Sung Bae Park

Correlation between Bone Mineral Density Measured by Dual-Energy X-Ray Absorptiometry and Hounsfield Units Measured by Diagnostic CT in Lumbar Spine

Objective Use of quantitative computed tomography (CT) to evaluate bone mineral density was suggested in the 1970s. Despite its reliability and accuracy, technical shortcomings restricted its usage, and dual-energy X-ray absorptiometry (DXA) became the gold standard evaluation method. Advances in CT technology have reduced its previous limitations, and CT evaluation of bone quality may now be applicable in clinical practice. The aim of this study was to determine if the Hounsfield unit (HU) values obtained from CT correlate with patient age and bone mineral density. Methods A total of 128 female patients who underwent lumbar CT for back pain were enrolled in the study. Their mean age was 66.4 years. Among them, 70 patients also underwent DXA. The patients were stratified by decade of life, forming five age groups. Lumbar vertebrae L1-4 were analyzed. The HU value of each vertebra was determined by averaging three measurements of the vertebras trabecular portion, as shown in consecutive axial CT images. The HU values were compared between age groups, and correlations of HU value with bone mineral density and T-scores were determined. Results The HU values consistently decreased with increasing age with significant differences between age groups (p<0.001). There were significant positive correlations (p<0.001) of HU value with bone mineral density and T-score. Conclusion The trabecular area HU value consistently decreases with age. Based on the strong positive correlation between HU value and bone mineral density, CT-based HU values might be useful in detecting bone mineral diseases, such as osteoporosis.

Changes in Cervical Sagittal Alignment after Single-Level Posterior Percutaneous Endoscopic Cervical Diskectomy

Study Design Case series. Objective Posterior percutaneous endoscopic cervical diskectomy (PECD) can preserve the disk in patients with a foraminal disk herniation. However, progressive angulation at the operated segment is a concern, especially for patients with cervical lordosis < 10 degrees. The change in cervical lordosis after posterior PECD was analyzed. Methods Medical records were reviewed of 32 consecutive patients (22 men, 10 women; mean age, 49 ± 12 years) who had single-level foraminal soft disk herniation. The operation levels were as follows: C4–5 in 1 patient, C5–6 in 12, C6–7 in 18, and C7–T1 in 1. All patients were discharged the day after the operation, and neck motion was encouraged. All patients were followed for 30 ± 7 months (range, 24 to 46 months), and 21/32 patients (66%) had radiographs taken at 25 ± 11 months (range, 12 to 45 months). Radiologic parameters were assessed, including cervical curvature (C2–7), segmental Cobbs angle (SA), and anterior and posterior disk height (AH and PH, respectively) at the operative level. Results At the last follow-up, 29/32 patients (91%) had no or minimal pain, and 3/32 patients had occasional pain. SA, AH, and PH were not significantly changed. Cervical lordosis < 10 degrees was present in 10/21 patients preoperatively and in 3/21 patients at the last follow-up. For patients with cervical lordosis < 10 degrees, cervical curvature changed from −2.5 ± 8.0 to −11.3 ± 9.3 degrees (p = 0.01). For patients with cervical lordosis ≥ 10 degrees, cervical curvature changed from −17.5 ± 5.8 to −19.9 ± 5.7 degrees (p = 0.24). Conclusions Cervical curvature does not worsen after posterior PECD.

The Surgical Outcome and the Surgical Strategy of Percutaneous Endoscopic Discectomy for Recurrent Disk Herniation

Study Design: A retrospective analysis. Objective: To present the surgical outcome of percutaneous endoscopic discectomy (PED) for recurrent herniated intervertebral disk disease (HIVD) and to suggest a surgical strategy. Summary of Background Data: Revision discectomy is technically demanding because of the scar tissue, unclear anatomic planes, and retraumatization to the posterior structures. Although open microdiscectomy is a standard method, endoscopic techniques have emerged as a surgical alternative with comparable results. PED was performed with either the transforaminal (PETD) or the interlaminar approach (PEID). Previous reports have shown the surgical outcomes of PETD or PEID for recurrent HIVD, but the application of each approach was not addressed clearly. Methods: Consecutive 26 patients (M:F=16:10, mean age 53.1±12.4 y), who underwent PED for recurrent HIVD, were enrolled. The previous operation was an open discectomy in 22, a PETD in 2, and a PEID in 2 patients. PETD was considered preferentially, if it was feasible (n=11), because of the scar tissue formed by the previous operation. PEID was chosen (n=15) because of a high iliac crest (8), high canal compromise (3), high-grade inferior migration (2), and narrow neural foramen (2). All patients were followed up for 19.3±11.3 months. Results: In all patients, the recurrent disk material was removed successfully, and conversion to an open surgery was not necessary. Postoperative magnetic resonance imaging revealed that the ruptured disk was removed successfully in all cases. A favorable outcome (excellent or good outcome by MacNab’s criteria) was achieved in 21 patients (81%). Re-recurrence occurred in 2 patients at 6 and 12 months postoperatively. Risk factors for an unfavorable outcome were not found in the present study (P>0.05). Conclusions: The relevant utilization of updated surgical techniques may be helpful in overcoming the difficulty of revision surgery.

