What is the role of CT-based Hounsfield unit assessment in the evaluation of bone mineral density in patients undergoing 1- or 2-level lumbar spinal fusion for degenerative spinal pathologies? A prospective study.

BACKGROUND CONTEXT: Computed tomography-based vertebral attenuation values (CT-based HU) have been shown to correlate with T-scores on DEXA scan; and have been acknowledged as an independent factor for predicting fragility fractures. Most patients undergoing lumbar surgeries require CT as part of their preoperative evaluation. PURPOSE: The current study was thus planned to evaluate the role of lumbar CT as an opportunistic investigation in determining BMD preoperatively in patients undergoing lumbar fusion. STUDY DESIGN: Prospective cohort study. PATIENT SAMPLE: Patients older than 45 years, who underwent one- to two-level lumbar (L3-S1 levels) fusions. OUTCOME MEASURES: Comparison of the quantitative assessment of osteoporosis using Hounsfield Units (HU) on CT (L1-L5) and mean lumbar T-scores on DEXA (Dual Energy X-ray Absorptiometry). HYPOTHESIS: HU on CT is comparable to T-score on DEXA as a suitable modality for the assessment of osteoporosis in patients undergoing one- to two-level lumbar fusion. METHODS: A prospective cohort study was conducted between January and December 2021. Patients older than 45 years, who underwent one- to two-level lumbar (L3-S1 levels) fusions and had complete clinico-radiological records, were prospectively enrolled. A comparison was drawn between the HU (measured by placing an oval region of interest [ROI] over axial, sagittal and coronal images of lumbar vertebrae) on CT and T-scores on DEXA, and analyzed statistically. The HU values correlating best with normal (group A), osteopenia (B) and osteoporosis (C) categories (classified based on T-scores of lumbar spines) were determined statistically. RESULTS: Overall, 87 patients (mean age of 60.56±11.63 years; 63 [72.4%] female patients) were prospectively studied. There was a statistically significant difference in the mean age (p=.01) and sex distribution (predominantly female patients; p=.03) of patients belonging to groups B (osteopenic) and C (osteoporotic patients), as compared with group A. The greatest correlation between T-score (on DEXA) and HU (on CT) for differentiating osteopenia (group B) from group A was observed at levels L1 (p<.001), L2 (p<.001) and L3 (p<.001). Based on receiver-operating characteristic (ROC) curve analysis, the cut-off values for HU for identifying osteopenia were 159 (at L1; sensitivity 81.6 and specificity 80) and 162 (at L2; sensitivity 80 and specificity 71.1). In addition, there was statistically significant correlation between T-score (on DEXA) and HU at all the lumbar levels for distinguishing osteoporosis (group C), although the difference was most evident at the upper lumbar (L1 and L2) levels (p<.001). Based on ROC analysis, cut-off HU values for defining osteoporosis were 127 (at L1; sensitivity 71.3 and specificity 70) and 117 (at L2; sensitivity 65.5 and specificity 90). CONCLUSION: Based on our study, the measurement of HU on CT at upper lumbar levels can be considered as "surrogate marker" for BMD in the diagnosis of osteopenia (cut-off: 159 at L1, 162 at L2) and osteoporosis (cut-off: 127 at L1, 117 at L2) in patients undergoing lumbar fusion surgeries. The HU measurements on CT at the lower lumbar levels (L4 and L5) are less reliable in this preoperative scenario.

Sublaminar banding as an adjunct to pedicle screw-rod constructs: a review and technical note on novel hybrid constructs in spinal deformity surgery.

Sublaminar implants that encircle cortical bone are well-established adjuncts to pedicle screw-rod constructs in pediatric deformity surgery. Sublaminar bands (SLBs) in particular carry the advantage of relatively greater bone contact surface area as compared to wires and pullout loads that are independent of bone mineral density, in contrast to pedicle screws. Whereas the relevant technical considerations have been reported for pediatric deformity correction, an understanding of the relative procedural specifics of these techniques is missing for adult spinal deformity (ASD), despite several case series that have used distinct posterior tethering techniques for proximal junctional kyphosis prevention. In this paper, the authors summarize the relevant literature and describe a novel technique wherein bilateral tensioned SLBs are introduced at the nonfused proximal junctional level of long-segment ASD constructs.

Biomechanical assessment of proximal junctional semi-rigid fixation in long-segment thoracolumbar constructs.

