Factor analysis of the SRS-22 outcome assessment instrument in patients with adult spinal deformity.

PURPOSE: Designed for patients with adolescent idiopathic scoliosis, the SRS-22 is now widely used as an outcome instrument in patients with adult spinal deformity (ASD). No studies have confirmed the four-factor structure (pain, function, self-image, mental health) of the SRS-22 in ASD and under different contexts. Factorial invariance of an instrument over time and in different languages is essential to allow for precise interpretations of treatment success and comparisons across studies. This study sought to evaluate the invariance of the SRS-22 structure across different languages and sub-groups of ASD patients. METHODS: Confirmatory factor analysis was performed on the 20 non-management items of the SRS-22 with data from 245 American English-, 428 Spanish-, 229 Turkish-, 95 French-, and 195 German-speaking patients. Item loading invariance was compared across languages, age groups, etiologies, treatment groups, and assessment times. A separate sample of SRS-22 data from 772 American surgical patients with ASD was used for cross-validation. RESULTS: The factor structure fitted significantly better to the proposed four-factor solution than to a unifactorial solution. However, items 14 (personal relationships), 15 (financial difficulties), and 17 (days off work) consistently showed weak item loading within their factors across all language versions and in both baseline and follow-up datasets. A trimmed SRS (16 non-management items) that used the four least problematic items in each of the four domains yielded better-fitting models across all languages, but equivalence was still not reached. With this shorter version there was equivalence of item loading with respect to treatment (surgery vs conservative), time of assessment (baseline vs 12 months follow-up), and etiology (degenerative vs idiopathic), but not age (< vs ≥50 years). All findings were confirmed in the cross-validation sample. CONCLUSION: We recommend removal of the worst-fitting items from each of the four domains of the SRS-instrument (items 3, 14, 15, 17), together with adaptation and standardization of other items across language versions, to provide an improved version of the instrument with just 16 non-management items.

Posterior lumbar interbody cages do not augment segmental biomechanical stability.

The effect on stiffness of installing posterior threaded interbody cages at LA-L5 was evaluated using fresh human cadaveric spine specimens. The cages did not increase spine stiffness significantly in any tested range of motion. Supplemental posterior pedicular screw/rod instrumentation, however, significantly increased stiffness. The assertion that use of cages as isolated posterior implants improves stability may be invalid.

Correlates of employment: a cohort study.

Employment is often viewed as a potent indicator of substance abuse treatment outcome. This study was conducted to determine if personality and/or demographic characteristics of a cohort of unemployed substance dependent persons presenting for addiction treatment might predict employment 9 months postadmission. By using stepwise discriminant function analysis, seven variables predictive of employment were identified. The positive value of employment was clearly documented. Those who gained employment were functioning better with regard to social and drug-use parameters than those who did not.

The effect of cigarette smoking and smoking cessation on spinal fusion.

STUDY DESIGN: The effect of cigarette smoking and smoking cessation on spinal fusion was studied in a retrospective review of 357 patients who had undergone instrumented spinal fusion. OBJECTIVE: To document the widely assumed but unreported benefit of cigarette smoking cessation on fusion rate and clinical outcome after spinal fusion surgery. BACKGROUND DATA: Cigarette smoking has been shown to inhibit lumbar spinal fusion and to adversely effect outcome in treatment of lumbar spinal disorders. Prior reports have compared smokers and nonsmokers, as opposed to comparing smokers and quitters. METHODS: This study retrospectively identified 357 patients who underwent a posterior instrumented fusion at either L4-L5 or L4-S1 between 1992 and 1996. Analysis of the medical record and follow-up telephone surveys were conducted. Clinical outcome and fusion status was analyzed in relation to preoperative and postoperative smoking parameters. RESULTS: In this study, the nonunion rate was 14.2% for nonsmokers and 26.5% for patients who continued to smoke after surgery (P < 0.05). Patients who quit smoking after surgery for longer than 6 months had a nonunion rate of 17.1%. The nonunion rate was not significantly affected by either the quantity that a patient smoked before surgery or the duration of preoperative smoking abatement. Return-to-work was achieved in 71% of nonsmokers, 53% of nonquitters, and 75% of patients who quit smoking for more than 6 months after surgery. DISCUSSION: These results validate the hypothetical assumption that postoperative smoking cessation helps to reverse the impact of cigarette smoking on outcome after spinal fusion.

