Effect of mono- or bisegmental lordosizing fusion on short term global and index sagittal balance: a radiographic study

BACKGROUND: Sagittal balance is widely recognized as an important outcome factor in reconstructive spinal surgery for lumbar degenerative conditions. However, its role in short segmental fixation is unknown. The aim of this study is to evaluate the preoperative and short-term postoperative spino-pelvic balance after short (1 or 2 levels) lordosizing lumbar fusion for degenerative disc disease (DDD).

MATERIALS AND METHODS: Twenty-six consecutive patients (13 males and 13 females) undergoing mono- or bisegmental lordosizing lumbar fusion (XLIF/TLIF) for lumbar DDD were included in the study. Clinical parameters were retrospectively collected from charts. Preoperative and early postoperative (6 weeks and 3 months) full-spine EOS x-rays were evaluated. Spinal parameters evaluating sagittal curvatures, pelvic orientation, global sagittal and coronal alignment, spino-pelvic balance, index level segmental lordosis and disc height were measured and statistically analyzed.

RESULTS: A total of n=16 TLIF and n=10 XLIF procedures were performed. N=18 were mono- and n=8 were bisegmental fixations for a total of 34 fused segments. N=7 patients (26.9%) showed a preoperative sagittal imbalance (defined as SVA >50 mm), n=7 patients presented preoperative severe pelvic retroversion (defined as PT>20°) and one patient had both. Disc height, intervertebral angle and segmental lordosis at the operated level significantly increased after surgery (p<0.01). No postoperative significant change in global sagittal alignment (SVA, TPA, T1SPi, T9SPi), pelvic orientation (SS, PT), coronal alignment, lumbar and L4-S1 lordosis and thoracic kyphosis has been observed.

CONCLUSION: Mono- and bisegmental lordosizing fusion techniques, as XLIF and TLIF, are able to restore disc height and improve segmental lordosis. However they do not allow restoration of sagittal balance or improvement of compensatory mechanisms. A limited spinal reconstructive surgery on symptomatic levels can be reasonably proposed to patients with hidden or evident sagittal imbalance with any short-term radiographic impact.