Surgical Treatment for the Immature Patient
A number of different surgical techniques have been employed to treat canine hip dysplasia. The procedure, which is ultimately selected, should be based upon careful observation and evaluation of the individual patient. Criteria, which must be addressed, include the age of the patient; the severity of subluxation (i.e., the angle of Wiberg); the angle of inclination and anteversion; the depth of the acetabulum; and the presence or absence of femoral head deformity and associated changes indicative of osteoarthritis.
The surgical procedures most commonly recommended for treatment include triple pelvic osteotomy; intertrochanteric de-rotational femoral osteotomy; excision arthroplasty with or without a bicep sling; and total hip replacement.
The advantages, as well as the indication for each of these procedures, will be discussed in this and in a future article.
The primary goal of surgical intervention for the treatment of canine hip dysplasia in the majority of immature patients is re-direction of the acetabulum. The restoration of hip stability promotes a more normal development of the hip and results in a decrease or halt of the osteoarthritic changes typically associated with a degerenative joint disease.
Because the ultimate goal in a young dog is to help reshape the acetabulum so as to create more depth to accommodate the femoral head and save the hip joint, the technique of choice is the triple pelvic osteotomy (TPO). This procedure presupposes that the femoral component of the hip is normal. Triple pelvic osteotomy is not designed to correct the subluxation problems associated with coxa valga, i.e., increased angle of inclination or increased anteversion of the proximal femur. Such problems need to be addressed by performing a varus osteotomy and demonstrated, however, that if the acetabular component is repositioned such that normal congruency of the joint is maintained, the femoral changes will revert toward normal with time.
Fortunately, in my experience, a femoral osteotomy is usually not necessary, although several studies have indicated that functional results tend to be less satisfactory in dogs having the largest angles of anteversion. Varus and/or intertrochanteric osteotomy is most appropriate in the young dog with subluxation and femoral dysplasia without acetabular dysplasia. As acetabular dysplasia is frequently present, these techniques are seldom employed as a sole means of surgical correction. As previously mentioned, the overwhelming majority of patients exhibit acetabular dysplasia, and the resulting new position obtained by a TPO produces adequate acetabular depth to provide hip stability. However, femoral osteotomy needs to be considered as an ancillary procedure in some cases.
The ideal candidates for a TPO are immature dogs with pain and/or lameness associated with hip subluxation. Since the purpose of the TPO is to prevent the development of degenerative joint disease, only those joints with minimal or no preexisting degenerative joint disease should be considered as candidates for the procedure. When radiographic changes of osteoarthritis are present, excision arthroplasty or total hip replacement may be indicated as the likelihood of success with a TPO is minimized.
The dog’s age is also an important consideration, as rapid breakdown of the dorsal acetabular rim occurs from 4 to 8 months of age in dysplastic puppies. For these reasons, the surgery should be performed prior to nine to ten months of age to achieve best results. However, if the other criteria mentioned previously have been met, good clinical results can still be achieved in older dogs.
Another prerequisite of surgery is the ability to reduce the hip while the patient is under general anesthesia. If the hip cannot be reduced and stabilized by the femoral abduction and internal rotation, there is a diminished chance of success that a TPO would produce good hip stability. Dogs with complete luxation of the hip (grade IV hip dysplasia) however, have been successfully treated with this procedure.
As with any other surgical procedure, numerous techniques and variations of TPO have been developed and used over the last several years to enhance success and minimize complications. The earlier techniques advocated a stair-step osteotomy of the ilium and internal stabilization consisting of screw and wire fixation with or without trochanteric osteotomy. More recently, techniques have employed straight osteotomy of the ilium and rigid internal fixation utilizing bone plates with or without ischial wiring. My own personal preference is to use an oscillating saw to perform the pubic, ischial, and ilial osteotomies through three separate skin incisions. The freely movable acetabular segment is then rotated and tilted into its new position, and rigid stability is achieved and maintained by application of a special pre-contoured bone plate.
Routine post-operative care consists of confinement and restriction of exercise throughout the immediate post-operative period. Strict rest and confinement should eliminate the potential complication of loss of fixation. Other complications include constipation, urethral impingement, and sciatic nerve injury. Constipation is usually easily alleviated with the administration of stool softener. The proper surgical technique should prevent complication related to urethral and/or sciatic injury. The overwhelming majority of animals will begin bearing weight on the operated limb within 24 to 48 hours, although significant additional time is required for complete healing.
All in all, a triple pelvic osteotomy is an extremely successful treatment of choice for hip dysplasia in the immature dog. This high degree of success, however, depends upon the careful selection of surgical candidates and familiarity with the surgical techniques available.