Extracapsular surgical procedure and surgical referencing instrument therefor

#This application relates to surgery for repair of injured articulating joints between bones in mammals, and to a method and a device for use therein.

#The caudal and cranial cruciate ligaments are the primary stabilizers of the stifle joint in mammals such as canines. The caudal cruciate ligament originates from the lateral side of the medial femoral condyle and inserts on the medial aspect of the popliteal notch of the tibia. The cranial cruciate ligament originates from the medial side of the lateral femoral condyle and inserts on the cranial medial tibial plateau. In canines, the stifle joint is normally capable of flexion and extension with a 110 degree range of motion, varus and valgus angulation, and internal and external rotation. The stifle is extended by the quadriceps muscle group. Injury to a cruciate ligament will commonly result in destabilization of the joint. The joint must be surgically stabilized following such an injury.

#Current surgical techniques for anterior cruciate ligament replacement and/or stabilization in canine knee or stifle joints are grouped into extracapsular procedures and intracapsular procedures. Intracapsular procedures require a graft from an adjacent tissue such as the straight patellar tendon or the fascia lata, which is detached from its origin and inserted or repositioned through tunnels bored in the distal femur and/or proximal tibia. This surgery is done inside the joint capsule, with both ends of the transplant being fixed to the walls of the tunnels and/or adjacent bone. Extracapsular procedures use tissues or suture implants placed outside of the joint capsule in order to stabilize the joint.

#FIG. 1 is a view of a radiograph of a canine stifle joint in a fully flexed position, showing use of a pair of dividers to measure a distance between respective points on the tibia and femur shown in the radiograph.

#FIG. 2 is a view of a radiograph of the same stifle joint shown in the radiograph depicted in FIG. 1, with the stifle joint in its fully extended position, showing use of a divider to measure between a selected point on the tibia and a point on the femur shown in the radiograph.

#FIG. 3 is an isometric view of a measuring and positioning device which is an exemplary embodiment of one aspect of the present invention.

#In a typical articulated joint, the ends of the bones which meet in the joint operate as cams such that when the joint is flexed and extended the distance between a given first point in a first bone and a second point on the second bone changes depending on the degree of flexion and extension. However, points typically exist in joints that have what can be described as an isometric relationship. The distance between a given point on one bone and its isometric point on the second bone changes during flexion and extension but is the same at full flexion and full extension. Such points can be said to have an isometric relationship, and herein will be referred to as isometric points. When connective structures such as cruciate ligaments in a joint are damaged and grafts or other replacement or substitute structures are employed to repair the joint, these replacement structures should ideally be fastened to points which have such an isometric relationship, in order to facilitate the proper function of the joint. When the replacement structure is attached at such isometric points, it is under equal tension at each limit of normal range of motion of the joint after surgical repair.

#Referring to the drawings, which form a part of the disclosure herein, a measuring and locating device and a method for its use as disclosed herein permit a surgeon to locate appropriate isometric points in articulated mammal joints, optimally after those points have been previously approximated or identified in radiographic or other two-dimensional images of the joint. A method of repairing a torn cranial cruciate ligament, a relatively frequent and significantly debilitating injury occurring in the stifle or knee joint in canines, and use of such a measuring and locating device to repair a cranial cruciate ligament in a dog's stifle joint is explained herein. The device and method may also be used to locate isometric points in any mammalian joint. The device and method may also be used to locate other medically relevant points, such as in locating an axis of rotation of a hinged or ginglymus type joint of any mammal.

#In placement of a replacement structure such as a graft, suture, or other structure in a joint, a first point of attachment of a replacement structure must be determined. In the exemplary surgical procedure described below, the joint to be repaired is a stifle, or knee, joint of a canine, although the procedure is generally the same in the stifle or knee of other mammals, and the device can be used to find medically relevant points in many other mammalian joints. As shown herein, the replacement structure to compensate for a torn anterior cranial cruciate ligament is an autograft 12 composed of a portion of the fascia lata and the cranial insertion of the biceps femoris muscle. These structures insert naturally at Gerdy's Tubercle 20. The combined insertions of the fascia lata and cranial insertion of the biceps femoris muscle on Gerdy's Tubercle form a strong, dynamic, vascularized ligamentous insertion at this tubercle. Because these structures are already attached to the tibia at Gerdy's Tubercle, and because Gerdy's Tubercle has an isometric relationship with a point on the lateral femoral condyle, Gerdy's Tubercle is a logical first point of attachment for the replacement structure employed in this particular surgery. The preferred points of attachments to be used may vary in other situations, depending on the joint, the surgical technique used, the nature of the replacement structure employed, and other factors.