Analysis of the risk factors for the development of post-operative spinal epidural haematoma.

In order to identify the risk factors and the incidence of post-operative spinal epidural haematoma, we analysed the records of 14 932 patients undergoing spinal surgery between 1984 and 2002. Of these, 32 (0.2%) required re-operation within one week of the initial procedure and had an International Classification of Diseases (ICD)-9 code for haematoma complicating a procedure (998.12). As controls, we selected those who had undergone a procedure of equal complexity by the same surgeon but who had not developed this complication. Risks identified before operation were older than 60 years of age, the use of pre-operative non-steroidal anti-inflammatories and Rh-positive blood type. Those during the procedure were involvement of more than five operative levels, a haemoglobin < 10 g/dL, and blood loss > 1 L, and after operation an international normalised ratio > 2.0 within the first 48 hours. All these were identified as significant (p < 0.03). Well-controlled anticoagulation and the use of drains were not associated with an increased risk of post-operative spinal epidural haematoma.

Cauda equina syndrome in ankylosing spondylitis (the CES-AS syndrome): meta-analysis of outcomes after medical and surgical treatments.

The cauda equina syndrome in ankylosing spondylitis (the CES-AS syndrome) is marked by slow, insidious progression and a high incidence of dural ectasia in the lumbosacral spine. A high index of suspicion for this problem must be maintained when evaluating the patient with ankylosing spondylitis with a history of incontinence and neurologic deficit on examination. There has been disagreement in the literature as to whether surgical treatment is warranted for this condition. A meta-analysis was thus performed comparing outcomes with treatment regimens. Our results suggest that leaving these patients untreated or treating with steroids alone is inappropriate. Nonsteroidal antiinflammatory drugs may improve back pain but do not improve neurologic deficit. Surgical treatment of the dural ectasia, either by lumboperitoneal shunting or laminectomy, may improve neurologic dysfunction or halt the progression of neurologic deficit.

Anterior spinal cord injury with preserved neurogenic 'motor' evoked potentials.

OBJECTIVE: To describe two cases in which intraoperative monitoring of neurogenic 'motor' evoked potentials (NMEPs) did not identify a spinal cord injury that resulted in paraplegia. METHODS: Bilateral tibial nerve somatosensory evoked potential (SEP) and NMEP testing was performed in two patients during spinal deformity corrective surgery using standard stimulation and recording parameters. These potentials were obtained repetitively throughout the primary procedures and were performed again during a subsequent procedure that took place after the discovery of paraplegia. RESULTS: SEP and NMEP signals were preserved in both patients and no adverse events were identified during the initial procedures. Postoperatively, paraplegia was identified immediately upon recovery from anesthesia and preserved posterior column function was apparent on clinical exam. In the procedures following the discovery of paraplegia, SEP and NMEP signals remained comparable with signals elicited in the initial surgeries. CONCLUSIONS: Based on these cases and previously published experimental evidence, we conclude that while 'NMEPs' remain a useful second test of spinal cord function, they are not reliable indicators of motor tract function. An alternate term, such as 'spinally-elicited peripheral nerve responses' should be used.

Does intraoperative fluid management in spine surgery predict intensive care unit length of stay?

STUDY OBJECTIVE: To determine whether intraoperative fluid management in spine surgery predicts postoperative intensive care unit length of stay (ICU LOS). DESIGN: Retrospective case series. SETTING: University-affiliated medical center. PATIENTS: 103 adult ASA physical status I, II, and III patients undergoing spine surgery. INTERVENTIONS: Patients were divided into three LOS groups: no ICU stay (LOS0) (n = 26), 1 day ICU stay (LOS1) (n = 48), and ICU stay > 1 day (LOS2) (n = 29). Measurements were analyzed by groups using the Kruskal-Wallis and Mann-Whitney tests, and linear regression. MEASUREMENTS: Demographics, comorbidity, length of surgery, surgical procedure, and intraoperative fluids were recorded. MAIN RESULTS: The important differences in perioperative fluid management among the three groups included estimated blood loss (612 +/- 480 mL, 1853 +/- 1175 mL, 2702 +/- 1771 mL, means +/- SD); total crystalloid administration (2715 +/- 1396 mL, 5717 +/- 2574 mL, 7281 +/- 3417 mL); and total blood administration (92 +/- 279 mL, 935 +/- 757 mL, 1542 +/- 1230 mL) in LOS0, LOS1, and LOS2, respectively. The mixture of surgical procedures was similar in LOS1 and LOS2; and differed from LOS0. Predictors of ICU LOS included age, ASA physical status, surgical procedure, total crystalloid administration, and platelet administration. Surgical procedure and total crystalloid administration correlated (Pearson correlation coefficient = 0.441; p = 0.000) and were not related to age or ASA physical status. CONCLUSIONS: Total crystalloid administration during spine surgery does predict ICU LOS. In addition, total crystalloid administration is closely related to the surgical procedure. Given that the mixture of surgical procedures was similar in LOS1 and LOS2, but differed in estimated blood loss, total crystalloid administration, and total blood administration; intraoperative fluid management during spine surgery only predicts ICU LOS insofar as total crystalloid administration is related to the surgical procedure.

