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Ken Ishii, Kazuhiro Chiba, Masahiko Watanabe, Hiroo Yabe, Yoshikazu Fujimura, and Yoshiaki Toyama

✓ Excision is the treatment of choice in cases of sacral chordoma. Local recurrences, however, have often been observed even after total en bloc resection. The authors assessed outcomes in four cases of tumor recurrence in patients who underwent total en bloc S2–3 resection for sacral chordomas that were located below S-3. The primary recurrences were located at either side of the lateral portion of the remaining sacrum in all patients. In two patients in whom preoperative magnetic resonance imaging indicated no invasion of the tumor into surrounding soft tissues, recurrence in the resected end of the gluteus maximus or piriformis muscle was also observed. The authors therefore recommend that the S2–3 sacrectomy should be performed over an adequate margin, including a part of sacroiliac joints at the bilateral portions of the sacrum and soft tissues such as the gluteus maximus or piriformis muscle.

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Masahiko Watanabe, Kazuhiro Chiba, Morio Matsumoto, Hirofumi Maruiwa, Yoshikazu Fujimura, and Yoshiaki Toyama

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Yuji Mikami, Masahiro Toda, Masahiko Watanabe, Masaya Nakamura, Yoshiaki Toyama, and Yutaka Kawakami

✓ To establish a simple and reliable method to assess the behavioral function after spinal cord injury (SCI) in mice, the authors used an automated animal movement analysis system, SCANET.

Two different SCI lesions were created in adult female BALB/c and C57BL/6 mice by transecting both the posterior columns and the left lateral and anterior funiculi or only the left lateral and anterior funiculi at T-8. Control mice underwent laminectomy only. The SCANET system consists of a cage equipped with two crossing sensor frames arranged at different heights, by which small (M1) and large (M2) horizontal movements and the vertical movement involved in rearing (RG) can be monitored. The authors assessed locomotor function by determining the M1, M2, and RG scores; to this end, they used the SCANET system and a previously established behavior test, the 21-point open-field Basso-Beattie-Bresnahan (BBB) Locomotor Rating Scale. The results indicated that the RG scores were significantly and consistently different between the spinal cord—injured and control mice, irrespective of the mouse strain or injury model, but that M1 and M2 scores were not. Moreover, there was a statistically positive correlation between the RG score and the BBB Scale score.

For the assessment of locomotor function after SCI, use of the SCANET sytem in behavioral analysis is simple and the method is highly reproducible. The analysis of vertical movement is useful for assessing the recovery of limb function in mice following thoracic hemisection.

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Masahiko Watanabe, Kazuhiro Chiba, Morio Matsumoto, Hirofumi Maruiwa, Yoshikazu Fujimura, and Yoshiaki Toyama

Object. Spinal cord herniation is a rare cause of progressive myelopathy and can be corrected surgically. In most previous reports, closure of the dural defect was the recommended procedure. The object of this paper is to describe a new procedure in which spinal cord constriction is released by enlarging the hiatus; additionally the postoperative results will be discussed.

Methods. In nine patients with spinal cord herniation, enlargement of the dural defect was performed. In eight patients, neurological deficits resolved immediately after surgery. In one patient with a severe preoperative neurological deficit whose spinal cord herniated massively, deterioration occurred postoperatively. To date, no recurrence of herniation has been observed.

Conclusions. The goals of surgery are to reduce the herniation, return the spinal cord to the normal position, and prevent the recurrence of herniation. The use of sutures to close the dural defect has been the method of choice to date. The surgical space in front of the spinal cord, however, is insufficient to accommodate this procedure safely. Because symptoms are caused by the constriction of the spinal cord at the hiatus, surgical expansion of the hiatus allows the goals of surgery to be achieved. This procedure, which is technically easier and less invasive with regard to the vulnerable spinal cord than the closure of the dural defect, could be a viable alternative for the treatment of this rare disease.

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Keisuke Watanabe, Keiji Hashizume, Masahiko Kawaguchi, Aki Fujiwara, Noriyuki Sasaoka, and Hitoshi Furuya

Object

Recent evidence has indicated that the efficacy of the epidural blood patch (EBP) in the treatment of spontaneous CSF hypovolemia (SCH) is still limited. Therefore, further improvement of the EBP technique is an important clinical challenge. The authors describe a series of cases of SCH treated with fluoroscopically guided placement of an EBP and followed up with subsequent spinal CT scans.

