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PubMed1997

Use of electromagnetic fields in a spinal fusion. A rabbit model.

STUDY DESIGN: The biomechanical and histologic characteristics of posterolateral spinal fusion in a rabbit model with and without the application of a pulsed electromagnetic field were analyzed in a prospective, randomized trial. In addition, fusion rate with and without a pulsed electromagnetic field in this model was assessed by biomechanical testing, radiographs, and manual palpation. OBJECTIVES: To evaluate the influence of a pulsed electromagnetic field on the spinal fusion rate and biomechanical characteristics in a rabbit model. SUMMARY OF BACKGROUND DATA: Previous studies performed to assess the benefits of a pulsed electromagnetic field in spinal fusion have been complicated by the use of instrumentation, and the animal models used do not have a pseudarthrosis rate comparable to that seen in humans. In contrast, the posterolateral intertransverse process fusion in the rabbit is uncomplicated by the use of instrumentation and has been shown to have a pseudarthrosis rate similar to that found in humans (5-35%). METHODS: Ten New Zealand white rabbits each were randomly assigned to undergo spinal fusion using either 1) autologous bone with electromagnetic fields, or 2) autologous bone without electromagnetic fields. A specially designed plastic constraint was used to focus the pulsed electromagnetic field over the rabbits' lumbar spine 4 hours per day. Animals were killed at 6 weeks for biomechanical and histologic testing. RESULTS: The rate of pseudarthrosis, as evaluated radiographically and manually in a blinded fashion, decreased from 40% to 20% with the pulsed electromagnetic field, but this decrease in the nonunion rate was not statistically significant given the number of animals per group. Biomechanical analysis of the fusion mass showed that a pulsed electromagnetic field resulted in statistically significant increases in stiffness (35%), area under the load-displacement curve (37%), and load to failure of the fusion mass (42%). Qualitative histologic assessment showed increased bone formation in those fusions exposed to a pulsed electromagnetic field. CONCLUSIONS: This study demonstrates the reproducibility of a rabbit fusion model, and the ability of a pulsed electromagnetic field to induce a statistically significant increase in stiffness, area under the load-displacement curve, and load to failure of the fusion mass. This investigation provides a basis for continued evaluation of biologic enhancement of spinal arthrodesis with the use of a pulsed electromagnetic field.

Animals↗
PubMed1988

Treatment of symptomatic flatback after spinal fusion.

Fifty-five patients who had loss of lumbar lordosis after spinal fusion and subsequently had corrective osteotomies were studied. When they were first seen, fifty-two patients (95 per cent) were unable to stand erect and forty-nine (89 per cent) had back pain. The previous use of distraction instrumentation with a hook placed at the level of the lower lumbar spine or the sacrum was the factor that was most frequently identified as leading to the development of the flatback syndrome. Sixty-six extension osteotomies were performed in these fifty-five patients. Nineteen patients (35 per cent) had an associated anterior spinal fusion. Thirty-three patients (60 per cent) had one or more complications, including pseudarthrosis, a dural tear, failure of hardware, neurapraxia, and urinary tract infection. The results of the operation were evaluated at follow-up by review of clinical records, radiographs, and questionnaires. At an average follow-up of six years (range, two to fourteen years), most patients felt that they had benefited from the corrective osteotomies. However, twenty-six patients (47 per cent) continued to lean forward and twenty patients (36 per cent) continued to have moderate or severe back pain. The failure to restore sagittal plane balance led to a higher rate of pseudarthrosis, which was associated with recurrent deformity. Anterior spinal fusion combined with posterior osteotomy resulted in greater maintenance of correction. The prevention of flatback syndrome is important, since its treatment is difficult. When a spinal fusion must be extended to the level of the lower lumbar spine or the sacrum, the use of distraction instrumentation should be avoided in order to prevent this deformity.

Adolescent↗
PubMed1996

The effects of nonsteroidal anti-inflammatory drugs on posterior spinal fusions in the rat.

