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Effect of Spinal Deformity on Pelvic Orientation from Standing to Sitting Position


The effect of fixed spinal deformities on a functional pelvis from standing to sitting is not fully understood. We aimed to assess the change in preoperative sagittal pelvic tilt angle (SPTA) from standing to sitting in patients undergoing total hip arthroplasty, comparing flexible and fixed spinal deformities.


Between July 2011 and October 2011, 68 consecutive unilateral total hip arthroplasties were implanted in 68 patients with a mean age of 71 ± 6 years. Fixed spinal deformity was defined as <10° of the change in SPTA from standing to sitting. Preoperative radiographic evaluation included standing (weight-bearing) anteroposterior and lateral pelvic and lumbosacral radiographs and a sitting lateral pelvic radiograph.


The mean standing and sitting SPTA was 3.7° of anterior tilt and 17.7° of posterior tilt, respectively (change of 21.4 ± 12.5°). Seventy-five percent had flexible pelvises, all of which had a posterior tilt from standing to sitting. One patient in the fixed pelvis (1.4%) had a loss of posterior tilt from standing to sitting. The mean change of SPTA from standing to sitting in the fixed and flexible pelvis groups was 5.9 ± 3.5° to 26.7 ± 9.6° of posterior tilt, which was statistically significant (P < .05).


There was a significant change in sagittal pelvic tilt from standing to sitting, especially in patients with a flexible spine, in which the functional anteversion increases with sitting. The patients with a fixed pelvis had significantly less SPTA in standing (less anteversion) with less posterior sagittal tilt in sitting, which should be incorporated in cup positioning.

Chitranjan S., Ranawat MD, Amar S.Ranawat MD, Joseph D.Lipman MS, Peter B.White BA, Morteza Meftah MD

The Journal of Arthroplasty

Volume 31, Issue 6, June 2016, Pages 1222-1227

Chitranjan S. Ranawat MDa, Amar S. Ranawat MDa, Joseph D. Lipman MSb, Peter B.White BAa, Morteza Meftah MDc

Department of Orthopaedics, Hospital for Special Surgery, New York, New YorkbDepartment of Biomechanics, Hospital for Special Surgery, New York, New YorkcDepartment of Orthopaedics, NYU Langone Medical Center, Hospital for Joint Disease, New York, New York

Received 11 October 2015, Revised 19 November 2015, Accepted 23 November 2015, Available online 7 December 2015.