WO2012051552A2

WO2012051552A2 - Modular humeral prosthesis with spherocentric feature

Info

Publication number: WO2012051552A2
Application number: PCT/US2011/056393
Authority: WO
Inventors: Gerhard Maale; Joshua Redstone
Original assignee: Gerhard Maale; Joshua Redstone
Priority date: 2010-10-15
Filing date: 2011-10-14
Publication date: 2012-04-19
Also published as: WO2012051552A3

Abstract

The improved humeral prosthesis includes a modular segmented humeral shaft design and an elbow assembly with a spherocentric ulnar stem. The humeral shaft segments can be adjusted to achieve varying shaft lengths allowing the surgeon to readily tailor the prosthesis to the patient. A modular metaphyseal segment allows attachment of a humeral head or a spherical cup insert for a reverse shoulder arrangement. The ulnar stem is rotatable within the elbow assembly to approximate the pronosupination movement of a patient's wrist.

Description

TITLE OF INVENTION

Modular Humeral Prosthesis With Spherocentric Feature

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of provisional Application No. 61/393,792, entitled "Modular Humeral Prosthesis With Spherocentric Feature," filed October 15, 2010.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR

DEVELOPMENT

[0002] Not Applicable

THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT

[0003] Not Applicable

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT

DISC

[0004] Not Applicable

BACKGROUND OF THE INVENTION

1 . Field of the Invention

[0005] The present invention relates to a prosthetic device for repairing the humerus in a human body.

2. Description of Related Art including information disclosed under 37 CFR 1 .97 and 1 .98

[0006] In human patients, disease or severe trauma can sometimes necessitate repair or replacement of a portion or even all of the patient's humerus, including the elbow joint and possibly even a portion of the radius or ulna. For example, a tumor that affects the proximal portion of the humor can require resection of the diseased portion and fixation of a humeral prosthesis that attempts to duplicate the functionality of the original humor. Such prosthesis typically includes the humeral head and humeral body, with a shaft feature that is cemented into a bore hole formed within the remaining humerus body medullary canal. The prosthesis humeral head engages with the glenoid cavity to complete the process.

[0007] One problem with current humeral prostheses is that the length of each patient's humerus varies. Because each case different, a hospital cannot realistically maintain an inventory of humeral prosthesis. For a diseased humerus it is often impossible to determine with reasonable certainty the amount of the humerus shaft that must be resected to accomplish the repair. To accommodate this, estimates must be made and a custom humeral prosthesis must be ordered in advance for each case. This results in increased manufacturing costs due given that economies of scale cannot be leveraged. Further, the time to

manufacture can result in delays that can be detrimental to the patient's health, with the disease process possibly claiming even more of the humerus shaft before the repairs can be made. As a consequence, the amount of the resection might be greater than originally estimated resulting in fixation of a prosthesis that is less than the ideal length.

10008] Another problem with current humeral prosthesis is that full humeral replacements requiring fixation in the ulna provide for insufficient rotation. With typical such humeral prosthesis the ulnar stem is fixed or provides for limited rotation of the patient's wrist and hand. This limited range of motion can result in physical and psychological discomfort as the patient recovers and attempts to return to daily activities.

BRIEF SUMMARY OF THE INVENTION

[0009] The improved humeral prosthetic device comprises: a metaphyseal segment having a first end arranged to accept a humeral head device or reverse shoulder device, and a second end arranged to accept a proximal humeral segment; and at least one proximal humeral segment, the proximal humeral segment having a predetermined fixed length, the proximal humeral segment including a first end for engaging the metaphyseal segment and a second end arranged to accept a distal humeral segment including a hinge axis, or a distal humeral segment including a humeral stem. In the embodiment including a distal humeral segment with a hinge axis, an elbow device that approximates the pronosupination movement of a patient's wrist is provided. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

[0010] The present invention will be more fully understood by reference to the following detailed description of the preferred embodiments of the present invention when read in conjunction with the accompanying drawings, wherein:

FIG. 1 is a lateral view of an assembled first embodiment as disclosed herein;

FIG. 2 is an exploded view of the embodiment;

FIG. 3 is an exploded view of a second embodiment;

FIG. 4A is an exploded view of the spherocentric elbow device of the present embodiment;

FIG. 4B is an enlarged isometric view of the lobe ring of the spherocentric ulnar stem portion of the embodiment;

FIG. 5 is a radiographic depiction of the first embodiment of the invention fixated within the right arm of a patient; and

FIG. 6 is a view of an assembled third embodiment as a partial humeral

prosthesis.

