Optimizing stability in distal humeral fracture fixation.

Restoration of painless and satisfactory elbow function after a fracture of the distal humerus requires anatomic reconstruction of the articular surface, restitution of the overall geometry of the distal humerus, and stable fixation of the fracture fragments to allow early and full rehabilitation. Although these goals are now widely accepted by the orthopaedic community, they may be technically difficult to achieve, especially in the presence of substantial osteoporosis or comminution. Failure, when it occurs, typically occurs at the supracondylar level through loss of fixation in the distal fragments. To prevent such failure and thereby maximize the potential for union and full elbow mobility after a severely fractured distal humerus, 2 principles must be satisfied: (1) fixation in the distal fragment must be maximized and (2) all fixation in distal fragments should contribute to stability between the distal fragments and the shaft. There are 8 technical objectives by which these principles are met: (1) every screw in the distal fragments should pass through a plate; (2) engage a fragment on the opposite side that is also fixed to a plate; (3) as many screws as possible should be placed in the distal fragments; (4) each screw should be as long as possible; (5) each screw should engage as many articular fragments as possible; (6) the screws in the distal fragments should lock together by interdigitation, creating a fixed-angle structure; (7) plates should be applied such that compression is achieved at the supracondylar level for both columns; and (8) the plates must be strong enough and stiff enough to resist breaking or bending before union occurs at the supracondylar level. These can be achieved with parallel plating. Severe metaphyseal comminution and bone loss are managed by supracondylar shortening. From the biomechanical data in the literature, 3 conclusions can be reached concerning fixation of distal humeral fractures. First, the concept that plates need to be placed perpendicular (90 degrees /90 degrees orientation) is unsubstantiated and incorrect. Second, parallel placement of 2 plates in the sagittal plane is as strong or stronger than the 90 degrees /90 degrees orientation. Finally, linking the plates together through the bone, thereby creating the architectural equivalent of an arch, offers the greatest biomechanical stability for comminuted distal humeral fractures. This can be done by interdigitating and locking the screws together as they pass through the distal fragments from the medial and lateral plates placed in the sagittal plane.