Pelvic parameters of sagittal balance in extreme lateral interbody fusion for degenerative lumbar disc disease.

There is increasing interest in the use of pelvic indices to evaluate sagittal balance and predict outcomes in patients with spinal disease. Conventional posterior lumbar fusion techniques may adversely affect lumbar lordosis and spinal balance. Minimally invasive fusion of the lumbar spine is rapidly becoming a mainstay of treatment of lumbar degenerative disc disease. To our knowledge there are no studies evaluating the effect of extreme lateral interbody fusion (XLIF) on pelvic indices. Hence, our aim was to study the effect of XLIF on pelvic indices related to sagittal balance, and report the results of a prospective longitudinal clinical study and retrospective radiographic analyses of patients undergoing XLIF in a single centre between January 2009 and July 2011. Clinical outcomes are reported for 30 patients and the retrospective analyses of radiographic data is reported for 22 of these patients to assess global and segmental lumbar lordosis and pelvic indices. Effect of XLIF on the correction of scoliotic deformity was assessed in 15 patients in this series. A significant improvement was seen in the visual analogue scale score, the Oswestry Disability Index and the Short Form-36 at 2months and 6months (p<0.0001). The mean pelvic index was 48.6°±11.9° (± standard deviation, SD) with corresponding mean sacral slopes and pelvic tilt of 32.0°±10.6° (SD) and 18.0°±9.5 (SD), respectively. XLIF did not significantly affect sacral slope or pelvic tilt (p>0.2). Global lumbar lordosis was not affected by XLIF (p>0.4). XLIF significantly increased segmental lumbar lordosis by 3.3° (p<0.0001) and significantly decreased the scoliotic Cobb angle by 5.9° (p=0.01). We found that XLIF improved scoliosis and segmental lordosis and was associated with significant clinical improvement in patients with lumbar degenerative disc disease. However, XLIF did not change overall lumbar lordosis or significantly alter pelvic indices associated with sagittal balance. Long-term follow-up with a larger cohort will be required to further evaluate the effects of XLIF on sagittal balance.