<p>Reigning MotoGP world champion Marc Marquez has undergone further surgery on his broken right arm, casting increasing doubt on his return at this weekend's Czech Grand Prix.</p>.<p>The Spaniard fractured his arm in the season opener in Spain on July 19 and missed the following race despite initially being declared fit to take part, just 48 hours after having a titanium plate inserted during surgery.</p>.<p>"The first operation was successful, what was not expected was that the plate was insufficient," said doctor Xavier Mir. "An accumulation of stress in the operated area has caused the plate to suffer some damage, so the titanium plate has been removed and replaced by a new fixation.</p>.<p>"The rider has not felt pain during this period. He has always followed the medical advice given and the feeling from his body. Unfortunately, an over-stress has caused this issue. Now we have to wait 48 hours to understand the recovery time," the doctor added.</p>.<p>Six-time world champion Marquez made a remarkable return in practice ahead of last month's Andalucia MotoGP, four days after surgery, but later dropped out of qualifying having struggled to keep pace.</p>.<p>The 27-year-old Marquez has yet to register a point this season and already trails championship leader Fabio Quartararo by 50, with the young French rider securing back-to-back victories at Jerez.</p>.<p>Next on the calendar, which has only 13 confirmed races, is Sunday's grand prix at Brno in the Czech Republic before a double-header at the Red Bull Ring in Spielberg, Austria, on August 16 and 23.</p>
<p>Reigning MotoGP world champion Marc Marquez has undergone further surgery on his broken right arm, casting increasing doubt on his return at this weekend's Czech Grand Prix.</p>.<p>The Spaniard fractured his arm in the season opener in Spain on July 19 and missed the following race despite initially being declared fit to take part, just 48 hours after having a titanium plate inserted during surgery.</p>.<p>"The first operation was successful, what was not expected was that the plate was insufficient," said doctor Xavier Mir. "An accumulation of stress in the operated area has caused the plate to suffer some damage, so the titanium plate has been removed and replaced by a new fixation.</p>.<p>"The rider has not felt pain during this period. He has always followed the medical advice given and the feeling from his body. Unfortunately, an over-stress has caused this issue. Now we have to wait 48 hours to understand the recovery time," the doctor added.</p>.<p>Six-time world champion Marquez made a remarkable return in practice ahead of last month's Andalucia MotoGP, four days after surgery, but later dropped out of qualifying having struggled to keep pace.</p>.<p>The 27-year-old Marquez has yet to register a point this season and already trails championship leader Fabio Quartararo by 50, with the young French rider securing back-to-back victories at Jerez.</p>.<p>Next on the calendar, which has only 13 confirmed races, is Sunday's grand prix at Brno in the Czech Republic before a double-header at the Red Bull Ring in Spielberg, Austria, on August 16 and 23.</p>