Patent Application
20180318096
Disease of the shoulder joint can be a source of pain and disability and represent significant medical and rehabilitative challenges. Degenerative conditions, such as arthritis, can be progressive, fail to respond to conservative measures and ultimately require surgical correction. Shoulder arthroplasty or replacement may be necessary to restore function and relieve pain.
The embodiments presented herein represent examples of a total shoulder replacement glenoid implant system with enhanced fixation features. The novelty of the designs lies in the specific details of the fixation projections (posts and pegs) from the backside of the glenoid implant body.
Anatomic shoulder replacement glenoid implants can have polyethylene bodies with convex backsides and concave articular sides of slightly varying curvatures and sizes. The designs presented herein do not describe a specific curvature or size and can be applied to a variety of curvatures and sizes. Anatomic shoulder replacement glenoid implant face may vary in shape along a spectrum from symmetric ovoid to egg/pear shaped. The designs presented herein are not limited to a specific glenoid implant face shape and may be applied to the spectrum of shapes.
The embodiments of an enhanced ingrowth glenoid system presented herein represent novel designs, that permit use of either an all-polyethylene central post and peripheral peg fixation or a hybrid polyethylene-porous metal central post and peripheral peg fixation. One set of instrumentation may be used for insertion and/or extraction of both the all-polyethylene design or the hybrid polyethylene—porous, metal designs. Extraction entails minimal additional bone sacrifice.
Central post length may be scaled to glenoid implant and patient bone dimensions; downsized in smaller size implants-patients and upsized in larger implants-patients. Central posts may insert into a three tiered, tapered drill hole in the bony glenoid. This tiered shape minimizes volumetric bone extraction in the depths of the V-shaped glenoid. These features (tapering and sizing to patient size) minimize the likelihood of perforation of the backside cortex or catastrophic splitting of the bony glenoid. The central posts form-fit the drill hole and are thus self-centering.
Peripheral pegs may be scaled to glenoid implant and native glenoid dimensions for better patient size match and decreased likelihood of backside cortex perforation. Peripheral peg features can improve cement interdigitation, increase implant pull-out strength and improve stability. Peripheral peg features also can improve bony interdigitation and can increase implant pull-out strength when inserted in a cementless fashion into a hole of slightly smaller diameter.
Unlike some previous systems, the components presented herein can be non-modular and therefore require no time-consuming intra-operative assembly. Therefore, quality control is not needed performed on the operative back table. Preassembly helps avoid operator assembly error and implantation of a device with material junctional defects, which may not be detected at all or not detected until final component assembly. The components in this system may be assembled in the factory, where final quality control may be performed before distribution.
Embodiments of the enhanced fixation glenoid implant system presented herein give the surgeon highly flexible new tools in glenoid replacement. The systems are more patient specific, are bone preserving, and streamline implantation and extraction. Embodiments of the systems can provide better fixation, durability and survivorship. Cemented and cementless options are included.
This invention is being described based on specific embodiments thereof. Other features and aspects of the invention can be appreciated with reference to the figures, in which:
As used herein, the term “a” means one or more.
The term “comprising” means “includes but is not limited to.”
The term “consists,” and “consists of,” means “includes but is limited to.”
The term “glenoid” means the portion of a shoulder blade (scapula) having a socket for articulation with the ball of the humerus.
Terms used in the singular include the plural, and terms used in the plural include the singular.
The following list is of different elements and their names as used herein.
Glenold Implant Replacement with Metal Tip
3-Tier Drill
3-Tier Drill Bit
The humeral side (ball) of a shoulder replacement rarely loosens or fails, but should revision be necessary it can usually be done with relative ease. Revision of the socket side (glenoid) of the shoulder typically represents the greater challenge in shoulder arthroplasty. The glenoid implant may fail prematurely, causing pain. A scarcity of bone stock on the glenoid side of the shoulder joint often makes revision of the glenoid implant difficult. Maximizing fixation and durability of the initial glenoid implant is, therefore, of paramount importance. This invention represents an improvement in designs and components of glenoid implants with improved fixation and longer life.
