Limbs : Upper Limb 77 



The omohyoid fascia is fastened to the conoid ligament and base of the coracoid 

 process, passes from this on to the upper margin of the suprascapular ligament, and 

 so gains the upper border of the bone behind the notch : here it encloses the Omo- 

 hyoid muscle which arises from this part of the bone. Further back on the upper 

 border, near the inner angle, fibres of Levator anguli scapulae are inserted, and their 

 attachment is continued round the angle on to the vertebral border as far as the " base " 

 of the spine. Here the lesser Rhomboid finds insertion, and below the level of the 

 spine the Rhomboideus major insertion extends down on the border nearly to the 

 lower angle. 



The axillary border is a secondary border, not present in the young bone, in which this margin 

 of the body is formed directly by the ventral bar : the adult border is slowly extended over this 

 and partly round it as the Subscapularis grows, and thus accurately marks the extent of that 

 muscle. 



The bone is laid obliquely on the upper, outer, and back aspect of the thorax, 

 so that its ventral surface really looks inwards as much as forwards, and in addition 

 slightly downwards. Put in this position it forms with its front muscles the posterior 

 (postero-external) wall of the axilla, being held out through its clavicular support and 

 slung up by its muscular attachments to the skull and neck above it. When the 

 clavicle is broken the bone and arm are no longer held out, but swing inwards on the 

 muscular attachments, being displaced downwards and inwards through a small arc 

 of a circle that has its centre at the muscular origins : this leads to depression of the 

 outer fragment of the broken clavicle below the inner, which is thus prominent under 

 the skin. True raising of the inner fragment occurs to a certain extent from unopposed 

 action of Sterno-mastoid, but it is limited by the costo-clavicular ligament, and a 

 good deal of the upward displacement is only apparent, the result of the lowering of 

 the outer piece. At the same time the inward and downward movement of the scapula 

 can only take place on the dorsal aspect of the trunk, so that the outer fragment of 

 the clavicle is also brought to a somewhat posterior plane, thus increasing the apparent 

 prominence of the inner portion. 



In the normal state the upper end of the vertebral border is nearer the middle 

 line than the lower, being only about 2 to 3 inches from it. The lower angle varies, 

 in this relation, with the position of the arm and the attitude of the shoulders. The 

 scapula is separated from the ribs and intercostal muscles by Subscapularis and Serratus 

 magnus, and in the ord nary position of rest the angle lies over the seventh rib or 

 space. The angle is not kept against the chest by the Serratus magnus, but by the 

 upper fibres of Latissimus dorsi (Fig. 39), which hold it like a strap against the chest- 

 wall : under this it can move round the wall for a distance of about an inch and a half 

 as a result of the action of Serratus magnus or Trapezius. 



The upper end of the bone is usually over the second rib. The base of the spine 

 can be located through the skin and is opposite the third dorsal spine : from this the 

 spine can be traced upwards and outwards to the acromion. The spine and acromion 

 are the only subcutaneous parts of the bone, but the inner and outer borders can be 

 felt through the muscles, and the coracoid process can be recognised through the 

 Deltoid about an inch below the junction of the middle and outer thirds of the clavicle.* 



The scapula rotates on the clavicular attachment of the coraco -clavicular liga- 

 ments, particularly of the conoid ligament, but the first part of its movement is round 

 an axis passing through the front part of the acromial joint. The partial upturning 



* The glenoid is practically on the same level as the base of the spine when the arm is hanging by the 



side. 



