Cranial Cruciate Ligament Insufficiency/Rupture

Cranial cruciate ligament (CrCL or ACL) insufficiency/rupture is the most common, acquired orthopedic condition in dogs. The very large majority of CrCL problems in dogs are associated with chronic ligament degeneration and is frequently not an acute, high energy/impact sport-related trauma. Unmanaged CrCL insufficiencies have been associated with increasing meniscal cartilage damage and chronic, progressive osteoarthritis.

Surgical techniques should involve complete evaluation and treatment of intra-articular structures, either by way of arthroscopy or, less preferably, arthrotomy for comprehensive surgical management of CrCL disease.  These treatments include debridement of damaged or diseased CrCL tissues and partial meniscectomies as required.

The Cranial Cruciate Ligament - Anatomy and Function

The knee - or stifle - joint of the dog relies upon soft tissue structures for stability and integrity. Along with the CrCL, other major soft tissue structures stabilizing the stifle are the caudal cruciate ligament and the meniscal cartilages, all of which are intra-articular (within the the joint), and the medial and lateral collateral ligaments (external to the joint). The quadriceps, hamstrings and calf muscles also play a significant role in the forces acting on the joint.

The CrCL is essentially composed of two bands - a craniomedial and a caudolateral band. The ligament functions to stop cranial (anterior) movement of the tibia relative to the femur, it limits hyperextension of the joint and controls internal rotation of the tibia. The CrCL is thought to be able to resist a force more than four times the weight of the dog before it ruptures.

The CrCL rupture may present in several different ways. There may be a single incident which causes a sudden, complete rupture of the ligament or a complete tearing may occur over time. Dogs may also partially tear or stretch the ligament due to trauma. With a partial CrCL tear, the dog typically experiences intermittent lameness. The majority of partial ruptures will progress, if untreated, to complete tears within a matter of weeks to months.

Obesity and conformational factors increase the risk of a CrCL tear. Dogs that have ruptured the CrCL may have up to a 70% likelihood of tearing the ligament in the opposite hind limb.

Meniscal Cartilages

The cresecent-shaped, medial and lateral meniscal cartlages are also key intra-articular structures that contribute to joint stability and help to evenly distribute weight bearing loads across the surfaces of the tibia.

The menisci are wedge-shaped and are both thicker at the outer edges and posteriorly. The meniscal cartilages have nerve fibers that tell the brain how load is transmitted through the joint. The medial meniscus is often secondarily damaged following CrCL tearing and affects as many as 70-80% of dogs. The medial meniscus may be at greater risk because it is firmly attached to the tibia and may become crushed during the abnormal cranial subluxation of the tibia.

Both the normal appearance of the meniscal cartilages (left) and typical meniscal tear configurations (right) are depicted schematically below.







Arthroscopic images of the normal medial meniscus below.












Arthroscopic images of several, typical, large bucket handle tears of medial meniscus may be seen below.














The Treatment of CrCL Tears in Dogs



Stifle Arthroscopy with Tibial Plateau Leveling Osteotomy (TPLO)... the "Gold Standard"


First described by Slocum in the mid-1980s, the TPLO procedure provides stability to the CrCL deficient knee during weight bearing by altering joint mechanics - the tibial plateau angle (slope) is acutely decreased to 5-6 degrees from an average slope of 24-28 degrees. During TPLO, the surgeon will use a bone saw to make a curved cut (osteotomy) in the proximal tibia and rotate the top (plateau) segment so that the load-bearing surface of the tibia is now "level" with the long axis of the tibia. A bone plate with screws is then applied to hold the tibial plateau in this new position and to allow the bone to permanently heal in the new orientation.

Recovery time and complete return to normal activities following the TPLO procedure is rapid - approimately 10-12 weeks. Immediately following knee arthroscopy and TPLO surgery, dogs will typically use the operated limb and are more comfortable much sooner than following extracapsular techniques (see below). For these reasons, and others, TPLO is considered by a majority of board-certified specialists to be the "gold standard" for management of CrCL tears in dogs.


