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[Singler-segment degenerative lumbar spondylolisthesis treated with an interspinous spacer]
Abstract
The term degenerative spondylolisthesis, coined by Newman in 1963, refers to the forward slippage of an immediately inferior vertebra without isthmic lysis. It occurs predominantly in individuals over 40 years of age and affects mainly women, with a female:male ratio of 4:1. Prevalence is 7.5% in males and 28% in females among patients over 50 years of age with low back pain.
Assess the one-year results of the use of dynamic spacers for Meyerding grade 1 listhesis with the Oswestry disability scale. The patient's electronic and radiographic records from January 2008 to December 2010 were reviewed according to different criteria to conduct a retrospective, longitudinal and observational cohort study.
The preoperative Oswestry score was 3.4% mild, 55.2% moderate, and 42.4% severe; the postoperative score was 79.3% mild and 20.7% moderate. The most common surgical procedure was exploration and release in 72.4% of patients; only 27.6% underwent diskectomy. Pain irradiating to the right pelvic limb occurred in 37.9% of patients, to the left pelvic limb in 44.8%, and to both pelvic limbs in 17.2%. Only 2.4% of patients experienced postoperative pain that irradiated to the pelvic limb, as 100% of cases had some type of irradiating pain. A DIAM spacer was used in 79.3% and a Wallis device in 20.7%.
Treatment with an interspinous spacer results in a low reoperation rate and, at least one year later, it resulted in a significant improvement in the disability rate.
... The incidence of degenerative spondylolisthesis is observed predominantly in people older than 40 years of age, with an average age of 61 years, with a predominance of 4:1 of females to males, having a prevalence of 7.5% in men and 28% in women in patients over 50 years of age with lumbalgia. 1,2 The etiopathogenesis of degenerative spondylolisthesis is multiple. The most frequently affected segment is L4-L5 (in 85% of cases), followed by L3-L4 and very rarely L5-S1. ...
... Damage to the tissues during the surgery can result in an increase in postoperative pain, recovery time, delay in rehabilitation, and deterioration of spinal function. 2,6,8 Minimally Invasive TLIF (MIS TLIF) is comparable to Open TLIF in terms of clinical outcomes and fusion rates, with the additional benefits of less postoperative pain, less blood loss, earlier rehabilitation, and a shorter hospitalization. The indications of MIS TLIF are generally the same as for the open procedure. ...
Objective:
To know the clinical and radiographic results of patients with L4-L5 degenerative spondylolisthesis grade I, II, and III surgically treated with minimally invasive 360-degree arthrodesis. To determine the clinical and radiographic results according to the Oswestry Index 6 months after surgery and the percentage of postsurgical reduction in these patients.
Methods:
The present study was developed in the Department of Spinal Surgery of the Unidad Médica de Alta Especialidad Lomas Verdes, from October 2016 to August 2017. It is a prospective, cross-sectional, comparative observational study. We evaluated the reduction of the listhesis using pre and post-operative radiographs, as well as the Oswestry Disability Index.
Results:
The sample was composed of 12 patients, eight females and four males, showing a statistical significance in the Student’s t test, with p=0.05 for both variables.
Conclusions:
Degenerative spondylolisthesis of the 4th lumbar level is a very frequent pathology that affects groups of productive age and represents a burden not only for the patient, but also for the community. This surgical technique showed a high level of security and confidence for its resolution, showing results comparable to the literature. However, it requires certain technical resources and training to be performed. Evidence Level II; Prospective comparative study.