The effect of neuromuscular blockade on pedicle screw stimulation thresholds.

STUDY DESIGN: Nerve root stimulation thresholds were studied relative to the level of neuromuscular blockade in patients undergoing lumbar decompression surgery. OBJECTIVES: To determine what levels of intraoperative neuromuscular blockade can be used during pedicle screw stimulation. BACKGROUND DATA: Previous studies of intraoperative pedicle screw stimulation thresholds have failed to determine the effect of neuromuscular blockade on the stimulation threshold. METHODS: Twenty-one roots in 10 patients undergoing lumbar decompression surgery were studied at different levels of neuromuscular blockade. Ninety-five nerve root thresholds were determined relative to level of blockade. RESULTS: Neuromuscular blockade below 80% provides nerve root thresholds similar to thresholds without blockade. CONCLUSIONS: Neuromuscular blockade should be less than 80% when using pedicle screw electrical stimulation testing.

Cauda equina syndrome secondary to lumbar disc herniation: a meta-analysis of surgical outcomes.

STUDY DESIGN: A meta-analysis of surgical outcomes of cauda equina syndrome secondary to lumbar disc herniation. OBJECTIVES: To determine the relationship between time to decompression after onset of cauda equina syndrome and clinical outcome, and to identify preoperative variables that were associated with outcomes. SUMMARY OF BACKGROUND DATA: The timing of surgical decompression for cauda equina syndrome is controversial. Although most surgeons recommend emergent decompression, results in certain studies show that delayed surgery may provide a satisfactory outcome. METHODS: A meta-analysis was performed to determine the correlation between timing of decompression and clinical outcome. One hundred four citations were reviewed, and 42 met the inclusion criteria. Preoperative and postoperative data were recorded. Length of time to surgery was broken down into five groups: less than 24 hours, 24-48 hours, 2-10 days, 11 days to 1 month, and more than 1 month. Logistic regression was used to determine the association between preoperative variables and postoperative outcomes. RESULTS: Outcomes were analyzed in 322 patients. Preoperative chronic back pain was associated with poorer outcomes in urinary and rectal function, and preoperative rectal dysfunction was associated with worsened outcome in urinary continence. In addition, increasing age was associated with poorer postoperative sexual function. No significant improvement in surgical outcome was identified with intervention less than 24 hours from the onset of cauda equina syndrome compared with patients treated within 24-48 hours. Similarly, no difference in outcome occurred in patients treated more than 48 hours after the onset of symptoms. Significant differences, however, were found in resolution of sensory and motor deficits as well as urinary and rectal function in patients treated within 48 hours compared with those treated more than 48 hours after onset of symptoms. CONCLUSIONS: There was a significant advantage to treating patients within 48 hours versus more than 48 hours after the onset of cauda equina syndrome. A significant improvement in sensory and motor deficits as well as urinary and rectal function occurred in patients who underwent decompression within 48 hours versus after 48 hours.

Relative effectiveness of electrically- vs mechanically-elicited EMGs in detecting pedicle wall perforation and surgically-induced nerve root damage.

