Traumatic fragmented medial coronoid process (TFMCP) is a condition in the elbow joint of dogs that appears to occur commonly in performance dogs.
Traumatic fragmented medial coronoid process (TFMCP) is a condition in the elbow joint of dogs that appears to occur commonly in performance dogs. Unlike the classic condition of fragmented medial coronoid process (FMCP) affecting the elbow joints of skeletally immature large to giant breed dogs, jump down syndrome (TFMCP) appears to have no age or size limitations.
The cause and pathogenesis of TFMCP are poorly understood. It is possible that abnormal repetitive loading, such as landing from a jump, hitting contacts or a flyball box, and so on, may lead to microfractures of the bone underneath the cartilage (subchondral fractures). Additionally, increased repetitive loading can arise from contraction of the biceps/ brachialis muscle complex. When the biceps/brachialis contracts, a force is generated that rotates the medial coronoid into the radius. These microcracks disturb the mechanical properties of bone, and if not repaired properly through normal body mechanisms, fatigue fractures develop. Additionally, loss of osteocytes (bone cells), indicated by decreased osteocyte densities, has been strongly associated with the presence of microdamage after fatigue loading. These studies imply that excess load may lead to fatigue microdamage of the subchondral trabecular bone and eventual fracture, which we believe may play an important role in the pathogenesis of TFMCP. Dogs may be further predisposed to this condition if they have elbow dysplasia. Dogs with elbow dysplasia had asymmetric growth of the radius and ulna during development, resulting in elbow joint incongruity. Elbow incongruity such as radioulnar step defects, humeroulnar incongruence/conflict, and varus deformity of the humerus causes abnormal contact patterns in the elbow, specifically at the coronoid trochlear articulation, which is theorized to increase the load on the medial coronoid process (MCP). Regardless of the etiology, if left untreated as a continual lameness, secondary osteoarthritis may progress as noted by damage to the cartilage such as softening, fibrillation, fissuring, and erosions as well as additional subchondral bone microcracks and fragmentation. The free fragments contribute to frictional abrasion ("kissing lesions") of the opposing surface including the medial aspect of the humeral condyle and radial head.
1. History and Clinical Signs
Dogs with TFMCP may present with a history ranging from a subtle intermittent offloading of the forelimb to significant unilateral or bilateral forelimb lameness. This lameness is typically exacerbated with exercise and heavy activity. The onset of lameness is insidious. As lameness persists, it may increase in severity. Affected dogs often place the carpus in an exaggerated valgus position (turned out) when sitting or standing, and circle the foreleg outward and move the elbow away from the midline (circumduct the antebrachium and abduct the elbow) during the swing phase of the stride. The history of dogs with TFMCP typically includes a lack of response to rest and non-steroidal anti-inflammatory drugs (NSAIDs). Many dogs with TFMCP are mistakenly treated for shoulder pathology because the attending veterinarian elicits a pain response when the shoulder is extended. The authors believe the pain response actually arises from the elbow because when the veterinarian performs an extension maneuver of the shoulder, the elbow is usually simultaneously extended. Extension of the shoulder and elbow causes tension in the biceps/brachialis muscle complex. Tension in the biceps/brachialis exerts pressure on the medial coronoid and overlying inflamed joint capsule causing the pain response.
2. Orthopedic Examination
On physical examination discomfort is usually noted on direct palpation of the medial compartment of the elbow joint, specifically the medial coronoid process. Discomfort may also be noted on hyperflexion of the elbow. Most dogs with TFMCP are reluctant to allow for full endrange flexion. In chronic cases, full flexion may not be obtained. Crepitus may be noted when placing the elbow through range of motion. Some investigators suggest that the carpus should be placed in a flexed, externally rotated position while the elbow is extended. Joint effusion may be detected as a fluctuant swelling beneath the lateral or medial epicondyle of the humerus. Depending on the chronicity, atrophy may be noted in the affected forelimb.
