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Competing Interests: The author reports no conflicts of interest.

Study Design: This is an anatomic study using cadaveric material., Objective: To provide anatomic descriptions of the normal lumbar sublaminar ridge in the lateral recess and its potential to impact on the exiting nerve root there, with implications to surgical technique in lumbar spinal stenosis., Summary of Background Data: The lateral extent of the sublaminar ridge-the bony, superior insertion site of the ligamenta flava-and its topological relationship to the nerve root are not described in the literature. In the setting of degenerative lumbar stenosis this structure can hypertrophy and impinge the nerve root within the lateral recess even after excision of the corresponding ligamentum flavum. Failure to address this may contribute to failed lateral recess decompression., Methods: Fifteen lumbar vertebrae, not obviously degenerated, were resected en bloc from three fixed adult human cadavers and then transected through the pedicles, leaving the posterior column and neural elements intact and articulated. The shape of the sublaminar ridge in the lateral recess and its relationship to the exiting nerve root were carefully examined., Results: The exiting nerve root consistently crosses the sublami- nar ridge immediately inferior to the mid-pedicle, lateral to the subarticular gutter, and on the medial aspect of the true intervertebral foramen. A hypertrophic ridge can compress the exiting root by elevating the nerve root superiorly against the bony underside of the pedicle or displacing it anteriorly against the disc or vertebral body., Conclusion: The sublaminar ridge in the lateral recess may contribute to degenerative lumbar stenosis. Comprehensive appreciation of this anatomy may facilitate thorough lateral recess decompression.Level of Evidence: 4., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Study Design: This is a prospective cohort study., Objective: The aim of this study was to define the probability of successful morning-after discharge after adult spine surgery achieved with a standard care protocol as applied to patients with a large variety of common degenerative spine disorders., Summary of Background Data: Qualifying criteria for ambulatory or overnight-stay adult spine surgery are not well defined in either the spine or anesthesia literature. Most reports simply go to American Society of Anesthesiology risk classification or surgical technique alternatives and do not present a clearly defined patient care and case management protocol., Methods: A standardized protocol of patient preparation, preoperative comorbidities optimization, and perioperative care was applied in a prospective cohort of 126 patients including 83 lumbar and 41 cervical procedures. Office and hospital chart records were reviewed for relevant outcomes., Results: Fully 122 of 124 appropriately selected cases were able to successfully achieve uneventful same-day discharge without any need for readmission, unscheduled early emergency room or clinic visits, or other major complications. Both failures were for urinary retention in senior males and resolved after a single-day admission to the main hospital., Conclusion: A wide variety of common degenerative spinal pathology in adults can be routinely and safely managed on an overnight-stay basis without requirement for formal hospital inpatient admission in patients appropriately selected and pre-educated to the experience and whose major comorbidities are preoperatively optimized., Level of Evidence: N/A.

Study Design: This is a retrospective study of sequential cohorts., Objective: To assess the efficacy of tranexamic acid in decreasing operative blood loss and the need for intraoperative transfusion in metastatic spine surgery., Summary of Background Data: Significant published data have established the efficacy of antifibrinolytic drugs in limiting surgical bleeding during heart surgery and total joint replacement. One study in scoliosis suggested benefit in spine surgery as well., Methods: During a 6-month trial period, 14 patients with spine cancer undergoing palliative intralesional tumor excision and concomitant instrumentation to stabilize the spine in the hands of a single surgeon were administered tranexamic acid intraoperatively in the attempt to minimize operative blood loss. They were then compared to the immediately preceding 14 patients., Results: Estimated operative blood loss was 1385 mL in the study group treated with tranexamic acid and 1815 mL in controls not receiving the drug, and was not found to be significantly decreased in this study., Conclusions: Control of operative bleeding in metastatic spine surgery can be problematical. Optimum protocol might include routine preoperative angiographic tumor embolization to decrease lesion vascularity in all cases, but angiography is not without risk. Noninvasive prophylaxis of tumor bleeding would have obvious desirable advantages but was, unfortunately, not achieved in this study.

Study Design: This repeated-measures biomechanical study evaluated the tensile force required to cause bipedicular (hangman's) fractures in isolated porcine C2 specimens, and the subsequent force to failure after direct fracture repair with bipedicular lag screws., Objectives: To assess the pullout strength of direct lag screw fixation of hangman's fracture, relative to the strength of the intact specimens., Summary of Background Data: Clinical studies have reported successful treatment of hangman's fractures by direct screw repair followed by a collar after surgery. However, to the authors' best knowledge, there has not yet been a biomechanical analysis of the force required for screw pullout after direct repair., Methods: Of 60 mounted porcine C2 specimens subjected to tensile anteroposterior force, hangman's fracture occurred in 15 cases, 12 of which were fixed with bipedicular 4.0-mm lag screws. These fixed specimens were retested to failure in the same manner., Results: Most specimens had laminar fractures after the application of tensile force, with 15 of 60 (25%) showing bipedicular fractures. The force to bipedicular failure was 3259.1 +/- 148.5 N (mean +/- standard error of the mean). After screw fixation, the force to failure of the same specimens was 882.0 +/- 108.5 N (mean +/- standard error of the mean), or 27.3% of the intact bone., Conclusions: The pullout strength was substantial (882 N), although the relative strength of fixation was only 27.3% of the fracture strength shown by the intact specimens. The findings are discussed in relation to previous studies. To the authors' best knowledge, this is the first study to examine screw pullout forces after direct repair of hangman's fracture.