[0011] The above figures are provided for the purpose of illustration and description only, and are not intended to define the limits of the disclosed invention. Use of the same reference number in muttiple figures is intended to designate the same or similar parts. Furthermore, when the terms "top," "bottom," "first," "second," "upper," "lower," "height," "width," "length," "end," "side," "horizontal," "vertical," and similar terms are used herein, it should be understood that these terms have reference only to the structure shown in the drawing and are utilized only to facilitate describing the particular embodiment. The extension of the figures with respect to number, position, relationship, and dimensions of the parts to form the preferred embodiment wilt be explained or will be within the skill of the art after the following teachings of the present invention have been read and understood. (58,266). DETAILED DESCRIPTION OF THE INVENTION

[0012] FIG. 1 depicts a lateral view of an assembled first embodiment of the modular humeral prosthesis. This configuration is intended for replacement of the entire humerus within a patient. Visible in the drawing is the humeral head (102), metaphyseal segment ( 104), proximal humeral segment (106), distal humeral segment (108) with an elbow assembly (1 14) and ulnar stem (1 12). The elbow assembly (1 14) is attached to the distal humeral segment (108) through use of a hinge axis (1 10). The hinge axis (1 10) allows the elbow assembly (1 14) to pivot in relation to the modular humeral segment (105) to approximate the functionality of the patient's original elbow joint.

[0013] FIG. 2 presents an exploded view of the embodiment, providing greater detail of the interconnectedness of the various modular components. As depicted, the humeral head (102) attaches to the metaphy seal segment ( 104) through use of an adaptor (204) and locking screws (202). The humeral head (102) approximates the function of the patient's original humerus head in its engagement with the patient's glenoid cavity. In situations in which the rotator cuff is non-functional, the device may be converted for use in a "reverse shoulder" configuration as depicted in FIG. 3. In this figure, a spherical insert (302) may be installed in the metaphyseal segment (104) to allow for engagement with a metal ball fixated in the area of the patient's glenoid cavity. Because the metaphyseal segment (104) is the same for both configurations, a hospital can readily stock the individual components for use in either situation.

1 014] With respect to FIG. 2, the metaphyseal segment (1 04) is attached to the proximal humeral segment (106), which is attached to the distal humeral segment (108). Each segment interlocks with the next by use of a machine taper ( 105). In the present embodiment, a Morse Taper is utilized. Although this embodiment utilizes a humeral shaft locking screw (206) to maintain segment attachment, other embodiments use only the Morse Taper joints to retain the segments. This is possible given the machining tolerances utilized to create the Morse Taper and the resulting tight fit of the joints in conjunction with the attached muscle tissue that provides essentially constant compressive forces (after prosthesis fixation) on the attached segments. Still other machine taper joints may also be used and are within the scope of the present invention. The proximal (106) and distal (108) humeral segments also feature a positive locking feature ( 109) that serves as a means to prevent rotation of one segment relative to the other. The present embodiment utilizes a tongue and groove arrangement (109) to accomplish this, but other embodiments may utilize an alternating tooth type arrangement such as found between meshed gear sets (i.e., square teeth, triangular teeth, etc.).

[0015] The Fixed length of the distal humeral segment (108) in this embodiment is approximately 173 millimeters in length as measured from the hinge axis (1 10) centerline to the mating surface ( 109). The proximal humeral segment (106) measures 60 millimeters, but is typically provided in multiple fixed lengths to allow a surgeon to readily adjust the working length of the prosthetic device during surgery. For example, multiple proximal humeral segments ( 106) in lengths of 10, 20, 30, and 60 millimeters can be provided to allow the surgeon to adjust the length in 10 millimeter increments. With this modularity, it is also possible to prepare the prosthetic device without use of a proximal humeral segment (106). The metaphyseal segment (104) can be attached directly to the distal humeral segment (108) to create an overall device working length of approximately 245millimeters. If a longer working length is necessary, one or more proximal humeral segments (106) may be added.

