Suken A. Shah

Neurophysiological detection of impending spinal cord injury during scoliosis surgery.

BACKGROUND Despite the many reports attesting to the efficacy of intraoperative somatosensory evoked potential monitoring in reducing the prevalence of iatrogenic spinal cord injury during corrective scoliosis surgery, these afferent neurophysiological signals can provide only indirect evidence of injury to the motor tracts since they monitor posterior column function. Early reports on the use of transcranial electric motor evoked potentials to monitor the corticospinal motor tracts directly suggested that the method holds great promise for improving detection of emerging spinal cord injury. We sought to compare the efficacy of these two methods of monitoring to detect impending iatrogenic neural injury during scoliosis surgery. METHODS We reviewed the intraoperative neurophysiological monitoring records of 1121 consecutive patients (834 female and 287 male) with adolescent idiopathic scoliosis (mean age, 13.9 years) treated between 2000 and 2004 at four pediatric spine centers. The same group of experienced surgical neurophysiologists monitored spinal cord function in all patients with use of a standardized multimodality technique with the patient under total intravenous anesthesia. A relevant neurophysiological change (an alert) was defined as a reduction in amplitude (unilateral or bilateral) of at least 50% for somatosensory evoked potentials and at least 65% for transcranial electric motor evoked potentials compared with baseline. RESULTS Thirty-eight (3.4%) of the 1121 patients had recordings that met the criteria for a relevant signal change (i.e., an alert). Of those thirty-eight patients, seventeen showed suppression of the amplitude of transcranial electric motor evoked potentials in excess of 65% without any evidence of changes in somatosensory evoked potentials. In nine of the thirty-eight patients, the signal change was related to hypotension and was corrected with augmentation of the blood pressure. The remaining twenty-nine patients had an alert that was related directly to a surgical maneuver. Three alerts occurred following segmental vessel clamping, and the remaining twenty-six were related to posterior instrumentation and correction. Nine (35%) of these twenty-six patients with an instrumentation-related alert, or 0.8% of the cohort, awoke with a transient motor and/or sensory deficit. Seven of these nine patients presented solely with a motor deficit, which was detected by intraoperative monitoring of transcranial electric motor evoked potentials in all cases, and two patients had only sensory symptoms. Somatosensory evoked potential monitoring failed to identify a motor deficit in four of the seven patients with a confirmed motor deficit. Furthermore, when changes in somatosensory evoked potentials occurred, they lagged behind the changes in transcranial electric motor evoked potentials by an average of approximately five minutes. With an appropriate response to the alert, the motor or sensory deficit resolved in all nine patients within one to ninety days. CONCLUSIONS This study underscores the advantage of monitoring the spinal cord motor tracts directly by recording transcranial electric motor evoked potentials in addition to somatosensory evoked potentials. Transcranial electric motor evoked potentials are exquisitely sensitive to altered spinal cord blood flow due to either hypotension or a vascular insult. Moreover, changes in transcranial electric motor evoked potentials are detected earlier than are changes in somatosensory evoked potentials, thereby facilitating more rapid identification of impending spinal cord injury.

Evaluation of Proximal Junctional Kyphosis in Adolescent Idiopathic Scoliosis Following Pedicle Screw, Hook, or Hybrid Instrumentation

Study Design. Retrospective review. Objective. To compare the incidence of and risk factors for proximal junctional kyphosis (PJK) in adolescent idiopathic scoliosis (AIS) following posterior spinal fusion using hook, pedicle screw, or hybrid constructs. Summary of Background Data. Proximal junctional kyphosis is a recently recognized phenomenon in adults and adolescents after AIS surgery. The postoperative effect on PJK with the use of hooks, hybrid constructs, or screws has not been compared in a multicenter study to date. Methods. From a multicenter database, the preoperative and 2-year follow-up radiographic measurements from 283 patients with AIS treated with posterior spinal fusion using hooks (group 1, n = 51), hybrid constructs (group 2, n = 177), pedicle screws (group 3, n = 37), and pedicle screws with hooks only at the top level (group 4, n = 18) were compared. Results. The average proximal level kyphosis at 2 years after surgery was 8.2° (range −1 to 18) in the all screw constructs, representing a significant increase when compared with hybrid and all hook constructs, 5.7° (P = 0.02) and 5.0° (P = 0.014), respectively. Conversely, average postoperative T5–T12 kyphosis was significantly less (P = 0.016) in the screw group compared with the all hook group. Of potential interest, but currently not statistically significant, was the trend towards a decrease in proximal kyphosis in constructs with all pedicle screws except hooks at the most cephalad segment, 6.4°. The incidence of PJK (assuming PJK is a kyphotic deformity greater than 15°) was 0% in group 1, 2.3% in group 2, 8.1% in group 3, and 5.6% in group 4 (P = 0.18). Patients with PJK had an increased body mass index compared with those who did not meet criteria for PJK (P = 0.013). Conclusion. Adjacent level proximal kyphosis was significantly increased with pedicle screws, but the clinical significance of this is unclear. A potential solution is the substitution of hooks at the upper-instrumented vertebrae, but further investigation is required.

