Spondylolisthesis

This intimidating term—spondylolisthesis—signifies a simple idea.  

In Latin, spondy means “spine” and olisthesis means “slippage.”  

Spondylolisthesis is then a “spine slippage.” Specifically, one vertebral bone is slipping in relation to a neighboring vertebral bone, resulting in a permanent dislocation.  

WHAT CAUSES SPONDYLOLISTHESIS?  

A spondylolisthesis involves a permanent misalignment of one or more regions of the spine. The root cause of all spondylolisthesis is instability.    

Here are the six causes of spondylolisthesis. These three are more common:  

• Isthmic— fracture of the delicate pars bones at the back of the vertebrae.  
• Degenerative — advanced disc injury and facet joint injury  
• Congenital (dysplastic) — a birth defect in which the neural arch is underdeveloped 

These three are more rare:  

• Traumatic — a physical injury that damages one or more spinal tissues 
• Pathologic— for example, a cancer growing into the spine   
•  Iatrogenic — instability arising following a spinal surgery   

The most common causes of spondylolisthesis are the isthmic and degenerative subtypes and those will be the focus of this article.    

WHAT CAUSES ISTHMIC SPONDYLOLISTHESIS?    

The delicate pars bones fracture when overloaded. The pars is stressed from: 

• Extension bending  
• Rotation  
• Shear loads  

Consequently, spondylolisthesis injuries clusters in sports that experience high levels of these forces:  

• Baseball 
• Cricket  
• Diving  
• Breast and butterfly swimmers 
• Gymnastics  

• Yoga  
• Pilates 
• Soccer  
• Wresting  
• Football 

• And weight-lifting 

• Deadlifts  
• Kettle-bell swings   

Most cases of spondylolysis—fracture of the pars—is a cumulative process. First, the pars is inflamed by overloading. Next, the pars will fracture on one or both sides of the neural arch, which is the ring of bone behind each vertebrae. And, finally, the instability slippage will occur, resulting in isthmic spondylolisthesis.    

CAN ISTHMIC SPONDYLOLISTHESIS BE PREVENTED?    

The answer is a resounding yes—provided you catch it early.    

The key to preventing isthmic spondylolisthesis is to prevent spondylolysis.    

But what if you have spondylolysis already? The answer is you must let the bone heal.    

If you have pars inflammation, rest will prevent it from fracturing. If you already have a pars fracture—but still no slippages—rest and rehabilitation will allow the pars bones to fuse and heal stronger than before.    

If, however, you don’t stop the offending forces, the spinal slippage resulting in spondylolisthesis will occur. At that point, there is no possibility of the spondylolysis fusing. Rest is necessary at this point to prevent progression of the amount of slippage.    

Healing depends on avoiding the triggering activities for about four months in children and adolescents. You must stop the offending sport—or you risk requiring a spinal fusion surgery to stabilize the region.    

Sad to say: To avoid missing a season, an athlete can lose a career.        

WHAT ARE THE SYMPTOMS OF ISTHMIC SPONDYLOLISTHESIS?    

There are three main types of symptoms:  

• An ache in the middle of the back — This pain will be in a specific spot and have a persistent quality, worse after aggravating activities. It corresponds with the bone pain of spondylolysis.  
• A sudden catch or buckling sensation in the middle of the back — This pain corresponds to an instability micromovement.  
• Sciatica down one or both legs — With slippage and misalignment, the spinal nerves and its roots can be pinched by the misaligned bones.    

WHAT IMAGING IS USED TO DIAGNOSE SPONDYLOLISTHESIS?    

Assessing spondylolisthesis may require multiple images.    

For assessing suspected spondylolysis:  

• X-rays
• Anteroposterior view 
• Lateral view (most sensitive)  
• Oblique view (most specific) 
• CT scan of the spine — gold standard that provides the best imaging of the bones (yes even better than the MRI)  

For assessing spondylolisthesis:  

• Dynamic X-rays  
• Lateralview  
• Neutral   Flexion (rounded spine) 
• Extension (arched spine)  
• MRI of the spine  

 WHAT DOES THE IMAGING TELL YOU ABOUT THE SPINE?  

1. Diagnoses spondylolysis. The x-rays can often detect spondylolysis fractures, even before they have progressed to spondylolisthesis injuries. A high resolution CT scan is sensitive enough to detect bone swelling (edema) even prior to the pars fracturing.  

1. Grading spondylolisthesis. Spondylolisthesis is graded with a scale known as the Myerding  classification. This grading scale is the most elegant in all spine medicine, based upon the relative slippage of one vertebrae over another on a standing, neutral lateral x-ray.   

