Study compares two T9 erector spinae block approaches in dogs
Bottom line
A new cadaveric study in Frontiers in Veterinary Science compared two ultrasound-guided erector spinae plane, or ESP, block approaches at the ninth thoracic vertebra in dogs: a transverse approach and a longitudinal approach. In 23 canine cadavers, researchers injected dye and contrast at T9 and then assessed spread with CT and dissection. Both techniques produced similar nerve staining and overall cranial-caudal spread, but the transverse approach had fewer placement errors: all transverse injections were placed over the intended dorsolateral edge of the transverse process, while 18.75% of longitudinal injections were misplaced laterally. The study also found that spread tended to favor the cranial direction, and that the dorsolateral edge landmark was consistently identifiable cranial to T11. (frontiersin.org)
Why it matters: For veterinary professionals using regional anesthesia, the findings suggest the transverse T9 ESP approach may offer a more reliable way to reach the intended plane without changing overall distribution compared with the longitudinal technique. That’s relevant because canine ESP work is still a developing evidence base: earlier cadaver studies established thoracic and thoracolumbar spread patterns, and a small clinical series in dogs undergoing sternotomy suggested ESP blocks can be part of multimodal analgesia, but called for more clinical outcome data. (frontiersin.org)
What to watch: The next step is whether these cadaveric findings translate into better block consistency, analgesia, and safety in live clinical patients undergoing thoracic procedures. (frontiersin.org)
Key facts
- Study type
- Cadaveric study
- Journal
- Frontiers in Veterinary Science
- Species
- Dogs
- Sample size
- 23 canine cadavers
- Intervention
- Ultrasound-guided erector spinae plane, or ESP, block at T9
- Compared approaches
- Transverse and longitudinal
- Main finding
- Both approaches had similar nerve staining and cranial-caudal spread
- Placement accuracy
- All transverse injections were over the intended dorsolateral edge, versus 18.75% lateral misplacement with longitudinal injections
- Anatomy finding
- The dorsolateral edge landmark was consistently identifiable cranial to T11
A newly published cadaveric study adds another piece to the growing literature on ultrasound-guided erector spinae plane blocks in dogs, this time focusing on the ninth thoracic vertebra. Investigators reported that transverse and longitudinal approaches at T9 produced broadly comparable injectate spread and nerve staining, but the transverse technique reduced misplacement, with all transverse injections landing over the intended dorsolateral edge of the transverse process compared with lateral misplacement in 18.75% of longitudinal injections. (frontiersin.org)
That matters because ESP blocks in dogs remain technically promising, but still relatively underdefined compared with more established regional techniques. Earlier canine cadaver work published in 2019 described thoracic ESP block spread at T5 and showed consistent dorsal ramus staining, though ventral ramus staining was limited and anatomic landmark identification could be inaccurate in a substantial share of injections. Subsequent thoracolumbar work in 2022 showed that anatomy changes caudal to T11 can affect target selection, supporting the use of different landmarks depending on spinal level. (pubmed.ncbi.nlm.nih.gov)
In the new study, the authors used 23 canine cadavers in a double-blinded experimental design. Twenty-one cadavers underwent bilateral injections of 0.6 mL/kg dye and contrast at T9 using either the transverse or longitudinal approach, followed by CT and dissection; five cadavers were later excluded from dissection analysis. Median spread was 8 vertebrae with the transverse approach and 8.5 with the longitudinal approach, with no significant difference between groups. Both techniques showed preferential cranial spread, and both stained medial and lateral branches of the dorsal rami, while ventral branch staining occurred in 62.5% of transverse injections and 68.75% of longitudinal injections. Epidural and sympathetic trunk spread were seen with both techniques, and one intravascular injection occurred in the longitudinal group. (frontiersin.org)
The authors also examined the anatomy behind the technique. They found the dorsolateral edge of the transverse process was smaller than the transverse process itself and was predominantly absent caudal to T10, but it was consistently identifiable cranial to T11. That anatomical point helps explain why the T9 level may be a practical target for this specific landmark-based approach, while other regions may need different guidance strategies. Their conclusion was measured: the two approaches were functionally similar in spread, but the transverse approach reduced injectate misplacement. (frontiersin.org)
There doesn’t appear to be a separate institutional press release or broad industry reaction tied to this paper, but the study fits a clear research trajectory from the same field: refine ultrasound-guided fascial plane blocks by spinal level, then test which landmarks are most reproducible. Related literature suggests the clinical interest is real. A 2022 report in dogs undergoing sternotomy found bilateral thoracic ESP blocks could be incorporated into multimodal analgesia with low rescue fentanyl use, although the authors emphasized that larger clinical studies are still needed to assess safety and efficacy. (pubmed.ncbi.nlm.nih.gov)
Why it matters: For veterinary anesthetists and surgeons, this is less about proving that ESP blocks work clinically, and more about improving technical reliability before wider adoption. A technique that produces similar spread but fewer misplaced injections could reduce variability between operators and help standardize training. The finding of frequent cranial spread may also inform where clinicians choose to inject relative to the intended surgical field. At the same time, this remains cadaveric evidence, so it can’t answer key clinical questions such as duration of analgesia, hemodynamic effects, complication rates in live patients, or whether better placement accuracy translates into better pain control. (frontiersin.org)
What to watch: Expect the next meaningful step to be prospective live-animal studies at thoracic levels that compare transverse and longitudinal ESP techniques on block success, perioperative opioid-sparing effects, and complications, especially in dogs undergoing thoracotomy, sternotomy, or other painful thoracic procedures. (frontiersin.org)