The ASG Scottsdale and Arizona Canine Orthopedics & Sports Medicine approach is locally unique and exceptional based on:

-  Stifle arthroscopy avoids excessive tissue trauma - no large incisions are required

-  Arthroscopy allows for improved visualization for much more precise joint manipulations

-  Arthroscopy allows for a now limited surgical approach to the tibia with less joint and muscle tissue trauma

-  Exclusive use of the finest orthopedic implants - the Synthes locking bone plate and cortex screws (see images below)

-  TPLO offers the greatest versatility and may be performed on dogs as small as 10 pounds up to 200 pounds or more 

-  An experienced ACVS board-certified surgeon who has performed more than 1900 TPLO procedures

-  Very early return of weight bearing function with significantly less complications

-  Earlier postoperative bone healing (est 45-50 days) as compared to published, national experience



Do your homework... all TPLOs are not the same!  What had once been a uniform and structured techique performed by a small number of board-certified specialists using the same instrumentation and orthopedic implants has today become a tremendously variable procedure with potentially equally variable outcomes.


Today, there are literally hundreds of combinations of techniques (arthroscopy vs. arthrotomy, muscle elevation, meniscus release), the use of and type of temporary alignment jigs and cutting guides, different saws and blade combinations and more than a half dozen different manufacturers of varying sizes and shapes of bone plates and screws implants.



In short, all TPLOs are not the same!






The Synthes Locking Bone Plate and Self-Tapping Locking Cortex Screws System... simply the best!





Incorporates the latest technological innovations in bone plating

Precontoured locking plate maintains proper alignment for improved joint function

Minimizes intra-op manipulations and reduces total surgery time 

Locking, fixed angle bone plate-screw construct provides the most stable fixation

Allows for early postoperative mobilization and weight bearing

The limited contact profile and anatomic design preserves blood supply to the bone

Least complicated and rapid bone healing - nearly half that of other implant systems







The immediate postoperative radiographic images below are examples of precise TPLO planning, excellent limb alignment and ideal orthopedic implants size and position.


“How and why is there so much variability in how a Tibial Plateau Leveling Osteotomy (TPLO) may be performed and how might this affect outcome?”


Following the earliest clinical investigations of TPLO in the mid- to late 1980s, this once tightly controlled and even regulated operation was approached with a very high degree of consistency, viz., smaller numbers of experienced, board-certified veterinary surgeons were using very similar techniques, the same instrumentation and implant systems. 


Originally consistent and reliably successful results reflected the uniformity of the surgical approach.


Presently, there are a very large number of veter-inarians - both specialists and general practitioners - with widely diverse backgrounds, surgical training and orthopedic experience performing TPLO.


In addition, there are now literally several hundreds of ways to perform TPLO based on differences in technique, instruments and very different implants.


And while there may be numerous acceptable TPLO techniques that lead to successful functional recoveries, only common sense suggests that with so much variability amongst surgeons and the procedure itself, there will likely be vastly different outcomes.  In other words, “all TPLO’s are not the same!”


Finally... why would a native of Dallas, Texas drive her breed national champion and master hunter Labrador Retriever more than 1000 miles over 15 hours to come see the surgeons of ASG Scottsdale and Arizona Canine Orthopedics & Sports Medicine? See for yourself and click here.




Below are four cases of previously operated dogs referred to ASG for salvage. Each is an example of poor TPLO techniques and outcomes.  In the case of the second series of radiographs, serious intra-operative complications associated with TPLO, a broken jig pin, poor surgical technique and resulting formation of a ring sequestrum resulted in uncontrolled infection and loss of the limb.







Other Bone Cutting Techniques


In additon to the standard TPLO, there are four alternative bone cutting techniques including the CORA-based TPLO (cbTPLO), the Tibial Tuberosity Advancement (TTA), Triple Tibial Osteotomy (TTO) and the Cranial Tibial Wedge Osteotomy (CWO or TWO).

The information below decribes these alternatives and, in plain language, addresses some of the common misconceptions and misleadings associated with the tibial osteotomies.




