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Case study on the bone density pattern of subaxial vertebral column in African apes. Introduction: African apes have been noted to experience fewer back ailments than humans and to have higher vertebral bone density. Yet, research on the subject is quite limited and has usually included only one or few vertebrae. However, to understand vertebral column as whole and how posture and locomotion might have affected it, we need to know how bone density varies between adjacent vertebrae. Materials and Methods: Bone density in the vertebral body was measured for all subaxial vertebrae of five specimens including two Pan troglodytes (1 male and 1 female) and three Gorilla gorilla (2 males and 1 female) using peripheral quantitative computed tomography (pQCT). Results: The results tentatively indicated differences between species, especially in the trabecular density of the cervical segment and support the need for further studies on this subject. [ABSTRACT FROM AUTHOR]

Background: Lateral mass screw (LMS) and transpedicular screw (TPS) techniques are the two major options for performing posterior cervical fusion of the subaxial cervical spine. Although these two techniques can cover the vast majority of patients who require posterior fixation of the cervical spine, they are not without their limitations. Objective: The objective of this study is to introduce a novel technique, lateral mass intrapedicular screw (LMIS) fixation, for posterior subaxial cervical spine (C3–C6) fixation. Materials and Methods: The starting point of the screw is defined as the midpoint of the lateral mass. In the axial plane, the screw is angled at 20°–25° with respect to the midline of the spinous process. In the sagittal plane, the screw is directed toward the rostral quarter (zone 1) of the vertebral body and placed within the pedicle. A preliminary, proof-of-concept experiment was performed using a bone model created with synthetic bone and computed tomography images before performing the operation on a patient. Results: During the preliminary experiment, insignificant breaching of the inner cortex of the pedicle was observed with one of the screws. However, no other screws breached the inner cortex in the same manner during the preliminary experiment or during the operation, and the intraoperative fixation was strong. Conclusion: LMIS is a relatively simple and safe technique that can be performed for the fixation of subaxial cervical spines with screws that are longer than those used in LMS. We believe that this technique may join the two existing techniques to become a common alternative technique, particularly for patients with poor bone quality.

This article reviews the historical context, indications, techniques, and complications of four posterior fixation techniques to stabilize the subaxial cervical spine. Specifically, posterior wiring, laminar screw fixation, lateral mass fixation, and pedicle screw fixation are among the common methods of operative fixation of the subaxial cervical spine. While wiring and laminar screw fixation are now rarely used, both lateral mass and pedicle screw fixation are technically challenging and present the risk of significant complications if performed incorrectly. With a sound understanding of anatomy and rigorous preoperative evaluation of bony structures, both lateral mass and pedicle screw fixation provide a safe and reliable method for subaxial cervical spine fixation.

Study Design: Observational study on prospectively collected data.Objectives: The aim of this study was to compare long-term patient-reported outcomes and complications after anterior or posterior cervical spine surgery for subaxial fractures.Summary Of Background Data: There is no consensus in the literature regarding the optimal surgical approach when treating spine fractures in the subaxial region.Methods: A total of 200 individuals who had been treated with either anterior or posterior surgery due to a subaxial single segment, or single vertebra, injury between 2006 and 2016 and had at least 1 year follow-up were identified in the Swedish Spine register. Cases were matched 1:1 for age (±5 years). Outcomes were Neck Disability Index (NDI) and EQ-5D-3L, and reoperations, mortality, and surgeon- and patient-reported wound complications within 90 days. t Tests and χ2 tests were used statistical comparisons.Results: At follow-up, NDI was 23 (21) in the anterior group and 29 (21) in the posterior group (P = 0.07). EQ-5D-3L index was 0.62 (0.37) in the anterior group and 0.54 (0.39) in the posterior group (P = 0.13). Patient satisfaction was higher in the anterior group (89% vs. 73%, P = 0.03). No deaths occurred within the first 90 days after surgery, six individuals in the anterior group and three individuals in the posterior group were reoperated (P = 0.31), and five individuals in the anterior group and 24 in the posterior group suffered a wound infection (P < 0.001).Conclusion: Anterior surgery and posterior surgery were associated with similar neck disability and general quality of life at follow-up, whereas anterior surgery was associated with higher patient satisfaction and lower infection rates.Level of Evidence: 3. [ABSTRACT FROM AUTHOR]

