IN VIVO MEASUREMENT OF TISSUE METABOLISM IN ROTATOR CUFF TENDONS: IMPLICATIONS FOR SURGICAL MANAGEMENT

Abstract

Aim To determine if tissue metabolism varies in supraspinatus tendons with distance from the edge of the rotator cuff tendon tear and also with differing size of tear.

Background Tissue metabolism can be assessed by measuring oxygen and nitrous oxide concentrations within the tissue. Viable tendon tissue consumes oxygen and contains nitrous oxide (used in the general anaesthetic) from the blood stream. Non-viable tendon tissue will not consume oxygen but will contain nitrous oxide.

Methods Oxygen and Nitrous Oxide concentrations were measured amperometrically using silver needle microelectrodes.

The needle was inserted into the supraspinatus tendon of patients with massive, large, medium and small full thickness rotator cuff tears and patients with partial thickness and no tears. Patients undergoing open stabilisation were used as controls. Measurements were made at a number of quantifiable points from the tendon edge to allow the creation of a topographical map of tissue metabolism. Oxygen consumption was calculated using measured oxygen and nitrous oxide levels at each point.

Results In patients with rotator cuff tears oxygen consumption was significantly lower near to the edge of the tear.

Patients with impingement syndrome but no evidence of a rotator cuff tear also showed a decreased level of oxygen consumption in the anterior part of supraspinatus, but this was significantly higher than the levels seen in the torn tendon.

The control group showed no significant alteration in oxygen levels

Conclusion Patients with rotator cuff tendon tear demonstrate significantly reduced levels of tissue metabolism. This reduction in tissue viability is significantly greater at the edge of the tear and in larger tears. Patients with intact tendons and impingement syndrome also demonstrate minor reduction in tissue tendon viability compared with controls.