Blood Loss of Pedicle Subtraction Osteotomy for Sagittal Imbalance Spinal Deformity

Pedicle subtraction osteotomies (PSO) have been used in the treatment of multiple spinal conditions involving a fixed sagittal imbalance. It is a complex, extensive surgery most often performed in the revision settings. The aim of our study is to review the major complications of this surgical technique with a focus on blood loss. Twenty patients were included, treated using PSO for sagittal imbalance, out of 255 corrective surgeries. Of the 12 female patients included in the study, the mean age was 64.33. Of the 8 male patients included in the study, the mean age was 51.85. For female patients, the mean blood loss was 2122.5 mL in comparison with male patients, with mean blood loss 1737.5 mL. The female patients had an operating time of 357.25 minutes in comparasion with male patients with an 328.5 minute operating time. Eight (5 female and 3 male) had postoperative neurological deficits and 6 (5 female and 1 male) had pseudarthrosis of adjacent levels.

Pelvic retroversion: a compensatory mechanism for lumbar stenosis

OBJECTIVEThe flexed posture of the proximal (L1–3) or distal (L4–S1) lumbar spine increases the diameter of the spinal canal and neuroforamina and can relieve symptoms of neurogenic claudication. Distal lumbar flexion can result in pelvic retroversion; therefore, in cases of flexible sagittal imbalance, pelvic retroversion may be compensatory for lumbar stenosis and not solely compensatory for the sagittal imbalance as previously thought. The authors investigate underlying causes for pelvic retroversion in patients with flexible sagittal imbalance.METHODSOne hundred thirty-eight patients with sagittal imbalance who underwent a total of 148 fusion procedures of the thoracolumbar spine were identified from a prospective clinical database. Radiographic parameters were obtained from images preoperatively, intraoperatively, and at 6-month and 2-year follow-up. A cohort of 24 patients with flexible sagittal imbalance was identified and individually matched with a control cohort of 23 patients with fixed deformities. Flexible deformities were defined as a 10° change in lumbar lordosis between weight-bearing and non–weight-bearing images. Pelvic retroversion was quantified as the ratio of pelvic tilt (PT) to pelvic incidence (PI).RESULTSThe average difference between lumbar lordosis on supine MR images and standing radiographs was 15° in the flexible cohort. Sixty-eight percent of the patients in the flexible cohort were diagnosed preoperatively with lumbar stenosis compared with only 22% in the fixed sagittal imbalance cohort (p = 0.0032). There was no difference between the flexible and fixed cohorts with regard to C-2 sagittal vertical axis (SVA) (p = 0.95) or C-7 SVA (p = 0.43). When assessing for postural compensation by pelvic retroversion in the stenotic patients and nonstenotic patients, the PT/PI ratio was found to be significantly greater in the patients with stenosis (p = 0.019).CONCLUSIONSFor flexible sagittal imbalance, preoperative attention should be given to the root cause of the sagittal misalignment, which could be compensation for lumbar stenosis. Pelvic retroversion can be compensatory for both the lumbar stenosis as well as for sagittal imbalance.