2017 ISAKOS Biennial Congress ePoster #2602

 

Contribution of the Lateral Cutaneous Nerve of Forearm in Wide Awake Thumb Surgery: A Sonographic Study

Gregory A. Hoy, FRACS, FAOrthA, FACSP, FASMF, Melbourne, VIC AUSTRALIA
Christopher Hasenkam, BAppSc, Melbourne, Victoria AUSTRALIA
Paul Soeding, PhD, FANZCA, Melbourne, Victoria AUSTRALIA

Melbourne Orthopaedic Group, Dept of Surgery Monash University, Melbourne, Victoria, AUSTRALIA

FDA Status Cleared

Summary

The Lateral Cutaneous Nerve of Forearm must be considered when blocking for base of thumb procedures due to nerve distribution overlap

Abstract

Purpose

Surgical intervention for basal osteoarthritis of the thumb involves incisions across the wrist joint on either the volar or dorsal side. With the advent of ultrasound-guided regional anaesthesia, basal thumb joint arthroplasties can be performed using targeted peripheral nerve blockade, to avoid the morbidity of whole arm regional anaesthesia. Conventional belief dictates that anaesthesia can be achieved by solely blocking the Median and Superficial Radial nerves. This study focuses on the anatomical variation of the Lateral Cutaneous Nerve of Forearm (LCNF) where distal innervation to the dorsolateral thumb may also occur. This has important implications for achieving total surgical anaesthesia in thumb surgery, with regional blockade.

Methods

Following informed consent, patients were placed supine and each nerve was identified using surface ultrasonography (18MHz linear array probe B-K400, Denmark). The sonographic appearance of each nerve was identified and documented in relation to surrounding anatomy. The nerve was then blocked by circumferential injection of lignocaine 2% (3-5mL) and the cutaneous innervation mapped using loss of sensation to fine touch and thermal modalities. The extent of distal numbness was related to the radiocarpal joint.

Results

Under ultrasonography, the LCNF was located deep to the Cephalic Vein in all cases (n=17). It was visualised and blocked 98.7mm ± 2.6mm distal to the Interepicondylar Line. The distal cutaneous distribution involved the Radiocarpal Joint and surgical field in 93% of cases (n=15). The Superficial Radial Nerve (n=3), and Median Nerve (n=3), followed typically understood patterns of cutaneous distribution.

Conclusion

The LCNF can be easily visualised and blocked using surface ultrasonography. In clinical practice, innervation of the cutaneous dorsolateral thumb by the LCNF must be considered when performing regional anaesthesia for thumb suspensionplasty and other basal thumb joint procedures.