Search Results

You are looking at 1 - 10 of 11 items for

  • Author or Editor: Masahiro Kanayama x
  • Refine by Access: all x
Clear All Modify Search
Restricted access

Masahiro Kanayama

The Xia 3 SUK Direct Vertebral Rotation (DVR) System was developed for performing the vertebral derotation maneuver in scoliosis surgery. The author applied this device to sagittal plane correction in pedicle subtraction osteotomy for adult spinal deformity. The surgical procedure included 1) preparing secure proximal and distal foundations for correction using mutisegmental pedicle screw-rod fixation (to avoid stress concentration to a specific screw-bone interface), 2) decancellating only the posterior two-thirds of the vertebral column, 3) providing supplemental interbody fusion above and below the osteotomy site (the anterior one-third of the vertebral column and interbody cages serve as an anterior column support and a pivot of correction), 4) closing the osteotomy by gradual approximation of SUK tubes secured to the proximal- and distal-most screw heads, and 5) connecting rods between the proximal and distal screw-rod constructs. Eight consecutive patients with fixed sagittal imbalance were treated using this surgical procedure. No patient required distal fixation points extending to the sacrum and/or pelvis. The sagittal plane correction was 43°. The mean anterior deviation of the C-7 plumb line was improved from 12.7 cm to 4.0 cm immediately after surgery, and it was 6.0 cm at the final follow-up. A pedicle subtraction osteotomy using the Xia 3 SUK DVR System ensures a safe and secure sagittal plane correction in adult spinal deformity.

Restricted access

Masahiro Kanayama, Tomoyuki Hashimoto, Keiichi Shigenobu, Fumihiro Oha, and Daisuke Togawa


Antimicrobial prophylaxis (AMP) reduces the rate of surgical site infection (SSI) in lumbar spine surgery, but a great deal of variation exists regarding the timing and duration of AMP. The authors had previously used prophylactic antibiotics for 5 to 7 postoperative days. Based on the Centers for Disease Control and Prevention (CDC) guideline, the AMP period was changed to the day of surgery only. In the current study, the authors compared the rate of SSI in lumbar spine surgeries between two different protocols of AMP.


Data from 1597 consecutive uninfected patients who had undergone lumbar spine surgery between January 1999 and September 2004 were reviewed. The pathophysiologies among these patients included disc herniation in 686, degenerative spondylolisthesis in 340, spinal stenosis in 259, failed lumbar surgeries in 73, degenerative scoliosis in 52, isthmic spondylolisthesis in 48, spinal trauma in 34, foraminal stenosis in 27, spinal tumor in 27, and miscellaneous in 51 patients. The rate of SSI was compared between the two AMP groups.

There were 1133 patients in the multiple-dose group, and 464 patients in the single-dose group. The rate of instrumentation surgery was not statistically different between the multiple-dose group (43%) and the single-dose group (39%). The overall rate of SSI was 0.7%. The SSI rate was 0.8% in the multiple-dose group and 0.4% in the single-dose group; the difference between the two was not significant. Regarding the organisms of SSI, resistant strains of bacteria were cultured in five (83.3%) of six patients in the multiple-dose group, whereas none was cultured in the single-dose group.


Data in the current study did not demonstrate a difference in the rate of SSI between the two different AMP protocols. Based on the CDC guideline, a single dose of AMP was proven to be efficacious for the prevention of SSI in lumbar spine surgeries. A shorter duration of first-generation cephalosporin use may effectively prevent the emergence of antibiotic-resistant bacterial infection.

Restricted access

Masahiro Kanayama, Tomoyuki Hashimoto, Keiichi Shigenobu, Fumihiro Oha, and Shigeru Yamane

Object. Serotonin or 5-hydroxytryptamine (5-HT) is a chemical mediator associated with nucleus pulposus—induced radiculopathy. Inhibition of 5-HT receptors may potentially alleviate symptoms in patients with lumbar disc herniation. This prospective randomized controlled study was performed to evaluate the efficacy of the 5-HT2A receptor inhibitor in the treatment of symptomatic lumbar disc herniation.

