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Can Vet J. 2010 October; 51(10): 1167–1168.
PMCID: PMC2942061

Walking the tightrope

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Surgical stabilization of cranial cruciate ligament rupture has been extensively reported on in orthopedic literature. DeAngelis and Lau (1) were the first to describe an extracapsular (EC) suture technique 4 decades ago and several variations have been described since. Extracapsular techniques involve the placement of a suture or sutures outside the joint capsule that spans the stifle joint to mimic the function of the cranial cruciate ligament in restraining cranial tibial thrust and internal rotation of the stifle. The position of the suture attachment points, the method of attachment, and the type of suture have been the major variants from one modification of the technique to another, but all variations share some common factors. The first of these is that EC repair techniques have a very good success rate that is comparable to other techniques and estimated at 85% or better (2). These techniques also are associated with almost invariable eventual failure of the EC suture which does not usually equate to clinical failure for the patient. Extracapsular techniques are also associated with other common problems including significant progression of osteoarthritis (3).

The latest variation of the EC repair is called the “Tightrope” technique (Arthrex Vet Systems, Naples, Florida, USA). Developed and patented by Dr. Jimi Cook of the University of Missouri, the technique is designed to address several of the deficiencies inherent in the EC approach, especially as it pertains to treatment of cranial cruciate ligament rupture in large breed dogs. When Drs. DeAngelis and Lau developed the first EC technique, the typical cruciate disease patient was an older, small breed dog (4). Many of the failures of these techniques in recent years have been attributable to the extreme forces placed on the repair by young, active, large-breed dogs which currently make up the majority of clinical cases. Tibial plateau leveling osteotomy (TPLO), tibial tuberosity advancement (TTA), and other geometry-modifying surgical procedures have been developed to meet the demands of a large-breed patient. These procedures have come with greater cost for the owner, more equipment and training requirements for the surgeon, and generally higher complication rates (58). Dr. Cook’s avowed goals for the Tightrope procedure are to develop a technique that is minimally invasive, cost-effective, less technically demanding, and stands up to the demands placed on the repair by all types of patients (9). Three characteristics of the technique set it apart and facilitate achievement of the stated goals.

  1. Rigid attachment of the EC suture — the suture is placed through a tunnel from the medial aspect of the distal femoral condyles where it is secured with a special “button.” The suture exits on the lateral side of the femoral condyle, crosses the joint and enters a tunnel on the lateral side of the proximal tibia, exiting again on the medial side of the proximal tibia where another attachment “button” is placed. Secure attachment of the EC suture has always been a significant issue in the success of the procedure since failure at an attachment point, most often the proximal-most attachment point, is the most common mode of suture failure. Some techniques pass the suture around the faballae, some use suture anchors or other variations, but all are prone to failure.
  2. “Isometric” placement of the EC suture — while the EC suture is placed on a stationary joint, the normal stifle joint flexes and extends which can produce cyclic loading and tightening or loosening of the suture as the stifle angle varies. In the worst case scenario this may restrict the range of motion of the stifle joint or promote suture failure. Isometric suture placement is achieved when flexion or extension of the stifle does not result in tightening or loosening of the EC suture. It has been proposed that placement of the femoral attachment point more cranial than the faballae to approximate the origin of the cranial cruciate ligament and the tibial attachment point in a more caudal position than the tibial tuberosity may be more “isometric” and may minimize some of these problems (10). Recent work casts some doubt on whether or not any suture position can truly be characterized as “isometric” (11), and the clinical significance of isometric placement has never been clearly established. Nevertheless, the Tightrope procedure endeavors to place the EC suture isometrically.
  3. Suture material of high tensile strength — many materials have been used for the EC suture with an aim of finding something that possesses and maintains great strength without stretching or producing other complications. The Tightrope procedure utilizes Fibertape (Arthrex Vet Systems), a braided, polyfilament, synthetic, non-absorbable material of great strength and minimal distensability (9). The search for the “perfect” EC suture material has looked at everything from surgical wire to most surgical sutures to nylon fishing line and leader materials! In general, monofilament materials haven’t been strong enough or have stretched while polyfilament materials have been associated with high rates of infections and fistulous tracts (12). This has been the major concern with Fibertape, although a review of more than 1000 cases reported an infection rate of 2.8% which would not exceed other techniques in common usage (13).

