Akihiro Okada

Axial symptoms after cervical laminoplasty with C3 laminectomy compared with conventional C3-C7 laminoplasty: a modified laminoplasty preserving the semispinalis cervicis inserted into axis.

Study Design. Results of C4–C7 laminoplasty with C3 laminectomy and C3–C7 laminoplasty were compared. Objectives. To clarify prospectively whether the modified laminoplasty preserving the semispinalis cervicis inserted into C2 could reduce the axial symptoms compared with conventional laminoplasty reattaching the muscle to C2. Summary of Background Data. Intraoperative damage of the semispinalis cervicis is relevant to the development of axial symptoms after laminoplasty. In C3–C7 laminoplasty, however, it is difficult to preserve the muscle insertion into C2 while opening the C3 lamina. Methods. The axial symptoms of 40 patients (Group A) with C4–C7 laminoplasty with C3 laminectomy were compared with those of 16 patients (Group B) with C3–C7 laminoplasty. The cross-sectional areas of the cervical posterior muscles were measured on magnetic resonance images. Results. The number of patients with no postoperative axial symptoms increased (P = 0.035) from 19% to 52.5%, and the number of patients whose symptoms worsened after surgery decreased (P = 0.020) from 50% to 17.5%. The average atrophy rate of cross-sectional area was smaller (P < 0.001) in Group A (2.4%) than in Group B (10.8%). Conclusions. This method was less invasive to the cervical posterior muscles than C3–C7 laminoplasty. This is an effective procedure for preventing postoperative axial symptoms.

Adult scoliosis in syringomyelia associated with Chiari I malformation.

Study Design. In adult syringomyelia associated with Chiari I malformation, the spinal deformity, the configuration of cerebellar tonsillar descent, the configuration of syrinx, and the clinical evaluation before and after surgery were investigated. Objectives. To investigate the characteristics of the scoliosis in syringomyelia associated with Chiari I malformation. Summary of Background Data. In previous studies, the clinical characteristics of pediatric scoliosis associated with syringomyelia have been reported. Methods. In this study, 42 patients with syringomyelia were treated. All the patients were 20 years of age or older. They were divided into three groups: Group 1 comprising those without scoliosis, Group 2 composed of those with scoliosis of 10° or more but less than 20°, and Group 3 consisting of those with scoliosis of 20° or more. Investigations conducted with the three groups included determining the curve patterns of scoliosis, the degree of thoracic kyphosis, the configuration of cerebellar tonsillar descent, the configuration of syrinx, the morbidity period, and the clinical evaluation before and after surgery. Results. There were 12 patients in Group 1, 21 patients in Group 2, and 9 patients in Group 3. The concomitant rate of adult syringomyelia with scoliosis was 71.4%. As scoliosis advanced, the kyphotic angle also increased. The concordance in laterality between the cerebellar tonsil and curve convex was 70%. Findings showed that the more advanced the scoliosis was, the more aggravated the neurologic symptoms were, and the poorer the surgical outcomes tended to be. Conclusions. In adult syringomyelia with scoliosis, the morbidity period is long, the syrinx is long, the neurologic symptoms are aggravated, and the surgical outcomes tend to be poor.

Pathophysiological Role of Endothelin in Ectopic Ossification of Human Spinal Ligaments Induced by Mechanical Stress

Ossification of the posterior longitudinal ligament (OPLL) of the spine is characterized by progressive ectopic bone formation in the spinal ligament. To identify the genes related to ossification affected by mechanical stress during OPLL, analyses using cDNA microarray were carried out using cultured human spinal ligament cells that had been subjected to uniaxial cyclic stretching. Samples were obtained from a total of 14 patients: seven cervical or thoracic OPLL patients and seven control patients. Spinal ligament cells derived from tissues of OPLL (OPLL cells) and control (non-OPLL cells) patients were subjected to uniaxial sinusoidal cyclic stretching (0.5 Hz, 20% stretch) for various time periods (0–9 hours). cDNA microarrays revealed that ranges of distribution of both up- and downregulated genes evoked by cyclic stretching were significantly wider in OPLL cells than in non-OPLL cells. Increases in the mRNA expression of endothelin-1 (ET-1) as well as various marker genes related to ossification were also observed. mRNA expression of ET-1 and alkaline phosphatase was increased by mechanical stress in a time-dependent manner, while addition of ET-1 to static cultures of OPLL cells increased mRNA expression of alkaline phosphatase in a dose-dependent manner. During 9 hours of cyclic stretching, ET-1 release increased to about sixfold the amount observed in nonstretched cells. In non-OPLL cells, neither cyclic stretching nor ET-1 induced any increase in alkaline phosphatase expression. These results suggest that mechanical stress promotes the progression of ossification in OPLL cells through autocrine and/or paracrine mechanisms of ET-1.

Age-related changes in proteoglycans of human ligamentum flavum

Age-related changes in proteoglycans of human ligamentum flavum were studied using specimens obtained from patients divided into four age groups. The proteoglycans were purified by ion-exchange and gel-filtration chromatography. A low-molecular-weight proteoglycan with the same molecular size was present in all each age groups. Conversely, high-molecular-weight proteoglycan increased with advancing age. Properties of the sugar chains, glycosaminoglycans, in these proteoglycans were studied using cellulose acetate membrane electrophoresis and chondroitinase digestion. It was found that the high-molecular-weight proteoglycan consisted mainly of chondroitin 6-sulfate, whereas the low-molecular-weight proteoglycan consisted mainly of dermatan sulfate, although the ratio of chondroitin 6-sulfate increased with age. These results indicate that proteoglycans of human ligamentum flavum show changes in amount and composition with age.