Building consensus: development of a Best Practice Guideline (BPG) for surgical site infection (SSI) prevention in high-risk pediatric spine surgery.

Background: Perioperative surgical site infection (SSI) after pediatric spine fusion is a recognized complication with rates between 0.5% and 1.6% in adolescent idiopathic scoliosis and up to 22% in “high risk” patients. Significant variation in the approach to infection prophylaxis has been well documented. The purpose of this initiative is to develop a consensus-based “Best Practice” Guideline (BPG), informed by both the available evidence in the literature and expert opinion, for high-risk pediatric patients undergoing spine fusion. For the purpose of this effort, high risk was defined as anything other than a primary fusion in a patient with idiopathic scoliosis without significant comorbidities. The ultimate goal of this initiative is to decrease the wide variability in SSI prevention strategies in this area, ultimately leading to improved patient outcomes and reduced health care costs. Methods: An expert panel composed of 20 pediatric spine surgeons and 3 infectious disease specialists from North America, selected for their extensive experience in the field of pediatric spine surgery, was developed. Using the Delphi process and iterative rounds using a nominal group technique, participants in this panel were as follows: (1) surveyed for current practices; (2) presented with a detailed systematic review of the relevant literature; (3) given the opportunity to voice opinion collectively; and (4) asked to vote regarding preferences privately. Round 1 was conducted using an electronic survey. Initial results were compiled and discussed face-to-face. Round 2 was conducted using the Audience Response System, allowing participants to vote for (strongly support or support) or against inclusion of each intervention. Agreement >80% was considered consensus. Interventions without consensus were discussed and revised, if feasible. Repeat voting for consensus was performed. Results: Consensus was reached to support 14 SSI prevention strategies and all participants agreed to implement the BPG in their practices. All agreed to participate in further studies assessing implementation and effectiveness of the BPG. The final consensus driven BPG for high-risk pediatric spine surgery patients includes: (1) patients should have a chlorhexidine skin wash the night before surgery; (2) patients should have preoperative urine cultures obtained; (3) patients should receive a preoperative Patient Education Sheet; (4) patients should have a preoperative nutritional assessment; (5) if removing hair, clipping is preferred to shaving; (6) patients should receive perioperative intravenous cefazolin; (7) patients should receive perioperative intravenous prophylaxis for gram-negative bacilli; (8) adherence to perioperative antimicrobial regimens should be monitored; (9) operating room access should be limited during scoliosis surgery (whenever practical); (10) UV lights need NOT be used in the operating room; (11) patients should have intraoperative wound irrigation; (12) vancomycin powder should be used in the bone graft and/or the surgical site; (13) impervious dressings are preferred postoperatively; (14) postoperative dressing changes should be minimized before discharge to the extent possible. Conclusions: In conclusion, we present a consensus-based BPG consisting of 14 recommendations for the prevention of SSIs after spine surgery in high-risk pediatric patients. This can serve as a tool to reduce the variability in practice in this area and help guide research priorities in the future. Pending such data, it is the unsubstantiated opinion of the authors of the current paper that adherence to recommendations in the BPG will not only decrease variability in practice but also result in fewer SSI in high-risk children undergoing spinal fusion. Level of Evidence: Not applicable.

Multimodality monitoring of transcranial electric motor and somatosensory-evoked potentials during surgical correction of spinal deformity in patients with cerebral palsy and other neuromuscular disorders.

