A comparison of plain radiographs and quantitative fluoroscopy for the measurement of translatory slip in the lumbar spine

Authors: Breen, A., Hemming, R. and Claerbout, E.

Start date: 15 November 2018

Purpose and background Static plain radiographs at the end of uncontrolled bending are the current standard of care for measuring translatory slip in back pain patients. Quantitative fluoroscopy systems (QF) that employ standardised bending protocols have been found to improve precision and reduce dose, but comparative data are lacking. We compared 4 QF methods with static radiographs in a control population, calculating ranges, population variation and measurement errors over 6 weeks. Methods Fifty-four healthy controls (F=22, M=23) received passive recumbent and active weight bearing QF screenings during controlled motion, plus still fluoro imaging in neutral, flexion and extension. The translatory slip of all levels from L2-S1 was determined for each condition using bespoke image tracking codes (Matlab) and pooled to provide means and ranges of variation (+/-1.96SD). The pooled measurement error, or minimal detectable change (MDC95), reflecting the intra subject repeatability over 6 weeks was calculated. Ranges of translation for each level (L2-S1), for each type of motion were also calculated.

Results Static radiographs at the end of uncontrolled flexion gave the greatest variation and the worst repeatability, while QF recumbent passive and active weight bearing motion with flexion recorded during the motion had ¼ less variation and twice the repeatability. For individual levels, L2-3 had significantly higher flexion ranges in controlled motion than uncontrolled motion, whereas the converse was true at L4-5 (P<0.001).

Conclusion Dynamic QF measurement of flexion translatory slip gives ¼ less population variation and half the measurement error of static radiographs when measured in the same participants.

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