Supercapsular percutaneously assisted total hip arthroplasty for osteoarthritis

Osteoarthritis, also known as degenerative joint disease, is a disorder of synovial joints. It occurs when damage triggers repair processes leading to structural changes in a joint. There are 2 main types of osteoarthritis: primary (more generalised osteoarthritis with unknown aetiology) and secondary (osteoarthritis with a known cause, such as injury or inflammation in the joint). When it affects the hip, symptoms include joint stiffness, pain and reduced function, such as difficulty walking.

Care and management of osteoarthritis is described in NICE's guideline on osteoarthritis in over 16s. Current management of hip osteoarthritis includes lifestyle changes (such as weight loss), physical or occupational therapy, medications and surgery (such as hip resurfacing, total hip arthroplasty and osteotomy).

Supercapsular percutaneously assisted total hip arthroplasty is also described as the 'SuperPath' approach. It is a minimally invasive approach to total hip arthroplasty. The aim, as with standard posterior or direct lateral approaches, is to reconstruct the hip to reduce symptoms and improve hip function, but with smaller cuts.

The procedure is done under general or regional anaesthesia. The patient is usually put in the standard lateral decubitus position, with the hip in 45 degrees of flexion and 10 to 15 degrees of internal rotation. A cut is made superior to the greater trochanter. The gluteal fascia is cut, the gluteus maximus muscle is split, the gluteus medius and minimus muscles are retracted anteriorly and the piriformis tendon is retracted posteriorly. Once the joint capsule is exposed, it is cut from the base of the greater trochanter to 1 cm proximal to the acetabular rim.

The femoral canal is then reamed and broached without dislocation. The femoral neck is osteotomised and the femoral head removed. A trial cup is placed into the acetabulum attached to an external alignment jig. A second skin portal is made distally and posteriorly once the correct acetabular position is set. A cannula is inserted to protect the adjacent sciatic nerve when using the power reamer. Once reamed, the acetabular components are inserted and a trial reduction done. The definitive components are inserted if the reduction is deemed satisfactory. The hip joint capsule is closed with a suture. Then the gluteal fascia and skin are closed with sutures.

This procedure uses a specific set of implants and specialised instruments. Postoperative rehabilitation is recommended for muscle strengthening and mobility.