Spondylolysis and spondylolistesis
Advanced spondylolisthesis; note the displacement of the vertebra and fracture of the pars interarticularis

Definition

The terms referring to these pathologies derive from ancient Greek. Spondylolysis sphondylos + lysis (vertebrae + rupture) and Spondylolisthesis sphondylos + olisthanein (vertebrae + falling) mean respectively, the fracture and the forward displacement of one vertebra relative the vertebra below.

Pathology

Spondylolisthesis arises when mechanical pressure to
the spine at the lumbo-sacral region induces the sliding of one vertebra towards the anterior, abdominal side of the body. It can also occur consequent to the weakening of the spine ligaments that keep the vertebrae aligned, making the spine vulnerable to displacement during movement and weight bearing. The disease is most common in women and ageing people. The alteration of the vertebral alignment may compress the nerves and cause neurological symptoms. 

Spondylolysis is the stress fracture of a vertebra more often affecting the 5th
lumbar vertebra. In ageing people spondylolisthesis ensues from degeneration of
the disk, its thinning and possibly herniation, which reduces the
intervertebral space. Consequent to vertebral mal-alignment the pressure on the
vertebra causes the fracture of the 
 interarticularis, leading to spondylolytic
spondylolisthesis
This
alteration reduces the spinal canal (stenosis) and puts pressure on the spinal
cord. 
 in adolescence, which later in
life can lead to disk degeneration and forward sliding of the vertebra or 

Classification

Grading of spondylolisthesis is done according to the Meyerding classification, based on the percentage of the overhanging part of the superior vertebra relative to anteroposterior column of the adjacent inferior vertebral body: 

Grade I: 0-25%

Grade II: 26-50% 

Grade III: 51-75% 

Grade IV: 76-100%

Grade V: >100% (spondyloptosis; most severe of translational spine injuries)

Two-part proximal humerus fracture

According to the Habermeyer Classification the fractures to the proximal humerus are divided into:

Type 0 one fractured part without dislocation

Type A two-part fracture of the great tuberosity and lesser tuberosity avulsion

Type B involves the humerus “surgical” neck below the femoral head as two-part, three-part and four-part with one or both tuberosities

Type C involves the humerus anatomical neck (between the head and greater tuberosity) as two-part, three-part and four-part with one or both the greater and lesser tuberosities.

These are defined further as:

One-part fractures are non-displaced fractures or fractures with minimal displacement

Two-part fractures only involve a single segment

Three-part fractures involve two segments

Four-part fractures occur when all humeral segments are involved (see image in pathology section)

The injury severity is proportional to the increasing number of fractures.

Three-part proximal humerus fractures

Degeneration, injury or congenital malformation of the facet joints and pars interarticularis are possible causes for spondylolisthesis and spondylolysis

Causes

Spondylolisthesis can have various origins.

Genetics: hereditary congenital vertebrae
malformation having thin bone structure, which can be aggravated with rapid
growth.

Overuse: Intensive sport activities that put
extreme pressure on the spine (gymnastic, weight lifting) or that involve
hyperextension of the lower spine (baseball, golf, cricket).

Generally, the causes are divided into the
following types:

congenital, abnormal development of the facet
joints that facilitate forward translation of the vertebrae in adolescence

isthmic spondylolisthesis caused by a stress
fracture of the pars interarticularis

degeneration of the facet joints due to
arthropathy in older people

traumatic injury to the facet joints or pars
interarticularis

Instability of the facet joints of iatrogenic
origin (facetectomy surgery).

Spondylolysis is essentially a stress fracture caused by repeated strains to the lower back.

Risk factors

Potential risk factors to acquire spondylolisthesis and spondylolysis are:

Adolescence (isthmic spondylolysis)

Ageing 

Female gender 

Anatomical predisposition (facet joint malformation, spine lordosis)

Congenital joint laxity

Sports involving repetitive spine hyperextension, rotation or flexion-extension may develop pars defects (gymnastics, football, weightlifting, judo)

Pregnancy 

African-American ethnicity 

Symptoms

Patients often visit a specialist when spondylolisthesis has degenerated to the extent of producing back pain and neurological symptoms due to the advanced compression of the nerves (radiculopathy), or to the spinal cord by disk herniation. 

