The effect and potential risks of using cement-augmented pedicle screw instrumentation on multiple segment fixation in osteoporotic spine with lumbar degenerative diseases

Background: Cement-augmented pedicle screw instrumentation (CAPSI) has been found to significantly increase the pedicle screws anchorage in the osteoporotic vertebral body, however, with the increase of augmented level and bone cement dose, the incidence of cement leakage (CL) or side complication of CAPSI also increased. But the effect and potential risks of CAPSI for osteoporotic lumbar degenerative diseases (LDD) have not been investigated in the cases of multiple segment fixation. The purpose of this study was to investigate potential complications of using cement-augmented screws for multilevel fixation (three or four levels) and the effectiveness of this method for treating LDD with low bone quality. Methods: Our clinical database was reviewed for osteoporotic patients who using CAPSI or conventional pedicle screw (CPS) for multilevel fixation (three or four levels) between February 2010 to February 2017. A total of 93 patients with multilevel LDD were divided into the CAPSI group (46 subjects) and the CPS group (47 subjects), including 75 cases for three levels (L2-L5 21 cases、L3-S1 54 cases), 18 cases for four levels (L1-L5 2 cases、L2-S1 16 cases), and the average follow-up was 33.72±18.78 months (range: 24-108). Relevant data were recorded, including age, gender, body mass index (BMI), bone mineral density (BMD), diagnosis, fusion methods, bone graft, fusion level, lumbosacral fixation, different patterns of S1 pedicle screw placement, operation time, blood loss, hospital stay, complications, CL, pulmonary cement embolism (PCE), screw loosening and nonunion patients. Besides, the visual analogue scale (VAS) and Oswestry disability index (ODI) at pre-operation, post-operation, and follow-up were also assessed. Results: In the CAPSI group, a total of 336 augmented screws were placed bilaterally, and the average injection dose of bone cement was 1.85±0.65 ml (range: 1-4). The CL was observed in 44 patients (95.65%) and 116 screws (34.52%). Three cemented screws (0.89%) and twenty-four S1 conventional screws (44.44%) were found loosening during the follow-up and the overall fusion rate was 93.47%. For perioperative complications, two patients (4.35%) experienced PCE, one patient augmented vertebral fracture and three patients (6.52%) wound infection. And in the CPS group, seventeen patients (36.17%) and thirty-three screws (8.46%) suffered loosening in cranial or caudal segments (seven cranial cases and twenty-six of caudal), four cases experienced nonunion, the fusion rate was 91.49% in total. The operation time and hospital stay were longer in CAPSI group, but with a lower percentage of screw loosening ( P ＜0. 05). And in terms of blood loss, perioperative complications, fusion rate, VAS and ODI scores at the follow-up times, no significant differences were found between the two groups. Conclusions: Patients with osteoporotic LDD underwent CPS at multiple segments have a high rate of screw loosening in the cranial and caudal segment. The application of cemented pedicle screws on multilevel LDD can achieve better stability and less screw loosening, but it also accompanied by longer operating time, higher incidence of CL, PCE and wound infections. Selective cement-augmenting the cranial and caudal pedicle screws may be a worthy strategy to decrease the complications.