Treating painful hips: nonsurgical and surgical modalities (Proceedings)

Hip Dysplasia

Hip dysplasia is an abnormal development of the coxofemoral joint. The syndrome is characterized by subluxation or complete luxation of the femoral head in the younger patient while in the older patient mild to severe degenerative joint disease is present. Laxity in the hip joint is responsible for the early clinical signs and joint changes. Subluxation stretches the fibrous joint capsule, producing pain and lameness. When the surface area of articulation is decreased, this concentrates the stress of weight bearing over a small area through the hip joint. Subsequently, fractures of the trabecular cancellous bone of the acetabulum can occur, causing pain and lameness. The cancellous bone of the acetabulum is easily deformed by the continual dorsal subluxation of the femoral head. This piston-like action causes a wearing of the acetabular articular surface from a horizontal plane to a more vertical plane causing subluxation to worsen. The physiologic response to joint laxity is proliferative fibroplasia of the joint capsule and increased thickness of the trabecular bone. This relieves the pain associated with capsular sprain and trabecular fractures. However, the surface area of articulation is still decreased causing premature wear of articular cartilage, exposure of subchondral pain fibers and lameness. This may occur early in the pathologic process or later in life. There are two general recognizable clinical syndromes associated with hip dysplasia: (1) patients 5 to 16 months of age, (2) patients with chronic degenerative joint disease. Patients in group 1 present with lameness between 5 to 8 months of age. Symptoms include difficulty when rising after periods of rest, exercise intolerance and intermittent or continual lameness. The majority of young patients will spontaneously improve clinically around 15 to 18 months of age. This clinical improvement is due to pain relief as proliferative fibrous tissue prevents further capsular sprain, and increased thickness of the subchondral bone prevents trabecular fractures. If symptoms occur later in life, they may include difficulty in rising, exercise intolerance, lameness following exercise, atrophy of the pelvic muscle mass, and a waddling gait with the rear quarters. Physical findings in the younger group of patients include pain during external rotation and abduction of the hip joint, poorly developed pelvic muscle mass, and exercise intolerance. Hip exam performed under general anesthesia will reveal abnormal angles of reduction and subluxation reflecting excessive joint laxity. Physical findings in the older group of patients include pain during extension of the hip joint, reduced range of motion, atrophy of the pelvic musculature, and exercise intolerance. Radio graphically, there are seven grades of variation in the congruity between the femoral head and acetabulum established by the Orthopedic Foundation for Animals. Excellent, good, fair, and near normal are considered within a range of normal. Dysplastic animals fall into the categories of mild, moderate, and severe. It is important to note that clinical signs do not always correlate with radiographic findings. Recently, patients have been evaluated using a distraction index where the degree of hyperlaxity is measured and correlated with standards for each breed.

Treatment is dependent upon the age of the patient, the degree of patient discomfort, physical and radiographic findings, client expectations of patient performance, and financial capability of the client. Conservative treatment is beneficial to a large number of patients in both the young and older patient groups. Conservative management is divided into acute management and long term management. When a dog exhibiting signs of hip dysplasia enters the clinic, it is generally because they have sprained the hip joint. The dysplastic joint is either hyperlax (young dog) has a limited range of motion (mature dog). In either case, the joint is easily sprained and the dog that is presented with symptoms has generally overused (sprained) the hip joint. The management of the case at this time period is the same as treating any other acute sprain. Rest, physical therapy, and non-steroidal analgesics will relieve signs in the majority of patients. Rest is just that!!!, controlled activity with slow walking on a leash only. There should be NO free activity for 2 weeks. Physical therapy includes cold therapy for the initial 1-4 days. Commercial cold packs are the most convenient and precise way to apply cold therapy. The application of cold should only be 5-10 minutes. NSAIDs recommended by the author are: 1. Aspirin (Ascriptin), carprofen (Rimadyl), etodolac (Etogesic), Deracoxib (Deramax). I would not recommend any other "over the counter NSAIDs). The advantage of aspirin (25mg/kg TID) is the low cost. The disadvantage of aspirin is the low efficacy and incidence of GI upset. Aspirin is a COX 1 inhibitor; inhibition of COX 1 de-regulates the balance of normal homeostasis giving rise to a higher incidence of side effects. Aspirin should always be given with a small amount of food. Preferably, give a dose late in the evening so higher blood levels are present early in the morning. Carprofen (1mg/lb BID or 2mg/lb OD) is FDA approved for use as an anti-arthritic medication in the dog. It too should be administerd with a small amount of food. Carprofen is a COX 2 inhibitor accounting for a low incidence of side effects. Carprofen is very effective in controlling discomfort associated with hip dysplasia. The attending veterinarian must always consult with owners relative to side effects of any NSAID. NSAIDs can cause serious side effects and even death in some humans and animals. There is a reported incidence of liver failure in dogs having been given carprofen. The common age of dogs afflicted is most commonly mature adults (8yrs) but liver failure can occur in any age. Although the incidence of liver failure is very low, the clients must be advised of this possibility. Etodolac (Etogesic) is also an NSAID aproved by the FDA for use in the dog. It too is very effective in controlling pain associated with arthritis in dogs and is administered 1/day (4-7mg/lb). Deracoxib is just recently approved for orthopedic pain in dogs. It is highly COX 2 selective which reportedly decreases the incidence of side effects. The attending veterinarian must emphasize that REST and PT are the most important considerations when treating an acute sprains.

