Use of a postoperative lumbar corset after lumbar spinal arthrodesis for degenerative conditions of the spine. A prospective randomized trial.

BACKGROUND: Lumbosacral corsets and braces have been used to treat a variety of spinal disorders. Although their use after lumbar arthrodesis for degenerative conditions has been reported, there is a lack of evidence on which to base guidelines on their use. The purpose of this study was to evaluate the effect of a postoperative corset on the outcome of lumbar arthrodesis. METHODS: A prospective randomized trial was performed in which patients who wore a postoperative lumbar corset for eight weeks full-time after a posterior lumbar arthrodesis for a degenerative spinal condition were compared with those who did not use a corset after such an operation. Ninety patients were randomized to one of the two treatments. A history was recorded and patients were assessed with a physical examination, radiographs, and functional outcome questionnaires (the Dallas Pain Questionnaire [DPQ] and the Short Form-36 [SF-36]) preoperatively and at one year and two years following the surgery. The primary outcome measure of the study was the DPQ, a disease-specific patient-derived functional measure of the spine, and secondary end points included the SF-36 scores, complications, rates of fusion as determined radiographically, and reoperation rates. RESULTS: Follow-up analysis was performed for seventy-two patients, thirty-seven randomized to the brace (experimental) group and thirty-five randomized to the control group. Regardless of the treatment method, the patients had substantial improvement in the disease-specific and general health measures by two years postoperatively. At two years, there was no difference in the DPQ category scores (the primary outcome parameter) of the two treatment groups. There was also no difference in the mean SF-36 component scores at two years. Postoperative complications occurred in 22% and 23% of patients in the experimental and control groups, respectively, and a subsequent lumbar spinal operation was performed in 19% and 14%, respectively. Seven patients (five in the experimental group and two in the control group) with radiographic evidence of nonunion underwent revision surgery. CONCLUSIONS: This study does not indicate a significant advantage or disadvantage to the use of a postoperative lumbar corset following spinal arthrodesis for degenerative conditions of the lumbar spine. LEVEL OF EVIDENCE: Therapeutic Level I. See Instructions to Authors for a complete description of levels of evidence.

Impact of smoking on the outcome of anterior cervical arthrodesis with interbody or strut-grafting.

BACKGROUND: An increased rate of pseudarthrosis has been documented following posterolateral lumbar spine grafting in patients who smoke. This same relationship has been assumed for anterior cervical interbody grafting, but to our knowledge it has never been proven. This study compared the long-term radiographic and clinical results of smokers and nonsmokers who had undergone arthrodesis with autogenous bone graft following multi-level anterior cervical decompression for the treatment of cervical radiculopathy or myelopathy, or both. METHODS: One hundred and ninety patients were followed clinically and radiographically for at least two years (range, two to fifteen years). Fifty-nine of the patients had corpectomy with strut-grafting, and 131 patients had multiple discectomies and interbody grafting. Fifty-five of the 190 patients had a history of active cigarette-smoking; fifteen of the fifty-five had corpectomy with strut-grafting, and forty had multilevel discectomies and interbody grafting. Internal fixation was not used in any patient. The reconstruction techniques and postoperative bracing regimen were similar between smokers and nonsmokers. Osseous union was judged on dynamic lateral radiographs made at least two years following surgery, and clinical outcomes were judged on the basis of pain level, medication usage, and daily activity level. RESULTS: Of the forty smokers who had undergone multilevel interbody grafting, twenty had a solid fusion at all levels, whereas sixty-nine of the ninety-one nonsmokers had solid fusion at all levels (p < 0.02; chi-square test). This difference was especially pronounced among patients who had had a two-level interbody grafting procedure (p < 0.002; chi-square test). With the numbers available, there was no difference in the rate of fusion between smokers (fourteen of fifteen) and nonsmokers (forty-one of forty-four) who had undergone corpectomy and strut-grafting, as 93% of both groups had a solid union. In addition, clinical outcomes were significantly worse among smokers when compared with nonsmokers (p < 0.03; rank-sum analysis). CONCLUSIONS: Smoking had a significant negative impact on healing and clinical recovery after multilevel anterior cervical decompression and fusion with autogenous interbody graft for radiculopathy or myelopathy. Since smoking had no apparent effect upon the healing of autogenous iliac-crest or fibular strut grafts, subtotal corpectomy and autogenous strut-grafting should be considered when a multilevel anterior cervical decompression and fusion is performed in patients who are unable or unwilling to stop smoking prior to surgical treatment.

