Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/02—Prostheses implantable into the body
  • A61F2/30—Joints
  • A61F2/38—Joints for elbows or knees
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
  • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
  • A61F2/02—Prostheses implantable into the body
  • A61F2/30—Joints
  • A61F2/38—Joints for elbows or knees
  • A61F2002/3895—Joints for elbows or knees unicompartimental

Definitions

• the invention relates to knee prostheses of the unicompartmental type.
• this type of prosthesis comprises femoral implants shaped to be impacted separately at the level of the internal and external condyles of the femur.
• the internal or external femoral implant generally cooperates in support and sliding, with an impacted tibial implant in the internal or external compartment of the tibia.
• the tibial implant essentially has a polyethylene plate fixed in a metal base, having different arrangements, to be fixed at the level of the tibial plate.
• the femoral implant has a bearing surface whose shape and profile correspond to the anatomical profile of the internal or external femoral condyle.
• the curvature of the condylar pads in the sagittal plane does not satisfactorily reproduce the kinematics of the knee and therefore does not respect the many aspects of the mechanics of a healthy knee.
• This state of the art can be illustrated by the teaching of patent WO-A-9110408.
• the object of the invention is to remedy these drawbacks in a simple, safe, effective and rational manner.
• the problem which the invention proposes to solve is to obtain a markedly improved congruence between the tibial implant and the corresponding condyle, by making bone cuts according to three determined planes and having the objective of producing a functioning knee prosthesis. optimally, by reproducing the kinematics of the knee, in the sagittal plane, firstly, then three-dimensionally, in a second time.
• each femoral implant has three bearing surfaces corresponding to three cutting planes, namely: an anterior surface capable of bearing on the distal cut perpendicular to the anatomical axis of the femur in profile and two surfaces arranged angularly following said anterior surface, to rest on the chamfer and posterior cuts of the condyle deduced from the distal reference cut, each of said femoral implants having, in the sagittal plane, a curvature resulting from a kinematic study and a computer simulation of a healthy knee.
• each femoral implant is equipped with two anchoring pads oriented to neutralize the shearing forces.
• these anchoring pads provide primary stabilization, because their diameter is slightly greater than that of the bone drilling carried out.
• Another problem that the invention proposes to solve is that the two anchoring pads are oriented to oppose the extraction forces, to which each condylar implant is subjected during its operation.
• Another problem which the invention proposes to solve is to be able to adapt to the morphology of each patient.
• the internal condylar femoral implant has in its upper part an anatomical shape determined to never come into conflict with the patella and allow, at the point of contact with the tibia, to always remain centered with respect to the tibial implant and, at the resulting forces at this point, to be always contained in the sagittal plane of the femur.
• the tibial implant which comprises a polyethylene plate and a metal base, capable of receiving in support and sliding the tibial implant as defined, the latter is remarkable in that each plate is produced in several thicknesses in order to regulate ligament tensions and has a symmetrical shape to be implanted both on the internal side and on the external side.
• the tray has a teardrop shape to guarantee good metal-polyethylene congruence in all areas of mobility and to avoid having material in places where it is not necessary.
• the tibial base has a determined shape to adapt perfectly to that of the tibia.
• the housing of the base capable of receiving the tibial plateau, is positioned so that said plateau is always vertically in line with the trajectory of the femoro-tibial contact.
• the tibial base has a through hole formed in coaxial alignment with a stud of flared shape, formed in overflow from the underside of said base, for the engagement of a fixing screw.
• the underside of the tibial base has, in overflow, anterior and posterior medial spurs, capable of improving the rotary stability of the tibial base, especially when tightening the screw.
• FIGS. 1A, 1B, 1C and 1D are perspective views showing before assembly of the main elements of the prosthetic assembly according to the invention
• FIG. 1A shows the femoral implant
• FIG. B shows the tibial plateau
• FIG. 1C shows the fixing screw of the tibial base
• Figure 1D shows the tibial base.
• Figure 2 is a sectional view of a femoral implant.
• Figure 2A is a sectional view of a form of preferred embodiment of the femoral implant, there is shown in broken lines, the femur with its mechanical axis (XX ').
• Figure 3 is a front view corresponding to any of Figures 2 and 2A.
• Figure 4 is a sectional view of the tibial implant.
• FIG. 5 is a plan view corresponding to FIG. 4.
• Figure 6 is a sectional view showing the implantation of the prosthetic assembly according to the invention.
• Figure 7 is a perspective view of an exemplary embodiment of an apparatus, capable of ensuring the tibial cuts.
• Figure 8 is a perspective view of an exemplary embodiment of devices capable of ensuring femoral cuts.
• the prosthetic assembly for the knee joint comprises a range of femoral implants (1) of the unicompartimental type, and a range of tibial implants (2).
• each tibial implant (1) has three bearing surfaces (1a) (1b) (1c) corresponding to three cutting planes.
• the median bearing surface (1a) is able to bear on the distal section of the condyle, which is formed perpendicular to the mechanical axis (XX ') of the lower limb. From this reference cut, the chamfer and the posterior cut of the condyle are deduced. Consequently, the bearing surfaces (1b) and (1c) are arranged angularly with respect to the median bearing surface (1a) to correspond respectively to the chamfer and to the posterior cut.
