Postoperative Spinal Deformity

Pathophysiology: Prevalence and Impact

Postoperative deformity is an important complication and a major reason for revision spine surgery. Reported revision rates for spine surgery are variable, and rates are dependent upon the primary pathology treated, patient factors including age, bone quality, and obesity, method of treatment, and choice of levels for arthrodesis. After fusion for degenerative disorders, including one- and two-level lumbar fusions, Leveque et al. demonstrated that 28% of patients had postoperative malalignment, specifically with a mismatch between postoperative lumbar lordosis and pelvic incidence. Postoperative malalignment is most common after surgery for spinal deformity. In a review of 122 adults undergoing multilevel fusion for spinal deformity, Passias et al. demonstrated high rates of undercorrection compared with age-adjusted goals for radiographic parameters, including sagittal vertical axis (SVA; 30%), pelvic tilt (41.0%), and lumbopelvic mismatch (pelvic tilt 43.6% and the difference between pelvic incidence and lumbar lordosis 43.6%). Reviewing a multicenter database, Ames et al. demonstrated high rates of postoperative sagittal plane malalignment in patients undergoing adult deformity surgery, with only 23% of patients achieving alignment goals for global and lumbopelvic alignment. Postoperative deformity and adjacent segment pathology are associated with significant disability, and are important and potentially avoidable causes of revision surgery. ^, Scheer et al. reported a revision surgery rate of 17% within 1 year after multilevel fusion for treatment of adult spinal deformity, and recommended careful preoperative assessment of alignment goals, as well as intraoperative rod and implant placement, to avoid revision surgery. The ability of surgeons to accurately predict postoperative alignment after deformity is imperfect. In a study evaluating the effectiveness of surgeons predicting postoperative alignment as a result of specific operative strategies, surgeons correctly predicted the actual postoperative radiographic parameters only 42% of the time, with postoperative thoracic kyphosis and lumbopelvic mismatch being the most inaccurate parameters. Overall, postoperative malalignment of the spine is an important challenge for surgeons performing decompressive or fusion procedures, and further work with predictive modeling will be useful to improve surgical planning. ^, Alignment goals for the cervical spine include restoring cervical lordosis and sagittal alignment of the C2 centroid with C7. Alignment goals for the thoracolumbar spine include restoration of the C7 SVA to within 4 cm of the posterior margin of the sacrum, matching lumbar lordosis to pelvic incidence, and restoration of pelvic tilt to less than 20 degrees. Alignment goals may vary significantly for elderly patients. Consideration of alignment goals is important in patients undergoing reconstructive procedures for the treatment of thoracolumbar deformity. Similarly, understanding regional and global alignment is also important in the surgical management of cervical and lumbar degenerative pathology to avoid postoperative deformity.