Are We Underestimating the Significance of Pedicle Screw Misplacement?

STUDY DESIGN: A retrospective review of charts, x-rays (XRs) and computed tomography (CT) scans was performed. OBJECTIVE: To evaluate the accuracy of pedicle screw placement using a novel classification system to determine potentially significant screw misplacement. SUMMARY OF BACKGROUND DATA: The accuracy rate of pedicle screw (PS) placement varies from 85% to 95% in the literature. This demonstrates technical ability but does not represent the impact of screw misplacement on individual patients. This study quantifies the rate of screw misplacement on a per-patient basis to highlight its effect on potential morbidity. METHODS: A retrospective review of charts, XRs and low-dose CT scans of 127 patients who underwent spinal fusion with pedicle screws for spinal deformity was performed. Screws were divided into four categories: screws at risk (SAR), indeterminate misplacements (IMP), benign misplacements (BMP), accurately placed (AP). RESULTS: A total of 2724 screws were placed in 127 patients. A total of 2396 screws were placed accurately (87.96%). A total of 247 screws (9.07%) were BMP, 52 (1.91%) were IMP, and 29 (1.06%) were considered SAR. Per-patient analysis showed 23 (18.11%) of patients had all screws AP. Thirty-five (27.56%) had IMP and 18 (14.17%) had SAR. Risk factor analysis showed smaller Cobb angles increased likelihood of all screws being AP. Sub-analysis of adolescent idiopathic scoliotic patients showed no curve or patient characteristic that correlated with IMP or SAR. Over 40% of patients had screws with either some/major concern. CONCLUSION: Overall reported screw misplacement is low, but it does not reflect the potential impact on patient morbidity. Per-patient analysis reveals more concerning numbers toward screw misplacement. With increasing pedicle screw usage, the number of patients with misplaced screws will likely increase proportionally. Better strategies need to be devised for evaluation of screw placement, including establishment of a national database of deformity surgery, use of intra-operative image guidance, and reevaluation of postoperative low-dose CT imaging. LEVEL OF EVIDENCE: 3.

Minimally Invasive Surgery in Patients With Adolescent Idiopathic Scoliosis: Is it Better than the Standard Approach? A 2-Year Follow-up Study.

STUDY DESIGN: This is a retrospective controlled study. OBJECTIVE: To compare the safety and efficacy of minimally invasive surgery (MIS) for the surgical management of adolescent idiopathic scoliosis (AIS) to the standard open posterior approach (PSF). SUMMARY OF BACKGROUND DATA: MIS approaches offer the potential to reduce soft-tissue trauma, intraoperative blood loss, and surgical-site infection. Thus far, MIS has been successfully utilized for the surgical correction of multilevel spine pathology in adults. It is not yet known if these results can be replicated in the surgical management of AIS. MATERIALS AND METHODS: Seven MIS patients were compared with 15 PSF patients using minimum 2-year follow-up data. Parameters studied included preoperative patient and deformity characteristics, perioperative details, extent of deformity correction, and complications. Data were compared using Mann-Whitney tests for continuous variables and Fisher exact tests for categorical variables. RESULTS: The MIS and PSF groups were similar for all preoperative characteristics collected (P>0.05). MIS patients had fewer fixation points (P=0.015), but a longer median operative time (P=0.011). There was no significant difference in estimated blood loss (EBL) (P=0.051), EBL/fixation point (P=0.204), or amount of fluids administered (P=0.888). Postoperative recovery did not differ between the 2 groups in number of intensive care unit days (P=0.362), length of hospital stay (P=0.472), time to mobilization (P=1.00), Visual Analogue Scale pain scores (P=0.698), or patient-controlled analgesia (P=1.00). The MIS technique had similar deformity correction, screw placement accuracy, and fusion status when compared with the PSF group. MIS patients had lower blood transfusion rate (P=0.02), shorter fusion (P=0.046) and fewer pedicle screws (P=0.015). CONCLUSIONS: The short-term advantages seen in MIS for adult scoliosis were not as obvious in our series. We found similar deformity correction and adequate fusion, however shortcomings related to learning curve, and instrumentation persist. MIS surgery is an innovative treatment for AIS that is technically feasible with significantly lower transfusion rate, shorter fusion lenghts and lesser pedicle screw fixation. Despite these advanatges, its role in AIS is currently difficut to define.

Complications associated with surgical repair of syndromic scoliosis.