Study Design. This prospective, descriptive study determined the reliability of transcranial electric motor and posterior tibial nerve somatosensory-evoked potentials in children with neuromuscular scoliosis. Objective. To assess the applicability of transcranial electric motor and posterior tibial nerve somatosensory-evoked potentials during surgical correction of neuromuscular scoliosis, particularly with cerebral palsy-related deformity. Summary of Background Data. During corrective spinal surgery for neuromuscular scoliosis, intraoperative multimodality spinal cord monitoring is recommended. There exist conflicting, retrospective studies regarding the reliability of spinal cord monitoring in patients with neuromuscular scoliosis. Methods. Transcranial electric motor potentials and posterior tibial nerve somatosensory-evoked potentials were monitored in all patients presenting for spinal fusion between 2000 and 2001. Anesthesia was standardized for all patients. Results. There were 68 patients subdivided into two subject groups. Group I consisted of 39 patients with neuromuscular scoliosis associated with cerebral palsy, and Group II consisted of 29 children with neuromuscular scoliosis due to a disease process other than cerebral palsy. Five of the 68 patients had significant amplitude changes in 1 or both monitoring methods during surgery relative to baseline. Of these, one had permanent neurologic deficit despite standard intervention. Somatosensory-evoked potentials were monitored successfully in 82% of the cerebral palsy and 86% of the noncerebral palsy patients. Transcranial electric motor-evoked potentials, on the other hand, were monitorable in 63% of patients with mild or moderate degrees of cerebral palsy and 39% of those with severe involvement. Eighty-six percent of those with noncerebral palsy-related neuromuscular scoliosis had recordable motor-evoked potentials at baseline. Conclusion. Both transcranial electric motor and posterior tibial nerve somatosensory-evoked potentials can be monitored reliably in most patients with neuromuscularscoliosis. Those with severe cerebral palsy present the greatest challenge to successful neurophysiologicmonitoring.

Lumbar Spondylolysis in Pediatric and Adolescent Soccer Players

Background Lumbar spondylolysis in young soccer players has not been studied extensively. Purpose The purpose of this study was to review lumbar spondylolysis in young soccer players, describe the causes, and report the results of nonoperative treatment emphasizing the cessation of activity for 3 months. Study Design Case series; Level of evidence, 4. Methods The authors reviewed 57 child and adolescent soccer players (35 boys and 22 girls) with lumbar spondylolysis who came to their outpatient clinic for back pain evaluation. These patients received different modalities of nonoperative treatment, including cessation of sports and wearing a thoracolumbosacral orthosis. Soccer skills, field position, side of dominant leg, age, initiating event of low back pain, duration of symptoms, and nonoperative treatment were reviewed. Clinical outcome of treatment was assessed by the Steiner-Micheli criteria at the most recent follow-up (minimum 2 years). The Fisher exact test was used to compare all the data. Results Of the patients, 43% noticed that pain started after a high-velocity kick. Thirty-three (58%) of 57 patients had excellent results with no pain during sports, 20 (35%) good, 3 (5%) fair, and 1 (2%) poor. Subjects who ceased playing soccer for 3 months had better results than those who did not comply with this restriction. Conclusion The authors recommend stopping sports for at least 3 months in cases of lumbar spondylolysis in young soccer players who hope to return to their previous level of play without back pain.

Complications after 147 consecutive vertebral column resections for severe pediatric spinal deformity: A multicenter analysis

Study Design. Retrospective multicenter review. Objective. Determine the definition, indications, results, and outcomes, focusing on complications of vertebral column resection (VCR) for severe pediatric spinal deformity. Summary of Background Data. The strict definition of the VCR procedure, indications, results, outcomes, and the numerous, potentially serious complications are unknown or controversial, and a large multicenter review has never been performed. Methods. A total of 147 patients treated by 7 pediatric spinal deformity surgeons were reviewed—seventy-four females and 73 males, with an average age of 13.7 years, an average of 1.6 (range, 1–5) vertebrae resected, and an average follow-up of 17 months (range, 0.5–64 mo). The strict definition of VCR used was a “3-column circumferential vertebral osteotomy creating a segmental defect with sufficient instability to require provisional instrumentation.” Results. Indications for a VCR were divided into 5 diagnostic categories: kyphoscoliosis (n = 52), severe scoliosis (n = 37), congenital deformity (n = 28), global kyphosis (n = 17), and angular kyphosis (n = 13). Eighty-four primary and 63 revision patients with 174 operative procedures, 127 posterior-only (17 staged), and 20 patients combined anterior-posterior (10 staged) were reviewed. Average preoperative upright, flexibility, and postoperative Cobb measures (% correction or average kyphosis decrease) were kyphoscoliosis: 91°, 65°, 44° (51% coronal), 104°, 81°, and 47° (decrease, 57° sagittal); severe scoliosis: 104°, 78°, and 33° (67%); congenital deformity: 47°, 38°, 22° (46% coronal), 56°, 48°, and 32° (decrease, 24° sagittal); global kyphosis: 101°, 79°, and 47° (decrease, 54°); and angular kyphosis: 88°, 90°, and 38° (decrease, 50°), respectively. Operative time averaged 545 minutes (range, 204–1355 min) and estimated blood loss averaged 1610 mL (range, 50–8244 mL) for an average 65% blood volume loss (range, 6%–316%). Eighty-six patients (59%) developed a complication, 39 patients (27%) having an intraoperative neurological event (spinal cord monitoring change or failed wake-up test); however, no patient had complete permanent paraplegia. Conclusion. A total of 147 consecutive pediatric VCRs performed by 7 surgeons demonstrated excellent radiographical correction. However, these complex reconstructions were associated with a 59% complication rate, thus emphasizing the challenging nature of these patients and procedures.

