Is the chin-brow vertical angle always a reliable parameter for surgical planning in the correction of thoracolumbar kyphosis secondary to ankylosing spondylitis?

J Neurosurg Spine 44:858–865, 2026

This clinical retrospective study evaluates whether the chin-brow vertical angle (CBVA) reliably predicts the osteotomized vertebra angle (OVA) when planning pedicle subtraction osteotomy for thoracolumbar kyphosis secondary to ankylosing spondylitis. Patients were stratified by cervical range of motion (CROM) and radiographic changes in CBVA, cervical Cobb angles, and global sagittal parameters were analyzed.

Results show a strong correlation between ΔCBVA and OVA in patients with limited CROM (≤20°), but no correlation when CROM exceeded 20°, indicating that CBVA alone is unreliable for OVA design in patients with flexible cervical spines. The study recommends considering cervical mobility when selecting OVA planning methods and suggests supplementing CBVA with measures of cervical compensation in flexible cases.

Objective Examine how well CBVA predicts needed correction (OVA) in ankylosing spondylitis (AS) thoracolumbar kyphosis across different cervical range of motion (CROM) values.

Design/Groups Retrospective cohort of AS patients undergoing single-level thoracic or lumbar pedicle subtraction osteotomy (PSO) (2015–2019) with ≥2-year follow-up; grouped by CROM: ≤10°, 10–20°, and >20°.

Key finding (CROM ≤20°) Strong correlation between ΔCBVA (preop→immediate postop) and OVA in CROM ≤10° and 10–20° groups (r = 0.881 and 0.932; both p < 0.001), supporting CBVA-based planning when cervical motion is limited.

Key finding (CROM >20°) No correlation between ΔCBVA and OVA when CROM > 20° (r = 0.198, p = 0.314), and most patients (89%) had ΔCBVA smaller than OVA, implying undercorrection risk if CBVA alone guides OVA.

Cervical adaptation mechanism With higher cervical mobility, postoperative cervical alignment changes substantially (CNA group cervical kyphosis change 20.25° vs 4.97° in CA), which can blunt CBVA change despite large osteotomy correction.

Improved predictor Adding cervical alignment change (ΔCobb C0–7) to CBVA change yields closer agreement with OVA (ΔCobb C0–7 + ΔCBVA correlated with OVA in both CA and CNA groups; CA r = 0.87 p < 0.001; CNA r = 0.38 p = 0.044).

Clinical recommendation CBVA is not consistently reliable for OVA design; it is not recommended as a guiding parameter when CROM > 20°.

Outcomes Both cervical-ankylosis–range (CROM ≤20°) and nonankylosis–range (CROM >20°) subgroups achieved satisfactory orthopedic improvement after surgery despite differences in cervical compensation.

Do all patients with adult scoliosis need instrumented fusion from T10 to the pelvis?

J Neurosurg Spine 44:195–204, 2026

This clinical review addresses whether adult scoliosis uniformly requires instrumented fusion from T10 to the pelvis, presenting diagnostic frameworks, radiographic assessment, and surgical decision-making. It contrasts full-length thoracolumbar–pelvic constructs with shorter, focal interventions, emphasizing individualized selection based on pain generators, balance, deformity location, and comorbidities.

The article reviews indications for extending fusions to upper thoracic levels, risks such as proximal junctional kyphosis, and evidence supporting limited fusion or decompression-only strategies when focal pathology (fractional curve, foraminal stenosis, olisthesis) explains symptoms. Multiple case examples illustrate practical application of the decision algorithm and outcomes.

Individualized Treatment: Not all adult scoliosis patients require instrumented fusion from T10 to the pelvis; surgical decisions should be based on the patient’s symptoms, pain generator, spinal balance, and radiographic findings rather than a one-size-fits-all approach.

Pain Source Identification: Careful identification of the pain generator (scoliosis-related, neurogenic, facet, or sacroiliac) is critical; many patients have back pain unrelated to scoliosis and may benefit from focal or limited procedures instead of extensive fusion.

Fusion Level Selection: The choice of upper instrumented vertebra (UIV) depends on curve characteristics, presence of kyphosis, risk of proximal junctional kyphosis (PJK), and patient-specific factors; fusion may end at T10, upper thoracic, or even lumbar levels as appropriate.

Limited/Focal Surgery: In select cases, limited fusion (e.g., of the major curve, concavity, or fractional curve) or even decompression alone can be effective, especially for patients with focal symptoms or significant comorbidities who cannot tolerate extensive surgery.

