Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Reexamination Certificate
1999-05-19
2001-05-08
Recla, Henry J. (Department: 3731)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
C623S023140
Reexamination Certificate
active
06228122
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to hip replacement systems and components thereof.
BACKGROUND OF THE INVENTION
Total hip replacement is considered the most successful orthopaedic surgical procedure ever devised. Its success has now spanned three decades. There are now approximately 120,000 hip replacements performed in the U.S. each year. About one-third of the operations performed are for revision replacement of previously implanted prosthetic hips. The main cause of revision is for aseptic loosening. Another reason for revision is dislocation of the components. Dislocation continues to be a problem in total hip replacement. Every surgeon who performs this operation has this complication, no matter how experienced he or she is with total hip replacement. The incidence of dislocation varies widely in the community. Most experienced surgeons expect less than a 3% incidence. Some community surgeons are known to have as high as 30% dislocation rate. Dislocations are proven to be associated with (i) the type of approach, posterior being the most common—90%, and (ii) whether the case is a revision (three times the incidence over primary replacements). About half of the dislocations occur in the first month after the procedure. The remainder of the dislocations occur over the span of many years. A dislocation can occur at any time in the lifetime of the arthroplasty. It is evident that dislocation remains a problem complication in the most successful orthopaedic procedure ever devised.
Attempts have been made to make the hip replacement operation more stable and thus reduce the incidence of dislocation. To preserve soft tissue attachments posteriorly, the surgical approach has been changed. The “direct lateral approach” has been utilized in the joint replacement, but residual pain, limp, and heterotopic ossification have tempered its use. It is not well proven that the incidence has been dramatically affected despite this change in the approach. Recently, unpublished reports have demonstrated an improved dislocation rate through the reattachment of soft tissues in conjunction with the posterior approach. This technique remains to be proven and additional study is needed. The posterior soft-tissue techniques do not address revision operations, since the soft tissues are deficient or absent in revision cases.
Modification of the components has also been undertaken to try and make the arthroplasty more stable. The use of a locking mechanism between the femoral ball and the acetabular socket has been fraught with problems. This so-called “constrained” socket fails early because of high stresses arising from impingement between the socket and femoral neck. This may cause the socket to pull out from the bone attachment in the pelvis, or dislodge the ring lock holding the devices together. Another modification is the simple addition of a buildup of the polyethylene rim. This modification does not appear to influence the dislocation rate in clinical studies. This is probably because of the reduction of a “safe zone” before impingement occurs between the femoral neck and the rim of the polyethylene socket. On the femoral side, attempts at enlarging the diameter of the femoral head had not influenced the rate of dislocation. Enlarging the femoral head has been unpopular largely because of the problem of increased polyethylene wear seen with large diameter heads.
SUMMARY OF THE INVENTION
The present invention is directed to overcome some of the disadvantages of the prior art. In particular, the present invention is directed toward an apparatus and method for preventing dislocation between an acetabular cup and a replacement femur.
In one aspect of the invention, a device is provided for hip replacement stability. The hip replacement uses an acetabular cup implantable into an adjacent bone and a replacement femur implantable into a femur. The device of the invention includes a connector which is adapted to connect to (1) at least one of an acetabular cup, or a component of an acetabular cup, or the adjacent bone, and (2) at least one of a replacement femur or a femur.
The connector is flexible.
In another aspect of the invention, the connector is adapted for allowing uninhibited movement between an acetabular cup and a replacement femur up to a limit.
In yet a further aspect of the invention, a connector is adapted for preventing a replacement femur from becoming dislocated from an acetabular cup.
In yet a further aspect of the invention, a connector is comprised of a net.
In still a further aspect of the invention, a method is provided for preventing dislocation between an acetabular cup and replacement femur comprising the steps of securing a connector to at least one of an acetabular cup, or a component thereof, or a bone located adjacent to an acetabular cup and securing a connector to at least one of the replacement femur or a femur.
In another aspect of the invention, a method is provided for preventing dislocation which method includes implanting an acetabular cup or component thereof which has selectively secured thereto a connector and selectively securing the connector to one of a replacement femur or a femur.
Other aspects and objects of the invention can be obtained through a review of the specification of the claims and the figures.
REFERENCES:
patent: 4731088 (1988-03-01), Collier
patent: 5718012 (1998-02-01), Cavallaro
patent: 5755807 (1998-05-01), Anstaett et al.
patent: 5916585 (1999-06-01), Cook et al.
patent: 5951605 (1999-09-01), Dennis et al.
“Cerclage Cable System” Acumed, Inc. p. 5, Jul. 1992.
Fliesler Dubb Meyer & Lovejoy
King Anthony S.
Recla Henry J.
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