Walking the TightRope on cruciate repairs

Patty Khuly, DVM
Updated: October 05, 2010
Published: March 02, 2009
Share this:

Got a pet with a cruciate ligament injury? Well then, get ready, I’m armed with information and opinions. 

This time it’s not about the injury itself or specifically about the cost of its repair (check out parts one and two of this series for more info). No, this post is about the new pup on the block, the so-called TightRope technique for cranial cruciate ligament repairs (“cruciates” for short)––with some money-oriented considerations thrown in out of necessity. 

In case you’re not super tuned-in to the happenings on the surgical side of veterinary medicine, here’s the skinny:

Cranial cruciate ligament injuries are a common problem in the canine knee. It can happen suddenly, but more often it’s a slow burn kind of injury that occurs as the ligament degrades over time. 

Often, owners have no idea their pet has a problem since pets are masterful at occulting their discomfort. In fact, it’s typical for me to have to “prove it” by asking owners to feel the "thicker" knee for themselves, compare it to the other, and observe the amount of loss of muscle on the affected side. 

The cranial cruciate ligament is a critical structure that plays an indispensable role in stabilizing the knee joint. It’s injury leads to destabilization of the joint and its inevitable descent into osteoarthritis––that is, unless surgery is undertaken.

The surgical approaches to this problem are as numerous, varied and debated as climate change and natural selection. Sure, there’s science...but then there’s the very human element of surgical talent, price, personal opinion and an almost-religious adherence to some technologies over others. 

To make it simple, you can think of the most common cruciate techniques as falling into two major categories. 

1. The TPLO (tibial plateau leveling osteotomy), or one of a variety of other leveling osteotomy procedures, is the surgery most board certified surgeons recommend for dogs weighing in at over 25 pounds. 

This procedure involves the placement of a metal plate at the knee. It’s goal is to closely replicate the natural position of the joint so as to limit the abnormal mechanical stresses caused by a destabilizing injury.

Sounds great. Lots of hard science backing it, too. Problem? It’s expensive. At $2,000 to $5,000 a knee, it can be a hard sell for pet owners when less expensive procedures are available. Furthermore, its use requires a certification process, making it less accessible to general practitioners. 

2. The extracapsular repair is perhaps the still most widely performed surgery for cruciate ligament injuries. Its the one even board certified surgeons tend to perform on smaller dogs (and cats). And its lower price-tag ($750 to $2,000) makes it more attractive to owners who might not be able to afford the board-certified surgeon’s best advice. Moreover, it’s an orthopedic procedure many general practitioners are willing and able to perform. 

The goal of this procedure is to mimic the ligamentous integrity of the knee by passing a strong suture material through two tunnels in the adjacent bone.

The trouble with extracapsular repairs is that while they may mimic the injured ligament, they can’t offer the same concessions to mechanical integrity that the TPLO and its variants do. The knee is never as stable as with the TPLO, say TPLO proponents––unless, that is, we’re talking about a smaller dog (or cat). 

The extracapsular repair is not so hard to do as the TPLO, but, as many boarded surgeons like to say...it’s hard to do well.

That’s why a new entry into the cruciate surgery market is making a big splash. The TightRope device, marketed by surgical equipment manufacturer Arthrex, promises to make extracapsular repairs more stable, more minimally invasive and more foolproof. 

Consisting of strong bone anchors and a super-strong, braided polyethylene band, the TightRope device has become so popular that it’s become synonymous with the procedure itself. Surgeons I’ve surveyed, however, urge caution in the face of popularity: It’s not a new procedure at all, they say, it’s more like a “new and improved” version of an extracapsular that may not be so “improved.”

If my read of the online surgical community’s consensus holds, the TightRope might be a great device for the same candidates who were formerly excellent subjects for exctracapsular repairs (cats and smaller dogs), but the TightRope is not a surefire fix for most cruciates that ail us. 

That’s because the TightRope, like other extracapsular repairs, does not limit the shearing forces that affect the unstable knee like the TPLO is designed to do. Therefore for larger breeds, it’s faulty by design, some say. This anti-TightRope camp proposes that its implementation in larger breed dogs is equally ineffective as any other extracapsular repair. 

In other words, the TightRope may well be a swan...but it’s still in the duck family. And at a higher pricetag (add another $250-$750 for the TightRope version of the extracapsular repair)...is it really worth it? 

Moreover, though the TightRope is touted as minimally invasive, it requires three bone tunnels instead of two and three incisions instead of one. Though the incisions are meant to be smaller, the ones I’ve seen online don’t measure up to my local surgeons’ smallish TPLO cuts. (The yellow lines below indicate skin incisions.)

And yet there’s no doubt that the TightRope’s new twist on and old stand-by is at least that––a novel approach––one that deserves the test of time to see whether it will truly make a difference over other extracapsular repairs...or maybe even measure up to the TPLO for large breed dogs (though most surgeons strongly doubt this latter possibility). 

The sad truth is that while a tremendous amount of research has gone into the study of this common injury and its surgical repair, studies evaluating the outcomes of surgical treatment are still lacking. Does it make a difference which procedure we choose? The degree of surgical skill employed? Which size or conformation of pet is treated? 

The answer is likely to be yes on all three fronts. But the degree of importance of each of these factors is missing from our knowledge base. And then there’s the issue of price: At what price is the TPLO repair too much? Is it worth the hefty price differential to have a boarded surgeon perform a repair (whatever your choice of procedures) rather than your general practitioner? 

If cruciate injuries in dogs will continue to occur, unabated (as we expect them to), and if  we don’t determine all of the answers to the above questions, then veterinarians like me will still have to make recommendations based on theoretical knowledge, our own observations and recommendations from those who know better than we. 

Since that’s the case I’ll parrot the surgical community I respect and urge caution should you choose to walk the TightRope. Novelty and innovation are necessary in veterinary medicine, but with what we know today, I would still expect your large and giant breed dogs to receive a board-certified recommendation for TPLO. 

If you do choose an extracapsular or its TightRope varietal just be sure your veterinarian can answer all your questions and offers significant cruciate experience (mo’ experience is always mo’ better). And remember, regardless of what anyone might say, a board-certified surgeon is always best––regardless of what you can or can’t afford.