Fractional Curve Fusion: Fusion of only the fractional curve (typically L4–S1) is effective for radicular pain referable to this segment; careful preoperative assessment of coronal alignment and curve type is necessary to avoid postoperative imbalance.

Radiographic-Clinical Correlation: Surgical planning should integrate both radiographic parameters (sagittal vertical axis, pelvic incidence–lumbar lordosis mismatch, coronal balance) and the patient’s clinical presentation, as discordance may require further investigation.

Risks of Extensive Fusion: Long-segment fusions (T10–pelvis or longer) carry significant morbidity and complication risks; such approaches are best reserved for cases with severe, disabling symptoms, progressive deformity, or global imbalance.

Patient Preferences and Expectations: Surgical decisions must consider patient quality of life, goals, psychological profile, and willingness to accept surgical risks or possible reoperation, with shared decision-making emphasized

Crossing the cervicothoracic junction: an evaluation of radiographic alignment, functional outcomes, and patient-reported outcomes

J Neurosurg Spine 38:653–661, 2023

There is currently no consensus regarding the appropriate lower instrumented vertebra (LIV) for multilevel posterior cervical fusion (PCF) constructs between C7 and crossing the cervicothoracic junction (CTJ). The goal of the present study was to compare postoperative sagittal alignment and functional outcomes among adult patients presenting with cervical myelopathy undergoing multilevel PCF terminating at C7 versus spanning the CTJ.

METHODS A single-institution retrospective analysis (January 2017–December 2018) was performed of patients undergoing multilevel PCF for cervical myelopathy that involved the C6–7 vertebrae. Pre- and postoperative cervical spine radiographs were analyzed for cervical lordosis, cervical sagittal vertical axis (cSVA), and first thoracic (T1) vertebral slope (T1S) in two randomized independent trials. Modified Japanese Orthopaedic Association (mJOA) and Patient-Reported Outcomes Measurement Information System (PROMIS) scores were used to compare functional and patient-reported outcomes at the 12-month postoperative follow-up.

RESULTS Sixty-six consecutive patients undergoing PCF and 53 age-matched controls were included in the study. There were 36 patients in the C7 LIV cohort and 30 patients in the LIV spanning the CTJ cohort. Despite significant correction, patients undergoing fusion remained less lordotic than asymptomatic controls, with a C2–7 Cobb angle of 17.7° versus 25.5° (p < 0.001) and a T1S of 25.6° versus 36.3° (p < 0.001). The CTJ cohort had superior alignment corrections in all radiographic parameters at the 12-month postoperative follow-up compared with the C7 cohort: increase in T1S (ΔT1S 14.1° vs 2.0°, p < 0.001), increase in C2–7 lordosis (ΔC2–7 lordosis 11.7° vs 1.5°, p < 0.001), and decrease in cSVA (ΔcSVA 8.9 vs 5.0 mm, p < 0.001). There were no differences in the mJOA motor and sensory scores between cohorts pre- and postoperatively. The C7 cohort reported significantly better PROMIS scores at 6 months (22.0 ± 3.2 vs 11.5 ± 0.5, p = 0.04) and 12 months (27.0 ± 5.2 vs 13.5 ± 0.9, p = 0.01) postoperatively.

CONCLUSIONS Crossing the CTJ may provide a greater cervical sagittal alignment correction in multilevel PCF surgeries. However, the improved alignment may not be associated with improved functional outcomes as measured by the mJOA scale. A new finding is that crossing the CTJ may be associated with worse patient-reported outcomes at 6 and 12 months of postoperative follow-up as measured by the PROMIS, which should be considered in surgical decision-making. Future prospective studies evaluating long-term radiographic, patient-reported, and functional outcomes are warranted.

Rod fractures in thoracolumbar fusions to the sacrum/pelvis for adult symptomatic lumbar scoliosis

J Neurosurg Spine 38:217–229, 2023

Previous reports of rod fracture (RF) in adult spinal deformity are limited by heterogeneous cohorts, low follow-up rates, and relatively short follow-up durations. Since the majority of RFs present > 2 years after surgery, true occurrence and revision rates remain unclear. The objectives of this study were to better understand the risk factors for RF and assess its occurrence and revision rates following primary thoracolumbar fusions to the sacrum/pelvis for adult symptomatic lumbar scoliosis (ASLS) in a prospective series with long-term follow-up.

