Shoulder prosthesis

Details Shoulder prosthesis Shoulder prosthesis

2000-01-18

2001-01-02

Isabella, David J (Department: 3738)

Prosthesis (i.e., artificial body members), parts thereof, or ai

Implantable prosthesis

Bone

C606S08600R

Utility Patent

active

06168627

ABSTRACT:

This invention relates generally to bone prostheses and more particularly to a shoulder prosthesis.
BACKGROUND OF THE INVENTION
When a joint, such as the hip or shoulder, becomes impaired due to arthritis, disease or trauma, it is sometimes necessary to replace all or part of the joint with a prosthesis to restore function. For instance, hip replacement, where a prosthesis is provided to replace the femoral head and in some cases all or part of the acetabulum, has become a common procedure to treat femoral head fractures and arthritis in elderly patients. As a result of anatomical constraints and challenges in the shoulder, shoulder implants have historically been much less successful and less common than hip replacements. Recently, however, shoulder arthroplasty has emerged as an accepted treatment for severe arthritis and humeral head fractures.
As a consequence of the increasing acceptance of shoulder prostheses, many different devices have been developed to address various problems that have arisen and to offer additional benefits and features. In the simplest form, a shoulder prosthesis is formed as a single piece with a head to articulate with the glenoid cavity, and a stem to extend down the medullary canal of the humerus and support the head. While simple to construct, unitary implants do not offer any adjustability to accommodate the natural variations in size and geometry that occur among joints of different patients. To accommodate these variations, a large stock of devices must be manufactured and maintained to insure that an adequate match can be achieved during an operation. Stocking the large number of devices is a significant expense with one-piece designs, and in some cases a surgeon may not be provided with sufficient flexibility to achieve an ideal fit to the patient.
To avoid the expense of maintaining a large stock of single-piece prosthetics and to provide increased flexibility to surgeons, many shoulder implant makers have gone to a modular design that is assembled during the operation from two or three pieces. These pieces include a head to articulate with the glenoid and a stem structure on which the head is mounted and secured to the bone. In some cases, the stem includes a separate body portion disposed between the head and an intermedullary portion of the stem that extends down the medullary canal. By utilizing a modular design, a wide variety of devices can be assembled from only a few pieces, thus providing increased flexibility to accommodate anatomical variation and eliminating much of the cost associated with maintaining a large selection of one-piece devices.
Existing modular shoulder designs most commonly rely on a taper lock mechanism to secure the head to the rest of the implant. In at least some devices the portion of the taper lock on the head is offset to compensate for anatomical posterior offset of the humeral head. For instance, the taper lock portion on the head may be offset by 2-4 millimeters. By rotating the head, any offset between plus and minus the 2-4 millimeters can be achieved. Unfortunately, rotating an offset head can introduce a medial/lateral and/or superior/inferior offset at the same time the anterior/posterior positioning is adjusted. Furthermore, the offset between the center of the taper lock and the geometrical center of the head creates a torque which tends to rotate the head relative to the remainder of the implant, thereby increasing the chance of loosening of the head. As the offset increases, the resultant torque increases as well, making this a greater problem for larger offsets. Although such problems are incumbent in existing offset head designs, a posterior offset is generally desirable to better match the natural anatomy.
In addition to the specific drawbacks associated with various existing implant designs, there are a number of general problems inherent in shoulder replacements. In particular, it is generally difficult to establish the proper position and orientation for the implant in the humerus. One of the more important variables is the rotational position, or retroversion, of the head on the humerus. Anatomically, the average retroversion between a plane defined by the perimeter of the anatomical head and the axis of the flexed forearm is approximately 30-degrees. Unfortunately, with existing implants and techniques for their installation, it has been very difficult to reliably reproduce desired retroversion. Establishing correct retroversion is important because incorrect retroversion can lead to problems with subsequent dislocation.
In addition to the retroversion of the implant, it is necessary to establish the correct height of the implant on the humeral shaft. With existing designs, the surgeon slips the stem into the medullary canal and makes an educated guess at the proper height. Excess height may create too much tension in the deltoid, while inserting the implant too far down the humerus can result in deltoid lag. Similarly, the offset of the face of the head relative to the stem must be established correctly or excess or insufficient tension in the rotator cuff may be created. Unfortunately, with existing designs there is no way to evaluate implant height or head offset prior to final installation, after which correction is difficult.
SUMMARY OF THE INVENTION
The present invention is a shoulder prosthesis having a head and an elongate stem portion including a proximal end connected to the head, a distal section for insertion into a medullary canal of a humeral bone and an alignment section disposed between the proximal end and distal section. The alignment section includes a plurality of reference marks positioned to facilitate placement of the prosthesis in the bone at a previously determined position.


