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Da Zou, Weishi Li, Fei Xu and Guohong Du

OBJECTIVE

The aim of this study was to evaluate the use of Hounsfield unit (HU) values of the S1 body to diagnose osteoporosis in patients with lumbar degenerative diseases.

METHODS

The records of 316 patients of ages ≥ 50 years and requiring surgery for lumbar degenerative diseases were reviewed. The bone mineral density (BMD) of the S1 body and L1 was measured in HU with preoperative lumbar CT. Circular regions of interest (ROIs) were placed on midaxial and midsagittal images of the S1 body. Dual-energy x-ray absorptiometry (DXA) and the criterion of L1 HU ≤ 110 HU were used to diagnose osteoporosis. The area under the receiver operating characteristic curve (AUC) was calculated to assess the use of HUs of the S1 body to diagnose osteoporosis.

RESULTS

The interobserver and intraobserver reliability of measuring HU of the S1 body was excellent with intraclass correlation coefficients over 0.8 (p < 0.001). The correlation between HUs of the S1 body and average T-score of L1–4 was significant with Pearson correlation coefficients ≥ 0.60 (p < 0.001). The AUCs for using HUs of the S1 body to diagnose osteoporosis were 0.86 and 0.88 for axial HU and sagittal HU, respectively (p < 0.001). The HU thresholds with balanced sensitivity and specificity for diagnosing osteoporosis were 202 HU for axial HU (sensitivity: 76%; specificity: 76%) and 185 HU for sagittal HU (sensitivity: 80%; specificity: 80%).

CONCLUSIONS

Both sagittal and axial HUs of the S1 body are useful tools for assessing BMD and diagnosing osteoporosis. Measuring HUs of the S1 body preoperatively from lumbar CT may help with surgical planning for patients with lumbar degenerative diseases.

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Da Zou, Aikeremujiang Muheremu, Zhuoran Sun, Woquan Zhong, Shuai Jiang and Weishi Li

OBJECTIVE

The authors investigated the relation between Hounsfield unit (HU) values measured on CT and the risk of pedicle screw loosening in patients who underwent lumbar pedicle screw fixation for degenerative lumbar spine disease.

METHODS

Patients who were treated with lumbar pedicle screw fixation between July 2011 and December 2015 at the authors’ department were reviewed. Age, sex, BMI, smoking and diabetes histories, range of fixation, and fusion method were recorded as the basic patient information. The HU values for lumbar bone mineral density (BMD) for the L1, L2, L3, and L4 vertebra were measured on CT scans. Logistic regression analysis was used to identify the independent influencing factors of pedicle screw loosening.

RESULTS

A total of 503 patients were included in the final analysis. The pedicle screw loosening rate at the 12-month follow-up was 30.0% (151 of 503 patients). There were no significant differences in sex, BMI, or histories of smoking and diabetes between the patients with (loosening group) and those without (nonloosening group) screw loosening (p > 0.05). The mean HU value of L1–4 was lower in the loosening group than the nonloosening group (106.3 ± 33.9 vs 132.6 ± 42.9, p < 0.001). In logistic regression analysis, being male (OR 2.065; 95% CI 1.242–3.433), HU value (OR 0.977; 95% CI 0.970–0.985), length of fixation (OR 3.616; 95% CI 2.617–4.996), and fixation to S1 (OR 1.699; 95% CI 1.039–2.777) were the independent influencing factors for screw loosening.

CONCLUSIONS

HU value measured on CT was an independent predictor for pedicle screw loosening, and lower HU value was significantly correlated with higher risk of screw loosening.

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Zhongqiang Chen, Yan Zeng, Weishi Li, Zhaoqing Guo, Qiang Qi and Chuiguo Sun

Object

In this paper, the authors' goal was to evaluate the feasibility, safety, and efficacy of apical segment resection osteotomy with dual axial rotation correction for severe focal kyphosis by examining outcomes.

Methods

Between May 2004 and December 2006, the authors treated 23 patients with severe focal kyphosis (average Cobb angle 86.9°, range 50°–130°) using apical segmental resection osteotomy with dual axial rotation correction and instrumented anterior column reconstruction and fusion. Radiographic assessment of sagittal plane balance and kyphotic Cobb angle (including a scoliosis Cobb angle in 9 cases) was performed in each patient before and immediately after surgery and at the last follow-up (minimum 2 years). The Frankel grading system for neurological function and Oswestry Disability Index for quality of life were evaluated before surgery and at the last follow-up. The patient satisfaction index was also used for clinical evaluation at the last follow-up.