Methods. Forty patients with sciatica due to L4–5 or L5—S1 disc herniation were randomly allocated to treatment with the 5-HT2A inhibitor (sarpogrelate 300 mg/day) or nonsteroidal antiinflammatory drugs (NSAIDs; diclofenac 75 mg/day). Low-back pain, leg pain, and numbness were evaluated using a visual analog scale (VAS) before and after a 2-week course of treatment. The patients received only allocated medicine during the 2-week regimen and were thereafter allowed to choose any treatment options depending on their residual symptoms. One-year clinical outcomes were assessed based on the rates of additional medical interventions.

The mean VAS score improvements in the 5-HT2A and NSAID groups were 33 and 46% for low-back pain, 32 and 32% for leg pain, and 35 and 22% for leg numbness, respectively. After the 2-week regimen, no additional medical interventions were required in 50% of 5-HT2A—treated patients and 15% of those receiving NSAIDs. Epidural or nerve root block procedures were performed in 35% of the 5-HT2A group and 45% of the NSAID group. Surgery was required in 20% of the 5-HT2A group and 30% of the NSAID group patients.

Conclusions. The current study provided evidence that the efficacy of the 5-HT2A inhibitor was comparable with that of NSAID therapy for lumbar disc herniation. The 5-HT2A inhibitor has the potential to alleviate symptoms in patients with lumbar disc herniation.

Restricted access
Restricted access

Masahiro Kanayama, Bryan W. Cunningham, Charles J. Haggerty, Kuniyoshi Abumi, Kiyoshi Kaneda, and Paul C. McAfee

Object. Interbody fusion devices are rapidly gaining acceptance as a method of ensuring lumbar interbody arthrodesis. Although different types of devices have been developed, the comparative reconstruction stability remains controversial. It also remains unclear how different stress-shielded environments are created within the devices. Using a calf spine model, this study was designed to compare the construct stiffness afforded by 11 differently designed lumbar interbody fusion devices and to quantify their stress-shielding effects by measuring pressure within the devices.

Methods. Sixty-six lumbar specimens obtained from calves were subjected to anterior interbody reconstruction at L4–5 by using one of the following interbody fusion devices: four different threaded fusion cages (BAK device, BAK Proximity, Ray TFC, and Danek TIBFD), five different nonthreaded fusion devices (oval and circular Harms cages, Brantigan PLIF and ALIF cages, and InFix device); two different types of allograft (femoral ring and bone dowel) were used. Construct stiffness was evaluated in axial compression, torsion, flexion, and lateral bending. Prior to testing, a silicon elastomer was injected into the cages and intracage pressures were measured using pressure needle transducers.

Conclusions. No statistical differences were observed in construct stiffness among the threaded cages and nonthreaded devices in most of the testing modalities. Threaded fusion cages demonstrated significantly lower intracage pressures compared with nonthreaded cages and structural allografts. Compared with nonthreaded cages and structural allografts, threaded fusion cages afforded equivalent reconstruction stiffness but provided more stress-shielded environment within the devices.

Restricted access

Ken Nagahama, Masahiro Kanayama, Daisuke Togawa, Tomoyuki Hashimoto, and Akio Minami


Bisphosphonate medications are widely used for the treatment of osteoporosis, but they might disturb the healing process of spinal fusion. The object of this prospective randomized controlled study was to evaluate the effect of bisphosphonate medication on spinal fusion through radiographic, clinical, and biological assessments.


