The effect of pedicle screw/plate fixation on lumbar/lumbosacral autogenous bone graft fusions in patients with degenerative disc disease

Anatomy of the L5 nerve root in the pelvis for safe sacral screw placement: a cadaveric study

OBJECTIVE

Previous reports have focused on the complications of L5 nerve root injury caused by anterolateral misplacement of the S1 pedicle screws. Anatomical knowledge of the L5 nerve root in the pelvis is essential for safe and effective placement of the sacral screw. This cadaveric study aimed to investigate the course of the L5 nerve root in the pelvis and to clarify a safe zone for inserting the sacral screw.

METHODS

Fifty-four L5 nerve roots located bilaterally in 27 formalin-fixed cadavers were studied. The ventral rami of the L5 nerve roots were dissected along their courses from the intervertebral foramina to the lesser pelvis. The running angles of the L5 nerve roots from the centerline were measured in the coronal plane. In addition, the distances from the ala of the sacrum to the L5 nerve roots were measured in the sagittal plane.

RESULTS

The authors found that the running angles of the L5 nerve roots changed at the most anterior surface of the ala of the sacrum. The angles of the bilateral L5 nerve roots from the right and left L5 intervertebral foramina to their inflection points were 13.77° ± 5.01° and 14.65° ± 4.71°, respectively. The angles of the bilateral L5 nerve roots from the right and left inflection points to the lesser pelvis were 19.66° ± 6.40° and 20.58° ± 5.78°, respectively. There were no significant differences between the angles measured in the right and left nerve roots. The majority of the L5 nerves coursed outward after changing their angles at the inflection point. The distances from the ala of the sacrum to the L5 nerve roots in the sagittal plane were less than 1 mm in all cases, which indicated that the L5 nerve roots were positioned close to the ala of the sacrum and had poor mobility.

CONCLUSIONS

All of the L5 nerve roots coursed outward after exiting the intervertebral foramina and never inward. To prevent iatrogenic L5 nerve root injury, surgeons should insert the S1 pedicle screw medially with an angle > 0° toward the inside of the S1 anterior foramina and the sacral alar screw laterally with an angle > 30°.

L5 nerve root injury caused by anterolateral malpositioning of loosened S1 pedicle screws: illustrative cases

BACKGROUND

Although malpositioning of pedicle screws into the spinal canal and intervertebral foramen can cause spinal nerve root injuries, there are few reports of L5 nerve root injuries when S1 pedicle screws have been inserted anterolaterally. The authors report two cases of L5 nerve root injury caused by anterolateral malpositioning of loosened S1 pedicle screws.

OBSERVATIONS

In both patients, S1 pedicle screws were inserted toward the outside of the S1 anterior foramen, and the tip of the screws perforated the anterior sacral cortex. L5 nerve root impairment was not observed immediately after surgery. However, severe leg pain in the L5 area was observed after the S1 pedicle screws became loosened. In case 1, the symptoms could not be controlled with conservative treatment. Reoperation was performed 3 months after the initial surgery. In case 2, the symptoms gradually improved with conservative treatment because the area around the loosened S1 screw was surrounded by newly formed bone that stabilized the screws, as observed with computed tomography 1 year after surgery.

LESSONS

Surgeons should recognize that anterolateral malpositioning of S1 pedicle screws can cause L5 nerve root injury. The screws should be inserted in the correct direction without loosening.

State of the union: a review of lumbar fusion indications and techniques for degenerative spine disease

Lumbar fusion is an accepted and effective technique for the treatment of lumbar degenerative disease. The practice has evolved continually since Albee and Hibbs independently reported the first cases in 1913, and advancements in both technique and patient selection continue through the present day. Clinical and radiological indications for surgery have been tested in trials, and other diagnostic modalities have developed and been studied. Fusion practices have also advanced; instrumentation, surgical approaches, biologics, and more recently, operative planning, have undergone stark changes at a seemingly increasing pace over the last decade. As the general population ages, treatment of degenerative lumbar disease will become a more prevalent-and costlier-issue for surgeons as well as the healthcare system overall. This review will cover the evolution of indications and techniques for fusion in degenerative lumbar disease, with emphasis on the evidence for current practices.

Autologous mesenchymal stromal cells embedded in tricalcium phosphate for posterolateral spinal fusion: results of a prospective phase I/II clinical trial with long-term follow-up

BACKGROUND

Posterolateral spinal fusion with autologous bone graft is considered the "gold standard" for lumbar degenerative disc disease (DDD) when surgical treatment is indicated. The potential role of mesenchymal stromal cells (MSCs) to replace the bone graft in this setting has not been fully addressed.

OBJECTIVE

To analyze the safety, feasibility and potential clinical efficacy of the implantation of autologous MSCs embedded with tricalcium phosphate as a therapeutic alternative to bone graft in patients with DDD during posterolateral spine fusion.

STUDY DESIGN

Phase I/II single-arm prospective clinical trial.

METHODS

Eleven patients with monosegmental DDD at L4-L5 or L5-S1 level were included. Autologous bone marrow-derived MSC were expanded in our Good Manufacturing Practice (GMP) Facility and implanted during spinal surgery embedded in a tricalcium phosphate carrier. Monitoring of patients included a postoperative period of 12 months with four visits (after the 1st, 3rd, 6th, and 12th month), with clinical and radiological assessment that included the visual analog scale (VAS), the Oswestry disability index (ODI), the Short-Form Health Survey (SF-36), the vertebral fusion grade observed through a simple Rx, and the evaluation of possible complications or adverse reactions. In addition, all patients were further followed up to 5 years for outcome.

RESULTS

Median age of patients included was 44 years (range 30-58 years), and male/female ratio was (6/5) L4-L5 and L5-S1 DDD was present five and six patients, respectively. Autologous MSCs were expanded in all cases. There were no adverse effects related to cell implantation. Regarding efficacy, both VAS and ODI scores improved after surgery. Radiologically, 80% of patients achieved lumbar fusion at the end of the follow-up. No adverse effects related to the procedure were recorded.

CONCLUSIONS

The use of autologous MSCs for spine fusion in patients with monosegmental degenerative disc disease is feasible, safe, and potentially effective.

TRIAL REGISTRATION

no. EudraCT: 2010-018335-17 ; code Identifier: NCT01513694 ( clinicaltrials.gov ).

Comparison of posterior lumbar interbody fusion with transforaminal lumbar interbody fusion for treatment of recurrent lumbar disc herniation: A retrospective study

Objective

To compare posterior lumbar interbody fusion (PLIF) with transforaminal lumbar interbody fusion (TLIF) for spinal fusion in patients previously treated by discectomy.

Methods

This retrospective study evaluated pre- and postoperative neurological status via Japan Orthopaedic Association (JOA) score. Surgical outcome was based on recovery rate percentage (RR%). Adverse event data were reviewed.

Results

Both PLIF (n = 26) and TLIF (n = 25) significantly improved neurological status. There were no significant between-group differences in postoperative JOA score, RR% or surgical outcome. Overall, 92.3% patients in the PLIF group and 84% in the TLIF group had an excellent or good outcome (RR ≥ 65%). No patient had a poor outcome (RR < 50%). There were six cases of dural tear in the PLIF group and two in the TLIF group.

Conclusions

PLIF and TLIF provided good outcomes for recurrent lumbar disc herniation. TLIF may be preferred because of its shorter operative time and fewer procedure-related complications than PLIF.

Artrodesis circunferencial: Plif más tornillos translaminofacetarios

OBJETIVO: Evaluar el resultado clínico y radiológico de 10 pacientes operados por patología degenerativa lumbar, en los que se les realizó artrodesis intersomática con injerto óseo tricortical de cresta ilíaca y artrodesis posterolateral instrumentada con tornillos translaminofacetarios. MÉTODOS: Se evaluaron 10 pacientes, 4 hombres y 6 mujeres operados por el mismo cirujano entre junio de 2006 y diciembre de 2007. RESULTADOS: Se obtuvo un significativo descenso de la discapacidad y del dolor (según las escalas de Oswestry y la escala visual analógica), obteniéndose una tasa de fusión del 100% al año de seguimiento. CONCLUSIONES: Los resultados clínicos y radiológicos de este estudio establecen a éste procedimiento como confiable, de bajo costo y baja morbilidad, con una alta tasa de fusión y buenos resultados clínicos.

Recurrent lumbar disk herniation

Recurrent lumbar disk herniation is the most common complication following primary open diskectomy. It is defined as recurrent back and/or leg pain after a definite pain-free period lasting at least 6 months from initial surgery. Careful neurologic examination is critical, and laboratory tests should be ordered to evaluate for infection. Imaging demonstrates disk herniation at the previously operated level. It is important to differentiate recurrent disk herniation from postoperative epidural scar because the latter may not benefit from reoperation. Treatment of recurrent lumbar disk herniation includes aggressive medical management and surgical intervention. Surgical techniques include conventional open diskectomy, minimally invasive open diskectomy, and open diskectomy with fusion. Fusion is necessary in the presence of concomitant segmental instability or significant foraminal stenosis resulting from disk space collapse.

A prospective, randomized, controlled, multicenter study of osteogenic protein-1 in instrumented posterolateral fusions: report on safety and feasibility

STUDY DESIGN

A prospective, randomized, controlled, multicenter clinical study.