A Change in Lumbar Sagittal Alignment After Single-Level Anterior Lumbar Interbody Fusion for Lumbar Degenerative Spondylolisthesis with Normal Sagittal Balance.

Study design: Retrospective analysis. Objective: The object is to assess the correlation between whole lumbar lordosis (LL) and the segmental angle (SA) after single-level anterior lumbar interbody fusion for degenerative lumbar spondylolisthesis. Summary of Background Data: The restoration of the SA at lower lumbar spine is meaningful, considering it contributes approximately 60% of LL, and revision surgery due to flat back or adjacent segment pathology was necessary decades after the initial surgery. However, little is known about the change of whole lumbar curvature after single-level lower lumbar fusion surgery, especially for balanced spine. Materials and Methods: We included 41 consecutive patients (M:F=9:32; mean age, 59.8±9.3 y) with a single-level anterior lumbar interbody fusion surgery for low-grade degenerative spinal spondylolisthesis, with C7 plumb line of <5 cm and ≥2-year follow-up period. The operated levels were L4–L5 in 34 patients and L5–S1 in 7 patients. Whole LL, SA, pelvic tilt, and sacral slope were compared. Results: According to the Macnab criteria, a favorable outcome (excellent, 21; good, 15) was achieved in 36/41 (88%; excellent, 21; good, 15) patients. LL and SA were significantly changed from −50.8±9.9 to −54.6±11.1 degrees and −15.6±6.1 to −18.7±5.1 degrees (P<0.01), and a positive correlation (r=0.43, P=0.01) was observed between LL and SA at postoperative month 24. The changes to the pelvic tilt and sacral slope were not significant. Conclusions: Whole lumbar sagittal alignment was influenced by single SA. Therefore, obtaining adequate segmental lordosis is desirable considering the effect on the whole spine for a long time.

Effect of a selective estrogen receptor modulator on bone formation in osteoporotic spine fusion using an ovariectomized rat model

BACKGROUND CONTEXT Selective estrogen receptor modulators (SERMs) are drugs used to treat osteoporosis. Selective estrogen receptor modulators improve bone mineral density and bone mechanical strength. However, there is a lack of data on the effect of SERMs on osteoporotic spinal fusion. PURPOSE This study aimed to investigate whether treatment with a SERM enhances spinal fusion in an ovariectomized (OVX) rat model. STUDY DESIGN An in vivo animal study was carried out. METHODS Female Sprague Dawley rats (n=90) were OVX or sham-operated, and randomized into three groups: control (sham-operated+fusion procedure+saline administration), OVX (OVX+fusion procedure+saline administration), and SERM (OVX+fusion procedure+administration of SERM). Eight weeks after OVX, a bilateral lumbar spinal fusion procedure was performed using autologous iliac bone. In each group, gene expression was evaluated at 2, 4, and 8 weeks after the fusion procedure, histologic analysis was performed at 4 and 8 weeks after the procedure, and bone parameters were measured by micro-computed tomography at 2 days, 4 weeks, and 8 weeks after the procedure. RESULTS Bone mineral density and trabecular quality of the vertebral body were significantly higher in the SERM group compared with the OVX group 16 weeks after OVX. The fusion rate and bone volume ratio were higher in the fusion bed of the SERM group compared with the OVX group 8 weeks after the fusion procedure. Real-time reverse transcription polymerase chain reaction at 4 and 8 weeks after the fusion procedure showed increased expression of the genes for osteoblast-related markers (alkaline phosphatase, osteocalcin, runt-related transcription factor 2, and transforming growth factor) in the SERM group compared with the OVX group. The OVX group showed sparse bone mass between transverse processes. By contrast, the SERM group exhibited a compact bridging fusion mass within the fusion bed at 8 weeks after the fusion procedure. CONCLUSIONS Selective estrogen receptor modulator treatment improved the trabecular quality of the vertebral body, enhanced spinal fusion, and increased the amount of compact bone mass within the fusion bed in rats that had received an ovariectomy. Therapeutic SERM treatment may be recommended to improve the fusion rate in osteoporotic patients who undergo spinal fusion.