Therefore, some aspects include a glenoid implant device, comprising:
a main body having a concave articular side and an opposite, convex side;
a central post affixed to said main body on said convex side, said central post having a cylindrical proximal portion having a first diameter, a middle cylindrical portion having a second diameter, and a cylindrical distal portion having a third diameter, said central post including:
one or more peripheral pegs, each of which is affixed to said main body on said convex side.
Additional aspects include a device of aspect 1, said first diameter being greater than said second diameter, and second diameter being greater than said third diameter.
Further aspects include a device of any of aspects 1 or 2, at least one of said peripheral pegs having one or more barbed disks thereon and having a wider diameter proximally than distally on said peripheral peg.
Yet further aspects include a device of any of aspects 1 to 3, at least one of said glenoid implant, said central post, said stacked barbed disks, said peripheral pegs, and said flutes comprising polyethylene.
Additional aspects include a device of any of aspects 1 to 4 where said glenoid implant is sized to fit the glenoid of a subject.
Still further aspects include a glenoid implant device, comprising:
a main body having a concave articular side an opposite, convex side;
a central post affixed to said main body on said convex side, said central post having a cylindrical proximal portion having a first diameter, a middle cylindrical portion having a second diameter, and a cylindrical distal portion having a third diameter, said central post including:
Additional aspects include a device of aspect 6, at least one of said peripheral pegs comprising a metal.
Yet further aspects include a device of any of aspects 6 or 7, at least one of said peripheral pegs comprising a metal tip.
Still further aspects include a device of any of aspects 6 to 8, said metal portion of said central post and at least one of said peripheral pegs being affixed to a proximal portion by way of a metal core.
Additional aspects include a device of any of aspects 6 to 9, said metal core having a screw attachment to said central post or said peripheral peg.
Yet other aspects include a device of any of aspects 6 to 10, said metal core having a proximal helical blade attached to said central post or said peripheral peg.
Further additional aspects include a device of any of aspects 6 to 11, said metal core having a proximal barb attached to said central post or said peripheral peg.
Other aspects include a device of any of aspects 6 to 12, said metal core having a proximal textured surface attached to said central post or said peripheral peg.
Yet other aspects include a drill, comprising:
a handle;
a base having said handle attached thereto;
a 3-tiered cutting tip, having:
said first diameter being greater than said second diameter; and
said second diameter being greater than said third diameter.
Further aspects include a drill of the prior aspect, said 3-tiered cutting tip further comprising a cutting groove.
The glenoid implant designs presented herein can be composed of a polyethylene main body 101 as in
Fixation may be provided by an enhanced ingrowth Central Post 107, 109 as in
Fixation of a Central Post is enhanced by the fluted proximal portion or by use of a tiered Central Post being “self-centering” as described further herein.
Cemented Peripheral Pegs provide a major portion of the initial fixation and stability for glenoid implants with fluted or stacked barb Central Posts. Cemented peg pull-out studies show fixation varies considerably with small, subtle changes in peg surface features. Pull-out strength of pegs with a smooth surface is inferior to that of pegs with a dimpled surface, which is inferior to that of pegs with a slotted surface, which is inferior to that of pegs with a ridged surface. All existing finned/fluted glenoid implants employ peripheral peg surface features that could be improved upon.
In pull-out studies, when ridged pegs fail, the pegs fail at the cement-implant interface. The polyethylene ridge can deform away from the direction of pull-out, permitting peg displacement. Designs presented herein increase resistance to pull-out and resistance to deformation by shifting a polyethylene ridge mass away from the direction of pull out to form a barb. The resultant shape formed is no longer a symmetric V- or U-shaped ridge, but a beveled barb with its horizontal base proximally and angled surface distally. Barbs better resist deformation and pull-out than ridges. A barb may extend all the way around the circumference of the peg to form a barbed disc. Barbed discs in the designs presented herein can be stacked directly one on top of the other, without an intervening peg shaft, to provide a desired number of barbs per length of peg, thereby increasing pull-out strength. A stacked, barbed disc feature can be employed on the peripheral peg polyethylene surfaces in both the all-polyethylene and hybrid designs 106A, B, E, F presented herein as in
A cement-free glenoid implant option can be desirable and provide a number of advantages. Cementless implantation avoids time-consuming cement mixture, application and curing. Cementless implants may avoid loosening problems associated as cement fatigue over time. Extraction and revision of a cementless device can be easier.