Following the acute phase of treatment, the attending veterinarian must consult with the owner regarding long term management of the dysplastic dog. The foundation for long term management of any arthritic joint is weight control, exercise therapy, and anti-inflammatory drugs or supplements. The majority of mature dogs with hip discomfort are over weight. Studies have shown a significant improvement in function if an ideal target weight is achieved. The foundation for weight control is exercise therapy, diet, and owner behavior modification. There are a number of excellent commercial diets on the market. The owner in conjunction with the dog undergo behavior modification. This is a weight reduction program; their dog will be hungry. The owner must not feel guilty but must understand the long term benefits of weight reduction. Convincing evidence might be pictures showing the outcome of previously treated dogs. The attending veterinarian should become familiar with them and chose one or two for use in their clinic. Exercise programs aimed at developing pelvic muscles should begin gradually. Swimming (if available) develops endurance and flexibility. Repetitions of sit-stand exercises also increase endurance and flexibility. Standing, forced flexion-extension exercises (squats) develop strength as does walking uphill with leg weights. If available, an underwater treadmill is an excellent method of exercise. The warm water relaxes sore muscles, the buoyancy lowers joint load, and the water resistance increases work effort.

Administration of drugs (NSAIDs, steroids, PSGAGs, Hyaluronate) or supplements (glucosamine, chondroitin sulfate, manganese) are useful to control discomfort. This is particularly true in the early stages of treatment before the benefits of weight reduction and exercise therapy are realized. The administration of drugs should be at a minimum level (dose and frequency) to achieve comfort. Supplements of glucosamine, chondroitin sulfate and manganese alone or in combination have been shown in vitro as well as in clinical studies to ameliorate discomfort or reduce the dose of drugs needed to control discomfort. The combination of glucosamine, chondriotin sulfate, and manganese ascorbate (Cosequin) has been shown to be significantly more effective in retarding the progression of OA in a rabbit model than was either supplement used alone. This combination has also recently been shown to increase proteoglycan formation in bovine explants and inhibit IL-1 induced collagenase activity. There are a number of supplements (alone and in combination) on the market. There is a great varience in the purity and quality of products. The attending veterinarian must become familiar with the manufacturing process and efficacy data of a supplement he/she intends to use.

Surgical intervention also is divided into techniques useful in the younger population and those useful in mature dogs. Techniques useful in the younger population include Triple Pelvic Osteotomy (TPO), femoral head ostectomy, and possibly total hip replacement. My preference in this aged dog is either a TPO or conservative mangement. In the older dogs, my preference is total hip replacement or conservative management. Femoral head ostectomy is a good option also in cases where conservative management is no longer effective of practical. Surgery is indicated when conservative treatment is not effective, when an athletic performance level is desired or in the young patient when the client wishes to arrest or slow the progression of degenerative joint disease. There are four surgical procedures commonly used for treatment of hip dysplasia: (1) Pelvic osteotomy, (3) Femoral osteotomy, (3) Total hip prosthesis, and (4) Femoral head ostectomy.

