome, the surgeon can rotate the handle 210 of device 200 coaxially without damaging the cement 45 while the cement 45 hardens. The modularity of the length of the nipple 240 allows the surgeon to customize the center of rotation relative to the patient to achieve appropriate tension, stability, limb length, and / or offset.
[0043] As disclosed herein, in some embodiments, the methods and devices of this disclosure can be used surgically after a total hip replacement has been removed from a patient (for example, due to infection). Standard care in many countries (including the United States) is the surgical placement of a temporary antibiotic bone-cement spacer. This disclosure enables a custom cement-on-cement spacer by fabricating a custom acetabular cup from bone cement. After the removal of a total hip replacement, a significant defect exists in the patient's acetabulum. This disclosure addresses this defect. The specific design, as well as the proportions and dimensions of the disclosed devices, are important to the disclosure's ability to address this defect. Several key aspects of the disclosed devices are discussed in more detail throughout this disclosure and below.
[0044] Body 220 shape - spherical cup and hemisphere The disclosed device 200 is configured to produce a hemispherical acetabular cement cup. For this reason, the body 220 of the device 200 is shaped like a spherical cup. This is typically a hemisphere with a certain diameter (e.g., diameter 222). The shape of the acetabular defect can change significantly depending on bone loss due to infection and / or surgery. Since the ultimate goal is to create an articular cement-on-cement spacer, the device 200 is configured to produce a hemispherical acetabular cup fabricated from bone cement. If the shape is larger than a hemisphere, it is not possible to reduce the size of a spherical femoral head of similar diameter and fit it into this cup. In some scenarios, it may be possible to somehow reduce the size to less than a hemisphere, but this may result in less coverage and / or risk of displacement of a spherical femoral head of similar diameter. By being hemispherical, the device body 220 produces a hemispherical recess cement acetabular cup plaque.
[0045] Body diameter 222 The size of the acetabular defect can vary significantly depending on bone loss due to infection and / or surgery. Therefore, the size of the acetabular cement cup must be adjusted accordingly. This disclosure allows for customization by the surgeon. First, the diameter of the defect is measured. Then, the disclosed device 200 having an appropriate diameter 222 can be selected. For example, several options may be available in the operating room for the surgeon to choose from. By selecting the appropriate size, the surgeon can also fill the defect with the largest and most appropriate acetabular cup and a femoral head of similar size. The larger the femoral head, the lower the risk of displacement, and therefore the greater the stability of the cement-on-cement integrated spacer. Considering the anatomy of the acetabulum, the hemispherical diameter can range from 48 mm to 66 mm. The reason for the large variation in dimensions is that the size of the acetabular defect depends on the size of the acetabular defect.
[0046] Nipple 240, and the height of nipple 240 242 The nipple 240 is an important aspect of the device 200. When fabricating a custom acetabular cement cup, the thickness of the cement cup may be measured and / or determined. The nipple 240 is important for at least the following reasons:
[0047] The thickness of the cement at the top 254 of the custom cemented cup determines the acetabular offset, as well as the overall cement-on-cement antibiotic integrated spacer. Offset is a crucial biomechanical aspect of the hip joint that allows for proper loading of the buttocks and joint stability. When a total hip replacement is removed and a conventional antibiotic bone-cement spacer is implanted, the offset often decreases because all acetabular components are no longer in place. Therefore, these conventional spacers carry a high risk of displacement.
[0048] In contrast, this disclosure allows for the restoration of the offset and, furthermore, the adjustment of the offset to a specific level required by a particular patient. An increased offset increases soft tissue tension, enabling greater stability of the buttocks. An excessively large offset generates excessive tension, resulting in pain and difficulty of movement. An excessively small offset creates buttock instability and a risk of displacement. For this reason alone, at least, the nipple 240 of device 200 can be modified to adjust to an appropriate offset, as further discussed herein.
