Background

The spina musculi recti lateralis (SMRL) is often visible along the lateral rim of the superior orbital fissure (SOF). Aim of this study is to characterize SMRL morphology and topography relative to known bony landmarks.

Methods

Orbits from 291 adult dry skulls and from 60 CT scans were analyzed to measure the distance between the SMRL and the SOF or the inferior orbital fissures (IOF) as well as its height, width and orientation. Processes other than SMRLs were also recorded. Fetal skulls were observed for comparison with adult samples.

Results

Forty-one per cent of orbits on dry skulls and 43.3% by CT showed an SMRL. Additional 32.9% of orbits on dry skulls had processes with a different shape. On average, SMRL were orientated almost along the transverse plane and showed implant bases as wide as 141.9° or as narrow as 36.8°. SMRLs were close to the infero-posterior angle of the orbital plate of the sphenoid, 1.21 ± 0.84 mm in front of the SOF, 5.8 ± 1.9 mm above the IOF and 12 ± 2.3 mm from the anterior end of the SOF. They were 1.58 ± 0.64 mm high and did not show any age or sex-related prevalence. By CT, the SMRL appeared as the insertion site for the lateral rectus, tendinous ring and, sometimes, inferior rectus.

Conclusions

The SMRL is a process of the sphenoidal orbital plate rather than of the SOF. It is also a reliable landmark for the insertion of the tendinous ring and lateral rectus. Orbital surgeons should be aware of this common variant of the orbital apex.

中文翻译：

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脊柱外侧直肌的临床解剖学：蝶骨大翼经常被忽视的变异

背景

沿着眶上裂 (SOF) 的外侧边缘经常可以看到脊柱外侧直肌 (SMRL)。本研究的目的是表征相对于已知骨标志的 SMRL 形态和地形。

方法

对 291 个成人干头骨和 60 个 CT 扫描的眼眶进行了分析，以测量 SMRL 和 SOF 或眶下裂 (IOF) 之间的距离及其高度、宽度和方向。除了 SMRL 之外的过程也被记录。观察胎儿头骨以与成人样本进行比较。

结果

干燥头骨上 41% 的眼眶和 CT 检测显示 43.3% 的眼眶存在 SMRL。另外 32.9% 的干燥头骨轨道具有不同形状的突起。平均而言，SMRL 几乎沿横向平面定向，种植体基底部宽达 141.9°，窄达 36.8°。SMRL 靠近蝶骨眶板下后角，位于 SOF 前方 1.21 ± 0.84 mm，位于 IOF 上方 5.8 ± 1.9 mm，距 SOF 前端 12 ± 2.3 mm。它们的高度为 1.58 ± 0.64 毫米，并且没有显示出任何与年龄或性别相关的患病率。通过 CT 检查，SMRL 似乎是外直肌、腱环，有时甚至是下直肌的插入部位。

结论

SMRL 是蝶骨轨道板的过程，而不是 SOF 的过程。它也是腱环和外直肌插入的可靠标志。眼眶外科医生应该意识到这种常见的眼眶顶端变异。