Thermal Damage in Orthopaedics.

There are numerous potential sources of thermal damage encountered in orthopaedic surgery. An understanding of the preclinical mechanisms of thermal damage in tissues is necessary to minimize iatrogenic injuries and use these mechanisms therapeutically. Heat generation is a phenomenon that can be used to a surgeon's benefit, most commonly for hemostasis and local control of tumors. It is simultaneously one of the most dangerous by-products of orthopaedic techniques as a result of burring, drilling, cementation, and electrocautery and can severely damage tissues if used improperly. Similarly, cooling can be used to a surgeon's advantage in some orthopaedic subspecialties, but the potential for harm to tissues is also great. Understanding the potential of a given technique to rapidly alter local temperature-and the range of temperatures tolerated by a given tissue-is imperative to harness the power of heat and cold. In all subspecialties of orthopaedic surgery, thermal damage is a relevant topic that represents a direct connection between preclinical and clinical practice.

Are all Cages Created Equal? Analysis of Cervical Cage Malfunctions Using FDA MAUDE Database.

STUDY DESIGN: Retrospective case series. OBJECTIVE: To characterize failure rates of cervical cages based on manufacturer and design characteristics using the nationwide database of reported malfunctions. BACKGROUND: The Food and Drug Administration (FDA) aims to ensure the safety and efficacy of cervical interbody implants postimplantation; however, intraoperative malfunctions may be overlooked. MATERIALS AND METHODS: The FDA's Manufacturer and User Facility Device Experience database was queried for reports of cervical cage device malfunctions from 2012 to 2021. Each report was categorized based on the failure type, implant design, and manufacturer. Two market analyses were performed. First, "failure-to-market share indices" were generated by dividing the number of failures per year for each implant material by its yearly US market share in cervical spine fusion. Second, "failure-to-revenue indices" were calculated by dividing the total number of failures per year for each manufacturer by their approximate yearly revenue from spinal implants in the US. Outlier analysis was performed to generate a threshold value above which failure rates were defined as greater than the normal index. RESULTS: In total, 1336 entries were identified, and 1225 met the inclusion criteria. Of these, 354 (28.9%) were cage breakages, 54 (4.4%) were cage migrations, 321 (26.2%) were instrumentation-related failures, 301 (24.6%) were assembly failures, and 195 (15.9%) were screw failures. Poly-ether-ether-ketone implants had higher failure by market share indices for both migration and breakage compared with titanium. Upon manufacturer market analysis, Seaspine, Zimmer-Biomet, K2M, and LDR exceeded the failure threshold. CONCLUSION: The most common cause of implant malfunction was breakage. Poly-ether-ether-ketone cages were more likely to break and migrate compared with titanium ones. Many of these implant failures occurred intraoperatively during instrumentation, which underscores the need for FDA evaluation of these implants and their accompanying instrumentation under the appropriate loading conditions before commercial approval.

Laminoplasty in Motion: Evolving Techniques and Complications.

Cervical laminoplasty is an increasingly popular surgical option for the treatment of cervical spondylotic myelopathy (CSM) and ossification of the posterior longitudinal ligament (OPLL). Over the past few decades, there have been substantial developments in both surgical technique and hardware options. As the field of cervical surgery rapidly evolves, there is a timely need to reassess the evolving complications associated with newer techniques. This review aims to synthesize the available literature on cervical laminoplasty and associated mechanical complications pertaining to different laminoplasty hinge fixation options.

Moderate sagittal plane deformity patients have similar radiographic and functional outcomes with either anterior or posterior surgery.

