An improved external fixation strut comprising: - an elongated body comprising a first and a second hollow tubular shaft; - opposite connectors (201; 202) respectively coupled to an end portion of the first or the second shaft and each including a ball and socket joint; - one shaft having an internal diameter that is slightly larger than the external diameter than the other shaft to host internally the other shaft in a slidable and telescopic manner; - said first and second shafts (210; 220) of the strut being realized by a synthetic radiolucent plastic material; - a clamp element provided in proximity of overlapping ends of the first and second shaft (210; 220) for providing a fast gripping action stopping the telescopic sliding of one shaft inside the other shaft; - a manually operated fixation element acting on the clamp element for exerting said fast gripping action; characterized in that a dynamization mechanism is associated to one of said opposite connectors and includes a first stage associated to one end of a shaft and comprising a ball joint of the ball and socket joint supported by a base portion, a screwed mechanism regulating the projection of the base portion against an internal elastic element and a final stage including a female connector; wherein said final stage is mechanically coupled to the ball joint of the first stage by a rod having one end screwed into the ball joint and an opposite end provided with a female element of the female connector; and wherein said rod is slidable inside the final stage against the elastic action of a spring-loaded mechanism incorporated in the final stage around the rod. - an elongated body comprising a first and a second hollow tubular shaft; - opposite connectors (201; 202) respectively coupled to an end portion of the first or the second shaft and each including a ball and socket joint; - one shaft having an internal diameter that is slightly larger than the external diameter than the other shaft to host internally the other shaft in a slidable and telescopic manner; - said first and second shafts (210; 220) of the strut being realized by a synthetic radiolucent plastic material; - a clamp element provided in proximity of overlapping ends of the first and second shaft (210; 220) for providing a fast gripping action stopping the telescopic sliding of one shaft inside the other shaft; - a manually operated fixation element acting on the clamp element for exerting said fast gripping action; characterized in that a dynamization mechanism is associated to one of said opposite connectors and includes a first stage associated to one end of a shaft and comprising a ball joint of the ball and socket joint supported by a base portion, a screwed mechanism regulating the projection of the base portion against an internal elastic element and a final stage including a female connector; wherein said final stage is mechanically coupled to the ball joint of the first stage by a rod having one end screwed into the ball joint and an opposite end provided with a female element of the female connector; and wherein said rod is slidable inside the final stage against the elastic action of a spring-loaded mechanism incorporated in the final stage around the rod.