Hip contact stress and femoral neck retroversion: a biomechanical study to evaluate implication of femoroacetabular impingement

Abstract

The current literature on femoroacetabular impingement (FAI) is focused on acetabular orientation and femoral head asphericity, with little emphasis on the effect of version of the femoral neck. A biomechanical model was developed to determine the causative effect, if any, of femoral retroversion on hip contact stress and, if present, delineate the type of FAI with femoral neck retroversion. Five pairs of cadaveric hips (n = 10) were tested by loading the hip in 90° of flexion and measured the peak joint pressure and the location of the peak joint pressure. The experiment was repeated after performing a subtrochanteric osteotomy and retroverting the proximal femur by 10°. Ten hips were successfully tested, with one hip excluded due to an outlier value for peak joint pressure. Retroversion of the proximal femur significantly increased the magnitude of mean peak joint pressure. With retroversion, the location of the peak joint pressure was shifted posteroinferiorly in all cases. In conclusion, femoral neck retroversion increases peak joint pressure in the flexed position and may act as a cause of femoroacetabular impingement. The location of peak joint pressure suggests a pincer-type impingement with retroversion. The version of femoral neck should be assessed as a possible causative factor in patients with FAI, especially those with pincer-type impingement.

Cam morphology and inguinal pathologies: is there a possible connection?

“…Femoroacetabular impingement (FAI) is a condition characterised by the presence of abnormal contact between the articular rim of the acetabulum and the proximal femur at the level of the femoral head-neck junction [ 1 , 2 ]. FAI was first described by Smith-Petersen in the 1930s [ 3 – 5 ].…”

“…The pincer morphology is characterised by over-coverage of the femoral head by the acetabulum, which leads to abnormal contact between the femoral neck and acetabular rim [ 1 , 2 , 7 ]. On the other hand, the cam morphology refers to an abnormal configuration of the femoral head in which an osteochondral bump is present at the femoral head-neck junction, leading to a decrease in the normal femoral head-neck offset [ 1 , 2 , 7 ]. Also, the pincer and cam morphologies may be present simultaneously, leading to a “mixed” type of FAI [ 8 – 10 ].…”

The Effect of Knee Flexion Angle on Contact Stress of Total Knee Arthroplasty

“…Small contact areas, in conjunctions with high joint loads, fatigue and delamination type wear of the polyethylene (PE). The knee implant design should take consideration of contact area stress of the knee joint same as applied to other joints such as hip or ankle [2][3][4][5].…”

Validität klinischer Tests zur Bestimmung des Antetorsionswinkels des Femurs

“…Es besteht die Hypothese, dass strukturelle Abweichungen im Hüftgelenk zu abnormalen Kontaktbelastungen innerhalb des physiologischen Bewegungsausmaßes führen, wie sie bei einem FAI zu beobachten sind. Mögliche Folgen sind degenerative Veränderungen des Knorpels und/oder Verletzungen des Labrum acetabulare und ein frühzeitiges Auftreten von Osteoarthrose bei jungen Patienten [15].…”