Inferior Peripheral Pegs 105, 106F/110B as shown in
Peripheral Pegs comprising of two or more polyethylene, stacked barbed discs can increase cementless pull-out strength and stability. Upon insertion into a bone hole, barbed edges of a peg and the surrounding bone can elastically deform slightly away from each other. Subsequent elastic recoil results in interdigitation of bone and barb. Pull-out is resisted at the interface between the barb base and bone, achieving improved stability. With successful press fitting of the Peripheral Pegs, the entire implant may be used in a cementless fashion.
A peg may have one or more slots running down the length of the polyethylene. In non-cemented implantation, a slot can improve bony interdigitation, providing rotational control.
Barb-Flute-Barb central post 107 has specific design features that improve central post cementless fixation
The proximal portion of a Central Post and distal central post stacked barbed discs can have one or more slots running down the length of the polyethylene. A slot can improve bony interdigitation, providing increased resistance to rotational motion.
The intermediate or middle portion of a Central Post can be composed of two or more horizontal fins or flutes 108 as in
A drill hole for the Central Post may have a plurality of tiers, for example, three steps or tiers; the smallest diameter being for the distal portion of Central Post stacked barbed discs 106D as shown in
In designs presented herein, both proximal and distal portions of a Central Post can comprise relatively rigid, stacked barbed discs to serve as a self-centering feature for the Central Post when inserted into the form fitting multi-tiered, or 3-tiered drill hole. This differs from prior fluted designs where there is no rigid component at the tip of the post. In those prior designs, flexible flutes that may deform non-uniformly are inserted down a drill hole of uniform diameter. There is no rigid component at the tip to form-fit with the distal hole, allowing the center of the distal tip to migrate. In those prior implants, the central post does not self-center. If bone density differs on one side the drill hole from the other, or if the implant is inserted at an angle, or if the large diameter distal drill hole perforates the side cortex, non-centering central post flute/fins designs may deviate to one side upon insertion. The flutes may deform asymmetrically, resulting in uneven horizontal spacing between flutes, leading to uneven osseointegration and compromised long-term stability. In contrast, with a centered Central Post, the implant can achieve better uniformity of spacing between flutes, more even osseointegration and better long-term implant stability and survivorship.
In systems presented herein, there may be a number of glenoid implant body sizes to match the spectrum of patient bony glenoid dimensions. Size of the central post may vary with size of the implant body. Use of a smaller body, with shorter central post, in a small patient may place the flutes in a more optimal position for osseointegration and prevent protrusion of the flutes through the backside cortex. Prevention of backside cortex protrusion may also help prevent catastrophic splitting of the glenoid. Use of a larger body, with longer post, in a large patient can provide greater surface area for interaction with bone and place the flutes and central post deeper for better stability, and durability. Adjusting post length may be achieved by either varying numbers of stacked barbed discs or flutes, altering the size of each stacked barb or changing the length of the junctional region with the main body.
Hybrid Central Post: Polyethylene Base with Metal Tip
Patient-specific variables, surgical training, and/or surgical preferences may make it desirable to implant a porous, metal central post, in preference to an all-polyethylene, fluted design. In certain embodiments, implants can allow for easy manufacture of a porous, metal Central Post. The main body, Peripheral Pegs and Central Post base may be similar to or identical to the all-polyethylene design 101, 102, 103, 104, 105, 106G as shown in
A solid metal core 109B as shown in
The junction of the proximal polyethylene Central Post and the porous metal coating 112B can be flat in nature, as shown in
There may be a number of glenoid implant body sizes to match the spectrum of patient bony glenoid dimensions. Size of the Central Post may vary with size of the implant body. Use of a smaller body, with shorter central post, in a small patient may place the central post tip in a more optimal position for osseointegration and prevent protrusion of the tip through the backside cortex. Prevention of backside cortex protrusion may also help prevent catastrophic splitting of the glenoid. Use of a larger body having a longer Central Post in a large patient can provide increased surface area for osseointegration and can place the Central Post tip deeper in the bone, thereby providing increased stability and durability. Central Post length may be adjusted for scale by varying either the dimensions of the polyethylene stacked barbed disc proximal base 106G as shown in
The metal tip's solid central core 109B as shown in
A 3-tier drill as shown in
The all-polyethylene and hybrid Central Posts may share common instrumentation and drills, allowing for seamless use of either all-polyethylene fluted or hybrid Central Post options.
