The main objective of this study is to predict cartilage contact pressures in the hip after periacetabular osteotomy (PAO).

PAO was designed as a joint preserving surgical procedure to compensate for a shallow acetabulum by re-orienting the acetabulum into a position that provides better coverage of the femoral head. Although the overall theory that increasing load bearing area (improving coverage of the femoral head) results in reduced joint stress is intuitive, the complex bony surface may not behave in this manner. It is possible that joint stress may increase when the acetabulum is reoriented into a position that increases load bearing area if post-operative joint congruency is worse than pre-operative.

Inclusion Criteria:

• Patients aged 18-40 years
• Patients who have undergone periacetabular osteotomy by Dr. Peters for treatment of hip dysplasia.
• Patients who have previously participated in IRB #10983 "Comparative Stress Analysis of Hip Dysplasia".

Exclusion Criteria:

• Persons with a history of allergies to lidocaine or seafood.
• Children under the age of 18.
• Persons incarcerated, on trial, or parole.
• Women who are pregnant.
• Subjects who do not have high quality pre-operative images available or have not been surgically treated by periacetabular osteotomy.

18-40 years old