Non-operative management of cruciate deficient dog stifles

Issues involving ear crops, declaws and knee and back surgery. Questions, answers, theories, and evidence. Why are these surgeries more common in the United States than Europe?

Non-operative management of cruciate deficient dog stifles

Postby guest » Fri Sep 26, 2003 4:47 pm

CRUCIATE DISEASE: PATHOPHYSIOLOGY AND EXPECTATIONS

Loïc M. Déjardin, DVM, MS, Diplomate ACVS, Michigan State University, East Lansing, Michigan
ACVS Symposium Equine and Small Animal Proceedings
October 1, 2002



CRUCIATE DISEASE: PATHOPHYSIOLOGY AND EXPECTATIONS

Loïc M. Déjardin, DVM, MS, Diplomate ACVS, Michigan State University, East Lansing, Michigan

2002 ACVS Veterinary Symposium Equine and Small Animal Proceedings

Small Animal Seminar

Arthrology Track

Keywords: cruciate ligament, pathophysiology, therapeutic, canine

Cranial cruciate ligament (CCL) rupture is the most common injury to the stifle joint of dogs and is the primary cause of degenerative arthritic changes diagnosed in that joint. As such, CCL injuries constitute one of the preponderant activities of many small animal practices.

Functional Stifle Anatomy

Relevant stifle anatomy: Cruciate and collateral ligaments are the major static stabilizers of the stifle, although menisci, joint capsule and peripheral musculature also contribute to joint stability. From its femoral origin to its tibial insertion, the CCL twists 90° on itself as it crosses the joint in a cranio-medial direction. The CCL comprises 2 functionally distinct bands: the thin cranio-medial band, taut throughout the range of motion (ROM) and the bulkier caudo-lateral band, which relaxes during stifle flexion.

Stifle kinematics: Stifle motion can be described with respect to 3 mutually orthogonal axes. Rotation about and translation along each axis describe 6 basic movements, each of which is limited by various ligamentous constraints. Normal stifle motion is a combination of flexion-extension about a medio-lateral axis with internal-external tibial rotation about a dorso-ventral axis. Hyperextension is prevented by progressive tensioning of the caudo-lateral band and to a lesser extent by CCL impingement on the intercondylar notch and by the collateral ligaments. Internal tibial rotation occurs during flexion due to lateral collateral ligament relaxation and is limited by the twisting of the cruciate ligaments about one another. Because of its spatial orientation and anatomical structure, the CCL also prevents cranial tibial translation throughout ROM. Accordingly, CCL failure allows for hyperextension, excessive tibial internal rotation, and cranial tibial translation. Such abnormal movements cannot be limited by secondary constraints (collateral ligaments, menisci) and consequently often induces abnormal stresses to these structures eventually leading to secondary injuries such as meniscal tears.

Stifle biomechanics: Ground reaction forces (GRF) are external forces exerted by the ground against the body in reaction to gravity. For the rear legs, GRF approximate 40% of body weight (BW) at rest and increase with body velocity and acceleration, reaching 70% BW at the trot. To maintain equilibrium or generate motion, GRF must be counter-acted by muscle forces which mechanical efficiency demands joint stability. The combination of GRF and muscle forces during physiological activity generates joint forces largely exceeding BW, which, in turn, may produce high stresses on passive restrains such as the CCL. For example, the resultant of GRF and extensor muscle forces during weight bearing generates compressive forces along the tibia. Because of the slope of the tibial plateau, tibial compression generates a cranially oriented shear force that induces cranial tibial translation in CCL deficient stifles. The shear component of the compressive force at the knee, termed cranial tibial thrust (CTT), is opposed by the intact CCL. The magnitude of the CTT essentially depends on the magnitude of the GRF and is likely amplified by greater tibial slope angles.



Pathogenesis

Rupture of the CCL occurs when the tensile strength of the ligament has been exceeded following acute severe trauma or more commonly because of chronic degenerative weakening. In the later case, even minor stresses during normal activity (running or jumping) may result in CCL rupture.

Traumatic CCL rupture: Acute, traumatic ruptures of the CCL are uncommon and are generally observed in younger animals. The injury occurs as a result of specific, sudden stresses such as internal rotation and/or hyperextension of the limb and may show as mid-substance tears or avulsions. Major trauma (e.g., hit by car) resulting in CCL rupture are commonly associated with concurrent ligamentous and/or meniscal injuries. More often, CCL weakening result from repetitive microtrauma. Such stress injuries may result from various conformational or anatomical causes. Increase in stifle angle (straight-legged dogs) results in continual relative stifle hyperextension, which may increase CCL stresses. Similarly, medial patellar luxation may increase the risk of CCL rupture by causing excessive tibial internal rotation and by compromising the cranial stability of the stifle. Congenital intercondylar notch (ICN) stenosis resulting in CCL impingement during motion has been proposed as a possible cause of CCL rupture in dogs. Its impact on CCL rupture, however, is unclear as ICN stenosis is a common consequence of degenerative joint disease. Because of the tibial plateau slope, the tibial condyles tend to slide cranially as the joint is loaded during stance phase. Cranial tibial translation, however, is primarily resisted by the CCL. Consequently, increases in tibial plateau slope angle could increase CCL stresses thus leading to fatigue failure. Finally, chronic joint overload resulting from obesity is a well-recognized contributing factor to further weakening of the CCL. The higher incidence of CCL rupture in spayed females has been attributed to the excessive weight gain that frequently follows neutering.