Background: Lateral mass screw (LMS) and transpedicular screw (TPS) techniques are the two major options for performing posterior cervical fusion of the subaxial cervical spine. Although these two techniques can cover the vast majority of patients who require posterior fixation of the cervical spine, they are not without their limitations. Objective: The objective of this study is to introduce a novel technique, lateral mass intrapedicular screw (LMIS) fixation, for posterior subaxial cervical spine (C3–C6) fixation. Materials and Methods: The starting point of the screw is defined as the midpoint of the lateral mass. In the axial plane, the screw is angled at 20°–25° with respect to the midline of the spinous process. In the sagittal plane, the screw is directed toward the rostral quarter (zone 1) of the vertebral body and placed within the pedicle. A preliminary, proof-of-concept experiment was performed using a bone model created with synthetic bone and computed tomography images before performing the operation on a patient. Results: During the preliminary experiment, insignificant breaching of the inner cortex of the pedicle was observed with one of the screws. However, no other screws breached the inner cortex in the same manner during the preliminary experiment or during the operation, and the intraoperative fixation was strong. Conclusion: LMIS is a relatively simple and safe technique that can be performed for the fixation of subaxial cervical spines with screws that are longer than those used in LMS. We believe that this technique may join the two existing techniques to become a common alternative technique, particularly for patients with poor bone quality. [ABSTRACT FROM AUTHOR]

Background  Surgical management of subaxial cervical spine injuries remains challenging. Although intraoperative fluoroscopy is usually used for intraoperative spinal level localization (SLL), it is unavailable in most developing countries. The surgeon therefore has to rely on anatomic landmarks. In our setting, in the absence of intraoperative fluoroscopy, we used the carotid tubercle for SLL. Herein we evaluate the accuracy and reliability of the carotid tubercle as a landmark during surgery for traumatic cervical spine injury. Methods  This was a retrospective cohort study on 34 patients undergoing anterior cervical surgery for subaxial cervical spine fractures and/or subluxation between January 2005 and February 2011. From their medical records, the patients' sociodemographic, clinical, radiological, and operative data were retrieved and analyzed. Results  Thirty-four patients were included in the study. The mean age was 36.2 years. Thirty patients were males. The mean duration between the trauma and surgical intervention was 9.6 days. Six patients were completely tetraplegic. Fourteen patients had fractures and 20 patients had subluxation. The carotid tubercle was palpable in all the 34 cases. Twenty-two (68.8%) patients had partial or complete neurologic recovery. Complete anatomic reduction was achieved in 30 cases. One case of slight malalignment of the plate was observed. No case of significant deviation nor penetration of the screw into the vertebral canal was found. One patient died. Conclusions  Carotid tubercle, a palpable intrinsic marker, is an attractive anatomic landmark for SLL during surgeries for traumatic spine injuries in resource-limited settings. [ABSTRACT FROM AUTHOR]

Studies have shown that the numbers of injuries of the cervical spine increase in elderly patients. An early clinical examination and adequate diagnostics are necessary to initiate the appropriate treatment. A computed tomography (CT) scan is recommended to exclude injuries of the cervical spine. Dynamic fluoroscopy and magnetic resonance imaging (MRI) can additionally be helpful to detect instabilities. The treatment of the injury depends on the extent of the fracture and includes conservative treatment options with soft or rigid ortheses for cervical spine immobilization, retention with a halo fixator or open/closed reduction and fixation. In the selection of treatment it should be taken into consideration that the use of rigid immobilization or a halo fixator is associated with a significant reduction of the quality of life. In the region of the upper cervical spine only unstable fractures of the atlas and of the axis should be operatively treated. In the region of the subaxial cervical spine fractures are prone to be unstable due to the lack of flexibility of the cervical spine in elderly patients. Therefore, fractures of types B and C according to AO Spine, for which operative treatment is recommended, are regularely seen. In addition, a pre-existing stenosis of the spinal cord may lead to neurological symptoms which negatively influence the clinical outcome. [ABSTRACT FROM AUTHOR]