BACKGROUND: There are a number of syndromes that have historically been associated with scoliosis e.g.: Marfan, Down, and Neurofibromatosis. These syndromes have been grouped together as one etiology of scoliosis, known as syndromic scoliosis. While multiple studies indicate that these patients are at high risk for perioperative complications, there is a paucity of literature regarding the collective complication rates and surgical needs of this population. METHODS: PubMed and Embase databases were searched for literature encompassing the surgical complications associated with the surgical management of patients undergoing correction of scoliosis in the syndromic scoliosis population. Following exclusion criteria, 24 articles were analyzed for data regarding these complications. RESULTS: The collective complication rates and findings of these articles were categorized based on specific syndrome. The rates and types of complications for each syndrome and the special needs of patients with each syndrome are discussed. Several complication trends of note were observed, including but not limited to the universally nearly high rate of wound infections (>5% in each group), high rate of pulmonary complications in patients with Rett syndrome (29.2%), high rate (>10%) of dural tears in Marfan and Ehlers-Danlos syndrome patients, high rate (>20%) of implant failure in Down and Prader-Willi syndrome patients, and high rate (>25%) of pseudarthrosis in Down and Ehlers-Danlos patients. CONCLUSIONS: Though these syndromes have been classically grouped together under the umbrella term "syndromic," there may be specific needs for patients with each of these ailments. Given the high rate of complications, further research is necessary to understand the unique needs for each of these patient groups in the preoperative, intraoperative, and postoperative settings.

Prevalence, Distribution, and Surgical Relevance of Abnormal Pedicles in Spines with Adolescent Idiopathic Scoliosis vs. No Deformity: A CT-Based Study.

BACKGROUND: A thorough understanding of pedicle morphology is necessary for pedicle screw placement. Previous studies classifying pedicle morphology, to our knowledge, have neither discussed the range of abnormal morphology nor correlated patient or curve characteristics with abnormal morphology to identify at-risk pedicles. METHODS: With the use of computed tomography (CT) images, we analyzed a total of 6116 pedicles from ninety-five patients without spinal deformity (forty-two females and fifty-three males) and ninety-one patients with adolescent idiopathic scoliosis (AIS) (sixty-eight females and twenty-three males). Pedicle morphology was classified as: Type A, a cancellous channel of >4 mm; Type B, a cancellous channel of 2 to 4 mm; Type C, a cortical channel of ≥2 mm; or Type D, a cortical or cancellous channel of <2 mm. Types B, C, and D were defined as abnormal. Patient demographic data and pedicle distribution were assessed for prevalence and likelihood of abnormal pedicle morphology. Postoperative CT images from fifty-nine patients with AIS were used to assess screw placement. RESULTS: There was a significantly higher rate of abnormal pedicles in patients with AIS (p = 0.001). More abnormal pedicles were located in the thoracic spine compared with the lumbar spine both in patients without deformity (13.3% versus 2.0%) and patients with AIS (31.9% versus 2.4%). Significantly more abnormal pedicles were located on the concavity (p < 0.001), within the periapical region (p = 0.02), and on the apex of the curve (p = 0.03). Three times as many pedicle screws were misplaced in abnormal pedicles compared with normal pedicles (21% versus 7%). CONCLUSIONS: Our study found a significantly higher prevalence of abnormal pedicles in the patients with AIS. Of the abnormal pedicles in these patients, most were in the thoracic spine, on the concave side, and in the periapical and apical regions. CLINICAL RELEVANCE: Knowledge of abnormal pedicles may enable surgeons to anticipate and plan for difficult screw placement and further decrease risk to the patient.

Pedicle screws adjacent to the great vessels or viscera: a study of 2132 pedicle screws in pediatric spine deformity.

STUDY DESIGN: A retrospective study. OBJECTIVE: To determine the incidence of pedicle screws close to vital structures and to identify patient or curve characteristics that increase the risk of screw misplacement. SUMMARY AND BACKGROUND: Most pedicle screw misplacements are asymptomatic, thus they are frequently undetected. This study identifies the rate of screw placement in proximity to vital structures using postoperative computed tomography scans. METHODS: A total of 2132 screws in 101 patients, who underwent posterior spinal fusion for spinal deformity, were reviewed. Screws adjacent to great vessels and viscera were identified and evaluated. Patients with screws at risk (group B) were compared with patients without screws at risk (group A). Patient and curve characteristics were analyzed to determine whether a correlation with screw misplacement exists. RESULTS: A total of 40 at risk screws (∼2%) were identified in 25 patients (∼25%). These 40 screws were in proximity to the aorta (31), left subclavian artery (1), esophagus (3), trachea (3), pleura (1), and diaphragm (1). Of the 31 screws close to the aorta, 10 screws in 6 patients were impinging or distorting the aortic wall. One hundred percent of misplaced screws were in the thoracic spine, 50% were misplaced laterally, 50% were 35 mm long, 57.5% were in pedicles with normal morphology, and 75% were in curves between 40 and 70 degrees. Median screw misplacement rate was 10% in group A and 13% in group B. Adjusted for age and preoperative Cobb angle, patients with a higher misplacement rate were more likely to have screws adjacent to vital organs [adjusted odds ratio: 1.06 (95% confidence interval, 1.01-1.13), P=0.033]. CONCLUSIONS: Although only a small number of screws were at risk, they occurred in a large percentage of patients (25%). A single at-risk screw causes a significant complication for the patient. Postoperative imaging beyond routine x-rays may be needed to detect at-risk screws in asymptomatic patients.

