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Background: In general, the diagnosis of pedicle screw (PS) loosening is evaluated qualitatively based on the presence of a radiolucent area around the implant wider than 1 mm on plain radiographs and computed tomography (CT). Digital tomosynthesis is a novel imaging technology that can acquire reconstructed tomographic images of patients in different postures with relatively low radiation. In this study, PS loosening is evaluated quantitatively by measuring the PS displacement angle in the vertebrae using digital tomosynthesis., Methods: We evaluated 41 patients who underwent posterior spinal fusion surgery using PS. The 72 pedicle screws at the cranial end of the fused segments were evaluated. The patients were divided in two groups, one with PS loosening (7 patients, 12 screws) and the other without PS loosening (34 patients, 60 screws), based on conventional CT findings. All patients underwent tomosynthesis in two different postures during a single CT session., Results: The displacement angles of the PS in patients in a lying position and in a standing position were measured using selected slices of the same cross-sectional view from digital tomosynthesis. The displacement angle was significantly greater in the PS loosening group (5.7°) than in the group without PS loosening (0.6°) (p<0.01). Based on the ROC analysis, the optimal cut-off value of the PS displacement angle for identification of loosened screws was 1.7° with a sensitivity of 100% and specificity of 93% (AUC = 0.98)., Conclusions: This new method using digital tomosynthesis has the potential to aid diagnosis of PS loosening quantitatively and more accurately than conventional evaluations., (© 2022. The Author(s).)

Background: The penetrating end plate screw (PES) technique improved the fixation strength of the pedicle screw by penetrating the end plate in posterior fusion. The "double" PES, which is a trajectory that penetrates both the upper end plate of the corresponding vertebra and the lower end plate of the upper adjacent vertebral body, provides a stronger tricortical fixation but requires a stricter trajectory. The purpose of this study was to measure the cephalad angles from T7-L5 that would allow a safe trajectory for "double" PES., Methods: We analyzed 1078 pedicles of 539 vertebral bodies of 50 consecutive cases (27 males and 23 females, mean age, 63.3 years) who underwent computed tomography (CT) myelography for evaluation of spinal disorders. The mean cephalad angle to obtain the double PES trajectory of each vertebra was examined, except for cases in which the appropriate trajectory would perforate the pedicles., Results: The cephalad angle for the appropriate trajectory of "double" PES ranged from 23.4 to 37.6 degrees in the thoracic spine and 34.8 to 40.8 degrees in the lumbar spine. The ratio of pedicle perforation was significantly higher at T7 (16%), L4 (26%), and L5 (52%)., Conclusions: It is important to measure the optimal cephalad angle by preoperative computed tomography imaging according to the vertebral level. In L4 and L5, "double" PES should be avoided because it is often unsafe., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Background: A high-riding vertebral artery (HRVA) is an intraosseous anomaly that narrows the trajectory for C2 pedicle screws. The prevalence of a HRVA is high in patients who need surgery at the craniovertebral junction, but reports about HRVAs in subaxial cervical spine disorders are limited. We sought to determine the prevalence of HRVAs among patients with subaxial cervical spine disorders to elucidate the potential risk for VA injury in subaxial cervical spine surgery., Methods: We included 215 patients, 94 were with a main lesion from C3 to C7 (subaxial group) and 121 were with a main lesion from T1 to L5 (thoracolumbar group). A HRVA was defined as a maximum C2 pedicle diameter of < 3.5 mm on axial CT. The sex, age of patients, body mass index (BMI), osteoarthritis of the atlantoaxial (C1-2) facet joints, and prevalence of a HRVA in the 2 groups were compared and logistic regression was used to identify the factors correlated with a HRVA., Results: The patients in the subaxial group were younger than those in the thoracolumbar group, but their sex and BMI did not differ significantly between the 2 groups. The mean osteoarthritis grade of the C1-2 facet joints of patients in the subaxial group was significantly higher than that in those in the thoracolumbar group. A HRVA was found in 26 patients of 94 (27.7 %) in the subaxial group and in 19 of 121 (15.7 %) in the thoracolumbar group. The prevalence of a HRVA in the subaxial group was significantly higher and osteoarthritis of C1-2 facet joints correlated significantly with a HRVA., Conclusions: The prevalence of a HRVA in patients with subaxial cervical spine disorders is higher than in those without and osteoarthritis of the C1-2 facet joints is correlated with a HRVA.

