The Use of High-Density Pedicle Screw Construct with Direct Vertebral Derotation of the Lowest Instrumented Vertebra in Selective Thoracic Fusion for Adolescent Idiopathic Scoliosis: Comparison of Two Surgical Strategies

Methods@#We reviewed consecutive patients with Lenke 1 AIS who underwent STF from 2000 to 2017. The patients were divided into two groups based on the surgical strategy used: low-density (LD) construct without DVR of the LIV (LD group) versus HD construct with DVR of the LIV (HD group). We collected data on the patient’s demographic characteristics, skeletal maturity, operative data, and measured radiological parameters in the preoperative and final follow-up radiographs. The occurrence of adding-on (AO) and coronal decompensation was also determined. @*Results@#In this study, 72 patients (five males and 67 females) with a mean age of 14.1±2.3 years were included. No significant differences in the demographics, skeletal maturity, and Lenke type distribution were observed between the two groups; however, the follow-up duration was significantly longer in the LD group (64.3±25.7 months vs. 40.7±22.2 months, p <0.001). The HD group had significantly shorter fusion segments (7.1±1.3 vs. 8.5±1.2, p <0.001) and a more proximal LIV level (12.1±0.9 vs. 12.7±1.0, p =0.009). In the radiological measurements, the improvement of LIV+1 rotation (Nash–Moe scale) was significantly larger in the HD group (0.53±0.51 vs. 0.21±0.41, p =0.008). AO and decompensation occurred in 7 (9.7%) and 4 (5.6%) patients in the HD and LD groups, respectively, without any significant difference between the two groups. @*Conclusions@#In this study, the HD group had a significantly shorter fusion level and a more proximal LIV than the LD group; however, the two groups had similar curve correction and adverse radiological outcome rates.

Volumetric Assessment of Fusion Mass and Its Clinical Correlations in Posterior Lumbar Interbody Fusion Depending on the Type of Bone Graft

Objectives@#This study was conducted to analyze associations between the volume of the fusion mass and clinical outcomes 1 year after posterior lumbar interbody fusion (PLIF).Summary of Literature Review: No study has investigated associations between the size of the fusion mass and clinical outcomes after PLIF. @*Materials and Methods@#The volume of the fusion mass and its clinical correlations after PLIF were analyzed in all patients and in subgroups. When a sufficient amount of local bone was available for grafting, only local bone without a graft extender was used (LbG group, n=20). If an inadequate amount of local bone was present for grafting, a local bone graft with porous hydroxyapatite bone chips was used (LbHa group, n=20). The same amount of demineralized bone matrix was used in both groups. The primary outcome was the relationship between the size of the fusion mass and clinical outcomes in all patients 1 year after surgery. The secondary outcome was a comparison of the size of the fusion mass and clinical outcomes by group. @*Results@#The volume of the fusion mass was not correlated with any clinical outcomes 1 year after surgery, either in the overall group of patients or in the subgroup analysis. @*Conclusions@#The volume of the interbody fusion mass was not related to any clinical outcomes 1 year after surgery. Furthermore, in cases with an insufficient amount of local bone for grafting, porous hydroxyapatite could be a relatively good alternative as a graft extender.

Restoration of the Spinous Process Following Muscle-Preserving Posterior Lumbar Decompression via Sagittal Splitting of the Spinous Process

