Hip dysplasia in dogs: treatment options and decision ...

COMPANION ANIMAL PR ACTICE

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Sandra Corr graduated from Glasgow in 1985, and spent six years in small animal and equine practice. She subsequently worked at the University of Zimbabwe as a lecturer in small animal surgery for two years, before returning to the UK to undertake a PhD in gait analysis at the Roslin Institute and a residency in orthopaedics at Glasgow. She is currently a lecturer in small animal surgery at the Royal Veterinary College. She is a European specialist in small animal surgery.

Ventrodorsal view of the pelvis and coxofemoral joints of a young dog with severe bilateral hip dysplasia. Marked degenerative changes are apparent bilaterally, with luxation of the femoral head and apparent infilling of the acetabulum on the right side

Hip dysplasia in dogs: treatment options and decision making

SANDRA CORR

HIP dysplasia remains a common orthopaedic disease of dogs despite many years of selective breeding based on early detection of affected animals through the British Veterinary Association/Kennel Club (BVA/KC) Hip Dysplasia Scheme. While selective breeding can alter an animal’s genes, factors such as diet, bodyweight and exercise have a major influence on the phenotypic expression of an individual’s genotype. For example, labrador retrievers fed 25 per cent less than littermates fed ad libitum have been found to have a lower frequency and severity of hip dysplasia and subsequent osteoarthritis. Although controversial, it has been suggested that as few as 24 per cent of young dogs with severe radiographic signs of hip dysplasia will actually develop clinically significant hip disease if managed appropriately. This can make it difficult to determine whether an individual dog should be managed conservatively or surgically and, if the latter, when the most appropriate time is to perform that surgery. This article reviews the current literature on the treatment of dogs with hip dysplasia and discusses the indications for surgical management of the condition.

PATHOPHYSIOLOGY

Hip dysplasia is a developmental disease and the major initiating factor is joint laxity. Dogs that are genetically predisposed to hip dysplasia have macroscopically normal hips at birth, but changes begin within the first few weeks of life (see top box on page 67). In the immature dog, osteophytes develop on the articular margins, the transitional zone where the joint capsule merges with the periosteum. As the dog matures,

joint remodelling creates a larger surface area over which the forces are distributed, reducing focal stresses, and resulting in the altered radiographic appearance of the femoral head and neck. Clinically, animals tend to present at two stages: ■ AT LESS THAN 12 MONTHS OF AGE, when laxity predominates, and pain arises due to increased focal stresses between the femoral head and acetabular rim; ■ AT OVER TWO YEARS OF AGE, when the clinical signs are a result of osteoarthritis. Pain is caused by exposure of subchondral bone and inflammation within the joints. Between these two stages, clinical signs often decrease, as periarticular tissues thicken and restricted movement occurs. Appropriate conservative management also encourages muscular development that provides support, further limiting clinical signs.

PATIENT ASSESSMENT

CLINICAL SIGNS

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Radiograph of a young dog with hip dysplasia. There is obvious remodelling of the subluxated femoral head, osteophytes at the articular margins (white arrow) and sclerosis of the acetabulum (black arrows)

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Clinical signs may range from mild stiffness on rising or a reluctance to jump, to the classical ‘wiggle’ seen as the dog rotates its pelvis to reduce painful extension of the hip. Younger animals may show increased joint laxity, while older animals typically show a reduced range of motion, with muscle atrophy and crepitus. Older animals, in particular, must be carefully assessed for In Practice

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Pathophysiology of hip dysplasia

Genetics

Decreased joint laxity ± clinical improvement

Stretching of fibrous joint capsule and ligament of femoral head, and joint effusion

Capsular fibrosis and decreased joint effusion Joint laxity

Environmental factors (eg, nutrition/ bodyweight/ weight gain/exercise)

Subluxation of the hip joint

Erosion of dorsal acetabular rim

Focal stresses

Perifoveal cartilage lesions

JOINT LAXITY The degree of laxity is influenced by muscle tension, the integrity of the joint capsule and ligament of the femoral head, and the condition of the dorsal acetabular rim. Assessment of laxity can often be painful, and is best performed with the animal anaesthetised (or heavily sedated), which will reduce or eliminate the effects of muscle tension. The three main tests for assessing laxity are the: ■ BARLOW TEST; ■ BARDENS TEST; ■ ORTOLANI TEST.

