Getting Real with Canine Hip Dysplasia

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Introduction

Canine Hip dysplasia is characterised by laxity of the hip joints with progressive development of osteoarthritis and debilitation. Any breed of dog can be affected by hip dysplasia.

The causes of hip dysplasia are multifactorial. The heritability of hip dysplasia is relatively low, so while genes play a part in development, environmental factors (such as nutrition, growth rate, activity, and other unidentified factors) also significantly influence the ultimate phenotype. The presence of two ‘good’ parents on hip scoring does not guarantee unaffected offspring.

The earliest and most consistent sign of hip dysplasia in the dog is laxity, which can be appreciated radiographically at about 7 weeks of age.1

There is typically a bimodal distribution of patients presenting with signs referable to hip dysplasia: young dogs from 5-12 months and older dogs several years of age. This article will focus on an approach to the common clinical presentations of canine hip dysplasia. The algorithm in figure 1 gives a guide to decision making with canine hip dysplasia.

Figure 1:

Figure 1: Simplified algorithm for the management of canine hip dysplasia. THR= Total Hip Replacement. FHO= Femoral Head and Neck Ostectomy.

1. Immature Susceptible Dogs.

The general practitioner is in a unique position to identify dogs at risk of hip dysplasia at a young age, when prophylactic procedures are applicable. Some puppies with severe hip laxity may display a bunny-hopping gait, although this is not a reliable indicator of hip dysplasia in immature dogs, and many do not show clinical signs at a young age. The practitioner should be cognizant of the potential for any young dog to be susceptible to hip dysplasia and discuss this with owners in the initial puppy visits, especially in high-risk breeds such as German shepherd dogs, Labrador retrievers, golden retrievers, and bulldogs, to name a few.

Demonstration of hip laxity is a key component of diagnosing hip dysplasia in the young dog:

  • The Ortolani manoeuvre is the most widely used technique, which relies on traumatic subluxation and reduction to cause an audible and palpable ‘clunk’, which is the positive Ortolani test (Figure 2). An Ortolani test is a painful procedure, and should only be performed in anaesthetised or heavily sedated animals.

    Figure 2: The Ortolani manoeuvre. The pelvis is supported with one hand, and the other hand is used to create a vertically oriented force up the shaft of the femur, simulating weight-bearing. This will result in subluxation of the hip in the dysplastic dog (top image). The femur is then abducted, and a palpable clunk is felt as the subluxated hip is reduced into the acetabulum (bottom image).

    Figure 2: The Ortolani manoeuvre. The pelvis is supported with one hand, and the other hand is used to create a vertically oriented force up the shaft of the femur, simulating weight-bearing. This will result in subluxation of the hip in the dysplastic dog (top image). The femur is then abducted, and a palpable clunk is felt as the subluxated hip is reduced into the acetabulum (bottom image).

  • Barden’s test is another manoeuvre which quantifies lateral excursion of the femoral head; again this should be performed on an anaesthetised animal (Figure 3).

    Figure 3: Barden’s test. One hand elevates the femur laterally, while the greater trochanter is palpated with the other hand. Lateral excursion of the greater trochanter of greater than 2mm is positive for laxity.

    Figure 3: Barden’s test. One hand elevates the femur laterally, while the greater trochanter is palpated with the other hand. Lateral excursion of the greater trochanter of greater than 2mm is positive for laxity.

  • Neither technique has perfect sensitivity or specificity. These may be positive in younger animals without signs of hip dysplasia, and may be negative in dysplastic animals with capsular fibrosis. However, in puppies 16 weeks of age the Ortolani manoeuvre has a low false negative and false positive rate,2 making the Ortolani test a sensitive screening tool for hip dysplasia.

Radiographic identification of hip dysplasia:

  • The extended VD radiograph is commonly taken to diagnose hip dysplasia, and this projection is great for evaluating osteoarthritis and is used widely in scoring systems. However in the young dog, this projection is very poor at diagnosing laxity – which we need to identify prior to the development of osteoarthritis.
    • As the hips are extended into the very unnatural position of the extended VD radiograph, the fibres of the joint capsule wind up and tighten, bringing the hip joint further into the acetabulum, thus reducing the apparent subluxation (Figure 4).