3. Advanced Diagnostics
In addition to history, gait analysis, physical examination, orthopedic and neurologic examinations, further diagnostic tests used to differentiate causes of elbow pathology currently consist of hematology, biochemical profile, urinalysis, arthrocentesis, imaging modalities, and arthroscopy. Unfortunately, radiographs have been shown to be of little value because of difficulty identifying the fragment or line of separation using standard radiography. In some chronic cases, however, radiographs may reveal secondary evidence of bony remodeling consistent with osteoarthritis. These changes may include sclerosis within the ulnar notch, and remodeling along the anconeal process and MCP. Advanced diagnostic imaging modalities such as CT scans, MRI, nuclear scans, and arthroscopy may allow confirmation of the condition. Arthroscopic evaluation of the elbow joint allows direct observation of all major intra-articular structures with magnification, "dynamic" evaluation of tissues during elbow range-of-motion tests, and "palpation" of intra-articular tissues using arthroscopic instrumentation. Arthroscopic exploration of the elbow provides a definitive diagnosis of TFMCP when a fragment or cartilage fissure. In a small percentage of cases, advanced imaging (nuclear scan, CT, MRI) indicates fragmentation of the coronoid but arthroscopic observation does not reveal a fissure or fragment. In such cases, the fissures (microcracks) are believed to be within the coronoid bone beneath the cartilage surface.
Treatment of TFMCP is multimodal and includes a combination of medical and surgical management as well as rehabilitation therapy. Through a multimodal approach it is possible to relieve pain and maintain limb function, as well as to return the dog to a normal level of activity and competition.
Arthroscopy is an excellent modality for diagnosing TFMCP as well as a minimally invasive means of treatment. Arthroscopic removal of the fragments is recommended not only to remove the inciting cause of lameness but also to help prevent/slow the progression of osteoarthritis. Arthroscopic treatment may include a combination of techniques such as fragment removal, debridement of diseased tissues, creation of vascular access by abrasion arthroplasty, forage, microfracture, and subtotal coronoid ostectomy depending on the progression and severity of disease. Arthroscopy is not only a great diagnostic modality, allowing for superior visualization of structures within the joint, but also has less soft tissue trauma, shorter surgery and hospitalization times, decreased risk of infection, and shorter recovery times compared to the traditional surgical approach of fully opening the joint (arthrotomy).
Following arthroscopic treatment, dogs are typically prescribed NSAIDs for 14 days to help decrease inflammation and discomfort. Polysulfated glycosaminoglycans (PSGAG) an injectible joint protective agent, is also recommended following arthroscopic treatment and is administered intramuscularly twice a week for up to four weeks. PSGAGs has been shown to decrease the amount of degradative enzymes (that stimulate inflammation and cartilage erosion) as well as promote repair and regeneration of cartilage. In addition, an oral joint protective agent such as glucosamine, chondroitin sulfate, and avocado/soybean unsaponifiables (ASU), is recommended as a daily supplement for life. The anti-inflammatory properties and pain-reducing effects of these supplements have been well-documented. There is also evidence that they may have a cartilageprotective effect.
As with any rehabilitation therapy program, elbow rehabilitation following elbow arthroscopy should follow a sequential and progressive multiphased approach. The ultimate goal of elbow rehabilitation is to return the patient to their previous functional level as quickly and safely as possible. However, each case is uniquely different, and several factors; including duration of injury/lameness prior to surgery, secondary osteoarthritc conditions, surgical intervention performed, all influence the rate at which the patient proceeds through the healing process.
The elbow is predisposed to flexion contractures due to the intimate congruency of the joint articulations, the tightness of the joint capsule, and the tendency of the anterior capsule to develop adhesions following injury. The biceps/brachialis complex also attaches to the capsule and crosses the elbow joint before becoming a tendinous structure and inserting on the ulnar tuberosity. Injury to the elbow may cause excessive scar tissue formation of the brachialis muscle as well as functional splinting of the elbow. Reestablishing full elbow extension is the primary goal of early ROM activities to minimize the occurrence of elbow flexion contractures.
Additional goals of this stage are to protect healing tissue, decrease pain and inflammation, restore weight bearing and retard muscular atrophy. The rehabilitation therapist must not overstress healing tissues during this phase. It is important that the owner restrict the dog's activity to short leash walking only with no running, jumping and rough play.
