[Acetabular rotations y triple pelvic osteotomy by the Tönnis method]

Lesions of the acetabular labrum should be treated by correcting the causes. In a steep acetabulum where the femoral head brings the acetabular labrum under tension and traction, the acetabulum should be rotated by triple pelvic osteotomy to slightly over-corrected acetabular measurements. Severely diminished acetabular and femoral anteversion can also lead to tears and impingement of the labrum. Then rotation of the femoral neck and/or rotations of the acetabulum by triple osteotomy to 15-20 degrees of anteversion are indicated. Our triple osteotomy technique differs from that of others mainly in the ischial osteotomy. It is performed from the posterior approach between the sciatic notch next to the ischial spine and the obturator foramen and is directed 20-30 degrees anteriorly from the frontal (coronal) plane. The osteotomies therefore are placed close enough to the acetabulum to allow free rotation, but they do not interfere with the circulation of the acetabulum, and the ligaments between the sacrum and ischium are left in normal tension. Our normal values of the acetabular position were tested by correlating the measurements with the absence of pain. The optimum is reached with a CE angle and a VCA angle of 30-35 degrees, an angle of the weight-bearing zone of +5 to -5 degrees and a migration index of 10-15%. Overcorrections again caused pain and should be avoided. Diminished anteversion of femur and acetabulum towards 0 degree also caused pain and should be corrected by triple and femoral osteotomy to 15-20 degrees of anteversion. In earlier follow-ups of 216 hips 5-10 years postoperatively, 82.3% of the joints showed no change in the degree of osteoarthrosis. Survival rate curves regarding the absence of pain demonstrated that pain was experienced again when joints were corrected insufficiently or overcorrected, while in good corrections the joints were free of pain in about 75%.