Lumbar Nonunion

Presentation

A 45-year-old man underwent an L5-S1 fusion for grade II spondylolisthesis 4 years ago and in recent months has started suffering a progressive mechanical low back pain. He is neurologically intact.

Radiologic Findings

Flexion/extension lumbar x-rays show mobile, grade II spondylolisthesis, with poor bony formation and a fractured S1 screw (Fig. 53-1).

FIGURE 53-1 Previous lumbar fusion with nonunion and a fractured S1 screw.

Diagnosis

Pseudarthrosis

Treatment

The patient had an L5-S1 anterior interbody fusion with femoral ring allograft.

Discussion

Nonunion is a risk of any fusion surgery. Risks for developing nonunion include smoking, morbid obesity, previous surgery, multilevel fusion, metabolic disorders such as diabetes mellitus, osteoporosis, and certain medications such as nonsteroidal anti-inflammatory drugs (NSAIDs) or steroids. Nonunion is a surgical problem and can be treated in a variety of ways.

Anterior lumbar interbody fusion (ALIF) is preferred in a patient with previous posterior fusion who presents with nonunion (mechanical low back pain) but without radiculopathy or other signs of neural element compression. Otherwise a redo posterior fusion will be necessary. Rarely do we resort to combined 360-degree fusion. Highlighted risks of ALIF are retrograde ejaculation and urethral or vascular injury.

This patient underwent an anterior lumbar interbody fusion and achieved a solid union. The recent introduction of osteoinductive materials such as bone morphogenetic protein has enhanced fusion rates, making nonunion less frequent.