Incidence of Late-Diagnosed Hip Dislocation After Universal Clinical Screening in Sweden

Abstract

Importance: Developmental dysplasia of the hip, including late-diagnosed hip dislocation, is the leading cause of hip arthroplasties in young adults. Early treatment is essential for a good prognosis. Before the institution of a national screening program, a minimum of 0.9 per 1000 Swedish children were affected.

Objectives: To evaluate the incidence of late-diagnosed hip dislocation among children who undergo clinical screening as neonates and to study antenatal and perinatal risk factors for late-diagnosed hip dislocation.

Design, setting, and participants: This nested case-control study included children born in Sweden from January 1, 2000, through December 31, 2009. All maternity wards, maternal health units, and orthopedic departments in Sweden participated. Children with a late-diagnosed hip dislocation were matched by sex and birth year to randomly selected controls in a 1:10 ratio. Potential risk factors in pregnant women and newborns were recorded, and cases of hip dislocation were registered. Observation time ranged from 8 to 18 years, with the last data analysis in January 2019.

Exposures: Clinical hip examinations neonatally and at 6 to 8 weeks, 6 months, and 10 to 12 months.

Main outcomes and measures: Hip dislocation diagnosed more than 14 days after birth, age at diagnosis, and severity of dislocation.

Results: Among 1 013 589 live births (521 728 [51.5%] boys), 126 children (0.12 [95% CI, 0.10-0.15] per 1000 live births) had a late-diagnosed hip dislocation at a median age of 31.4 weeks (interquartile range, 16.1-67.1 weeks; 95% CI, 27.4-44.1 weeks). The incidence of late-diagnosed hip dislocation was 9 times higher among girls (113 of 491 861; 0.23 [95% CI, 0.19-0.28] per 1000 live births) than among boys (13 of 521 728; 0.02 [95% CI, 0.01-0.04] per 1000 live births). Twenty-one children (0.02 per 1000 live births) had high (severe) dislocations. Breech delivery (adjusted odds ratio, 3.07; 95% CI, 1.34-7.02), short body length at birth (adjusted odds ratio, 0.86; 95% CI, 0.76-0.98, per additional 1 cm), and being large for gestational age (adjusted odds ratio, 3.59; 95% CI, 1.30-9.95) were independent risk factors. Maternal smoking at the first visit to the maternal health care center was less common among children with hip dislocation (adjusted odds ratio, 0.16; 95% CI, 0.04-0.70).

Conclusions and relevance: Compared with historical data, the incidence of late-diagnosed hip dislocation in Swedish-born children appears to have decreased substantially since the screening program was initiated, as have the age at detection and disease severity. Similar screening programs should also be possible to institute in upper-middle- and lower-middle-income countries.

Figure 1.. Tönnis Classification

A, Grade 1: the center of the femoral head lies medial to the Perkin line (a vertical line drawn from the most lateral point of the acetabulum). Radiograph is of an infant girl with a dislocatable right hip discovered at routine examination. B, Grade 2: the center of the left femoral head lies lateral to the Perkin line. Radiograph is of an infant girl referred because of decreased hip abduction at routine examination. C, Grade 3: the center of the left femoral head lies at the level of the lateral aspect of the acetabulum. Radiograph is of an infant girl referred because of limited abduction. The mother had noted shortening of the leg. D, Grade 4: the center of the right femoral head lies above the lateral aspect of the acetabulum. Radiograph is of a male child referred because of leg length discrepancy. The parents had sought medical attention for some time before the diagnosis was made.

Figure 2.. Yearly Incidence (95% CI) of Late-Diagnosed Hip Dislocation in Sweden

Error bars indicate 95% CIs.

Figure 3.. Age at Diagnosis Among 126 Children With Late-Diagnosed Hip Dislocation in Sweden

In bilateral cases, the Tönnis grade of the more severely affected hip is given. Among 8 children, there was no prereduction radiograph.