Microfracture and sclerosis of subchondral bone

Joint pain, articular cartilage degeneration and bone remodelling

Inflammatory ‘soup’ of cytokines, metalloproteinases, and so on

concurrent neurological disease, such as lumbosacral stenosis or degenerative myelopathy, which are common in dogs of the same signalment.

Development of osteoarthritis

Ortolani test

The Ortolani test is generally considered to be the most useful of the three tests for assessing joint laxity, and is performed with the animal anaesthetised and in dorsal recumbency. The femurs are positioned perpendicularly to the table top, and gentle pressure is applied downwards from the stifles. This mimics the effect of weightbearing, and will luxate the femoral head if the animal has

Decision making in the management of hip dysplasia in the immature dog Immature dog with PAINFUL hip(s) General anaesthesia

Barlow test

With the dog anaesthetised and positioned in dorsal recumbency, the clinician stands at the tail end, with the palm of the right hand placed on the lateral aspect of the animal’s flexed left stifle, and the thumb over the medial femoral condyle. The hip is initially allowed to abduct, reducing the femoral head into the acetabulum. If the femoral head is felt to ‘shift’ as the hip is slowly adducted, the Barlow test is positive, indicating sufficient laxity to allow (sub)luxation of the femoral head (Slocum and Slocum 1990). Bardens test

Bardens test (‘hip lift’) has been described for use in anaesthetised six- to eight-week-old puppies, but is not a definitive test for hip dysplasia. The pup is placed in left lateral recumbency to test the right (upper) hip. The clinician’s left hand is positioned with the middle finger on the wing of the ilium, the index finger on the greater trochanter of the femur, and the thumb on the tuber ischium. The right hand grasps the femur just below the greater trochanter, and applies a medial to lateral force, effectively ‘lifting’ the hip. In pups of this age under anaesthesia, translation of the trochanter of 1 to 2 mm is considered to be normal, with movement of 5 to 6 mm or more being indicative of hip dysplasia (Slocum and Slocum 1990). In Practice

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Abnormal weightbearing

Assess hip joint laxity

+ve Ortolani test, with solid ‘clunk’

Standard radiographic views

TPO

–ve Ortolani test, or +ve but with poor ‘clunk’

Minimal radiographic evidence of degenerative joint disease Degenerative joint disease

Conservative management Controlled exercise, weight control and NSAIDs

Limited

Adequate

Assess response Good Continue conservative management, but regularly reassess (ie, six weekly) If the condition deteriorates and pain becomes refractory

Consider owner finances

Perform TPO Assess outcome

Poor

Excision arthroplasty if: ■ Pain is uncontrollable ■ Finances are limited Otherwise, manage until total hip replacement can be performed at skeletal maturity

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Good


Assessing patient suitability for triple pelvic osteotomy

(A)

The difference between the angles of reduction and subluxation equates to the degree that the acetabulum should theoretically be rotated during TPO to retain the femoral head within the acetabulum. Recent literature suggests that the angle itself is less important, but assessment of the ‘quality’ of the Ortolani sign remains critical in determining a dog’s suitability for TPO. Palpation of a solid ‘clunk’ on reduction suggests that a decent acetabular rim and depth of acetabulum exist. A sensation that the femoral head is sliding or grating back into place suggests a worn rim and infilled acetabulum. TPO is less likely to be successful in the latter case.

