Triangle of auscultation is impoant in clinical practise. The boundary of which is not formed by:
The triangle of auscultation is a small triangular interval bounded,Superiorly by the trapezius muscleInferiorly by the latissimus dorsiLaterally by the medial border of the scapulaThis is the only pa of the back which is not covered with muscles. Respiratory sounds are better heard with a stethoscope here than that heard elsewhere in the back. Ref: Anatomy Dissector By Carmine D. Clemente, 2010, Page 244.
Serratus anterior
Scapula
Trapezius
Latissimus dorsi