Ligament and tendon oxygenation measurements using polarographic oxygen sensors

This pilot study was designed to investigate a new flexible polarographic oxygen sensor for intraarticular oxygen tissue tension monitoring, as a first step in designing a combined simultaneous oxygen and perfusion monitor. The tendoachilles in the sheep provided the initial testing model, which was followed by in vivo testing in the human knee. In the animal model, the tendoachilles was perforated by a single needle through which the new flexible multichannel polarographic oxygen sensor probe was passed. Variations in blood and oxygen delivery to the hindlimb were then produced by tourniquet and fraction of inspired oxygen (FiO2) changes. The oxygen sensors appropriately recorded current variations proportional to the hypothesized oxygen delivery. In the human model, the anterior cruciate ligament (ACL) in five human knees was exposed during routine total knee replacement surgery and stripped of the fat pad and synovial attachments. The probe was inserted into the substance of the ligament from distal to proximal. Oxygen measurements were taken with the tourniquet elevated and then inflated, in an effort to evaluate the response of the oxygen sensors and to establish the degree of oxygenation that the bone blood supply provides to the ACL. In the sheep, 100% of the time (13 of 13 events), the current changed appropriately to a change in the FiO2. Ninety-four percent of the time (17 of 18 events), the current changed appropriately to a tourniquet change. In the human ACL, the probe was 83% sensitive (5 of 6 events) to a tourniquet change. The FiO2 changes were inconclusive owing to an insufficient amount of time allowed for tissue perfusion.(ABSTRACT TRUNCATED AT 250 WORDS)