OBJECTIVE

To evaluate the safety and feasibility of osteogenic protein (OP)-1 in 1-level lumbar spine instrumented posterolateral fusions.

SUMMARY OF BACKGROUND DATA

Instrumented posterolateral fusion with the use of autograft is a commonly performed procedure for a variety of spinal disorders. However, harvesting of bone from the iliac crest is associated with complications. A promising alternative for autograft are bone morphogenetic proteins.

METHODS

As part of a larger prospective, randomized, multicenter study, 36 patients were included, who received a 1-level instrumented posterolateral fusion of the lumbar spine. All patients had a degenerative or isthmic spondylolisthesis with symptoms of neurologic compression. There were 2 treatment arms: OP-1 combined with locally available bone from laminectomy (OP-1 group) or iliac crest autograft (autograft group). The primary outcome was the fusion rate based on a computed tomography scan after 1-year follow-up. The clinical outcome was measured using the Oswestry Disability Index. Additionally, the safety of OP-1 was evaluated by comparing the number and severity of adverse events that occurred between both groups.

RESULTS

Using strict criteria, fusion rates of 63% were found in the OP-1 group and 67% in the control group (P = 0.95). There was a decrease in Oswestry scores at subsequent postoperative time points compared with preoperative values (P > 0.001). There were no significant differences in the mean Oswestry scores between the study group and control group at any time point (P = 0.56). No product-related adverse events occurred.

CONCLUSION

The results demonstrate that OP-1 combined with locally obtained autograft is a safe and effective alternative for iliac crest autograft in instrumented single-level posterolateral fusions of the lumbar spine. The main advantage of OP-1 is that it avoids morbidity associated with the harvesting of autogenous bone grafts from the iliac crest.

In situ local autograft for instrumented lower lumbar or lumbosacral posterolateral fusion

This study evaluated the effectiveness of local in situ autografts in instrumented posterolateral fusion of the lower lumbar or lumbosacral spine for treating degenerative spondylolisthesis. The subjects were 182 degenerative spondylolisthesis patients with spinal canal stenosis who, in one operation, underwent lumbar laminectomy with two-level (L3-4, L4-5 or L5-S1) transpedicle screw/rod system instrumentation and posterolateral fusion using autogenous spinous processes and laminae as the only source of bone grafts. The surgical results were assessed clinically and radiologically. All patients received follow-up for at least eighteen months. At the end of follow-up, bilateral fusion mass was radiographically confirmed in 113 (62%) patients, unilateral fusion mass was observed in fifty-seven (31%) patients, and twelve (7%) patients exhibited no fusion mass at the arthrodesis level. The clinical outcome was rated excellent/good in 138 (76%) patients, fair in thirty-five (19%) and poor in nine (5%). Use of in situ local autografts yields satisfactory clinical results in instrumented posterolateral spinal fusion. No significant correlation was noted between the level of arthrodesis and the radiological outcome, nor between the level of arthrodesis and the clinical outcome. Radiographic evaluation of bony fusion mass was not predictive of the clinical findings.

Residual motion on flexion-extension radiographs after simulated lumbar arthrodesis in human cadavers

Flexion-extension radiographs are commonly used to assess lumbar fusion. Recommended criteria for solid fusion have varied from 1 to 5 degrees of angular motion between vertebrae. Notwithstanding this wide variation, the validity of these criteria have never been biomechanically tested. As a preliminary and initial step, it was the authors' purpose to quantify measurable angular motion after simulating solid lumbar fusion in human cadaver spines. Seven cadaveric spines (L1 to L4) were tested in a radiolucent jig fixed to a servohydraulic testing apparatus. Flexion and extension moments of 10 Nm were applied. Fusion was simulated using metallic implants spanning the L2-L3 motion segment. These included transverse process plates, a spinous process plate, pedicle screw construct, or an anterior vertebral body plate to simulate an intertransverse, interspinous process, facet, and interbody fusions, respectively. Angular movements were measured on lateral radiographs and statistically compared using a repeated measures analysis of variance. Simulated intertransverse fusion resulted in 13+/-4 degrees of motion; interspinous fusion, 9+/-4 degrees; posterior facet fusion, 5+/-3 degrees; and interbody fusion with plate, 3+/-2 degrees. Compared with the intact, only posterior facet fusion and interbody fusion with plate had statistically significantly less motion (P=0.006 and 0.0001, respectively). The amount of radiographically detectable flexion-extension motion with simulated fusions varies widely and seems to be influenced by fusion type. This study documents a range of measurable motion on flexion-extension radiographs after several types of simulated lumbar fusion. However, as the degrees of motion seemed to be high, future studies should use a fusion simulation other than metallic implants that more closely resembles bony arthrodesis.

A brief overview of evidence-informed management of chronic low back pain with surgery

The management of chronic low back pain (CLBP) has proven to be very challenging in North America, as evidenced by its mounting socioeconomic burden. Choosing among available nonsurgical therapies can be overwhelming for many stakeholders, including patients, health providers, policy makers, and third-party payers. Although all parties share a common goal and wish to use limited health-care resources to support interventions most likely to result in clinically meaningful improvements, there is often uncertainty about the most appropriate intervention for a particular patient. To help understand and evaluate the various commonly used nonsurgical approaches to CLBP, the North American Spine Society has sponsored this special focus issue of The Spine Journal, titled Evidence-informed management of chronic low back pain without surgery. Articles in this special focus issue were contributed by leading spine practitioners and researchers, who were invited to summarize the best available evidence for a particular intervention and encouraged to make this information accessible to nonexperts. Although this special focus issue was focused on nonoperative care, it was deemed important to provide an overview of the surgical management of CLBP. This is intended to inform stakeholders of surgical options that are available to them should nonsurgical interventions prove ineffective or contraindicated. It is hoped that articles in this special focus issue will be informative and aid in decision making for the many stakeholders evaluating nonsurgical interventions for CLBP.

Residual sagittal motion after lumbar fusion: a finite element analysis with implications on radiographic flexion-extension criteria

STUDY DESIGN

Finite element analysis of a lumbar fusion model.

OBJECTIVES

To quantify residual sagittal angular motion following various types and levels of completeness of lumbar fusion in order to understand better the validity of current recommendations for interpreting flexion-extension radiographs to assess fusion.

SUMMARY OF BACKGROUND DATA

Recommended threshold criteria for solid fusion using flexion-extension radiographs have varied from 0 degrees to 5 degrees of angular motion between vertebrae. Notwithstanding this wide variation and lack of uniform consensus, the validity of these criteria has not been previously biomechanically assessed to the authors' knowledge. To investigate this issue, the authors sought to test various types of simulated healed, noninstrumented lumbar fusions using finite element modeling to determine the amount of residual angular motion under physiologic stresses.

METHODS

A validated 3-dimensional, nonlinear finite element model of an intact adult human L3-L4 motion segment was developed. Four fusion types were simulated using this model, including anterior lumbar interbody fusion (ALIF), posterior lumbar interbody fusion (PLIF), intertransverse process fusion, and interspinous process fusion. Variations of completeness of fusion were also represented. For ALIF and PLIF, this included tests of solid bridging bone within the posterior or anterior 75%, 50%, or 25% disc space. In addition, PLIF was also tested with either a unilateral or bilateral facetectomy to simulate commonly used surgical techniques. Variations of intertransverse process fusion included unilateral or bilateral bridging bone with or without medial fusion to the pars interarticularis. Only 1 scenario of a healed, solid interspinous process fusion was tested. The intact model and all fusion models were stressed with 10.6-Nm flexion and extension moments. The angular deflections were recorded in degrees.

RESULTS

A wide range of sagittal angular motion was recorded. For ALIF, this ranged from 0.8 degrees (complete, 100% fusion) to 3.3 degrees (solid fusion of the posterior 25% disc space). For PLIF, the numbers were more varied, ranging from 0.7 degrees (complete, 100% fusion) to 6.9 degrees (solid fusion of posterior 25% disc space with bilateral facetectomy). For intertransverse process fusion, the least motion was with a solid bilateral fusion, with medial healing to the pars (2.0 degrees); the greatest motion was found with a solid unilateral fusion without medial healing (6.0 degrees). Interspinous process fusion allowed only 1.9 degrees of motion.

CONCLUSIONS

The amount of residual flexion-extension motion with simulated lumbar fusions (presumably allowed by the bone's inherent elasticity) under physiologically comparable moments varies with fusion type and, more substantially, with varying amounts of completeness. The current study documents a range of sagittal angular motion after several types of simulated lumbar fusion that appear to have considerable overlap with previously purported radiographic criteria for solid fusion using flexion-extension radiographs. However, it also suggests the possibility that some scenarios of solid, yet incomplete, fusion may allow motion that is substantially greater than 5 degrees, which is beyond the most liberal of previously published threshold criteria.