BACKGROUND: In lumbar spinal stenosis, spinous process-splitting decompression has demonstrated good clinical outcomes with preservation of the posterior ligamentous complex and paraspinal muscles in comparison to conventional laminectomy, but the radiological consequence and clinical impact of the split spinous processes have not been fully understood. METHODS: Seventy-three patients who underwent spinous process-splitting decompression were included. The bone union rate and pattern were evaluated by computed tomography performed 6–18 months after surgery and compared among subgroups divided according to the number of levels decompressed and the extent of spinous process splitting. The bone union pattern was classified into three categories: complete union, partial union, and nonunion. The visual analog scale (VAS) score, Oswestry disability index (ODI), and walking distance assessed both before and 24–36 months after surgery were compared among subgroups divided according to the union pattern of the split spinous process. RESULTS: Overall, the rates of complete union, partial union, and nonunion were 51.7%, 43.2%, and 5.1%, respectively. In the subgroup with partial splitting of the spinous process, the rates were 85.7%, 14.3%, and 0%, respectively; those of the subgroup with total splitting of the spinous process were 32.9%, 59.2%, and 7.9%, respectively. With single-level decompression, a higher rate of union was observed compared with multilevel decompression. The VAS, ODI, and walking distance were significantly improved after surgery and did not differ according to the degree of union of the split spinous process. CONCLUSIONS: We found that the single-level operation and partial splitting of the spinous process were favourable factors for obtaining complete restoration of the posterior bony structure of the lumbar spine in spinous process-splitting decompression.

Clinical Significance of Resection Type and Margin following Surgical Treatment for Primary Sarcoma of the Spine: A Multi-Center Retrospective Study

OBJECTIVES@#To analyze oncological outcomes according to the resection type and surgical margin following surgical treatment for primary spinal sarcoma.SUMMARY OF LITERATURE REVIEW: Previous studies using registry databases have shown that surgery and negative margins were associated with improved survival for primary spinal sarcoma. However, few studies have comprehensively analyzed the clinical significance of the resection type and surgical margin for the oncological outcomes of this rare malignancy.@*MATERIALS AND METHODS@#We retrospectively reviewed consecutive patients who underwent surgical resection for primary spinal sarcoma between 1997 and 2016 at two tertiary medical centers. Overall survival and the occurrence of local recurrence and distant metastasis were compared between the groups using Kaplan-Meier curve analysis and the log-rank test.@*RESULTS@#Thirty-three patients (21 males,12 females) with a mean age of 45.1 years and a median follow-up of 36 months were included. There were 13 (39.4%) chondrosarcomas, 12 (36.4%) osteosarcomas, and eight different histological diagnoses. The cohort was categorized into four groups: 1) total en bloc resection with a negative margin (n=12; 36.4%), 2) total en bloc resection with a positive margin: (n=5; 15.2%), 3) total piecemeal resection (n=12; 36.4%), and 4) subtotal resection (n=4; 12.1%). Total en bloc resection with a negative margin was associated with improved overall survival (p=0.030) and less distant metastasis (p=0.025) and local recurrence (p=0.004).@*CONCLUSIONS@#Achieving a negative margin through total en bloc resection, although technically demanding, improves oncological outcomes in primary spinal sarcoma.

Clinical Significance of Resection Type and Margin following Surgical Treatment for Primary Sarcoma of the Spine: A Multi-Center Retrospective Study / 대한척추외과학회지

STUDY DESIGN: A retrospective multi-center study.OBJECTIVES: To analyze oncological outcomes according to the resection type and surgical margin following surgical treatment for primary spinal sarcoma.SUMMARY OF LITERATURE REVIEW: Previous studies using registry databases have shown that surgery and negative margins were associated with improved survival for primary spinal sarcoma. However, few studies have comprehensively analyzed the clinical significance of the resection type and surgical margin for the oncological outcomes of this rare malignancy.MATERIALS AND METHODS: We retrospectively reviewed consecutive patients who underwent surgical resection for primary spinal sarcoma between 1997 and 2016 at two tertiary medical centers. Overall survival and the occurrence of local recurrence and distant metastasis were compared between the groups using Kaplan-Meier curve analysis and the log-rank test.RESULTS: Thirty-three patients (21 males,12 females) with a mean age of 45.1 years and a median follow-up of 36 months were included. There were 13 (39.4%) chondrosarcomas, 12 (36.4%) osteosarcomas, and eight different histological diagnoses. The cohort was categorized into four groups: 1) total en bloc resection with a negative margin (n=12; 36.4%), 2) total en bloc resection with a positive margin: (n=5; 15.2%), 3) total piecemeal resection (n=12; 36.4%), and 4) subtotal resection (n=4; 12.1%). Total en bloc resection with a negative margin was associated with improved overall survival (p=0.030) and less distant metastasis (p=0.025) and local recurrence (p=0.004).CONCLUSIONS: Achieving a negative margin through total en bloc resection, although technically demanding, improves oncological outcomes in primary spinal sarcoma.

