The durability of small-diameter rods in lumbar spinal fusion.

The use of a small-diameter rod in lumbar fusion offers a lower hardware profile and reduced implant bulk. Concern has been raised, however, about the ability of smaller rods to withstand the cyclic loads placed on them until fusion is achieved. This study is a retrospective radiographic review designed to evaluate the durability of a 4.75-mm diameter rod in the early postoperative period before fusion healing. Examination of postoperative radiographs revealed two instances of rod failure that occurred more than 24 months after operation among 85 cases of pedicle screw instrumentation followed for an average of 32 months. Based on these preliminary data, the benefits of a small-diameter rod can be obtained without an increased incidence of rod failure during the initial healing period.

Effect of prior lumbar discectomy on outcome of lumbar fusion: a prospective analysis using the SF-36 measure.

This study prospectively measured patient-reported quality-of-life outcome in patients undergoing fusion for recurrent symptoms after prior discectomy. Analysis of SF-36 data revealed statistically significant improvement in physical function, social function, and bodily pain 1 year postoperatively. Analysis of variance revealed significant interactions based on worker's compensation, litigation status, educational level, and age. The results support the conclusion that the SF-36 is a useful and applicable tool for measuring patient perception and quality-of-life parameters after spinal surgery. SF-36 outcomes demonstrated a reasonable level of success for lumbar fusion in revision spine surgery, with the most significant improvements noted in the categories of pain, physical function, and social function.

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.

Management of iatrogenic spinal stenosis complicating placement of a fusion cage. A case report.

STUDY DESIGN: A case of iatrogenic spinal stenosis secondary to fusion cage retropulsion is presented. OBJECTIVES: To highlight fusion cage retropulsion, a potential complication that may become more prevalent as the use of fusion cage instrumentation expands. The difficulty in management of this complication is emphasized. SUMMARY OF BACKGROUND DATA: Early reports regarding fusion cage instrumentation have been encouraging. At this point, however, the potential benefits are better defined than the potential complications. METHODS: A significant complication of fusion cage instrumentation and the limited literature on this subject are reviewed. RESULTS: The patient underwent successful revision surgery after retropulsion of a fusion cage, however, an extensive surgical procedure including partial vertebral body resection was required. CONCLUSIONS: The frequency and severity of complications related to fusion cage instrumentation remain poorly defined. Caution should be used in patient selection until additional experience more clearly defines the risk-to-benefit ratio for a given application of this new technology.

Salvage of instrumental lumbar fusions complicated by surgical wound infection.

STUDY DESIGN: This study retrospectively reviewed instrumented lumbar fusions complicated by surgical wound infection and managed by a protocol including antibiotic impregnated beads. OBJECTIVE: To evaluate the potential for an acceptable clinical outcome in cases of instrumented lumbar fusion complicated by wound infection. SUMMARY OF BACKGROUND DATA: Initial studies of pedicle screw instrumentation suggested an increased infection rate versus noninstrumented fusion. The presence of a metallic implant also complicates wound management. METHODS: Eight hundred fifty-eight instrumented fusions were reviewed with 22 (2.6%) deep wound infections identified. Analysis included preoperative risk factors, surgical procedure, postoperative course, and clinical outcome. RESULTS: Nineteen patients (mean age, 55 years) were reviewed at a minimum of 1 year after surgery. Sixteen (83%) reported significant preoperative health problems. Forty-seven percent of the patients had three- and four-level fusions. Mean operative time was 342 minutes. Mean estimated blood loss was 1620 mL. Infection was diagnosed at an average of 16 days after surgery with wound drainage as the most common presenting feature. Patients underwent between two and 10 (mean, 4.7) irrigation procedures. Seven patients had other significant noninfectious complications. At follow-up evaluation, no patient had recurrence of infection. By comparison to preoperative symptoms, 15 patients were improved, three were unchanged, and one deteriorated. Fusion was apparently solid in 14 patients, probable in four patients, and nonunion occurred in one patient. CONCLUSION: Although wound infection is a significant complication, this study suggests that aggressive surgical management can result in preservation of an adequate fusion rate and maintenance of an acceptable postoperative outcome.

Perioperative complications of anterior procedures on the spine.

