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European Spine Journal, 2007
Anterior cervical plate fixation is an approved surgical technique for cervical spine stabilization in the presence of anterior cervical instability. Rigid plate design with screws rigidly locked to the plate is widely used and is thought to provide a better fixation for the treated spinal segment than a dynamic design in which the screws may slide when the graft is settling. Recent biomechanical studies showed that dynamic anterior plates provide a better graft loading possibly leading to accelerated spinal fusion with a lower incidence of implant complications. This, however, was investigated in vitro and does not necessarily mean to be the case in vivo, as well. Thus, the two major aspects of this study were to compare the speed of bone fusion and the rate of implant complications using either rigid-or dynamic plates. The study design is prospective, randomized, controlled, and multi-centric, having been approved by respective ethic committees of all participating sites. One hundred and thirty-two patients were included in this study and randomly assigned to one of the two groups, both undergoing routine level-1-or level-2 anterior cervical discectomy with autograft fusion receiving either a dynamic plate with screws being locked in ap-position (ABC, Aesculap, Germany), or a rigid plate (CSLP, Synthes, Switzerland). Segmental mobility and implant complications were compared after 3-and 6 months, respectively. All measurements were performed by an independent radiologist. Mobility results after 6 months were available for 77 patients (43 ABC/34 CSLP). Mean segmental mobility for the ABC group was 1.7 mm at the time of discharge, 1.4 mm after 3 months, and 0.8 mm after 6 months. For the CSLPgroup the measurements were 1.0, 1.8, and 1.7 mm, respectively. The differences of mean segmental mobility were statistically significant between both groups after 6 months (P = 0.02). Four patients of the CSLP-group demonstrated surgical hardware complications, whereas no implant complications were observed within the ABC-group (P = 0.0375). Dynamic plate designs provided a faster fusion of the cervical spine compared with rigid plate designs after prior spinal surgery. Moreover, the rate of implant complications was lower within the group of patients receiving a dynamic plate. These interim results refer to a follow-up period of 6 months after prior spinal surgery. Further investigations will be performed 2 years postoperatively.
Static versus dynamic plating for multilevel anterior cervical discectomy and fusion
The Spine Journal, 2007
BACKGROUND CONTEXT: Dynamic anterior plates have been popularized to promote cervical spine fusion by allowing controlled settling, thereby promoting load sharing across the construct. To date these proposed benefits have been largely theoretical and there are no studies confirming any benefits over more traditional static plates. PURPOSE: To compare the clinical and radiographic outcomes of patients undergoing an instrumented multilevel anterior cervical discectomy and fusion (ACDF) with either a static or dynamic plate design. STUDY DESIGN: A retrospective clinical and radiographic study. PATIENT SAMPLE: From 1997 to 2002, 52 patients with either radiculopathy or myelopathy underwent two-or three-level ACDF with either static or dynamic plate fixation. OUTCOME MEASURES: Functional outcome, fusion status, radiographic measurements. METHODS: A statically locked plating system was used in 21 patients, and a dynamic plating system was used in 31 patients. Functional outcome, fusion status, plate migration, settling, and adjacent-level disc space impingement were evaluated. RESULTS: Clinical outcome was found to be similar between the statically and dynamically plated groups. Eighty-four percent of patients in both groups experienced good or excellent results at final follow-up. We observed a higher rate of nonunion in patients treated with a dynamic plate (16% [5 of 31]) compared with a rate of 5% (1 of 21) in those patients treated with a static plate (p5.05). Settling of the construct and plate migration was similar between the study groups at all time points. CONCLUSIONS: This study failed to confirm our hypothesis that a dynamic plate (that allows angular motion between the screws and plate) confers any clinical or radiographic advantage over earlier design static plates. A higher rate of nonunion was actually seen in the dynamically plated patients; however, clinical results were similar between the two groups.
