Double-compartment knee joint prosthesisTechnical Field
The invention belongs to the technical field of medical orthopedic prostheses, and particularly relates to a bicompartmental knee joint prosthesis.
Background
Knee prostheses currently existing in the market are mainly classified into two types: one is a unicompartmental knee joint prosthesis, which comprises a unicondylar prosthesis for replacing a unilateral femoral tibia joint surface and a patellofemoral joint prosthesis for replacing a patellofemoral joint surface; the other type is a three-compartment knee joint prosthesis which needs to be replaced by a patellofemoral joint surface and two lateral femoral-tibial joint surfaces.
When a patient suffers from unicompartmental knee joint pathological changes, a unicondylar prosthesis or a patellofemoral joint prosthesis can be adopted, and when the patient suffers from tricompartmental knee joint pathological changes, a tricompartmental knee joint prosthesis can be adopted; however, when the patient suffers from only a bicompartmental knee joint lesion on the medial and lateral femoral-tibial articular surfaces, the knee joint replacement can be performed only by using a tricompartmental knee joint prosthesis due to the restriction of the type of the knee joint prosthesis.
As shown in fig. 1, the inner surface of the currently marketed tricuspid knee prosthesis consists of five planes angled with respect to each other. When the patient only suffers from the pathological changes of the medial and lateral femoral-tibial articular surfaces but the patellofemoral joint is intact, the patellofemoral articular surfaces have to be replaced together due to the limitation of the types of knee joint prostheses. The amount of osteotomy of the femoral condyle increases as the patellofemoral facet that is not diseased is replaced. Research data prove that if a three-compartment knee joint prosthesis is used, the patella of a patient body is kept in the knee joint replacement process (the patellofemoral joint surface of the patient body cannot be kept at the same time), and due to the design factors of the patellofemoral joint surface of the three-compartment knee joint prosthesis, the patella of the patient body is easy to be unstable and even dislocated, and the knee joint cannot move freely. The incidence of patella instability is 16.7% -28.6%, which is quite high. If can remain patient's body patellofemoral articular surface at knee joint replacement in-process for patient's body patellofemoral moves in body thighbone pulley groove, the unstable incidence of patella can greatly reduced. Meanwhile, since the inner surface of the tricuspid knee prosthesis is generally composed of five planes at an angle, this structure cannot maximally maintain the bone mass of the femur, and since there is an angle between the planes, a stress concentration phenomenon is easily generated, resulting in fracture of the femur.
The tricuspid knee joint prosthesis is usually made of alloy materials, the hardness of the alloy materials is far higher than that of patellar cartilage, and long-term relative movement between the patellar and a patellar joint surface of the tricuspid knee joint prosthesis can cause abrasion of the patellar cartilage and even fracture of the patella.
In addition, the knee joint prosthesis is generally required to be matched with a tibial gasket for use, so the wear amount of the knee joint prosthesis on the tibial gasket is an important index for measuring the performance of the knee joint prosthesis.
Disclosure of Invention
The invention provides a bi-compartmental knee joint prosthesis, which does not need to replace the patellofemoral joint surface of a patient, and the inner side surface of the knee joint prosthesis is formed by a plurality of sections of tangent circular arcs; one of the purposes of the invention is to enable the patellar femur to naturally move on a healthy femur sliding surface, keep a normal movement track and have no problem of patellar abrasion; meanwhile, the bone cutting amount of the femoral condyle is reduced, the stress concentration is reduced, and the fracture of a patient is prevented.
The invention provides a bicompartmental knee joint prosthesis, and the second purpose is to reduce the abrasion loss of the knee joint prosthesis to a tibia liner by reasonably setting the shapes of the inner side surface and the outer side surface of the knee joint prosthesis.
The technical scheme provided by the invention is as follows:
a bicompartmental knee prosthesis comprising:
two main body parts connected by a cross beam; wherein,
the longitudinal cross-section of the body portion comprises a longitudinal inner contour and a longitudinal outer contour;
the longitudinal inner contour line consists of a plurality of longitudinal circular arcs, and the adjacent longitudinal circular arcs are tangent;
a longitudinal outer contour line having the same shape as the longitudinal inner contour line, the longitudinal outer contour line and the longitudinal inner contour line being connected at both ends thereof by a transition line, respectively;
the transverse cross section of the body portion comprises a transverse inner contour line and a transverse outer contour line;
a transverse inner contour line which is a straight line;
the transverse outer contour line is composed of a plurality of sections of transverse circular arcs, and the adjacent transverse circular arcs are tangent.