Cervical spondylotic myelopathy: diagnosis and treatment.

The delineation of cervical spondylotic myelopathy as a clinical entity has improved with the development of high-quality cross-sectional neuroradiologic imaging. The natural history of this disorder is usually slow deterioration in a stepwise fashion, with worsening symptoms of gait abnormalities, weakness, sensory changes, and often pain. The diagnosis can usually be made on the basis of findings from the history, physical examination, and plain radiographs, but confirmation by magnetic resonance imaging or computed tomography and myelography is necessary. Minimal symptoms without hard evidence of gait disturbance or pathologic reflexes warrant nonoperative treatment, but patients with demonstrable myelopathy and spinal cord compression are candidates for operative intervention. Both anterior and posterior approaches have been utilized for surgical treatment of cervical myelopathy. Anterior decompression frequently requires corpectomy at one or more levels and strut grafting with bone from the ilium or fibula. Multilevel laminectomies were initially used for posterior decompression but now are either combined with fusion or replaced by laminoplasty. Any operative technique requires proper patient selection and demands adequate decompression of the canal to effect neurologic improvement. Perioperative complications can be devastating in this group of high-risk patients with cervical spondylotic myelopathy, but careful attention to detail, meticulous technique, and experience can result in excellent outcomes.

Anterior cervical decompression and arthrodesis for the treatment of cervical spondylotic myelopathy. Two to seventeen-year follow-up.

We reviewed the cases of 108 patients with cervical spondylotic myelopathy who had been managed with anterior decompression and arthrodesis at our institution. Operative treatment consisted of anterior discectomy, partial corpectomy, or subtotal corpectomy at one level or more, followed by placement of autogenous bone graft from the iliac crest or the fibula. At the latest follow-up examination, thirty-eight of the eighty-two patients who had had a preoperative gait abnormality had a normal gait, thirty-three had an improvement in gait, six had no change, four had improvement and later deterioration, and one had a worse gait abnormality. Of the eighty-seven patients who had had a preoperative motor deficit, fifty-four had complete recovery; twenty-six, partial recovery; six, no change; and one had a worse deficit. The average grade according to the system of Nurick improved from 2.4 preoperatively to 1.2 (range, 0.0 to 5.0) postoperatively. A pseudarthrosis developed in sixteen patients, thirteen of whom had had a multilevel discectomy. Only one of thirty-eight arthrodeses that had been performed with use of a fibular strut graft was followed by a non-union. An unsatisfactory outcome with respect to pain was significantly associated with pseudarthrosis (p < 0.001). The development of complications other than non-union was associated with a history of one previous operative procedure or more (p = 0.005). Recurrent myelopathy was rare, but when it occurred it was associated with a pseudarthrosis or stenosis at a new level. The strongest predictive factor for recovery from myelopathy was the severity of the myelopathy before the operative intervention--that is, better preoperative neurological function was associated with a better neurological outcome. Anterior decompression and arthrodesis with autogenous bone-grafting can be performed safely, and is associated with a high rate of neurological recovery, functional improvement, and pain relief, in patients who have cervical spondylotic myelopathy.

A kinematic study of the cervical spine before and after segmental arthrodesis.

