Tool and method for forming custom cement-on-cement joint-type hip joint spacer

Abstract

To provide a device for forming a custom cement cast of an acetabular implant.SOLUTION: A device includes a slender handle and a head connected to a proximal end of the slender handle. The head includes a body, a lip in a circumferential direction, and a nipple. The body of the head is formed as a spherical crown, and includes a circular base part and a top part. The lip in the circumferential direction is extended radially outward from the circular base part of the body. The nipple is extended from the top part of the body in a vertical direction with respect to the circular base part.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to and the benefit of U.S. Provisional Patent Application No. 62 / 898,691, filed September 11, 2019, which is incorporated herein by reference in its entirety.

[0002] Technical Field The present disclosure relates to devices for assisting in orthopedic surgery. In particular, the present disclosure relates to devices for intraoperatively creating custom cement-on-cement articulating hip spacers. [Background technology]

[0003] background A total of 500,000 total hip replacements are performed each year in the United States. Due to an aging population, that number is expected to exceed 1 million. Busy orthopedic surgeons perform 10 procedures per day. However, the overall infection rate for total hip replacements is typically 5%. Infections are morbid, potentially life-threatening, and costly. Infections can occur due to biofilm growth on metal implants. A second surgery after infection is riskier and usually more complicated. Summary of the Invention

[0004] overview 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 period of time. The cement spacer is a cast made from an impression 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 technique allows for custom-made cement to articulate the hip spacer during surgery.

[0005] Aspects of the present disclosure include a device for forming a custom cemented cast of an acetabular implant for a patient. The device includes an elongated handle and a head coupled to a 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 an apex. The circumferential lip extends radially outward from the circular base of the body. The nipple extends from the apex of the body in a direction perpendicular to the circular base.

[0006] In some embodiments, the head body is shaped as a hemisphere. In some embodiments, the head body is shaped to fit with a prosthetic femoral head fitted to the patient. In some embodiments, the body radius is sized to fit (e.g., be variable based on) the patient's acetabular defect. The body radius is the radius of the sphere that forms the base of the spherical crown. In some embodiments, the apex is at the pole of the spherical 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 body radius is 27.5 mm; the body height is 27.5 mm; the circular base radius is 55 mm; the circumferential lip extends radially outward from the circular base by 5 mm; the circumferential lip thickness is 5 mm; and the nipple height 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 instances, the head can be coaxially rotated around the nipple while the cement hardens without destroying the cement. In some instances, the thickness of the custom cement cast is the same as the height of the nipple. In some instances, the length of the nipple is sized based on the intended thickness of the custom cement cast.

[0009] An additional aspect of the present disclosure includes a method for treating an infected total hip replacement in a patient. The method includes removing an implant associated with the patient's infected total hip replacement. Cement is placed into the patient's acetabulum. A device is forced into the cement, thereby forming a concave cemented acetabular cast. The device is advanced toward the patient's acetabular bone. The device includes an elongated handle and a head coupled to a proximal end of the elongated handle. The head includes a body, a circumferential lip, and a nipple. The body is spherically shaped. The circumferential lip extends radially outward from a base of the body. The nipple extends from the top of the body in a direction perpendicular to the base. The device is advanced until the nipple on the head contacts the acetabular bone, 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 match a prosthetic femoral head fitted to the patient.

[0011] In some embodiments, the cement comprises an 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 variable based on the patient's acetabular defect. The radius of the body is the radius of the sphere on which the spherical crown 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 variable based on the appropriate thickness of the cemented acetabular cast. In some embodiments, the head can be coaxially rotated around the nipple while the cement hardens without destroying the cement.

