The purpose of this study is to find out the good and bad effects of an investigational drug called CP-533,536 in patients with closed fracture of the tibial shaft undergoing internal fixation using reamed inter-locked IM nailing procedure

Inclusion Criteria:

• Males or females 17 years or older with confirmed closure of the tibial epiphyses, with a closed fracture of the tibial diaphysis undergoing treatment with reamed locked IM nailing procedure and the absence of an associated compartment syndrome or vascular injury;
• Closed tibial fractures Types A, B & C (See OTA fracture classification) can be included.

Exclusion Criteria:

• Previous fractures of the same tibia that may impact nailing procedure or impaired visibility of current fracture or a history of osteomyelitis;
• Subjects with any other clinically significant injuries, which may significantly impair weight bearing of the affected limb;
• Subjects with a fracture gap of >1cm after initial surgery and prior to drug administration;
• Any other planned invasive or non invasive interventions intended to promote bone healing of the tibial fracture under study are not allowed in the first 24 weeks after treatment.