Degenerative changes in the spine often cause the loss of normal structure and/or function in a spinal segment or segments and can be painful. Degenerative spondylolisthesis is a mechanical micro instability created by degenerative changes in a vertebral segment that results in the slippage of one vertebral body over the one caudal to it. According to the Framingham Heart Study,1 which assessed the prevalence and incidence of degenerative slippage in 617 men and women, 1% of men and 1.5% women already had slippage at the baseline measurement at the mean age of 54 years. Over the following 25 years, 11% of men and 25% of women developed degenerative vertebral slippage. The study concluded that the degenerative displacement of lumbar vertebrae is common in an older population and is associated with an increased prevalence of daily back symptoms.
Wiltse et al.2 classified spondylolisthesis into five major categories, identifying type III degenerative spondylolisthesis as the most common type. The L4-L5 vertebral segment has a great range of flexion and extension motion, and this area is most likely prone to slippage, followed by L3-L4 and L5-S1.3,4
Osteoarthritic changes in the spine are the culprit behind the symptoms of degenerative spondylolisthesis. With aging, high stresses and motion produce degeneration of the intervertebral disc, resulting in the loss of water content in the nucleus pulposus and disc height. As the disc in the anterior column deteriorates, it loses its ability to resist motion in the affected spinal segment.5 Pashman6 reported that the posterior facet joints and ligaments hypertrophy in an attempt to stabilize the affected segment. As a result, the unstable vertebral segment moves forward and narrows the spinal canal or nerve roots, leading to the characteristic nerve compression problems found in degenerative spondylolisthesis.
For most cases of degenerative spondylolisthesis, conservative therapy is often recommended. It is uncommon for degenerative spondylolisthesis to place pressure on the nerves to the bowel and bladder, requiring urgent surgery. Epidural steroid injections are often used to alleviate the inflammation of the nerve roots producing temporary, symptomatic relief. Physical therapy can improve the back pain associated with the slipping of the vertebra. Those patients whose symptoms do not respond to conservative treatments are usually considered candidates for surgery.
Surgical treatment of degenerative spondylolisthesis is well documented.3–10 The goal of surgery for degenerative spondylolisthesis is the removal of the mechanical pressure on the lumbar spinal nerves and stabilization of the spinal segment with the spondylolisthesis. Reports on nonoperative treatment of this specific disorder with an orthosis as a primary modality of treatment are sparse.
Willner11 treated seven patients with spinal stenosis with a Flexaform (Boston Brace International, Avon, MA) delordosating brace. Six reported pain relief. However, the study did not specify whether the stenosis was accompanied with disc degenerative spondylolisthesis. Prateepavanich et al.12 demonstrated the positive effect of the lumbosacral corset in 21 patients with symptomatic lumbar spinal stenosis. The investigators advocated a larger study size to examine individual groups of coexisting findings such as degenerative spondylolisthesis. Gavin et al.13 proposed that for adult patients with slippage of L5 on S1, increasing flexion in sagittal plane is the most critical bracing objective, and achieving and maintaining optimal lumbar geometry are the primary mechanisms of action. In contrast, Spratt et al.14 found that patients with degenerative spondylolisthesis felt pain relief in an extension posture and postulated that an extension posture locks the facet joints and thus stabilizes the unstable symptomatic motion segments.
The purpose of this paper is to present a case that outlines a biomechanical approach in treating a 66-year-woman with degenerative spondylolisthesis with a custom lumbosacral orthosis (LSO).
The patient, a 66-year-old married female, mother of seven, reported severe, chronic radiculating pain down her right lower extremity. Notable medical history included bilateral knee replacements for bicompartmental osteoarthritis. The patient reported that the original onset of back pain was in February 1999. She described her pain as a gradually worsening, achy, burning pain originating at the right buttock and extending down the calf toward her foot. She reported her pain score to be 8 (of 10) in intensity on a Visual Analog Scale (VAS). The patient worked full-time in retail but was unable to walk more than about 50 yards before having to sit down for a few minutes for the pain to subside. She walked with her torso bent forward. She reported regular restless sleep and cramping and numbness at night bilaterally in the lower extremities.
To treat her pain, the patient was taking analgesics on a daily basis, reporting a daily intake as high as 6 Advil or Motrin tablets. Before visiting our clinic, she had attempted physical therapy, but her pain levels precluded her from regular participation. She also had attempted a series of transforaminal epidural steroid injections at the L5-S1 interspace. After these unsuccessful visits to the neurologist, physical medicine doctor, and a pain management clinic, she was referred to a neurosurgeon who recommended spinal decompression with fusion.