Two column lesions in the thoracolumbar junction: anterior, posterior or combined approach? A comparative biomechanical in vitro investigation

There are various surgical techniques for the treatment of spinal fractures in the thoracolumbar region. Several implants have been developed for anterior or posterior instrumentation. Optimal treatment of unstable thoracolumbar osseous and ligamentous injuries remains controversial. To compare the stabilizing effects of an antero-lateral, thoracoscopically implantable plate system (macsTL, Aesculap, Germany) with the stability provided by a fixateur interne (SOCON, Aesculap, Germany), this in vitro investigation examined six human bisegmental (T12-L2) spinal units. Specimens were tested intact, and with simulation of osseous lesions in the anterior and ligamentous lesions in the posterior column (combined A/B-fracture). While loaded in the main anatomical planes such as flexion/extension, left and right lateral bending and left and right axial rotation with a bending moment of 7.5 Nm in a special testing jigs, motion analysis was performed. Quantitative interpretation of the stabilizing effect was achieved using a contactless three-dimensional motion analysis system. Each specimen was tested in four different scenarios: the first step measured movements of intact spinal segments. For the second step, specimens underwent simulation of combined A/B-fracture provided with bisegmental (T12/L2) antero-lateral fixation and bone strut graft from the iliac crest. For the third step, segments were additionally stabilized by the fixateur interne. The last measurement (fourth step) was performed after removing the anterior instrumentation. Range of motion (ROM) values were compared and statistically evaluated. Compared to the intact specimens the anterior instrumentation of the combined lesion, simulated A/B-fracture, leads to a stabilizing effect in flexion/extension and lateral bending. In contrast to these findings the torsional instability increased for the upper segment and bisegmentally. A maximum rigidity, beyond intact values, was registered for each anatomical plane with the combined instrumentation: antero-lateral and fixateur interne. After removing the anterior screw plate system maximum movements, in all segments for flexion/extension and lateral bending, bisegmentally and for the upper segment in axial rotation, were less than ROM values measured with the anterior system only. With respect to these findings a combined ventro-dorsal stabilization procedure should be considered for ligamentous disruptions of the posterior column in combination with A-fractures in the thoracolumbar junction.

Direct current stimulation for spine fusion in a nicotine exposure model

BACKGROUND CONTEXT

Decreased effectiveness in spinal fusion procedures in patients who smoke before, during, or after the operation has been noted in several clinical studies. In previous work, direct current (DC) electrical stimulation has been shown to enhance inter-transverse process fusion in a rabbit model.

PURPOSE

To test the efficacy of DC stimulation on bone healing in spinal fusion in rabbits exposed to nicotine.

STUDY DESIGN/SETTING

A randomized and controlled interventional study.

METHODS

Thirty male New Zealand white rabbits received a single level posterolateral, inter-transverse process fusion with autologous iliac crest bone. One group (control) acted as a control without nicotine or electrical stimulation. A second group (Nic) received a continuous dose of nicotine via a transdermal patch to simulate a heavy smoker, and a third group, nicotine/stimulator group (Nic/Stim), additionally received a 100-microamp DC stimulator. The fusion masses (L5-L6) and the adjacent unfused control segment (L4-L5) were evaluated radiographically, manually, and biomechanically.

RESULTS

The Nic group showed significantly higher fusion rate compared with the control group. The Nic/Stim group also demonstrated significantly higher fusion rate and X-ray trabeculation compared with the control group. However, the Nic/Stim group was not significantly higher than the Nic group in fusion rate or X-ray trabeculation.

CONCLUSIONS

Nicotine significantly improved fusion rate compared with controls, and DC stimulation significantly increased X-ray trabeculation of nicotine treated rabbits compared with controls.

Surgical treatment for the painful motion segment: matching technology with the indications: posterior lumbar fusion

STUDY DESIGN

A convenience literature-based review of the different techniques of posterior lumbar fusion.

OBJECTIVE

To describe the history, specific techniques, and outcomes of different methods of posterior lumbar fusion. The specific methods that were described include 1) uninstrumented posterior, posterolateral, and facet fusion, and 2) instrumented fusion using pedicle screws or facet screws.

SUMMARY OF BACKGROUND DATA

There are various posterior fusion techniques available for the treatment of degenerative lumbar spine conditions. Each individual technique has specific technical demands, indications, advantages, and disadvantages which should be taken into consideration when performing these procedures.

METHODS

The published scientific literature on the different methods of posterior lumbar fusion was reviewed. The history, indications, advantages, disadvantages, and clinical and radiographic outcomes were described based on the literature search.

RESULTS/CONCLUSIONS

Posterior fusion techniques have been and will continue to be among the most commonly performed procedures in lumbar spine surgery. The different methods of fusion are well defined, as are the possible complications and outcomes. They are effective techniques when performed on appropriately selected patients by a surgeon knowledgeable in the techniques and indications. Further studies are needed regarding promising but relatively unproven developments such as minimally invasive surgery and the use of osteoinductive agents.

A critical analysis of the literature regarding surgical approach and outcome for adult low-grade isthmic spondylolisthesis

OBJECTIVE

A systematic review of the radiographic and clinical outcomes of adult patients undergoing surgery for low-grade isthmic spondylolisthesis was performed to determine whether conclusions could be made regarding the optimal choice of surgically managing adult low-grade isthmic spondylolisthesis.

METHODS

We tabulated the radiographic and clinical outcomes of patients who underwent a posterior procedure alone, an anterior procedure alone, or a combined anterior and posterior procedure. We also evaluated the influence of covariates such as laminectomy, spinal internal fixation, smoking, and secondary gain issues on these outcomes. Patients were pooled, and a chi analysis was performed to determine the relationship between surgical approach and patient outcome. A covariate analysis was performed to determine the influence of a laminectomy, spinal fixation, smoking, and secondary gain issues on these outcomes.

RESULTS

The available literature consisted primarily of retrospective case series, with only 4 of 34 reports being prospective randomized controlled studies. Patients with combined anterior and posterior procedures were most likely to achieve a solid fusion and a successful clinical outcome. The use of spinal fixation also increased the chance of fusion and successful clinical outcome.

CONCLUSIONS

A pooling of the surgical literature on adult low-grade spondylolisthesis indicates that a combined anterior and posterior procedure most reliably achieves fusion and a successful clinical outcome. The literature, however, is primarily retrospective and heterogeneous with respect to indications for surgery and methods of evaluating outcome, providing a compelling rationale for a prospective randomized controlled trial of the various surgical approaches to this problem.

Clinical studies in spinal surgery

There is a growing interest in applying evidence-based approaches also in orthopedic surgery. Despite many challenges to the validity of clinical trials in orthopedic surgery, it is possible to conduct well-designed trials in this field and to produce clinically important findings and reasonably valid conclusions about effectiveness, prognosis and diagnosis in orthopedic surgery. We describe the main principles for conducting clinical trials in this field as well as some of the most common errors and ways to avoid them.

Is a single anterolateral screw-plate fixation sufficient for the treatment of spinal fractures in the thoracolumbar junction? A biomechanical in vitro investigation

Controversy exists about the indications, advantages and disadvantages of various surgical techniques used for anterior interbody fusion of spinal fractures in the thoracolumbar junction. The purpose of this study was to evaluate the stabilizing effect of an anterolateral and thoracoscopically implantable screw-plate system. Six human bisegmental spinal units (T12-L2) were used for the biomechanical in vitro testing procedure. Each specimen was tested in three different scenarios: (1) intact spinal segments vs (2) monosegmental (T12/L1) anterolateral fixation (macsTL, Aesculap, Germany) with an interbody bone strut graft from the iliac crest after both partial corpectomy (L1) and discectomy (T12/L1) vs (3) bisegmental anterolateral instrumentation after extended partial corpectomy (L1), and bisegmental discectomy (T12/L1 and L1/L2). Specimens were loaded with an alternating, nondestructive maximum bending moment of +/-7.5 Nm in six directions: flexion/extension, right and left lateral bending, and right and left axial rotation. Motion analysis was performed by a contact-less three-dimensional optical measuring system. Segmental stiffness of the three different scenarios was evaluated by the relative alteration of the intervertebral angles in the three main anatomical planes. With each stabilization technique, the specimens were more rigid, compared with the intact spine, for flexion/extension (sagittal plane) as well as in left and right lateral bending (frontal plane). In these planes the bisegmental instrumentation compared to the monosegmental case had an even larger stiffening effect on the specimens. In contrast to these findings, axial rotation showed a modest increase of motion after bisegmental instrumentation. To conclude, the immobilization of monosegmental fractures in the thoracolumbar junction can be secured by means of bone grafting and the implant used in this study for all three anatomical planes. After bisegmental anterolateral stabilization a sufficient reduction of the movements was registered for flexion/extension and lateral bending. However, the observed slight increase of the range of motion in the transversal plane may lead to loosening of the implant before union. Therefore, the use of an additional dorsal fixation device should be considered.

The influence of subdiagnosis on radiographic and clinical outcomes after lumbar fusion for degenerative disc disorders: an analysis of the literature from two decades

STUDY DESIGN

A critical review of published literature from 2 decades.

OBJECTIVE

To critically analyze the literature from 1979 to 2000 in order to examine the influence of subdiagnosis on outcome after fusion for lumbar degenerative disc disorders.

SUMMARY OF BACKGROUND DATA

Numerous diagnostic subgroups of degenerative disc disorders exist. Although it is commonly believed that surgical outcomes after lumbar fusion are influenced by these subdiagnoses, there is a paucity of literature demonstrating differences in clinical outcomes or fusion rates among them. As the indications for fusion have been under greater scrutiny recently, this information would be useful in prognosticating outcomes and optimizing patient selection.

