Goto Shin-ichi, Umehara Jutaro, Aizawa Toshimi, Kokubun Shoichi
Department of Orthopaedic Surgery, Senboku Kumiai General Hospital, Daisen, Akita, Japan.
J Orthop Sci. 2010 Jan;15(1):97-103. doi: 10.1007/s00776-009-1427-7. Epub 2010 Feb 12.
Cervical myelopathy is more common among Japanese than Westerners. The shorter anteroposterior diameter of the cervical spinal canals (AP diameter) is its probable cause. In recent years, builds of younger Japanese have become larger and been approaching those of Westerners. The purpose of this study was to investigate whether the cervical spinal canal had enlarged in the younger Japanese as well as any cross-sectional improvement in their builds.
The subjects included 300 men and 300 women who were healthy and without symptoms related to the cervical spine. They were divided into six age groups at 10-year intervals from the twenties to the seventies. Height, body weight, and arm span were measured as physical factors. Using lateral dynamic radiographs of the cervical spine, the AP diameter from C3 to C6 in the neutral position and Penning's jaw diameter in extension (jaw diameter) from C2/3 to C5/6 were measured. The number of trapezoid-shaped vertebral bodies with a thickened posterior margin were also counted as such thickening might be one of the causes of spinal canal narrowing. Statistical analysis was performed for the following associations in both sexes: (1) age and physical factors; (2) age and the AP diameter; (3) age and jaw diameter; and (4) the difference of the AP diameter of the canal within and outside the trapezoid-shaped deformity of the vertebral body.
In both men and women, the younger generations statistically had a larger height, arm span, and AP diameter. Older generations showed a significantly narrower jaw diameter at all measured spinal levels in both sexes. Trapezoid-shaped vertebral bodies were found in 3.5% of the men and in 1.3% of the women in their fifties, sixties, and seventies, which statistically had no effect on the AP diameter being wider in the younger generations.
Younger generations had larger builds and a wider canal of the cervical spine. A narrow spinal canal is a fundamental risk factor for cervical myelopathy. Therefore, cervical myelopathy might be expected to decrease in Japan in the near future when the present younger generations have aged.
脊髓型颈椎病在日本人中比西方人更常见。颈椎管前后径较短可能是其原因。近年来，日本年轻人的体型变大，已接近西方人。本研究的目的是调查日本年轻人的颈椎管是否也已扩大，以及他们体型的横断面是否有所改善。
研究对象包括300名男性和300名女性，他们身体健康，无颈椎相关症状。他们按十年间隔分为六个年龄组，从二十多岁到七十多岁。测量身高、体重和臂展作为身体因素。使用颈椎侧位动态X线片，测量中立位时C3至C6的前后径以及伸展位时C2/3至C5/6的彭宁下颌径（下颌径）。还对后缘增厚的梯形椎体数量进行计数，因为这种增厚可能是椎管狭窄的原因之一。对男女的以下关联进行了统计分析：（1）年龄与身体因素；（2）年龄与前后径；（3）年龄与下颌径；（4）椎体梯形畸形内外椎管前后径的差异。
在男性和女性中，年轻一代在统计学上身高、臂展和前后径更大。在所有测量的脊柱节段，年长一代的下颌径在男女中均显著更窄。在五十多岁、六十多岁和七十多岁的男性中，3.5%发现有梯形椎体，女性中为1.3%，这在统计学上对年轻一代前后径变宽没有影响。
年轻一代体型更大，颈椎管更宽。椎管狭窄是脊髓型颈椎病的一个基本危险因素。因此，当目前的年轻一代变老时，预计在不久的将来日本脊髓型颈椎病的发病率可能会下降。
