Muneharu Ando

Background and Objectives: Proximal junctional kyphosis (PJK) and failure (PJF), the most prevalent complications following long-segment thoracolumbar fusions for adult spinal deformity (ASD), remain lacking in defined preventive measures. We studied whether one of the previously reported strategies with successful results—a prophylactic augmentation of the uppermost instrumented vertebra (UIV) and supra-adjacent vertebra to the UIV (UIV + 1) with polymethylmethacrylate (PMMA)—could also serve as a preventive measure of PJK/PJF in minimally invasive surgery (MIS). Materials and Methods: The study included 29 ASD patients who underwent a combination of minimally invasive lateral lumbar interbody fusion (MIS-LLIF) at L1-2 through L4-5, all-pedicle-screw instrumentation from the lower thoracic spine to the sacrum, S2-alar-iliac fixation, and two-level balloon-assisted PMMA vertebroplasty at the UIV and UIV + 1. Results: With a minimum 3-year follow-up, non-PJK/PJF group accounted for fifteen patients (52%), PJK for eight patients (28%), and PJF requiring surgical revision for six patients (21%). We had a total of seven patients with proximal junctional fracture, even though no patients showed implant/bone interface failure with screw pullout, probably through the effect of PMMA. In contrast to the PJK cohort, six PJF patients all had varying degrees of neurologic deficits from modified Frankel grade C to D3, which recovered to grades D3 and to grade D2 in three patients each, after a revision operation of proximal extension of instrumented fusion with or without neural decompression. None of the possible demographic and radiologic risk factors showed statistical differences between the non-PJK/PJF, PJK, and PJF groups. Conclusions: Compared with the traditional open surgical approach used in the previous studies with a positive result for the prophylactic two-level cement augmentation, the MIS procedures with substantial benefits to patients in terms of less access-related morbidity and less blood loss also provide a greater segmental stability, which, however, may have a negative effect on the development of PJK/PJF.

This study aimed to devise measures and investigate their effect on coronal imbalance (CI) after circumferential minimally invasive correction surgery (CMIS) with lateral lumbar interbody fusion and percutaneous pedicle screw for adult spinal deformity (ASD). A total of 115 patients with ASD who underwent CMIS from the lower thoracic spine to the ilium were included. Patients were stratified based on the distance between the spinous process of the upper instrumented vertebra and central sacrum vertical line (UIV-CSVL) after the first intraoperative rod application into groups P (UIV-CSVL > 10 mm, n = 50) and G (UIV-CSVL < 10 mm, n = 65). Measures to correct postoperative CI introduced during surgery, preoperative and postoperative UIV-CSVL, and changes in UIV-CSVL after various measures (ΔUIV-CSVL) were investigated in group P. Rod rotation (RR), S2 alar-iliac screw distraction (SD), and kickstand-rod (KR) technique were performed in group P. Group P was further divided into group RR (n = 38), group SD (RR and SD) (n = 7), and group KR (RR and KR) (n = 5); the ΔUIV-CSVLs were 13.9 mm, 20.1 mm, and 24.4 mm in these three groups, respectively. Postoperative C7-CSVL < 10 mm was achieved in all three correction groups. In conclusion, our measures enabled sufficient correction of the UIV-CSVL and are useful for preventing CI after CMIS for ASD.

