Fig. 121.8 Serratus posterior superior. Injection of trigger point (x) in the right serratus posterior superior. Localize the trigger point by palpation and direct the needle in the direction of a rib and tangentially in relation to the chest wall to avoid entering the intercostal space. Aspirate before injection. Trigger points in the region of muscle insertion are more easily palpated with abduction of the right scapula. Observe precautions to prevent pneumothorax. Inset, Trigger point pain pattern is shown by stippling.