This muscle is located above the tail head on either side of the dorsal spinous processes of the sacrocoxygeal vertebra. Do not go too far cranially or laterally, this region is not diagnostic as it has too few slow twitch fibers.


  • Lidocaine is injected under the skin but not into the muscle belly. This area has many nerves so 5-7 ml of lidocaine may be necessary.
  • A 2 inch incision is made through the skin and subcutaneous fat and fascia. The skin is not flexible in this area so a larger skin incision is needed.
  • Use skin retractors for visualization.
  • Parallel longitudinal incisions are made in the muscle 1/4 inch apart.
  • The cranial aspect of the muscle is grasped with forceps and the muscle is dissected out one-quarter inch deep and one-half inch long. Don’t pull this muscle out via forceps as that squishing creates atrophy. •This area can have a lot of subcutaneous fat. Make sure the sample is deep enough to obtain muscle tissue.
Sacrocaudalis Dorsalis Medialis Biopsy