Ghana defender Isaac Vorsah has undergone successful surgery to correct an excruciating knee injury.The Red Bull Salzburg player ruptured his anterior cruciate ligament in his right knee and collateral ligament sprain during last Tuesday’s Austrian Cup semi-final defeat to FC Traun.The centre-back went under the knife on Friday and doctors have confirmed the lanky player will need six months to recover.Vorsah will miss the remainder of the season and also the opening stages of the first half of next term.The 25-year-old has been ruled out of Ghana’s double 2014 FIFA World Cup qualifiers against Sudan and Lesotho next month.Vorsah has been one of Kwesi Appiah’s trusted men at the back and will be sorely missed for the busy month of June.