Pushing the Limits of the Prone Position in the Intraoperative Magnetic Resonance Suite.

BACKGROUND: Patient positioning is an integral part of surgical planning, and numerous variations have been suggested to optimize the prone position. So far, however, little attention has been given to address the restrictions and special needs in an intraoperative MRI suite. OBJECTIVE: To share our experience of transforming the modified prone position from the conventional operating room to the intraoperative MRI suite. METHODS: Two-room 3T intraoperative MRI suite. Detailed description of the technical pearls is provided. RESULTS: Ten procedures in 9 consecutive patients (2 female and 7 male) were performed. The median age was 8 years ranging from 4 to 71 years. We experienced no complication from patient positioning. Neither size (range 104-182 cm) nor weight (range 18-98 kg) of the patients was a limiting factor. In none of them, the surgeon experienced an adverse event from inadequate patient positioning and the surgical goals could be achieved without restrictions. An intraoperative MRI could be acquired in all of them with the same image quality as observed for standard positions. CONCLUSION: A transition of the modified prone position from the conventional operating room to the intraoperative MRI suite is feasible, if some crucial steps are considered. We provide a detailed technical description that could be used as a guide by others.

Treatment of benign bone lesions with an injectable biphasic bone substitute.

BACKGROUND: Injectable biphasic ceramic bone substitutes (BCBSs) represent a modern alternative to conventional options for bone defect filling, as they further open the possibilities for percutaneous cavity reconstruction. Although recent studies have shown good surgical outcomes after treatment with BCBSs, mid-term follow-up data are still missing. PATIENTS AND METHODS: Between 2013 and 2017, 18 patients were [1] treated with BCBS [2] for benign bone lesions and [3] had a complete set of retrospective information, including surgical protocols, imaging, patient dismission letters and outpatient clinic protocols, [4] with a minimum follow-up time of one year. Eleven patients received percutaneous surgery, while 7 patients had open curettage and BCBS filling. The median follow-up time was 36.5 (range 12-80) months. RESULTS: Local recurrence was reported in four patients. A distinctive bone remodelling pattern was noted on follow-up X-ray and magnetic resonance imaging showing a double-line phenomenon and continuously increasing cortical thickness one year after treatment in nine of thirteen patients. Regarding surgical complications, one patient suffered from a septic complication that required BCBS removal and lavage. One patient experienced superficial surgical site inflammation with redness and swelling, while two other patients had prolonged wound secretion. CONCLUSION: In a limited case series, the studied BCBS demonstrated acceptable surgical outcomes. Initial wound leakage and recurrence seemed to be associated with percutaneous injection. Further studies are needed to compare recurrence and bone graft resorption after open and percutaneous bone cyst surgeries and to further evaluate postoperative surgical site inflammation, which appears self-limiting in most cases.

Mapping of Venous Sinus Anatomy and Occipital Bone Thickness for Safe Screw Placement in 100 Patients with 46,200 Standardized Measurements Using Computed Tomography Angiography.

STUDY DESIGN: Retrospective descriptive study. OBJECTIVE: The aim of this study was to create topographical maps of occipital bone thickness and venous sinus (VS) presence to assess the risks of screw insertion in four commercially available occipital plates. SUMMARY OF BACKGROUND DATA: Craniocervical junction instability and deformity are serious pathological conditions that require posterior fixation of the occipital bone to the cervical vertebrae. Insertion of occipital bone screws requires evaluation of both occipital bone thickness for effective internal fixation and intracranial VS presence for vascular injury prevention. Despite the surgical risks, there is a paucity of research on safe screw placement. METHODS: We created a matrix of 231 standardized measurement points to analyze the occipital bone thickness and VS presence in cervical spine CT angiograms. These measurements were used to create topographical maps of occipital bone thickness and likelihood of VS presence, which we then compared to the screw hole configurations of four occipital plates. RESULTS: Hundred patients were assessed. Maximum occipital bone thickness of 13.9 ±â€Š3.3 mm was midline in the occipital bone, 45 mm from the foramen magnum, around the external occipital protuberance (EOP). Regions with thicknesses >8 mm were 2 cm lateral to the EOP at the level of the superior nuchal line and 2.5 cm inferior to the EOP. The area with the highest VS presence rate was around the EOP and the superior nuchal line. The right transverse VS was more prominent in both sexes. CONCLUSION: There is a limited area of the occipital bone with thicknesses for enough screw purchase. Previous studies have shown 8 mm as the minimum screw length to reduce the risk of implant failure. In our analysis, only "T"-shaped plates had configurations with thicknesses >8 mm for each screw hole. For every screw hole in the analyzed occipital plates, there was a possibility of VS presence ranging from 8% to 33%.Level of Evidence: 5.

