Tönnis Triple Pelvic Osteotomy
There are a number of redirectional osteotomies that have been described to treat acetabular dysplasia in patients with an open triradiate cartilage. Classically, these procedures are described by the number of osteotomies made in the ilium and/or the surgeon who described the procedure: single/Salter, double/Sutherland, and triple/Steel, Carlioz, and Tönnis. The most significant alteration in Tönnis’s version of the triple innominate osteotomy, described in 1976, is the location of the ischial osteotomy. This osteotomy is proximal to the sacrospinous ligament, which allows greater freedom of movement and, particularly, medialization of the acetabular block. In addition, this technique preserves the ligaments coursing from the sacrum to the ischium. The original description directs the surgeon to perform the operation in a staged fashion; first, the patient is positioned prone to complete the osteotomy of the ischium and then repositioned supine to perform the iliac and pubic osteotomies. Alternatively, the procedure may be performed with the patient in the semi-lateral position, which is described in the technique below.