Segmental Instability

Presentation

A 37-year-old man presented with mechanical back pain after a previous discectomy. On examination, he had decreased sensation in the right L5 dermatome and limited lumbosacral flexion. Preoperative imaging demonstrated a mild disc bulge at L4-L5.

Radiologic Findings

Postoperative lumbar spine x-rays (Figs. 42-1 and 42-2) show interbody fusion and percutaneously placed pedicle screws at the L4 and L5 levels.

Diagnosis

Segmental instability

Treatment

The patient was treated with a percutaneous L4-L5 trans-foraminal lumbar interbody fusion and bilateral L4-L5 pedicle screw fixation and arthrodesis. At follow-up, he was pain free and able to return to work.

Discussion

Mechanical low back pain can sometimes become worse after a decompressive surgery. Segmental instability manifests as axial pain that is worsened by motion and improved by rest, which is typical of mechanical low back pain.

There is a differential for failed back syndrome, particularly in the immediate postsurgical period. Low back pain with fever and a reddened wound with discharge are obvious signs of infection. Persistence of a severe radiculopathy may represent a retained disc fragment, incorrect procedural level, or a complex regional pain syndrome. Magnetic resonance imaging (MRI) is an excellent diagnostic aid in these cases and should be done with and without gadolinium.