Takashi Asazuma

An Experimental Study of the Regeneration of the Intervertebral Disc With an Allograft of Cultured Annulus Fibrosus Cells Using a Tissue-Engineering Method

Study Design. Cultured annulus fibrosus cells within an atelocollagen honeycomb-shaped scaffold with a membrane seal were allografted into the lacunas of intervertebral discs of which the nucleus pulposus had been vaporized using an indocyanine green dye-enhanced laser. Regeneration of the intervertebral disc was assessed based on the viability and histologic status of the allografted annulus fibrosus cells, as well as the prevention of narrowing disc space. Objectives. To study the regeneration of intervertebral disc after laser discectomy using tissue-engineering methods. Summary of Background Data. Intervertebral disc is the most avascular tissue in the human body, and its ability to regenerate is as low as that of articular cartilage. When nucleotomy is carried out, little regeneration of the annulus fibrosus is observed; consequently, intervertebral disc degeneration is inevitable. Methods. Annulus fibrosus cells isolated from 20 Japanese white rabbits were labeled with a PKH-26 fluorescent dye and seeded within an atelocollagen honeycomb-shaped scaffold with a membrane seal. Annulus fibrosus cells cultured in atelocollagen honeycomb-shaped scaffold with a membrane seal for 1 week were allografted into the lacunas of intervertebral discs of recipient rabbit of which the nucleus pulposus had been vaporized using an ICG dye-enhanced laser. Soft radiograph photographs of the lumbar spine of these anesthetized rabbits were taken, the disc space measured, and the lumbar spine extracted 2, 4, 8, and 12 weeks after the operation. The proliferation of allografted annulus fibrosus cells with 5-bromo-2′-deoxyuridine/PKH-26 fluorescent labels was assessed using consecutive frozen sections, and safranin-O staining carried out for histologic evaluation. Results. The allografted annulus fibrosus cells were viable and showed proliferation activity with a hyaline-like cartilage being produced. The narrowing of the intervertebral disc space of the cell translation group was significantly prevented, as shown, up to 12 postoperative weeks. Conclusion. The annulus fibrosus cells cultured in an ACHMS-scaffold were allografted into the lacunae of nucleus pulposus (obtained using laser vaporization), as well as the hole of annulus fibrosus (obtained by laser fiber insertion) of rabbit intervertebral discs. These cells were viable and showed cell proliferation in the disc tissues of recipients.

In vivo analysis of insertional torque during pedicle screwing using cortical bone trajectory technique.

Study Design. The insertional torque of pedicle screws using the cortical bone trajectory (CBT) was measured in vivo. Objective. To investigate the effectiveness of the CBT technique by measurement of the insertional torque. Summary of Background Data. The CBT follows a mediolateral and caudocephalad directed path, engaging with cortical bone maximally from the pedicle to the vertebral body. Some biomechanical studies have demonstrated favorable characteristics of the CBT technique in cadaveric lumbar spine. However, no in vivo study has been reported on the mechanical behavior of this new trajectory. Methods. The insertional torque of pedicle screws using CBT and traditional techniques were measured intraoperatively in 48 consecutive patients. A total of 162 screws using the CBT technique and 36 screws using the traditional technique were compared. In 8 of 48 patients, the side-by-side comparison of 2 different insertional techniques for each vertebra were performed, which formed the H group. In addition, the insertional torque was correlated with bone mineral density. Results. The mean maximum insertional torque of CBT screws and traditional screws were 2.49 ± 0.99 Nm and 1.24 ± 0.54 Nm, respectively. The CBT screws showed 2.01 times higher torque and the difference was significant between the 2 techniques (P < 0.01). In the H group, the insertional torque were 2.71 ± 1.36 Nm in the CBT screws and 1.58 ± 0.44 Nm in the traditional screws. The CBT screws demonstrated 1.71 times higher torque and statistical significance was achieved (P < 0.01). Positive linear correlations between maximum insertional torque and bone mineral density were found in both technique, the correlation coefficient of traditional screws (r = 0.63, P < 0.01) was higher than that of the CBT screws (r = 0.59, P < 0.01). Conclusion. The insertional torque using the CBT technique is about 1.7 times higher than the traditional technique. Level of Evidence: 2

Tissue engineering of the intervertebral disc with cultured annulus fibrosus cells using atelocollagen honeycomb-shaped scaffold with a membrane seal (ACHMS scaffold).

