Congenital thumb contractures are a well described but complex deformity to manage. Thumb contractures are common in patients with arthrogryposis. Many patients with arthrogryposis develop a supination, adduction, and flexion contracture at the thumb carpometacarpal join. Despite some thumb function, their thumb position and contracted first webspace precludes effective pinch or grasp, with the thumb opposing only to the palmar space. An extension, reorientation metacarpal osteotomy that places thumb in an efficient position has the potential to improve function in of these patients. This report provides a new classification system for congenital thumb deformities that can dictate management based upon thumb joint positions. We describe a previously unreported, arthrogrypotic thumb contracture that can be managed with an extension/pronation metacarpal osteotomy with simultaneous widening of the first webspace.