Risk factors associated with non-union after triple pelvic osteotomy (Toennis and Kalchschmidt technique): a case-control study and review of the literature.

INTRODUCTION

Dysplasia of the hip is a well known cause of secondary osteoarthritis of the hip. The triple pelvic osteotomy (TPO), according to the technique described by Toennis and Kalchschmidt, is a well established procedure to address dysplasia of the hip joint. Non-unions after triple pelvic osteotomies are rare and can occur at each of these osteotomies. The literature is lacking in studies investigating larger group of patients with non-unions after triple pelvic osteotomy. The aim of this study is to evaluate risk factors leading to a non-union after triple pelvic osteotomy.

METHODS

A total of 53 patients with a non-union after triple pelvic osteotomy were included in this retrospective case-control. In addition, we identified a cohort of randomly selected patients undergoing hardware removal after triple pelvic osteotomy ("union" group) but had not developed non-union as the control group. This control group underwent the same procedure by the same group of surgeons in the same time period. The variables obtained from the review of the two groups were analyzed using appropriate statistical methods including Bivariable Analysis (p < 0.005) and Multivariable logistic regression analysis (p < 0.015).

RESULTS

We identified a total of 53 patients out of the 3269 who had undergone TPO and had developed a non-union. The control group consisted of 117 patients who did not experience a non-union. Bivariable analysis of basic demographic characteristics demonstrated that gender, BMI, smoking, preoperative CE angle and degree of surgical correction did not differ significantly between the groups. There was a statistically significant (p < 0.05) difference between age (31.5 ± 9.4 vs. 27.5 ± 9.0 in the non-union and union groups, respectively; p = < 0.001) and postoperative CE angle (34.4 ± 5.0 vs. 32.8 ± 3.5 in the non-union and union groups, respectively; p = 0.02). Multivariable analysis demonstrated that an age over 30 was significantly associated with non-union (p = 0.01, OR 2.6, 95% CI 1.3-5.3).

CONCLUSION

Non-unions after TPO are rare. A higher age and higher degree of surgical correction might be associated risk factors for developing a non-union. Furthermore, smoking, obesity and previous hip surgeries might also contribute to developing a non-union after triple pelvic osteotomy.