Management of Fixed Sagittal Plane Deformity: Outcome of Combined Anterior and Posterior Surgery

UC San Francisco, San Francisco, CA, USA

INTRODUCTION: Combined anterior and posterior arthrodesis of the spine is useful in the management of fixed deformity involving the coronal and sagittal planes. The specific indications for combined surgery in the patient with regional and global imbalance have not been well defined. The purpose of this paper is to review the radiographic and clinical results of patients with preoperative fixed sagittal imbalance treated with combined anterior and posterior arthrodesis, and to determine factors that predict good clinical outcome.

METHODS: Retrospective review of 25 consecutive patients treated with combined anterior and posterior spinal fusion. Inclusion criteria included a preoperative global sagittal imbalance of at least 5cm. Patients treated with vertebral column resection were excluded. Outcome variables included radiographic measures of preoperative, post-operative, and follow-up films, and a clinical assessment using the Modified SRS Outcomes Instrument (MSRSI) and a review of post-operative complications.

RESULTS: 25 consecutive cases by a single surgeon were reviewed. Average age 58 years (range 38-77), and average follow up was 55 months (range 24-81) for clinical and 44.5 (range 24-81) months for radiographic outcome variables. Etiologies of deformity included progressive idiopathic scoliosis in 8 patients, post-operative deformity in 15 patients, and de novo deformity in 2 patients. The average pre-operative sagittal imbalance was 10.5cm (range 5.2-23.3), which improved to 2.9cm (range 0-12.6) postoperatively, and was maintained as 3.3cm (range 0-13.5) at follow-up. Average lumbar lordosis was -23° (range +40 to -47) preoperatively, and increased to -42° at follow-up (range -21° to -47°), an average increase of 21°. 18/25 patients had preoperative regional hypolordosis to the lumbar spine(› -30º lordosis). Follow-up MSRSI total outcome scores averaged 68% (range 46-85). In patients with preoperative regional hypolordosis in the lumbar spine, MSRSI scores averaged 73%, compared with patients with preoperative lordosis in the physiologic range average 62% (p=0.078). In the 4 patients who had no improvement of lumbar lordosis after surgery, MSRSI total scores averaged 47%, compared with 75% in patients who had an increase in lumbar lordosis postoperatively (p ‹ 0.001). Patient satisfaction with surgical management averaged 89% (range 50-100). Correlation analysis of clinical outcome domains demonstrated that patient satisfaction correlated poorly with domains of pain (r=0.37), function (r=0.4), and total score (r=0.6). Within the domains self image showed highest correlation with patient satisfaction and total scores (Pearson correlation: 0.65-0.89; p ‹ 0.003). Structural curves averaged 47º preoperatively and improved to 27º at follow-up (46%). Coronal plane deformity and correction did not predict clinical outcome (p › 0.05). There were 8 perioperative complications including 4 postoperative wound infections and one failure in fixation. 10 patients (40%) required revision surgery during the follow-up period.

CONCLUSIONS: Patients with regional hypolordosis in the lumbar spine, with global sagittal imbalance were effectively treated with a combined anterior and posterior arthrodesis as measured by radiographic parameters. Patient satisfaction with surgery, and overall clinical outcomes were best in cases that resulted in an increase in lumbar lordosis. A combined anterior and posterior arthrodesis for management of fixed sagittal imbalance is most effective in patients with pre-operative regional hypolordosis of the lumbar spine.