The ratio of femoral head diameter to pelvic height in the normal hips of a Chinese population

Is Ranawat triangle method accurate in estimating hip joint center in Japanese population?

BACKGROUND

Little information has been available regarding the usefulness of Ranawat triangle method in estimating anatomical hip joint center in the Japanese population. In this study, we aimed to determine the accuracy of the method in estimating hip joint center.

METHODS

Using digitally reconstructed radiographs of 123 normal hips (123 patients), we measured the hip joint center coordinates (Cx, Cy) with reference to the ipsilateral lowest point of the teardrop, the pelvic width, and the pelvic height. Using these measurement values, we performed the following analyses: (1) the relationship of hip joint center location with pelvic dimensions; (2) accuracy of Ranawat method in estimating hip joint center; (3) alternative methods to estimate hip joint center using pelvic height.

RESULTS

The mean Cx and Cy were 32 ± 3.0 mm and 13 ± 2.1 mm, respectively. Pelvic height was positively correlated with Cx (r = 0.51, p < 0.001) and Cy (r = 0.69, p < 0.001), but the correlations of pelvic width with Cx and Cy were negligible. The mean estimation error of the Ranawat method was -6.7 ± 2.6 mm in x-axis and 6.6 ± 1.9 mm in y-axis, respectively. The hip joint center was estimated within a 5 mm error in both axes in only 8 hips (6.5%). Thus, we developed two estimating methods using pelvic height, modified Ranawat method and pelvic height ratio method, and the estimation errors of these methods were within 5 mm in both axes in 118 hips (96%) and 116 hips (94%), respectively.

CONCLUSIONS

Ranawat method showed poor accuracy in estimating anatomical hip joint center and is not recommended for clinical use. Our alternative methods may be useful for surgeons planning the position of the acetabular component in total hip arthroplasty.

Anatomical study based on 3D-CT image reconstruction of the hip rotation center and femoral offset in a Chinese population: preoperative implications in total hip arthroplasty

BACKGROUND

Several anatomical studies regarding the value of hip rotation center (HRC) and femoral offset (FO) have been performed in Western populations. However, there are a few data on hip morphological values in the Chinese population based on CT scans. This study measured the values of the hip and pelvis, especially HRC and FO, in a Chinese population and compared them with the published values obtained from Western populations.

PATIENTS AND METHODS

One hundred patients (50 females and 50 males) were included in the present study, and 3D-CT reconstructions of the hip and pelvis were generated. The mean age was 51.4 ± 8.9 years and mean body mass index (BMI) was 23.5 ± 2.6 kg/m². All the morphologic measurements were compared between genders and sides, and the relationships between different parameters were analyzed.

RESULTS

The mean FO values were 38.4 ± 4.7 mm and 35.6 ± 4.4 mm for the males and females, respectively. A significant negative correlation was noted between FO and neck shaft angle (NSA) in both genders (r = - 0.262, P = 0.009 for the males, r = - 0.350, P ≤ 0.001 for the females). A significant positive correlation was found between horizontal distance (HD) and diameter of the femoral head (DFH) in both genders (r = 0.734, P ≤ 0.001 for the males, r = 0.658, P ≤ 0.001 for the females). A significant positive correlation was noted between HD and pelvic width (PW) in males (r = 0.455, P ≤ 0.001). A significant positive correlation was also noted between HD and pelvic height (PH) in males (r = 0.318, P ≤ 0.001). A significant positive correlation was observed between FO and pelvic cavity height (PCH) in males (r = 0.411, P ≤ 0.001), and a significant positive correlation was observed between VD and PCH in females (r = 0.497, P ≤ 0.001). The tip of the greater trochanter was, on average, 7.0 mm higher than the femoral head center. Relationships between DFH and pelvic morphometric parameters were also observed.

CONCLUSION

The present morphological data and the relationships between them can be applied to design better ethnic-specific THA prostheses and preoperative plans.

Effects of long-term high-load exercise on the anatomy of the hip joints: a preliminary report

The aim of this study was to assess the impact of different sports on hip joint anatomic parameters in athletes. This was a cross-sectional study of eight male trampolinists, eight male weightlifters, and eight male volunteers enrolled in July 2014. Hip joint anatomic parameters were measured from plain radiographs taken at the level of the lesser trochanter center. Data were compared between groups using the χ-test or one-way analysis of variance with the Bonferroni post-hoc test. There were no significant differences among groups in age, height, or weight. Compared with the controls, trampolinists showed higher pelvic width, femoral neck length, metaphyseal width (T0), width 20 mm above T0 (T+20), width 20 mm below T0 (T-20) and center edge (CE) angle, and lower head-trochanter ratio, joint space, neck-shaft angle, and articular cartilage angle (P<0.05). Compared with the controls, weightlifters showed lower pelvic femoral index, joint space, length of femoral neck, eccentricity, neck-shaft, and AC angle, and higher pelvic width, femoral head radius, and CE angle (P<0.05). Compared with trampolinists, weightlifters showed higher head-trochanter ratio and femoral head radius, and lower pelvic femoral index, femoral neck length, eccentricity, T0, T+20, T-20, neck-shaft angle, CE angle, and articular cartilage angle (P<0.05). Long-term high-intensity training causes adaptive changes in the hip joint structure that differ between trampolinists and weightlifters.