Lumbar pedicle subtraction osteotomy: clinical and radiographic

Abstract

Anton A. Thompkins, MD, Courtney W. Brown, MD, David H. Donaldson, MD, John L. Brugman, MD, Douglas C. Wong, MD, James S. Gebhard, MD, Barbara J. Muff, RN, BSN, ONC, Golden, CO, USAIntroduction: Patients that have the diagnosis of “flat back syndrome” often have chronic debilitating back pain secondary to degenerative changes and global imbalance. The fixed sagittal imbalance places the spinal musculature at a mechanical disadvantage, increasing muscle fatigue, spasms and therefore pain. This difficult problem has been addressed in the past with either an anteroposterior spinal osteotomy and fusion or a Smith-Peterson osteotomy. By the very nature of these procedures, the spinal cord can be placed at risk secondary to the lengthening of the anterior spinal column. Pedicle subtraction osteotomy achieves a rebalanced spine without lengthening neural elements.Purpose: The purpose of this review is to report the clinical and radiographic outcome of patients who have undergone pedicle subtraction osteotomy in order to achieve significant correction of sagittal and coronal imbalance.Materials and methods: The clinical course and radiographic analysis of 27 consecutive patients who underwent pedicle subtraction osteotomy were evaluated. The clinical evaluation included operative time, blood loss, hospital stay, complications and the pre- and postoperative pain medication use. This information was gathered from both clinic and hospital charts and by direct contact with the patients. The radiographic analysis compared preoperative sagittal and coronal balance with postoperative sagittal and coronal balance. In addition, the amount of correction obtained at the osteotomy site and the overall lumbar sagittal contour change from pre- and postoperative radiographs were evaluated. The coronal balance was measured from C7 to the middle of the sacrum on an AP film with a plum line. The overall sagittal balance was measured from the anterior/inferior edge of C7 to the posterior aspect of S1 again, with a plum line. The osteotomy correction was measured using the Cobb angle technique from the end plate immediately above and below the operative level. The degree of lumbar lordosis was measured from the inferior end plate of T12 to the superior end plate of S1.Results: Sixteen female and 11 male patients underwent pedicle subtraction osteotomy between 1996 and 2000. The average age was 49 years, with the mean number of previous spinal operations of three. Even in the multiply operated spine, pedicle fixation was obtained 100% of the time in the lumbar spine to aid in maintaining the appropriated sagittal contour. The average blood loss was 1,116 cc and the average operative time was 6 hours and 45 minutes, with a mean hospital stay of 6 days. The average preoperative coronal and sagittal imbalance were 4.38 cm and 12.22 cm, respectively. The postoperative correction on the immediate follow-up showed coronal and sagittal balance of 1.84 cm and 3.42 cm, respectively. This represents a 58% correction in the coronal plane and a 72% correction in the sagittal plane. This correction was maintained at the latest follow-up with only a .09 cm average loss of correction in the coronal plane and .04 cm average loss of correction in the sagittal plane. This loss of correction is well within measurement error and is considered to be negligible. The average follow-up examination was 15 months from the index procedure. The correction obtained through the osteotomy site was 31 degrees on average with an increase in lumbar lordosis from 28 degrees preoperatively to 49 degrees postoperatively. The overall satisfaction with surgery was quite high, even with nine patients having complications. There were no incidences of spinal cord injury or nerve root loss. There were four infections (one deep, three superficial), which resolved with the appropriate antibiotic course. There were four cases of pseudarthrosis requiring a second operation, all of which went on to a solid union. In evaluating the amount of pain medicines used pre- and postoperatively, 60% of patients went from narcotic use to only an anti-inflammatory agent or nothing for pain management. Seventeen percent of the patients still used an occasional narcotic pain pill to manage their back pain, but all patients had an overall decrease in the use of pain medicines.Conclusion: Pedicle subtraction osteotomy is a safe and effect treatment for patients who have flat back syndrome. It is the authors' belief that pedicle subtraction osteotomy is a safer approach than the previously described methods of treating this problem. Pedicle subtraction osteotomy can be performed on patients who have had multiple spinal operations. This simple posterior procedure offers excellent radiographic and clinical improvements with limited complications.