Preferably, the cross member is connected to one end of the two main body portions in a transverse direction of the main body portions.
Preferably, the longitudinal inner contour line sequentially comprises a first longitudinal arc, a second longitudinal arc and a third longitudinal arc from one end far away from the cross beam to one end close to the cross beam; wherein,
the curvature radius of the first longitudinal arc is 30-50 mm;
the curvature radius of the second longitudinal arc is 18-26 mm;
the curvature radius of the third longitudinal arc is 13-18 mm.
It is preferable that the first and second liquid crystal layers are formed of,
the central angle corresponding to the first longitudinal arc is 27-28 degrees;
the central angle corresponding to the second longitudinal arc is 62-63 degrees;
the central angle corresponding to the third longitudinal arc is 70-71 degrees.
Preferably, the transverse outer contour line comprises, in sequence, a first transverse arc and a second transverse arc from a side remote from the cross beam to a side close to the cross beam, wherein,
the curvature radius of the first transverse arc is 43 mm-44 mm;
the curvature radius of the second transverse arc is 27-28 mm.
It is preferable that the first and second liquid crystal layers are formed of,
the central angle corresponding to the first transverse arc is 9-23 degrees;
the central angle corresponding to the second transverse circular arc is 35-36 degrees.
Preferably, the inner side surfaces of the cross member are extended surfaces of the inner side surfaces of the two main bodies.
Preferably, the outer side surface of the cross beam is a curved surface, and the outer side surface of the cross beam smoothly transitions with the outer side surfaces of the two main body parts, so that the thickness of the cross beam gradually decreases from two ends to the middle to form a concave part.
Preferably, the length of the cross beam is 16mm to 17 mm.
Preferably, the two main bodies are provided with fixing pins on the inner sides thereof, respectively.
The invention has the beneficial effects that:
(1) the double-compartment knee joint prosthesis provided by the invention is suitable for patients with only femoral tibia internal and external articular surface pathological changes; the patellofemoral joint surface of a patient does not need to be replaced, so that the patellofemoral joint can naturally move on a healthy femoral sliding surface, a normal movement track is kept, and the problem of patella abrasion does not exist.
(2) The bicompartmental knee joint prosthesis provided by the invention can reduce the bone cutting amount of the femoral condyle, furthest reserve the bone amount of the femur of a patient, reduce stress concentration and prevent fracture of the patient.
(3) The bicompartmental knee joint prosthesis provided by the invention can reduce the size of skin and soft tissue incisions and reduce the bone cutting amount and the bleeding amount, and is suitable for minimally invasive surgery.
(4) The bicompartmental knee joint prosthesis provided by the invention has small abrasion loss to the tibial gasket, so that the service life of the tibial gasket is prolonged, and the period of knee joint replacement surgery is prolonged.
Drawings
Fig. 1 is a schematic structural view of a conventional tricuspid knee prosthesis.
FIG. 2 is a schematic medial side view of a bicompartmental knee prosthesis of the present invention.
FIG. 3 is a schematic lateral view of a bicompartmental knee prosthesis of the present invention.
Fig. 4 is a longitudinal cross-sectional view of a joint according to the invention.
Figure 5 is a transverse cross-sectional view of a joint according to the invention.
Detailed Description
The present invention is further described in detail below with reference to the attached drawings so that those skilled in the art can implement the invention by referring to the description text.
As shown in fig. 2-3, the present invention provides a bicompartmental knee prosthesis, which comprises a main body part 110 and a main body part 120, wherein the main body part 110 and the main body part 120 are respectively used for replacing a medial condyle articular surface and a lateral condyle articular surface of a femoral condyle, and the main body part 110 and the main body part 120 are connected through a crossbeam 130; the cross beam 130 is disposed along the transverse direction of the main body, the cross beam 130 is connected to one end of the main body 110 and one end of the main body 120, and the other end of the main body 110 and the other end of the main body 120 are free ends. In the longitudinal direction of the knee joint prosthesis, the outer edge line 130a of the cross member 130 does not extend beyond the end 111 of the body portion 110 and the end 121 of the body portion 120. The main body 110 and the main body 120 have the same structure, and are provided at both ends of the cross member 130 in mirror symmetry. The insides of the body portions 110 and 120 are provided with fixing pins 110a and 120a, respectively, for preventing the bicompartmental knee prosthesis from rotating on the femur.