[0016] The humeral retroversion of the hinge axis ( 1 14), or elbow assembly (1 14), in relation to the head (102) is adjustable in the present embodiment by use of a positive engagement feature (107) between the proximal segment (106) and the metaphyseal segment ( 104) joints. In this embodiment the engagement feature (107) utilizes interlocking teeth such as those found on a crown gear set. The number of teeth is such that the retroversion angle may be adjusted as little as 10 degree increments or less, depending on the number of teeth provided. Other embodiments may increase or decrease the number of teeth to provide varying degrees of adjustment.

[0017] The outer surface of the metaphyseal segment (104), the proximal segment (106) and the distal segment (108) are textured to provide a means for increased surface area for adhesion of soft tissue and apposition of bone. The present embodiment utilizes

hydroxyapatite which is chemically similar to the mineral component of bones. However, one of ordinary skill will appreciate that other attachment means that simulate the physical and mechanical properties of natural bone and permit direct apposition of natural bone may^¬ be utilized and are within the scope of the present invention. For example, macro-texture and Trabecular Metal are two such additional means. [0018] The elhow assembly body (1 14) is attached to the distal humeral segment (108) through use of the hinge axis (1 10) and corresponding retaining screw (208). Because this hinge axis ( 1 10), elbow assembly (1 14) and distal segment (108) must articulate in relation to one another, materials appropriate for articulating surfaces are chosen. For example, in one embodiment the hinge axis ( 1 10) is cobalt chrome plated and rides within an ultra high molecular weight poly ethylene (UHMWPE) sleeve located in either the distal segment (108) or the elbow assembly (1 14) receiving orifice. One of ordinary skill will appreciate that other material appropriate for articular surfaces may be utilized and is within the scope of the invention.

[0019] FIG. 4A presents an exploded view of the spherocentric elbow device in the present embodiment. In this embodiment the ulnar stem (1 12) features longitudinal grooves extending from the distal end to the proximal end of the stem for rotational stability when cemented into the patient's ulna or radius bone. Also featured is a taper segment (416) that is also coated with a means for apposition of bone. The proximal end of the ulnar stem (1 12) includes a shaft segment that fits within and passes through a first plastic sleeve (402) and a second plastic sleeve (404), and ultimately engages within the positive engagement features (41 ) of the lobe ring (406). A lobe ring fastener (408) engages the ulnar stem shaft (420) and maintains the assembly. The plastic sleeves (402 and 404) fit within machined recesses within the elbow assembly (1 14) body. The first sleeve (402) features a thrust surface that minimizes friction between the ulnar stem taper (416) and the elbow assembly body (1 14). As depicted, the thrust surface is comprised of the same plast ic as the sleeve (402). However, the thrust surface may also be comprised of a suitable medical grade metal or polymer different from that of the sleeve.

[0020] To afford rotation and to minimize friction while doing so, the ulnar stem shaft (420) utilizes similar materials as the articulating surfaces. For example, the shaft may be coated with cobalt chrome, pyrocarbon, ceramic, or another medical-grade, corrosion inhibiting, friction-reducing material. Likewise, the plastic sleeves (402 and 404) utilize a medical grade polymer, including UHMWPE, to reduce friction.

[0021] FIG. 4B presents an enlarged isometric view of the lobe ring (406). As shown, a positive engagement feature (412) is provided that mates (or interlocks) with a related feature (414) on the ulnar stem shaft (420), causing the lobe ring and ulnar stem to rotate in unison. A tab feature (410) on the outer radius of the lobe ring (406) moves within a rotational groove feature (422) and serves to limit the degree of rotation within the elbow assembly body (1 14). In this embodiment the groove (422) is machined within the elbow assembly body (1 14) and is sized to allow the ulnar stem (1 12) to rotate approximately 180 degrees to approximate the normal range of rotational motion of a patient's wrist and hand, with the tab feature (410) contacting the ends of the groove feature (422). The overall range of motion may be adjusted by changing the overall length of the rotational groove (422) to either increase or decrease this range (i.e., greater than or less than 180 degrees). Although the image shows the lobe ring (406) and groove feature (422) at the rear (proximal) end of the ulnar stem shaft (420) and elbow assembly body (1 14), one of ordinary skill will appreciate that, in another embodiment, the lobe ring (406) may engage the shaft (420) at another location, with a corresponding change in location of the groove feature (422) within the elbow assembly body (1 14). Thus, the lobe ring (406) may even be located between the two plastic sleeves (402 and 404). Further, in another embodiment, the lobe ring is a machined feature of the ulnar stem shaft (420).

