Christian R. Fraitzl

Introduction Risk factors for nontraumatic osteonecrosis of the femoral head have in common that they trigger intravascular coagulation and thus lead to devascularization of the femoral head. In part of the patients, however, no risk factors seem to be evident. Mechanical reasons contributing to nontraumatic osteonecrosis have not been discussed so far. We hypothesized that recurrent traumatization of the vessels supplying the femoral head by a cam-type mechanism as in femoroacetabular impingement could add to intravascular coagulation. We, therefore, asked whether structural abnormalities at the femoral head–neck junction indicative of such a mechanism could be observed in radiographs of patients with osteonecrosis of the femoral head. Materials and methods The preoperative anteroposterior and lateral radiographs of 77 patients who underwent surgery because of osteonecrosis of the femoral head were retrospectively screened for a reduced head–neck offset by measuring the α-angle. For comparison, the α-angle was measured on anteroposterior and lateral radiographs of 339 control subjects without evident underlying hip pathology. Results The mean α-angle was 62.8° (SD 18.7°) for anteroposterior and 67.6° (SD 13.2°) for lateral radiographs in patients with nontraumatic osteonecrosis of the femoral head, whereas in control subjects, the mean α-angle was 47.2° (SD 9.6°) (p < 0.0001) and 47.6° (SD 10.3°) (p < 0.0001), respectively. Conclusions A reduced head–neck offset in patients with nontraumatic osteonecrosis of the femoral head may act as a mechanical (co-)factor in developing osteonecrosis of the femoral head.

Purpose: The α‐angle is a frequently used measurement to quantify head‐neck offset pathology in cam‐type femoroacetabular impingement. However, diverging norm values and reference intervals have been described, especially in men.Methods: The α‐angle, the head‐neck offset ratio and the triangular index were measured on anteroposterior and lateral radiographs of 339 (170 men and 169 women) subjects without evident underlying hip pathology.Results: For male subjects, the mean α‐angle was 49.4° (SD 10.5°) on anteroposterior and 49.1° (SD 10.6°) on lateral radiographs, whereas for female subjects, it was 45.0° (SD 8.0°) and 46.1° (SD 9.9°), respectively. Thus, calculated upper limits of reference intervals in the population screened were 70° for both radiographic projections in men and 61° (anteroposterior) and 66° (lateral) in women.Conclusion: These data substantiate recent findings that the pathological threshold of the α‐angle in male subjects may be lower than that previously assumed.Level of evidence: Diagnostic, Level III.

Studienziel: Ziel dieser Studie war es, die Frage zu klären, ob und in welchem Ausmaß ein femoroazetabuläres Impingement (FAI) 10 bis 20 Jahre nach transphysärer Epiphysenfixation bei milder Epiphyseolysis capitis femoris (ECF) vorliegt. Methode: Klinische und radiologische Nachuntersuchung von 20 Patienten, die von Oktober 1984 bis Dezember 1995 mit einer beidseitigen transphysären Epiphysenfixation mittels Schrauben oder Kirschner-Drähten bei einseitiger ECF behandelt worden waren. Die klinische Nachuntersuchung bestand in der Erfassung des Harris-Hip-Scores, des Aktivitätsgrads nach Tegner und Lysholm, der Hüftgelenksbeweglichkeit und der Durchführung eines Impingementtests. Die radiologische Nachuntersuchung umfasste die qualitative Beurteilung des Femurkopf-/Schenkelhals-Übergangs in anteroposterioren Beckenübersichts- und lateralen „cross table“-Aufnahmen beider Hüftgelenke. Zur quantitativen Beurteilung wurde der α-Winkel nach Nötzli et al. in diesen Aufnahmen bestimmt. Ergebnisse: Mithilfe des Harris-Hip-Scores wurden hervorragende Ergebnisse belegt, der Aktivitätsgrad der Patienten lag dagegen mehrheitlich nur im unteren Mittelfeld. Für die Beweglichkeit des betroffenen Hüftgelenks zeigte sich im Vergleich zur nicht betroffenen Gegenseite keine statistisch signifikante Einschränkung der Flexion, dagegen der Innenrotation und Abduktion (p = 0,135, p = 0,002 bzw. p = 0,007). Der Impingementtest war in acht Fällen auf der betroffenen Seite und in fünf Fällen auf der nicht betroffenen Seite positiv (p = 0,004). Die radiologische Nachuntersuchung zeigte einen statistisch signfikanten Unterschied zwischen betroffener und nicht betroffener Seite für den α-Winkel im Beckenübersichtsbild (86 vs. 61°; p < 0,001), dagegen nicht in den lateralen Hüftgelenksaufnahmen (52 vs. 46°; p = 0,145). Schlussfolgerung: Die klinischen Nachuntersuchungsergebnisse zeigen Hinweise für die Entwicklung eines FAI nach abgelaufener milder Hüftkopfepiphysenlösung, die mittels transphysärer Epiphysenfixation behandelt wurde. Die radiologischen Nachuntersuchungsergebnisse lassen auf eine laterale und weniger anteriore Lokalisation des FAI schließen. Aim: It was the aim of this study to reveal whether and to what extent femoro-acetabular impingement (FAI) was present 10 to 20 years after transfixation of the gliding epiphysis in patients treated for unilateral slipped capital femoral epiphysis (SCFE). Method: Clinical and radiological evaluations were undertaken of 20 patients who were treated with a bilateral transfixation of the epiphysis with screws or Kirschner wires because of mild unilateral SCFE. The Harris hip score, the activity level according to Tegner and Lysholm and the range of motion of both hip joints were noted. An impingement provocation test was performed on both sides. The femoral head-neck junction was qualitatively and quantitatively assessed in anteroposterior radiographs of the pelvis and “cross table” lateral radiographs of both hip joints. Quantitative assessment was achieved by measuring the α angle according to Nötzli et al. Results: All except one patient showed excellent results in the Harris hip score. The activity levels of the majority of patients, however, were mediocre. There was no difference for flexion, whereas internal rotation and abduction significantly differed between affected and non-affected hips (p = 0.135, p = 0.002 and p = 0.007, respectively). The impingement provocation test was found positive in eight affected and five non-affected hips (p = 0.004). The α angle was significantly different between affected and non-affected hips in the anteroposterior radiographs of the pelvis (86 vs. 61°; p < 0.001), but not so, however, in the “cross table” lateral radiographs (52 vs. 46°; p = 0.145). Conclusion: Clinical evaluation of 20 patients at a mean of 14.9 years after transfixation of the epiphysis revealed some evidence for the presence of FAI in affected hip joints. Radiological evaluation suggests that its localisation is more lateral and less anterior.

