Search Results

You are looking at 1 - 10 of 11 items for

  • Author or Editor: Fumihiko Kato x
  • All content x
Clear All Modify Search
Full access

Shunsuke Kanbara, Yasutsugu Yukawa, Keigo Ito, Masaaki Machino, and Fumihiko Kato

The lumbar spinous process–splitting laminectomy (LSPSL) procedure was developed as an alternative to lumbar laminectomy. In the LSPSL procedure, the spinous process is evenly split longitudinally and then divided at its base from the posterior arch, leaving the bilateral paravertebral muscle attached to the lateral aspects. This procedure allows for better exposure of intraspinal nerve tissues, comparable to that achieved by conventional laminectomy while minimizing damage to posterior supporting structures. In this study, the authors make some modifications to the original LSPSL procedure (modified LSPSL), in which laminoplasty is performed instead of laminectomy. The purpose of this study was to compare postoperative outcomes in modified LSPSL with those in conventional laminectomy (CL) and to evaluate bone unions between the split spinous process and residual laminae following modified LSPSL.

Forty-seven patients with lumbar spinal stenosis were enrolled in this study. Twenty-six patients underwent modified LSPSL and 21 patients underwent CL. Intraoperative blood loss and surgical duration were evaluated. The Japanese Orthopaedic Association (JOA) scale scores were used to assess parameters before surgery and 12 months after surgery. The recovery rates were also evaluated. Postoperative paravertebral muscle atrophy was assessed using MRI. Bone union rates between the split spinous process and residual laminae were also examined.

The mean surgical time and intraoperative blood loss were 25.7 minutes and 42.4 ml per 1 level in modified LSPSL, respectively, and 22.7 minutes and 29.5 ml in CL, respectively. The recovery rate of the JOA score was 64.2% in modified LSPSL and 68.7% in CL. The degree of paravertebral muscle atrophy was 7.8% in modified LSPSL and 22.2% in CL at 12 months after surgery (p < 0.05). The fusion rates of the spinous process with the arcus vertebrae at 6 and 12 months in modified LSPSL were 56.3% and 81.3%, respectively.

The modified LSPSL procedure was less invasive to the paravertebral muscles and could be a laminoplasty; therefore, the modified LSPSL procedure presents an effective alternative to lumbar laminectomy.

Restricted access

Noriaki Kawakami, Kentaro Mimatsu, Fumihiko Kato, Yuji Kondo, Hisao Itoh, and Toshiyuki Matsunaka

✓ Although ultrasonography during spinal cord surgery has been widely accepted, it still has limitations in clinical application because of the size of the transducers needed and the immersion method. The authors report on newly designed microprobe transducers used to evaluate intramedullary spinal cord lesions and to monitor surgical procedures. This microprobe system permitted the microscopic use of intraoperative ultra-sonography without requiring saline immersion.

Restricted access

Yasutsugu Yukawa, Fumihiko Kato, Hisatake Yoshihara, Makoto Yanase, and Keigo Ito

Object

The authors conducted a study to introduce the imaging technique in which pedicle axis views are obtained using fluoroscopy to match the screw entry point with pedicle orientation and to report the clinical results and safety of cervical pedicle screw fixation (PSF) in patients treated for unstable cervical injuries.

Methods

One hundred consecutive patients with unstable cervical injuries underwent PSF in which the authors used fluoroscopic imaging to acquire pedicle axis views. There were 87 men and 13 women whose mean age was 42.5 years. The accuracy of PS placement was examined postoperatively using axial computed tomography (CT) and oblique radiography. Screw malpositioning was classified either as screw exposure (< 50% of the screw outside the pedicle) or pedicle perforation (> 50% of the screw outside the pedicle boundaries).

The mean operative time was 97.6 minutes, and the mean estimated blood loss was 221 ml. Local vertebral alignment around the injured segment measured 6.0° of kyphosis preoperatively and 6.7° of lordosis postoperatively. Solid posterior bone fusion was achieved in all but three patients who died shortly after surgery. There was no secondary dislodgment of instrumentation in 95% of these 97 cases. Of the 419 cervical PSs, 43 (10.3%) were of the screw-exposure type and 17 (4.0%) of the pedicle-perforation type. There were two surgery-related complications: one penetration of a probe into the vertebral artery and one radiculopathy. There were six postoperative complications: two cases of instrumentation failure associated with loss of correction, three cases of correction loss (> 10°), and one case of deep wound infection.