Implant failure after externally magnetic-controlled nail lengthening.

The number of intramedullary procedures to treat leg length discrepancy (LLD) has risen in the past decade and this has led to increased complications such as nail breakage. The aim of this study was to reveal our experience with implant failure after externally magnetic-controlled telescopic bone lengthening. We observed nail-breakage in 4 out of 24 patients (16.7%) after 6 to 15 months (median 13.5 months) following lower limb lengthening for LLD due to non-union or insufficient bone healing. Three femora and one tibia were treated in one posttraumatic and three congenital cases. Three out of the four patients had an elevated Charleston Comorbidity Index (CCI). Revision surgery involved removal of the broken nail and implantation of a trauma nail. At final follow-up all patients showed subjective satisfaction, achievement of desired lengthening with complete bone healing. Based on our results no unequivocal risk factor including number of previous surgeries, comorbidities and age was identified. In cases of delayed bone formation, early revision surgery with an exchange to a trauma nail has to be considered to prevent breakage of the intramedullary telescopic device.

Heel Lift for Skiing to Compensate for Corrected Sagittal Vertical Axis After Spinal Surgery: A Case Report.

Lateral lumbar interbody fusion (LLIF) and pedicle subtraction osteotomy are common procedures to correct adult spinal deformities. Little is known about returning postoperatively to a high-performance sport such as skiing after spinal surgery. We report a case of an alpine skier who underwent a LLIF procedure combined with a posterior corrective osteotomy and posterior instrumentation, who had difficulties returning to skiing postoperatively because of new spinal biomechanics. The case report describes the possible consequences of spinal sagittal deformity surgery on postoperative skiing. A 63-year-old man with a complex lumbar spinal surgery history showed severe adjacent segment degenerative spondylolistheses at L1-L2 and at L5-S1. A lateral approach at L1-L2 combined with a posterior corrective osteotomy at L3 and instrumentation from T10 to the pelvis were performed. At his 1-year follow up, he made excellent progress and returned to skiing. However, he reported that skiing did not feel the same, and his center of gravity felt as if it shifted backwards. Consequently, he placed a 2-cm wedge in his ski binding, which improved his skiing experience. Sagittal vertical axis changes after spinal surgery affect the biomechanics of the entire body. After surgery, the body's ligaments, muscles, and fascia adapt to the new body posture. Activities such as skiing, where body posture plays an essential role, are particularly affected by spine surgeries. Surgeons should discuss this issue before spinal surgery with patients, especially if patients are involved in high-intensity sports.

Determinants of Postoperative Spinal Height Change among Adult Spinal Deformity Patients with Long Construct Circumferential Fusion.

STUDY DESIGN: Retrospective clinical study. PURPOSE: To describe postoperative height changes and identify the predictive factors of spinal height (SH) changes among patients with adult spinal deformity (ASD) who underwent circumferential lumbar fusion with instrumentation. OVERVIEW OF LITERATURE: Postoperative height changes remain an important issue after spinal fusion surgery that affects the overall satisfaction with surgery. Previous studies of postoperative height change have focused exclusively on young patients with adolescent idiopathic scoliosis (AIS). METHODS: We retrospectively reviewed the clinical and imaging data of ASD patients who underwent lumbar corrective circumferential fusion of ≥3 levels (n=106). SH was defined as the vertical distance between C2 and S1 on a standing lateral image. As potential predictors of postoperative height change, the number of lateral lumbar interbody fusion (LLIF) levels, change in spino-pelvic parameters, total number of levels fused, and pedicle subtraction osteotomies (PSO) were documented. Univariate and multivariate linear regression analyses were performed to identify the predictors of postoperative height change. RESULTS: The mean SH change was -2.39±50.8 mm (range, -160 to 172 mm). The univariate analyses showed that the number of LLIF levels (coefficient=10.9, p=0.03), the absolute coronal vertical axis change (coefficient=0.6, p=0.01), and the absolute Cobb angle change (coefficient=-0.9, p=0.03) were significant predictors for height change. Patients with PSOs (n=14) tended to have a shorter height postoperatively (coefficient=-26.1); however, this difference was not significant (p=0.07). Multivariate analyses conducted with variables of p<0.20 showed that pelvic tilt (PT) change is an independent contributor to SH change (coefficient=-0.99, p=0.04, R2=0.11). CONCLUSIONS: Utilizing a modified definition of SH used in previous AIS studies, we demonstrated that patients with ASD lose SH postoperatively and that PT change was an independent contributor of SH change.