Abstract Objective Cervical spine can be stabilized by different techniques. One of the common techniques used is the lateral mass screws (LMSs), which can be inserted either by freehand techniques or three-dimensional (3D) navigation system. The purpose of this study is to evaluate the difference between the 3D navigation system and the freehand technique for cervical spine LMS placement in terms of complications. Including intraoperative complications (vertebral artery injury [VAI], nerve root injury [NRI], spinal cord injury [SCI], lateral mass fracture [LMF]) and postoperative complications (screw malposition, screw complications). Methods Patients who had LMS fixation for their subaxial cervical spine from January 2014 to April 2015 at the Ottawa Hospital were included. A total of 284 subaxial cervical LMS were inserted in 40 consecutive patients. Surgical indications were cervical myelopathy and fractures. The screws' size was 3.5 mm in diameter and 8 to 16 mm in length. During the insertion of the subaxial cervical LMS, the 3D navigation system was used for 20 patients, and the freehand technique was used for the remaining 20 patients. We reviewed the charts, X-rays, computed tomography (CT) scans, and follow-up notes for all the patients pre- and postoperatively. Results Postoperative assessment showed that the incidence of VAI, SCI, and NRI were the same between the two groups. The CT scan analysis showed that the screw breakage, screw pull-outs, and screw loosening were the same between the two groups. LMF was less in the 3D navigation group but statistically insignificant. Screw malposition was less in the 3D navigation group compared with the freehand group and was statistically significant. The hospital stay, operative time, and blood loss were statistically insignificant between the two groups. Conclusions The use of CT-based navigation in LMS insertion decreased the rate of screw malpositions as compared with the freehand technique. Further investigations and trials will determine the effect of malpositions on the c-spine biomechanics. The use of navigation in LMS insertion did not show a significant difference in VAI, LMF, SCI, or NRI as compared with the freehand technique.

Objective: The main aim of this study was to analyse the compex clinical and radiographic findings in a group of RA patients with atlanto-axial slip (AAS) treated with free-hand short C1 lateral mass and C2 trans-pedicular screw fixation. The surgical technique used and the pathology treated were the same in all patients, producing a very homogeneous cohort of patients This allowed the study and measurement of radiographic parameters and fusion process. Methods: Twenty-nine patients (21 female, 8 male, mean age 54.9 years, duration of RA 17.3 years) with AAS and without CS were treated by short C1/2 fixation. Mean follow-up was 4.5 years. Pain intensity was monitored using VAS. Radiographic assessment consisted of lateral cervical radiographs in neutral and dynamic views, MR and CT of the cervical spine. The AADI, PADI, AAA, sub-axial cervical Cobb angle and canal-clivus angle (CCA) were measured pre-operatively and during the follow-up. Results: Significant malposition was recorded in 4 (3.4%) out of 116 inserted screws. AADI, PADI, AAA and CCA values changed significantly after surgery and remained stable during follow-up. The Cobb C angle value showed no significant change after surgery. There was a significant decrease of the VAS after the surgery. Fusion or a stable situation was achieved in all patients at 2-year follow-up. Pannus regression was observed in the vast majority of patients; only in two cases was rheumatic tissue detected on MR at 2 years post-operatively. Conclusion: C1 lateral mass and C2 trans-pedicular fixation with polyaxial screws followed by an autograft between C1 and C2 lamina allowed, with an acceptable complication rate and favourable clinical results, adequate slip reposition, introduction of optimal sagittal alignment in terms of the final AAA with no radiographic consequences for the sub-axial cervical spine and assurance of long-term stability. [ABSTRACT FROM AUTHOR]