[0012] The above summary is not intended to represent each embodiment or every aspect of the present disclosure. Rather, the foregoing summary merely provides examples of some of the novel aspects 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 exemplary embodiments and modes for carrying out the invention when taken in conjunction with the accompanying drawings and appended claims. [The present invention 1001] 1. A device for forming a custom cemented cast of an acetabular implant for a patient, comprising: A long, slender handle and a head coupled to the proximal end of the elongated handle, a body formed as a spherical crown, including a circular base and a top; a circumferential lip extending radially outward from the circular base of the body; and a nipple extending from the top of the body in a direction perpendicular to the circular base; the head, The device comprising: [The present invention 1002] 1001. The device of claim 10, wherein the body of the head is shaped as a hemisphere. [The present invention 1003] Any of the devices of inventions 1001 to 1002, wherein the radius of the body is sized to fit the patient's acetabular defect, and the radius of the body is the radius of the sphere on which the spherical cap is based. [The present invention 1004] The device of the present invention 1003, wherein the radius of the body is 27.5 mm. [The present invention 1005] 1005. The device of any one of claims 1001 to 1004, wherein the height of the body is 27.5 mm. [The present invention 1006] 1006. The device of any one of claims 1001 to 1005, wherein the radius of the circular base is 55 mm. [The present invention 1007] The device of any one of claims 1001 to 1006, wherein the apex is at the pole of the spherical cap. [The present invention 1008] The device of any one of claims 1001 to 1007, wherein said circumferential lip extends generally along the same plane as said circular base. [The present invention 1009] The device of any one of claims 1001 to 1008, wherein the circumferential lip extends radially outward from the circular base by 5 mm. [The present invention 1010] 1009. The device of any one of claims 1001 to 1009, wherein the circumferential lip has a thickness of 5 mm. [The present invention 1011] 1010. The device of any one of claims 1001 to 1010, wherein the nipple has a height of 5 mm. [The present invention 1012] The device of any one of claims 1001 to 1011, wherein the nipple is sized to contact both cement and the patient's acetabular bone, thereby forming the custom cement cast. [The present invention 1013] 1012. The device of claim 1012, wherein said head is coaxially rotatable about said nipple while said cement hardens without destroying said cement. [The present invention 1014] 1012-1013. A device according to any one of claims 1012-1013, wherein the thickness of the custom cement cast is the same as the height of the nipple. [The present invention 1015] The device of any one of claims 1012 to 1014, wherein the length of the nipple is sized based on the intended thickness of the custom cement cast. [The present invention 1016] The device of any one of claims 1001 to 1015, wherein the body of the head is shaped to fit with a prosthetic femoral head fitted to the patient. [The present invention 1017] The device of any one of claims 1001 to 1016, wherein the nipple is the center of rotation of the device. [The present invention 1018] 1. A method for treating an infected total hip replacement in a patient, comprising: removing an implant associated with said infected total hip replacement in said patient; placing cement in the patient's acetabulum; A long, slender handle and a head coupled to the proximal end of the elongated handle, the head including a body formed as a spherical crown, a circumferential lip extending radially outward from a base of the body, and a nipple extending from a top of the body in a direction perpendicular to the base; forcing a device comprising: advancing the device toward the patient's acetabulum until the nipple on the head contacts the acetabulum, thereby ensuring an adequate thickness of the cemented acetabular cast; The method comprising: [The present invention 1019] The method of claim 1018, wherein the body of the head is shaped as a hemisphere and includes a circular base. [The present invention 1020] Any of methods 1018 to 1019 of the present invention, wherein the radius of the body is variable based on the patient's acetabular defect, and the radius of the body is the radius of the sphere on which the spherical cap is based. [The present invention 1021] 1021. The method of any one of claims 1018 to 1020, wherein the nipple of the head is the center of rotation of the device. [The present invention 1022] 1022. The method of claim 1021, wherein said head is coaxially rotatable about said nipple while said cement hardens without destroying said cement. [The present invention 1023] The method of any one of claims 1018 to 1022, wherein the length of the nipple is variable based on the appropriate thickness of the cemented acetabular cast. [The present invention 1024] 1024. The method of any one of claims 1018 to 1023, further comprising placing mineral oil between said cement and said device, thereby preventing said device from adhering to said cement. [The present invention 1025] 1025. The method of any one of claims 1018 to 1024, wherein the cement comprises an antibiotic bone cement. [The present invention 1026] 1026. The method of any one of claims 1018 to 1025, further comprising shaping the body of the head to fit with a prosthetic femoral head fitted to the patient.