STUDY DESIGN: The acute kinematic consequence of segmental arthrodesis in the cervical spine on the remaining open motion segments was studied in a cadaveric model. OBJECTIVES: To evaluate the distribution of motion across unfused cervical motion segments after a segmental arthrodesis. The applied load was determined as a function of arthrodesis length and level by using a fixed range of motion for the cervical spine (C2-T1). SUMMARY OF BACKGROUND DATA: An increased incidence of degenerative disease may exist at the levels immediately adjacent to a cervical arthrodesis as a result of alteration in biomechanical behavior at these levels. METHODS: One-, two-, and three-level fusions were simulated in multilevel ligamentous human cervical spines. Specimens were tested nondestructively through a 30 degrees range of sagittal plane rotation. Motion was recorded using three-dimensional stereophotogrammetry. Sagittal plane rotation of each motion segment in the fusion models was compared with the corresponding rotation in the unfused specimen. RESULTS: In the C2-C4 fusion, the increase in motion at C5-C6 was statistically less (P < 0.05) than the increase at C7-T1. In the C2-C5 fusion, the increase in motion at C5-C6 was statistically less (P < 0.05) than the increases at C6-C7 and C7-T1. For each of the five other fusion types tested, no statistical differences existed between the increases in sagittal rotation at any of the open motion segments. The bending moment necessary to produce 30 degrees of sagittal rotation increased nonlinearly as the number of motion segments fused increased. CONCLUSIONS: Under what was considered a realistic loading paradigm, sagittal plane rotation was not increased disproportionately at the motion segments immediately adjacent to a segmental arthrodesis in the cervical spine. The nonlinear rise in applied bending moment to achieve constant displacement was characteristic of the behavior of the ligaments and intervertebral discs throughout the spine as they underwent increasing deformation.

Three-level anterior cervical discectomy and fusion: radiographic and clinical results.

STUDY DESIGN: A retrospective study of 16 patients who underwent the modified Robinson anterior cervical discectomy and fusion at three operative levels. OBJECTIVES: To provide long-term follow-up data on the surgical success and patient outcome of three-level anterior cervical discectomies and fusions. SUMMARY OF BACKGROUND DATA: The success of arthrodesis for anterior cervical fusion depends on several factors, including the number of surgical levels. To the authors' knowledge, there are no long-term follow-up reports to describe the arthrodesis rate and outcome for patients having specifically three-level discectomy and fusion procedures. METHODS: Sixteen patients, with an average age of 59 years, were followed for an average of 37 months. All had an anterior discectomy, burring of the endplates, and placement of an autogenous tricortical iliac crest graft at three levels. All patients had follow-up office visits with examinations and radiographs. Radiographic union, postoperative pain relief, and neurologic recovery were evaluated. RESULTS: Only 9 (56%) of the 16 patients went on to achieve solid arthrodesis at all three levels. Of the seven patients with pseudarthrosis, two had severe pain and required revision; two had moderate pain and three no pain. Of the nine with the solid fusion, three had mild pain and six no pain, a statistically significant difference in comparing the two outcomes (P < 0.01). All patients with preoperative motor deficit recovered, but two patients in whom a pseudarthrosis had developed had limited improvement in function until the nonunion was surgically repaired. CONCLUSIONS: A three-level modified Robinson cervical discectomy and fusion results in an unacceptably high rate of pseudarthrosis. Although not all pseudarthroses are painful, these data suggest that those with a successful fusion have a better outcome. It is recommended that these patients undergo additional or alternative measures to achieve arthrodesis consistently.

Anterior cervical pseudarthrosis. Natural history and treatment.

STUDY DESIGN: A retrospective study of long-term clinical outcomes in 48 patients with pseudarthroses after anterior cervical discectomy and fusion. OBJECTIVES: To determine the natural history, risk factors, and treatment outcomes in a large population with documented pseudarthrosis after anterior cervical discectomy and fusion. SUMMARY OF BACKGROUND DATA: Recent reports suggest that pseudarthrosis after anterior cervical discectomy and fusion adversely affects clinical outcome. Little data regarding cervical pseudarthroses have been published, and conclusions have been drawn from reports with small patient populations and short-term follow-up periods. METHODS: Forty-eight patients with radiographically documented pseudarthrosis after anterior cervical discectomy and fusion were studied. Patients were examined and radiographs made at regular intervals (mean follow-up, 66 months). Clinical results were based on patients' assessment of pain, prescription drug use, activity level and Odom's criteria. Clinical outcomes in patients who underwent surgical repair of the pseudarthrosis are reported. RESULTS: Of the 48 patients, 32 (67%) with pseudarthroses were symptomatic at latest follow-up or at the time of further surgery. Of the 32 patients, 9 had a symptom-free period of at least 2 years after the anterior cervical discectomy and fusion before redeveloping cervical symptoms after a traumatic episode. Of 48 patients with pseudarthroses, 16 (33%) remained asymptomatic at a mean of 5.1 years after anterior cervical discectomy and fusion. A younger age at the time of anterior cervical discectomy and fusion increased the likelihood of the pseudarthrosis becoming symptomatic. After multiple level anterior cervical discectomy and fusion, the caudal-most operated level accounted for 82% of the pseudarthroses. Sixteen patients had an anterior repair of the pseudarthrosis, and fusion was achieved in 14. Six patients underwent posterior pseudarthrosis repair, and all healed. In patients in whom fusion was achieved with a second cervical operation, the results were excellent in 19 and good in 1. CONCLUSION: A pseudarthrosis after anterior cervical discectomy and fusion is frequently associated with a poor clinical outcome. Surgical repair of the pseudarthrosis with an anterior or posterior approach seems to have a high likelihood of a successful clinical outcome.

