Conservative and operative therapy of AVN is determined by several factors. The type of previous treatment (conservative/operative) and if surgical treatment was performed the type of the used implant (angular stable plate, intramedullary nail, screws, K-wires, etc.) and whether the implant is still in place are important factors to consider. Bedsides these factors it is important to know whether the fracture is healed in an anatomic or nearly anatomic position or if mal-or non-union is present.

In a retrospective study on 121 patients who sustained angular stable plating for proximal humeral fractures and were referred for further treatment due to complications, AVN was the major complication in 68 % (82 cases) [10]. The majority of cases were associated with other complications like non-union, mal-union or loss of reduction. Only in 33 cases AVN developed as result after an anatomic reduction. Thirty-seven of these cases were initially malreduced, 13 cases showed secondary loss of reduction and in 9 cases non-union was present whereas in 59 of these cases a secondary screw cut out was recognizable [10].

These fracture sequelae are best described using the Boileau classification system [1]. The authors were the first to report about a classification system of proximal humeral fracture sequelae. They divided the classification in two surgically important parts according to the need of performing an osteotomy of the greater tuberosity in case of an operative revision using an anatomic shoulder prosthesis was necessary. Accordingly, category 1 describes intra-capsular impacted fracture sequelae with a non- or only minimally displaced greater tuberosity and no need for an osteotomy including AVN and cephalic collapse of the humeral head. In contrast category 2 describes extra-capsular, non-impacted fragments with the need of performing an osteotomy or refixation of the greater tuberosity. Again both categories are divided in two types of fracture sequelae resulting in a total of four types as follows: type 1 shows a cephalic collapse or necrosis of the humeral head, for type 2 a locked dislocation or fracture dislocation (category 1) is described, type 3 shows a surgical non-union of the humeral neck and type 4 presents with a severe malunion of the tuberosity (category 4). In all of these cases AVN may be also associated. I did not find percentages in the literature.

Moreover in a recent study of Moineau et al. a sub-classification system of proximal humeral fracture sequelae type 1 was published. The sub-classification comprised either the absence (types 1A and 1B) or the presence (types 1C and 1D) of osseous deformation of the proximal humerus whereas type 1A represents a cephalic collapse of the proximal humerus, type 1B is associated with gleno-humeral osteoarthritis and type 1C comes along with valgus malunion and type 1D with varus malunion [13].