Top seed Justine Henin-Hardenne continued her Family Circle Cup dominance Thursday with a 6-4, 6-4 victory over Croatian baseliner Karolina Sprem.

World number three Henin-Hardenne, eliminated in the first round of her previous tournament at Miami [ Images ], appeared to gain strength in her second Charleston match to reach the quarter-finals of the event she won in 2003 and 2005.

"I don't have any problems physically," the Belgian told reporters.

"I mean, there are still a few issues with my shoulder but not something major that is bothering me right now."

All the top four seeds advanced Thursday, including Russians Nadia Petrova [ Images ] and Svetlana Kuznetsova [ Images ] and Swiss Patty Schnyder [ Images ].

Second seed Petrova, coming off a title at Amelia Island last week, overpowered 14th seeded Lucie Safarova [ Images ] of the Czech Republic 6-1, 6-3 to set up a match with Colombia's Catalina Castano, the only unseeded player to reach the quarterfinals.

World number 48 Castano advanced when France's [ Images ] Marion Bartoli [ Images ] retired with left knee inflammation with Castano leading the 5-4 in the first set.

Kuznetsova, the fourth seed, overcame hip and elbow worries to defeat Lourdes Dominguez-Lino of Spain 6-2, 6-1. She will play sixth seeded Anna-Lena Groenefeld, a 7-6(3), 6-3 winner over Anabel Medina Garrigues.

Third seeded Schnyder defeated Mara Santangelo 3-6, 7-6(2), 6-3 after the Italian played brilliantly in the first set, making only eight unforced errors.

"It was a really big struggle, and I didn't feel comfortable," Schnyder said.

Schnyder on Friday will play France's Nathalie Dechy [ Images ], the eighth seed. Dechy, finally healthy and playing some of her best tennis of the year, defeated 11th seeded Katarina Srebotnik of Slovenia 6-2, 6-3.

Henin-Hardenne will face Russian Dinara Safina [ Images ] in the quarterfinals. Safina, the seventh seed, ousted qualifier Julia Vakulenko of the Ukraine 6-7(6), 6-2, 6-2.