We reviewed the operative and hospital records of 447 patients in order to determine the rates of perioperative complications associated with an anterior procedure on the thoracic, thoracolumbar, or lumbar spine. The anterior procedures were performed to treat spinal deformity or for débridement or decompression of the spinal canal. The diagnostic groups that we studied included idiopathic scoliosis in adolescents or young adults (100 patients), scoliosis in mature adults (sixty-three patients), kyphosis (sixty-one patients), neuromuscular scoliosis (sixty patients), fracture (forty-seven patients), a revision procedure (thirty-nine patients), congenital scoliosis (thirty-six patients), tumor (nineteen patients), vertebral osteomyelitis or discitis (eight patients), and miscellaneous (fourteen patients). Complications occurred in 140 (31 per cent) of the 447 patients and were classified as major or minor. Forty-seven patients (11 per cent) had at least one major complication and 109 (24 per cent) had at least one minor complication. Two patients died, both from pulmonary complications after the operation. The most common type of major complication was pulmonary; the most common type of minor complication was genito-urinary. The adolescent or young adult patients who had idiopathic scoliosis had the lowest rate of complications, and the patients who had neuromuscular scoliosis had the highest. An age of more than sixty years at the time of the operation was associated with a higher risk of complications. The duration of the procedures involving a thoracic approach was shorter than that of those involving a thoracolumbar or lumbar approach; however, the rate of complications was not significantly different among the three approaches. Vertebrectomies took longer to perform and were associated with a greater estimated blood loss than discectomies; however, there was no significant difference in the rate of complications between the two types of procedures. The patients who had a fracture or a tumor lost more blood than those from the other diagnostic groups. Blood loss increased as the duration of the operation increased for all procedures. Combined anterior and posterior procedures performed during the same anesthesia session were associated with a higher rate of major complications than were procedures that were staged. A logistical regression analysis showed that the variables that increased the risk of a major complication were an estimated blood loss of more than 520 milliliters and an anterior and posterior procedure performed sequentially under the same anesthesia session. This analysis also demonstrated that the diagnosis of idiopathic scoliosis in adolescents or young adults was associated with a reduced risk of major complications. Compared with other major operations, an anterior procedure on the thoracic, thoracolumbar, or lumbar spine performed for the indications mentioned in this study is relatively safe.

Thoracolumbar burst fractures treated with combined anterior and posterior surgery.

Between 1985 and 1992, 84 burst fractures were surgically managed with anterior decompression, autologous iliac crest strut graft, and posterior instrumentation and fusion. Fifteen were lost to follow-up, leaving 69 patients for detailed review. Of the 22 patients with complete or partial neurologic injury, 12 patients either totally or partially recovered function following surgery. Of these 12 patients, 6 improved 1 Frankel grade; 5 improved 2 Frankel grades, and 1 improved 3 Frankel grades. Follow-up was 12 to 91 months (average 41 months). For all of the fractures in this series, the mean operative correction in sagittal kyphosis was 14 degrees, but this decreased to 7 degrees at final review. No patient had significant scoliosis, and 66 patients achieved solid arthrodesis with 3 pseudoarthroses (4%). Mean operative time for 2-in-1 procedures was 5 hours 42 minutes, with an estimated blood loss of 1,455 mL. Of 62 patients available for follow-up telephone interview, 42 (68%) had minimal or no pain; 11, mild pain; 8, moderate pain; and 1, severe pain. Function in daily activities was assessed as normal or minimally impaired in 43 of 51 patients (84%) with normal neurologic function by physical examination. We conclude that anterior decompression, strut autografting, and posterior instrumented autogenous fusion, either as a combined or staged procedure, is a safe surgical option for thoracolumbar burst fractures.

Functional outcome of patients with salvageable limbs with grades III-B and III-C open fractures of the tibia.

Numerous reports list predictive criteria to determine whether Gustilio-type tibial III-B and III-C fractures of the tibia are salvageable. What is lacking are long-term reports of comprehensive functional outcome of these severe injuries. We evaluated the functional outcome of patients with our own seven-scale score. Fifty-four patients with 57 types III-B (n = 41) and III-C (n = 16) open tibial fractures sustained between 1980 and 1989 were recalled for evaluation. There were 45 men and 9 women (average age, 28.4 years; range, 4-68 years). Follow-up periods averaged 48.2 months (range, 12-116 months). Salvage rate for the III-B fractures was 75% (n = 31) and for the III-C fractures 37% (n = 6). We conclude that the functional score is a simple and complete method for assessing the functional outcome of patients undergoing limb salvage procedures.

Idiopathic juvenile osteoporosis. An unusual cause of back pain in an adolescent.

