The effect of knee-spanning external fixation on compartment pressures in the leg.

OBJECTIVES: External fixation is frequently used for provisional and/or definitive stabilization of open and closed fractures and dislocations involving the lower extremity. There is some concern, however, that application of an external fixator with subsequent reduction of the fractures with distraction may precipitate the development of compartment syndrome. The hypothesis of this study was that application of external fixation and restoration of limb length would have no effect on the compartment pressures.

DESIGN: Prospective cohort study.

SETTING: Academic medical center, 2 level 1 trauma centers.

PATIENTS: Between October 2003 and May 2006, 25 patients who met inclusion criteria and underwent immediate knee-spanning external fixation.

INTERVENTION: All 4 compartments of the injured leg were measured with a Solid-State Transducer Intra Compartment device or an arterial line set-up during the temporizing procedure at 4 different time points. In addition, at the time each pressure reading was taken, the patient's diastolic pressure was recorded from the anesthesia monitor.

MAIN OUTCOME MEASUREMENT: Elevation of compartment pressure at any of 4 distinct time points during the procedure. Each of the compartments was measured and recorded 4 times: (1) after the patient had been draped but before any fixation or reduction of the fracture, (2) immediately after the insertion of the fixator pins, (3) immediately after reduction of the fracture, and (4) 5 minutes after the reduction. A threshold of less than 30 mm Hg differential from diastolic pressure in conjunction with clinical examination was set as an indication for 4-compartment fasciotomy.

RESULTS: : Twenty-five patients with a mean age of 52 years (range, 21-69 years) were enrolled in the study. Injuries included proximal tibial fractures (Orthopaedic Trauma Association types, 41) in 21 patients; knee fracture-dislocation (Moore type II) in 2 patients, and knee (femoro-tibial) dislocations in 2 patients. Two fractures were open, and all other injuries were closed. Fasciotomy was required in 3 cases at initial compartment measurement. In the remaining 22, there were no significant trends toward increased compartment pressures as a result of external fixation placement and knee reduction. There were 9 patients (41%) who had a transient DeltaP < 30 mm Hg at some point during surgery. No patient had a DeltaP < 30 mm Hg sustained through the conclusion of the procedure, and no compartments were released in any of these patients. None of the patients in the study developed compartment syndrome after surgery, and no sequelae of compartment syndrome were noted at minimum 6-month follow-up.

CONCLUSIONS: Application of knee-spanning external fixation as a temporary measure for stabilization of high-energy proximal tibial fractures and dislocations may result in transient elevation of intracompartmental pressure of the leg. Although DeltaP may fall below the threshold of 30 mm Hg, this does not appear to lead to compartment syndrome.