Recently, numerous types of posterior dynamic stabilization (PDS) devices have been introduced as an alternative to the fusion devices for the surgical treatment of degenerative lumbar spine. It is hypothesized that the use of 'compliant' materials such as Nitinol (Ni-Ti alloy, elastic modulus = 75 GPa) or polyether-etherketone (PEEK, elastic modulus = 3.2 GPa) in PDS can restore stability of the lumbar spine without adverse stress-shielding effects that have often been found with 'rigid' fusion devices made of 'rigid' Ti alloys (elastic modulus = 114 GPa). Previous studies have shown that suitably designed PDS devices made of more compliant material may be able to help retain kinematic behavior of the normal spine with optimal load sharing between the anterior and posterior spinal elements. However, only a few studies on their biomechanical efficacies are available. In this study, we conducted a finite-element (FE) study to investigate changes in load-sharing characteristics of PDS devices. The implanted models were constructed after modifying the previously validated intact model of L3-4 spine. Posterior lumbar fusion with three different types of pedicle screw systems was simulated: a conventional rigid fixation system (Ti6Al4V, Phi = 6.0 mm) and two kinds of PDS devices (one with Nitinol rod with a three-coiled turn manner, Phi = 4.0 mm; the other with PEEK rod with a uniform cylindrical shape, Phi = 6.0 mm). To simulate the load on the lumbar spine in a neutral posture, an axial compressive load (400 N) was applied. Subsequently, the changes in load-sharing characteristics and stresses were investigated. When the compressive load was applied on the implanted models (Nitinol rod, PEEK rod, Ti-alloy rod), the predicted axial compressive loads transmitted through the devices were 141.8 N, 109.8 N and 266.8 N, respectively. Axial forces across the PDS devices (Nitinol rod, PEEK rod) and rigid system (Ti-alloy rod) with facet joints were predicted to take over 41%, 33% and 71% of the applied compression load, respectively. Our results confirmed the hypothesis on the PDS devices by showing the substantial reduction in stress-shielding characteristics. Higher axial load was noted across the anterior structure with the PDS devices, which could slow the degeneration process of bony structures and lower the possibility of implant failure.
A bilateral dynamic stabilization device is assumed to alter favorable the movement and load transmission of a spinal segment without the intention of fusion of that segment. Little is known about the effect of a posterior dynamic fixation device on the mechanical behavior of the lumbar spine. Muscle forces were disregarded in the few biomechanical studies published. The aim of this study was to determine how the spinal loads are affected by a bilateral posterior dynamic implant compared to a rigid fixator which does not claim to maintain mobility. A paired monosegmental posterior dynamic implant was inserted at level L3/L4 in a validated finite element model of the lumbar spine. Both a healthy and a slightly degenerated disc were assumed at implant level. Distraction of the bridged segment was also simulated. For comparison, a monosegmental rigid fixation device as well as the effect of implant stiffness on intersegmental rotation were studied. The model was loaded with the upper body weight and muscle forces to simulate the four loading cases standing, 30 degrees flexion, 20 degrees extension, and 10 degrees axial rotation. Intersegmental rotations, intradiscal pressure and facet joint forces were calculated at implant level and at the adjacent level above the implant. Implant forces were also determined. Compared to an intact spine, a dynamic implant reduces intersegmental rotation at implant level, decreases intradiscal pressure in a healthy disc for extension and standing, and decreases facet joint forces at implant level. With a rigid implant, these effects are more pronounced. With a slightly degenerated disc intersegmental rotation at implant level is mildly increased for extension and axial rotation and intradiscal pressure is strongly reduced for extension. After distraction, intradiscal pressure values are markedly reduced only for the rigid implant. At the adjacent level L2/L3, a posterior implant has only a minor effect on intradiscal pressure. However, it increases facet joint forces at this level for axial rotation and extension. Posterior implants are mostly loaded in compression. Forces in the implant are generally higher in a rigid fixator than in a dynamic implant. Distraction strongly increases both axial and shear forces in the implant. A stiffness of the implant greater than 1,000 N/mm has only a minor effect on intersegmental rotation. The mechanical effects of a dynamic implant are similar to those of a rigid fixation device, except after distraction, when intradiscal pressure is considerably lower for rigid than for dynamic implants. Thus, the results of this study demonstrate that a dynamic implant does not necessarily reduce axial spinal loads compared to an un-instrumented spine.
Management of degenerative spondylolisthesis with spinal stenosis is controversial. Surgery is widely used, but its effectiveness in comparison with that of nonsurgical treatment has not been demonstrated in controlled trials.
Surgical candidates from 13 centers in 11 U.S. states who had at least 12 weeks of symptoms and image-confirmed degenerative spondylolisthesis were offered enrollment in a randomized cohort or an observational cohort. Treatment was standard decompressive laminectomy (with or without fusion) or usual nonsurgical care. The primary outcome measures were the Medical Outcomes Study 36-Item Short-Form General Health Survey (SF-36) bodily pain and physical function scores (100-point scales, with higher scores indicating less severe symptoms) and the modified Oswestry Disability Index (100-point scale, with lower scores indicating less severe symptoms) at 6 weeks, 3 months, 6 months, 1 year, and 2 years.