OBJECTIVEProximal junctional kyphosis (PJK) and failure (PJF) are potentially catastrophic complications that result from abrupt changes in stress across rigid instrumented and mobile non-fused segments of the spine (transition zone) after adult spinal deformity surgery. Recently, data have indicated that extension (widening) of the transitional zone via use of proximal junctional (PJ) semi-rigid fixation can mitigate this complication. To assess the biomechanical effectiveness of 3 semi-rigid fixation constructs (compared to pedicle screw fixation alone), the authors performed cadaveric studies that measured the extent of PJ motion and intradiscal pressure changes (ΔIDP).METHODSTo measure flexibility and ΔIDP at the PJ segments, moments in flexion, extension, lateral bending (LB), and torsion were conducted in 13 fresh-frozen human cadaveric specimens. Five testing cycles were conducted, including intact (INT), T10-L2 pedicle screw-rod fixation alone (PSF), supplemental hybrid T9 Mersilene tape insertion (MT), hybrid T9 sublaminar band insertion (SLB1), and hybrid T8/T9 sublaminar band insertion (SLB2).RESULTSCompared to PSF, SLB1 significantly reduced flexibility at the level rostral to the upper-instrumented vertebral level (UIV+1) under moments in 3 directions (flexion, LB, and torsion, p ≤ 0.01). SLB2 significantly reduced motion in all directions at UIV+1 (flexion, extension, LB, torsion, p < 0.05) and at UIV+2 (LB, torsion, p ≤ 0.03). MT only reduced flexibility in extension at UIV+1 (p = 0.02). All 3 constructs revealed significant reductions in ΔIDP at UIV+1 in flexion (MT, SLB1, SLB2, p ≤ 0.02) and torsion (MT, SLB1, SLB2, p ≤ 0.05), while SLB1 and SLB2 significantly reduced ΔIDP in extension (SLB1, SLB2, p ≤ 0.02) and SLB2 reduced ΔIDP in LB (p = 0.05). At UIV+2, SLB2 similarly significantly reduced ΔIDP in extension, LB, and torsion (p ≤ 0.05).CONCLUSIONSCompared to MT, the SLB1 and SLB2 constructs significantly reduced flexibility and ΔIDP in various directions through the application of robust anteroposterior force vectors at UIV+1 and UIV+2. These findings indicate that semi-rigid sublaminar banding can most effectively expand the transition zone and mitigate stresses at the PJ levels of long-segment thoracolumbar constructs.

Surgical management of adult type 1 split cord malformation. Report of two cases with literature review.

Split cord malformation (SCM) is a rare form of spinal dysraphism wherein the spinal cord is divided longitudinally into two distinct hemicords. Surgery is usually performed in children while management in adults, who rarely manifest symptoms, remains controversial. Both expectant management and prophylactic surgery have been variously advocated. The present article describes our experience in two adult patients with predominant pain-related complaints who underwent surgical excision of type 1 SCM lesions. A comprehensive review of the literature on SCM in adults is also provided. While pain, disability, and quality of life scores improved in these two patients, further larger studies will be required to define the role of surgery in adults with type 1 SCM and a pain-dominant presentation.

Prospective assessment of the safety and early outcomes of sublaminar band placement for the prevention of proximal junctional kyphosis.

OBJECTIVE Proximal junctional kyphosis (PJK) can progress to proximal junctional failure (PJF), a widely recognized early and serious complication of multisegment spinal instrumentation for the treatment of adult spinal deformity (ASD). Sublaminar band placement has been suggested as a possible technique to prevent PJK and PJF but carries the theoretical possibility of a paradoxical increase in these complications as a result of the required muscle dissection and posterior ligamentous disruption. In this study, the authors prospectively assess the safety as well as the early clinical and radiological outcomes of sublaminar band insertion at the upper instrumented vertebra (UIV) plus 1 level (UIV+1). METHODS Between August 2015 and February 2017, 40 consecutive patients underwent either upper (T2-4) or lower (T8-10) thoracic sublaminar band placement at the UIV+1 during long-segment thoracolumbar arthrodesis surgery. Outcome measures were prospectively collected and uploaded to a web-based REDCap database specifically designed to include demographic, clinical, and radiological data. All patients underwent clinical assessment, as well as radiological assessment with anteroposterior and lateral 36-inch whole-spine standing radiographs both pre- and postoperatively. RESULTS Forty patients (24 women and 16 men) were included in this study. Median age at surgery was 64.0 years with an IQR of 57.7-70.0 years. Median follow-up was 12 months (IQR 6-15 months). Three procedure-related complications were noted, including 2 intraoperative cerebrospinal spinal fluid leaks and 1 transient neurological deficit. Median visual analog scale (VAS) scores for back pain significantly improved after surgery (preoperatively: 8.0, IQR 6.0-10.0; 1-year follow-up: 2.0, IQR 0.0-6.0; p = 0.001). Median Oswestry Disability Index (version 2.1a) scores also significantly improved after surgery (preoperatively: 56.0, IQR 45.0-64.0; 1-year follow-up: 46.0, IQR 22.2-54.0; p < 0.001). Sagittal vertical axis (preoperatively: 9.0 cm, IQR 5.3-11.6 cm; final follow-up: 4.7 cm, IQR 2.0-6.6 cm; p < 0.001), pelvic incidence-lumbar lordosis mismatch (24.7°, IQR 11.2°-31.2°; 7.7°, IQR -1.2° to 19.5°; p < 0.001), and pelvic tilt (28.7°, IQR 20.4°-32.6°; 17.1°, IQR 10.8°-25.2°; p < 0.001) were all improved at the final follow-up. While proximal junctional (PJ) Cobb angles increased overall at the final follow-up (preoperatively: 4.2°, IQR 1.9°-7.4°; final follow-up: 8.0°, IQR 5.8°-10.3°; p = 0.002), the significant increase was primarily noted starting at the immediate postoperative time point (7.2°, IQR 4.4°-11.8°; p = 0.001) and not beyond. Three patients (7.5%) developed radiological PJK (mean ΔPJ Cobb 15.5°), while there were no instances of PJF in this cohort. CONCLUSIONS Sublaminar band placement at the UIV+1 during long-segment thoracolumbar instrumented arthrodesis is relatively safe and is not associated with an increased rate of PJK. Moreover, no subjects developed PJF. Prospective large-scale and long-term analysis is needed to define the potential benefit of sublaminar bands in reducing the incidence of PJK and PJF following surgery for ASD. Clinical trial registration no.: NCT02411799 (clinicaltrials.gov).

