Glenn R. Buttermann

Operative compared with nonoperative treatment of a thoracolumbar burst fracture without neurological deficit: a prospective randomized study with follow-up at sixteen to twenty-two years.

Background: To our knowledge, a prospective, randomized study comparing operative and nonoperative treatment of a thoracolumbar burst fracture in patients without a neurological deficit has never been performed. Our hypothesis was that operative treatment would lead to superior long-term clinical outcomes. Methods: From 1994 to 1998, forty-seven consecutive patients (thirty-two men and fifteen women) with a stable thoracolumbar burst fracture and no neurological deficit were randomized to one of two treatment groups: operative (posterior or anterior arthrodesis and instrumentation) or nonoperative treatment (application of a body cast or orthosis). Radiographs and computed tomography scans were analyzed for sagittal alignment and canal compromise. All patients completed a questionnaire to assess any disability they may have had before the injury, and they indicated the degree of pain at the time of presentation with use of a visual analog scale. The average duration of follow-up was forty-four months (minimum, twenty-four months). After treatment, patients indicated the degree of pain with use of the visual analog scale and they completed the Roland and Morris disability questionnaire, the Oswestry back-pain questionnaire, and the Short Form-36 (SF-36) health survey. Results: In the operative group (twenty-four patients), the average fracture kyphosis was 10.1° at the time of admission and 13° at the final follow-up evaluation. The average canal compromise was 39% on admission, and it improved to 22% at the final follow-up examination. In the nonoperative group (twenty-three patients), the average kyphosis was 11.3° at the time of admission and 13.8° at the final follow-up examination after treatment. The average canal compromise was 34% at the time of admission and improved to 19% at the final follow-up examination. On the basis of the numbers available, no significant difference was found between the two groups with respect to return to work. The average pain scores at the time of the latest follow-up were similar for both groups. The preinjury scores were similar for both groups; however, at the time of the final follow-up, those who were treated nonoperatively reported less disability. Final scores on the SF-36 and Oswestry questionnaires were similar for the two groups, although certain trends favored those treated without surgery. Complications were more frequent in the operative group. Conclusion: We found that operative treatment of patients with a stable thoracolumbar burst fracture and normal findings on the neurological examination provided no major long-term advantage compared with nonoperative treatment. Level of Evidence: Therapeutic study, Level II-2 (poor-quality randomized controlled trial [e.g., <80% follow-up]). See Instructions to Authors for a complete description of levels of evidence.

Treatment Of Lumbar Disc Herniation: Epidural Steroid Injection Compared With Discectomy

BACKGROUND Epidural steroid injection is a low-risk alternative to surgical intervention in the treatment of lumbar disc herniation. The objective of this study was to determine the efficacy of epidural steroid injection in the treatment of patients with a large, symptomatic lumbar herniated nucleus pulposus who are surgical candidates. METHODS One hundred and sixty-nine patients with a large herniation of the lumbar nucleus pulposus (a herniation of >25% of the cross-sectional area of the spinal canal) were followed over a three-year period. One hundred patients who had no improvement after a minimum of six weeks of noninvasive treatment were enrolled in a prospective, non-blinded study and were randomly assigned to receive either epidural steroid injection or discectomy. Evaluation was performed with the use of outcomes scales and neurological examination. RESULTS Patients who had undergone discectomy had the most rapid decrease in symptoms, with 92% to 98% of the patients reporting that the treatment had been successful over the various follow-up periods. Only 42% to 56% of the fifty patients who had undergone the epidural steroid injection reported that the treatment had been effective. Those who did not obtain relief from the injection had a subsequent discectomy, and their outcomes did not appear to have been adversely affected by the delay in surgery resulting from the trial of epidural steroid injection. CONCLUSIONS Epidural steroid injection was not as effective as discectomy with regard to reducing symptoms and disability associated with a large herniation of the lumbar disc. However, epidural steroid injection did have a role: it was found to be effective for up to three years by nearly one-half of the patients who had not had improvement with six or more weeks of noninvasive care.