Medial Loop of V2 Segment of Vertebral Artery Causing Compression of Proximal Cervical Root

Objective It is rare that the medial loop in the V2 segment of the vertebral artery (VA) causes compression of the proximal cervical root of the spinal cord without leading to bony erosion and an enlarged foramen. We evaluated the clinical significance and incidence of the medial loop in the V2 segment of the VA. Methods We reviewed the records from 1000 consecutive patients who had undergone magnetic resonance imaging evaluation of the cervical spine between January 2005 and January 2008. The inclusion criteria were that over a third of the axial aspect of the VA located in the intervertebral foramen was inside the line between the most ventral points of the bilateral lateral mass, and that the ipsilateral proximal root deviated dorsally because of the medial loop of the VA. We excluded cases of bone erosion, a widened foramen at the medial loop of the VA, any bony abnormalities, tumors displacing VA, or vertebral fractures. The medical records were reviewed retrospectively to search for factors of clinical significance. Results In six patients (0.6%), the VA formed a medial loop that caused compression of the proximal cervical root. One of these patients had the cervical radiculopathy that developed after minor trauma but the others did not present with cervical radiculopathy related to the medial loop of the VA. Conclusion The medial loop of the VA might have a direct effect on cervical radiculopathy. Therefore, this feature should be of critical consideration in preoperative planning and during surgery.

Sagittal imbalance in patients with lumbar spinal stenosis and outcomes after simple decompression surgery

BACKGROUND CONTEXT Lumbar spinal stenosis (LSS) is the most common lumbar degenerative disease, and sagittal imbalance is uncommon. Forward-bending posture, which is primarily caused by buckling of the ligamentum flavum, may be improved via simple decompression surgery. PURPOSE The objectives of this study were to identify the risk factors for sagittal imbalance and to describe the outcomes of simple decompression surgery. STUDY DESIGN This is a retrospective nested case-control study PATIENT SAMPLE: This was a retrospective study that included 83 consecutive patients (M:F=46:37; mean age, 68.5±7.7 years) who underwent decompression surgery and a minimum of 12 months of follow-up. OUTCOME MEASURES The primary end point was normalization of sagittal imbalance after decompression surgery. METHODS Sagittal imbalance was defined as a C7 sagittal vertical axis (SVA) ≥40 mm on a 36-inch-long lateral whole spine radiograph. Logistic regression analysis was used to identify the risk factors for sagittal imbalance. Bilateral decompression was performed via a unilateral approach with a tubular retractor. The SVA was measured on serial radiographs performed 1, 3, 6, and 12 months postoperatively. The prognostic factors for sagittal balance recovery were determined based on various clinical and radiological parameters. RESULTS Sagittal imbalance was observed in 54% (45/83) of patients, and its risk factors were old age and a large mismatch between pelvic incidence and lumbar lordosis. The 1-year normalization rate was 73% after decompression surgery, and the median time to normalization was 1 to 3 months. Patients who did not experience SVA normalization exhibited low thoracic kyphosis (hazard ratio [HR], 1.04; 95% confidence interval [CI], 1.02-1.10) (p<.01) and spondylolisthesis (HR, 0.33; 95% CI, 0.17-0.61) before surgery. CONCLUSIONS Sagittal imbalance was observed in more than 50% of LSS patients, but this imbalance was correctable via simple decompression surgery in 70% of patients.

Prevalence and Incidence of Osteoporosis and Osteoporotic Vertebral Fracture in Korea: Nationwide Epidemiological Study Focusing on Differences in Socioeconomic Status.

