The Fragility of Statistical Findings in Cervical Disc Arthroplasty: a Systematic Review of Randomized Controlled Trials.

PURPOSE: This study employs both the fragility index (FI) and fragility quotient (FQ) to assess the level of robustness in the cervical disc arthroplasty (CDA) literature. We hypothesize that dichotomous outcomes involving CDA would exhibit statistical vulnerability. METHODS: A PubMed search was conducted to evaluate dichotomous data for randomized controlled trials (RCTs) in CDA literature from 2000 to 2023. The FI of each outcome was calculated through the reversal of a single outcome event until significance was reversed. The FQ was calculated by dividing each fragility index by the study sample size. The interquartile range (IQR) was also calculated for the FI and FQ. RESULTS: Of the 1561 articles screened, 111 met the search criteria, with 35 RCTs evaluating CDA included for analysis. Six hundred and ninety-three outcome events with 130 significant (P < 0.05) outcomes and 563 nonsignificant (P ≥ 0.05) outcomes were identified. The overall FI and FQ for all 693 outcomes were 5 (IQR 3-7) and 0.019 (IQR 0.011-0.043). Fragility analysis of statistically significant outcomes and nonsignificant outcomes both revealed an FI of 5. All of the studies reported loss to follow-up (LTF) data where 65.7% (23) did not report or reported an LTF greater or equal to 5. CONCLUSIONS: The literature regarding CDA RCTs lacks statistical robustness and may misrepresent the conclusions with the sole use of the P value. By implementing the FI and FQ along with the P value, we believe the interpretation and contextualization of the clinical data surrounding CDA will be better understood.

The iliac kickstand screw: anatomic CT analysis of screw trajectory and osseous corridor for screw placement.

INTRODUCTION: The 'kickstand screw-rod' technique has been recently described for correction of coronal malalignment. This technique utilizes powerful 'construct-to-ilium' distraction between a fixed multi-screw thoracic construct and the ilium, facilitated by a novel 'iliac kickstand screw'. The 'iliac kickstand screw' traverses a previously undescribed osseous corridor in the ilium. OBJECTIVE: Using a radiographic CT study, the objective is to describe a large osseous corridor within the ilium to accommodate the novel iliac kickstand screw. METHODS: 50 consecutive patients with pelvic CTs at an academic medical center were queried. Simulated iliac kickstand screw trajectories for the left and right hemipelvis were analyzed with 3D visualization software. Maximal screw lengths and dimensions, and trajectories in the osseous corridor were measured. RESULTS: 50 patients' (31 female, 19 male) pelvic CTs were measured with a total of 100 simulated screws. The mean age was 52.4 years and BMI 28.1 ± 7.9. The average length is 119.7 ± 6.6 mm (range 98.7 - 135.3). The narrowest width (maximum potential screw diameter) is 17.8 ± 2.9 mm (coronal) and 20.8 ± 5.3 mm (sagittal). The starting point to the top of the iliac crest is 66.4 mm lateral to midline, and 15.9° caudal in the sagittal and 6.1° lateral in the coronal planes. CONCLUSIONS: The novel iliac kickstand screw traverses a consistent and large osseous corridor within the ilium. The average simulated screw length is 119.7 mm and maximum potential diameter of 17.8 mm. Starting points relative to the iliac crest are identified.

Quantitative and qualitative analyses of spinal canal encroachment during cervical laminectomy using the kerrison rongeur versus High-Speed burr.