Idiopathic juvenile osteoporosis represents a rare bone disorder that affects prepubescent children of both sexes. The diagnosis is generally one of exclusion, ruling out other potential metabolic bone diseases. Here, the authors present a representative case of this rare disorder in an otherwise healthy male, along with the clinical history, physical presentation, and review of the available literature. Finally, it is important to note that patients with this disorder often have profound involvement of the spinal column with multiple compression fractures.

A prospective analysis of intraoperative electromyographic monitoring of pedicle screw placement with computed tomographic scan confirmation.

STUDY DESIGN: In a prospective study of 90 patients undergoing lumbar pedicle screw instrumentation, 512 screws were tested intraoperatively using electrical stimulation. The accuracy of this technique was verified after surgery by computed tomography. OBJECTIVES: Computed tomographic scans taken after surgery were used to evaluate the efficacy of intraoperative screw stimulation and electromyographic monitoring of pedicle screw placement. SUMMARY OF BACKGROUND DATA: Previous cadaveric and clinical studies showed the risk of pedicle screw malposition and the inadequate reliability of intraoperative radiographs to identify misplaced screws. METHODS: Screws (total, 512) in 90 patients were stimulated intraoperatively, and stimulation threshold was recorded. Computed tomographic scans were taken after surgery to document pedicle screw position. Electromyographic thresholds and computed tomographic data were evaluated independently and compared to assess the accuracy of the electromyographic screw stimulation technique. RESULTS: Intraoperative screw stimulation was extremely accurate in confirming the adequacy of screw position. A stimulation threshold greater than 15 mA provided a 98% confidence that the screw was within the pedicle. In eight of 90 patients (9%), electromyographic monitoring detected a screw malposition that was not identified on lateral radiograph. CONCLUSIONS: Screw stimulation monitoring is a valuable and efficacious adjunct to lumbar pedicle screw instrumentation. A stimulation threshold greater than 15 mA reliably indicates adequate screw position. A stimulation threshold between 10 and 15 mA was generally associated with adequate screw position, although exploration of the pedicle is recommended. A stimulation threshold less than 10 mA was associated with a significant cortical perforation in most instances.

The use of somatosensory evoked potentials to prevent ischemic neural damage during preoperative embolization of a vascular renal metastasis.

Tumors at the spinal cord level present challenging surgical problems. Hypernephromas and other tumors may have copious bleeding at the time of resection. This bleeding can be reduced by preoperative embolization resulting in a dramatic decrease in surgical morbidity. However, embolization does carry a risk of spinal cord infarction and resultant neurologic injury. To monitor this, somatosensory evoked potentials (SSEPs) were evaluated during embolization, with a resultant termination of the procedure after significant SSEP changes and clinical symptoms indicated cord ischemia. The SSEP readings normalized 24 hours later, by the time of surgical resection. We present a relevant case history and review of the literature on this subject. Clearly, SSEPs, and in the future, motor evoked potentials (MEPs), serve as a valuable adjunct to monitoring spinal cord function during embolization and may prevent preoperative ischemic injury.

Surgical treatment of idiopathic thoracolumbar and lumbar scoliosis in adolescent patients.

The surgical management of idiopathic thoracolumbar and lumbar scoliosis is complex because of the surgeon's desire to achieve curve correction while maintaining normal lumbar lordosis with as many distal mobile lumbar segments as possible. By doing so, the surgeon is able to maintain normal sagittal alignment and decrease the chance of degenerative lumbar spine disease below the scoliosis fusion. This article discusses the surgical treatment of the thoracolumbar and lumbar curve, and, it is hoped, provides a better understanding of this complex problem.

Cotrel-Dubousset instrumentation in idiopathic scoliosis.

Although well accepted in the patient undergoing Harrington instrumentation, the validity of King's criteria in patients undergoing correction of idiopathic scoliosis using the Cotrel-Dubousset system has been questioned. The cases of 64 patients with Type II (N = 40) and Type III (N = 24) idiopathic scoliosis treated with Cotrel-Dubousset instrumentation were reviewed. The average curve correction for Type II spinal curvature was 69.4% after surgery and 57.8% at follow-up examination. Decompensation was evident in 40% of the curves that were fused beyond the stable vertebra. However, the patients were only aware of their trunk decompensation if it was larger than 10 mm, and this was found in 35% of the patients. Decompensation occurred in 60% of those that were fused short of or to the stable vertebra. Only 42% of this group were aware of their decompensation. Decompensation was measured to the left of the spine in all patients. The difference between the subgroups based on the choice of distal fusion levels was not statistically significant (P greater than 0.05). The average curve correction for Type III scoliosis was 62.9% after surgery and 54.6% at the time of follow-up examination. There was no correlation between caudal fusion levels and the incidence of decompensation with Type III curves. It was concluded that there was no statistically significant relationship between choice of distal fusion level and the amount of decompensation, thereby indicating that the use of King's criteria for the selection of fusion levels in patients undergoing correction of idiopathic scoliosis using the Cotrel-Dubousset instrumentation may not be useful.