Study Design. A cross-national study. Objective. To determine the prevalence and incidence of osteoporosis (OP) and osteoporotic vertebral fracture (OVF) in Korea and to investigate if socioeconomic status has an effect. Summary of Background Data. As life expectancy increases, OP and related fragility fractures are also increasing. This presents a serious challenge, not only for health authorities but also for individuals, their families, and society overall. Determining the prevalence and incidence of OP and related fragility fractures is the first step in developing strategies to reduce their increasing disease burdens. Concurrently, we need to confirm whether people with low socioeconomic status are more susceptible to these diseases. Methods. Using the Health Insurance Review and Assessment Service (HIRA) database from 2008 to 2012, we estimated the annual prevalence and incidence of OP and OVF and investigated the differences according to socioeconomic status by National Health Insurance (NHI) beneficiaries and Medical Aid (MA) recipients. Results. In 2012, the standardized prevalence of OP in the NHI and MA groups was 3968 and 6927 per 100,000, respectively (odds ratio, 3.83). The standardized incidence of OP in the MA group was significantly higher than in the NHI group in 2011 and 2012 (odds ratios, 2.34 and 2.19, respectively). In addition, the standardized incidence of OVF in the MA group in 2011 and 2012 was 408 and 389 per 100,000, respectively, and the incidence in the MA group was significantly higher than in the NHI group (odds ratios, 4.13 and 4.12, respectively; P < 0.001). Conclusion. We confirmed that the prevalence and incidence of OP and OVF in the MA group were higher than those in the NHI group. It showed that low income might be a significant factor related to OP and OVF. Level of Evidence: 3

Quantitative Analysis of Intraoperative Indocyanine Green Video Angiography in Aneurysm Surgery

Objective Indocyanine green (ICG) videoangiography (VA) is being used in assessment of blood flow during cerebrovascular surgery. However, data collected during ICG angiography are usually interpreted qualitatively. In this study, quantitative analysis of ICG angiogram was attempted. Materials and Methods ICG VA, performed during aneurysm surgery was analyzed retrospectively. The angiogram was captured serially in regular time interval. The stacked images were then fed into an image analysis program, ImageJ. The selected areas of interest were as follows: parent and branch vessels, and dome of aneurysm. Changes of signals of measurement points were plotted. The time to peak, washout time, and the peak intensity between areas were compared. Results Among the 16 cases enrolled in this study, five cases were anterior communicating artery aneurysms, and 11 cases were middle cerebral artery bifurcation aneurysms. There was no signal intensity of aneurysm dome in our series. No difference in time to peak or maximum signal intensity was observed between vessels in each case. The average time to peak was 9.0 and washout time was 31.3 seconds. No significant difference in time profile was observed between anterior communicating artery aneurysms and middle cerebral artery bifurcation aneurysms. Conclusion Findings of this study demonstrate that quantitative analysis is possible using a personal computer and common video capture and analysis software. It can be a good adjunctive to evaluation of vascular status during aneurysm surgery. It displays time profiles of multiple points of interest over time, and is helpful in objective evaluation of changes of blood flow over time. It might be helpful in various fields of cerebrovascular surgery.

The Impact of Menopause on Bone Fusion after the Single-Level Anterior Cervical Discectomy and Fusion

Objective To evaluate the successful fusion rate in postmenopausal women with single-level anterior cervical discectomy and successful fusion (ACDF) and identify the significant factors related to bone successful fusion in pre- and postmenopausal women. Methods From July 2004 to December 2010, 108 consecutive patients who underwent single-level ACDF were prospectively selected as candidates. Among these, the charts and radiological data of 39 women were reviewed retrospectively. These 39 women were divided into two groups : a premenopausal group (n=11) and a postmenopausal group (n=28). To evaluate the significant factors affecting the successful fusion rate, the following were analyzed : the presence of successful fusion, successful fusion type, age, operated level, bone mineral density, graft materials, stand-alone cage or plating with autologous iliac bone, subsidence, adjacent segment degeneration, smoking, diabetes mellitus, and renal disease. Results The successful fusion rates of the pre- and postmenopausal groups were 90.9% and 89.2%, respectively. There was no significant difference in the successful fusion rate or successful fusion type between the two groups. In the postmenopausal group, three patients (10.8%) had successful fusion failure. In the postmenopausal group, age and subsidence significantly affected the successful fusion rate (p=0.016 and 0.011, respectively), and the incidence of subsidence in patients with a cage was higher than that in patients with a plate (p=0.030). Conclusion Menopausal status did not significantly affect bone successful fusion in patients with single-level ACDF. However, in older women with single-level ACDF, the combination of use of a cage and subsidence may unfavorably affect successful fusion.