COMPLICATIONS OF LOCKING PLATES USED FOR FRACTURES OF THE PROXIMAL HUMERUS.

Abstract

Introduction: Locking plates and screws have been developed to increase stability of internal fixation in osteoporotic bone. The anatomic design should also facilitate the fracture’s reduction in complex cases.

The aim of this study was analyse the results of locking plates used for fractures of the proximal humerus and to look for specific complications.

Method: Forty four patients (mean age 60; 28 males and 16 females) were treated with a locking plate (Philos, Synthes-Sratec Medical, Switzerland) for trauma of the proximal humerus. There were fourteen 2-part (32%), ten 3-part (23%), ten valgus impacted 4-part (23%), 3 classical 4-part (7%) fractures and 7 non-unions (15%). Five patients presented an associated gleno-humeral dislocation. Patients were reviewed clinically and radiologically at a mean follow-up of 21 months (6–42). A particular attention was paid to the occurrence of specific complications.

Results: A deep infection occurred in two patients (4,5%); two others lost the reduction (4,5%), and one broke his plate (2,3%). We observed 9 cases (20,5%) of avascular necrosis. Six patients (13,6%) had an impaction of the fracture with secondary intraarticular protrusion of the locked screws, which induced a secondary glenoid wear. The impaction sometimes occurred even without any evidence of AVN. Protrusion of screws were more frequent in elderly patients or in cases of non-union. Revision surgery (18 operations) was performed in 16 patients (36%) : 9 isolated material removal; 3 revisions for loss of reduction and malposition of the plate; 2 debridement including implantation of a cement spacer with antibiotics; 4 arthroplasties (2 hemi and 2 total shoulder prostheses).

Conclusions: Proximal humerus locking plates and screws, designed to improve stability in osteoporotic bone, may have specific complications. They do not prevent fracture’s impaction, resulting in an intraarticular protrusion of the locked screws, which may induce a severe secondary wear of the glenoid. This phenomenon could be due to the direction of the forces and stresses applied on the humeral head, which is mainly parallel to the screws and not perpendicular to them. Accordingly, patients operated on with proximal humerus locking plates should be regularly controlled. In case of progressive humeral head impaction, the material should be removed before it damages the glenoid.