METHODS

A computer search of the English literature using the keywords "degenerative," "lumbar," and "fusion" was performed. Disorders were organized according to the following subdiagnostic groups: degenerative spondylolisthesis (DDDsp), herniated disc (DH), degenerative scoliosis (DDDsc), stable DDD (DDDs), dynamically unstable DDD (DDDu), and DDD that was not specified as either DDDu or DDDs (DDDn). For each group, the type of instrumentation, fusion location, fusion rate, clinical outcome, and complication rate were recorded in a computer database. Data were pooled by simple summation and statistically analyzed using a chi test or Fisher exact test.

RESULTS

Of 244 articles identified, 78 satisfied inclusion criteria with data from 4454 patients recorded. The most common diagnosis was DDDn (50%), followed by DDDsp (25%), DH (14%), DDDu (6%), DDDs (3%), and DDDsc (2%). The DDDn group had a higher fusion rate than DDDsp (P = 0.025), but a lower clinical outcome (P = 0.051). Complication rates were highest in DDDsc, whereas this subdiagnosis also had the best reported clinical outcomes. In comparing individual subgroups, a trend towards higher fusion rate and better clinical outcome was noted in DDDsp cases with instrumentation compared to noninstrumented cases. This trend was reversed for patients in the DDDn group, in whom better clinical outcomes were noted after noninstrumented fusions regardless of a lower fusion rate.

CONCLUSIONS

The present data indicate that clinical outcomes and fusion rates statistically differ among the various subgroups of degenerative disc disease. Concerning the use of instrumentation, it appears that it may have greater clinical benefit in patients with DDDsp than DDDn. These findings underscore the importance of delineating specific clinical diagnoses when documenting results of lumbar fusion. This information might also be useful for both selecting surgical candidates and discussing anticipated operative outcomes.

Prospective Assessment of Outcomes Improvement Following Fusion for Low Back Pain

BACKGROUND

This prospective study was performed to improve the quality of outcomes data in patients undergoing spinal fusion for low back pain. There is an accepted deficiency of this form of outcomes assessment in the literature. The aim was to determine the effectiveness of the surgical procedure in terms of patient satisfaction, outcome scores, and third-party measures.

METHODS

The measures of outcomes assessment included patient satisfaction, pain scores, low back outcome and Prolo scores, medication use, and employment status. Data collection was prospective prior to and at final follow-up. Eighty percent of 35 patients were followed for a mean of 31 months.

RESULTS

Patient satisfaction was 71%; however, only 28.6% of patients followed achieved good or excellent low back outcome scores. Yet significant improvement occurred: 46.4% achieved a good or excellent outcome using the Prolo score. There was a 75% reduction in medication usage, and 75% of nonworking compensation patients returned to gainful employment. Patient satisfaction was markedly higher than improvement measured by the outcome scores. Dramatic improvements in medication usage and return to work were achieved, despite less than spectacular outcome scores.

CONCLUSIONS

These findings support cautious use of posterior spinal fusion. Patients must appreciate improvement rather than normality as a realistic aim.

Rigid, semirigid versus dynamic instrumentation for degenerative lumbar spinal stenosis: a correlative radiological and clinical analysis of short-term results

STUDY DESIGN

Prospective comparative randomized clinical and radiologic study.

OBJECTIVE

This study was conducted to compare the short-term effects of rigid versus semirigid and dynamic instrumentation on the global and segmental lumbar spine profile, subjective evaluation of the result, and the associated complications.

BACKGROUND DATA

Lumbar spine fusion with rigid instrumentation for degenerative spinal disorders seems to increase the fusion rate. However, rigid instrumentation may be associated with some undesirable effects, such as increased low back pain following decrease of lumbar lordosis, fracture of the vertebral body and pedicle, pedicle screw loosening, and adjacent segment degeneration. The use of semirigid and dynamic devices has been advocated to reduce such adverse effects of the rigid instrumentation and thus to achieve a more physiologic bony fusion.

MATERIALS AND METHODS

This study compared 3 equal groups of 45 adult patients, who underwent primary decompression and stabilization for symptomatic degenerative lumbar spinal stenosis. The patients of each group were randomly selected and received either the rigid (Group A), or semirigid (Group B), or dynamic (Group C) spinal instrumentation with formal decompression and fusion. The mean ages of the patients who received rigid, semirigid, and dynamic instrumentation were 65 +/- 9, 59 +/- 16, and 62 +/- 10 years, respectively. All patients had detailed roentgenographic study including computed tomography scan and magnetic resonance imaging before surgery to the latest follow-up observation. The following roentgenographic parameters were measured and compared in all spines: lumbar lordosis (L1-S1), total lumbar lordosis (T12-S1), sacral tilt, distal lordosis (L4-S1), segmental lordosis, vertebral inclination, and disc index. The SF-36 health survey and Visual Analogue Scale was used before surgery to the latest evaluation.

RESULTS

All patients were evaluated after a mean follow-up of 47 +/- 14 months. Both lumbar and total lordosis correction did not correlate with the number of the levels instrumented in any group. Total lordosis was slightly decreased after surgery (3%, P < 0.05) in Group C. The segmentallordosis L2-L3 was increased after surgery by 8.5% (P < 0.05) in Group C, whereas the segmentallordosis L4-L5 was significantly decreased in Group Aand C by 9.8% (P = 0.01) and 16.2% (P < 0.01), respectively. The disc index L2-L3 was decreased after surgery in Group A and C by 17% (P < 0.05) and 23.5% (P < 0.05), respectively. The disc index L3-L4 was increased in Group C by 18.74% (P < 0.01). The disc index L4-L5 was after surgery decreased in all 3 groups: Group A by 21% (P = 0.01), Group B by 13% (P < 0.05), and Group C by 13.23% (P < 0.05). The disc index L5-S1 was significantly decreased in Group B by 13% (P < 0.05). The mean preoperative scores of the SF-36 before surgery were 11, 14, and 13 for Groups C, B, and A, respectively. In the first year after surgery, there was a significant increase of the preoperative SF-36 scores to 65, 61, and 61 for Groups C, B, and A, respectively, that represents an improvement of 83%, 77%, and 79%, respectively. In the second year after surgery and thereafter, there was a further increase of SF-36 scores of 19%, 23%, and 21% for Groups C, B, and A, respectively. The mean preoperative scores of Visual Analogue Scale for low back pain for Groups C, B, and A were 5, 4.5, and 4.3, respectively, and decreased after surgery to 1.9, 1.5, and 1.6, respectively. The mean preoperative scores of the Visual Analogue Scale for leg pain for Groups C, B, and A were 7.6, 7.1, and 6.9, respectively, and decreased after surgery to 2.5, 2.5, and 2.7, respectively. All fusions healed radiologically within the expected time in all three groups without pseudarthrosis or malunion. Delayed hardware failure (1 screw and 2 rod breakages) 1 year and 18 months after surgery without radiologic pseudarthrosis was observed in 2 patients in Group C. Asymptomatic radiolucent areas were shown around pedicle screws in the pedd pedicle screws in the pedicles L5 and S1 in 2, 3, and 4 cases in Group C, A, and B, respectively. There was no adjacent segment degeneration in any spine until the last evaluation.

DISCUSSION AND CONCLUSION

This comparative study showed that all three instrumentations applied over a short area for symptomatic degenerative spinal stenosis almost equally after surgery maintained the preoperative global and segmental sagittal profile of the lumbosacral spine and was followed by similarly significant improvement of both self-assessment and pain scores. Hardware failure occurred at a low rate following dynamic instrumentation solely without radiologically visible pseudarthrosis or loss of correction. Because of the similar clinical and radiologic data in all three groups and the relative small number of patients that were included in each group, it is difficult for the authors to make any recommendation in favor of any instrumentation.

Critical analysis of trends in fusion for degenerative disc disease over the past 20 years: influence of technique on fusion rate and clinical outcome

STUDY DESIGN

Critical analysis of the results reported in published literature.

OBJECTIVES

The purpose of this study was to evaluate whether various technical advancements have affected the outcome of lumbar spinal fusion for degenerative disease by critically analyzing the available literature from the past two decades.

SUMMARY OF BACKGROUND DATA

To improve fusion rate and clinical outcome, various surgical options for lumbar spinal fusion for degenerative disc disorders have been introduced over the past 20 years. However, an important fundamental question still remains: What has been the impact of these new techniques and innovations on surgical results?

METHODS

A comprehensive computer search of the English literature from 1979 to 2000 concerning lumbar/lumbosacral spinal fusion was performed using the keywords degenerative, lumbar, and fusion.

RESULTS

Numerous deficiencies were noted in the reviewed literature. Nearly half of the studies failed to specify methodologic design, and documentation of brace use, graft source, fusion location, and fusion rate was missing in 38, 10, 2, and 4 of the 84 articles reviewed, respectively. From the data gathered, a noticeable trend toward the increasing use of internal fixation was noted, accounting for 23% of fusions in the 1980s versus 41% in the 1990s. Despite this trend, an improvement in overall fusion rate or clinical outcome could not be demonstrated.

CONCLUSIONS

Numerous technologic advancements in lumbar spine fusion have been made over the past 20 years. Future advances in care are dependent on review of reported results. The numerous deficiencies detected in the analyzed literature herald the necessity for a uniform system of outcomes reporting containing a core of critical demographic, perioperative, and postsurgical information. Although a shift toward a greater use of technology was noted in the published literature, the clinical benefit of this trend remains unclear.

