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Tutorial, Revision Surgery

The need to operate on the spine after an original surgical procedure is unfortunately not that uncommon. Much of this stems from the fact that the spine is a tremendously complex structure and our surgical techniques are not one hundred percent effective in treating problems of the spine. Although our success rate is certainly higher than ever in the past, this does not mean that even in the best of hands some patients require multiple surgeries to treat a spinal disorder.

Aside from the complexity of spinal problems that may require multiple surgeries to correct, there is the added factor of time which can lead to a gradual deterioration of the spinal column and progressive instability or deformity. In other words even if a surgical procedure appears to have effectively treated a problem, over time there may a failure of other segments along the spine, and with that a progression of symptoms that a person experiences. These later problems of the spine can develop months or years after an initial surgery.

Given that each case is unique and requires individual attention, it is difficult to generalize regarding failed back surgery, or revision surgery of the spine. In order to outline some of the common problems encountered in revision surgery, the topic has been divided into several sections. By one approach one can analyze these problems in the time course after initial surgery: early failure, delayed problems and late onset problems. Another way to summarize the common factors related to surgical failures is to review the topic by the original surgical procedure performed.

A. Early post-operative problems:

Spinal surgery is performed for a large number of different conditions. The more common operative procedures include either a decompression of the spine (discectomy, laminectomy…) and/or a fusion of the spine (fusion for instability, fusion for fracture, fusion for deformity…). There are many different techniques applied to obtain the goals of a surgical plan. The problems or difficulties, which can arise in the course of surgery or thereafter, are numerous and may in no way reflect the capability or intentions of the treating physician. Even the best specialists face challenging cases that do not achieve the intended success. When post-operative problems do develop it is essential to pursue proper evaluation and treatment by a team experienced in these challenging cases.

Decompression related problems:

A spinal canal decompression involves removing soft tissues and/or bone in order to free compression around neural elements. This is commonly performed in the treatment of spinal stenosis and large herniated discs. The success rates for these procedures in carefully selected patients are very high. However, suboptimal results may occur due to reasons such as:

  1. Recurrent disc herniation

  2. Recurrent spinal stenosis

  3. Chronic nerve injury

  4. Infection

  5. Incomplete diagnosis

  6. Incomplete decompression

Common problems can thus involve a new piece of disc, which may herniate (up to 10-20% occurrence), or narrowing of the spinal canal that redevelops (recurrent spinal stenosis) despite an initially excellent result. Compression of nerves or the spinal cord may also develop at another level despite proper decompression at the original segment. In some cases continued nerve problems may be present even if a full decompression has been performed. This may be due to permanent injury to a nerve from the original problem. Less common causes of poor outcome include infection, other associated problems, incomplete diagnosis of the entire problem at hand, and technically incomplete decompression of an affected level.

In the treatment of early problems related to surgery it is essential to pursue a complete evaluation and clearly identify the source of trouble. This is not always an easy task and thus effective remedies are not always available. In many cases, once the problem has been isolated relief can be obtained with proper treatment. This may range from medical management to revision surgery.

Fusion related problems:

A spinal fusion in general terms involves the growth of bone across levels of the spine that previously had the ability to move independently of one another. This procedure may involve the use of instrumentation (such as pedicle screws), the use of the patient's own bone (autograft, ex. Iliac crest bone) or synthetic or bone bank tissue.

In a successful fusion, solid and complete bone growth occurs across the desired levels of the spine. This process can take many months and in some cases over a year to occur. The common problems that may develop after an operation for spinal fusion include:

  1. Pain from the bone harvest site

  2. Failure of fusion to develop

  3. Loosening of instrumentation

  4. Nerve irritation from instrumentation

  5. Infection

  6. Incomplete diagnosis of problem

  7. Poor alignment of the spine

In order to obtain a solid spinal fusion, it is essential to place fragments of bone into the selected area of the spine. These bone fragments may be obtained from the immediate area where the surgery is performed or from the iliac crest (often referred to as the hip region although in fact the bone is not taken from the hip itself). Synthetic bone can also be used to avoid having to make a separate incision over the iliac crest. There are numerous studies that have shown significant pain and sometimes long-term problems related to graft taken from the iliac crest. This procedure is therefore avoided unless necessary. The reason why one continues to harvest bone from the crest is its strong potential to lead to a solid fusion.

Failure for a solid fusion to develop can occur in the best of hands and even when instrumentation is applied. There are many details of bone growth that are not clear to us yet. The local tissue factors that lead to successful fusion certainly play a role and in some patients fusion may be much easier to obtain than others. Use of the patient's own bone, instrumentation and good surgical technique can improve the chance of developing a solid spinal fusion. When a solid fusion does not develop then there is a risk of the instrumentation (such as pedicle screws and rods) to loosen and move from their original positions or even break. Conversely, if instrumentation is loose or malpositioned from the start then the chances of successful fusion may be reduced. If fusion fails to properly develop this is called a non-union or pseudarthrosis. This is not always easy to identify because new bone formation may appear solid on x-rays and even CT scan yet have a crevice running across it that is filled with scar tissue instead of solid bone.

In addition to loosening, instrumentation (screws, hooks or wires) may lead to nerve irritation and this may lead to nerve related deficits or pain after surgery. The monitoring of nerves during surgery with electrophysiologic potentials (such as SSEP) may reduce the risk or nerve related problems due to irritation or compression from inserted devices.

