The accuracy of navigation and 3D image-guided placement for the placement of pedicle screws in congenital spine deformity.

BACKGROUND: Treatment of congenital spine deformity has high surgical risk due to abnormal anatomy and dysmorphic pedicles. We hypothesized that an image-guided navigation system would result in a low rate of screw revision due to malposition. METHODS: From 2007 to 2010, 142 screws were placed in 14 consecutive patients with congenital spine deformity using an intraoperative computer tomography (CT) (O-arm) and image-guided navigation system (Stealth). Mean age was 8.8 years (range, 1 to 18 y). Deformities included scoliosis (12), kyphosis (1), and spinal dysgenesis (1). Screws were placed from T2 to S1. An intraoperative CT verified screw position. Need for intraoperative screw revision is the primary outcome measure. RESULTS: Of the 142 screws placed, 1 required revision intraoperatively due to malposition (99.3% screw accuracy rate). The screw was at L3 and was successfully redirected. There were no complications due to screw malposition. This navigated congenital screw accuracy rate (99.3%) is higher than the 94.9% accuracy rate reported for non-navigated screws in all children undergoing pedicle screw fixation in a recent systematic literature review and higher than the reported 96.4% accuracy rate for navigated pedicle screws in children. Kosmopoulos and colleagues found a lower accuracy rate (86.6%) in adult non-navigated screws (P<0.0001) and adult navigated screws (93.7%). Of note, 9 pedicles were noted on navigation to be absent. Despite the goal of bilateral screw placement at each fusion level, 31 of 173 pedicles were left unfilled due to technical impossibility based on intraoperative CT imaging. This represents an 18% screw dropout rate. CONCLUSIONS: CT-guided navigation resulted in the successful placement of 142 pedicle screws in patients with congenital deformity and altered anatomy, which represents a 99.3% screw accuracy rate. This is comparable with the screw accuracy rate of 93.7% reported for adult navigated pedicle screws. Further, navigation prevented attempts of screw placement at levels with absent or impassable pedicles. Image-guided navigation and intraoperative CT are valuable tools for the safe placement of pedicle screws in patients with significant congenital spine deformity and altered anatomy. LEVEL OF EVIDENCE: IV, Case Series.

Acinetobacter baumannii is not associated with osteomyelitis in a rat model: a pilot study.

BACKGROUND: Multidrug resistant Acinetobacter baumannii (MDR AB) with and without Staphylococcus aureus (SA) is a commonly isolated organism in infected segmental bone defects in combat-related trauma in Iraq and Afghanistan. Although MDR AB in visceral infections is a therapeutic challenge, control of infection appears more common for combat-related osteomyelitis. QUESTIONS/PURPOSES: Using a rat model, we explored the virulence of MDR AB in segmental bone defects alone and in combination with SA. METHODS: Segmental defects in 60 rat femurs were created, stabilized, and inoculated with MDR AB alone and 60 with MDR AB and SA. We performed qualitative and quantitative bacteriology and radiographic assessments at 2, 4, and 8 weeks for MDR AB and at 1, 2, and 3 weeks for MDR AB and SA. RESULTS: Quantitative bacteriology revealed a 3- to 5-log decrease in MDR AB from the initial inoculum. After polymicrobial inoculation, only 10 of 60 animals had positive cultures for MDR AB, whereas 59 of 60 animals had positive cultures for SA. Recovered SA were 2 to 5 log greater than the initial inoculum, while there again was a 3- to 5-log decrease in MDR AB. MDR AB alone did not cause bony lysis, but there was radiographic evidence of new bone formation in 67% of the segmental defects. Osteolysis was noted with MDR AB and SA. CONCLUSIONS: MDR AB did not appear to cause or contribute to clinically apparent osteomyelitis in this pilot study. CLINICAL RELEVANCE: Resolution of infections in combat-related segmental bone defects inoculated with MDR AB may be attributable to low virulence. Additional studies are needed to confirm low virulence and bone formation with MDR AB.

