Table 1.

Characteristics of the 1,837 patients who received an invitation to participate in the study in the period from March 1, 2010 to March 1, 2011

Patient characteristics	Patients who agreed to participate	Patients who declined participation	p-value
Population (n (%))	1,335 (73)	502 (27)
Age a years, median (range)	68 (23–94)	70 (24–96)	< 0.001
18–50, n	71	27	1.0
50–70, n (%)	706 (53)	223 (44)	0.001
> 70, n (%)	558 (42)	252 (50)	0.001
Female sex, n (%)	720 (54)	295 (59)	0.06
Diagnosis, n (%) b
Idiopathic OA	1,175 (90)	397 (84)	0.001
Other arthritis	45	13	0.5
Childhood hip diseases	30	21	0.02
Sequel from fracture	6	5	0.2
Necrosis of femoral head	7	3	0.8

^aAge of patients on date of inclusion start.

^bIdiopathic OA, other arthritis (Mb. Bechterew, other arthritis), childhood hip diseases (congenital hip dislocation, Mb. Calvé-Legg-Perthes, epiphysiolysis, acetabular dysplasia), sequel from fracture (late sequel from fracture of proximal femur), and necrosis of femoral head (atraumatic necrosis of femoral head). Patients with fracture of acetabulum (29 patients accepted, 24 patients declined), traumatic hip dislocation (5 patients accepted, 6 patients declined), and fresh fracture of proximal femur (15 patients accepted, 4 patients declined) were excluded from the study.