Experimental measurement of ligament force, facet force, and segment motion in the human lumbar spine

Facet forces, longitudinal ligament loads, and vertebral body motion were experimentally measured in five fresh human lumbar spine segments, L1-L2. Strain gages on the bone surface were used to quantify facet loads. Buckle transducers were used to measure anterior and posterior longitudinal ligament loads. The three-dimensional motion of the motion segment was measured with an instrumented spatial linkage. The facets were found to carry no load in flexion, large loads during extension (205 N at a 10 Nm moment and a 190 N axial load), torsion (65 N at a 10 Nm moment and a 150 N axial load), and lateral bending (78 N at a 3 Nm moment and a 160 N axial load). The facet contact site on the inferior articular process of L1 was found to move inferiorly to a position of tip impingement near the lamina as extension moments increased. Impingement occurred in the range of 4-6 Nm extension. The posterior and anterior longitudinal ligaments were predominantly loaded in flexion and extension, respectively. No ligament loads occurred in lateral bending and torsion. A 1 cm strip of the anterior longitudinal ligament carried loads up to 130 N at the largest extension moment of 11.4 Nm. The posterior longitudinal ligament had a 60 N load at the largest flexion moment of 7.1 Nm. There was no pre-load in the ligament detectable with the buckle transducers (> 4 N). The facets and ligaments began carrying load immediately with applied load, without a lax region. The experimental technique developed and used provides a good tool for obtaining simultaneous facet joint loads, ligament loads, and vertebral body motion without altering the motion segment.

Revision of Failed Lumbar Fusions: A Comparison of Anterior Autograft and Allograft

Study Design. The radiographic and clinical results of two different anterior structural grafts were compared in 38 patients who had combined anterior‐posterior revision surgery for failed lumbar fusion. Objectives. Failed lumbar fusion surgery, such as pseudarthrosis or flatback deformity, may result in disabling pain. The optimum revision technique has yet to be defined. The authors of the current study sought to determine which of two different types of anterior graft yields the best results. Summary of Background Data. Posterior procedures for revision of a failed lumbar fusion have not yielded reliably successful results. A combined anterior‐posterior approach may be effective in restoring sagittal balance and enhancing fusion rates. Recent studies have shown femoral ring allografts to be effective in lumbar fusion revision, but no studies have compared these with other types of structural grafts. Methods. Thirty‐eight patients with pseudarthrosis were treated with combined anterior‐posterior lumbar spine fusion using either femoral ring allografts (26 patients) or tricortical iliac autografts (12 patients). Radiographic follow‐up examination and retrospective patient self‐assessment questionnaires were used to evaluate outcomes. Results were assessed by independent reviewers after a mean follow‐up period of 35 months. Results. Radiographic follow‐up examination revealed acceptably low pseudarthrosis rates for structural autografts (0%) and allografts (6%). The questionnaires revealed significant improvement in pain for both groups. Allograft patients showed greater improvement in function, less pain medication usage, and higher overall success rates (83%) than autograft patients (64%). Conclusions. Femoral ring allografts are as effective, clinically and radiographically, as tricortical iliac autografts when used as an anterior structural element in revision lumbar spine fusion in patients who have undergone multiple surgical procedures for pseudarthrosis or flatback deformity. The slightly greater improvement for the allograft group needs to be confirmed in a larger study.

The use of bone allografts in the spine.

Bone allografts are commonly used in spinal surgery. Structural allografts placed anteriorly in the spine may be used as interbody grafts or as strut grafts spanning multiple segments. Posterior allografts are used to supplement autologous bone for spinal fusions in patients who lack sufficient host bone and to avoid significant donor site morbidity. In this paper the authors review their experience with allograft bone in spine surgery and the results reported in the literature. In the anterior cervical spine, interbody allografts have been used most successfully in single-level fusions. For thoracolumbar deformity, posterior allograft with instrumentation gives satisfactory results in pediatric patients but yields inferior results in adults unless it is combined with an anterior fusion. Fresh-frozen allograft bone has been shown to have higher fusion rates than freeze-dried allograft; ethylene oxide-sterilized allograft has shown uniformly poor results. Structural allografts have been useful for thoracolumbar deformity in both interbody and strut-grafting procedures. In the lumbar spine, allograft has a limited role in posterolateral fusion. For anterior interbody fusions, structural allografts, such as femoral ring allografts, have been used successfully to maintain intervertebral distraction, despite delayed incorporation. Successful use of allograft bone in the spine is dependent on the type of allograft bone used, its anatomic site of fusion, and the age of the patient.

