title: Improvement of sagittal balance and lumbar lordosis following less invasive adult spinal deformity surgery with expandable cages and percutaneous instrumentation.
abstract: OBJECTIVE
  The treatment of adult spinal deformity (ASD) remains a challenge for the spine surgeon. While minimally invasive surgery (MIS) has many favorable attributes that would be of great benefit for the ASD population, improvements in lordosis and sagittal balance have remained elusive in cases involving the MIS approach. This report describes the evolution of an MIS method for treating ASD with attention to sagittal correction.
  
  
  METHODS
  Over an 18-month period 25 patients with thoracolumbar scoliosis were treated surgically. The mean patient age was 72 years, and 68% of the population was female. Patients were treated with multilevel facet osteotomies and interbody fusion in which expandable cages (mean 3.2 levels) were placed and percutaneous screw fixation (mean 5.3 levels) was performed. Seven patients underwent supplemental percutaneous iliac fixation.
  
  
  RESULTS
  All patients underwent MIS without conversion to a traditional open procedure. The mean operative time was 273 mins and the mean blood loss was 416 ml. There were no intraoperative complications. The Cobb angle over the scoliotic deformity improved from a mean of 29.2° to that of 9.0° (p < 0.001). Lumbar lordosis between L-1 and S-1 improved from a mean of 27.8° to one of 42.6° (p < 0.001). Sagittal vertical axis improved from 7.4 cm to 4.3 cm (p = 0.001). Numeric pain scale scores improved as well, an average of 3.3 and 4.2 for the leg and back, respectively. A mean improvement of 20.8 points on the Oswestry Disability Index was seen at 12 months. Complications included: two cases requiring hardware repositioning, one case of screw pullout, one asymptomatic pedicle screw breach, prolonged hospitalization from constipation, and one acute coronary syndrome developing 3 days after surgery without myocardial damage.
  
  
  CONCLUSIONS
  An expanding body of evidence suggests that sagittal balance remains a keystone for good outcomes after ASD surgery. Minimally invasive surgery that involves a combination of osteotomies, interbody height restoration, and advanced fixation techniques may achieve this goal in patients with less severe deformities. While feasibility will have to be proven with larger series and improved surgical methods, the present technique holds promise as a means of reducing the significant morbidity associated with surgery in the ASD population.
authors.affiliation: Department of Neurological Surgery, University of Miami Miller School of Medicine, Miami, FL, USA. MWang2@med.miami.edu
authors.forename: Michael Y
authors.initials: MY
authors.lastname: Wang
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001863:Bone Screws; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D010027:Osteotomy / Q000295:instrumentation*; D011859:Radiography; D012600:Scoliosis / Q000000981:diagnostic imaging / Q000601:surgery*; D013123:Spinal Fusion / Q000295:instrumentation*; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D016896:Treatment Outcome