Hip dysplasia hiding in plain sight: A retrospective analysis of radiology reports

Timely recognition of dysplastic hip morphology is critical to facilitate appropriate management before significant joint damage has developed. It is likely that radiologist under reporting contributes to delays in diagnosis. This study aimed to assess how often adult hip dysplasia goes undetected in radiological reports and to identify clinical and radiological variables that impact the likelihood of detection of dysplasia by radiologists.

Referral details and radiology reports of patients who underwent periacetabular osteotomy by a single surgeon for symptomatic hip dysplasia between 1 January 2016 and 30 June 2020 were reviewed. Four assessors measured the lateral centre edge angle from the pelvic radiograph performed at time of referral. Film quality and other radiographic parameters were also assessed.

Sixty-eight patients were included, 84% were female and the median age was 28.1 years. Dysplasia was not documented in the radiology report in 49% of cases. Dysplasia was more likely to be reported with no history of injury, an aspherical femoral head, lower lateral centre edge angle, higher acetabular index, increased femoral head shaft angle, higher femoro-epiphyseal acetabular roof index, or if there was disruption of Shenton's line, with the first three variables being independent predictors of radiologist detection.

Hip dysplasia should be considered in all adolescents/young adults presenting with hip pain. Causes of radiologist under reporting are likely multifactorial. Clinical information can cause cognitive biases and result in selective looking. A systematic approach to pelvis radiographs should include assessment of acetabular coverage and active search for evidence of femoral head migration.