Fig. 1From: Cementless total hip arthroplasty for treatment of acetabular protrusion secondary to rheumatoid arthritisA sketch diagram of the hip joint shows how the distance of pelvic invagination distances was calculated. Kohler's line (or Nelaton’s line): taking a line drawn tangentially to the bottom of between the inner edges of ischium and ilium as the reference line, the distance of acetabular protrusion is acetabular site moved over Kohler’s line (a)Back to article page