This invention relates to surgical inserters for aiding in installing orthopedic prostheses, and more specifically, to an improved grasping mechanism for installing acetabular implants in the acetabular socket.
A double mobility prosthetic cup is a type of acetabular implant that is designed to increase a patient's range of hip mobility. Unlike other types of acetabular implants, double mobility prosthetic cups do not have an opening through the cup portion which allows for easy manipulation during implantation. For example, a rod is typically threaded through the cup opening to the apex of the cup dome where there is typically a threaded hole. This rod is used like a handle with which to control and guide the implant during implantation. Double mobility implants, on the other hand, do not have such an opening and therefore create a challenge in controlling them during implantation. The present invention solves this problem and provides an effective novel means of manipulating the double mobility implant during implantation.
Complicated mechanical devices have crevices and recesses that are difficult, if not almost impossible to clean with ease. Devices that are not properly cleaned and sterilized run the risk of disease transfer from patient to patient following the emergence of certain “prions” that are not killed by normal hospital sterilization and need to be physically removed by washing and rinsing.
During implantation of the prosthetic cup, a great amount of mechanical force is delivered to the cup implant. Generally, an impacting force is delivered to the proximal end of the inserter which is then imparted to the prosthetic cup at the distal end. The application of such mechanical impacting forces could damage the implant cup, particularly a double mobility prosthetic cup implant since these types of cup implants generally lack the mechanical strength to withstand the application of these forces throughout the prosthetic cup.
Furthermore, these double mobility prosthetic cups are precisely machined with smooth surfaces and as such, these implants could become structurally deformed, cracked or scratched during implantation. Such damage to the cup could result in a decrease of mobility for the patient or the need to repeat the prosthetic cup implantation process. The damage could also increase the risk of higher wear rates from the bearing components leading to possible earlier device failure.
Further, in surgical procedures in which access to the treatment site is limited, it is difficult to use current solutions without subjecting the patient to repeated abrasion and tissue trauma when inserting, operating and extracting surgical instruments.
Still further, once the appropriate position of the implant is selected, it is often difficult to ensure that the position does not change upon insertion of the assembly through the incision.
What is needed therefore is a double mobility implant inserter that minimizes the potential of damaging the cup implant during implantation. Further, the present invention provides an inserter that is easily adjustable, operatable, disassemblable, and cleanable. Still further, what is needed is an inserter that enables the surgeon to better maneuver, position and install the double mobility implant in a particular angular orientation.
The present invention relates to an acetabular inserter that aids a surgeon in controlling the installation of a double mobility acetabular cup prosthesis. The inserter has a housing which encloses a drive train having, at a far end, a double mobility prosthetic engaging subassembly, and at the opposite end, a handle which facilitates activation of the drive train and movement of the subassembly. The inserter enables easy orientation of a double mobility prosthesis attached to its end. This is important because precise control of the prosthetic is critical in implantation of the prosthetic in a patient.
The subassembly comprises a series of components, a domed nose, an impaction plate and a grasping plate having a plurality of legs with grasping hook ends extending from its central region. The grasping hook ends work in concert to grip the outside perimeter of the prosthetic cup.
An objective of the invention is to provide a novel design by which the double mobility cup prosthesis is manipulated and inserted into the body with minimum stresses imparted to the cup. The present invention provides an inserter by which potential damage caused by the implantation procedure is minimized to the implant, thereby reducing the possibility that the cup is damaged during the implantation process.
A further objective is to provide an inserter that can be “easily cleaned” by quick and modular disassembly which enables access to all surfaces that can be cleaned. The reduction in the number of small radius internal corners, crevices and small gaps and the absence of blind holes also aids in the sterilization of the instrument.
Referring now to
The prosthesis engaging subassembly 18, as illustrated in
The nose 22 is positioned at the distal end of the prosthesis engaging subassembly 18. The nose 22 is designed with a curved, domed outer surface 40 that is designed to be positioned within an inside cavity 43 of the double mobility acetabular cup prosthesis 12. As shown in
As the name implies, the grasping plate 24 is designed to grasp and hold the double mobility prosthesis implant 12. The grasping plate 24 comprises a plurality of legs 46 that extend from a central region 48 of the plate 24. A hook 50 is formed at the distal end of each of the respective legs 46 along the periphery of the plate 24. As will be described in more detail, the hooks 50 are designed with a lip 52 that engages a groove 54 (
Furthermore, each of the legs 46 is preferably angled such that they extend in a proximal direction towards the handle 20 and away from the central region 48 of the plate 24. As illustrated in
In a preferred embodiment, the second portion 62 is substantially perpendicular to the longitudinal axis A-A. When the grasping plate 24 is assembled in the prosthesis engaging subassembly 18, it is preferred that the second portion 62 of the leg 46 resides within an inlet opening 64 of the impaction plate 28. It is further preferred that a backside surface 66 of the second leg portion 62 is about flush with a proximal surface 68 of the impaction plate 28.
