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PubMed2002

The use of electrical stimulation to enhance spinal fusion.

The goal of spinal arthrodesis is a solid osseous union across one or more spinal segments. A solid bone union after arthrodesis is commonly known as a spinal fusion. Surgeons have begun to understand the biomechanical and biological factors that influence the bone-healing process. One of the most commonly used adjuncts is spinal instrumentation. Instrumentation has increased the spinal fusion rate; however, fusion failure (that is, nonunion or pseudarthrosis) remains significant. A less commonly used adjunct is electrical stimulation (ES). Investigators in experimental studies have demonstrated the beneficial effects of ES on increasing the fusion rate. In this review the authors discuss the evidence concerning the benefits of ES as an adjunct to spinal arthrodesis. In addition, the different types of ES devices are described along with the current experimental and clinical evidence for each type of device.

Animals↗
PubMed2006

Consequence of paraspinal muscle after spinal fusion: an experimental study.

Posterior lumbar spinal fusion is a common surgery of spine. The parapsinal muscular dysfunction was postulated to be due to injured paraspinal muscle inflicted by the surgery. To better understand the muscle dysfunction after spinal fusion, this descriptive study evaluated electrophysiology and histology changes in paraspinal muscle of rabbits with and without fusion. Three New Zealand white rabbits underwent 2-level posterior spinal fusion with instrumentation. Anothor 3 rabbits underwent surgical exposure alone and served as sham control. Pre-operative and follow-up electromyography (EMG) and histological assessment were performed in a 6-month interval. All fusion achieved solid union judged by post-mortem examination. Root mean square (RMS) of EMG showed decrease in both fusion and control group immediately after surgery, but the control group recovered to pre-operative value at 6 months follow-up. At 6 months after operation, the fusion group showed lower RMS in fused region than adjacent region. In term of median frequency (MF) changes, the control group did not show obvious difference between pre- and post-operative period. However, fusion group showed obvious decrease of MF in fusion region, but increase in lower adjacent region. Histology reviewed fatty infiltration in fusion region at 6 months after spinal fusion. In addition, the muscle fiber size presented smaller in fusion region than that of pre-operative status. These results would demonstrate the lower activities and muscle disuse atrophy of paraspinal muscles in the fusion region. While, higher muscular activities were found in the lower adjacent region, which may indicate muscle hypertrophy.

Animals↗
PubMed1982

Anterior spinal fusion: experimental evaluation of technique.

Anterior spinal fusion was carried out in 29 adult mongrel dogs in order to evaluate: (a) the degree to which intervertebral discs and endplates should be removed; (b) the optimum source of bone graft material and the best technique for implantation; (c) the effect of a previous posterior spinal fusion on the outcome of anterior spinal surgery; and (d) possible deleterious effects on the spinal canal. A total of 54 disc spaces were fused. In those fusions where none of the disc was resected, a 38% rate of successful fusion was achieved; this compares with 70% when one-half of the disc and endplates was removed and 67% when the entire disc and endplates were removed. The best fusions resulted when cancellous bone was packed tightly into disc spaces. Strut grafts were not successful. Posterior spinal fusions provided good stability for subsequent anterior fusions. Anterior spinal fusion carries a significant risk of spinal stenosis, either through osteophyte formation caused by surgical trauma or through hypertrophy of the bone related to the healing process.

Animals↗
PubMed1994

Spine update. The use of animal models to study spinal fusion.

The outcome of a spinal fusion depends upon a multifactorial process. Therefore, it is difficult and impractical to study individual variables clinically. Animal models have been useful in studying the parameters that influence the spinal fusion process. Despite the knowledge gained from previous animal studies, there exists a large void in our basic understanding of this complex process. The purpose of this update is to review the concept of animal models of spine fusion by summarizing previous models, identifying strengths and deficiencies, reviewing the strategy for selecting a model, and highlighting knowledge gaps suitable for future research. With recent advances in the knowledge regarding gene-specific therapies and the availability of osteoinductive proteins, we have entered a new era of biologic manipulation of bone formation. Animal data, however, are only as applicable as the model from which it is derived, and future animal models must overcome the deficiencies highlighted in this review. A valid animal model will prove essential in studying the use of growth factors for spinal fusion. The ultimate goal is that fusion nonunions will no longer be of clinical concern.

Animals↗
PubMed1999

Bone grafting for spinal fusion.

At least 250,000 spinal fusions are performed in the United States each year, nearly all requiring implantation of bone graft material. The preferred technique for most of these operations is the transplantation of structured or morcellized autologous corticocancellous bone from the iliac crest. Further, because of the increasing frequency of spinal fusion surgery during the 1990s, arthrodesis of the spine has become the most common reason for autologous bone graft harvest. This article reviews the current clinical status of autogenous bone grafts and alternative materials in spinal fusion surgery.