Electrical stimulation of a pedicle hole and screw with recording EMGs from the lower extremities has been used as an indicator in detecting perforations of the pedicle. Mechanically-elicited EMGs are reported to be sensitive to mechanical irritation of nerve roots. This study analyzed the sensitivity of the data elicited by two EMG monitoring methods in the presence of a neurologic deficit caused by a malpositioned screw to determine the relative effectiveness of electrically- vs mechanically-elicited EMGs in detecting pedicle wall perforations and nerve root damage in patients undergoing spinal surgery utilizing transpedicular instrumentation. One hundred and four surgeries were monitored using the two EMG methods. Six hundred and fifty-four pedicle holes were prepared and 650 placed pedicle screws were electrically tested. Mechanically-elicited EMGs were monitored from a total of 618 muscles. Electrically-elicited EMGs showed a 62% true-positive rate and a 0.2% false-negative rate in detecting pedicle wall perforations. None of the patients who initially demonstrated abnormal electrically-elicited EMGs demonstrated any post-operative neurologic problems due to an incorrect screw placement. Only one patient who had abnormal mechanically-elicited EMGs during the procedures related to instrumentation developed new L4 radiculopathy immediately post-operatively which was consistent with the level of mechanically-elicited EMGs. Mechanically-elicited EMGs showed a 100% true-positive rate for nerve root irritation and a 3.5% false-negative rate in detecting pedicle wall perforations by malpositioned screw. In conclusion, although mechanically-elicited EMGs were an insensitive technique in detecting a perforation of the pedicle, mechanically-elicited EMGs were more beneficial than electrically-elicited EMGs in detecting the risk of nerve root irritation.

Pseudarthrosis repair. Autogenous iliac crest versus femoral ring allograft.

Pseudarthrosis repair in the lumbar spine is one of the most challenging problems faced by spine surgeons. Historically high failure rates with posterior repair have led to the use of anterior lumbar interbody fusion with tricortical iliac crest autograft in these difficult cases. More recently, femoral ring allografts packed with autograft bone have been advocated as another method that would decrease donor site morbidity. Two series of patients underwent anterior lumbar interbody fusion with anterior instrumentation to repair pseudarthrosis (Group I, 33 patients with tricortical autogenous iliac crest and Group II, 20 patients with femoral ring allografts). At minimum 2-year followup, there was no difference in fusion rates (Group I, 32 of 33 versus Group II, 20 of 20). Patients in Group I had radiographic fusion develop more rapidly than patients in Group II (12 months versus 18 months), but a significant proportion of patients in Group I (35%) had an average of 2 mm of graft subsidence. Despite excellent fusion rates in both groups, functional outcomes were not as good with only 28% of patients in Group I and 36% of patients in Group II returning to work. Using anterior instrumentation, anterior interbody fusion offers an excellent method to repair pseudarthrosis using femoral ring allografts or autogenous iliac crest. However, femoral ring allografts offer the potential to decrease donor site morbidity, allowing the surgeon to treat multiple spine levels.

Extension to the sacrum of previous adolescent scoliosis fusions in adult life.

Numerous reports have indicated an increased risk for the development of precocious degenerative changes leading to pain in patients who had fusions done in adolescence for scoliosis, which extended into the lower lumbar spine. The anatomic situation may lead to instability, or spinal stenosis or both. This paper represents the evolving experience in reconstructive surgery for patients in whom a fusion was to be extended to the sacrum. Reconstructive surgery will require, if necessary, decompression posteriorly for spinal stenosis if present. Stabilization is acquired through an anterior and posterior approach with anterior and posterior instrumentation. The evolution of treatment modalities since 1976 shows a decreased pseudarthrosis rate from an initial 83% to 3% at present.

Functional outcome of plate fusions for disorders of the occipitocervical junction.