[0013] These and other advantages of the present disclosure will become apparent upon reading the following detailed description and upon reference to the drawings. [Brief explanation of the drawings]

[0014] [Figure 1] 1 illustrates an anterior view of an exemplary implant in a total hip replacement, according to some embodiments of the present disclosure. [Figure 2] 2 shows an exploded view of the implant of FIG. 1. [Figure 3] 2 illustrates a front view of the implant of FIG. 1 installed in a patient's hip joint, according to some embodiments of the present disclosure. [Figure 4] 1 shows a side view of a device for forming a custom cemented cast of an acetabular implant for a patient, according to some embodiments of the present disclosure. [Figure 5] FIG. 5 shows a first perspective side view of the device of FIG. 4. [Figure 6] FIG. 5 shows a second perspective side view of the device of FIG. 4. [Figure 7] 1 illustrates a patient's pelvic bone before installation of a custom cemented cast of an acetabular implant, according to some embodiments of the present disclosure. [Figure 8] 8 illustrates bone cement placed in the acetabulum of the pelvic bone of FIG. 7 according to some embodiments of the present disclosure. [Figure 9]9 illustrates the device of FIG. 8 pressed into the bone cement to form a custom cement cast, according to some embodiments of the present disclosure. [Figure 10] 8 shows a device impacted into the acetabulum of the pelvic bone of FIG. 7 without bone cement, according to some embodiments of the present disclosure. [Figure 11] 10 illustrates the resulting bone cement after the device of FIG. 9 is removed, according to some embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0015] While the present disclosure is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the disclosure is not intended to be limited to the particular forms disclosed. Rather, the present disclosure is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure as defined by the appended claims.

[0016] Detailed Description The present invention is described with reference to the accompanying drawings, in which like reference numerals are used throughout the drawings to indicate similar or equivalent elements. The figures are not drawn to scale and are provided solely to illustrate the present invention. Several aspects of the present invention are described below with reference to exemplary applications for illustration. It should be understood that numerous specific details, relationships, and methods are set forth to provide a thorough understanding of the present invention. However, one skilled in the art will readily recognize that the present invention can be practiced without one or more of the specific details, or in other ways. In other instances, well-known structures or operations have not been shown in detail to avoid obscuring the invention. The present invention is not limited by the illustrated order of acts or events, as some acts may occur in different orders and / or concurrently with other acts or events. Furthermore, not all illustrated acts or events are required to implement a methodology in accordance with the present invention.

[0017] The standard treatment for chronically infected total hip replacements is to remove all implants and place 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 an impression 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 a custom-made, low-cost, cemented articulating hip spacer during surgery. In some instances, the articulating hip spacer is an antibiotic hip spacer.

[0018] In a total hip replacement (e.g., a total hip arthroplasty), damaged bone and cartilage are removed and replaced with prosthetic components, such as implant 100. Referring generally to FIGS. 1-2 , implant 100 includes a prosthetic cup 110, a liner 120, a prosthetic femoral head 130, and a prosthetic femoral stem 140. In some examples, prosthetic cup 110, prosthetic femoral head 130, and prosthetic femoral stem 140 are formed from metal, ceramic, or the like. In some examples, the material used for the implant can also be any type that is capable of incorporating into bone and likely to stimulate bone growth over the implant.

[0019] Referring now to FIG. 3 , the patient's damaged femoral head is removed and replaced with a prosthetic femoral stem 140 inserted into the hollow center of the femur 35. The prosthetic femoral stem 140 may be cemented, or "press-fit," into the bone of the femur 35. A prosthetic femoral head 130 is placed on top of the prosthetic femoral stem 140. In some instances, 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 contacts the bone of the acetabulum 15 with or without screws, rarely cemented. The liner is inserted between the prosthetic femoral head 130 and the prosthetic cup 110 to provide a smooth sliding surface. In some instances, the liner is made of plastic, ceramic, metal, or the like.

[0020] However, the infection rate for total hip replacements is typically 5%. Infections can be morbid, life-threatening, and costly. Infections can occur due to biofilm growth on metallic implants. A second surgery after infection is riskier and usually more complicated. If an infection occurs and is treated early (usually within six weeks of the initial procedure), treatment includes irrigation and debridement, followed by replacement of the liner 120 and prosthetic femoral head 130. This early treatment works in 50% to 80% of cases. If the infection recurs or is treated beyond six weeks (e.g., in chronic infections), the standard of care for treatment in many countries (e.g., the United States) is removal of all components and placement of an antibiotic cement spacer.