BACKGROUND: Several cervical laminectomy techniques have been described. One commonly used method involves making bilateral trough laminotomies using either a Kerrison rongeur or a high speed burr, and then removing the lamina en-bloc. Alternatively, some surgeons prefer to thin the lamina with the burr, and then remove the lamina in a piecemeal fashion using Kerrison rongeurs. Some surgeons have warned against the potential risk of iatrogenic spinal cord injury from inserting the Kerrison footplate into a stenotic canal. We aim to quantify the amount of canal encroachment for various methods of cervical laminectomies. METHODS: Three attending spine surgeons and two fellows each performed laminectomies using C5 sawbones models. The canal was completely filled with modeling putty to simulate a stenotic spinal cord. Bilateral trough laminotomies were performed using a 1 mm Kerrison, a 2 mm Kerrison, and a 3 mm matchstick high-speed burr. Piecemeal laminectomies were performed with a 2 mm Kerrison. A blinded spine surgery fellow performed all quantitative measurements. Three blinded researchers qualitatively ranked the amount of "canal encroachment". RESULTS: The average canal encroachment was 0.50 ± 0.45mm for the burr, 1.37 ± 0.68 mm for the 1 mm Kerrison, and 1.47 ± 0.37 mm for the 2 mm Kerrison (p = .002). There was a statistically significant difference between the burr and 1 mm Kerrison (p = .01) and between the burr and the 2 mm Kerrison (p = .001). There was no statistical difference between the 1 mm and 2 mm Kerrison (p = .78). The mean rank of the burr group, the Kerrison rongeur group, and the piecemeal group were 1.41, 1.94, and 2.65, respectively, on an ordinal scale of 1-3. CONCLUSION: When performing a trough laminotomy, the high-speed burr results in less canal encroachment compared to 1 mm or 2 mm Kerrison rongeurs. In the setting of a stenotic spinal canal, spine surgeons should consider using the burr to perform laminectomy to minimize the degree of canal encroachment.

Trapeziometacarpal joint stability: the evolving importance of the dorsal ligaments.

BACKGROUND: Trapeziometacarpal (TMC) arthritis of the thumb is a common source of hand pain and disability. TMC ligamentous instability may play a role in TMC degeneration. However, the relative importance of the TMC ligaments in the etiology of degeneration and the use of surgery to treat instability in early-stage arthritis are unclear. QUESTIONS/PURPOSES: In this review, we addressed several questions: (1) What are the primary ligamentous stabilizers of the thumb TMC joint? (2) What is the evidence for ligament reconstruction or ligament imbrication in the treatment of thumb TMC joint osteoarthritis? And (3) what is the evidence for thumb metacarpal osteotomy in the treatment of thumb TMC joint osteoarthritis? METHODS: We performed a systematic review of the literature using PubMed (MEDLINE(®)) and Scopus(®) (EMBASE(®)) for peer-reviewed articles published until November 2012. Fifty-two studies fit the inclusion criteria. Twenty-four studies were anatomic, biomechanical, or histopathologic studies on TMC joint ligamentous anatomy, 16 studies were clinical studies concerning ligament reconstruction, and 12 studies were clinical studies on thumb metacarpal osteotomy. RESULTS: Over the past two decades, increasing evidence suggests the dorsoradial ligament is the most important stabilizer of the TMC joint. Other ligaments consistently identified are the superficial anterior oblique, deep anterior oblique, intermetacarpal, ulnar collateral, and posterior oblique ligaments. Ligament reconstruction and metacarpal osteotomy relieve pain and improve grip strength based on Level IV studies. CONCLUSIONS: The dorsal ligaments are the primary stabilizers of the TMC joint. Ligament reconstruction and metacarpal osteotomy ameliorate ligamentous laxity and relieve pain based on Level IV studies.

Closed soft tissue extensor mechanism injuries (mallet, boutonniere, and sagittal band).

The extensor mechanism of the hand is complex and can be disrupted at several different points, from hand trauma. This article summarizes current concepts relating to the presentation and treatment of closed soft tissue injuries of the extensor mechanism in zones I, III, and V, commonly known as mallet finger and boutonniere deformities and sagittal band injuries.

A New Objective Radiographic Criteria for Diagnosis of Adult Idiopathic Scoliosis: Apical Pedicle Diameter Asymmetry.