PURPOSE: This study aimed to compare the functional and radiographic outcomes of two surgical interventions for adult spinal deformity (ASD): anterior lumbar interbody fusion with anterior column realignment (ALIF-ACR) and posterior approach using Smith-Peterson osteotomy with transforaminal lumbar interbody fusion and pedicle screw fixation (TLIF-Schwab2). METHODS: A retrospective cohort study included 61 ASD patients treated surgically between 2019 and 2020 at a single tertiary orthopedic specialty hospital. Patients were divided into two groups: Group 1 (ALIF-ACR, 29 patients) and Group 2 (TLIF-Schwab2, 32 patients). Spinopelvic radiographic parameters and functional outcomes were evaluated at 3, 6, and 12 months postsurgery. RESULTS: Perioperative outcomes favored the ALIF-ACR group, with significantly smaller blood loss, shorter hospital stay, and operative time. Radiographic and functional outcomes were similar for both groups; however, the ALIF-ACR group did have a greater degree of correction in lumbar lordosis at 12 months. Complication profiles varied, with the ALIF-ACR group experiencing mostly hardware-related complications, while the TLIF-Schwab2 group faced dural tears, wound dehiscence, and proximal junctional kyphosis. Both groups had similar revision rates. CONCLUSION: Both ALIF-ACR and TLIF-Schwab2 achieved similar radiographic and functional outcomes in ASD patients with moderate sagittal plane deformity at 1-year follow-up. However, the safety profiles of the two techniques differed. Further research is required to optimize patient selection for each surgical approach, aiming to minimize perioperative complications and reoperation rates in this challenging patient population.

Cross-cultural adaptation, reliability, and validity of the Russian version of the Spine Oncology Study Group Outcomes Questionnaire (SOSGOQ2.0).

OBJECTIVE: The most validated health-related quality-of-life (HRQOL) questionnaire specific to the metastatic spine cancer population is the Spine Oncology Study Group Outcomes Questionnaire version 2 (SOSGOQ2.0). The purpose of this study was to translate and validate a Russian version of the SOSGOQ2.0. METHODS: The SOSGOQ2.0 was translated into Russian and cross-culturally adapted. In this study, 64 eligible patients completed the SOSGOQ2.0_RUS along with the EQ-5D 5 Level, SF-36 quality-of-life questionnaires, and visual analog scale for pain assessment scale (VAS). Internal consistency was measured using Cronbach's alpha, in which a score of 0.65 or higher is acceptable. Test-retest reliability was evaluated by examining the intraclass correlation coefficient (ICC). RESULTS: Included in this study were 64 Russian-speaking patients (median age 59 years) with metastatic spine disease. The most common primary tumors were breast, kidney, and prostate cancers. The overall Cronbach's alpha was 0.87, indicating high internal consistency. The overall ICC for the SOSGOQ2.0_RUS was 0.88 (95% CI 0.81-0.93), indicating high reliability and consistency of the measure. The physical function, pain, and mental health domains of the SF-36 moderately correlated with the same domains of the SOSGOQ2.0_RUS, with correlation coefficients ranging from 0.65 to 0.71. CONCLUSIONS: The SOSGOQ2.0_RUS is a reliable and valid questionnaire for assessing the HRQOL in patients with metastatic spinal tumors. The questionnaire showed high internal consistency, test-retest reliability, and good construct validity when compared with other established questionnaires.

Spinolaminar locking plates improve fixation strength compared to pedicle screws: a biomechanical analysis.

INTRODUCTION: Pedicle screw loosening is a significant complication of posterior spinal fixation, particularly among osteoporotic patients and in deformity constructs. In orthopedic trauma surgery, locking plates and screws have revolutionized the fixation of osteoporotic fractures. We have combined the traumatology principle of fixed-angle locking plate fixation with the spine principles of segmental instrumentation. METHODS: A novel spinolaminar locking plate was designed based on morphometric studies of human thoracolumbar vertebrae. The plates were fixed to cadaveric human lumbar spines and connected to form 1-level L1-L2 or L4-L5 constructs and compared to similar pedicle screw constructs. Pure moment testing was performed to assess range of motion before and after 30,000 cycles of cyclic fatigue. Post-fatigue fixture pullout strength was assessed by applying a continuous axial tensile force oriented to the principal axis of the pedicle until pullout was observed. RESULTS: Spinolaminar plate fixation resulted in superior pullout strength compared to pedicle screws (1,065 ± 400N vs. 714 ± 284N, p = 0.028). Spinolaminar plates performed equivalently to pedicle screws in range of motion reduction during flexion/extension and axial rotation. Pedicle screws outperformed the spinolaminar plates in lateral bending. Finally, no spinolaminar constructs failed during cyclic fatigue testing, whereas one pedicle screw construct did. CONCLUSIONS: The spinolaminar locking plate maintained adequate fixation post-fatigue, particularly in flexion/extension and axial rotation compared to pedicle screws. Moreover, spinolaminar plates were superior to pedicle screw fixation with respect to cyclic fatiguing and pullout strength. The spinolaminar plates offer a viable option for posterior lumbar instrumentation in the adult spine.

