(Adds details, quotes)
* Park Joo-ho called up
* Kim Jin-su forced out with an ankle problem
* Hong Jeong-ho to have ankle checked at hospital
By Narae Kim
SEOUL, May 29 (Reuters) - German-based defender Park Joo-ho was called into the South Korea World Cup squad on Thursday after first choice left back Kim Jin-su was forced to drop out of the 23 because of an ankle ligament injury.
Kim, 21, suffered the injury playing for Japanese club Albirex Niigata earlier this month with the Koreans deciding against surgery in the hope he could recover in time ahead of their opening game in Brazil against Russia on June 17.
But those hopes were dashed late on Wednesday, leaving Mainz defender Park to battle Yun Suk-young of Queens Park Rangers for the starting place in Brazil.
"Unlike knee ligament injuries, those around ankles do not necessitate surgery so we opted to go through treatment without surgery," team doctor Song Jun-seob told reporters in Seoul on Thursday.
"We did our best to treat the injury till yesterday but we concluded after a meeting last night that one of the ligaments won't be healed till the World Cup."
The Koreans received more positive news about central defender Hong Jeong-ho, who was forced off in the 13th minute of Wednesday's 1-0 home loss to Tunisia with an ankle problem.
Hong left the field on a stretcher but, after scans on Thursday, Song said he expected the Augsburg defender to be back within a week.
"He has a bruise under his skin. He was hit hard by the tackle and thankfully his ankle was not twisted," the doctor said.
The Koreans will be thankful their leaky defence, which was badly exposed by the Africans, was not hit further.
Forward Zouheir Dhaouadi was given far too much freedom as he burst through the heart of the hosts from deep to score the only goal shortly before halftime to upset the 50,000 home fans who had come for the Seoul send off.
Yun started the match at left back despite fears of jet lag after arriving late from England because of club commitments, but Park will be hopeful of usurping him in Brazil, where the Koreans also face Algeria and Belgium in Group H.
The Mainz defender had a strong first season in Germany after switching from Swiss side Basel and his initial snub from the World Cup squad was one of the main talking points amongst fans and local media.
Head coach Hong Myung-bo said he left the 27-year-old out because he had been suffering foot inflammation since the conclusion of the Bundesliga season earlier this month.
Song said that was all cleared up now and the fullback would be ready to play in their final pre-World Cup friendly against Ghana in Miami on June 9.
"What is important about this injury, cellulitis, is whether it would recur or not and at the time the entry was made public the medical team was not sure if it'd relapse," he said.
"But after one week after the entry was announced on May 8, we removed the stitches as it was fully healed and since then Park has been working on the rehabilitation program under the guidance of our medical team and it's been successful." (Writing by Patrick Johnston; Editing by Greg Stutchbury/Amlan Chakraborty)