Introduction: Whereas in traumatic avascular necrosis of the femoral head (ANFH) loss of the femoral head’s blood supply is due to a mechanical event, in non-traumatic AFNH it is the result of a wide variety of etiologies (e.g. alcoholism, hypercortisonism, etc.), which have in common that they lead to an intravascular complication with subsequent malperfusion of the femoral head. Additionally, for part of non-traumatic ANFH no causative factors are known, why they are called idiopathic. A mechanical cause for nontraumatic ANFH – as e.g. a repetitive trauma of the femoral head supplying deep branch of the medial femoral circumflex artery and its terminal branches by abutment of the femur against the acetabulum as in femoroacetabular impingement (FAI) – has not been discussed so far.

Methods: The anteroposterior and lateral radiographs of 118 hips in 77 patients, who were operated in our institution between January 1995 and December 2005 because of nontraumatic ANFH, were evaluated with respect to the configuration of the head-neck junction.

In a qualitative analysis the head-neck contour of all femora was assigned to one of the following four groups: regular waisting, mildly reduced waisting, reduced to distinctly reduced waisting or completely lacking waisting.

Results: In this retrospective analysis, for 44.1% of the hip joints hypercortisonism, for 40.7% alcoholism, for 12.7% hypercholesterinemia and for 11.0% no risk factors were found documented in the patients’ files. In AP and lateral radiographs a regular waisting was found in 60.2% and 9.3%, a mildly reduced waisting in 32.2% and 37.3%, a reduced waisting or distinctly reduced waisting in 7.6% and 35.6%, and a completely lacking waisting in 0% and 16.9%, respectively, and the mean angle alpha was 63° ± 18° and 67° ± 14°, respectively. On average, the (frontally projected) CCD angle was 133° ± 6°, the LCE angle 30° ± 7° and the acetabular index of the weightbearing zone 4° ± 5°.

Conclusion: Nötzli et al. found an angle alpha of 42° ± 2° for healthy individuals. A markedly increased angle alpha in both radiographic planes of the 118 investigated hips with nontraumatic ANFH was found, demonstrating a reduced shape of their head-neck junction in the anterior and lateral aspect. Together with the fact that no gross pathological deviations for the orientation of the femoral neck and the acetabulum were found, this may hint at cam-type FAI to occur in this hips and thus potentially at a mechanical (co-) factor in developing non-traumatic ANFH.

Introduction: There is rather broad consent that mildly slipped capital femoral epiphyses (SCFE) should be treated by in situ fixation with wires or dynamic screws. There is recent evidence, however, that even mild slips lead to early damage of the acetabular labrum and cartilage by abutment of a prominent femoral metaphysis. It is therefore proposed that treatment of mildly slipped capital femoral epiphyses should not only prevent further slipping of the epiphysis, but also address potential femoro-acetabular impingement (FAI) by restoring the anatomy of the proximal femur. To find proof for this newly proposed therapeutical approach, we reviewed all patients treated in our department ten to twenty years ago for unilateral slipped capital femoral epiphysis by in situ fixation without restoration of the anatomy of the proximal femur.

Methods: From forty-four patients treated between October 1984 and December 1995, twenty-eight could be contacted and eighteen reviewed. Development of FAI was documented by clinical examination (range of motion, “impingement provocation test”) and radiological evaluation (AP radiographs of the pelvis and lateral cross-table radiographs of both hips). Statistical analysis was performed with paired t test and Wilcoxon matched-pairs signed-ranks test in case of numerical data, and Fisher’s Exact Test and Chi-squared Test for Independence in case of ordinal data. The level of significance was set at p < 0.05.

Results: Comparing involved to non-involved hips, mean internal rotation and abduction differed significantly (15° ± 7.9° vs. 21° ± 7.9° (p < 0.01) and 37° ± 7.7° vs. 42° ± 6.7° (p < 0.01), respectively), but the “impingement provocation test” was found positive in only four vs. six hips (p = 0.71). Radiological examination showed significantly difference with respect to waisting of the femoral neck (p < 0.01) and bony appositions at the femoral head neck junction (p < 0.01). No regular waisting was found in all involved hips, whereas it was present in nine non-involved hips. A distinctly reduced or absent waisting was seen in twelve of the involved hips but in only four of the non-involved hips. Bony appositions were found in fourteen of the involved hips, but in only four of the non-involved hips. Furthermore the angle α according to Nötzli et al. (2002) showed a significant difference in its mean on AP radiographs (84° ± 10° vs. 60° ± 15°, p < 0.01), not so, however, in lateral cross-table radiographs (50° ± 8° vs. 48° ± 11°, p = 0.3).

Conclusion: From a clinical point of view, in situ fixation may be sufficient in treating mildly SCFE, whereas radiological data suggest that restoration of the anatomy of the head-neck junction of the proximal femur might be sensible to prevent or delay FAI and thus development of osteoarthritis of the respective hip joint.