An Analysis of a Decade of Lumbar Interbody Cage Failures in the United States: A MAUDE Database Study.

STUDY DESIGN: A retrospective case series. OBJECTIVE: This study aims to assess the rates of lumbar interbody cage failures based on their material and manufacturer. SUMMARY OF BACKGROUND DATA: Perioperative lumbar interbody cage malfunctions are underreported events in the spine literature and may result in complications. Although the Food and Drug Administration ensures the safety of these devices under physiological conditions after implantation, these devices may experience nonphysiological conditions during implantation, which may be overlooked. MATERIALS AND METHODS: The MAUDE database was examined for reports of lumbar cage device malfunctions from 2012 to 2021. Each report was categorized based on failure type and implant design. A market analysis was performed by dividing the total number of failures per year for each manufacturer by their approximate yearly revenue from spinal implants in the United States. Outlier analysis was performed to generate a threshold value above which failure rates were defined as greater than the normal index. RESULTS: Overall, 1875 lumbar cage malfunctions were identified. Of these, 1230 (65.6%) were cage breakages, 257 (13.7%) were instrument malfunctions, 177 (9.4%) were cage migrations, 143 (7.6%) were assembly failures, 70 (4.5%) were screw-related failures, and 21 (1.1%) were cage collapses. Of the breakages, 923 (74.9%) occurred during insertion or impaction and 97 entries detailed a medical complication or a retained foreign body. Of the migrations, 155 (88.6%) were identified postoperatively, of which 73 (47.1%) detailed complications and 52 (33.5%) required a revision procedure. Market analysis demonstrated that Medtronic, Zimmer Biomet, Stryker, Seaspine, and K2M exceeded the calculated threshold. CONCLUSIONS: Lumbar cages with polyether ether ketone core material failed more frequently by breakage, whereas titanium surface cages failed more frequently by migration. Failure rates varied depending on the manufacturer. Most cage breakages identified in the present study occurred intraoperatively during implantation. These findings call for a more detailed Food and Drug Administration evaluation of these intraoperative malfunctions before commercial approval. LEVEL OF EVIDENCE: Level 4.

Does the Bone Mineral Density of the Lumbar Spine Correlate With Dual-Energy X-ray Absorptiometry T Score? A Cadaveric-Based Analysis of Computed Tomography Densitometry.

BACKGROUND: Pedicle screw loosening is a complication of spinal instrumentation in osteoporotic patients. Dual-energy x-ray absorptiometry scans are not able to detect variations in bone mineral density (BMD) within specific regions of vertebrae. The purpose of this study was to investigate whether spine T scores correlate with cortical and cancellous BMD of pedicles and other 6 anatomical regions of lumbar spine. METHODS: Eleven cadaveric spines with a mean age of 73 years were digitally isolated by applying filters for cortical and cancellous bone on computed tomography images. Eleven L5 vertebrae were separated into 7 anatomical regions of interest using 3-dimensional software modeling. Hounsfield units (HU) were determined for each region and converted to cortical and cancellous BMD with calibration phantoms of known BMD. Correlations between T scores and HU values were calculated using Pearson correlation coefficient. RESULTS: Mean vertebral T score was 0.15. Cortical BMD of pedicles was strongly correlated with T score (R 2 = 0.74). There was moderate correlation between T score and cortical BMD of lamina, inferior articular process (IAP), superior articular process (SAP), spinous process, and vertebral body. There was weak correlation between T score and cortical BMD of transverse process (R 2 = 0.16). Cancellous BMD of vertebral body was strongly correlated with T score (R 2 = 0.82). There was moderate correlation between T score and cancellous BMD of pedicles, spinous process, and transverse process. There was weak correlation between T scores and cancellous BMD of lamina, IAP, and SAP. CONCLUSIONS: There is a strong correlation between T scores and cortical BMD of lumbar pedicle. There is strong correlation between T scores and cancellous BMD of vertebral body. Cortical and cancellous BMD of transverse process and lamina were weakly correlated with T score and less affected by osteoporosis. CLINICAL RELEVANCE: Patients with osteoporosis may especially benefit from the development of extrapedicular fusion strategies due to the relatively higher bone density of these fixation sites.