OBJECTIVE: We sought to test the hypothesis that a difference of ≥1 mm in pedicle diameter between the convex and concave pedicles at the apex of a lumbar curve is a sensitive and/or specific criteria for adult idiopathic scoliosis (AdIS). METHODS: Thirty-nine operative patients with adult deformity and lumbar major curves were identified. A chart review was performed. Radiographic measurements included lumbar Cobb, curve apex, and Cobb levels involved. Apical pedicle diameter at the concavity and convexity of the curve apex were measured. RESULTS: Among these 39 patients, the average Cobb angle was 48.3 degrees. Curve apex averaged at L1/2 (range L1-L3). The curves spanned 4.7 levels (range 3-7). Twenty-five curves had the apex to the left, while 14 had the apex to the right. The average pedicle diameter at the apex was 6.1 mm. Fourteen patients had apical pedicle diameter asymmetry (APDA) >1 mm. Most (7 of 8, or 87.5%) of the patients with a history of adult idiopathic scoliosis had APDA >1 mm. A minority (7 of 31, 22.5%) of patients without known history of adult idiopathic scoliosis had APDA >1 mm (P < 0.01). CONCLUSIONS: Apical pedicle diameter asymmetry is among the sensitive diagnostic criteria for AdIS and may be useful for differentiating lumbar major AdIS from degenerative lumbar scoliosis. The sensitivity of APDA >1 mm is 87.5%, with specificity of 77.4%. We propose a new, sensitive radiographic criterion for adult idiopathic scoliosis. A difference of ≥1 mm in pedicle diameter between the convex and concave pedicles at that apex of a lumbar curve has a sensitivity of 87.5% and specificity of 77.4% for patient-reported history of adolescent scoliosis. It can be a useful tool as exclusion criteria for studies on AdIS.

Postoperative Opioid Use and Prescribing Patterns among Patients Undergoing Cervical Laminectomy with Instrumented Fusion versus Cervical Laminoplasty with Reconstruction.

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: To compare patterns in opioid usage and prescriptions between patients who undergo cervical laminectomy with instrumented fusion (LF) vs cervical laminoplasty with reconstruction (LP) within single surgeon and national database cohorts. METHODS: We identified patients with cervical myelopathy undergoing primary LF or LP in both a single-surgeon series cohort (2004-2018) and a nationally representative cohort drawn from the IBM® Marketscan® database (2014-2016). We recorded opioid usage within 6 months of surgery and identified differences in unadjusted opioid use rates between LF and LP patients. Multivariable logistic regression was used to evaluate the association between procedure type and postoperative opioid use. RESULTS: Without adjusting for covariates, LF patients had a higher rate of 6-month opioid use in the single-surgeon cohort (15.7% vs 5.1%, P = .02). After adjusting for covariates, LF patients had higher odds of 6-month postoperative opioid use (OR 2.8 [95% CI 1.0-7.7], P = .04). In the national cohort, without adjusting for covariates, there was no significant difference in 6-month opioid use between LF and LP patients. Even after adjusting for covariates, we found no significant difference in odds. CONCLUSIONS: Findings from a single-surgeon cohort reveal that LF is associated with a higher rate of 6-month opioid use than LP. This is at odds with findings from a national database cohort, which suggested that LP and LF patients have similar rates of opioid usage at 6-months postoperatively. To prevent overuse of narcotics, surgeons must consider the distinct pain requirements associated with different procedures even in treatment of the same condition.

Freehand Juxtapedicular Screws Placed in the Apical Concavity of Adult Idiopathic Scoliosis Patients: Technique, Computed Tomography Confirmation, and Radiographic Results.

OBJECTIVE: The purpose of this study is to highlight our technique for freehand placement of juxtapedicular screws along with intraoperative computed tomography (CT) and radiographic results. METHODS: Consecutive patients with adult idiopathic scoliosis undergoing primary surgery by the senior author were identified. All type D (absent/slit like channel) pedicles were identified on preoperative CT. Three-dimensional visualization software was used to measure screw angulation and purchase. Radiographs were measured by a fellowship trained spine surgeon. The freehand technique was used to place all screws in a juxtapedicular fashion without any fluoroscopic, radiographic, navigational or robotic assistance. RESULTS: Seventy-three juxtapedicular screws were analyzed. The most common level was T7 (9 screws) on the left and T5 (12 screws) on the right. The average medial angulation was 20.7° (range, 7.1°-36.3°), lateral vertebral body purchase was 13.4 mm (range, 0-28.9 mm), and medial vertebral body purchase was 21.1 mm (range, 8.9-31.8 mm). More than half (53.4%) of the screws had bicortical purchase. Two screws were lateral on CT scan, defined by the screw axis lateral to the lateral vertebral body cortex. No screws were medial. There was a difference in medial angulation between screws with (n = 58) and without (n = 15) lateral body purchase (22.0 ± 4.9 vs. 15.5 ± 4.5, p < 0.001). Three of 73 screws were repositioned after intraoperative CT. There were no neurovascular complications. The mean coronal cobb corrections for main thoracic and lumbar curves were 83.0% and 80.5%, respectively, at an average of 17.5 months postoperative. CONCLUSION: Freehand juxtapedicular screw placement is a safe technique for type D pedicles in adult idiopathic scoliosis patients.

