[Stress on the ligamentum transversum acetabuli in physiological stress on the hip joint]

We investigated the strain on the transverse acetabular ligament (TAL) and the labrum close to the anterior and posterior horn of the lunate surface using Omega strain gauges [5] while increasing loads were applied to the hip joint. Two fresh hip joint specimens and four specimens fixed in 3.7% formalin were examined. The two components of the joint were disarticulated and soaked in physiological saline and then placed in a material-testing machine (Zwick) in the neutral position of the joint. The strain on the TAL and the labrum was measured at loads of 10 N, 350 N, 700 N, 1050 N, 1400 N, 2100 N and 2800 N. Finally, the contact areas were measured at a load of 350 N using a polyether casting method. Depending on load, the length of the TAL increased by up to about 3.2% at a load of 2800 N, but the length of the labrum increased by only 0.5% at the same load. Following rotation of the femoral head to positions corresponding to 15 degrees extension and 15 degrees and 30 degrees flexion, only slight differences of about 0.2% for the TAL and even less for the labrum were measured. The contact areas are all located in the anterior and posterior horn of the lunate surface. The measured changes in strain on the TAL confirm the widening of the acetabular notch and a subsequent stretching of the TAL as the load on the hip joint increases.(ABSTRACT TRUNCATED AT 250 WORDS)