Anterior femoroacetabular impingement after periacetabular osteotomy

As experience with the Bernese periacetabular osteotomy has grown, an unexp ected observation in a group of patients has alerted the authors to the ris k of a secondary impingement syndrome that may occur some time after the pe riacetabular osteotomy, This possibly may explain residual pain and limited range of motion in a larger group of patients, The impingement is produced by abutment of the femoral head or head to neck junction on the anterior r im of the properly aligned acetabulum. The symptoms are those of restricted flexion, and limited or absent internal rotation in flexion, with variable groin pain. Magnetic resonance imaging studies may reveal acetabular labra l disease and adjacent cartilage damage associated with the impingement. La ck of anterior or anterolateral offset between the femoral neck and head re sults in neck to rim contact when the hip is flexed and/or internally rotat ed. Before the periacetabular osteotomy this is compensated by the lack of anterior acetabular coverage, but after proper correction the mismatch beco mes apparent. The authors recently have devised a routine during the periac etabular osteotomy procedure whereby after the acetabular fragment is corre cted into the desired position, the joint is opened, visually inspected, an d palpated for impingement with the hip flexed and internally rotated. When necessary, a resection osteoplasty of the femoral neck to head junction is performed to improve the head and neck offset and reduce the anterior cont act. This, in the short term, has provided satisfactory prevention of posto perative impingement.