Pedicle screw fixation for isthmic spondylolisthesis: does posterior lumbar interbody fusion improve outcome over posterolateral fusion?

OBJECT

Posterolateral fusion involving instrumentation-assisted segmental fixation represents a valid procedure in the treatment of lumbar instability. In cases of anterior column failure, such as in isthmic spondylolisthesis, supplemental posterior lumbar interbody fusion (PLIF) may improve the fusion rate and endurance of the construct. Posterior lumbar interbody fusion is, however, a more demanding procedure and increases costs and risks of the intervention. The advantages of this technique must, therefore, be weighed against those of a simple posterior lumbar fusion.

METHODS

Thirty-five consecutive patients underwent pedicle screw fixation for isthmic spondylolisthesis. In 18 patients posterior lumbar fusion was performed, and in 17 patients PLIF was added. Clinical, economic, functional, and radiographic data were assessed to determine differences in clinical and functional results and biomechanical properties. At 2-year follow-up examination, the correction of subluxation, disc height, and foraminal area were maintained in the group in which a PLIF procedure was performed, but not in the posterolateral fusion-only group (p < 0.05). Nevertheless, no statistical intergroup differences were demonstrated in terms of neurological improvement (p = 1), economic (p = 0.43), or functional (p = 0.95) outcome, nor in terms of fusion rate (p = 0.49).

CONCLUSIONS

The authors' findings support the view that an interbody fusion confers superior mechanical strength to the spinal construct; when posterolateral fusion is the sole intervention, progressive loss of the extreme correction can be expected. Such mechanical insufficiency, however, did not influence clinical outcome.

Indications, techniques, and outcomes of posterior surgery for chronic low back pain

This article summarizes a number of issues surrounding the diagnosis, indications, and techniques of posterior lumbar spine surgery for chronic low back pain. It would not be entirely unjustified for a spine surgeon to adhere to a totally avoidant approach to chronic low back pain, rationalized by a reasonably legitimate nihilism regarding the presently available means of diagnosing and surgically managing low back pain [64]. Judging by the number of lumbar fusions performed in North America and the tremendous intellectual and financial investment currently being made in technologies to enhance spinal fusion, such an approach is evidently not achieving wide-spread acceptance on this continent. A rationale approach is therefore required for the many low back pain sufferers with degenerative disk disease who arrive in the office having exhausted almost every imaginable form of nonoperative therapy. Every effort should be made to establish a pathoanatomic etiology of the back pain with a combination of diagnostic modalities. Surgical intervention should be approached cautiously and only after extensive dialog with the patient to establish realistic goals and expectations. Posteriorly performed interbody fusion procedures may provide a high fusion rate and satisfactory clinical outcomes for this challenging problem, although further research is necessary to determine more conclusively the role of surgery and the relative effectiveness of the various arthrodesis techniques.

Black disc disease: a commentary

Internal disc disruption associated with axial back pain but not radicular pain is a disease entity that was recognized about two decades ago as a disorder that could potentially be treated by spinal fusion. In this article the authors describe the clinical syndrome, magnetic resonance imaging and discography findings of pathophysiological pain generation, and the available surgical options. Based on the current understanding of this disease entity, the optimum surgical procedure entails radical discectomy, anterior column support, adequate amounts of auto- or allograft bone, bone extenders and enhancers, and rigid stabilization of the motion segment.

Stress fracture of the pedicle after extensive decompression and contralateral posterior fusion for lumbar stenosis. Report of three cases

Lumbar spinal stenosis can be effectively treated by performing an extensive ipsilateral spinal decompression, including a partial pediculotomy, and contralateral posterior bone fusion. Infrequently, complications can arise following radical decompression to alleviate symptoms of stenosis, and one such complication is a pedicle fracture. Three reports of pedicle fractures following extensive spinal decompression and contralateral posterior fusion are detailed. This complication is emphasized, and interventions are discussed. Three patients presented with symptoms attributable to lumbar stenosis; they were initially treated with an ipsilateral decompression, achieved in part, through a partial pediculotomy followed by contralateral autologous bone fusion. Initially, all three patients improved postoperatively; however, they later developed neurological symptoms ipsilateral to the side of spinal decompression. Computerized tomography scanning demonstrated pedicle fractures on the decompressed side. This complication has not yet been reported in association with decompression and fusion for lumbar stenosis. Two of the patients developed leg pain necessitating reoperation whereas the third experienced only mild transient symptoms. The fractured pedicle was removed in one patient; laminar and spinous process fusion was performed again. Another patient underwent a total laminectomy, removal of the fractured pedicle, and bilateral transverse process fusion. Reoperation yielded satisfactory outcomes. The third patient's symptoms resolved without intervention. Pedicle fractures are a potential complication of extensive lumbar decompression and contralateral posterior fusion. Loading forces from the facets or transverse processes are possibly the cause of such fractures. Removal of the fractured pedicle, additional decompression, and enhanced bone fusion are recommended when the symptoms warrant surgical intervention.

Degenerative disc disease treated with combined anterior and posterior arthrodesis and posterior instrumentation

STUDY DESIGN

This study retrospectively reviewed the outcome of 58 patients all diagnosed with severe low back pain secondary to degenerative disc disease and treated with anterior arthrodesis and posterior instrumented arthrodesis.

OBJECTIVES

To evaluate the outcome of a select group of patients with degenerative disc disease treated with this surgical intervention at a minimum of 2 years of follow-up.

SUMMARY OF BACKGROUND DATA

Patients with degenerative disc disease who fail nonoperative treatment generally have disappointing outcomes with traditional surgical intervention. The literature analyzing posterior instrumented arthrodesis tends to exhibit the best results, but the numbers of patients with degenerative disc disease in these articles are few, and their outcomes are worse than the other low back conditions. Even patients with solid posterior arthrodesis have been noted to have continued low back pain. No articles have evaluated this specific surgical procedure in a group of patients all with the diagnosis of degenerative disc disease and no previous surgery.

METHODS

All patients were diagnosed with degenerative disc disease and had failed prolonged nonoperative treatment (average 4.9 years). Fusion levels were delineated by MRI and provocative discography in correlation with history and physical examination. The senior author (M.R.P.) performed the identical operative procedure on all patients, under a single anesthetic. The arthrodesis solidity was evaluated with radiographic studies and operative posterior exploration when necessary. Final outcomes were determined using a functional and satisfaction questionnaire, return to work, narcotic use, and the rate of solid arthrodesis. Charts, radiographs, and questionnaires were reviewed by an independent evaluator at final follow-up (average 35 months).

RESULTS

The solid arthrodesis rate was 95%. The three pseudoarthroses were all in patients with a three-level arthrodesis. Eighty-eight percent of the patients were able to return to work. Nineteen percent of patients required long-term narcotics, whereas 48% of the patient population were on narcotics before surgery. Eighty-six percent of the patients had a "better" rating at final follow-up. This included patients with decreased pain by visual analog scale, improved functional questionnaire, and those who would recommend the procedure to a friend or family member. Ten percent of the patients were "the same," and 3% were "worse." Lumbar lordosis was maintained or improved. Complications did not exceed literature controls.

CONCLUSIONS

Selected patients with discography-proven severe low back pain secondary to degenerative disc disease, who failed extensive nonoperative treatment, were treated successfully with anterior-posterior instrumented arthrodesis. The good arthrodesis rate, return to work rate, and patient satisfaction may justify the consideration of this aggressive treatment option in this specific patient population.

The effect of osteogenic protein-1 in instrumented and noninstrumented posterolateral fusion in rabbits

BACKGROUND CONTEXT

The use of rigid instrumentation combined with bone graft makes intuitive sense given the requirements for vascular ingrowth, bone formation and a stable environment for the cellular events of healing to develop. However, with the advances of potent osteoinductive growth factors, the role of internal fixation may come into question. Whether bone morphogenic proteins (BMPs) would benefit from a more "stable" spinal segment for bone production and modeling remains unknown. In addition, it is unknown whether BMP and rigid fixation may have an additive effect on fusion healing.

PURPOSE

This study is proposed to test the hypothesis that rigid fixation in the lumbar spine would be advantageous to achieve fusion for autogenous bone grafting, but fusion would occur regardless of fixation with the use of osteogenic protein (OP)-1.

STUDY DESIGN/SETTING

A histologic and radiographic analysis of BMP in a rabbit lumbar fusion model.

METHODS

Thirty-two rabbits were randomized into four groups: 1) control animals: in situ posterolateral L5-L6 arthrodesis using autogenous iliac crest bone graft; 2) fixation group: posterolateral arthrodesis L5-L6 with autogenous bone graft and interspinous fixation; 3) OP-1 group: in situ posterolateral L5-L6 arthrodesis using OP-1 and 4) combined OP-1 and fixation group. Radiographic fusion analysis was performed with computed tomography scans at 3 and 12 weeks after surgery. Decalcified histology was performed to assess tissue morphology and cellularity.

RESULTS

Minimal evidence of fusion was noted at 3 weeks with autograft or OP-1. By 12 weeks, all OP-1-treated animals had solid fusion, whereas no fusion was noted in autograft animals. The addition of fixation slightly increased radiographic fusion at 3 weeks in autograft and OP-1 groups but did not affect OP-1 animals at 12 weeks where all were fused. Decalcified histologic results confirmed the proliferative bone formation noted with OP-1 and the variable cellular response with autograft.

