<prompt> A patient on colles cast present after two weeks with the inability to extend his thumb, the most likely reason is:Rupture of extensor pollicis longus tendonCompartment syndromeCarpal tunnel syndromeSudeks osteodystrophy  <response>: Ans: A Rupture of extensor pollicis longus tendon Ref: Apleys System of Orthopaedics and Fractures, 9th edition, p 774Explanation:Rupture of extensor pollicis longus occasionally occurs a few- weeks after an apparently trivial undisplaced fracture of the lower radius.The patient should be warned of the possibility and told that operative treatment is available. 