The Spinal Instability Neoplastic Score (SINS) as a Surgical Decision-Making Tool for the Treatment of Spine Metastasis

OBJECTIVES@#To investigate the potential clinical use of the spinal instability neoplastic score (SINS) for determining the surgical strategy, especially regarding the need for anterior support.SUMMARY OF LITERATURE REVIEW: The SINS seems to enable an improved qualitative and quantitative assessment of spinal instability in patients with spinal metastasis.@*MATERIALS AND METHODS@#We retrospectively reviewed 69 consecutive patients who underwent surgical treatment for spinal metastasis. We assessed the patients' preoperative status with respect to each component of the SINS. Multiple logistic regression was performed to calculate odds ratios (ORs) representing the associations among SINS, age, Eastern Cooperative Oncology Group performance status, modified Tokuhashi score, as well as the preoperative Nurick grade variables and reconstruction of the anterior spinal column.@*RESULTS@#Among the 6 items in the SINS, those indicating the degree of collapse and alignment had significantly higher scores in those who underwent corpectomy and anterior support (p<0.001). Multiple logistic regression revealed that the total SINS was the only factor significantly associated with predicting whether anterior support should be performed (adjusted OR=1.595). Receiver operating characteristic (ROC) curve analysis suggested that a cut-off value of 10 points on the SINS scale could be used to decide whether anterior support following corpectomy should be performed (AUC=0.706).@*CONCLUSIONS@#The SINS, insofar as it assesses the degree of collapse and alignment, is a potentially useful tool for determining the surgical strategy in patients with spinal metastasis, especially for deciding upon the necessity of additional anterior support procedures.

Radiographic and Clinical Outcomes of Robot-Assisted Posterior Pedicle Screw Fixation: Two-Year Results from a Randomized Controlled Trial

PURPOSE: We prospectively assessed the early radiographic and clinical outcomes (minimum follow-up of 2 years) of robot-assisted pedicle screw fixation (Robot-PSF) and conventional freehand pedicle screw fixation (Conv-PSF). MATERIALS AND METHODS: Patients were randomly assigned to Robot-PSF (37 patients) or Conv-PSF (41 patients) for posterior interbody fusion surgery. The Robot-PSF group underwent minimally invasive pedicle screw fixation using a pre-planned robot-guided screw trajectory. The Conv-PSF underwent screw fixation using the freehand technique. Radiographic adjacent segment degeneration (ASD) was measured on plain radiographs, and clinical outcomes were measured using visual analogue scale (VAS) and Oswestry disability index (ODI) scores regularly after surgery. RESULTS: The two groups had similar values for radiographic ASD, including University California at Los Angeles grade, vertebral translation, angular motion, and loss of disc height (p=0.320). At final follow-up, both groups had experienced significant improvements in back VAS, leg VAS, and ODI scores after surgery (p < 0.001), although inter-group differences were not significant for back VAS (p=0.876), leg VAS (p=0.429), and ODI scores (p=0.952). In the Conv-PSF group, revision surgery was required for two of the 25 patients (8%), compared to no patients in the Robot-PSF group. CONCLUSION: There were no significant differences in radiographic ASD and clinical outcomes between Robot-PSF and Conv-PSF. Thus, the advantages of robot-assisted surgery (accurate pedicle screw insertion and minimal facet joint violation) do not appear to be clinically significant.