CONCLUSIONS

The results of the present study suggest that the osteoinductive effect of OP-1 may be only minimally enhanced early in the bone healing process but does not appear to be affected in the long term by spinal fixation in the rabbit intertransverse fusion model. Fixation appeared to enhance early fusion in the autograft group.

Clinical results of single-level posterior lumbar interbody fusion using the Brantigan I/F carbon cage filled with a mixture of local morselized bone and bioactive ceramic granules

STUDY DESIGN

A retrospective study to evaluate the results of single-level posterior lumbar interbody fusion (PLIF) using the Brantigan I/F cage (DePuy AcroMed Corp., Raynham, MA) filled with a mixture of local morselized autologous bone and bioactive ceramic granules.

OBJECTIVES

To report the clinical and radiologic results of PLIF using the Brantigan I/F cage for lumbar degenerative pathologies with instability.

SUMMARY OF BACKGROUND DATA

The Brantigan I/F cage for PLIF was designed to improve the fusion success of interbody fusion by separating the mechanical and biologic functions of PLIF using an implant device and autologous bone from the iliac crest. Although high fusion rates have been reported, donor site morbidity caused by bone harvest from the iliac crest remains a concern. The possibility of accomplishing cage PLIF using a mixture of local morselized bone and a bone extender was studied.

METHODS

A total of 25 patients underwent single-level PLIF using the Brantigan I/F cage filled with a mixture of local morselized bone and bioactive ceramic granules. All patients were observed for more than 2 years (average 2 years 7 months) and evaluated by clinical rating and radiograph.

RESULTS

Preoperative Japanese Orthopedic Association clinical scores were significantly improved in all patients at the time of follow-up. The average improvement rate was 83.1%. There were no serious complications. Minor complications included two dural tears and two cases of thrombophlebitis. No patient required blood transfusion. All patients achieved radiographic fusion and radiographic stability, although two patients fused in a collapsed position. Regional alignment of the operated segments was restored at surgery and maintained at the time of final follow-up. There were statistical improvements in percent slip and percent posterior disc height in patients with spondylolisthesis.

CONCLUSIONS

Posterior lumbar interbody fusion using the Brantigan I/F cage with a mixture of local morselized bone and bioactive ceramic granules can yield a solid union with satisfactory regional alignment and adequate disc height without harvest of iliac crest bone.

Unilateral transforaminal posterior lumbar interbody fusion

A prospective analysis of consecutive patients who had lumbar fusion using the unilateral transforaminal posterior lumbar interbody fusion with pedicle screw fixation is presented to assess the clinical and radiographic outcomes of the transforaminal posterior lumbar interbody fusion procedure and describe the technique and indication in the treatment of degenerative disease of the lumbar spine. Forty patients treated with transforaminal posterior lumbar interbody fusion for degenerative diseases of the lumbar spine (with anterior column deficiency) were followed up for a minimum of 3 years (mean, 3.4 years; range, 3-3.9 years). Radiographic assessment included plain and flexion and extension radiographs. Clinical outcome was based on pain relief, ability to do activities of daily living, and return to work. Thirty-six patients (90%) had solid fusions and at latest followup, segmental lordosis has increased in all patients. Eighty-five percent of patients had excellent or good clinical outcome(s). The unilateral transforaminal posterior lumbar interbody fusion provides bilateral anterior column support through a unilateral approach. The patients had high fusion rates and patient satisfaction as reported with similar complications found in other methods commonly used for spinal decompression and stabilization.

Lumbar posterolateral fusion alone or with transpedicular instrumentation in L4--L5 degenerative spondylolisthesis

We retrospectively reviewed 57 patients with L4--L5 degenerative spondylolisthesis (L4--L5 DS) who underwent posterior decompression and posterolateral fusion of L4--L5 without (Group A) or with (Group B) transpedicular screw instrumentation at least 2 years earlier. The clinical results and fusion rate were similar between Groups A and B, that is, a 72.4% satisfactory outcome with a fusion rate of 82.8% in Group A versus 82.1% satisfactory outcome with a 92.8% fusion rate in Group B. Screw instrumentation reduced postoperative low back pain and resulted in a lordotic slip angle of L4--L5. However, in patients with radiologically excessive segmental motion showing a translational motion of 3 mm or more, flexion angulation of -5 degrees or less, and a slip angle of -5 degrees or less at the site of spondylolisthesis (L4--L5), the kyphotic slip angle (L4--L5) tended to increase after surgery. In the future, in patients with radiologically excessive segmental motion, this point should be considered, and surgical techniques should be evaluated. Our results suggest that the validity of the general addition of screw instrumentation to L4--L5 fusion for L4--L5 degenerative spondylolisthesis is low.

The efficacy of direct current stimulation for lumbar intertransverse process fusions in an animal model

STUDY DESIGN

Posterolateral lumbar intertransverse process fusion using a rabbit model with autologous bone graft and direct current stimulation was compared with fusion achieved by using autologous bone graft alone.

OBJECTIVES

To determine the efficacy of direct current electrical stimulation for the posterolateral lumbar intertransverse process fusion technique by using a 20-microA current and the more recently developed 60-microA current delivered by an implantable direct current stimulator.

SUMMARY OF BACKGROUND DATA

Previous studies have demonstrated a positive effect of direct current electrical stimulation on posterior spinal fusion techniques. However, until recently, the environment of an intertransverse fusion was not well simulated. The current research examined the posterolateral lumbar intertransverse process fusion technique with direct current electrical stimulation using a rabbit model. This appears to parallel human fusion techniques more closely and allows for lower cost and technical ease.

METHODS

In this study, 44 adult New Zealand white rabbits underwent an L5-L6 intertransverse process fusion. All the fusions used an autologous bone graft obtained from bilateral posterior iliac crests. A device was implanted in all the rabbits subcutaneously, and they were divided randomly into three groups: a sham or nonfunctioning group, a 20-microA low-current stimulator group, and a 60-microA higher-current stimulator group. Spinal fusion was evaluated radiographically, histologically, and manually as well as by biomechanical testing 5 weeks after surgery.

RESULTS

Radiographic grades, manual palpation, biomechanical strength, and stiffness showed an increasing trend from sham or inactive stimulator groups to low-current and then to high-current stimulator groups. Histologic analysis revealed that the higher-current stimulator showed that, statistically, the healing response of the host tissue to the autograft had increased significantly, as compared with the sham.

CONCLUSIONS

Direct current electrical stimulation is efficacious in improving both the healing rate and strength in this posterolateral lumbar fusion model. In addition, it appears that this effect is enhanced by increasing the stimulation current from 20 microA to 60 microA.

Posterior fusion compared with posterior interbody fusion in segmental spinal fixation for adult spondylolisthesis

OBJECT

Clinical and radiographic results in 30 consecutive patients who underwent posterior lumbar fixation and posterior facet joint or posterior interbody fusion for Meyerding Grade II/III spondylolisthesis were assessed: 1) to address the suitability of a dynamic stabilization; and 2) to investigate whether there are differences in terms of clinical and functional results and biomechanical properties between these two types of arthrodesis.

METHODS

Between June 1998 and April 2000, 16 patients underwent posterior interfacet fusion and implantation of the SOCON-SRI system. In 14 patients posterior lumbar interbody fusion (PLIF) and placement of the same system were performed. Clinical, economic, functional, and radiographic data were recorded pre- and postoperatively. The average changes in the Prolo Scale economic and functional scores were 1.25 and 1.62, respectively, in patients who underwent posterior fusion; the average measured preoperative vertebral slippage was 47.8% (range 30-65%), and postoperatively it was 18.5% (range 15-25%). In patients in whom PLIF was performed, the average changes in economic and functional score were 1.21 and 1.36, respectively, and the average preoperative vertebral slippage was 43.5% (range 30-55%) compared with 20% (range 15-25%) postoperatively.

CONCLUSIONS

The use of a segmental pedicle screw fixation with the SOCON-SRI system successfully combines the goal of solid fusion with the requirements of nerve root decompression. When the two fusion techniques were compared, an overall superior reliability and resistance of the systems was associated with the PLIF procedure (p = 0.04) but clinical outcomes did not differ greatly (p < 0.05).

Improved lumbar vertebral interbody fusion using rhOP-1: a comparison of autogenous bone graft, bovine hydroxylapatite (Bio-Oss), and BMP-7 (rhOP-1) in sheep

STUDY DESIGN

After disc removal and monosegmental instrumentation of the sheep lumbar spine, interbody fusion was compared for 6 months after administration of autogenous bone graft, hydroxylapatite, or rhOP-1.

OBJECTIVE

To determine whether the use of rhOP-1 or hydroxylapatite would improve on the intercorporal fusion achieved by autologous bone grafting.

SUMMARY OF BACKGROUND DATA

Spinal fusion often fails or shows loss of correction despite large-scale conventional techniques using posterior and anterior access. Also, additional operations to obtain bone grafts are required, which increase morbidity and strain for the patient, but do not always provide bone with sufficient primary stability and high osteogenic potential.

METHODS

Vertebral fusion quality was examined by plain radiograph at 4-week intervals, by scintigraphy at 3 and 6 months, and by computed tomography scan, magnetic resonance imaging, biomechanical testing, and histologic evaluation.