[0049] The thickness of the cement in a custom cement cup also determines the strength of the cement. A thicker cement mantle increases the resistance of the cement to cracking. If it is too thick, there will be insufficient space to position the properly sized femoral head. If it is too thin, there is a risk of cracking in the cement mantle. For this reason alone, at least, the nipple 240 of device 200 can be modified to adjust to the appropriate cement mantle, which will be discussed further herein.
[0050] For these reasons, this disclosure makes it possible to adjust the cement thickness of the cement cup. In some embodiments, adjusting and / or modifying the cement thickness can be done using the nipple 240 of the device 200. In some such embodiments, the height 242 of the nipple 240 helps determine the cement thickness as follows: First, the required cement thickness can be determined. Next, a nipple 240 having an appropriate height 242 is selected. Several options may be available in the operating room. The selected device 200 is then pressed into soft antibiotic bone cement to make a cast for the cemented acetabular cup. With the nipple 240 at the top, the device 200 is pressed into the cartilage cement until the nipple 240 contacts the inside of the acetabulum 15 and provides resistance. At this point, the appropriate depth is achieved. The device 200 can be held in place until the cement hardens.
[0051] For example, if the height 242 of nipple 240 is 5 mm, the resulting thickness of the custom cemented cast will be approximately 5 mm. In a non-infected total hip replacement, the thickness of a standard metal cup and liner is approximately 10 mm at the apex. Therefore, to recover the offset of the previous center of rotation of the acetabulum 15, the height 242 of nipple 240 needs to be approximately 10 mm. However, this height may vary depending on the size of the new acetabulum and femoral head. Therefore, nipples with heights ranging from 5 mm to 20 mm can be used to determine the exact offset required.
[0052] Circumferential lip 230, and diameter 232 of the circumferential lip 230 This disclosure includes a circumferential lip 230, which is essential when fabricating a cemented acetabular cup. This circumferential lip 230 is present to ensure that only hemispherical cups are fabricated and not cups larger than a hemisphere. Without the circumferential lip 230, when the device 200 is pressed into the soft cement, the cement moves outward from the device 200, enveloping it and creating a cup larger than a hemisphere. If the fabricated cup is larger than a hemisphere, the femoral head will not fit, making it less likely that a properly sized femoral head will be positioned in this cup.
[0053] Instead, the circumferential lip 230 is designed so that as the cement moves out of the acetabular defect, the cement moves radially from the device 200 at the base 252 of the hemisphere. This ensures that a hemisphere, and only a hemisphere, is fabricated. It is also possible to easily remove any excess cement without destroying the fabricated acetabular cement cup. The diameter 232 of the circumferential lip 230 varies according to the diameter 222 of the body 220 of the device 200 selected for a specific acetabular defect. The diameter 232 of the circumferential lip 230 varies so that at the edge of the base 252 of the body 220, it extends circumferentially by at least 5 mm (236 and 238) beyond the diameter 222 of the body 220. Thus, the diameter 232 of the circumferential lip 230 must be at least 10 mm in addition to the diameter 222 of the body 220.
[0054] One or more elements, aspects, or processes, or any part(s) thereof, described in any one or more of the following claims 1 to 26, can be combined with one or more elements, aspects, or processes, or any part(s) thereof, described in any one or more of the other claims 1 to 26, or any combination thereof, to form one or more further embodiments and / or claims of the present disclosure.
[0055] Any patent, patent application, patent application publication, and other material, such as articles, books, specifications, publications, documents, works, and / or other materials referenced herein are incorporated herein by reference in their entirety for all purposes, except for any prosecution history of the same or related patents, any identical or disputed patents that do not conform to this document, or any identical patents that may, currently or in the future, have a limited effect on the broadest scope of claims relating to this document. For example, if there is any inconsistency or contradiction between the definitions, definitions, and / or use of terms relating to any of the incorporated materials and the definitions, definitions, and / or use of terms relating to this document, the definitions, definitions, and / or use of terms relating to this document shall prevail.