Ceramic anterior spinal fusion. Biologic and biomechanical comparison in a canine model.

STUDY DESIGN: Three types of porous ceramic bone graft substitutes were used for anterior interbody fusion in the canine thoracic spine. OBJECTIVES: To compare the biomechanical stiffness and histologic appearance of fused spinal segments using ceramic graft substitutes versus autogenous bone graft. SUMMARY OF BACKGROUND DATA: The relative success or failure of ceramic grafts is influenced by many variables, including the composition of the ceramic, location in the spine, stability, and the animal model used. METHODS: Four experimental groups were evaluated: autogenous tricortical iliac crest (n = 6); hydroxyapatite ceramic (Interpore-200; n = 6); biphasic (60 : 40) hydroxyapatite/tricalcium phosphate ceramic (Zimmer; n = 4); and calcium carbonate ceramic (Inoteb; n = 4). All dogs were killed 8 weeks after surgery. After postmortem removal of anterior spinal instrumentation, the spinal segments underwent nondestructive biomechanical testing and light microscopic histologic evaluation. RESULTS: Biomechanical testing showed that spines from the autogenous tricortical iliac crest group were statistically significantly stiffer in flexion, extension, left and right bending, and torsion than all ceramic groups. No differences in stiffnesses were observed among the three ceramic groups. Histologically, the autogenous tricortical iliac crest graft performed best, with osseous union at 10 of 12 interfaces. Of the ceramic grafts, hydroxyapatite/tricalcium phosphate and calcium carbonate demonstrated more consistent junction healing than the hydroxyapatite group, where four of 12 interfaces resulted in a nonunion. In the ceramic groups, a variable amount of revascularization and new bone was observed within the grafts. CONCLUSIONS: Autogenous iliac crest bone graft provides superior healing in this anterior spine fusion model. Additional investigation is needed before ceramic grafts can be considered satisfactory alternatives to anterior autogenous bone grafts.

The effects of internal fixation on calcium carbonate. Ceramic anterior spinal fusion in dogs.

STUDY DESIGN: An anterior interbody fusion was performed in the canine thoracic spine. Either calcium carbonate or autologous iliac crest bone graft was used to fill a surgically created spinal defect between T7 and T8. Some of the spines were stabilized intraoperatively with anterior instrumentation. Four experimental arthrodesis groups were studied: iliac crest bone graft with or without instrumentation and ceramic with or without instrumentation. OBJECTIVE: To evaluate the effects of internal fixation on an anterior interbody fusion using calcium carbonate ceramic, and to compare this with autologous iliac crest bone grafting. SUMMARY OF BACKGROUND DATA: Bone grafting can be associated with significant morbidity, and an acceptable substitute material is sought. In vivo analysis of ceramic as a substitute has revealed fracture and failure of the implant. Creating a stable environment with internal fixation may improve the performance of ceramic as a bone graft substitute. METHODS: Fusions were evaluated in 20 adult beagles 8 weeks after surgery. Structural properties of the fusion segment were evaluated with biomechanical testing. Histologic analysis was performed to determine junction healing, new bone formation, and revascularization. RESULTS: Fusion segments with iliac crest bone graft and instrumentation were significantly stiffer than the other three groups in all tested modes of angular deformation. Greater junction healing was seen when instrumentation was used with iliac crest bone graft. Greater junction healing, new bone formation, and revascularization were observed when instrumentation was used with calcium carbonate ceramic. Most of the ceramic implants without fixation demonstrated near complete isolation with no revascularization. CONCLUSIONS: Internal fixation resulted in histologically and biomechanically superior healing of autologous iliac crest bone graft in this canine model of anterior interbody fusion. Although fixation did not statistically improve the biomechanical properties of ceramic fusion segments, it had a profound effect on the ability of the ceramic to be revascularized and remodeled. Porous ceramic bone graft substitutes appear to depend on a stable environment for incorporation.

