Milling apparatus for implanting a joint prosthesis

#The article of manufacture and method relate broadly to a joint prosthesis and method of implanting same, and more particularly to a mammalian joint prosthesis and novel and improved method of implanting same.

#The majority of mammalian joints are hinge-type synovial joints formed where a distal end of a bone articulates with a proximal end of an opposite or complementary bone. Joint dysplasia is a common debilitating condition that affects mammals and more specifically the canine elbow joint. The current surgical techniques result in an unacceptable failure rate of the implant due to the technical difficulties associated with the implantation procedure as well as excessive post-surgical physical therapy needs as a result of the invasiveness of the procedure and the abundance of soft tissue damage.

#There is therefore a need for a novel and improved joint arthroplasty that involves a minimally invasive surgical technique with a novel implant. The following embodiments and aspects thereof are described and illustrated in conjunction with systems, tools and methods which are meant to be exemplary and illustrative, not limiting in scope. In various embodiments, one or more of the above described problems have been reduced or eliminated, while further embodiments are directed to other improvements.

#FIG. 1 is a perspective view of an embodiment of a joint prosthesis including a set plate;

#FIG. 2 is a side view of the implant of FIG. 1 including the humerus, radius and ulna;

#FIG. 3 is a side view of the implant of FIG. 1 without a set plate;

#Exemplary embodiments are illustrated in referenced figures. of the drawings. It is intended by the embodiments and figures disclosed herein are to be considered illustrative rather than limiting.

#In the embodiments shown in FIGS. 1-14, there is provided an implant 11′ with a humeral condylar component 13′ and a radioulnar component 29′. The humeral component 13′ includes a first articulating surface portion 17′ of substantially saddle-shaped configuration, as shown in FIGS. 1, 9 and 10, and an opposite first bone fixation portion 14′, as shown in FIGS. 1, 4 and 9. Geometrically, the saddle-shaped configuration of the first articulating surface portion 17′ is broadly in the form of a concave configuration along planes parallel to its major axis and generally convex in planes transverse to the major axis, the degree of convexity lessening or flattening out, toward the center of the major axis. The humeral condylar component 13′ is generally half-moon shaped, having an outer convex articulating surface 17′ and inner concave surface, and made of cobalt-chrome molybdenum (Co—CrMb), titanium, Ti-alloy or ceramic but may also be made of other materials. The first articulating surface 17′ as shown in FIG. 10 has a longitudinally extending angular groove 15′ and simulates or approximates the natural shape of a trochlea humerus which on a canine for example, is a medially located, arcuate pulley-shaped member. The groove 15′ extends diagonally across the surface and extends at an acute angle to an imaginary plane through a major axis of the first articulating surface portion 17′. The first bone fixation portion 14′ of the humeral component 13′ has a concave, semi-circular surface 21′. The concave surface 21′ is complementary to the first articulating surface 17′ and includes transversely extending cylindrical retaining members or protuberances 40′, 40″. The retaining members 40′, 40″ may be hollow or have shallow openings 41′, 41″ at one end with the open end extending up to outer peripheral edges 16′ of the first bone fixation portion 14′. The openings 41′, 41″ are designed to receive a set plate 47′ which will be discussed in more detail at a later point. The retaining members 40′, 40″ typically are evenly spaced from the ends and extend transversely to a major axis of the humeral component 13′. The retaining members 40′, 40″ may extend the width of the component 13′ and in this embodiment do not extend beyond the outer peripheral edge 16′ of the humeral component 13′. Alternatively, the retaining members 40′, 40″ could extend beyond the outer edges of the component or could end short of the outer edges of the component. The first bone fixation portion 14′ may also include porous members, such as, PCA beads 27′ which also promote bone growth. The PCA beads are manufactured by Bio-Vac, Inc., of Michigan, USA. Other possible fixation members include hydroxyl apatite (HA) coating, titanium plasma spray coating or Resorbably Blast Media Coating to name a few. Bony fixation of prosthetic implants is encouraged with surface extensions, such as, the retaining members 40′, 40″ which form a primary fixation for the implant. Beaded porous members provide secondary fixation allowing for bony ingrowth. A proximal portion 20′ of the humeral component 13′ which is the first bone fixation portion 14′ contacts a distal surface 28′ of the humerus 12′ providing for an interference fit between the bone fixation portion and the humerus 12′, as shown in FIG. 2

#The radioulnar component 29′ has opposing surfaces including a second articulating surface portion 31′ and a second bone fixation portion 33′. The radioulnar component 29′ is half-moon shaped and in the embodiment shown is slightly tapered at a posterior end 30′. Other forms of the component may also be used without a slightly tapered end as the component is designed to approximate the joint component of a particular species. The second articulating surface portion 31′ has a saddle-shaped or concave configuration that faces cranially. The articulating surface portion 31′ contains a medial ridge member 37′ having intersecting convex and concave surfaces defining alternate upwardly and downwardly curved projections. The ridge member 37′, in the embodiment shown, simulates a trochlear ridge but may also be designed to simulate the approximate anatomy of the joint such as an intercondylar eminence, articulating surface of the talus or trochlea of the human, and is complementary to the groove 15′ of the first articulating surface portion of the corresponding component 13′. The ridge 37′ as shown in FIG. 11, extends diagonally across the concave surface at a substantially mid-level portion between the concave and convex surfaces and extends at an acute angle to an imaginary line through a major axis of the second articulating surface portion 31′. The extension of the ridge 37′ approximates the natural helical shape of a trochlear notch in a canine.