Authors

Dr Keran Sundaraj MBBS, MSc (Trauma), FRACS, FAOA

Total hip replacement is a highly effective treatment for end-stage conditions such as osteoarthritis. Quality of Life scores are high, with impressive levels of patients satisfaction.

Residual pain after total hip replacement is uncommon. The causes for this include a wide variety of diagnoses. Examples include infection, loosening of the components, heterotopic ossification (extra bone formation), fracture (break), and 'referred' pain from the spine. Psoas impingement (iliopsoas impingement/bursitis) is one of these rare causes.  

Anatomy

The hip is a ball and socket joint. The socket is formed by the acetabulum (part of the pelvis), and the ball is formed by the femoral head (upper end of the thigh bone). In arthritis, the

protective cartilage cap is lost, and the joint surface becomes irregular. The surfaces are no longer smooth and free running, and this leads to stiffness and pain. Eventually, the joint wears away to such an extent that the bone upper end of the femur rubs on the acetabulum. In severe stages, the surgical solution is a total hip replacement. 

During surgery, the bones are shaped with special instruments to fit a range of sizes for the implants. Occasionally, there may be a slight difference between the implant and your bone. Such a situation can lead to an 'overhang' of a prosthesis. This is particularly relevant for the acetabular (cup/socket) component. With this 'overhang', the tendons that pass over the top may become irritated. This is seen in the circumstance of the psoas tendon, which passes over the front of the acetabular socket.

Over time this can cause inflammation due to the constant rubbing. Typically patients have groin pain (front of the hip), which is made worse with hip flexion. Some patients report difficulty in raising their leg and may use their hands to help with lifting them.

Imaging Tests

X-rays

• This helps to determine if there are any implants out of position, extra bone formation, or components that may be loose

CT

• This provides a three-dimensional picture of the bones and the implants.

• Sometimes a "metal-artefact reduction CT" is performed. This is a particular type of scan that improved the quality of the picture, which the implant metal can affect.

MRI

• Occasionally an MRI is ordered to look at soft tissues.

• Sometimes a "metal-artefact reduction MRI" is performed. This is a particular type of scan that improved the quality of the picture, which the implant metal can affect.

Rationale for Treatment

Diagnosis of psoas impingement can be challenging. Other diagnoses, such as infection and loosening, may need to be excluded first. Treatment will always begin with attempting the most straightforward and least invasive measures. This may include treatments such as anti-inflammatory, pain-relieving medication and physiotherapy.

Treatment

Conservative

• Anti-inflammatory medications and pain relief is used to help with managing the symptoms. Ideally, you should avoid strong narcotic medications. These medications are addictive and not necessarily effective at controlling this type of pain.

• Physiotherapy helps strength, stretch and regain motion. Targeted physiotherapy may be helpful to get you moving again.

• Corticosteroid injections are used for both 'diagnostic' and 'therapeutic' purposes. Local anaesthetic is used for 'diagnosis'. If you have relief from your symptoms (even if for a few hours), this may help pinpoint your symptoms coming from the psoas tendon. Steroid in the injection has a 'therapeutic' role. The steroid helps to settle inflammation at a local level. Some patients achieve excellent control of symptoms, though other see symptoms recur.

Surgery

• This is reserved for the most extreme cases and avoid if the conservative measures are effective.

• Surgery has a broad application and is tailored specifically to the underlying reason for psoas impingement. For some patients, this may be a minor operation to release the tendon. For others, it may mean a more major operation requiring adjustments to the implants.

• In all circumstances, surgery is avoided for the risk of infection with implants in place.