Scoliosis surgery in patients with adolescent idiopathic scoliosis does not alter lung volume: a 3-dimensional computed tomography-based study.

STUDY DESIGN: Retrospective study of surgically treated patients with adolescent idiopathic scoliosis. OBJECTIVE: To determine the change in lung volume after the surgical correction of scoliosis using a volumetric reconstruction of lung volume from computed tomographic (CT) scans. SUMMARY OF BACKGROUND DATA: Previously published studies have shown that pulmonary function tests improve after scoliosis correction; however, these results are not consistent. CT-based volumetric studies in patients with scoliosis have previously shown differences in lung volume and lung volume ratio when compared with a normal population. To date, no study exists that analyzes changes in these parameters after scoliosis surgery. METHODS: A total of 29 patients with adolescent idiopathic scoliosis who had pre- and postoperative CT scans on file were included in this study. Three-dimensional lung volume reconstruction was performed (TeraRecon software, TeraRecon, Inc., Foster City, CA). Appropriate masking methods were used to isolate the lung tissue. Total lung volumes, left and right lung volumes, and left/right lung volume ratio were obtained from the pre- and postoperative CT scans. Hemithoracic symmetry, pre- and postoperative Cobb angle, and kyphosis were also calculated. RESULTS: Neither total lung volume nor left/right lung volume ratio changed significantly postoperatively. Surgery did not significantly change total lung volume (P = 0.87), right lung volume (P = 0.69), left lung volume (P = 0.70), or the ratio between right and left lung volumes (P = 0.87). Hemithoracic asymmetry was significantly improved (P < 0.001). Median preoperative major Cobb angle was 53.2° and median preoperative kyphosis was 32.8°. Postoperatively, the median major Cobb angle was 15.0°, resulting in a 70% Cobb correction, and mean postoperative kyphosis was 31.1°. CONCLUSION: Corrective scoliosis surgery does not alter total lung volume or the ratio of right-to-left lung volume. Deformity correction leads to an improvement in the symmetry of the thoracic architecture and costovertebral joint mechanics, as evidenced by the improved hemithoracic asymmetry. Thus, the change in pulmonary function tests, which has been previously documented, may be a dynamic rather than a static phenomenon. LEVEL OF EVIDENCE: 4.

Timing of surgical staging in adult spinal deformity surgery: is later better?

COMMENTARY ON: Hassanzadeh H, Gjolaj JP, El Dafrawy MH, et al. The timing of surgical staging has a significant impact on the complications and functional outcomes of adult spinal deformity surgery. Spine J 2013;13:1717-22 (in this issue).

Anterior release generates more thoracic rotation than posterior osteotomy: a biomechanical study of human cadaver spines.

STUDY DESIGN: Biomechanical testing of human cadaveric spines. OBJECTIVE: To determine the effect of anterior and posterior anatomic structures on the rotational stability of the thoracic spine. SUMMARY OF BACKGROUND DATA: Historically, large and/or stiff spinal deformities were treated with anterior release to facilitate correction. However, anterior release increases risks and requires a 2-part procedure. Recently, large or rigid deformities have been treated with a single posterior procedure using pedicle screws and spinal osteotomies. No study has yet evaluated the effect of anterior release or posterior osteotomy on thoracic spinal column rotation. METHODS: Thoracolumbar spines were obtained from cadavers and segmented into upper, middle, and lower specimens. Specimens were cyclically loaded with a ±5 N·m moment in axial rotation for 10 cycles. Specimens were tested intact and then retested after sectioning or removal of each structure to simulate those removed during anterior release and posterior osteotomy. The total increases in axial rotation after posterior and anterior resections were calculated using a 3-dimensional motion capture camera system. For each ligament resection, the absolute and percent change in degrees of rotation was calculated from comparison with the intact specimen. The median data points were compared to account for outliers. RESULTS: Resection of anterior structures was more efficacious than resection of posterior structures. An 8.8% to 71.9% increase in the amount of axial rotation was achieved by a posterior release, whereas resection of anterior structures led to a 141% to 288% increase in rotation. The differences between the anterior and posterior resections at all levels tested (T2-T3, T6-T7, and T10-T11) were significant (P < 0.05). CONCLUSION: Anterior release generated significantly more thoracic rotation than posterior osteotomy in biomechanical testing of human cadaver spines. LEVEL OF EVIDENCE: N/A.

