In spine surgery, loss of lordosis seems to be associated with poorer outcomes. “Lordosis” refers to the “c” shaped curve of the cervical and lumbar spines. In the thoracic spine, the opposite curve is labeled a “kyphosis”.
About 70% of adults will suffer neck pain at some point in their lives. Most people have transient symptoms, but about 5% have disabling symptoms. However, the surgical patient may be different. We know that in patients undergoing posterior decompression without fusion, about 15-20% develop neck pain which seems be related to loss of lordosis and even development of post-laminectomy kyphosis. Their necks fall forward and they may develop pain 6-12 months later.
We know that posterior decompression with fusion may avoid the progressive worsening kyphosis over time, but posterior approaches by themselves have a difficult time restoring lordosis and can lead to fusing patients in the abnormal kyphosis. This can result in persistent pain. The way a cervical procedure is performed may affect the ability to maintain or restore cervical lordosis.
About 80% of adults will suffer back pain at some point in their lives. About 1-2% have disabling symptoms. “Normal” lumbar lordosis appears to range somewhere between 40-60 degrees. Lumbar lordosis is unique to the human spine and may be necessary to facilitate upright posture. About 60% of lumbar lordosis is created by the bottom two spinal levels L4-5 and L5-S1, and 85% by the L3-S1 segment.
In contrast to the cervical spine, loss of lumbar lordosis has a greater relationship to low back pain in the general population. This is termed, “flat back syndrome”.Post-laminectomy syndrome also may develop in multi-level lumbar decompressions without fusion.Maintaining lumbar lordosis following fusion surgery seems to be important. Failing to achieve proper lordosis could worsen the outcome of spinal fusion (more pain and forward inclination of the trunk) and may increase the risk of adjacent segment disease, because limited lordosis may increase the shear forces in the upper adjacent level.
Breakdown of the adjacent level has been identified as a cause of postoperative pain and disability. Fusing the spine straight may cause the body to lean forward, leading to compensatory neck hyperextension, knee flexion and hip extension. These compensatory maneuvers can cause chronic pain and muscle fatigue. Placing an interbody cage and lordotic rods may aid in lumbar fusion lordosis. When a cage is not placed or the rods are straight, the spine may fuse straight and lead to poorer outcome.