We investigated the use of the autologous iliac bone and unidirectional porous beta-tricalcium phosphate (UDPTCP) in posterolateral lumbar spine fusion (PLF). Ten canine PLF models were prepared. Using only the autologous bone as the control group, 100%, 75%, 50%, and 25% groups were prepared according to the mixing ratios of UDPTCP. Radiological evaluation and histological analysis were performed 12 weeks after surgery. Bone fusion was evaluated according to anteroposterior plain X-rays and coronal reconstruction CT views using four grades: 0 = no osteogenesis, 1 = only slight discontinuous osteogenesis between transverse processes, 2 = discontinuous osteogenesis between transverse processes, and 3 = continuous osteogenesis between transverse processes. Bone fusion determined by X-ray was 2.8 ± 0.5 in the control group, 0 in the 100% UDPTCP group (p = 0.02), 1.8 ± 0.5 (p = 0.03) in the 75% UDPTCP group, 2.5 ± 0.6 (p = 0.54) in the 50% UDPTCP group, and 2.8 ± 0.5 (p = 1.0) in the 25% UDPTCP group. The bone fusion score was significantly lower in the 75% and 100% UDPTCP groups than in the control group. Bone fusion determined by CT was 2.8 ± 0.5 in the control group, 1.0 ± 0.8 (p = 0.01) in the 100% UDPTCP group, 2.0 ± 0.0 (p = 0.02) in the 75% UDPTCP group, 2.5 ± 0.6 (p = 0.54) in the 50% UDPTCP group, and 2.8 ± 0.5 (p = 1.0) in the 25% UDPTCP group. Similar to the bone fusion determination by X-ray, the bone fusion score was significantly lower in the 75% and 100% UDPTCP groups. These data suggest that, in a canine PLF model, the appropriate mixing ratio of UDPTCP is 50% or less.

The aim of this study was to elucidate the bone regeneration-inducing capability of Affinos®, a newly developed, high-porosity unidirectional porous β-TCP artificial bone. We compared the ability of Affinos® and OSferion®, a commercially available β-TCP product, to induce bone regeneration following implantation into bony defects left after fibula harvesting for spinal fusion surgery. Study subjects underwent surgery to harvest non-vascularized fibula grafts for spinal fusion surgery and were implanted with either Affinos® (19 patients) or OSferion® (15 patients, control group) at the defect site. The minimal and mean follow up periods were 6 and 11 months after surgery, respectively. X-rays of the lower leg taken 1-2 weeks after surgery and at the final follow-up visit were used to evaluate fibular-β-TCP continuity and fibula defect filling ratio. There was no significant difference in radiographic continuity in the fibula between the two groups. The fibula defect filling ratio for the Affinos® group decreased from 0.94 ± 0.17 at 1-2 weeks to 0.77 ± 0.14 at 10 months. For the OSferion® control group, the fibula defect filling ratio decreased from 0.94 ± 0.14 at 1-2 weeks to 0.52 ± 0.27 at final follow-up. The Affinos® group showed a significantly higher fibula defect filling ratio compared to that for the OSferion® group (p = 0.003). These results indicate that Affinos® has slow absorption rates and significant defect filling activity compared with OSferion®. Thus, Affinos® could be a suitable substitute to fill bony defects induced by fibula harvesting for spinal reconstruction surgery., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

