Practical Matters: Early screening and the role of DARthroplasty as an intervention in young dogs with hip dysplasia

For too long, many veterinarians who have diagnosed hip dysplasia in young patients have informed the owners that the consequences will have to be dealt with later in life, when signs of osteoarthritis develop. When this time comes, we treat the pain associated with osteoarthritis with medications, we advise weight loss, and, for owners who can afford it, we recommend a total hip replacement.

David Luck, DVM

DIAGNOSTIC EVALUATION IN PUPPIES

A proactive hip wellness program, on the other hand, would attempt to modify the course of dysplasia toward normalcy at an early age, which might result in little if any osteoarthritis during the course of the affected animal's life. This comprehensive hip wellness program would ideally begin by evaluating 4-month-old puppies of breeds susceptible to dysplasia. These puppies would be sedated or anesthetized and examined for a positive Ortolani sign. If an Ortolani sign is present, confirm joint laxity with a radiographic examination (PennHIP), or possibly an ultrasonographic examination. These procedures can be easily accomplished as part of an early-age wellness diagnostic examination (Figure 1). Hip laxity identified in puppies < 5 months old might benefit from juvenile pubic symphysiodesis.1-3

Figure 1: Comprehensive Hip Wellness Program for Large-Breed Puppies

For puppies examined later in adolescence, from 6 to 12 months of age, the same diagnostic evaluations should be performed. Puppies in this age group showing laxity may benefit from one of two procedures: triple pelvic osteotomy (TPO) or dorsal acetabular rim arthroplasty (DARthroplasty). For patients that do not qualify for a TPO procedure because of a lack of dorsal acetabular rim, excessive subluxation of the femoral head, or beginning osteoarthritic changes,4 DARthroplasty may be appropriate (Figure 2).5

2. A ventrodorsal hip-extended pelvic radiograph of a young dog reveals subluxation of the femoral head (solid white arrow), little if any dorsal rim of the acetabulum (solid black arrow), early osteoarthritic changes (dashed arrow), and shallow acetabuli (dotted arrows).

DARTHROPLASTY: AN OVERVIEW

You will most likely refer patients for DARthroplasty. The procedure involves harvesting autogenous bone grafts from the wing of the ilium and placing them to fuse over the deficient dorsal acetabular rim.6,7 A caudodorsal approach to the coxofemoral joint is used. The exposed bony portion of the dorsal rim of the acetabulum is prepared to accept bone grafts by the drilling of multiple holes along the bony portion of the dorsal acetabulum, exposing activated cancellous bone. The cortical-cancellous strips harvested from the ilium through a separate incision are formed into a cup, tucked under the muscle separation between the deep gluteal muscle and the gemelli muscle, and tied to the joint capsule with a preplaced suture (Figure 3). A cancellous bone graft from the ilium is packed into the area of the drill holes in the acetabular rim and covered with additional pieces of cortical graft from the ilium (Figure 4).6,7 Sutures are placed between the deep gluteal and gemelli muscles to help hold the free graft in place, and the two surgical wounds are closed with a standard layered protocol.

3. The harvested cortical-cancellous strips of bone from the ilium have been sutured into a cup and are ready to be placed under the deep gluteal and gemelli muscles directly over the joint capsule. The heavy suture, which has been preplaced in the joint capsule, when tied, will hold the implant in place. The patient is in lateral recumbency. The access incision to the wing of the ilium for harvesting the bone grafts is seen on the left.

The aftercare protocol is strict: Patients must have cage rest with short leash walks only for elimination for eight weeks. After this initial healing time, a dorsal acetabular rim position radiographic examination is done to verify the graft presence and position (Figure 5). A physical therapy regimen to rebuild muscle strength and agility can then begin and will continue for another eight weeks. If rehabilitation is successful, patients can resume normal activity.

4. A transection view of the coxofemoral joint shows the relative position of the harvested graft (free cortical-cancellous­ strips) sutured to the joint capsule, the layering of the cancellous bone graft into the drill holes along the dorsal rim of the acetabulum, and the blocking strips (cortical graft from the ilium) holding the cancellous graft in place.

A comprehensive, proactive hip wellness program can be used to correct deficiencies of the canine hip in young, growing, dysplastic patients, resulting in diminished hip osteoarthritis and pain and better activity as adults. DARthroplasty may be especially useful in severely affected patients when hip dysplasia is diagnosed at an early age.8

5. A dorsal acetabular rim position radiograph taken eight weeks after a DARthroplasty procedure in a dog showing positive graft formation (white arrows) and increased width of the dorsal acetabular rim (black arrows).

David Luck, DVM

Veterinary Surgical Relief Services

2237 Meade St.

Denver, CO 80211

REFERENCES

1. Dueland RT, Adams WM, Fialkowski JP, et al. Effects of pubic symphysiodesis in dysplastic puppies. Vet Surg 2001;30(3):201-217.

2. Patricelli AJ, Dueland RT, Adams WM, et al. Juvenile pubic symphysiodesis in dysplastic puppies at 15 and 20 weeks of age. Vet Surg 2002;31(5):435-444.

3. Dueland RT. Juvenile pubic symphysiodesis (JPS) update, in Proceedings. Am Coll Vet Surg Summit 2007.

4. Fossum TW. Triple pelvic osteotomy. In: Small animal surgery. 3rd ed. Philadelphia, Pa: Mosby Elsevier, 2007;1238.

5. Luck DR. DARthroplasty: overlooked and underused (poster presentation). Veterinary Orthopedic Society Proceedings, Sun Valley, Idaho, 2007.

6. DARthroplasty. In: Bojrab MJ, ed. Current techniques in small animal surgery. 4th ed. Baltimore, Md: Williams & Wilkins, 1998;1168-1170.

7. Slocum B, Slocum TD. DARthroplasty. Slocum Enterprises, Inc., Eugene, Ore. Available at: http://www.slocumenterprises.com/Articles/darthroplasty.htm.

8. Gahring DR. Long-term results with DARthroplasty. San Carlos Veterinary Hospital, San Diego, Calif. Available at: http://www.sancarlosvet.com/Other/Prof/DARthroplasty/DARthroplasty_Long_Term_Followup.html