Biocompatible Materials↗
PubMed2006

Comparison of the lowest instrumented, stable, and lower end vertebrae in "single overhang" thoracic adolescent idiopathic scoliosis: anterior versus posterior spinal fusion.

STUDY DESIGN: A retrospective multicenter study. OBJECTIVE: To investigate the relationship between the lowest instrumented, stable, and lower end vertebrae in patients with "single overhang" thoracic (main thoracic) curves treated with anterior or posterior spinal fusion. SUMMARY OF BACKGROUND DATA: Previous studies have shown "saving" fusion levels with anterior spinal fusion, as opposed to posterior spinal fusion; however, to our knowledge, none of these studies evaluated the relative position to the lower end vertebra to compare study groups accurately. For clarification, "single overhang" includes Lenke 1A and 1B curves. For these thoracic curves, the lumbar curve does not cross the midline. MATERIALS AND METHODS: A retrospective multicenter study of adolescent idiopathic scoliosis was performed to identify specifically patients with "single overhang" thoracic (Lenke 1A and 1B) curves with more than a 2-year follow-up. To analyze relative fusion levels, the differences were computed as follows: (1) the difference between the vertebra position for the stable vertebra of the main thoracic (MT) curve and the lowest instrumented vertebra, as noted on postoperative radiographs, or [equation: see text] (2) the difference between the vertebra position for the lower end vertebra of the main thoracic (MT) curve and the lowest instrumented vertebra, as noted on postoperative radiographs, or [equation: see text]. RESULTS: A total of 298 "single overhang" thoracic curves (148 Lenke 1A, 150 Lenke 1B) were identified, of which 293 had either an anterior spinal fusion or posterior spinal fusion; 5 patients underwent a combined anterior-posterior spinal fusion. Anterior spinal fusion was performed in 70 patients (23.9%) and posterior spinal fusion in 223 (76.1%). While comparing the lowest instrumented vertebra to the stable vertebra with anterior spinal fusion, the lowest instrumented vertebra was identified either at the level of the stable vertebra or above in 97% of 1A/B curves (P < 0.001). Using posterior spinal fusion techniques, the lowest instrumented vertebra was identified either at the stable vertebra or above in 65% of the 1A/B curves (P < 0.05). CONCLUSIONS: These data confirm that anterior spinal fusion techniques result in a mean shorter fusion of 1.5 vertebral segments/patient when compared to posterior spinal fusion techniques with respect to the position of the lowest instrumented and stable vertebrae for "single overhang" thoracic (Lenke 1A/B) curves. However, because this is a retrospective multicenter study over 10 years, it represents various posterior spinal fusion techniques that do not include all pedicle screw constructs.

Adolescent↗
PubMed1998

The effect of postoperative nonsteroidal anti-inflammatory drug administration on spinal fusion.

STUDY DESIGN: The influence of ketorolac on spinal fusion was studied in a retrospective review of 288 patients who underwent an instrumented spinal fusion. OBJECTIVE: To assess the effect of postoperative ketorolac administration on subsequent fusion rates. SUMMARY OF BACKGROUND DATA: Nonsteroidal anti-inflammatory drugs are widely used compounds, which are known to inhibit osteogenic activity and have been shown to decrease spinal fusion in an animal model. No previous studies have examined the influence of nonsteroidal anti-inflammatory drugs on spinal fusion in clinical practice. METHODS: The medical records of 288 patients who underwent instrumented spinal fusion from L4 to the sacrum between 1991 and 1993 were reviewed retrospectively. The 121 patients who received no nonsteroidal anti-inflammatory drugs were compared with the 167 patients who received ketorolac after surgery. The groups were demographically equivalent. RESULTS: Ketorolac had a significant adverse effect on fusion, with five nonunions in the nondrug group and 29 nonunions in the ketorolac group (P > 0.001). Ketorolac administration also significantly decreased the fusion rate for subgroups including men, women, smokers, and nonsmokers. The odds ratio demonstrated that nonunion was approximately five times more likely after ketorolac administration. Cigarette smoking also decreased the fusion rate (P > 0.01); smokers were 2.8 times more likely to develop nonunion. CONCLUSION: These data suggest that nonsteroidal anti-inflammatory drugs significantly inhibit spinal fusion at doses typically used for postoperative pain control. The authors recommend that these drugs be avoided in the early postoperative period.