The Spinal Instability Neoplastic Score (SINS) as a Surgical Decision-Making Tool for the Treatment of Spine Metastasis / 대한척추외과학회지

STUDY DESIGN: Retrospective cohort study. OBJECTIVES: To investigate the potential clinical use of the spinal instability neoplastic score (SINS) for determining the surgical strategy, especially regarding the need for anterior support. SUMMARY OF LITERATURE REVIEW: The SINS seems to enable an improved qualitative and quantitative assessment of spinal instability in patients with spinal metastasis. MATERIALS AND METHODS: We retrospectively reviewed 69 consecutive patients who underwent surgical treatment for spinal metastasis. We assessed the patients' preoperative status with respect to each component of the SINS. Multiple logistic regression was performed to calculate odds ratios (ORs) representing the associations among SINS, age, Eastern Cooperative Oncology Group performance status, modified Tokuhashi score, as well as the preoperative Nurick grade variables and reconstruction of the anterior spinal column. RESULTS: Among the 6 items in the SINS, those indicating the degree of collapse and alignment had significantly higher scores in those who underwent corpectomy and anterior support (p<0.001). Multiple logistic regression revealed that the total SINS was the only factor significantly associated with predicting whether anterior support should be performed (adjusted OR=1.595). Receiver operating characteristic (ROC) curve analysis suggested that a cut-off value of 10 points on the SINS scale could be used to decide whether anterior support following corpectomy should be performed (AUC=0.706). CONCLUSIONS: The SINS, insofar as it assesses the degree of collapse and alignment, is a potentially useful tool for determining the surgical strategy in patients with spinal metastasis, especially for deciding upon the necessity of additional anterior support procedures.

Prognosis of Single Spinal Metastatic Tumors: Predictive Value of the Spinal Instability Neoplastic Score System for Spinal Adverse Events

STUDY DESIGN: This was a retrospective cohort study. PURPOSE: We evaluated the predictive value of the Spinal Instability Neoplastic Score (SINS) system for spinal adverse events (SAEs) in patients with single spinal metastatic tumor. OVERVIEW OF LITERATURE: The SINS system was developed to assess spinal instability in patients with single metastatic spinal tumor. However, the system’s potential predictive value for SAEs has been partially studied. METHODS: This system was applied to a retrospective cohort of 78 patients with single spinal metastatic tumors. The patients underwent surgical treatment and were postoperatively followed up for at least 2 years or until death. The attribution of each score and total SINS to SAE (vertebral compression fracture [VCF] and spinal cord compression [SCC]) occurrence was assessed using the Cox proportional hazards model. RESULTS: SAEs occurred on average 7 months after diagnosis of spinal metastasis. The mean survival rate post diagnosis was 43 months. Multivariate analysis using the Cox proportional hazards model revealed that the pain (p=0.029) and spinal alignment (p=0.001) scores were significantly related to VCF occurrence, whereas the pain (p=0.008) and posterolateral involvement (p=0.009) scores were related to SCC occurrence. CONCLUSIONS: Among the components of the SINS system, while pain and spinal alignment showed a significant association with VCF occurrence, pain and posterolateral involvement showed association with SCC occurrence.

Prevalence of Frailty in Patients with Osteoporotic Vertebral Compression Fracture and Its Association with Numbers of Fractures