A total of 40 patients with osteoporosis who were candidates for single-level posterior lumbar interbody fusion were randomly assigned to the alendronate group (alendronate sodium 35 mg/week) or the control group (vitamin D, alfacalcidol 1 μg/day). Pedicle screw fixation and carbon polyetheretherketone cages were used for all the patients. Bone graft material was prepared as a mixture of local bone and β-tricalcium phosphate in a ratio of 2:1. Functional radiography and CT scans were used to evaluate fusion status and cage subsidence. The incidence of vertebral compression fractures (VCFs) occurring after surgery (subsequent VCFs) was assessed by means of MR imaging. Bridging bone formation was graded into 3 categories: Grade A (bridging bone through bilateral cages), Grade B (bridging bone through a unilateral cage), or Grade C (incomplete bony bridging). A solid fusion was defined as less than 5° of angular motion in flexion-extension radiographs and the presence of bridging bone through the cage (Grade A or B). Clinical outcome was evaluated by means of the Oswestry Disability Index. Bone metabolic markers (serum bone alkaline phosphatase, serum and urine Type I collagen cross-linked N-telopeptides) were measured to investigate the biological effects of alendronate on spinal fusion.


Bridging bone formation (Grade A or B) was more frequently observed in the alendronate group at all postoperative assessment periods. At 1-year postoperative follow-up, a solid fusion was achieved in 95% of the patients in the alendronate group and 65% of those in the control group. Cage subsidence (> 2 mm) was observed in 5% of the alendronate group and 29% of the control group. No vertebral fractures were observed in the alendronate group, whereas 24% of patients in the control group showed subsequent VCFs. There was no statistically significant between-groups difference in clinical outcomes, but poor clinical results in the control group were associated with pseudarthrosis and subsequent VCFs. Biochemical analysis of bone turnover demonstrated that alendronate inhibited bone resorption from the early phase of the fusion process and also suppressed bone formation after 6 months postoperatively.


Favorable mechanical circumstances provided by alendronate overcame its detrimental biological effect on the healing process of spinal fusion. The authors recommend that osteoporosis patients undergoing spinal fusion take bisphosphonates throughout the postoperative period.

Restricted access

Masahiro Kanayama, Daisuke Togawa, Chihiro Takahashi, Tomoya Terai, and Tomoyuki Hashimoto


The current cross-sectional observational MR imaging study aimed to investigate the prevalence and risk factors of lumbar disc degeneration in a healthy population and to establish the baseline data for a prospective longitudinal study.


Two hundred healthy volunteers participated in this study after providing informed consent. The status of lumbar disc degeneration was assessed by 3 independent observers, who used sagittal T2-weighted MR imaging. Demographic data collected included age, sex, body mass index, episode(s) of low-back pain, smoking status, hours of standing and sitting, and Roland-Morris Disability Questionnaire scores. There were 68 men and 132 women whose mean age was 39.7 years (range 30–55 years). Eighty-two individuals (41%) were smokers, and the Roland-Morris Disability Questionnaire scores were averaged to 0.6/24.


The prevalence of disc degeneration was 7.0% in L1–2, 12.0% in L2–3, 15.5% in L3–4, 49.5% in L4–5, and 53.0% in L5–S1. A herniated disc was observed at the corresponding levels in 0.5, 3.5, 6.5, 25.0, and 35.0% of cases respectively. Spondylolisthesis was observed in < 3% of this population. Multiple logistic regression analysis demonstrated that age and hours sitting were significantly related to L4–5 disc herniation. Episode of low-back pain, smoking status, body mass index, and hours standing did not affect the prevalence of disc degeneration.


The current study established the baseline data of lumbar disc degeneration in a 30- to 55-year-old healthy population for a prospective longitudinal study. Hours spent sitting significantly increased the prevalence of disc herniation, but episode of low-back pain, smoking status, obesity, and standing hours were not significant risk factors.

Restricted access

Michael G. Fehlings and Reza Mobasheri

Restricted access

Masahiro Kanayama, Tomoyuki Hashimoto, Keiichi Shigenobu, Masahito Harada, Fumihiro Oha, Yasumitsu Ohkoshi, Hiroshi Tada, Kazuki Yamamoto, and Shigeru Yamane

Object. Of concern to spine surgeons are accelerated degenerative changes of motion segments located above and below where spinal fusion has been performed. Graf artificial ligament stabilization has been developed to avoid the adverse effect of spinal fusion. The object of this study was to assess the adjacent-segment morbidity of Graf ligamentoplasty compared with posterolateral fusion (PF) in which instrumentation was used.