We enrolled 304 patients in the randomized cohort and 303 in the observational cohort. The baseline characteristics of the two cohorts were similar. The one-year crossover rates were high in the randomized cohort (approximately 40% in each direction) but moderate in the observational cohort (17% crossover to surgery and 3% crossover to nonsurgical care). The intention-to-treat analysis for the randomized cohort showed no statistically significant effects for the primary outcomes. The as-treated analysis for both cohorts combined showed a significant advantage for surgery at 3 months that increased at 1 year and diminished only slightly at 2 years. The treatment effects at 2 years were 18.1 for bodily pain (95% confidence interval [CI], 14.5 to 21.7), 18.3 for physical function (95% CI, 14.6 to 21.9), and -16.7 for the Oswestry Disability Index (95% CI, -19.5 to -13.9). There was little evidence of harm from either treatment.
In nonrandomized as-treated comparisons with careful control for potentially confounding baseline factors, patients with degenerative spondylolisthesis and spinal stenosis treated surgically showed substantially greater improvement in pain and function during a period of 2 years than patients treated nonsurgically. (ClinicalTrials.gov number, NCT00000409 [ClinicalTrials.gov].).
Degenerative spondylolisthesis is most common at the L4/L5 level and in women. There are several possible reasons for its predilection at this site, but there is no satisfactory explanation for the predominance in women. We considered that pregnancy was a possible influence.
We reviewed the records and radiographs of 949 women and 120 men aged 50 years and over who had attended a spinal surgeon for low back pain over a five-year period. We found that women who had borne children had a significantly higher incidence of degenerative spondylolisthesis than nulliparous women (28% v 16.7%; p = 0.043). The men had a 7.5% incidence, significantly less than nulliparous women (p = 0.031). Our results suggest that pregnancy is an important factor in the aetiology of degenerative spondylolisthesis.
Epidemiological analysis using CTs.
To investigate the true incidence of lumbar spondylolysis in the general population in Japan.
Although there have been several reports on the incidence of lumbar spondylolysis, they had some weakness. One of them concerns the subjects investigated, because the incidence of lumbar spondylolysis varies considerably, and some patients are asymptomatic. In addition, most of the past studies used plain radiograph films or skeletal investigation. Therefore, the past reported incidence may not correspond to that of the general population.
We reviewed the computed tomography (CT) scans of 2000 subjects (age: 20-92 years) who had undergone abdominal and pelvic CT on a single multidetector CT scanner for reasons unrelated to low back pain. We reviewed them for spondylolysis, spondylolytic spondylolisthesis, and spina bifida occulta (SBO) in the lumbosacral region. The grade (I-IV) of spondylolisthesis was measured using midsagittal reconstructions.
Lumbar spondylolysis was found in 117 subjects (5.9%). Their male-female ratio was 2:1. Multiple-level spondylolysis was found in 5 subjects (0.3%). Among these 117 subjects, there were 124 vertebrae with spondylolysis. Of them, 112 (90.3%) corresponded to L5, and 26 (21.0%) had unilateral spondylolysis.SBO was found in 154 subjects. Of them, 25 had spondylolysis (16.2%), whereas, in 1846 subjects without SBO, 92 had spondylolysis (5.0%). The incidence of spondylolysis among the patients with SBO was significantly higher than that in subjects without SBO (Odd ratio was 3.7-fold).Of 124 vertebrae with spondylolysis, 75 (60.5%) showed low-grade (Meyerding grade I or II) spondylolisthesis, and no subject presented high-grade spondylolisthesis. Spondylolisthesis was found in 74.5% of the subjects with bilateral spondylolysis, and in 7.7% of those with unilateral spondylolysis.
The incidence of lumbar spondylolysis in the Japanese general population was 5.9% (males: 7.9%, females: 3.9%).
