Inversion of the acetabular labrum causes increased localized contact pressure on the femoral head: a biomechanical study

Abstract

Purpose Although studies suggest that subchondral insufficiency fracture of the femoral head may cause rapidly progressive osteoarthritis of the hip, the mechanism of that relationship remains unclear. Our biomechanical study aimed to provide more data in this area by quantifying pressure distribution on the femoral head for normal and inverted hips and by determining the effects of labral inversion on pressure distribution across the joint, focusing on types of fracture under load. Methods We tested mid-sized fourth-generation composite femurs at 15°of adduction, and applied 1 mm/min of axial compressive force to the femoral heads until failure. Additionally, single loads (3000 N) were applied using Prescale film to investigate pressure distribution on the femoral head, with or without silicone rubber representing entrapment of an inverted acetabular labrum. ResultsIn tests with an external load of 3000 N, the mean pressure for 10 × 5 mm of silicone rubber was 11.09 MPa, significantly greater (about 5.7-fold) than 1.94 MPa without silicone rubber. Different fracture patterns were observed with and without the 10 × 5 mm silicone rubber; when the 10 × 5 mm silicone rubber specimens were used, all eight cases showed fractures in the anterior femoral head. Conclusions When silicone rubber representing an inverted acetabular labrum was placed between a hemispherical metallic platen and a composite bone model, the silicone rubber areas were subjected to extreme concentration of stress. The fractures that developed at the silicone rubber areas clearly represented subchondral fractures of the femoral head, rather than fractures of the femoral neck.Keywords Inverted acetabular labrum . Subchondral fracture of the femoral head . Rapidly progressive osteoarthritis of the hip . Contact pressure . Biomechanical study * Kiyokazu Fukui

Subchondral fracture caused by unevenly stiffened meniscus after radiofrequency-assisted arthroscopic knee meniscectomy: A case report and review of the literature

“…In this case, we speculate that the unevenly stiffened meniscus may have concentrated stress on the fractured lesion, resulting in subchondral fracture. This phenomenon may be similar to that reported by Fukui et al, who noted inversion of the acetabular labrum in the initial stage of rapidly destructive hip osteoarthritis and proposed that this inversion may relate to subchondral fracture of the femoral head due to the concentration of stress on the subchondral bone [[46], [47], [48], [49]].…”

Does labral repair have a clinical benefit during arthroscopic treatment of femoro-acetabular impingement? Prospective multicentre study with 2-year follow-up

“…The short-term and long-term functional outcomes of the two treatments have been compared and neither was found to be superior [6,7,9]. In return, Wang et al [27] showed that poor labrum fixation increases the risk of osteoarthritis and subchondral fracture. The final decision on treatment is based on the observations during arthroscopy: a healthy, non-degenerated labrum more than 4mm thick in a young, non-smoker adult is the typical indication for labral repair [11].…”

The fate of inverted limbus in children with developmental dysplasia of the hip: Clinical observation

“…These clinical observations demonstrate that an inverted limbus between the femoral head and acetabulum can lead to the degeneration of acetabular cartilage. Furthermore, Wang et al 28 performed a biomechanical analysis using a silicone rubber model to simulate an inverted acetabular labrum and confirmed that the simulated structures were subjected to an extreme concentration of stress, which could be the primary cause of destructive degeneration of the articular cartilage.…”