Conclusions

Solid posterior fusion without secondary dislodgment of hardware was demonstrated in 95% of the cases. The incidence of complications associated with cervical PSF was not high. Postoperative CT scanning showed that 17 (4.0%) of 419 screws perforated the pedicle. It appears that fluoroscopy performed using pedicle axis views improves the accuracy and safety of cervical PS insertion.

Restricted access

Go Yoshida, Mituhiro Kamiya, Hisatake Yoshihara, Tokumi Kanemura, Fumihiko Kato, Yasutugu Yukawa, Keigo Ito, Yukihiro Matsuyama, and Yoshihito Sakai

Object

The purpose of this study was to evaluate the effect of a fixed atlantoaxial angle on subaxial sagittal alignment, and that of atlantoaxial fixation on adjacent-segment motion and degeneration.

Methods

The authors retrospectively reviewed 65 patients in whom atlantoaxial instability was treated with atlantoaxial fixation by C-1 lateral mass and C-2 pedicle screw fixation (30 patients, Goel-Harms [GH] group) or a combination of transarticular screw fixation and posterior wiring (35 patients, Magerl-Brooks [MB] group). Angles of Oc–C1, C1–2, C2–3, and C2–7 were determined based on an upright lateral radiograph in flexion, neutral, and extension positions. The range of motion (ROM) at Oc–C1 and C2–3 was also determined. All patients were examined before and 2 years after surgery.

Results

The mean preoperative atlantoaxial angles in the GH and MB groups were 20.9 ± 8.3° and 18.3 ± 7.2°, respectively, and the mean postoperative atlantoaxial angles in the same groups were 23.5 ± 5.6° and 29.7 ± 6.3°, respectively, with a statistically significant difference between the 2 groups (p < 0.05). The mean preoperative angles of C2–7 in the GH and MB groups were 15.4 ± 7.8° and 13.7 ± 9.5°, respectively, and after surgery, the angles were 11.8 ± 12° and 2.48 ± 12°, respectively, with a statistically significant difference between the 2 groups (p < 0.05). The postoperative angle of C1–2 showed a negative correlation with the extent of change observed in the C2–7 angle preand postoperatively in each of these 2 surgical procedures. The Oc–C1 ROM increased after surgery in both groups, but the difference was not statistically significant (p = 0.38). The C2–3 ROM decreased after surgery in both groups, and the difference was statistically significant (p < 0.05).

Conclusions

Atlantoaxial fixation in a hyperlordotic position produced kyphotic sagittal alignment after surgery in both GH and MB groups. Reduction of the atlantoaxial joint can be easily achieved through screw fixation at an optimal angle, thereby ameliorating the risk for subsequent subaxial kyphosis. Degeneration of lower adjacent segments appeared to be less with this procedure compared with using a combination of transarticular screw fixation and posterior wiring.

Restricted access

Hiroaki Nakashima, Shiro Imagama, Yasutsugu Yukawa, Tokumi Kanemura, Mitsuhiro Kamiya, Makoto Yanase, Keigo Ito, Masaaki Machino, Go Yoshida, Yoshimoto Ishikawa, Yukihiro Matsuyama, Nobuyuki Hamajima, Naoki Ishiguro, and Fumihiko Kato

Object

Postoperative C-5 palsy is a significant complication resulting from cervical decompression procedures. Moreover, when cervical degenerative diseases are treated with a combination of decompression and posterior instrumented fusion, patients are at increased risk for C-5 palsy. However, the clinical and radiological features of this condition remain unclear. Therefore, the purpose of this study was to clarify the risk factors for developing postoperative C-5 palsy.

Methods

Eighty-four patients (mean age 60.1 years) who had undergone posterior instrumented fusion using cervical pedicle screws to treat nontraumatic lesions were independently reviewed. The authors analyzed the medical records of some of these patients who developed postoperative C-5 palsy, paying particular attention to their plain radiographs, MRI studies, and CT scans. Risk factors for postoperative C-5 palsy were assessed using multivariate logistic regression analysis. The cutoff values for the pre- and postoperative width of the intervertebral foramen (C4–5) were determined by receiver operating characteristic curve analysis.