[0021] Current common spacers have one of two options: (1) remove all components and place an antibiotic cement mold of the femoral head and femoral stem, and (2) place 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 must be removed once the infection is gone.

[0022] Furthermore, treatment of chronically infected hip replacements can occur in one or two stages. In a one-stage treatment, the infected hip replacement implant is removed and a new hip replacement implant is installed. The new hip replacement implant often contains antibiotic bone cement. A drawback of a one-stage treatment is a high reinfection rate, meaning that expensive components are installed with the risk of reinfection. In a two-stage treatment, the infected hip replacement implant is removed, an antibiotic spacer is installed, and after a waiting period, a new hip replacement implant is then installed. Two-stage treatment is the standard of care in many countries (including the United States) and requires two separate procedures. This can be difficult in an already unhealthy patient population. Therefore, the effective and low-cost antibiotic cement spacer of the present disclosure would greatly benefit these patients, especially in the first stage.

[0023] Some antibiotic spacer designs use metal-on-polyethylene implants. This is done by placing cement in the acetabulum and then placing a polyethylene component within the cement. A conventional metal femoral head and femoral stem are then implanted in place of the cemented spacer and held in place with antibiotic cement. This approach has at least two drawbacks. First, the new implant significantly increases the cost of the procedure. Second, the metal-on-polyethylene implant provides a new, foreign surface for bacteria to form a biofilm (glycocalyx), allowing the bacteria to evade antibiotics and the immune system. In some cases, surgeons can purchase prefabricated cemented antibiotic acetabular and femoral components that allow for cement-on-cement articulation. The drawback is that the cost of prefabricating such implants can be higher compared to fabricating custom cement-on-cement implants during surgery. These options exist to find ways to protect the acetabulum and / or prevent pain caused by the cement occluding the bone.

[0024] The present disclosure allows surgeons to create low-cost, custom, cement-on-cement articulating antibiotic hip spacers. The present disclosure has several advantages over other solutions. Compared to metal-on-polyethylene articulating hip spacers, the present disclosure allows for articulating hip spacers without metal or polyethylene implants. Such metal or polyethylene implants increase the cost of surgery and leave foreign bodies in the infected wound due to potential biofilm formation. Compared to pre-fabricated antibiotic acetabular and femoral components, the present disclosure allows for a custom, low-cost solution instead of paying for pre-fabricated implants. Furthermore, in some embodiments, the present disclosure also allows surgeons to determine and / or customize the type and / or dosage of antibiotics in the bone cement, which may often be unsuitable with pre-fabricated cement components.

[0025] As discussed herein, typical implant cement spacers can be painful for patients. The present disclosure allows surgeons to mold cement-on-cement spacers for the treatment of infected total hip replacements. The present disclosure forms a cement cast from a mold of an acetabular implant and enables a cement-on-cement articulating spacer, thus eliminating the pain of the cement articulating with the natural acetabulum. The present disclosure includes a device that is inexpensive and helps reduce spacer-related patient pain. In some embodiments, the device is a medical device used to create a custom cement-on-cement articulating antibiotic hip spacer during surgery. In some embodiments, the device is used to treat infected total hip replacements. The device is a tool and is not implanted into the body during surgery. It is sterile and reusable. The device can be formed in various sizes and customized for the patient. The device's hemispherical head is important for achieving the correct shape of the resulting spacer, and its nipple is important for achieving the correct thickness of the resulting spacer.

[0026] 4-6 , disclosed herein is a device 200 for forming a custom cemented cast of an acetabular implant for a patient. The device 200 includes an elongated handle 210 and a head 250 coupled to a 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 an apex 254. The circumferential lip 230 extends radially outward from the circular base 252 of the body 220. The nipple 240 extends from the apex 254 of the body 220 in a direction perpendicular to the circular base 252.

[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 with a prosthetic femoral head fitted to the patient. In some embodiments, the radius of the body 220 is sized to fit (e.g., be variable based on) the patient's acetabular defect. The radius of the body 220 is the radius of the base sphere of the spherical crown. In some embodiments, the apex 254 is at the pole of the spherical crown. In some embodiments, the circumferential lip 230 extends generally 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] 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, in which the body 220 is shaped as a special type of spherical cap (hemisphere), the diameter 222 of the circular base 252 is the same as the diameter 222 of the body 220 (e.g., the diameter of the underlying sphere). However, in other examples, it is contemplated that the body 220 may be shaped as other types of spherical caps, in which the diameter of the underlying sphere is different from the diameter of the circular base.

