Patent Application
20160296336
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1. Field of the Invention
The present invention relates to orthopedic implant technology and, more specifically, to endoprosthetic devices for repairing segmental skeletal defects of the arm and shoulder or leg and hip of a human patient.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
In human patients, disease or extreme trauma can sometimes necessitate the repair or replacement of a portion or all of the bones and/or joints that comprise a patient's arm or leg. For example, a tumor that affects the proximal portion of a patient's humerus can require resection of the diseased portion and fixation of a humeral prosthesis that attempts to duplicate the functionality of the original humerus. Such an endoprosthetic device may typically include the humeral head, shaft, and even the elbow joint, with affixation at the distal end via a shaft feature that is cemented into a borehole formed within the remaining ulna or radial bone of the patient. While such extreme limb-salvage surgical repairs are made nowadays on a somewhat routine basis, existing prosthetic device technology falls short with regard to duplication of the range of movement of the original joints. Consequently, patients are typically left with limited functionality of the replaced anatomy due to limited range of motion. Moreover, patients with such repairs, who attempt arm movements to the limits of these prosthetic devices often weaken or damage the affixation site and may even cause dislocation of the shoulder joint, resulting in additional trauma to the bone and surrounding soft tissue.
The instant inventor made tremendous advances in orthopedic implant technology with his invention disclosed in PCT Application No. PCT/US2011/056393 entitled “Modular Humeral Prosthesis With Spherocentric Feature,” filed on Oct. 14, 2011, the disclosure of which is incorporated by reference herein for all purposes. As the title states, this invention discloses a modular humeral prosthesis having a new and unique spherocentric elbow joint that allows full supination and pronation of the patient's hand post-recovery. However, as with this and other current humeral prostheses it was discovered that upon repeated medial and lateral rotation of the patient's repaired arm excessive torsional stresses were imparted on the humeral prosthesis shaft. In the case of complete shoulder repairs the excessive torsional stresses resulted in full separation and dislocation of the shoulder joint with resultant damage to the joint and surrounding soft tissue. In the case of partial humerus repair the excessive torsional stresses resulted in “windshield wiper” loosening of the cemented stem from the fixation site. The instant invention addresses these shortcomings and others as will be understood by one of ordinary skill upon a thorough study of the embodiments described herein.
The present invention in a first embodiment is drawn to a torsionally stabilized humeral or femoral prosthesis, the humeral or femoral prosthesis comprising: a first rotational component and a shaft component affixed intermediate to a proximal articulation and a respective distal articulation, with the first rotational component axis of rotation substantially coaxial with the shaft component, the first rotational component allowing rotation of the distal articulation relative to the proximal articulation. Additional embodiments include a first rotational component comprising a Morse taper for affixation with one or more additional prosthesis segments to establish a desired length of the shaft component; a first rotational component comprising a porous mesh metal surface treatment for soft tissue attachment thereto; a first rotational component comprising a lobe ring for limiting the degree of the relative joint rotation; a first rotational component comprising a lobe ring for limiting the degree of rotation, the lobe ring comprising a ramp feature for gradually arresting the relative joint rotation; a first rotational component comprising a humeroulnar articulation; a first rotational component comprising a humeroulnar articulation, the a humeroulnar articulation further comprising a second rotational component; and a first rotational component wherein the first rotational component is modular comprising Morse tapers for affixing with one or more additional prosthesis segments.
The present invention in another embodiment is also drawn to a method for reducing the torsional stresses on a humeral prosthesis, the method steps comprising: affixing a first rotational component at a location along a humeral shaft intermediate to the humeral proximal articulation and the humeral distal articulation. Additional embodiments include the method steps further comprising: locating the first rotational component nearer to an intramedullary stem of the humeral prosthesis; and locating the first rotational component nearer to the distal articulation of the humeral prosthesis. Another embodiment is drawn to a method for reducing the torsional stresses on a femoral prosthesis, the method steps comprising: affixing a first rotational component at a location along a femoral shaft intermediate to the femoral proximal articulation and the femoral distal articulation. Additional embodiments include the method steps further comprising: locating the first rotational component nearer to an intramedullary stem of the femoral prosthesis; and locating the first rotational component nearer to the distal articulation of the femoral prosthesis.