Fifty patients who had spinal stenosis associated with degenerative lumbar spondylolisthesis were prospectively studied clinically and radiographically to determine if concomitant intertransverse-process arthrodesis provided better results than decompressive laminectomy alone. There were thirty-six women and fourteen men. The mean age of the twenty-five patients who had had an arthrodesis was 63.5 years and that of the twenty-five patients who had not had an arthrodesis, sixty-five years. The level of the operation was between the fourth and fifth lumbar vertebrae in forty-one patients and between the third and fourth lumbar vertebrae in nine patients. The patients were followed for a mean of three years (range, 2.4 to four years). In the patients who had had a concomitant arthrodesis, the results were significantly better with respect to relief of pain in the back and lower limbs.
We performed a prospective roentgenographic study to determine the incidence of spondylolysis, spondylolisthesis, or both, in 500 unselected first-grade children from 1955 through 1957. The families of the children with spondylolysis were followed in a similar manner. The incidence of spondylolysis at the age of six years was 4.4 per cent and increased to 6 per cent in adulthood. The degree of spondylolisthesis was as much as 28 per cent, and progression of the olisthesis was unusual. The data support the hypothesis that the spondylolytic defect is the result of a defect in the cartilaginous anlage of a vertebra. There is a hereditary pre-disposition to the defect and a strong association with spina bifida occulta. Progression of a slip was unlikely after adolescence and the slip was never symptomatic in the population that we studied.
The questionnaire is divided into ten sections selected from a series of experimental questionnaires designed to assess limitations of various activities of daily living. The chosen sections were those found to be most relevant to the problems suffered by people with low back pain. Each section contains six statements. A study of 25 patients with primary low back pain has already been mentioned. Their symptoms tended to resolve quickly and changes in their mean disability score can be seen over the first three weeks after referral to the spinal disorders department. The disability score was also used to demonstrate that there was no difference in the severity of symptoms in two sub-groups of patients in the same study. All new patients referred to the department complete the questionnaire when they first attend. The disability score is used as a guide to a patient's treatment programme. It cannot be used in isolation since it makes no allowance for the demands of a patient's job, his age or psychological make-up. However, it does ensure that important aspects of disability which are often forgotten are recorded in the patient's notes. Later, changes in the score may be used in monitoring the subsequent progress of the patient through treatment.
An in vivo experimental investigation of internal disc mechanics and discogenic pain.
To test the hypotheses: 1) The pattern of internal loading of intervertebral discs in vivo is similar to that measured previously in vitro; 2) stress concentrations also are found in clinically degenerate discs in vivo; and stress concentrations are associated with discogenic pain.
Stress concentrations corresponding to potentially painful loading patterns of the intervertebral disc and endplate have been observed in vitro.
The distribution of stress within the lumbar intervertebral discs of patients with chronic discogenic pain was measured using stress profilometry. The severity of their pain was assessed using provocative discography.
Discogenic pain was found to be associated with anomalous loading of the posterolateral anulus (P < 0.001) and nucleus (P < 0.01). Painful discs were found to have a 38% wider posterolateral anulus (P < 0.023) than painless discs and to have a 63% lower mean nuclear stress (P < 0.017).
Stress profilometry is an effective investigation of the mechanics of intervertebral discs in vivo. Discogenic pain is caused by changes in the pattern of loading of the posterolateral anulus or nucleus pulposus.
A novel soft implant design for resisting the instability of the lumbar spine in the sagittal plane was mechanically tested.
To ascertain whether a soft preformed implant made of differing grades of silicone would contribute to stabilizing the lumbar spine in the sagittal plane.
Methods of stabilizing the lumbar spine in patients who present with chronic low back pain have usually concentrated on rigidly fixing the associated segment. This has many inherent problems with both the surgical methods and the long-term rigidity at and away from the stabilized site. To the authors knowledge, no "soft" interspinous spacer that would allow a certain amount of flexion but still stabilize the movements associated with instability at the level of the lesion has been investigated mechanically as an alternative to rigid fixation or prosthetic replacement.
The apparatus was designed to allow a cadaveric lumbar motion segment to be tested in compression at four angles of flexion with loads up to 700 N. The intradiscal pressure and sagittal plane stiffness were recorded during loading, with and without various sizes of the soft silicone implants placed between the spinous processes.
Insertion of the silicone implants between the spinous processes reduced the intradiscal pressure under load at the angles of flexion tested. The size of the interspinous space determines the optimal diameter of the implant that afforded sagittal stability, the load-bearing contribution of the implant, and the prevention of disc space narrowing at the level investigated.