Lumbar Fusion Results Related to Diagnosis

Study Design. Pain outcome and functional outcome after primary lumbar fusion surgery were determined by a self‐assessment questionnaire. The responses were correlated with various clinical parameters. Objectives. To determine the result of fusion surgery among patients in various diagnostic groups using semiquantitative outcome scales. Summary of Background Data. Most previous studies on the results of primary lumbar fusion have reported the presence of pain, but few have addressed function outcomes. Results of a literature review were inconclusive as to whether a patients diagnosis is a predictor of improved results. Methods. During the 3‐year period from 1988 to 1990, 165 patients underwent a primary lumbar fusion procedure. They had a chart and radiograph review and were categorized into five major diagnostic groups: 1) pediatric, 2) grade I‐II spondylolisthesis (low‐slip), 3) grade III‐IV spondylolisthesis (high‐slip), 4) degenerative disc disease, and 5) postdiscectomy. At a follow‐up period of 5 years (mean) after the fusion, patients were mailed a questionnaire in which they described their pain and functional status before and after their lumbar fusion surgery. Questionnaires were returned by 92% of the patients. The questionnaire scores, complications, and revision procedures were grouped by patient diagnosis and analyzed. Results. Patient satisfaction with the results of primary lumbar fusion ranged from 69% (for the postdiscectomy group) to 100% (for the pediatric and high‐slip groups). For all diagnostic groups, lumbar fusion resulted in a significant decrease in back pain and leg pain (visual analog scale), which was maintained throughout the follow‐up period. For back pain, the pediatric and high‐slip groups showed significantly more improvement than the degenerative disc disease or postdiscectomy groups. Leg pain among patients in the pediatric and high‐slip groups was significantly more improved than leg pain among patients in the low‐slip, degenerative disc disease, or postdiscectomy groups. There was no deterioration of pain scores during the follow‐up period. After fusion, all groups had a significant decrease in Oswestry disability scores; patients in the pediatric and high‐slip group had significantly more improvement than patients in the degenerative disc disease or postdiscectomy groups. High‐ and low‐slip groups had a significant improvement in their pain drawing score. Medication use was substantially reduced in all groups. After fusion, a lack of improvement in back pain score or disability score was significantly correlated with pseudarthrosis. Conclusions. The outcome of primary lumbar fusion surgery was decreased pain and increased function for the majority of patients in all five diagnostic categories. The amount of improvement varied by diagnostic group. Patients with developmental conditions showed greater improvement than patients with degenerative conditions.

Vertebral body MRI related to lumbar fusion results

The evaluation of continued pain after a technically successful posterolateral lumbar spine fusion is often challenging. Although the intervertebral disc is often a source of low back pain, abnormal endplates may also be a focus of pain, and possibly a source of continued pain after a posterolateral fusion. MRI allows noninvasive evaluation for disc degeneration, as well as for abnormal endplates and adjacent vertebral body marrow. Previous studies have found inflammatory marrow changes, adjacent to abnormal endplates, associated with disc degeneration in low back pain patients. In this study, preoperative MRI scans in 89 posterolateral lumbar fusion patients were reviewed, by an independent radiologist, to determine whether vertebral body marrow changes adjacent to the endplates were related to contined pain. Independent chart review and follow-up telephone interview of all patients at a 4-year follow-up (mean) formed the basis for the clinical results. Vertebral body MRI signals consistent with inflammatory or fatty changes were found in 38% of patients, and always occurred adjacent to a degenerated disc. Inflammatory MRI vertebral body changes were significantly related to continued low back pain atP = 0.03. We conclude that posterolateral lumbar fusion has a less predictable result for the subset of degenerative disc patients with abnormal endplates and associated marrow inflammation. More research is needed to determine the biological and biomechanical effects of a posterolateral fusion upon the endplate within the fused segments. If indeed further study supports the hypothesis that abnormal endplates associated with inflammation are a source of pain, then treating the endplates directly by anterior fusion may be a preferred treatment for this subset of degenerative patients.

In vitro analysis of anterior and posterior fixation in an experimental unstable burst fracture model.

Study Design A biomechanical comparison of fixation constructs in an experimental fracture model. Objective To determine the relative postoperative stability of anterior graft and plating with that of posterior or combined fixation constructs in an unstable thoracolumbar burst fracture model. Summary of Background Data Several treatment modalities have been proposed for unstable thoracolumbar burst fractures, but the optimal technique is unclear. Previous cadaveric biomechanical studies in unstable burst fracture models have not considered the commonly used posterior (interpedicular) and anterior (plate) constructs. Methods Nine human spine segments (T11-L3) were potted in epoxy and scanned using dual energy x-ray absorptiometry and computed tomography. Intact specimens had baseline flexibility testing. Unstable L1 burst fractures as verified by computed tomography were created using an impulse load and posterior surgical osteoligamentous destabilization (ie, transection of the lamina, interspinous ligaments, facet capsules, and ligamentum flavum). Specimens were instrumented posteriorly with pedicle screws and rods and tested to 6 Nm in flexion-extension, lateral bending, and torsion. Corpectomy and strut grafting were then performed, and testing was repeated in varying order with posterior fixation, anterior plating and circumferential fixation. Range of motion (ROM) and neutral zone was calculated for each test and fixation groups were compared using analysis of variance. Results All specimens had AO B1.2 (unstable burst) fractures. Mean ROM for posterior-only constructs was significantly less than that of the intact in lateral bending, flexion, and extension (P<0.001). Anterior-only constructs after corpectomy and strut grafting generally resulted in a smaller ROM versus intact in flexion (NS: P=0.1) and lateral bending (P<0.001). In contrast, all anterior-only and posterior constructs had greater ROM than intact in torsion (all at P<0.05). Circumferential fixation resulted in statistically smaller ROM compared with all other constructs (P≤0.04), and reached that of the intact specimen in torsion. Increased ROM was correlated with greater fracture comminution for posterior-only fixation (P<0.05), and was weakly correlated with lower dual energy x-ray absorptiometry score (R2=0.3) for anterior-only fixation. Conclusions Circumferential instrumentation provided the most rigid fixation, followed by posterior fixation with anterior strut grafting, posterior fixation alone, and by anterior fixation with strut grafting. These results were dependent on bone quality and the comminution severity of the fracture. These results should aid surgical decision making in addition to other factors in the overall clinical situation.