[0022] Normally, during surgery, the ulnar stem (1 12) is affixed to the patient's ulna.

Following resection of the appropriate length of the ulna, the medullary canal is reamed to receive the stem (1 12) to a depth up to the stem taper (416) and is packed with cement. If the prosthetic device is being fixated in the patient's right arm, the stem (1 12) is rotated counterclockwise as viewed from the distal end to the stop of its rotation and, with the patient's palm facing skyward, the stem is inserted into the medullary canal. The longitudinal channels (418) of the ulnar stem in conjunction with the cement provide rotational stability within the ulna. If the patient's ulna is not serviceable, then the device may also be affixed to the patient's radius in the same fashion.

[0023] FIG. 5 presents a radiographic depiction of the first embodiment of the invention fixated within the right arm of a patient. As shown, the humeral head ( 102) is visibly attached to the glenoid cavity (504) of the patient. Also visible are the metaphyseal segment ( 104), proximal humeral segment (106) and distal humeral segment (108). The elbow assembly (1 14) is shown with the arm extended. The ulnar stem (1 12) is shown fixated with the patient's ulna (504), with the depth of the ream such that the ulna (504) covers at least a portion of the taper region (416) of the ulnar stem (1 12). This promotes apposition of the bone in this area and improves fixation of the device. [0024] FIG. 6 presents a view of another embodiment of the invention as a partial humeral prosthesis with a reverse shoulder arrangement (302). Because the device is modular, a humeral stem (604) may be attached to the distal humeral segment (108) machine taper. Overall length of this device may be adjusted by utilizing proximal segments (106) or distal segments (108) of desired lengths. Fixation of this device requires resection of the appropriate length of the humerus, reaming of the humerus medullary canal to accept the humeral stem (604), and cementing of the humeral stem (604) within the reamed canal.

[00251 With regard to materials chosen for the various components of the embodiments described herein, the metaphyseal segment (104), humeral segments (106 and 108), elbow assembly (1 14) and ulnar stem (1 12) components are constructed from titanium. However, one of ordinary skill will appreciate that other material suitable for implantable prosthetic devices and capable of approximating the functionality of a humerus may be utilized and are within the scope of the present invention. The articular surface of the humeral head (102) is constructed from cobalt chrome, while the spherical insert (302) is constructed from

UHMWPE. One of ordinary skill will appreciate that other materials appropriate for use on articular surfaces of prosthetics (for example, ceramic or pyrocarbon) may be utilized and are also within the scope of the present invention.

[0026] The following clauses are illustrative of various embodiments and features of the device disclosed herein.

[0027] Clause 1 : A humeral prosthetic device, the device comprising: a metaphyseal segment having a first end arranged to accept a humeral head device or reverse shoulder device, and a second end arranged to accept a proximal humeral segment; and at least one proximal humeral segment, the proximal humeral segment having a predetermined fixed length, the proximal humeral segment including a first end for engaging the metaphyseal segment and a second end arranged to accept a distal humeral segment including a hinge axis, or a distal humeral segment including a humeral stem.

[0028] Clause 2: The humeral prosthetic device of Clause 1, wherein the proximal humeral segment or the distal humeral segment fixed length is chosen to establish the working length of the device. [0029] Clause 3 : The humeral prosthetic device of Clauses 1 or 2, the device further comprising: a positive engagement feature between the metaphyseal segment second end and the proximal humeral segment first end, the positive engagement feature for establishing retroversion of the device.

[0030] Clause 4: The humeral prosthetic device of Clauses 1 or 2, the device further comprising: a machine taper feature for attachment of the metaphyseal segment second end with the proximal humeral segment first end, or the proximal humeral segment second end with a distal humeral segment.

[0031] Clause 5 : The humeral prosthetic device of Clauses 1 or 2, the device further comprising: a machine taper feature for attachment of the metaphyseal segment second end with the proximal humeral segment first end, or the proximal humeral segment second end with a distal humeral segment, wherein at least one of said taper joints includes a positive locking feature to prevent rotation of the joined segments relative to one another.