The inner surface 131 of the cross member 130 is an extension of the inner surface of the body 110 and the inner surface of the body 120. The outer side 132 of the cross member 130 is a curved surface, and smoothly transits between the outer side of the main body 110 and the outer side of the main body 112, so that the thickness of the cross member 130 gradually decreases from two ends to the middle, and a smooth recess 132a is formed at the middle of the cross member 130 for engaging with the tibial pad. The cross member 130 is configured to be smoothly curved at an inner edge line 130b near the free ends of the main body 110 and the main body 120 and to form a smooth transition with the main body 110 and the main body 120.
In this embodiment, the length of the beam 130 is 16mm to 17mm, the width of both ends (the widest part) of the beam 130 is 15mm, and the width of the middle (the narrowest part) of the beam 130 is 3 mm.
As shown in fig. 4, taking the body portion 110 as an example, the longitudinal section of the body portion 110 includes a longitudinal inner contour line 112 and a longitudinal outer contour line 113; and a transition line 114 and a transition line 115 connected at both ends of the longitudinal inner contour line 112 and the longitudinal outer contour line 113; the transition line 114 at the free end of the body portion 110 is composed of a rounded curve 114a connected with the longitudinal inner contour line 112 and a rounded curve 114b connected with the longitudinal outer contour line 113, and the rounded curve 114a and the rounded curve 114b respectively form a rounded transition between the longitudinal inner contour line 112 and the longitudinal outer contour line 113. The transition line 115 near one end of the cross beam 130 is a multi-segment line, which forms a smooth transition with the longitudinal inner contour line 112 and the longitudinal outer contour line 113, respectively, and the transition line 115 forms the end surface shape of the knee joint prosthesis. The longitudinal inner contour line 112 is composed of a plurality of longitudinal circular arcs, and the adjacent longitudinal circular arcs are tangent; the longitudinal outer contour line 113 and the longitudinal inner contour line 112 are identical in shape and size.
In the present embodiment, the longitudinal inner contour line 112 and the longitudinal outer contour line 113 are each composed of three tangential longitudinal arcs. Taking the longitudinal inner contour line 112 as an example, it includes a first longitudinal circular arc 112a, a second longitudinal circular arc 112b and a third longitudinal circular arc 112 c; the curvature radius of the first longitudinal arc 112a is 30 mm-50 mm, and the corresponding central angle is 27-28 degrees; the curvature radius of the second longitudinal arc 112b is 18 mm-26 mm, and the corresponding central angle is 62-63 degrees; the curvature radius of the third longitudinal arc is 13 mm-18 mm, and the corresponding central angle is 70-71 degrees. The first longitudinal arc 112a is connected to a transition line 114, and the third longitudinal arc 112c is connected to a transition line 115.
As shown in fig. 5, taking the body portion 110 as an example, the transverse cross section of the body portion 110 includes a transverse inner contour line 116 and a transverse outer contour line 117; the transverse inner contour line 116 and the transverse outer contour line 117 are connected through a transition line 118 and a transition line 119, the transition line 118 and the transition line 119 are straight lines, and the connection positions of the transition line 118 and the transition line 119 and the transverse outer contour line 117 are respectively rounded. The transverse inner contour line 116 is a straight line, and the transverse outer contour line 117 is composed of a plurality of transverse circular arcs, and adjacent transverse circular arcs are tangent.
In this embodiment, the transverse outer contour line 117 sequentially includes a first transverse arc 117a and a second transverse arc 117b from a side away from the cross beam to a side close to the cross beam 130, wherein a curvature radius of the first transverse arc 117a is 43mm to 44mm, and a central angle corresponding to the first transverse arc is 9 ° to 23 °; the curvature radius of the second transverse circular arc 117b is 27 mm-28 mm, and the central angle corresponding to the second transverse circular arc is 35-36 degrees.
In the knee joint prosthesis replacement surgery, a guide tool, a milling cutter or a surgical robot is used for arc-shaped grinding treatment of the femoral condyle, holes are punched on the inner side and the outer side of the far end of the femur (fixing pins for inserting the bicompartmental knee joint prosthesis), and the bicompartmental knee joint prosthesis is implanted. The bicompartmental knee joint prosthesis can reduce the incision size of skin and soft tissue, reduce the bone cutting amount and the bleeding amount, and is suitable for minimally invasive surgery. The inner surface of the double-compartment knee joint prosthesis is attached to the bone surface, the double-compartment knee joint prosthesis can be fixed through bone cement or natural bone ingrowth between the bone and the prosthesis, and the outer surface of the double-compartment knee joint prosthesis is used for replacing the inner and outer condyle articular surfaces of the femur. The fixing pins on both sides are used for preventing the bicompartmental knee prosthesis from rotating on the femur. The external surface of the bicompartmental knee joint prosthesis is contacted with the tibia prosthesis to form a femoral-tibial joint surface, and the knee joint movement of the patient body is replaced by the relative movement between the prostheses. Because the patellofemoral joint surface is not replaced, the patellofemoral joint can naturally move on a healthy femoral trochlear surface, and a normal movement track is kept.
