Use Of Lateral Mass Screws Research Articles

Pedicle or lateral mass screws in Goel-Harms construct? A biomechanical analysis

BackgroundThe use of the posterior arch of C1 as pedicle has shown beneficial stability regarding screw loosening, however, the C1 pedicle screw placement is challenging. Therefore, the study aimed to analyse the bending forces of the Harms construct used in fixation of C1/C2 when using pedicle screws compared to lateral mass screws. MethodsFive cadaveric specimens with a mean age of 72 years at death and bone mineral density measuring for 512.4 Hounsfield Units (HU) on average were used. A custom-made biomechanical setup was used to test the specimens with a C1/C2 Harms construct each with the use of lateral mass screws and pedicle screws in sequence. Strain gauges were used to analyse the bending forces from C1 to C2 in cyclic axial compression (μm/m). All underwent cyclic biomechanical testing using 50, 75 and 100 N. FindingsIn all specimens, placement of lateral mass screws and pedicle screws was feasible. All underwent cyclic biomechanical testing. For the lateral mass screw, a bending of 142.04 µm/m at 50 N, 166.56 µm/m at 75 N and 188.54 µm/m at 100 N was measured. For the pedicle screws, bending force was slightly elevated with 165.98 µm/m at 50 N, 190.58 µm/m at 75 N and 195.95 µm/m at 100 N. However, bending forces did not vary significantly. In all measurements, no statistical significance was found when comparing pedicle screws and lateral mass screws. InterpretationThe lateral mass screw used in the Harms Construct to stabilize C1/2 showed less bending forces, therefore the construct with lateral mass screws appears more stable in axial compression compared to the one with pedicle screws. However, bending forces did not vary significantly.

Combined Anterior-Posterior Fusion Versus Posterior Alone Fusion for Cervical Myelopathy in Athetoid-Cerebral Palsy.

Study Design:Retrospective comparative study.Objectives:Although some studies have discussed the use of lateral mass screws (LMSs) in patients with cerebral palsy (CP), it is unclear whether posterior LMS fixation alone is a suitable method. We aimed to compare the clinical, radiological, and surgical outcomes of 2 surgical modalities, namely, combined anterior-posterior (A-P) instrumented fusion and posterior fusion alone, in athetoid-type CP patients with cervical myelopathy (CM).Methods:We analyzed 63 patients with athetoid-CP and CM who underwent posterior fusion only with LMS (group A, 35 patients) and A-P fusion (group B, 28 patients). The primary outcome was the 1- and 3-year fusion rates for the surgical segments. The secondary outcomes included the clinical outcomes based on pain intensity determined using the visual analog scale score, neck disability index, and 17-point Japanese Orthopedic Association score, radiological, and surgical outcomes.Results:Fusion was achieved at 3 years postoperatively in 22 of 35 patients (63%) in group A and in 26 of 28 patients (93%) in group B (P = 0.02). The posterior neck pain intensity was also significantly lower in group B than in group A 2 and 3 years postoperatively (P = 0.02 and 0.01, respectively). The incidence of screw loosening and implant-related problems was higher in group A (60%) than in group B (21%) (P = 0.01). The other clinical and radiological parameters were similar between the groups.Conclusions:For athetoid CP-induced CM, combined A-P fusion would result in superior clinical and radiological outcomes compared to posterior fusion alone.

Quantitative Anatomy of C7 Vertebra in Southern Chinese for Insertion of Lateral Mass Screws and Pedicle Screws.

