Long-term clinical and radiological outcomes following stand-alone PLIF surgery using expandable cylindrical threaded cages in patients with degenerative lumbar spine disease

Purpose Although posterior lumbar interbody fusion (PLIF) using stand-alone cages was a popular arthrodesis method, the effectiveness of using such cages has been questioned. We assessed retrospectively the long-term clinical and radiological outcomes of PLIF surgery using stand-alone cages for the treatment of degenerative lumbar spine disease, the incidences of pseudoarthrosis, and its risk factors. Methods Between May 2000 and May 2005, we performed surgery on 211 patients with degenerative lumbar disease. Among those patients, 180 were clinically and radiologically followed for more than 60 months. All 180 patients underwent postoperative follow-up X-rays, including a dynamic view after 3, 6, 12, 24, and 60 months, and computed tomography (CT) after 24 months. The clinical outcomes were analyzed using the mean numeric rating scale (NRS), Oswestry Disability Index (ODI), and Odom’s criteria. The factors affecting the clinical success and nonfusion were also analyzed. Results The mean NRS scores for the back and leg were 7.1 and 6.9 preoperatively, and 3.0 and 2.7 at 60 months postoperatively, respectively. The ODI decreased from 29.5 preoperatively to 14.1 at 60 months postoperatively. The clinical success rate was only 74.4% in the Odom’s criteria, and the significant factor affecting the clinical success was radiological fusion. The radiological fusion assessment at 24 months postoperatively indicated success at 167 levels (85.2%) and failure at 29 levels (14.8%). Disc height changed from 10.25 mm preoperatively to 15.02 mm immediately postoperatively, and gradually decreased to 12.28 mm for 60 months after surgery. The gradual decrease was statistically significant (p<0.001). The segmental angle changed from 13.59° preoperatively to 12.85° immediately postoperatively, and to 12.76° 60 months after surgery. There was no statistically significant change of the segmental angle during any time (p>0.05). Conclusion The use of PLIF with stand-alone threaded cages in degenerative lumbar disease patients resulted in a long-term clinical success rate of 74.4%. Although the radiological fusion rate was 85.2%, continuous reduction of disc height and poor alignment preservation were observed. We conclude, therefore, that PLIF using only stand-alone cages is a poor surgical option for achieving good alignment and disc height restoration in patients with degenerative lumbar disease.