[0029] Further, circumferential lip 230 includes an average thickness 234 of 5 mm, and circumferential lip 230 extends radially outward 5 mm from circular base 252. Circumferential lip 230 extends a distance 236 from a first side of body 220 and a distance 238 from an opposite side of body 220. In some examples, circumferential lip 230 extends radially outward a constant distance from the entire periphery, and thus distance 236 and distance 238 are the same. In some such examples, total diameter 232 of the disk (including circular base 252 and 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 nipple height 242.

[0031] The specific dimensions of the elements of device 200 described herein are intended as examples only. Other dimensions are contemplated according to medical practice. In some aspects, diameter 222 of body 220 is variable so that molds of different sizes of acetabulum (e.g., acetabulum 15) can be made. According to some embodiments of the present disclosure, a set of heads (e.g., hemispheres) of various sizes each include a circumferential lip of the same size (e.g., 5 mm). Alternatively, a set of heads of various sizes includes proportionally sized circumferential lips. 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 set of heads can have its own handle, or alternatively, they can be removably attached to a single universal handle. In some instances, the diameter of prefabricated or intraoperatively molded cemented femoral heads ranges from 48 mm to 64 mm. Accordingly, the diameter of the hemispheres disclosed herein ranges from 48 mm to 66 mm. The reason for the large dimensional variability is that the size of the acetabular defect depends on the patient's size, previous acetabular component, bone loss, or any combination thereof. Thus, acetabular defects vary from small to large among patients. Therefore, one size of device head may not fit all patients. Additionally or alternatively, the hemisphere selected for the acetabular mold is 1-2 mm larger in diameter than the femoral head to allow 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 acetabular bone, thereby forming a custom cement cast (FIG. 9). In some instances, the head 250 can be coaxially rotated around the nipple 240 while the cement 45 hardens without destroying the cement 45. In some embodiments, the thickness of the custom cement cast is the same as the height of the nipple 240. For example, if the nipple height 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 instances, the length of the nipple 240 is sized based on the intended acetabular offset from the pelvis required by the surgeon to achieve appropriate tension and / or stability of the hip joint.

[0034] The nipple 240 is also dimensionally adjustable, allowing the surgeon to precisely dial in the required cement mantle thickness. Thickness is important for several reasons. First, the proper thickness is required to provide sufficient strength to the cement construct. Second, sufficient cement is required for proper antibiotic elution. Third, the correct thickness helps restore offset to the hip joint's center of rotation. To further illustrate the third point, significant bone loss often occurs when the previous acetabular component is removed. Conventional antibiotic spacers that articulate with raw bone experience a significant reduction in offset due to the absence of the acetabular component. This reduction in offset can lead to a reduction in the biomechanics of the spacer, which in turn can lead to spacer dislocation. However, the offset can be restored by creating a mold of the acetabular component, which allows the surgeon to dial in the required offset with the nipple 240.

[0035] According to some embodiments of the present disclosure, the dimensions of the nipple 240 are further based on the patient's bone loss and / or natural hip joint anatomy. For example, the thickness of a standard metal cup (including a polyethylene liner) is approximately 10 mm at the top. Therefore, the height of the nipple 240 for restoring only the previous hardware is theoretically 10 mm; however, taking into account the offsets 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 other examples, the nipple 240 is removably attached to the body 220 and is therefore replaceable. Regarding the diameter of the nipple, 5 mm is preferred to create a relatively small defect in the acetabular mold.

[0036] According to some embodiments of the present disclosure, nipple 240 is cylindrically shaped to prevent the cement mantle from being destroyed while the device is rotated on the nipple axis as the cement hardens. Additionally, being cylindrically shaped allows for the diameter necessary to create the appropriate mold thickness and restore the offset, while creating minimal defects in the mold. While it is contemplated that nipple 240 can be other shapes (e.g., rectangular), a cylindrical shape is generally preferred when rotating the device as the cement hardens.

