Figure 1: Hip dysplasia is a common diagnosis in dogs. Images courtesy Kendra Freeman Most of us in general practice as well as referral centers have been inundated with puppies during the COVID pandemic. Along with healthy puppies needing vaccines and routine care, our hospital has seen an increase in orthopedic referrals in a population of young dogs. One of the most common referrals is for hind limb lameness, reluctance to jump and soreness after activity. Along with cranial cruciate ligament injury, hip dysplasia is a common finding (Figure 1). The timing of this diagnosis is critical for the recommendations made to intervene and modulate growth, treat discomfort, and alter anatomy of the joint. Early diagnosis allows for less invasive treatments to be successful. Pathophysiology Puppies are born with normal hips, but changes associated with dysplasia can develop rapidly with earliest changes noted as soon as 30 days after birth. In developing puppies, joint incongruity or malalignment prevents normal development of the acetabulum and femoral head, perpetuating the development of dysplasia. Hip dysplasia is a heritable condition influenced by environmental factors. The heritability of hip dysplasia is long studied; however, results of studies are often conflicting. Recent genetic sequencing of the canine genome has identified specific mutations linked to the development of dysplasia. Monitoring of breeding stock with various radiographic techniques have decreased the incidence of dysplasia in certain breeding lines, but despite this hip dysplasia remains common. Treatment Many treatment options are available for the dysplastic hip. Some are time/age sensitive, some made based on anatomy, and other recommendations made with finances and athletic expectations in mind. Juvenile pelvic symphodesis Juvenile pelvis symphodesis (JPS) is a technically simple procedure performed in young puppies. Thermal damage to the pelvic symphysis causes cessation of growth from this location and encourages acetabular coverage of the femoral head as the puppy continues to grow. This procedure is best performed no later than 20 weeks of age. With the puppy is dorsal recumbency, a ventral approach to the public symphysis is performed. The peritoneum is punctured just cranial to the symphysis so a small malleable retractor can be advanced dorsal to the symphysis to protect the underlying tissues, most importantly the urethra. Electrocautery is applied to the cranial one-third or one-half of the symphysis. Routine closure of the muscle, subcutaneous tissues, and skin is performed. An Elizabethan collar is recommended to prevent licking and irritation of the surgery site for the first two following the procedure. Explosive activity should be restricted for a period of two weeks after surgery. In a study by Vezzoni et al1 greater than 40 percent of puppies had regression or lack of progression of clinical disease after the JPS procedure. Complications of this procedure are low, but may include seroma formation, thermal damage to urethra, and/or rectum and lack of improvement in clinical disease. Studies have shown minimal to no benefit in performing this surgery after 24 weeks of age. Pelvic osteotomy Figure 2: A cementless system used here. Three different osteotomy procedures have been described to increase acetabular coverage of the femoral head have been described. The goal of any of these osteotomy procedures is rotate the acetabulum in a ventrolateral direction to improve femoral head coverage. Because the osteotomy procedures rely on continued growth of the patient, they are best performed prior to 11 months of age and in patients without evidence of osteoarthritis. (Jenkins et al 2020)2 Careful case selection is needed to ensure the best outcome from any of these procedure. Triple pelvic osteotomy (TPO) involves osteotomy of the pubis, ischium, and ilium. This procedure has been shown to increase acetabular coverage, have a good functional outcome, and decrease the progression of osteoarthritis. Double pelvic osteotomy involves osteotomy of the pubis and ilium. This procedure is successful in preventing radiographic progression of osteoarthritis and is less likely to cause excessive coverage of the femoral head compared to the triple pelvic osteotomy procedure. Recently, a 2.5 pelvic osteotomy procedure has been described (Tamburro et al 2018).3 This procedure involves complete osteotomies of the pubis and ilium with a partial osteotomy of the ischium. In a cadaver study, this procedure was noted to be feasible, but no clinical cases were reported. Complications reported with these osteotomy procedures include screw loosening, pelvic canal narrowing, progression of osteoarthritis, and excessive coverage of the femoral head. These procedures require technical experience for best outcome as well as specialized bone plates. Total hip arthroplasty Total hip arthroplasty (THA), or joint replacement, is a technically challenging procedure performed with the goal of removing the source of pain and return to an active lifestyle. Many different systems are available including cemented, cementless, cup-less, and hybrid. The overall complication rate for this procedure is estimated to be between five