      Figure 4: Extended ventrodorsal projection in a young dog with palpable laxity. Moderate subluxation is present; this is likely underestimated due to capsular windup. This patient had Juvenile Pubic Symphysiodesis performed.

      Figure 4: Extended ventrodorsal projection in a young dog with palpable laxity. Moderate subluxation is present; this is likely underestimated due to capsular windup. This patient had Juvenile Pubic Symphysiodesis performed.

  • To increase the accuracy of diagnostic imaging in diagnosing early hip dysplasia, distraction radiography has been introduced. The most well-known of these systems is PennHIP (University of Pennsylvania Hip Improvement Program).
    • This involves taking two radiographs, one with the femoral heads forced into the acetabulum and one with the heads forced out, and the difference in femoral head position between the two measured to give a distraction index (DI).
    • PennHIP radiography can be performed in dogs greater than 16 weeks of age.
    • A DI of 0 indicates perfect congruence and a DI of 1 indicates complete luxation. Dogs with a DI of <0.3 are at low risk of developing signs of hip dysplasia, while a DI of >0.7 indicates a high risk of clinical hip dysplasia and osteoarthritis. 3
    • PennHIP radiography requires certification. This is achieved by attending a one day workshop and submitting multiple radiographs for examination and critique.

Identification of susceptibility to hip dysplasia at a young age (<20 weeks) allows early intervention to minimise the development of a dysplastic phenotype. I strongly recommend examining dogs at 16-18 weeks of age with radiography and palpation to identify susceptible dogs. To choose which dogs to examine, I would recommend it for any dog of a highly susceptible breed, or those with familial history. This requires an additional anaesthetic episode before desexing, but most owners are open to this if the rationale has been appropriately discussed.

One of the most important interventions at this stage is diet; institution of a restricted feeding regime has been demonstrated to result in less hip laxity, later onset of osteoarthritis, and lower osteoarthritis scores.4 Surgical intervention (Juvenile Pubic Symphysiodesis) is a valuable prophylactic procedure in young susceptible dogs.

A. Juvenile Pubic Symphysiodesis

Juvenile Pubic Symphysiodesis (JPS) is a procedure which aims to influence growth of the pelvis by surgical thermal necrosis of the pubic symphysis, which results in the pelvis growing ‘outward’ with more dorsal coverage of the acetabulum.5

  • To be successful, the procedure must be performed at a specific age while the pelvis has residual growth potential – this window is between 16 and 22 weeks, with earlier surgery having a more pronounced effect on pelvic growth.
  • Some dogs may be too severely affected to benefit from a JPS – subluxation is too severe for any growth modification to ‘capture’ the femoral heads.6
  • The key is to identify which dogs will benefit from a JPS. My rationale for performing JPS is to include those dogs of appropriate age, with a risk of developing HD (either breed or parents), and with a positive Ortolani sign and distraction radiography showing mild-moderate laxity.
  • It can be difficult to convince clients to do a two-stage procedure (as the distraction radiography results will take 7-10 days to come back if using the PennHIP system); as such in some cases a subjective evaluation of the amount of radiographic laxity can be made on the spot. JPS is a procedure with very low morbidity, which makes it acceptable as a prophylactic procedure.
  • It is very important to desex patients at the same time as performing JPS, as the procedure will alter the phenotype which may result in a better score on any hip scoring radiographs performed in the future, while the genotype of the patient has not changed. These dogs should not be used for breeding.

2. Young Symptomatic Dogs.

Younger dogs (5-12 months) typically present with unilateral or bilateral hindlimb lameness, bunny-hopping gait, reluctance to exercise (including frequent stops when walking), and difficulty rising or climbing stairs; these dogs are lame due to the pain associated with subluxation of the hip.

