OSTEOTOMY OF THE PELVIS
CHARLES D. NEWTON
Pelvic osteotomy is a procedure used to help reshape the acetabulum in the dysplastic animal. Historically, Salter, a pediatric orthopaedic surgeon, began this procedure by cutting the acetabular portion of the pelvis free and then repositioning it. His triple osteotomy, that is, osteotomy of the ilium, pubis, and ischium, allowed him to rotate the acetabulum so as to create more depth to accommodate the femoral head. In young children with unilateral or bilateral hip subluxation (dysplasia), this procedure proved very successful.(18) It is important to realize that young animals (puppies or kittens) or children are more able to reform a suitable hip following such a procedure than is the mature or nearly mature patient.
Immature dogs with pain or lameness associated with hip subluxation are candidates for pelvic osteotomy. Radiographically the hip must not demonstrate evidence of deformity or degenerative arthritis. Should deformity or degenerative joint disease (DJD) be present, the likelihood of success is minimized.
The animal's age is also an important consideration. The immature animal, 5 to 9 months old, is much more likely to reform a functional hip than the older dog. This procedure should be done prior to 9 months of age to achieve the best result.
Pelvic osteotomy is more likely to result in a fully functional, anatomical end result than is excision arthroplasty. For this reason it is the best option to consider for the immature working dog in the midst of expensive training. The procedures should return a seeing eye dog or security dog to near normal function. Surely the end result will be more functional than excision arthroplasty.
These procedures are designed to provide greater acetabular depth and presuppose that the femoral component of the hip is normal. Pelvic osteotomy is not designed to correct the subluxation problems associated with coxa valga or increased anteversion of the proximal femur. Such problems must be corrected by femoral osteotomy. (See Chapter 43.)
Dogs with complete luxation of the hip, grade IV hip dysplasia, are not candidates for this procedure.
PELVIC OSTEOTOMY (TECHNIQUE OF HOHN)
A lateral approach to the iliac shaft is made to expose the osteotomy site. Simultaneously, a trochanteric osteotomy is performed to expose the hip and facilitate retraction of the gluteal muscle mass.
A 2-cm incision is made parallel to the long axis of the body over the ischium; blunt dissection dorsal and ventral to the ischium elevates the internal and external obturator muscles to allow passage of Gigli wire through the obturator foramen. The ischiatic table is osteotomized to allow rotation of the ilium. It is not necessary to osteotomize the pubis.
The medial surface of the iliac shaft must also be dissected free of muscle to facilitate osteotomy. A malleable band retractor will protect the ischiatic nerve from the saw. With an oscillating saw, the ilium is cut in a step-like fashion, and the ischium is osteotomized.
By gentle elevation of the dorsal-most iliac step and digital displacement of the ischiatic fragments, the iliac fragments are realigned. The relocation results in the caudal fragment, which contains the acetabulum, being displaced both ventrally and laterally. This rotates the acetabular roof laterally on the iliac-ischiatic axis and deepens the acetabulum (Fig. 42-1). The iliac fragments are anchored using two interfragmentary bone screws.
If laxity persists, a dorsal capsulotomy may be performed over the dorsal 120¡ of the joint. The capsule is imbricated with simple interrupted horizontal mattress sutures. A synthetic nonabsorbable suture material is preferred. The hip should be held in abduction when the sutures are tightened and tied.
Further correction can be accomplished by trochanteric relocation. By moving the greater trochanter both distally and caudally, the resultant gluteal pull will internally rotate and abduct the hip, creating temporarily a more stable hip.
Postoperative management should include cage confinement, leash walking, and immobilization of the hip in an Ehmer sling for 12 to 14 days.
The results of pelvic osteotomy using this technique are good (Fig. 42-2). After 2 years most dogs do well. Corrected hips may continue to subluxate, but less than initially and less than the uncorrected side. Corrected hips become osteoarthritis, but to a lesser extent than the uncorrected side.(35)
FIG, 42-1 Drawing of the pelvic osteotomy technique of Hohn shows the sites of osteotomy (A). Lateral (B) and dorsal-ventral (C) views demonstrate displacement and fixation of the ilial and ischial osteotomy
FIG. 42-2 (A) Ventral-dorsal radiograph of a 9-month-old German shepherd demonstrates subluxation of the left and right hips. (B) Radiograph demonstrates the right hip 2 months following pelvic osteotomy. (Courtesy of Dr. RB. Hohn)
A variation of the Hohn double osteotomy technique has been described by Stoll, Rosen, and Tarvin.(10) The ilial shaft osteotomy is performed as in the Hohn technique; however, the pubic symphysis rather than the caudal ischiatic table is cut. Fixation is with a full cerclage wire on the symphysis, and the ilial stair-step osteotomy is fixed with a cerclage wire and a bone screw. Recent reports state that this technique results in more lateral rotation of the acetabulum than triple osteotomy techniques and therefore produces better joint stability.(6)
ACETABULOPLASTY (TECHNIQUE OF BRINKER)
The coxofemoral joint is approached dorsally. In the very young dog this should be accomplished by gluteal tenotomy; older animals can be exposed by greater trochanteric osteotomy. The middle and deep gluteal muscles are reflected dorsally and cranially from the underlying joint capsule and bone.
The acetabular periosteum is incised on a line 3 mm medial and parallel to the dorsal rim of the acetabulum. By using a periosteal elevator, the subperiosteal reflection of these muscles and periosteum is continued dorsally and cranially and caudally to expose the bone beyond the rim of the acetabulum.