A circular silicone spacer placed between the spinous processes appears to contribute to the stability of the cadaveric lumbar spine. There are many attractions to using a simple, soft implant that can be placed with minimal surgery between the spinous processes.
This prospective study analyzed the influence of transpedicular instrumented on the operative treatment of patients with degenerative spondylolisthesis and spinal stenosis.
To determine whether the addition of transpedicular instrumented improves the clinical outcome and fusion rate of patients undergoing posterolateral fusion after decompression for spinal stenosis with concomitant degenerative spondylolisthesis.
Decompression is often necessary in the treatment of symptomatic patients who have degenerative spondylolisthesis and spinal stenosis. Results of recent studies demonstrated that outcomes are significantly improved if posterolateral arthrodesis is performed at the listhesed level. A meta-analysis of the literature concluded that adjunctive spinal instrumentation for this procedure can enhance the fusion rate, although the effect on clinical outcome remains uncertain.
Seventy-six patients who had symptomatic spinal stenosis associated with degenerative lumbar spondylolisthesis were prospectively studied. All patients underwent posterior decompression with concomitant posterolateral intertransverse process arthrodesis. The patients were randomized to a segmental transpedicular instrumented or noninstrumented group.
Sixty-seven patients were available for a 2-year follow-up. Clinical outcome was excellent or good in 76% of the patients in whom instrumentation was placed and in 85% of those in whom no instrumentation was placed (P = 0.45). Successful arthrodesis occurred in 82% of the instrumented cases versus 45% of the noninstrumented cases (P = 0.0015). Overall, successful fusion did not influence patient outcome (P = 0.435).
In patients undergoing single-level posterolateral fusion for degenerative spondylolisthesis with spinal stenosis, the use of pedicle screws may lead to a higher fusion rate, but clinical outcome shows no improvement in pain in the back and lower limbs.
The Oswestry Disability Index (ODI) has become one of the principal condition-specific outcome measures used in the management of spinal disorders. This review is based on publications using the ODI identified from the authors' personal databases, the Science Citation Index, and hand searches of Spine and current textbooks of spinal disorders.
To review the versions of this instrument, document methods by which it has been validated, collate data from scores found in normal and back pain populations, provide curves for power calculations in studies using the ODI, and maintain the ODI as a gold standard outcome measure.
It has now been 20 years since its original publication. More than 200 citations exist in the Science Citation Index. The authors have a large correspondence file relating to the ODI, that is cited in most of the large textbooks related to spinal disorders.
All the published versions of the questionnaire were identified. A systematic review of this literature was made. The various reports of validation were collated and related to a version.
Four versions of the ODI are available in English and nine in other languages. Some published versions contain misprints, and many omit the scoring system. At least 114 studies contain usable data. These data provide both validation and standards for other users and indicate the power of the instrument for detecting change in sample populations.
The ODI remains a valid and vigorous measure and has been a worthwhile outcome measure. The process of using the ODI is reviewed and should be the subject of further research. The receiver operating characteristics should be explored in a population with higher self-report disabilities. The behavior of the instrument is incompletely understood, particularly in sensitivity to real change.
The apparent clinical success of spinal stabilization methods that restrict rather than abolish movement in relieving mechanical back pain indicates that the concept of the aetiology of back pain should be reviewed. Further understanding of how degeneration affects disc biomechanics, and an understanding of how current soft stabilization systems alters them, may allow us to define more precisely what are the essential requirements of an ideal soft stabilization system. It appears that abnormal patterns of loading rather than abnormal movement are the reason that disc degeneration causes back pain in some patients. Abnormal load transmission is the principal cause of pain in osteoarthritic joints, and both osteotomy and, indeed, joint replacement succeed because they alter the load transmission across the joint. This concept is supported by the fact that abnormal patterns of stress distribution measured across the disc correlate with painful discs on discography. Clinically, it is often noted that back pain is primarily related to position or posture, rather than movement of the lumbar spine. Clinical success after solid fusion is unpredictable because it does not necessarily prevent painful loading across the disc, and also it may interfere with maintenance of sagittal balance in varying postures. The Graf ligament restricted flexion, and was modestly successful. It unfortunately increased the load over the posterior annulus. The Dynesys system reduces movement both in flexion and extension, and appears to be more successful. However, often it also unloads the disc to a degree that is unpredictable. The authors believe that this unloading of the disc is an important feature of a flexible stabilization system. A new a design of a flexible stabilization system has recently been described in an in vitro study, which unloads the disc by introduction of a load-sharing fulcrum near the axis of movement together with an elastic posterior ligament. This design produces maximal unloading of the disc, whilst allowing a restricted range of movement, which serves the important purpose of allowing the patient to maintain sagittal balance in varying postures.