• These different cutting planes (1a) (1b) and (1c) are advantageously combined with the curved profile (1d) of the implant.
• this curved profile (1d) results from a kinematic study and from a computer simulation of a healthy knee, in order to obtain a prosthesis functioning in an optimal manner, while respecting the numerous aspects of knee mechanics, to give the knee joint optimal movements.
• the bearing surfaces have two anchoring pads (1e) (1f) whose orientation is determined for the neutralization of shear forces (anchoring pad - condyle).
• one of the anchoring pads (1f) is centered on the middle of the median bearing surface (1a), at an angle of 90 ° with this surface.
• the other stud (1e) is arranged on the middle of the bearing surface (1c), being oriented in a parallel manner to the stud (1f). Under these conditions, the two anchoring pads (1e) and (1f) oppose the extraction forces, to which each condylar implant is subjected during its operation.
• Such anchoring is reinforced by a surface treatment allowing the bone or the surgical cement to adhere.
• the state of the internal surface of the condyle is seed, that is to say that its geometry is composed of recesses of diameter of approximately 150 to 200 ⁇ m, thus increasing the surface of contact with the bone or cement. This geometry is such that it is optimal for bone regrowth.
• the condyle can be laid without cement.
• the diameter of the studs is greater than that of the holes made in the bone, to allow force impaction and ensure primary stabilization.
• the implant is perfectly stable and reliable in its positioning and therefore ensures good transmission of the forces to the bone, by limiting the shearing forces.
• the thickness of metal added by the placement of the implant determines compliance with the joint space, namely its strict orthogonality with respect to the mechanical axis of the femur (quantity of resected bone + missing cartilage).
• the prosthetic assembly according to the invention has a range of femoral implants (1), distributed by size to adapt to the morphology of each patient, being divided into three sub-families, namely:
• the internal condylar femoral implant has, in its upper part, an anatomical shape determined to never come into conflict with the patella. In addition, this shape is determined so that at all times, the condylar implant is, on the one hand, centered with respect to the tibial implant and that, on the other hand, the forces are always exerted in its middle. , leaving little room for shearing.
• the tibial implant (2) comprises, in a known manner, a polyethylene plate (2a) and a metal base (2b), in particular made of titanium.
• the plate (2a) receives in support and sliding, the condylar implant (1).
• the tray is executed in several thicknesses, to adjust the ligament tensions and has a symmetrical shape to be implanted both on the internal side and on the external side.
• This plate (2a) also has a teardrop shape, to guarantee good metal-polyethylene congruence in all areas of mobility and to avoid having material in places where this is not necessary. On the other hand, this teardrop shape allows the maximum amount of material to be obtained where the wear is greatest.
• the tibial base (2b) has a determined shape to adapt perfectly to the corresponding tibial compartment.
• the base is fixed in the corresponding tibial compartment by means of a screw (3) which passes through a stud (2b2) formed in overflow from the underside of said base (2b).
• This stud (2b2) is flared to give retentivity relative to the cement or the bone, after the bone regrowth.
• the underside of the base has lateral spurs (2b3) for blocking the rotation of said base.
• the tibial cuts are carried out by means of an apparatus of the type of that illustrated in FIG. 7.
• This apparatus comprises a body (4) having a slot (4a) for the passage of a saw blade or the like, in order to ensure horizontal cutting.
• the body (4) receives a turret (5) mounted with displacement capacity guided in translation.
• This turret is also mounted with angular orientation capacity, on the body (4) and has a vertical slot (5a) for the passage of a saw blade, in order to make the vertical cut.
• the entire device is stabilized relative to the tiba, for example by means of nails.
• FIG. 8 an assembly of the type illustrated in FIG. 8 is used.
• This assembly comprises a femoral cutting guide (6) able to be mounted on a support member (7), at means of pins (8).
• the support member (7) cooperates with a central medullary rod.
• the guide (6) has a block (6a) equipped with slots (6b), to ensure the distal cut perpendicular to the anatomical axis of the femur of the profile.
• the posterior and chamfer cuts are made by a profiled block (9) having slots (9a) and (9b), for the passage of a saw blade.
• the prosthetic assembly according to the characteristics of the invention, respects the kinematics, therefore the movement of the knee, while minimizing the forces acting within this joint, by making profiles known as kinematically admissible, which are not a simple replica of the anatomy.
• profiles known as kinematically admissible which are not a simple replica of the anatomy.

Landscapes

• Health & Medical Sciences (AREA)
• Orthopedic Medicine & Surgery (AREA)
• Physical Education & Sports Medicine (AREA)
• Cardiology (AREA)
• Oral & Maxillofacial Surgery (AREA)
• Transplantation (AREA)
• Engineering & Computer Science (AREA)
• Biomedical Technology (AREA)
• Heart & Thoracic Surgery (AREA)
• Vascular Medicine (AREA)
• Life Sciences & Earth Sciences (AREA)
• Animal Behavior & Ethology (AREA)
• General Health & Medical Sciences (AREA)
• Public Health (AREA)
• Veterinary Medicine (AREA)
• Prostheses (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=9461363

Family Applications (1)

Country Status (3)

Families Citing this family (15)

Family Cites Families (7)

• 1994
  • 1994-03-17 FR FR9403436A patent/FR2717373B1/fr not_active Expired - Lifetime
• 1995
  • 1995-03-17 EP EP95913210A patent/EP0699059A1/de not_active Withdrawn
  • 1995-03-17 WO PCT/FR1995/000324 patent/WO1995024874A1/fr not_active Ceased

Non-Patent Citations (1)

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