Tyrolean tensiometer: A new instrument for easy intraoperative tension measurement before nerve coaptation

In reconstructive surgery microsurgical repair of dissected nerves can be done end-to-end or by using a nerve graft. Guidelines to support an objective decision, whether tension associated with direct suture is acceptable or grafting is needed, do not exist. All experimental data found concerned the clinical outcome when a certain length defect was treated in various animal models. The aim of this study was to show the feasibility of a new instrument for measuring the tension needed to coapt nerve stumps before beginning nerve suture.

A tension spring balance was modified in a way that the thread of the first suture is used to measure the force applied to the two nerve stumps by the suture before knotting. Immediately after measuring, the suture can be completed by knotting. Twenty-four rat sciatic nerves were dissected, segments of various length were resected, and tension needed for approximation was measured. These ex vivo data were combined with clinical outcome data of previous animal trials.

Data obtained showed that tension measured increased almost proportionally to the size of the gap created. The average additional time needed to measure the tension using the Tyrolean Tensiometer was 11 (+/-4) seconds.

None of the methods described before allow intraoperative tension measurement at a time when changes in strategy are still possible. The Tyrolean Tensiometer allows fast and reliable measurement of the tension acting on the first suture and might hereby be useful in predicting final operative outcome.