The 2019 coronavirus disease (COVID-19) pandemic outbreak has rapidly spread to the globe, causing severe global socioeconomic disruption on an unprecedented scale. As the first wave of COVID-19 pandemic is now going to settle down, many medical organizations are in the process of reopening surgical services. This paper describes a few key factors that spine surgeons should consider prior to resuming elective spine services namely, local outbreak situations, availability of hospital resources, manpower and personal protective equipment (PPE). Spine surgeons should prioritize their operating list based on clinical indications and likely benefits from surgical intervention so as to make optimum use of hospital resources and operating room listings. International organizations have published on general principles and recommendations on how to restart elective surgery. However, with different regions at varying phases of the outbreak and unpredictable nature of the COVID-19 pandemic, a general set of practice guidelines may not be applicable. This paper also proposes, on top of peri-operative precautionary measures already in place, clearly-defined risk stratification algorithms for hospital visitors, as well as a disease-testing protocol for patients planned for elective surgery. It is of critical importance for surgeons to define key areas of concern and assimilate these principles into clearly-defined algorithms which can be applied to the field of spine surgery so as to help re-establish continuity of care for patients.

Patients with lumbar spinal canal stenosis (LSS) have impaired activities of daily living because of pain or motor paralysis, but no effective preventive treatment is currently available. The number of patients with LSS is predicted to continually increase as the average age of the global population increases. To provide a conceptual framework for improving healthy life expectancy, the Japanese Orthopaedic Association introduced the concept of locomotive syndrome, to which LSS is related. Ours and other studies have shown that LSS exacerbates locomotive syndrome and that surgical treatment is one method for improving it. Furthermore, we propose that the two-step test, a locomotive syndrome risk test, is effective for assessing the risk for falls and severity of LSS. Meanwhile, lumbar spinal epidural lipomatosis (LSEL), which is a manifestation of LSS, has been shown to be related to metabolic syndrome. Previous studies have suggested that the whole LSS can be also associated with metabolic syndrome. Although locomotive syndrome is very different from metabolic syndrome, which involves lipid metabolism, these two syndromes overlap, such as in LSS. Conducting research on LSS from the perspectives of both locomotive syndrome and metabolic syndrome may lead to novel methods for prevention and treatment of LSS and, conversely, may yield clues for resolving symptoms of the two syndromes. This review provides an overview of LSS from the perspective of locomotive syndrome and metabolic syndrome, along with findings from our research group.

Introduction: There are few reports on body composition, particularly muscle mass, in patients with adolescent idiopathic scoliosis (AIS). The purpose of this study was to measure body composition including muscle mass and estimated bone mass of patients with AIS using bioelectrical impedance analysis (BIA) and to clarify the relationship between the degree of scoliosis and body composition.

Methods: The subjects were 210 girls (mean age 14.0 years, range 10-18 years) whose body composition was evaluated using BIA (Tanita MC-780). Body mass index (BMI), percent body fat (%BF), lean muscle mass index (LMI: muscle mass/height^2), and estimated bone mass index (eBoneMI: estimated bone mass/height^2) were determined by age and compared with those of previous reports. We divided 111 subjects whose bone maturation was complete into two groups for comparison of body composition metrics: those with Cobb angle <40° (moderate scoliosis group) and those with Cobb angle ≥40° (severe scoliosis group). The relationships between Cobb angle and each body composition parameter were evaluated.

Results: Age-adjusted BMI, %BF, and LMI tended to be low at all ages compared with means for the healthy Japanese population as previously reported. BMI, LMI, and eBoneMI were significantly lower in the severe scoliosis group compared with those in the moderate scoliosis group (p<0.05). In addition, all BMI, LMI, and eBoneMI were weakly correlated with Cobb angle (r= −0.20, −0.26, and −0.24).

Conclusions: On the basis of the results of this study, patients with AIS are thinner, with lower BMI, %BF, and LMI compared with healthy girls of the same age. Furthermore, factors such as lower BMI, lower muscle mass, and lower estimated bone mass were correlated with progressive scoliosis.

Introduction: Proximal junctional kyphosis (PJK) is an acute complication of adult spinal deformity (ASD) surgery and may require re-operation because of proximal junctional failure (PJF). PJK causes and prevention strategies remain unknown. This study aimed to investigate the differences in the backgrounds of patients with PJK, compared to those without PJK, in ASD surgery.

Methods: We included data from 86 patients who underwent ASD surgery between 2012 and 2018. There were 40 patients (46.5%) with PJK; 46 patients did not have PJK until the last follow-up. We evaluated patient demographics, clinical outcomes, and radiographic parameters, such as Cobb angle and spinopelvic parameters on standing X-ray films, in each group.