The objective of the study was to investigate the regeneration of intervertebral discs after laser discectomy using tissue engineering procedures. Annulus fibrosus (AF) cells from the intervertebral discs of Japanese white rabbits were cultured in an atelocollagen honeycomb-shaped scaffold with a membrane seal (ACHMS scaffold), to produce a high-density, three-dimensional culture for up to 3 weeks. Although the DNA content in the scaffold increased at a lower rate than that in the monolayer culture, expression of type ll collagen and glycosaminoglycan accumulation in the scaffold were at higher levels than in the monolayer. The AF cells that had been cultured in the scaffold for 7 days were allografted into the lacunae of intervertebral discs of recipients (40 rabbits, 14–16 weeks old; average weight, 3.2kg), whose nucleus pulposus (NP) had been vaporised with an ICG dye-enhanced laser. The allografted cultured AF cells survived and produced hyaline-like cartilage. Furthermore, the narrowing of the intervertebral disc space of the cell-containing scaffold insertion groups was significantly inhibited after 12 post-operative weeks.

Realignment of postoperative cervical kyphosis in children by vertebral remodeling

Study Design This study analyzed radiographically change in the sagittal curvature of the cervical spine after atlantoaxial (C1–C2) posterior fusion in children. Objectives This study clarified the process of spinal remodeling after postoperative cervical deformation in children. Summary of Background Data Postoperative spinal deformations in children are observed frequently. However, there have been only a few reports on postoperative changes in the sagittal curvature of the cervical spine and spinal remodeling after those changes. Methods Between 1979 and 1991, there was a total of 12 children who underwent C1–C2 posterior fusions. The average age at the time of surgary was 9.8 years. The alignment of the cervical spine was classified into four groups (lordosis, straight, kyphosis, and swan-neck deformity). radiographic findings suggestive of the remodeling were as follows: 1) new bone formation on the anterior vertabral cortex, and 2) increase in body/canal ratio (BCR). The follow-up period averaged 6.2 years. Results Postoperative cervical malalignment (kyphosis or swan-neck deformity) occurred in four patients. In all four patients, new bone forma tion and increase in BCR at the apex of kyphosis were observed. Therefore, there was gradual improvement of the malalignment by vertebral remodeling. This phenomenon was not observed in eight patients with normal alignment. Conclusion Realignment of postoperative cervical kyphosis by vertebral remodeling was observed in children. the results of this study suggested that remodeling occurred even in the spine, which was similar to the remodeling in long bones.

Postoperative change of the cross-sectional area of back musculature after 5 surgical procedures as assessed by magnetic resonance imaging.

Many investigators have reported that persistent low back pain may occur after posterior surgical intervention, and studies have investigated the histologic and histochemical changes in back muscle after posterior lumbar spine surgery. The purpose of the current study is to compare the pre- and postoperative cross-sectional area of the back musculature among 5 surgical groups including anterior lumbar interbody fusion, which has no direct invasion of the back musculature, using magnetic resonance imaging, and to correlate the clinical results with the degree of atrophy. The cross-sectional area of the back musculature was measured before and after surgery in T2-weighted axial magnetic resonance images using a computer-linked digitizer. The degree of atrophy (atrophy ratio) was calculated as a ratio of the postoperative cross-sectional area to the preoperative cross-sectional area. Clinical results were evaluated using the Japanese Orthopaedic Associations scores for the management of low back pain. Atrophy of the back musculature was confirmed in each group. However, no significant difference was seen in the atrophy ratio between the groups. Back musculature atrophy occurred even in anterior lumbar interbody fusion, which does not involve any direct surgery of the back muscle. A positive correlation was noted between the atrophy ratio and operation time only in posterior surgery, especially in nonfusion surgery. In conclusion, the current study suggests that a shorter operation time may minimize back muscle injury, and shows that factors inducing back musculature atrophy include not only direct invasion of the back muscle via a posterior approach, but also postoperative external fixation.

Intersegmental spinal flexibility with lumbosacral instrumentation. An in vitro biomechanical investigation.

