Knotless TightRope® Repair
The Knotless TightRope is an advancement in minimally invasive CCL repair developed for the experienced surgeon who is familiar with arthroscopy. The Knotless TightRope allows for placement of a lateral extracapsular femoro-tibial implant for stabilization of the CCL deficient stifle through a small, single incision. The Knotless TightRope has biomechanical properties for CCL stabilization when appropriately placed in femoral and tibial bone tunnels as described. The Knotless TightRope uses the same instrumentation and tunnel locations as the TightRope CCL in dogs, making the addition of the Knotless TightRope technique readily accomplished for the experienced surgeon.
The Knotless TightRope is to be implanted after comprehensive arthroscopic assessment of the stifle joint with appropriate assessment and treatment of the deficient CCL and meniscus. To implant the Knotless TightRope as minimally invasive as possible, a
2–5 cm skin incision is made on the lateral side of the stifle from the fabella-femoral junction to the extensor groove of the tibia.
The start site for the femoral tunnel is just distal to the lateral
fabella-femoral condyle junction (i.e. 2 mm from the caudal edge of the lateral femoral condyle). The tibial start site is located caudally within the groove of the long digital extensor tendon.
Insert the Guidewire 2 mm distal to the lateral fabella and within the caudal portion of the lateral femoral condyle. With the stifle held in extension, advance the Guidewire at a 45°-60° angle proximally. The Guidewire traverses the distal femur and exits at the cranial-caudal midpoint of the distal diaphysis of the femur on the medial side, immediately caudal to the vastus medialis muscle and at the level of the proximal patella.
The Cannulated Drill Bit is inserted onto the Guidewire and advanced through the femur until it exits through the medial side of the femur. Carefully ream the femoral tunnel back and forth with the drill bit (protect the soft tissue). Grasp the Guidewire on the medial side of the stifle with a needle driver to maintain its location in the femoral tunnel while the drill bit is removed laterally.
Place the Guidewire within the tibial extensor groove proximally and resting against its caudal ridge. Advance the Guidewire through the tibia at a 45°-60° angle to exit medially within the footprint of the caudal Sartorius insertion. Drill over the Guidewire with the Cannulated Drill Bit (protect the soft tissues). Grasp the Guidewire on the medial side of the stifle with a needle driver to maintain its location in the femoral tunnel while the drill bit is removed laterally.
Remove each Guidewire as the TightRope needles are inserted through the tunnels in a lateral to medial direction deep to the fascia and superficial to the joint capsule. As tension is applied to the needle and FiberWire, the toggle button will lay down to allow it to advance through the tunnel.
Once the toggle button has exited the tunnel, the button is flipped by pulling the lead suture in a slight upward direction and by pulling back on the FiberWire strands laterally. Ensure that the toggle is flipped and seated fully on the medial bone by palpation.
On the lateral side locate the two parts of the construct:
(1) Splice section (2) Interconnecting section. Isolate theinterconnecting section.
Gradually apply tension to the interconnecting section from each direction of the tunnel. The splice section will "walk down" until it sits next to the capsule. Alternate tension toward the femoral and tibial tunnels so that the implant tightens with the splice sections as close to the middle of the incision as possible while also keeping the interconnecting section centered.
A probe or hook can be used to pull the interconnecting section, allowing the splice section to be pulled tight against the tissue. Once properly seated for implant tightening, the splice section will sit firm against the joint capsule with the middle point of the splice still in sight. Verify which suture tail is the femoral and which is the tibial. (See Pearl #3)
After tensioning sufficiently for the splice section to rest against tissue and tail direction is verified, (tibial tail distally and femoral tail proximally, along the axis of the suture), place a probe or rod under the interconnecting section and have an assistant maintain tension on the TightRope during tightening. Start pulling each splice tail little by little, alternating between tibial and femoral tails to cinch down the interconnecting section.
Tighten the TightRope snug against the probe first, cycle the stifle through a full range of motion repeatedly, and then remove the probe and tighten it firmly against the joint capsule. Keep repeating ROM cycling and retightening against the joint capsule until there is no slack in the implant, cranial drawer and internal rotation of the stifle are at desired levels of stability. Avoid over-tensioning. If slack remains, desired levels of stability cannot be attained, and/or preoperative stifle ROM is not maintained, then tunnel location, toggle seating and implant integrity should be examined to determine the source of the problem, which should then be addressed intraoperatively.
After final assessment of the TightRope placement and function, cut and remove the two suture tails 2 mm from the splice section. To remove the lead wires cut one limb of the attached white suture and pull the needles away from the skin. The suture will come with it.
The lateral fascia should be imbricated over the Knotless TightRope. Imbrication sutures of 2-0 or 0 PDS or Maxon should be placed.
Recommended Postoperative Management
• Cefazolin - 22 mg/kg IV 30 minutes prior to incision, 90 minutes later, then every six hours until oral antibiotic therapy is initiated
• Oral antibiotics (e.g. Cephalexin 22-30 mg/kg every 8-12 hours) for at least ten days post-op
• Bandaging at your discretion (soft-padded bandage for at least 24 hours is typical)
• Restrict to kennel rest when unobserved and controlled muscle-building activities (i.e. leash walking) for eight weeks post-op
• Professional rehabilitation is encouraged
Knotless TightRope Pearls
1. If a partial medial meniscectomy is not performed to address a definitive meniscal tear, then a caudal meniscal release is recommended.
2. Keep the TightRope in the package until both tunnels are drilled in the appropriate locations and everything is prepared for its placement. Then put on a new pair of sterile surgical gloves to handle and place the TightRope.
3. To verify which tail belongs to which tunnel, pull in the same direction it exits the splice point, and mark one with a sterile marking pen.
4. Hold onto the white 2-0 suture, rather than the TightRope needle when pulling it through the tunnels to keep the suture from pulling free from the needle.
5. When pulling the buttons through the tunnel use a forward and back motion so the button does not come through the skin.
6. To ensure the suture starts sliding on the button easily, after the buttons are flipped, grab each arm of the suture from the button and slide back and forth to free it up.
7. If tension cannot be maintained and/or if the drawer is not counteracted appropriately while maintaining good ROM, the TightRope should be assessed. When this occurs, it is likely that the tunnels are not in the proper location and/or a button is not seated directly onto the bone well. The surgeon must decide if correction
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