Pyogenic spinal infections warrant a total spine MRI.

Study design: retrospective case series. Objective: the presenting clinical symptoms of spinal infections are often nonspecific and a delay in diagnosis can lead to adverse patient outcomes. The morbidity and mortality of patients with multifocal spinal infections is significantly higher compared to unifocal infections. The purpose of the current study was to analyse the risk factors for multifocal spinal infections. Methods: we conducted a retrospective review of all pyogenic non-tuberculous spinal infections treated surgically at a single tertiary care medical center from 2006-2020. The medical records, imaging studies, and laboratory data of 43 patients during this time period were reviewed and analysed after receiving Institutional Review Board approval. Univariate and multivariate analyses were performed to identify factors associated with a multifocal spinal infection. Results: 15 patients (35 %) had multifocal infections. In univariate analysis, there was a significant association with chronic kidney disease ( p = 0.040 ), gender ( p = 0.003 ), a white blood cell count ( p = 0.011 ), and cervical ( p < 0.001 ) or thoracic ( p < 0 .001) involvement. In multivariate analysis, both cervical and thoracic involvement remained statistically significant ( p = 0.001 and p < 0.001 , respectively). Conclusions: patients with infections in the thoracic or cervical region are more likely to have a multifocal infection. Multifocal pyogenic spinal infections remain a common entity and a total spine MRI should be performed to aid in prompt diagnosis.

Conditional survival after surgery for metastatic tumors of the spine: does prognosis change over time?

PURPOSE: Conditional survival (CS) provides a dynamic prediction of patient survival by incorporating the time an individual has already survived given their disease specific characteristics. The objective of the current study was to estimate CS among patients after surgery for spinal cord compression or spinal instability, as well as stratify CS according to relevant patient- and disease-related characteristics. METHODS: The clinical outcomes of 361 patients undergoing surgical management of metastatic spinal tumors were retrospectively analyzed. Stratification of this cohort according to disease and surgery-specific characteristics allowed for univariate and multivariate statistical analyses of our study population. Observed overall and conditional survival estimates were calculated by the Kaplan-Meier method. RESULTS: 12-month conditional survival in patients undergoing surgical management of metastatic spine tumors increased from 57% at baseline to 70% at 24 months following spine surgery. Overall survival (OS) was influenced by CCI grade, Katagiri tumor type, presence of lung metastasis, type of spine surgery, presence of postoperative systemic therapy and ambulatory status at follow-up. Analyses of OS and CS by prognostic strata were similar with exception of stratification by surgery type. Differences in survival between strata tend to converge over time. Unfavorable factors for OS appear to be less relevant after a period of 24 months following spine surgery. CONCLUSION: Patients after surgery for metastatic tumors of the spine can expect a positive trend in conditional survival as survivorship increases. Even patients with a more severe disease can be encouraged with gains in conditional survival over time. LEVEL OF EVIDENCE: Level IV (retrospective cohort study).

C1-C2 Facet Joint Penetration by C2 Pedicle Screws: Influence of Local Anatomy, Bone Mineral Density, and Screw Length.