[0056] Although various embodiments of this disclosure have been described above, it should be understood that these are presented for illustrative purposes only and are not limiting. Various modifications to the disclosed embodiments can be made in accordance with the disclosure herein without departing from the spirit or scope of the invention. Therefore, the breadth and scope of the invention should not be limited by any of the embodiments described above. Rather, the scope of the invention should be defined in accordance with the following claims and their equivalents.
[0057] Although the present invention is described and written in relation to one or more embodiments, equivalent changes and modifications will be made by those skilled in the art as they read and understand this specification and the accompanying drawings. Furthermore, although specific features of the present invention are disclosed in relation to one of the multiple embodiments, such features can be combined with one or more other features of other embodiments where desired and where advantageous for any given or specific application.
[0058] The terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the invention. Unless otherwise specified in the context, the singular forms "a," "an," and "the" used herein are intended to include the plural forms as well. Furthermore, the terms "including," "includes," "having," "has," "with," or variations thereof, used in either the detailed description and / or the claims, are intended to be comprehensive, in a similar manner to the term "comprising." Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as generally understood by those skilled in the art to which the invention belongs. Furthermore, terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technical field and not as idealized or overly formal unless expressly defined herein.
Claims
1. A device for forming custom cemented casts for patient acetabular implants, With a long, slender handle, A head detachably attached to the proximal end of the elongated handle, A body formed as a spherical crown, including a circular base and a apex. A circumferential lip extending radially outward from the circular base of the main body, and A nipple extending from the top of the main body in a direction perpendicular to the circular base. Including the head and The device, including the device.
2. The device according to claim 1, wherein the head body is shaped as a hemisphere.
3. The device according to any one of claims 1 to 2, wherein the radius of the main body is sized to fit the acetabular defect of the patient, and the radius of the main body is the radius of the sphere that forms the base of the crown.
4. The device according to claim 3, wherein the radius of the main body is 27.5 mm.
5. The device according to any one of claims 1 to 4, wherein the height of the main body is 27.5 mm.
6. The device according to any one of claims 1 to 5, wherein the radius of the circular base is 27.5 mm.
7. The device according to any one of claims 1 to 6, wherein the apex is located at the pole of the spherical cap.
8. The device according to any one of claims 1 to 7, wherein the circumferential lip extends generally along the same plane as the circular base.
9. The device according to any one of claims 1 to 8, wherein the circumferential lip extends 5 mm radially outward from the circular base.
10. The device according to any one of claims 1 to 9, wherein the thickness of the circumferential lip is 5 mm.
11. The device according to any one of claims 1 to 10, wherein the height of the nipple is 5 mm.
12. The device according to any one of claims 1 to 11, wherein the nipple is sized to contact both the cement and the patient's acetabulum, thereby forming the custom cement cast.
13. The device according to claim 12, wherein the head is rotatable coaxially around the nipple without damaging the cement while the cement hardens.
14. The device according to any one of claims 12 to 13, wherein the thickness of the custom cement cast is the same as the height of the nipple.
15. The device according to any one of claims 12 to 14, wherein the height of the nipple is sized based on the intended thickness of the custom cement cast.
16. The device according to any one of claims 1 to 15, wherein the head of the main body is shaped to fit a prosthetic femoral head fitted to the patient.
17. The device according to any one of claims 1 to 16, wherein the nipple is configured to function as the center of rotation of the device while the cement hardens.
18. The device according to claim 1, wherein the elongated handle is configured to be interchangeable with a separate head which includes another body formed to be of a different size from the body of the head.
19. The device according to claim 18, wherein the body of the head and the other body of the separate head are both shaped as hemispheres, and the diameter of the hemispheres is in the range of 48 mm to 66 mm.
20. The device according to any one of claims 12 to 14, wherein the height of the nipple is adjustable based on the intended thickness of the custom cement cast.