Pedicle subtraction osteotomy in the cervical spine.

STUDY DESIGN: Description of surgical technique with review of literature. OBJECTIVE: To describe the surgical management of cervical spine deformity, using pedicle subtraction osteotomy. SUMMARY OF BACKGROUND DATA: Previous articles have primarily described Smith-Petersen osteotomies and Simmons' modifications to correct fixed cervical deformity. Those were typically performed with the patient awake and sedated in a seated position and without the use of spinal instrumentation. METHODS: Description of a single surgeon's technique for performing pedicle subtraction osteotomy to treat fixed cervical deformity. CONCLUSION: The use of pedicle subtraction osteotomy in the cervical spine is a safe and effective procedure when performed by experienced surgeons and can result in a satisfying outcome for both the patient and the surgeon.

Patient evaluation and clinical assessment of adult spinal deformity.

The clinical evaluation of adults with spinal deformity can be challenging for both general orthopaedic surgeons and spinal specialists. To properly treat these patients, the physician must be aware of the various types of adult spinal deformity and the basic principles of spinal misalignment. A complete patient assessment must include a thorough history and physical examination. Appropriate imaging studies can be used to characterize the extent of the deformity and determine the need for surgical intervention or referral to a spine specialist. The ultimate goal of the evaluation of an adult with spinal deformity is to determine the impact of the deformity on the patient's quality of life, including the ability to work and perform activities of daily living. For patients considering surgical treatment, additional factors must be included in the assessment because of the high rate of complications associated with adult deformity procedures.

Pediatric spinal deformity: what every orthopaedic surgeon needs to know.

Pediatric spinal deformity is an integral part of orthopaedic surgical practice. In a general or specialized practice, the well-versed orthopaedic surgeon should be aware of the diagnostic methods and the natural history from which practice standards are derived. It is important to be aware of the spectrum of spinal deformity in children (from early-onset scoliosis to adolescent idiopathic scoliosis, kyphosis, and spondylolisthesis) and current principles of growth and maturation as applied to the spine and the thorax. This information should be helpful in attaining the appropriate diagnosis, treatment, and/or referral for a pediatric patient with a spinal deformity.

Minimally invasive scoliosis surgery: an innovative technique in patients with adolescent idiopathic scoliosis.

Minimally invasive spine surgery is becoming more common in the treatment of adult lumbar degenerative disorders. Minimally invasive techniques have been utilized for multilevel pathology, including adult lumbar degenerative scoliosis. The next logical step is to apply minimally invasive surgical techniques to the treatment of adolescent idiopathic scoliosis (AIS). However, there are significant technical challenges of performing minimally invasive surgery on this patient population. For more than two years, we have been utilizing minimally invasive spine surgery techniques in patients with adolescent idiopathic scoliosis. We have developed the present technique to allow for utilization of all standard reduction maneuvers through three small midline skin incisions. Our technique allows easy passage of contoured rods, placement of pedicle screws without image guidance, and allows adequate facet osteotomy to enable fusion. There are multiple potential advantages of this technique, including: less blood loss, shorter hospital stay, earlier mobilization, and relatively less pain and need for pain medication. The operative time needed to complete this surgery is longer. We feel that a minimally invasive approach, although technically challenging, is a feasible option in patients with adolescent idiopathic scoliosis. Although there are multiple perceived benefits, long term data is needed before it can be recommended for routine use.

Nerve injury during the transpsoas approach for lumbar fusion.

A lateral transpsoas approach to achieve interbody fusion in the lumbar spine using either the extreme lateral interbody fusion or direct lateral interbody fusion technique is an increasingly popular method to treat spinal disease. Dissection and dilation through the iliopsoas muscle places the lumbosacral plexus at risk for injury, but there is very limited information in the published literature about adverse clinical events resulting in postoperative motor deficits or reports of failure of electrophysiological monitoring to detect nerve injury. The authors present 2 cases of postoperative motor deficits following the transpsoas approach not detected by intraoperative monitoring, review the medical literature, and discuss strategies for complication avoidance.