Intracranial pressure-alterations during controlled intramedullary reaming of femoral fractures: an animal study.

Reaming during intramedullary nailing increases the intramedullary pressure (IMP) and can cause fat intravasation and subsequently lead to pulmonary dysfunction, especially in polytraumatized patients with lung contusion as well as increases in intracranial pressure (ICP).ICP changes were measured in two groups consisting of 12 sheep each with either a fractured or intact femur. The animals were exposed to haemorrhagic shock and were resuscitated by autoinfusion. Transverse midshaft fractures were created bilaterally in one group before reaming of both femoral shafts. Controlled reaming was performed at 15 and 50 mm/s driving speed (DS) and at 150 and 450 revolutions per minute (RPM) with a reaming control system using AO-Reamers. Fat intravasation was measured by transoesophageal sonography (TES) and Gurd test. ICP monitoring was performed with a piezo-electric epidural catheter. Haemodynamic and respiratory parameters, ICP, and cerebral perfusion pressure were measured continuously. High DS and low RPM caused higher IMP and ICP increases in both groups. Significantly higher microemboli were observed in TES in the fractured group as compared to the unfractured group with the same reaming parameters (P=0.021). However, the existence of a femoral fracture did not show a significant influence on changes in ICP (P-value=0.057). Reaming should be performed at a low DS and high RPM to minimize the risk of fat intravasation and the subsequent ICP increase.