Purpose:

To examine the correlation of intraoperative distraction of intervertebral disc with the postoperative central canal and foramen expansion by oblique lumbar interbody fusion (OLIF) with indirect decompression.

Methods:

Patients who underwent OLIF between October 2013 and April 2017 were included. Clinical outcomes included back and leg pain evaluated by visual analog scale (VAS) and Oswestry Disability Index (ODI). Intraoperative radiographic parameters of height ratio [(HR) = disc height/intervertebral body height)] and cage location were evaluated on intraoperative fluoroscopic images. Disc height (DH), foraminal height (FH), cross-sectional area of spinal canal (CSAC), and CSA of the foramen (CSAF) were measured.

Results:

A total of 47 patients involving 62 levels were enrolled in this study. Mean follow-up was 43.8 ± 12.0 months. These patients reported an improvement of 61.7% in VAS back, 68.1% in VAS leg, and 46% in ODI (all p < 0.01). Radiographic parameters including HR, DH, FH, CSAC, and CSAF were also significantly increased by 32.6%, 48.2%, 21.4%, 44.0%, and 40.1% (left-side CSAF) or 45.4% (right-side CSAF), respectively (p < 0.05). HR increment was correlated with CSA (canal and foramen) increment. Slightly higher improvements of HR, DH, FH, CSAC, and CSAF (both sides) were noted when cage was located at middle rather than anterior (p > 0.05).

Conclusions:

The ligamentotaxis effect of OLIF is capable of supporting indirect decompression of central canal and neural foramina and clinical improvement. HR is a reliable intraoperative assessment method. In addition, intraoperative HR increment was correlated with postoperative neural elements expansion.