Results

Ten (11.9%) of 84 patients developed postoperative C-5 palsy. Seven patients recovered fully from the neurological complications. The pre- and postoperative C4–5 angles showed significant kyphosis in the C-5 palsy group. The pre- and postoperative diameters of the C4–5 foramen on the palsy side were significantly smaller than those on the opposite side in the C-5 palsy group and those bilaterally in the non–C5 palsy group. Risk factors identified by multivariate logistic regression analysis were as follows: 1) ossification of the posterior longitudinal ligament (relative risk [RR] 7.22 [95% CI 1.03–50.55]); 2) posterior shift of the spinal cord (C4–5) (RR 1.73 [95% CI 1.00–2.98]); and 3) postoperative width of the C-5 intervertebral foramen (RR 0.33 [95% CI 0.14–0.79]). The cutoff values of the pre- and postoperative widths of the C-5 intervertebral foramen for C-5 palsy were 2.2 and 2.3 mm, respectively.

Conclusions

Patients with preoperative foraminal stenosis, posterior shift of the spinal cord, and additional iatrogenic foraminal stenosis due to cervical alignment correction were more likely to develop postoperative C-5 palsy after posterior instrumentation with fusion. Prophylactic foraminotomy at C4–5 might be useful when preoperative foraminal stenosis is present on CT. Furthermore, it might be useful for treating postoperative C-5 palsy. To prevent excessive posterior shift of the spinal cord, the authors recommend that appropriate kyphosis reduction should be considered carefully.

Restricted access

Masaaki Machino, Kei Ando, Kazuyoshi Kobayashi, Hiroaki Nakashima, Shunsuke Kanbara, Sadayuki Ito, Taro Inoue, Hidetoshi Yamaguchi, Hiroyuki Koshimizu, Keigo Ito, Fumihiko Kato, Naoki Ishiguro, and Shiro Imagama

OBJECTIVE

Although increased signal intensity (ISI) on MRI is observed in patients with cervical spinal cord injury (SCI) without major bone injury, alterations in ISI have not been evaluated. The association between postoperative ISI and surgical outcomes remains unclear. This study elucidated whether or not the postoperative classification and alterations in MRI-based ISI of the spinal cord reflected the postoperative symptom severity and surgical outcomes in patients with SCI without major bone injury.

METHODS

One hundred consecutive patients with SCI without major bone injury (79 male and 21 female) with a mean age of 55 years (range 20–87 years) were included. All patients were treated with laminoplasty and underwent MRI pre- and postoperatively (mean 12.5 ± 0.8 months). ISI was classified into three groups on the basis of sagittal T2-weighted MRI: grade 0, none; grade 1, light (obscure); and grade 2, intense (bright). The neurological statuses were evaluated according to the Japanese Orthopaedic Association (JOA) scoring system and the American Spinal Injury Association Impairment Scale (AIS).

RESULTS

Preoperatively, 8 patients had grade 0 ISI, 49 had grade 1, and 43 had grade 2; and postoperatively, 20 patients had grade 0, 24 had grade 1, and 56 had grade 2. The postoperative JOA scores and recovery rate (RR) decreased significantly with increasing postoperative ISI grade. The postoperative ISI grade tended to increase with the postoperative AIS grade. Postoperative grade 2 ISI was observed in severely paralyzed patients. The postoperative ISI grade improved in 23 patients (23%), worsened in 25 (25%), and remained unchanged in 52 (52%). Patients with an improved ISI grade had a better RR than those with a worsened ISI grade.

CONCLUSIONS

Postoperative ISI reflected postoperative symptom severity and surgical outcomes. Alterations in ISI were seen postoperatively in 48 patients (48%) and were associated with surgical outcomes.

Restricted access

Yasutsugu Yukawa, Fumihiko Kato, Keigo Ito, Yumiko Horie, Tetsurou Hida, Masaaki Machino, Zen-ya Ito, and Yukihiro Matsuyama

Object

Increased signal intensity of the spinal cord on magnetic resonance (MR) imaging was classified pre- and postoperatively in patients with cervical compressive myelopathy. It was investigated whether postoperative classification and alterations of increased signal intensity could reflect the postoperative severity of symptoms and surgical outcomes.