BACKGROUND: A challenge of C2 pedicle screw placement is to avoid penetration into the C1-C2 facet joint, as this may alter normal biomechanics and accelerate joint degeneration. Our objective was to clarify how local anatomy and surgical technique may relate to C2 pedicle screw penetration into the C1-C2 facet joint. METHODS: C2 pedicle screws were inserted using a fluoroscopically assisted freehand technique. Independent fellowship-trained spine surgeons blindly reviewed intraoperative fluoroscopic and postoperative computed tomography (CT) images for evidence of facet joint penetration (FJP). C2 pedicle morphometry, the sagittal angle of the facet joint, axial and sagittal pedicle screw angles, and screw length were measured on the relevant CT images. RESULTS: A total of 34 patients fulfilled the study criteria, and a total of 68 C2 pedicle screws were placed. Eight screws (16%) penetrated the C1-C2 facet joint. The mean sagittal angle of the C1-C2 facet joint was significantly lower in the FJP group compared with the non-FJP group. The mean sagittal angle of the screws was significantly higher in the FJP group compared with the non-FJP group. The mean screw length was significantly greater for screws causing FJP compared with the non-FJP group. The mean axial screw angle was significantly lower in the FJP group compared with the non-FJP group. Pedicle width, length, height, and transverse angle were not significantly associated with FJP. Independent reviewers were able to identify FJP on intraoperative fluoroscopic imaging in 2 out of 8 cases. CONCLUSION: Lower sagittal angle of the facet joint, higher sagittal angle of the pedicle screw, and screw length >24 mm are associated with higher risk of C1-C2 FJP. When placing C2 pedicle screws under these conditions, caution should be taken to avoid FJP. CLINICAL RELEVANCE: Several anatomical and technical factors may increase the risk of C1-C2 FJP during placement of C2 pedicle screws using a fluoroscopically assisted freehand technique, underscoring the importance of preoperative planning and limiting screw length.

Fusion Mass Screws in Revision Spinal Deformity Surgery: A Simple and Safe Alternative Fixation.

BACKGROUND: Revision spinal deformity surgery has a high rate of complications. Fixation may be challenging due to altered anatomy. Screws through a fusion mass are an alternative to pedicle screw fixation. OBJECTIVE: The purpose of this retrospective study was to further elucidate the safety and efficacy of fusion mass screws (FMSs) in revision spinal deformity surgery. DESIGN: Retrospective case series. METHODS: Fifteen freehand FMSs were placed in 6 patients with adult spinal deformity between 2016 and 2018 by the senior author. FMSs were combined with pedicle screws, at times at the same level. FMSs were used to save distal levels from fusion, assist in closing a 3-column osteotomy and provide additional fixation in cases of severe instability. Computed tomography (CT) was used to assess bone mineral density (BMD) and thickness of each fusion mass preoperatively along with accuracy of FMS placement postoperatively. RESULTS: The mean BMD of the fusion mass was 397 Hounsfield units (HU; range: 156-628 HU). The mean AP thickness of the fusion mass was 15.5 ± 4.8 mm (range: 8.6-24.4 mm). The mean FMS length was 35.3 ± 5.5 mm (range: 25-40 mm). There was no evidence of FMS loosening, breakage, or pseudarthrosis at latest follow-up (mean: 2.2 years, range: 1.4-3.1 years). No neurologic deficits were observed. 1/15 screws had a low-grade breach into the canal (<2 mm). No patients required revision surgery. CONCLUSION: FMSs may be used to augment fixation in revision spinal deformity cases when pedicle screw placement may be challenging. FMSs may also provide an additional anchor at levels with pedicular fixation.

Hardware Failure in Spinal Tumor Surgery: A Hallmark of Longer Survival?

