Perineural entrapment of an interscalene stimulating catheter.

A patient undergoing elective total shoulder arthroplasty had an Arrow Stimucath™ (Arrow International Reading, PA, USA) stimulating catheter inserted in the region of the interscalene brachial plexus using an ultrasound-guided in-plane approach. There was subsequent difficulty in removing the catheter and traction was associated with painful paraesthesia in the patient's thumb. Plain X-ray revealed a hook-shaped deformity of the tip and surgical exploration was required to remove the catheter, the tip of which appeared to be trapped within the sheath of the brachial plexus. We speculate that the mechanism for entrapment in this case was deformation of the catheter tip into a hook-like shape. The subsequent catheter-neural interaction prevented asymptomatic removal. We recommend that removal of peripheral nerve catheters be attempted only after resolution of sensory block so as to enable patients to report pain or paraesthesia. Imaging with ultrasound or X-rays may help ascertain catheter tip location and confirm whether deformity is present. We also recommend a low threshold for proceeding to surgical extraction, particularly if neurological symptoms are present.