An Experimental Method for Measuring Force on the Spinal Facet Joint: Description and Application of the Method

A technique is described for measuring load magnitude and resultant load contact location in the facet joint in response to applied loads and moments, and the technique applied to the canine lumbar spine motion segment. Due to the cantilever beam geometry of the cranial articular process, facet joint loads result in surface strains on the lateral aspect of the cranial articular process. Strains were quantified by four strain gages cemented to the bony surface of the process. Strain measured at any one gage depended on the loading site on the articular surface of the caudal facet and on the magnitude of the facet load. Determination of facet loads during in vitro motion segment testing required calibration of the strains to known loads of various magnitudes applied to multiple sites on the caudal facet. The technique is described in detail, including placement of the strain gages. There is good repeatability of strains to applied facet loads and the strains appear independent of load distribution area. Error in the technique depends on the location of the applied facet loads, but is only significant in nonphysiologic locations. The technique was validated by two independent methods in axial torsion. Application of the technique to five in vitro canine L2-3 motion segments testing resulted in facet loads (in newtons, N) of 74+ / -23 N (mean + / -STD) in 2 newton-meter, Nm, extension, to unloaded in flexion. Lateral bending resulted in loads in the right facet of 40+ / -32 N for 1 Nm right lateral bending and 54+ / -29 N for 1 Nm left lateral bending. 4 Nm Torsion with and without 100 N axial compression resulted in facet loads of 92+ / -27 N and 69+ / -19 N, respectively. The technique is applicable to dynamic and in vivo studies.

Posterior augmentation of an anterior lumbar interbody fusion: minimally invasive fixation versus pedicle screws in vitro.

Study Design. An in vitro biomechanical comparison of four posterior fixation techniques in the setting of an anterior lumbar interbody fusion (ALIF). Objective. To compare the initial stability, in terms of range of motion and neutral zone, provided by pedicle screws, facet screws, translaminar facet screws, and H-graft plus interspinous cables in the presence of an anteriorly placed femoral ring allograft. Summary of Background Data. Pedicular fixation has been used to increase ALIF fusion rates but has also been linked with increased morbidity. Alternative posterior fixation options are available, but comprehensive biomechanical comparisons of these techniques do not exist. Methods. Twelve cadaveric lumbar motion segments were loaded to 5 Nm in unconstrained flexion-extension, lateral bending, and axial torsion. Specimens were tested intact, after ALIF, and after applying pedicle screws, translaminar screws, facet screws, and H-graft plus cables. The resulting neutral zones and ranges of motion were measured. Results. The mean (±SEM) range of motion for each construct in flexion-extension was as follows: intact: 6.39° (±0.47°); ALIF alone: 3.31° (±0.22°); (ALIF+) pedicle screws: 0.6° (±0.06°); facet screws: 0.75° (±0.12°); translaminar screws: 0.61° (±0.09°); and H-graft: 1.74° (±0.26°). Pedicle, translaminar facet, and facet screws significantly decreased range of motion and neutral zone compared to ALIF alone in flexion-extension, lateral bending, and axial torsion (all at P < 0.04, except translaminar screws in torsion neutral zone where P = 0.09). H-graft decreasedflexion-extension range of motion and neutral zone only (P < 0.01) and resulted in a significantly greater neutral zone than pedicle and facet screws in torsion and lateral bending neutral zones (P < 0.03). Conclusions. In the ALIF setting, facet screw and translaminar screw techniques, which may be associated with less morbidity than pedicle screws clinically, provided initial posterior stabilization similar to pedicular fixation in this in vitro study.