Spinal anaesthesia (or spinal anesthesia), also called spinal analgesia, spinal block or subarachnoid block (SAB), is a form of regional anaesthesia involving injection of a local anaesthetic into the subarachnoid space, generally through a fine needle, usually 9 cm long (3.5 inches). For extremely obese patients longer needles are available (12.7 cm / 5 inches). The tip of the spinal needle has a point or small bevel.