OBJECTIVE: Instrumentation failure in spine tumor surgery is a common reason for revision operation. Increases in patient survival demand a better understanding of the hardware longevity. The study objective was to investigate risk factors for instrumentation failure requiring revision surgery in patients with spinal tumors. METHODS: A retrospective cohort from a single tertiary care specialty hospital from January 2005 to January 2021, for patients with spinal primary or metastatic tumors who underwent surgical intervention with instrumentation. Demographic and treatment data were collected and analyzed. Kaplan-Meier analysis was performed for overall survival, and separate univariate and multivariate regression analysis was performed. RESULTS: Three hundred fifty-one patients underwent surgical intervention for spinal tumor, of which 23 experienced instrumentation failure requiring revision surgery (6.6%). Multivariate regression analysis identified pelvic fixation (odds ratio [OR], 10.9), spinal metastasis invasiveness index (OR, 1.11), and survival of greater than 5 years (OR, 3.6) as significant risk factors for hardware failure. One- and 5-year survival rates were 57% and 8%, respectively. CONCLUSION: Instrumentation failure after spinal tumor surgery is a common reason for revision surgery. Our study suggests that the use of pelvic fixation, invasiveness of the surgery, and survival greater than 5 years are independent risk factors for instrumentation failure.

Whole-Spine Magnetic Resonance Imaging: A Review of Suggested Indications.

¼: The spinal column has a propensity for lesions to manifest in a multifocal manner, and identification of the lesions can be difficult. ¼: When used to image the spine, magnetic resonance imaging (MRI) most accurately identifies the presence and location of lesions, guiding the treatment plan and preventing potentially devastating complications that are known to be associated with unidentified lesions. ¼: Certain conditions clearly warrant evaluation with whole-spine MRI, whereas the use of whole-spine MRI with other conditions is more controversial. ¼: We suggest whole-spine MRI when evaluating and treating any spinal infection, lumbar stenosis with upper motor neuron signs, ankylosing disorders of the spine with concern for fracture, congenital scoliosis undergoing surgical correction, and metastatic spinal tumors. ¼: Use of whole-spine MRI in patients with idiopathic scoliosis and acute spinal trauma remains controversial.

Alternatives to Traditional Pedicle Screws for Posterior Fixation of the Degenerative Lumbar Spine.

BACKGROUND: Traditional pedicle screws are currently the gold standard to achieve stable 3-column fixation of the degenerative lumbar spine. However, there are cases in which pedicle screw fixation may not be ideal. Due to their starting point lateral to the pars interarticularis, pedicle screws require a relatively wide dissection along with a medialized trajectory directed toward the centrally located neural elements and prevertebral vasculature. In addition, low bone mineral density remains a major risk factor for pedicle screw loosening, pullout, and pseudarthrosis. The purpose of this article is to review the indications, advantages, disadvantages, and complications associated with posterior fixation techniques of the degenerative lumbar spine beyond the traditional pedicle screws. METHODS: Comprehensive literature searches of the PubMed, Scopus, and Web of Science databases were performed for 5 methods of posterior spinal fixation, including (1) cortical bone trajectory (CBT) screws, (2) transfacet screws, (3) translaminar screws, (4) spinous process plates, and (5) fusion mass screws and hooks. Articles that had been published between January 1, 1990, and January 1, 2020, were considered. Non-English-language articles and studies involving fixation of the cervical or thoracic spine were excluded from our review. RESULTS: After reviewing over 1,700 articles pertaining to CBT and non-pedicular fixation techniques, a total of 284 articles met our inclusion criteria. CBT and transfacet screws require less-extensive exposure and paraspinal muscle dissection compared with traditional pedicle screws and may therefore reduce blood loss, postoperative pain, and length of hospital stay. In addition, several methods of non-pedicular fixation such as translaminar and fusion mass screws have trajectories that are directed away from or posterior to the spinal canal, potentially decreasing the risk of neurologic injury. CBT, transfacet, and fusion mass screws can also be used as salvage techniques when traditional pedicle screw constructs fail. CONCLUSIONS: CBT and non-pedicular fixation may be preferred in certain lumbar degenerative cases, particularly among patients with osteoporosis. Limitations of non-pedicular techniques include their reliance on intact posterior elements and the lack of 3-column fixation of the spine. As a result, transfacet and translaminar screws are infrequently used as the primary method of fixation. CBT, transfacet, and translaminar screws are effective in augmenting interbody fixation and have been shown to significantly improve fusion rates and clinical outcomes compared with stand-alone anterior lumbar interbody fusion. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

In-vitro 3D Analysis of Sacroiliac Joint Kinematics: Primary and Coupled Motions.