METHODS Patient records were obtained from the Adult Symptomatic Lumbar Scoliosis–1 (ASLS-1) database, an NIH-sponsored multicenter, prospective study. Inclusion criteria were as follows: patients aged 40–80 years undergoing primary surgeries for ASLS (Cobb angle ≥ 30° and Oswestry Disability Index ≥ 20 or Scoliosis Research Society-22r ≤ 4.0 in pain, function, and/or self-image) with instrumented fusion of ≥ 7 levels that included the sacrum/pelvis. Patients with and without RF were compared to assess risk factors for RF and revision surgery.

RESULTS Inclusion criteria were met by 160 patients (median age 62 years, IQR 55.7–67.9 years). At a median followup of 5.1 years (IQR 3.8–6.6 years), there were 92 RFs in 62 patients (38.8%). The median time to RF was 3.0 years (IQR 1.9–4.54 years), and 73% occurred > 2 years following surgery. Based on Kaplan-Meier analyses, estimated RF rates at 2, 4, 5, and 8 years after surgery were 11%, 24%, 35%, and 49%, respectively. Baseline radiographic, clinical, and demographic characteristics were similar between patients with and without RF. In Cox regression models, greater postoperative pelvic tilt (HR 1.895, 95% CI 1.196–3.002, p = 0.0065) and greater estimated blood loss (HR 1.02, 95% CI 1.005–1.036, p = 0.0088) were associated with increased risk of RF. Thirty-eight patients (61% of all RFs) underwent revision surgery. Bilateral RF was predictive of revision surgery (HR 3.52, 95% CI 1.8–6.9, p = 0.0002), while patients with unilateral nondisplaced RFs were less likely to require revision (HR 0.39, 95% CI 0.18–0.84, p = 0.016).

CONCLUSIONS This study provides what is to the authors’ knowledge the highest-quality data to date on RF rates following ASLS surgery. At a median follow-up of 5.1 years, 38.8% of patients had at least one RF. Estimated RF rates at 2, 4, 5, and 8 years after surgery were 11%, 24%, 35%, and 49%, respectively. Greater estimated blood loss and postoperative pelvic tilt were significant risk factors for RF. These findings emphasize the importance of long-term follow-up to realize the true prevalence and cumulative incidence of RF.

Surgical anatomy of minimally invasive lateral approaches to the thoracolumbar junction

J Neurosurg Spine 36:937–944, 2022

The thoracolumbar (TL) junction spanning T11 to L2 is difficult to access because of the convergence of multiple anatomical structures and tissue planes. Earlier studies have described different approaches and anatomical
structures relevant to the TL junction. This anatomical study aims to build a conceptual framework for selecting and executing a minimally invasive lateral approach to the spine for interbody fusion at any level of the TL junction with appropriate adjustments for local anatomical variations.

METHODS The authors reviewed anatomical dissections from 9 fresh-frozen cadaveric specimens as well as clinical case examples to denote key anatomical relationships and considerations for approach selection.

RESULTS The retroperitoneal and retropleural spaces reside within the same extracoelomic cavity and are separated from each other by the lateral attachments of the diaphragm to the rib and the L1 transverse process. If the lateral diaphragmatic attachments are dissected and the diaphragm is retracted anteriorly, the retroperitoneal and retropleural spaces will be in direct continuity, allowing full access to the TL junction. The T12–L2 disc spaces can be reached by a conventional lateral retroperitoneal exposure with the rostral displacement of the 11th and 12th ribs. With caudally
displaced ribs, or to expose T12–L1 disc spaces, the diaphragm can be freed from its lateral attachments to perform a retrodiaphragmatic approach. The T11–12 disc space can be accessed purely through a retropleural approach without significant mobilization of the diaphragm.

CONCLUSIONS The entirety of the TL junction can be accessed through a minimally invasive extracoelomic approach, with or without manipulation of the diaphragm. Approach selection is determined by the region of interest, degree of diaphragmatic mobilization required, and rib anatomy.

C7 extension crosswise osteotomy: a novel osteotomy for correction of chin-on-chest deformity in a patient with ankylosing spondylitis

J Neurosurg Spine 34:424–429, 2021

Extension crosswise osteotomy at C7 (C7 ECO) was developed for the correction of forward gaze in patients with chinon- chest deformity due to ankylosing spondylitis.

