ciw. xi. j THE CLAVICLE. 195 



against the thorax, with the result that its outer 

 extremity (and with it, of course, the outer fragment 

 of the clavicle) is dragged outwards and backwards. 

 Some surgeons, recognising this important action of the 

 scapula in remedying the displacement in these cases, 

 strap the scapula firmly against the trunk, while at 

 the same time they elevate the arm. 



Fractures due to direct violence are usually 

 transverse, and may be at any part of the bone. 

 When about the middle third they present the 

 displacement just described. When the fracture is 

 between the conoid and trapezoid ligaments no dis- 

 placement is possible. When beyond these ligaments 

 the outer end of the outer fragment is carried forwards 

 by the pectorals and serratus, and its inner end is 

 a little drawn up by the trapezius. In this fracture 

 there is no general displacement downwards of the 

 outer fragment, since it cannot move in that direction 

 unless the scapula go with it, and the scapula remains 

 fixed by the coraco-clavicular ligaments to the inner 

 fragment of the clavicle. 



The clavicle may be broken by muscular violence 

 alone. Polaillon, from a careful analysis of the 

 reported cases, concludes that the muscles that break 

 the bone are the deltoid and clavicular part of the 

 great pectoral. In no case does the fracture appear 

 to have been produced by the sterno-mastoid muscle. 

 The commonest movements producing fracture appear 

 to be violent movements of the limb forwards and 

 inwards, or upwards. These fractures are usually 

 about the middle of the bone, and show no displace- 

 ment other than that of both fragments forwards, i.e. 

 in the direction of the fibres of the two muscles first 

 named. 



The clavicle is more frequently the seat of 

 green-stick fracture than is any other bone in the 

 body. Indeed, one-half of the cases of broken collar 