Patient-specific variables, training and/or surgical preference may dictate implantation of an enhanced ingrowth glenoid implant where a Central Post and Peripheral Pegs can have metal tips. Designs presented herein can allow for easy manufacture of an all metal-tipped design option.
Metal tips 110A, 110B as shown in
A layer of porous metal, such as porous titanium may be applied over the solid central core. Porous metal may have a flat interface with the polyethylene base 112A as shown in
Solid core 109A as shown in
Because of the porous nature of such a metal surface, Peripheral Pegs may be cemented into drill holes of a larger diameter with excellent fixation provided by the cement interdigitating in the metal pores. Porous metal-tipped Peripheral Pegs can also be used without cement and inserted scratch-fit into drill holes of a slightly smaller diameter. Peg pull-out is resisted at the porous metal-bone interface (as well as at the stacked barbed peg proximally), increasing stability. With a successful press-fit Peripheral Peg option, the entire implant can be cementless.
Polyethylene (
The drill 113A, 113B may be cannulated as shown in
A combined drill guide can expedite bony preparation of the glenoid, thereby allowing preparation of central and peripheral drill holes with one guide-bit. In certain embodiments, there can be a separate scaled tiered drill for each size implant post.
During a total shoulder replacement procedure, the shoulder joint is exposed surgically and prepared. The humeral side preparation and replacement are performed according to routine methods and will not be further addressed here. The glenoid is exposed and prepared in the usual manner. A guide wire is inserted in a perpendicular fashion into the center of the bony glenoid socket and into the deep portion of the glenoid. The glenoid is sized to select the appropriate size for the glenoid implant. A cannulated reamer is used to ream the glenoid to the desired diameter and congruency.
A cannulated 3-tier drill as shown in
Either the all-polyethylene barb-flute-barb design as shown in
Peripheral Pegs help provide initial fixation stability for the implant. Peripheral Pegs may be press-fit or cemented. In a cemented option, cement interdigitating between bone and the stacked barbed disc 106A, 106B, 106E, 106F as shown in
A Central Post also provides initial bony fixation. In the fluted design, the proximal and distal stacked barbed regions 106C,106D as shown in
A Central Post can provide long-term fixation as bone grows into spaces on the Central Post, either between, above or below the flutes or into the porous spaces on the metal tip surface (osseointegration).
If total hybrid designs depicted in
A single piece, all polyethylene fluted implant can be made by compression molding, ram-extruding, and/or otherwise engineering the main body, Peripheral Pegs and Central Post, as shown in
A metal tip can be constructed starting with a solid metal cylinder core 109A, 109B as shown in
A 3-tiered drill as shown in
Because of the finite lifespans of glenoid implants and the difficulty in removing or revising a glenoid implant, initial and long term fixation strength and stability, and therefore ultimate survivorship are important. Specific features of backside projections (posts and pegs) that determine initial and long term fixation, stability and survivorship of glenoid implants. Backside projections also determine an implant's ease of instrumentation, implantation or extraction and an implant's ability to match to a specific patient's size. Optimization of backside projection features enhance implant performance and desirability for a surgeon.
Prior, all-polyethylene glenoid implants relied entirely on cementation of backside projections for fixation and survivorship. Cement, however, eventually develops fatigue cracks. Cemented implants may loosen and require revision or removal. In order to minimize problems with cement fatigue and fixation failure, current generation glenoid designs employ a non-cemented central post. Central posts as described in embodiments were designed to allow bony ingrowth and osseointegration directly into spaces in the post. Both metal and polyethylene features can be incorporated into Central Posts for such purposes. Metal surfaces having porous cavities and polyethylene may have a series of flutes extending horizontally with intervening spaces. Bone can form between these voids, locking the post into the native bone. Depending on patient specific conditions (such as age, bone quality, bone quantity, osteoporosis) and surgeon preference, either metal or polyethylene features can be more desirable for a given patient and surgeon. Systems presented herein offer both porous metal and polyethylene fluteed options for enhanced, cementless Central Post fixation.