The Tibial Tuberosity Advancement (TTA)

TTA is a newer (ca. 2004), alternative "bone cutting" surgical procedure designed to correct the CrCL deficient stifle and relies upon the patella tendon to provide joint stability. The objective of the TTA is to neutralize tibiofemoral shear force during weight bearing loads.

TTA advances the tibial tuberosity (patella tendon insertion) forward and thereby changes the angle of the patella tendon such that it is perpendicular to the tibial plateau at normal standing angles. This movement relieves the load required of the CrCL and applies that load to the patella tendon.


During TTA, the tibial tuberosity is cut vertically and moved forward a predetermined distance. The advanced bone is classically, and according to the original described technique, held in place by a titanium "cage", fork and tension band plate. Bone is expected to grow over and through the cage-like spacer and fills the void between the tibia and the advanced tibial tuberosity. See images at right.


Now for some straight talk on TTA...


1. The TTA technique is claimed by some to be less invasive than the TPLO.


FALSE. TTA is a bone-cutting operation that requires a saw to break the bone of the tibia, to move that bone and hold it in place with permanent, metallic orthopedic implants. As such, it is by definition an invasive technique. Ironically, these same practitioners will perform open approaches (arthrotomy) to the knee to treat the torn CrCL and meniscus. Arthrotomy requires much longer and deeper incisions through the muscle of the thigh and joint capsule.


2. As with TPLO, the TTA is appropriate for most dogs with a CrCL tear.


FALSE. TTA is not appropriate for dogs with tibial slopes greater than 27-30 degrees. TTA may also not be suitable for large or giant breed dogs because of the limitation in the size/width of the cage implants. Lastly, TTA is not recommended in dogs with normal variations of tibial conformation, viz. a "low" tibial tuberosity.


3. TTA presents numerous problems should implants removal be required.


TRUE. New healing bone will grow into and over the TTA cage with time. Should implants removal be required due to pain, loosening, breakage and/or infection, aggressive surgery may be required to extract the cage with the creation of a large and potentially unstable bone defect.


4. Be wary of newer and alternative TTA fixation techniques.


TRUE. Certain wedge-like ceramics or biofoams have been suggested as an alternative to the classical technique. Bone fixation may be limted to a single pin and be grossly inadequate resulting in tibial crest instability, fracture and loss of tuberosity advancement with recurrent joint instability.




Triple Tibial Osteotomy (TTO)



By changing the geometry of the forces and muscle contractions that at on the stifle during weight bearing, TTO aims to neutralize the shear force that causes the cranial movement of the tibia with respect to the femur.


Shear force develops because the dog's tibial plateau - the weight bearing surface of the joint - is sloped caudally (downwards towards the back of the joint) and there is an acute angle between the tibial plateau slope and the patellar tendon.


In the TTO procedure, three distinct osteotomies (saw cuts into the bone) performed to adjust the tibial slope so that it is aligned at right angles to the patellar tendon - as with the TTA - instead of sloping backwards. By this approach, shear forces within the joint are neutralized and the joint is stable as the dog bears weight.


The TTO procedure had been developed as a certain hybrid of the two previously reviewed techniques - the Tibial Tuberosity Advancement (TTA) and the Tibial Plateau Leveling Osteotomy (TPLO). The TTA neutralizes shear force within the stifle by advancing the tibial tuberosity until the tibial plateau is at right angles to the patellar tendon. The TPLO neutralzies shear forces by rotating the tibial plateau so that it is approximately horizontal (5-6 degrees) with respect to the long axis of the tibia. The TTO combines these very different approaches and, as such, less radical bone excursions are theoretically required.


The TTO involves removing a small, horizontal wedge of bone (average 12 degrees) halfway along a vertical osteotomy in the tibial tuberosity (as with TTA). By removing this wedge of bone and "closing" of the resulting horizontal defect, the tibial plateau may be levelled and the tibial tuberosity advanced simultaneously. The end result yields an average of 20 degrees of tibial plateau leveling as with the TPLO and approximately 9-12 mm of tibial tuberosity advancement like TTA.