A new modular radiographic classification of adult idiopathic scoliosis as an extension of the Lenke classification of adolescent idiopathic scoliosis.

PURPOSE: To propose and test the reliability of a radiographic classification system for adult idiopathic scoliosis. METHODS: A three-component radiographic classification for adult idiopathic scoliosis consisting of curve type, a lumbosacral modifier, and a global alignment modifier is presented. Twelve spine surgeons graded 30 pre-marked cases twice, approximately 1 week apart. Case order was randomized between sessions. RESULTS: The interrater reliability (Fleiss' kappa coefficient) for curve type was 0.660 and 0.798, for the lumbosacral modifier 0.944 and 0.965, and for the global alignment modifier 0.922 and 0.916, for round 1 and 2 respectively. Mean intrarater reliability was 0.807. CONCLUSIONS: This new radiographic classification of adult idiopathic scoliosis maintains the curve types from the Lenke classification and introduces the lumbosacral and global alignment modifiers. The reliability of the lumbosacral modifier and global alignment modifier shows near perfect agreement, and sets the foundation for further studies to validate the reliability, utility, and applicability of this classification system.

Sequential Radiographic Evaluation During Closed Treatment of Distal Radius Fracture.

OBJECTIVES: To test the null hypothesis that there is no significant change in radiographic parameters, which determines an acceptable reduction, beyond 3 weeks in distal radius fractures with closed treatment. DESIGN: Retrospective review of a prospectively gathered registry of distal radius fractures. SETTING: Academic medical center. PATIENTS: Patients who underwent closed treatment of distal radius fracture. INTERVENTION: Sequential radiographic evaluation. MAIN OUTCOME MEASUREMENTS: Change of radiographic measurement including radial inclination, radial height, ulnar variance, articular tilt, teardrop angle, anteroposterior distance, intra-articular gap, and step-off. We compared postreduction radiographic parameters once within 2 weeks, at the third week, at cessation of immobilization, and analyzed the interobserver reliability test. RESULTS: There was a statistically significant difference between radiographic measurements, which determined an acceptable reduction between radiographs performed within 2 weeks versus the third week. Radial inclination and ulnar variance were statistically different at the third week compared with the time of cessation of immobilization. Seventy-seven percent of patients who had an acceptable reduction after 2 weeks maintained acceptable alignment at cessation of immobilization. Eighty-five percent of patients with acceptable reduction after 3 weeks maintained acceptable alignment at cessation of immobilization. Radial shortening >1.8 mm at the third week predicts an unacceptable radiographic outcome at cessation of immobilization (sensitivity 94.5% and specificity 90%). CONCLUSION: Radiographic parameters that determine acceptable reduction for closed treatment of distal radius fractures change minimally after 3-week postacceptable closed reduction. Radial shortening at the third week can be used to predict an unacceptable radiographic outcome. LEVEL OF EVIDENCE: Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Dual S2 Alar-Iliac Screw Technique With a Multirod Construct Across the Lumbosacral Junction: Obtaining Adequate Stability at the Lumbosacral Junction in Spinal Deformity Surgery.

To illustrate the safe placement of a 5-screw/5-rod construct across the spinopelvic junction in a complex revision case utilizing 4 S2 alar-iliac (S2AI) screws as well as an iliac screw for a kickstand rod. The S2AI screws are often used for lumbosacral fixation at the base of long spinal deformity constructs. In severe spinal deformities, additional pelvic fixation beyond the standard 2 screws may help achieve and maintain correction, and also increase the rigidity of the construct. With a thorough understanding of pelvic anatomy, multiple pelvic screws, such as bilateral dual S2AI screws, may be placed safely to achieve stability and accommodate additional rods to perform powerful correction techniques. We illustrate the safe use of multiple rods across the lumbosacral junction in this case, by using both a hook rod construct and domino connectors - ultimately though these additional rods rely on the integrity of the pelvic fixation to provide their support. We recommend at least 3 rods across the lumbosacral junction in any adult spinal deformity case requiring pelvic fixation, and would recommend considering more than 3 rods, especially across 3-column osteotomy sites. For long spinal constructs in patients with significant adult spinal deformity, we believe the use of multiple pelvic screws to a multirod construct is a safe and effective way to provide long-term correction and clinical success.

