The piriformis muscle goes from the sacrum to the hip joint where it inserts. There is one on each side of the body. It is a small muscle that directly overlaps the sciatic nerve as it exits the pelvis into the leg. In 8 percent of patients, the muscle actually goes through the nerve or the nerve goes through the muscle.
When the piriformis gets inflamed or swollen, it can irritate the sciatic nerve and cause leg pain that can simulate the pain of a pinched nerve root (lumbar radiculopathy). Piriformis irritation is often associated with sacroiliac dysfunction but can also occur on its own.
Sacroiliac stabilization (by surgery) may sensitize the piriformis, but this is often temporary and responds well to physical therapy (with, for example, ultrasound applications) and muscle relaxants. Less often, the piriformis may need injections and sometimes surgery.
Conservative treatment involves physical therapy and injections with a numbing agent and cortisone derivatives to decrease the inflammation. More recently, Botox injections have been used to try to relax the muscle. Often, Botox is not reimbursed by the insurance companies for that purpose and can be expensive. Please, check with your insurance provider.
The diagnosis of piriformis syndrome is often made by a special nerve study that demonstrates a compression of the sciatic nerve when the leg is placed in a position that tenses the muscle. A significant improvement with injections can also be considered diagnostic. More recently, MRI neurography has started to be used on a large scale. This directly visualizes the nerves. Each technique has its limitations.
The surgery is relatively easy. The tendon of the muscle is cut at the site of insertion on the bone (the trochanter of the femur), therefore relaxing it. The closure is with dissolvable stitches and skin glue. It requires an extra incision (also about 1.5 to 2 inches long) when done with sacroiliac surgery. A more involved surgery that directly explores the nerve is only used if the more simple procedure fails.
The problem with this surgery is that this anatomical area is well innervated and therefore more sensitive to pain than the sacroiliac region. Also, the muscle takes some time realizing that it is no longer attached and occasionally goes in bouts of uncomfortable spasms. Even though this procedure is easier than the sacroiliac surgery, most patients say that it is the most uncomfortable.
Even though the wounds usually heal in a couple of weeks, it may take longer (months) for the piriformis and surrounding tissues to settle down. However, this usually does not prevent a return to work and regular activities.
Piriformis surgery, when done with sacroiliac surgery, often adds to the hospitalization time and somewhat slows the recovery.
1. Piriformis muscle section