Adult↗
PubMed1990

Unstable lumbar spine without hypermobility in postlaminectomy cases. Mechanism of symptoms and effect of spinal fusion with and without spinal instrumentation.

The morbid conditions of unstable lumbar spine that are not associated with hypermobility in postlaminectomy cases were studied. The dura and the nerve roots with adhesion could be affected by minimal movement of the spine, which seemed to be the mechanism of symptoms of instability without hypermobility. The effects of spinal instrumentation on this particular instability were studied. The spinal instrumentation provides instantaneous rigid fixation, and maintains it until fusion is obtained, which might prevent adhesion, new bone formation, and re-stenosis. Spinal instrumentation seemed to be the effective treatment for this particular instability.

Aged↗
PubMed2002

Evaluation of ventilatory efficiency during exercise in patients with idiopathic scoliosis undergoing spinal fusion.

STUDY DESIGN: A prospective evaluation of ventilatory function following spinal fusion in adolescent idiopathic scoliosis. OBJECTIVES: To prospectively evaluate pulmonary function, maximal oxygen uptake, and ventilatory efficiency during exercise in patients with adolescent idiopathic scoliosis before surgery and a minimum of 2 years postoperation. SUMMARY OF BACKGROUND DATA: For reasons that are unclear, patients with untreated adolescent idiopathic scoliosis tend to avoid aerobic exercise. Their reluctance may be the result of low ventilatory efficiency, as they often approach their ventilatory ceiling at maximum oxygen uptake despite forced vital capacities that are near normal. This inefficiency of ventilation with exercise may explain the reluctance of patients with scoliosis to pursue aerobic fitness. No study has evaluated the effect spinal fusion has on the ventilatory function of patients with scoliosis during exercise. METHODS: Forty-two patients with adolescent idiopathic scoliosis (36 female and 6 male) at an average age of 14 +/- 3 years (range 10-18 years) underwent spinal fusion. Twenty patients underwent a posterior spinal fusion alone, 20 an anterior spinal fusion alone, and 2 an anterior spinal fusion and posterior spinal fusion. The average Cobb measurement was 55 degrees (range 40-85 degrees). Pulmonary function values (forced vital capacity, total lung capacity, maximum voluntary ventilation), maximum oxygen uptake (VO2max), and ventilatory efficiency were obtained before surgery and a minimum of 2 years postoperation. RESULTS: For all patients, forced vital capacity percent predicted decreased from 88.1% to 81.4% (P < 0.0001). Total lung capacity also declined from 90.5% to 88.5% but was not statistically significant (P = 0.189). Percent predicted maximum oxygen uptake (VO2max) declined from 93.6% to 85.1% (P = 0.00029). Ventilatory efficiency, as measured by VEmax/maximum voluntary ventilation, improved from 0.76 to 0.68 (P = 0.005), whereas measured by VEmax/FEV1 x 40 was unchanged from 0.69 to 0.70 (P = 0.172) postoperation. The choice of operative approach [anterior (n = 20) versus posterior (n = 20)] or whether rib graft was harvested (n = 33) versus iliac crest graft (n = 7) did not change these results. CONCLUSION: Improvement in ventilatory efficiency during exercise does not occur in the majority of patients with adolescent idiopathic scoliosis following spinal fusion and thus cannot be relied on to foster increases in aerobic activity.

Adolescent↗
PubMed2001

Nanoindentation study of interfaces between calcium phosphate and bone in an animal spinal fusion model.

Intertransverse process spinal fusion is a common surgical procedure for the treatment of spinal disorders. In the present study, a porous hydroxyapatite (HA)/beta-tricalcium phosphate (beta-TCP) ceramic was tested as graft material using a rabbit lumbar transverse process (L5-L6) fusion model. The porous ceramic blocks were implanted onto the dorsal decorticated surface of the lumbar transverse processes. The specimens were harvested at the seventh week after implantation. Histomorphological observation revealed that the integration of HA/beta-TCP with the host bone of the transverse process occurred by both cancellous bone formation and cartilage formation. Scanning electron microscopy-wavelength dispersive X-ray spectrometry examinations showed significant differences in calcium, phosphorus, and sulfur contents in the newly formed tissues and the porous HA/TCP implants. Nanoindentations were used to evaluate the intrinsic mechanical properties of the implants and the newly formed tissues. The Young's moduli of the newly formed cartilage, new cancellous bone, and HA/TCP, were 0.66 +/- 0.02 GPa, 2.36 +/- 0.50 GPa, and 10.2 +/- 1.21 GPa, respectively. Nanoindentation results revealed degradation of the porous ceramics and incomplete calcification of the new cancellous bone at the seventh week after implantation. Nanoindentation appeared to be a useful technique for assessing the mechanical status of spinal fusion in animal models.