A first-generation implant for non-rigid stabilization of lumbar segments was developed in 1986. It included a titanium interspinous blocker and an artificial ligament made of dacron. Following an initial observational study in 1988 and a prospective controlled study from 1988 to 1993, more than 300 patients have been treated for degenerative lesions with this type of implant with clinical and mechanical follow-up. After careful analysis of the points that could be improved, a second-generation implant called the "Wallis" implant, was developed. This interspinous blocker, which was made of metal in the preliminary version, is made of PEEK (polyetheretherketone) in the new model. The overall implant constitutes a "floating" system, with no permanent fixation in the vertebral bone, to avoid the risk of loosening. It achieves an increase in the rigidity of destabilized segments beyond normal values. The clinical trials of the first-generation implant provided evidence that the interspinous system of non-rigid stabilization is efficacious against low-back pain due to degenerative instability and free of serious complications. The first-generation devices achieved marked, significant resolution of residual low-back pain. These results warrant confirmation. A randomized clinical trial and an observational study of the new implant are currently underway. Non-rigid fixation clearly appears to be a useful technique in the management of initial forms of degenerative intervertebral lumbar disc disease. This method should rapidly assume a specific role along with total disc prostheses in the new step-wise surgical strategy to obviate definitive fusion of degenerative intervertebral segments. At present, the Wallis system is recommended for lumbar disc disease in the following indications: (i) discectomy for massive herniated disc leading to substantial loss of disc material, (ii) a second discectomy for recurrence of herniated disc, (iii) discectomy for herniation of a transitional disc with sacralization of L5, (iv) degenerative disc disease at a level adjacent to a previous fusion, and (v) isolated Modic I lesion leading to chronic low-back pain.
Measurement of the kinematics of the lumbar spine after insertion of an interspinous spacer in vitro.
To understand the kinematics of the instrumented and adjacent levels due to the insertion of this interspinous implant.
An interspinous spacer (X Stop, SFMT, Concord, California) has been developed to treat neurogenic intermittent claudication by placing the stenotic segment in slight flexion and preventing extension. This restriction of motion by the interspinous implant may affect the kinematics of levels adjacent to the instrumented level.
Seven lumbar spines (L2-L5) were tested in flexion-extension, lateral bending, and axial rotation. Images were taken during each test to determine the kinematics of each motion segment. The interspinous implant was placed at the L3-L4 level, and the test protocol was repeated.
The flexion-extension range of motion was significantly reduced at the instrumented level. Axial rotation and lateral bending ranges of motion were not affected at the instrumented level. The range of motion in flexion-extension, axial rotation, and lateral bending at the adjacent segments was not significantly affected by the implant.
The implant does not significantly alter the kinematics of the motion segments adjacent to the instrumented level.
A literature review.
To evaluate the mechanisms of action and effectiveness of interspinous distraction devices in managing symptomatic lumbar spinal pathology.
Fusion operations have traditionally been used to manage many disorders of the lumbar spine related to deformity, pain, or instability. Concern over the long-term effects of fusion on adjacent segments has led to the development of the concept of dynamic stabilization.
A Medline search was performed using the key words "interspinous implants," "interspinous devices," and "lumbar dynamic stabilization." The abstracts of each were reviewed. Relevant articles were reviewed in detail and other appropriate references obtained. In addition, when available, nonpublished manufacturer's information was reviewed.
Articles describing the following implants were included in this review: the Minns Device, the Interspinous "U," the Diam, the Wallis Implant, and the X STOP.
These devices continue to be evaluated in clinical trials. Early results suggest a possible role in the management of degenerative disorders of the lumbar spine.
A literature review.
To evaluate the mechanisms of action and effectiveness of posterior dynamic stabilization devices in the management of painful spinal disorders.
Dynamic stabilization may provide pain relief by altering the transmission of abnormal loads across the degenerated disc space.