In some cases despite a successful spinal fusion pain may persist after surgery. A thorough evaluation is essential in order to identify possible sources of continued trouble. Sometimes the possibility of infection or incomplete diagnoses of the original pain source are considered. In some patients despite technically excellent surgical treatment the outcome from surgery may not be good. Spine surgery remains a challenging field and an inexact science.

B. Delayed Problems:

Once recovery from spinal surgery has occurred and the tissues appear to be healing, problems may persist or arise. Even the leading specialists and centers have patients that do not achieve the desired level of relief and response to treatment. Once such a problem has developed specialized evaluation and treatment is essential. A team with experience in such challenging cases is essential. Some of the common problems that may be encountered some time after a surgical procedure of the spine include the following:

  1. Recurrent disc problems or stenosis

  2. Failure of spinal fusion (pseudarthrosis)

  3. Junctional failure of the spine

  4. Decompensation

As outlined in the section on early post-operative problems a patient successfully treated for disc herniation may present with a repeated portion of disc material moving out of the disc space. Likewise, a patient treated for spinal stenosis may redevelop stenosis at the treated level or develop the problem at an adjacent level of the spine. In primary spinal surgery one can not always anticipate future problems of the spine and a decision to treat with a minimal approach only the most severely affected levels of the spine does not eliminate the possibility of future symptoms.

As discussed in the section of early post-operative problems, pseudarthrosis (failure of successful spinal fusion) is a common problem in patients where fusion is planned. This can occur even in the best of hands and under optimal conditions. Sometimes, the symptoms related to a failed fusion do not surface until months or years after surgery. Persistent pain and loosening or breakage of spinal instrumentation must raise the suspicion of a pseudarthrosis. X-rays and CT scan do not always show a pseudarthrosis and sometimes surgery with exploration remains the only sure way to diagnose and treat this problem.

Junctional failure of the spine refers to failure (or collapse, instability) of a spine segment adjacent to a previously operated level of the spine. The reaction of levels next to an operated level of the spine can not always be anticipated. The additional forces across a spinal level adjacent to a fusion can be quite abnormal and thereby lead to accelerated degeneration with pain and/or nerve related symptoms. Such problems can occur months or years after an apparent successful original surgery. This may in no way reflect a poor initial treatment and may reflect an inevitable degeneration of the spine.

Decompensation of the spine will be further discussed in the section of late onset problems. This term refers to the loss of proper spinal balance that may set in some time after an apparent successful surgery. Gradual imbalance with a shift of the trunk and tipping over or stooping over can develop. This may reflect the inability of the non-operated levels of the spine to maintain proper alignment and balance.

C. Late onset Problems

In some cases, problems may surface related to the spinal column long after initial surgery. The spine is a dynamic structure that continuously adapts to movement and position of the body. In the setting of spinal pathology, and following surgery, the normal function of the spinal column may be significantly altered. This can lead to accelerated wear and tear (degeneration) of some levels in the spine as well as a failure of normal function in the muscles and ligaments that support the spine. In some cases such as scoliosis, continued growth of the spine may also occur after surgery and this can lead to further deformity and imbalance of the spinal column. All these potential problems can be difficult or impossible to predict and even in the best of hands late problems can arise after spinal surgery. Significant expertise is required to treat these late onset problems and only few centers in the country are able to manage these challenging cases. Some of the common late onset problems include:

  1. Crankshaft

  2. Progressive curvature after scoliosis surgery

  3. Junctional failure of the spine

  4. Decompensation

  5. Compensatory spinal curvatures

Surgical treatment of scoliosis in adolescents or younger children can offer excellent correction of deformity. However, despite an initial excellent result late progressive deformity of the spinal column can occur due to continued growth of the spine. When this occurs in the anterior portion of the spine, which has been fused posteriorly, this is called the crankshaft phenomenon. Despite a solid fusion in the back of the spine, the front can continue to grow and twist the spine in such a way that progressive deformity can develop.

Another problem that can arise after scoliosis surgery in adolescents or children is the continued deformity of the spinal column in an area that has not been fused. This type of progressive curvature may be due to a partial fusion of a scoliotic curve or the response of the non-fused spine to a somewhat imbalanced fusion.

Many years after a successful fusion, accelerated degeneration (wear and tear) may occur at levels adjacent to previous surgery. This is called junctional failure, and can lead to pain, instability (excessive motion between levels of the spine), and sometimes nerve compression or even significant deformity of the spinal column. More on this topic is listed under the early and delayed problems sections.

Decompensation of the spine refers to a loss of normal spinal balance such that the head and trunk are no longer well centered over the pelvis in normal standing posture. Such a deformity can arise after spinal surgery and particularly after surgery for scoliosis. In that setting, especially when Harrington rods were used and the patient is developing a stooped-over posture, the term Flatback syndrome has been applied. This problem may develop many years or even decades after initial surgery and can progress very slowly. Most patients describe their problem as lower back fatigue with inability to comfortably stand up straight. In some cases the only way to walk may be with knees and hips flexed.

In some patients, over time the spine that has been treated surgically ages in an accelerated fashion. With aging and a continued attempt by the body to overcome the effects of a spinal fusion or deformity of the spine, new deformities may develop in the spinal column. For example, some patients that have been treated for scoliosis as adolescents with a long fusion may have some element of poor spinal alignment. In order to overcome poor balance, a patient may excessively posture remaining portions of the spine in a certain position that become rigid over time or even progressively deformed. These compensatory curvatures can become painful and disabling requiring treatment.


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