Minimal Access Spinal Technology (MAST) Fusion for Osteomyelitis: Case Report

This 84 year old man was initially reviewed in September 2001 after having had a laminectomy performed by an outside institution for presumed spinal stenosis. He had had a poor outcome from the surgery in terms of hip and thigh pain and postoperative MR scanning at that time confirmed multiple lesions throughout the lumbosacral spine, which on CT-guided biopsy confirmed underlying metastatic prostate cancer. He was managed non-surgically with appropriate chemotherapy and radiotherapy. This man presented in April 2003 with severe mechanical back pain, in the absence of neurological symptoms in his lower limbs and without bladder or bowel dysfunction. On examination he was noted to be somewhat cachectic, neurologically intact, with an elevated white cell count and ESR. His initial imaging is shown below:

Figure 1. Marked osteopenia is present. The L2/3 disc space is ill-defined and there appears to be a crush fracture in the L3 vertebral body.

Figure 2. T1-weighted sagittal MR scanning showing low signal change in the L3 body and lower portion of the L2 vertebral body. The L2/3 disc space is poorly defined. No epidural collection was identified on the imaging.

Initially it was felt that the changes in the L3 body were due to metastatic prostate cancer. Because of the peridiscal changes however, a CT-guided aspiration biopsy of the disc space was effected and tissue taken for culture. Enterococcus was cultured from the disc space and appropriate antibiotic therapy was commenced. A preoperative DEXA scan gave a lumbar T score of -3.4.

After 2 weeks of antibiotic therapy, repeat MR scanning was unchanged and the patient still suffered from severe mechanical back pain resistant to bracing and relieve with bed rest. He again had no neurological symptoms in his lower limbs and was neurologically intact. It was felt that the loss of the posterior columns from his initial surgery had left him with a grossly unstable spine that may fuse over time with the smouldering discitis/osteomyelitis, however until that occurred he was at major risk of developing kyphosis, collapse and neurological compromise. Assessment by our medical and anaesthetic services deemed him unfit for a major reconstructive procedure to perform either an anterior or posterior vertebrectomy. In view of this, a minimally invasive procedure was offered in hopes of maintaining a posterior tension band whilst fusion of the anterior column occurred.