Symptomatic Herniation Pit of the Femoral Neck: A Case Report

We read the case report by Borody about “Symptomatic Herniation Pit of the Femoral Neck: A Case Report” (J Manipulative Physiol Ther 2005;28(6):449-51) with interest.

Herniation pits have been described only sparsely since the first publication by Pitt et al1 in 1982. Several theories about the origin of these cysts have been made, going from osteoid osteomas to mechanical stress from anterior soft tissues. Their treatment also remained unsuccessful.2

The clinical symptoms of the presented patient (reduced internal rotation and pain with hip flexion, adduction, and internal rotation, so-called impingement test3) as well as the x-ray picture (Fig 1) are very suggestive of a femoroacetabular impingement syndrome.4

Ganz et al4 have thoroughly studied this entity over the last 15 years and showed that morphological abnormalities of the femoral neck (cam-type) or acetabular version (pincer-type) lead to an abnormal contact between the femoral head-neck junction and the acetabular rim. This contact induces shear stresses on the acetabular cartilage and labrum undersurface (cam-type) or compressive forces on the labrum at the rim (pincer-type), leading to early cartilage and labrum lesions.4

Even if this interpretation should be confirmed on a pelvic x-ray, Fig 1 shows signs of both types of impingement, which is most frequent, as isolated forms only represent 28% of the cases.5

On the femoral side, the head-neck junction is aspheric, forming a so-called “pistol-grip deformity,”6 which is smashed into the acetabulum during flexion and internal rotation and leads to a cleavage of the cartilage from the subchondral bone. On the acetabular side, the anterior rim crosses the posterior wall, even if this is partly hidden because of a probable insufficient orientation of the pelvis on the x-rays. This forms the “cross-over sign”7 and means that the acetabulum is retroverted. During flexion, the anterior femoral neck abuts against the bony acetabular rim, compresses the labrum, and induces the herniation pit. This mechanism has been very clearly shown during surgical dislocation of the hip.8, 9

Therefore, we cannot confirm the theory of Borody and other authors. As it has been shown that femoroacetabular impingement leads to early osteoarthritis,4 we think that a prolonged conservative therapy should be avoided and these patients should undergo surgical treatment, which is the only causal therapy.