Distribution of radiodense contrast medium after perineural injection of the palmar and palmar metacarpal nerves (low 4-point nerve block): an in vivo and ex vivo study in horses.
Abstract: Evidence-based information is limited on distribution of local anaesthetic solution following perineural analgesia of the palmar (Pa) and palmar metacarpal (PaM) nerves in the distal aspect of the metacarpal (Mc) region ('low 4-point nerve block'). Objective: To demonstrate the potential distribution of local anaesthetic solution after a low 4-point nerve block using a radiographic contrast model. Methods: A radiodense contrast medium was injected subcutaneously over the medial or the lateral Pa nerve at the junction of the proximal three-quarters and distal quarter of the Mc region (Pa injection) and over the ipsilateral PaM nerve immediately distal to the distal aspect of the second or fourth Mc bones (PaM injection) in both forelimbs of 10 mature horses free from lameness. Radiographs were obtained 0, 10 and 20 min after injection and analysed subjectively and objectively. Methylene blue and a radiodense contrast medium were injected in 20 cadaver limbs using the same techniques. Radiographs were obtained and the limbs dissected. Results: After 31/40 (77.5%) Pa injections, the pattern of the contrast medium suggested distribution in the neurovascular bundle. There was significant proximal diffusion with time, but the main contrast medium patch never progressed proximal to the mid-Mc region. The radiological appearance of 2 limbs suggested that contrast medium was present in the digital flexor tendon sheath (DFTS). After PaM injections, the contrast medium was distributed diffusely around the injection site in the majority of the limbs. In cadaver limbs, after Pa injections, the contrast medium and the dye were distributed in the neurovascular bundle in 8/20 (40%) limbs and in the DFTS in 6/20 (30%) of limbs. After PaM injections, the contrast and dye were distributed diffusely around the injection site in 9/20 (45%) limbs and showed diffuse and tubular distribution in 11/20 (55%) limbs. Conclusions: Proximal diffusion of local anaesthetic solution after a low 4-point nerve block is unlikely to be responsible for decreasing lameness caused by pain in the proximal Mc region. The DFTS may be penetrated inadvertently when performing a low 4-point nerve block.
Publication Date: 2010-08-19 PubMed ID: 20716191DOI: 10.1111/j.2042-3306.2010.00076.xGoogle Scholar: Lookup
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- Clinical Trial
- Journal Article
Summary
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This study investigates the dispersion of local anaesthetic solution in horses following a specific method of nerve block known as a ‘low 4-point nerve block.’ Using radiodense contrast medium and radiographs, the researchers visualized the spread of the injected solution in both live horses and cadaver limbs, noting a key finding that an inadvertent penetration of the digital flexor tendon sheath (DFTS) might occur during this procedure.
Objective and Methods
- The primary aim of this study was to observe the potential dispersion of local anaesthetic solution following a ‘low 4-point nerve block’ in horses, using a radiographic contrast model.
- This nerve block procedure targets the palmar (Pa) and palmar metacarpal (PaM) nerves in the distal aspect of the metacarpal (Mc) region. The researchers injected a radiodense contrast medium (which shows up on radiographs) into these areas in both forelimbs of 10 mature, lameness-free horses.
- Immediately after the injection and 10 and 20 minutes post-injection, radiographs were taken and analysed to examine the pattern of the contrast medium’s spread.
- This procedure was repeated with a mixture of methylene blue and the contrast medium in 20 cadaver horse limbs, which were then dissected for further analysis.
Results
- The outcomes revealed that in 77.5% of the live injections, the contrast medium appeared to spread within the neurovascular bundle. Over time, the contrast medium diffused proximally but never moved beyond the mid-Mc region. In two cases, there was an indication of the medium being present in the digital flexor tendon sheath (DFTS).
- Following the PaM injections, the contrast medium mainly scattered around the injection site. In the cadaver limbs, contrast medium and dye distribution within the neurovascular bundle was observed in 40% of instances, while penetration into the DFTS was noted in 30% of cases.
- After PaM injections into cadaver limbs, 45% showed diffusion around the injection site and 55% showed both diffuse and tubular distribution patterns.
Conclusions
- Based on these findings, the study suggests that local anaesthetic solution diffusion following a ‘low 4-point nerve block’ is unlikely to alleviate lameness caused by pain in the proximal Mc region, as the solution does not reach beyond the mid-Mc region.
- However, the research also demonstrated a potential risk of the DFTS being unintentionally penetrated during the nerve block procedure, a crucial insight for veterinarians during application.
Cite This Article
APA
Nagy A, Bodò G, Dyson SJ, Compostella F, Barr AR.
(2010).
Distribution of radiodense contrast medium after perineural injection of the palmar and palmar metacarpal nerves (low 4-point nerve block): an in vivo and ex vivo study in horses.
Equine Vet J, 42(6), 512-518.
https://doi.org/10.1111/j.2042-3306.2010.00076.x Publication
Researcher Affiliations
- Equine Diagnostic Centre, University of Bristol, UK. annamaria.nagy@aht.org.uk
MeSH Terms
- Animals
- Cadaver
- Contrast Media / pharmacokinetics
- Foot / diagnostic imaging
- Foot / innervation
- Forelimb / diagnostic imaging
- Forelimb / innervation
- Horse Diseases
- Horses
- Injections, Intra-Articular / methods
- Injections, Intra-Articular / veterinary
- Metacarpophalangeal Joint
- Nerve Block / methods
- Nerve Block / veterinary
- Radiography
- Tissue Distribution
Citations
This article has been cited 1 times.- de Souza AF, Pascual CJ, Maia BT, do Valle De Zoppa AL. Diffusion of dye after perineural injection of the palmar/plantar nerves in two different sites in horses: an ex-vivo study.. Vet Res Commun 2022 Feb;46(1):283-288.
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