Physical examination revealed that she presented with a normal gait, was capable of heel and toe walking, and was able to perform 10 toe-ups on each side. Motor examination was 5/5 in lower extremities. Both lower extremities had normal sensation to light touch. Reflexes were 2+ and symmetric at the knees and zero at the ankles, with plantar grade Babinski. Hip motion and knee motion were performed pain free. The skin over the spine was normal, and her spine was not tender to palpation and percussion.
Clinically, she was diagnosed with degenerative disc disease in the lumbar spine and degenerative spondylolisthesis of L5 on S1. At L5-S1, her initial radiograph (Figure 1) indicated a grade 1 anterolisthesis of L5 on S1 with degenerative changes of the facet joints. There was no evidence of spondylolysis. The MRI (Figure 2) revealed a disc protrusion with moderately severe central canal narrowing at L5-S1. There was moderate right and left neural foraminal narrowing at this level. At L4-L5, the radiograph revealed advanced degenerative changes at the L4-L5 disc space. MRI confirmed degenerative changes of the facet joints, moderate bulging of the intervertebral disc with disc space narrowing, and mild to moderate right and left neural foraminal narrowing. Mild degenerative changes were also noted at L2-L3 and L3-L4 levels. Flexion and extension radiographs indicated hypermobility at the affected L5/S1 level.
The patient declined surgical treatment, opting for orthotic treatment to control her pain.
After the patient consented to our orthotic treatment plan, a supine, bivalved plaster impression was taken of the patient. First, the patient was positioned supine, and a 2-inch beveled Plastizote pad was placed at the sacral-coccyx junction to induce a posterior pelvic tilt. The patient remained on the pad for 15 minutes before the cast was taken, in an effort to relax the soft tissues of the pelvis and lumbar spine and to ensure comfort of the patient. Because the patient had relief in the flexed or seated position, the hips and knees were flexed to 60 to maximize the posterior tilt of the pelvis and sacrum. These two maneuvers were an attempt to reduce the angulation between the L5 and S1 endplates.
A 3-inch beveled Plastizote pad was placed under the lumbar spine in an attempt to maintain some lordosis of the patient. Our concern was that in our attempt to maximize posterior sacral tilt, we could reduce too much lordosis. This could potentially pitch the patient's torso too far forward and overload the anterior column of the lumbar spine, which was already having degenerative changes. The patient reported no discomfort in this position. Five-inch plaster splints were applied horizontally from the pubis to the xiphoid process. After setting, the anterior impression was secured with straps, and the patient was rolled prone.
For the posterior aspect of the mold, the patient's legs were positioned over the edge of the table to maximize the posterior tilt of the sacrum. The patient was able to raise her upper torso on her elbows while prone. Five-inch plaster splints were applied vertically in this position until the impression was completed.
A custom, anterior-opening LSO was fabricated from this impression. The LSO was made of 3/16-inch modified polyethylene with a reinforcement of two strips of 1/8-inch copolymer plastic overlying the paraspinal musculature to stiffen the posterior. The posterior trim line was 1 inch inferior to the apex of the inferior angle of the scapulae (Figure 3).
The patient returned for follow-up 4 months after the initial visit. During this visit, a 3/16-inch beveled pad was added just superior to the sacral coccygeal junction to encourage more reduction in the sacral angle. Further follow-up appointments, in person, were difficult because the patient lived in another state. Follow-up calls were made at regular 4-month intervals to monitor the condition of the patient.
Radiographs were reviewed to determine the effects of the orthosis, if any, on her lumbar spine geometry. The following variables were measured as defined by Wiltse and Winter15 to assess gross and segmental changes in the lumbar spine: the sacrohorizontal angle (angle between a line drawn across the cranial border of the body of the first sacral vertebra and the horizontal; Figure 4); and the angle of lumbar lordosis (angle between lines drawn across the top of the body of the first lumbar vertebra and one drawn across the top of the body of the fifth lumbar vertebrae; Figure 5).
The distance from the perpendicular line drawn from the midpoint of the superior endplate of L1 through the superior endplate of the sacrum was measured to evaluate gross sagittal balance of the torso over the pelvis. These measurements were recorded to determine the effect of a segmental change in the lower lumbar segments while minimizing the loss of lumbar lordosis.
The patient reported immediate pain relief when originally donning the new orthosis and her first complete and uninterrupted night of rest in 6 months. Four months after the initial visit, she reported being able to remain on her feet for up to 30 minutes at time and had returned to work on a regular basis. At 6-month follow-up, she reported her pain to be a 2 on the VAS scale, and she reported discontinuation of daily pain medication.
