Why Learn Extracapsular Suture Stifle Stabilization?

Once upon a time, TPLO and TTA did not exist as treatments for cranial cruciate ligament-deficient (CrCLD) stifles. There was a day kids, when the only surgical options were some means of recreating the stabilizing function of the CrCL, and Extracapsular Suture Stifle Stabilization (ExCap) techniques were chief amongst them.  Then, along came the various tibial osteotomies with their claim to negate the need for the CrCL beginning with Slocum’s original tibial cranial closing wedge ostectomy in 1984.  Fast forward 40 years and, while tibial osteotomies have demonstrated positive treatment outcomes in the hands of trained surgeons, ExCap techniques are still around. While ExCap techniques persist, it begs the question, “should a veterinarian today invest time and energy into learning ExCap techniques?”.

I can think of at least 3 reasons that it makes sense for you to develop ExCap surgical skills as well.

1. Referral to an ACVS or ECVS Specialist is not available to all pet owners.

Whether one wishes it to be true or not, on a global scale, there will always be the necessity for some, if not most, CrCLD surgical procedures to be performed by primary care veterinarians (pc-DVM’s). Currently, those of us in specialty referral practice like to believe that we perform the majority of CrCLD surgical treatments, but the peer reviewed literature says otherwise. In fact, an epidemiological study performed in the UK showed that of cases diagnosed with CrCLD in primary care practices, 2/3 were treated surgically, but only 21% were referred.¹   Referral was more frequent in insured dogs which suggests a relationship may exist between affordability and access to specialty care.  Wilke et al reported in 2005 that ~1 million CrCLD surgical treatments are performed annually in the US.²   Of these procedures, ~92% were performed by pc-DVM’s with only 8% being performed by Diplomates of the American College of Veterinary Surgeons.  Globally, one can only expect that access to and the ability to afford specialty level veterinary care are unattainable to most pet owners.  As much as we might want to believe otherwise, economic, geographic, and other barriers prevent many pet owners from accessing specialty level care for their CrCLD affected pet. Taken as a whole, most veterinarians have some patients who would benefit from surgical stifle stabilization, but referral to an ACVS or ECVS specialist surgeon is not available to the pet owner due to financial, geographic, or other constraints.

2. Orthopedic Surgery is a learning pathway, and you may not be ready to perform TPLO or TTA yet.

Nobody was ever born as an orthopedic surgeon. Orthopedic surgical skills are acquired through ongoing training, experience, critique and correction.  Likewise, capital investment in orthopedic instrumentation and equipment is often progressive.  When a veterinarian is starting down their orthopedic pathway, it may not be feasible to invest heavily in expensive orthopedic systems.  Treatment of more routine patients with simpler procedures often makes sense at this stage provide that case selection is emphasized.  Then, as one’s orthopedic skills and caseload build, the projected financial return on investment (ROI) strengthens.  Therefore, it only makes sense that a complex surgical procedure like TPLO or TTA or even anchored ExCap stifle stabilization is not your first step down a progressive learning and investment pathway.  That said, it is also important to understand that one’s inability to perform TPLO or TTA combined with the inaccessibility of a board-certified surgeon does not mean that ExCap stabilization is indicated by default. Case selection is as important in one’s training as is surgical technique.  Let me be clear, ExCap suture stabilization is not a second-class surgical treatment … instead, it is a very logical treatment for properly selected patients.  Patient-specific treatment recommendations, including ExCap stabilization, for CrCLD-affected patients was the focus of a recent treatise.³  Even in the simplest of ExCap techniques, the lateral fabellar suture, much has changed over the years such that high-quality, comprehensive training is as important as ever. Treatment success is the combined result of case selection, surgical technique, and perioperative care.

