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ORIGINAL ARTICLE
Year : 2007  |  Volume : 1  |  Issue : 2  |  Page : 53-56

Sonoanatomy of the ulnar nerve in the distal forearm


1 Consultant Anesthetist, King Khalid University Hospital, Riyadh, Saudi Arabia
2 Professor of Anesthesia, College of Medicine, King Saud University, Riyadh, Saudi Arabia
3 Associate Professor, Chairman Department of Anesthesia, College of Medicine, King Saud University., Saudi Arabia
4 Resident in Anesthesia, King Khalid University Hospital., Saudi Arabia
5 Registrar in Anesthesia, King Khalid University Hospital., Saudi Arabia

Correspondence Address:
A Thallaj
Riyadh 11471, P.O.Box 7805
Saudi Arabia
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Source of Support: None, Conflict of Interest: None


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Date of Web Publication18-Jul-2009
 


How to cite this article:
Thallaj A, El-Dawlatly A, Turkistani A, Zoraigi O, Al-Deen M S. Sonoanatomy of the ulnar nerve in the distal forearm. Saudi J Anaesth 2007;1:53-6

How to cite this URL:
Thallaj A, El-Dawlatly A, Turkistani A, Zoraigi O, Al-Deen M S. Sonoanatomy of the ulnar nerve in the distal forearm. Saudi J Anaesth [serial online] 2007 [cited 2020 Feb 29];1:53-6. Available from: http://www.saudija.org/text.asp?2007/1/2/53/51861


   Background Top


THE PRACTICE OF ULTRASOUND guided regional anesthesia requires excellent knowledge of the related clinical anatomy. In the distal forearm, the ulnar nerve gives off a dorsal cutaneous branch which supplies sensation to the dorsomedial hand and digits [1] . Ulnar verve block in the distal forearm with conventional technique may spare the dorsal branch and result in incomplete block [2],[3] . Ultrasound represents a unique modality for visualizing peripheral nerves, because of its ability to scan the nerve over a long distance, and it has been used to visualize and to guide ulnar nerve block in the distal forearm [4],[5],[6] . We aimed to describe the sonographic appearance of the ulnar nerve division in the distal forearm, test the reliability of ultrasound to depict the dorsal cutaneous branch and to examine the relationship of the ulnar nerve division point and other palpable bony landmarks.


   Methods Top


After institutional approval and informed consent, 100 male and female volunteers (equal gender distribution) were recruited from king khalid university hospital staff. Exclusion criteria include injury or deformity to the upper extremity. Initially, volunteers had their anthropometric data recorded, including age, gender, height and weight. Using high frequency (5-13MHz) linear transducer (LOGIQ e, GE), we scanned the medial aspect of the left distal forearm. A transverse view of the ulnar nerve, the division point and the dorsal cutaneous branch were obtained. The skin over the division point (D point) was marked in agreement between two anesthetists [Figure 1]. Two measurements were taken to map out the ulnar nerve division point [Figure 2]. A line was drawn from the ulnar styloid process to the olecranon and this distance was recorded as (OS), and the distance between the division point and the ulnar styloid process was recorded as (DS).


   Results Top


All subjects completed the study. Demographics of the sample can be summarized as follows [Figure 3]: Age (mean+/- SD; male: 32.9+/- 8.9, female: 39.3+/­10yr; p< .01), weight (male: 75.9+/-19, female: 61.8+/- 10 Kg; p< .0001), height (male: 172.6+/-7.1, female: 158.4+/-6 Cm; p< .0001). The ulnar nerve in the distal forearm appeared as hyper-echoic triangle with gross internal hypo-echoic punctuate and lying medial to the ulnar artery between the flexor carpi ulnaris, flexor digitorum profondus and flexor digitorum superficialis muscles [Figure 4]. Moving the transducer distally, the ulnar nerve appeared to have a 'flank' (division -D point), the dorsal coetaneous branch consistently leaves the main ulnar nerve beneath the flexor carpi ulnaris muscle and winds around it [Figure 5]. In the study group, male subjects have longer OS distance (26.8+/-1.6cm) than females (24.6+/-1.4cm); p< .0001 [Figure 6]. But there were no significant differences in the DS distance (male: 5.9+/-1.4 vs. female 5.7+/-1.2 cm; p = .43) or the DS/OS ratio (male: 0.21+/- .05 vs. female 0.23+/- .04; p = .12), [Figure 7].


