Broadly, there are two types of elbow fracture - those of the distal (lower) end of the humerus (the bone in the upper arm) and those of the bones of the lower arm (typically of the olecranon process of the ulna).
Interested readers may find these two links on the web site of the American Academy of Orthopaedic Surgeons to be informative reading: Elbow (Olecranon) Fractures and Distal Humerus Fractures.
In his report, on page 8 Dr. Shepherd refers to the physiotherapy report from April 1992 (TVP/10/0134), "The note records that there was full flexion of the elbow but that extension of the elbow was reduced by 15 [degrees].".
With regard to both olecranon process fractures and distal humeral fracture it is common that there is some less of extension (i.e. the arm cannot be fully straightened).
Each type of fracture is commonly associated with the later development of arthritis. For example, in the olecranon fracture article we read,
Elbow arthritis causes the elbow joint to become stiff and painful. It is an unfortunate, but relatively common, long-term outcome of olecranon fractures. Elbow arthritis can occur rapidly following an olecranon fracture, or it may take years to develop.
I'll return in a subsequent post to the inadequacy of Dr. Shepherd's report in its treatment of that aspect of the situation.