Thoracolumbar burst fracture: evaluating stability.

The burst fracture is an injury characterized by anterior vertebral body height loss and retropulsion of the posterior aspect of the vertebral body into the spinal canal. The vertebral body injury frequently is associated with fractures through the neural arch. Using a three-column concept of spinal stability, the division of these fractures into stable and unstable injuries is difficult. Radiographic signs of instability include widening of the interspinous and interlaminar distance, translation of more than 2mm, kyphosis of more than 20 degrees, dislocation, height loss of more than 50%, and articular process fractures. However, fractures may be unstable in the absence of these signs. Unrecognized supraspinous ligament disruption contributes to this instability. This structure is best evaluated by MR examination. Confirmation of posterior ligamentous disruption occurring in conjunction with the burst fracture leads to reevaluation of the presumed mechanism of injury. This article discusses the many issues surrounding the division of burst fractures into stable and unstable injuries and reexamines the common classification systems of thoracolumbar spine injuries.

Factors affecting bone graft incorporation.

Successful graft incorporation requires that an appropriate match be made among the biologic activity of a bone graft, the condition of the perigraft environment, and the mechanical environment. The authors have studied, in a wide variety of animal models, the factors that affect the main components of bone graft incorporation: revascularization, new bone formation, and host-graft union. The principal determinant of the rate, pattern, and amount of revascularization is the presence or absence of a vascular pedicle. The nonvascularized bone graft is entirely dependent on the surrounding tissue for its revascularization, which results in a noticeable delay in vessel ingrowth. The principal determinant of the rate and amount of new bone formation on, in, or about a bone graft is the presence or absence of living, histocompatible, committed bone-forming cells. When living cells are not part of the graft at the time of implantation, the cells that form new bone are derived from host tissues, and new bone formation is delayed. The principal determinants of host-graft union are stability of the construct and contact between host bone and the graft. Factors that slow or inhibit all of these processes are reduction of the biologic activity of the graft by freezing or some other treatment, histocompatibility antigen disparities between donor and recipient, mechanical instability between the graft and the perigraft environment, and local and systemic interference with the biologic activity of the graft and surrounding tissue, for example, by irradiation or the administration of cisplatin. The task of the clinician who does a bone grafting procedure is to choose the right graft or combination of grafts for the biologic and mechanical environment into which the graft will be placed.

Biologic and biomechanic evaluation of posterior lumbar fusion in the rabbit. The effect of fixation rigidity.

STUDY DESIGN: The histologic and biomechanic characteristics of posterior lumbar fusion with varying rigidity of a novel internal fixation construct in the rabbit were analyzed. OBJECTIVES: To evaluate this rabbit model for future studies of fusion augmentation. SUMMARY OF BACKGROUND DATA: Previous studies in goats and dogs showed internal fixation enhances spinal arthrodesis. METHODS: Twenty eight New Zealand white rabbits underwent a posterior midline fusion from L4 to L6. Some animals received autogenous iliac crest bone graft, stabilized by wiring the superior facets bilaterally, and supplementation with polymethylmethacrylate. The experimental groups were iliac crest bone graft with either no fixation, wire fixation, or wire and polymethylmethacrylate fixation; and no graft and either no fixation, wire fixation, or wire and polymethylmethacrylate fixation. Animals were killed 2 months after surgery, and the specimens were nondestructively tested biomechanically for stiffness in six modes (flexion, extension, left and right bending, compression, and torsion) and histologically for evidence of fusion, revascularization, and new bone formation. RESULTS: Fusions with either wire or wire and polymethylmethacrylate fixation were significantly stiffer than those without fixation (P < 0.05). There was no statistical difference between the iliac crest bone graft and wire group and the iliac crest bone graft, wire, and polymethylmethacrylate group in the modes tested. Nine of 14 motion segments receiving the stiffest construct (iliac crest bone graft, wire, and polymethylmethacrylate) had evidence of solid bony fusion. None of the 12 motion segments receiving iliac crest bone graft and wire had evidence of bony fusion, but five had a fibrocartilage union with some ossification present. Eight of 12 motion segments receiving iliac crest bone graft and no fixation had predominantly fibrous unions with some fibrocartilage, and only one motion segment of 12 showed bony fusion. CONCLUSIONS: This study suggests that more rigid fixation produces more successful union in rabbit posterior spinal fusion. This model may be useful in evaluating the ability of various biomaterials to augment spinal arthrodesis.