Flexibility of the porcine lumbosacral spine was measured after application of six different types of surgical instrumentation, and in a control state. Fifteen adult pig spines were tested with flexion, extension, lateral bending, and axial rotation torques applied to the upper end with the pelvis fixed. Instrumentation was applied across two lumbar segments and the lumbosacral level (L5-6, L6-7, and L7-S1). Stereophotogrammetry was used to track markers applied to each vertebra. Intersegmental motion was measured as three angles and as the relative linear translation of adjacent transverse processes and spinous processes. Results showed that all instrumentation systems reduced intersegmental motion compared with the control state, except for minimal reduction at L5-6 by Harrington instrumentation in all loading directions, especially axial rotation. The pedicle screw systems were always the most rigid. After applying instrumentation, there were differences in the motion occurring at different anatomic levels, most commonly with the least motion occurring in the middle of the instrumented segment (L6-7). When intervertebral motion was expressed as the linear motion between adjacent spinous and transverse processes, the usual site of posterolateral fusion, it was 0.6 to 1.8 mm per degree of angular motion at the transverse processes and 1.3 to 2.1 mm per degree at spinous processes.

Morphometric measurement of cortical bone trajectory for lumbar pedicle screw insertion using computed tomography

Study Design: A morphometric measurement of cortical bone trajectory (CBT) for the lumbar pedicle screw insertion using computed tomography (CT). Objective: The aim of this study was to conduct a detailed morphometric measurement of the CBT. Summary of Background Data: The CBT is a novel lumbar pedicle screw trajectory, which follows a caudocephalad path sagittally and a laterally directed path in the transverse plane. The advantage associated with this modified technique is increased cortical bone contact, providing an enhanced screw purchase. However, little is known about the possible screw size or detailed direction of the trajectory. Methods: The CT scans of 100 adults who underwent examination for spinal problems were studied. A total of 470 lumbar vertebrae excluding spondylosis, malformation, and tumor were observed. In this trajectory, the starting point was supposed to be the junction of the center of the superior articular process and 1 mm inferior to the inferior border of the transverse process. The CT images were analyzed using 3-dimensional reconstruction software. The diameter, length, lateral angle to the vertebral sagittal plane, and cephalad angle to the vertebral horizontal plane of the trajectory were measured. Results: The mean diameter gradually increased from L1 to L5 (from 6.2 mm at L1 to 8.4 mm at L5). The mean length from L1 to L5 were 36.8, 38.2, 39.3, 39.8, and 38.3 mm, respectively. The lateral angle from L1 to L5 were 8.6, 8.5, 9.1, 9.1, and 8.8 degrees, respectively. The cephalad angle from L1 to L5 were 26.2, 25.5, 26.2, 26.0, and 25.8 degrees, respectively. Conclusions: The morphology of the pedicle, such as shape and pedicle axis angle, differed over the lumbar levels, our measurements demonstrated similar data excluding the diameter of the trajectory. There were no significant differences between each level of the lateral and cephalad angles.

Ependymomas of the spinal cord and cauda equina : An analysis of 26 cases and a review of the literature

Study design: Retrospective review. Objectives: To clarify the clinical features of patients with spinal ependymomas and to compare the clinical results between the patients in whom microsurgical technique and spinal cord monitoring were used intraoperatively and the patients in whom they were not used. Setting: Keio University Hospital, Tokyo, Japan. Methods: Twenty-six consecutive patients with spinal ependymomas were treated surgically between 1958 and 1995. All patients underwent tumor resection through a posterior approach. Complete tumor resection was possible in 15 patients (57.7%), and subtotal tumor resection (more than 90%) was done in two patients (7.7%). Only a partial tumor resection (less than 90%) was performed in the remainder of the patients (34.6%). The operative results of the patients were evaluated by the Japanese Orthopaedic Association Scoring System (JOA score) and its recovery rate. Results: The overall average recovery rate was 18.3%. The mean recovery rate was 14.4% in cervical lesion, 11.1% in thoracic lesion and 40% in lumbar lesion. The recovery rate of eight patients with cervical ependymomas who underwent tumor resection under both microscopic surgical procedure and intraoperative spinal cord monitoring was 37.1% although the recovery rate of the rest of the patients was −1.6%. There was a statistical difference between the two groups (P<0.02). The survival rate of patients following complete excision was statistically better compared to that of patients after incomplete resection. Conclusion: Both microsurgical technique and spinal cord monitoring are indispensable to achieve total removal of ependymomas and to obtain improvement of neurological recovery.

Surgical strategy for cervical dumbbell tumors based on a three-dimensional classification.