Predictive Value and Interrater Reliability of Radiographic Factors in Neurofibromatosis Patients With Dystrophic Scoliosis.

BACKGROUND: Scoliosis in patients with neurofibromatosis type I (NF1) can manifest as dystrophic or nondystrophic curves. Dystrophic scoliosis is rapidly progressive, rendering treatment challenging. Radiographic characteristics have been reported to predict dystrophic scoliosis, but their reliability and predictive value have not been well described. The purpose of this study is to assess the interobserver reliability for eight radiographic characteristics of dystrophic scoliosis and to evaluate the sensitivity and specificity of these characteristics relative to the gold standard of a definitive clinical diagnosis. METHODS: Spine radiographs of 122 NF1 patients from multiple institutions were graded by five spine surgeons as dystrophic or nondystrophic, based on eight radiographic characteristics of dystrophic modulation: rib penciling, vertebral rotation, scalloping, wedging, spindling of transverse processes, short sharp angular curve, widened interpedicular distance, and atypical location. The curves were classified by each submitting institution as dystrophic or nondystrophic based on clinical outcome. Interobserver reliability analysis was performed using Fleiss kappa. RESULTS: For the 122 cases, the interrater agreement among the five readers for the diagnosis of dystrophic scoliosis was good at 0.61. The agreement for individual radiographic characteristic ranged from 0.62 for wedging to 0.14 (poor) for scalloping. Surgeons underestimated the number of dystrophic curves, rating from 45% to 67% of the curve patterns as dystrophic, compared to the gold standard, which revealed 68% of the curves to be dystrophic. On multivariate analysis, rib penciling, vertebral rotation, vertebral wedging, and atypical location were significantly associated with true dystrophic status (odds ratios of 2.4, 3.0, 2.4, and 3.0, respectively). CONCLUSION: Overall dystrophic diagnosis can be assessed by radiographic characteristics. Better understanding of the predictive value of specific radiographic features may assist in early diagnosis of patients with dystrophic NF and assist surgeons in identifying dystrophic curve patterns and instituting prompt, appropriate treatment. LEVEL OF EVIDENCE: Level III.

Pulmonary function tests correlated with thoracic volumes in adolescent idiopathic scoliosis.

Scoliosis deformity has been linked with deleterious changes in the thoracic cavity that affect pulmonary function. The causal relationship between spinal deformity and pulmonary function has yet to be fully defined. It has been hypothesized that deformity correction improves pulmonary function by restoring both respiratory muscle efficiency and increasing the space available to the lungs. This research aims to correlate pulmonary function and thoracic volume before and after scoliosis correction. Retrospective correlational analysis between thoracic volume modeling from plain x-rays and pulmonary function tests was conducted. Adolescent idiopathic scoliosis patients enrolled in a multicenter database were sorted by pre-operative Total Lung Capacities (TLC) % predicted values from their Pulmonary Function Tests (PFT). Ten patients with the best and ten patients with the worst TLC values were included. Modeled thoracic volume and TLC values were compared before and 2 years after surgery. Scoliosis correction resulted in an increase in the thoracic volume for patients with the worst initial TLCs (11.7%) and those with the best initial TLCs (12.5%). The adolescents with the most severe pulmonary restriction prior to surgery strongly correlated with post-operative change in total lung capacity and thoracic volume (r2 = 0.839; p < 0.001). The mean increase in thoracic volume in this group was 373.1 cm3 (11.7%) which correlated with a 21.2% improvement in TLC. Scoliosis correction in adolescents was found to increase thoracic volume and is strongly correlated with improved TLC in cases with severe restrictive pulmonary function, but no correlation was found in cases with normal pulmonary function. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:175-182, 2017.

Comparison of nonnavigated and 3-dimensional image-based computer navigated balloon kyphoplasty.

