Hip dysplasia is a common problem in many breeds of dogs however retrievers certainly suffer more than their share of this potentially debilitating problem. 

When a dog is mature and has debilitating disease of the hip joint surgical intervention must be considered. 

Total hip replacements offer the best chance at normal or near normal function in dogs with incapacitating disease of the hip joint. 

Introduction

• Total hip replacements in dogs are a complex surgical procedure that has become fairly common place in veterinary surgery.  There are several reasons that a dog would require a total hip replacement including broken bones in the hip, injury to blood supply in the hip, certain tumors, hip dysplasia, and other causes of arthritis.  Hip dysplasia is a common problem in many breeds of dogs however retrievers certainly suffer more than their share of this potentially debilitating problem.  We have previously discussed the development of hip dysplasia and how it is actually a problem of the soft tissue supporting structures in the hips of puppies.  The loose fit of the bones making up the hip joint results in abnormal weight bearing forces.  This results in destruction of the cartilage surface of the joint.  As the disease progresses, bone spurs are laid down around the affected joint, resulting in the arthritis that we see on dogs with hip dysplasia.  The cartilage will continue to erode, however the rate of erosion and the effect of the erosion on a dog’s comfort level varies from individual to individual.  These variables as well as individual personality differences account for the reason that most dogs with hip dysplasia never require surgical intervention.

Conservative Treatment

• What about the dogs that do suffer chronic discomfort secondary to hip disease and arthritis?  There are surgical and non-surgical (conservative) treatments.  The cornerstones of conservative management of arthritis include weight management, exercise modifications, judicious use of aspirin like medications (often referred to as NSAID’s), and lifelong administration of glucosamine/chondroitin sulfate products.  This treatment regimen, when followed in its entirety, allows many dogs’ month, years, or even lifelong comfort without surgical intervention.  The challenge for you and your veterinarian occurs when conservative management loses its effectiveness or is just not a desirable alternative any longer.  These are the dogs that require surgical intervention.
• When a dog is mature and has debilitating disease of the hip joint surgical intervention must be considered.  This may be in a dog that is 9 months of age or older.  Unlike the situation seen in humans that have joint replacement, dogs that have hip replacements done do not typically wear out the artificial joint, regardless of the age of the patient. This is why total hip replacement is a viable option in young dogs, even while they are still technically puppies.

Total Hip Replacement Versus Femoral Head and Neck Excision

• There are two predominant surgeries that may be done in mature dogs with debilitating hip disease.  One is called a femoral head and neck ostectomy (FHO) and the other is a total hip replacement (THR).  The hip is typically referred to as a ball and socket design.  When an FHO is done the ball portion is removed and a false joint, consisting of scar tissue, develops around the previous hip joint.  The goal of this surgery is to provide a pain-free functional limb however it is not going to be normal.  The FHO is a very good option in cats and small dogs however as the size of the patient increases, deviation from normal limb function increases.  Typically large dogs with an FHO have decreases in range of motion, decrease in thigh muscle size (atrophy), and an abnormal walking or running stride.  Many dogs continue to suffer intermittent bouts of discomfort and most are unable to comfortably perform athletic activities, especially for any length of time. 
• Total hip replacements offer the best chance at normal or near normal function in dogs with incapacitating disease of the hip joint.  When a THR is done the socket portion of the joint is removed and replaced with a plastic polymer cup and the ball portion of the joint is removed and replaced with a cobalt chromium stainless steel stem and ball.  There are two broad classifications of implants used, cemented and uncemented.  The cemented type of total hip replacement has been in use in dogs for the longest period of time and, as the name implies, relies on bone cement to hold the implants in place.  The uncemented implants use newer technology, relying on bone in growth into tiny pores on the implant.  This results in bone securing the implants and ultimately less foreign material in and around the joint.  Pre-operative planning helps decide appropriate implant size and type of implants but the final decision is made during surgery and is in part, dependent on the surgeon’s experience.   

Potential Complications of Total Hip Replacement

• The most common postoperative complication after THR is dislocation of the artificial joint.  This complication usually occurs within the first few months after surgery, and may require additional surgery.  Other more problematic but less common complications have to do with the security of the implants.  When the implants become loose the patient experiences discomfort which can be severe.  There are two reasons for implants to become loose.  First is termed aseptic loosening.  This means the implant becomes loose in the absence of an infection.  This occurs when small particles of the plastic cup break loose and migrate around the implant.  The body tries to clean up the particles; it destroys small amounts of bone which can lead to loose implants.  When aseptic loosening is the cause of loosening, the implants can often be removed and replaced.  Occasionally bacteria are involved in loosening of the implant.  This is termed septic loosening of the implants.  In this instance, the bacteria destroy bone, resulting in loosening of the implants.  When cemented implants have been used, there is no effective treatment and the implants must be removed, resulting in an FHO.
• Dislocation of the joint can occur with either method of hip replacement however the use of cementless implants appears to reduce both septic and aseptic loosening of implants.  There have even been reports of infected implants being removed and replaced with uncemented implants at the same surgery and the infection is defeated.  The likely reason for this advantage is that the cementless implants work with bone to become secure, thus avoiding the introduction of the large amounts of foreign bone cement.  In other words, the cementless total hip is a more biologic method of replacing the joint.  In addition to the decrease in postoperative complications, cementless total hip replacements transfer weight bearing forces across the joint in a more natural manner.  This can result in more normal bone structure surrounding the hip replacement.

Conclusion

• TO summarize, when you are considering a total hip replacement for your companion, there are many questions to answer.  Experience of the surgeon is very important, and is best assured by seeking a board certified veterinary surgeon (American College of Veterinary Surgeons).  After deciding on a surgeon ask about implant choices.  There are instances where only a cemented implant will function however the cementless total hip implants may have certain advantages over older cemented types and should be discussed prior to surgery.

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