A Medline search was conducted.
Articles supporting abnormal load transmission across the disc space and clinical reviews of currently available posterior dynamic systems were included.
Posterior dynamic stabilization systems may provide benefit comparable to fusion techniques, but without the elimination of movement. Further study is required to determine optimal design and clinical indications.
Soft stabilization has an important role in the treatment of the degenerative lumbar spine. Fusion of one or two motion segments may not make a big difference in the total range of motion of the lumbar spine, but preserving flexibility of a motion segment may prevent adjacent segment disease and may permit disc replacement, even when facet joints need to be excised. A favourable environment is created in the motion segment by unloading the disc and permitting near normal motion, the disc may be able to repair itself or may supplement reparative potential of gene therapy.
X-STOP is the first interspinous process decompression device that was shown to be superior to nonoperative therapy in patients with neurogenic intermittent claudication secondary to spinal stenosis in the multicenter randomized study at 1 and 2 years. We present 4-year follow-up data on the X-STOP patients. Patient records were screened to identify potentially eligible subjects who underwent X-STOP implantation as part of the FDA clinical trial. The inclusion criteria for the trial were age of at least 50 years, leg, buttock, or groin pain with or without back pain relieved during flexion, being able to walk at least 50 feet and sit for at least 50 minutes. The exclusion criteria were fixed motor deficit, cauda equina syndrome, previous lumbar surgery or spondylolisthesis greater than grade I at the affected level. Eighteen X-STOP subjects participated in the study. The average follow-up was 51 months and the average age was 67 years. Twelve patients had the X-STOP implanted at either L3-4 or L4-5 levels. Six patients had the X-STOP implanted at both L3-4 and L4-5 levels. Six patients had a grade I spondylolisthesis. The mean preoperative Oswestry score was 45. The mean postoperative Oswestry score was 15. The mean improvement score was 29. Using a 15-point improvement from baseline Oswestry Disability Index score as a success criterion, 14 out of 18 patients (78%) had successful outcomes. Our results have demonstrated that the success rate in the X-STOP interspinous process decompression group was 78% at an average of 4.2 years postoperatively and are consistent with 2-year results reported by Zucherman et al previously and those reported by Lee et al. Our results suggest that intermediate-term outcomes of X-STOP surgery are stable over time as measured by the Oswestry Disability Index.
The purpose of the study was to explore the construct validity of three versions of the Oswestry Disability Questionnaire for low back pain using Rasch analysis. The three versions of the ODQ share 9 items and differ on one other. About 100 patients with non-specific low back pain seeking physiotherapy treatment at hospital outpatient departments and physiotherapy private practices completed the 12 Oswestry items as part of a battery of questionnaires. Rasch analysis revealed that four items (Personal Care, Standing, Sex Life and Social Life) had disordered response thresholds and one item (Walking) showed differential item functioning by age. The 10 standard Oswestry items and a modified version in which Sex Life is replaced by Work/Housework showed adequate overall fit to the Rasch model (chi(2)P>.01). The third version, in which Sex Life is replaced by Changing Degree of Pain, did not fit the model (chi(2)P=.006) and the Changing Degree of Pain item was misfitting (residual 2.34, P=.007). These findings suggest that either of the first two of the three versions of this widely used low back pain outcome measure should be selected over the third. Users should also be aware that for some items the rating scale steps do not perform as intended.
A prospective, randomized, multicenter, Food and Drug Administration-regulated Investigational Device Exemption clinical trial.
To evaluate the safety and effectiveness of the ProDisc-L (Synthes Spine, West Chester, PA) lumbar total disc replacement compared to circumferential spinal fusion for the treatment of discogenic pain at 1 vertebral level between L3 and S1.
As part of the Investigational Device Exemption clinical trial, favorable single center results of lumbar total disc replacement with the ProDisc-L have been reported previously.
Two hundred eighty-six (286) patients were treated on protocol. Patients were evaluated before and after surgery, at 6 weeks, 3, 6, 12, 18, and 24 months. Evaluation at each visit included patient self-assessments, physical and neurologic examinations, and radiographic evaluation.