Study DesignRetrospective study.PurposeTo analyze the quantitative anatomy of C7 vertebra for insertion of lateral mass screws and pedicle screws in Southern Chinese patients.Overview of LiteratureC7 lateral mass is smaller when compared to other subaxial cervical levels, which limits the length of lateral mass screws that can be used. Some studies have suggested pedicle screws for better fixation. But, this option is limited by the narrow pedicle width.MethodsWe have obtained computed tomography (CT) cervical spine data in 0.625 mm slices from our radiology department. The patients were adults. CTs were from May to August, 2015. The lateral mass screw length was measured using Margerl's technique and pedicle width and pedicle screw trajectory were determined in three-dimensional reformated images.ResultsCT scans of cervical spines of 94 patients were obtained and 188 lateral masses and pedicles of C7 vertebrae were measured. The mean lateral mass screw length was 13.2 mm (standard deviation [SD] 1.6 mm), mean outer pedicle width was 5.9 mm (SD 1.0 mm) and mean pedicle screw trajectory was 29.4 degrees (SD 3.6 degrees). Most (91.0%) of the pedicles had an outer diameter ≥4.5 mm.ConclusionsThe mean lateral mass screw length was longer when compared with other similar studies, while the mean outer pedicle width was narrower. Nearly 10% of the pedicles were unable to accommodate 3.5 mm screws. These findings favor the use of lateral mass screws to provide a safe and stable fixation for C7 vertebrae in Southern Chinese patients, while the final choice of fixation method should only be confirmed after careful preoperative planning with CT scan.

Lateral Mass Fixation in the Subaxial Cervical Spine.

The use of lateral mass screws and rods in the subaxial spine has become the standard method of fixation for posterior cervical spine fusions. Multiple techniques have been described for the placement of lateral mass screws, including the Magerl, the Anderson, and the An techniques. While these techniques are all slightly different, the overall goal is to obtain solid bony fixation while avoiding the neurovascular structures. The use of lateral mass screws has been shown to be a safe and effective technique for achieving a posterior cervical fusion.

Cost effectiveness of subaxial fusion—lateral mass screws versus transarticular facet screws

As health care reform continues to evolve, demonstrating the cost effectiveness of spinal fusion procedures will be of critical value. Posterior subaxial cervical fusion with lateral mass screw and rod instrumentation is a well-established fixation technique. Subaxial transarticular facet fixation is a lesser known fusion technique that has been shown to be biomechanically equivalent to lateral mass screws for short constructs. Although there has not been a widespread adoption of transarticular facet screws, the screws potentially represent a cost-effective alternative to lateral mass rod and screw constructs. In this review, the authors describe an institutional experience with the use of lateral mass screws and provide a theoretical cost comparison with the use of transarticular facet screws.

Lateral Mass Screws: Anatomy is the Key, Not Image Guidance!

To the Editor: We read with interest the article by Roche et al1 on Posterior Cervical Screw Placement without Image Guidance: A Safe and Reliable Practice. We find the title of the article somewhat misleading, in that, it is very common to be not able to visualize the lateral mass screws on patients even below C4. Thus, we only use fluoroscopy at the start of the surgery to insure proper alignment of the cervical spine and for localization of the levels for screw placement. We agree with Roche et al that the placement of lateral mass screws is safe and highly effective if, and only if, the surgeon is aware of neurovascular anatomy in the cervical spine and how to manage complications should they occur. We would like to add a few comments that support Roche et al and are the basics for our routine use of lateral mass screws, with virtually no serious complications to date. First, the most basic understanding of the lateral mass and its neurovascular content has been reviewed by several surgeons and there are several basic techniques in the trajectory for safe screw placement to avoid nerve root injury and vertebral artery injury.2–6 We typically use the Cherny et al6 technique with a screw trajectory of approximately 20 degrees laterally and 25 to 30 degrees rostrally. As with all surgeries, preoperative planning is of utmost importance and thus should the axial magnetic resonance imaging studies be insufficient for visualization of the vertebral artery, we then order axial computed tomography scans of the cervical spine to assess the foramen transversarium and rule out any possible anomalies.7 Second, a basic rule we follow, when placing lateral mass screws, is to start with right-sided screw placement; in case a vertebral artery injury does occur, it will typically not be the dominant vertebral artery injured. As previously mentioned, all surgeons should be able to appropriately manage such an injury.8 In terms of screw depth, a landmark study by Seybold et al,9 on the use of unicortical versus bicortical purchase for safety and stability, demonstrated that over 92% of unicortical screws were determined safe whereas only 68% of bicortical screws were safe.9 Surprisingly, when comparing pullout strength of the bicortical versus unicortical screws, there was no significant difference, leading support to the authors' conclusions that 11 mm of effective screw length is strong and safe.9 Lastly, a recent study by Katonis et al10 reported a risk of 0.01% for violating the foramen transversarium with a lateral mass screw after following 70 patients who underwent lateral mass screw fixation, with a total of 356 screws, of which only 5 screws minimally violated the foramen trasversarium without neurologic sequlae. In closing, we support Roche et al that fluoroscopy is not required for safe placement but clarify this support by urging surgeons to know the neurovascular anatomy and, most importantly, how to manage complications should they occur. Rob D. Dickerman, DO, PhD Ashley S. Reynolds, RN Matthew T. Bennett, MD Brent C. Morgan, MD Neurosurgery Research Foundation of Texas, North Texas Neurosurgical Associates, Plano Presbyterian and Medical Center of Plano Hospitals Plano, TX

