Lateral bending differentiates early-stage spondylolysis from nonspecific low back pain in adolescents

Key points

1. 01Lateral bending was the only one of four movement tests that differed between groups, with higher pain in the spondylolysis group (2.9 versus 2.2, p = .04).
2. 02Hyperextension, long assumed to be the key sign, did not differ between groups (4.1 versus 4.1), so it did not help distinguish the two conditions here.
3. 03A side-bending pain score above 3.5 had low sensitivity (0.437) and modest specificity (0.732), meaning it misses many true cases.
4. 04Overall pain (VAS) and disability (ODI) scores were similar in both groups, so they did not help separate the conditions.
5. 05The authors suggest using a positive side-bending test to decide who should be sent for MRI, not as a stand-alone diagnosis.

How it was conducted

Design

Retrospective comparative cohort study

Participants

112 adolescents (aged 18 years or younger) with acute low back pain of less than 1 month, recruited at one rehabilitation clinic (Sept 2012 to Sept 2013)

Groups

Early-stage spondylolysis (n = 71) versus nonspecific low back pain (n = 41), classified by MRI

Tests evaluated

Pain on hyperextension, hyperflexion, rotation, and lateral bending, scored 0 to 10 on a numerical rating scale in standing

Reference standard

MRI (high signal on fat-saturated T2 and low signal on T1 in the pedicle defined spondylolysis)

Primary outcome

Difference in provoked pain between groups and ROC-derived cut-off for predicting spondylolysis

What they found

• Lateral bending pain was higher in the spondylolysis group: 2.9 plus or minus 2.5 versus 2.2 plus or minus 2.5 (p = .0429).
• Hyperextension did not differ: 4.1 plus or minus 3.0 versus 4.1 plus or minus 2.5 (p > .99).
• Hyperflexion did not differ: 2.4 plus or minus 2.8 versus 3.0 plus or minus 2.8 (p = .9889).
• Rotation did not differ: 2.1 plus or minus 2.4 versus 2.2 plus or minus 2.4 (p > .99).
• A lateral bending cut-off above 3.5 gave sensitivity 0.437, specificity 0.732, positive likelihood ratio 1.63, and negative likelihood ratio 0.77.
• Baseline pain (VAS 6.5 versus 6.0, p = .23) and disability (ODI 19.7 versus 24.6, p = .20) did not differ between groups.
• Affected levels were L2, L3, L4, L5, and both L3 and L5 in 4, 4, 26, 36, and 1 patient; 22 lesions were bilateral and 49 unilateral.

Limitations

• Retrospective single-centre study with no asymptomatic comparison group, so early painless cases were not captured.
• The side-bending test had low sensitivity (0.437) and only a small positive likelihood ratio (1.63), so it misses many true cases and is not diagnostic on its own.
• Groups were modest in size (71 versus 41) and tests were performed only once with active motion and no overpressure, which may have limited pain provocation.
• Pain at rest was not measured, so the contribution of resting versus movement pain could not be separated.

Why it matters

For patients

If side-bending clearly worsens a teenager's recent back pain, it is a reason to ask the doctor about an MRI rather than assume it is ordinary strain.

For clinicians

Use significant lateral-bending-provoked pain (above 3.5 on a 0 to 10 scale) as a flag to consider MRI for early spondylolysis, but do not rely on hyperextension or on this test alone given its low sensitivity.

For readers

This early evidence challenges the long-held emphasis on the hyperextension test and points to side-bending as a more useful, though still imperfect, screening cue.