The inner surface of the bicompartmental knee joint prosthesis is a smooth curved surface formed by a plurality of sections of circular arc surfaces, so that the bone cutting amount of the femoral condyle can be reduced compared with the tricompartmental knee joint prosthesis, the bone amount of the femur of a patient is reserved to the maximum extent, the stress concentration is reduced, and the fracture of the patient is prevented.
Test example 1
And (3) carrying out osteotomy on the artificial knee joint artificial bone and then installing the bicompartmental knee joint prosthesis. The knee joint artificial bone is flexed to enable the patella to move from top to bottom along the femoral trochlear groove until the patella completely enters the intercondylar notch. And evaluating whether the track in the patella movement process is good or not.
Test samples:
artificial knee prosthesis model 10 pieces; a bicompartmental knee prosthesis 10.
And (4) test conclusion:
the patella in the artificial knee joint artificial bone can keep a good motion track in the knee joint buckling process, and the phenomena of patella dislocation, instability and the like do not occur. When the knee joint is highly flexed, the patella can smoothly transit on the patellofemoral joint surface and the bicompartmental knee joint prosthesis until completely entering the intercondylar notch.
Test example 2
And carrying out stress analysis on the conventional three-compartment femoral condyle prosthesis model and the bicompartmental knee prosthesis model through finite element analysis software.
The test method comprises the following steps:
simulating the state of the conventional three-compartment femoral condyle prosthesis and the double-compartment knee joint prosthesis after being implanted into a human body, setting the elastic modulus of the prosthesis to be 225Gpa and the Poisson ratio to be 0.3, applying longitudinal load to the prosthesis and the Poisson ratio to be 1500N (equivalent to 2 times of the weight of an adult), and calculating the maximum Mises stress generated by the prosthesis and the Poisson ratio through finite element analysis. The test was performed in two groups, 5 persons each, the first group calculating the maximum Mises stress of a conventional three compartment femoral condyle prosthesis and the second group calculating the maximum Mises stress of a bicompartmental knee prosthesis.
And (3) test results:
specific test data are shown in table 1.
TABLE 1 test results
And (4) test conclusion:
the first set of maximum stresses is generally higher than the second set, the maximum stresses occurring at the intersection of the planes of the inner surface of the prosthesis (cusps).
As can be seen from test example 2, the bicompartmental knee prosthesis is uniformly stressed and can reduce the stress generated by the prosthesis compared with the traditional knee prosthesis.
Test example 3
Wear comparative tests were performed on a bicompartmental knee prosthesis and a tricompartmental knee prosthesis.
Test samples:
a bicompartmental knee prosthesis 5 piece and a tibial insert 5 piece fitted thereto.
The component 5 of the tricuspid knee joint prosthesis with the patellofemoral joint surface, and the tibial gasket and the patellar component which are matched with the component 5.
The specific test sample numbers are shown in Table 2.
TABLE 2 Knee prosthesis numbering
The test method comprises the following steps:
the wear tests were carried out according to ISO 14243-1 on both groups of products, respectively, using the method of wear testing under load control.
The control group required simultaneous loading of the patellar component at 2500N.
Number of load cycles 5X 106。
The wear measurement was carried out according to the gravimetric method provided by ISO 14243-2.
And (3) test results:
specific test data are shown in table 3.
TABLE 3 test data
And (4) test conclusion:
the amount of wear that a bicompartmental knee prosthesis generates on the tibial gasket is much less than that of a tricompartmental knee prosthesis.
As can be seen from test example 3, the bicompartmental knee prosthesis provided by the invention has small abrasion loss to the tibial gasket, can prolong the service life of the tibial gasket, and thus prolongs the period of knee replacement surgery.
While embodiments of the invention have been described above, it is not limited to the applications set forth in the description and the embodiments, which are fully applicable in various fields of endeavor to which the invention pertains, and further modifications may readily be made by those skilled in the art, it being understood that the invention is not limited to the details shown and described herein without departing from the general concept defined by the appended claims and their equivalents.