3. TPLO sometimes requires the addition of an ExCap Stabilizing Suture

Let’s begin by asking, “is the premise that TPLO negates the need for the CrCL actually true?”.  The answer is “sort of”.  In general, the TPLO does minimize cranial tibial thrust instability during the weight-bearing phase of canine gait, but it does not fully restore normal knee kinematics. For most patients, TPLO is our best surgical option and dramatically improves knee kinematics, patient comfort, and resolves lameness. That said, what works in “most patients” does not work in “all patients”. The unfortunate fact is that, on occasion, severe rotational knee instability may persist following TPLO; this may be noted intraoperatively or postoperatively. Intraoperatively, this may be noted as a dramatic internal tibial rotation when performing the tibial compression test – this rotatory instability noted upon manual testing is what I call a “passive pivot shift”. Postoperatively, this may be apparent as an “active pivot shift” which appears as an abrupt lateral buckling of the knee during mid-stance phase of the gait. While pivot shift instability following TPLO was described as early as 2011,⁴ detection and treatment of pivot shift has recently become the focus of numerous studies including the description of a new palpation test called the tibial pivot compression test (TPCT).^5-7 Various patient-specific factors are thought to predispose to postoperative pivot shift instability including acute complete CrCL tear, pre-existing or iatrogenic pelvic limb malalignment, and the need for medial meniscectomy.  It also appears that the TPLO may be unique in its predisposition to the postoperative pivot shift phenomenon.   Tibial plateau rotation has the effect of increased stifle flexion upon the stifle collateral ligaments; because the lateral collateral ligament (LCL) is somewhat caudally positioned, increased LCL laxity which permits increased internal rotatory freedom within the stifle joint.   “This is all very interesting, but what does this have to do with my ability to perform an ExCap Stifle stabilization?” you may wonder.  Several recent reports describe application of an extracapsular suture as a successful means of controlling this post-TPLO instability and resolving active pivot shift during ambulation.^{8, 9}   The biomechanical evidence in support of TPLO + ExCap suture in these highly unstable stifles is compelling.⁶   So the fact is, even if you are trained in TPLO, eventually you will have the patient who needs an ExCap on top of their TPLO.  Placement of this ExCap suture can be either a modification of traditional lateral fabellar suture or, more elegantly, as a commercially available anchored technique called TPLO Internal Brace (Arthrex Vet Systems, Naples, FL), but confident skills in these ExCap techniques is a pre-requisite to their combination with TPLO.

One of the great things about veterinary orthopedics is that we’re never done learning and there’s always new skills to be developed and added to our “tool kit”.  So, if you’re just starting down your orthopedic learning pathway you should consider taking a course in lateral fabellar suture stifle stabilization … if you’re a little further down the pathway, it may be time to consider training in an anchored ExCap stifle stabilization like TightRope^® … and even if you’re experienced in TPLO, you’ve learned to be wary of selected patients whom may require addition of an ExCap suture. Regardless of where you are on that learning pathway, training in ExCap stifle stabilization remains a logical investment of your time and energy.

Reference Reading & Resources:

1. Taylor-Brown FE, Meason RL, Brodbelt DC, et al. Epidemiology of cranial cruciate ligament disease diagnosis in dogs attending primary-care veterinary practices in England. Vet Surg 2015 (DOI:10:1111/vsu. 12349).
2. Wilke VL, Robinson DA, Evans RB, et al. Estimte of the annual economic impact of treatment of cranial cruciate ligament injury in dogs in the United States. J Am Vet Med Assoc 2005;227:1604-1607.
3. Lampart M, Knell S, Pozzi A. A new approach to treatment selection in dog with CrCL rupture: patient-specific treatment recommendations. https://doi.org/ 10.17236/sat00261
4. Gatineau M, Dupuis J, Plante J, Moreau M. Retrospective study of 476 TPLO’s – Rate of subsequent ‘pivot shift’, meniscal tear and other complications. Vet Comp Orthop Traumatol 2011;24:333-341.
5. Lampart M, Park BH, Husi B, et al. Evaluation of the accuracy and intra-interobserver reliability of three manual laxity tests for canine cranial cruciate rupture – An ex vivo kinetic and kinematic study. Vet Surg 2023;52:704-715.
6. Husi B, Park B, Lampart M, et al. Comparative kinetic and kinematic evaluation of TPLO and TPLO combined with extra-articular lateral augmentation: a biomechanical study. Vet Surg 2023;52:686-696.
7. Yu J, Griffon DJ, Wisser G, Mostafa AA and Dong F (2023). Validation of a novel 3D printed positioning device and dynamic radiographic technique to quantify rotational laxity of the stifle in dogs. Vet. Sci. 10:1118755.doi: 10.3389/fvets.2023.1118755
8. Knight RC, et al. Surgical management of pivot-shift phenomenon (PSP) in a dog. JAVMA 2017;250:676-680.
9. Schaible M, Ben-Amotz R, et al. JSAP 2017;58:219-226. Combined TPLO and lateral fabellotibial suture for CrCL rupture with severe rotational instability in dogs. JSAP 2017:58:219-226.

Ross’ career has spanned both private practice and academia. Along the way, he has been actively engaged in orthopedic training of veterinarians for more than 30 years. Ross is a professor Orthopedics at Colorado State University, Associate Director of Education at the Translational Medicine Institute and a frequent educator at orthopedic courses held here at CSUVetCE and around the world.  If you, too, believe that “what if … thinking” is the key to innovation and advancement beyond that status quo, please get to know us at www.CSUVetCE.com because nothing fuels our passion like rubbing elbows with those who are similarly driven.