Cranial Cruciate ligament (CCL) disease is one of the most common orthopaedic conditions encountered in dogs, with certain breeds (retrievers, rottweilers, mastiffs & terriers etc.) being over represented. While numerous techniques have been tried over the years, none has proved optimal in terms of limiting the progression of degenerative changes to the stifle joint or avoiding potential complications which may require further surgical intervention; published rates are quoted as high as 10-15% in some review papers. A relatively new technique in use at the Downs, shows early promise in addressing these concerns.
Established techniques in common usage can broadly be divided into two categories:
a) those that address instability –
‘cranial tibial thrust’ on weight-bearing, namely; extracapsular retinacular suture, advancement of the fibular head and the ‘over-the-top’ technique,
b) those that focus on functional neutralisation of the tibial thrust force vector, namely; tibial plateau levelling osteotomy (TPLO – both Slocum and closing wedge); tibial tuberosity advancement (TTA) and triple tibial osteotomy (TTO).
Unfortunately, each of the above approaches can suffer several drawbacks, from failure of the stabilisation suture to issues with bone-healing and late meniscal injury. The TightRope® technique is a unique extra-articular stabilisation that accurately addresses both cranial drawer and internal rotation.
fig. 1 — diagram illustrating bone tunnels and fixation points for fibre-tape suture
fig. 2 - intraoperative photograph of TightRope® implant
The technique involves reconstructing the isometric points of the CCL whilst anchoring the implant using bone tunnels in the metaphyseal region of the femur and proximal tibia (fig. 1). However, stability and long term success of the procedure is entirely dependant on the precise location of said tunnels.
Established benefits of TightRope® over the standard extracapsular fabellotibial suture are:
1. Superior and reproducible accuracy in the reconstruction of the CCL ligament using isometric fixation points.
2. Fixation is bone-to-bone rather than bone-to-ligament; the latter is more prone to loosening over time as the soft tissues inevitably stretch.
3. The TightRope® technique utilises a braided fibre-tape suture (fig. 2), which possesses inherently superior mechanical properties for creep, stiffness, yield load and load at failure compared to various other cruciate sutures including leaderline1.
4. There is no upper weight limit with this repair making it suitable for patients where previously only TPLO, TTO or TTA would have been considered.
fig. 3 - model of stifle joint with TightRope® implant and tensioning device in place. This device avoids over-tightening of the lateral aspect of the joint, which might otherwise lead to joint pain resulting from impingement of the lateral meniscal cartilage.
5. Tensioning of the implant is carefully controlled (see fig. 3) to avoid over-tightening the joint.
So what are the benefits of TightRope® over the TPLO or TTA?
- Lower morbidity as it does not involve osteotomy of the tibia, therefore serious complications such as fracture, mal- and non- unions are avoided.
- In clinical trials, when compared to TPLO, there was no difference in six month outcome with regards to radiographic progression of OA, complications and client evaluated level of function1. Clinical assessment of tibial thrust and cranial drawer found no difference between pre– and post-operative stifles after TPLO, whereas cranial drawer was significantly reduced in those having undergone the TightRope® procedure1.
The TightRope® procedure therefore has the potential to address all abnormal forces generated within the stifle post CCL deficiency whilst avoiding potentially serious complications associated with delayed bone-healing.
So what complications might one expect with TightRope®?
Infection is the main concern due to the braided nature of the suture. Strict aseptic technique (as with all joint-surgery) is therefore mandatory, as well as prevention of wound interference by the patient postoperatively. Other complications such as implant failure and late meniscal injury can also occur. However, with this procedure there are no ‘burnt bridges’ and should the implant fail or become infected, it can be relatively easily removed and another procedure considered.
Relative Contraindications:
- Medical conditions likely to lead to wound healing issues such as diabetes/Cushings, etc.
- The presence of infection, or potential presence of infection.
- A tibial plateau angle greater than 32º (in which case a TPLO/ TTA or TTO may be appropriate).
- Angular limb deformity.
- Body weight less than 18kg or femoral condyle length less than 12mm cranial to caudal (in these instances a mini-TightRope® set would be suitable).
Irrespective of the technique selected, thorough examination of the joint and debridement of any ligament remnants and damaged menisci remain vital to the success of any treatment plan. It must also be stressed that without strict owner compliance any procedure is likely to fail.
Ultimately, a technique that addresses all the abnormal forces within a CCL-deficient joint in any size of patient, without the risk of serious complications, yet has statistically the same outcome as a TPLO is in our view, worthy of consideration.
Reference:
1. Cook JL, Luther JK, Beetem J, Karnes J, Cook CR. 2010. Clinical comparison of a novel extra capsular stabilisation procedure and tibial plateau levelling osteotomy for treatment of cranial cruciate ligament deficiency in dogs. Veterinary Surgery 39: 315-323
TightRope® is a registered trademark of Arthrex Vet Systems