Animals↗
PubMed2003

Prospective comparison of gait and trunk range of motion in adolescents with idiopathic thoracic scoliosis undergoing anterior or posterior spinal fusion.

STUDY DESIGN: Prospective evaluation of gait and spinal range of motion (ROM) in adolescent idiopathic scoliosis (AIS) patients undergoing either an anterior or a posterior spinal fusion. OBJECTIVE: Compare changes in gait and spine ROM between AIS patients undergoing either an anterior or posterior spinal fusion. SUMMARY AND BACKGROUND DATA: Problems with AIS posterior spinal fusion and attempts to minimize the number of spinal segments fused have led to the promotion of anterior spinal fusion. Comparison of functional outcomes of the two surgeries has not been reported. MATERIALS AND METHODS: Thirty-one patients with single or double thoracic AIS undergoing an anterior (n = 16) or posterior (n = 15) instrumented spinal fusion underwent gait and triplanar ROM tests before surgery and 24 months postoperative. Videography with reflective surface markers on the scapula, spine, and pelvis were used to quantify changes in gait and trunk ROM. RESULTS: Surgical results indicated that an average of four fewer levels was fused and the lowest instrumented vertebrae were one level higher in the spine for the anterior group compared to the posterior group. Gait results showed no change in gait speed and no change in coronal and sagittal plane kinematics, regardless of group. Transverse plane motion during gait was reduced in both groups. Spinal ROM results indicated motion loss in all three planes, regardless of group, with the posterior group having less postoperative ROM than the anterior group. Unlinking surgical approach from number of fused levels and lowest instrumented vertebrae with a subset of subjects also indicated less postoperative ROM for the posterior group. CONCLUSIONS: The surgical and ROM results seem to favor the anterior approach over the posterior approach for the classification of patients in this investigation. However, it should be noted that both groups had decreased postoperative ROM.

Adolescent↗
PubMed2002

The radiological outcome of lumbar spinal fusion using a South African-developed dynamic spinal fixation system.

OBJECTIVES: To investigate the radiological outcome of the use of a new Cape Town-developed spinal fixation system. DESIGN: One hundred and fifty-five patients underwent posterior lumbar spinal fusions with this fixation system and autogenous bone graft more than a year ago. Of these 121 were available for radiological follow-up. SETTING: Spinal pedicle fixation systems are in common use in spinal fusion surgery. Most systems use rigid screws with a high rate of implant failure. In South Africa most spinal implants are imported and expensive, and this prompted the development of a locally manufactured dynamic spinal fixation system with the aim of producing a cheaper and more effective system with a lower risk of implant failure. OUTCOME MEASURES: A visual assessment of 1-year post-surgery radiographs by a qualified independent observer looking particularly at the rate of fusion and the incidence of implant failure. RESULTS: Bone fusion rates were comparable to all other pedicle fixation systems but implant failure rates were considerably less than in systems using rigid screws and more comparable to a similar dynamic spinal fixation system. CONCLUSIONS: This spinal fixation system is safe and effective in aiding bone fusion. It has a low rate of implant failure and is currently cheaper than all imported spinal fixation systems. It has therefore achieved the objectives that prompted its inception.

Adult↗
PubMed2005

Bone graft substitute using hydroxyapatite scaffold seeded with tissue engineered autologous osteoprogenitor cells in spinal fusion: early result in a sheep model.

Spinal fusion using autologous bone graft is performed in an increasing rate for many spinal disorders. However, graft harvesting procedure is associated with prolonged operation time and potential donor site morbidity. We produced an engineered 'bone graft' substitute by using porous hydroxyapatite (HA) scaffold seeded with autologous bone marrow osteoprogenitor cells (OPCs) and fibrin. This obviates bone graft harvesting, thus eliminates donor site morbidity and shortens the operation time. The aim of this study is to evaluate Hydroxyapatite (HA) ceramics as scaffold for autologous tissue engineered bone construct for spinal fusion in a sheep model. The sheep's marrow was aspirated from iliac crest. The bone marrow mesenchymal stem cells (BMMSCs) were cultured for several passages in the presence of growth and differentiation factors to increase the number of OPCs. After the cultures reached confluence, they were trypsinized and seeded on Hydroxyapatite scaffold (HA). Approximately 5 million cells were generated after 3 weeks of culture. Microscopically, very tight Colony Forming Units (CFU-Fs) were seen on monolayer culture. The Von Kossa and Alizarin Red staining of monolayer culture showed positive mineralization areas; indicating the presence of OPCs. Sheep underwent a posterolateral spinal fusion in which scaffolds with or without OPCs seeded were implanted on both sides of the lumbar spine (L1-L2). Intended fusion segments were immobilized using wires. At the end of third month, the fusion constructs were harvested for histological examination. Fibrous tissue infiltration found in the inter-connecting pores of plain HA ceramics indicates inefficient new bone regeneration. New bone was found surrounding the HA ceramics seeded with autologous cells. The new bone is probably formed by the sheep BMMSCs that were initially encapsulating HA while it remained intact. The new bone is naturally fused with the vertebrae. In conclusion, the incorporation of autologous bone marrow cells improved the effectiveness of HA ceramics as 'bone graft' substitute for spinal fusion.

