Pubic/ischial stress fractures after eccentric rotational acetabular osteotomy.

BACKGROUND

Although there have been several reports on the complications of periacetabular osteotomy, stress fractures occurring in the pubic and ischial bones are less well recognised. The purpose of this study was to analyse the incidence of stress fracture, factors and treatment outcomes of stress fractures in the pubic/ischial bone after eccentric rotational acetabular osteotomy (ERAO).

MATERIALS AND METHODS

We examined 340 hips of 290 patients (male 35 hips, female 305 hips; mean age 42 years) with whom it was possible to conduct a minimum of 1 year of follow-up observations after ERAO. The following items were investigated: presence of a pubic/ischial stress fracture after surgery; gender; age; bilateral or unilateral osteoarthritis; height, weight and body mass index; preoperative and final stages of osteoarthritis of the hip; preoperative and final center-edge (CE) angle, acetabular head index and minimum joint space; preoperative and final Japan Orthopaedic Association score; and presence of a pubic discontinuity. We then compared cases with pubic/ischial stress fracture (fractured group) with those with no fracture (nonfractured group). For the fractured group, we also investigated the onset time of the fracture.

RESULTS

The fractured group consisted entirely of women with a mean age of 47 years, and comprised 10 (2.9%) of the 340 patient hips examined. A statistically significant difference was observed between the two groups in pubic discontinuities (fractured group 8/10, nonfractured group 16/330; P < 0.0001) and postoperative CE angle (fractured group; 43°, nonfractured group; 36°, P = 0.0338) according to univariate analysis. However, only the pubic discontinuity rate differed significantly between the groups according to multivariate analysis (P < 0.0001). In all cases, a pubic/ischial stress fracture occurred within 3 months after surgery, and all cases had bony union. Recurrent fracture occurred in only one hip. There was no difference in the clinical outcomes of the fractured and nonfractured groups at the time of final follow-up.

CONCLUSIONS

The patients with pubic discontinuities were significantly more susceptible to a pubic/ischial stress fracture after ERAO. The presence of a pubic/ischial stress fracture did not influence the clinical outcome.