RESULTS

All examination methods demonstrated superior fusion after administration of rhOP-1, with radiologic fusion apparent at 4 months. Autologous bone grafts eventually produced bony healing in most cases, albeit of a lower quality than with rhOP-1. Hydroxylapatite use led only to the formation of a tight pseudarthrosis.

CONCLUSIONS

The results indicate that rhOP-1 use is an appropriate method for improving interbody fusion in the sheep spine. In addition to offering the potential for improved bone healing, rhOP-1 use may permit less invasive surgery such as transpedicular fusion and the use of cages.

Intradiscal electrothermal treatment for chronic discogenic low back pain: a prospective outcome study with minimum 1-year follow-up

STUDY DESIGN

Prospective case series.

OBJECTIVE

To determine the outcome of patients with chronic low back pain whose symptoms did not improve with aggressive nonoperative care and who chose (intradiscal electrothermal anuloplasty) IDET as an alternative to chronic pain management or interbody fusion surgery.

SUMMARY OF BACKGROUND DATA

Patients with unremitting chronic discogenic low back pain are faced with the choice of long-term pain management or fusion surgery. Intradiscal electrothermal anuloplasty (IDET) was developed as an alternative minimally invasive treatment.

MATERIALS AND METHODS

Sixty-two patients from the author's practice who had chronic low back pain unresponsive to nonoperative care, no evidence of compressive radiculopathy, and concordant pain reproduction at one or more disc levels on provocative discography were enrolled in the study. Visual analog scale (VAS) pain scores and Short Form (SF)-36 Health Status Questionnaire Physical Function subscale and SF-36 Bodily Pain subscale scores were assessed at baseline and at least 1 year later.

RESULTS

Mean follow-up was 16 months, and mean preoperative duration of symptoms was 60 months. Baseline and follow-up outcome measures demonstrated a mean change in VAS score of 3.0 (P < 0.001), mean change in SF-36 physical function of 20 (P < 0.001), and mean change in SF-36 bodily pain of 17 (P < 0.001). Symptoms improved in 44 (71%) of 62 of the study group on the SF-36 physical function subscale, in 46 (74%) of 62 on the SF-36 Bodily Pain subscale, and in 44 (71%) of 62 on the VAS scores. Twelve (19%) of 62 of the patients did not show improvement on any scale.

CONCLUSION

A cohort of patients with chronic unremitting low back pain of discogenic origin whose symptoms had failed to improve with aggressive nonoperative care demonstrated a statistically significant and clinically meaningful improvement on the SF-36 and the VAS scores at a minimum follow-up of 1 year after IDET. The positive results should be validated with placebo-controlled randomized trials and studies that compare IDET with alternative treatments.-

Management of chronic discogenic low back pain with a thermal intradiscal catheter. A preliminary report

STUDY DESIGN

A prospective nonrandomized clinical trial.

OBJECTIVE

To determine the outcome in a group of patients with chronic, function-limiting low back pain who met the criteria for interbody fusion surgery, but were instead treated with an intradiscal thermal catheter (SpineCath, Oratec Interventions, Inc., Menlo Park, CA).

SUMMARY OF BACKGROUND DATA

This study represents the first reported trial of treatment for chronic discogenic low back pain with a novel thermal intradiscal catheter.

METHODS

The authors evaluated 25 consecutive patients. The minimum duration of nonoperative care with the authors was 6 months. The visual analog pain scores, sitting tolerance times, and SF-36 summary scores were tabulated.

RESULTS

The mean follow-up period was 7 months, and the mean duration of symptoms 58.5 months. Of the 25 patients, 20 (80%) reported a reduction of at least 2 points in visual analog pain scores, and 18 (72%) reported an improvement in sitting tolerance as well as reduction or discontinuance of analgesic medication. Visual analog pain scores improved by a mean reduction of 3.74, a 51% change (P = 0.0001). On the SF-36 physical function subscale, 72% of the patients improved by a mean increase of 15 points (P = 0.001), a mean change of 38%, and by a mean increase of 14 points on the bodily pain subscale (P = 0.004), a mean change of 48%.

CONCLUSIONS

A statistically significant improvement in functional outcome was obtained in patients with chronic discogenic low back pain treated thermally by the SpineCath.

Does spinal instrumentation influence the healing process of posterolateral spinal fusion? An in vivo animal model

STUDY DESIGN

An in vivo sheep model was used to investigate the effect of spinal instrumentation on the healing process of posterolateral spinal fusion.

OBJECTIVES

To examine the role of spinal instrumentation during the healing process of posterolateral fusion.

SUMMARY OF BACKGROUND DATA

In long bone fractures, internal fixation improves the union rate but does not accelerate the healing process. Spinal instrumentation also improves the fusion rate in spinal arthrodesis. However, it remains unclear whether the use of spinal instrumentation expedites the healing process of spinal fusion.

METHODS

Sixteen sheep underwent posterolateral spinal arthrodeses at L2-L3 and L4-L5 using equal amounts of autologous bone. One of those segments was selected randomly to be augmented with transpedicular screw fixation (Texas Scottish Rite Hospital spinal system). The animals were killed at 8 weeks or 16 weeks after surgery. Fusion status was evaluated by biomechanical testing, manual palpation, plain radiography, computed tomography, and histology.

RESULTS

Instrumented fusion segments demonstrated significantly higher stiffness than did uninstrumented fusions at 8 weeks after surgery. Radiographic assessment and manual palpation showed that the use of spinal instrumentation improved the fusion rate at 8 weeks (47% versus 38% in radiographs, 86% versus 57% in manual palpation). Histologically, the instrumented fusions consisted of more woven bone than the uninstrumented fusions at 8 weeks after surgery. The 16-week-old fusion mass was diagnosed biomechanically, radiographically, and histologically as solid, regardless of pedicle screw augmentation.

CONCLUSION

The current study's results demonstrated that spinal instrumentation creates a stable mechanical environment to enhance the early bone healing of spinal fusion.

A randomized prospective study of posterolateral lumbar fusion. Outcomes with and without pedicle screw instrumentation

STUDY DESIGN

A prospective evaluation of the clinical and radiographic outcomes of 71 patients who underwent lumbar fusion, with or without transpedicular instrumentation. The patients completed a questionnaire that determined pain relief, medication use, return to work, and overall satisfaction with surgery.

OBJECTIVES

To explore the effect, if any, of instrumentation on the outcome of lumbar fusion surgery, according to reports of the patients, and whether there is a correlation between the radiographic determination of a solid fusion and the same patient-reported outcome.

SUMMARY OF BACKGROUND DATA

The literature on this topic reports pseudarthrosis rates from 0% to 57% and good to excellent results from 56% to 95%. These studies provide no clear-cut recommendations concerning the effect of added lumbar instrumentation on patient-reported outcome in a prospective manner using concurrent control subjects.

METHODS

The patients were randomized to groups with and without instrumentation after deciding to undergo a lumbar fusion and consenting to enter the study. Radiographs were obtained and questionnaires filled out at 6 weeks, 6 months, 1 year, and 2 years after surgery.

RESULTS

There was no statistical difference in patient-reported outcome between the two groups. There was a slight nonsignificant trend toward increased radiographic fusion rate in the group with instrumentation that did not correlate with an increased patient-reported improvement rate.

CONCLUSIONS

These results do not provide data that indicate a benefit in outcome from added instrumentation in elective lumbar fusions.

Thoracic and lumbar fusions for degenerative disorders: rationale for selecting the appropriate fusion techniques

This article defines the indications for spinal fusion surgery based on the current literature as well as a rationale for selecting the appropriate spinal fusion techniques for the more common degenerative lumbar and thoracic conditions.

The Bagby and Kuslich method of lumbar interbody fusion. History, techniques, and 2-year follow-up results of a United States prospective, multicenter trial

STUDY DESIGN

A prospective, multicenter trial of the Bagby and Kuslich method of lumbar interbody stabilization for chronic discogenic low back pain, with follow-up evaluation at 3 months, 6 months, and yearly thereafter, with independent radiographic analysis.

OBJECTIVES

To report the history of development, the surgical techniques, and results of the Bagby and Kuslich method when used to manage discogenic pain of the lumbar spine in humans.

SUMMARY OF BACKGROUND DATA

Disabling chronic low back pain frequently is resistant to conservative management. The "Bagby Basket" effectively has fused the equine and baboon spine. The results of biomechanical and animal studies performed over the last 20 years have suggested that a similar but improved design--the Bagby and Kuslich device--would be useful in stabilizing the human spine.

METHODS

From 1992 to 1995, 947 patients with chronic discogenic low back pain were treated by Bagby and Kuslich interbody fusion in a strict, multicenter, prospective clinical trial by using either the open anterior or open posterior approach. The study involved 42 surgeons at 19 medical centers. The authors of the current report analyzed the fusion rates, pain relief, functional status, and complications occurring in patients who underwent long-term follow-up observation.

RESULTS

The Bagby and Kuslich method is safe and effective when compared with methods described in previous reports of posterior and anterior lumbar interbody arthrodesis performed by using bone graft alone. Fusion occurred in 91% of patients at 24 months after surgery, and pain was eliminated or reduced in 84%. Function was improved in 91%. There were no device-related deaths, cases of major paralyses, device failures, or deep infections.

