肩峰とは
以下は「船戸和弥のホームページ」の解説文となる。
「肩甲棘そのものは、尖端が扁平な大突起となって関節窩を越えて突き出ている。この部分を特に肩峰（肩甲棘から肩峰にかけて僧帽筋がつき、三角筋が起こる）と呼ばれ、その突起近くの内側面には鎖骨と連結する小楕円形の関節面（輪郭はあまり明瞭でない）がある。肩甲棘のつけ根（肩甲骨背側面から起こる基部）の外側端の所では、棘上窩と棘下窩が関節窩のすぐそばでたがいに交通している。」
そして以下は「Wikipedia」の解説文となる。
「In human anatomy, the acromion (from Greek: akros, "highest", ?mos, "shoulder", plural: acromia) is a bony process on the scapula (shoulder blade). Together with the coracoid process it extends laterally over the shoulder joint. The acromion is a continuation of the scapular spine, and hooks over anteriorly. It articulates with the clavicle (collar bone) to form the acromioclavicular joint.
Structure: The acromion forms the summit of the shoulder, and is a large, somewhat triangular or oblong process, flattened from behind forward, projecting at first lateralward, and then curving forward and upward, so as to overhang the glenoid cavity.[1]
Surfaces: Its superior surface, directed upward, backward, and lateralward, is convex, rough, and gives attachment to some fibers of the deltoideus, and in the rest of its extent is subcutaneous. Its inferior surface is smooth and concave.[1]
Borders: Its lateral border is thick and irregular, and presents three or four tubercles for the tendinous origins of the deltoid. Its medial border, shorter than the lateral, is concave, gives attachment to a portion of the trapezius, and presents about its center a small oval surface for articulation with the acromial end of the clavicle.[1]
Variation: There are three morphologically distinct types of acromia and a correlation between these morphologies and rotator cuff tear:[2]
Type |
Prevalence |
Angle of
anterior slope |
Rotator
cuff tear |
Flat |
17.1% |
13.18 |
3.0% |
Curved |
42.9% |
29.98 |
24.2% |
Hooked |
39.3% |
26.98 |
69.8% |
Os acromiale: The acromion has four ossification centers called (from tip to base) pre-acromion, meso-acromion, meta-acromion, and basi-acromion. In most cases, the first three fuse at 15–18 years, whereas the base part fuses to the scapular spine at 12 years. However, in between 1% and 15% of cases, this osseous union fails and the acromion remains a separate bone. This condition is referred to as os acromiale, but rarely causes pain. Earlier estimates of its prevalence were as low as 1.4%, and this higher estimate was made by Sammarco in the year 2000, based on radiographic and anatomical studies.[3][4]
Four types of os acromiale can be distinguished:[5]
- ・A non-union between the meso- and meta-acromia, the most common or typical os acromiale
- ・A non-union between the pre- and meso-acromia
- ・A non-union between the pre- and meso-acromia; and between the meso- and meta-acromia, atypical
- ・A non-union between the pre- and meso-acromia; between the pre- and meso-acromia; and between the meta- and basi-acromia
This feature was common in skeletons recovered from the Mary Rose shipwreck: it is thought that in those men, much archery practice from childhood on with the mediaeval war bow (which needs a pull three times as strong as the modern standard Olympic bow) pulled at the acromion so much that it prevented bony fusion of the acromion with the scapula.
Although historically regarded as an incidental finding, the os acromiale may occasionally produce symptoms from subacromial impingement or instability at the site of non-union.[6] Dynamic US evaluation may demonstrate hypermobility of the non-union during shoulder motion or graded compression with the probe in symptomatic individuals.[7]」
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