The aim of this study was to investigate the incidence and characteristics of implant failure in posterior cervical long-segment fusion surgery. We retrospectively reviewed 51 cases of posterior cervical long-segment fusion surgery that used pedicle screws, lateral mass screws, or laminar screws. The cranial end of the fusion was C2 or C3, and the caudal end of the fusion was C7 or T1. All patients were observed with CT scans at 6 months postoperatively. We evaluated the loosening and breakage of the implanted screws or rods. In the 51 patients, 257 pedicle screws, 9 laminar screws and 233 lateral mass screws were placed. Implant failure occurred in 25 patients (49.0%). Screw loosening was found in 42 screws (8.4%). Screw breakage occurred in 6 (1.2%) screws. The implant failures were particularly observed in both ends of the fusion level. When C7 was the end of the lower instrumented level, the incidence was 40% without C6 pedicle screws, 33% with unilateral C6 pedicle screws, and 0% with bilateral C6 pedicle screws. The present study revealed that the incidence of implant failures of the screws in long-segment posterior cervical fusion surgery was higher, especially in the caudal end of the fusion levels. In cases where C7 was the lowest instrumented vertebra, buttress screw insertion to C6 is recommended to avoid implant failure of C7 pedicle screws., (Copyright © 2019. Published by Elsevier Ltd.)

Charcot spinal arthropathy (CSA) is a rare spinal disorder presenting neuropathic osteoarthropathy of facet joints leading to progressive destruction. After L4-5 PLIF, a 63-year-old woman with Parkinson's disease (PD) underwent L3-4 and L5-S1 PLIF for primary adjacent segment disease caused by degenerative change, which was found as facet joint osteophytes and a vacuum disc phenomenon with endplate sclerosis. However, her postural disorder from PD deteriorated, and strong opioid analgesics were administered for severe recurring low back pain. Anterior subluxation at L2-3 occurred because of destructive secondary adjacent segment disease, which was found as destruction of the endplate and the facet without degenerative change, and formation of paravertebral osteophytes and fluid collection in the intervertebral space. The appearance on imaging met that for neuroarthropathic change, which was previously reported as CSA. L2-3 PLIF following extension of posterior fusion to T10 was additionally performed, and the postoperative course was uneventful with symptomatic improvement. In this case, the important finding was in the different appearance of the disease between adjacent segments on imaging. It is possible that deterioration of PD and administration of the analgesics inhibited deep pain sensation, and concentration of mechanical stress in the proximal adjacent segment by the long lever arm because of extension of the fusion level resulted in neuroarthropathic change of the facets in the secondary adjacent segments. The pathophysiology of association of CSA and PD remains unknown. However, we recommend vigilance for destructive neuroarthropathic facet change as CSA after spinal surgery in patients with severe PD., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Lateral lumbar interbody fusion (LLIF) often requires the use of allograft or artificial bone. We used β-tricalcium phosphate artificial bone with a porosity of 57% consisting of a novel unidirectional porous structure (Affinos®) in patients (5 male and 9 female) who underwent LLIF from August 2015 as a substitute for autologous bone. We evaluated 60 graft windows in the cages at 30 intervertebral levels. To evaluate interbody bony fusion, CT multi-planar reconstruction coronal and sagittal images obtained 1 year after surgery were assessed. Intra-cage bony fusion was observed in 39 of 60 graft windows and so total bony fusion rate was 65%. Intra-cage bony fusion was confirmed in 17 of 29 (58.6%) graft windows with autologous bone and 22 of 31 (70.9%) graft windows with Affinos®. There was no significant difference in the rate of bony fusion between autologous bone and Affinos® (p = 0.418). In conclusion, the rate of bony fusion using Affinos® in LLIF cages was not inferior to that using autologous bone graft. Affinos® is a candidate for graft material in LLIF surgery and further exploration is warranted., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

