# Adjacent segment disease induced by spinal tophus: a case report

## TL;DR

A rare case of spinal tophus causing adjacent segment disease is reported, highlighting unusual gout-related complications in the spine.

## Contribution

This case report documents a rare instance of lumbar adjacent segment disease caused by monosodium urate crystal deposition.

## Key findings

- Spinal tophus can lead to lumbar adjacent segment disease and spinal stenosis.
- Magnetic resonance imaging and computed tomography can identify MUC deposition in the spine.
- Surgical excision and fusion extension provided stabilization and confirmed MUC pathology.

## Abstract

Tophus, a hallmark feature of chronic gout, typically develops in the joints of the extremities, skin, and mucosal tissues. Although several case reports have described spinal tophus deposition leading to spinal stenosis and radiculopathy, documented cases of lumbar adjacent segment disease (ASD) caused by monosodium urate crystal (MUC) deposition remain exceedingly rare. Here, we report the case of a 56-year-old male who underwent L4-S1 lumbar fusion surgery two years prior for L4-S1 disc herniation with radiculopathy. The patient presented with recurrent low back pain, radiculopathy, and systemic tophus involvement. Magnetic resonance imaging (MRI) T2-weighted sequences revealed a hypointense signal at the posterior margin of the L3 vertebral body, while computed tomography (CT) demonstrated a hyperdense lesion. These radiographic findings suggested dural sac compression and spinal stenosis, though the definitive etiology warranted further evaluation. Surgical intervention involved excision of the L3 posterior lesion and extension of the fusion construct from L4-S1 to L2-S1 based on the existing L4-S1 instrumentation for spinal stabilization. Histopathological examination confirmed extensive MUC deposition. This report details the clinical presentation, imaging characteristics, pathological findings, surgical management, and potential pathogenic mechanisms underlying this rare complication.