CONCLUSIONS

Carefully selected middle-aged patients with chronic low back pain secondary to degenerative disc disease can be treated effectively and safely by skilled surgeons using the Bagby and Kuslich device for one- and two-level interbody fusion.

The effects of rigid spinal instrumentation and solid bony fusion on spinal kinematics. A posterolateral spinal arthrodesis model

STUDY DESIGN

Spinal kinematics after the implementation of rigid spinal instrumentation or the achievement of a solid fusion was studied using a sheep posterolateral spinal arthrodesis model.

OBJECTIVE

To investigate the effects of rigid spinal instrumentation or solid fusion on spinal kinematic parameters.

SUMMARY OF BACKGROUND DATA

Numerous studies have attempted to define spinal instability in terms of kinematics. Recent in vitro studies have documented the neutral zone, or a measure of spinal laxity, as more sensitive to spinal instability than the range of motion.

METHODS

Seven skeletally mature sheep underwent a single-level posterolateral lumbar arthrodesis using autologous bone graft augmented with transpedicular screw fixation. The animals were killed 4 months after surgery. The identical surgical procedures were performed in seven sheep cadaveric spines, which served as acute postoperative controls. Each functional spinal unit was tested biomechanically before and after hardware removal. The experimental control groups consisted of destabilized spines and spines that underwent transpedicular screw fixation alone, whereas the fusion groups included spines that underwent posterolateral fusion alone or posterolateral fusion with instrumentation.

RESULTS

Rigid instrumentation and solid fusion significantly decreased the neutral zone and range of motion in all testing modes. In axial rotation and lateral bending, solid fusion reduced the range of motion significantly more than transpedicular screw fixation alone. However, in all testing modes, the neutral zones showed no statistical difference between transpedicular screw fixation alone and fusion groups.

CONCLUSIONS

The range of motion was an equivalent or better indicator of fixation or fusion stability compared with the neutral zone. Moreover, the immediate postoperative fixation stability, even if using transpedicular screw fixation, was less than the stability present after a solid fusion.

1997 Volvo Award winner in clinical studies. The effect of pedicle screw instrumentation on functional outcome and fusion rates in posterolateral lumbar spinal fusion: a prospective, randomized clinical study

STUDY DESIGN

A prospective randomized clinical study.

OBJECTIVES

To evaluate supplementary pedicle screw fixation (Cotrel-Dubousset) in posterolateral lumbar spinal fusion.

SUMMARY OF BACKGROUND DATA

The rationale behind lumbar fusion is to eliminate pathologic motion to relieve pain. To improve fusion rates and to allow reduction, a rigid transpedicular screw fixation may be beneficial, but the positive effect of this may be counter-balanced by an increase in complications.

METHODS

The inclusion criteria were severe, chronic low back pain from spondylolisthesis Grades 1 and 2 or from primary or secondary degenerative segmental instability. One hundred thirty patients were randomly allocated to receive no instrumentation (n = 66) or Cotrel-Dubousset instrumentation (n = 64) in posterolateral lumbar fusion. Variables were registered at the time of surgery and at 1 and 2 years after surgery.

RESULTS

Follow-up was achieved in 97.7% of the patients. Fusion rates deduced from plain radiographs were not significantly different between instrumented and noninstrumented groups. The functional outcome assessed by the Dallas Pain Questionnaire improved significantly in both groups, and there were no significant differences in results between the two groups, except for significantly better (P < 0.06) functional outcome in relation to daily activities in the instrumented group when neural decompression had been performed. The global patients' satisfaction was 82% in the instrumented group versus 74% in the noninstrumented group (not significant). Fixation of instrumentation increased operation time, blood loss, and early reoperation rate significantly. Patients experienced only a few minor postoperative complications; none were major. Two infections appeared in the Cotrel-Dubousset group. Significant symptoms from misplacement of pedicle screws were seen in 4.8% of the instrumented patients.

CONCLUSIONS

Lumbar posterolateral fusion with pedicle screw fixation increases the operation time, blood loss, and reoperation rate, and leads to a significant risk of nerve injury. The functional outcome improves significantly with high patient satisfaction, with or without instrumentation. No significant differences were observed between the two groups in functional outcome and fusion rate. The only gain in functional outcome from instrumentation was found in the daily activity category in patients with supplementary neural decompression. The results of this study do not justify the general use of pedicle screw fixation alone as an adjunct to posterolateral lumbar fusion.

Survivorship analysis of DKS instrumentation in the treatment of spondylolisthesis

This retrospective study analyzed the survivorship of DKS instrumentation and the clinical outcomes in 185 patients with spondylolisthesis. These patients were treated with Zielke DKS instrumentation for a mean followup period of 3.5 years. Eight (4.3%) patients had late removal of implants, 25 (14%) had rod breakage, three (1.7%) had screw breakage, and 16 (8.7%) had nut loosening. The survivor rate of DKS instrumentation was 96% within 3 months after operation, 80% at 2 years, and 61% at 5 years after surgery. One hundred sixty-three (88%) patients had solid posterolateral fusion, and 167 (90%) patients had good to excellent results. Adjacent instability developed in 18 (9.7%) patients. Although Zielke DKS instrumentation has a smaller rod and relatively insecure locking system between the rod and screw, it is an effective implant for the treatment of spondylolisthesis.

Threaded fusion cages for lumbar interbody fusions. An economic comparison with 360 degrees fusions

STUDY DESIGN

This study compared the surgical and hospitalization costs, operating times, and blood loss attributable to lumbar interbody fusions at one and two lumbar levels by the use of two device systems: 1) the Ray Threaded Fusion Cage, and 2) an anteroposterior interbody technique with pedicle screw and rod stabilization (360 degrees fusion). The clinical efficacy and complication rate of each method were similar.

OBJECTIVES

Data were analyzed to compare the newer threaded fusion cage method with the well established 360 degrees technique.

SUMMARY OF BACKGROUND DATA

Interbody bone grafts are a proven concept to obtain solid spinal fusions. A variety of mechanical means are used to stabilize the graft material during the fusion growth and have been shown to be important in facilitating both the rate and ultimate quality of the fusion.

METHODS

In a cohort of 50 prospectively selected patients having severe, disabling back pain with discal degeneration, 25 received Ray Threaded Fusion Cages and 25 had anteroposterior interbody fusion procedures using pedicle screws (360 degrees technique) over the period 1991 to 1995. All implants were performed by the same surgeon in the same hospital. All fusions were judged solid by established radiologic criteria. Cost comparisons were made from pertinent medical records using inflation-corrected 1995 U.S. dollars.

RESULTS

The average combined (surgeon, hospital, anesthesiologist) costs attributed to one-level threaded fusion cage procedures were $25,171, and $41,813 to equivalent 360 degrees procedures, a difference of 40% or $16,642. Costs for two-level cases were $33,113 and $47,320, respectively, differing by 30% or $14,207. The average saving through preferential use of the threaded fusion cage was $14,639 per case, or $365,966 for the 25-patient subgroup. Ten of the 360 degrees fusion cases required later instrumentation removal, adding $8,635 to the costs of each such case, a final difference of $22,889 compared with an equivalent threaded fusion cage case. The actual collections on threaded fusion cage cases were 81% of billed costs and the actual collections on 360 degrees cases were 73% of billed costs.

CONCLUSIONS

Assuming that the fusion success, clinical outcome, and complication rates are sufficiently similar between these two techniques, the striking improvement in overall surgical and hospitalization costs, surgical time, and blood losses provided by the threaded fusion cage technique can be major decision points in method selection. Further, no threaded fusion cage case having a normal adjacent level preoperatively developed a fusion transition syndrome over a followup period from 3 to 29 months (averaging 24 months) that required a second fusion procedure, and no cage had to be removed because of instrumentation-associated pain, although each of these problems are known to occur in at lease 10% of pedicle screw implants. Ten of the 25 (40%) 360 degrees fusion cases in this study required subsequent instrumentation removal, although no case has required adjacent level surgery for transition syndrome.

Posterolateral lumbar fusion using facet joint fixation with biodegradable rods: a pilot study

Roentgen stereophotogrammetric analysis (RSA) was used to assess whether there is a potential for biodegradable rods crossing the denuded facet joints to increase the stability and healing rate of lumbar posterolateral fusions. Eleven consecutive patients with lumbosacral disc/facet joint degeneration had a posterolateral fusion augmented with 2- or 3.2-mm biodegradable rods passing perpendicularly through the center of the denuded facet joints. The patients were followed-up with RSA in supine and erect positions monthly from the 2nd to the 6th postoperative month, and again 1 year postoperatively. All seven L5-S1 fusions healed. Four cases were stable as defined by RSA within 3 months, two within 6 months, and one within 1 year. One L4-S1 fusion could not be evaluated by RSA. None of the remaining three L4-S1 fusions fully healed. In all three cases 1- to 3-mm intervertebral translations remained at 1 year. None of the 11 fusions showed any radiographic signs of osteolysis around the biodegradable rods. The promising results of this pilot study indicate that posterolateral L5-S1 fusion augmented with transarticular biodegradable rods crossing the denuded facet joints may yield rapid intervertebral stabilization and a high healing rate without any adverse rod effects. This may be due to enhanced initial fusion stabilization and/or increased ossification induced by the rods.