Investigation of Cranial Cruciate Ligament Deficiency and Associated Surgical Interventions Using Computer Simulation

Speaker: Gina Bertocci, PhD, PE, University of Louisville

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Dr. Bertocci has combined her life-long passion for animals with her expertise in biomechanics to investigate orthopedic conditions affecting the canine stifle joint (corollary to the human knee). The cranial cruciate ligament (CrCL) is synonymous with the human anterior cruciate ligament (ACL). Why is the CrCL important? Because with injury the dog suffers lameness, pain, inflammation and osteoarthritis. Common treatments are various surgical procedures, but none have proven to be superior or consistent in results.

Collaborating with veterinarians, Dr. Bertocci has applied engineering tools such as 3D computer simulation modeling to better understand the biomechanics of the canine hind limb with a healthy stifle as compared to one with a ruptured cranial cruciate ligament (CrCL) during walking. Additionally, she and her team have implemented various common surgical procedures used to stabilize the stifle following CrCL rupture into their computer model to investigate how effectively these procedures restore normal stifle biomechanics. They are also using their computer model to evaluate the influence of various anatomical characteristics and surgical factors on outcomes. To address alternative solutions for dogs who rupture their CrCL but are not surgical candidates, they are evaluating the effectiveness of an orthosis (a brace) in stabilizing the stifle, and plan to use their computer model to aid in assessing the influence of the different types of brace design.   

An Overview

A cruciate ligament rupture is a rip, or tear, of one of the cruciate ligaments. The cruciate ligaments are ligaments (strong tissues that connects one bone to another bone) that stabilize the knee. They are located within the knee joint forming an "X" pattern and connect the femur (thigh bone) to the tibia (lower leg bone). There are two cruciate ligaments, the cranial (anterior, or in the front) and the caudal (posterior, or in the rear). A cranial cruciate ligament (CCL) rupture is the most common, like human ACL, and is what will be discussed in this article. The CCL functions to stabilize the tibia. It keeps the tibia (lower leg bone) from sliding out of position and also prevents hyperextension and twisting. A rupture can occur in one or both of the rear legs and there are multiple factors associated with it. Any breed of dog can have a cruciate ligament rupture but they are normally seen in large dogs. Overweight dogs are at a higher risk of tearing their CCL than dogs at a healthy weight are due to increase stress put on the knees.

Causes of Cruciate Ligament Rupture

The most common cause of a CCL rupture is sudden trauma. This trauma can be caused by any movement that puts excessive pressure on the knee such as stepping in a hole while running, twisting while the foot remains planted, landing incorrectly when jumping or general rough play. This acute rupture is normally seen in young, large dogs. A chronic rupture is also possible. In this type of injury the ligament degrades (deteriorates) over time. As this occurs the ligament will tear partially causing symptoms to come and go. Eventually a complete tear will occur. This type of rupture is normally seen in older dogs (5 - 7 years old) and in most cases will involve both rear legs.

Prevention of Cruciate Ligament Rupture

Prevention of cruciate ligament rupture is difficult. However, there are some steps you can take to decrease the potential for injury. Maintaining a healthy weight and a regular exercise program are the most important things to consider. Additionally, if a dog has had an early diagnosis of an orthopedic health issue, such as patellar luxation, he/she may be more prone to cruciate ligament rupture. To decrease the probability, surgical correction of these orthopedic issues is recommended as soon as possible.

Symptoms of Cruciate Ligament Rupture

Lameness in the rear leg is the most common sign of a CCL rupture. Other symptoms can include pain and swelling of the joint. Crepitus, a crackling sound, may be heard when the dog walks due to bone rubbing on bone. A popping or snapping sound may also be present if there is damage to the cartilage in the knee in addition to the ligament rupture.

Dr. Bertocci elaborates in her lecture notes:

Cranial cruciate ligament (CrCL) deficiency affects the canine stifle (knee) and is one of the most common canine orthopedic injuries, having an economic impact of more than $1 billion in the United States in 2003. CrCL deficiency has a prevalence of 2.55% across all breeds.