A modification of cervicothoracic extension osteoclasis (C/T EO), C7 ECO replaces osteoclasis of the anterior column with a crosswise cut of the C7 vertebral body to eliminate the risks of unintended dislocation of the cervical spine. C7 ECO also eliminates the risks of C7 and T1 pedicle subtraction osteotomies (C/T PSOs), in which a posteriorly based wedge excision may lead to stretching injuries of the lower cervical roots and/or failure to achieve the exact angle of excision required for an optimal correction.

Furthermore, opening the osteotomy anteriorly, as in the authors’ method, instead of closing it posteriorly, as in PSO, eliminates the risks related to shortening of the posterior column, such as buckling of the dura, kinking of the spinal cord, and stretching of the lower cervical nerve roots.

Here, the authors report the use of C7 ECO for the surgical treatment of a 69-year-old man with severe compromise of his forward gaze due to chin-on-chest deformity in the course of ankylosing spondylitis. After uneventful correction surgery, the patient regained the ability to see objects, namely faces of people, at the level of his head while standing and to perform work tasks at a desk.

Safety and accuracy of robot-assisted versus fluoroscopy-assisted pedicle screw insertion in thoracolumbar spinal surgery

J Neurosurg Spine 30:615–622, 2019

The object of this study was to compare the safety and accuracy of pedicle screw placement using the TiRobot system versus conventional fluoroscopy in thoracolumbar spinal surgery.

METHODS Patients with degenerative or traumatic thoracolumbar spinal disorders requiring spinal instrumentation were randomly assigned to either the TiRobot-assisted group (RG) or the freehand fluoroscopy-assisted group (FG) at a 1:1 ratio. The primary outcome measure was the accuracy of screw placement according to the Gertzbein-Robbins scale; grades A and B (pedicle breach < 2 mm) were considered clinically acceptable. In the RG, discrepancies between the planned and actual screw placements were measured by merging postoperative CT images with the trajectory planning images. Secondary outcome parameters included proximal facet joint violation, duration of surgery, intraoperative blood loss, conversion to freehand approach in the RG, postoperative hospital stay, and radiation exposure.

RESULTS A total of 1116 pedicle screws were implanted in 234 patients (119 in the FG, and 115 in the RG). In the RG, 95.3% of the screws were perfectly positioned (grade A); the remaining screws were graded B (3.4%), C (0.9%), and D (0.4%). In the FG, 86.1% screws were perfectly positioned (grade A); the remaining screws were graded B (7.4%), C (4.6%), D (1.4%), and E (0.5%). The proportion of clinically acceptable screws was significantly greater in the RG than in the FG (p < 0.01). In the RG, the mean deviation was 1.5 ± 0.8 mm for each screw. The most common direction of screw deviation was lateral in the RG and medial in the FG. Two misplaced screws in the FG required revision surgery, whereas no revision was required in the RG. None of the screws in the RG violated the proximal facet joint, whereas 12 screws (2.1%) in the FG violated the proximal facet joint (p < 0.01). The RG had significantly less blood loss (186.0 ± 255.3 ml) than the FG (217.0 ± 174.3 ml; p < 0.05). There were no significant differences between the two groups in terms of surgical time and postoperative hospital stay. The mean cumulative radiation time was 81.5 ± 38.6 seconds in the RG and 71.5 ± 44.2 seconds in the FG (p = 0.07). Surgeon radiation exposure was significantly less in the RG (21.7 ± 11.5 μSv) than in the FG (70.5 ± 42.0 μSv; p < 0.01).

CONCLUSIONS TiRobot-guided pedicle screw placement is safe and useful in thoracolumbar spinal surgery. Clinical trial registration no.: NCT02890043 (clinicaltrials.gov)

 

Use of the Airo mobile intraoperative CT system versus the O-arm for transpedicular screw fixation in the thoracic and lumbar spine

J Neurosurg Spine 29:397–406, 2018

Navigation-enabling technology such as 3D-platform (O-arm) or intraoperative mobile CT (iCT-Airo) systems for use in spinal surgery has considerably improved accuracy over that of traditional fluoroscopy-guided techniques during pedicular screw positioning. In this study, the authors compared 2 intraoperative imaging systems with navigation, available in their neurosurgical unit, in terms of the accuracy they provided for transpedicular screw fixation in the thoracic and lumbar spine.

