Osseous defect of the anteroinferior femoral head: is it associated with femoroacetabular impingement (FAI)?

Abstract

Objective To evaluate the prevalence, morphology, and clinical significance of a repeatedly observed yet not examined circumscript osseous defect at the anteroinferior aspect of the femoral head, termed femoral head defect. Materials and methods Retrospective study with approval of the institutional review board. There was informed consent by all individuals. Magnetic resonance imaging (MRI) hip examinations of 970 individuals (age 15 to 55) were analyzed for femoral head defect. Patients with femoral head defect were matched for age and gender with patients without defect. Two readers independently assessed MRI images regarding presence, location, and morphology of the defect. MR images and radiographs were analyzed for findings of femoroacetabular impingement (FAI). Femoral torsion was measured. Independent t test and chi-square test were used for statistics. Results Sixty-eight (7%) of 970 MRI examinations exhibited a femoral head defect in an anteroinferior location of the femoral head (29/400 men, 7.3%; 39/570 women, 6.8%; p = 0.8). The most frequent morphology of femoral head defect was type I, dent-like (34; 50%), followed by type II, crater-like (27; 40%), and III, cystic (7; 10%). Femoral head defect was slightly more common on the right hip (39 individuals; 57%) compared to left (29 individuals; 43%), non-significantly (p = 0.115). There was no association between FAI or its subtypes and the presence of femoral head defect (p = 0.890). Femoral antetorsion was reduced in patients with femoral head defect (12.9° ± 8.6) compared to patients without defect (15.2° ± 8.5), without statistical significance (p = 0.121). Conclusion The femoral head defect is a common finding in MRI examinations of the hip and is situated in the anteroinferior location. There was no association with FAI yet a non-significant trend towards lower femoral antetorsion in patients with femoral head defects.

Hip Impingement Location in Maximal Hip Flexion in Patients With Femoroacetabular Impingement With and Without Femoral Retroversion

“…1 Another study reported cysts and femoral head defects on the anterior-inferior femoral head and found an association with reduced FV. 4 A previous study evaluated hips with femoral retroversion and bipolar hemiarthroplasty and found an osseous impingement conflict in flexion in all hips. 47 The authors reported extra-articular subspine impingement in 51 of 60 hips (85%).…”

“…1 Another study reported cysts and femoral head defects on the anterior-inferior femoral head and found an association with reduced FV. 4…”

Imaging of Anatomical Variants Around the Hip

“…8 This defect is suggested as a variant of the herniation pit; however, an association with repeated impaction in individuals with reduced femoral antetorsion has also been proposed. 8,9 Herniation pits are thought to result from mechanical forces originating from the anterior joint capsule and overlying muscles, causing herniation of soft tissue and synovium through a defect or perforation in the bony cortex. An association with FAI was suggested as a possible causative factor of these lesions 10 ; however, this association is widely disputed.…”

“…4 ). 8 This defect is suggested as a variant of the herniation pit; however, an association with repeated impaction in individuals with reduced femoral antetorsion has also been proposed. 8 9…”