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Andersson lesion refers to a discovertebral destructive lesion seen in patients with Ankylosing spondylitis (AS).

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Etiopathogenesis

Cause Type Mechanism
Inflammatory Chronic enthesitis and discovertebral inflammation in fused spine
Traumatic Minor trauma in a stiff ankylosed spine → fracture/nonunion
Mechanical stress Repetitive microtrauma due to rigidity and altered biomechanics
Infection theory Largely refuted; Andersson lesions are sterile

![Schematic presentation of the development of discovertebral (Andersson) lesions; lesions may originate from inflammation combined with unfused segments (last mobile segment; a), fractures trough the ankylosed disc (b) or fractures trough the vertebral body (c). Finally, a characteristic Andersson lesion develops, with (e) or without (d) a kyphotic deformity

Bron JL, de Vries MK, Snieders MN, van der Horst-Bruinsma IE, van Royen BJ. Discovertebral (Andersson) lesions of the spine in ankylosing spondylitis revisited. Clin Rheumatol. 2009;28(8):883-892. doi:10.1007/s10067-009-1151-x](https://prod-files-secure.s3.us-west-2.amazonaws.com/2aa05644-4658-4c26-84d3-64c36b55fb6c/ff0fff72-c691-4b13-ae23-eea6247dcc6e/Andersson_lesion.jpg)

Schematic presentation of the development of discovertebral (Andersson) lesions; lesions may originate from inflammation combined with unfused segments (last mobile segment; a), fractures trough the ankylosed disc (b) or fractures trough the vertebral body (c). Finally, a characteristic Andersson lesion develops, with (e) or without (d) a kyphotic deformity

Bron JL, de Vries MK, Snieders MN, van der Horst-Bruinsma IE, van Royen BJ. Discovertebral (Andersson) lesions of the spine in ankylosing spondylitis revisited. Clin Rheumatol. 2009;28(8):883-892. doi:10.1007/s10067-009-1151-x

Clinical Features

Symptom Notes
New or worsening back pain Often localized to the lesion site
Spinal tenderness Especially at thoracolumbar area
Mechanical instability May cause neurologic symptoms in severe cases
Neurological deficits Rare but possible in unstable lesions

Typical locations:

Region Comment
Thoracolumbar junction Most commonly affected (e.g., T11–L2)
Cervical spine Also possible, less frequent

Radiology

https://doi.org/10.1007/s10067-009-1151-x

https://doi.org/10.1136/bcr-2021-248542

Modality Imaging features
XR • Lucency at discovertebral junction: Appears as erosion or "break" in fused vertebrae
• Sclerosis and irregular margins: Surrounds the lesion site
• Widening of disc space: Suggestive of pseudoarthrosis
• Paravertebral ossifications: May be interrupted or displaced
CT • High resolution: Best for bony changes, fracture lines
• Sclerotic margins + cleft: Confirms pseudoarthrosis
MR • T1: Hypointense erosions or clefts at discovertebral interface
• T2: Hyperintensity due to marrow edema, inflammation
• STIR: Highlights active inflammation
• CEMR: May show enhancement if active inflammatory lesion (differentiates from infection)

![(A) Antero-posterior and (B) lateral radiograph of lumbosacral spine, (C) dorsal spine radiograph showing bilateral decreased SI joint space, and sclerosis around SI joints, suggestive of sacroiliitis (red arrows). Syndesmophytes are seen (blue arrows) as paravertebral ossifications, causing the spine to have diffuse syndesmophytic ankylosis and giving the bamboo spine appearance (green arrow). Irregularities, erosions and sclerosis of vertebral end plates of D11–D12 are noted (yellow arrow), which are suggestive of Andersson lesion. SI, sacroiliac.

Pai SN, Karthik Kailash, Vignesh Jayabalan, Ganesan S. Andersson lesion in ankylosing spondylitis. BMJ Case Reports CP. 2022;15(2):e248542. doi:https://doi.org/10.1136/bcr-2021-248542 ‌](https://prod-files-secure.s3.us-west-2.amazonaws.com/2aa05644-4658-4c26-84d3-64c36b55fb6c/df63ff8a-275c-41b8-991b-4ddd748d05ab/Andersson_lesion_xr.jpg)

(A) Antero-posterior and (B) lateral radiograph of lumbosacral spine, (C) dorsal spine radiograph showing bilateral decreased SI joint space, and sclerosis around SI joints, suggestive of sacroiliitis (red arrows). Syndesmophytes are seen (blue arrows) as paravertebral ossifications, causing the spine to have diffuse syndesmophytic ankylosis and giving the bamboo spine appearance (green arrow). Irregularities, erosions and sclerosis of vertebral end plates of D11–D12 are noted (yellow arrow), which are suggestive of Andersson lesion. SI, sacroiliac.

Pai SN, Karthik Kailash, Vignesh Jayabalan, Ganesan S. Andersson lesion in ankylosing spondylitis. BMJ Case Reports CP. 2022;15(2):e248542. doi:https://doi.org/10.1136/bcr-2021-248542 ‌

Differential Diagnosis