X-ray or gamma ray systems or devices – Accessory – Alignment
Reexamination Certificate
1999-09-30
2003-03-18
Reip, David O. (Department: 2882)
X-ray or gamma ray systems or devices
Accessory
Alignment
C378S063000
Reexamination Certificate
active
06533454
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to surgical tissue fixation equipment and systems and, more particularly, to bioabsorbable fixation systems including bodily tissue fixation hardware comprising biocompatible, bioabsorbable (resorbable) polymeric or composite plates and fasteners for securing the plates to bodily tissue for fixation thereof, and an installation instrument which triggers (strikes) fasteners one after one into through-bores (holes) made through the plate and into the underlying bodily tissue.
BACKGROUND OF THE INVENTION
Traditional orthopedic and traumatological and cranio-maxillo-facial fixation systems to facilitate bone fracture healing (osteosynthesis) or soft tissue-to-bone healing typically employ metallic hardware, e.g., plates, screws, rods and the like, formed of biocompatible, corrosion resistant metals such as titanium and stainless steel. Typical metallic plates are described, e.g., in the book F. Séquin and R. Texhammar, AO/ASIF Instrumentation, Springer-Verlag, Berlin, Heidelberg, 1981, p. 21-22, 55-79, 107-108, 117-122, the entire disclosure of which is incorporated herein by way of this reference. While such systems are generally effective for their intended purposes, they possess a number of inherent shortcomings. For example, metal release to the surrounding tissues (see, e.g., L.-E. Moberg et al. Int. J. Oral. Maxillofac. Surg. 18 (1989) p. 311-314, the entire disclosure of which is incorporated herein by reference) has been reported. Other reported shortcomings are stress shielding (e.g., P. Paavolainen et al., Clin Orthop. Rel. Res. 136 (1978) 287-293, the entire disclosure of which is incorporated herein by reference) and growth restriction in young individuals (e.g., K. Lin et al., Plast. Reconstr. Surg. 87 (1991) 229-235, the entire disclosure of which is incorporated herein by reference). In infants and young children there is the risk that metallic plates and screws sink, as a consequence of skull bone growth, into and below the cranial bone threatening brain (J. Fearon et al., Plast. Reconstr. Surg. 4 (1995) 634-637, the entire disclosure of which is incorporated herein by reference). Therefore, it is recommended generally that non-functional implants should be removed, at least in growing individuals (see, e.g., C. Lindqvist, Brit. J. Oral Maxillofac. Surg. 33 (1995) p. 69-70, the entire disclosure of which is incorporated herein by reference).
Especially in maxillofacial and in cranial surgery metallic mini plates are popular (see, e.g., W. Muhlbauer et al., Clin. Plast. Surg. 14 (1987) 101-111; A. Sadove and B. Eppleg, Ann. Plast. Surg. 27 (1991) 36-43; R. Suuronen, Biodegradable Self-reinforced Polylactide Plates and Screws in the Fixation of Osteotomies in the Mandible, Doctoral Thesis, Helsinki University, Helsinki, 1992, p. 16, the entire disclosures of which are incorporated herein by reference; and see the references cited in the previous references). Mini plates are small, thin, narrow plates, which have holes for screw fixation. They are located typically on bone perpendicularly over the fracture to fix the bone mass on both sides of the fracture to each others. Typical geometries of mini plates are described, e.g., in U.S. Pat. No. 5,290,281, in
FIGS. 6A-6F
, the entire disclosure of which is incorporated herein by reference.
The main advantage of metallic plates, screws, etc. (like titanium, stainless steel and cobalt chrome molybdenum plates or screws), is that they are strong, and tough. Ductile metal plates can be deformed or shaped (bent) at room temperature in an operation room by hand or with special instruments to the shape of a form that corresponds to the surface topography of the bone to be fixed, so that the plate can be fixed flush on the bone surface to which the plate is applied.
Because of the shortcomings of metallic plates, bioabsorbable plates have been developed for fracture fixation. Longitudinal, six-hole plates were developed by Eitenmüller et al. for orthopaedic animal studies (European Congress on Biomaterials, Abstracts, Instituto Rizzoli, Bologna, 1986, p. 94, the entire disclosure of which is incorporated herein by reference). However, because of inadequate strength, some of the plates were broken in animal experiments involving fracture fixation.
A particular advantage of bioabsorbable plates is that they can be provided with openings for the insertion of surgical fasteners (like screws) therethrough, while also allowing means to permit the formation of additional fastener openings therethrough during a surgical procedure at the surgeon's discretion, as has been described in European Patent specification EP 0 449 867 B1, the entire disclosure of which is incorporated herein by reference.
However, the main disadvantage of most prior art bioabsorbable plates is that they can be deformed (bent) permanently and safely only at elevated temperatures above the glass transition temperature (T
g
) of the bioabsorbable polymer, as has been described, e.g., in EP 0 449 867 B1, U.S. Pat. No. 5,569,250 and U.S. Pat. No. 5,607,427, the entire disclosures of which are incorporated herein by reference. Below the respective glass transition temperatures of the bioabsorbable polymers from which they are made, most prior art bioabsorbable plates are brittle and break easily when deformed. Only at temperatures above the T
g
of the bioabsorbable polymer from which a given plate is made does the molecular structure of most prior art plates have enough mobility to allow shaping and bending of the plate, without the risk of breaking.
Because the thermal conductivity of most polymeric materials is generally poor, both heating and cooling of bioabsorbable plates are slow processes. Therefore, the clinical use of such prior art plates is tedious, slow and complex, especially if the surgeon must shape the plate several times to make it fit exactly to the form of the bone to be fixed.
K. Bessho et al., J. Oral. Maxillofac. Surg. 55 (1997) 941-945, the entire disclosure of which is incorporated herein by reference, describe a bioabsorbable poly-L-lactide miniplate and screw system for osteosynthesis in oral and maxillofacial surgery. The plates of that reference also must be heated by immersion in a hot sterilized physiologic salt solution, or by the application of hot air, until they become plastic, and only then can those plates be fitted to the surface of the bone being repaired.
EP 0 449 867 B1, the entire disclosure of which is incorporated herein by reference, describes a plate for fixation of a bone fracture, osteotomy, arthrodesis, etc., said plate being intended to be fixed on bone with at least one fixation device, like a screw, rod, clamp or some other corresponding device. The plates of that reference comprise at least two essentially superimposed plates, so as to provide a multilayer plate construction, so that the individual plates of said multilayer plate construction are flexible to provide a change of form of said multilayer plate construction to substantially assume the shape of the bone surface under the operation conditions. That change of form is accomplished by means of an external force, such as by hand and/or by a bending instrument directed to said multilayer plate construction, whereby each individual plate assumes the position of its own with respect to other individual plates by differential motion along the surfaces of the coinciding plates.
Although the above multilayer plate can fit the curved bone surface without heating of the individual plates, the clinical use of such multilayer plates is tedious, because the single plates easily slip in relation to each other before fixation. Additionally the thickness of multilayer plate system easily becomes too thick for cranio maxillofacial applications, causing cosmetic disturbance and increased risks of foreign body reaction.
To avoid the above mentioned shortcomings in the prior art devices, U.S. Pat. Appl. Ser. No. 09/036,259, the entire disclosure of which is incorporated herein by reference, describes strong a
Haers Piet E.
Happonen Harri
Kaikkonen Auvo
Karhi Olli
Sailer Hermann
Bionx Implants Oy
Kenyon & Kenyon
Reip David O.
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