Session III Tibia

*Pulsatile Plantar Compression and Tissue Viability during Compartment Syndrome

James P. Stannard, MD, Robert M. Harris, MD, Paul Mongan, MD, Michelle Leland, DVM

Brooke Army Medical Center, Orthopaedic Surgery Service, Ft. Sam Houston, TX

Pulsatile plantar compression is a relatively new form of mechanical DVT prophylaxis. In addition to numerous reports of low rates of DVT in patients treated with pulsatile foot pumps, investigators have recently reported increased blood flow and decreased swelling as a result of pulsatile plantar compression. There have been no studies reported investigating the use of foot pumps to improve tissue oxygenation during compartment syndrome.

A prospective animal study was performed using a four compartment lower extremity baboon (papio sp.) model. Primates were utilized because of their marked anatomic similarity to human lower extremities and the need for a foot with a plantar venous plexus. Fourteen large adult male baboons had a compartment syndrome experimentally induced by infusion of lactated Ringers solution into each of the four lower extremity compartments bilaterally. Pressures were maintained between 5-20mm Hg below the animals diastolic blood pressure. Pulsatile plantar compression was accomplished with Plexipulse (NuTech, San Antonio) foot pumps. Nerve function the deep branch of the Peroneal nerve and the Tibial nerve was monitored using motor evoked potentials. Capillary blood flow was quantified in the anterior and deep posterior compartments using 18g needle laser doppler (Transonics Systems, Ithaca NY). Gross and microscopic pathology of the anterior and deep posterior compartments was performed. Capillary blood flow was increased in both the anterior and deep posterior compartments in animals that had foot pumps compared with controls (p < .05). Analysis of motor evoked potentials demonstrated significant improvements in function in the deep posterior compartment (p < .05) with a trend toward improved function in the anterior compartment. The deep Peroneal branch did not show as much decrease in amplitude on the motor evoked potentials as the Tibial nerve. Gross pathology analysis of muscle tissue in the anterior and deep posterior compartments also showed improved muscle tissue viability (p < .05) in foot pump animals compared with controls. Muscle tissue was blindly scored by two investigators for color, consistency, and contractility.

Results of this animal model suggest increased blood flow despite compartment pressures of 60-80 mm Hg. As a result of the increased blood flow, nerve function and muscle viability were both significantly improved. The results of this study suggest that pulsatile plantar compression may have a role in "borderline" compartment syndrome in humans. Additional studies are currently underway to clarify the roles of this new modality in trauma patients with increased lower compartment pressures.