CZ21503U1 - Joint implant, particularly knee joint implant - Google Patents

Description

Joint implant, especially a knee joint

Technical field

The invention relates to a joint implant, in particular a knee joint consisting of a femoral part, an insert and a tibial part.

BACKGROUND OF THE INVENTION

There are a number of causes that can lead to joint disease. Most often it is degeneration, ie aging and wear of joint cartilage - osteoarthritis, primary and secondary. The causes of primary osteoarthritis are not exactly known. Secondary osteoarthritis occurs as a result of other diseases such as traumatic involvement, metabolic disease - gout, autoimmune involvement - rheumatoid arthritis, etc.

An example would be physiological movement in the knee joint, which is a complex combination of rolling, rotating and sliding movements. The joint load when walking on a flat surface is several times the body weight, while walking up the stairs, uphill and carrying loads, the load increases further. These facts determine the level of demands on implant design, surgical technique and postoperative rehabilitation.

There are many research and development centers around the world dealing with the treatment problem with a number of existing solutions that are commonly used to treat the knee joint. Known solutions are described, for example, in: HIDEOMIWATΑΝΑΒΕ, ADEL REFAAT AHMED, TETSUYA SHINOZAKI, TAKASHI YANANAGAWA, MASANORI TERAUCHI AND KENJI TAKAGISHI. Reconstruction with autologous pasteurized whole knee joint II: application for osteosarcoma of the proximal tibia, In: Journal of Orthopaedic Science. Volume 8, Number 2 / March, 2003, pp. 676; G. PAPACHRISTOU. Photoelastic study of intemal and contact stresses on knee joint before and after osteotomy Journal. Archives of Orthopedic and Trauma Surgery. Volume 124, Number 5 / June, 2004, pp. 533; JOEL L. LANOVAZ AND RANDY E. ELLIS. Experimental Validation of 3D Dynamic Finite-Element Model of Total Knee Replacement. Medical Image Computing and Computer-Assisted Intervention. Volume 3749/2005, p. J, BRUNS, M. VOLKMER AND S. LUESSENHOP. Pressure distribution at knee joint. Archives of Orthopedic and Trauma Surgery. Volume 113, Number 1 / December, 1993, pp. 224; MAHONEY, O., McClung C., PHIL M., SCHMALZRIED, T. Improved Extensor Mechanism Function with Scoipio Total Knee Replacement, Orthopedic Research Society Annual Meeting, 1999. Available at: www.stiyker.com/orthopaedics/sites/scorpioknee /scorpiorefs.php; SEDLÁK, J. Prototyping Technology with Support of Reverse Engineering and CAD / CAM: Dissertation. Bmo: Brno University of Technology, Faculty of Mechanical Engineering, Institute of Manufacturing Technology, 2008, 104 s, 11 supplements. Thesis supervisor doc. Ing. Miroslav PISKA, CSc .; SEDLÁK, J .; PÍŠKA, M. Modem technologies of implant products with reverse engineering and CAD / CAM support. In TRANSFER 2008. Trenčín: Digital Graphic, 2008. pp. 66-67. ISBN: 97880-8075-357-3; MARC-ANTOINE ROUSSEAU, JEAN-YVES LAZENNEC AND YVES CATONNE. Early mechanical failure in total knee arthroplasty International Orthopedics. International Orthopedics 10.1007 / s00264-006-0276-7, 2005, p.117; ROZKOŠNÝ, L. How to make fully functional metal parts directly from 3D CAD data. [online]. February 2008 [cit. May 20, 2008]. Available on the World Wide Web:

<http://www.techtydenik.cz/detail.php?action=show&id=3698&mark=>. Wohlers, T. "Wohlers Report 2007, State of the Industry Annual Worldwide Progress Report", Wohlers Associates, Inc. 2007; LEYENS, Ch., PETERS, M. Titanium and Titanium Alloys. Fundamentals and Applications. Willet-VCH., Cologne, Germany, 2nd ed., 2005, p. 513, ISBN 3-527-30534-3. The treatment is usually accompanied by a relatively extensive surgical intervention into the patient's body and is quite expensive.