Safety of ProDisc-L implantation was demonstrated with 0% major complications. At 24 months, 91.8% of investigational and 84.5% of control patients reported improvement in the Oswestry Low Back Pain Disability Questionnaire (Oswestry Disability Index [ODI]) from preoperative levels, and 77.2% of investigational and 64.8% of control patients met the > or =15% Oswestry Disability Index improvement criteria. Overall neurologic success in the investigational group was superior to the control group (91.2% investigational and 81.4% control; P = 0.0341). At 6 weeks and 3 months follow-up time points, the ProDisc-L patients recorded SF-36 Health Survey scores significantly higher than the control group (P = 0.018, P = 0.0036, respectively). The visual analog scale pain assessment showed statistically significant improvement from preoperative levels regardless of treatment (P < 0.0001). Visual analog scale patient satisfaction at 24 months showed a statistically significant difference favoring investigational patients over the control group (P = 0.015). Radiographic range of motion was maintained within a normal functional range in 93.7% of investigational patients and averaged 7.7 degrees.
ProDisc-L has been found to be safe and efficacious. In properly chosen patients, ProDisc-L has been shown to be superior to circumferential fusion by multiple clinical criteria.
The DIAM is a polyester-encased silicone interspinous dynamic stabilization device that can unload the anterior column and reestablish the functional integrity of the posterior column.
The DIAM was implanted in 104 patients between May 1, 2001 and October 30, 2001. A retrospective evaluation was performed based on chart review and patient questionnaire at a median follow-up interval of 18.1 months. There were no implant migrations, infections, or neurological injuries. Of the 20 patients who suffered adverse events, 13 underwent second lumbar spinal operations 0 to 19 months after the initial surgery (in seven the event occurred in a location other than the lumbar spine). The pain level as recorded by the physician showed improvement in 88.5%, no change in 9.6%, aggravation in 0%, and was indeterminate in 1.9%. The questionnaire revealed that at 18 months postoperatively, analgesic usage was decreased in 63.1%, increased in 12.3%, and unchanged in 24.6% of patients, and activities of daily living were improved in 46.2%, decreased in 30.8%, and unchanged in 23.1%. Specific outcomes measures for sitting, standing, physical activity, and psychosocial functioning revealed similar results.
The DIAM implant appears to be a useful and effective alternative in the surgical management of a wide range of lumbar disorders. Patient complications are few and satisfaction is high.
Target of the study was to predict the biomechanics of the instrumented and adjacent levels due to the insertion of the DIAM spinal stabilization system (Medtronic Ltd). For this purpose, a 3-dimensional finite element model of the intact L3/S1 segment was developed and subjected to different loading conditions (flexion, extension, lateral bending, axial rotation). The model was then instrumented at the L4/L5 level and the same loading conditions were reapplied. Within the assumptions of our model, the simulation results suggested that the implant caused a reduction in range of motion of the instrumented level by 17% in flexion and by 43% in extension, whereas at the adjacent levels, no significant changes were predicted. Numerical results in terms of intradiscal pressure, relative to the intact condition, predicted that the intervertebral disc at the instrumented level was unloaded by 27% in flexion, by 51% in extension, and by 6% in axial rotation, while no variations in pressure were caused by the device in lateral bending. At the adjacent levels, a change of relative intradiscal pressure was predicted in extension, both at the L3/L4 level, which resulted unloaded by 26% and at the L5/S1 level, unloaded by 8%. Furthermore, a reduction in terms of principal compressive stress in the annulus fibrosus of the L4/L5 instrumented level was predicted, as compared with the intact condition. These numerical predictions have to be regarded as a theoretical representation of the behavior of the spine, because any finite element model represents only a simplification of the real structure.
Spondylolisthesis is a common condition that can be managed both nonsurgically and surgically. More than 80% of children treated nonsurgically have resolution of symptoms. For those patients requiring surgical treatment, fusion in situ may provide adequate treatment for young patients. Patients with neural compression may require decompression to relieve symptoms, and fusion is also usually indicated. High-grade and degenerative spondylolisthesis require care that is unique to those conditions. Spondylolysis is a defect in the pars interarticularis that occurs in approximately 5% of the general population. Approximately 15% of individuals with a pars interarticularis lesion have progression to spondylolisthesis.
The etiology of spondylolisthesis
- P H Newman
- K H Sonte
Newman PH, Sonte KH: The etiology of spondylolisthesis. J Bone
Joint Surg Br. 1963; 45: 39-59.