The use of fresh osteochondral allografts is a popular approach to treat articular cartilage lesions. Immunological reactions of the recipient elicited by the allograft's osseous portion, however, frequently result in their deterioration. So far, little emphasis has been put on describing morphology and biological activity in fresh allografts and paralleling these to the immunological processes triggered in the host. Therefore, in the present study murine neonatal femora, serving as osteochondral grafts, were transplanted as fresh isografts (controls) or allografts (the latter in non- or presensitized mice) and retrieved after 2, 5, 10, and 20 days. It was shown that (1) in isografts active bone cells (osteoblasts, osteoclasts) were present, the bone marrow was repopulated with hematopoietic cells, the diaphysis increased in length, and no specific immunological reaction by the recipient was evoked. (2) Allografts transplanted into nonsensitized hosts initially appeared similar as isografts, but activated T lymphocytes at the transplantation site preceded loss of active bone cells within the graft and development of fibrosis within the marrow cavity. (3) In allografts transplanted into presensitized recipients, severe deterioration of the graft was observed with very few active bone cells, accompanied by an invasion of T lymphocytes and fibrosis in the marrow cavity already in early stages. Similar to vital organ transplantation, the function of cells within osteochondral allografts is severely impaired after being recognized by the immune system. Therefore, emphasis has to be placed on the development of procedures preserving cartilage biology while reducing the antigenicity of the allograft's osseous portion.

Conventional treatment of mild slipped capital femoral epiphysis consists of fixation in situ with wires or screws. Recent contributions to the literature suggest that even a mild slip may lead to early damage of the acetabular labrum and adjacent cartilage by abutment of a prominent femoral metaphysis. It has been suggested that the appropriate treatment in mild slipped capital femoral epiphysis should not only prevent further slipping of the epiphysis, but also address potential femoroacetabular impingement by restoring the anatomy of the proximal femur. Between October 1984 and December 1995 we treated 16 patients for unilateral mild slipped capital femoral epiphysis by fixation in situ with Kirschner wires. In this study we have reviewed these patients for clinical and radiological evidence of femoroacetabular impingement. There was little clinical indication of impingement but radiological evaluation assessing the femoral head-neck ratio and measuring the Nötzli α angle on the anteroposterior and cross-table radiographs showed significant alterations in the proximal femur. None of the affected hips had a normal head-neck ratio and the mean α angle was 86° (55° to 99°) and 55° (40° to 94°) on the anteroposterior and lateral cross-table radiographs, respectively. While our clinical data favours conventional treatment, our radiological findings are in support of restoring the anatomy of the proximal femur to avoid or delay the development of femoroacetabular impingement following mild slipped capital femoral epiphysis.