CCL degeneration: Most often, CCL weakening result from age related degeneration. Indeed, by 5 years of age, the CCL of large dogs (BW>15kg) consistently shows microscopic evidence of degeneration, which results in a significant deterioration of its material properties. In smaller dogs (BW<15 kg), CCL degeneration tends to occur later in life and to a lesser extent. Histologically, most changes occur within the poorly vascularized central 1/3 of the CCL and include loss of fibroblasts, chondroid metaplasia, decreased vascularity and loss of the collagen crimping. Similarly, studies have demonstrated that decreased physiological stresses result in a rapid and significant decline in mechanical properties of tendons and ligaments. This may explain the frequency of CCL rupture in dogs having sedentary life styles. Immune-mediated arthropathies such as rheumatoid arthritis have long been associated with CCL rupture. The immune-mediated origin of CCL rupture has been strengthened by the increasingly frequent diagnosis of lymphocytic plasmacytic synovitis and the finding of anticollagen antibodies against type I and II collagen in the serum and/or synovial fluid of dogs with CCL rupture. It is unclear, however, whether such immune reactions cause or follow CCL ruptures.

Regardless of its cause, stifle instability following CCL rupture induces a consistent cascade of events, which include capsulitis, synovitis, articular cartilage degeneration, osteophytosis, bone sclerosis, and meniscal injuries. Because of the severe morbidity associated with CCL rupture the ultimate therapeutic objective is to prevent or limit the progression of degenerative joint disease (DJD) through the appropriate combination of medical, surgical and post-operative treatments.
<snip>

Non-operative management of CCL deficient stifles: Along with controlled activity for 2 to 3 months (leash walks, swimming) and passive ROM with massages and heat, weight control is essential to clinical improvement of chronic lameness via improved muscular fitness, decreased adhesions and improved lymphatic drainage. In addition, anti-inflammatory drugs can be used to reduce inflammation resulting from joint instability. Aspirin (a cyclo-oxygenase inhibitor) is one of the most potent nonsteroidal anti-inflammatory drugs (NSAID) and the most commonly used in the treatment of osteoarthritis. As with most NSAID, side effects result from prostaglandin synthesis inhibition and include GI upsets/ulcerations and coagulopathies. The safety margin of NSAID has greatly improved since the recent introduction of selective prostaglandin inhibitors (known as COX-2 inhibitors) such as carprofen and etogesic. Although efficient in reducing cartilage erosion and osteophytosis, steroids are fraught with serious systemic side effects and should only be used as a last resort. Chondroprotective drugs (hyaluronic acid, polysulfated glycosaminoglycan, and glucosamine) are the newest, recently approved, drugs used in the treatment of osteoarthritis in dogs. Although of great potential, cautious use of such drugs is recommended until conclusive results of clinical trials are available.

<snip>
Primary repair of CCL tears or avulsion are rarely attempted because of technical difficulties inherent to CCL degeneration, poor healing ability, or small size of the avulsed bone fragment.

<snip>

With careful treatment selection, management of CCL deficient stifles has yielded 85% to 90% of favorable results regardless of the treatment modality. Further improvement may require implementation of better medical and rehabilitation protocols
<snip>
guest
 

neuter increase risk of ACL tear

Postby drmalernee » Thu Mar 17, 2005 6:49 am

Canine ovariohysterectomy and orchiectomy increases the prevalence of ACL injury.
Clin Orthop [429]:301-5 2004 Dec

Slauterbeck JR, Pankratz K, Xu KT, Bozeman SC, Hardy DM
Texas Tech University Health Sciences Center, Department of Orthopaedic Surgery, 3601 4th St., 4A136, Lubbock, TX 79430, USA. jimmy.slauterbeck@ttuhsc.edu
To determine whether canine ovariohysterectomy or orchiectomy affects the prevalence of anterior cruciate ligament injury, we compared injury rates of anterior cruciate ligaments of animals that had gonadectomy and animals that were sexually intact as a function of gender, breed, or size. Records of 3218 dogs treated in one orthopaedic veterinary practice during a 2-year period were retrospectively reviewed. Anterior cruciate ligament injury, diagnosed by a history of acute hind limb lameness and by positive anterior drawer test, was confirmed at the time of surgery. The prevalence of anterior cruciate ligament rupture in all dogs was 3.48%. Females that had ovariohysterectomy and males that had orchiectomy had a significantly higher prevalence of anterior cruciate ligament rupture than the sexually intact dogs. Larger dogs had an increased prevalence of anterior cruciate ligament injury compared with smaller or medium-sized dogs, with the increased rupture rates for sterilized animals holding across breeds and sizes. Sterilization of either gender increased the prevalence of anterior cruciate ligament injury, suggesting a potential effect of gonadal gender on prevalence of injury of this ligament.
drmalernee
 
Posts: 5
Joined: Sat Aug 16, 2003 8:01 am


Return to Ear Crops, Declaws Knee and back Surgery

Who is online

Users browsing this forum: No registered users and 2 guests

cron