Background and Objectives: This study aimed to investigate the process and morphology of thoracic and lumbosacral bone fusion in patients with adult spinal deformity (ASD) who underwent circumferential minimally invasive spine surgery (CMIS) by lateral lumbar interbody fusion (LLIF) and percutaneous pedicle screws (PPSs) without bone grafting in the thoracic spine and who have risk factors for bone fusion failure in the thoracic spine. Materials and Methods: This retrospective study included 61 patients with spinal deformities (46 women and 15 men) who underwent CMIS with LLIF and PPSs at our hospital after 2016 and completed a 3-year postoperative follow-up. The rate and morphology of bone fusion and rod fracture rate in the thoracic and lumbosacral vertebrae were evaluated. Patients were divided into the thoracic spine spontaneous bone fusion group and the bone fusion failure group. The data of various spinopelvic parameters and the incidence of complications were compared. The vertebral body conditions in the thoracic spine were classified as less degenerative (type N), osteophyte (type O), and diffuse idiopathic skeletal hyperostosis (DISH) (type D). Results: After three postoperative years, the bone fusion rates were 54%, 95%, and 89% for the thoracic, lumbar, and lumbosacral spine, respectively. Screw loosening in the thoracic vertebrae was significantly higher in the bone fusion failure group, while no significant differences were observed in the spinopelvic parameters, Oswestry Disability Index (ODI), and rate of proximal junctional kyphosis and rod fractures. Type N vertebral body condition and screw loosening were identified as risk factors for spontaneous bone fusion failure in the thoracic spine. Conclusion: This study indicated that spontaneous bone fusion is likely to be obtained without screw loosening, and even if bone fusion is not obtained, there is no effect on clinical results with the mid-term (3-year) results of CMIS without bone grafting in the thoracic spine.

Background and Objectives: Spinal minimally invasive surgery (MIS) experts at the university hospital worked as a team to develop a new treatment algorithm for pyogenic spondylodiscitis in lumbar and thoracic spines. They modified a flow chart introduced for this condition in a pre-MIS era to incorporate MIS techniques based on their extensive experiences accumulated over the years, both in MIS for degenerative lumbar diseases and in the treatment of spine infections. The MIS procedures incorporated in this algorithm consisted of percutaneous pedicle screw (PPS)–rod fixation and transpsoas lateral lumbar interbody fusion (LLIF). The current study analyzed a series of 34 patients treated with prospective selection of the methods according to this new algorithm. Materials and Methods: The algorithm first divided the patients into those who had escaped complicated disease conditions, such as neurologic impairment, extensive bone destruction, and the need to be mobilized without delay (Group 1) (19), and those with complicated pyogenic spondylodiscitis (Group 2) (15). Group 1 had image-guided needle biopsy followed by conservative treatment alone with antibiotics and a spinal brace (12) (Group 1-A) or a subsequent addition of non-fused PPS–rod fixation (7) (Group 1-B). Group 2 underwent an immediate single-stage MIS with non-fused PPS–rod fixation followed by posterior exposure for decompression and debridement through a small midline incision (12) (Group 2-A) or an additional LLIF procedure after an interval of 3 weeks (3) (Group 2-B). Results: All patients, except four, who either died from causes unrelated to the spondylodiscitis (2) or became lost to follow up (2), were cured of infection with normalized CRP at an average follow up of 606 days (105–1522 days). A solid interbody fusion occurred at the affected vertebrae in 15 patients (50%). Of the patients in Group 2, all but two regained a nearly normal function. Despite concerns about non-fused PPS–rod instrumentation, only seven patients (21%) required implant removal or replacement. Conclusions: Non-fused PPS–rod placements into infection-free vertebrae alone or in combination with posterior debridement through a small incision worked effectively in providing local stabilization without contamination of the metal implant from the infected tissue. MIS LLIF allowed for direct access to the infected focus for bone grafting in cases of extensive vertebral body destruction.

This retrospective study aimed to evaluate the clinical outcomes of circumferential minimally invasive surgery (CMIS) using lateral lumbar interbody fusion (LLIF) and percutaneous pedicle screw (PPS) in adult spinal deformity (ASD) patients, and to clarify the conditions for achieving postoperative pelvic incidence-lumbar lordosis (PI-LL) < 10°. Demographics and other parameters of ASD patients who underwent CMIS and who were divided into groups G (achieved postoperative PI-LL < 10°) and P (PI-LL ≥ 10°) were compared. Of the 145 included ASD patients who underwent CMIS, the average fused level, bleeding volume, operative time, and number of intervertebral discs that underwent LLIF were 10.3 ± 0.5 segments, 723 ± 375 mL, 366 ± 70 min, and 4.0 segments, respectively. The rod material was titanium alloy in all the cases. The PI-LL significantly improved from 37.3 ± 17.9° to 1.2 ± 12.2° postoperatively. Pre- and postoperative PI, postoperative LL, preoperative PI-LL, PI-LL after LLIF, and postoperative PI-LL were significantly larger in group P. PI-LL after LLIF was identified as a significant risk factor of postoperative PI-LL < 10° by logistic regression, and the cut-off value on receiver operating characteristic curve analysis was 20°. Sufficient correction was achieved by CMIS. If PI-LL after LLIF was ≤20°, it was corrected to the ideal alignment by the PPS procedure.