-1 CZ 21503 Ul

The known total knee replacement is an assembly consisting primarily of three major components used to restore the natural function of the knee joint. It is the femoral part, the insert and the tibial part. The basic segment of the total knee replacement assembly is its femoral component.

The currently used femoral components are now manufactured from biocompatible Cr-Co-Mo or Ti-alloys by casting and chip machining methods. Femoral components are manufactured in standardized sizes to suit the widest possible range of patients. The inner shape of the femoral component is formed by five planes ensuring a proper fit of the restoration to the distal part of the femur. The fixation of the restoration is in most cases ensured by means of two pins and bone cement - in case of using a cemented restoration. In the case of a cementless restoration, fixation is ensured by gradual ingrowth of the bone into the porous interior of the restoration. The disadvantages of these solutions are, in particular, the relatively excessive weight and high rigidity of the femoral components, given both by the size range, the shape and the applied material. These attributes contribute to a higher specific load on the contact points, mainly due to gravity and inertia forces, which can lead to implant loosening and repeated surgery. Another disadvantage is the relatively large loss of the patient's own bone due to osteotomy and implant implantation to the bone. Also, there is a need to repeat the operation after some time, accompanied by further loss of the original bone and increasing the size of the implant.

Another disadvantage is the method of fixing the pins by drilling, which is technologically simple but does not prevent axial release of the restoration.

The essence of the technical solution

The above drawbacks are largely eliminated by a joint implant, in particular a knee joint, consisting of a femoral portion, an insert and a tibial portion, according to the present invention. Its essence is that the femoral portion of the knee replacement consists of a shell attachable to the distal femur, using a trimmed, offset, and smoothed surface of the distal portion of the patient's femur that respects the total curvature of the knee joint as the reference surface.

Preferably, the outer transverse and anterior-posterior dimensions of the shell correspond to the particular knee joint of the patient.

In a preferred embodiment, the shell is provided on its inside with ribs positioned transversely and longitudinally to engage grooves operatively formed in the distal portion of the patient's femur. The shell is preferably made of a biocompatible material.

The aforementioned joint implant is made by evaluating the CT data of the patient's affected knee joint and creating an individual 3D shell model based on editing this data in a CAx application. The final 3D model is then converted to STL format in high resolution, whereupon the shell is made using, for example, the additive DMLS (Direct Metal Laser Sintering) method, where:

CT - Computed tomography - is a medical imaging technique utilizing computed tomography and providing a three-dimensional image of an object;

CAx - Computer-Aided Technologies - is a term covering a wide field of application of computer technology for design, analysis and production of components;

STL - Stereolithography - is a type of format for storing three-dimensional object data and is used for a number of computer programs supporting part production; and

DMLS - Direct Metal Laser Sintering - is a manufacturing method that uses the technology of gradual bonding of particles using a laser.

-2EN 21503 Ul

The trimmed, offset and smoothed area of the distal portion of the patient's femur, which respects the total curvature of the knee joint, is used as a reference surface to determine the inner and outer shape of the shell. The external dimensions are chosen with respect to the specific knee joint, and individually for each patient. When the layer thickness is assigned to the reference surface, the desired knee joint shell is formed. The thickness of the shell is chosen with a view to maintaining the correct functioning of the implant.

Fixation to the knee joint is accomplished by a system of ribs suitably positioned in the transverse and longitudinal directions on the inside of the knee replacement shell. The ribs fit into grooves operatively formed in the distal portion of the patient's femur.

The replacement is made, for example, by additive DMLS technology from a biocompatible material characterized by low density, high strength to density ratio and specific tribological properties.

The subject of the technical solution is a new type of shell joint implant, including the overall concept and implementation of its production technology. The shell-type implant may be useful as a replacement for cartilage degradation not only in human knee joints. The concept of the proposed technology consists of acquiring the patient's CT data, processing it and obtaining the desired joint model. Based on these data, the corresponding joint replacement model is created in the CAx application, which is then implemented in an additive way of production from a biocompatible alloy.

A significant benefit of this type of joint replacement is the achievement of less intervention in the patient's body with a reduction in the femoral incision, a significant preservation of the bone mass itself, a reduction in surgery time and a reduction in cost.