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:
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 multiple 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 will be explained or will be within the skill of the art after the following teachings of the present invention have been read and understood.
The following invention makes reference to the glenohumeral articulation (shoulder joint), the humeroulnar/humeroradial articulation (elbow joint), the acetabulofemoral articulation (hip joint), and the tibiofemoral/patellofemoral articulation (knee joint) of a patient. With regard to a humerus, the proximal articulation refers to the glenohumeral articulation and the respective distal articulation refers to the humeroulnar/humeroradial articulation. With regard to a femur, the proximal articulation refers to the acetabulofemoral articulation and the respective distal articulation refers to the tibiofemoral/patellofemoral articulation.
The housing component proximal end (110) features a through-hole axial bore within which a proximal sleeve (108) is located. The proximal sleeve (108) in this embodiment utilizes ultra-high molecular weight polyethylene (UHMWPE), but may be made from any other friction-reducing biocompatible polymer. The proximal sleeve (108), likewise, has a through-hole axial bore within which the stem feature (104) is positioned. A lip on the proximal sleeve (108) prevents the assembled axial component from directly contacting the housing component (110), thereby reducing rotational friction of the components relative to one another.
The stem feature (104) further extends into the distal end of the housing component (112), which includes an additional axial bore section within which a distal sleeve (114) is located. As with the proximal sleeve (108), the distal sleeve (114) utilizes UHMWPE as a friction-reducing and biocompatible bearing for rotation of the stem (104) relative the housing (110). The distal end of the stem feature (104) is drilled and tapped to accept a threaded fastener (118). The threaded fastener in this embodiment is a hex fastener (118), which allows for easier manufacturability due to the positive engagement of hex wrench tools, but may be any fastener known in the art. The use of a thread locking material ensures positive retention of the fastener (118) when affixed within a patient.
The fastener (118) also retains a lobe ring (116) on the end of the stem (104). The lobe ring (116) fits within a mating groove feature (120) within the distal end of the housing (112), and is designed to provide a positive and gradual stop to rotation of the stem (104) to prevent over-rotation.
In another embodiment the lobe ring (116) does not utilize a physical rotation stop. Inside the patient, this embodiment allows the stem (104) to rotate to the fullest extent allowed by the patient's soft tissue. This can be advantageous because it prevents the harsh rotational stop “hammering” impulses that might be perceived by the patient as with the previous embodiment. The stops may be removed from within the groove (120), or the ramps may be removed from the lobe ring, making the lobe ring more circular in shape.
The machined axial component, the housing component, and all other metal components of the embodiment are manufactured from biologically compatible and stable metals. In the instant embodiment the axial and housing components are titanium, but may be surgical stainless steel, niobium, gold, platinum, or the like. Moreover, combinations of metals and/or biocompatible polymers may also be utilized and are within the scope of the claimed invention. Internal components, likewise, are manufactured from these same metals and/or polymers. For example, the lobe ring component (116) of the present embodiment is manufactured from UHMWPE to reduce impulse forces that can result from rapid rotation of the device to a limit. However, metals may also be utilized to improve the wear resistance of the component. In another embodiment the comprises a combination of metal and polymer coating on the outer wear surface to soften the impulse. Yet another embodiment may utilize a polymer body with a metal layer on the outer wear surface to improve the wear characteristics while providing a reduction in impulse.
The modular rotational component in other embodiments may include combined joint features. For example,
To complete the construction of a humeral prosthesis with a humeroulnar articulation, it is helpful to describe the component that, when combined with the previous embodiment, may form the humeroulnar articulation.