Methods

Thirteen patients with SCH that was proven on CT myelography studies underwent epidural puncture under fluoroscopic guidance and received an injection of a mixture of contrast medium and autologous blood. Contrast medium was injected to cover the area of CSF leakage during EBP guided by fluoroscopy, and the spread of the blood was subsequently evaluated using spinal CT scanning. If the amount of blood injected was insufficient to cover the leakage area, a second EBP was performed at a later date.

Results

At the first EBP procedure, a mixture with a mean volume of 9.4 ml (range 3–20 ml) was injected, and subsequent spinal CT scans revealed contrast enhancement in the desired epidural space in 12 of 13 patients. In 2 patients, a second EBP was required because of insufficient coverage of the leakage area or delayed recurrence of headache. In all patients, a complete recovery from orthostatic headache was obtained after the last EBP.

Conclusions

The results indicated that fluoroscopically guided EBP and subsequent spinal CT scans may provide a highly effective therapy in patients with SCH proven on CT myelography studies.

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Daisuke Sakai, Jordy Schol, Akihiko Hiyama, Hiroyuki Katoh, Masahiro Tanaka, Masato Sato, and Masahiko Watanabe

OBJECTIVE

The objectives of this study were to apply the simultaneous translation on two rods (ST2R) maneuver involving rods contoured with a convexity at the desired thoracic kyphosis (TK) apex level and to assess the effects on the ability to support triplanar deformity corrections, including TK apex improvement, in patients with hypokyphotic adolescent idiopathic scoliosis (AIS).

METHODS

Using retrospective analysis, the authors examined the digital records that included 2- to 4-week, 1-year, and 2-year postoperative radiographic follow-up data of female hypokyphotic (TK < 20°) AIS patients (Lenke type 1–3) treated with ST2R. The authors assessed the corrections of triplanar deformities by examining the main Cobb angle, TK, rib hump, apical vertebral rotation, Scoliosis Research Society 22-item questionnaire scores, and TK apex translocation. In order to better grasp the potential of ST2R, the outcomes were compared with those of a historical matched case-control cohort treated with a standard rod rotation (RR) maneuver.

RESULTS

Data were analyzed for 25 AIS patients treated with ST2R and 27 patients treated with RR. The ST2R group had significant improvements in the main Cobb angle and TK, reduction in the rib hump size at each time point, and a final correction rate of 72%. ST2R treatment significantly increased the kyphosis apex by an average of 2.2 levels. The correction rate was higher at each time point in the ST2R group than in the RR group. ST2R engendered favorable TK corrections, although the differences were nonsignificant, at 2 years compared with the RR group (p = 0.056). The TK apex location was significantly improved in the ST2R cohort (p < 0.001). At the 1-month follow-up, hypokyphosis was resolved in 92% of the ST2R cohort compared with 30% of the RR cohort.

CONCLUSIONS

Resolving hypokyphotic AIS remains challenging. The ST2R technique supported significant triplanar corrections, including TK apex translocation and restoration of hypokyphosis in most patients. Comparisons with the RR cohort require caution because of differences in the implant profile. However, ST2R significantly improved the coronal and sagittal corrections. It also allowed for distribution of correctional forces over two rod implants instead of one, which should decrease the risk of screw pullout and rod flattening. It is hoped that the description here of commercially available reducers used with the authors’ surgical technique will encourage other clinicians to consider using the ST2R technique.

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Masahiko Watanabe, Daisuke Sakai, Yukihiro Yamamoto, Masato Sato, and Joji Mochida

Object

Extension teardrop fracture of the axis is an extremely rare cervical spinal injury. The classic clinical features, which have mainly been described by radiologists rather than spine surgeons, include its occurrence in elderly patients with osteoporosis, an association with minimal or no prevertebral soft-tissue swelling, and an absence of associated neurological deficit. However, recent case studies indicate notable exceptions to these clinical features, although few studies have investigated osteoporosis in these patients. The purpose of the present study was to clarify the clinical features of extension teardrop fracture of the axis.

Methods

The authors retrospectively reviewed data obtained in 13 patients with regard to their injury etiology, neurological deficit, treatment and outcome (residual neck pain), and imaging findings (size and displacement of the fragment, C2–3 subluxation, disc injury, and osteoporosis of the axis).

Results

Extension teardrop fracture of the axis constituted 11.6% of upper cervical spinal injuries at the authors' institute. The mean age of the patients was 49.5 years and distinct osteoporosis was identified in only 1 patient. A C2–3 subluxation was observed in 2 patients, in whom the displacement of the fragment was significant, although its size did not appear to have an effect. Magnetic resonance imaging, undertaken in 7 patients within 48 hours of injury, showed no disc injuries. Instability of the cervical spine was absent in all patient at follow-up. Only one patient underwent surgery for the presenting symptoms of dysphagia. The other patients were treated conservatively. The authors examined 9 patients directly; these patients had bony fusion and did not complain of neck pain, except for a patient with traumatic spondylolisthesis.

