Various osteotomies have been designed to address the complex deformities associated with acetabular dysplasia1,4,5,8,16,17,21,22,23,27
. For example, the Chiari osteotomy is a salvage procedure designed to enhance femoral head coverage with nonarticular fibrocartilage. In Chiari's original work, he emphasized the importance of decreasing the lever arm of the hip abductors in the lateral plane as a goal of osteotomy surgery1
. Since that time, many osteotomies have been described, each with a varying ability to normalize joint biomechanics and correct the multiple associated deformities of the dysplastic hip. Hogh et al. reported on their results following 94 Chiari osteotomies in 81 patients6
. Medial displacement was measured as the percentage of displacement of the acetabular side of the osteotomy from its original location. In this study, the osteotomy was translated an average of 68% of the width of the ilium. However, by measuring the horizontal distance from the medial aspect of the femoral head to the most inferior point of the teardrop, he noted an average of 1 mm of lateral subluxation of the femoral head within the acetabulum. Therefore, while the hip joint center is displaced medially, the actual position of the femoral head within the acetabulum may be inconsistent. Kubo evaluated changes in hip center position using CT scans before and after Chiari osteotomies in 23 patients7
. He documented an average medial displacement of the center of the hip joint of 6 mm. Therefore, these studies support the feasibility of medial translation of the hip joint center with the Chiari osteotomy. Nevertheless, despite some ability to achieve medial translation, the major weakness of the Chiari procedure is lack of femoral head coverage with articular hyaline cartilage. Rather, coverage is achieved with metaplastic fibrocartilage, which is suboptimal.
Salter described his innominate osteotomy as a treatment for hip dysplasia in both children and adults. In this procedure a single osteotomy allows the surgeon to rotate the acetabulum to improve both anterior and lateral coverage of the femoral head17
. In our review of the literature, we found no studies which documented medial translation achieved with Salter's innominate osteotomy. Therefore, while the innominate osteotomy may theoretically improve on the Chiari, by maintaining the congruity of the hip joint and enhancing articular cartilage coverage, the ability to reliably translate the hip joint medially, to our knowledge, has not been established.
Double and triple innominate osteotomies have also been employed in the treatment of acetabular dysplasia. Sutherland and Greenfield acknowledged the benefit of medial displacement in reconstructive pelvic osteotomy and proposed that one advantage of the double osteotomy over the Salter innominate osteotomy is the ability to translate the hip center toward the midline. They reported their results on 25 patients in whom they performed the double innominate osteotomy22
. This procedure began with the iliac osteotomy described by Salter, but was then followed by a second osteotomy placed medial to the obturator foramen between the pubic tubercle and the symphysis pubis. Radiographic follow-up revealed an average measurement of 15 mm of medial translation22
. In terms of medial translation of the hip, their data clearly improve on the correction obtained by the single osteotomy. Additionally, Steel proposed a triple innominate osteotomy with the intention of further improving the ability to correct the multiplanar deformity associated with developmental dysplasia of the hip21
. Frick et al. reported on seven patients who underwent CT scanning before and after triple innominate osteotomy3
. While these patients represented more complex cases which the authors felt required pre-operative CT evaluation, no significant change in horizontal position of the hip was found after surgery. Despite its small sample size, this study describes a decreased ability to reliably translate the hip joint center with a triple innominate osteotomy. These results reflect inherent difficulties in controlling the correction of a multiplanar deformity with a relatively large acetabular fragment that can be tethered with muscular and ligamentous attachments. Nevertheless, it should be noted that the Tönnis triple innominate osteotomy23
may provide medial translation as the inferior osteotomy is superior to the sacrospinous ligamentous attachment which may facilitate acetabular repositioning.
Another class of osteotomies have been proposed and evaluated in terms of deformity correction in dysplastic hips. Wagner introduced the spherical osteotomy27
, and subsequently described the Type III modification of his original osteotomy. This Type III osteotomy was intended for treatment of patients with dysplasia characterized by lateralization of the hip center. In such cases, he performed his original spherical osteotomy, and then displaced the hip center medially via a combined Chiari osteotomy. Unfortunately, to our knowledge no data have been reported on the actual medial translation achieved by adding this modification to the procedure. His work does, however, reinforce the biomechanical principles of hip joint preservation by reduction in joint reactive force acting on the hip.
Nakamura, et al. reported on 97 patients in whom they performed a rotational acetabular osteotomy16
. They found an average medial displacement of 7 mm measured from the medial border of the femoral head to the ilioischial line. In their study, 58 of 97 patients were optimally corrected, defined as translation of the hip 2.5 to 12.5 mm medial to its starting position. They achieved no change in the horizontal direction in 22 patients (22%). Twelve patients were overcorrected, defined as translation more than 12.5 mm, while 5 hips moved more than 2.5 mm in the lateral direction. Based on their criteria, 58% of patients were optimally corrected with respect to medial translation of the hip joint center.16
Thus, the rotational acetabular osteotomy does enable medial translation in the majority of cases.
In attempts to improve on the rotational osteotomy, Hasegawa et al. describe an eccentric rotational osteotomy, which maintains all of the benefits of the spherical osteotomies, but also adds the ability to translate the hip center toward the midline. They performed the procedure on 132 hips and found an average medial displacement of 4.1 mm5
. While this data is promising, the amount of medial translation achieved appears to be less than that afforded by the PAO, and the operation is technically more demanding. Sotelo-Sanchez et al., in a recent review, state that the spherical osteotomies are limited in translating the hip joint center medially18
, since the medial aspect of the quadrilateral plate remains intact with these osteotomies.
Since its description4
, the Bernese periacetabular osteotomy has gained favor in terms of its ability to improve the acetabular position in multiple planes. Siebenrock et al. reported on their first 75 procedures in 63 patients and demonstrated an average correction of 6 mm of medial translation of the hip joint20
. Other investigators12,13 14 24 25 26
have also reported that, in general, medial translation of the acetabulum can be achieved with the periacetabular osteotomy. Nevertheless, the magnitude of correction and the reproducibility of medial translation has not been emphasized in the literature. Our data, collected from our learning curve experience, indicate that medial translation can be achieved consistently with this technique. Specifically, we obtained an average 9.8 mm of medial translation in our cases. Perhaps, more importantly, some degree of medial translation was obtained in 92% of hips and 72% were thought to have an optimal correction. Thus, in addition to major corrections of anterior and lateral femoral head coverage, reliable medial translation of the hip joint is a distinct advantage of the Bernese periacetabular osteotomy. This advantage is most notable in severely dysplastic hips with major lateral subluxation ().