To afford rotation and to minimize friction while doing so, the ulnar stem shaft (614) utilizes similar materials as the articulating surfaces. For example, the shaft may be coated with cobalt chrome, pyrocarbon, ceramic, or other medical-grade, corrosion inhibiting, friction-reducing material. Likewise, the plastic sleeves (610 and 606) may utilize a medical-grade polymer, including UHMWPE, to reduce friction.
The lobe ring (604) in this embodiment is similar in form and function to the previously discussed lobe ring. As shown, a positive engagement feature is provided that mates (or interlocks) with a related feature (612) on the ulnar stem shaft (614), causing the lobe ring and ulnar stem to rotate in unison. A tab feature (624) on the outer radius of the lobe ring (604) moves within a rotational groove feature (622) in the body (608) and serves to limit the degree of rotation within the elbow assembly body (608). In this embodiment the groove (622) is machined within the elbow assembly body (608) and is sized to allow the ulnar stem (620) to rotate approximately 180 degrees to approximate the normal range of rotational motion of a patient's wrist and hand, with the tab feature (624) contacting the ends of the groove feature (622) as in previous embodiments. The overall range of motion may be adjusted by changing the overall length of the rotational groove (622) to either increase or decrease this range (i.e., greater than or less than 180 degrees). Further, in another embodiment, the lobe ring is a machined feature of the ulnar stem shaft (420).
The proximal end of the spacer features a Morse taper (702) followed by threads (704) for engaging a mating female end on another spacer. The Morse taper is a common machined taper that is used to positively join machined components. The proximal end (708) of the body of the spacer includes holes (706) for suture attachment of soft tissue. As with the modular rotational component embodiments, the body includes a hex feature (712) for engagement by an open ended wrench of appropriate size, which is used during assembly of the modular components. The distal end (710) features a complimentary female threaded coupler (not visible) for engaging with the male threaded coupler (see 702/704) of another spacer or rotational component.
A successful limb-sparing procedure for oncological purposes can be divided into three stages. The first stage involves tumor resection, and must spare significant tissue structures to support reconstruction while obtaining adequate oncologic margin to eliminate diseased tissue. The second stage involves the affixation of a stable, painless skeletal reconstruction (typically an endoprosthetic device). Third, the surrounding and supporting soft tissue is required to restore functionality to the skeletal reconstruction. The performance of the first two steps of this procedure is well understood, so it is not necessary to provide such detail herein. However, the endoprosthetic device and its use disclosed herein have heretofore never been contemplated.
To complete the procedure (third stage) it is necessary to reattach the surrounding and supporting soft tissue to the prosthesis. The present embodiment provides a porous mesh surface treatment and strategic suture attachments to effect reattachment. For example, the subscapularis must be reattached to the area of the prosthetic device that represents the lesser tuberosity of the original humerus (1006). The subscapularis tendon is affixed to a suture attachment feature in this area (1006) and, over time, the tendon collagen fibers anchor the tendon into the porous mesh surface treatment present at this enthesis. Likewise, the pectoralis major must be reattached to the area of the prosthetic device that represents the lateral lip of intertubercular groove of original humerus (1008). Accordingly, the pectoralis major tendon is affixed to a suture attachment feature in this area (1008) and, over time, this tendon collagen fibers anchor the tendon into the porous mesh surface treatment present at this enthesis. This is repeated for the remaining muscles, including the rotator cuff muscles, triceps, brachialis, and brachioradialis (1010).
The rotational component embodiment may also be utilized with femoral prosthetic devices to, likewise, prevent excessive torsional stresses during rapid full rotation of the patient's lower leg with respect to the hip. These torsional stresses can weaken the stem fixation site, and can cause dislocation of the acetabulofemoral articulation (hip socket) due to the impulse felt at the acetabulofemoral articulation at full rotation. As with the humeral prosthetic device, the rotational component is positioned proximate the intramedullary stem. Such a configuration is depicted in
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 that come within the meaning and range of equivalency of the claims are intended 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.
