A bone fixation device (1) comprises an elongated member (2) and a washer (3) assembled in a manner to prevent relative longitudinal displacement at the same time allowing axial rotation of the washer (3) with respect of the elongated member (2). The elongated member (2) comprises a proximal head (4) and an elongated shaft (5). The proximal head (4) comprises at least a distal spherical portion (8) having a diameter (D) and defining a maximum transversal dimension (Dh) of the proximal head (4). The washer (3) has a central cavity (14) configured to seat the proximal head (4) and comprising a central spherical portion (15) having the same diameter (D) of the distal spherical portion (8) of the proximal head (4). The central spherical portion (15) extends between a distal rim (16) and a proximal rim (17). The distal rim (16) has a distal transversal dimension (Dd) larger than a maximum transversal dimension (d) of the elongated shaft (5) and smaller than the maximum transversal dimension (Dh) of the proximal head (4). The proximal rim (17) has a proximal transversal dimension (Dw) larger than the maximum transversal dimension (d) of the elongated shaft (5) and slightly smaller than the maximum transversal dimension (Dw) of the proximal head (4). The proximal transversal dimension (Dw) of the proximal rim (17) is larger than the distal transversal dimension (Dd) of the distal rim (16). The proximal rim (17) is configured to be elastically deformable by pressing the proximal head (4) through the proximal rim (17).L'invention concerne un dispositif de fixation d'os (1) qui comprend un élément allongé (2) et une rondelle (3) assemblés de façon à empêcher un déplacement longitudinal relatif, tout en permettant une rotation axiale de la rondelle (3) par rapport à l'élément allongé (2). L'élément allongé (2) comprend une tête proximale (4) et une tige allongée (5). La tête proximale (4) comprend au moins une partie sphérique distale (8) ayant un diamètre (D) et délimitant un