[0037] An additional aspect of the present disclosure includes a method for treating an infected total hip replacement in a patient. The method may be illustrated by Figures 7-11 of the present disclosure. For example, Figure 7 shows the patient's pelvic bone 25 prior to installation of a custom cemented cast of an acetabular implant, Figure 8 shows bone cement 45 installed in the acetabulum of the patient's pelvic bone 25, Figure 9 shows the device 200 impacted into the bone cement 45 to form the custom cemented cast, Figure 10 shows the device 200 impacted into the acetabulum of the patient's pelvic bone 25 without the use of bone cement, and Figure 11 shows the resulting bone cement 45 after the device 200 has been removed.

[0038] The method includes removing an implant associated with an infected total hip replacement in a patient. Referring now to FIGS. 8-9 and 11 , cement 45 (e.g., bone cement) is placed in the patient's acetabulum. A device 200 (such as the device 200 of FIGS. 4-6 ) is forced into the cement 45, thereby forming a concave cemented acetabular cast ( FIG. 11 ). The device 200 is advanced toward the patient's acetabular bone. As shown herein with respect to FIGS. 4-6 , the device 200 includes an elongated handle 210 and a head 250 coupled to a 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 crown. The circumferential lip 230 extends radially outward from a base 252 of the body 220. The nipple 240 extends from the top 254 of the 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 offset of the acetabulum from the pelvis. More specifically, with reference to FIG. 11 , after the device 200 is removed, a concave cemented acetabular cast is formed, showing a negative indentation 440 (e.g., in the shape of a recessed point) in the nipple 240 and a negative indentation 430 (e.g., in the shape of a recessed ring) in the circumferential lip 230.

[0040] In some embodiments, the cement comprises an antibiotic bone cement. In some embodiments, the method further comprises placing mineral oil between the cement 45 and the device 200, thereby preventing the device from adhering to the cement 45. In some embodiments, the method further comprises shaping the body 220 of the 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 can be varied based on the patient's acetabular defect. The radius of the body 220 is the radius of the sphere that forms the base of the spherical crown. 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 can be varied based on the appropriate thickness of the cemented acetabular cast. In some embodiments, the head 250 can be coaxially rotated around the nipple 240 while the cement hardens without destroying the cement.

[0042] In contrast to knee replacement surgery, measuring cement thickness in the knee is easier because the tibial plateau is exposed during surgery. However, in the hip, the acetabulum 15 is not visible once the cement is inserted. Therefore, the nipple 240 of the device 200 is important in measuring the cement mantle thickness 234. Thus, while other methods of measuring depth exist in orthopedic surgery or other fields (e.g., using pins, depth gauges, or rulers), the specific and important fact in this disclosure is the presence of the nipple 240 at the very apex 254 of the dome of the device 200. Placing the nipple 240 at the apex 254 of the dome allows the surgeon to coaxially rotate the handle 210 of the device 200 without destroying the cement 45 while it cures. The modularity of the nipple 240 length allows the surgeon to customize the center of rotation for the patient to achieve the appropriate tension, stability, limb length, and / or offset.

[0043] As disclosed herein, in some embodiments, the disclosed methods and devices can be used in surgery after a total hip replacement has been removed from a patient (e.g., due to infection). The standard of care in many countries (including the United States) is to surgically place a temporary antibiotic bone cement spacer. The present disclosure enables a unique cement-on-cement spacer by creating a unique acetabular cup made of bone cement. After a total hip replacement is removed, a large defect exists in the patient's acetabulum. The present disclosure addresses this defect. The specific design of the disclosed devices, as well as their proportions and dimensions, are critical to their ability to address this defect. Several important 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 create an acetabular bone cement hemispherical cup. For this reason, the body 220 of the device 200 is shaped like a spherical cup, typically a hemisphere with a diameter (e.g., diameter 222). The shape of the acetabular defect can change significantly depending on bone loss due to infection and / or surgery. Because the ultimate goal is to create an articulating cement-on-cement spacer, the device 200 is configured to create a hemispherical acetabular cup made from bone cement. If the shape were larger than a hemisphere, a spherical femoral head of a similar diameter would not be able to be shrunk to fit into the cup. In some scenarios, it may be possible to achieve a shape smaller than a hemisphere, but this may result in less coverage and / or risk dislocation than a spherical femoral head of a similar diameter. By having a hemispherical shape, the device body 220 creates a cast of a hemispherical recess cemented acetabular cup.