Clinical and Radiologic Outcomes After Fenestration and Partial Wall Excision of Idiopathic Intradural Spinal Arachnoid Cysts Presenting with Myelopathy.

BACKGROUND: Intradural spinal arachnoid cysts (ISACs) with associated neurologic deficits are encountered infrequently. Various management strategies have been proposed with minimal data on comparative outcomes. OBJECTIVE: We describe the clinical and radiologic presentation as well as the outcomes of 14 surgically managed patients who presented with an ISAC and associated myelopathy. METHODS: We retrospectively reviewed the clinical course of consecutive patients presenting with neurologic deficits associated with idiopathic ISACs at our institution. The diagnoses were based on preoperative magnetic resonance imaging studies followed by intraoperative and histopathological confirmation. RESULTS: A total of 14 consecutive patients with ISACs (1 cervicothoracic, 12 thoracic, and 1 thoracolumbar) and associated myelopathy were identified. Syringomyelia was noted in 8 patients. All ISACs were treated with cyst fenestration and partial wall resection through a posterior approach. Preoperative neurologic symptoms were noted to be stable or improved in all patients starting at 6-week postoperative follow-up. The median (interquartile range) preoperative mJOA score was 13 (12.0-14.8), whereas the postoperative median score at a mean follow-up of 22 months (range 6-50 months) was 16 (14.0-17.0), which represents a median improvement (ΔmJOA) of 2.0 (1.3-3.0) (P < 0.001). Comparison of ΔmJOA scores between cases without and with associated syrinxes did not reveal a significant difference (P = 0.23). Postoperative magnetic resonance imaging scans revealed spinal cord re-expansion at the level of the ISAC in all cases and either complete or partial syrinx resolution in 7 of 8 cases. CONCLUSIONS: Early treatment with fenestration and partial wall resection allows for cord decompression, syrinx resolution, and gradual resolution of myelopathic symptoms in most cases.

Early, reliable, utilitarian predictive factors for fat embolism syndrome in polytrauma patients.

BACKGROUND: Fat embolism is one of the apocalyptic pulmonary complications following high energy trauma situations. Since delay in diagnosis may have devastating consequences, early, easily accessible and relatively inexpensive investigations for risk stratification may prove useful, especially in developing nations. MATERIALS AND METHODS: This prospective trial included a total of 67 young polytrauma patients, in whom the role of nine easily available, rapidly performable clinical or laboratory investigations (or observations noted at admission) in predicting the later occurrence of fat embolism syndrome were assessed. All the patients also underwent continuous monitoring of oxygen saturation with pulsoximetry. RESULTS: The correlation between initial serum lactate (within 12 hours of injury) and hypoxia was statistically significant. There was a trend towards correlation with FES(by Gurd's criteria) (P=0.07), Sensitivity of 24-hour monitoring of oxygen saturation in predicting later pulmonary deterioration approached 100%. CONCLUSIONS: The combination of three factors including polytrauma (with NISS >17), serum lactate >22 mmol/l at admission (within 12 hours of injury) fall in oxygen saturation (SaO2 below 90% in the initial 24 hours) predict the development of post-traumatic pulmonary complications, especially the fat embolism syndrome.