Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Reexamination Certificate
1998-04-03
2001-03-06
Mancene, Gene (Department: 3308)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
Reexamination Certificate
active
06197063
ABSTRACT:
BACKGROUND OF THE INVENTION
During the procedure of a shoulder replacement operation, at least a portion of the proximal section of the humeral shaft will be replaced by a metal prosthesis. This prosthesis will generally consist of two parts: a stem that is mounted into the medullary canal of the humerus, and a head component connected in some manner to the stem. The head component replaces the bearing surfaces of the humerus and articulates with the surface of the scapula to allow the movement of the shoulder.
Modular humeral prostheses are known. The stem and head component may be supplied in “modular” form, that is, as separate connectable components. Different stem sizes and head sizes in a modular implant design provide the surgeon with some degree of inter-operative flexibility, which facilitates reconstruction of the original anatomy of the patient.
With a range of stem sizes and a range of head sizes available, the surgeon can choose a particular combination to suit the anatomy of each individual patient without having to have a large inventory of “integral” or “unitary” humeral prosthesis. As used herein, “integral” and “unitary” mean formed in one continuous piece in contrast to the separate connectable components of a modular prosthesis. For example, one patient might require a relatively small head and a relatively long stem. With a unitary prosthesis a wide range of stem lengths would be required for each head size whereas with a modular arrangement a particular head can be used with a range of stem sizes and visa versa.
Additional variations arise also as a result of individual patients requiring differing angles of inclination of the head relative to the stem and of differing offsets between the axis of the head and the axis of the stem. Thus, in one patient the offset may be posterior and in another anterior.
Various shoulder prostheses are disclosed in European Patent Publication No. EP-A 0 679 375; EP-A 0 712 617; French Patent No. FR-A 2 664 809; U.S. Pat. Nos. 3,694,820; 3,803,641; 4,045,825; 4,106,130; 4,179,758; 4,865,605; 4,919,670; 5,358,526; 5,549,682; 5,462,563 and 5,702,457; and PCT International Patent Publication No. WO 96/17553.
SUMMARY OF THE INVENTION
This invention provides a modular prosthesis in which a humeral head, chosen to suit a patient, is attached to a stem chosen to suit the resected humerus of the patient by means of an intermediate connecting member. The prosthesis can accommodate a wide range of variation, in a relatively cheap manner, by providing the variations required in the intermediate connecting member rather than in the very much more expensive head.
The modular humeral prosthesis generally comprises a stem to be fitted to a resected humerus, a head sized and configured to approximate the humeral head, and an intermediate connecting member for connecting the stem to the head. The intermediate connecting member includes first engagement means for mounting the intermediate connecting member on the stem. The first engagement means has an axis about which the intermediate connecting member can be rotated through 360° relative to the stem and thereafter secured at a selected relative orientation. The intermediate connecting member further includes second engagement means for mounting the head on the intermediate connecting member. The second engagement means has an axis about which the head can be rotated through 360° relative to the intermediate connecting member and thereafter secured at a selected relative rotation. The axis of rotation of the first and second engagement means is not coincident, whereby the first and second engagement means allow the head to be given a desired offset relative to the stem.
Preferably, the axis of rotation of the first and second engagement means are not parallel, whereby the engagement means allow a desired inclination of the head relative to the stem.
Also, preferably, the first and second engagement means of the intermediate connecting member are positioned relative to one another to provide a desired separation between the head and the stem.
The first and second engagement means of the intermediate connecting member are preferably positioned relative to one another to provide a desired separation between the head and the stem. Most preferably, the separation or “neck length” between the head and the stem is no greater than 5 mm.
Also, preferably, the first and second engagement means each comprise a male portion, and the head and stem are provided with corresponding mating female portions. The male and female portions preferably each have a substantially circular cross-sections, and a substantially self-locking tapered configuration (i.e., a Morse taper).
Most preferably, a bore is provided through the first and second engagement means and extends through the intermediate connecting member, and the prosthesis further comprising a fastener inserted through the bore to engage the stem to further secure the intermediate connecting member to the stem.
In a second aspect of the invention modular humeral prosthesis kit is provided for replacement of the humeral head of a humerus, The kit generally comprises a stem to be fitted to a resected humerus, a head sized and configured to approximate the humeral head, and a plurality of intermediate connecting members of which one may be selected to connect the stem to the head. Each intermediate connecting member includes first engagement means for mounting the intermediate connecting member on the stem, and second engagement means for mounting the head on the intermediate connecting member. The plurality of the intermediate connecting members of the kit include:
A. At least one intermediate connecting member in which the first and second engagement means have generally parallel and coincident central axii;
B. At least one intermediate connecting member in which the first and second engagement means have generally parallel but not coincident central axii;
C. At least one intermediate connecting member in which the first and second engagement means have an angle of inclination between one another that is different than the angle of inclination between the first and second engagement means of another intermediate connecting member of the kit; and
D. At least one intermediate connecting member in which the first and second engagement means are separated by a different neck length than the neck length separating the first and second engagement means of another intermediate connecting member of the kit.
The specifications for the plurality of intermediate connecting members set out at A-D above may be met by combining features in some of the intermediate connecting member of the kit. For example, two intermediate connecting members may have different neck lengths, angles of inclination and offsets or zero offset.
Preferably, the first engagement means of each intermediate connecting member has an axis about which the intermediate connecting member can be rotated through 360° relative to the stem and thereafter secured at a selected relative orientation, and the second engagement means of each intermediate connecting member has an axis about which the head can be rotated through 360° relative to the intermediate connecting member and thereafter secured at a selected relative rotation.
Also, preferably, the first and second engagement means of each intermediate connecting member comprise male portions, and the head and stem are provided with corresponding mating female portions. Most preferably, the male and female portions each have a substantially circular cross-section, and a substantially self-locking tapered configuration (i.e., a Morse taper).
Most preferably, each intermediate connecting member is provided with a bore through the first and second engagement means, and the kit further comprises a fastener inserted through the bore to engage the stem to further secure the intermediate connecting member to the stem.
A third aspect of the invention is a method of replacing a humeral head in a patient. The method generally comprises:
(a) Resecting the proxim
Ewing, IV James L.
Kilpatrick & Stockton LLP
Mallatt Kristin D.
Mancene Gene
Robert Eduardo C.
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