In vivo measurement of tissue metabolism in rotator cuff tendons: Implications for surgical management

Authors: A.J. Carr, T.J.W. Matthews, S.R. Smith, J.G. Urban

References: SECEC 2005

Abstract
AIMS: To determine if tissue metabolism varies in supraspinatus tendons with distance from the edge of the rotator cuff tendon tear and also with different size of tear.

MATERIAL: Tissue metabolism can be assessed by measuring oxygen and nitrous oxide. Viable tendon tissue consumes oxygen and contains nitrous oxide (used in the general anaesthetic) from the blood stream. Non-viable tendon tissue does not consume oxygen although contains nitrous oxide. 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 tears 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 the 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 is tissue viability is significantly greater at the edge of the tear and in large tears. Patients with intact tendons and impingement syndrome also demonstrate minor reduction in tissue tendon viability compared with controls.