Longitudinal forearm instability, or Essex-Lopresti syndrome, associates radial head fracture and rupture of the structures uniting the 2 bones, mainly the interosseous membrane and triangular fibrocartilage complex adjacent to the distal radioulnar joint.

It is often overlooked at first, and should be screened for in case of comminuted radial head fracture without elbow dislocation or instability.

Treatment should be prompt, within 4 weeks of trauma, to avoid soft-tissue retraction and hopefully allow healing. This interval is anecdotal, without firm evidence, but matches observations regularly reported in the literature [1Barret H., Favard L., Mansat P., Winter M., Clavert P., Sirveaux F., et al. Results of radial head prostheses implanted during Essex-Lopresti syndrome in multicentric study Int Orthop 2021 ;  45 : 1549-155710.1007/s00264-021-04987-6

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In the acute phase, treatment consists in rigid, usually unipolar, radial head replacement, protected healing of the interosseous membrane by a TightRope suture button between the bones, radioulnar pinning and triangular fibrocartilage complex suture, followed by 6 weeks’ immobilization. Progression is usually favorable.

Chronic forms, beyond 4 weeks, when soft-tissue healing is impossible, require interosseous membrane reconstruction. In case of radiocarpal impingement due to ascension of the radius, ulnar shortening osteotomy must be associated. Medium-term results in such cases are much less certain.

As a last resort, the “one-bone forearm” is a solution.