1. Degree of instability. The degree of instability is measured by the relative amount of slippage between different spine positions on the lateral x-rays. A change in the amount of slippage of 3.5 millimeters or more indicates an unstable spondylolisthesis which is associated with: 

• More pain  
• Higher risk of progression to higher grades 
• And higher risk for requiring a fusion surgery.  

HOW DOES DEGENERATIVE SPONDYLOLISTHESIS DIFFER FROM ISTHMIC SPONDYLOLISTHESIS?  

Degenerative spondylolisthesis tends to not be so severe as isthmic spondylolisthesis. The main overall reason is that the degenerative changes from disc height loss and ligament laxity is not nearly so destabilizing as the loss of structural bone support as occurs in spondylolysis.  

Here a table comparing degenerative and isthmic spondylolisthesis.  

WHAT EXERCISES ARE SAFEST FOR SPONDYLOLISTHESIS?  

Here are general exercise principles:  

• Exercises featuring extension cause risk of short- and long- term severe pain  
• Exercises featuring shear stresses are probably dangerous as well 
• Flexion-only exercises are safer than extension-only exercises based on the level/rate of moderate to severe pain: 

The safest exercises for spondylolisthesis are:  

• Isometric: Don’t bend the spine into flexion or extension. 
• Shear-free: There’s not place for deadlifts and bent over rows in spinal rehabilitation of spondylolisthesis.  
• Limit high compression loads  
• Non-aggravating to back or sciatic symptoms  

WHEN IS SURGERY INDICATED FOR SPONDYLOLISTHESIS?  

Surgical Indications 

Relative indications for surgery:  

• Persistent sciatica despite conservative treatment 
• Progressive neurologic deficit 
• Persistent and unremitting low back pain for more than 6 months 
• And loss of quality of life because of neurogenic claudication.  
• Absolute indications for surgery include cauda equina syndrome symptoms:  

• Urinary incontinence — urinating on self 
• Urinary retention — unable to urinate  
• Bowel incontinence — soiling on self.  

Your risks of surgery increase if you have:  

• A grade 2 or higher spondylolisthesis  
• An instability slippage of more than 3.5 millimeters on dynamic x-ray series 
• Persistent symptoms that are not modifiable with changes in your posture, motions, or activities.  

CAN I HEAL FROM SPONDYLOLISTHESIS?  

 Probably — most cases of spondylolisthesis can heal with non-operative measures involving:  

• Correction of posture and movement flaws 
• Avoidance of aggravating activities, particularly exercises that involve extension, shear, twisting, and high compression  
• An individualized treatment program emphasizing movement quality and isometric lumbar stabilization exercises that doesn’t bend, twist, or shear the spine.  

There are certainly indications for which surgical intervention is necessary. Here the key is recognizing:  

• When your spine is beyond non-operative repair 
• The type of surgical approach for spondylolisthesis — it is not one-size-fits-all.   

Types of Surgery:  

• Decompression Alone — Presuming the presence of stability of the slippage, a decompression alone is a less typical surgical approach. The presence of stability would be established by dynamic x-rays showing 2 millimeters or less of slippage between the flexion and extension postures. This surgical approach is considered for the treatment of degenerative spondylolisthesis with stenosis. It would not be appropriate for the management of isthmic spondylolisthesis.  
• Laminectomy and Posterior Spinal Fusion (without interpedicled instrumentation) 
• Decompression with Posterolateral Instrumented Fusion  
• Decompression with Anterior and Posterior Spinal Fusion    

Select References   

Meyerding, Henry W. “Spondylolisthesis.” JBJS 13.1 (1931): 39-48.   

Wiltse, Leon L., P. H. Newman, and I. A. N. Macnab. “Classification of spondyloisis and spondylolisthesis.” Clinical Orthopaedics and Related Research® 117 (1976): 23-29.   

Sengupta, Dilip K., and Harry N. Herkowitz. “Degenerative spondylolisthesis: review of current trends and controversies.” Spine 30.6S (2005): S71-S81. 

Lonstein, John E. “Spondylolisthesis in children: cause, natural history, and management.” Spine 24.24 (1999): 2640.   

Gramse RR, Sinaki M, Ilstrup DM. Lumbar spondylolisthesis: A rational approach to conservative treatment. Mayo Clin Proc. 1980;55:681-686.   

Sinaki M, Lutness MP, Ilstrup DM, Chu CP, Gramse RR. Lumbar spondylolisthesis: A retrospective comparison and three year follow-up of two conservative treatment programs. Arch Phys Med Rehabil. 1989;70:594-598.