Balloon kyphoplasty is a common treatment for osteoporotic and pathologic compression fractures. Advantages include minimal tissue disruption, quick recovery, pain relief, and in some cases prevention of progressive sagittal deformity. The benefit of image-based navigation in kyphoplasty has not been established. The goal of this study was to determine whether there is a difference between fluoroscopy-guided balloon kyphoplasty and 3-dimensional image-based navigation in terms of needle malposition rate, cement leakage rate, and radiation exposure time. The authors compared navigated and nonnavigated needle placement in 30 balloon kyphoplasty procedures (47 levels). Intraoperative 3-dimensional image-based navigation was used for needle placement in 21 cases (36 levels); conventional 2-dimensional fluoroscopy was used in the other 9 cases (11 levels). The 2 groups were compared for rates of needle malposition and cement leakage as well as radiation exposure time. Three of 11 (27%) nonnavigated cases were complicated by a malpositioned needle, and 2 of these had to be repositioned. The navigated group had a significantly lower malposition rate (1 of 36; 3%; P=.04). The overall rate of cement leakage was also similar in both groups (P=.29). Radiation exposure time was similar in both groups (navigated, 98 s/level; nonnavigated, 125 s/level; P=.10). Navigated kyphoplasty procedures did not differ significantly from nonnavigated procedures except in terms of needle malposition rate, where navigation may have decreased the need for needle repositioning.

Comparison of cranial facet joint violation rates between open and percutaneous pedicle screw placement using intraoperative 3-D CT (O-arm) computer navigation.

STUDY DESIGN: Retrospective study comparing cranial facet joint violation rates of open and percutaneous pedicle screws inserted using 3-dimensional image-guidance. OBJECTIVE: To determine the rate of cranial facet joint violation in intraoperative computed tomography (CT) image-guided lumbar pedicle screw instrumentation and compare facet joint violation rates between CT image-guided open and percutaneous techniques. SUMMARY OF BACKGROUND DATA: Facet joint violation by pedicle screws can potentially result in a higher rate of adjacent segment degeneration. Reported cranial facet joint violation rates range from 7% to 100%. Intraoperative image-guidance, which has enhanced pedicle screw placement accuracy, may aid in avoiding impingement of the cranial facet joints. METHODS: We reviewed 188 cases of 3-dimensional image-guided lumbar pedicle screw instrumentation from November 2006 to December 2011. The cranial screws of each construct were graded by 3 reviewers according to the Seo classification (0 = no impingement; 1 = screw head in contact/suspected to be in contact with joint; 2 = screw clearly invaded the joint) on intraoperative axial CT images. If there was a difference in evaluation, a consensus was reached to arrive at a single grade. The χ2 test was used to determine significance between the open and percutaneous group (α = 0.05). RESULTS: A total of 370 screws (245 open, 125 percutaneous) were graded. Overall facet joint violation rate was 18.9% (grade 1 = 16.2%, grade 2 = 2.7%). Open technique (grade 1 = 22.4%, grade 2 = 4.1%) had a significantly higher violation rate than percutaneous technique (grade 1 = 4%, grade 2 = 0%) (P < 0.0001). There is a trend of an increasing likelihood of facet joint violation from L1 to L5. CONCLUSION: The use of intraoperative CT image-guidance in lumbar pedicle screw placement resulted in a facet joint violation rate at the lower end of the reported range in literature. The percutaneous technique has a significantly lower facet violation rate than the open technique. LEVEL OF EVIDENCE: 4.

Intraoperative 3-dimensional imaging (O-arm) for assessment of pedicle screw position: Does it prevent unacceptable screw placement?