Spondylolisthesis progressively leads to low back pain, muscle spasms, stiffening and weakening of the muscles in the lower back and hamstrings. Additional neurologic symptoms include numbness, tingling and pain, particularly with long standing and walking. In adolescents symptoms may manifest during a growth spur.

With spinal trauma symptoms of spondylolisthesis become acute and more likely neurological involving bladder/bowel function and claudication due to compression of the cauda equina.

Symptoms of spondylolysis include low back pain and stiffness. Pain is aggravated with activity. With time, pain may radiate down to one or both legs. During the healing process of the fracture, tissue growth may interfere with the nerve exit at the foramen thus worsening neurological symptoms.  

MRI of the lumbosacral spine showing L5-S1 spondylolisthesis with mild disk bulge and stenosis at L5

Diagnosis

Medical history and physical examination are essential for the diagnosis of spondylolysis and spondylolisthesis. Palpation of the spine and observing the patient during spinal bending and twisting may trigger pain and help the detection of anatomical abnormalities.

X-ray of the lower spine is the easiest method to diagnose both spondylolysis and spondylolisthesis. This will reveal the presence of a fracture or the sliding of one vertebra relative to the spine. The doctor will measure the anatomical changes to assess the gravity of the condition. If these pathologies are complicated by neurological symptoms, a CT or MRI scan will allow to visualise degenerative changes of the disks, spinal canal, spinal cord to address a suitable therapy.

Electromyography is also used to assess neurological changes such as radiculopathy or vertebral canal stenosis, which may occur as a consequence of spondylolisthesis.

Treatment

Local steroid injection can alleviate the symptoms of spondylolistesis

Nonoperative treatment

Conservative treatment is the standard initial approach to address spondylolisthesis. This will improve the symptoms but not reverse vertebral sliding. The strategy focuses on the interruption of any strenuous physical activities and the administration of analgesics and non-steroidal antiinflammatory drugs (NSAIDs) or steroid injection in the local epidural space to ease pain. Ongoing degeneration in the alignment of the spine will be monitored regularly by repeated X-rays in standing position. Although controversial, bracing is also adopted by some orthopaedic surgeons in form of thoraco-lumbosacral spinal orthosis or modified Boston Brace for 3-6 months. These are recommended only in isolated spondylolysis and not spondylolisthesis. Physical therapy usually begins when the acute symptoms have subsided paying particular attention to strengthen the core muscles of the spine and abdomen in support of the affected region and stretching of the lower sacral spine.

X-ray showing laminectomy and spinal fusion at L3, L4, L5 with transpendicular screws

Surgical treatment

If conservative treatment over 3 to 12 months fails to improve pain and neurological symptoms, or when spondylolisthesis is aggravated with further displacement of the vertebrae over 50%, in Type 1 and 2 slips, with a severe neurological component, or after traumatic spondylolisthesis, surgery is required. The preferred method of choice is a spinal fusion of the lumbar vertebra and the sacrum. In case of both degenerative spondylolisthesis and spondylolytic spondylolisthesis the aim of surgery is to relieve the pressure to the nerves with a laminectomy and perform a spinal fusion to restore alignment and stability of the spine. For a detailed description of surgical methods please refer to the pathology Disk herniation.

Strengthening exercises of the deep abdominal and lower back muscles and stretching of the leg muscles

Rehabilitation

Working with isotonic and isometric exercises to strengthen the deep abdominal muscles and the muscles of the trunk surrounding the spine provide beneficial stability to the vertebrae to delay further misalignment, aggravating the spondylolisthesis. Stretching exercises alleviate the pressure to the lower back when flexing or extending the spine. In addition, the following measures are recommended:

Gait training

Walking

Hydrotherapy

Swimming

Balance exercises

Antilordotic postures to reduce the curvature of the lumbar spine

 Educating young people in sport is pivotal to avoid spine injuries and degenerative diseases

Prevention

In the young athletic population preventing spondylolisthesis translates into avoiding strenuous physical activities and bending the back in hyperextension. In the elderly it is key to maintain strong core muscles to support the spine and delay spinal degeneration caused by ageing. Educating both groups on the risks of developing these conditions by adopting proper movements and postures while exercising is also critical.