Elbow dysplasia is the leading cause of forelimb lameness in dogs. Elbow dysplasia is a term used to describe pathology of the elbow joint usually as a result of abnormal bone growth, joint stresses, or cartilage development and includes the presence of one or more diseases of the elbow joint, specifically: fragmented medial coronoid process (FCP)/medial compartment disease (MCD), osteochondrosis (OC) and/or osteochondrosis dissecans (OCD), ununited anconeal process (UAP) and joint incongruency. These conditions may occur individually or in combination within the same joint and often affect both elbows of the same individual. The etiology of these processes is not completely understood. Present theory proposes that unequal development of the radius and ulna during growth is the underlying cause of poor joint confirmation. Other theories include vascular or cartilage development abnormalities. It is generally accepted that there is a genetic basis and these conditions are heritable. Elbow dysplasia predominantly affects juvenile large to giant breed dogs but is also seen in medium and small breed dogs. However, traumatic FCP and elbow incogurency caused by trauma to the growth plates can be seen in any breed.
A brief description of the disease processes associated with elbow dysplasia is provided, however, for the purpose of this article, we will focus on the presentation, diagnosis and treatment of chronic elbow dysplasia.
Contributing Disease Processes
1. Fragmented Coronoid Process (FCP)/Medial Compartment Disease (MCD)
FCP is, by a considerable margin, the most common disease of the elbow. FCP results from abnormal biomechanical stresses to the medial coronoid process resulting in fragmentation of the process. There may be a single or multiple fragments. Damage to the articular cartilage is typically found on arthroscopy (minimally invasive evaluation of the joint using a scope) of the joint and may be mild or in severe cases, full-thickness cartilage loss is seen. Further destruction of the cartilage can occur as the fragment(s) moves around within the joint. The term "kissing lesions" is used to describe damage to opposing cartilage surfaces.
Traumatic FCP resulting from "Jump Down Syndrome" is different in that the cause of the fragment(s) is due to trauma, however, if left untreated, can result in similar destruction of the articular cartilage and development of secondary degenerative joint disease (DJD).
In recent years the term medial compartment disease (MCD) has been utilized to describe fragmented cornoid process as well as other pathology limited to the medial aspect of the elbow joint in which most or all of the cartilage within the medial aspect of the joint is worn away. For this reason, prognosis of MCD is less certain. Unfortunately, MCD can afflict dogs as young as one year of age. Dogs with MCD will likely have some degree of lameness even after arthroscopic treatment for FCP. These dogs usually require continuous medical management.
Early identification and intervention for FCP consisting of arthroscopic excision of the fragment(s) and debridement of the damaged cartilage to the level of subchondrol bone so that the body can form fibrocartilage (similar to articular cartilage) to fill in the defects provides the best possible prognosis. If lameness does not resolve, further diagnostics such at CT (computerized tomography) or arthroscopic re-evaluation may be recommended.
2. Osteochondrosis (OC) or Osteocondrosis Dissecans (OCD)
OC is a defect in the development of subchondrol bone resulting in the formation of a cartilage flap. This is most often seen along the medial aspect of the humeral condyle. If the flap remains adhered to the bone it is referred to as OC. OCD is when the flap separates and is free floating within the joint.
Here again, early identification and intervention consisting of arthroscopic treatment to remove the flap and debride the damaged articular surfaces provides the best possible chance for formation of fibrocartilage and an improved prognosis.
3. Ununited Anconeal Process (UAP)
The anconeal process develops as a separate center of ossification (bone formation) from the ulna and fuses to the ulna by approximately 20 weeks of age. If the union is not present by this time, spontaneous fusion will not occur. Secondary degenerative changes begin to occur as a result.
As with the above disease processes, early identification and treatment is essential in reducing and potentially eliminating the secondary degenerative effects. Treatment may involve attachment of the anconeal process to the ulna or more often complete excision of the process.
4. Joint Incongruency
Elbow incongruency is typically recognized as a step in the articular surface between the radius and ulna. This can result in deformation of contact areas of the elbow joint which leads to subsequent disease.