Objective The far-lateral approach has traditionally been used as an approach to ventral foramen magnum pathologies. Ventral pathologies in the cervical spine and cervicodorsal regions also provide unique surgical challenges. Traditional posterior surgical approaches to the ventral cervical pathologies require significant cord retraction, and anterior approaches require significant bone removal with implant stabilization. We approached these lesions using a modification of the far-lateral approach for lesions in the subaxial spine. Methods Four patients underwent operations using this approach for ventral intradural pathologies in the subaxial spine. Two of the patients had recurrence of the lesions and underwent previous operations using a traditional midline approach. Results All 4 patients underwent operations using this approach. This provided a unique view of the ventral pathologies and a scarless field in recurrent cases. All 4 patients improved neurologically after the surgery and had no deterioration or complications related to the surgery. Conclusion We propose extension of far-lateral approach to ventral intradural extramedullary lesions in the subaxial spine up to the cervicothoracic junction. The far-lateral approach can be extended safely to the ventral and ventrolateral lesions of the subaxial cervical spine, especially for recurrent or residual lesions previously approached from the midline posteriorly. [ABSTRACT FROM AUTHOR]

Abstract: Background context: There have been several reports describing the usage of subaxial cervical laminar screws. However, the anatomic feasibility of placing such screws has not been thoroughly evaluated yet. Purpose: To determine the feasibility of the laminar screw placement in the subaxial cervical spine using a large number of computed tomography (CT) scans and three-dimensional screw trajectory software. Study design: Three-dimensional simulation study of screw placement. Patient sample: Computed tomography scans of 215 consecutive patients were examined, for a total of 430 screws at each level of the subaxial cervical spine. Outcome measures: Successful screw placement without laminar cortical breach, facet joint violation, and collision between two screws in the same level. Methods: We simulated the placement of 4.0-mm subaxial (C3–C7) cervical laminar screws. Unilateral and bilateral screw placement was simulated, and their success rates were evaluated at each level of the subaxial cervical spine. This study was not supported by any financial sources. One of the authors received royalties for a posterior cervical fixation system, which is not the topic of this article and is not used or mentioned in this article. Results: The success rate of unilateral screw placement was the highest at C7 (91.4%), followed by C6 (31.9%), C3 (30.2%), C4 (6.3%), and C5 (4.0%). It was significantly higher (p<.001) in men than in women at C6 and C7 but not at the other levels. The success rate of bilateral screw placement was the highest at C7 (68.8%), followed by C3 (13.5%), C6 (8.8%), C4 (1.9%), and C5 (0.9%). It was significantly higher in men (83.5%) than in women (52.0%) at C7 (p<.001) but not at the other levels. Conclusions: The relatively high success rate at C7, particularly of unilateral placement, suggests that laminar screw placement can be a sound alternative method for fixation at this level. However, careful preoperative CT scan evaluation and patient selection are required, particularly for bilateral fixation in women. At C3 and C6, unilateral screw placement can be considered in approximately 30% of patients after careful selection using preoperative CT scans. At C4 and C5, neither unilateral nor bilateral screw fixation is recommended for most patients. [Copyright &y& Elsevier]

An experimental in vitro biomechanical study was conducted on human cadaveric spines to evaluate the motion segment (C4–C5) and global subaxial cervical spine motion after placement of a cervical arthroplasty device (Altia TDI™,Amedica, Salt Lake City, UT) as compared to both the intact spine and a single-level fusion. Six specimens (C2–C7) were tested in flexion/extension, lateral bending, and axial rotation under a ± 1.5 Nm moment with a 100 N axial follower load. Following the intact spine was tested; the cervical arthroplasty device was implanted at C4–C5 and tested. Then, a fusion using lateral mass fixation and an anterior plate was simulated and tested. Stiffness and range of motion (ROM) data were calculated. The ROM of the C4–C5 motion segment with the arthroplasty device was similar to that of the intact spine in flexion/extension and slightly less in lateral bending and rotation, while the fusion construct allowed significantly less motion in all directions. The fusion construct caused broader effects of increasing motion in the remaining segments of the subaxial cervical spine, whereas the TDI did not alter the adjacent and remote motion segments. The fusion construct was also far stiffer in all motion planes than the intact motion segment and the TDI, while the artificial disc treated level was slightly stiffer than the intact segment. The Altia TDI allows for a magnitude of motion similar to that of the intact spine at the treated and adjacent levels in the in vitro setting. [ABSTRACT FROM AUTHOR]