STUDY DESIGN: This was a prospective study to determine the potential effects of indomethacin on spinal fusions in the rat. OBJECTIVES: To determine if indomethacin exerts a deleterious effect on spinal fusions in the rat model. SUMMARY OF BACKGROUND DATA: Nonsteroidal anti-inflammatory drugs are a class of compound that affect bone osteogenesis during fracture healing and heterotopic ossification. Spinal fusion is a process that occurs via osteogenesis and, therefore, may be similarly affected. METHODS: Thirty-nine adult, Sprague-Dawley rats underwent a three-level posterior spinal fusion. Fusion was performed using morselized autogenous vertebral bone graft obtained via caudectomy and stabilized using a cerclage wiring technique. The 39 rats were divided into two groups consisting of 17 study animals and 22 control animals. The control group was injected with 1.5 cc of 0.9 normal saline subcutaneously for 12 weeks, whereas the test animals were injected on an identical schedule using 3 mg/kg of indomethacin sodium salt. Two control animals died, and three animals in the treatment group died of drug-related complications. Twelve weeks after surgery, all animals were killed, and the involved spinal segments were evaluated by direct manual examination. A fusion was probable if the spinal segments exhibited decreased scaled micromotion. RESULTS: Sixty segmental levels in 20 control animals were assessed. Overall, 27 of 60 levels (45%) achieved fusion. In the indomethacin-treated group, 42 levels in 14 animals were evaluated. Overall, four of 42 levels (10%) achieved a fusion. Chi-square analysis demonstrated a significant difference (P < 0.001) between the control and indomethacin-treated groups. CONCLUSIONS: This study raises serious questions about the inhibitory effects of nonsteroidal anti-inflammatory drugs on spinal fusion. Clinically, the widespread use of nonsteroidal anti-inflammatory drugs in the postoperative period after spinal fusion may need to be avoided.

Animals↗
PubMed2002

How does recombinant human bone morphogenetic protein-4 enhance posterior spinal fusion?

STUDY DESIGN: A rabbit posterolateral intertransverse process fusion model was used to evaluate the effect that different doses of recombinant human bone morphogenetic protein-4 delivered in a porous hydroxyapatite-tricalcium phosphate ceramic had on osteogenesis and spinal fusion. OBJECTIVE: To study the biologic effect and threshold dose of recombinant human bone morphogenetic protein-4 in enhancing spinal fusion. SUMMARY OF BACKGROUND DATA: Biologic manipulation for spinal fusion is an area undergoing active research. The enhancing effects of recombinant human bone morphogenetic proteins 2 and 7 on spinal fusion have been proved, and clinical trials of their application are in progress. Recombinant human bone morphogenetic protein-4 is another osteoinductive protein that has the ability to induce heterotopic bone formation, and its potential for enhancing spinal fusion has not yet been studied. METHODS: For this study, 24 adult New Zealand white rabbits underwent single-level unilateral posterior intertransverse process spinal fusion at L5-L6. The animals were divided into four groups using different graft materials: allograft as well as hydroxyapatite-tricalcium phosphate augmented with 0, 1.25, and 5 microgram of recombinant human bone morphogenetic protein-4, respectively. The local changes were evaluated by sequential radiograph, manual palpation, histomorphology, and microradiography. RESULTS: At week 7, ossification in the intertransverse process area ceased in groups without recombinant human bone morphogenetic protein-4, whereas active multicentric endochondral bone formation was demonstrated in groups with this growth factor. The success rate of contiguous bony bridging was found to correlate positively with the dose of recombinant human bone morphogenetic protein-4. CONCLUSIONS: Recombinant human bone morphogenetic protein-4 effectively enhances new bone formation and accelerates fusion in the rabbit posterolateral posterior spinal fusion model. The effective dose of recombinant human bone morphogenetic protein-4 is 10 times lower than the reported dosage of recombinant human bone morphogenetic proteins 2 and 7.

Animals↗
PubMed1988

Use of cortical cancellous allograft for posterior spinal fusion.