The Association Between Endplate Changes and Risk for Early Severe Cage Subsidence Among Standalone Lateral Lumbar Interbody Fusion Patients.

STUDY DESIGN: Retrospective case series. OBJECTIVE: The aim of this study was to investigate the association of Modic type endplate changes with the risk of severe subsidence after standalone lateral lumbar interbody fusion (SA-LLIF). SUMMARY OF BACKGROUND DATA: It has been reported that certain endplate radiolographic features are associated with higher regional bone mineral density (BMD) in the adjacent vertebrae in the lumbar spine. It remains unclear whether these changes have protective effects against osteoporotic complications such as cage subsidence after lumbar surgery. METHODS: We reviewed patients undergoing SA-LLIF from 2007 to 2016 with a follow-up >6 months. Cage subsidence was assessed utilizing the grading system by Marchi et al. As potential contributing factors for cage subsidence, we measured the endplate volumetric BMD (EP-vBMD) and the standard trabecular volumetric BMD measurement in the vertebral body. Modic changes (MC) on magnetic resonance imaging were measured as a qualitative factor for endplate condition. Univariate analysis and multivariate logistic regression analyses with a generalized mixed model were conducted. RESULTS: Two hundred six levels in 97 patients were included in the final analysis. Mean age (± SD) was 66.7 ±â€Š10.7. Sisty-sdpercent of the patients were female. Severe subsidence was observed in 66 levels (32.0%). After adjusting for age, bone morphogenetic protein (BMP) use, and number of levels fused, the presence of MC type 2 was significantly associated with lower risk of severe subsidence (OR = 0.28 [0.09-0.88], P = 0.029). Whereas, EP-vBMD did not demonstrate a statistical significance (p = 0.600). CONCLUSION: The presence of a Modic type 2 change was significantly associated with lower odds of severe subsidence after SA-LLIF. Nonetheless, this significant association was independent from regional EP-vBMD values. This finding suggests that microstructural and/or material property changes associated with Modic type 2 changes might have a protective effect in this patient population. LEVEL OF EVIDENCE: 4.

Radiofrequency Chondroplasty May Not Have A Long-Lasting Effect in the Treatment of Concomitant Grade II Patellar Cartilage Defects in Humans.

The effect of radiofrequency chondroplasty on cartilage tissue is not well studied. This prospective pilot study investigates the effect of radiofrequency chondroplasty on International Cartilage Repair Society (ICRS) grade II patellar cartilage defects using high-resolution magnetic resonance imaging (MRI) with T2 mapping. Six consecutive patients were treated for ICRS grade II patellar cartilage defects using radiofrequency chondroplasty. Before surgery and at defined follow-ups (2 weeks, 4 and 12 months) a high-resolution morphological 3 Tesla MRI with quantitative T2 mapping was performed. At baseline MRI, global T2 values of cartilage defects were increased (46.8 ms ± 9.7) compared to healthy cartilage (35.2 ms ± 4.5) in the same knee which served as reference. Two weeks after treatment, global T2 values (39.2 ms ± 7.7) of the defect areas decreased. However, global T2 values of the defect areas increased beyond the preoperative levels at 4 months (47.4 ms ± 3.1) and 12 months (51.5 ms ± 5.9), respectively. Zonal T2 mapping revealed that the predominant changes in T2 values occurred at the superficial cartilage layer. T2 mapping appears to be an ideal method to monitor cartilage degeneration after chondroplasty. Based on the small sample size of this pilot study, radiofrequency chondroplasty may cause cartilage damage and may not have a long-lasting effect in the treatment of grade II patellar cartilage defects. In five out of six patients, postoperative cartilage damage was observed on quantitative MRI. This study was therefore terminated before completion. We recommend only addressing the pathology which indicated arthroscopy and leaving concomitant cartilage lesions untreated.