METHODS The authors performed a retrospective analysis of clinical and surgical data of 263 consecutive patients who underwent thoracic and lumbar spine screw placement in the same center. Data on 97 patients who underwent surgery with iCT-Airo navigation (iCT-Airo group) and 166 with O-arm navigation (O-arm group) were analyzed. Most patients underwent surgery for a degenerative or traumatic condition that involved thoracic and lumbar pedicle screw fixation using an open or percutaneous technique. The primary endpoint was the proportion of patients with at least 1 screw not correctly positioned according to the last intraoperative image. Secondary endpoints were the proportion of screws that were repositioned during surgery, the proportion of patients with a postoperative complication related to screw malposition, surgical time, and radiation exposure. A blinded radiologist graded screw positions in the last intraoperative image according to the Heary classification (grade 1–3 screws were considered correctly placed).

RESULTS A total of 1361 screws placed in 97 patients in the iCT-Airo group (503 screws) and in 166 in the O-arm group (858 screws) were graded. Of those screws, 3 (0.6%) in the iCT-Airo group and 4 (0.5%) in the O-arm group were misplaced. No statistically significant difference in final accuracy between these 2 groups or in the subpopulation of patients who underwent percutaneous surgery was found. Three patients in the iCT-Airo group (3.1%, 95% CI 0%–6.9%) and 3 in the O-arm group (1.8%, 95% CI 0%–4.0%) had a misplaced screw (Heary grade 4 or 5). Seven (1.4%) screws in the iCT-Airo group and 37 (4.3%) in the O-arm group were repositioned intraoperatively (p = 0.003). One patient in the iCT-Airo group and 2 in the O-arm group experienced postoperative neurological deficits related to hardware malposition. The mean surgical times in both groups were similar (276 [iCT-Airo] and 279 [O-arm] minutes). The mean exposure to radiation in the iCT-Airo group was significantly lower than that in the O-arm group (15.82 vs 19.12 mSv, respectively; p = 0.02).

CONCLUSIONS Introduction of a mobile CT scanner reduced the rate of screw repositioning, which enhanced patient safety and diminished radiation exposure for patients, but it did not improve overall accuracy compared to that of a mobile 3D platform.

 

Posterior thoracic corpectomy with cage reconstruction for metastatic spinal tumors

mini-open and open transpedicular corpectomy

J Neurosurg Spine 23:217–227, 2015

Spinal metastases most commonly affect the vertebral bodies of the spinal column, and spinal cord compression is an indication for surgery. Commonly, an open posterior approach is employed to perform a transpedicular costotransversectomy or lateral extracavitary corpectomy. Because of the short life expectancies in patients with metastatic spinal disease, decreasing the morbidity of surgical treatment and recovery time is critical. One potential approach to decreasing morbidity is utilizing minimally invasive surgery (MIS). Although significant advances have been made in MIS of the spine, data supporting the utility of MIS are still emerging. This study compared outcomes of patients who underwent mini-open versus traditional open transpedicular corpectomy for spinal metastases in the thoracic spine.

Methods A consecutive cohort from 2006 to 2013 of 49 adult patients who underwent thoracic transpedicular corpectomies for spinal metastases was retrospectively identified. Patients were categorized into one of 2 groups: open surgery and mini-open surgery. Mini-open transpedicular corpectomy was performed with a midline fascial incision over only the corpectomy level of interest and percutaneous instrumentation above and below that level. The open procedure consisted of a traditional posterior transpedicular corpectomy. Chi-square test, 2-tailed t-test, and ANOVA models were employed to compare perioperative and follow-up outcomes between the 2 groups.

Results In the analysis, there were 21 patients who had mini-open surgery and 28 patients who had open surgery. The mean age was 57.9 years, and 59.2% were male. The tumor types encountered were lung (18.3%), renal/bladder (16.3%), breast (14.3%), hematological (14.3%), gastrointestinal tract (10.2%), prostate (8.2%), melanoma (4.1%), and other/unknown (14.3%). There were no significant intergroup differences in demographics, comorbidities, neurological status (American Spinal Injury Association [ASIA] grade), number of corpectomies performed, and number of levels instrumented. The open group had a mean operative time of 413.6 minutes, and the mini-open group had a mean operative time of 452.4 minutes (p = 0.329). Compared with the open group, the mini-open group had significantly less blood loss (917.7 ml vs 1697.3 ml, p = 0.019) and a significantly shorter hospital stay (7.4 days vs 11.4 days, p = 0.001). There was a trend toward a lower perioperative complication rate in the mini-open group (9.5%) compared with the open group (21.4%), but this was not statistically significant (p = 0.265). At follow-up, there were no significant differences in ASIA grade (p = 0.342), complication rate after the 30-day postoperative period (p = 0.999), or need for surgical revision (p = 0.803). The open approach had a higher overall infection rate of 17.9% compared with that in the mini-open approach of 9.5%, but this was not statistically significant (p = 0.409).

