Patent Application
20080044244
In the accompanying drawings that form a part of the specification and that are to be read in conjunction therewith and in which like reference numerals are used to indicate like parts in the various views:
As shown in
First and second jig legs 18 and 20, shown in
Saw guide assembly 14 includes saw fixation member 68, a first slide bar 70, a second slide bar 72, and an adjustment bar 74. Saw guide assembly 14 is preferably formed from stainless steel, plastic, or any other material suitable for use in veterinary surgery. Saw fixation member 68 may be any shape having rounded edges for safety purposes. In one embodiment as shown in
Second slide bar 72 as shown in
Adjustment bar 74 is generally cylindrical and may have a shorter length than that of either first or second slide bars 70 and 72. Adjustment bar 74 includes a generally rounded first end 106 and an opposing second end 108 having a second adjustment member 110, one embodiment of which is shown in
In use, an animal patient is maintained on isofluorane anesthesia with constant anesthetic monitoring in dorsal recumbency and with complete body drape and the surgery leg free in a vertical plane. Routine pre-operative betadyne preparation is performed prior to draping. The patient's leg is extended and flexed to evaluate pre-operative anatomy and to determine if any valgus or varus deviation or torsion of distal extremity exists. Pre-operative radiographs have identified a desired plateau slope change of from 5-40 degrees. The surgical blade chosen varies based on the anterior-posterior thickness of the tibia. The tibial plateau rotation is calculated based on the chosen blade, and the degree of rotation.
The skin and subcutaneous fascia are incised down to the periosteum, from the tibial plateau to approximately 2 cm distal to the tibial crest in an anteromedial plane approximately 1.5 cm caudal to the palpable anterior midline edge of the tibial crest and distally parallel with the tibial shaft. The skin and subcutaneous incision is extended proximally and caudally in a slightly curved fashion to the level of the proximal patella. The periosteum starting at the tibial plateau is incised distally to the limits of the skin-subcutaneous incision. The periosteum is then reflected anteriorly to the edge of the tibial crest, with a periosteal elevator, and also posteriorly beneath the muscle attachments of the pes ansorimus group to the posterior edge of tibia 120 by a combination of sharp scalpel dissection and periosteal elevation. This landmark dissection reveals the 1) medical aspect of the stifle joint, 2) the medial collateral ligament, and 3) the muscle fiber attachment of the popliteus to the caudal femur. From the tibial plateau, the periosteal incision is carried proximal, deeper through fascial planes to the sartorius muscle attachment. Care should be taken to not enter the femorotibial joint space. Three 25 gauge needles are used to identify the tibial plateau, and the caudal aspect of the tibia 120, just caudal to the medial collateral ligament.
A 5 mm incision is made immediately caudal to the posterior edge of the medial collateral ligament, through the joint capsule with a #15 blade. Through this 5 mm incision, a #11 blade is inserted, pointed anterolateral at an imaginary point halfway between the tibial crest and the fibular head, and used to cut the medial meniscus, releasing it to fall posteriorly. The 5 mm incision is closed with cruciate 2-0 PDS. Three 25 gauge needles are placed in the knee joint as close to the tibial plateau as possible, the first caudal to the patellar ligament, the second approximately 5-8 mm caudal to the meniscal release incision, and the third at the posterior but most proximal point on tibia 120.
The popliteus muscle fibers, as attached to posterior tibia 120, are cut close to tibia 120, from approximately 2 cm distal to the caudal edge of the femorotibial joint (as previously found with a 25 gauge needle) for approximately 4 cm. Using a sharp periosteal elevator, all muscle fibers and soft tissue are separated from the posterior-lateral aspect of the femur. The pocket created is packed with 3-4 saline-soaked gauze sponges. The tibialis anterior muscle is separated from its tibial plateau attachment from 2 cm below the femoral tibial joint and distally 3-4 cm by using sharp periosteal elevator dissection. The pocket created is packed with saline-soaked gauze sponges.
The patient's leg should be positioned accurately to pinpoint accurate placement of the upper and lower tibial positioning pins 58 and 64 that hold jig assembly 12 in place. The stifle and hock joints are flexed with the femur perpendicular thereto. That is, the femur is vertical to the table and the patient's foot/metatarsus is held or positioned against the surgeon's chest. Tibia 120 is held substantially parallel to the surgical table and substantially perpendicular to the femur. If a valgus or varus tibial deviation is present, the foot/metatarsus will not appear vertical or parallel with the femur.
In another embodiment of the method of the present invention, the patient is positioned in lateral recumbency and the surgery leg placed on the table, in a substantially perfect horizontal plane with stifle and tibiotarsal joints partially flexed. After the patient is placed in lateral recumbency, a vacuum positioner bag is placed beneath the surgical leg. A horizontal laser beam is used to position the distal leg, from just above the patella, so that the horizontal beam of the laser lays center of the patellar ligament, center of the proximal to distal tibia, and to the center of the torsus. The vacuum positioner bag is deflated when the leg is parallel to the horizontal beam.
