JP4.1 The resistance during hip labrum probing correlates with its mechanical property.

Abstract Background In hip arthroscopic surgery, probing the acetabular labrum with an arthroscopic probe prior to treatment is considered important for determining the appropriate treatment area. However, there have been only a few reports that have quantitatively evaluated this process. These studies have shown that by quantitatively measuring the reactive force of the labrum during probing, a significant decrease in reactive force is observed when the continuity between the labrum and the adjacent acetabular bone is disrupted. Furthermore, they have demonstrated that the reactive force can recover following repair. Nevertheless, it remains unclear whether the intrinsic mechanical properties of the labrum itself influence the probing measurements. Objective Here, we investigated the relationship between two parameters by the probing force of the labrum in cadaveric tissue and its mechanical properties using a tensile testing machine. Methods Twelve specimens of the pelvis and proximal femur were obtained. The donors included three men and five women who had a mean age of 64.1 years at the time of death. All specimens were screened radiographically to confirm the absence of osseous abnormality. Each specimen was mounted with a special device and each femur was dislocated in order to simulate hip arthroscopy. Labrum resistance was measured by the probing device. Then, the labrum was excised in segments measuring 15–25 mm in length. The stiffness and the elastic modulus of the specimens were measured by an in-house tensile test device. Spearman’s rank correlations were calculated between the probing force and the mechanical properties of the acetabular labrum. Results The stiffness and the tensile elastic modulus showed a moderate correlation with the probing force (R=0.74; stiffness, R=0.65; tensile elastic modulus). Discussions It is important to keep in mind that the tactile sensation transmitted to the hand during labral probing, which reflects the resistance force of the labrum, may also be influenced by the mechanical properties of the labrum itself.