Implant Complications in 20 Triple Pelvic Osteotomies

Abstract

SummaryIn 12 dogs with hip dysplasia, 20 triple pelvic osteotomies (eight bilateral and four unilateral) were performed. Screw loosening, occurring in six of 12 dogs (seven of 20 osteotomies), was the most common complication after surgery. Implants loosened from the cranial ilium in six hemipelvises (30%) and from both fragments in one hemipelvis, two to six weeks (mean — three) after the operation. Medial acetabular displace-ment caused pelvic narrowing (6 to 9%, mean = 8%) in three of four dogs. Medial ischial displacement decreased pelvic diameter (11 to 21%, mean = 17%) in four of seven osteotomies. All of the dogs with implant failure were treated conservatively with cage rest and in two cases Ehmer slings were used. Although none were lame, gait abnormalities were evident in three of seven dogs on follow-up examinations four to 12 months (mean = six) later.Screw loosening, occurring in seven of 20 hemipelvises, was the most common postoperative complication associated with triple pelvic osteotomy. Fixation failures were managed conservatively. Despite decreased pelvic diameter in four of seven animals, none were lame or showed signs of pelvic obstruction at follow-up examinations four to 12 months later.

Evaluation of ilial screw loosening after triple pelvic osteotomy in dogs: 227 cases (1991–1999)

“…The 5 breeds most commonly represented were Labrador Retriever (n = 49), Golden Retriever (47), mixed breed (37), Rottweiler (16), and German Shepherd Dog (15); also included were 63 other dogs representing 28 other breeds.…”

“…Twenty-five percent of the complications were the result of screw loosening, results that were similar to complication rates reported in other studies. [14][15][16][17]21 An ischial interfragmentary wire had been placed in 99% of the TPO surgeries evaluated in the present study. The remaining 1% did not involve an ischial interfragmentary wire and included 2 instances in which screws loosened.…”

“…It has been proposed that increasing sacral engagement with screws and increasing the number of screws engaging the sacrum can mitigate screw migration. 15,16,20,21 However, those results are in conflict with findings from other studies, 22,23 in which screws that spanned the sacroiliac joint were associated with unfavorable results. In an in vitro model in 1 study, 24 4.0-mm cancellous screws had higher pullout strengths in immature pelvic bone than did 3.5-mm cortical screws.…”

“…[11][12][13] The postoperative complication rate associated with the TPO procedure ranges from 35% to 70%, with screw loosening being the most common complication. [14][15][16][17] Screw loosening develops in the first 2 to 6 weeks after surgery [18][19][20][21] and is thought to be the result of decreased retention of screws in less-dense juvenile bone. [17][18][19] Early screw loosening can lead to loss of alignment between the ilial and acetabular segments, and improper alignment and medial displacement of the acetabular segment can result in pelvic canal impingement.…”

“…It has been speculated that the ischial interfragmentary wire adds stability to the caudal acetabular segment, thereby increasing stability of the repair. Results from the few studies 12,15,16 in which the role of ischial interfragmen-…”