This section is from the book "Applied Anatomy: The Construction Of The Human Body", by Gwilym G. Davis. Also available from Amazon: Applied anatomy: The construction of the human body.
The condyles (page 280) have been described as the lateral bony projections of the lower end of the humerus which are extra-articular. Therefore the trochlea and capitellum are not parts of the condyles, and the epicondyles are simply the tips of the condyles.
Bearing this in mind it is evident that fractures involving the condyles may be confined to them and not implicate the articular surfaces. They are then extra-articular fractures of the condyles, or they can with some reason be called fractures of the epicondyles. Other fractures may not only implicate the condyles, but pass through them into the articular surfaces. These will be called intra-articular fractures of the condyles. The internal epicondyle (epicondylus medialis) is sometimes called the epitrochlea.
The medial (internal) condyle projects far beyond the body of the bone as a distinct bony 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 condyle (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 displaced 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. hdra-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 because the fracture is so extensive as to also involve the trochlea. This, like the other fractures of this region, is to be diagnosed by grasping the fractured part and detecting crepitus and excessive mobility. The medial (internal) condyle is felt firmly attached to the humerus and the olecranon to the ulna, but the lateral (external) condyle is felt to move independently of the others. It is efficiently treated by an anterior (not internal) angular splint.
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.