Midline Spinous Process Splitting Laminoplasty Using Hydroxyapatite Spacers

Posterior decompression and reconstruction of the cervical spinal canal is a common treatment for cervical myelopathy. Since laminoplasty by midline splitting of the spinous processes was reported by Kurokawa in 1982 [1], we have used this method to treat cervical myelopathy due to spondylotic changes or ossification of the posterior longitudinal ligament (OPLL). Since 1986, we have used hydroxyapatite (HA) interspinous spacers instead of an iliac bone graft to maintain the enlargement of the cervical spinal canal [2]. There have been no problems with dislocation of the HA spacers, and good fusion has been achieved. The use of HA spacers eliminates the problems of buttock pain caused by harvesting autogenous bone from the posterior ilium. It also shortens the operating time,reduces intraoperative blood loss, and improves the range of motion below C2/3. Since 1995, we have also used a wire thread saw (T-saw) instead of an airtome for the splitting process.

Longitudinal length of the spinal cord after cervical laminoplasty

Abstract Purpose of study: In cases of cervical myelopathy, the relationship between surgical outcome after laminoplasty and the sagittal alignment is controversial. In our cases with OPLL of unexpected poor surgical outcome, we often found a straight, tense spinal cord on postoperative magnetic resonance imaging, (MRI). So we tried to measure a longitudinal length of the cervical spinal cord (LSC) as a new parameter. The purpose of this study is to prove our hypothesis that an increase of LSC after cervical laminoplasty may be a risk factor for poor surgical outcome. Methods used: Thirty-six patients (24 male and 12 female) with cervical myelopathy were operated on at an age of 33 to 76 years (average, 59 years). The follow-up period was 12 to 86 months (average, 39 months). There were 25 patients in the laminoplasty (LP) group (13 cervical spondylotic myelopathy and 12 OPLL) and 11 in the anterior fusion (AT) group as control (8 cervical spondylotic myelopathy and 3 OPLL). There were no significant differences in the age, sex and follow-up period between the two groups. We evaluated surgical outcome with the recovery rate with the scoring system for cervical myelopathy of the Japanese Orthopedic Association (JOA score). We used the sagittal T2-weighted MRI and computed LSC that was a summation of the distance of each spinal cord midpoint at the intervertebral line between the C1 upper line and the T1 vertebral upper line. We defined the LSC gap as the subtraction value from preoperative to last follow-up LSC. A plus quantity of LSC gap represents an increase of LSC after surgery. Mann-Whitney U test was used statistically and p values less than .05 were considered statistically significant. of findings: In the LP group, LSC gaps ranged from −21 to +4 mm (average, −1.0; SD, 4.9 mm). In the AF group, LSC gaps ranged from −5 to +7 mm (average, 0 mm; SD, 3.4 mm). There was no significant difference in LSC gaps and recovery rate between the two groups. In the LP group, seven cases (28%) had under −2 mm LSC gaps and six cases (24%) had over +2 mm LSC gaps, and recovery rate in seven cases under −2 mm LSC gaps ranged from 13% to 67% (average, 47%) and in six cases over +2 mm LSC gaps ranged from −200% to 20% (average, −53%). There was a significant difference between the cases under −2 mm LSC gap and the cases over +2 mm LSC gap (p=.025). Of six cases over +2 mm LSC gap, five cases had straight alignment and five cases had OPLL. In the AF group, four cases (36%) had over +2 mm LSC gaps, and recovery rate in the four cases ranged from 0% to 100% (average, 75%). There was significant difference between six cases over +2 mm LSC gaps in the group LP and four cases over +2 mm LSC gaps in the AF group (p=.049). Relationship between findings and existing knowledge: Chiba et al. proposed a new concept that the shortening in the longitudinal distance of the cervical spine caused by multiple disc space narrowing may have a certain impact on the postoperative results. We agreed with their hypothesis because of our first result that the patients with over +2 mm LSC gaps had worse surgical outcomes than under −2 mm LSC gaps. Moreover, five of the six cases with over +2 mm LSC gaps had OPLL and straight alignment. From the second result, anterior mass and dynamic motion played important roles in impeding the neurological recovery in the cases over +2 mm LSC gaps. Overall significance of findings: An increase of the longitudinal length of the spinal cord after cervical laminoplasty is a risk factor for poor surgical outcome. Disclosures: No disclosures. Conflict of interest: No conflicts.

The role of proteoglycans in ossification of spinal ligaments

Abstract Proteoglycans (PGs) are considered to have important functions that influence the properties of the extracellular matrix. In this study, PGs were purified from human yellow ligaments by ion-exchange and gel-filtration chromatography. Age-related changes in PG and glycosaminoglycan (GAG) chains were studied using specimens obtained from patients divided into four age groups. Small PGs were present in similar amounts in all groups. Conversely, large PGs increased with aging. GAG in large PGs mainly consisted of chondroitin 6-sulfate (Ch6S), whereas in small PGs, it mainly consisted of dermatan sulfate (DS), although the ratio of Ch6S increased with aging. The major components of GAG chains in normal and ossified yellow ligaments were DS and ChS, respectively. Also, the affinity of high-performance liquid chromatography (HPLC) on hydroxyapatite columns showed that DS chains bound to the hydroxyapatite more strongly than ChS chains. These results indicate that the change from DS to ChS is important in age-related changes and ossification of the ligaments, because ChS chains, which have a lower affinity for hydroxyapatite, might contribute to facilitation of the crystallization of hydroxyapatite.