Introduction:

Calcar screws remain under the humeral head in some patients when osteosynthesis is performed with locking systems. This favors displacement of the head in varus and failure of osteosynthesis.

Objective:

To determine the relationship between the calcar distance and the diameter of the humeral head, the humeral isthmus or height, in cases where the screws are under the head of the humerus.

Methods:

Patients with probable proximal humerus fracture were studied, from April to December 2022, in the Orthopedics Service of Rebagliati Hospital in Lima, Peru. Digital preoperative with PHILoS plate template was planned. The calcar distance, humeral head and isthmus diameter were measured, and height was recorded. The average calcar distance and the percentage of cases with a calcar screw under the head of the humerus were obtained. The relationship between measurements was determined using linear regression. Results: One hundred one patients were included. The average calcar distance was 0.55 ± 4.51 mm and it was lower in women (-0.67 ± 3.90 mm). The calcar screw remained under the humeral head in 38 patients (43.18%). A direct linear relationship was reached between the calcar distance and the diameter of the humeral head (p = < 0.001), but not with height (p = 0.691) or diameter of the isthmus (p = 0.970).

Conclusions:

In most patients the calcar screw remained under the humeral head. Calcar distance was directly related to the diameter of the humeral head, but it was not so to the height or diameter of the humeral isthmus.

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