A ⅛″ threaded pin is inserted through a small stab wound approximately 5 mm distal to the second 25 gauge needle and midway between the posterior edge of the medial collateral ligament and the third 25 gauge needle. The pin is started to make a small pilot hole and then removed. Prior to drilling the proximal pin, the laser horizontal beam is used to confirm that the lower leg is in a substantially perfect horizontal plane. If the leg is positioned correctly, the laser beam bisects the patella, the patellar ligament, the tibia, and the metatarsus. In general, if the leg is positioned correctly prior to surgery on the vacuum positioner bag and, if the leg has not been repositioned, then no adjustments in positioning of the leg should be necessary.
Preplaced 25 gauge needles identify the posterior edge of the proximal tibia 120, and the posterior edge of the femorotibial joint. A 25 gauge needle is placed just caudal to the medial collateral ligament in the joint. A second 25 gauge needle is “walked” off the posterior-proximal edge of tibia 120. The tip of the proximal pin is placed 2-5 mm caudal to the medial collateral ligament, and 3-5 mm below the joint. In general the pin will be placed caudal of the medial collateral ligament, ⅔ of the distance between the medial collateral ligament and the posterior edge of tibia 120.
The proximal pin is verified to be substantially vertical to the plane of tibia 120 with the vertical laser beam and then it is seated through tibia 120. The laser insures accuracy of the pin placement, that is, the pin is desirably substantially perpendicular to the horizontal plane of the tibia.
Precision fixation device 10 is substantially preassembled for a left or right leg surgery by an assistant. Assembled device 10 is slid over upper tibial positioning pin 58 via upper tibial positioning aperture 56. The lower tibial positioning pin 64 is positioned in the distal one-third of tibia 120 via lower tibial positioning aperture 62. A 5 mm skin incision makes a window for pin 64 to enter the bone of tibia 120. The laser is now used to verify that device 10 is in a substantially perfect horizontal plane and parallel to the plane of the tibia 120. Device 10 is generally held tight against the proximal tibia 120 and the lower 64 pin is then set. The laser again is used to verify the absolute vertical position of the lower tibial pin 64 as it is seated through tibia 120.
The appropriate cutting blade is generally chosen prior to surgery. Any diameter blade may be used in connection with device 10. Saw fixation member 68 is slid onto the first and second slide bars 70 and 72, the blade of saw 82 is positioned on tibia 120 so that the proximal edge of the saw 82 will cut the proximal end tibia 120. Set screws are tightened within screw apertures 77 to prevent saw 82 from rotating within saw fixation member 68. At 90# of pressure, saw 82 is capable of guiding itself through the bone of tibia 120 thereby insuring a substantially perfect 90° cut in all planes relative to tibia 120.
Saw 82 should not move out of the precision plane when it is fixed in position by the saw fixation member 68 on slide bars 70 and 72. Saw 82 is then activated and, with aggressive flushing, tibia 120 is cut approximately two-thirds of the way through. The saw blade is then retracted and chisel marks are made to accurately delineate the mm of rotation. The saw cut is completed with rigorous irrigation by inserting saw 82 into the previous saw cut and activating saw 82. The saw blade is not rotated or twisted by the surgeon, but instead allowed to slowly cut by the actual blade vibration on tibia 120.
Once tibia 120 is cut, jig assembly 12 is checked to confirm that it is secure. The saline soaked gauze is removed from the lateral aspect of tibia 1420. A threaded ⅛″ pin is drilled medial to lateral, obliquely, through the proximal cut fragment, close to the saw line. A second pin is then used to rotate the proximal cut segment so that the rotation is complete and the chisel lines meet. A 1/16″ threaded pin is inserted just lateral to the patellar ligament attachment to the tibial crest and is driven posterior into the proximal cut fragment.
Prior to plating, the cut line is visualized for plate placement. The appropriate TPLO plate is contoured to fit the cut surface and proximal shaft of tibia 120. Care is taken to get a perfect anatomical fit. The distal 3 holes are drilled, tapped, and screws placed in a neutral position. Holes 4 & 5 are drilled and 4.0 mm cancellous screws are placed in a loading position, but are tightened together. Hole 6 is drilled parallel to the tibial plateau, and a 4.0 mm cancellous screw is tightened.
A culture is taken prior to closure. O-PDS is used to close the periosteum and pes ansorinus group over the plate with simple interrupted sutures. The fascia and subcutaneous are closed with 2-0 PDS sutures. If possible, a subeuticular pattern is run with 2-0 vicryl. Stainless steel staples close the skin. A light pressure wrap over the incision and down tibia 120 to the hock joint is applied. Post-op x-rays are taken to evaluate the bone cut line, closure of the saw line, and final degrees of rotation.
From the foregoing, it may be seen that the inventive precision fixation device and method of using the same is particularly well suited for the proposed usages thereof. Furthermore, since certain changes may be made in the above invention without departing from the scope hereof, it is intended that all matter contained in the above description or shown in the accompanying drawing be interpreted as illustrative and not in a limiting sense. It is also to be understood that the following claims are to cover certain generic and specific features described herein.