Endplate volumetric bone mineral density measured by quantitative computed tomography as a novel predictive measure of severe cage subsidence after standalone lateral lumbar fusion.

PURPOSE: Quantitative computed tomography (QCT) is an alternate imaging method to dual X-ray absorptiometry to measure bone mineral density (BMD). One advantage of QCT is that it allows site-specific volumetric BMD (vBMD) measurements in a small region. In this study, we utilized site-specific, endplate vBMD (EP-vBMD) as a potential predictive marker of severe cage subsidence in standalone lateral lumbar interbody fusion (SA-LLIF) patients and conducted a retrospective comparative study between EP-vBMD and trabecular vBMDs (Tb-vBMD) in the vertebrae. METHODS: Patients undergoing SA-LLIF from 2007 to 2016 were retrospectively reviewed. EP-vBMD was defined as the average of the upper and lower endplate volumetric BMDs measured in cortical and trabecular bone included in a 5-mm area of interest beneath the cage contact surfaces. We compared Tb-vBMDs and EP-vBMDs between disk levels that had severe cage subsidence and levels with no severe subsidence. RESULTS: Both EP-vBMD and Tb-vBMD could be measured in 210 levels of 96 patients. Severe cage subsidence was observed in 58 levels in 38 patients. Median (IQR) Tb-vBMD was 120.5 mg/cm3 (100.8-153.7) in the non-severe subsidence group and 117.9 mg/cm3 (90.6-149.5) in the severe subsidence group (p = 0.393), whereas EP-vBMD was significantly lower in the severe subsidence group than the non-severe subsidence group (non-severe subsidence 257.4 mg/cm3 (216.3-299.4), severe subsidence 233.5 mg/cm3 (193.4-273.3), p = 0.026). CONCLUSION: We introduced a novel site-specific vBMD measurement for cage subsidence risk assessment. Our results showed that EP-vBMD was a reproducible measurement and appeared more predictive for severe cage subsidence after SA-LLIF than Tb-vBMD. These slides can be retrieved under Electronic Supplementary Material.

Correlation between Urine N-Terminal Telopeptide and Fourier Transform Infrared Spectroscopy Parameters: A Preliminary Study.

N-terminal telopeptide (NTX) is a bone resorption marker that is commonly referenced in clinical practice. Bone remodeling is also associated with changes in mineral components. Fourier transform infrared spectroscopy (FTIR) is utilized in the assessment of bone material properties and some parameters are reported to have associations with bone remodeling. The aim of this cross-sectional study is to investigate the relationship between uNTX levels and FTIR parameters, utilizing prospectively collected study data for patients who underwent lumbar fusion surgery. Bone specimens were taken from iliac crest (IC) and vertebrae (V). Cortical (C) and trabecular (T) bones were separately analyzed. 22 patients (mean age 60.0 years (35.9-73.3), male : female 9 : 13) were included in the final analysis. Women showed significantly higher uNTX levels (male : female, median [range] 21.0 [11.0-39.0] : 36.0 [15.0-74.0] nM·BCE/mM, p=0.033). Among women, a significant positive correlation was observed between uNTX and mineral-to-matrix ratio in IC-C. Among men, uNTX demonstrated significant negative correlation with collagen crosslinks (XLR: ratio of mature to immature collagen crosslinks) in IC-C, V-T, and V-C. In addition, uNTX was positively correlated with acid phosphate substitution (HPO4, a parameter of new bone formation) in IC-C, IC-T, and V-C. After age adjustment, HPO4 in IC-T and V-C among men showed significant positive associations with uNTX (IC-T: p=0.018, R 2 = 0.544; V-C: p=0.007, R 2 = 0.672). We found associations between FTIR parameters and uNTX in men, but not in women. The correlations between uNTX and FTIR parameters in men might suggest a better balance of bone breakdown (uNTX) and new bone formation (FTIR parameters: XLR, HPO4) than in women.