Biomechanical analysis of transpedicular rod systems. A preliminary report.

Two transpedicular spinal instrumentation systems were developed for fixation of the lumbosacral junction: a transpedicular fixator and the transpedicular screw/rod system. Mechanical testing showed that the new systems have a rigidity that is intermediate between conventional wired implants (Galveston and Luque ring) and plate systems (Steffee plate). Neither pedicular implant approached the rigidity of the Steffee plate with S2 fixation, but in compression and anterior bending both were more rigid than the Steffee plate without S2 fixation. Despite the apparent mechanical advantages of the transpedicular fixator, it is currently too bulky for clinical use. The transpedicular screw/rod system is more appealing because the size leaves adequate area for bone grafting, and device placement is technically simple. Furthermore, it may be contoured to any plane, while retaining stability provided by the clamps and screws.

Long-term effects of tibial angular malunion on the knee and ankle joints.

Twenty-seven patients with 28 tibial fractures were evaluated for an average of 8.2 years (range 6.0-12.3 years) following their injuries. There were 16 closed and 12 open fractures, all of which healed uneventfully. Overall, 50% of the ankles and 75% of the knees were rated good to excellent. The patients' knee and ankle joint malalignments were extrapolated using a method previously published. This was made possible by knowing both the degree and site of angular deformity. Correlation between joint malalignments and clinical outcome were performed. Analysis showed that greater degrees of ankle malalignment produce poorer clinical results (p = 0.001). Conversely, the patients with lesser degrees of ankle joint malalignment had a higher percentage of good to excellent results (p = 0.006, p = 0.003, p = 0.03). The knee results did not correlate with the degree of joint malalignment (p = 0.82). The findings in this study show that there is merit in reducing tibial fractures as close to anatomical configuration as possible to lessen the chance of early degenerative arthritis.

Analysis of the primary and compensatory curvatures following Zielke instrumentation for idiopathic scoliosis.

The behavior of the primary and compensatory curvatures of 34 patients (follow-up, 24-48 months) with solid fusions following Zielke instrumentation were evaluated. All patients showed correction of their primary curvatures (range, 40-112%; average, 70%) postoperatively. Thirty-one showed loss of correction (range, 2.8-78.5%; mean, 25%). There was a higher tendency to lose correction if the curve was fused short of the Cobb measurement (35% vs. 17%). The majority of both the thoracic and the lumbosacral compensatory curves improved postoperatively (average of 38.6 and 66%, respectively). However, when the instrumentation was carried cephalad to the primary curve, there was a high probability that the upper compensatory curve would be worse after the surgery. Trunk list tended to improve during the course of follow-up.

Reduction in cement-bone interface shear strength between primary and revision arthroplasty.

This study quantified changes in the cement-bone interface shear strength between primary and first- and second-revision arthroplasties as a function of mechanical interlock between the cement and bone. There were 128 segments obtained from four pairs of fresh human femora that were prepared sequentially as for primary and first and second revisions, taking care to maintain original canal morphology. Cement was pressurized into the cavity of the anatomic specimens, and the maximum interface shear strength between the cement plug and the bone was experimentally determined for each revision. First-revision interface shear strength was reduced to 20.6% of primary strength, and second revision strength to 6.8% of primary strength.

A method of determining the angular malalignments of the knee and ankle joints resulting from a tibial malunion.

Malalignments of the knee and ankle joints resulting from tibial angular malunion can be determined using mathematical analysis. The angular deformity of the tibia is equal to the sum of the angular malalignments formed by the knee and ankle joints in relation to the horizontal plane. These malalignments are not equal. A larger percentage of the deformity is reflected inferiorly as the deformity approaches the ankle joint. A table was formulated to provide the corresponding degrees of joint malalignment (knee and ankle) for tibial angular deformities at different positions along the tibia. The analysis provides a useful tool to quantify the knee and ankle joint malalignments secondary to tibial angular malunion. Although designation of prognosis at different degrees of angular deformity is beyond the scope of this study, it does provide improved correlation between tibial angular deformities and the clinical outcome, e.g., degenerative arthroses of the adjacent joints, in future studies on tibial fractures.