Methods

One hundred and four patients with cervical compressive myelopathy were prospectively enrolled. All were treated using cervical expansive laminoplasty. Magnetic resonance imaging was performed in all patients preoperatively and after an average of 39.7 months postoperatively (range 12–90 months). Increased signal intensity of the spinal cord was divided into 3 grades based on sagittal T2-weighted MR images as follows: Grade 0, none; Grade 1, light (obscure); and Grade 2, intense (bright). The severity of myelopathy was evaluated according to the Japanese Orthopedic Association (JOA) score for cervical myelopathy and its recovery rate (100% = full recovery).

Results

Increased signal intensity was seen in 83% of cases preoperatively and in 70% postoperatively. Preoperatively, there were 18 patients with Grade 0 increased signal intensity, 49 with Grade 1, and 37 with Grade 2; postoperatively, there were 31 with Grade 0, 31 with Grade 1, and 42 with Grade 2. The respective postoperative JOA scores and recovery rates (%) were 13.9/56.7% in patients with postoperative Grade 0, 13.2/50.7% in those with Grade 1, and 12.8/40.1% in those with Grade 2, and these differences were not statistically significant. The postoperative increased signal intensity grade was improved in 16 patients, worsened in 8, and unchanged in 80 (77%). There was no significant correlation between the alterations of increased signal intensity and surgical outcomes.

Conclusions

The postoperative increased signal intensity classification reflected postoperative symptomatology and surgical outcomes to some extent, without statistically significant differences. The alteration of increased signal intensity was seen postoperatively in 24 patients (23%) and was not correlated with surgical outcome.

Restricted access

Toru Doi, Ryuji Sakamoto, Chiaki Horii, Naoki Okamoto, Koji Nakajima, Shima Hirai, Fumihiko Oguchi, So Kato, Yuki Taniguchi, Yoshitaka Matsubayashi, Naoto Hayashi, Sakae Tanaka, and Yasushi Oshima

OBJECTIVE

The incidence and risk factors for the progression of ossification of the posterior longitudinal ligament (OPLL) have been previously reported in surgically and nonsurgically treated symptomatic patients. However, the correlates of OPLL progression in asymptomatic subjects with OPLL are not well characterized. This study aimed to clarify the incidence and risk factors for OPLL progression in asymptomatic subjects based on whole-body CT.

METHODS

The authors retrospectively reviewed 2585 healthy subjects who underwent whole-body CT at a single health center from September 2007 to December 2011. This study included asymptomatic subjects with OPLL who underwent CT scans twice with an interval of at least 5 years. Progression of OPLL was assessed based on initial and final CT scan. Subjects were divided into two groups: nonprogression (OPLL-NP) and progression (OPLL-P) groups. Clinical characteristics, bone mineral density status, OPLL types, and OPLL involvement of multiple vertebral levels between the two groups were compared. Risk factors for progression of OPLL were identified by logistic regression analysis after propensity score adjustment.

RESULTS

Of the 109 subjects with OPLL (91 men and 18 women), 20 (18.3%) exhibited OPLL progression (OPLL-P group). Subjects in the OPLL-P group were significantly younger (p = 0.031), had higher prevalence of multilevel OPLL involvement (p = 0.041) and continuous type of OPLL (p = 0.015), and had higher uric acid (UA) levels (p = 0.004) at the time of initial CT examination compared to the OPLL-NP group. Younger age (adjusted odds ratio [aOR] 0.95, 95% CI 0.90–0.99), OPLL involvement of multiple vertebral levels (aOR 2.88, 95% CI 1.06–7.83), continuous type of OPLL (aOR 4.21, 95% CI 1.35–13.10), and higher UA levels (aOR 2.09, 95% CI 1.24–3.53) were significant risk factors for OPLL progression.

CONCLUSIONS

Younger age, OPLL involvement of multiple vertebral levels, continuous type of OPLL, and higher UA levels are significant risk factors for OPLL progression in asymptomatic subjects.