Cranial Tibial Wedge Osteotomy (CWO) 


In certain circumstances of CrCL insufficiency and due to either (1) very small patient size and/or (2) excessive tibial plateau angle, s small wedge of bone may be remnoved from the proximal tibia with "closing" bone reduction and plate/screws fixation to reduce the tibial slope.





Extracapsular Suture Techniques



There are numerous methods of CrCL “repair” which attempt to provide stability to the stifle joint by using suture prostheses made of varying sizes and types of material (nylon, fishing line, polypropylene, FiberWire®, Ethibond™, etc.), with varying numbers of sutures, locations and methods of fixation. Some materials and techniques, naturally, are likely better than others. And in the case of commonly used fishing line, well... it's probably best-suited for fishing!


One of the most common approaches, also known as a Lateral Extracapsular Suture Stabilization (LESS) involves placement of a single suture loop external to the joint from over/around the lateral femoral fabella and through a bone tunnel drilled in the tibial crest to mimic the orientation of the CrCL.  When tensioned appropriately, these suture prostheses control, to some degree, abnormal joint motion - for a time.  A common misnomer is to refer to this approach as an “artificial ligament” - it is not.  The suture(s) provide only temporary stabilization and will loosen, break or fail over time.  These techniques rely upon degenerative, joint capsule thickening (scar tissue) to provide long term joint support.  Peak, though not necessarily complete, recovery following LESS is typically seen at 18-20 weeks postoperative.


At ASG, we believe the best and most appropriate implant for this technique is Arthrex FiberWire - a major advancement in orthopedicsurgery.  FiberWire is constructed of a multi-stranded long chain ultra-high molecular weight polyethylene (UHMWPE) core with a braided jacket of polyester and UHMWPE that gives FiberWire superior strength, soft feel, unequaled abrasion resistance and outstanding biocompatibility.


Common complications and technique error of LESS is an inappropriately positioned tibial tunnel and over-tightening of the suture implant(s).  This leads to pain, decreased joint range of motion, excessive joint compression, cartilage damage, risk of meniscal injury and early implant failure.                                                                                                                                 



The next progression... Arthrex FASTak™, Corkscrew®, SwiveLock® and TightRope®



The Corkscrew and FASTak suture anchors (see product images at right) were designed to provide the highest strength possible in a variety of indications - including the cranial cruciate ligament insufficiency in the dog.


These anchors make operations simple, safe and, importantly, reproducible with easy to use depth and alignment aids.   Combined with the high strength characteristics and increased abrasion-resistance of FiberWire, suture breakage is virtually eliminated during tensioning and knot tying.


The FASTak and Corkscrew implants are suitable for dogs ranging from xx-yy and aa-bb pounds, respectively.




In clinical application at ASG, at left is the postoperative radiographic appearance of the FASTak anchor in a Cocker Spaniel dog for management of cranial cruciate ligament rupture/insufficiency.















The TightRope® CCL technique was introduced in 2005-2006 and provides an option for extracapsular stabilization of the cranial cruciate ligament-deficient stifle.


TightRope® CCL utilizes very strong and stiff bands of synthetic material called FiberTape® (as opposed to previously used, conventional suture materials) passed through small bone tunnels of the tibia and femur.


The objective of TightRope® CCL is to counteract cranial tibial thrust, cranial drawer and internal tibial rotational instability while providing more optimal joint range of motion.


The TightRope® CCL technique avoids the trauma of cutting through the bone of the tibia like a TPLO, TTA or TTO (see below). 


The TightRope® CCL technique is based on the lateral fabello-tibial suture (LESS) principle. The purported advantages of TightRope (TR) over the LESS include bone fixation at both tibial and femoral attachments, more accurate isometric placement and the superior strength, stiffness and creep characteristics of the implant.


Multicenter data suggests TightRope® CCL can be safely performed in medium, large and giant-breed dogs with variable outcomes and nearly 10 percent complications requiring additional treatment.