Hip-Spine Syndrome: Lumbosacral Spine Transitional Vertebral Anomalies Are Frequent in Adult Acetabular Dysplasia -- A Cross-Sectional Evaluation of a Prospective Hip Registry Cohort

BACKGROUND: A subset of patients presenting with hip pain and instability who are found to have acetabular dysplasia (AD) do not experience resolution of symptoms after surgical management. Hip-spine syndrome is a possible underlying cause. OBJECTIVE: We hypothesized that there is increased frequency of radiographic spine anomalies in patients with AD. A secondary aim was to assess between radiographic severity of AD and frequency of spine anomalies. METHODS: This was a cross-sectional analysis of 122 hips in 122 patients who presented with hip pain and had the final diagnosis of AD. Two readers analyzed hip and spine variables using standard hip radiographic series. Frequency of lumbosacral transitional vertebra (LSTV) along with associated Castellvi grade, pars interarticularis defect, and spinal morphological measurements were recorded and correlated with radiographic severity of AD. RESULTS: Out of 122 patients, 110 were females and 12 were males. We analyzed 122 hip radiographic series, 59 from patients with symptoms in the left hip and 63 from patients with symptoms in the right hip. Average age at time of presentation was 34.2 ± 11.2 years. Frequency of LSTV was high (39-43%), compared to historic records from the general population, with Castellvi type 3b being the most common (60-63%). Patients with AD have increased L4 and L5 interpedicular distance (IPD) compared to published values. Frequency of pars interarticularis defect was 4%. Intraclass correlation coefficient (ICC) for hip and spine variables assessed ranged from good (0.60 - 0.75) to excellent (0.75 - 1.00). Severity of AD did not demonstrate statistically significant correlation with frequency of radiographic spine anomalies. CONCLUSION: Patients with AD have increased frequency of spinal anomalies seen on standard hip radiographs. However, there exists no correlation between radiographic severity of AD and frequency of spine anomalies. In managing AD patients, clinicians should also assess spinal anomalies that are easily found on standard hip radiographs.