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Motion Preservation

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Dear Patient

The following information was put together to help in the decision-making process. The graphs show the answers of the members of EuroSpine, the Spine Society of Europe, considered to be the European experts in the field of treatment of spine pathology. This information should help you to learn and understand what most of the experts in the field would do in each specific situation. The information reflects a “common sense” approach to treatment of the members of EuroSpine, yet does not replace a careful evaluation of your individual situation. Therefore, if you find a significant difference between the answers below and you doctor’s opinion, ask your doctor what made him/her reach this decision.

Each specific situation has to be evaluated on an individual basis. EuroSpine and its members cannot be held responsible for any misunderstandings (or misdiagnosis) based on the information provided here, which in no way attempts to replace a targeted evaluation.

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THE HEALTHY LUMBAR SPINE

Fig 1
The lumbar spine (LS) consists of five lumbar vertebrae (in about 8–12% of the population there is an anatomic variance of either four or six lumbar vertebrae) and five intervertebral discs. The normal shape of the lumbar spine shows a slight curvature (lordosis). The magnitude of this curve is determined by the adjacent curvatures of the spine and the position of the pelvis and is essential for the balance of the whole spine.
Fig 2
Motion is possible between two adjacent vertebrae. The intervertebral disc in front, a pair of so-called facet joints (small joints that connect two vertebrae) posteriorly and various ligaments and muscles form a functional spinal unit (FSU). The lumbar spine has five FSUs. These provide stability and motion in the lumbar spine.

The average range of motion of a lumbar FSU is around 10 degrees flexion and 5 degrees extension, 5 degrees lateral bending and around 3 degrees rotation. The sum of these ranges of motion provides the total flexibility of this anatomical structure.
Fig 3
Fig 4
The limitation of these different components of segmental motion is set by characteristics (compressibility, elasticity) of the intervertebral disc and the ligaments in and around the FSU and the facet joints.

The spinal nerves run through the spinal canal formed by the posterior parts of the vertebrae. At each level, a pair of spinal nerves leaves the spinal canal down to the legs.
Fig 5

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DEGENERATIVE CHANGES OF THE LUMBAR SPINE

General remarks

Motion and load create adaptive tissue changes during life. These changes include loss of tissue elasticity, growth of osteophytes and calcification of ligaments. The motion of an FSU changes as a consequence of this degenerative process in the aging spine. Increased or decreased mobility of an FSU may result.
Fig 6

Intervertebral disc

The intervertebral disc and facet joints, as structures most exposed to load, determine the extent of degeneration of the spine.

This is the largest fibrous tissue organ in the human body. It consists of an outer annulus (annulus fibrosus made of strong collagen fibres which attach the disc to the adjacent vertebral bodies) and an inner nucleus (nucleus pulposus). It is a soft cartilaginous tissue containing cells (chondrocytes) that form the so-called matrix (ground substance) which consists of high molecular weight substances (proteoglycanes such as chondroitin-sulfate). These substances have a high water-binding capacity (water content of lumbar discs: 75–90%). As the disc is not directly connected to the body's vascular system, the nutrition of the disc is only secured by perfusion through the cartilaginous and bony endplates of the adjacent vertebral bodies. This makes the disc susceptible to degeneration.
Fig 7
Disc degeneration is characterised by a quantitative loss and/or decrease in the quality of the ground substance. Water content and disc height decrease. The continuous load on the annulus fibrosus increases the rate of fissures which weakens the mechanical resistance. This can cause bulging of the disc into the spinal canal and compression of nerve roots. The decreased disc height increases the load on the facets and accelerates osteoarthritic changes. As a result, the motion pattern of the FSU undergoes significant change.
Fig 8

Facet Joints

The above-mentioned degenerative changes also involve the facet joints. Similar to other joints in the body, the facets are covered with a layer of cartilage. This ensures a harmonious, pain-free motion between the two bony articular masses. Continuous load and motion cause erosion of this cartilage, direct bony contact and finally painful osteoarthritis.

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DIAGNOSTIC PROCEDURES

The primary diagnostic procedure for degenerative changes of the lumbar spine involves a careful evaluation of the patient’s history and a clinical investigation. Indispensable adjuncts to the diagnostic procedure are the various imaging techniques of the spine and injections.

Normal, conventional radiographs: Conventional x-rays provide an excellent overview of the bony structures and allow anatomical orientation of the spine. Information about the bone density and changes in the shape and size of the vertebral bodies can be seen. Degenerative changes such as the formation of osteophytes or narrowing of the disc space can also be seen. As x-rays only depict structures containing calcium, soft tissues cannot be directly visualised.

Computer tomography (CT), magnetic resonance imaging (MRI): These newer techniques represent the standard imaging methods of the spine. Changes in bony structures as well as in soft tissue can be visualized and analyzed.

The interpretation of the clinical significance of the images of degenerative changes may be difficult, since not all changes seen in x-rays, CT or MRI are painful.