What is the verdict on the Tightrope procedure? It is fair to say that it is still early days where this question is concerned but some encouraging data have emerged. Dr. Cook has presented data suggesting that the procedure may produce results similar to TPLO with a lower complication rate (9,13). The reports need to be viewed with some caution, however, since although they include results from over 1000 cases, they primarily present subjective measures based on owner questionnaires and evaluation of radiographic osteoarthritis. At this point it would be fair to conclude that Tightrope does not represent anything “revolutionary” in the treatment of cranial cruciate ligament rupture since it is a variation on a long-established technique. However, it may well prove to be an example of “building a better mousetrap” and could provide an important treatment alternative to TPLO or TTA, especially in active, large-breed dogs.

Footnotes

Use of this article is limited to a single copy for personal study. Anyone interested in obtaining reprints should contact the CVMA office (gro.vmca-amvc@nothguorbh) for additional copies or permission to use this material elsewhere.

References

1. DeAngelis M, Lau RE. A lateral retinacular imbrication technique for the surgical correction of anterior cruciate ligament rupture in the dog. J Am Vet Med Assoc. 1970;157:79–84. [PubMed]
2. Moore KW, Read RA. Rupture of the cranial cruciate ligament in dogs. Part II: Diagnosis and management. Compend Contin Educ Pract Vet. 1996;18:381–405.
3. Elkins AD, Pechman R, Kearney MT, Herron M. A retrospective study evaluating the degree of degenerative joint disease in the stifle joint following surgical repair of anterior cruciate ligament rupture. J Am Anim Hosp Assoc. 1991;27:533–540.
4. Harasen G. A Retrospective study of 165 cases of rupture of the canine cranial cruciate ligament. Can Vet J. 1995;36:250–251. [PMC free article] [PubMed]
5. Pacchiana PD, Morris E, Gillings SL, Jessen CR, Lipowitz AJ. Surgical and postoperative complications associated with tibial plateau leveling osteotomy in dogs with cranial cruciate ligament rupture: 397 cases (1998–2001) J Am Vet Med Assoc. 2003;222:184–193. [PubMed]
6. Theoret MC, Whitney WO, Beale BS. Complications associated with tibial plateau leveling osteotomy during the first two years. (abstract) Proc Vet Orthop Soc. 2003:80.
7. Priddy NH, Tomlinson JL, Dodam JR, Hornbostel JE. Complications with and owner assessment of the outcome of tibial plateau leveling osteotomy for treatment of cranial cruciate ligament rupture in dogs: 193 cases (1997–2001) J Am Vet Med Assoc. 2003;222:1726–1732. [PubMed]
8. Stauffer KD, Tuttle TA, Elkins AD, Wehrenberg AP, Character BJ. Complications associated with 696 tibial plateau leveling osteotomies (2001–2003) J Am Anim Hosp Assoc. 2006;42:44–50. [PubMed]
9. Cook JL, Luther JK, Beetem J, Karnes J, Cook CR. Clinical comparison of a novel extracapsular stabilization procedure and tibial plateau leveling osteotomy for treatment of cranial cruciate ligament deficiency in dogs. Vet Surg. 2010;39:315–323. [PubMed]
10. Roe SC, Kue J, Gemma J. Isometry of potential suture attachment sites for the cranial cruciate ligament deficient canine stifle. Vet Comp Orthop Traumatol. 2008;3:215–220. [PubMed]
11. Fischer C, Cherres M, Grevel V, Oechtering G, Bottcher P. Effects of attachment sites and joint angle at the time of lateral suture fixation on tension in the suture for stabilization of the cranial cruciate ligament deficient stifle in dogs. Vet Surg. 2010;39:334–342. [PubMed]
12. Burgess R, Elder S, McLaughlin R, Constable P. In vitro biomechanical evaluation and comparison of Fiberwire, Fibertape, Orthofiber, and nylon leader line for potential use during extraarticular stabilization of canine cruciate deficient stifles. Vet Surg. 2010;39:208–215. [PubMed]
13. Cook JL. Multicenter outcomes study for evaluation of Tightrope CCL for treatment of cranial cruciate deficiency in dogs: The first 1000 cases. (abstract) Proc Vet Orthop Soc. 2008

Articles from The Canadian Veterinary Journal are provided here courtesy of Canadian Veterinary Medical Association