Evaluation of a Novel Method for Determining Transverse Plane Pelvic Obliquity In Neuromuscular Scoliosis

Saturday, October 15, 2011: 8:07 AM
Otis (Westin Waterfront)
Lee S. Segal, MD1, Joel A. Toretti, MD2, Rodney E. Brenneman, BS2, M. Wade Shrader, MD1, Vernon M. Chinchilli, PhD2 and Kelly L. Vanderhave, MD1, (1)Orthopaedics, Phoenix Childrens Hospital, Phoenix, AZ, (2)Phoenix Childrens Hospital, Phoenix, AZ

Purpose:  The evaluation of pelvic obliquity in the transverse plane has not been thoroughly studied, but is important in children with severe neuromuscular scoliosis.  Severe rotational pelvic deformities can lead to truncal imbalance and significant difficulty with seating for children who are mostly wheelchair ambulators.  A true appreciation of the magnitude of pelvic rotational obliquity is important for preoperative planning when one is considering surgery for these children with severe scoliosis.  One technique of evaluating the rotational pelvic obliquity has been suggested in the literature (Lucas et al).  The purpose of this study is to evaluate the utility of a recently described method of determining transverse plane pelvic obliquity using standard radiographs in patients with cerebral palsy and neuromuscular scoliosis.

Methods:   This was a retrospective review of neuromuscular scoliosis radiographs evaluating inter- and intra-observer error for a novel method of transverse plane pelvic obliquity.  40 radiographs were chosen from patients with cerebral palsy and neuromuscular scoliosis.  The radiographs were examined independently by four observers at different levels of training on two dates one week apart. The measurements recorded by each observer were described by Lucas et al. (E, FR, FL, and β). Reproducibility of the measurements were analyzed using the concordance correlation coefficient (CCC). A CCC of 0.90 or higher was considered excellent agreement.

Results:   The CCC between the first and second sets of measurements was lowest for E (distance measured on lateral radiographs between the ilium at the inferior part of the SI joint and the lateral edge of the ASIS), and highest for the calculated β, although none of the CCC calculations were found to be statistically significant, demonstrating poor agreement.

Conclusion:   The ability to reliably measure and calculate the degree of transverse plane rotation by radiographs in cerebral palsy patients with spino-pelvic deformity with currently described techniques is poor.  The low correlations were likely due to our inability to consistently identify pelvic landmarks and was most compromised in the evaluation of the sitting lateral x-rays.  The ranking of agreements did not correspond to the amount of experience of the observer.

Reference:  Lucas B, Asher M, McIff T, Lark R, Burton D: Estimation of transverse plane pelvic rotation using a posterior-anterior radiograph. Spine 30: E20-E27, 2004.