Radiographic results are recorded in Table 1. Geometric changes with orthosis on are depicted in Figures 6 and 7. Geometric changes with orthosis on are depicted in Figures (6 and 7).
At 6-month follow up, in orthosis, the sacrohorizontal angle had reduced by 15 degrees, and the vertical line drawn from the midpoint of the L1 vertebral endplate had moved 1.3 cm toward the center of the sacral midpoint. Based on these angular changes, the reduction in shear versus normal force can be calculated by using trigonometry (Figure 8).
The most change is the 42% reduction in the ratio of shear force to normal force. This is independent of body weight and reflects the change in the geometry, specifically, the angle between L5 and S1.
Eighteen months after initialization of orthotic treatment, the patient is maintaining out of orthosis a sacrohorizontal angle of 38 degrees, 31 degrees of lordosis, with good sagittal balance, and is exercising. She reported that she wears the brace 4 to 6 hours a day, usually during her most active periods.
Sharma et al.16 performed a three-dimensional, nonlinear finite element analysis on the L3-L4 motion segments and determined that a facet that is more sagittally oriented may be linked to the cause of spondylolisthesis. High stresses on the articular processes under flexion-shear loads may lead to facet osteoarthritis or hypertrophy. Spinal stenosis is also likely in the presence of flexion anterior shear loading.
Mimura et al.17 noted that disc degeneration creates more joint laxity and affects the multidirectional flexibility of the lumbar spine. Fujiwara et al.18 tested 110 cadaveric lumbar motion segments and concluded that the segmental flexibility of the lumbar spine is affected by the severity of disc and cartilage degeneration as well as gender. The authors speculated that female segments showed more motion than male spinal segments because of smaller endplate size in female segments.
The goal in this case was to try to reduce the shear stress, defined as the stress component parallel to a given surface as result of applying a force parallel to the surface, at the L5-S1 segment by reducing the sacrohorizontal angle, to create a more horizontal orientation of the posterior facets. Another goal was to maintain the intersegmental angles that make up lumbar lordosis, between L3 and L4 and L4 and L5, due to the significant amount of degeneration at those levels. By taking advantage of the existing microinstability, or the increased flexion and extension range of motion at L5-S1 created by the hypermobile segment, the segmental angle between L5 and S1 could be reduced to address the spondylolisthesis. The lordosis above this segment was maintained to alleviate the anterior compression of the degenerated discs, disperse the vertical load more evenly across the three columns of the spine, and encourage a more balanced sagittal standing posture. By maintaining or even accentuating the lordosis, a more erect posture for the patient could be achieved, moving the center of gravity posteriorly toward its natural position just anterior to S2. This would in turn reduce the bending moment of the upper torso around this point.
According to some literature, orthoses have no scientific evidence for efficacy and probably have no place in the treatment of lumbar spinal disorders.19 In some instances, orthotic treatment is not mentioned as a modality of treatment. This case is an example that might challenge these claims or lack thereof. Stoll et al.20 investigated that as an alternative to fusion, a mobile, dynamic stabilization restricting segmental motion would be advantageous in various indications, allowing greater physiological function and reducing the inherent disadvantages of rigid instrumentation and fusion. Similarly, the orthotic approach presented here accomplished a specific segmental and stabilizing change.
Ultimately, the most important role of the orthosis is to reduce pain. Reducing the angulation of the affected segments to reduce the shear stress at the hypermobile segment is critical in achieving this outcome. A custom orthosis allowed our patient to become active again. Gramse et al.21 outlined a flexion-oriented exercise program that resulted in less pain and less need for continued use of back supports. Because the orthosis controlled the pain, our patient was able to start an exercise program, and, over time, has not become completely dependent on the brace. A therapy or exercise program used in conjunction with brace wear can further optimize patient outcome and minimize patient dependence on the orthosis.
Although our results reflect only a 1.7-year treatment period in a single subject, we consider it successful in that surgery was avoided for this period, pain medication dependency was decreased, and quality of life was improved. This patient did not want surgery. Many patients are not ideal surgical candidates, given their age and quality of bone. These are the patients who need alternatives. We acknowledge the fact that this is only one case, and further investigation of similar cases is necessary to substantiate a scientific claim to treatment efficacy. There are multiple methods for measuring a custom lumbar orthosis, and there are multiple prefabricated devices available for purchase. Our discussion of shear force and its importance in the treatment of spondylolisthesis parallel the discussions on spondylolisthesis presented in the biomechanical literature.22 Whatever path of orthotic treatment chosen, we think it is important to ascertain and delineate the biomechanical goal of reducing shear stress at the affected level when using orthotic treatment to successfully treat cases that present similarly to that reported here.
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