Methods: A database of patients with AIS with Lenke 1 and 2 curves treated with PSF without PO and instrumented with PSs and ≥2-year follow-up was reviewed. The preoperative, immediate, and final follow-up postoperative radiographs were analyzed. The correlation between PS density and the following factors were determined: major curve correction (MCC), correction index (CI; MCC/curve flexibility), kyphosis angle change, and rib index (RI) correction. Then, patients were divided into low-density (LD) and high-density (HD) groups according to mean PS density for the entire cohort (1.5 PS per level). Demographics and radiographic and clinical outcomes were compared between groups. Results: The study included 99 patients with Lenke 1 and 23 patients with Lenke 2 AIS. The average MCC was 67.2%. There was no correlation between screw density and these parameters: MCC (r=0.10, p=0.26), CI (r=0.16, p=0.07), change in T2–T12 kyphosis angle (r=−0.13, p=0.14), and RI correction (r=−0.09, p=0.37). Demographic and preoperative radiographic parameters were similar between the LD and HD groups. At the latest follow-up, there were no differences between the two groups in regard to MCC, CI, change in T2–T12 kyphosis angle, RI correction, and Scoliosis Research Society-30 scores (all p>0.05). Conclusions This study revealed no significant correlation between screw density and curve correction in any planes. HD construct may not provide better deformity correction in patients with flexible and moderate thoracic AIS undergoing PSF without PO.

STUDY DESIGN: Cross-sectional, matched-pair comparative study. PURPOSE: To determine whether a thin-sliced pedicular-oriented computed tomography (TPCT) scan reconstructed from an existing conventional computed tomography (CCT) scan is more accurate for identifying vertebral artery groove (VAG) anomalies than CCT. OVERVIEW OF LITERATURE: Posterior atlantoaxial transarticular screw fixation and C2 pedicle screws can cause vertebral artery (VA) injury. Two anatomic variations of VAG anomalies are associated with VA injury: a high-riding VA (HRVA) and a narrow pedicle of the C2 vertebra. CCT scan is a reliable method used to evaluate VAG anomalies; however, its accuracy level remains debatable. Literature comparing the prevalence of C2 VAG anomalies between CCT and TPCT is limited. METHODS: A total of 200 computed tomography scans of the upper cervical spine obtained between January 2008 and December 2011 were evaluated for C2 VAG anomalies (HRVA and narrow pedicular width) using CCT and TPCT. The prevalence of C2 VAG anomalies was compared using these two different measurement methods via a McNemar's test. RESULTS: Of the 200 patients studied, 23 HRVA (6.01%; 95% confidence interval [CI], 3.61%–8.39%) were detected with CCT, whereas 66 HRVA (16.54%; 95% CI, 12.85%–20.23%) were detected with TPCT (p<0.001). Sixty-two narrow pedicles (15.58%; 95% CI, 11.99%–19.15%) were detected with CCT, whereas 90 narrow pedicles (22.83%; 95% CI, 18.58%–26.87%) were detected with TPCT (p<0.001). CONCLUSIONS: VAG anomalies are commonly observed. A preoperative evaluation using TPCT reconstructed from an existing CCT revealed a significantly higher prevalence of C2 VAG anomalies than did CCT and showed comparable prevalence to previously published studies using more sophisticated and higher risk techniques. Therefore, we propose TPCT as an alternative preoperative evaluation for C2 screw placement and trajectory planning.
Humans ; Methods ; Pedicle Screws ; Prevalence* ; Spine ; Tomography, X-Ray Computed ; Vertebral Artery*

STUDY DESIGN: Anatomical study. PURPOSE: To evaluate the anatomy of intervertebral disc (IVD) area in the triangular working zone of the lumbar spine based on cadaveric measurements. OVERVIEW OF LITERATURE: The posterolateral percutaneous approach to the lumbar spine has been widely used as a minimally invasive spinal surgery. However, to our knowledge, the actual perspective of disc boundaries and areas through posterolateral endoscopic approach are not well defined. METHODS: Ninety-six measurements for areas and dimensions of IVD in Kambin's triangle on bilateral sides of L1–S1 in 5 fresh human cadavers were studied. RESULTS: The trapezoidal IVD area (mean±standard deviation) for true working space was 63.65±14.70 mm2 at L1–2, 70.79±21.88 mm2 at L2–3, 99.03±15.83 mm2 at L3–4, 116.22±20.93 mm2 at L4–5, and 92.18±23.63 mm2 at L5–S1. The average dimension of calculated largest ellipsoidal cannula that could be placed in IVD area was 5.83×11.02 mm at L1–2, 6.97×10.78 mm at L2–3, 9.30×10.67 mm at L3–4, 8.84×13.15 mm at L4–5, and 6.61×14.07 mm at L5–S1. CONCLUSIONS: The trapezoidal perspective of working zone of IVD in Kambin's triangle is important and limited. This should be taken into consideration when developing the tools and instruments for posterolateral endoscopic lumbar spine surgery.
Cadaver* ; Catheters ; Humans ; Intervertebral Disc* ; Spine

Background: Many scoring systems that predict overall patient survival are based on clinical parameters and primary tumor type. To date, no consensus exists regarding which scoring system has the greatest predictive survival accuracy, especially when applied to specific primary tumors. Additionally, such scores usually fail to include modern treatment modalities, which influence patient survival. This study aimed to evaluate both the overall predictive accuracy of such scoring systems and the predictive accuracy based on the primary tumor. Methods: A retrospective review on spinal metastasis patients who were aged more than 18 years and underwent surgical treatment was conducted between October 2008 and August 2018. Patients were scored based on data before the time of surgery. A survival probability was calculated for each patient using the given scoring systems. The predictive ability of each scoring system was assessed using receiver operating characteristic analysis at postoperative time points; area under the curve was then calculated to quantify predictive accuracy. Results: A total of 186 patients were included in this analysis: 101 (54.3%) were men and the mean age was 57.1 years. Primary tumors were lung in 37 (20%), breast in 26 (14%), prostate in 20 (10.8%), hematologic malignancy in 18 (9.7%), thyroid in 10 (5.4%), gastrointestinal tumor in 25 (13.4%), and others in 40 (21.5%). The primary tumor was unidentified in 10 patients (5.3%). The overall survival was 201 days. For survival prediction, the Skeletal Oncology Research Group (SORG) nomogram showed the highest performance when compared to other prognosis scores in all tumor metastasis but a lower performance to predict survival with lung cancer. The revised Katagiri score demonstrated acceptable performance to predict death for breast cancer metastasis. The Tomita and revised Tokuhashi scores revealed acceptable performance in lung cancer metastasis. The New England Spinal Metastasis Score showed acceptable performance for predicting death in prostate cancer metastasis. SORG nomogram demonstrated acceptable performance for predicting death in hematologic malignancy metastasis at all time points. Conclusions The results of this study demonstrated inconsistent predictive performance among the prediction models for the specific primary tumor types. The SORG nomogram revealed the highest predictive performance when compared to previous survival prediction models.