THE EFFECT OF TOTAL DISC ARTHROPLASTY ON SAGITTAL BALANCE1

Abstract

Introduction Lumbar fusion may alter the sagittal balance of the spine, including a decrease in the sacral tilt ST and lumbar lordosis. Postoperative pain following a spinal fusion has been shown to be related to changes in sagittal balance, independent of other factors including pseudarthrosis.

The goal of this radiological study was to prospectively determine the effect of a single-level, total disc replacement on the sagittal balance of the spine, especially on sacral tilt (ST), pelvic tilt (PT), and lumbar lordosis (Le Huec J, et al; Spine J. 2004).

Method 35 patients received a single level disc replacement using the Maverick Total Disc Arthroplasty system (Medtronic Sofamor Danek). The preoperative and postoperative radiographic evaluation included standing anteroposterior and lateral full spine films that included the femoral heads. The parameters studied were ST, PT, global and segmental lordosis, and global kyphosis. The average age of the 35 patients studied was 44.3 years (range 35–57). There were 18 females and 17 males. The disc arthroplasty was performed at the L4–L5 level in 19 patients and at the L5-S1 level in 16 patients. The average follow-up was 14 months (range 6–22 months).

Results The preoperative values of global lordosis, ST, PT and global lordosis were not significantly different at last follow-up. When the groups were compared according to the level operated, there was no statistical difference with regard to the overall lordosis, ST, PT or kyphosis from pre- to postoperative period or when the two groups were compared with each other. The level above the prosthesis has significantly less lordosis.

Discussion In the present study with use of a motion-preserving intervertebral disc prosthesis, it appears that the patient is able to maintain the preoperative sagittal balance. The prosthesis has enough freedom of motion to allow the patient to maintain the natural sagittal and spinopelvic balance needed to prevent potentially undue stress on the muscles and the sacroiliac joint. Although the number of patients is small, this is the first study that evaluates the sagittal balance after motion-preserving total disc arthroplasty.