The trapezo-metacarpal dislocation is a rare injury, sometimes misunderstood, of which the diagnosis is essentially radiographic. We report a case of a 22-year-old athlete presented following a fall onto an outstretched hand during a handball match,pain with edema of the right thumb without obvious deformation. Clinically, we found pain on palpation and mobilization of the right thumb making examination very difficult. Plain radiography of the right hand failed to reveal a fracture. However, the trapezo-metacarpal dislocation went unnoticed (Figure 1). The diagnosis of a severe sprain trapezo-metacarpal was unfortunately retained and the patient has benefited from an immobilization with a thumb orthesis associated with an analgesic and an anti-inflammatory. Due to the persistence of pain and the appearance of a deformation, another plain radiography were performed one week later which objectified an unstable trapezo-metacarpal dislocation (Figure 2) requiring surgical management by the realization of a pinning, associated with immobilization for three weeks (Figure 3). The pin was withdrawn after three weeks and reeducation was started quickly with a good clinical outcome.

The trapezo-metacarpal dislocations are not uncommon but deserve special attention, and may sometimes go unnoticed. Their diagnosis is essentially radiological; we must insist on the rigor of radiological incidences and slightest doubt, we should have recourse to a dynamic test [1]. The complexity of the joint system, capsular ligament and neuromuscular system of the trapezo-metacarpal joint complicates diagnosis and requires introducing therapies that do not suffer of any approximation [2] . The clinical signs are discreet, rapidly masked by edema and moderate functional impotence which makes a clinical diagnosis very difficult [3]. The concept of trapezo-metacarpal dislocation easily reducible but extremely unstable with iterative dislocation is classic. The aim of treatment is the restoration of congruency and stability of joint. Any imperfection may induce to chronic instability and a secondary to rhizarthrosis [4].

1. Pequignot JP, Giordano P, Boatier C, Allieu Y. Luxation traumatique de la trapézo-métacarpienne. In Annales de Chirurgie de la Main 1988;7:14–24.    
2. Aude Q, Jean Claude C, Raymond-Gilbert D. 23 ENTORSES ET LUXATIONS. Rééducation de l'appareil locomoteur: Membre supérieur 2008;2:329.    
3. Jaaouane M. "La luxation trapézo-métacarpienne (A propos de 06 cas) 2010.    
4. Amar MF, Loudyi D, Chbani B, Daoudi A, Boutayeb F. Acute traumatic dislocation of the trapeziometacarpal joint treated by percutaneous pinning. Review of six cases. Chir Main 2009;28(2):82–6. [Article in French].   [CrossRef]   [Pubmed]