Results

The mean surgical time was 6.7 hours. The average blood loss was 2960 ml. All patients underwent follow-up for 2 or more years after surgery. The fusion rate was 95.65%. The average kyphotic angle improved from 86.9° preoperatively to 25.6° immediately postoperatively, with an average correction rate of 72.17%. At the last follow-up, the average kyphotic angle was 27.4°, making the final correction rate 69.87%. The sagittal plane balance was significantly improved at the last follow-up. Preoperatively, 15 patients had neurological deficits, and the Frankel grade was E in 8 cases, D in 8 cases, C in 6 cases, and B in 1 case. At the last follow-up, 15 cases were Grade E, 5 were Grade D, and 3 were Grade C. The average improvement in the Oswestry Disability Index score was 43.30%. The patient satisfaction index result showed a total satisfaction rate of 91.30%. Complications included 1 case of late neurological deficit due to shifting of an expandable artificial vertebra, 5 cases of nerve root injury, 3 cases of dural tear, and 1 case of transient lower-extremity weakness due to insufficient blood supply to the spinal cord during surgery.

Conclusions

Apical segmental resection osteotomy with dual axial rotation correction and instrumented fusion is an effective and safe way to treat severe focal kyphosis of the thoracolumbar spine.

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Xin-Zhi Sun, Zhong-Qiang Chen, Qiang Qi, Zhao-Qing Guo, Chui-Guo Sun, Wei-Shi Li and Yan Zeng

Object

In this paper, the authors aimed to summarize the clinical characteristics of ossification of the ligamentum flavum (OLF) associated with dural ossification (DO) and to identify improved methods for preoperative diagnosis.

Methods

Thirty-six patients who had undergone OLF surgery between February 2005 and September 2009 were included in this retrospective study. The patients were divided into 2 groups: one that included patients with intraoperative evidence of DO and a second group that included patients without DO. The clinical features of DO were summarized and the neurological status of the patients was evaluated pre- and postoperatively.

Results

The incidence rate of DO associated with OLF was 39% (14/36). The sensitivity and specificity of the tram track sign were found to be 93% and 59%, respectively. Dural ossification was found among 86% of the patients with tuberous type Sato classification. The postoperative neurological status of patients was generally improved relative to that observed prior to surgery, although neurological recovery did not differ between the 2 groups. Cerebrospinal fluid leakage was the main complication, occurring predominantly in the patients with DO, and all leaks resolved in all patients after comprehensive treatments.

Conclusions

The tram track sign and Sato classification were found to be useful for preoperative diagnosis of DO and for determining the surgical procedure to be performed. Dural ossification had no effect on postoperative neurological recovery.

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Yan Zeng, Zhongqiang Chen, Qiang Qi, Zhaoqing Guo, Weishi Li, Chuiguo Sun and Andrew P. White

Object

The object of this study was to compare the clinical and radiographic outcomes of 36 patients with posttuberculosis kyphosis who underwent one of two types of osteotomy.

Methods

Each patient underwent single-stage correction via a posterior surgical approach. A modified pedicle subtraction osteotomy (mPSO) was performed when the kyphotic deformity was less than 70° (7 cases), whereas a posterior vertebral column resection (VCR) was performed when the kyphotic deformity exceeded 70° (29 cases). Full-length standing radiographs were obtained before surgery and at follow-up visits. These images were used to measure the kyphosis angle; sagittal alignment of the lumbar, thoracic, and cervical regions; and sagittal balance of the spine. Back pain was rated using the visual analog scale (VAS), and neurological function was classified based on the American Spinal Injury Association (ASIA) grading system. Each patient's overall satisfaction with surgical treatment was measured with the Patient Satisfaction Index. For purposes of comparison, patients were studied in 2 groups based on the region of their kyphotic apex. Half of the cohort had apical kyphosis in the lower thoracic spine or thoracolumbar junction (TL group). Using both radiographic and clinical assessments, the authors compared this group with the other half of the patients who had apical kyphosis in the upper to mid thoracic spine (MT group).

Results

The cohort included 15 males and 21 females, with an average age of 34 years at the time of surgery. The minimum follow-up was 24 months, and the mean follow-up was 31 months. Following surgery, kyphosis across the treated segments was reduced by an average of 60°. Lumbar lordosis also improved by an average of 24°, and thoracic kyphosis improved by an average of 20°. Both back pain and neurological function improved after surgical treatment. There was a 67% improvement in VAS scores, and 13 of the 36 patients had improvement in their ASIA grade. The 2 surgical procedures used for deformity correction (mPSO and VCR) demonstrated comparable radiographic and clinical results. Note, however, that differences were found in both radiographic and clinical outcomes in comparing patients who had lower thoracic or thoracolumbar (TL group) versus upper to midthoracic (MT group) apical kyphosis.

Conclusions

Posterior tubercular kyphosis can be effectively improved through corrective surgery, and deformity correction can be accompanied by improvement in clinical symptoms. When appropriately selected, both the mPSO and the VCR can be expected to yield satisfactory reduction of post-tuberculosis kyphotic deformities. Differences in radiographic and clinical outcomes should be anticipated, however, when treating such deformities in different regions of the spine.