Methods. Data obtained in 45 patients who underwent L4–5 Graf ligamentoplasty (18 patients) or PF with instrumentation (27 patients) were reviewed retrospectively. The minimum follow-up period was 5 years. In the PF group a solid fusion rate of 92.6% was achieved. Radiographic evaluation included assessment of lumbar sagittal alignment, range of motion (ROM), and adjacent-disc degeneration. Adjacent-segment morbidity was clinically assessed by determining the reoperation rate.

Graf ligamentoplasty maintained regional lordosis and flexibility (13° in L4–5 lordosis; 4.4° in L4–5 ROM). Although there was no difference in preoperative adjacent-disc condition between the two groups, radiographic evidence of adjacent-disc deterioration was observed more frequently in patients in the PF group than the Graf group (25% and 6% at L1–2; 38% and 6% at L2–3; 38% and 18% at L3–4; and 43% and 18% at L5—sacrum, respectively). One case in the Graf group (5.6%) and five cases in the PF group (18.5%) required additional surgeries for adjacent-segment lesions.

Conclusions. Graf ligamentoplasty cannot completely replace spinal fusion. In a well-selected group of patients, however, it was shown to maintain lumbar mobility and sagittal alignment, and it decreased the risk of adjacent-segment deterioration compared with PF with instrumentation.

Free access

Takamasa Watanabe, Masahiro Kanayama, Masahiko Takahata, Itaru Oda, Kota Suda, Yuichiro Abe, Junichiro Okumura, Yoshihiro Hojo, and Norimasa Iwasaki


The number of spine surgeries performed in elderly patients is consistently increasing. However, to date the prevalence of and risk factors for perioperative complications remain unclear, especially in patients 80 years of age or older. This study had two goals: 1) determine the perioperative complications of spine surgery associated with patients 80 years of age or older; and 2) investigate the risk factors for perioperative systemic complications.


In this paper, the authors describe a multicenter prospective cohort study. Seven spine centers with board-certified spine surgeons participated in this all-case investigation. A total of 270 consecutively enrolled patients (109 males and 161 females), 80 years of age or older, underwent spine surgery between January and December 2017. Patients with trauma, infection, or tumor were excluded in this cohort. Perioperative complications were defined as adverse events that occurred intraoperatively or within 30 days postoperatively. The patients’ preoperative health status was determined using the following means of assessment: 1) the Charlson Comorbidity Index, 2) the American Society of Anesthesiologists Physical Status Classification System, 3) the Eastern Cooperative Oncology Group Performance Status (ECOG-PS), 4) the presence of sarcopenia, and 5) the Geriatric Nutritional Risk Index. Associations among patient age, preoperative health status, surgical factors (instrumentation surgery, operation time, number of spinal levels treated, and estimated blood loss), and perioperative systemic complications were analyzed.


Overall perioperative, surgical site, and minor systemic complications were observed in 20.0%, 8.1%, and 14.8% of patients, respectively. Major systemic complications, on the other hand, were not observed. The reoperation rate was low—only 4.1%. Multivariate analysis revealed that the ECOG-PS (p = 0.013), instrumentation surgery (p = 0.024), and an operation time longer than 180 minutes (p = 0.016) were associated with minor systemic complications.


To the best of the authors’ knowledge, this is the first multicenter prospective all-case investigation of perioperative complications of spine surgery in elderly patients. Although decreased daily activity (ECOG-PS), instrumentation surgery, and longer operation time were associated with minor systemic complications, no major systemic complications were observed in these elderly patients. Thus, spine surgery can be safely performed in elderly patients 80 years of age or older.