BACKGROUND: Pedicle screws are biomechanically superior over other spinal fixation devices. When improperly positioned, they lose this advantage and put adjacent structures at risk. Accurate placement is therefore critical. Postoperative computed tomography (CT) scans are the imaging gold standard and have shown malposition rates ranging from 2% to 41%. The O-arm (Medtronic Navigation, Louisville, Colorado) is an intraoperative CT scanner that may allow intervention for malpositioned screws while patients are still in the operating room. However, this has not yet been shown in clinical studies. The primary objective of this study was to assess the usefulness of the O-arm for evaluating pedicle screw position by answering the following question: What is the rate of intraoperative pedicle screw revision brought about by O-arm imaging information? A secondary question was also addressed: What is the rate of unacceptable thoracic and lumbar pedicle screw placement as assessed by intraoperative O-arm imaging? METHODS: This is a case series of consecutive patients who have undergone spine surgery for which an intraoperative 3-dimensional (3D) CT scan was used to assess pedicle screw position. The study comprised 602 pedicle screws (235 thoracic and 367 lumbar/sacral) placed in 76 patients, and intraoperative 3D (O-arm) imaging was obtained to assess screw position. Action taken at the time of surgery based on imaging information was noted. An independent review of all scans was also conducted, and all screws were graded as either optimal (no breach), acceptable (breach ≤2 mm), or unacceptable (breach >2 mm). The rate of pedicle screw revision, as detected by intraoperative 3D CT scan, was determined. RESULTS: On the basis of 3D imaging information, 17 of 602 screws (2.8%) in 14 of 76 cases (18.4%) were revised at the time of surgery. On independent review of multiplanar images, 11 screws (1.8%) were found to be unacceptable, 32 (5.3%) were acceptable, and 559 (92.9%) were optimal. All unacceptable screws were revised to an optimal or acceptable position, and an additional 6 acceptable screws were revised to an optimal position. Thus, by the end of the cases, none of the 602 pedicle screws in the 76 surgical procedures was in an unacceptable position. CONCLUSION: The new-generation intraoperative 3D imaging system (O-arm) is a useful tool that allows more accurate assessment of pedicle screw position than plain radiographs or fluoroscopy alone. It prompted intraoperative repositioning of 2.8% of pedicle screws in our series. Most importantly, it allowed identification and revision of all unacceptably placed pedicle screws without the need for reoperation.

Pediatric pedicle screws: comparative effectiveness and safety: a systematic literature review from the Scoliosis Research Society and the Pediatric Orthopaedic Society of North America task force.

BACKGROUND: Pedicle screws are widely used in spinal surgery. There is extensive published literature concerning the use of pedicle screw instrumentation for spinal surgery in adults. Now there is a trend to use pedicle screws in pediatric patients, including the very young. A systematic review of the current English-language literature on the use of pedicle screw instrumentation in the pediatric age group was performed to specifically determine (1) the pedicle screw placement accuracy in patients with spine deformity and (2) the effect size of all-pedicle screw constructs compared with other methods of spinal instrumentation in terms of the percentage of scoliosis correction. METHODS: English-language studies of pedicle screw use in pediatric patients (defined as those younger than eighteen years of age) were included. Descriptive statistics synthesized the accuracy of pedicle screw placement. Accuracy rates were compared between pediatric and adult patients. The effect of pedicle screw instrumentation on scoliosis correction was calculated with use of Cobb angle measurements. RESULTS: On the basis of the literature search, 1181 articles were screened, 320 abstracts were examined, and ninety full-text articles representing 5761 patients were reviewed in detail. Seventeen studies met the inclusion criteria for the analysis of pedicle screw placement accuracy. A total of 13,536 pedicle screws were placed in 1353 pediatric patients. The overall placement accuracy rate in pediatric patients was 94.9%, which was higher than the rate of 91.5% reported for adults. The weighted, geometric, and 5% trimmed mean accuracy rates of pedicle screw placement were 91.9%, 88.5%, and 89.1%, respectively (standard deviation = 10%; interquartile range = 10%). Sixteen comparative studies met the inclusion criteria for the analysis of the effect of pedicle screw instrumentation on scoliosis correction. Pedicle screw constructs had a significantly larger percentage of Cobb angle correction compared with hooks (Cohen's d = 1.14) and hybrid constructs (Cohen's d = 0.49). CONCLUSIONS: The accuracy of pedicle screw placement in the pediatric spine exceeds the accuracy rate reported in adults. Pedicle screw instrumentation constructs are significantly more effective for scoliosis correction, as determined on the basis of Cobb angle measurements, than are hook constructs and hybrid constructs.