[0045] Body 220 diameter 222 The size of an acetabular defect can vary significantly depending on bone loss due to infection and / or surgery. Therefore, the size of the acetabular bone cement cup must be adjusted accordingly. The present disclosure allows for customization by the surgeon. First, the diameter of the defect is measured. Next, the disclosed device 200 with the appropriate diameter 222 can be selected. For example, several options may be available in the operating room for the surgeon to choose from. Selecting the appropriate size also allows the surgeon to fill the defect with the largest and most appropriate acetabular cup and a similarly sized femoral head. A larger femoral head reduces the risk of dislocation and therefore increases the stability of the cement-on-cement spacer. Considering the anatomy of the acetabulum, the diameter of the hemisphere can range from 48 mm to 66 mm. The reason for the large dimensional variation is that the size of the acetabular defect depends on the size of the acetabular defect.

[0046] Nipple 240 and height 242 of nipple 240 Nipple 240 is an important aspect of device 200. When fabricating a custom acetabular bone cement cup, the thickness of the cement cup can be measured and / or determined. Nipple 240 is important for at least the following reasons:

[0047] The thickness of the cement at the top 254 of the custom cement cup determines the offset of the acetabulum, as well as the entire cement-on-cement antibiotic spacer. Offset is an important biomechanical aspect of the hip joint that allows for proper loading of the hip 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 have a high risk of dislocation.

[0048] In contrast, the present disclosure allows for offset restoration and further adjustment to the specific offset needed for a particular patient. Increasing the offset increases soft tissue tension, allowing for greater hip stability. Too much offset creates too much tension, resulting in pain and difficulty with movement. Too little offset creates hip instability and risk of dislocation. For at least this reason alone, the nipple 240 of the device 200 can be modified to adjust for the appropriate offset, as discussed further herein.

[0049] The thickness of the cement in the 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 place the appropriately sized femoral head. If it is too thin, there is a risk of the cement mantle cracking. For at least this reason alone, the nipple 240 of the device 200 can be modified to adjust for the appropriate cement mantle, as discussed further herein.

[0050] For these reasons, the present disclosure allows for adjustment of the cement thickness of the cement cup. In some embodiments, adjusting and / or modifying the cement thickness can be accomplished 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 with the appropriate height 242 is selected. There may be several options available in the operating room. The selected device 200 is then pressed into the soft antibiotic bone cement to create a cast of the cemented acetabular cup. Once the nipple 240 is 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 the nipple 240 is 5 mm, the resulting thickness of the custom cemented cast will be approximately 5 mm. In an uninfected total hip replacement, the standard metal cup and liner are approximately 10 mm thick at the top. Therefore, to restore the previous center of rotation offset of the acetabulum 15, the height 242 of the nipple 240 needs to be approximately 10 mm. However, depending on the size of the new acetabulum and femoral head, this height may vary. Therefore, nipples ranging in height from 5 mm to 20 mm are available to determine the exact offset required.

[0052] Circumferential lip 230 and diameter 232 of circumferential lip 230 The present disclosure includes a circumferential lip 230, which is essential when creating a cemented acetabular cup. This circumferential lip 230 is present to ensure that only hemispherical cups are created, and not cups larger than a hemisphere. Without the circumferential lip 230, when the device 200 is pressed into the soft cement, the cement would migrate outward from the device 200, enveloping it and creating a cup larger than a hemisphere. If a cup is created that is larger than a hemisphere, the femoral head will not fit, reducing the likelihood that the correctly sized femoral head will be placed in the cup.

[0053] Instead, the circumferential lip 230 is designed so that as the cement moves out of the acetabular defect, the cement moves radially away from the device 200 at the base 252 of the hemisphere. This ensures that a hemisphere, and only a hemisphere, is created. Any excess cement can also be easily removed without destroying the resulting acetabular cement cup. The diameter 232 of the circumferential lip 230 varies depending on the diameter 222 of the body 220 of the device 200 selected for a particular acetabular defect. At the edge of the base 252 of the body 220, the diameter 232 of the circumferential lip 230 varies to extend circumferentially at least 5 mm (236 and 238) beyond the diameter 222 of the body 220. Therefore, the diameter 232 of the circumferential lip 230 must be at least 10 mm larger than the diameter 222 of the body 220.

