Instr. vs. Non-instr. Posterolateral Spinal Fusion in Patients With Spinal Stenosis and Degenerative Listhesis

Lumbar spinal stenosis (LSS) is a common disease with a large impact on the quality of life of the patient. LSS is defined as narrowing of the spinal canal, nerve root canal or intervertebral foramina. Spinal stenosis is caused by degenerative changes in the lumbar spine, including thickening of the ligamentum flavum, osteophyte formation and disc protrusion. Pain is worse with standing upright and with exercise, and relieved with spine flexion or sitting down.

In the Wakayama Spine Study, investigators found radiographic severe spinal stenosis, defined as narrowing of more than two-thirds of the spinal canal area, in 30,4% of all patients, but only 17,5% were symptomatic.

Many of the patients suffering from LSS are pensioners, with an average age of 65 years. With current changes in demographics and the aging global population it is estimated that prevalence of LSS will increase to nearly 60% by 2025.

In a Danish epidemiological study, degenerative spondylolisthesis was found in 2,7% of men and 8,4% of women above 50 years. Every year, more than 3500 patients aged 60 and above are referred to Center of Spine Surgery Middelfart for LSS. According to the national Danish surgical spine database, DaneSpine, 7936 patients with LSS had surgery during a period from 2009-2013.

Patients suffering from LSS and instability are treated with decompression and posterolateral spinal fusion with or without instrumentation. According to DaneSpine, this group of patients showed improvements on both physical and psychological parameters. In countries outside of Scandinavia, these patients are usually treated with decompression and posterolateral spinal fusion with supplementary pedicle screw fixation. Instrumentation with pedicle screws and rods provides an internal splint, preventing motion during fusion healing. The fusion rate in non-instrumented arthrodesis is reported to be as low as 30-45% In contrast the fusion rate with instrumented arthrodesis have been reported to be above 80%. Although some studies have shown similar outcomes after decompression with or without instrumentation, long-term follow up has shown that a solid fusion improves clinical outcome.

In recent retrospective studies, the spinal sagittal balance, specifically the sagittal vertical axis (SVA) has been shown to affect the outcome of patients undergoing laminectomy. Decompression surgery has been shown to improve sagittal balance in patients with a preoperative imbalance, compared to patients treated with rehabilitation. The preoperative sagittal imbalance has not been shown to significantly affect health-related quality of life(HRQoL)outcomes although a residual imbalance after decompression is related to a poorer outcome. No prospective studies to our knowledge have compared the sagittal balance and outcomes in patients with spinal stenosis and spondylolisthesis, treated with decompression and spinal fusion with or without supplemental pedicle screw fixation.

Inclusion criteria

• Patients diagnosed with Lumbar Spinal stenosis, with neurogenic claudication, radicular pain and,
• Confirmatory MRI scan showing lumbar spinal stenosis on 1-2 levels from L1-S1
• Standing X-ray showing grade 1 spondylolisthesis on one level
• Age 60 and above
• Symptom duration of 3+ months

Exclusion criteria

• Stenosis caused by herniated disc
• Prior vertebral compression fracture in the affected segments
• Active malignancy
• Current fracture, infection og deformity of the spine
• Stenosis on 3 or more levels
• MMSE test score below 24
• Neuromuscular disease
• Obligatory peroral steroid treatment
• ASA grade 3 or more.