Karen S. Myung

A Classification of Growth Friendly Spine Implants

Background: Various types of spinal implants have been used with the objective of minimizing spinal deformities while maximizing the spine and thoracic growth in a growing child with a spinal deformity. Purpose: The aim of this study was to describe a classification system of growth friendly spinal implants to allow researchers and clinicians to have a common language and facilitate comparative studies. Growth friendly spinal implant systems fall into 3 categories based upon the forces of correction the implants exert on the spine, which are as follows: Distraction-based systems correct spinal deformities by mechanically applying a distractive force across a deformed segment with anchors at the top and bottom of the implants, which commonly attach to the spine, rib, and/or the pelvis. The present examples of distraction-based implants are spine-based or rib-based growing rods, vertical expandable titanium rib prosthesis, and remotely expandable devices. Compression-based systems correct spinal deformities with a compressive force applied to the convexity of the curve causing convex growth inhibition. This compressive force may be generated both mechanically at the time of implantation, as well as over time resulting from longitudinal growth of vertebral endplates hindered by the spinal implants. Examples of compression-based systems are vertebral staples and tethers. Guided growth systems correct spinal deformity by anchoring multiple vertebrae (usually including the apical vertebrae) to rods with mechanical forces including translation at the time of the initial implant. The majority of the anchors are not rigidly attached to the rods, thus permitting longitudinal growth over time as the anchors slide over the rods. Examples of guided growth systems include the Luque trolley and Shilla. Conclusions: Each system has its benefits and shortcomings. Knowledge of the fundamental principles upon which these systems are based may aid the clinician to choose an appropriate treatment for patients. Having a common language for these systems may aid in comparative research. Vertical expandable titanium rib prosthesis is used with humanitarian exemption. The other devices mentioned in this manuscript are not approved for growing constructs by the Food and Drug Administration and are used off-label.

Intensive Care Unit Versus Hospital Floor: A Comparative Study of Postoperative Management of Patients with Adolescent Idiopathic Scoliosis

BACKGROUND Patients undergoing posterior spinal instrumentation and fusion surgery for adolescent idiopathic scoliosis were admitted to the intensive care unit until two years ago, at which time we changed our protocol to admit these patients to the general hospital floor following a brief stay in a postanesthesia care unit. This study compared postoperative management on a hospital floor with that in the intensive care unit for patients with adolescent idiopathic scoliosis undergoing posterior spinal fusion. METHODS A retrospective review of 124 consecutive patients with adolescent idiopathic scoliosis treated with spinal fusion from August 2007 to August 2010 was performed. Inclusion criteria were a diagnosis of adolescent idiopathic scoliosis and posterior spinal instrumentation and fusion surgery. RESULTS Of 124 patients, sixty-six were managed postoperatively in the intensive care unit and fifty-eight, on the hospital floor. The mean age at the time of surgery was fourteen years. A mean of eleven vertebral levels (range, six to fifteen levels) were fused. No significant difference between the groups was found with respect to the mean age at the time of surgery, mean weight, mean preoperative and postoperative Cobb angles, and mean number of levels fused (p ≥ 0.12). However, the use of analgesic and antianxiety medication, number of postoperative blood tests, days of hospital stay, and number of physical therapy sessions were significantly decreased in the floor group compared with the intensive care unit group (p ≤ 0.05). No patient from the floor group had to be admitted to the intensive care unit. The mean charge was

Clay-shoveler's fracture equivalent in children.

33,121 for the floor group and

Early pelvic fixation failure in neuromuscular scoliosis.

39,252 for the intensive care unit group (p < 0.001). CONCLUSIONS Initial postoperative management of patients with adolescent idiopathic scoliosis following a posterior spinal instrumentation and fusion surgery on a general hospital floor, rather than in an intensive care unit, was associated with a shorter hospital stay, fewer blood tests, less analgesic and antianxiety medication usage, and fewer physical therapy sessions at this high-volume, academic, tertiary-care childrens hospital. In addition to improved patient outcomes, there was a significant decrease of 16% in hospital charges for the group that did not go to the intensive care unit.