The impact of degenerative disc disease on regional volumetric bone mineral density (vBMD) measured by quantitative computed tomography.

BACKGROUND CONTEXT: It has been reported that degenerative disc disease (DDD) is associated with higher spinal bone mineral density (BMD) based on previous studies that used dual X-ray absorptiometry (DXA). However, DDD is often associated with proliferative bone changes and can lead to an overestimation of BMD measured with DXA. Trabecular volumetric BMD (vBMD) in the vertebral body measured with quantitative computed tomography (QCT) is less affected by those changes and can be a favorable alternative to DXA for patients with degenerative spinal changes. PURPOSE: The purpose of this study is to investigate the effect of DDD on regional trabecular vBMDs in the vertebral body measured by QCT. STUDY DESIGN/SETTING: Cross-sectional observational study at a single academic institution. PATIENTS SAMPLE: Consecutive patients undergoing posterior lumbar spinal fusion between 2014 and 2017 who had a routine preoperative CT scan and magnetic resonance imaging (MRI) within a 90-day interval. OUTCOME MEASURES: Regional trabecular vBMDs in the vertebral body by QCT. METHODS: QCT measurements were conducted in L1-S1 vertebral trabecular bone. Any apparent sclerotic lesions that might affect vBMD values were excluded from the region of interest. The vBMDs of each level were defined as the average vBMD of the upper and lower vertebrae. To evaluate DDD, Pfirrmann grade, Modic grade, total end plate score, and vacuum phenomenon were documented. Univariate regression analysis and multivariate analyses with a linear mixed model adjusted with individual variability of segmental vBMDs were conducted with vBMD as the response variable. RESULTS: Of 143 patients and 715 disc levels, 125 patients and 596 discs met our inclusion criteria. Mean vBMD (±standard deviation [SD]) of all levels was 119.0±39.6 mg/cm3. After adjusting for all covariates, Pfirrmann grade was not an independent contributor to vBMD, but the presence of any Modic change (type 1, ß=6.8, p≤.001; type 2, ß=6.7, p<.001; type 3, ß=43.6, p<.001), high TEPS (score 10-12, ß=14.2, p<.001), or vacuum phenomenon (ß=9.0, p<.001) was shown to be independent contributors to vBMD. CONCLUSIONS: Our results showed that the presence of certain end plate lesions (Modic changes and high TEPS) on MRI was significantly associated with increased regional QCT-vBMDs in the vertebral body, but no significant association was observed with disc nucleus pathology, unless it was associated with a vacuum phenomenon. When end plate lesions with Modic changes and high TEPS are present at the measuring level, care must be taken to interpret vBMD values, which might be overestimations even if the trabecular area appears normal.

A Novel and Reproducible Classification of the Vertebral Artery in the Subaxial Cervical Spine.

BACKGROUND: An injury of the vertebral artery (VA) is one of the most catastrophic complications in the setting of cervical spine surgery. Anatomic variations of the VA can increase the risk of iatrogenic lacerations. OBJECTIVE: To propose a novel and reproducible classification system that describes the position of the VA based on a 2-dimensional map on computed tomography angiographs (CTA). METHODS: This cross-sectional retrospective study reviewed 248 consecutive CTAs of the cervical spine at a single academic institution between 2007 and 2018. The classification consists of a number that characterizes the location of the VA from the medio-lateral (ML) aspect of the vertebral body. In addition, a letter describes the VA location from the anterior-posterior (AP) aspect. The reliability and reproducibility were assessed by 2 independent raters on 200 VAs. RESULTS: The inter- and intrarater reliability values showed the classification's reproducibility. The inter-rater reliability weighted κ-value for the ML aspect was 0.93 (95% CI: 0.93-0.93). The unweighted κ-value was 0.93 (95% CI: 0.86-1.00) for "at-risk" positions (ML grade ≥1), and 0.87 (95% CI: 0.75-1.00) for "high-risk" positions (ML grade ≥2). The weighted κ-value for the intrarater reliability was 0.94 (95% CI: 0.95-0.95). The unweighted κ-values for the intrarater reliability were 0.95 (95% CI: 0.91-0.99) for "at-risk" positions, and 0.87 (95% CI: 0.78-0.96) for "high-risk" positions. CONCLUSION: The proposed classification is reliable, reproducible, and independent of individual anatomic size variations. The use of this novel grading system could improve the understanding and interdisciplinary communication about VA anomalies.