Failure of full osseointegration of prior fluted central post designs has been observed in a concerning number of study patients. Excessive micromotion can prevent bony healing and osseointegration in a variety of biologic situations involving bone-forming cells (osteoblasts) and can be a cause of failed osseointegration as has been seen in fluted designs.
Micromotion can be more problematic in patients with asymmetric glenoid wear, where the implant may have to be seated at a nonanatomic angle of version. Larger shear forces across the implant cause this increased micromotion. Excessive micromotion and failure of bony osseointegration may compromise long-term survival of an implant. Insufficient initial central post and implant fixation can permit excessive implant micromotion and can be a cause of incomplete osseointegration. As a result, the use of previous fluted central post glenoid designs in patients with certain asymmetric wear patterns may be limited. Improved central post fixation and stability can be desirable to improve implant osseointegration and survival of the implant, to raise confidence in the use of fluted designs, and to expand the surgical indications of fluted designs.
In prior fluted designs, flexible flutes serve two purposes. The first purpose is to act as the main stabilizer of the central post. The second purpose is to act as the feature that allows osseointegration of the central post. The prior, non-rigid, flexible flutes, however, are suboptimal for the purpose of stabilizing the post. More rigid features, including stacked barbed discs, and a multi-tiered Central Post as described herein can better stabilize the post. Moreover, in prior designs, a large percentage of total post length above and/or below the fluted region serves as a mere spacer, functioning neither in stabilization nor osseointegration.
In designs presented herein, every portion of the central post can be put to work either for stabilization or osseointegration purposes. Middle, fluted regions can enhance osseointegeration. Proximal and distal regions can function as stabilizers and centralizers.
Prior fluted central post designs may fail due to asymmetrical insertion into a bony drill hole. Prior flutes have larger diameters than the drill holes and thus require deformation in order for the implant to be inserted. This process goes well if the surrounding bone is of uniform density, adequate depth and the device is inserted in a perfectly straight trajectory. However, if bone is osteoporotic on one side of the hole, or extra dense on another side of the hole, the post may deviate to the weak side. A V-shaped glenoid is narrower at the deep base than superficially. Many glenoids have substantial superficial wear and may have less depth than the implant central post length. If a pilot drill perforates the outer cortex on one side of the drill hole, the flutes and post may deviate to the side of the perforation upon insertion. This deviation results in an off-centering of the post and creates a deforming rotational force. The deforming force may either prevent full symmetric seating of the implant body or act as a destabilizing force on a fully seated implant. The likelihood of such a deviation is increased the larger the distal hole diameter becomes, and the more distal the flutes are positioned on a post.
In designs exemplified and presented herein, flutes can be positioned proximally up the post to the middle section. The distal post and hole into which it inserts are of lesser diameter than the flutes. Both of these features decrease the likelihood of backside cortex perforation. A rigid, smaller diameter, region at the post tip, press-fit into the bottom of a tiered drill hole, also acts to center the post and implant. The flexible central flutes follow in line, avoiding potential asymmetric seating. Additionally, one or more slits in one or more flutes can permit the flute(s) to flex without buckling. Such flexing allows the central post to remain in a desired position within the drill hole, and to avoid asymmetric seating.
Peripheral Pegs of designs presented herein can be put to work to stabilize the implant. Stacked barbed discs can extend the entire length of a peripheral peg, and can provide improved fixation. Improved peripheral fixation can decrease central post micromotion and thereby enhance osseointegration.
Metal central posts or pegs offer an additional challenge if extraction is required, such as in cases of infection, revision, or conversion to reverse arthroplasty. Extraction of current metal designs can be difficult and can require removal of an undesirably large volume of bone. A trephine may be necessary to cut out a long cylinder, sacrificing additional bone and leaving a large diameter hole defect in the depths of the glenoid. In designs exemplified and presented herein, a cannulated, 3-tiered drill can be used to morsalize a porous metal coating of the Central Post using the solid core as a drill guide, thus minimizing bone loss. A cannulated drill can be similarly used to morsalize a Peripheral Peg porous coating using the solid central core as a drill guide.
