REGION OF THE ELBOW. 297 



process, while the lateral (external) condyle is low, flat, and not prominent. For 

 these reasons fractures of the medial condyle not involving the joint are more common 

 than those of the lateral condyle. In fact extra-articular fractures of the lateral con- 

 dyle (detachment of the epicondyle) are almost unknown, but they have been proven 

 to exist. 



In extra-articular fractures of the medial condyle, the fragment has been dis- 

 placed downward by the flexor muscles which arise from it. To counteract this 

 tendency the arm is treated in a flexed position. As the ulnar nerve runs in the 

 groove on the posterior surface of the condyle it has also been injured, and vesicles 

 and impairment of sensation in the course of the nerve have been observed. As 

 the articular surfaces are not involved, no serious deformity or disability need be 

 expected. 



Intra-articular Fractures of the Condyle s. The line of fracture in these injuries 

 usually starts above the epicondyle and passes toward the middle of the bone, 

 chipping off a portion of the trochlear surface or the capitellum. Fractures involving 

 the lateral are probably more frequent than those involving the medial condyle. 



Intra-articular Fracture of the Medial Condyle. The line of fracture passes 

 obliquely through the condyle, entering just above its tip and emerging on the artic- 

 ular surface of the trochlea either in the groove sepa- 

 rating the two portions of the trochlea or the groove 

 between the trochlea and capitellum. As already ex- 

 plained (page 282), the integrity of the joint and the 

 line of the arm depend on the trochlea and not on 

 the capitellum, therefore the farther over toward the 

 capitellum the line of fracture goes the more likely is 

 there to be lateral mobility (Fig. 312). 



The fragment may be pushed up; this carries the 

 ulna up with it while the radius is prevented from 

 following by the capitellum. Therefore the forearm 

 bends inward, making a lateral deformity. The carry- 

 ing angle (page 282) becomes obliterated and what is 



known as gunstock deformity or cubitus varus is pro- 



duced. It is mainly to the researches of Dr. O. H. p IG . 3]t2 Fracture of internal 



Allis that we are indebted for our knowledge of the s t f k yle de a fo^ 



mechanism of this deformity. The attachment of the From a photograph of a preparation 



n 11 ii.ic if in the Mutter Museum of the Col- 



flexor muscles does not keep the fragment from rising. i ege of Physicians. 

 The deformity is difficult to detect when the elbow is 



flexed. The condyles and olecranon and shaft of the humerus may all be in the 

 same straight line and still the medial (internal) condyle be higher than normal. If 

 the injury is treated with a right-angled splint the radius and ulna remain in their 

 proper positions but the ulna and medial condyle may both be higher than normal. 

 If this is the case, then, when the forearm is extended, instead of it making an angle 

 of 10 degrees outwardly with the line of the humerus, it may incline 10 degrees or 

 even 20 degrees inwardly: thus it may deviate as much as 30 degrees from the normal 

 direction. To guard against this deformity Allis advised treating the injury with the 

 arm in full extension. Any tendency to lateral deformity wi) T then be at once evident 

 and can be corrected by additional lateral support. Cert i it is that no e ~rious 

 fracture of the elbow ought to be treated without frequent examinations of t.ie arm 

 in full or almost complete extension being made from time to time, so as to be sure 

 this deformity is not becoming established. 



The treatment of fractures involving the joint by placing the elbow in a position 

 of complete flexion has been strongly advocated, although it has not entirely super- 

 seded other methods. 



Intra-articular Fracture of the Lateral {External} Condyle. This is also a fairly 

 common injury. The line of the fracture passes from above the tip of the lateral 

 condyle down into the joint through the capitellum or between it and the trochlea. 

 As is to be expected, this does not show the same tendency to lateral deformity 

 as does fracture of the trochlea. When lateral deformity does occur it is be- 

 cause the fracture is so extensive as to also involve the tr< hlea. This, like the 



