Assessment of spine length in scoliosis patients using EOS imaging valid and reliable

Knowledge about spinal length and subsequently growth of each individual patient with adolescent idiopathic scoliosis (AIS) helps with accurate timing of both conservative and surgical treatment. Radiographs taken by a biplanar low dose X-ray device (EOS) have no divergence in the vertical plane and can provide three-dimensional (3D) measurements. C. M. M. Peeters et al conducted a study to investigate the criterion validity and reliability of EOS spinal length measurements in AIS patients. The article has been published in ‘European Spine Journal.’

Prior to routine EOS radiograph, a radiographic calibrated metal beads chain (MBC) with metal beads (5 mm in diameter) was taped to the skin on the spinous processes from vertebra C7 to L5 of 120 patients with AIS to calibrate the images. The physician assistant (JB) placed the chain on the skin of all included patients by carefully palpating each individual spinous process to position the chain parallel to the curve before the patient was positioned on the EOS platform in standing position. Subsequently, the biplanar low-dose radiographs of the spine were conducted. Two observers (CP and FW) independently examined the EOS images for eligibility. Only radiographs with the metal beads chain (MBC) positioned accurately over the spinous processes in parallel to the spine were included for analysis. Any differences or uncertainty concerning the inclusion of the radiographs was solved in a consensus meeting.

Spinal lengths were measured from vertebra to vertebra on EOS anteroposterior (AP), lateral view and on the combined 3D EOS view (EOS 3D). These measurements were compared with MBC length measurements. Secondly, intra- and interobserver reliability of length measurements on EOS-images were determined.

Key findings of the study:

• Of the 120 patients fulfilling the inclusion criteria, 50 patients (41.7%) had good parallel placement of the MBC and were included for analysis.

• The mean age of the 50 included patients at time of inclusion was 17.6 years (SD=3.3) with a range from 12 to 29 years.

• Forty-five patients (90%) were female.

• The correlations between EOS and MBC were highest for the 3D length measurements.

• Compared to EOS 3D measurements, the total spinal length was systematically measured 4.3% (mean difference=1.97±1.12 cm) and 1.9% (mean difference=0.86±0.63 cm) smaller on individual EOS two-dimensional (2D) AP and lateral view images, respectively.

• Both intra- and interobserver reliability were excellent for all length measurements on EOS-images.

The authors concluded that – “this study shows a good validity and reliability for spinal length measurements on EOS radiographs. The EOS 3D length measure method is preferred above 2D spinal length measurements on EOS AP or lateral views and can be used for total, thoracic, lumbar or segmental spinal length measurements in AIS patients. When the EOS 3D measure method is not possible, spinal length measurements on EOS 2D (lateral view) could be preferred above measurements on EOS 2D (AP view) when coronal Cobb angle is below 40 degrees. In the future, an automated spinal length measurement system would be helpful in accurate timing of treatment.”

Further reading:

Assessment of spine length in scoliosis patients using EOS imaging: a validity and reliability study

C. M. M. Peeters, G. J. F. J. Bos et al

European Spine Journal (2022) 31:3527–3535

https://doi.org/10.1007/s00586-022-07326-4