STUDY DESIGN: An in-vitro biomechanical study of human cadaver sacroiliac joints. OBJECTIVE: Our study aimed to develop a more comprehensive understanding of the native motion of the SIJ within the context of spinal kinematics and spinal implant evaluation. SUMMARY OF BACKGROUND DATA: Increasing attention has been given to the sacroiliac joint (SIJ) as a source of low back pain, despite its limited range of motion. We sought to characterize the rotational and translational motion in each axis utilizing standard pure moment flexion-extension (FE), lateral bending (LB), and axial rotation (AR) testing. METHODS: Sixteen sacroiliac joints were evaluated from eight lumbosacral cadaver specimens (six females, two males) from subjects aged 28 to 57 years (mean age 46.8) with body mass index (BMI) 22 to 36 (mean BMI 30). Single leg stance was modeled by clamping the blocks on one ischium in a vise and letting the contralateral ischium hang freely. Pure moment loading was applied in FE, right/left AR, and right/left LB. Relative motions were collected with infrared markers. RESULTS: The on-axis ratio was significantly lower in LB than in FE (P = 0.012) and in AR (P = 0.017). The rotation deviation angle measured 13.9 ±â€Š9.1° in FE, 17.1 ±â€Š8.7° in AR, and 35.7 ±â€Š25.7° in LB. In LB the rotational deviation angle is significantly higher than both FE and AR (P = 0.003 and P = 0.011, respectively). In-plane translation was significantly higher (P = 0.005) in FE loading than in LB loading. CONCLUSION: A nontrivial amount of rotation and translation occurred out of the expected axis of motion. The largest amount of off-axis rotation was observed in lateral bending. Relative to resultant translation, in-plane translation was lowest in lateral bending. Our results indicate that rotation of the SIJ is not fully described with the in-plane metrics which are normally reported in evaluation of fusion devices. Future studies of the SIJ may need to consider including off-axis rotation measurements when describing SIJ kinematics.Level of Evidence: 5.

Pedicle Screws Challenged: Lumbar Cortical Density and Thickness Are Greater in the Posterior Elements Than in the Pedicles.

STUDY DESIGN: Controlled laboratory study. OBJECTIVE: To measure the total bone mineral density (BMD), cortical volume, and cortical thickness in seven different anatomical regions of the lumbar spine. METHODS: Using computed tomography (CT) images, 3 cadaveric spines were digitally isolated by applying filters for cortical and cancellous bone. Each spine model was separated into 5 lumbar vertebrae, followed by segmentation of each vertebra into 7 anatomical regions of interest using 3-dimensional software modeling. The average Hounsfield units (HU) was determined for each region and converted to BMD with calibration phantoms of known BMD. These BMD measurements were further analyzed by the total volume, cortical volume, and cancellous volume. The cortical thickness was also measured. A similar analysis was performed by vertebral segment. St Mary's Medical Center's Institutional Review Board approved this study. No external funding was received for this work. RESULTS: The lamina and inferior articular process contained the highest total BMD, thickest cortical shell, and largest percent volumes of cortical bone. The vertebral body demonstrated the lowest BMD. The BMDs of the L4 and L5 segments were lower; however, there were no statistically significant differences in BMD between the L1-L5 vertebral segments. CONCLUSION: Extrapedicular regions of the lumbar vertebrae, including the lamina and inferior articular process, contain denser bone than the pedicles. Since screw pullout strength relies greatly on bone density, the lamina and inferior articular processes may offer stronger fixation of the lumbar spine.

Non-Pedicular Fixation Techniques for the Treatment of Spinal Deformity: A Systematic Review.