Study Design. Forty-two patients with cervical dumbbell tumors were analyzed retrospectively using a new three-dimensional classification. Objectives. To establish optimal surgical strategies, we considered shapes and three-dimensional locations of cervical dumbbell tumors based on diagnostic images and intraoperative findings. Summary of Background Data. Eden’s classification for dumbbell tumors of the spine, long considered a “gold standard,” no longer is sufficient to determine surgical strategy in view of recent advances in computed tomography and magnetic resonance imaging. Methods. Forty-two cervical dumbbell tumors were characterized according to transverse-section images (Toyama classification; nine types) and craniocaudal extent of intervertebral and transverse foraminal involvement (IF and TF staging; three stages each). Results. Type IIIa tumors, involving dura plus an intervertebral foramen, accounted for 50% of cases. A posterior approach was used in 35 patients; 7 others underwent a combined anterior and posterior approach. A posterior approach was used for all type IIa and IIIa tumors, and for some type IIIb (upper cervical), IV, and VI tumors; a combined posterior and anterior approach was used for type IIb and the remainder of type IV and VI. Reconstruction was performed using spinal instrumentation in 4 patients (9.5%). Resection was subtotal in 6 patients (14.3%) and total in 36 (85.7%). Conclusions. Systematic, imaging-based three-dimensional characterization of shape and location of cervical dumbbell tumors is essential for planning optimal surgery. The classification used here fulfills this need.

Reoperation rate and risk factors of elective spinal surgery for degenerative spondylolisthesis: minimum 5-year follow-up

BACKGROUND CONTEXT The favorable outcome of surgical treatment for degenerative lumbar spondylolisthesis (DS) is widely recognized, but some patients require reoperation because of complications, such as pseudoarthrosis, persistent pain, infection, and progressive degenerative changes. Among these changes, adjacent segmental disease (ASD) and same segmental disease (SSD) are common reasons for reoperation. However, the relative risks of the various factors and their interactions are unclear. PURPOSE The purpose of this study was to determine the longitudinal reoperation rate after surgery for DS and to assess the incidence and independent risk factors for ASD and SSD. STUDY DESIGN This study is a retrospective consecutive case series of patients with DS who were surgically treated. PATIENT SAMPLE We assessed 163 consecutive patients who were surgically treated for DS between 2003 and 2008. Individual patients were followed for at least 5 years after the initial surgery. OUTCOME MEASURES The primary end point was any type of second lumbar surgery. Radiographic measurements and demographic data were reviewed. We compared patients who underwent reoperation with those who did not. Logistic regression analysis was used to determine the relative risk of ASD and SSD in patients surgically treated for DS. METHODS Radiographic measurements and demographic data were reviewed. We identified the incidence and risk factors for reoperation, and we performed univariate and multivariate analyses to determine the independent risk factors for revision surgery for SSD and for ASD as the two distinct reasons for the reoperation. Age, gender, etiology, body mass index (BMI), and other radiographic data were analyzed to determine the risk factors for developing SSD and ASD. RESULTS The average patient age was 65.8 (50-81 years; 73 women and 90 men; mean follow-up, 5.9±1.6 years). Eighty-nine patients had posterior lumbar interbody fusion and 74 had laminotomies. Twenty-two patients had L3-L4 involvement and 141 had L4-L5 involvement. The cumulative reoperation rate was 6.1% at 1 year, 8.5% at 2 years, 15.2% at 3 years, 17.7% at 5 years, and 23.3% (38/163 patients) at the final follow-up. A significantly higher reoperation rate was observed for patients undergoing laminotomy than for patients undergoing posterior lumbar interbody fusion (33.8% vs. 14.4%, p=.01). Eighteen patients (11.0%) had SSD, and 13 patients (8.9%) developed ASD. Higher BMI (obesity) and greater disc height (greater than 10 mm) predicted the occurrence of SSD in the multivariate model (BMI=odds ratio 4.11 [95% confidence interval 1.29-13.11], p=.016; disc height=3.18 [1.03-9.82], p=.044), and gender (male) and facet degeneration (Fujiwara grade greater than 3) predicted the development of ASD in the multivariate model (gender=4.74 [1.09-20.45], p=.037; facet degeneration=6.31 [1.09-36.52], p=.039). CONCLUSIONS The incidence of reoperation in patients surgically treated for DS was 23.2% at a mean time of 5.9 years. A significantly higher incidence of reoperation was observed in patients treated with decompression alone compared with those treated with decompression and fusion. Body mass index and disc height were identified as independent risk factors for SSD, whereas male gender and facet degeneration were identified as independent risk factors for ASD. The results of this comprehensive review will guide spine surgeons in their preoperative planning and in the surgical management of patients with DS, thereby reducing the reoperation rate.