Injections: Discs and facets can be injected with contrast mediums and/or anaesthetic agents. Pain provocation or elimination can verify that a degenerative change identified in the imaging diagnostic is the source of pain. These injections are routinely performed under imaging control.

Sensitivity and specificity of this type of diagnostic procedure is controversial due to the high rates of false positive results.
Fig 9
Specialist's opinion:
1) Diagnostics in degenerative lumbar spine: Discography
Discography is a valuable tool in identifying a painful disc in the lumbar spine

21 votes
Discography is not reliable

21 votes
Other

3 votes
Total: 46 Specialists answered
2) Diagnostics in degenerative lumbar spine: Facet infiltration
Facet infiltration is a reliable tool for identifying painful facets in the lumbar spine

29 votes
Facet infiltration is not reliable

17 votes
Other

0 votes
Total: 46 Specialists answered


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TREATMENT

Degeneration of the lumbar spine represents a normal aging process and is frequently asymptomatic. Conservative, non-operative treatment deals with mild and moderate pain. Only in situations of unbearable pain and resistance to conservative treatment can spine surgery be discussed with a well-identified pain structure of the spine.

Surgical treatment
For many years, treatment of degenerative changes of the lumbar spine has been fusion, the strategy of this procedure being the removal or elimination of the painful structure (e.g. disc) and restoration of normal curvature and anatomy.
Fig 10
Even if this technique has been successful on numerous occasions with acceptable results, certain disadvantages are associated with the procedure:
  • “unnatural” changes of motion pattern by immobilization
  • increased frequency of degeneration of adjacent segments
  • compensatory hypermobility of adjacent segments
  • increased rate of spondylolysis (instability) of adjacent segments
Given this, new methods have been developed to achieve the main goals of fusion surgery (elimination of pain, restoration of normal curvature and anatomy), but with preservation of motion. The most frequently used implants are currently total (or partial) disc replacement, posterior dynamic stabilization and interspinous spacers.

Clinical experience in the last years seems to show initial evidence that total disc replacement can be an alternative to fusion. Dynamic posterior fixation and interspinous spacers still lack clear evidence.

Specialist's opinion:
3) Motion-preserving techniques are a new treatment concept. Not all implants come with sufficient clinical data and experience. Please rate the relevance and reliability of the data available in the literature of the following implants (0 = no clinical experience, experimental; 100 = relevant clinical experience, solid background)
Total disc replacement

100 %
Nucleus replacement

33 %
Interspinous delordosing implant

61 %
Dynamic posterior stabilization

74 %
Facet replacement

18 %
Total: 43 Specialists answered

Anterior procedures: Intervertebral disc

Total or partial replacement of the disc can be performed to eliminate pain originating from the disc.
Fig 11
Specialist's opinion:
4) Contraindications for disc prosthesis are (multiple answers possible)
More than three levels

36 votes
Significant osteoarthritis

37 votes
Degenerative spondylolisthesis

37 votes
Isthmic spondylolisthesis

41 votes
Scoliotic deformity

38 votes
Segmental kyphos

27 votes
Negative pain provocation (discography)

24 votes
Previous disc surgery in the same segment

7 votes
Previous retroperitoneal surgery

22 votes
Total: 44 Specialists answered


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SURGICAL TECHNIQUES

Total disc replacement: The surgical approach to the spine is performed anteriorly through an abdominal incision. After dissection of the abdominal wall, the peritoneum and the bowels can be mobilized and laterally displaced. After careful retraction of the great vessels, the anterior aspect of the spine can be seen. The disc can be removed and the endplates of the vertebral bodies cleaned. With gentle distraction, the disc prosthesis can be placed between the two vertebral bodies. After releasing the distraction, the prosthesis is locked into place.

Partial replacement: Newer techniques attempt to replace only the nucleus (inner part of the disc). This procedure is less invasive and is usually performed by a posterior approach. Some implants allow a percutaneous procedure. This type of partial disc replacement lacks general experience and is only performed in some spine centres.

Posterior procedures: Ligaments, facets

Similar to the intervertebral disc, the posterior elements – mainly the facets – are subject to degeneration and can become potential sources of pain. With the introduction of motion-preserving techniques, this process may be stopped or even inversed. Currently, the dynamic fixation with pedicle screws is in clinical application. By altering the motion and unloading the facets, pain is expected to decrease. There is limited evidence of the efficacy and mechanism of pain relief. Prosthesis of the facet joints is currently under investigation.
Fig 12
Interspinous implants are spacers made of titanium or PEEK that are placed between the spinous processes of two adjacent vertebrae. This light segmental distraction opens the space for the exiting nerve root and unfolds the ligaments in the spinal canal, thereby providing more space for the spinal nerves. The indication for this technique is mild spinal stenosis.
Fig 13
Motion preserving techniques gained wide recognition among professionals and patients. The concept ov avoiding rigid fixation is indeed tempting. The future will show if these innovations are more efficient than “traditional” procedures and in what indications they will become the standard.
© The above text, figures and data are property of EUROSPINE®, the Spine Society of Europe and may not be reproduced or used in any other way.

EUROSPINE, April 2007

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