Exploratory evaluation of spinopelvic and lumbar parameters in adolescent athletes with isthmic spondylolisthesis: feasibility and reliability of upright MRI compared to radiography

Introduction Isthmic spondylolisthesis is prevalent among adolescent athletes (AA). Upright MRI (uMRI) offers a radiation-free alternative to radiographs, combining imaging of the loaded spine with detailed depiction of the adjacent structures. This study evaluates the feasibility and intra-rater measurement repeatability of spinopelvic and lumbar parameter assessment in AA using uMRI and radiography, as well as cross-modality agreement between both imaging techniques. Material and methods Lumbar sagittal T2-weighted low-field uMRI and lateral standing radiographs from 38 AA with isthmic spondylolisthesis were retrospectively reviewed. Cases of both imaging techniques without motion artifacts, performed within one year, presenting the lumbar spine and spinopelvic junction were included. Spinopelvic and lumbar parameters [e.g., anterior translation (AT)] were determined. Relative reliability was measured by intraclass correlation coefficient (ICC). Absolute reliability measures included standard error of measurement (SEM), test-retest variability (TRV), minimal detectable change (MDC), and Bland-Altman analysis. Results Images from 16 AA (13.5 ± 1.8years; 159 ± 7 cm; 50 ± 9 kg) fulfilled the inclusion criteria. Data exclusion mainly occurred due to time discrepancy ( n = 9) and poor image quality ( n = 8). Relative reliability ranged from 0.89 to 0.95 for radiographs, 0.61 to 0.94 for uMRI and from 0.61 to 0.88 between the methods. Absolute reliability showed lower variability for radiographs (SEM: 3–8%; TRV: 5–14%, AT-MDC: 1.4 mm) compared to uMRI (SEM: 2–29%; TRV: 9–49%; AT-MDC: 2.0 mm) and between methods (SEM: 4–34%; TRV: 11–46%; AT-MDC: 3.2 mm). Discussion and conclusion On evaluable images, uMRI demonstrated moderate-to-excellent intra-rater measurement repeatability for several parameters. However, cross-modality agreement with radiography was variable and does not support interchangeability between the two modalities. uMRI may therefore represent a complementary radiation-free imaging modality for selected patients and parameters, pending prospective validation.