Background: Tibial shaft fractures are the commonest cause of compartment syndromes. Intramedullary nails have been the more accepted treatment. Raised pressures after nailing don’t mean a compartment syndrome, but are an important factor to consider in the decision of treatment.

Methods: A clinical study was performed including 80 cases diagnosed of tibial shaft fractures treated with reamed intramedullary nails. Measurement method for compartment pressures was the slit catheter. Pressures were calculated before and just after surgery. Delta P values were calculated too. Patients with overpressures but no clinical suspicion of compartment syndrome were monitored during 24 hours. Patients diagnosed of compartment syndrome were treated by fasciotomy.

Descriptive and statistical study was performed with a ninety-five percent confidence intervals and significant difference p< 0,05.

Results: A statistical significant raising pressure was observed after surgery. Delta-P values showed a decrease after nailing only in the anterior compartment, but it was not significative (p ≥ 0,05). 4 cases were necessary for monitoring during 24 hours. 11 patients were diagnosed of compartment syndrome after surgery, with absolute pressures that showed values over 30 mm Hg, and delta P less than 40 mmHg.

Conclusions: Reamed intramedullary nails can increase compartment pressures in tibial shaft fractures. Delta P value can infiuence decisions for performing a fasciotomy. Diagnosis of a compartment syndrome must be based on clinical findings. If any doubt is present, we recommend pressure measurement, with a cut off value for fasciotomy of delta P ≤ 40 mm Hg. Delaying deffinitive treatment is suggested until pressure values were secure.