The role of directly applied hypothermia in spinal cord injury.

STUDY DESIGN: The effect of intense local hypothermia was evaluated in a precision model of spinal canal narrowing and spinal cord injury in rats. The spinal cord injury was cooled with a custom cooling well used over the epidural surface. Basso, Beattie, and Bresnahan (BBB) motor scores and transcranial magnetic motor-evoked potential (tcMMEP) responses were used after injury to accurately evaluate neurologic recovery. OBJECTIVE: This study was undertaken to determine whether the prognosis for neurologic recovery in a standardized rat spinal cord injury model is altered by the direct application of precisely controlled hypothermia to the area of injury. SUMMARY OF BACKGROUND DATA: The role of hypothermia in the treatment of spinal cord injuries with neurologic deficits remains undefined. Hypothermia may decrease an area of spinal cord injury and limit secondary damage, therefore improving neurologic recovery. However, it has been difficult to consistently apply localized cooling to an area of spinal cord injury, and the use of systemic hypothermia is fraught with complications. This fact, along with the unavailability of a precise spinal cord injury model, has resulted in inconsistent results, both clinically and in the laboratory. In a rat model of spinal cord injury, 37 C and 19 C temperatures were used to study the role of hypothermia on neurologic recovery. METHODS: Male Spraque-Dawley rats (n = 52; weight, 277.7 g) were anesthetized with pentobarbital and subjected to laminectomy at T10. The rats were divided into three groups: 1) placement of a 50% spacer in the epidural space (16 rats), 2) severe (25 g/cm) spinal cord injury (16 rats), 3) 50% spacer in combination with spinal cord injury (16 rats). Eight rats in each group were tested at two temperatures: normothermic (37 C) and hypothermic (19 C). With the use of a specially designed hypothermic pool placed directly over the spinal cord for 2 hours, epidural heating to 37 C, and epidural cooling to 19 C was accomplished. Simultaneous measurements of spinal cord and body temperatures were performed. The rats underwent behavior testing using the BBB motor scores and serial tcMMEPs for 5 weeks. Statistical methods consisted of Student's t tests, one-way analysis of variance, Tukey post hoc t tests and chi2 tests. RESULTS: There was a significant improvement in motor scores in rats subjected to hypothermia compared with those that were normothermic after insertion of a 50% spacer. This improvement was observed during the 5-week duration of follow-up. In the severe spinal cord injury group and the spinal cord injury-spacer groups, no significant improvement in motor scores were obtained when the spinal cord was exposed to hypothermia. CONCLUSION: The results demonstrate that there is a statistically significant (P < 0.05) improvement in neurologic function in rats subjected to hypothermia (19 C) after insertion of a spacer that induced an ischemic spinal cord injury. This indicates that directly applied hypothermia may be beneficial in preventing injury secondary to ischemic cellular damage. The data demonstrated minimal therapeutic benefit of hypothermia (19 C) after a severe spinal cord injury.

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.

Surgical treatment of lumbar spinal stenosis in patients older than 75 years of age.

OBJECT: The purpose of this study was to evaluate the safety and efficacy of the surgical treatment of lumbar spinal stenosis in patients older than 75 years of age. METHODS: The authors reviewed the records of 65 patients with lumbar spinal stenosis who were at least 75 years of age at the time of surgery, which was performed between November 1990 and May 1996. The 65 patients (43 women, 22 men; average age 78 years) underwent a total of 71 operations (one patient underwent three, and four patients underwent two). Fifteen patients (21%) underwent isolated lumbar decompression, and 56 patients (79%) underwent decompression in conjunction with posterior spinal fusion. There was an average of 1.7 levels decompressed per isolated lumbar decompression and 2.6 levels per decompression and fusion procedure. Seven patients (10%) experienced one or more serious postoperative complication, which included wound infection, septicemia, small bowel obstruction, stroke, myocardial infarction, gastrointestinal bleeding, and pulmonary embolus. In addition there was one intraoperative complication (hypotension [1%]) that required modification of the planned surgical procedure. No deaths were documented in the perioperative period. CONCLUSIONS: With appropriate preoperative selection and evaluation, careful intraoperative monitoring, and attentive perioperative care, the surgical treatment of elderly patients with lumbar spinal stenosis can effect significant improvement with acceptable levels of morbidity and mortality.

