What is the difference between Schober's test and modified Schober's test?

Difference Between Schober's and Modified Schober's Test

The main difference between Schober's test (original) and modified Schober's test is the initial marking placement and measurement distance: the original Schober test uses a 10 cm distance from a single lumbosacral junction mark, while the modified version uses marks 10 cm above and 5 cm below the lumbosacral junction for a total 15 cm distance.

Original Schober Test (OST)

• Measures lumbar flexion by marking a point at the lumbosacral junction, then measuring 10 cm directly above this point 1
• The patient then bends forward maximally, and the new distance between these points is measured 1
• The difference between the measurements in standing and flexed positions indicates lumbar spine mobility 1

Modified Schober Test (MST)

• Uses three marks: one at the lumbosacral junction, one 10 cm above, and one 5 cm below this point (total initial distance of 15 cm) 2
• The patient bends forward maximally, and the new distance between the uppermost and lowermost marks is measured 2
• The difference between the initial 15 cm and the new measurement represents lumbar spine mobility 2

Clinical Significance and Comparison

• Both tests are used to assess spinal mobility, particularly in conditions like ankylosing spondylitis and other spondyloarthropathies 3
• The modified Schober test is included in the ASAS core set for clinical record keeping in ankylosing spondylitis 3
• Studies show a strong correlation between the 10-cm and 15-cm Schober tests (r = 0.89 in healthy individuals, r = 0.93 in patients with axial spondyloarthritis) 2
• The 10-cm Schober test systematically yields lower values than the 15-cm test, with a mean difference of approximately 1.5 cm in patients with axial spondyloarthritis 2
• This systematic difference affects the calculation of the Bath Ankylosing Spondylitis Metrology Index (BASMI), resulting in a higher BASMI score when using the 10-cm method 2

Validity and Reliability

• Both tests show excellent intrarater reliability but only weak correlation with radiographic measurements of lumbar spine mobility 1
• The modified Schober test appears to reflect spinal mobility better than the original Schober test, though both have limitations in accurately representing lumbar spine angular motion 1
• When compared with radiographic assessment of lumbar spine mobility, the modified Schober test shows correlation coefficients of r = 0.333 (p = 0.018) for L1-S1 mobility and r = 0.363 (p = 0.009) for L3-S1 mobility in patients with ankylosing spondylitis 1

Clinical Application

• These tests are recommended as part of the core set of measurements for assessing physical function in patients with ankylosing spondylitis 3
• They are particularly useful in monitoring disease progression and treatment response in spondyloarthropathies 3
• The modified Schober test, along with chest expansion and occiput-to-wall distance, is specifically recommended for spinal mobility assessment in the ASAS core set 3
• These tests have also shown utility in assessing spinal involvement in other conditions like psoriatic arthritis 4

Important Considerations

• Examiner differences must be taken into account when performing the modified Schober test, as inter-observer variability can affect results 5
• Immediate repetition of the testing procedure can improve performance in forward bending tests, which may affect test reliability 5
• Neither test perfectly correlates with radiographic assessment of lumbar spine mobility, suggesting they should be used as part of a comprehensive assessment rather than in isolation 1