Symptomatic Herniation Pit of the Femoral Neck: A Case Report

SYMPTOMATIC HERNIATION PIT OF THE FEMORAL NECK: A CASE REPORT To the Editor : We read the case report by Borody about bSymptomatic Herniation Pit of the Femoral Neck: A Case Report Q (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 al 1 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 test 3) as well as the x-ray picture (Fig 1) are very suggestive of a femoroacetabular impingement syndrome.4 Ganz et al 4 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 b pistol-grip deformity,Q 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 bcross-over signQ 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. Michael Wettstein, MD Olivier Borens, MD Raffaele Garofalo, MD Elyazid Mouhsine, MD Centre Hospitalier Universitaire Vaudois Lausanne, Vaud, Switzerland

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DOI of original article 10.1016/j.jmpt.2005.06.003 Copyright D 2006 National University of Health Sciences doi:10.1016/j.jmpt.2005.10.004

REFERENCES 1. Pitt MJ, Graham AR, Shipman JH, Birkby W. Herniation pit of the femoral neck. Am J Radiol 1982;138:1115 - 21. 2. Daenen B, Preidler K, Padmanabhan S, Brossmann J, Tyson R, Goodwin DW, et al. Symptomatic herniation pits of the femoral neck: anatomic and clinical study. AJR Am J Roentgenol 1997;168:149 - 53. 3. MacDonald SJ, Garbuz D, Ganz R. Clinical evaluation of the symptomatic young adult hip. Semin Arthroplasty 1997;8:3 - 9. 4. Ganz R, Parvizi J, Beck M, Leunig M, Nftzli HP, Siebenrock KA. Femoroacetabular impingement. A cause for osteoarthritis of the hip. Clin Orthop 2003;417:112 - 20. 5. Beck M, Kalhor M, Leunig M, Ganz R. Hip morphology influences the pattern of damage to the acetabular cartilage: femoroacetabular impingement as a cause of early osteoarthritis of the hip. J Bone Joint Surg Br 2005;87:1012 - 8. 6. Stulberg SD, Cordell LD, Harris WH, Ramsey PL, MacEwen GD. Unrecognized childhood hip disease: a major cause of idiopathic osteoarthritis of the hip. The hip: proceedings of the third open scientific meeting of the Hip Society. St Louis (Mo)7 CV Mosby Co; 1975. p. 212 - 28. 7. Reynolds D, Lucas J, Klaue K. Retroversion of the acetabulum. A cause of hip pain. J Bone Joint Surg Br 1999;81:281 - 8. 8. Ganz R, Gill TJ, Gautier E, Ganz K, Krqgel N, Berlemann U. Surgical dislocation of the adult hip: a technique with full access to the femoral head and acetabulum without the risk of avascular necrosis. J Bone Joint Surg Br 2001;83-B:1119 - 24. 9. Leunig M, Beck M, Kalhor M, Kim YJ, Werlen S, Ganz R. Fibrocystic changes at anterosuperior femoral neck: prevalence in hips with femoroacetabular impingement. Radiology 2005;236:237 - 46.

RESPONSE TO LETTER TO EDITOR In Response: In the letter to the editor regarding bSymptomatic herniation pit of the femoral neck: a case report,Q Dr Wettstein et al (J Manipulative Physiol Ther 2005;28:449-51) draw a comparison between the case described and recent descriptions of femoroacetabular impingement syndrome (FAI).1-3 After reviewing some of the literature they cited, I find their observation to be valid. Recent publications1,2 have brought the original theory regarding the pathomechanics leading to the development of herniation pits into question, suggesting that they may not be related to synovial invagination subsequent to tight capsular and associated structures and repetitive hip extension. They may be best explained by direct compressive and shear forces subsequent to morphological abnormalities of the femoral head and neck, acetabulum, or both.2 The case in question appears to fit the clinical presentation of FAI with reproduction of the symptoms upon hip flexion, internal rotation, and adduction. The radiographs are suggestive of the cam type of FAI with a mildly aspheric femoral head.