Complications of Intrathecal Baclofen Pump Therapy in Pediatric Patients

Background The aim of this study was to investigate and evaluate complications of intrathecal baclofen (ITB) pump implantation and maintenance in children with cerebral palsy. Methods We reviewed our entire consecutive series of pediatric patients treated with ITB between 1997 and 2006 at our hospital. There were 174 patients with a diagnosis of cerebral palsy, 8 with mixed dystonia, 2 with athetosis, and 3 with pure dystonia. During follow-up, 8 deaths occurred with no evidence of pump or catheter malfunction in any way contributing to the cause of death. Acute infection within 60 days of the surgery and late infection rates were calculated on the basis of number of incidents and incidents/follow-up patient years, respectively. Independently, a blinded caregiver phone questionnaire was completed in 92 cases. Results There were 316 surgical procedures; 161 were initial ITB pump implants at our institution. The average age at initial implant was 12 years, with an average follow-up of 3 years, 2 months. There were 80 planned replacement procedures (46 battery expirations and 3 planned pump replacements during posterior spinal fusion, 26 catheter replacements for posterior spinal fusion, and 5 reinsertions). There were 78 procedures in 57 patients related to complications, and the acute infection rate was 4.0%. The probability of developing a late infection was 1.0% per year of follow-up. On the basis of the follow-up questionnaire, 81% of parents/caregivers were satisfied with the treatment, and 87% would recommend ITB therapy. Conclusions ITB therapy is a safe and effective treatment for severe spasticity in the pediatric population, but does have a 31% rate of complications requiring surgical management over a 3-year treatment period. Parents and caregivers have a high rate of satisfaction and most would recommend the treatment to others.

The risk of progression of scoliosis in cerebral palsy patients after intrathecal baclofen therapy.

Study Design. Retrospective radiographic and medical chart review with matched control group. Objective. To identify the effect of intrathecal baclofen on the incidence of scoliosis, rate of curve progression, and pelvic obliquity compared with a matched cohort. Summary of Background Data. Although intrathecal baclofen therapy (ITB) has been shown to be effective in decreasing spasticity, case reports have described some children receiving ITB in whom progressive scoliosis was noted; other authors have described no effect on the spinal column. A controlled study has not been performed. Methods. All patients with spastic CP treated with ITB between 1997 and 2003 at a single institution were reviewed. A total of 107 patients undergoing ITB for a minimum of 2 years were identified, of which 26 patients subsequently developed or had progression of scoliosis. Twenty-five age, gender, and gross motor function classification system (GMFCS) score-matched quadriplegic CP patients with scoliosis who did not receive ITB constituted the control group used to compare the rate of curve progression and pelvic obliquity. Results. The average curve progression for the baclofen group after pump implantation was 16.3° per year; and for the control group was 16.1° per year. Both groups’ curves progressed over time during growth (P = 0.001), but baclofen did not have an independent effect on curve progression (P = 0.181). Average pelvic obliquity for the 2 groups increased over time (P = 0.001), but there was no difference between the groups (P = 0.536). Twelve of 57 patients (21%) developed scoliosis after pump implantation during a mean of 3.6 years of follow-up. Thirty of 92 matched control patients (32%) not treated with ITB within the same time interval had scoliosis by maturity. Conclusion. This study demonstrates that ITB has no significant effect on curve progression, pelvic obliquity, or the incidence of scoliosis when compared with an age, gender, and GMFCS score-matched control group of patients with spastic CP without ITB.

Antibiotic-loaded allograft decreases the rate of acute deep wound infection after spinal fusion in cerebral palsy.

