Long-term follow-up of Chiari pelvic osteotomy in myelomeningocele

A computer model for evaluating the osteotomy parameters of Chiari pelvic osteotomy

This study was conducted to evaluate the effect of the various osteotomy parameters on the biomechanical aspects of the hip joint on a computerised model. The data of the radiographs and a three-dimensional (3D) CT scan of six patients with coverage deficient hip joint were used to construct a 3D computer model. Then Chiari type osteotomies were simulated using various heights, angles and fibrocartilage thicknesses. A new angle called the mid acetabular center edge (MACE) angle was defined in a mid coronal CT cut. The optimum displacement for obtaining the maximum coverage averaged 73%. The angle and height of the osteotomy had a significant effect on the MACE angle (P value < 0.01). Our findings of these Chiari parameters may change the results of the osteotomy. The probability of adapting the proximal osteotomy segment to a deformed femoral head was explained by the model and a modified osteotomy "multiple height osteotomy" was proposed.

The results of Chiari pelvic osteotomy in adolescents with a brief literature review

PURPOSE

Chiari medial displacement osteotomy is a procedure that uses the cancellous bone of the ilium to contain the femoral head and bear weight. It is the most contraversial osteotomy of the hip joint. This study was therefore conducted to determine the results of this osteotomy with mid-term follow-up in children.

METHODS

From 1995 to 2004, 20 Chiari pelvic osteotomies (in 18 patients) were performed. There were 15 male and 3 female patients. The average age at operation was 12.6 years and the mean follow-up was 54 months. The operative technique was as described by Chiari. An iliofemoral approach was used without utilizing a traction table. If there was anterior or anterolateral uncoverage of the femoral head, bone graft augmentation was performed.

RESULTS

The angle of the osteotomy averaged 12 degrees , with the distance from the acetabulum averaging 3.2 mm. The average displacement was 42%. Of the 20 Chiari osteotomies, 11 were categorized as excellent, 8 as good and one as fair in terms of clinical and radiological results. Student's t test statistics showed improvements in all radiologic parameters of the hip joint (Sharp angle, center-edge angle and coverage of the femoral head). Graft resorption was observed in 25% of the patients.

CONCLUSION

There are very rare indications of Chiari osteotomy in patients younger than 10 years. Because of the high rate of graft resorption, Chiari osteotomy should be the last treatment option when there is anterior or anterolateral uncoverage of the hip joint.