PURPOSE: To assess the association between frailty and osteoporotic vertebral compression fracture (OVCF) and to evaluate the relationship between numbers of OVCFs and frailty. MATERIALS AND METHODS: We enrolled 760 subjects, including 59 patients (with OVCF) and 701 controls (without OVCF). Successful matching provided 56 patient-control pairs. We analyzed principal clinical and demographic information, which included sex, age, height, weight, body mass index (BMI), variable frailty phenotypes, and Oswestry Disability Index (ODI) and EuroQol 5-dimension questionnaire (EQ-5D) scores. The association between frailty and OVCF was ascertained. In addition, the degrees of disability and quality of life attributable to frailty were determined. RESULTS: The prevalence of frailty was significantly higher in the OVCF group than in the control group (p < 0.001). Most of the frailty phenotypes, such as exhaustion, physical inactivity, slowness, and handgrip strength, were also significantly observed in the OVCF group. Within the OVCF group, the participants with frailty had significantly higher disability and lower quality of life than those in a robust state (p < 0.001 for ODI and EQ-5D). In addition, the multivariate logistic regression analysis demonstrated that the patients with low BMI [odds ratio (OR)=0.704; 95% confidence interval (CI), 0.543–0.913] and ≥3 fractures (OR=9.213; 95% CI, 1.529–55.501) within the OVCF group were associated with higher odds of frailty. CONCLUSION: The present study showed significant relationships between frailty and OVCF, severity of symptoms, and disability induced by OVCF. Furthermore, frailty could be a causal and/or resulting factor of OVCFs.

Spinopelvic Reconstruction with Femoral Allograft and Vertical Rectus Abdominis Myocutaneous Flap after Total Sacrectomy in Recurrent Sacral Chordoma: A Case Report

STUDY DESIGN: Case report. OBJECTIVES: To report a case of recurrent sacral chordoma treated with total sacrectomy and spinopelvic reconstruction. SUMMARY OF LITERATURE REVIEW: Sacral chordoma is a musculoskeletal tumor reported to have a low incidence. Surgical treatment is considered difficult due to the complicated sacropelvic structure, so the prognosis for patients with sacral chordoma has been considered poor. MATERIALS AND METHODS: We report a surgical technique and outcomes from spinopelvic reconstruction with femoral allograft and vertical rectus abdominis myocutaneous flap after total sacrectomy. RESULTS: We report no tumor recurrence at 43 months postoperatively. CONCLUSIONS: Spinopelvic reconstruction with thorough surgical planning after total sacrectomy was found to be a safe and effective treatment method.

Considerations for Surgical Treatment of Osteoporotic Spinal Fracture: Surgical Indication, Approach, Fixation, and Graft Material

STUDY DESIGN: A review of the literature. OBJECTIVES: To review the current evidence on the development of a viable surgical strategy for successful treatment of patients with osteoporotic vertebral fractures. SUMMARY OF LITERATURE REVIEW: Achieving rigid and stable spinal column reconstruction in elderly patients with osteoporosis is challenging because of the poor healing capacity and weak mechanical strength of their bones. MATERIALS AND METHODS: A literature search of clinical and biomechanical studies on the issues of surgical treatment of patients with osteoporotic vertebral collapse was performed and reviewed in terms of the surgical approach, fixation, graft material, and medical considerations. Illustrative cases of the authors' experiences were presented and reflected upon. RESULTS: Posterior spinal fusion and vertebral augmentation showed shorter operating times, less bleeding, and fewer complications with comparable or superior clinical results than anterior corpectomy and fusion or a posterior closing wedge vertebral shortening procedure in multiple studies. Therefore, we recommend the former as a first-line surgical plan for patients with osteoporotic vertebral collapse. However, in some patients who suffer fixed kyphosis, or spinal cord compression by a retropulsed bony fragment or bone cement, or infected vertebroplasty, an anterior approach could be considered to remove the pertinent lesion and to restore anterior spinal column. For the enhancement of the purchasing strength of the screw in the osteoporotic vertebra (e), a technique of prefilled bone cement in the instrumented vertebra(e) or injection of bone cement through a fenestrated screw is useful. Further, preoperative assessment and correction of systemic and local factors that affect bone healing is required when spinal fusion surgery is considered in elderly osteoporotic patients. The selection of the graft material should be individualized according to the property among osteoconduction, osteoinduction, and ostegenesis, or structural support that is the most important for the successful bone healing of each patient. CONCLUSIONS: Comprehensive geriatric assessment and management of elderly patients before surgery and careful and meticulous surgical planning with respect to the surgical approach, instrumentation, and the graft material are important to achieve the best outcome of the surgical treatment of patients with osteoporotic vertebral collapse.