Upper thoracic pedicle screw loss of fixation causing spinal cord injury: A review of the literature and multicenter case series

Study Design. Case report and literature review. Objective. This article reports 2 cases of clay-shovelers fracture equivalent in children presenting acutely after participation in sports. Summary of Background Data. The clay-shovelers fracture in adults is an avulsion fracture of the lower cervical or upper thoracic spinous process. To our knowledge, this is the first report in English literature on soft-tissue avulsion injury of the spinous process in children presenting with history and symptoms similar to clay-shovelers fractures. Methods. Retrospective review of 2 cases. Results. A 14-year-old baseball player and a 16-year-old wrestler experienced acute posterior neck pain after participation in sports. Both patients presented with a history and physical examination suggestive of clay-shovelers fracture but showed no evidence of injury on radiographs. Subsequent magnetic resonance images demonstrated an acute soft-tissue avulsion of the spinous process at C7 in 1 patient and T2 in the other. With nonoperative therapy, both patients returned to sports by 4 months, with occasional, intermittent discomfort a year after injury, which did not limit any activities. Conclusion. In adolescents, if the history and physical examination are consistent with a clay-shovelers fracture, but radiographs are normal, magnetic resonance imaging may be indicated to diagnose a soft-tissue avulsion.

Simple steps to minimize spine infections in adolescent idiopathic scoliosis.

Background: To report on early failures of pelvic fixation in posterior spinal fusions for neuromuscular scoliosis. Methods: A retrospective review of posterior-only spinal instrumentation and fusion to the pelvis with iliac screws was performed. Forty-one patients with a mean age of 14 years and mean 16 levels fused met the inclusion criteria. Diagnoses include cerebral palsy (22), Duchenne muscular dystrophy (7), other neuromuscular (10), and spina bifida (2). Cox proportional hazards regression modeling was used to compare rates of failure. Results: The mean preoperative primary Cobb angle was 82 degrees (range, 21 to 144 degrees). The pelvic obliquity correction was 76%. The fixation in the pelvis failed in 12/41 patients (29%). Failures include: screw head disengaged from screw shaft (5), iliac screw disengaged from rod (2), iliac connector disengaged from rod (2), iliac connector disengaged from iliac screw (4), and iliac screw loosened from bone (3). No failures occurred if there were at least 6 screws in L5, S1, and pelvis (0/7 patients). The failure rate with <6 screws in L5, S1, and pelvis was higher at 35% (12/34 patients) (P=0.16). When using traditional iliac screws with connectors to rods, all constructs had <6 screws in L5, S1, and pelvis. Only 1 failure occurred when S2-iliac screws were used, but was without clinical consequence. The mean time from surgery to failure was 18 months (range, 1 to 49 mo). Conclusion: Not placing bilateral pedicle screws at L5 and S1, in addition to 2 iliac screws, was associated with a 35% early failure rate of pelvic fixation. Level of Evidence: Level IV.

Ten Percent of Patients with Adolescent Idiopathic Scoliosis Have Variations in the Number of Thoracic or Lumbar Vertebrae

Study Design: Case Series and Review of the Literature. Objective: To report on cases of spinal cord injury from loss of fixation of upper thoracic pedicle screws. Summary of Background Data: Despite generally low rates of intraoperative neurological injury from pedicle screws, there is 1 reported case of T2 pedicle screw pullout causing spinal cord injury. Methods: A review of the literature and an informal poll of 2 professional societies searching for cases in which thoracic pedicle screws migrated postoperatively into the spinal canal was performed. Results: Three patients had failure of spinal instrumentation with the most cephalad pedicle screws (T2, T4 and T4) plowing into the spinal canal, causing direct trauma to the spinal cord with resulting clinical and neurological injury. Failure of fixation occurred at 1 month, 1 year, and 2 years after index procedure. In 2 patients, neurological injury was severe enough that they became nonambulatory; the third patient had rapidly progressive leg weakness. In each case, there were only 1 or 2 pedicle screws at the top of the construct, and a span of 6 to 7 vertebrae without rigid fixation below this. One similar case was found in the literature. Conclusions: Spinal instrumentation with only 1 to 2 pedicle screws at the top of the construct, and a span of >5 vertebrae below these screws without rigid fixation may be at risk for implant failure and catastrophic spinal cord injury. In the rare instance in which only 1 to 2 pedicle screws can be placed at the cephalad half of long spinal constructs, one may consider using hooks that would fail posteriorly and may present less risk to the spinal cord.