Conclusions The mini-open transpedicular corpectomy is associated with less blood loss and shorter hospital stay compared with open transpedicular corpectomy. The mini-open corpectomy also trended toward lower infection and complication rates, but these did not reach statistical significance.

Surgical manifestations of thoracic arachnoid pathology

Thoracic arachnoid pathology

J Neurosurg Spine 20:30–40, 2014

Various pathologies involving the thoracic arachnoid mater uniformly manifest as thoracic myelopathy and may present a significant management dilemma. The authors undertook this study to assess outcome in cases of thoracic myelopathy due to thoracic arachnoid pathology.

Methods. The authors have cared for and followed 28 patients with thoracic myelopathy from thoracic arachnoid pathology over the last 17 years. A chart review and contemporary follow-up of these patients was performed and outcomes were reported.

Results. Patients with thoracic myelopathy from thoracic arachnoid pathology often have improvement in their condition after surgical decompression/detethering procedures. While not universal, patients in this series had improvement in mJOA scores at 1 year after surgery (p = 0.0001) and at last follow-up (p = 0.04). Results indicated that across a wide variety of pathologies the extent of thoracic spinal cord involvement is a predictor of the disease course and outcome. Comparison of the group of patients with cord involvement limited to 2 vertebral segments (short-segment pathology) versus the group with cord tethering of more than 2 segments (long-segment pathology) showed that patients in the short-segment group more frequently had ventral or dorsal arachnoid bands (p = 0.003), more frequently had signal change in the cord on MRI (p = 0.02), and less frequently presented with a syrinx (p = 0.02), and a smaller percentage of patients in this group underwent reoperation (p = 0.02). While patients with shortsegment pathology typically improved after a single operative intervention, patients with long-segment pathology typically improved after multiple operations, frequently for CSF diversion.

Conclusions. Thoracic arachnoid pathology causing thoracic cord dysfunction and myelopathy is varied, has multiple etiologies, and can be difficult to treat over the long term. Surgical management, when indicated, is case specific. Serial long-term follow-up is essential to document enduring clinical and radiographic success.

Accuracy of Free-Hand Pedicle Screws in the Thoracic and Lumbar Spine: Analysis of 6816 Consecutive Screws

Neurosurgery 68:170–178, 2011 DOI: 10.1227/NEU.0b013e3181fdfaf4

Pedicle screws are used to stabilize all 3 columns of the spine, but can be technically demanding to place. Although intraoperative fluoroscopy and stereotactic- guided techniques slightly increase placement accuracy, they are also associated with increased radiation exposure to patient and surgeon as well as increased operative time.

OBJECTIVE: To describe and critically evaluate our 7-year institutional experience with placement of pedicle screws in the thoracic and lumbar spine using a free-hand technique.

METHODS: We retrospectively reviewed records of all patients undergoing free-hand pedicle screw placement without fluoroscopy in the thoracic or lumbar spine between June 2002 and June 2009. Incidence and extent of cortical breach by misplaced pedicle screw was determined by review of postoperative computed tomography scans. We defined breach as more than 25% of the screw diameter residing outside of the pedicle or vertebral body cortex.

RESULTS: A total of 964 patients received 6816 free-hand placed pedicle screws in the thoracic or lumbar spine. Indications for hardware placement were degenerative/deformity disease (51.2%), spondylolisthesis (23.7%), tumor (22.7%), trauma (11.3%), infection (7.6%), and congenital (0.9%). A total of 115 screws (1.7%) were identified as breaching the pedicle in 87 patients (9.0%). Breach occurred more frequently in the thoracic than the lumbar spine (2.5% and 0.9%, respectively; P , .0001) and was more often lateral (61.3%) than medial (32.8%) or superior (2.5%). T4 (4.1%) and T6 (4.0%) experienced the highest breach rate, whereas L5 and S1 had the lowest breach rate. Eight patients (0.8%) underwent revision surgery to correct malpositioned screws.

CONCLUSION: Free-hand pedicle screw placement based on external anatomy alone can be performed with acceptable safety and accuracy and allows avoidance of radiation exposure encountered in fluoroscopic techniques. Image-guided assistance may be most valuable when placing screws between T4 and T6, where breach rates are highest