It is uncommon to remove pedicle screws after posterolateral lumbar interbody fusion (PLIF), and there are a few case reports of vertebral fracture involving holes remaining after screw removal. We report a case of the vertebral fracture after removing pedicle screws instrumented for PLIF. A 66-year-old woman with osteopenia, who underwent PLIF at L4-S1 10 years earlier, underwent PLIF at L3-L4 to correct adjacent-segment degeneration. We removed L5 and S1 pedicle screws, and inserted L3 pedicle screws. After surgery, she presented with severe progressive low back pain. Computed tomography (CT) and magnetic resonance imaging (MRI) revealed an L5 body fracture involving the pedicle screw holes. Revision surgery, including posterolateral fusion from L3 to S2 alar iliac and L5 vertebroplasty, was performed. One year after the revision surgery, the patient remained pain-free and returned to normal activity. Possible reasons for instrumented vertebral body fracture after pedicle screw removal are decrease of vertebral mass, increased mechanical stress caused by PLIF at the adjacent segment, stress-shielding-related osteopenia, and spinal imbalance. Vertebral body fractures associated with spinal implant removal are rare, but possible, especially in elderly patients with osteopenia and osteoporosis., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

A 75-year-old Japanese woman with Parkinson's disease complained of lower back pain and gait disturbance because of iatrogenic flatback syndrome. The preoperative global spinal parameters were as follows: C7SVA, 168 mm; TK, 52°; LL, -0.8°; PI, 57°; PT, 55°; TPA, 60°. We performed 3D gait analysis using a VICON System and calculated the dynamic SVA. Preoperatively, her flexion deformity gradually progressed during walking. The dynamic parameters gradually increased as follows: thoracic SVA, 216-241 mm; lumbar SVA, 53-69 mm; spinal SVA, 270-311 mm. We performed two-stage corrective surgery. Her lower back pain and gait disturbance significantly improved. The postoperative global spinal parameters were as follows: C7SVA, 1 mm; TK, 47°; LL, 61°; PI, 52°; PT, 20°; TPA, 13°. Dynamic SVA detected by our 3D gait analysis using VICON were as follows: thoracic SVA, 128 mm; lumbar SVA, 4.9 mm; and spinal SVA, 133 mm. The postoperative dynamic SVA did not change during walking. This is the first report of a patient with iatrogenic flatback syndrome whose postoperative improvement of dynamic spinal sagittal alignment was successfully detected with a newly developed 3D gait analysis system that enabled us to analyze a dynamic change of SVA based on the patient's actual walking with a continuous long-distance gait. Our 3D gait analysis has potential usefulness for evaluating postoperative sagittal balance for iatrogenic flatback syndrome., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

The number of elderly people who undergo lumbar fusion surgery (LFS) has been increasing. Postoperative rehabilitation for them can be problematic due to lumbar stiffness. This is the first case report describing exercise therapy using the lumbar-type hybrid assistive limb (HAL) after multiple LFS in an elderly patient. An 83-year-old man underwent LFS at L4-S1. Additional fusion surgery at L2-3 for adjacent segment disease was performed 2 years after the primary surgery. Although the patient's leg pain declined, he had severe locomotive dysfunction at 3 months after his final surgery. He started exercise therapy using the lumbar-type HAL including sit-to-stand training and squat training 4 months after his final surgery. He performed 3 sets of 20 sit-to-stand and 20 squat repetitions with adequate rests in between sets. The HAL training was safely conducted every day for 12 weeks without adverse event. Timed up and go test (TUG), 1-minute sit to stand test (1MSTS), one-leg stand test (OLST), and Berg balance scale (BBS) were assessed as locomotive function measurement. Before HAL therapy, TUG, 1MSTS, OLST, and BBS were 18.1 sec, 20 times, less than 1 sec, and 47, respectively. He could not walk without assistance. After the exercise therapy with the lumbar-type HAL, his locomotive function dramatically improved. TUG, 1MSTS, OLST, and BBS were 12.2 sec, 25 times, 3.9 sec, and 52, respectively. Moreover, the patient could walk 60 meters continuously without assistance. The unique characteristics of the lumbar-type HAL to prevent the lumbar overload and assist the voluntary hip joint motion during exercise therapy may be effective for this patient with lumbar stiffness after LFS. Sit-to-stand training and squat training using the lumbar-type HAL are promising options to improve locomotive function in elderly patients after LFS. [ABSTRACT FROM AUTHOR]