In cases of premature closure of ulnar growth plate (the area of growth of bones) bowing of the radius can occur as it continues to grow without the ulna. In addition, subluxation of the elbow joint occurs as the radius pushes the humerus out of the joint space. If the incongruency and subluxation is overt, surgical intervention is indicated and may consist of simply cutting the ulna to allow for continued unimpeded growth of the radius. When the ulna is released, the subluxation of the joint is immediately improved. If limb length is grossly affected, a second procedure to lengthen the bone (distraction osteogenesis) is performed.
As with all of the disease processes discussed previously, early identification and treatment provide the best possible outcome.
These therapies are beneficial for patients in which the elbow condition was not diagnosed early on and osteoarthritis has already progressed; for dogs intolerant or nonresponsive to NSAIDs; for frequent episodes of acute exacerbation of their underlying elbow disease; or for dogs who have residual postoperative symptoms (effusion, discomfort on range of motion and lameness) despite surgical and/or medical management and rehabilitation therapy and include:
• Intra-articular injections (injections directly into the joint) of hylauronic acid (HA), cortisone, or stem and regenerative cells (SCT)
• Sliding Humeral Osteotomy
• Total Elbow Replacement
1. Hyaluronic Acid
Hyaluronic Acid (sodium hyaluronate, hyaluronan, HA) is naturally secreted by the joint capsule, however, in an arthritic joint, production and molecular size of the HA is decreased. Intra-articular HA is a form of viscosupplementation which restores the physical properties of joint fluid to aid in the lubrication of the joint, decrease inflammation and degradation and help in cartilage repair. Intra-articular HA has been widely used in the treatment of OA in horses and humans. Several clinical studies in humans have demonstrated relief of joint pain associated with OA following intra-articular injections of HA. Information regarding the effects of intra-articular HA on naturally occurring OA in dogs is not available; however, several experimental studies using intra-articular HA in dogs have been reported. Results from these studies have demonstrated decreases in pain, lameness, and cartilage degradation. There are several forms of hylauronic acid available for intra-articular injection however, Hylartin®V (Pfizer) which is approved for use in horses and used off-label in dogs, is preferred by this author due to its a high molecular weight and response to therapy.
Studies evaluating the effects of intra-articular HA in dogs have shown efficacy with 3 weekly injections. The injections must be given under sterile conditions and may be performed unsedated, sedated or under general anesthesia depending on the patient. Complications from these injections may include temporary increased pain and lameness and septic arthritis. Reportably, over 70% of dogs respond well to HA and improvement can be noted for over 6 months following administration. The author's clinical impression is that HA used alone is useful for mild to moderate elbow OA, but in the treatment of severe elbow OA intra-articular corticosteroid or stem cell therapy is recommended.
In humans intra-articular corticosteroids are recommended in several guidelines for the treatment of patients with OA. The benefits of corticosteroids are reduction in inflammation and improved comfort. Methylprednisolone Acetate (Depo-Medrol®) and triamcinolone acetonide (Vetalog®) are most commonly used. The intra-articular dosing of Depo-Medrol used by this author is two injections performed three weeks apart; or one injection of Vetalog. Intra-articular administration of corticosteroids is performed under sterile conditions with the patient unsedated, sedated or under general anesthesia depending on the patient. Side effects are minimal; however, some dogs show signs of discomfort for the first 12 hours following injection. Administration of Depo-Medrol or Vetalog typically results in pain relief in 24 hours and can last for weeks to months. In humans up to 3-4 injections can be given during a year period. Studies evaluating the safety and efficacy of long-term treatment in dogs are not well reported.
3. Regenerative Stem Cell Therapy (SCT)
Regenerative stem cell therapy (SCT) can also be used in the management of persistent clinical elbow osteoarthritis. Adult regenerative stem cells are multipotent cells located in bone marrow, joint capsule and fat tissue and are capable of maturing into bone, cartilage, tendon or ligament cells and can be used to repair and regenerate damaged tissues such as the cartilage in osteoarthritis. This is performed by harvesting cells from the fat located behind the shoulder, between the back legs, or falciform. The fat is removed surgically and sent to Vet Stem, a company in southern California, where it is purified into regenerative stem cells. Two days after tissue harvest, the regenerative stem cells are returned in sterile syringes and under sedation, the cells are injected into the osteoarthritic joint(s).
