With rare exceptions, pseudoarthroses are accompanied by the loss of bone tissue, i.e., by an anatomic defect. However, from a practical point of view, a clear definition of both “pseudoarthrosis” and “defect” is of fundamental importance in the correct selection of the extent and tactics of both treatment and rehabilitation measures. A pseudoarthrosis refers to the condition in which it is anticipated that despite medical interventions the achieved degree of union of the bone fragments will not lead to humeral shortening by >8–10 mm, or shortening of one of the forearm bones by >5 mm, or of the femur and leg bones by >10–15 mm.