PRACTICAL CONSIDERATIONS : THE TIBIA. 



387 



According to French statistics, this in whites is from 70 to 80 ; in savage . races it is 

 much lower. The method of reckoning it at the level of the nutrient foramen is 

 likely to be superseded by one choosing the middle of the bone. 



Structure. — The shaft has strong walls in the middle, being especially thick 

 under the crest. At both ends the walls become thin. The head contains a large 

 amount of cancellated tissue with comparatively thin walls. The architectural arrange- 

 ment of the trabeculae at the ends is very clear. A frontal section of the upper end 

 shows successive vertical plates springing from the sides to support the expanding 

 tuberosities, with an irregular system in the middle. Sagittal sections show plates 

 from the walls meeting each other in arches, A somewhat similar pattern is seen 

 at the lower end. In a frontal section there are several transverse plates, of which 

 the strongest marks the border of the epiphysis. Several of these from the outer 

 side turn down to join the lower surface at the origin of the malleolus, where there 

 is a distinct thickening of the crust. There is sometimes an imperfect bony canal 

 for the nutrient artery for a short distance after its entrance into the cancellated 

 tissue. 



Development. — There are only three centres of ossification : one for the 

 shaft, appearing in the seventh or eighth foetal week ; one for the upper end, appear- 

 ing usually in the last month of foetal life ; and one in the lower, appearing in the 

 second half-year.^ These epiphyses correspond to what has- been described as the 



Ossification of tibia and fibula. A, at eighth fietal month ; B, at birth ; C, at two and one-half years ; D, at four 

 years ; B, at about fifteen years, a, centre for shafts ; b, for upper epiphysis of tibia ; c, for lower epiphysis of fibula : 

 d, for lower epiphysis of tibia ; e, for upper epiphysis of fibula ; /, for tubercle of tibia. 



ends of the bone. The upper extends farthest down on the front, including the 

 tubercle, which may have a separate nucleus. According to Rambaud and Renault, 

 this is of usual occurrence, appearing at from eight to fourteen years and quickly 

 joining the epiphysis. The lower end joins the shaft at about eighteen and the 

 upper at nineteen or twenty. 



PRACTICAL CONSIDERATIONS. 



The upper epiphysis of the tibia is separated only by traumatism of marked 

 severity because of : (i) its great width; (2) its irregularly cupped surface; (3) 

 the downward projection in which the tibial tubercle is developed, or to which the 

 latter becomes united when it arises -from a separate centre ; (4) the protection 

 afforded it (a) on the outer side by the head of the fibula (which is connected 

 exclusively with this epiphysis), the anterior and posterior upper tibio-fibular liga- 

 ments, and indirecdy by the external lateral ligament ; (d) on the inner side by 

 the internal lateral ligament, and (c) on both sides by the fibres of insertion of the 



' Fagerlund : loc. cit. 