Does the Global Alignment and Proportion score overestimate mechanical complications after adult spinal deformity correction?

OBJECTIVE: The goal of this study was to validate the Global Alignment and Proportion (GAP) score in a cohort of patients undergoing adult spinal deformity (ASD) surgery. The GAP score is a novel measure that uses sagittal parameters relative to each patient's lumbosacral anatomy to predict mechanical complications after ASD surgery. External validation is required. METHODS: Adult ASD patients undergoing > 4 levels of posterior fusion with a minimum 2-year follow-up were included. Six-week postoperative standing radiographs were used to calculate the GAP score, classified into a spinopelvic state as proportioned (P), moderately disproportioned (MD), or severely disproportioned (SD). A chi-square analysis, receiver operating characteristic curve, and Cochran-Armitage analysis were performed to assess the relationship between the GAP score and mechanical complications. RESULTS: Sixty-seven patients with a mean age of 52.5 years (range 18-75 years) and a mean follow-up of 2.04 years were included. Patients with < 2 years of follow-up were included only if they had an early mechanical complication. Twenty of 67 patients (29.8%) had a mechanical complication. The spinopelvic state breakdown was as follows: P group, 21/67 (31.3%); MD group, 23/67 (34.3%); and SD group, 23/67 (34.3%). Mechanical complication rates were not significantly different among all groups: P group, 19.0%; MD group, 30.3%; and SD group, 39.1% (χ2 = 1.70, p = 0.19). The rates of mechanical complications between the MD and SD groups (30.4% and 39.1%) were less than those observed in the original GAP study (MD group 36.4%-57.1% and SD group 72.7%-100%). Within the P group, the rates in this study were higher than in the original study (19.0% vs 4.0%, respectively). CONCLUSIONS: The authors found no statistically significant difference in the rate of mechanical complications between the P, MD, and SD groups. The current validation study revealed poor generalizability toward the authors' patient population.

The risks, reasons, and costs for 30- and 90-day readmissions after fusion surgery for adolescent idiopathic scoliosis.

OBJECTIVE: With the continued evolution of bundled payment plans, there has been a greater focus within orthopedic surgery on quality metrics up to 90 days of care. Although the Centers for Medicare and Medicaid Services does not currently penalize hospitals based on their pediatric readmission rates, it is important to understand the drivers for unplanned readmission to improve the quality of care and reduce costs. METHODS: The National Readmission Database provides a nationally representative sample of all discharges from US hospitals and allows follow-up across hospitals up to 1 calendar year. Adolescents (age 10-18 years) who underwent idiopathic scoliosis surgery from 2012 to 2015 were included. Patients were separated into those with and those without readmission within 30 days or between 31 and 90 days. Demographics, operative conditions, hospital factors, and surgical outcomes were compared using the chi-square test and t-test. Independent predictors for readmissions were identified using stepwise multivariate logistic regression. RESULTS: A total of 30,677 patients underwent adolescent idiopathic scoliosis surgery from 2012 to 2015. The rates of 30- and 90-day readmissions were 2.9% and 1.4%, respectively. The mean costs associated with the index admission and 30- and 90-day readmissions were $60,680, $23,567, and $16,916, respectively. Common risk factors for readmissions included length of stay > 5 days, obesity, neurological disorders, and chronic use of antiplatelets or anticoagulants. The index admission complications associated with readmissions were unintended durotomy, syndrome of inappropriate antidiuretic hormone, and superior mesenteric artery syndrome. Hospital factors, discharge disposition, and operative conditions appeared to be less important for readmission risk. The top reasons for 30-day and 90-day readmissions were wound infection (34.7%) and implant complications (17.3%), respectively. Readmissions requiring a reoperation were significantly higher for those that occurred between 31 and 90 days after the index readmission. CONCLUSIONS: Readmission rates were low for both 30- and 90-day readmissions for adolescent idiopathic scoliosis surgery patients. Nevertheless, readmissions are costly and appear to be associated with potentially modifiable risk factors, although some risk factors remain potentially unavoidable.