Fifty consecutive patients had posterior spinal fusion using only graft from bone banks. They were studied retrospectively in order to determine the pseudarthrosis rate, the quality of fusion mass obtained, the rate of infection, volume of blood lost, and operative time. The results showed that it is likely that the graft material used is not as important as the fusion technique. Strict adherence to facet obliteration, posterior element decortication, thorough removal of all soft tissue, and stable, well-planned instrumentation are probably the most important factors in preventing pseudarthrosis. With the complications associated with iliac crest graft and the potential benefits of reduced operative time and blood loss, use of allogeneic bone appears justified.

Bone Transplantation↗
PubMed2000

Efficacy of the laparoscopic approach for anterior lumbar spinal fusion.

BACKGROUND: This study compares the immediate postoperative outcomes in patients who undergo laparoscopic and open anterior lumbar spinal fusion and describes the learning curve associated with the performance of this procedure. METHODS: The charts of patients who underwent anterior lumbar spinal fusion between January 1995 and July 1999 were reviewed. Data pertaining to the operation and postoperative course were analyzed and compared. RESULTS: Eighty-nine patients underwent anterior lumbar spinal fusion. Fourteen patients were excluded; a full analysis was performed on the records of the remaining 75 patients. Fifty-five patients underwent an attempted laparoscopic procedure, and 20 patients underwent an open procedure. The conversion rate was 38% (21/55 patients) in the group who underwent the laparoscopic procedure. In the 34 patients whose laparoscopic procedure was completed, there was significantly less blood loss and shorter postoperative ileus, but the operative time was longer, when compared with patients who underwent the open procedure. The laparoscopic procedures performed in 1999 resulted in fewer conversions, less blood loss, and a shorter operating room time, when compared with the laparoscopic procedures in 1998. CONCLUSIONS: Laparoscopic anterior lumbar spinal fusion improves immediate postoperative results when compared with open anterior lumbar spinal fusion.

Adult↗
PubMed2000

Implantable spinal fusion stimulator: assessment of MR safety and artifacts.

The objective of this investigation was to perform magnetic resonance (MR) imaging safety and artifact testing of an implantable spinal fusion stimulator. Magnetic field interactions, artifacts, and operational aspects of an implantable spinal fusion stimulator were evaluated in association with a 1.5 T MR system. Magnetic field-related translational attraction was measured using the deflection angle test. A special test apparatus was used to determine torque at 4.7 T. Artifacts were characterized using fast multiplanar spoiled gradient-echo, T1-weighted spin-echo, and T1-weighted fast spin-echo sequences. Operational aspects of the implantable spinal fusion stimulator before and after exposure to MR imaging at 1.5 T were assessed. In addition, nine patients (six lumbar spine and three cervical spine) with implantable spinal fusion stimulators underwent MR imaging. The findings indicated that magnetic field interactions were relatively minor, artifacts were well characterized and should not create diagnostic problems, and there were no changes in the operation of the spinal fusion stimulator. The nine patients underwent MR procedures without substantial adverse events or complaints. Based on the results of this investigation and in consideration of the findings from previous studies of MR imaging safety for the implantable spinal fusion stimulator, MR imaging may be performed safely in patients using MR systems operating at 1.5 T or less following specific recommendations and precautions.

Artifacts↗
PubMed1999

Proximal kyphosis after posterior spinal fusion in patients with idiopathic scoliosis.

