PRACTICAL CONSIDERATIONS : THE TIBIA. 



389 



Fig. 406. 



P«» 



triangular and the other circular, the former has the greater power of resistance 

 (Tillaux), the shape of the tibia in this region is thought to be an additional source 

 of weakness. 



For all these reasons it is the most frequent seat of fracture from indirect vio- 

 lence. As in such cases the breaking strain is usually continued for a moment 

 after the tibia gives way, the weak fibula is apt to be broken also. The line of 

 fracture usually runs from^its level on the crest upward and backward, and under 

 tUe action of the calf muscles and the weight of the body the sharp lower end of 

 the upper fragment frequently protrudes, making the fracture compound. 



Fracture at about the same level from direct violence is also very common on 

 account of the exposed position of the bone, and all fractures are apt to be com- 

 pound as a result of the large proportionate area of the bone which is subcutaneous. 



Fracture of the shaft at the upper end involving the knee-joint is rare, and is 

 usually from either direct violence or a fall from a considerable height, — "com- 

 pression fracture. ' ' Fracture of the lower end of the shaft involving 

 the ankle-joint is a not infrequent complication of Pott's fracture. 



Separation of the lower epiphysis is nearly three times as fre- 

 quent as that of the upper. It is caused usually by a considerable 

 degree of violence, and in fifty per cent, of recorded cases has been 

 associated with fracture of the lower end of the fibula or separation 

 of the fibular epiphysis, in which case the displacement is often 

 outward ; usually it is backward. 



It may be mistaken for dislocation of the ankle. In patients 

 from eleven to seventeen years of age disjunction of the epiph- 

 ysis is more frequent than dislocation ; as the malleolus and the foot 

 go backward with the epiphysis, the inner malleolus preserves its 

 normal relation to the foot, but not to the leg or outer ankle. In 

 dislocation the reverse is the case. 



The ankle-joint usually escapes, as both anteriorly and pos- 

 teriorly the synovial membrane is below the epiphyseal line. The 

 synovial pouch of the lower tibio-fibular joint that extends upward 

 between these two bones is in close relation to that line, but is sepa- 

 rated by the periosteum which is continuous over the epiphysis, and 

 thus also escapes injury. 



Arrest of growth is not common, but has occurred, and severe 

 ankle sprains in the young should be treated with especial care on 

 account of the possibility of involvement of the epiphyseal joint and 

 later disease or deformity. 



Disease of the tibia, if infectious, is most common in the neigh- 

 borhood of its two epiphyses and at the junction of the middle and 

 lower thirds. The region is a favorable one for " juxta-epiphyseal 

 sprain," in which the violence is expended on the spongy tissue of 

 the diaphysis near the epiphyseal line. " Many of the pains called 

 ' growing pains' are due to juxta-epiphyseal sprain or injury. Such 

 a sprain is often nothing but the first degree of an epiphyseal separation, in the 

 same way that an articular sprain is nothing but the first degree of dislocation' ' 

 (Poland). 



The usual causes — strain, traumatism, cold, etc. — influence the localization of 

 tuberculous disease in or near the epiphyses. If recognized early, and if the 

 infected focus is removed by operation, the knee- and ankle-joints will usually escape. 

 In the later stages the products of liquefaction may find their way from the upper 

 epiphyseal line to the knee-joint, either direcdy through the intervening half-inch of 

 bone or by way of the tibio-fibular joint, — which is in close relation to the epiphysis 

 (Fig. 425), — and then to the subpopliteus bursa, which always communicates with 

 the knee-joint and often with both ; or they may gain the surface of the tibia and 

 extend upward beneath the periosteum. 



If the lower epiphysis is involved a similar direct or indirect infection of the 

 ankle-joint may occur, the tibio-fibular synovial pouch being sometimes first 

 involved. 



Lines of fracture of 

 tibia and fibula. 



