6o THE SUPERIOR EXTREMITY 



the extra -sy no vial pads of fat (p. 54). It rapidly involves 

 the sy no vial membrane and attacks the joint. The last- 

 mentioned is the usual direction of spread (Stiles). When a 

 focus is recognised before it has penetrated the periosteum, the 

 distal part of the diaphysis may be resected subperiosteally, 

 without the joint being opened. 



Surgical Approach to the Distal Part of the Humerus. 

 In subperiosteal resection of the distal part of the shaft of the 

 humerus for tuberculous disease, the bone is approached on the 

 postero-lateral aspect of the arm. The incision extends from 

 just below the radial (musculo-spiral) groove to the lateral 

 epicondyle. The medial head of the triceps is split and the 

 bone is exposed. After the periosteum has been separated, 

 the humerus is cut through at a level proximal to the disease, 

 and the distal part of the diaphysis is wrenched out. The bone 

 tears away from the epiphyseal cartilage, which is left attached 

 to the epiphysis. Although the capsule is attached to the 

 periosteum beyond the epiphyseal line, the elbow-joint is not 

 opened because the periosteum is firmly attached to the 

 epiphyseal cartilage. 



When a tuberculous focus occurs in the Proximal Extremity 

 of the Radial Diaphysis, it is intra-capsular . Any extension 

 of the disease through the periosteum of the neck will certainly 

 infect the synovial membrane of the elbow-joint, on account 

 of the relations which these structures bear to one another 

 (Fig. 17). Extension in a distal direction will involve the shaft. 

 (See p. 75 for resection of proximal part of radius.) 



A tuberculous focus in the Proximal End of the Ulna is 

 extra-capsular. It may spread (i) forwards through the articular 

 cartilage into the joint ; (2) distally into the shaft, or (3) it may 

 perforate the periosteum on the lateral or medial side of the 

 bone and infect the soft parts. The last mentioned is the 

 commonest direction of spread. 



The proximal end of the ulna is unsuitable for complete sub- 

 periosteal resection as, by removal of the shaft and semilunar 

 notch (greater sigmoid cavity), the elbow-joint is widely opened. 



Dislocation Of the Elbow. (a) Posterior. This injury 

 results from a fall on the hand, the arm being abducted at the 

 shoulder and extended at the elbow. The line of force passes 

 upwards behind the transverse axis of the elbow-joint, and, as 

 a result, the forearm is hyper-extended. All the ligaments 

 give way, except the annular (orbicular), and the distal extremity 