Physical examination of the younger dog with hip dysplasia will identify unilateral or bilateral coxofemoral pain, reduced muscle mass, and prominent greater trochanters. A swaying hindlimb gait is classic, as lateral movement of the pelvis is used to compensate for reduced hip movement; the same is true for bunny-hopping gait. Young dogs may have a wide-based stance to keep the femoral head reduced in the acetabulum, although this may develop into a narrow-based stance as osteoarthritis progresses.

As osteoarthritis develops, periarticular fibrosis will stabilise the dysplastic joint to some degree, so clinical signs often abate in all but the worst affected dogs as they reach skeletal maturity.

Clinical evaluation of young symptomatic dogs:

  • In a dog that presents with signs of hip dysplasia, again investigation by palpation and radiography should be performed to quantify laxity and detect osteoarthritis.
    • The earliest radiographic signs of osteoarthritis are the caudolateral curvilinear osteophyte (CCO, also called the Morgan line) and the circumferential femoral head osteophyte (CFHO).
  • If there are no signs of osteoarthritis and the hips are not severely lax, then surgical procedures should be considered (Figure 5).

    Figure 5: Young dog with canine hip dysplasia. No signs of osteoarthritis are present; this patient would be a candidate for Triple or Double Pelvic Osteotomy.

    Figure 5: Young dog with canine hip dysplasia. No signs of osteoarthritis are present; this patient would be a candidate for Triple or Double Pelvic Osteotomy.

  • If radiographic osteoarthritis is present or if laxity is too severe, then surgery will not prevent the progression of osteoarthritis (Figure 6). These animals should be conservatively managed with a view to a total hip replacement or femoral head and neck ostectomy once skeletal maturity has been reached, if indicated.

    Figure 6: Young dog with severe hip dysplasia. In this dog, laxity is too severe to be treated by pelvic osteotomy. Early signs of osteoarthritis are also present – the Circumferential Femoral Head Osteophyte (CFHO, arrow) and Caudolateral Curvilinear Osteophyte (CCO or Morgan line, arrowhead). Conservative management and eventual Total Hip Replacement were recommended.

    Figure 6: Young dog with severe hip dysplasia.
    In this dog, laxity is too severe to be treated by pelvic osteotomy. Early signs of osteoarthritis are also present – the Circumferential Femoral Head Osteophyte (CFHO, arrow) and Caudolateral Curvilinear Osteophyte (CCO or Morgan line, arrowhead). Conservative management and eventual Total Hip Replacement were recommended.

B. Triple Pelvic Osteotomy or Double Pelvic Osteotomy

The Triple or Double Pelvic Osteotomy (TPO or DPO) are procedures which provide increased dorsal femoral head coverage by surgically rotating the acetabulum dorsally; initially this was described with three cuts in the pelvis, but many surgeons are now performing the less morbid DPO.

  • As with the JPS (the JPS can be thought of as a ‘physiological’ TPO) some dogs will be too severely affected for surgery to provide benefit.
  • Also, the presence of radiographically visible osteoarthritis at the time of surgery will worsen the prognosis following surgery; thus the ideal candidate for a TPO is a young dog (5-9 months) with demonstrated laxity, clinical signs attributable to hip dysplasia, and no radiographic evidence of osteoarthritis.
  • There is evidence that TPO/DPO will not prevent the development of osteoarthritis even in the ideal candidate; 7 as such it should be thought of as a tool in the management of hip dysplasia rather than a preventative measure.

C. Total Hip Replacement

Total hip replacement (THR) is considered the ‘gold standard’ procedure in restoring function to dogs with hip dysplasia.

  • The procedure can be performed on dogs as young as 10 months. Anecdotally the risk of complications is higher in immature animals, although a recent retrospective study showed good results in dogs as young as 6 months.8
  • Either cemented, cementless (press-fit), or screw-in configurations are available, which is mostly determined by surgeon preference. The cemented systems are now available for toy breed dogs and cats.9
  • The success rates of THR are generally greater than 90%, although complications may be catastrophic and require explantation (effectively creating an FHO) or amputation.
  • Staged bilateral hip replacement is commonly performed, although approximately 80% of dogs with bilateral hip dysplasia will return to acceptable function after unilateral surgery only.

