title: Comparison of the volar and medial approach in peripheral block of ulnar nerve at the wrist - a cadaveric study.
abstract: BACKGROUND
  Two standard approaches are described to block the ulnar nerve at wrist. These include a) the traditional Volar approach where the needle is inserted lateral to tendon of flexor carpi ulnaris (FCU) b) Medial approach where the needle is inserted posterior to the tendon of FCU. Caution must be exercised to avoid puncture of the ulnar artery and/or intraneural injection of the ulnar nerve in both the approaches.
  
  
  OBJECTIVE
  This study compares the volar and medial approach to the peripheral block of ulnar nerve at the wrist. The objective was two fold: a) to analyze the position of the ulnar nerve and the ulnar artery in relation to the Flexor Carpi Ulnaris tendon b) to assess the risk of injury to ulnar artery in both the volar and medial approach.
  
  
  METHODS
  Twelve cadaveric upper limbs were used and both approaches compared by an observational study.
  
  
  METHODS
  Two 18 G needles were inserted up to a depth of 7 mm using the standard volar and medial approach. The pattern of arrangement and positions of the ulnar artery and nerve in relation to FCU tendon were observed. The distance between the tip of needle and its proximity to the ulnar artery, and risk of injury were determined. Statistical analysis was done using SPSS for Windows, Version 16.0. Chicago, SPSS Inc.
  
  
  RESULTS
  Three patterns of arrangement and position of the ulnar nerve and artery were observed. Puncture of ulnar artery was seen in 50% of cases in the volar approach as compared to no injury at all in the medial approach. The ulnar artery is highly liable to injury during the volar approach in type I and II and safe only in type III arrangement of ulnar artery. The medial approach showed no injury to the ulnar artery or nerve at a penetration depth of 7mm.
  
  
  CONCLUSIONS
  The medial approach is safer compared to volar approach for peripheral block of ulnar nerve at wrist.
authors.affiliation: Associate Professor, Department of Anatomy, Christian Medical College , Vellore, India .
authors.forename: Ivan James
authors.initials: IJ
authors.lastname: Prithishkumar
authors.affiliation: Postgraduate Registrar, Department of Anatomy, Christian Medical College , Vellore, India .
authors.forename: Praisy
authors.initials: P
authors.lastname: Joy
authors.affiliation: Assistant Professor, Department of Anaesthesia, Christian Medical College , Vellore, India .
authors.forename: Cephas
authors.initials: C
authors.lastname: Satyanandan
keywords: Medial approach; Peripheral block; Ulnar nerve; Wrist