Pelvic parameters directly influence ideal S2 alar-iliac (S2AI) screw trajectory.

BACKGROUND: The utilization of the S2 Alar-Iliac (S2AI) screw provides an optimal method of spinopelvic fixation. The free-hand placement of these screws obviates the use of intra-operative fluoroscopy and relies heavily on sacropelvic anatomy; variations of this anatomy could alter the ideal screw trajectory. The S2AI corridor is near several neurovascular structures, thus an accurate trajectory is critical. The reported angles of trajectory vary within the literature and a paucity of data exists on how patient morphometry influences ideal screw trajectory. We sought to examine the relationship between ideal screw trajectory and pelvic parameters. METHODS: The records of 99 consecutive patients with degenerative thoracolumbar pathology were reviewed and pelvic parameters including sacral slope, pelvic tilt, and pelvic incidence were measured with preoperative standing radiographs. Using 3-dimensional computed tomography (CT) reconstructions, an ideal S2AI trajectory was defined and anteroposterior (horizontal) and cephalocaudal (sagittal) angles were recorded. RESULTS: Pelvic tilt was found to have a moderate inverse correlation with cephalocaudal screw trajectory (r=-0.467, p-value=0.006). Pelvic incidence and sacral slope had weaker correlations with cephalocaudal screw angle. In subgroup analysis, patients with high pelvic tilt (>20°) had a significantly lower cephalocaudal screw trajectory (24.9 ± 3.7° versus 29.8 ± 2.8°, p-value=<0.001) compared to those with a normal pelvic tilt (≤20°). CONCLUSIONS: This study found an inverse relationship between pelvic tilt and cephalocaudal S2AI screw trajectory. Therefore, the sagittal angle of insertion becomes increasingly more perpendicular to the floor (less caudally orientated) as pelvic tilt increases in reference to a patient positioned prone on an operating table parallel to the floor. This may bolster safety and efficacy when utilizing the free-hand technique for placement of the S2AI screw as it allows the surgeon to plan a more ideal trajectory by accounting for pelvic parameters.

Minimally invasive approach to the lumbosacral junction with a single position, 360° fusion.

Degenerative lumbar pathologies are commonly encountered at the lumbosacral junction. The transition from the mobile lumbar spine to the stiff sacroiliac segment results in high biomechanical stresses and can lead to disc degeneration, ligamentum flavum hypertrophy, neural foraminal stenosis, and other causes of pain or neurologic deficit. Surgical intervention at the lumbosacral junction must be tailored to maximize pain relief and relieve neural compression and reverse neurologic deficit while preserving the spine's natural biomechanical strength and flexibility and preventing the slow march of adjacent segment degeneration cranially into the thoracolumbar spine. It is our practice to offer combined anterior and posterior minimally invasive options when appropriate to maximize neural decompression and pain relief while ensuring proper segmental alignment and maximizing fusion rates through a minimally disruptive approach. In this article we detail a common presentation of lumbosacral pathology and the approach and considerations for a single position, minimally invasive anterior and posterior approach at the L5/S1 segment.

The effect of c-arm tilt on accuracy of intraoperative fluoroscopy in assessing acetabular component position during direct anterior approach for hip arthroplasty.

Intraoperative fluoroscopy can improve the precision of acetabular component positioning during direct anterior hip arthroplasty. However, changes in pelvic tilt with c-arm positioning may compromise accuracy. A geometric model of an acetabular component's projection onto fluoroscopy images was created and manipulated to simulate c-arm tilt. An apparently ideally-placed cup will have its effective anteversion changed by 7.5° with just 10° of caudal/cephalad tilt of the c-arm. This effect is greater in cups that are more horizontally placed or less anteverted. Accurate c-arm positioning is crucial, as small errors in tilt can have considerable effects on final cup position.

