Department of Anatomy, Sri Aurobindo Institute of Medical Sciences (SAIMS), Indore-Ujjain Highway, Bhawrasala, Indore, Madhya Pradesh 452 010, India.
Spine J. 2010 Oct;10(10):910-5. doi: 10.1016/j.spinee.2010.07.392.
Transitional states of vertebrae at the lumbosacral junction are associated with low back pain. Lumbarization may present as partial (incomplete separation of S1-S2 bodies and their neural arches) or complete separation of the S1 from the S2 segment in a sacrum. Separation of S1 entails alteration of the anatomy at the lumbosacral junction that affects load bearing at the region.
To 1) identify characteristic structural features in sacra associated with lumbarization of the S1 sacral element; 2) compare linear dimensions and surface areas in such sacra with that of the normal samples; 3) calculate relative contributions of different dimensions in the variant sacral corpuses by working out indices; and 4) analyze load bearing at these sacra in light of their altered morphology.
Three hundred thirty-two dried human sacra were measured for specific dimensions and surface areas. They were screened for partial or complete lumbarization of the S1 segment.
All parameters and indices of the lumbarized specimen were compared with those in the normal sacra.
Seven linear dimensions and five surface areas were measured in 332 sacra. Nine indices were formulated from them. Sacra with partial or complete lumbarization of S1 were analyzed for all the parameters and evaluated for their morphological variations and traits.
A total of 3.9% of sacra presented lumbarization, seven (2.1%) with partial and six (1.8%) with complete separation of the S1. Sacrum with partial lumbarization presented parameters similar to the normal variety. Auricular surfaces in these sacra were situated lower than normal with negligible contribution from the S1 segments. Parameters in sacral samples showing complete separation of S1 (with remaining S2-S5 segments) were smaller than normal dimensions except for some. These "baseline" (S2-S5) sacra transmitted load to the sacroiliac joints via the S2 and S3 elements. Four of six of these samples demonstrated unilateral or bilateral accessory facets between the transverse elements of the free S1 segment and the ala of the remaining sacrum (formed by S2). Significant load passed through the accessory articulations that abutted near the sacroiliac joints. A good number of these sacra showed highly attenuated laminae and at times presented incomplete fusion at the spines (spina bifida).
Lumbarization involved distinct anatomical alterations at the S1-S2 junctions. Partially lumbarized samples showed 1) gap (mean 1.43 mm) between S1 and S2 bodies; 2) incomplete separation between S1 and S2 neural arch elements with the S1 arches resembling lumbar laminae; 3) well-developed "baseline" (S2-S5) segments; and 4) "low-down" (positioned at S2-S3) auricular surfaces. Complete separation of S1 involved 1) smaller overall dimensions with diminished facet depth, sacral height, and facet area at S1; 2) auricular surface areas comparable to the normal and greater than those found in the partially lumbarized specimen; 3) large "baseline" (S2-S5) sacra with "high-up" auricular surfaces (positioned at S2-S3); 4) occasional S1-S2 accessory articulations; and 5) small zygapophyseal joints and attenuated sacral laminae with high sacral hiatuses associated at times, with "spina bifida."
腰骶关节的椎体过渡状态与下腰痛有关。腰椎化可能表现为 S1-S2 体部和神经弓的部分（不完全分离）或 S1 从骶骨的 S2 段完全分离。S1 的分离导致腰骶关节的解剖结构发生改变，从而影响该区域的承重能力。
1）确定与 S1 骶骨元素腰椎化相关的骶骨的特征结构；2）比较此类骶骨与正常样本的线性尺寸和表面积；3）通过计算指数来计算不同尺寸在变体骶骨体中的相对贡献；4）根据其改变的形态分析这些骶骨的承重能力。
测量了 332 个干燥的人骶骨的特定尺寸和表面积。对它们进行筛选，以确定 S1 节段是否存在部分或完全腰椎化。
所有参数和指数的腰椎化标本与正常骶骨进行比较。
在 332 个骶骨中测量了 7 个线性尺寸和 5 个表面积。从中制定了 9 个指数。对具有 S1 部分或完全腰椎化的骶骨进行了所有参数的分析，并对其形态变化和特征进行了评估。
共有 3.9%的骶骨出现腰椎化，其中 7 例（2.1%）为部分腰椎化，6 例（1.8%）为完全腰椎化。具有部分腰椎化的骶骨表现出与正常类型相似的参数。这些骶骨的耳状面位置较低，与 S1 节段的贡献可忽略不计。完全分离 S1 的骶骨样本（剩余 S2-S5 节段）的参数小于正常尺寸，除了一些参数。这些“基线”（S2-S5）骶骨通过 S2 和 S3 节段将负荷传递到骶髂关节。在这 6 个样本中有 4 个显示了在自由 S1 节段的横突之间和剩余骶骨的翼（由 S2 形成）之间存在单侧或双侧副关节面。大量的负荷通过毗邻骶髂关节的副关节面传递。这些骶骨中有相当数量的表现出高度衰减的椎板，有时在棘突处表现出不完全融合（脊柱裂）。
腰椎化涉及 S1-S2 交界处的明显解剖改变。部分腰椎化样本表现为 1）S1 和 S2 体之间存在间隙（平均 1.43 毫米）；2）S1 和 S2 神经弓之间不完全分离，S1 弓类似于腰椎椎板；3）发育良好的“基线”（S2-S5）节段；和 4）“低位”（位于 S2-S3）耳状面。S1 的完全分离涉及 1）整体尺寸较小，S1 面关节深度、骶骨高度和关节面积减小；2）耳状面面积与正常相比可比拟，大于部分腰椎化样本；3）“高位”（位于 S2-S3）耳状面的较大“基线”（S2-S5）骶骨；4）偶尔的 S1-S2 副关节面；和 5）小的关节突关节和衰减的骶骨椎板，有时伴有高骶骨裂，伴有“脊柱裂”。
