DARthroplasty – case study
A six and a half month old Belgian Shepherd female dog was referred to the surgical center due to severe disability in both posterior limbs. She weighed 15kg at this time. The owner of the dog described difficulties in lying down and getting up from that position, frequent crying when changing body position, difficulties with stair climbing and lameness.
Visual observation revealed deformation of the croup region with laterally protruding greater trochanters. Orthopedic examination revealed severe pain on passive extension and on abduction with concurrent external rotation of both coxofemoral joints. There was a positive trochanteric compression test bilaterally, confirming that the femoral heads were on a permanently subluxated position.
The x-ray image on figure 1 documents the bilateral subluxation compatible with the diagnosis of hip dysplasia. A one stage bilateral DARthroplasty was executed to address the dog’s symptoms.
The dog was premedicated with Tramadol and Acepromazine. General anesthesia was induced with Propofol and Diazepam and maintained with Isofluorane. An epidural anesthesia was administered using a mixture of Lidocaine, Bupivacaine and Morphine.
A caudal approach to the hip joint was performed. The muscles were elevated from the hip capsule and from the dorsal acetabulum as described by Slocum and Slocum (1). A 2,5 millimeter Steinman pin was hammered onto the ilium, dorsal to the cranial end of the acetabular rim and bent cranially to retract the gluteal muscles and create a stable space for the technique. A groove was created by removing the lateral cortex of the pelvis (to the level of bleeding spongiosa) with a straight 4 millimeter Lexer gouge from the caudal to the cranial end of the acetabulum just dorsal to the capsular insertion. A second incision was performed as described by Slocum (1) to expose the entire wing of the ilium and collect, with a curved 10 mm Lexer gouge, as many cancellous and corticocancellous bone strips as possible without interfering with the iliac bone structural function. The length of the strips was estimated from x-ray images and by measuring directly over the palpable femoral head. The first strip was inserted over the capsule, parallel to the created cortical groove, and under the tendon of the deep gluteal muscle cranially, and under the tendon of the internal obturator caudally, constituting the most lateral part of the first layer of the augmentation. Additional strips were inserted parallel and medially to the first, until the last strip covers the groove on the dorsal acetabulum, making a continuous first layer. A second layer of strips was inserted parallel to the first and manually compressed over the first layer making the graft as thick as possible. Sutures were not used to stabilize the graft. The graft was maintained in position by the referred tendons and by limiting dissection to the space estimated to be necessary for the graft.
Postoperative radiographs were obtained immediately after the procedure (fig. 2) and 5 months later (fig. 3) in the full hip extended with internal rotation view. At this time the dog was 11 months old and weighed 24 Kg. A Computed Tomography Scan was performed 1 year after the surgery (figs. 4, 5 and 6 ) in moderate hip extension.
At 5 months post-operatively the dog was fully functional in all activities including running and jumping. The range of hip motion was normal in flexion and extension. Abduction was limited by the graft, causing no detectable impairment on locomotion. Muscle mass was considered normal. No pain was detected on extending the hips. The results of these observations remain unchanged 1 year after the surgery.
Images 34 months after surgery. The functional observations remain unchanged from the last evaluation.
The current knowledge in Veterinary Medicine cannot accurately define the indications, effectiveness and postsurgical prognosis of the DARthroplasty or other shelf acetabuloplasties. Referring to the universe of veterinary medical publications only Slocum’s description of technique and results are available to date. In their series of cases, none of the patients that have undergone DARthroplasty have demonstrated painful signs that would suggest the need for a total hip replacement (1).
The Shelf Acetabuloplasty techniques deserve to be thoroughly investigated as a surgical option for the treatment of canine hip dysplasia. Collection of objective data from the largest possible series of cases using a reproducible surgical technique would be a rational goal.
Slocum B, Slocum T. D. DARthroplasty.
In: Bojrab, M. J., ed. Current Techniques in Small Animal Surgery, 4th Ed. Baltimore: Williams & Wilkins 1998: 1168 – 1170