In theory, if the needle is long enough you can stick it wherever you want, but whether or not growth will occur is another story. Basically the body has three different types of muscle tissue, Smooth muscle, called so because it's the only one lacking striations, cardiac muscle, or what forms the contractile wall of your heart, and skeletal muscle. Skeletal muscle is what you inject anabolic steroids into, and skeletal muscles are what control voluntary movement. Growth occurs when a steroid hormone complex stimulates the transcription of mRNA which is translated into a specific protein. Unlike smooth muscles and cardiac muscles, the protein receptors in skeletal muscles interact with some hormones (in this case, anabolic) by means of intercellular reception. This is how hydrophobic molecules pass over the phospholipid bilayer, and steroid hormones are hydrophobic, which is why your skeletal muscles can increase protein uptake with the administration of anabolics but your cardiac and smooth muscles don't.