Using a Hall drill, a curved osteotomy of the ilium and ischium is performed by cutting approximately 3mm to 5mm behind the rim of the acetabulum and parallel to it. The final cut through the opposite cortex is made by an osteotome malleable retractor. After this osteotomy, the acetabulum remains attached to the pubis.
The bony fragments are separated using Cloward forceps. The separation is maintained by packing with a bone graft, usually taken from the crest of the same ilium (Fig. 42-3).
In instances in which joint instability remains, capsulorrhaphy or trochanteric repositioning should result in a stable hip.
Routine surgical closure is followed by 12 to 14 days of further external immobilization in an Ehmer sling. The average time for healing and return to function without lameness is 5 to 8 weeks.
FIG. 42-3 Drawings of the acetabuloplasty technique of Brinker show the site of osteotomy (A) and the position of the acetabulum (B) following osteotomy displacement and bone grafting.
FIG. 42-4 (A) Ventral-dorsal radiograph of a l-year-old Labrador retriever demonstrates subluxation of the left hip. (B) Radiograph demonstrates the left hip immediately following acetabuloplasty. (C) Radiograph demonstrates the near normal left hip 6 years following acetabuloplasty. Note that the right hip shows considerable degenerative joint disease. (Courtesy of Dr. W.O. Brinker)
Results are better in young dogs than in the older dogs. Overall results of acetabuloplasty are reported to be good (Fig. 42-4).(1)
TRIPLE OSTEOTOMY (TECHNIQUE OF RUDY)
Triple osteotomy allows the acetabulum to rotate laterally on its axis and most closely resembles the innominate osteotomy of Salter.(79)
Pubic osteotomy is the first step of this procedure. It is accomplished with the dog in dorsal recumbency, and a ventral incision is made over the pelvis. The pubis must be osteotomized as close to the acetabulum as possible. Use of a rongeur may be best so that a bony deficit results.
A lateral approach to the hip by biceps retraction and gluteal elevation dorsally will allow for visualization of the ischium and ilium. The ischium is transected caudal to the acetabulum after adequate protection of the sciatic nerve. The ilium is osteotomized transversely about mid-ilial shaft.
The result of the above triple osteotomy is a completely free acetabulum. Fixation is accomplished by Steinmann pins or a plate on the ilial shaft. Fixation is applied after allowing the acetabulum to rotate laterally approximately 20¡ to 25¡. The resulting new position should produce adequate acetabular depth to provide hip stability.
Postoperative management necessitates use of an Ehmer sling for 10 to 14 days and additional leash walking to prevent fixation failure. Rudy has had considerable success with the procedure when performed on mature dogs. Dogs as large as St. Bernard pups have met with success. A variation of triple osteotomy, which combines aspects of both the Hohn(4) and Rudy(2) techniques has been proposed by Schrader.(9) His technique utilizes a step osteotomy of the ilial shaft, pubic osteotomy, and ischial osteotomy through the sciatic notch.
None of the above surgical procedures is simple, and all require a period of learning in order to perform them well in a short intraoperative time. Most surgeons performing a pelvic osteotomy procedure for the first or second time require 2 to 4 hours or more of intraoperative time. Such extended periods lead to great likelihood of soft tissue desiccation, fluid loss, and risk of contamination and infection. Prolonged surgical time can be considered a complication.
All procedures require a complete knowledge of regional anatomy in order not to injure the sciatic nerve or intrapelvic arteries. Bruising, stretching, or laceration of the sciatic nerve can lead to permanent dysfunction. Adequate retractors are the best means of eliminating this problem.
Inadequate internal fixation or premature use of the operated limb may result in metal failure. Use of plates and screws generally is more successful than smooth pin fixation.
REFERENCES1. Brinker WO: Pelvic osteotomy for the treatment of hip dysplasia. Vet Clin North Am, Sept 1971, p 470
2. Datt SC, Rudy RL: Development of a Technique for Acetabular Rotation as a Possible Treatment of Chronic Coxofemoral Subluxation in the Dog. Master's thesis Ohio State University, 1966
3. Henry WB, Wadsworth PL: Pelvic osteotomy in the treatment of subluxation associated with hip dysplasia. J Am Anim Hosp Assoc 11:636, 1975
4. Hohn RB, Janes JM: Pelvic osteotomy in the treatment of canine hip dysplasia. Clin Orthop 62:70, 1969
5. Nunamaker DM, Newton CD: Canine hip disorders. In Bojrab MJ (ed): Current Techniques in Small Animal Surgery, pp 436-442. Philadelphia, Lea & Febiger, 1975
6. Pijanowski GJ, Tarvin GB, Sommer HJ: In vitro analysis of two canine pelvic osteotomy techniques. Vet Surg 10:139, 1981
7. Salter RB: Innominate osteotomy in the treatment of congenital dislocation and subluxation of the hip. J Bone Joint Surg 43B:518, 1961
8. Salter RB: Role of innominate osteotomy in the treatment of congenital dislocation and subluxation of the hip in the older child. J Bone Joint Surg 48A:1413, 1966
9. Schrader SC: Triple osteotomy of the pelvis as a treatment of canine hip dysplasia. J Am Vet Med Assoc 178:39, 1981
10. Stoll S. Rosen H. Tarvin GB: Pelvic osteotomy for the correction of hip dysplasia. In Proceedings of the Fifth Annual Meeting, Veterinary Orthopaedic Society, Snowmass, Colorado, 1978