and 30 percent (Kidd et al 2016).4 I often describe this procedure to clients as “high risk, high reward.” In our hospital, a cementless system is used (Figure 2). This means bone ingrowth must occur to stabilize the implants, and we expect this process to take approximately 12 weeks. If clients can commit to strict activity restriction, physical therapy, and controlled return to normal activity, the results are excellent with up to 95 percent success rate. If, however, a client is unable to commit to activity restriction and gradual return to normal activity, the results can be disastrous. Potential complications can include luxation of the joint, subsidence of the implants (i.e. ventral displacement or sinking of the femoral stem implant deeper into the medullary canal, which alters the alignment of the joint), infection, fracture of the femur, and pulmonary embolism. THA is best performed when a patient is at or near skeletal maturity. Femoral head and neck excision Femoral head and neck excision involves sharp removal of both the femoral head and neck (Figure 3). The goal of this surgery is to reduce pain from bone on bone contact in a degenerative, dysplastic joint. Removal of the femoral head alone will lead to crepitus and chronic pain. A line can be made from the intertrochanteric fossa to the lesser trochanter for the excision. A sagittal saw is efficient for making this cut; however, the procedure can be completed with an osteotome and mallet. It is critical to take the joint through a range of motion prior to closure of the soft tissues to ensure enough bone has been removed. In a study published by Gendreau et al,5 38 percent of cases were without lameness after surgery, 20 percent had mild lameness, and 42 percent of patients had persistent lameness. The femoral head and neck excision procedure has limitations and is considered a salvage procedure. Too much activity in the early recovery period can lead to chronic pain. Excessive activity restriction will encourage robust scar tissue formation at the surgical site leading to very limited range of motion. Nonsurgical management Figure 3: Femoral head and neck excision involves sharp removal of both the femoral head and neck. The goal of this surgery is to reduce pain from bone-on-bone contact in a degenerative, dysplastic joint. Non-surgical treatment of hip dysplasia focuses on comfort, management of osteoarthritis, and maintenance of mobility. Maintenance of lean body weight alone can lesion the severity of lameness in patients with osteoarthritis. Medications and supplements are generally classified as either symptom modifying or disease modifying. The most common class of medications and supplements is symptom modifying meaning to they modulate pain associated with osteoarthritis. This includes non-steroidal anti-inflammatory drugs (NSAIDs), amantadine, gabapentin, opioids, and corticosteroids. Alternatively, disease modifying agents slow, stop or potentially reverse pathology within the articular cartilage. Agents in this class include polysulfated glycosaminoglycan and pentosan polysulfate. Nutritional supplements are often recommended and may include chondroitin sulfate, glucosamine and essential fatty acids. Biologics including stem cells, platelet rich plasma, and autologous conditioned serum continue to be an area of interest for management of canine osteoarthritis. Despite monitoring and certification by various groups for breeding animals, hip dysplasia remains common in our patients. Laxity of the coxofemoral joint is the biggest risk factor for the development of dysplasia and subsequently osteoarthritis. Early recognition of laxity allows for less invasive and successful interventions. Ideally, joint laxity should be assessed during puppy wellness and vaccination appointments so that early treatment can be performed. Kendra Freeman, DVM, MS, DACVS, is a graduate of Colorado State University and maintains dual certification with the American College of Veterinary Surgeons. She is an associate surgeon in Albuquerque, N.M., where she mainly works in orthopedics, general soft tissue, and sports medicine cases. References Vezzoni, A., et al. “Comparison of conservative management and juvenile pubic symphysiodesis in the early treatment of canine hip dysplasia.” Veterinary and Comparative Orthopaedics and Traumatology 21.03 (2008): 267-279. Jenkins, Paul L., et al. “Assessment of the medium- to long-term radiographically confirmed outcome for juvenile dogs with hip dysplasia treated with double pelvic osteotomy.”Veterinary Surgery 49.4 (2020): 685-693. Tamburro, Roberto, et al. “Comparison of rotation force to maintain acetabular ventroversion after double pelvic osteotomy and 2.5 pelvic osteotomy in a canine cadaveric model.” Veterinary and Comparative Orthopaedics and Traumatology 31.01 (2018): 062-066. Kidd, Scott W., Christopher A. Preston, and George E. Moore. “Complications of porous-coated press-fit cementless total hip replacement in dogs.” Veterinary and Comparative Orthopaedics and Traumatology 29.05 (2016): 402-408. Gendreau, C., and A. J. Cawley. “Excision of femoral-head and neck-long-term results of 35 operations.” Journal of the American Animal Hospital Association 13.5 (1977): 605-608.