Anterior stabilization of thoracolumbar burst fractures using the Kaneda device: a preliminary report.

Anterior decompression and fusion is a valuable technique in the treatment of thoracolumbar burst fractures. Anterior instrumentation has evolved to correct deformity and stabilize the spinal segments during decompression and bone grafting as a single-stage procedure. One anterior device developed by Kaneda has been used in our institution since 1989. This study is an initial review of our experience with this instrumentation. Anterior decompression and fusion augmented with the Kaneda device was performed in 20 patients with thoracolumbar burst fractures. Timing of surgery was early (< 15 days) in 13 patients, intermediate (16 to 120 days) in 2, and delayed (> 121 days) in 5. Sixteen patients were neurologically intact (Eismont grade D), 3 with distal weakness (Eismont grade B or C) and 1 with complete paraplegia (Eismont grade A). All patients with deficits recovered one Eismont grade after anterior decompression and fusion. Complications included pulmonary problems in 2 patients, a thoracic duct laceration requiring ligation, and a sympathectomy effect of the lower extremity. One patient had a pulmonary embolus and developed a hematoma at the graft harvest site while on anticoagulants with resultant meralgia paresthetica. There have been three screw failures and one definite pseudarthrosis. Anterior decompression and fusion supplemented by the Kaneda device was performed on 20 patients with thoracolumbar burst fractures. The average correction of kyphosis was approximately 50% acutely, with loss of approximately 50% of correction at follow up. In some patients, coronal plane deformity was created by the device. No effect on neurologic recovery could be shown with this small series. Perioperative complication rate was 30%, and 1 patient developed pseudarthrosis.

Thoracolumbar burst fractures: evaluation with MR imaging.

PURPOSE: To determine the frequency of posterior ligamentous injury that occurs in patients with thoracolumbar burst fractures and to correlate ligamentous disruption with radiographic appearance. MATERIALS AND METHODS: Magnetic resonance (MR) imaging examinations of 21 patients with 25 thoracolumbar burst fractures were retrospectively evaluated to determine spinal ligament integrity. Radiographic and computed tomographic (CT) examinations were evaluated for interpediculate widening, midsagittal canal narrowing, posterior element fractures, and kyphosis; a radiographic assessment of posterior ligamentous integrity was made. These findings were then correlated with the status of the spinal ligaments. RESULTS: The patients were divided into two groups on the basis of the status of their supraspinous ligament (SSL). Six patients had disrupted SSLs, and 15 had intact SSLs. Radiographic and CT findings did not correlate with supraspinous ligament disruption. Radiographic indicators of posterior ligamentous disruption were present in only 33% of patients with SSL disruption. CONCLUSION: SSL disruption is a frequent occurrence in patients with burst fractures. No radiographic features of burst fractures correlate with SSL disruption, and radiographic signs of posterior ligamentous disruption are insensitive.

Effects of irradiation on posterior spinal fusions. A rabbit model.