Validation of the Korean Version of the DN4 Diagnostic Questionnaire for Neuropathic Pain in Patients with Lumbar or Lumbar-Radicular Pain

PURPOSE: To evaluate the diagnostic value of the Korean version of the Douleur Neuropathique 4 (DN4) questionnaire and to validate this questionnaire in terms of psychometric properties in patients with chronic pain due to degenerative spinal disease. MATERIALS AND METHODS: The Korean version of the DN4 questionnaire, which was translated and linguistically validated by the MAPI Research Group, was tested on 83 patients with lumbar or lumbar-radicular pain. Test-retest reliability was evaluated in a subsample of 40 patients who completed two assessments with an interval of 2 weeks. Nociceptive pain and neuropathic component pain were diagnosed in 40 and 43 patients, respectively. RESULTS: The Cronbach's alpha coefficient of internal consistency was 0.819, and the test-retest intraclass correlation coefficient (3, 1) (95% confidence interval) was 0.813 (0.776-0.847) (n=40). The area under the receiver-operator characteristics curve was 0.953 (p<0.001), with 95% confidence interval between 0.869 and 0.990. The Korean version of the DN4 questionnaire showed a sensitivity of 100% and 87.1%, and a specificity of 88.2% and 94.1% at the cutoff value of 3/10 and 4/10, respectively, for discriminating neuropathic component pain. CONCLUSION: The present study demonstrated the good discriminatory power of DN4 between nociceptive pain and neuropathic component pain in patients with lumbar or lumbar-radicular pain.

Finite Element Analysis for Comparison of Spinous Process Osteotomies Technique with Conventional Laminectomy as Lumbar Decompression Procedure

PURPOSE: The purpose of this study was to evaluate and compare the biomechanical behavior of the lumbar spine after posterior decompression with the spinous process osteotomy (SPiO) technique or the conventional laminectomy (CL) technique using a finite element (FE) model. MATERIALS AND METHODS: Three validated lumbar FE models (L2-5) which represented intact spine and two decompression models using SPiO and CL techniques at the L3-4 segment were developed. In each model, the ranges of motion, the maximal von Mises stress of the annulus fibrosus, and the intradiscal pressures at the index segment (L3-4) and adjacent segments (L2-3 and L4-5) under 7.5 Nm moments were analyzed. Facet contact forces were also compared among three models under the extension and torsion moments. RESULTS: Compared to the intact model, the CL and SPiO models had increased range of motion and annulus stress at both the index segment (L3-4) and the adjacent segments under flexion and torsion. However, the SPiO model demonstrated a reduced range of motion and annulus stress than the CL model. Both CL and SPiO models had an increase of facet contact force at the L3-4 segment under the torsion moment compared to that of the intact model. Under the extension moment, however, three models demonstrated a similar facet contact force even at the L3-4 model. CONCLUSION: Both decompression methods lead to postoperative segmental instability compared to the intact model. However, SPiO technique leads to better segmental stability compared to the CL technique.

The Effect of Poloxamer 407-Based Hydrogel on the Osteoinductivity of Demineralized Bone Matrix