Restricted access

Hiroaki Nakashima, Yasutsugu Yukawa, Shiro Imagama, Tokumi Kanemura, Mitsuhiro Kamiya, Makoto Yanase, Keigo Ito, Masaaki Machino, Go Yoshida, Yoshimoto Ishikawa, Yukihiro Matsuyama, Naoki Ishiguro, and Fumihiko Kato

Object

The cervical pedicle screw (PS) provides strong stabilization but poses a potential risk to the neurovascular system, which may be catastrophic. In particular, vertebrae with degenerative changes complicate the process of screw insertion, and PS misplacement and subsequent complications are more frequent. The purpose of this study was to evaluate the peri- and postoperative complications of PS fixation for nontraumatic lesions and to determine the risk factors of each complication.

Methods

Eighty-four patients who underwent cervical PS fixation for nontraumatic lesions were independently reviewed to identify associated complications. The mean age of the patients was 60.1 years, and the mean follow-up period was 4.1 years (range 6–168 months). Pedicle screw malpositioning was classified on postoperative CT scans as Grade I (< 50% of the screw outside the pedicle) or Grade II (≥ 50% of the screw outside the pedicle). Risk factors of each complication were evaluated using a multivariate analysis.

Results

Three hundred ninety cervical PSs and 24 lateral mass screws were inserted. The incidence of PS misplacement was 19.5% (76 screws); in terms of malpositioning, 60 screws (15.4%) were classified as Grade I and 16 (4.1%) as Grade II. In total, 33 complications were observed. These included postoperative neurological complications in 11 patients in whom there was no evidence of screw misplacement (C-5 palsy in 10 and C-7 palsy in 1), implant failure in 11 patients (screw loosening in 5, broken screws in 4, and loss of reduction in 2), complications directly attributable to screw insertion in 5 patients (nerve root injury by PS in 3 and vertebral artery injury in 2), and other complications in 6 patients (pseudarthrosis in 2, infection in 1, transient dyspnea in 1, transient dysphagia in 1, and adjacent-segment degeneration in 1). The multivariate analysis showed that a primary diagnosis of cerebral palsy was a risk factor for postoperative implant failure (HR 10.91, p = 0.03) and that the presence of preoperative cervical spinal instability was a risk factor for both Grade I and Grade II screw misplacement (RR 2.12, p = 0.03), while there were no statistically significant risk factors for postoperative neurological complications in the absence of evidence of screw misplacement or complications directly attributable to screw insertion.

Conclusions

In the present study, misplacement of cervical PSs and associated complications occurred more often than in previous studies. The rates of screw-related neurovascular complications and neurological deterioration unrelated to PSs were high. Insertion of a PS for nontraumatic lesions is surgically more challenging than that for trauma; consequently, experienced surgeons should use PS fixation for nontraumatic cervical lesions only after thorough preoperative evaluation of each patient's cervical anatomy and after considering the risk factors specified in the present study.

Restricted access

Kei Ando, Shiro Imagama, Norimitsu Wakao, Kenichi Hirano, Ryoji Tauchi, Akio Muramoto, Fumihiko Kato, Yasutsugu Yukawa, Noriaki Kawakami, Koji Sato, Yuji Matsubara, Tokumi Kanemura, Yukihiro Matsuyama, and Naoki Ishiguro

Object

The purpose of this study was to provide the first evidence for the influence of an ossified anterior longitudinal ligament (OALL) on the clinical features and surgical outcomes in an ossified ligamentum flavum (OLF) in the thoracic region.

Methods

Sixty-three patients who underwent surgery for a 1-level thoracic OLF were identified, and preoperative symptoms, severity of symptoms and myelopathy, disease duration, MR imaging and CT findings, surgical procedure, intraoperative findings, complications, and postoperative recovery were investigated in these patients. Entities of OALLs were found on sagittal CT images to be adjacent to or at the same vertebral level as the OLF were classified into 4 types: no discernible type (Type N), one-sided (Type O), discontinuous (Type D), and continuous (Type C).

Results

The duration of symptoms was especially long for Types D and C OALLs. Patients with Type D OALLs had a significantly worse percentage of recovery, as well as worse preoperative JOA scores.

Conclusions

The authors' results showed that a Type D OALL had strong associations with preoperative severity of symptoms and surgical outcomes. These findings may allow surgeons to determine the severity of preoperative symptoms and the probable surgical outcomes from the OALL classifications. Moreover, surgery with instrumentation for Type D OALLs may produce better surgical outcomes.