[0032] Clause 6: The humeral prosthetic device of any of the preceding Clauses 1 through 5, the device further comprising: a spherocentric elbow device that approximates the pronosupination movement of a patient's wrist.

[0033] Clause 7: The humeral prosthetic device of any of the preceding Clauses 1 through 5. the device further comprising: a spherocentric elbow device that approximates the pronosupination movement of a patient's wrist, the spherocentric elbow device including an ulnar stem with a stem taper for positive placement and affixation of the ulnar stem within a patient's ulna or radius.

[0034] Clause 8: The humeral prosthetic device of any of the preceding Clauses 1 through 5, the device further comprising: a spherocentric elbow device that approximates the pronosupination movement of a patient's wrist, the spherocentric elbow device including an elbow assembly body, an ulnar stem, and a lobe ring positively engaging the ulnar stem and a tab feature for travel within a corresponding rotational groove feature within the elbow assembly body.

[0035] Clause 9: The humeral prosthetic device of any of the preceding Clauses 1 through 5, the device further comprising: a spherocentric elbow device that approximates the pronosupination movement of a patient's wrist, the spherocentric elbow device including an elbow assembly body, an ulnar stem, and a lobe ring positively engaging the ulnar stem and a tab feature for travel within a corresponding rotational groove feature within the elbow assembly body, the spherocentric elbow device further including a thrust surface for minimizing friction between the ulnar stem and the elbow assembly body.

[0036] The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive. Accordingly, the scope of the invention is established by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Further, the recitation of method steps does not denote a particular sequence for execution of the steps. Such method steps may therefore be performed in a sequence other than that recited unless the particular claim expressly states otherwise.

Claims

We claim:

Claim 1 A humeral prosthetic device, the device comprising: a metaphyseal segment having a first end arranged to accept a humeral head device or reverse shoulder device, and a second end arranged to accept a proximal humeral segment; and at least one proximal humeral segment, the proximal humeral segment having a predetermined fixed length, the proximal humeral segment including a first end for engaging the metaphyseal segment and a second end arranged to accept a distal humeral segment including a hinge axis, or a distal humeral segment including a humeral stem.

Claim 2 The humeral prosthetic device of Claim 1 , wherein the proximal humeral

segment or the distal humeral segment fixed length is chosen to establish the working length of the device.

Claim 3 The humeral prosthetic device of Claim 1 , the device further comprising: a positive engagement feature between the metaphyseal segment second end and the proximal humeral segment first end, the positive engagement feature for establishing retroversion of the device.

Claim 4 Phe humeral prosthetic device of Claim 1 , the device further comprising: a machine taper feature for attachment of the metaphyseal segment second end with the proximal humeral segment first end, or the proximal humeral segment second end with a distal humeral segment. Claim 5 The humeral prosthetic device of Claim 1, the device further comprising: a machine taper feature for attachment of the metaphyseal segment second end with the proximal humeral segment first end, or the proximal humeral segment second end with a distal humeral segment, wherein at least one of said taper joints includes a positive locking feature to prevent rotation of the joined segments relative to one another.

Claim 6 The humeral prosthetic device of Claim 1. the device further comprising: a spherocentric elbow device that approximates the pronosupination movement of a patient's wrist.

Claim 7 The humeral prosthetic device of Claim 1 , the device further comprising: a spherocentric elbow device that approximates the pronosupination movement of a patient's wrist, the spherocentric elbow device including an ulnar stem with a stem taper for positive placement and affixation of the ulnar stem within a patient's ulna or radius.

Claim 8 The h meral prosthetic device of Claim 1 , the device further comprising: a spherocentric elbow device that approximates the pronosupination movement of a patient's wrist, the spherocentric elbow device including an elbow assembly body, an ulnar stem, and a lobe ring positively engaging the ulnar stem and a tab feature for travel within a corresponding rotational groove feature within the elbow assembly body.

The humeral prosthetic device of Claim 1 , the device further comprising: a spherocentric elbow device that approximates the pronosupination movement of a patient's wrist, the spherocentric elbow device including an elbow assembly body, an ulnar stem, and a lobe ring positively engaging the ulnar stem and a tab feature for travel within a corresponding rotational groove feature within the elbow assembly body, the spherocentric elbow device further including a thrust surface for minimizing friction between the ulnar stem and the elbow assembly body.