Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Reexamination Certificate
2002-02-07
2004-04-13
Snow, Bruce (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
Reexamination Certificate
active
06719796
ABSTRACT:
FIELD OF INVENTION
The present invention relates to an improved spinal surgical prosthesis and more particularly to apparatus and methods for achieving stability of adjacent vertebrae and preserving the inter-disc space following disectomy by internal fixation or fusion.
BACKGROUND OF THE INVENTION
Fusion commonly performed for adjacent bone structures and those not adjacent provides for long term replacement as a result of degenerative or deteriorated disorders in bone.
An inter-vertebral disc is a ligamentous cushion disposed between vertebrae and as a result of injury, disease or other disorders may deteriorate in part or in whole, thereby leading to mechanical instability and painful disc translocations and often necessitating bed rest or hospitalization. If left untreated possible subsequent involvement of adjacent nerves and muscular involvement may occur. In such cases, if treatment is delayed, permanent damage to the nerves may result in muscular atrophy and severe dysfunction.
Procedures for disc surgery may involve partial or total excision of the injured disc portion and replacement with biocompatible devices of bone or bone-like material.
EARLY TECHNIQUES
Bone material was simply disposed between the adjacent vertebrae, typically at the posterior aspect of the vertebrae and the spinal column was stabilized by way of a plate or rod connecting the involved vertebrae. However, the use of bone may require undesired additional surgery and is of limited availability in its most useful form. In addition, the risk of infection and rejection is a significant consequence. In any event, bone is only marginally structural and with bone it is difficult to stabilize both the implant against dislodgment and stabilize the adjacent vertebrae. It becomes desirable to find solutions for stabilization of an excised disc space by fusing the vertebrae between their respective end plates without the need for anterior or posterior plating or rods.
PRIOR ART
A review of the prior art clearly reveals attempts to achieve such solutions in two distinct areas, namely:
I. Static inter-body fusion devices
II. Adjustable inter-body fusion devices that can restore and stabilize varying heights of the intra-discal space.
I. Static Inter-body Fusion Devices
An extensive number of static inter-body fusion devices commonly called “cages” have evolved for replacement of a damaged disc while still maintaining stability of the disc inter-space between the adjacent vertebrae.
However, existing static inter-body fusion devices encountered some problems. They require drilling, boring or tapping of the end plates which sometimes results in removal of an excessive amount of supporting bone with possible damage to adjacent structures. Moreover, threads of the implant or cage may inadvertently engage the prepared threads of the vertebrae in an improper manner so as to cause a misalignment of the vertebrae in an anterior-posterior direction as well as laterally. If a second cage is needed, it involves the drilling, boring or tapping of the vertebral end plates for both cages so that the threads direct the cages into their proper respective positions. Such preparation requires highly skilled precision that may not be afforded or attainable under normal working conditions.
When a second cage is inserted, due to the unevenness of the vertebral end plates concave engaging surfaces, an unwanted increase in the inter-vertebral space may result in the loosening and possible dislodgment of the initially placed implant cage.
The anatomical configurations of the vertebrae necessitates that the two cages be positioned at an angle in respect to each other so as to be totally within the confines of the lateral borders of the vertebrae involved.
Use of tapered cages that are dimensionally greater in height anteriorally than posteriorally so as to provide the proper lordosis when such cage implants are employed creates complications. When the posterior approach is utilized and drilling, boring or tapping is necessary for placing threads on the vertebral end plates, difficulties exist in creating threads that will have a pitch compatible with those exhibited by the threads of such cages. A further complication is present when utilizing tapered cages via the posterior approach in that the dimensionally higher anterior threaded portion of the tapered cage is initially inserted and advanced to its most anterior final resting position. These cages are self-tapping to some degree and may result in the unwanted excessive removal of bone from the posterior portion of the lumbar segments where the lordosis is greatest.
Drilling and other types of preparation of the vertebral end plates may result in the removal of excessive amounts of supporting bone, and may cause the cage implants to rest upon the cancellous portion of the vertebrae. In such instances the cages may settle into said vertebrae resulting in a decreased inter-vertebral space other than that desired with subsequent complications of stabilization, pain and discomfort.
II. Adjustable Inter-body Fusion Devices
These are designed for restoring and maintaining the inter-vertebral space thereby providing for the normal contour of the fused spinal segments. Once the disc is removed, the normal lordotic or kyphotic curvature is eliminated and adjustable inter-body fusion implants are employed for re-establishing the proper curvature and stabilization of the spine.
Adjustable inter-body fusion devices have universal applicability and may eliminate the need for surgical preparation of the vertebral end plates such as contouring of bone and drilling, boring and tapping of said vertebral end plates. Such devices restore and preserve the inter-space and the integrity of the adjacent vertebrae thereby making the selection of the proper implant easier. They result in preservation of the highly specialized weight bearing cortical bone thereby preventing end plate perforation into the highly vascular cancellous bone marrow and unwanted subsequent bleeding may result in many complications due to excessive blood loss risks (e.g. hypoglycemic shock, transfusion, and possible diseases such as hepatitis and Acquired Immune Deficiency Syndrome, etc.),. Another advantage of such devices is the elimination of incorrect implant size selection as no significant amount of bone is removed and the correct size implants are easily fitted to restore the proper inter-space. In addition, the implant is self-stabilizing without the use of threads and may be further enhanced by surface treating of the implant for bone in-growth and osseous integration of the implant.
DESCRIPTION OF THE RELATED ART
The following patents disclose Static Inter-Body Fusion Devices: U.S. Pat. Nos. 5,785,710; 5,782,919; 5,766,253; 5,609,636; 5,425,772; 4,878,915; 4,501,269; 4,961,240 and 5,055,104.
The following patents disclose Adjustable Inter-Body Fusion devices: U.S. Pat. Nos. 5,782,832; 5,766,199; 5,702,455; 5,609,635; 5,336,223; 5,306,310.
ADVANTAGES OF INVENTION
The present invention overcomes the disadvantages represented by the prior art by not requiring drilling procedures for threaded engagement of adjacent vertebrae and subsequent end plate preservation. It restores and preserves the disc inter-vertebral space with the proper curvature of the spine. As taught by this invention, the methods and devices for insertion following disc removal requires no specialized surgical technique and allows for precise placement of the device and subsequent re-establishment of the proper inter-vertebral space and lordosis by either an anterior or posterior surgical approach. Further, this invention permits precise implant size to fit within the space allowed and not endanger or damage adjacent structures. Hence, incorrect implant size selection and the need for a variety of implant sizes is eliminated. An added advantage is, if removal is necessary it would not result in iatrogenic destruction of the adjacent vertebrae. Also, spinal stability is obtained without the use of threads since such threads may adversely affect the vertebrae
Biro Ladislau
Cohen Howard
Cohen Matthew S.
Advanced Prosthetic Technologies, Inc.
Esq. Gloria Tsui-Yip
Miskin, Esq. Howard C.
Snow Bruce
LandOfFree
Spinal surgical 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 Spinal surgical prosthesis, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Spinal surgical prosthesis will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3216410