STUDY DESIGN: For this retrospective study, preoperative and postoperative radiographs of posterior spinal fusions for idiopathic scoliosis were reviewed. OBJECTIVES: To determine the prevalence and possible causes of proximal kyphosis after posterior spinal fusion for idiopathic scoliosis. SUMMARY OF BACKGROUND DATA: Proximal kyphosis has been anecdotally noted after the insertion of Harrington rods and after use of the new posterior multisegmented hook/rod systems. In this study no attempt was made to determine whether this condition is painful or an adverse outcome for the patient or just a radiographic abnormality; however, it is suspected that this may be a problem in the long term, and it may be worthwhile to try to avoid it if predictive values can be ascertained. METHODS: Patients with adolescent idiopathic scoliosis who had undergone posterior spinal fusion not extending above T3 with good-quality radiographs of the proximal thoracic spine and a minimum 2-year follow-up were studied. Of the 106 patients who underwent posterior spinal fusion from 1990 through 1994, 69 met the inclusion criteria. Abnormal kyphosis from T2 to the proximal level of the instrumented fusion was defined as kyphosis of more than 5 degrees above the summed normal angular segments. RESULTS: Of 69 patients, 37 (54%) had normal proximal kyphosis, and 32 (46%) of the 69 were defined as having abnormal proximal kyphosis. In the 32 patients with abnormal proximal kyphosis, the measurement from T2 to the fusion was 10.3 degrees before surgery and 21.2 degrees after surgery. The normal group had kyphosis measuring 2.7 degrees from T2 to fusion before surgery and 5.3 degrees after surgery (P < 0.00001). Junctional kyphosis in the kyphosis group measured 6.5 degrees before surgery and 12.6 degrees after surgery, compared with normal kyphosis of 1.7 degrees and 2.6 degrees, respectively (P < 0.00001). When analyzing who would develop proximal kyphosis, preoperative one-level junctional kyphosis of more than 5 degrees above the proposed proximal instrumented vertebrae was shown to have the highest sensitivity (78%) and specificity (84%). CONCLUSIONS: In this study, 32 (46%) of 69 patients had abnormal proximal kyphosis after undergoing posterior spinal fusion. A preoperative junctional kyphosis of more than 5 degrees above the proposed proximal instrumented vertebrae indicates that extending the fusion to a higher level in the thoracic spine would be beneficial in avoiding this problem.

Adolescent↗
PubMed2004

Posterior spinal fusion for lumbar degenerative diseases using the Crock-Yamagishi (C-Y) spinal fixation system.

Although many transpedicular screw systems have been developed and have undergone wide clinical use, experience with semirigid transpedicular systems has rarely been reported. We evaluated the efficacy and safety of the Crock-Yamagishi (C-Y) system for posterior spinal fusion in lumbar degenerative diseases. The outcomes for 26 patients (14 men, 12 women) with lumbar degenerative diseases who underwent posterior spinal fusion using the C-Y system were analyzed (posterior lumbar interbody fusion (PLIF), 11 patients; posterolateral fusion (PLF), 14; and facet fusion (FF), 1. Symptoms were evaluated using the Japanese Orthopaedic Association Assessment of Treatment for Low Back Pain (JOA score). Preoperative scores ranged from -1 to 23 points (mean, 12.8), while postoperative scores ranged from 19 to 29 points (mean, 26.4). Degree of recovery ranged from 23.1% to 100% (mean, 83.2%). Overall fusion rate was 96.2% (25/26). Neither breakage nor loosening of implants was observed radiographically. Intra- and postoperative complications included one case of transient L5 nerve root palsy attributable to surgical technique, and one deep postoperative infection. The C-Y system, categorized as semirigid, is effective when used with one- or two-level PLIF or PLF for lumbar degenerative disorders, grade I to II spondylolisthesis, and failed back syndrome.

Adult↗
PubMed1998

The biology of posterolateral lumbar spinal fusion.

This article reviews the existing knowledge base concerning the biology of spinal fusion, with the understanding that the focus is weighted toward posterolateral lumbar spinal fusion because of a relative paucity of biologic information on healing of other types of fusions. The discussion focuses first on the basic science of spinal fusion healing from the standpoint of animal modeling. Next, the discussion centers on the multitude of local factors that can affect fusion healing. Finally, the numerous systemic factors known to affect fusion healing are discussed.

Animals↗
PubMed1999

Spinal fusion in patients with congenital heart disease. Predictors of outcome.

