Methods: Twenty vertebrae (T12 and L1) from 10 patients with osteoporosis (two males and eight females; mean age, 74.7 years) were obtained to create the 10 FE models. First, a single screw was placed with TT and SEPST/DEPST, and the fixation strength was compared by axial pullout strength (POS) and multidirectional loading tests. Second, two screws were placed on the bilateral pedicles with TT and SEPST/DEPST, and the fixation force of the vertebrae in the constructs in flexion, extension, lateral flexion, and axial rotation was examined. Results: SEPST and DEPST had 140% and 171% higher POS values than TT, respectively, and the DEPST result was statistically significant (p =0.007). The multidirectional fixation strength was significantly higher in DEPST and SEPST than in TT in the cranial, caudal, and medial directions (p <0.05) but not in the lateral direction (p =0.05). The vertebral fracture strength at the lower instrumented vertebra of the DEPST tended to be higher than that of TT. The vertebral motion angles in SEPST and DEPST were significantly smaller in lateral bending (p =0.02) and tended to be smaller in flexion and extension than in TT (p =0.13). Conclusions This study may provide useful information for spine surgeons in deciding whether to choose the SEPS or DEPS technique for augmenting fixation in osteoporotic vertebral fracture surgery.

A man in his 70s was transported to our hospital for acute exacerbation of chronic kidney disease. After arrival, he began having visual hallucinations, which were attributed to cognitive decline. We subsequently found that he had been taking amantadine 100 mg/day prescribed by another hospital. We thought that the visual hallucinations were caused by overdose of amantadine and discontinued the drug. Since abrupt discontinuation of antiparkinsonian drugs has a risk of neuroleptic malignant syndrome, tapering the dosage is desirable in most cases. However, the half-life of amantadine in patients with severe renal dysfunction is estimated to be 7-10 days, and thus the blood concentration of amantadine can be inferred to decrease slowly. Therefore, we chose to discontinue amantadine without tapering in the expectation of rapid improvement of the visual hallucinations, considering that the risk of neuroleptic malignant syndrome would be lower than that in patients with normal renal function who discontinued amantadine immediately. After the discontinuation of amantadine, no increase in creatine kinase level or muscle rigidity was observed, and the visual hallucinations improved on day 7 after discontinuation.