Results: There was no significant difference in patient demographics, clinical outcomes, or preoperative radiographic parameters. Postoperative pelvic incidence minus lumbar lordosis (PI-LL) and pelvic tilt (PT) were significantly lower in the PJK group, and thoracic kyphosis (TK) was higher. The cutoff values were 34.5° for TK, 0.5° for PI-LL, and 15.5° for PT. Other radiographic parameters were not significantly different. PJF developed in seven patients (17.5%) in the PJK group. PJF patients had significantly older age, higher postoperative TK, higher postoperative proximal junctional Cobb angle (PJA), more changes between pre- and postoperative PJA, and lower satisfaction scores on the Scoliosis Research Society Outcomes Questionnaire (SRS-22 satisfaction) than non-PJF patients in the PJK group.

Conclusions: One risk factor for PJK was lower postoperative PI-LL that was 0° or less. In ASD surgery, the most critical factor in a PJK prevention strategy is to obtain a postoperative LL adjusted by PI, which is >0°.

Introduction: The revised Tokuhashi scoring system has been used to predict survival in patients with metastatic spinal tumors. Because of the rapid progress of cancer therapy, the original criteria of the revised Tokuhashi scoring system became in recent years unsuitable. The study aim was to evaluate the validity of the revised Tokuhashi scoring system in patients who underwent spinal surgery and to establish new prognostic criteria.

Methods: The study enrolled 85 patients with metastatic spinal tumors who underwent spinal surgery. The patients' survival outcomes in October 2019 were as follows: 57 patients died; 10 were alive; and 18 had unknown prognoses. The study evaluated the validity of the Tokuhashi scoring system, and established and validated the new prognostic criteria.

Results: The accuracies of the Tokuhashi scoring system were 66.7% in the short-term group, 60% in the midterm group, and 100% in the long-term group. Among the patients who died, the survival period and total score were significantly correlated. Total score cutoff point was six points in the patients whose predicted survival was <6 months. Total score cutoff point was eight points in the patients whose predicted survival was ≥1 year.

Conclusions: As the prognosis of patients has improved in recent years, the original criteria of the revised Tokuhashi scoring system have been questioned as to their suitability to current treatments. Especially, the survival period among the patients with total scores of 7 and 8 points was not accurate. According to this study, the new prognostic criteria of the revised Tokuhashi scoring system were set to 0 to 6 points for the short-term group, 7 points for the midterm group, and 8 to 15 points for the long-term group.

Introduction: Transpsoas lumbar spine surgery is minimally invasive and has very good corrective effects. However, approach-side nerve complications delay post-operative rehabilitation. We anatomically investigated the localization of the lumbar plexus running in the psoas muscle.

Methods: We examined 27 formalin-fixed cadavers. The left-sided psoas muscle was extracted and cut parallel to the intervertebral disc at the L2/3, L3/4, and L4/5 disc levels. Using digitized photographs, we calculated the ratio of the distance from the front edge of the psoas muscle to the center of the lumbar plexus in the anteroposterior diameter of the psoas muscle (%). Then, we calculated the ratio of the distance from the lateral edge of the psoas muscle to the center of the lumbar plexus in the lateral diameter of the psoas muscle (%).

Results: The anterior-posterior lumbar plexus localization was 74.5 at L2/3, 74.7 at L3/4, and 81.2 at L4/5. There was a significant difference between L2/3 and L4/5 and between L3/4 and L4/5, but not between L2/3 and L3/4 (P=0.02, 0.01, and 0.94, respectively). The lateral and medial lumbar plexus localization was 85.4 at L2/3, 83.9 at L3/4, and 77.7 at L4/5. There was a significant difference between L2/3 and L4/5 and between L3/4 and L4/5, but not between L2/3 and L3/4 (P=0.01, 0.04, and 0.41, respectively).

Conclusions: The lumbar plexus was localized in the posterior one-third and medial one-third of the psoas muscle and moved to a posterolateral location at L4/5. To avoid neuropathy, consider the psoas muscle's position relative to that of the intervertebral disc. It is essential to understand lumbar plexus localization in the psoas muscle when looking directly at this muscle to enter the pricking point or route with a lower risk of nerve damage.

Introduction: Despite technical developments in decompression without fusion, many studies still assert that instability could be increased in patients with spinal stenosis and lumbar degenerative spondylolisthesis after spinal decompression surgery without fusion. Thus, this study aimed to describe and assess the clinical outcomes of the semi-circumferential decompression (SCD) technique used for microsurgical en-bloc total ligamentum flavectomy with preservation of the facet joint in treating patients who have lumbar spinal stenosis with two-level degenerative spondylolisthesis.

Methods: We retrospectively analyzed the clinical and radiologic outcomes of 14 patients who had spinal stenosis with two-level Meyerding grade I degenerative spondylolisthesis. We evaluated improvements in back pain and radiating pain using a visual analogue scale (VAS) and the Oswestry Disability Index (ODI). We have also examined the occurrence of spinal instability on a radiological exam using slip percentage and slip angle.