Animals↗
PubMed1984

Acquired spondylolysis after spinal fusion.

Spondylolysis occurring after a spinal fusion is considered to result from operative damage to the pars interarticularis on both sides. Fourteen cases are reported, and compared with the 23 cases which have previously been published. The defects are usually recognised within five years of fusion, and usually occur immediately above the fusion mass. Other contributory causes may be: fatigue fracture from concentration of stress; damage and altered function of the posterior ligament complex; and degenerative disc disease immediately above or below the fusion. Fusion technique is critical, since virtually all cases occurred after posterior interlaminar fusions. This complication is easily overlooked in patients with recurrent back pain after an originally successful posterior spinal fusion.

Adult↗
PubMedDate not supplied

Adjacent segment degeneration and adjacent segment disease: the consequences of spinal fusion?

Given the number of spinal fusions performed annually, concerns have mounted over the potential for adjacent segment degeneration (radiographic changes of degeneration at levels adjacent to a spinal fusion) and adjacent segment disease (development of new symptoms correlating with adjacent segment degeneration). This article reviews documented evidence on adjacent segment degeneration and disease as it relates to cervical and lumbar arthrodesis. There appears to be an incidence of adjacent segment degeneration and disease after arthrodesis that may be related to natural degeneration or the adjacent fusion. It remains to be seen whether restoration of motion with disc arthroplasty will alter the rate of adjacent segment degeneration or disease.

Biomechanical Phenomena↗
PubMed1997

Wound infections following spinal fusion with posterior segmental spinal instrumentation.

Twenty-three of 238 patients (9.7%) developed wound infections following segmental spinal instrumentation. When the infected group and a matched control group were compared, the infected group had a significantly higher number of patients with cerebral palsy and myelodysplasia (nonambulatory), patients with wound hematomas, patients with fusions that extended into the sacral region, and patients who were incontinent of urine. A high incidence of infections with gram-negative aerobic bacilli correlated with the extension of the surgery into the sacral region and bowel and/or bladder incontinence. Prophylactic antibiotics with broader coverage for gram-negative bacilli may be warranted for these procedures. Postoperative wound infections were managed by surgical drainage and debridement as well as antibiotics. Removal of the hardware was not necessary to control the infection in these patients who underwent segmental spinal instrumentation.

Adolescent↗
PubMed2002

Prospective evaluation of trunk range of motion in adolescents with idiopathic scoliosis undergoing spinal fusion surgery.

STUDY DESIGN: Prospective evaluation of spinal range of motion in patients with adolescent idiopathic scoliosis undergoing a spinal fusion. OBJECTIVE: Evaluate changes in triplanar spine range of motion following spinal fusion. SUMMARY AND BACKGROUND DATA: Preoperative and postoperative radiographs have been the major form of outcome analysis of adolescent idiopathic scoliosis fusions. Although the radiographs document static positions of the skeletal system, they do not document dynamic changes. METHODS: Thirty patients with adolescent idiopathic scoliosis undergoing an instrumented spinal fusion underwent triplanar range of motion tests before surgery and at 12 and 24 months after surgery. Videography with reflective surface markers was used to capture the motions. A fused region, unfused regions above and below the fusion, and a global spinal measure were used to assess changes. RESULTS: Results indicated a loss of motion in the coronal and sagittal planes for the fused and unfused spinal regions and a loss of motion in the coronal, sagittal, and transverse planes for the global measurements. Results also indicated preoperative and continued postoperative right and left lateral flexion asymmetries. No significant correlations were found between the total fused levels and changes in range of motion. No significant correlations were found between the lowest instrumented vertebra and changes in range of motion. CONCLUSIONS: Whereas range of motion was reduced in the fused regions of the spine, it was also reduced in unfused regions. The lack of compensatory increase in motion at unfused regions contradicts current theory and suggests early postoperative range of motion therapy to facilitate motion in unfused regions.

Adolescent↗