Study Design. A retrospective matched cohort study with control group. Objective. To compare the infection rate after posterior spinal fusion with unit rod instrumentation with or without gentamicin-impregnated allograft bone in children with cerebral palsy (CP). Summary of Background Data. Previous studies evaluating wound infection rates after spinal fusion surgery in children with CP report an 8.7% to 10% wound infection rate. The concept of using antibiotic-loaded bone graft (AbBGF) to provide local antibiotics has been explored in high risk patients, such as those with osteomyelitis or infected joint arthroplasty. There have been no reports of using AbBGF prophylactically in spine surgery. Methods. After IRB approval, the medical records of 220 children with CP who underwent spinal fusion with unit rod instrumentation for a primary spinal deformity between January 2000 through December 2006 at a single institution were retrospectively reviewed. We evaluated the incidence of postoperative wound infection in patients with AbBGF and those without bone graft (BGF). Results. One hundred fifty-four patients received AbBGF during spinal fusion surgery and 6 patients (3.9%) developed a deep wound infection. Ten (15.2%) of the 66 patients without AbBGF developed a deep wound infection. The difference between groups was statistically different (P = 0.003). The mean age at surgery, preoperative Cobb angle, correction rate, operative time, and estimated blood loss were not statistically different between the 2 groups (P > 0.05). The length of hospital stay was decreased in the AbBGF group (P < 0.05). Conclusion. The incidence of deep wound infection after spinal fusion in 220 children with CP scoliosis decreased from 15% to 4% with the use of prophylactic antibiotics in the corticocancellous allograft bone.

Comparative analysis of hook, hybrid, and pedicle screw instrumentation in the posterior treatment of adolescent idiopathic scoliosis.

Background: Spinal instrumentation in adolescent idiopathic scoliosis (AIS) aims to correct spinal deformity and maintain long-term spinal stability until bony healing is ensured. The purpose of this study was to compare the minimum 2-year postoperative radiographic and clinical results of posterior spine correction and fusion with all-hook instrumentation versus hybrid segmental instrumentation versus pedicle screw instrumentation for AIS from a single institution. Methods: A total of 105 patients with AIS who underwent a posterior spinal fusion with segmental pedicle screw (35), hook (35), or hybrid (35) instrumentation were sorted and matched according to the following criteria: similar age at surgery, identical Lenke curve types, curve magnitude, and Risser grade. Patients were evaluated before, immediately after, and at 2 years after surgery for radiographic parameters, complications, and outcome, as well as on the basis of the Scoliosis Research Society (SRS) questionnaire. Results: The age and Risser grade, major curve Cobb angle, apical vertebral rotation (AVR), apical vertebral translation (AVT), lowest instrumented vertebral tilt, global coronal and sagittal balance, lumbar lordosis, and thoracic kyphosis were determined as part of preoperative evaluation. All 3 groups showed significant differences between the preoperative and postoperative major curve Cobb angle, lowest instrumented vertebral tilt, AVT, and AVR. At the latest follow-up, lumbar lordosis, thoracic kyphosis, and global coronal and sagittal balance remained similar among the 3 groups. Major curve Cobb angle, AVT, and AVR were significantly different—the hook group’s measurements were significantly higher than the other groups, but there was no difference between the pedicle screw and hybrid groups. Major curve correction rate was significantly different among all groups (screw=71.9%±13.8%, hybrid=61.4%±16.6%, hook=48.1%±19.7%) (P<0.001). The pedicle screw group had the least amount of correction loss but there was no statistically significant difference between groups (screw=2.6±6.7 degrees, hybrid=4.5±7.4 degrees, hook=4.4±6.2 degrees) (P=0.35). The hook group had the least amount of AVT correction, but the screw group and the hybrid groups were similar (pedicle=67.3%±15.5%, hybrid=57.5%±22.4%, hook=39.9%±32.5%) (P<0.001). Surgery time and blood loss were higher in the screw group. No differences in global SRS-22 scores were demonstrated between the patients treated with pedicle screw, hybrid, and hook constructs; however, the satisfaction domain was higher in the screw group at the latest follow-up. Conclusions: Pedicle screw and hybrid instrumentations offer significantly better spinal deformity correction than hook constructs in major curve coronal correction, AVT, and AVR. Patients with pedicle screw instrumentation had the greatest curve correction percentage, maintenance of this correction in the coronal and sagittal planes, and higher patient satisfaction by the SRS outcome scores. Global SRS-22 scores were similar at 2-year follow-up in all groups. Level of Evidence: Therapeutic level III retrospective comparative study.