The Effect of Osteopenia and Osteoporosis on Screw Loosening in MIS-TLIF and Dynamic Stabilization.

ABSTRACT

STUDY DESIGN: Retrospective series. OBJECTIVE: Screw loosening in the surgical treatment of lumbar spine disease is a major complication of osteopenia or osteoporosis. This study investigated the risk of screw loosening following either MIS-TLIF or pedicle screw-based dynamic stabilization (DS) in patients with osteopenia or osteoporosis. METHODS: We retrospectively enrolled patients receiving 1- or 2-level MIS-TLIF or DS in a single institute. All patients were diagnosed as having lumbar spondylosis without concurrent spondylolisthesis and found by dual-energy X-ray absorptiometry to have osteopenia or osteoporosis. Screw loosening was identified by X-ray and CT. Clinical outcomes were also assessed. RESULTS: A total of 103 patients (50 MIS-TLIF and 53 DS) were confirmed to have osteopenia (-2.5osteoporosis (T-score≦-2.5). The two groups, which were followed for 33.6 ± 24.7 and 52 ± 34.5 months, had similar T-scores (-1.97 ± 0.7 and -1.97 ± 0.6, respectively, P = 0.960). While both groups had significant improvements in back and leg pain assessed by VAS, ODI, and JOA scores, there was a significant difference in overall screw loosening rates between the MIS-TLIF and DS groups analyzed by percent of patients 38% and 18.9% (P = 0.039*) and by percent of screws 16.9% and 8% (P = 0.002*), respectively. Subgroup analysis showed a significant difference in screw loosening rate in osteopenia patients (P = 0.039* by person; P = 0.002* by screw), but no difference in osteoporosis patients.

CONCLUSION:

The screw loosening rate was higher in the MIS-TLIF group in the entire cohort. Osteopenia patients receiving MIS-TLIF were at significantly higher risk of screw loosening, while that risk was not different for osteoporosis patients, compared to DS.