[Morphological changes of proximal femur in patients with Crowe II/III developmental dysplasia of hip and their implication to total hip arthroplasty].

OBJECTIVE

To investigate the morphological changes of the proximal femur and their implication to the total hip arthroplasty in patients with Crowe II/III developmental dysplasia of the hip (DDH).

METHODS

The experimental group was composed of 15 hips in 14 patients (Crowe II, 9 hips; Crowe III, 6 hips ) with osteoarthritis secondary to Crowe II/III DDH (2 males, 12 females; age, 35-61 years). None of the patients had accepted any osteotomy treatment. The control group was composed of 15 normal hips in 15 patients with unilateral DDH (3 males, 12 females; age, 35-57 years). Twelve hips came from the experimental group and the other 3 came from the patients with unilateral Crowe I DDH. The femurs were examined with the CT scanning. The following parameters were measured: the height of the center of the femoral head (HCFH), the isthmus position (IP), the neck-shaft angle(NS), the anteversion angle, the canal flare index, and the canal width. Then, the analysis of the data was conducted.

RESULTS

HCFH and IP in the experimental group and the control group were 50.1 +/- 6.7 mm, 50.1 +/- 7.4 mm, and 107.4 +/- 21.5 mm, 108.7 +/- 18.1 mm, respectively, which had no significant difference between the two groups (P > 0.05). In the experimental group and the control group, the NS were 138.3 +/- 10.0 degrees and 126.7 +/- 5.7 degrees, the anteversion angles were 36.5 +/- 15.9 degrees and 18.8 +/- 5.4 degrees, and the canal flare indexes were 4.47 +/- 0.40 and 5.01 +/- 0.43. There was a significant difference between the two groups in the above 3 parameters (P < 0.05). As for the canal width of the femur, there was a significant difference in the interior/exterior widths and the anterior/posterior widths at the level of 2 cm above the lesser trochanter and 4 cm below the lesser trochanter between the two groups (P < 0.05); however, there was no significant difference in the canal width of the femur at the isthmus between the two groups (P > 0.05).

CONCLUSION

It is necessary to evaluate the morphology of the proximal femur before the total hip arthroplasty performed in patients with Crowe II /III DDH. The straight and smaller femoral prosthesis should be chosen and implanted in the proper anteversion position during operation.