The strong association between congenital heart disease and spinal deformity is well established, but data on the risks and outcome of spinal fusion surgery in patients with congenital heart disease are scarce. The purpose of this study was to identify predictors of perioperative risk and outcome in a large series of children and adolescents with congenital heart disease who underwent spinal fusion for scoliosis or kyphosis. In the authors' retrospective analysis of 74 consecutive patients with congenital heart disease undergoing spinal fusion, there were two deaths (2.7%) and 18 significant complications (24.3%) in the perioperative period. Preoperative cyanosis (arterial oxygen saturation < 90% at rest) with uncorrected or incompletely corrected congenital heart disease was associated with both deaths. Complications occurred in nine of 18 (50%) patients with cyanosis and in 11 of 56 (20%) patients without cyanosis. As judged by multivariate analysis the best predictors of perioperative outcome were the overall physical status of the patient as represented by the American Society of Anesthesiologists' preoperative score and a higher rate of intraoperative blood loss. Seventeen of 43 patients (40%) with an American Society of Anesthesiologists score of 3 or higher experienced complications including two perioperative deaths. Successful spinal fusion and correction were achieved in 97% of patients. Children and adolescents with congenital heart disease can undergo elective spinal fusion with risks that relate to overall cardiac status. Careful assessment of preoperative status by pediatric cardiologists and cardiac anesthesiologists familiar with surgical treatment of patients with congenital heart disease will assist the orthopaedic surgeon in providing the most realistic estimate of risk.

Adolescent↗
PubMedDate not supplied

Electrical stimulation of spinal fusion: a scientific and clinical update.

BACKGROUND CONTEXT: For over two decades, a number of electrical stimulation devices have achieved increasing acceptance as adjuncts to lumbar spinal fusion. Direct current electrical stimulation, pulsed electromagnetic fields and more recently capacitive coupling have been shown to have varying effectiveness when used to increase the success of lumbar spinal fusion. PURPOSE: The various electrical stimulation devices will be reviewed with respect to the available basic science evidence validating their use as spinal fusion adjuncts, as well as a review of the current clinical data available to allow not only a discussion of their overall clinical applicability, but more specifically their use in specific spinal disorders and spinal fusion techniques. METHODS: The existing peer-reviewed scientific literature will be used to ascertain the scientific and clinical efficacy of electrical stimulation to enhance lumbar spinal fusion. CONCLUSION: Electrical stimulation devices have emerged as valid adjuncts to attaining a solid lumbar spinal fusion. However, not all stimulators are equally scientifically effective nor are they equally effective clinically in achieving increased fusion success.

Electric Stimulation Therapy↗
PubMed2026

Comparison of Ketamine and Pregabalin on Postoperative Opioid Usage and Pain Management in Spinal Fusion: Systematic Review and Network Meta-analysis.

BACKGROUND CONTEXT: Spinal fusion is associated with substantial early postoperative pain and opioid exposure. Both ketamine and pregabalin are widely incorporated into Enhanced Recovery After Surgery (ERAS) protocols as opioid-sparing adjuncts. However, their comparative efficacy and safety in this specific setting remain uncertain. Our objective was to compare ketamine and pregabalin indirectly for early postoperative opioid consumption, pain, and adverse events in adults undergoing spinal fusion. METHODS: Pubmed, Embase, and Cochrane Trials were searched from inception through October 2025. Eligible studies were randomized trials enrolling adults undergoing instrumented spinal fusion, randomized to perioperative ketamine, pregabalin, or control, and reported extractable 24-hour opioid consumption or pain outcomes. Continuous outcomes were pooled as mean differences in MME or VAS units, and adverse events were reported descriptively. A connected treatment network was analyzed using random-effects models. Risk of bias (RoB) was assessed with the Cochrane RoB 2 tool. RESULTS: Thirteen trials (n=879) were included: ketamine (n=210), pregabalin (n=271), and control (n=398). Six trials contributed opioid data (3 ketamine, 3 pregabalin). Using pregabalin 150 mg as reference, ketamine was associated with lower 0-24-hour opioid use (MD -56.99 mg MME; 95% CI -99.56 to -14.43). Control (MD +21.31; 95% CI -1.05 to +43.66) and pregabalin 300 mg (MD -13.22; 95% CI -40.41 to +13.96) did not significantly differ from pregabalin 150 mg. Seven trials contributed 24-hour VAS data, with control being associated with higher pain versus pregabalin 150 mg (MD +0.84; 95% CI +0.01 to +1.66), while ketamine and pregabalin 300 mg were not k significantly different. Adverse events were generally infrequent and similar to control. CONCLUSIONS: Both ketamine and pregabalin provide early opioid sparing with comparable 24-hour analgesia. Ketamine showed a larger opioid-sparing point estimate, but indirect comparisons are imprecise. Adequately powered head-to-head trials with standardized protocols and adverse event reporting are needed.