Objective: To report our experience with a novel construct for traumatic and nontraumatic cervical spine lesions that was validated by biomechanical studies of cadaver cervical spine. Study Design: Consecutive cases of anterior cervical spine fixation performed over six years reviewed for stability offered by a construct comprising of a plate fixed by a single screw to each vertebral body. Setting: A university hospital and a biomechanical lab. Materials and Methods: Data were coded and entered into a statistical worksheet for multivariate analysis. Cadaver spine models applied for biomechanical study of stability. Results: Total of 103 cases reviewed; 86 with single-level disease; traumatic in 66 (64%) cases and degenerative in 33 (32%) cases, including hard disks, OPLL, and spondylitis (4% with other causes). Fixation was with diskectomy in 59 and with corpectomy in 40. A bone graft was utilized for fusion in 87 and a bone-filled titanium spacer in 13. A single screw was placed in each vertebral body with a locking plate (having linear arrangement of holes). This construct remained strong in 95% of cases at the end of 6.24 months. Five cases failed requiring reoperation. Five patients with cervical spinal cord injury (SCI) died. On statistical analysis, construct was stronger with diskectomy compared with corpectomy. Construct used on cadavers confirmed the biomechanical stability in short segment fixation (C5.6). Conclusion: A conservative construct utilizing a single screw per vertebral body and a one-holed plate system appears to be strong enough to afford stability in both traumatic and nontraumatic lesions of subaxial cervical spine, comparable to others. [ABSTRACT FROM AUTHOR]

Abstract: Background context: Surgical instrumentation used for posterior craniocervical instability has evolved from simple wiring techniques to sophisticated implant systems that incorporate multiple means of rigid fixation for the cervical spine. Polyaxial screws and lamina hooks in conjunction with occipital plating and transitional rods for caudal fixation theoretically allow for fixation points at each vertebra along the posterior aspect of the cervical spine. However, the potential for anatomical constraints to prevent intraoperative instrumentation at the desired vertebral level exists. The biomechanical implications of such “skipped segments” have not been well documented. Purpose: The purpose of this study was to determine the biomechanical effects of partial three-point fixation versus sequential fixation at all levels of the cervical spine from the occiput to T1. Study design/setting: Fresh frozen human cadaveric cervical spines from the occiput (CO) to T1 were prepared and mounted on a spine simulator. Motion was assessed by a three-dimensional optoelectronic motion measurement system. Kinematic data were collected and range of motion (ROM) was analyzed and reported. Methods: Eight human noninstrumented intact spines (Treatment 1) were tested for baseline ROM which was subclassified into axial (CO–C2), upper subaxial (C2–C4), lower subaxial (C4–T1), and total (CO–T1) ROM. Flexion extension, lateral bending, and axial torsion testing with an applied ±3Nm moment was conducted. The same testing protocol was performed after three-point fixation in which screws were placed at the CO, C4, and T1 (Treatment 2), and also after sequential fixation at all levels from CO through T1 (Treatment 3). Fixation was achieved using an occipital plate, 12-mm lateral mass screws for C3 through C6, and 20-mm lateral mass or pedicle screws were used for C1, C2, C7, and T1. Results: Intact spine testing (Treatment 1) showed statistically significant larger ROM for all segments and for overall ROM when compared with both Treatment 2 (partial fixation CO, C4, and T1) and Treatment 3 (sequential fixation at all levels from the occiput to T1). When comparing Treatment 2 with Treatment 3, no significant difference in flexion extension ROM was detected between axial, upper subaxial, lower subaxial, and total overall ROM (p > .05). Lateral bending showed statistically significant increased ROM for Treatment 2 constructs compared with Treatment 3 constructs in total overall lateral bend ROM. For axial rotation, there was significantly increased ROM for Treatment 2 at the lower subaxial segment and total overall ROM (p < .05) when compared with Treatment 3. Conclusions: There was no statistical difference between the three-point fixation treatment group and the sequential fixation group in flexion extension bending. Lateral bending and axial rotation demonstrated an increase in total overall ROM with partial fixation compared with fixation at all levels. Axial rotation in particular showed increased mobility in the lower cervical spine for the partial fixation group. In the instance where surgeons are not able to apply sequential fixation at diseased levels, especially for the lower subaxial cervical spine, particular attention to limitation of lateral bending and axial rotation by the use of external orthotics must be considered. [Copyright &y& Elsevier]