INITIAL SIGNS FOR FEMORO-ACETABULAR IMPINGEMENT 10 TO 20 YEARS AFTER IN SITU FIXATION OF MILDLY SLIPPED CAPITAL FEMORAL EPIPHYSES

Abstract

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.