BACKGROUND: In recent years, the use of pedicle screws has become the gold standard for achieving stable, 3-column fixation of the spine. However, pedicle screw placement may not always be ideal, such as in adolescent idiopathic scoliosis, because of pedicle morphology. An understanding of the alternatives to pedicle screw fixation is therefore important in the treatment of patients with spinal deformity. The purpose of this article is to review the indications, advantages, disadvantages, and complications associated with non-pedicular fixation techniques of the thoracolumbar spine. METHODS: Comprehensive literature searches of PubMed, Scopus, and Web of Science databases were performed for 10 methods of non-pedicular fixation. Articles published between January 1, 1990, and June 1, 2019, were considered. Non-English-language articles and studies involving fixation of the cervical spine were excluded from our review. RESULTS: After reviewing >1,600 titles and abstracts pertaining to non-pedicular fixation, a total of 213 articles met our inclusion criteria. Non-pedicular fixation may be preferred in certain cases of spinal deformity and may provide stronger fixation in osteoporotic bone. The use of non-pedicular fixation techniques is often limited by the inability to place multilevel constructs on intact posterior elements. Additionally, some methods of non-pedicular fixation, such as spinous process tethering, primarily have utility for the end of constructs to minimize junctional problems. CONCLUSIONS: Pedicle screws remain the anchor of choice in spinal deformity surgery because of their ability to engage all 3 columns of the spine and provide safe correction in all 3 planes. Nevertheless, non-pedicular fixation may be useful in cases in which pedicle screw placement is extremely difficult. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Anterior Lumbar Interbody Fusion May Provide Superior Decompression of the Foraminal Space Compared with Direct Foraminotomy: Biomechanical Cadaveric Study.

OBJECTIVE: The objective of this cadaveric biomechanical study was to compare the area of the foraminal space during motion in the intact condition, after direct decompression via foraminotomy, and after indirect decompression via anterior lumbar interbody spacer insertion. METHODS: Eight (8) L5-S1 cadaver specimens were used for testing. Each specimen was tested in the intact state, after posterior foraminotomy, and after standalone anterior lumbar interbody fusion (ALIF). Each specimen was 3-dimensional imaged under neutral loading, flexion, and extension. The 3-dimensional images were analyzed for changes in the foraminal area under each loading scenario. A repeat-measures design was used. Outcome measures from testing included the frequency in which an increase in cross-sectional area was observed, as well as the percent increase of the foraminal area for each surgical group and loading direction. RESULTS: Direct foraminotomy and ALIF maintained the foraminal space during initial distraction under no loading with areas 99.7% and 96.5% of the native foraminal area, respectively (P = 0.955 and P = 0.455). Direct foraminotomy increased the foraminal area significantly during flexion to 112.2% of the area before motion (P = 0.008) while ALIF did not. Direct foraminotomy significantly decreased the foraminal area during extension to 89.2% of the area before motion (P = 0.006). ALIF, however, maintained its initial distraction during extension with 98.2% of the area before motion (P = 0.808). CONCLUSIONS: ALIF maintains the foraminal area in extension while direct posterior foraminotomy does not.

Motion Preservation at All Costs? Multilevel Hinge Nonunion, Plate Breakage, and Intradural Plate Migration After Cervical Laminoplasty: A Case Report and Literature Review.

BACKGROUND: Cervical laminoplasty is a motion-preserving procedure that addresses spinal cord compression and avoids postlaminectomy kyphosis associated with cervical laminectomy. The most common complications include C5 nerve palsy, axial neck pain, hinge nonunion, and premature closure. Plating is a relatively newer method of laminoplasty fixation that may provide greater stabilization postoperatively and reduce the risk of laminoplasty closure compared with less rigid (e.g., suture) fixation techniques. Although prior studies have reported low rates of laminar/lateral mass screw back out, plate breakage and migration have not been previously described in the literature. The purpose of this paper is to present a case of multilevel hinge nonunion, plate breakage, and plate fragment migration. Although rare, plate failure may result in a dural tear and spinal cord injury/compression. CASE DESCRIPTION: In this case, a 61-year-old man with a history of cervical spondylotic myelopathy treated with C3-7 laminoplasty 7 years prior presented to our hospital with severe headaches and electrical-type pain through the left upper and lower extremities. Imaging studies revealed several broken laminoplasty plates and intradural migration of a fragment of the C7 plate. CONCLUSIONS: We provide recommendations for preventing hinge nonunion because resultant micromotion likely contributed to the plate breakages observed in this patient.