The length 70 of the legs 46 may range from about 5 cm to about 20 cm depending on the design and diameter of the impaction plate 28. It is also preferred that the width 72 of the hook end 50 may range from about 1 cm to about 5 cm. It is important that each leg 46 of the grasping plate 24 is designed such that its length 70 does not extend past the outer perimeter of the impaction plate 28. This design feature minimizes potential contact of the leg 46, particularly the hook end 50, with body tissue as the legs 46 are drawn in a proximal direction, through their respective inlet openings 64. Such contact between the hook end 50 and body tissue could result in the tearing of tissue and potential damage to the inserter itself as the prosthetic cup 12 is impacted into position within the body.
It is further preferred that a grasping plate diameter 74 range from about 5 cm to about 20 cm. The diameter 74 of the grasping plate 24 is defined as the distance between opposing hook surfaces 76. The diameter 74 of the grasping plate 24 is illustrated in
In a further embodiment, the grasping plate 24 comprises a standoff 78 that extends from a distal surface 80 of the grasping plate 24. The standoff 78 is further positioned such that it resides about the central region 48 of the grasping plate 24. The standoff 78 has a curved shaped with a diameter that ranges from about 2 cm to about 10 cm and a height that ranges from about 1 cm to about 5 cm. The standoff 78 further comprises a standoff wall 81 that surrounds a standoff through-bore 32. The standoff 78 is designed to be positioned within a receiving end of the underside of the nose 22 and serves to secure the nose 22 to the grasping plate 24. As illustrated, the standoff 78 may comprise an opening 82 through the wall 81 of the standoff 78 such that when the standoff 78 is engaged within the receiving end of the nose 22, a fastener (not shown), such as a pin or screw, may be positioned through a corresponding opening 84 of the nose, thus securing the grasping plate 24 therebetween.
The impaction plate 28 is positioned proximal of the nose 22 and grasping plate 24. The impaction plate 28 serves as a back stop for the prosthesis engaging subassembly 18. As such, the impaction plate 28 remains in a fixed position at the distal end of the inserter 10 and at the proximal end of the prosthesis engaging subassembly 18. The impaction plate 28 is designed with a curved shape and more preferably, of a circular shape. In a preferred embodiment, the impaction plate 28 has a diameter that approximates the diameter of the prosthetic cup implant 12. As such, a diameter 83 of the impaction plate 28 may range from about 5 cm to about 20 cm depending of the diameter of the cup implant 12. The plurality of inlet openings 64 each extend through the outer perimeter of the plate 28 to a region about the axial through-bore 30. The inlet openings 64 are designed such that the backside surface 66 of the second leg portion 62 is about flush with the proximal surface 68 of the impaction plate 28. The inlet openings 64 are further designed such that a portion of the legs 46 and hook ends 50 of the grasping plate 24 pass therethrough without obstruction.
When activated by the drive train 16 of the inserter 10, the grasping plate 24 moves in a proximal direction within the prosthesis engaging subassembly 18. As the grasping plate 24 moves proximally, the combination of the grasping plate 24 and nose 22, compresses the spring 26 against a distal surface 85 of the impaction plate 28. As the grasping plate 28 continues to move in a proximal direction, the legs 46 of the grasping plate 24 pass through their respective inlet opening 64 of the impaction plate 28, thus providing room for the grasping plate 24 to move. As the grasping plate 24 moves in a proximal direction, the hook ends 50 of the legs 46 move along with the legs 46 in a proximal direction securing the mobility acetabular cup prosthesis 12 to the distal end of the inserter 10.
In a preferred embodiment, the prosthesis engaging subassembly 18 is connected to the distal end of the housing 14. A cylindrical rod 86, which is connected to a cylindrical piston 88, slides through the axial bore 30 that penetrates through the impaction plate 28 and into the grasping plate 24, respectively. The cylindrical rod 86 is preferably threaded. The cylindrical rod 86 is threaded into a corresponding threaded groove of the axial through-bore 32 of the grasping plate 24 securing it in place as shown in
With respect to the drive train 16, the piston 88 is connected by way of a first U-joint 90 to a lever 92 which slides in a pivoting sleeve 94 fixed to the housing 14 via a pivot 96. The lever 92 is connected via a second U-joint 97 to a second pivoting lever 98 which is fixed to pivot in a catch 101 (
A slideable sleeve 102 slides over the lever 98 and has a trunnion 104 to which a rod 106 is pivotally attached. The rod 106 passes through a one-way catch 108 in the housing 14. The one-way catch 108 can be a captured split wedge sleeve 110 having an inner diameter that just matches the outer diameter of the rod 106. The split wedge sleeve 110 is captured in a recess having a matching conical surface that surrounds the sleeve so as to allow the rod 106 to slide into the housing 14, but to prevent the rod 106 from sliding out of the housing 14 unless an unlock lever 112 (
As previously mentioned, the legs 46 of the grasping plate 24 preferably comprise a hook end 50. These hook ends 50 are designed to slide over and engage the groove 54 of the cup implant 12. As shown in the embodiment of
As shown in
In a preferred embodiment, a base 120 of the domed nose 22 has a diameter that is smaller than the diameter 83 of the impaction plate 28. This mismatch in diameters between the base 120 of the nose 22 and the diameter 83 of the impaction plate 28 creates an impaction strike surface 122 (
The nose 22 is sized to be positioned within a multitude of different double mobility implants 12 having different diameters and depths. As such, the diameter of the base 120 of the dome nose 22 may range from about 2 cm to about 20 cm. The depth of the nose 22 may range from about 2 cm to about 10 cm.
