540 



APPLIED ANATOMY. 



are wider apart are usually those in which the upper fragment has been subsequently 

 pulled up by the contraction of the quadriceps. A fracture which when recent may 

 have had only i cm. separation may subsequently show 7.5 to 10 cm. (3 to 4 in.). 

 When the union is fibrous subsequent stretching may occur, also refracture increases 

 the tendency to wide separation. 



Fracture by direct violence is due to the direct impact of a blow or a crushing of 

 the patella between the femur and some foreign body. In this case the capsule on 

 the sides is but little torn and although there may be several fragments they do not 

 become widely separated. 



Macewen has pointed out that the torn fibrous portion of the quadriceps over 

 the patella may hang down between the fragments and hinder union. 



Treatment. The method of treatment to be employed varies according to the 

 character of the injury. When the fracture is from indirect force, means must 



be employed not only to hold the fragments to- 

 gether, but also to repair the rent in the capsule. 

 Obviously the limb is to be kept in the extended 

 position to relax the quadriceps. The rectus, on ac- 

 count of taking its origin from the pelvis, is also to be 

 relaxed by elevating the limb. A common method 

 of treatment is by open operation. First a flap is 

 raised, exposing the fracture, then the fragments 

 are approximated with wire or other sutures and 

 the rent in the capsule closed with chromic catgut 

 or silk. 



In fractures by direct violence, when separa- 

 tion is not marked, the lateral fascial expansion re- 

 mains untorn and no open operation is necessary ; 

 in others, when separation is more marked, and 

 especially if the fracture is compound, a flap may 

 be turned back and the patella surrounded with a 

 strong suture of chromic gut or silk and the frag- 

 ments thereby drawn together; the suture may also 

 be introduced subcutaneously. 



By open operation the blood and clots which 

 usually fill the joint can be removed as well as any 

 fibrous tissue from the tendon of the quadriceps 

 which may lie between the fragments. 



Dislocation of the Patella. The articular 

 surface of the patella is divided by a longitudinal 

 ridge into an outer and inner part, which articulate 

 with the corresponding condyles of the femur. 

 The outer surface for the external condyle is much 

 the larger. The outer condyle is also much higher than the inner and thus tends 

 to prevent luxations. The lateral fibrous expansions on each side of the patella also 

 help to hold it in place. 



Favoring dislocation is the inclination inward of the knee and the oblique pull 

 of the quadriceps. When a person is standing upright with the feet together the 

 femurs diverge from the knee as they approach the hip, the knees forming an angle 

 of 165 degrees with its apex in. When the quadriceps muscle contracts it tends 

 to straighten this angle and so pull the patella out. If the ligaments are normal 

 and the pull not too violent, luxation does not occur. When, however, from long 

 disuse or disease the ligaments become relaxed, then a sudden and perhaps unusual 

 contraction of the quadriceps will dislocate the patella. This also occurs if the outer 

 condyle is abnormally flat or. if the muscular contraction lifts the patella off or above 

 the condyles, as occurs when the tendo patellae is too long. In these, as in almost all 

 other cases, the patella is dislocated outward (Fig. 552). Inward dislocation is almost 

 unknown. Direct injury also produces dislocations, practically always outward. The 

 most common form is for the articular surface of the patella to rest on the outer sur- 

 face of the external condyle. Other forms, which are more rare, are for the inner 



Flo. 551. Fracture of patella, showing 

 lateral tear of capsule. 