Some prior, modular glenoid designs use uniformly sized central posts and uniformly sized peripheral pegs on implants of different sizes in patients with different sized glenoids.
Oversizing posts and pegs in a small patient may lead to unwanted backside cortex perforation, which may compromise cement pressurization and/or risk of splitting the bony glenoid. Undersizing posts and pegs in a large patient may fail to fully utilize available bone and lead to non-optimal fixation, stability, osseointegration and durability. Enhanced glenoid implant systems exemplified and presented herein can be used to select appropriate sized posts and pegs to implant with patient size to avoid these problems.
Modularity can be used to allow a surgeon to adjust for a condition seen at surgery, such as a better size-matching to patient anatomy. No prior designs use modularity in this fashion. Modularity, as it is currently used, permits attachment of either a one-sized fluted or one-sized metal central post to a common glenoid body, and can be undesirable for one or more of several reasons. Modularity requires time-consuming un-packaging and intraoperative assembly of an implant. A surgeon may have to stop progress with the case to perform the assembly or rely on a technician, who may not be familiar with device assembly. Operator error is a possibility. Improper assembly or accidental dropping of or other damage to a small attachment with loss of sterility may occur. Quality control of the junctional attachment is typically performed on the operative back table, where manufacturing defects may either go unnoticed or be detected too late to rectify. Implantation of a device with a junctional defect may cause premature device failure, recall, disability and result in possible litigation. Most prior enhanced ingrowth designs are non-modular and avoid modularity downsides. Prior designs, however, offer only one or the other enhanced ingrowth post options (flutes or metal). The one design that offers both flutes or metal options is modular, but has only one size post and carries the drawbacks previously mentioned. In the systems exemplified and presented herein, both porous metal and fluted designs may be options and can be non-modular. The components are assembled in the factory, where final quality control may be performed before distribution.
A cement-free glenoid implant option can be desirable and can eliminate time-consuming cement mixture, application and curing. A cementless device can avoid loosening problems associated with cement fatigue and facilitate extraction and revision. All previous attempts to acquire FDA approval for entirely cement-free, enhanced ingrowth implants have failed due to concerns with initial implant pull out strength and stability. All prior enhanced fixation glenoid implants require use of some cement around peripheral pegs or ridges. A reliable, highly stable, cement-free, enhanced ingrowth glenoid implant can be desired and is wanted in the marketplace, thus meeting a long-felt, unmet need in the field. More stable Central Post and Peripheral Pegs of systems presented herein can provide multiple points of fixation. Such features permit the cementless use of these glenoid implants.
Examples of enhanced glenoid implants and methods for their use are presented herein. Self-centering systems as described can increase implant stability and fixation, reduce micromotion, enhance osseointegration, improve functional result, extend long-term survival of the implant, and expand useful indications. In embodiments, non-modular, porous metal, and fluted options can utilize the same guides and central drills, and are designed to expedite implantation and extraction with minimal bone sacrifice. Size-matched, peg and post lengths and cemented or cementless options can provide a full spectrum of implant choices to optimally address individual patient needs and individual surgeon preference.
It can be readily appreciated that the descriptions and drawings herein are for purposes of illustration only and are not intended to limit the scope of these inventions. Rather, using the descriptions and teachings herein, other embodiments can be created by persons of skill in the art, and all such embodiments are considered part of this invention.
This Continuation Application is filed under 35 U.S.C. 111a claiming priority to International Application No. PCT/US2014/063681, filed 3 Nov. 2014, which claims priority to U.S. Provisional Patent Application No. 61/899,711 filed Nov. 4, 2013, entitled “Shoulder Replacement: Enhanced Glenoid Fixation,” Craig Boulris, Inventor. These applications are incorporated herein fully by reference as if separately so incorporated.
| Number | Date | Country | |
|---|---|---|---|
| 61899711 | Nov 2013 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 15143997 | May 2016 | US |
| Child | 16030434 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/US2014/063681 | Nov 2014 | US |
| Child | 15143997 | US |