STUDY DESIGN: The biological and biomechanical effects of irradiation on posterior bone graft healing in the lumbar spine of rabbits were investigated. Twenty-seven New Zealand white rabbits were divided into four groups. Each rabbit underwent a posterior lumbar spine fusion with autogenous iliac crest bone graft, and three of the experimental groups received perioperative irradiation. OBJECTIVES: This study evaluated the histologic and biomechanical effects of perioperative irradiation on posterior spinal fusions using a rabbit model. SUMMARY OF BACKGROUND DATA: Treatment of metastatic disease of the spine depends on the neurologic status of the patient, stability of the spine, location of the tumor, and the tissue of origin. Some patients require surgical decompression and stabilization. The response of a posterior spinal bone graft to irradiation has not been studied previously. METHODS: Group 1 (n = 7), the control group, did not receive irradiation. Group 2 (n = 6) received preoperative irradiation. Group 3 (n = 7) received immediate (day 3) postoperative irradiation, and Group 4 (n = 7) received delayed (day 21) postoperative irradiation. The radiation protocol consisted of 480 centigrade/fraction for 5 consecutive days. At 3 months, the rabbits were euthanatized. Nondestructive biomechanical testing was performed, followed by histologic evaluation of the fusion mass. RESULTS: Compared with the control group, Group 3 (immediate postoperative irradiation) specimens were less stiff in extension (P = .0001), flexion (P = .0006), compression (P = .018), and left lateral bending (P = .018). The preoperatively irradiated spines (Group 2) were less stiff in extension (P = .0008) and in compression (P = .035) than controls. The control group and the delayed irradiation group had the highest histologic scores and more mature fusion mass. The immediate postoperative irradiation group had the worst results, with consistent fibrous union of the graft. CONCLUSION: Healing of a posterior spinal fusion is influenced by the timing of radiation therapy. Adjuvant radiation therapy for patients with spinal neoplasm requiring a posterior fusion should, if possible, be delayed for 3 to 6 weeks postoperatively to maximize the probability of successful arthrodesis.

The biological and biomechanical effects of irradiation on anterior spinal bone grafts in a canine model.

We evaluated the effects of irradiation on the healing of anterior vertebral strut grafts with use of a canine model. Through a left thoracotomy, a partial corpectomy of the seventh thoracic vertebra and autogenous iliac strut-grafting from the sixth to the eighth thoracic levels were performed in twenty-two adult beagles. Four groups were established: Group I (control) received no irradiation, Group II received preoperative irradiation, Group III received postoperative irradiation that began on the third postoperative day, and Group IV received postoperative irradiation that began on the twenty-first postoperative day. The irradiation protocol was five treatments of 500 centigray three times a week for a total of 2500 centigray. Fluorochromes were administered at regular intervals postoperatively. The beagles were killed three months postoperatively, and non-destructive biomechanical testing was done to evaluate the stiffness of the construct. The quality of healing at the junctions of the graft with the sixth and eighth thoracic vertebrae, the degree of revascularization of the graft, and the amount of new-bone formation were evaluated histologically. Statistical evaluation of the biomechanical data revealed no significant difference in the stiffness of the construct between Groups I, II, and IV. The specimens from Group III were significantly less stiff than those from Group I (the control group) in torsion (p = 0.03) and left lateral bending (p = 0.04) and than those from Group II in flexion (p = 0.02) and left lateral bending (p = 0.005).(ABSTRACT TRUNCATED AT 250 WORDS)

Robinson anterior cervical fusion comparison of the standard and modified techniques.

In 1990 the authors modified the Robinson anterior cervical interbody fusion technique by burring the endplates to expose subchondral bone. The authors compared 31 patients having the standard technique and 29 patients having the modified technique to evaluate 1) setting of the bone graft, 2) kyphotic angulation, 3) pseudarthrosis rate, and 4) pain outcome. In the standard Robinson fusion technique, the average loss of height across the fused segments was 0.8 mm and the average increase in kyphosis 4.9 degrees. Values for the modified technique were 1.9 mm and 3.1 degrees, respectively. The change in height was statistically significant (P = .01), as was the difference in angulation (P = .028), though the latter was in the opposite direction predicted. The pseudarthrosis rate using the modified technique decreased to 4.4% per level. Pain outcome for the two groups was equivalent. Burring of the endplates for anterior cervical interbody arthrodesis results in a detectable but not clinically important amount of graft settling with a higher success rate for arthrodesis.

Pedicular transvertebral screw fixation of the lumbosacral spine in spondylolisthesis. A new technique for stabilization.

Controversy exists about which method is most appropriate for treating moderate- to high-grade spondylolisthesis and symptomatic pseudarthrosis. The authors report preliminary results of pedicular transvertebral screw fixation, a new technique for stabilizing the lumbosacral junction in moderate- to high-grade spondylolisthesis. Using this technique, fusion was successful in three patients, two with an established pseudarthrosis. Pedicular transvertebral screw fixation provides immediate three-column stabilization of the lumbosacral junction. The technique is safe, effective, and employs instrumentation common to spine surgery. Its use in high-grade slips makes the technique more simple to perform than other methods of lumbosacral stabilization.