Postocclusive transcutaneous oximetry in followup assessment of tibial nonunion and healed tibia fractures

Transcutaneous oximetry measurements were performed on 25 limbs in 25 patients with clinical and radiographic nonunion, and compared with data obtained from patients with healed tibia fractures and a control group of nonfractured extremities. A technique of "stress testing" vascular inflow patterns by temporary occlusion of arterial inflow was utilized to accentuate differences in perfusion not apparent at rest between normal limbs and those with inflow impairment. Changes in postocclusive hyperemic response were monitored by changes in transcutaneous oxygen detected by sensors placed over the dorsum of the foot, at the fracture site, over the anterior compartment, and at the chest. No statistically significant differences were found between the control group and the group of united tibia fractures. Analysis of results using the unpaired Student's t-test demonstrated statistically significant differences between the control and nonunion groups at each limb site tested (p less than 0.05). The prolonged oxygen recovery time values found in more than half the limbs with nonunion are consistent with the presence of impaired oxygenation following physiologic stress. The impairment of oxygenation appears to be on a perfusion basis and reflects the limited capacity of many limbs with tibial nonunion to respond to experimental ischemia with immediate compensatory hyperemia. Clinical relevance: This technique is a feasible method for serially assessing the regional oxygenation of a limb, and substantiates ischemia as a possible factor in the genesis of tibial nonunion.