Measurement of knee joint space width with bi-planar radiography

TL;DR

This study compares the reproducibility of knee joint space width measurements using bi-planar imaging and conventional radiography.

Contribution

The study demonstrates that bi-planar radiography can produce reproducible knee joint space width measurements comparable to conventional radiography.

Findings

Bi-planar radiography showed comparable precision to conventional radiography (RMSCV 6.46% vs 7.66%).

Bi-planar imaging measured greater joint space width than conventional radiography, especially in specific knee compartments.

Accurate bi-planar measurements are feasible if knee position and alignment are controlled.

Abstract

The objective of this study was to identify whether the joint space width (JSW) of the knee, measured by bi-planar imaging, is reproducible compared to the clinical reference radiography. Our cross-sectional study design included a cohort of uninjured individuals (N = 30, 26.7 ± 5.1 yr) who underwent scanning to determine the short-term precision of the technique, involving repeat scans by bi-planar radiograph. Additionally, repeat conventional tunnel view knee radiographs were used as a comparator. The minimum apparent tibiofemoral JSW was collected for each leg side and compartment for both modalities. The root-mean-square coefficient of variation (RMSCV) and least significant change (LSC) for bi-planar scans (RMSCV = 6.46%, LSC = 1.07 mm) were comparable to conventional radiography (CR) (RMSCV = 7.66%, LSC = 1.15 mm). There was a bias for greater JSW by bi-planar radiography than CR (9.0%, p < .01), particularly for the forward unloaded left leg lateral (15.5%) and medial (17.6%) compartments. In conclusion, we found that JSW measurements from bi-planar scanners are reproducible and comparable to CR. While radiography remains accessible clinically, accurate and precise JSW by bi-planar scanners is feasible provided knee position and alignment are controlled.

Graphical Abstract

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