BACKGROUND: Demineralized bone matrix (DBM) is used for bone healing due to its osteoinductivity, but it requires a carrier for clinical application. Here, we report the effects on the osteoinductivity of DBM by use of a poloxamer 407-based hydrogel as the carrier, compared to sterile water. METHODS: DBM-W and DBM-H represent 27 wt% of DBM with sterile water and DBM with a poloxamer 407-based hydrogel, respectively. Both of the compositions were applied to human mesenchymal stem cell (MSC) cultures, and monitored for alkaline phosphatase (ALP) staining and ALP activity. Six 10-week-old athymic nude rats were used for abdominal muscle grafting with either DBM-W or DBM-H, and were tested by plane radiography, microfocus X-ray computed tomography (CT), and decalcified histology to evaluate ectopic bone formation. RESULTS: The DBM-W group showed stronger ALP staining at 7, 14, and 21 days of treatment, and significantly higher ALP activity at 7 and 14 days of treatment, compared to the DBM-H group. Plane radiography could not confirm the radio-opaque lesions in the rat ectopic bone formulation model. However, ectopic bone formation was observed in both groups by micro-CT. Compared to the DBM-H group, the DBM-W group showed higher bone volume, percent bone volume and trabecular number, and the difference in percent bone volume was statistically significant. Decalcified histology found bony tissue with lamellation in both groups. CONCLUSIONS: Our results suggest that poloxamer 407-based hydrogel has efficacy as a DBM carrier since it shows ectopic bone formation, but its effects on the quality and quantity of osteoblastic differentiation in rat abdominal ectopic bone and MSC are considered negative.

Total Uncinatectomy Revisited: Revision Surgery for Persistent Radiculopathy Following Anterior Cervical Discectomy and Fusion (ACDF) / 대한정형외과학회잡지

We report on a case involving total en bloc uncinatectomy of C7 without removal of the previously inserted cage, performed on a patient with a history of previous anterior cervical discectomy and fusion without uncoforaminotomy at C5-6-7 who had persistent pain radiating to the upper extremity along with progressive weakness. Satisfactory results were achieved. This procedure should be regarded as an effective option for surgical treatment of persistent or recurrent radiculopathy caused by remaining foraminal stenosis following anterior cervical fusion, and we suggest it as a new indication for this procedure.

Infectious Spondylitis Mimicking Osteoporotic Vertebral Compression Fractures: Report of Two Cases

STUDY DESIGN: Case study of two cases. OBJECTIVES: The aim of our study is to describe the rare MR imaging patterns of infectious spondylitis. SUMMARY OF LITERATURE REVIEW: It is generally accepted that the intravertebral cleft sign is not shown in cases of infection or malignancy, and thus, its recognition can obviate unnecessary imaging or biopsy because of its benign significance. MATERIALS AND METHODS: Two patients are presented who developed worsening back pain after a minor trauma. Preoperative MR images of these patients showed intravertebral fluid and benign vertebral compression fractures. Anterior decompression and fusion were done and the bacteria isolated from the intraoperative cultures were Listeria monocytogenes and Mycobacterium tuberculosis, respectively. RESULTS: After 2 years of follow-up, the patients were free of pain, without signs of infection, and showed correct fusion. CONCLUSIONS: MR findings in infectious spondylitis may simulate the patterns of osteoporotic VCFs.

Biomechanical Analysis of Fusion Segment Rigidity Upon Stress at Both the Fusion and Adjacent Segments: A Comparison between Unilateral and Bilateral Pedicle Screw Fixation

PURPOSE: The purpose of this study was to investigate the effects of unilateral pedicle screw fixation on the fusion segment and the superior adjacent segment after one segment lumbar fusion using validated finite element models. MATERIALS AND METHODS: Four L3-4 fusion models were simulated according to the extent of decompression and the method of pedicle screws fixation in L3-4 lumbar fusion. These models included hemi-laminectomy with bilateral pedicle screw fixation in the L3-4 segment (BF-HL model), total laminectomy with bilateral pedicle screw fixation (BF-TL model), hemi-laminectomy with unilateral pedicle screw fixation (UF-HL model), and total laminectomy with unilateral pedicle screw fixation (UF-TL model). In each scenario, intradiscal pressures, annulus stress, and range of motion at the L2-3 and L3-4 segments were analyzed under flexion, extension, lateral bending, and torsional moments. RESULTS: Under four pure moments, the unilateral fixation leads to a reduction in increment of range of motion at the adjacent segment, but larger motions were noted at the fusion segment (L3-4) in the unilateral fixation (UF-HL and UF-TL) models when compared to bilateral fixation. The maximal von Mises stress showed similar patterns to range of motion at both superior adjacent L2-3 segments and fusion segment. CONCLUSION: The current study suggests that unilateral pedicle screw fixation seems to be unable to afford sufficient biomechanical stability in case of bilateral total laminectomy. Conversely, in the case of hemi-laminectomy, unilateral fixation could be an alternative option, which also has potential benefit to reduce the stress of the adjacent segment.

