Normal Post-Operative MRI¶

Expected Findings After Lumbar Discectomy/Laminectomy¶

Laminectomy defect in the posterior elements
Epidural scar tissue (enhancing soft tissue in the epidural space) — develops over weeks to months and is expected
Residual or recurrent disc material — small residual fragments are common
Endplate signal changes at the operative level (Modic-type changes)
Muscle edema and enhancement along the surgical approach (resolves over weeks)
Small epidural fluid collections (seromas) — common in early post-op period

Expected Findings After Spinal Fusion¶

Hardware in expected position (pedicle screws, rods, interbody cages)
Endplate edema at the fusion level (low T1, high STIR) — normal for 6–12 months
Bone graft incorporation (signal evolves from edema to mature bone/fatty marrow)
Enhancement at the fusion bed — normal during active healing

Expected Findings After ACDF¶

Anterior plate and screws at the operative level
Interbody graft or cage between the vertebral bodies
Prevertebral soft tissue swelling — normal for several weeks after anterior approach
Endplate edema at the graft-bone interface — normal during fusion maturation

Clinical Pearl

The most common misinterpretation in post-operative spine imaging is mistaking normal epidural scar for recurrent disc herniation. Both appear as epidural soft tissue on T2. The key distinction: scar enhances diffusely and homogeneously on post-contrast MRI, while recurrent disc does not enhance (or enhances only at the periphery). Post-contrast imaging is essential for this distinction.

Key Points¶

Epidural scar enhancement is expected and normal after discectomy
Endplate edema at fusion levels is normal for 6–12 months
Prevertebral swelling is normal after anterior cervical surgery
Small epidural fluid collections are common early post-op
Post-contrast MRI is essential to distinguish scar from recurrent disc

References¶

Ross JS, Obuchowski N, Zepp R. The postoperative lumbar spine: evaluation of epidural scar over a 1-year period. AJNR Am J Neuroradiol. 1998;19(1):183-186.
Abel F, Tan ET, Chazen JL, Lebl DR, Sneag DB. MRI after Lumbar Spine Decompression and Fusion Surgery: Technical Considerations, Expected Findings, and Complications. Radiology. 2023;308(1):e222732.
Passavanti Z, Leschka S, Wildermuth S, Forster T, Dietrich TJ. Differentiating epidural fibrosis from disc herniation on contrast-enhanced and unenhanced MRI in the postoperative lumbar spine. Skeletal Radiol. 2020;49(11):1819-1827.
Hayashi D, Roemer FW, Mian A, Gharaibeh M, Müller B, Guermazi A. Imaging features of postoperative complications after spinal surgery and instrumentation. AJR Am J Roentgenol. 2012;199(1):W123-W129.
Girão MMV, Miyahara LK, Dwan VSY, Baptista E, Taneja AK, Gotfryd A, Castro AAE. Imaging features of the postoperative spine: a guide to basic understanding of spine surgical procedures. Insights Imaging. 2023;14(1):103.
Corona-Cedillo R, Saavedra-Navarrete MT, Espinoza-Garcia JJ, Mendoza-Aguilar AN, Ternovoy SK, Roldan-Valadez E. Imaging Assessment of the Postoperative Spine: An Updated Pictorial Review of Selected Complications. Biomed Res Int. 2021;2021:9940001.