Clinical improvement from SCT has been noted in dogs 2-4 weeks after injection and improvement has been seen lasting for up to 2 years. A recent report in Veterinary Therapeutics 2008 evaluated the effect of intra-articular stem cell therapy for the treatment of elbow OA in dogs. This study showed a significant improvement in lameness and range of motion as well as a significant difference in client evaluation (functional disability scores) in patients treated with intra-articular SCT.
4. Sliding Humeral Osteotomy (SHO)
Where extensive erosion of the cartilage surface of the medial compartment of the elbow is evident and is producing significant pain and lameness, a SHO may be performed. This procedure is based on similar procedures that are performed in humans suffering OA of the knee. The procedure realigns the limb to shift the forces off the area of cartilage damage and onto healthy cartilage thereby relieving the pain of grinding of bone and gives the damaged area the opportunity to heal. A horizontal cut through the midshaft of the humerus is made and then by sliding the bottom portion of the humerus toward the inside of the leg, weight-bearing is distributed toward the healthy lateral portion of the elbow joint. This lessens the load to the arthritic medial aspect of the joint. After the cut in the humerus is made, a special plate is applied to the bone, holding it in this new position during healing. As with a traumatic fracture, the bone takes approximately 8 to 12 weeks to heal. Early and long-term clinical follow up have shown favorable response and second look arthroscopy has revealed in-growth of cartilage into the eroded areas of the medial compartment as proof of principle unloading.
5. Total Elbow Replacement (TER)
TER is an option in dogs with severe OA that have discomfort refractory to any of the above modalities and for dogs in which the lateral compartment is affected eliminating use of the SHO procedure. The first TER system was described in 1996. Since then variations of TER systems have been developed. Presently, the TATE Elbow™, developed by Acker and Van Der Meulen, is commercially available. Ten years in development, the impetus for the TATE Elbow™ was Acker's own yellow Labrador retriever, Tate. Tate developed severe elbow dysplasia and while Acker tried the common treatments of injections, arthroscopic surgery, acupuncture and pain medication, the outcome was unsuccessful. Ultimately, the TATE Elbow™ System became the eventual result.
Implementation of the TATE Elbow™ was first performed in July 2007. Since then many dogs affected with intractable elbow arthritis have been treated with this new prosthesis. The TATE Elbow™ is pressed fit as opposed to a stemmed and cemented system. Long term stability relies on bone ingrowth into the porous structure of the implants (osteointegration). Cementless prostheses have potential advantages over cemented models, including reduced risk of infection and reduced rate of implant wear, both of which are regarding as leading causes of post-operative failure. Because the components of this system are impacted simultaneously as a pre-assembled cartridge, there is reduced trauma to the patient and accurate alignment and tracking of the prosthetic components throughout range of motion is guaranteed. A post-operative 8-12 week restorative period is needed for the patient's full functional recovery. There are no long term studies to date evaluating this system.
Elbow dysplasia is a devastating disease. Early identification and treatment of elbow disease is essential for the best possible long-term health of the joint. Unfortunately, early identification can be challenging due to the lack of correlation between the severity of clinical signs and radiographic findings. This is a great source of frustration as a delayed diagnosis can have a profoundly negative effect on prognosis. Therefore, a through physical examination including gait analysis, good radiographic technique, careful scrutiny of the films by a knowledgeable practitioner and arthroscopic evaluation of the joint if any elbow disease is suspected provides the greatest opportunity for appropriate diagnosis, treatment and improved prognosis for the dog. Left untreated or treated after the onset of secondary degenerative changes, DJD can progress to cause obvious discomfort and lameness. In addition, dogs with MCD, despite early intervention of identified pathologies, will likely require ongoing management for osteoarthritis. For these dogs, we can offer treatments from oral or injectable medications and rehabilitation therapy to surgical intervention to help improve function and comfort.