The influence of spinal canal narrowing and timing of decompression on neurologic recovery after spinal cord contusion in a rat model.

STUDY DESIGN: The effect of spinal canal narrowing and the timing of decompression after a spinal cord injury were evaluated using a rat model. OBJECTIVE: To evaluate whether progressive spinal canal narrowing after a spinal cord injury results in a less favorable neurologic recovery. Additionally, to evaluate the effect of the timing of decompression after spinal cord injury on neurologic recovery. SUMMARY OF BACKGROUND DATA: Results in previous studies are contradictory about whether the amount of canal narrowing or the timing of decompression after a spinal cord injury affects the degree of neurologic recovery. METHODS: Forty adult male Sprague-Dawley rats were equally divided into a control group, in which spacers of 20%, 35%, and 50% were placed into the spinal canal after laminectomy, and an injury group in which the spacers were placed after a standardized incomplete spinal cord injury. After spacer removal, neurologic recovery in both was monitored by Basso, Beattie, Bresnahan (BBB) Locomotor Rating Scale (Ohio State University, Columbus, OH) motor scores and transcranial magnetic motor evoked potentials for 6 weeks followed by histologic examination of the spinal cords. Subsequently, 42 rats were divided into five groups in which, after spacer placement, the time until decompression was lengthened 0, 2, 6, 24, and 72 hours. Again, serial BBB motor scores and transcranial magnetic motor evoked potentials were used to assess neurologic recovery for 6 weeks until the animals were killed for histologic evaluation. RESULTS: Spacer placement alone in the control animals resulted in no neurologic injury until canal narrowing reached 50%. All of the control groups (spacer only) exhibited significantly better (P < 0.05) motor scores compared with the injury groups (injury followed by spacer insertion). Within the injury groups the motor scores were progressively lower as spacer sizes increased from the no-spacer group to the 35% group. The results in the 35% and 50% groups were not statistically different. The results of the time until decompression demonstrated that the motor scores were consistently better the shorter the duration of spacer placement (P < 0.05) for each of the time groups (0, 2, 6, 24, and 72 hours) over the 6-week recovery period. Histologic analysis showed more severe spinal cord damage as both spinal canal narrowing and the time until decompression increased. CONCLUSION: The results in this study present strong evidence that the prognosis for neurologic recovery is adversely affected by both a higher percentage of canal narrowing and a longer duration of canal narrowing after a spinal cord injury. The tolerance for spinal canal narrowing with a contused cord appears diminished, indicating that an injured spinal cord may benefit from early decompression. Additionally, it appears that the longer the spinal cord compression exists after an incomplete spinal cord injury, the worse the prognosis for neurologic recovery.

Preoperative SF-36 responses as a predictor of reoperation following lumbar fusion.

This study examined preoperative SF-36 (Medical Outcomes Study Short Form 36-item questionnaire) data in patients who required a subsequent surgical procedure following lumbar spine fusion to identify potential predictors of this adverse surgical outcome. Of the 235 patients treated by lumbar fusion, 27 patients required an additional procedure. Analysis of preoperative SF-36 responses revealed higher scores in social function (P=.013), and pain (P=.021) for the 208 patients who underwent only the initial fusion versus the 27 patients requiring a subsequent intervention. This study suggests that components of the SF-36 carry prognostic value for lumbar spinal surgery.

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.

Clinical outcome after fusion of the thoracic or lumbar spine in the adult patient.

This article highlights those disease processes for which fusion is used most frequently in the adult. Although the focus is on clinical outcome after fusion, the indications and natural history of the process itself are also briefly discussed to provide a comparative basis on which outcomes may be judged.