   Discussion Top


The dorsal cutaneous branch of the ulnar nerve is a terminal sensory branch. It arises proximal to the wrist and winds around the ulnar side of the forearm to supply sensation to the dorsomedial aspect of the hand and digits. In this study, we were able to visualize the division point and the dorsal cutaneous branch in our 100 volunteer subjects. Unlike the ulnar nerve which was identifiable in static images because of its typical "honeycomb" appearance, the dorsal cutaneous branch was best visualized in video clips through its appearance passing under the fascial plane of the flexor carpi ulnaris muscle. Previous anatomical studies (Grossman et al [7] ) have found that the dorsal branch originated at an average distance of 5.5 cm proximal to the ulnar head. In our study, we measured the distance between the ulnar nerve division point and the ulnar styloid process (the average length of the ulnar styloid process is 4.2 mm [8] ), our sonographic estimates of the DS distance (~ 5.9 cm) confirmed the previous anatomical findings. We found also that the DS distance has no correlation with other measured variables. In conclusion, high-end ultrasound machines with high frequency broad band transducers can reliably visualize the ulnar nerve division point and the dorsal cutaneous branch in the distal forearm.

 
   References Top

1.Carol A. Boles, Srilatha Kannam, AnneB. Cardwell: The Forearm; Anatomy of the muscle compartments and nerves. American Journal of Roentgenology 2000; 174; 151-159.  Back to cited text no. 1    
2.M.j. Botte, M.S.Cohen, C.J.Lavernia, H.P.Von Schreder,H.Gellman,E.M.Zinberg. The dorsal branch of the ulnar nerve: An anatomical study. Journal of Hand Surgery; 15A (1990), pp: 603-607.  Back to cited text no. 2    
3.A.Tindall, M.Patel, A.Frost, I.Parkin, J.Compson: The anatomy of the dorsal cutaneous branch of the ulnar nerve­a safe zone for positioning of the 6R portal in wrist arthroscopy. Journal of Hand Surgery; Vol 31,Issue 2, April 2006, PP: 203-205.  Back to cited text no. 3    
4.Ingeborg Schfthalter-zoppoth M.D, Andrew T. Gray M.D: Ultrasound-guided ulnar nerve block in the presence of a superficial ulnar artery. Regional Anesthesia and Pain Medicine. Vol29, Issue 3; May-June 2004, PP:297-298.  Back to cited text no. 4    
5.Andrew T. GrayM.D, Ingeborg Schfthalter-zoppoth M.D: Ultrasound guidance for ulnar nerve block in the forearm. . Regional Anesthesia and Pain Medicine. Vol 28, Issue 4, July-August; PP: 335-339.  Back to cited text no. 5    
6.A. Kathirgamanathan, J.French, G.L. Foxall, J.G. Hardman, N.M. Bedforth: Ultrasound anatomy of the ulnar nerve in the upper and forearm. . Regional Anesthesia and Pain Medicine. Vol 32, Issue5. Sep 2007; Page 3.  Back to cited text no. 6    
7.Grossman J A, Yen L, Rapaport D: The dorsal cutaneous branch of the ulnar nerve. An anatomic clarification with six case reports. Chir Main. 1998;17(2): 154-8.  Back to cited text no. 7    
8.Brigitte Van Der Heijden M.D, Sadra Groot M.D, Arnold H. Shuurman M.D: Evaluation of the ulnar styloid length. Journal of Hand Surgery. Vol 30, Issue 5. Sept 2005; pp: 954-959.  Back to cited text no. 8    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]



 

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