Posterior Cervical Screw Placement Without Image Guidance

The use of lateral mass screws for posterior cervical fixation has become widespread. It allows for stable fixation in the absence of the posterior elements and confers immediate stability. Lateral mass fixation has been shown to impart equal or greater biomechanical stability when compared to posterior interosseous wiring or anterior plating. The utilization of intraoperative fluoroscopy to guide screw placement has been recommended previously and is considered routine practice in many centers. This prospective study shows that lateral mass screws can be safely positioned without intraoperative fluoroscopy. The procedure is both safe and effective, provided that the operator has a thorough understanding of lateral mass anatomy coupled with careful adherence to the established guidelines for screw positioning. Exposure to radiation is reduced and time taken for operation can be shortened.

Avoiding Complications in Patients With Ankylosing Spondylitis Undergoing Spine Surgery

Dr. Bono is Assistant Professor of Orthopaedic Surgery, Harvard Medical School, and Chief of Orthopaedic Spine Service, Brigham and Women's Hospital, Department of Orthopaedic Surgery, 75 Francis Street, Boston, MA 02115, E-mail: [email protected]; and Dr. Min is Orthopaedic Resident, NYU Hospital for Joint Diseases, New York, NY. The authors have disclosed that they have no significant relationships with or financial interests in any commercial organizations pertaining to this educational activity. They also have disclosed that the use of lateral mass screws for treatment of cervical spine disorders as discussed in this article has not been approved by the U.S. Food and Drug Administration. Lippincott CME Institute, Inc., has identified and resolved all faculty conflicts of interest regarding this educational activity. This article was published originally in Current Opinion in Orthopaedics 16:178–183, 2005.