Spinal ligament loading during axial distraction: a biomechanical model.

The objective of this study was to develop a method of measuring spinal ligament forces during axial distraction to understand the load-bearing contributions of the individual ligamentous structures in the lumbar spine. A sequential ligament-cutting technique and the arthroscopically implantable force probe (AIFP, MicroStrain, Burlington, VT) were used to determine loading of the anterior longitudinal ligament (ALL), the posterior longitudinal ligament (PLL), and the remaining posterolateral complex (PLC) in an in vitro corpectomy model. During axial spinal distraction, the relative percentages of the total axial load in the individual structures were as follows: ALL, 37.5%; PLL, 17.2%; PLC, 45.3%.

A human cadaver model for determination of pathologic fracture threshold resulting from tumorous destruction of the vertebral body.

STUDY DESIGN: Thoracic vertebrae were subjected to compressive loads after drilling of the centrum to simulate destruction from metastatic tumorous involvement. OBJECTIVE: To determine whether a threshold exists that is predictive of fractures to establish a correlation between significant variables and vertebral strength. SUMMARY OF BACKGROUND DATA: The mechanical effects of metastatic destruction of thoracic vertebral bodies and their correlation to pathologic fractures has been analyzed in few studies. In additional studies on intact vertebral strength, investigators have determined that bone mineral density and geometric factors are important. METHOD: Fifty-four cadaveric thoracic vertebrae were studied. All were examined by quantitative computed tomography. T4 and T10 served as mechanical controls to predict the intact strength of T7. The test vertebrae were drilled from the anterior cortex through to the posterior cortex before they were loaded. RESULTS: Linear correlation between the strength of T4 and T10 in each spine supported the predicted strengths of T7. Because of variation from other factors, no threshold defect size was noted beyond which failure consistently occurred. Results of linear correlation analyses showed that the best combination of parameters for predicting vertebral strength was the product of bone mineral density and the remaining intact vertebral body cross-sectional area. This vertebral strength index correlated linearly with the strength of intact and compromised T7 vertebrae (r2 = 0.52). CONCLUSIONS: The vertebral strength index can be used to predict the strength of any thoracic vertebra. When compared with an idealized vertebral strength index based on the intact vertebral cross-sectional area and normal bone mineral density, a patient's actual vertebral strength index can be used as one of the criteria for prophylactic stabilization.

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.

Patient treatment choice and compliance. Data from a substance abuse treatment program.

The authors tested the hypothesis that patients (treatment-seeking cocaine-dependent persons) given the opportunity to choose between treatment approaches would do better than patients randomly assigned to the same approaches in treatment retention and 9-month outcome. Subjects were 34 patients who voluntarily chose to enter individual therapy 1 hour per week (IND) and 33 who chose intensive group therapy for 3 hours, 3 times weekly (INT). There were no significant differences between these two groups on demographic, personality, or addiction severity variables or in treatment retention or 9-month outcome. Comparison with samples of 30 patients who had been randomly assigned to IND and 30 to INT did not confirm the hypothesis that patients who chose their treatment would either remain in treatment for longer periods of time or manifest improved 9-month outcomes. The authors raise several motivational issues.

Biomechanics of in situ rod contouring of short-segment pedicle screw instrumentation in the thoracolumbar spine.

In situ rod contouring is proposed as a means of three-dimensionally controlling the three columns of the spine. Our goal was to determine the biomechanical effectiveness of the technique for both clinical application and future research. Six cadaver specimens were tested with pedicle screw instrumentation from T12 to L2 in an L1 corpectomy model with all longitudinal ligaments retained across the defect. Contouring moment, anterior longitudinal ligament (ALL) forces, and distraction and lordosis across L1 were monitored. Rods were contoured to 26 degrees, and axial distraction averaged 6.9 mm. Bone/screw-interface failure began during contouring in every case < 10 degrees with no resulting increase in lordosis across L1. High tensile forces generated in the ALL resisted the moment applied by the rod benders and instead caused failure of the weaker bone/screw interface.

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.

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.