Pelvic osteotomy is used in the group of younger patients to axially rotate and lateralize the acetabulum in an effort to increase dorsal coverage of the femoral head. This procedure is indicated in patients that will lead athletic lives such as the working breeds or in those patients in which the client wishes to arrest or slow the progress of osteoarthritis associated with hip dysplasia. The most favorable prognosis is in patients having minimal existing radiographic degenerative changes and an angle of reduction less than 45 degrees and angle of subluxation less than 15 degrees. The prognosis is less favorable in patients with existing degenerative changes and angles of reduction and subluxation greater than those given above. Of the procedures described, the transverse osteotomy (Slocum Technique) is the most effective method of obtaining axial rotation and lateralization of the acetabulum. The details of the technique are beyond the scope of this handout. Briefly, the degree of axial rotation of the acetabulum is set by the previously determined angles of reduction and subluxation. The angle of reduction is the maximum degree of rotation and the angle of subluxation is the minimum degree of rotation. The most commonly used angle of acetabular axial rotation is slightly less than the measured angle of reduction. The pelvis is cut through the pubic brim, ischial floor and body of the ilium. The acetabulum is rotated axially, lateralized and stabilized with the appropriate Slocum osteotomy plate. Postoperatively the patient is restricted to exercise on a leash only until radiographic healing of the osteotomies is complete. If the contralateral side is to be operated, the second surgery can be performed as soon as the patient is clinically functional with the limb initially operated. Reported complications include implant failure, loss of limb abduction, and pelvic outlet narrowing. However, the incidence of complications is very low and the reports of long term clinical function are good to excellent.

Coxofemoral luxation

Dislocation of the hip is usually due to some sort of violent injury eg. vehicular trauma or a significant fall. If there is hip dysplasia, however, the hip can be dislocated by relatively minor trauma eg. catching the foot in a closing door. Dislocation of the joint requires rupture of the teres ligament and severe damage to the joint capsule. It generally requires significant trauma to dislocate a normal hip and there will often be additional injuries eg. other musculoskeletal injuries, thoracic or abdominal trauma. As usual in trauma patients, it is important to examine and assess the whole patient rather than concentrating on an obvious orthopedic injury immediately.

The hip may be dislocated craniodorsally (most common), caudally, ventrally or cranioventrally. The following remarks relate to craniodorsal dislocation. Diagnosis of craniodorsal hip dislocation can usually be suspected based upon the presence of some or all of the following physical signs:Lameness, affected limb is held adducted & externally rotated, affected limb appears shorter than contralateral limb, asymmetry of palpable pelvic landmarks, pain or crepitus upon hip manipulation (especially internal – external rotation), positive thumb displacement test. The diagnosis of hip dislocation should always be confirmed radiographically. There are several reasons for this: confirmation of the diagnosis, assessment of coxofemoral anatomy, many dogs have hip dysplasia and the reduced joint congruity, joint stability and dorsal acetabular rim coverage will compromise treatment, detection of concomitant musculoskeletal injuries. Assuming that there are no complicating features, closed reduction may be attempted initially. Closed reduction will be unsuccessful if acetabular anatomy or stability is compromised. Closed reduction requires general anaesthesia. The patient should be positioned in lateral recumbency with the affected leg uppermost. A towel or similar is passed around the groin on the lower side and held by an assistant. The operator should grasp the foot, rotate the limb slightly externally and apply traction caudally and ventrally whilst the assistant applies counter-traction. When the femoral head engages the acetabular rim the limb should be rotated internally, reducing the hip. Following closed reduction the hip should be flexed and extended briskly for 2-3 minutes whilst medially-directed pressure is applied to the greater trochanter. If the hip appears sufficiently stable a flexion or figure-of-eight sling should be applied. If closed reduction is unsuccessful (i.e. incongruent or unstable) or dislocation recurs despite apparently successful reduction, further attempts at closed treatment will usually be unsuccessful and surgical intervention should be considered. A number of surgical techniques have been described and most clinicians have their personal favourite. Whatever surgical procedure is elected for, it is very important to ensure that the acetabulum is cleared of all soft tissues during open reduction and that the joint capsule is repaired as fully as possible. Healing of periarticular soft tissues is critical for long – term success as most surgical techniques are only capable of supporting the hip temporarily.