Perioperative Risk Factors for Early Revisions in Stand-Alone Lateral Lumbar Interbody Fusion.

BACKGROUND: Lateral lumbar interbody fusion can be performed without supplemental posterior instrumentation. Previous reports have shown favorable results with stand-alone lateral lumbar interbody fusion (SA-LLIF); however, a reoperation rate of up to 26% has been reported. It remains unclear what perioperative factors are associated with early failure after SA-LLIF. The objective of this study is to determine perioperative factors that increase the risk of early revisions after SA-LLIF. METHODS: Data of consecutive patients with SA-LLIF were reviewed. All revisions or recommendations for revision surgery within 12 months after the LLIF procedure were documented. As potential contributors, operative levels, preoperative clinical diagnosis, number of fusion levels, and the average L1/L2 quantitative computed tomography-volumetric bone mineral density value were obtained along with other demographic factors. Cage subsidence (grade 0-III as per Marchi et al.), was also evaluated in patients who had radiographs/computed tomography between 6 and 12 months postoperatively (n = 122). Logistic regression analyses were conducted. RESULTS: Of 133 eligible patients, 21 (15.8%) underwent revision surgery and 4 (3.0%) were recommended for revision surgery within 1 year primarily because of neurologic symptoms or pain (68%). Baseline demographics showed no significant difference between the revision and the nonrevision group. The average number of levels fused was 2.12 (revision group) and 2.14 (nonrevision group) (P = 0.55). Significantly more patients in the revision group had the diagnosis of foraminal stenosis (64.0% vs. 39.8%; P = 0.04). CONCLUSIONS: Patients with foraminal stenosis were more likely to have early revision surgery after SA-LLIF primarily because of neurologic symptoms/pain. This information can assist in preoperative discussions and management of patient expectations.

Intercostal artery hemorrhage with hemothorax following combined lateral and posterior lumbar interbody fusion: a case report.

Introduction: Lateral lumbar interbody fusion (LLIF) is a safe treatment for degenerative spine conditions. However, risk of complications such as vascular injuries remains. We report a unique case of an intercostal artery (ICA) hemorrhage with hemothorax following LLIF. Case presentation: One hour after a right-sided LLIF L3-4 with posterior decompression L2-4 and L3-5 instrumentation, the patient became hypotensive, anemic and required vasopressor support. Evaluation revealed a right-sided hemothorax, which was caused by a bleeding intercostal artery, laterally at the 10th intercostal space. A lateral thoracotomy was performed to stop the bleeding. After vessel ligation and placement of two chest tubes, the patients' hemodynamics improved. The patient remained intubated overnight and was extubated on the first postoperative day. Discussion: Vascular injury is a rare complication of LLIF procedures. Most vascular injuries are segmental vessel lacerations, which resolve postoperatively. This is the first case description of ICA bleeding associated with LLIF surgery. Spontaneous ICA bleeding exists, but surgeons should be aware of careful handling in patients with vascular risk factors, especially with regard to patient positioning required in certain spinal surgical approaches. Timely vascular injury identification is critical for hemostasis and clinical management.

Skin Ultrasound Measurement as a Potential Marker of Bone Quality: A Prospective Pilot Study of Patients undergoing Lumbar Spinal Fusion.

Bone mineral density (BMD) is not the sole predictor of fracture development. Qualitative markers including bone collagen maturity contribute to bone fragility. Bone and related type I collagen containing connective tissues degenerate in parallel fashion. With aging, changes in skin collagen content and quality have been observed that can be detected on ultrasound (US) as a decrease in dermal thickness and an increase in reticular layer echogenicity. We hypothesized that US dermal thickness and echogenicity correlate with bone collagen maturity. Data of 43 prospectively enrolled patients (mean age 61 years, 24 females), who underwent instrumented, posterior lumbar fusion was analyzed. Besides preoperative quantitative computed tomography (QCT) and skin US measurements, intraoperative bone biopsies were obtained and analyzed with Fourier-transform infrared spectroscopy. Among men, there was no correlation between US measurements and collagen maturity. Among women, dermal layer thickness correlated negatively with collagen maturity in trabecular bone of the iliac crest (r = -0.51, p = 0.01) and vertebra (r = -0.59, p = 0.01) as well as in cortical bone of the iliac crest (r = -0.50, p = 0.02) and vertebra (r = -0.50, p = 0.04). In addition, echogenicity correlated positively with collagen maturity in trabecular vertebral bone (r = 0.59, p = 0.01). In both genders, US measurements showed no correlation with QCT BMD. In summary, ultrasound skin parameters are associated with bone quality factors such as collagen maturity, rather than bone quantity (BMD). Ultrasound of the skin may thereby be an easy and accessible take off point for diagnosis of bone collagen maturity and connective tissue degeneration in the future. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2508-2515, 2019.