Neuromonitoring Changes Are Common and Reversible With Temporary Internal Distraction for Severe Scoliosis

Background: To examine the surgical site infection (SSI) rates in patients undergoing posterior spinal fusion surgery for adolescent idiopathic scoliosis (AIS) after implementation of a change in antibiotic prophylaxis and intraoperative irrigation. Methods: A retrospective review of all consecutive spinal fusions for AIS from 1996 to 2008 was performed. In 2003, 2 changes in our protocol were implemented: (1) routine antibiotic prophylaxis was changed from cefazolin alone to vancomycin and ceftazidime; (2) intraoperative irrigation technique was changed from bulb syringe to pulse lavage irrigation. We compared the rates of deep SSI requiring irrigation and debridement before institution of these changes (1996 to 2002) to the rates after these changes (2003 to 2008). Results: Before the change in the antibiotic and lavage regimen, 261 spinal fusions were performed. Of these, 28/261 (11%) patients underwent irrigation and debridement for SSI. The most common infecting pathogen was coagulase-negative Staphylococcus aureus (47%). Between the years 2003 and 2008, 263 spinal fusions were performed. Only 2/263 (0.7%) patients underwent irrigation and debridement for SSI. This decrease in infection rate is highly significant (P<0.001). Conclusions: Routine use of vancomycin and ceftazidime and pulsatile lavage for posterior spinal fusion in AIS patients decreased the rates of postoperative infection by 10 fold. As 2 variables were changed, it is impossible to know the relative effect of each. However, as spine infections can be so devastating, and the potential risks of these changes are small, we recommend both the new antibiotic and irrigation protocol. Level of Evidence: Level III.

Some Connectors in Distraction-based Growing Rods Fail More Than Others

BACKGROUND Surveys have demonstrated that wrong-site surgery of the spine is performed by up to 50% of spine surgeons over the course of a career. Inaccurate identification of appropriate vertebral levels is a common reason for wrong-site spine surgery. The present study examined the prevalence of variations in the number of vertebrae in patients with adolescent idiopathic scoliosis. METHODS A retrospective review of radiographs and reports of 364 consecutive patients undergoing operative treatment for adolescent idiopathic scoliosis at a single center was performed. The study included eighty-eight male patients (24%) and 276 female patients (76%) with a mean age of fourteen years (range, ten to twenty years). Radiographs were reviewed to assess the number of thoracic and lumbar vertebrae and the presence of a lumbosacral transitional vertebra. RESULTS Ten percent of the patients (thirty-eight) had an atypical number of vertebrae in the thoracic and/or lumbar spine. Twenty-one patients (5.8%) had an atypical number of thoracic vertebrae, with fourteen having eleven thoracic vertebrae and seven patients having thirteen. Twenty-four patients (6.6%) had an atypical number of lumbar vertebrae, with four having four lumbar vertebrae and twenty patients having six. A lumbosacral transitional vertebra was present in 6.3% (twenty-three) of the patients. Multilevel vertebral anomalies were present in 1.9% of the patients (seven of 364). A variation in the number of vertebrae had been identified in 0.5% (two) of the reports by the radiologist. CONCLUSIONS Variations in the number of thoracic or lumbar vertebrae were found in 10% of patients with adolescent idiopathic scoliosis but had been identified in only 0.5% of the radiology reports.

Are pedicle screw constructs really more expensive than hybrid constructs

STUDY DESIGN Retrospective review of consecutive cases. OBJECTIVE To examine the neurologic implications of applying intraoperative distraction to large curves. SUMMARY OF BACKGROUND DATA Temporary rods provide internal distraction during correction of severe scoliosis and may be an alternative to prolonged halo traction or vertebral column resection. METHODS A single surgeons consecutive experience with posterior-only spinal fusion with temporary distraction rods was reviewed retrospectively. Inclusion criteria were long posterior-only spinal fusion (10 or more levels) for severe scoliosis (major Cobb angle 80° or greater), treated with temporary internal distraction. Records were reviewed for age, gender, diagnosis, intraoperative course, and complications. Radiographs were reviewed for Cobb angles, T1-S1 length, and space available for each lung. RESULTS Twenty-two patients with a mean age of 14 years and a mean of 15 levels fused (range, 10-18 levels) were included. The mean preoperative coronal Cobb angle was 113° (range, 83°-144°), and a mean correction of 62° (54%) was achieved. There was a mean T1-S1 increase of 8.4 cm (range, 2.4-14 cm). Nine patients had 2-stage procedures separated by a mean of 7 days. Thirteen patients had a single procedure. Of 22 patients, 9 (41%) had intraoperative neuromonitoring changes. All neuromonitoring changes were reversed after releasing distraction on the temporary rod, except in 1 case. No patient had a clinical neurologic deficit. CONCLUSIONS Use of temporary distraction rods for severe scoliosis produces curve correction while providing a mean increase in T1-S1 height of 8 cm. Most steps in this surgery are reversible. Neuromonitoring changes are common, but they are reversible with release of some distraction. Neuromonitoring changes did not affect the final magnitude of correction, and there were no clinical neurologic deficits. We recommend that this procedure be performed only with good neuromonitoring.