Acute Intravenous Injection Toxicity Study of Escherichia coli-Derived Recombinant Human Bone Morphogenetic Protein-2 in Rat

STUDY DESIGN: Prospective in vivo toxicity study. PURPOSE: To evaluate the conducted acute toxicity study of Escherichia coli (E. coli)-derived recombinant human bone morphogenetic protein-2 (rhBMP-2) with 6-weeks old Sprague-Dawley rats. OVERVIEW OF LITERATURE: rhBMP-2 has well-known osteoinductivity and it is used as a bone graft substitute. E. coli-derived rhBMP-2 can be mass-produced with relatively low costs. E. coli-derived rhBMP-2 facilitates osteoblastic differentiation and bone formation in vitro and in vivo. However, studies regarding side effects or toxicity of E. coli-derived rhBMP-2 have not been published. Thus, we conducted the acute toxicity study of E. coli-derived rhBMP-2 on 6-weeks old Sprague-Dawley rats. METHODS: One mg of BMP-2 was diluted in 0.285 mL of glycine buffer to prepare high BMP-2 concentrations (3.5 mg/mL). Intermediate (0.9 mg/mL) or low (0.35 mg/mL) concentrations of BMP-2 solution was prepared by serial dilutions. The compound was administrated at a dose of 0, 0.7, 1.8, 7 mg/kg by single intravenous injection to five of male and female rats. After the injection, the gross general observations including changes of body weight and histopathological analysis was performed for 14 days. RESULTS: No animal was found dead during the experiment and the body weight changes were both statistically insignificant in the control and experimental groups. No abnormal sign was shown in general observations and autopsy examinations. CONCLUSIONS: Thus, the lethal dose of E. coli-derived rhBMP-2 should be higher than 7 mg/kg with a single intravenous injection.

Clinical and Radiological Predictive Factors to be Related with the Degree of Lumbar Back Muscle Degeneration: Difference by Gender

BACKGROUND: The prediction of lumbar back muscle degeneration is important because chronic low back pain and spino-pelvic imbalance have been known to be related to it. However, gender difference should be considered because there are different quality and volume of muscles between genders. The purpose of this study was to search for clinical and radiological factors to predict the degree of lumbar back muscle degeneration according to gender difference. METHODS: We reviewed 112 patients (44 men and 68 women) with spinal stenosis who underwent a decompressive surgery between 1 January 2009 and 31 December 2011. Degrees of lumbar back muscle degeneration were classified into three categories by the fatty infiltration at each L3-4 disc level on the axial view of T1 magnetic resonance imaging (MRI). Age, sex, bone marrow density score, and body mass index (BMI) were obtained from chart reviews. Lumbar lordosis, sacral slope, pelvic tilt (PT), and pelvic incidence were calculated with lumbar spine standing lateral radiographs. The degrees of spinal stenosis and facet arthropathy were checked with MRI. Student t-test, chi-square test, or Fisher exact test were used to compare clinical and radiological parameters between genders. Analysis of variance (ANOVA) and linear regression analysis were used to search for a relationship between lumbar back muscle degeneration and possible predictive factors in each gender group. RESULTS: Many clinical and radiological parameters were different according to gender. The age, BMI, and PT in the female group (p = 0.013, 0.001, and 0.019, respectively) and the PT in the men group (p = 0.018) were predictive factors to be correlated with lumbar back muscle degeneration. CONCLUSIONS: The PT was the important predictive factor for lumbar back muscle degeneration in both, the male and the female group. However, age and BMI were predictive factors in the female group only.