D. Femoral Head and Neck Ostectomy

Excision arthroplasty of the femoral head and neck, commonly called FHO or FHNE, is a salvage procedure that creates a pseudarthrosis between the femur and acetabulum, with pelvic limb support provided by periarticular muscles.

  • The procedure is well known to have a better outcome in small breed dogs compared to large breed dogs, however it has been demonstrated that even small breed dogs the long term functional outcome is often disappointing, with lameness persisting in 56%, muscle atrophy in 75%, and a poor objective functional outcome in 42%.10
  • In a patient with osteoarthritis refractory to medical management, FHO still presents a viable treatment tool in reducing discomfort, even in select large breed dogs.
  • Proper selection of patients, meticulous surgical technique, and intensive post-operative rehabilitation are important for a successful outcome.

3. Older Dogs With Osteoarthritis.

In an older dog with osteoarthritis, standard multi-modal management should be instituted (Figure 7).

Figure 7: Severe osteoarthritis in an adult dog. Total Hip Replacement was recommended in this case.

Figure 7: Severe osteoarthritis in an adult dog. Total Hip Replacement was recommended in this case.

  • In my opinion, non-steroidal anti-inflammatory drugs (NSAIDs) should not be used as a last resort, but instituted early, at therapeutic doses, and for several months initially, after which they may be tapered off if possible. This will allow exercise, weight loss, maintenance of muscle mass, and maintenance of joint motion, which will reduce the long-term reliance on NSAIDs. 11 Modern NSAIDs are safe drugs and daily medication for prolonged periods should not be feared, but encouraged in the appropriate patient. I use the following doses of NSAIDs:
    • Meloxicam 0.1mg/kg SID
    • Carprofen 2mg/kg BID
    • Robenacoxib 1-2mg/kg SID
    • Firocoxib 5.5mg/kg SID
  • Chondroprotective agents (such as cartrophen, glucosamine, chondroitin) are unlikely to have a demonstrable effect if instituted without NSAIDs, weight loss, and exercise moderation.12
  • Dietary modification with omega-3 fatty acids (eicosapentanoic acid and docosahexanoic acid), either as a fish oil supplement or in a balanced diet such as Hill’s J/D, are an important part of management in helping reduce the production of pro-inflammatory prostaglandins.13
    • Fish oils can be given at doses of up to 200mg/kg/day
  • Other medications such as amantadine, gabapentin, and tramadol may be added to improve response.14
    • Amantadine is dosed at 3-5mg/kg SID. Capsules are only available in 100mg, which often leads to an arbitrary dose of 100mg/dog SID. In my experience, this is well tolerated in dogs heavier than 10-15kg. Amantadine may be compounded for use in smaller patients.
    • I use gabapentin at 10-15mg/kg TID. Again, a limited range of capsule sizes necessitate compounding in smaller dogs.
    • Tramadol has variable effects in dogs, and may not provide analgesia in many patients. It has a wide dose range of 2-5mg/kg BID-QID, highlighting the individual variation in effectiveness.
  • If pain and dysfunction from osteoarthritis are refractory to medical management, then salvage procedures such as total hip replacement should be considered.

Author
Dr Mark Newman BVSc, MVS, MANZVCS, Diplomate ECVS
Veterinary Specialist in Small Animal Surgery
The Animal Hospital at Murdoch University

Mark works in the Murdoch University Veterinary Hospital in both the Orthopaedic/Neurosurgery and Soft Tissue/Oncologic Surgery departments. He is also a Lecturer in Small Animal Surgery at Murdoch University.