Despite such high prevalence, CrCL deficiency is still poorly understood and is thought to be due to degradation and not the result of trauma. Surgical intervention is often employed to stabilize the CrCL-deficient stifle, but no single surgical procedure is conclusively supported to suggest long-term success, osteoarthritis prevention or superiority. We developed acanine pelvic limb 3D computer simulation model of walking to gain an improved understanding of stifle biomechanics, as well as factors that may predispose dogs to CrCL rupture. This model allows noninvasive visualization and analysis of stifle biomechanics, simulates the intact and CrCL-deficient stifle, and was utilized to investigate anatomical characteristics and biomechanical parameters such as ligament stiffness and tibial plateau angle to gain an understanding of their role in producing CrCL deficiency.  

Our computer model was based on a healthy male Golden Retriever with no orthopedic or neurologic diseases. A pelvic limb computed tomography (CT) scan was conducted to obtain anatomical geometry, and gait was recorded using a motion capture system and force platform. The computer model was developed in computer-aided engineering software and included canine-specific bone geometry, ligaments, muscles and ground reaction forces. Model simulation of the stance phase of walking was used to evaluate loads placed on stifle ligaments, translation and rotation of the tibia relative to the femur, and contact forces between the femur and menisci in both the intact and deficient stifle.  

Commonly employed surgical procedures tibial plateau leveling osteotomy (TPLO), tibial tuberosity advancement (TTA), lateral femoro-tibial suture stabilization (LFTS) and TightRopeTM stabilization (TR) were implemented in the model through collaboration with a veterinary orthopedic surgeon to evaluate the ability of procedures to restore normal, CrCL-intact stifle biomechanics. Ligament loads, along with translation and rotation of the tibia relative to the femur and meniscal loads were evaluated across surgical procedures. Additionally, we will investigate parameters specific to each surgical procedure (e.g. suture tension, tibial plateau rotation angle, etc.) to further our understanding of their influence on surgical efficacy.   

Finally, stifle orthoses (braces) offer an alternative to surgical intervention, especially in patients that are poor anesthesia candidates with significant co-morbidities, that are of advanced age or whose owners lack the financial means for more costly surgery. In partnership with a veterinary prosthetics and orthotics clinic we are characterizing stifle orthosis-using dogs. Additionally, we have implemented a preliminary representation of a customized stifle brace in our computer model to investigate associated stifle biomechanics. Once finalized, we will compare stifle biomechanics during gait in a CrCL-deficient stifle with and without an orthosis to a CrCL-intact stifle. Furthermore, we will investigate stifle orthosis design and fit parameters (e.g., hinge type and strap tension), along with patient-specific parameters, using our computer model to understand their role in orthosis effectiveness.

Funded Research Grant 01892-A: Development of Novel Knee Braces As an Alternative to Surgical Intervention in Cranial Cruciate Ligament Disease

Learn More about Canine Cruciate Rupture

  • Canine Cruciate Rupture - an overview of causes, symptoms, preventions and treatments
  • Stifle Joint Anatomy - a beautiful picture that shows the ligaments attach muscles to bones, and ligaments attach bones to bones, as in the knee and stifle joint

Dr. Bertocci has her BS and MS degrees in Mechanical Engineering and her PhD in Bioengineering. She is a Licensed Professional Engineer. She has three yellow Labradors.

Dr. Bertocci is a professor and Director of the Injury Risk Assessment and Prevention Laboratory at the University of Louisville. She has published more than 60 peer-reviewed journal papers, 125 conference proceedings and 2 patents. Her research interests are in the areas of rehabilitation, assistive technology, injury biomechanics and more recently, canine biomechanics. Dr. Bertocci’s injury biomechanics research has focused on the application of engineering technologies in the early diagnosis and detection of physical child abuse. Her research in the field of rehabilitation engineering has been incorporated into both national and international wheelchair safety standards. Dr. Bertocci’s rehabilitation research has also included the development of technologies to prevent secondary complications, such as pressure ulcers, associated with paralysis to advance the quality of life for humans and animals with disabilities.



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