Regional bone mineral density differences measured by quantitative computed tomography: does the standard clinically used L1-L2 average correlate with the entire lumbosacral spine?

BACKGROUND CONTEXT: Quantitative computed tomography (QCT) of the lumbar spine is used as an alternative to dual-energy X-ray absorptiometry in assessing bone mineral density (BMD). The average BMD of L1-L2 is the standard reportable metric used for diagnostic purposes according to current recommendations. The density of L1 and L2 has also been proposed as a reference value for the remaining lumbosacral vertebrae and is commonly used as a surrogate marker for overall bone health. Since regional BMD differences within the spine have been proposed, it is unclear if the L1-L2 average correlates with the remainder of the lumbosacral spine. PURPOSE: The aim of this study was to determine possible BMD variations throughout the lumbosacral spine in patients undergoing lumbar fusion and to assess the correlation between the clinically used L1-L2 average and the remaining lumbosacral vertebral levels. STUDY DESIGN/SETTING: This is a retrospective case series. PATIENT SAMPLE: Patients undergoing posterior lumbar spinal fusion from 2014 to 2017 at a single, academic institution with available preoperative CT imaging were included in this study. OUTCOME MEASURES: The outcome measure was BMD measured by QCT. METHODS: Standard QCT measurements at the L1 and L2 vertebra and additional experimental measurements of L3, L4, L5, and S1 were performed. Subjects with missing preoperative lumbar spine CT imaging were excluded. The correlations between the L1-L2 average and the other vertebral bodies of the lumbosacral spine (L3, L4, L5, S1) were evaluated. RESULTS: In total, 296 consecutive patients (55.4% female, mean age of 63.1 years) with available preoperative CT were included. The vertebral BMD values showed a gradual decrease from L1 to L3 and increase from L4 to S1 (L1=118.8 mg/cm3, L2=116.6 mg/cm3, L3=112.5 mg/cm3, L4=122.4 mg/cm3, L5=135.3 mg/cm3, S1=157.4 mg/cm3). There was strong correlation between the L1-L2 average and the average of the other lumbosacral vertebrae (L3-S1) with a Pearson's correlation coefficient (r=0.85). We also analyzed the correlation between the L1-L2 average and each individual lumbosacral vertebra. Similar relationships were observed (r value, 0.67-0.87), with the strongest correlation between the L1-L2 average and L3 (r=0.87). CONCLUSIONS: Our data demonstrate regional BMD differences throughout the lumbosacral spine. Nevertheless, there is high correlation between the clinically used L1-L2 average and the BMD values in the other lumbosacral vertebrae. We, therefore, conclude the standard clinically used L1-L2 BMD average is a useful bone quantity measure of the entire lumbosacral spine in patients undergoing lumbar spinal fusion.

Off-Label Iliac Side Branch Application for Salvage of an Accessory Renal Artery.

PURPOSE: To present the off-label use of an iliac side branch device to connect an accessory right renal artery to a bifurcated endograft in infrarenal aortic aneurysm repair. CASE REPORT: An 83-year-old woman with a 54-mm infrarenal abdominal aortic aneurysm underwent endovascular repair using an iliac side branch device for accessory renal artery salvage. The procedure was technically successful, and no immediate perioperative adverse events were encountered. The creatinine level increased slightly. Six-month follow-up imaging revealed no endoleaks or occlusion. CONCLUSION: Considering the higher perioperative risk associated with open or hybrid procedures for similar cases, this off-label application of a well-recognized endovascular device deserves consideration as an alternative treatment option.