Humans↗
PubMed1998

Reversing the inhibitory effect of nicotine on spinal fusion using an osteoinductive protein extract.

STUDY DESIGN: The effect on spinal fusion of an osteoinductive bone protein extract in the presence of a known inhibitor of spinal fusion (systemic nicotine) was studied prospectively in an animal model of posterolateral lumbar fusion. OBJECTIVES: To evaluate the ability of a bovine-derived osteoinductive bone protein extract to overcome the inhibitory effect of nicotine in a rabbit spine fusion model. SUMMARY OF BACKGROUND DATA: Multiple studies have demonstrated the ability of a variety of osteoinductive growth factors to serve as a bone graft substitute for lumbar spinal fusion under "normal" healing conditions. METHODS: Forty-eight adult female New Zealand white rabbits underwent spine arthrodesis at L5-L6 while receiving systemic nicotine through a subcutaneous miniosmotic pump. Arthrodesis was performed using one of the following three graft materials: 1) autogenous iliac crest, 2) osteoinductive bone protein delivered in an allogeneic demineralized bone matrix/ collagen carrier, or 3) osteoinductive bone protein delivered with autogenous iliac crest. Fusions were assessed by blinded manual palpation, radiography, and biomechanical testing. RESULTS: Of the 44 rabbits manually tested by blinded observers, all 14 in the osteoinductive bone protein plus autogenous iliac crest bone group had solid fusions (14 of 14), whereas the fusion rate was less in the osteoinductive bone protein plus demineralized bone matrix group (nine of 14, 64%; P = 0.02), and there were no fusions in the autogenous iliac crest only group (0 of 16, 0%; P = 0.000001). The use of osteoinductive bone protein with autogenous bone produced stronger and stiffer fusions compared with those using autogenous bone alone or osteoinductive bone protein with allograft bone. CONCLUSIONS: Cigarette smoking and nicotine are inhibitory factors in the healing of fractures and spine fusions. This study shows that the inhibitory effect of nicotine can be overcome with an osteoinductive bone growth factor in an animal model.

Animals↗
PubMed1999

The value of scintigraphy in the diagnosis of pseudarthrosis after spinal fusion surgery.

The utility of planar bone scintigraphy was evaluated for discerning bony union after spinal fusion surgery, especially in cases of clinically and radiologically suggested pseudarthrosis. Between 1991 and 1996, the authors performed bone scintigraphy on 42 patients (21 women, 21 men; mean age, 42 years) after spinal fusion surgery (32 posterolateral, 10 combined) and just before their admission to the hospital for material removal. The fusions consisted of 29 lumbosacral, 6 thoracolumbar, 3 lumbar, 2 thoracolumbosacral, 1 thoracic, and 1 cervical. The mean fusion spanned four segments, and the mean time between spinal fusion and material removal was 27 months. The scintigraphy was performed using the tracer Tc-99m. Based on the scintigraphy data, the radiologist suspected pseudarthrosis in five patients (12%), and the condition was confirmed in four patients during operation (10%), two diagnosed and two undiagnosed. The accuracy of the method was 88%; sensitivity, 50%, specificity, 93%; positive predictive value, 40%; and negative predictive value, 95%. The sensitivity and positive predictive value of bone scintigraphy are low for possible instability after spinal fusion. The method is not sufficient to reliably diagnose pseudarthrosis after spondylodesis.

Adult↗
PubMed1998

Results and morbidity in a consecutive series of patients undergoing spinal fusion for neuromuscular scoliosis.

