+At the Ends of Bones.+ Fractures occurring at the ends of bones receive the name of the part which the line of fracture transverses; for example, fractures of the _neck_ of a bone, of a _tuberosity_, of a _process_, of a _condyle_, etc. There are two forms of fracture that require special mention in connection with their location. These are _epiphyseal separations_ and _articular fractures_. +Epiphyseal Separations.+ The union of the epiphysis to the diaphysis commences during puberty, hence these fractures are less common in childhood than after the ages of eleven or twelve. As a rule, they can only occur before the twentieth year. The periosteum is more resisting and tougher during the early years of life than later on. +Articular Fracture+ (_joint fractures_). Like epiphyseal separations, recognition and proper treatment of these fractures have assumed great importance. Articular fractures may be divided into three classes: 1. _Intra-articular._ In these the line of fracture lies entirely within the joint. Such fractures are most frequently found in the elbow and knee joint. 2. _Para articular._ In these the line of fracture extends close to the joint but not into it. An example of this class is the _supracondyloid_ fracture of the humerus. 3. _Articular fractures proper._ The majority of joint fractures belong to this class. The line of fracture either extends into the joint from without or it extends from the joint outward. As example, the ankle joint; the majority of the typical supramalleolar, malleolar, and spiral fractures of the tibia and fibula. +Etiology.+ Fractures may be divided into two groups: the _traumatic_ and the _pathologic_ or _spontaneous_. In the traumatic, the fracture is the result of violence acting upon a bone which is either normal or shows slight changes due to the physiologic causes mentioned. A pathologic or spontaneous fracture is one which occurs in a bone, the strength of which has been diminished by some preceding abnormal or pathologic changes. In this variety the degree of force which produced the fracture would not be sufficient to cause a fracture in a healthy bone. The causes of traumatic fractures may be either predisposing or exciting. +Predisposing Causes.+ The bones of the human body attain their greatest strength toward middle age. From infancy up to that time the bones are very elastic and yielding. Toward old age an interstitial atrophy occurs. It causes a thinning of the cortex of the shafts and of the trabeculae of the spongy portions of the long and short bones. It is an actual diminution of the bone substance and a corresponding increase of the fat. This is especially seen in the neck of the femur. When it occurs in old age, it acts as a predisposing cause, but when it occurs prematurely or reaches an extreme degree, it must be considered as pathologic. EXISTING OR DETERMINING CAUSES OF FRACTURES