The shell implant of the femoral component is designed to maintain the same performance parameters as the existing implants manufactured in series. Compared to existing implants, the shell implant allows the patient to retain more bone mass, reduce the extent of surgery as well as surgical and postoperative trauma. The main advantage of the shell implant is its shape, derived from the actual shape of the patient's femur with relatively small thickness, which makes it unnecessary to perform extensive resection of the distal part of the femur, as with commonly used femoral components. The rib system on the inside of the implant ensures simple fixation and stiffness of the implant. It is also apparent from the foregoing description that the shell replacement is lighter in weight and overall, the operation is more patient friendly.

For the formation of the shell replacement, CT data of the patient's affected knee joint is sufficient, from which the STL model of the knee joint is subsequently created. Based on the editing of this data in the CAx application, an individual 3D model of the shell replacement is created. The final 3D model is then converted to STL format in high resolution, which ensures sufficient surface quality of the shell implant. The production itself is performed, for example, by the additive DMLS method belonging to the rapid prototyping technology of biocompatible material. This alloy is characterized by excellent mechanical properties and corrosion resistance combined with low specific gravity.

The new type of shell implant provides the following benefits: the preservation of the femur to a much greater extent than previously necessary for the necessary revision operations; maintaining the range of momentum and anatomical load; reducing the risk of displacement of the shell implant; restoring the natural function of the knee joint with a long-lasting, highly durable implant; lower production and operating costs due to reduced material consumption, shortened operation time, etc .; another advantage is a significant reduction in the weight of the shell implant relative to the existing implant type, and more advantageous specific loading of the implant-bone interface surfaces. Advantages also include less post-operative trauma to patients - reducing treatment time and reducing or eliminating repetitive surgery and implant replacement.

-3 CZ 21503 Ul

Overview of the drawings

The articular implant according to the present invention will be described in more detail with reference to the accompanying drawing, in which: Fig. 1 is a perspective view of a shell implant implanted on the distal part of the femur. FIG. 2 is an axonometric view showing the inside of a shell implant with fixation ribs.

Examples of technical solution

An exemplary knee joint implant consists of a femoral portion, a PE insert, and a tibial portion. The femoral part of the knee replacement consists of a shell i attachable to the distal part of the femur 2. The trimmed, offset and smoothed surface of the distal part of the femur 2 of the patient that respects the total curvature of the knee joint is used as the reference surface. The external transverse and anterior-posterior dimensions of the shell 1 correspond to the particular knee joint of the patient. The thickness of the X shell is selected with a view to maintaining the correct functionality of the implant. The shell 1 is provided on its inner side with ribs 3 positioned in a transverse and longitudinal direction, engaging grooves operatively formed in the distal part of the patient's femur 2. The shell 1 is made, for example, of a biocompatible material Ti16A14V.

The fixation of the shell 1 on the knee joint is accomplished by a system of ribs 3 which fit into grooves operatively formed in the distal portion of the patient's femur 2.

In the method of manufacturing this joint implant, the CT data of the patient's affected knee joint is evaluated. By editing this data in a CAx application, an individual 3D shell model 1 is created. The final 3D model is then converted to STL format in high resolution, then the shell 1 is made using, for example, the additive DMLS method. The replacement is made of a biocompatible material that is characterized by low density, high strength to density ratio and specific tribological properties.

Industrial applicability

The articular implant according to this technical solution finds application especially in medicine surgery and orthopedics.

PROTECTION REQUIREMENTS

Claims (4)

Joint implant, in particular a knee joint, comprising a femoral portion, an insert and a tibial portion, characterized in that the femoral portion of the knee replacement is formed by a shell (1) attachable to the distal portion of the femur (2), the outer shape of the shell (1) is in the shape of a cropped, offset and smoothed area of the distal portion of the patient's femur (2), respecting the total curvature of the knee joint. Joint implant according to claim 1, characterized in that the external transverse and anterior-posterior dimensions of the shell (1) have dimensions corresponding to the particular knee joint of the patient. An articular implant according to claim 1, characterized in that the shell (1) is provided on its inner side with ribs (3) positioned transversely and longitudinally with the grooves operatively formed in the distal part of the patient's femur (2). Joint implant according to claim 1, characterized in that the shell (1) is made of a biocompatible material.