Study Design: Repeated in vitro mechanical tests were performed on porcine and human interspinous ligament specimens with progressive disruption of the collagen fiber network to evaluate the existence of mechanical interactions between collagen fibers., Objective: To evaluate the existence of a load pathway in the interspinous ligament whereby loads are transmitted between collagen fibers., Summary of Background Data: Mechanical tests demonstrate that the interspinous ligament resists spinal flexion, but the collagen fibers are not oriented to oppose separation of the spinous processes. This seeming contradiction could be explained by the existence of mechanical interactions between collagen fibers of the interspinous ligament., Methods: In vitro mechanical tests were performed on porcine and human bone-interspinous ligament-bone specimens. The collagen network of the ligament substance was disrupted by passing a scalpel blade though the ligament substance. Repeated tests were performed with progressive disruption of the collagen fiber network., Results: The stiffness of the interspinous ligament specimens was reduced as the collagen fiber network was disrupted, but approximately half of the initial stiffness was maintained when the collagen fiber network was severely disrupted. In this case, no intact collagen fibers remained., Conclusions: Mechanical interactions exist between collagen fibers in the interspinous ligament. The mechanism of the interactions is unknown.

Study Design: This was a retrospective prevalence study., Objective: A review of structural cervical spine injuries (fracture or dislocation) treated at a regional spine injury referral center from 1987 to 1992 was undertaken to identify and analyze patients who had secondary neurologic deterioration after they had arrived and had primary assessment in stable neurologic condition (intact or compromised, but not evolving)., Summary of Background Data: Multiple case reports and cohort studies have suggested possible risk factors for late neurologic deterioration without probabilities analysis., Methods: Information was obtained retrospectively from clinical records and radiographs. Three-hundred-twelve cases were reviewed. Thirty-one were excluded and 281 were analyzed., Results: An index group of 15 patients (5%) had motor neurologic deterioration after primary assessment at the referral center. Control group "A" was composed of 70 patients (25%) who had a motor neurologic deficit on admission and did not deteriorate. Control group "B" was the balance of 196 patients (70%) with structural cervical injuries, but no neurologic compromise. Factors distinguishing the index group from control subjects included flexural mechanism of injury and chronic multilevel spinal arthritis with ankylosis. All secondary deteriorations occurred with the injury level caudad to the fourth cervical vertebra. Routine three-view cervical radiographs were relatively insensitive in detecting injury in the index group compared with the pooled control subjects. Patients' ability to comply with recommended treatment was not a factor in secondary deteriorations and there generally was no identifiable precipitant event before secondary deterioration., Conclusion: Cervical traumatized patients with flexural injury or chronic multilevel spinal arthritis with ankylosis are at increased risk of having secondary motor neurologic deterioration.

Study Design: Human tissue specimens were examined for the presence of neural end-organs under light and electron microscopy., Objectives: To define the innervation of the thoracolumbar fascia in problem back pain patients who have articular abnormality defined through pain-provocation discography or facet blocks., Summary of Background Data: Previous investigators have defined the presence of innervation in control (no back pain) tissue specimens., Methods: Tissue specimens were harvested during surgery from 24 back pain patients who had not undergone previous lumbar surgery. Specimens were fixed immediately in the operating room and later processed and studied under light and electron microscopy., Results: Structural and ultrastructural studies failed to identify specific neural end-organs in any of the specimens. Serendipidously, microscopic changes suggestive of ischemia or inflammation in this tissue were found., Conclusions: These findings suggest that the thoracolumbar fascia may be deficiently innervated in problem back pain patients.

Surgical treatment of odontoid fractures has usually been carried out by C1-2 arthrodesis rather than by fracture fixation. An alternative treatment of compression screw fixation was used to treat selected acute odontoid fractures and nonunions. Ten patients were operated on. A variety of lag-screw types were used to compress and secure the fracture. Screw placement was considered excellent in five cases; in four, the screw tip protruded through the posterosuperior cortex of the dens by 1-3 mm. One patient died as a result of multiple injuries 2 days after surgery. In all other cases, including four cases of odontoid pseudarthroses, the fractures achieved solid union. It was concluded that screw fixation can be used for the successful treatment of selected odontoid fractures and nonunions.