After graduation, Mark completed an internship at University College Dublin in 2007, followed by several years of general practice in New Zealand and Adelaide. Mark completed a Residency in Small Animal Surgery at the University of Sydney, and finished a Masters in Veterinary Studies (Small Animal Practice) during this time. In February 2015 Mark was awarded the status of Diplomate of the European College of Veterinary Surgeons. Mark is also an active Member of the Australian and New Zealand College of Veterinary Scientists. Mark’s particular interests include neurosurgery, arthroscopy and fracture repair.

References

  1. Riser WH. The dog as a model for the study of hip dysplasia: growth, form, and development of the normal and dysplastic hip joint. Vet Pathol 1975; 12(4):235-238.
  2. Adams WM, Dueland RT, Meinen J, et al. Early detection of canine hip dysplasia: comparison of two palpation and five radiographic methods. J Am Anim Hosp Assoc 1998; 34(4):339-347.
  3. Smith GK, Lawler DF, Biery DN, et al. Comparison of primary osteoarthritis of the hip with the secondary osteoarthritis of canine hip dysplasia. In Proceedings of the 36th Annual Conference of the Veterinary Orthopedic Society, Steamboat Springs, CO, February 28–March 6, 2009, Vol 23.
  4. Smith GK, Paster ER, Powers MY, et al. Lifelong diet restriction and radiographic evidence of osteoarthritis of the hip joint in dogs. J Am Vet Med Assoc 2006; 229(5):690-693.
  5. Dueland RT, Adams WM, Fialkowski JP, et al. Effects of pubic symphysiodesis in dysplastic puppies. Vet Surg 2001; 30(3):201-217.
  6. Vezzoni A,Dravelli G, Vezzoni L, et al. Comparison of conservative management and juvenile pubic symphysiodesis in the early treatment of canine hip dysplasia. Vet Comp Orthop Traumatol 2008; 21(3):267-279.
  7. RasmussenLM, Kramek BA, Lipowitz AJ. Preoperative variables affecting long-term outcome of triple pelvic osteotomy for treatment of naturally developing hip dysplasia in dogs. J Am Vet Med Assoc 1998; 213(1):80.
  8. FitzpatrickN, Law AY, Bielecki M, Girling S. Cementless total hip replacement in 20 juveniles using BFX™ arthroplasty. Vet Surg 2014; 43(6):715-725.
  9. IreifejS, Marino D, Loughin C. Nano total hip replacement in 12 dogs. Vet Surg 2012; 41(1):130-135.
  10. Off W, Matis U. Excision arthroplasty of the hip joint in dogs and cats. Clinical, radiographic, and gait analysis findings from the Department of Surgery, Veterinary Faculty of the Ludwig-Maximilians-University of Munich, Germany. Vet Comp Orthop Traumatol 2010; 23(5):297-305.
  11. Wernham BG, Trumpatori B, Hash J, Lipsett J, Davidson G, Wackerow P, Thomson A, Lascelles BD. Dose reduction of meloxicam in dogs with osteoarthritis-associated pain and impaired mobility. J Vet Intern Med 2011; 25(6):1298-1305.
  12. Vandeweerd JM, Coisnon C, Clegg P, Cambier C, Pierson A, Hontoir F, Saegerman C, Gustin P, Buczinski S. Systematic review of efficacy of nutraceuticals to alleviate clinical signs ofosteoarthritis. J Vet Intern Med 2012; 26(3):448-456.
  13. Fritsch DA, Allen TA, Dodd CE, Jewell DE, Sixby KA, Leventhal PS, Brejda J, Hahn KA. A multicenter study of the effect of dietary supplementation with fish oilomega-3 fatty acidson carprofen dosage in dogs with osteoarthritis. J Am Vet Med Assoc 2010; 236(5):535-539.
  14. Lascelles BD, Gaynor JS, Smith ES, Roe SC, Marcellin-Little DJ, Davidson G, Boland E, Carr J. Amantadine in a multimodal analgesic regimen for alleviation of refractoryosteoarthritis pain indogs. J Vet Intern Med 2008, 22(1):53-59.

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