Conclusions

Extension teardrop fracture of the axis is generally caused by hyperextension of the cervical spine caused by a direct high-energy blow to the forehead or mandible. Based on the present case study, the authors believe that osteopenia and older age should not be considered risk factors. Most patients with an extension teardrop fracture of the axis can be treated conservatively, and surgical intervention may only be indicated for specific cases, such as those in which a patient presents with dysphagia or with other complicated fractures.

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Takehiko Takagi, Yosuke Ogiri, Ryu Kato, Mitsuhiko Kodama, Yusuke Yamanoi, Wataru Nishino, Yoshihisa Masakado, and Masahiko Watanabe

An amputated nerve transferred to a nearby muscle produces a transcutaneously detectable electromyographic signal corresponding to the transferred nerve; this technique is known as targeted muscle reinnervation (TMR). There are 2 issues to overcome to improve this technique: the caliber and the selectivity of the transferred nerve. It is optimal to select and transfer each motor fascicle to achieve highly developed myoelectric arms with multiple degrees-of-freedom motion. The authors report on a case in which they first identified the remnant stumps of the amputated median and radial nerves and then identified the sensory fascicles using somatosensory evoked potentials. Each median nerve fascicle was transferred to the long head branch of the biceps or the brachialis branch, while the short head branch of the biceps was retained for elbow flexion. Each radial nerve fascicle was transferred to the medial or lateral head branch of the triceps, while the long head branch of the triceps was retained for elbow extension. Electrophysiological and functional tests were conducted in the reinnervated muscles. Functional and electrophysiological improvement was noted, with marked improvement in the identification rate for each digit, forearm, and elbow motion after the selective nerve transfers. The authors note that more selective nerve transfers may be required for the development of prostheses with multiple degrees of freedom.

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Masahiko Watanabe, Daisuke Sakai, Daisuke Matsuyama, Yukihiro Yamamoto, Masato Sato, and Joji Mochida

Object

The purpose of this study was to identify risk factors for surgical site infection after spine surgery, noting the amount of saline used for intraoperative irrigation to minimize wound contamination.

Methods

The authors studied 223 consecutive spine operations from January 2006 through December 2006 at our institute. For a case to meet inclusion criteria as a site infection, it needed to require surgical incision and drainage and show positive intraoperative cultures. Preoperative and intraoperative data regarding each patient were collected. Patient characteristics recorded included age, sex, and body mass index (BMI). Preoperative risk factors included preoperative hospital stay, history of smoking, presence of diabetes, and an operation for a traumatized spine. Intraoperative factors that might have been risk factors for infection were collected and analyzed; these included type of procedure, estimated blood loss, duration of operation, and mean amount of saline used for irrigation per hour. Data were subjected to univariate and multivariate logistic regression analyses.

Results

The incidence of surgical site infection in this population was 6.3%. According to the univariate analysis, there was a significant difference in the mean duration of operation and intraoperative blood loss, but not in patient age, BMI, or preoperative hospital stay. The mean amount of saline used for irrigation in the infected group was less than in the noninfected group, but was not significantly different. In the multivariate analysis, sex, advanced age (> 60 years), smoking history, and obesity (BMI > 25 kg/m2) did not show significant differences. In the analysis of patient characteristics, only diabetes (patients receiving any medications or insulin therapy at the time of surgery) was independently associated with an increased risk of surgical site infection (OR 4.88). In the comparison of trauma and elective surgery, trauma showed a significant association with surgical site infection (OR 9.42). In the analysis of surgical factors, a sufficient amount of saline for irrigation (mean > 2000 ml/hour) showed a strong association with the prevention of surgical site infection (OR 0.08), but prolonged operation time (> 3 hours), high blood loss (> 300 g), and instrumentation were not associated with surgical site infection.

Conclusions

Diabetes, trauma, and insufficient intraoperative irrigation of the surgical wound were independent and direct risk factors for surgical site infection following spine surgery. To prevent surgical site infection in spine surgery, it is important to control the perioperative serum glucose levels in patients with diabetes, avoid any delay of surgery in patients with trauma, and decrease intraoperative contamination by irrigating > 2000 ml/hour of saline in all patients.