Osteoarthritis of the hip joint in elderly patients is most commonly atrophic, with low parameters of acetabular dysplasia and possible involvement of osteoporosis

Abstract

As elderly patients with hip osteoarthritis aged, acetabular dysplasia parameters decreased (Sharp's angle, acetabular roof obliquity angle, and acetabular head index) and the incidence of the atrophic type increased. Vertebral body fracture was more frequent in the atrophic type, suggesting the involvement of osteoporosis at the onset of hip osteoarthritis.

Introduction: Osteoarthritis (OA) is associated with increased bone formation at a local site. However, excessive bone resorption has also been found to occur in the early stages of OA. Osteoporosis may be involved in the onset of OA in elderly patients. We conducted a cross-sectional radiographic study of patients with hip OA and examined the association between age and factors of acetabular dysplasia (Sharp's angle, acetabular roof obliquity angle, and acetabular head index) as well as the osteoblastic response to determine the potential involvement of osteoporosis.

Methods: This study included 366 patients (58 men, 308 women) who had undergone total hip arthroplasty for the diagnosis of hip OA. We measured the parameters of acetabular dysplasia using preoperative frontal X-ray images and evaluated each patient according to Bombelli classification of OA (hypertrophic, normotrophic, or atrophic type).

Results: As the patients aged, the parameters of acetabular dysplasia decreased. The incidence of the atrophic type of OA was significantly higher in older patients. Vertebral body fractures were more frequent in the atrophic type than in the other types. Additionally, the index of acetabular dysplasia was lower in the atrophic type. By contrast, the hypertrophic type was present in relatively younger patients and was associated with an increased index of acetabular dysplasia.

Conclusion: In elderly patients with hip OA, the parameters of acetabular dysplasia decreased and the incidence of the atrophic type increased as the patients aged. The frequency of vertebral body fracture was high in patients with the atrophic type, suggesting the involvement of osteoporosis in the onset of hip OA.

Keywords: Acetabular dysplasia; Aging; Osteoarthritis; Osteoporosis.

Fig. 1

Radiographs of OA according to the Bombelli classification. Typical radiographs of hypertrophic (a), normotrophic (b), and atrophic (c) OA

Fig. 2

The correlation between the acetabular index and age. Single regression analysis was performed for statistical analysis of the correlation between the parameters of acetabular dysplasia and age. ARO acetabular roof obliquity, AHI acetabular head index

Fig. 3

The comparison of acetabular index in age groups. The Steel–Dwass test was used as a nonparametric multiple comparison test in each age group. ARO acetabular roof obliquity, AHI acetabular head index. *p < 0.05; **p < 0.01

Fig. 4

Bombelli classification in age groups. The Steel–Dwass test was used as a nonparametric multiple comparison test in each age group. H hypertrophic type, N normotrophic type, A atrophic type. *p < 0.05; **p < 0.01

Fig. 5

The incidence of vertebral body fracture. The Steel–Dwass test was used as a nonparametric multiple comparison test for the results of Bombelli classification. H hypertrophic type, N normotrophic type, A atrophic type. *p < 0.05

Fig. 6

The comparison of acetabular index in Bombelli classification. The Steel–Dwass test was used as a nonparametric multiple comparison test for the results of Bombelli classification. H hypertrophic type, N normotrophic type, A atrophic type, ARO acetabular roof obliquity, AHI acetabular head index. *p < 0.05; **p < 0.01