Review Question - QID 211430

This patient underwent ORIF of his proximal humerus fracture and subsequently developed varus collapse. It has been shown that optimizing the location of the calcar screws within the inferomedial quadrant of the proximal humerus helps prevent the risk of varus collapse fixation failure.

Proximal humerus fractures are most often seen in the elderly, as they account for the third most common non-vertebral fracture pattern in this age group. In younger patients, they are typically secondary to high energy trauma. Indications for ORIF include greater tuberosity displacement >5mm, displaced 2-part fractures, and younger patients with 3- and 4-part fractures and head-splitting fractures. Locking plates are the preferred construct, and the appropriate placement of the plate should be guided by the location of the calcar screw. The term calcar screw denotes the screw(s) that crosses the calcar, which is the inferomedial aspect of the humeral neck. Calcar comminution can lead to varus collapse if appropriate support of this area is not provided. Illustration A depicts an example of the trajectory of a calcar screw. Several studies have documented a significant decrease in varus collapse with the use of a calcar screw. More recent studies have attempted to specify the parameters for the location within the inferomedial aspect of the humeral neck based on distance to the calcar, distance to the articular surface, as well as the calcar ratio (which is the ratio of the distance of the calcar screw to the apex of the arch of the calcar to the width the humeral head).

Gardner et al. reviewed what factors influence the maintenance of fracture reduction after locked plating of proximal humerus fractures, and particularly the role of medial column support. They report that the presence of medial support had a significant effect on the magnitude of subsequent reduction loss and that achieving mechanical support of the inferomedial region of the proximal humerus is important for maintaining fracture reduction. They concluded that achieving an anatomic or slightly valgus-impacted stable reduction, as well as meticulously placing a superiorly directed oblique locked screw in the inferomedial quadrant of the proximal fragment achieves more stable medial column support and allows for better maintenance of reduction.

Ponce et al. reviewed how medial comminution affects fracture stability and determined the effect of calcar fixation on osteosynthesis stability of proximal humerus fractures. They found that the use of calcar screw fixation increased the mean load and energy to failure by 31% and 44%, respectively. They concluded that medial comminution significantly decreased the stability of proximal humeral fracture fixation constructs, but calcar restoration with screw fixation significantly improved the stability of repaired fractures (in cadaveric specimens).

Padegimas et al. performed a retrospective study on 168 shoulders that underwent ORIF for a proximal humerus fracture to determine factors associated with fixation failure. They reported 15.5% had radiographic failure, and that quality of reduction, calcar distance (the distance of the inferior screw to the calcar), as well as the ratio of the calcar distance to the head diameter (calcar ratio) were significantly associated with radiographic success. They found that the quantifiable thresholds of 12mm or within the bottom 25% of the humeral head to be measures of fixation placement preventative of fixation failure.

Figure A demonstrates ORIF of a left proximal humerus fracture and Figure B demonstrates fixation failure and varus collapse. Illustration A depicts an example of the trajectory of a calcar screw. Illustration B demonstrates an AP radiograph of an adequately reduced right proximal humerus fracture after ORIF with a neck-shaft angle of 127.3°, calcar distance of 4.1 mm, and distance from the tip of the calcar screw to the humeral head of 1.6 mm.

Incorrect Answers:
Answers 1, 2, 4 & 5: The calcar of the proximal humerus is located in the inferomedial quadrant and appropriate screw placement here has been shown to significantly decrease the risk of developing varus collapse.