The "Kickstand Rod" technique for correction of coronal imbalance in patients with adult spinal deformity: theory and technical considerations.

The "Kickstand-Rod" technique: new surgical procedure for correction of coronal imbalance (CI) in spinal deformity patients. Coronal plane correction is difficult to achieve and maintain. We developed the technique for CI in deformity patients. The technique is a safe and effective method for correction of CI in deformity patients.

Evaluation of a more ventral starting point for thoracic pedicle screws: higher maximal insertional arc and more medial and safer screw angulation.

OBJECTIVETo demonstrate that a more ventral starting point for thoracic pedicle screw insertion, produced by aggressively removing the dorsal transverse process bone down to the superior articular facet (SAF), results in a larger margin for error and more medial screw angulation compared to the traditional dorsal starting point (DSP). The margin for error will be quantified by the maximal insertional arc (MIA).METHODSThe study population included 10 consecutive operative patients with adult idiopathic scoliosis who underwent primary surgery. All measurements were performed using 3D visualization software by an attending spine surgeon. The screw starting points were 2 mm lateral to the midline of the SAF in the mediolateral direction and in the center of the pedicle in the cephalocaudal direction. The DSP was on the dorsal cortex. The ventral starting point (VSP) was at the depth of the SAF. Measurements included distance to the pedicle isthmus, MIA, and screw trajectories.RESULTSTen patients and 110 vertebral levels (T1-11) were measured. The patients' average age was 41.4 years (range 18-64 years). The pedicle isthmus was largest at T1 (4.04 ± 1.09 mm), and smallest at T5 (1.05 ± 0.93 mm). The distance to the pedicle isthmus was 7.47 mm for the VSP and 11.92 mm for the DSP (p < 0.001). The MIA was 15.3° for the VSP and 10.1° for the DSP (p < 0.001). Screw angulation was 21.7° for the VSP and 16.8° for the DSP (p < 0.001).CONCLUSIONSA more ventral starting point for thoracic pedicle screws results in increased MIA and more medial screw angulation. The increased MIA represents an increased tolerance for error that should improve the safety of pedicle screw placement. More medial screw angulation allows improved triangulation of pedicle screws.

The Free-Hand Technique for S2-Alar-Iliac Screw Placement: A Safe and Effective Method for Sacropelvic Fixation in Adult Spinal Deformity.

BACKGROUND: Spinopelvic fixation is an integral part of achieving solid fusion across the lumbosacral junction, especially in deformity procedures requiring substantial correction or long-segment constructs. Traditional S2-alar-iliac (S2AI) screw-placement techniques utilize fluoroscopy, increasing operative time and radiation exposure to the patient and surgeon. We describe a novel free-hand technique for S2AI screw placement in patients with adult spinal deformity. METHODS: We reviewed the records of 45 consecutive patients who underwent spinopelvic fixation performed with use of S2AI screws by the senior surgeon and various fellows or residents over a 12-month period (2015 to 2016). In each case, the S2AI screws were placed utilizing a free-hand technique without fluoroscopic or image guidance. Screw position and accuracy were assessed by intraoperative O-arm imaging and analyzed using 3-dimensional interactive manipulation of computed tomography images. RESULTS: A total of 100 screws were placed, 51 by the senior surgeon and 49 by trainees. The mean patient age was 57.4 ± 12.7 years at the time of surgery; 37 (82.2%) of the patients were female. Preoperative diagnoses included adult idiopathic scoliosis (n = 19), adult degenerative scoliosis (n = 15), flatback syndrome (n = 2), fixed sagittal imbalance (n = 6), and distal junctional kyphosis (n = 3). Five (5%) of the screws were placed with moderate to severe cortical breaches, all of which perforated the pelvis posteriorly, with no clinically notable neurovascular or visceral complications. The breach rate did not differ significantly between the senior surgeon and trainees. CONCLUSIONS: The free-hand technique for S2AI screw placement, when performed in a standardized manner, was demonstrated to be safe and reliable in constructs requiring spinopelvic fixation. The accuracy of screw placement relies on visible and palpable anatomic landmarks that obviate the need for intraoperative fluoroscopy or image guidance, potentially reducing operative time and radiation exposure. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.