A Cadaveric Examination of Pediatric Cervical Pedicle Morphology

A retrospective radiographic analysis of 47 intact cadaver pediatric cervical spines at the Hamann-Todd Osteology Collection in Cleveland, Ohio. Evaluate the morphology of the pediatric cervical spine pedicle, the feasibility of surgical pedicle screw instrumentation, and examine the contribution of growth to the pedicle axis. The adult cervical spine has been studied extensively and the morphology of the pedicles well documented. The morphology of the pediatric cervical, thoracic, and thoracolumbar spine has been studied radiographically, but, to our knowledge, no study has specifically examined the cervical spine pedicle, pedicle axis, and their changes with growth. A total of 47 pediatric human cadaver spines with a mean age of 13 years (range 3-18 years at death) from the Hamann-Todd Osteology Collection at the Cleveland Museum of Natural History were analyzed radiographically. There were 25 females and 22 males. The C3-C7 vertebrae were used in this study. The 228 vertebral specimens were evaluated in the axial and sagittal planes. The radiographs were subsequently digitized and measured for 5 parameters on the axial view: pedicle axis length, pedicle length, pedicle width, cervical spinal canal anteroposterior spinal canal diameter, and interpedicular distance. The pedicle axis length increased with advancing age. The pedicle length remained relatively constant throughout growth, and the pedicle diameter showed a statistically significant increase with growth. Mean pedicle diameter width was 3.0 mm at C3 and 4.2 mm at C7 in the 3-5 year-old group compared to 4.3 mm and 6.1 mm, respectively, at C3 and C7 at 18 years of age. The anteroposterior spinal canal diameter remained relatively constant with increasing age. The interpedicular distance achieved 80% of its adult size by 3-5 years of age. Regarding pedicle axis growth, the 3 components of the pedicle axis (i.e., vertebral body, pedicle, and lateral mass) were analyzed with regards to their contribution to growth. The vertebral body contributed an increasing percentage to overall pedicle axis growth with age, while the pedicle itself contributed a progressively smaller percentage. Our results showed an overall increase in the pedicle axis and pedicle width but no significant change in pedicle length. The data in this study indicate that pedicle screws may not be safe for use in the pediatric cervical spine, particularly younger children. The use of lateral mass screws was not specifically addressed in this study. As in the thoracolumbar spine, growth of the pedicles in relation to the spinal canal is lateral to the canal. The vertebral body itself appears to contribute most to overall pedicle axis growth, while the pedicle itself contributes a progressively smaller percentage over time.

Lateral mass screw fixation for cervical spine trauma: associated complications and efficacy in maintaining alignment

Background context Many studies have documented the efficacy of lateral mass screws, but there are no studies examining the alignment maintenance capability and few large studies examining the complications associated with the use of these devices in cervical spine trauma. Purpose To evaluate complications and alignment maintenance capability associated with lateral mass screw placement for cervical spine trauma by one surgeon at one institution. Study design A retrospective chart and radiograph review of adult patients who underwent lateral mass screw fixation after traumatic injuries to the cervical spine. Patient sample Of 34 consecutive patients with cervical spine injuries who were treated surgically at a level-I regional trauma center, 29 met the inclusion criteria and formed the study group. Outcome measures Sagittal alignment, screw placement, and fusion were assessed on postoperative radiographs. Methods Inclusion criteria included an unstable cervical vertebral fracture or a fracture-dislocation treated with posterior spine fusion and lateral mass instrumentation and a minimum follow-up of 24 months. A review of hospital charts, operative reports, clinic notes, and plain radiographs for the 29 patients was performed, with an emphasis on operative and postoperative complications and alignment maintenance. Results For 28 of the 29 patients, the mean change in sagittal alignment from the immediate postoperative to the most recent follow-up radiographic examination was 2° (range, 0° to 6°). Radiographically, there was one case of instrumentation/fixation failure and loss of sagittal alignment 3 months postoperatively. Other complications included one case of C5 nerve root injury and four wound infections. Conclusions The use of lateral mass screws for traumatic injuries of the cervical spine is associated with excellent maintenance of alignment and minimal complications.

The use of lateral mass screws and pedicle screws for the treatment of injury of lower cervical spine

To discuss the effect of the use of the cervical lateral mass plates screws and T(1) pedicle screws for the treatment of C(6) to C(7) injury through posterior approach. There were 8 patients in the study group; Each of them had been injured with low cervical spine C(6) or C(7). There were 6 cases with C(6)-C(7) injury and 2 cases with C(7) injury. According to ASIA classification, 3 cases were in grade C and 5 cases in D. The lateral mass screws were placed on the lateral masses using Margel technique. Lamina or facet bone allografting were used to achieve a long-term stability. All 8 patients were followed up from 5 to 37 months (mean 15 months). No operative death occurred. There were no cord or vertebral artery injury, cerebrospinal fluid leak, nerve roots injury, screw malposition or back out, loose of alignment or implant failure. Clinical symptom and ASIA classification were improved in all patients. Postoperative MRI scanning confirmed satisfactory screw placement in all cases. This technique is safe and benefit to patients with low cervical spine C(6) or C(7) injury.