Results: The mean VAS score of back pain and radiating pain has been determined to decrease significantly from 6.7 to 3.3 and from 8.6 to 2.7, respectively. Meanwhile, the ODI score significantly improved from 27.3 preoperatively to 9.8 postoperatively. Statistically significant change was not observed in the slip percentage in both upper and lower levels. Dynamic slip percentage, which is defined as the difference in the slip percentage between flexion and extension, also did not significantly change. No statistically significant change was found in the slip angle and dynamic slip angle.

Conclusions: SCD is a recommendable procedure that can improve clinical results. This procedure does not cause spinal instability when treating patients who have spinal stenosis with two-level degenerative spondylolisthesis.

Introduction: Posterior lumbar interbody fusion (PLIF) is a widely used effective, safe, and established treatment for degenerative spinal disorders. Adjacent segment disease (ASD) is one of the serious concerns governing the clinical results following spinal fusion surgery. Cortical bone trajectory (CBT) is an alternative and less-invasive technique for lumbar pedicle screw placement. Its unique medial and caudal entry point has the potential to prevent an iatrogenic facet joint violence leading to the ASD; however, the incidence of ASD following PLIF using the CBT technique (CBT-PLIF) remains unknown.

Methods: Among patients surgically treated with CBT-PLIF in our institute, 52 consecutive patients (13 males, 39 females) with single-level degenerative lumbar spondylolisthesis (DLS) who were followed up for at least 24 months were exclusively enrolled. Their clinical and radiological features, including the incidence of radiographical and symptomatic ASD and significantly associated factor for the developing radiographical ASD, were retrospectively measured.

Results: In the present study, we could confirm significant neurological improvement and reduction of the spondylolisthesis with mean follow-up period of 43 months. Radiographical and symptomatic ASD was observed in 14 (27%) and 2 (3.8%) cases, respectively. We compared these two groups and found that the latest lumbar lordosis was significantly different between the two groups, but not in age, body mass index, and Japan Orthopaedic Association score. Two patients with symptomatic ASD required additional surgical treatment around 1 year following the initial surgery.

Conclusions: The present study, even though it is preliminary, revealed that CBT-PLIF can achieve a neurological improvement and an effective reduction of spondylolisthesis for the treatment of single-level DLS. The CBT technique is capable of reducing the incidence of ASD compared with the traditional technique; however, we must keep in mind that appropriate postoperative lumbar lordosis should be achieved. Larger, longer-term follow-up studies are required to elucidate the clinical output of CBT-PLIF.

Introduction: Recent literature has associated pseudarthrosis and pedicle screw loosening with subchronic infection at the pedicle of the vertebra. The positive culture results of a previous retrieval analysis show that such patients have a high frequency of bacterial contamination. The objective of this study is to visually capture the architecture of these undiagnosed infections, which have been described in other studies as biofilms on supposedly "aseptic" screw loosening.

Methods: Explants from 10 consecutive patients undergoing revision spine surgery for pseudarthrosis were collected and fixed in glutaraldehyde solution. Each of these implants was imaged thoroughly by using scanning electron microscopy and x-ray spectroscopy to evaluate the architecture of the biofilm. Additionally, eight patient swabs from tissues around the implants were sent for cultures to assess bacterial infiltration in tissues beyond the biofilm. The implants were also analyzed using energy dispersive x-ray spectroscopy. The exclusion criteria included clinically diagnosed infection (current or previous) and/or mechanical failure of the implant due to falls/accidents.

Results: The study was successful in capturing the visual architecture of the biofilm on retrieved implants. A total of 77% of pseudarthrosis cases presented with loose pedicle screws, which were diagnosed by a preoperative computed tomography scan showing radiolucency along the screw track and were confirmed intraoperatively, and 72% of the cases showed biofilm on explants.

Conclusions: In the absence of the clinical presentation of infection, impregnated bacteria could form a biofilm around an implant, and this biofilm can remain undetected via contemporary diagnostic methods, including swabbing. Implant biofilm is frequently present in "aseptic" pseudarthrosis cases.

Introduction: Spinal muscular atrophy (SMA) is defined as a neuromuscular disorder induced by progressive weakness of the skeletal muscle and is usually accompanied by progressive spinal deformity including scoliosis. The newly developed Nusinersen, which is the first approved drug worldwide for SMA, requires accurate intrathecal injection, which is sometimes difficult in patients with severe spinal deformity.

Technical Note: For an accurate intrathecal approach in patients who have spinal fusion surgery to treat neuromuscular scoliosis, we have combined an L3 laminectomy with spinal correction and fusion surgery. Here, we review four cases of SMA in patients who underwent the additional L3 laminectomy during surgery to treat spinal scoliosis. A successful intrathecal approach was made using fluoroscopic guidance in all four patients, who were then administered with Nusinersen.

Conclusions: Our findings show that additional lumbar laminectomy during surgery for spinal scoliosis has effectively allowed for intrathecal injection of Nusinersen.