Posterior Lateral Mass Screw Fixation Research Articles

Management of post-traumatic neglected cervical facet dislocation.

Post-traumatic unilateral or bilateral sub-axial cervical spine dislocations with locked facets are quite common. In developing countries like India, many patients with cervical injuries report late due to many reasons like rural backgrounds, lack of infrastructures and skilled surgeons, unawareness, poor socioeconomic status, lack of transportation to the specialized center with proper facility, etc. Early management is essential to maximize better neurological outcome. Delayed or neglected presentation makes treatment more challenging. Very few literatures are currently available regarding management of neglected cervical facet dislocation but no one offers clear cut management. Purpose of our study is to evaluate treatment outcome of 15 patients with post-traumatic neglected cervical facet dislocation. Here we have reviewed 15 patients with post-traumatic neglected presentation of cervical facet dislocations and evaluated their treatment outcome. This is a retrospective type of study done in spine care unit of VMMC and Safdarjung Hospital, New Delhi from July 2013 to June 2016. Record of 15 patients with neglected cervical dislocation who were undergone anterior cervical discectomy and fusion along with posterior lateral mass screw fixation depending upon close reduction and integrity of disco-ligamentous complex. 15 patients were included in this study. 4 patients underwent only anterior cervical discectomy and fusion (ACDF) after complete close reduction with intact disco-ligamentous complex. Remaining 11 patients who failed to achieve complete reduction or had posterior disco-ligamentous injuries underwent posterior partial facetectomy and lateral mass screw fixation with anterior discectomy and fusion concomitantly. Mean follow up period was 14 months. All patients achieved pain relief and sufficient neck movements. 1 patient with only nerve root injuries recovered completely. 6 out of 11 patients with incomplete spinal cord injuries, improved by one Frankel grade and remaining 5 patients by two grades. 3 patients with complete quadriplegia showed no clinical and neurological improvement. Proper decompression, reduction and fixation should be done in neglected cervical dislocation as it provides mechanical stability and alignment, facilitates rehabilitation, prevent kyphotic deformity as well as offers a fair chance of neurological recovery.

Deep surgical site infection after anterior decompression and fusion with plate fixation for cervical spondylotic radiculopathy or myelopathy

ObjectivesTo analyze the diagnosis and management of deep surgical site infection (SSI) with implant involved after anterior decompression and fusion for cervical spondylotic radiculopathy/myelopathy (CSR/CSM). Patients and methodsData of the patients who underwent anterior cervical decompression and fusion with plate fixation due to CSR/CSM were retrospectively reviewed. Cases with postoperative deep SSI with implant involved were identified and analyzed. ResultsA total of 1287 patients were finally included. Five patients (0.4%) were found to be with deep SSI. Bone fusion was not obtained when SSI was confirmed in each patient. Three cases were cured using one or two debridement and postoperative antibiotic therapy. Two cases with delayed diagnosis needed anterior implants removal, interbody fusion with autologous iliac bone and posterior lateral mass screw fixation at the first/second debridement. One of the two patients developed esophagus perforation after a second debridement and experienced one-month open drainage. All of the patients were cured without relapse of infection. ConclusionFor early deep SSI after anterior cervical decompression and fusion, surgical debridement was effective to eradicate infection. But for cases with delayed diagnosis, anterior debridement with prophylactic implant removal and posterior reconstruction was an ideal option. Esophagus perforation complicated with multiple debridements should be paid attention to and avoided.

Cortical bone facet spacers for cervical spine decompression: effects on intervertebral kinetics and foraminal area.

Nerve root decompression to relieve pain and radiculopathy remains one of the main goals of fusion-promoting procedures in the subaxial cervical spine. The use of allograft facet spacers has been suggested as a potential alternative for performing foraminotomies to increase the space available for the cervical nerve roots while providing segmental stiffening. Therefore, the goal of this cadaveric biomechanical study was to determine the acute changes in kinetics and foraminal area after the insertion of cortical bone facet spacers into the subaxial cervical spine. Allograft spacers (2 mm in height) were placed bilaterally into cadaveric cervical spine specimens (C2-T1, age of donors 57.5 ± 9.5 years, n = 7) at 1 (C4-5) and 3 (C3-6) levels with and without laminectomies and posterior lateral mass screw fixation. Standard stereophotogrammetry under pure moment loading was used to assess spinal kinetics. In addition, the authors performed 3D principal component analysis of CT scans to determine changes in foraminal cross-sectional area (FCSA) available for the spinal nerve roots. Generally, the introduction of 2-mm-height facet spacers to the cervical spine produced mild, statistically insignificant reductions in motion with particular exceptions at the levels of implantation. No significant adjacent-level motion effects in any bending plane were observed. The addition of the posterior instrumentation (PI) to the intact spines resulted in statistically significant reductions in motion at all cervical levels and bending planes. The same kinetic results were obtained when PI was added to spines that also had facet spacers at 3 levels and spines that had been destabilized by en bloc laminectomy. The addition of 2-mm facet spacers at C3-4, C4-5, and C5-6 did produce statistically significant increases in FCSA at those levels. The addition of allograft cervical facet spacers should be considered a potential option to accomplish indirect foraminal decompression as measured in this cadaveric biomechanical study. However, 2-mm spacers without supplemental instrumentation do not provide significantly increased spinal segmental stability.

