Fracture at the Ischio-Pubic Junction After Periacetabular Osteotomy in the Adolescent Population.

INTRODUCTION: The Ganz periacetabular osteotomy (PAO) is a well-accepted surgical intervention for hip dysplasia. In the adolescent population it is performed in patients who are skeletally mature with symptoms related to acetabular dysplasia. Redistribution of stresses through the hemipelvis after PAO can lead to a fracture at the ischio-pubic junction (IPJ).

METHODS: This is an IRB-approved, retrospective analysis of adolescent patients treated with a PAO for acetabular dysplasia from 1999 to 2012 at a single institution. Radiographic measurements were performed to include the lateral center-edge angle, Sharp acetabular index, and acetabular index of the weight-bearing zone. These were measured preoperatively and at 6-weeks and 1 year postoperatively from a standing anterior posterior pelvis radiograph. Postoperative modified Harris hip scores (mHHS) were also analyzed. Patients over the age of 21 at time of surgery and those with <2 years of follow-up were excluded.

RESULTS: One hundred sixty-six patients (187 operated hips) at an average age of 15.6±2.5 were included. Twelve (6.4%) fractures at the IPJ were identified in 12 patients. Seven were identified on the initial postoperative films, whereas 5 were identified after the 6-week visit. Seven (58.3%) fractures had an associated superior posterior ramus nonunion. Six (50%) healed by 2 years after surgery; the remaining 6 (50%) went on to nonunion. Compared with those without a fracture, there was no significant difference in preoperative, 6 weeks postoperative, and final center-edge angle (P=0.94, 0.29, 0.27), Sharp acetabular index (P=0.95, 0.38, 0.16), or AIBWZ (P=0.37, 0.21, 0.54). There was no difference in postoperative mean modified Harris hip scores (P=0.63). Analysis of predisposing factors demonstrated that patients with Charcot-Marie-Tooth (CMT) disease were more likely to develop an IPJ fracture (P=0.001). Patients with an IPJ fracture were older (17.1 vs. 15.5, P=0.05). There was no difference based on patient sex (P=0.22).

DISCUSSION AND CONCLUSIONS: The incidence of fracture at the IPJ after PAO in the adolescent population is 6.4% with some occurring at the time of surgery. These fractures are also associated with a nonunion at the superior posterior ramus cut and an underlying diagnosis of Charcot-Marie-Tooth. These fractures are not clinically significant and in this series did not merit further intervention when identified.

LEVEL OF EVIDENCE: Level III.