First dorsal metacarpal artery flap (Foucher flap) could fit in.

To answer your question we need to talk first about the remained fuction of the tendon and the Joint - and how is the exposed bone coverd so far?

For sure it's true that the deficit needs to be defined however either way I agree with the first reply -the  Foucher ( 1st dorsal MC artery ) flap is perfect - it's reach is always adequate to the dorsum of the P1 - the flap can accomodate not only skin loss and exposed joint but if there is extensor tendon loss then you can harvest a vascularised strip of extensor tendon from the radial aspect of the extensor hood of the index. I will try to post photos of one of our very similar cases where we covered an open IPJ and reconstructed the entire EPL with tendon from the index using a Foucher flap

Dear Mark Ross thanks for your answer.

Thank you for showing this interesting case. Thumb seems to be burnt several weeks ago and destroy much deeper: open IP joint infection, bone necrosis, tendon loss with extensive scars. Decision making should be done after debridment- scar excision, dead bone necrectomy and probably IP resection. The reconstructive procedure will depend on bone and IP joint condition. In older patients IP arthrodesis with or without bone graft and the first dorsal metacarpal artery flap should be considered as the simplest option giving stable thumb. In good cartilage condition of IP joint you can perform even onestage multitissues reconstruction using this first dorsal metacarpal artery flap with the part of tendon (fragments of both radial and ulnar part of extensor hood of the index) with periosteum and vascularized bone graft from the basis and shaft of proximal phalanx of the index. 

Dear Marek Molski thanks for your answer.

Dear Carlos Acosta-Batista, With a great pleasure.

Cordiales saludos.

I absolutely agree with the opinions above. The fact that the mode of reconstruction is to be determined after adequate debridement needs to be stressed especially. Proper debridement and coverage with either Foucher or Moschella flap. Judging from the picture, a secondary joint fusion is likely. Concerning the EPL, this depends on retained function. 

Dear Jonas thanks for your answer.