[0054] One or more elements or aspects or steps, or any portion(s) thereof, set forth in any one or more of the following claims 1 to 26 may be combined with one or more elements or aspects or steps, or any portion(s) thereof, set forth in any one or more other claims 1 to 26, or combinations thereof, to form one or more further embodiments and / or claims of the present disclosure.

[0055] All patents, patent applications, patent application publications, and other materials, such as articles, books, specifications, publications, documents, works, and / or other materials, referenced herein are incorporated by reference in their entirety for all purposes, except for any prosecution history relating to the same, either inconsistent with or pending against the same hereof, or which may have a limiting effect on the broadest scope of any claims now or hereafter related to the same hereof. For example, in the event of any inconsistency or contradiction between the description, definition, and / or use of a term in connection with any of the incorporated materials and the description, definition, and / or use of a term in connection with this document, the description, definition, and / or use of the term in this document shall control.

[0056] While various embodiments of the present disclosure have been described above, it should be understood that they have been presented by way of example only, and not limitation. Various modifications to the disclosed embodiments may be made in accordance with the disclosure herein without departing from the spirit or scope of the present invention. Thus, the breadth and scope of the present invention should not be limited by any of the above-described embodiments. Rather, the scope of the present invention should be defined in accordance with the following claims and their equivalents.

[0057] While the present invention has been illustrated and described with respect to one or more embodiments, equivalent alterations and modifications will occur to those skilled in the art upon reading and understanding this specification and the accompanying drawings. Furthermore, while a particular feature of the invention may be disclosed with respect to any one of several embodiments, such feature may be combined with one or more other features of the other embodiments, where desirable and where advantageous for any given or particular application.

[0058] The terms used herein are for the purpose of describing particular embodiments only and are not intended to be limiting of the present invention. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. Furthermore, when the terms "including," "includes," "having," "has," "with," or variations thereof are used in either the detailed description and / or the claims, such terms are intended to be inclusive in the same manner as the term "comprising." Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Furthermore, terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning consistent with the meaning in the context of the relevant technical field and should not be interpreted in an idealized or overly formal sense unless expressly defined herein.

Claims

1. 1. A device for forming a custom cemented cast of an acetabular implant for a patient, comprising: A long, slender handle and a head coupled to the proximal end of the elongated handle, a body formed as a spherical crown, including a circular base and a top; a circumferential lip extending radially outward from the circular base of the body; and a nipple extending from the top of the body in a direction perpendicular to the circular base; the head, The device comprising:

2. The device of claim 1 , wherein the body of the head is shaped as a hemisphere.

3. 3. The device of claim 1, wherein the radius of the body is sized to fit the patient's acetabular defect, and the radius of the body is the radius of the sphere on which the spherical cap is based.

4. 4. The device of claim 3, wherein the body has a radius of 27.5 mm.

5. 5. The device of claim 1, wherein the body has a height of 27.5 mm.

6. 6. The device of claim 1, wherein the radius of the circular base is 27.5 mm.

7. The device of claim 1 , wherein the apex is at a pole of the spherical cap.

8. 8. The device of claim 1, wherein the circumferential lip extends generally along the same plane as the circular base.

9. 9. The device of claim 1, wherein the circumferential lip extends radially outward from the circular base by 5 mm.

10. 10. A device according to any one of claims 1 to 9, wherein the circumferential lip has a thickness of 5 mm.

11. 11. The device of claim 1, wherein the nipple has a height of 5 mm.

12. 12. The device of claim 1, wherein the nipple is sized to contact both cement and the patient's acetabular bone, thereby forming the custom cement cast.

13. 13. The device of claim 12, wherein the head is coaxially rotatable about the nipple while the cement sets without destroying the cement.

14. 14. The device of any one of claims 12-13, wherein the thickness of the custom cement cast is the same as the height of the nipple.

15. 15. The device of 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. 16. The device of claim 1, wherein the body of the head is shaped to fit with a prosthetic femoral head fitted to the patient.

17. 17. The device of any one of claims 1 to 16, wherein the nipple is configured to act as a center of rotation for the device while cement sets.

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