Posterior Cervical Lateral Mass Screw Fixation and Fusion to Treat Pseudarthrosis of Anterior Cervical Fusion

Retrospective clinical cohort study. To determine the efficacy of posterior lateral mass screw/rod fixation and fusion for the treatment of symptomatic pseudarthrosis of anterior cervical fusion. Both anterior revision and posterior repair of cervical pseudarthrosis have been reported. To date, there is still debate in the literature as how the patient with symptomatic cervical pseudarthrosis should be addressed. Thirty-eight consecutive patients with symptomatic anterior cervical pseudarthrosis were treated with posterior lateral mass screw/rod fixation and fusion. The average follow-up was 28 months (24 to 60 mo) and patients were assessed with clinical examination, questionnaires, flexion-extension lateral radiographs, and/or computed tomography scans. The clinical results were classified as excellent, good, fair, or poor, according to Zdeblick criteria. All patients achieved a solid radiographic fusion at the final follow-up. The result was excellent in 10 patients, good in 22, fair in 6, and poor in none. Patients with symptomatic cervical pseudarthrosis that develops after anterior cervical discectomy and fusion may be managed successfully with posterior lateral mass screw fixation and fusion.

A Biomechanical Comparison of Modern Anterior and Posterior Plate Fixation of the Cervical Spine

A biomechanical study was designed to assess relative rigidity provided by anterior, posterior, or combined cervical fixation using cadaveric cervical spine models for flexion-distraction injury and burst fracture. To compare the construct stability provided by anterior plating with locked fixation screws, posterior plating with lateral mass screws, and combined anterior-posterior fixation in clinically simulated 3-column injury or corpectomy models. Anterior plating with locked fixation screws is the most recent design and is found to provide better stability than the conventional unlocked anterior plating. However, there are few data on the direct comparison of biomechanical stability provided by anterior plating with locked fixation screws versus posterior plating with lateral mass screws. Biomechanical advantages of using combined anterior-posterior fixation compared with that of using either anterior or posterior fixation alone also have not been well investigated yet. Biomechanical flexibility tests were performed using cervical spines (C2-T1) obtained from 10 fresh human cadavers. In group I (5 specimens), one-level, 3-column injury was created at C4-C5 by removing the ligamentum flavum and bilateral facet capsules, the posterior longitudinal ligament, and the posterior half of the intervertebral disc. In group II (5 specimens), complete corpectomy of C5 was performed to simulate burst injury. In each specimen, the intact spine underwent flexibility tests, and the following constructs were tested: (1) posterior lateral mass screw fixation (Axis plate) after injury; (2) polymethylmethacrylate anterior fusion block plus posterior fixation; (3) polymethylmethacrylate block plus anterior (Orion plate) and posterior plate fixation; and (4) polymethylmethacrylate block plus anterior fixation. Rotational angles of the C4-C5 (or C4-C6) segment were measured and normalized by the corresponding angles of the intact specimen to study the overall stabilizing effects. Posterior plating with an interbody graft showed effective stabilization of the unstable cervical segments in all loading modes in all cases. There was no significant stability improvement by the use of combined fixation compared with the posterior fixation with interbody grafting, although combined anterior-posterior fixation tended to provide greater stability than both anterior and posterior fixation alone. Anterior fixation alone was found to fail in stabilizing the cervical spine, particularly in the flexion-distraction injury model in which no contribution of posterior ligaments is available. Anterior plating fixation provided much greater fixation in the corpectomy model than in the flexion-distraction injury model. This finding suggests that preservation of the posterior ligaments may be an important factor in anterior plating fixation. This study showed that the posterior plating with interbody grafting is biomechanically superior to anterior plating with locked fixation screws for stabilizing the one-level flexion-distraction injury or burst injury. More rigid postoperative external orthoses should be considered if the anterior plating is used alone for the treatment of unstable cervical injuries. It was also found that combined anterior and posterior fixation may not improve the stability significantly as compared with posterior grafting with lateral mass screws and interbody grafting.

The location of the vertebral artery foramen and its relation to posterior lateral mass screw fixation.

This study evaluated the anatomic relationship between the vertebral artery foramen and the posterior midpoint of the cervical lateral mass using cervical spine specimens. To determine quantitatively the location of the vertebral artery foramens from C3 to C6 and their relationship to the posterior midpoints of the lateral masses. Anatomic studies of the cervical nerve root and facet relative to lateral mass screw placement have been addressed. It is necessary to know the correct location of the vertebral artery foramen during lateral mass screw placement to minimize the risk of injury to the vertebral artery. Forty-three cervical spines from C3 to C6 were directly evaluated for this study. Anatomic evaluation included the dimension of the vertebral artery foramen and its projection on the posterior aspect of the lateral mass. The vertical distance from the posterior midpoint of the lateral mass to the posterior border of the vertebral artery foramen, and the angle between the parasagittal plane and the line connecting the posterior midpoint of the lateral mass with the lateral limit of the vertebral artery foramen, were also measured. The vertical distances from the posterior midpoint of the lateral mass to the vertebral artery foramens at C3-C6 averaged from 9.3 to 12.2 mm for male and female specimens. The average angles medial to the sagittal plane, between the parasagittal plane and the line connecting the posterior midpoint of the lateral mass with the lateral limit of the vertebral artery foramen, from C3 to C5, were found to range from 6.0 degrees to 6.3 degrees for male specimens and from 5.3 degrees to 5.5 degrees for female specimens. At C6, the average angles lateral to the sagittal plane, between the parasagittal plane and the line connecting the posterior midpoint of the lateral mass with the lateral limit of the vertebral artery foramen, were 6.4 degrees for male specimens and 5.4 degrees for female specimens. The present study indicated that there is no risk of damaging the vertebral artery if a screw is directed perpendicular to the posterior aspect of the lateral mass at C3-C5 and 10 degrees lateral to the sagittal plane at C6 starting at the midpoint of the lateral mass.