Study Design.: A prospective, multicenter study. Objective.: To evaluate the usefulness of transcranial motor-evoked potentials (Tc-MEPs) during supine-to-prone position change for thoracic ossification of the posterior longitudinal ligament (T-OPLL). Summary of Background Data.: Supine-to-prone position change might be a risk of spinal cord injury in posterior decompression and fusion surgeries for T-OPLL. Methods.: The subjects were 145 patients with T-OPLL surgically treated with posterior decompression and fusion using Tc-MEPs in 14 institutes. Tc-MEPs were monitored before surgery from supine-to-prone position and intraoperatively in seven institutes and only intraoperatively in the other seven institutes because of disapproval of the anesthesia department. In cases of Tc-MEP alert after position change, we adjusted the cervicothoracic posture. When the MEP did not recover, we reverted the position to supine and monitored the Tc-MEPs in supine position. Results.: There were 83 and 62 patients with/without Tc-MEP before position change to prone (group A and B). The true-positive rate was lower in group A than group B, but without statistical significance (8.4% vs. 16.1%, P = 0.12). In group A, five patients who had Tc-MEP alert during supine-to-prone position change were all female and had larger body mass index values and upper thoracic lesions. Among the patients, three underwent surgeries after cervicothoracic alignment adjustment, and two had postponed operations to 1 week later with halo-vest fixation because of repeated Tc-MEP alerts during position change to prone. The Tc-MEP alert at exposure was statistically more frequent in group B than in group A (P = 0.033). Conclusion.: Tc-MEP alert during position change is an important sign of spinal cord injury due to alignment change at the upper thoracic spine. Tc-MEP monitoring before supine-to-prone position change was necessary to prevent spinal cord injury in surgeries for T-OPLL.

To study if spinal motor evoked potentials (SpMEPs), muscle responses after electrical stimulation of the spinal cord, can monitor the corticospinal tract. Study 1 comprised 10 consecutive cervical or thoracic myelopathic patients. We recorded three types of muscle responses intraoperatively: (1) transcranial motor evoked potentials (TcMEPs), (2) SpMEPs and (3) SpMEPs + TcMEPs from the abductor hallucis (AH) using train stimulation. Study 2 dealt with 5 patients, who underwent paired train stimulation to the spinal cord with intertrain interval of 50–60 ms for recording AH SpMEPs. We will also describe two illustrative cases to demonstrate the clinical value of AH SpMEPs for monitoring the motor pathway. In Study 1, SpMEPs and SpMEPs + TcMEPs recorded from AH measured nearly the same, suggesting the collision of the cranially evoked volleys with the antidromic signals induced by spinal cord stimulation via the corticospinal tracts. In Study 2, the first and second train stimuli elicited almost identical SpMEPs, indicating a quick return of transmission after 50–60 ms considered characteristic of the corticospinal tract rather than the dorsal column, which would have recovered much more slowly. Of the two patients presented, one had no post-operative neurological deteriorations as anticipated by stable SpMEPs, despite otherwise insufficient IONM, and the other developed post-operative motor deficits as predicted by simultaneous reduction of TcMEPs and SpMEPs in the face of normal SEPs. Electrical stimulation of the spinal cord primarily activates the corticospinal tract to mediate SpMEPs.