Twenty-eight patients with average followup of 27 months (range, 12-51 months) required occipitocervical fusion with plates. A 1992 to 1996 consecutive case series enrolled patients prospectively from two institutions. Five surgeons participated. Sixteen patients had inflammatory arthritis; four, osteogenesis imperfecta; three, tumors; three, congenital anomalies; one, pseudarthrosis after odontoid fracture; and one, osteoarthritis. Twenty-two of 28 (78.6%) patients had serious comorbid medical conditions. Additional halo immobilization of 6 weeks was used in 16 of 27 patients. Four patients required revision surgery. No patients showed a decline in neurologic status and average neurologic improvement was one Nurick grade. Two-year followup showed 13 (50%) excellent, nine (34.6%) good, two (7.7%) fair, and two (7.7%) poor outcomes based on a functional outcome scale. There were three deaths during the followup period (overall mortality rate of 10.7%). One death was attributable to airway obstruction, one death 14 months postoperatively was attributable to late Methicillin resistant Staphylococcus aureus sepsis at the bone graft donor site, and one death 41 months postoperatively was attributable to a stroke. The overall fusion rate was 85.2% (23 of 27 patients), with a 96.3% (26 of 27 patients) occipitocervical fusion rate. Three patients had a possible asymptomatic end segment pseudarthrosis with screw loosening. Twenty-two of 26 (84.6%) interviewed patients would choose the surgery again if given the choice.

Complications of spinal fusion in adult patients more than 60 years of age.

This article describes the overall rate, characteristics, and predictive factors for major and minor complications in spinal fusion patients over 60 years of age (or greater) cared for in the authors' institution. Special emphasis is placed on establishing the most valid incidence of complications after spinal fusion by extracting the information directly from the pateint's permanent medical or clinical database record. Once the spinal surgery risk profile for the elderly patient is established, treatment interventions to modify these risks can be implemented and evaluated prospectively and longitudinally to maximize spinal surgery outcomes.

Alternatives to spinal fusion.

Techniques have changed significantly with the advent of less invasive surgical techniques for disc excision and spinal fusion; these include the development of rigid internal fixation devices using multiple points of fixation and the better knowledge of the biology of spinal fusion. Despite these improvements in technology, room exists for alternative forms of surgical treatment because of significant failures particularly related to spinal fusions.

Biomechanical testing of the lumbosacral spine.

OBJECTIVE: To assess various forms of anterior and posterior sacral fixation and to study the influence of anterior lumbosacral fixation and posterior pedicle fixation at L5 in conjunction with lumbosacral fixation. SUMMARY OF BACKGROUND DATA: Moments at the lumbosacral junction are high in the long constructs requiring lumbosacral fixation. The purpose of this study was to assess bending moments in flexion-extension and lateral bending and rotational forces at the lumbosacral junction involving a variety of long constructs to the lumbosacral junction. The incidence of pseudarthrosis in such constructs in the adult spine literature ranges from 7% to 40%. METHODS: An alignment jig was designed to display three-dimensional motion in the three orthogonal planes. Nine constructs of five specimens each were tested. These consisted of fixation at T12-L5-S1 (construct 1), T12-L5-S1 with anterior L5-S1 fixation and grafting (construct 2), T12-L5-S1, S2 with and without L5-S1 fixation and grafting anterior (constructs 3 and 4, respectfully), T12-S1, S2 with and without L5-S1 anterior grafting and fixation (constructs 5 and 6, respectfully), T12 Jackson intrasacral fixation with or without L5-S1 grafting anteriorly at the anterior fixation (constructs 7 and 8, respectfully), and T12-L5-S1, S2 fixation with anterior grafting only (construct 9). RESULTS: The use of anterior fixation statistically increased stiffness in extension. There was a trend toward increasing stiffness in constructs with anterior fixation (two anterior anterior-oblique L5-S1 screws) and in other loading modes as well. Failure to use L5 screw fixation significantly decreased torsional rigidity in long constructs without anterior fixation. CONCLUSIONS: In long constructs, particularly in scoliosis surgery requiring lumbosacral fixation, the addition of anterior fixation at L5-S1 is recommended. The addition of L5 fixation in addition to sacral fixation significantly decreases rotational stresses and is recommended as well.

Higher electrical stimulus intensities are required to activate chronically compressed nerve roots. Implications for intraoperative electromyographic pedicle screw testing.