STUDY DESIGN: A retrospective clinical and radiographic review. OBJECTIVES: To provide current data on the results and complications of patients who have undergone spinal fusion for neuromuscular scoliosis at a center with physicians experienced in these types of cases. SUMMARY OF BACKGROUND DATA: The reported complication rate in the management of neuromuscular scoliosis ranges from 44% to 62% in the recent literature. This literature is that of 1991 or earlier reflecting operative techniques of the mid-1980s, and it has been used to argue against the efficacy of neuromuscular spinal fusions. METHODS: A retrospective chart and radiographic review of 50 consecutive spinal fusions for neuromuscular scoliosis was performed at Connecticut Children's Medical Center between January 1990 and January 1994. The three most common diagnoses were spastic quadriplegic cerebral palsy (20 patients), myelomeningocele (13 patients), and muscle disease (8 patients). There were 38 posterior spinal fusions including two kyphectomies and 12 anteroposterior spinal fusions. The Luque-Galveston technique was used in 39 of 50 patients. The average age at surgery was 13 years and 6 months, with an average follow-up of 40 months (minimum, 24 months). RESULTS: Before surgery, the mean major scoliosis measured 72 degrees, with mean best bend or traction view of 35 degrees. At most recent follow-up, the mean scoliosis magnitude was 25 degrees (mean correction, 65%). There were 17 minor complications in 14 patients and three major complications (deep wound infections) in three myelomeningocele patients. Rod breakage was noted in two patients, one of whom had an asymptomatic pseudarthrosis. There were no neurologic complications or deaths, and none of the complications affected the final results. CONCLUSIONS: The data in the current study support the authors' belief that with current surgical techniques and perioperative management in an experienced center, the results for patients undergoing spinal fusion for neuromuscular scoliosis have been improved, and major complications have been minimized.

Adolescent↗
PubMed1996

Overpowering the crankshaft mechanism. The effect of posterior spinal fusion with and without stiff transpedicular fixation on anterior spinal column growth in immature canines.

STUDY DESIGN: This experimental study was designed to test the hypothesis that posterior spinal fusion and internal fixation, using a stiff transpedicular construct, would withstand additional anterior column growth without the need for an anterior procedure and would prevent the development of deformity secondary to asymmetric growth of the anterior column in the immature canine model. OBJECTIVES: This model revealed that a mechanical epiphysiodesis of the anterior spinal column can be created through a posterior approach in an immature growing animal using a stiff transpedicular construct. These results were correlated to the crankshaft mechanism clinically to provide a possible rationale for transpedicular posterior spinal instrumentation and fusion, without a concomitant anterior procedure, in immature patients. SUMMARY OF BACKGROUND DATA: All operative immature canines underwent posterior fusion of L1-L5 vertebral bodies with autogenous iliac crest bone graft. Instrumented canines underwent the additional placement of transpedicular screws at L1, L3, and L5 as well as 3/16-inch rods and a transverse connector. Previous studies have revealed that continued anterior spinal column growth after posterior arthrodesis causes a resultant deformity in quadrupeds. No previous study has assessed whether a transpedicular construct can overpower the anterior spinal growth plate in an immature growing model. METHODS: Twenty-five skeletally immature canines were randomized into four groups: control, fusion only, screw and fusion, and instrumentation and fusion. Disc space growth, vertebral body growth, and sagittal plane angulation were the variables analyzed. Management response variables were visualized graphically and radiographically. RESULTS: Posterior tethering and anterior column growth occurred in the noninstrumented fusion groups, producing substantial lordosis. Anterior column growth was arrested in the instrumented canines as demonstrated by decreased vertebral body length, disc space narrowing, and, most importantly, prevention of lordosis. CONCLUSIONS: The present study confirmed that in immature canines anterior column growth continues after posterior fusion without instrumentation. The magnitude of this growth, combined with a posterior tether, is sufficient to cause significant lordosis. The results are the first to document that a stiff posterior spinal instrumentation system is sufficient to overpower the residual anterior growth centers, even in the presence of a posterior tether (fusion mass). This technique creates a mechanical epiphysiodesis evidenced by arresting vertebral body length, narrowing disc space, and preventing lordosis, thus thwarting the deformity-producing mechanism without an additional anterior procedure.

Age Factors↗