112 CLINICAL APPLIED ANATOMY. 



accurately correspond to the level at which the dislocation has 

 occurred. 



In fracture-dislocation between the fifth and sixth cervical 

 vertebrae, with the usual resulting pressure upon or laceration of 

 the spinal cord, all the parts supplied distally will probably be 

 completely paralysed. There is therefore motor paralysis of 

 every voluntary muscle and anaesthesia of skin and mucous 

 membrane. The patient's respiration is entirely abdominal, 

 that is, it is carried on by the action of the diaphragm alone, 

 this muscle receiving its innervation through the phrenic 

 arising higher than the lesion. Owing to the irritation of the 

 cord close above the actual site of injury, a zone of hyperaesthesia 

 is generally present in the skin supplied by the fifth and sixth 

 cervical nerves, which is roughly over the outer side of the arm 

 and forearm. The centres for defaecation and micturition (and 

 also for parturition) will remain intact in the lumbar segment of 

 the cord. Hence it follows that the rectum will be emptied, 

 though unconsciously, and the bladder will fill and then involun- 

 tarily evacuate itself or overflow. Priapism may be present. 



Fracture-dislocation involving the third, fourth or fifth cervical 

 vertebra will almost certainly involve the origin of the phrenic 

 nerve from the third, fourth, and fifth cervical roots, and will 

 lead to very rapid death by failure of the respiratory movements, 

 the diaphragm as well as the intercostals being paralysed. 



Fracture-dislocation of the first two cervical vertebrae is usually 

 fatal at once owing to the proximity and compression of the vital 

 centres in the medulla. Barely the displacement is slight and 

 death is not immediate. In such cases incautious voluntary 

 movement may cause further dislocation with fatal consequences. 



In the dorsi-lumbar region, fracture-dislocation involves the 

 nerve supply of the lower extremities, causing painful paraplegia, 

 with muscular wasting. 



Since the spinal cord terminates at the lower end of the first lum- 

 bar vertebra in the adult, fractures below this level can only involve 

 the long roots of the cauda equina and these may escape compres- 

 sion since they occupy a smaller space in the vertebral canal. 