When activated, the cylindrical rod 86 slides proximally towards the distal end of the housing 14. The rod 86 pulls the attached grasping plate 24 and nose 22 combination proximally towards the impaction plate 28 of the subassembly 18. The spring 26, positioned between a first recessed portion 128 of the distal surface 85 of the impaction plate 28 and a second recessed portion 130 of a proximal surface 132 of the grasping plate 24, provides a resistive mechanical force between the two plates 24, 28. In addition, the spring 26 provides a space 134 between the grasping plate 24 and the impaction plate 28 (
It is this space 134 between the impaction plate 28 and the grasping plate 24, provided by the spring 26, that further minimizes the transfer of mechanical impaction forces to the structure of the cup implant 12. In other words, the gap 134 between the impaction plate 28 and the grasping plate 24 holding the cup implant 12 in place minimizes transfer of the impaction forces from the impaction plate 28 through the prosthesis engaging subassembly 18 to the nose 22. Instead, the impaction force is preferably concentrated at the rim surface 126 of the cup implant 12. Therefore, the magnitude of the impaction force being delivered throughout the remaining structure of the implant cup 12 is minimized and the potential of resulting implant cup 12 damage is decreased.
Referring now to
The operator may rotate the handle 20 about its axis to turn the drive train 16 in order to orient the prosthesis in what he believes to be a correct or an initial position. Then, the proximal end 98B of the lever 98 is urged downwardly toward the housing 14. Such downward movement acts through the drive train 16 to draw the piston 88 into the housing 14, and thus to cause the grasping plate 24 and attached nose 22 to move proximally against the spring 26 towards the impaction plate 28. The lip 52 of the hook ends 50 of the grasping plate 24 are thus drawn proximally within the groove track 118 of the cup prosthesis 12 pulling the rim 126 of the prosthetic 12 against the strike surface 122 of the impaction plate 28.
The operator may use the one way locking mechanism 106 to lock the lever 98 in a position so as to lock the rim 126 of the cup implant 12 against the impaction plate 28, thus enabling the surgeon to pre-set and lock the position of the prosthesis 12 prior to the installation thereof.
Once correctly positioned within the body, impaction forces are delivered to the proximal end of the inserter 10. These impaction forces are intended to drive the prosthetic cup implant 12 to the desired location within the body. Once the cup implant 12 is securely in place, the tension between the lip 52 of the hook end 50 and the groove track 118 is released. The release button 112 (
The inserter 10 is designed to be disassembled for cleaning by simply sliding the slide back so as to release the pivot 101 and then lifting the drive train 16 out of the housing, but allow it to remain pivotally connected at pivot 96. As the drive train 16 is pivoted, the piston 88 is drawn out of the housing cavity 89. To reassemble after cleaning, the piston 88 is reinserted into the housing cavity 89 and the drive train 16 is rotated back into position, with the one way locking mechanism entering its receiver and the pivot 96 again entering into the catch 101. The slide is then slid over the pivot 96 and the inserter 10 is again ready for use.
The present invention can be packaged in a kit offering a variety of double mobility prosthetic implants 12 of different sizes and diameters. The inserter 10 and assorted double mobility implants 12 and subassemblies 18 can be packaged in a case with recesses which conveniently holds the components in a convenient, easy to access manner.
The attached drawings represent, by way of example, different embodiments of the subject of the invention. Multiple variations and modifications are possible in the embodiments of the invention described here. Although certain illustrative embodiments of the invention have been shown and described here, a wide range of modifications, changes, and substitutions is contemplated in the foregoing disclosure. In some instances, some features of the present invention may be employed without a corresponding use of the other features. Accordingly, it is appropriate that the foregoing description be construed broadly and understood as being given by way of illustration and example only, the spirit and scope of the invention being limited only by the appended claims.
This application claims priority to U.S. provisional application Ser. No. 61/377,701, filed on Aug. 27, 2010.
Number | Date | Country | |
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61377701 | Aug 2010 | US |