Cruciate Ligament Disease in Dogs

Cruciate disease is common in general practice. Two questions that are frequently asked when it comes to extracapsular stabilisation of cruciate disease are:

1) What suture material should I use?

Ex vivo and in vitro models provide evidence with regards to choice of material, method of fixation and site of attachment of implants for extracapsular stabilisation. Monofilament nylon leader material has been shown to have superior mechanical characteristics compared to other commercially available suture materials1. Specifically Mason hard-type nylon leader (Otisville, MI) has been shown to have best mechanical properties (compared to 4 other types of fishing line) following ethylene oxide and steam sterilisation2. Additionally ethylene oxide sterilisation has higher preservation of the mechanical properties of the tested fishing lines compared to steam sterilisation. Recently polyethylene sutures marketed specifically for extracapsular stabilisation have been shown to have superior mechanical properties compared to nylon leader materials3. Potentially FibreTape, Arthrex Vet Systems (Napels FL) has superior mechanical properties compared to other commercially available polyethylene sutures. However in a later study LigFiba was shown to have greatest tensile strength followed by Xgen Orthofibre that was stronger than Fibre Tape and Fibre wire, and the weakest was monofilament nylon leader line. LigaFibre was found to be the stiffest of all tested materials at 3 mm of elongation. Cyclic elongation was greatest for the Monofilament nylon leader line elongating 3.75 mm after 1000 cycles. All polyblend braided materials continued to elongate throughout the 1000 cycles under physiologic loads4. The clinical significance of utilising materials with superior mechanical properties (i.e. polyethylene sutures vs. nylon leader materials) is not known.

2) What suture configuration should I use and how do I secure the suture?

The attachment site of the extracapsular stabilisation suture is being revised with papers assessing tension across an extracapsular suture at varying joint angles. The traditional attachment points of a proximal and cranial tibial tunnel and the lateral fabellum do not provide isometric attachment points4. A proximal and cranial tibial tunnel combined with a femoral attachment as close to the origin of the cranial cruciate ligament has been suggested to provide isometric attachment locations. The ‘TightRope CCL technique and a transcondylar toggle system utilise isometric attachment points by creating both a tibial tunnel and a femoral tunnel at the desired locations (Figure 1) 5, 6. In reality the cruciate ligament is not isometric as the craniomedial is taunt throughout the stifle range of motion whereas the caudolateral portion is taut in extension but lax in flexion hence the suggestion of truly isometric attachment sites is unlikely. This is likely to account for the variations in results across publications. Of the traditional suture configurations it has been suggested that a double tibial tunnel combined with the suture placed around the fabellum provides a suture with the least change in tension across the stifle range of motion (Figure 2.) 7. Additionally the most consistent tension across the stifle range of motion was achieved when the suture was tied with the stifle at 100 degrees of flexion.

Figure 1. Isometric points utilized for the tight rope procedure. The tibial tunnel is drilled at the tubercule of Gerdy under the digital extensor tendon. The femoral tunnel is drilled at the level of the origin of the cranial cruciate ligament.

Figure 2. A double tibial tunnel combined with the suture placed around the lateral fabellum (B) provides a suture with the least change in tension across the stifle range of motion in this ex vivo study. From Fischer C., et al 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 Veterinary Surgery 39 (2010) 334–342.

Suture configuration has been evaluated from the perspective of stiffness, load at failure and resisting elongation over time. A recent study identified that double loop single strand configurations were preferential to double loop double strand configurations (Figure 3) 8.

Figure 3. Double loop single strand configurations were demonstrated to have preferential mechanical properties to double loop double strand configurations. The double loop single strand locking loop (box) had the most preferential properties. From Wallace M., A biomechanical comparison of six different double loop configurations for use in the lateral fabella suture technique. Vet Comp Orthop Traumatol 5/2008:

The use of crimps rather than knots for securing the extra capsular suture results in superior mechanical properties for nylon leader materials and polyethylene sutures 1,2,9. The Securos crimping system appears to have superior mechanical properties compared with the Veterinary Instrumentation system though this could relate to individual surgeon grip strength10. A mismatch between the suture used and the crimp diameter can result in poor mechanical properties of the implanted loop11.

Resources:

1. Lewis D.D., (1997) Mechanical comparison of materials used for extra-capsular stabilisation of the stifle joint in dogs. Aust. Vet. J. Dec;75(12):890-6.
2. Sicard G.K., et.al. Evaluation of 5 types of fishing material, 2 sterilization methods, and a crimp-crimp system for extra-articular stabilization of the canine stifle joint. Vet. Surg. Jan-Feb;31(1):78-84.
3. Burgess R., et.al. (2010) In vitro biomechanical evaluation and comparison of Fiberwire, FiberTape, OrthoFiber and nylon leader line for the potential use during etraarticular stabilization of canine cruciate deficient stifles. Vet. Surg. Feb;39(2):208-15.
4. Rose ND, Goerke D, Evans RB, Conzemius MG Mechanical Testing of Orthopedic Suture Material Used for Extra-Articular Stabilization of Canine Cruciate Ligament-Deficient Stifles. Vet Surg. 2011 Sep 23.
5. Roe S.C., et.al. (2008) Isometry of potential suture attachment sites for the cranial cruciate ligament deficient canine stifle Vet. Comp. Orthop. Traumatol. 21(3):215-20.
6. Kunkel K.A., et.al. (2009) Evaluation of a transcondylar toggle system for stabilisation of the cranial cruciate deficient stifle in small dogs and cats. Vet. Surg. Dec;38(8):975-82
7. D. Hulse; W. Hyman; B. Beale; B. Saunders; I. Peycke; G. Hosgood, Determination of isometric points for placement of a lateral suture in treatment of the cranial cruciate ligament deficient stifle. Vet Comp Orthop Traumatol 3/2010
8. Fischer C., et al 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 Veterinary Surgery 39 (2010) 334–342
9. Wallace M., A biomechanical comparison of six different double loop configurations for use in the lateral fabella suture technique. Vet Comp Orthop Traumatol 5/2008
10. Vianna M.L., Roe S.C. (2006) Mechanical comparison of two knots and two crimp systems for securing nylon line used for extra-articular stabilisation of the canine stifle. Vet. Surg. Aug;35(6):567-72.
11. Moores A.P., et.al. (2006) Mechanical evaluation of two crimp clamp systems for extracapsular stabilization of the cranial cruciate ligament-deficient canine stifle. Vet. Surg. Jul;35(5):470-5.
12. Banwell M.N., et.al. In vitro evaluation of the 18 and 36 kg Securos Cranial Cruciate Ligament Repair System. Vet. Surg. May-Jun;34(3):283-8.