REFERENCES:
patent: 2682265 (1954-06-01), Collison
patent: 2719522 (1955-10-01), Hudack
patent: 2765787 (1956-10-01), Pellet
patent: 2781758 (1957-02-01), Chevalier
patent: 2785673 (1957-03-01), Anderson
patent: 3064645 (1962-11-01), Ficat et al.
patent: 3067740 (1962-12-01), Haboush
patent: 3102536 (1963-09-01), Rose et al.
patent: 3658056 (1972-04-01), Huggler et al.
patent: 3670724 (1972-06-01), Bosacco
patent: 3694820 (1972-10-01), Scales et al.
patent: 3765034 (1973-10-01), Johnston
patent: 3782373 (1974-01-01), Smythe
patent: 3806957 (1974-04-01), Shersher
patent: 3814089 (1974-06-01), Deyerle
patent: 3818512 (1974-06-01), Shersher
patent: 3859669 (1975-01-01), Shersher
patent: 3863273 (1975-02-01), Averill
patent: 3874003 (1975-04-01), Moser et al.
patent: 3906550 (1975-09-01), Rostoker et al.
patent: 3916451 (1975-11-01), Buechel et al.
patent: 3918441 (1975-11-01), Getscher
patent: 3974527 (1976-08-01), Shersher
patent: 3979778 (1976-09-01), Stroot
patent: 3987499 (1976-10-01), Scharbach et al.
patent: 4004300 (1977-01-01), English
patent: 4030143 (1977-06-01), Elloy et al.
patent: 4040131 (1977-08-01), Gristina
patent: 4042980 (1977-08-01), Swanson et al.
patent: 4051559 (1977-10-01), Pifferi
patent: 4115875 (1978-09-01), Rambert et al.
patent: 4261062 (1981-04-01), Amstutz et al.
patent: 4404691 (1983-09-01), Buning et al.
patent: 4406023 (1983-09-01), Harris
patent: 4430761 (1984-02-01), Niederer et al.
patent: 4459708 (1984-07-01), Buttazzoni
patent: 4488319 (1984-12-01), von Recum
patent: 4532660 (1985-08-01), Field
patent: 4550450 (1985-11-01), Kinnett
patent: 4578081 (1986-03-01), Harder et al.
patent: 4624674 (1986-11-01), Pappas et al.
patent: 4645506 (1987-02-01), Link
patent: 4655778 (1987-04-01), Koeneman
patent: 4676797 (1987-06-01), Anapliotis et al.
patent: 4693723 (1987-09-01), Gabard
patent: 4693724 (1987-09-01), Rhenter et al.
patent: 4698063 (1987-10-01), Link et al.
patent: 4822370 (1989-04-01), Schelhas
patent: 4840632 (1989-06-01), Kampner
patent: 4842606 (1989-06-01), Kranz et al.
patent: 4865605 (1989-09-01), Dines et al.
patent: 4865609 (1989-09-01), Roche
patent: 4895572 (1990-01-01), Chernoff
patent: 4904266 (1990-02-01), Barber
patent: 4908032 (1990-03-01), Keller
patent: 4919669 (1990-04-01), Lannelongue
patent: 4919670 (1990-04-01), Dale et al.
pat

Affiliated with

Also associated with

Rating

Shoulder prosthesis does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Shoulder prosthesis, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Shoulder prosthesis will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2489538