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 pars interarticularis, leading to spondylolytic spondylolisthesisThis alteration reduces the spinal canal (stenosis) and puts pressure on the spinal cord. Spondylolytic spondylolisthesis may occur as a consequence of an older fracture of the pars interarticularis in adolescence, which later in life can lead to disk degeneration and forward sliding of the vertebra or spondylolisthesis.

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)

Left: Distal radius intraarticular, displaced fracture; Middle: Older distal radius fracture with callus formation; Right: Distal radius and ulna fracture, extraarticular and displaced

No 2.

Intra-articular fracture extends to the wrist joint (or articulation)

Extra-articular fracture is located outside of the wrist joint

Open fracture when bone fragments perforate the skin

Comminuted fracture when the bone breaks into multiple fragments

Non-displaced when the anatomical alignment of the bone is maintained or displaced when the bone fragments move apart.

Melone’s classification describes the characteristics of intra-articular fractures of the radius:

i    Stable fracture

ii    Unstable "die-punch"

iii   "Spike" fracture

iv Split fracture

v   Explosion injuries

Acetabular fracture of the pelvis

Acetabular fractures

These fractures are divided into:

Anterior pillar (not weight bearing part of joint)

Posterior pillar (often associated with dislocation of the hip including the weight bearing part of joint)

Transverse

Comminuted involving both column type 

Sacral / coccygeal fractures

The sacrum is a triangular-shaped bone formed by 5 fused vertebrae, which provide a posterior wall to the pelvic ring. At each side of the sacrum, the ala structures articulate with the ilium bones forming the sacro-iliac joints. Sacral fractures are usually parallel to the spine and can involve the ala. Less frequently sacral fractures may display an “H” shape, including a transversal fracture uniting both sides of the sacrum. Three zones are described where sacral fractures can occur that are along vertical lines relative to the alignment of the foramina. Sacral fractures may result in sacral instability and require treatment via sacroplasty (injection of bone glue into the fracture). Surgery is necessary in case of associated neurological symptoms.

Fractures of the coccyx involve the tailbone, the terminal portion of the spine situated below the sacrum formed by 3 to 5 fused vertebrae. Coccyx fractures occur when falling on a seated position. They are more common in elderly women and seldom require surgical treatment.

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:

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

Type II isthmic spondylolisthesis caused by a stress fracture of the pars interarticularis

Type III degeneration of the facet joints due to arthropathy in older people

Type IV traumatic injury to the facet joints or pars interarticularis

Type V 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.