(B)

Ortolani test. (A) Position the anaesthetised animal in dorsal recumbency, with the femurs held perpendicularly to the table top, and apply gentle pressure downwards from the stifles. This mimics the effect of weightbearing, and will subluxate or luxate the femoral head if the animal has hip dysplasia (B). (C) Abduct the leg gently, to reduce the femoral head back into the acetabulum (D). The white arrows show the forces being directed on the joint

is felt to reluxate is the angle of subluxation. This angle reflects the state of the dorsal acetabular rim, and degree of infilling of the acetabulum.

RADIOGRAPHY Good quality well-positioned radiographs are required to assess hips for dysplasia and most animals should be anaesthetised to facilitate this. Ventrodorsal extended femur and lateral pelvic views are standard; frog-leg views are useful for potential triple pelvic osteotomy (TPO) candidates (with the degree of reduction indicating acetabular infilling). If the animal is to be used for breeding, the radiographs should be submitted to the BVA/KC Hip Dysplasia Scheme for assessment.

(C)

CONSERVATIVE MANAGEMENT

(D) hip dysplasia. The leg is then gently abducted, causing the femoral head to reduce back into the acetabulum. The angle (to the perpendicular) at which the femoral head is felt to relocate into the acetabulum is the angle of reduction, and is mainly determined by the degree of stretching of the joint capsule. Following reduction, the leg is adducted, and the angle (to the perpendicular) at which the femoral head

Treatment options for hip dysplasia As with any condition for which there is no ‘cure’, many treatment options exist. As shown in the table below, the choice will depend partly on the age of the dog. TREATMENT OPTIONS

Conservative management must be seen as a proactive option, and a programme should be designed for the individual dog to address weight control, exercise management, physiotherapy and pain control.

WEIGHT CONTROL Excessive weight gain should be prevented in puppies, and adults should be maintained at or below normal adult bodyweight. Restricting food intake in growing dogs has been reported to produce significant benefits (Kealy and others 1992, 1997). Likewise, simple weight reduction has been shown to result in a significant improvement in lameness in adult dogs with osteoarthritis secondary to hip dysplasia (Impellizeri and others 2000).

EXERCISE MANAGEMENT An appropriate level of exercise should be determined for each individual dog to maintain muscle development and fitness, and to meet owner lifestyle expectations, without exacerbating the clinical signs. Regular low impact exercise is preferable to intermittent, forced or high impact activities such as chasing balls.

Immature

Mature

Non-surgical

Conservative management

✓

✓

Surgical ‘Prophylactic’

Triple pelvic osteotomy

✓

✓

Pectineal myectomy

✓

✓

Intertrochanteric osteotomy

✓

X

DARthroplasty

✓

✓

PHYSIOTHERAPY

Pubic symphysiodesis

✓

X

Femoral head and neck excision

✓

✓

Total hip replacement

X

✓

The potential benefits of physiotherapy in animal rehabilitation have recently been recognised, although little objective data relating to veterinary patients is available as yet. Hydrotherapy, in particular, can provide a means

Salvage

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In Practice

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of exercising animals that are very overweight, unfit or disabled, as the buoyancy that the water imparts overcomes some effects of gravity. One study showed that, compared with standing on dry ground, dogs standing in water to the level of the tarsus, stifle and greater trochanter weighed the equivalent of 91, 85 and 38 per cent of their bodyweight, respectively (Tragauer and others 2002). Interestingly, most studies published to date suggest that swimming or walking in water produces greater joint flexion but less extension compared with walking on dry land. The field of veterinary physiotherapy is rapidly expanding, and it is essential that owners are directed to properly trained practitioners (see www.acpat.org for a list of chartered animal physiotherapists).

