<p><b>BACKGROUND: </b>Few data are available on the occurrence after stand-alone lateral lumbar interbody fusion (LLIF) of implant subsidence, whose definition and incidence vary across studies. The primary objective of this work was to determine the incidence of subsidence 1 year postoperatively, using an original measurement method, whose validity was first assessed. The secondary objective was to assess the clinical impact of subsidence.</p><p><b>HYPOTHESIS: </b>Implant subsidence after stand-alone LLIF is a common complication that can adversely affect clinical outcomes.</p><p><b>MATERIAL AND METHODS: </b>Of 69 included patients who underwent stand-alone LLIF, 67 (97%) were re-evaluated at least 1 year later. Furthermore, 63 (91%) patients had two available computed tomography (CT) scans for assessing subsidence, one performed immediately after surgery and the other 1 year later. Reproducibility of the original measurement method was assessed in a preliminary study. Subsidence was defined as at least 4mm loss of fused space height.</p><p><b>RESULTS: </b>The incidence of subsidence was 32% (20 patients). Subsidence was global in 7 (11%) patients and partial in 13 (21%) patients. Mean loss of height was 5.5±1.5mm. Subsidence predominated anteriorly in 50% of cases. The lordotic curvature of the fused segment was altered in 50% of patients, by a mean of 8°±3°. Fusion was achieved in 67/69 (97%) patients. The Oswestry score and visual analogue scale scores for low-back and nerve-root pain were significantly improved after 1 year in the overall population and in the groups with and without subsidence.</p><p><b>DISCUSSION: </b>Reproducibility of our measurement method was found to be excellent. Subsidence was common but without significant clinical effects after 1 year. Nevertheless, subsidence can be associated with pain and can result in loss of lumbar lordosis, which is a potential risk factor for degenerative disease of the adjacent segments. A score for predicting the risk of subsidence will now be developed by our group as a tool for improving patient selection to stand-alone LLIF.</p><p><b>LEVEL OF EVIDENCE: </b>IV, retrospective cohort study.</p>
Incidence and impact of implant subsidence after stand-alone lateral lumbar interbody fusion.
Orthop Traumatol Surg Res. 2018;104(3):405-410.
MeSH terms: Aged; Female; Follow-Up Studies; Humans; Incidence; Internal Fixators; Lumbar Vertebrae; Male; Middle Aged; Postoperative Complications; Prostheses and Implants; Prosthesis Failure; Reproducibility of Results; Retrospective Studies; Spinal Fusion; Tomography, X-Ray Computed; Treatment Outcome