STUDY DESIGN: A comparison of the electrical thresholds required to evoke myogenic responses from direct stimulation of normal and chronically compressed nerve roots. OBJECTIVE: To determine whether intraoperative electromyographic testing to confirm the integrity of instrumented pedicles should be performed at higher stimulus intensities in cases where there is preoperative lumbosacral radiculopathy. SUMMARY OF BACKGROUND DATA: Postoperative neurologic deficits may occur as a result of pedicle screw misplacement during spinal instrumentation. The failure to evoke myogenic responses from stimulation of pedicle holes and screws at intensities of 6-8 mA is commonly used to exclude bony pedicular wall perforation. METHODS: Direct nerve root stimulation was used to compare the stimulus thresholds of normal and compressed nerve roots in six patients with limb weakness from chronic lumbosacral radiculopathy. RESULTS: The stimulus thresholds of chronically compressed nerve roots significantly exceeded those of normal nerve roots, indicating partial axonal loss (axonotmesis). In most cases, the direct stimulus thresholds of compressed nerve roots exceeded 10 mA. CONCLUSIONS: When instrumentation is placed at spinal levels where there is preexisting chronic lumbosacral radiculopathy, holes and screws may need to be stimulated at higher intensities to exclude pedicular perforation and prevent further iatrogenic nerve root injury.

A comparison of impedance and electromyogram measurements in detecting the presence of pedicle wall breakthrough.

STUDY DESIGN: A prospective comparison of impedance measurements, electrically elicited electromyograms, and mechanically elicited electromyograms to detect pedicle wall breakthrough. OBJECTIVE: To determine whether impedance measurements are as sensitive as electromyogram measurements in evaluating pedicle wall breakthrough. SUMMARY OF BACKGROUND DATA: In a previous animal study, impedance values in pedicle screw placement were tested, to determine a baseline value for an intact pedicle. If pedicle wall breakthrough occurred, it was thought that the impedance values should be significantly lower. METHODS: Impedance measurements, electrically elicited electromyograms and mechanically elicited electromyograms were recorded in 20 patients undergoing surgery for spinal degeneration, using previously described standard protocol. Analysis of variance statistics were used to evaluate the data. RESULTS: Impedance values for the pedicle holes varied from 500 ohms to 31,000 ohms. There was no correlation between these values and those of the two pedicles in which breaches were detected on visual inspection. Electrically elicited electromyograms detected the breakthroughs in both pedicles, whereas mechanically elicited electromyograms detected one of the breakthroughs. CONCLUSIONS: Electrically elicited electromyograms were more sensitive in detecting pedicle wall breakthrough than were impedance measurements. This may be because of the inability to ascribe absolute impedance values to human pedicle bone caused by the wide variability in bone quality.

Continuous electromyographic monitoring to detect nerve root injury during thoracolumbar scoliosis surgery.

STUDY DESIGN: The results of intraoperative monitoring during a case of nerve root injury sustained from scoliosis surgery to the thoracolumbar spine are described. OBJECTIVES: To improve the efficacy of intraoperative monitoring in preventing nerve root injury during scoliosis surgery. SUMMARY OF BACKGROUND DATA: Posterior tibial nerve somatosensory-evoked potentials are the electrophysiologic modality most commonly used for spinal cord monitoring during thoracolumbar spine surgery. Although radiculopathy is a more frequent postoperative complication than myelopathy, monitoring of mixed-nerve, somatosensory-evoked potentials may not detect injuries to individual nerve roots. METHODS: The patient described in this report developed left L5 radiculopathy after scoliosis surgery to the thoracolumbar spine. During surgery, intraoperative electromyographic monitoring identified frequent trains of neurotonic discharges in the left anterior tibial muscle. Bilateral, posterior, tibial nerve, somatosensory-evoked potentials remained normal. The left L5 nerve root was explored 9 days after the original surgery and was found to be compressed by bony structures. Electrophysiologic testing showed that the nerve root had undergone significant Wallerian degeneration, but remained in partial continuity. RESULTS: Nerve root injury was detected by neurotonic discharges identified during intraoperative electromyographic monitoring, but not by somatosensory-evoked potentials, which remained normal. When the injured nerve root was explored, a simple electromyographic technique was used to characterize the extent and type of injury. CONCLUSIONS: The authors of this study recommend electromyographic monitoring of appropriate lumbosacral myotomes in addition to somatosensory-evoked potentials during this type of procedure.

Spine epidural steroids for patients with lumbar spinal stenosis.

The use of epidural steroid injections to relieve sciatic pain from spinal stenosis is extremely variable and controversial. Drs. Cohen and Kostuik take the position that most studies do not support their use and highlight the potential complications. Dr. Rydevik believes that epidural steroids might be considered as a nonsurgical alternative, especially in elderly patients where surgery carries greater risk.