PAIN CONTROL An important part of the inflammatory cascade involves the production of inflammatory mediators from arachidonic acid through the action of either cyclo-oxygenase enzymes (producing prostaglandins) or lipoxygenase enzyme (producing leukotrienes). Most modern nonsteroidal anti-inflammatory drugs (NSAIDs) block the cyclo-oxygenase pathway (meloxicam, carprofen), but some also act on the lipoxygenase pathway (tepoxalin). Toxicity arises because these drugs block both the inducible (COX-2) and endogenous (COX-1) enzymes; the latter have important physiological roles, such as maintenance of renal and hepatic function as well as the gastric mucosal barrier. Modern NSAIDs are less toxic because they preferentially inhibit COX-2 enzymes, but this apparent safety can lead to misuse. The requirement for NSAIDs should be regularly reassessed; the dose should be reduced as soon as possible, and it should be recognised that not all animals require continuous medication. Equally, individual tolerance and responses will vary, and one NSAID may be more effective, or more toxic, in a particular animal. The use of corticosteroids (intra-articularly or systemically) is controversial because, although they will reduce inflammation within the joint, they have detrimental effects on cartilage health by decreasing collagen and proteoglycan formation. In general, short-term use (eg, a single intra-

Use of nutraceuticals and chondroprotective drugs for the control of osteoarthritis Nutraceuticals and chondroprotective drugs are slow-acting, disease modifying agents that may help to control osteoarthritis. Although there is abundant anecdotal evidence about the beneficial effects of these types of drugs, to the author’s knowledge no controlled studies to date have shown any significant improvements in clinical measurements between clinically affected dogs receiving nutraceuticals compared with a placebo. A study by Read and others (1996) showed that calcium pentosan polysulphate (PPS) given to geriatric dogs with osteoarthritis reduced their clinical signs, but assessment and lameness scoring was subjective. A more recent double-blind, placebo-controlled clinical trial by Innes and others (2000) on dogs surgically treated for cranial cruciate ligament disease and given PPS found no differences in functional outcome or radiographic progression of osteoarthritis between the treatment and placebo groups at 50 weeks. Orally administered forms of glucosamine sulphate and chondroitin sulphate have been shown to alleviate the symptoms of osteoarthritis and improve joint function in humans; although the onset of action is delayed (six to eight weeks), it continues long after the administration of the treatment has stopped. However, the validity of extrapolating results of human trials to dogs has been questioned, as the mechanisms of osteoarthritis may differ.

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articular injection) is likely to have fewer adverse effects than long-term use, although steroid arthropathy has been reported. Corticosteroids should not be administered simultaneously with NSAIDs due to the greatly increased risk of side effects, particularly gastric ulceration. Where gastrointestinal irritation is suspected, the following gastroprotectant drugs may be useful: ■ OMEPRAZOLE (LOSEC; ASTRA ZENECA). This is a proton pump inhibitor, estimated to be 10 times more potent than cimetidine. – DOGS. Administer 0·5 to 1·5 mg/kg intravenously or orally every 24 hours for a maximum of eight weeks; – CATS. Administer 0·75 to 1 mg/kg orally every 24 hours; ■ SUCRALFATE (ANTEPSIN; CHUGAI). This forms a ‘protective coating’ over ulcers, and stimulates mucosal defences and repair mechanisms. It should be given at least one hour before feeding. – DOGS. For dogs 20 kg, give 1 to 2 g/dog every six to eight hours; – CATS. Give 250 mg/cat orally every eight to 12 hours. See Tennant (2005) for further information on these drugs, including contraindications. It should be recognised that animals with osteoarthritis will occasionally suffer acute ‘flare-ups’, but usually recover if managed appropriately in the short term. It is as important, however, to regularly reassess an animal to determine whether conservative management is enabling it to achieve a reasonable quality of life. This is particularly vital in young dogs, where extended periods of restricted exercise can take a lot of the fun out of being (and having) a puppy.

SURGICAL TREATMENT

‘PROPHYLACTIC’ MANAGEMENT Triple pelvic osteotomy

TPO is indicated in young animals with painful hips that have failed to improve with conservative treatment. Stabilisation of the hip produces clinical improvement and reduces the progression of degenerative joint disease. It can be performed in any age of dog, but it is more likely that young dogs (