Osteotomy (Hip)

Periacetabular Osteotomy is a hip preserving procedure performed to correct a congenital deficiency of the acetabulum:

Acetabular dysplasia

Acetabular dysplasia is a condition of inadequate development of an individual's hip socket (acetabulum). The resulting acetabulum is shallow and "dish shaped" rather than "cupshaped". The upper portion (roof) of the acetabulum is obliquely inclined outward rather than having the normal horizontal orientation. This causes the head of the femur (ball) to be more uncovered, which can result in earlier arthritis due to the abnormal pressure and shearing placed on the head of the femur.


Severities of Dysplasia

Individuals with acetabular dysplasia usually develop through childhood and adolescence without symptoms or knowledge of their abnormality. By the age of 30, however, the patient typically experiences pain from their hip and they often seek medical evaluation. An X-ray typically discloses the abnormality

Other patients may have been treated for hip problems as an infant or child. A severe form of dysplasia called DDH (developmental dysplasia of the Hip) can be associated with a hip dislocation. This is usually treated as a child, but as the patient ages, can have a higher risk for early arthritis.

In 1979 Dr. John F. Crowe proposed a classification to define the degree of malformation and dislocation. Grouped from least severe Crowe I dysplasia to most severe Crowe IV

Crowe Groups

CROWE I: Minimal abnormal development

CROWE II: Rim of the acetabulum is not horizontal. Femoral head is not dislocated.

CROWE III: The joint is fully or nearly dislocated. The socket lacks a roof. A false socket starts to form.

CROWE IV: The joint is dislocated. The femur is positioned high up on the pelvis. Significant underdevelopment of the acetabulum.

Acetabular dysplasia is often also associated with abnormalities in the shape of the upper femur which may contribute to the patient's hip symptoms. Acetabular dysplasia is associated with an abnormally high stress on the outer edge (rim) of the acetabulum which leads to degeneration of the articular cartilage (arthritis). It is also possible for breakdown of the acetabular labrum (rim cartilage of the acetabulum) or a fatigue fracture of the rim of the acetabulum to occur as a result of this rim overload. Anyone or a combination of these conditions can cause hip pain sufficient for the patient to seek medical evaluation and treatment.

Surgical Options for the treatment of Dysplasia:

The treatment is based on multiple factors, which include age, severity of the dysplasia, severity of the arthritis and the type of symptoms.

  • Total Hip Replacement
  • Surface Replacement
  • Hip Arthroscopy
  • Periacetabular Osteotomy
  • Periacetabular Osteotomy with a Femoral Osteotomy

PAO or sometimes called a Ganz Osteotomy

"Periacetabular" means around the acetabulum."Osteotomy" means to cut bone. PAO cuts the bone around the hip socket (acetabulum). Once the acetabulum is detached from the rest of the pelvis by a series of carefully controlled cuts, it is rotated to a position of ideal coverage as dictated by the specific acetabulum's unique anatomy. The dysplastic roof that incompletely covers the femoral head is brought over the head to give the head a normal coverage and also brings the roof from an oblique to a horizontal position.

The results of the PAO is variable and is usually dependent on the amount of arthritis. The goal of the PAO is to preserve the patients existing hip and normalize the acetabulum for improving the results of a later hip replacement if needed. The success rate as defined as Excellent (normal hip function) to Good (some pain with vigorous activities) is around 75%. Poor results (pain requiring further surgery) is approximately 10%. However, the re-operation is usually not needed immediately and is generally required because of the patients advancing hip arthritis.

As with any other major surgery, there is some risk of complications. Non-union (lack of healing) of the bone following the osteotomy and continued pain, requiring a hip replacement are possible complications. Another reported but very rare complication is avascular necrosis of the acetabulum. In this situation, the acetabulum that has been separated from the pelvis lacks a blood supply and is at risk for deterioration. As with any hip operation, other risks include: blood clots and embolus, infection, nerve injury. The risk of surgery is approximately 1%.

Recovery is generally 3 months. There is some limitations in the amount of weight the patient can bear on the leg after surgery. Full weight bearing is generally started at 8 weeks after surgery. Until then, the patient walks with a walker or crutches.