Journal of Spinal Disorders & Techniques, 2010
A retrospective review of clinical data at 1 institution was performed. Objectives: To compare the clinical and radiologic outcomes between fixed-hole and slotted-hole dynamic cervical plates. Summary of Background Data: Anterior cervical plating is commonly used to increase stability and promote spinal fusion. Two techniques, fixed-hole dynamic plating that uses variable angled screws and slotted-hole dynamic plating that permits sliding, are viable options, but there have been no clinical studies comparing their effectiveness. Methods: Fifty-six patients at 1 institution having anterior cervical discectomy and fusion for degenerative disease over a 5year period were entered into this study. Surgeries were performed with 1 of the dynamic plates for 1 to 3 levels. For the slotted-hole dynamic plate group, a slotted-hole plate was used (ABC, Aesculap, Tuttlingen, Germany or C-tek, Biomet, Parssipany, NJ) and for the fixed-hole dynamic plated group, a variable angled screw was used (C-tek, Biomet, Parssipany, NJ). Radiographic measurements included were graft subsidence, lordotic angle change from each end plate of fusion construct, and implant translation from end plates after a minimum of 12 months follow-up. Fusion state and clinical outcome using Odom's criteria were also evaluated. Results: Demographics were not different among patient populations. The average age of the patients was 51.0 years (range: 27 to 77 y). Mean follow-up period was 20.6 months (range: 12 to 41 mo). Slotted-hole dynamic plates were used for 29 patients (ABC plate, 17; C-tek plate, 12) and fixed-hole dynamic plates for 27 patients. Clinical outcomes and pseudoarthrosis rates were similar for both types of plates. Radiographic measurements showed a statistically significant increased incidence of graft subsidence and implant translation with the slotted-hole dynamic plates. Loss of lordosis was also greater in the slotted-hole dynamic plated group, although the difference was not statistically significant. Conclusions: The use of a fixed-hole dynamic plate is more favorable in regards to graft subsidence and implant translation in the follow-up period, although clinical outcome and fusion rates are similar in patients with either the fixed-hole or slottedhole dynamic plates.
American journal of orthopedics (Belle Mead, N.J.)
This study addressed radiographically the evaluation, presence, location, and degree of subsidence with secondary focus on the various clinical parameters and outcomes in 32 patients who underwent anterior cervical discectomy and fusion (ACDF) with tricortical iliac crest bone grafts and rigid anterior plate fixation. Postoperative follow-up plain radiographs were evaluated to determine subsidence on lateral neutral images by measuring the change in height of interscrew distance (ISD) and anterior (AVD), mid (MVD), and posterior (PVD) vertebral endplate-to-endplate vertical distances. Clinical functional outcome and various risk factors were also addressed. A 100% fusion rate was achieved, no instrumentation-related complications were noted, and mild graft subsidence occurred in each patient after the initial 2 months of surgery. Mean AVD, MVD, and PVD were 1.2 mm, 0.4 mm and 0.6 mm, respectively. Mean ISD was 0.6 mm. Percent change for AVD, MVD, PVD, and ISD was 2.3%, 0.8%, 1.2%, a...
Treatment of multilevel cervical fusion with cages
Surgical Neurology, 2004
BACKGROUND Multilevel cervical discectomy usually requires plate and screw fixation for maintaining the spinal curvature, and increasing the graft fusion rate. However, the use of plate and screw fixation may cause a few complications, such as screw breakage, screw pullout, esophagus perforation, and cord or nerve root injury. In this study, we try to use cages to replace plate function in multilevel cervical fusion. METHODS From January 1997 to June 2001, there were 180 consecutive cases of multilevel cervical degenerative disease. We randomized them into three groups: Group A (60 patients) underwent anterior discectomy and polyetheretherketone (PEEK) fusion, Group B (50 patients) underwent anterior discectomy, autogenous iliac crest graft (AICG) fusion and plate fixation, and Group C (70 patients) underwent anterior discectomy and AICG only. X-ray of cervical spine was taken every 3 months until fusion was complete. Spinal curvature was measured by lateral view of X-ray. The functional and working status were evaluated by Prolo scale. Blood loss and operation time were recorded, respectively. RESULTS The total complication rates were 3.3%, 16%, and 54.3% in Groups A, B, and C respectively. The graft complications were evaluated by radiographic findings (graft collapse, nonunion, or dislodged graft). However, only 37.1% of patients (13/35) with graft complications had clinical symptoms (severe neck pain, radicular pain, or neurologic deficits). The fusion rate was better, and the time to fusion was sooner in Groups A and B than Group C, p Ͻ 0.001 (2 test). PEEK cage is statistically better than plating group in total complications, p Ͻ 0.05. Graft collapse and nonunion were the major graft complications in Group C (AICG without plating). Screw pullout, and screw breakage were the main causes of plating complication. Blood loss was minimum in Group A, p Ͻ 0.05. Spinal lordosis increased by a mean of 4.61 Ϯ 2.93 mm and 1.68 Ϯ 5.02 mm in Groups A and B, respectively, but spinal kyphosis increased by a mean of Ϫ2.09 Ϯ 4.77 mm in Group C. Group A had a statistically better Prolo scale than Group C, p Ͻ 0.0001. CONCLUSIONS Both PEEK cage without plating and AICG with plating are good methods for interbody fusion in multilevel cervical degenerative diseases. They increase spinal lordosis and graft fusion rate, and cause fewer surgical complications. However, PEEK cage is preferred in our study for multilevel fusion, because it has the fewest complication rates and the least amount of blood loss.
Review Article - Anterior cervical plating
2005
Although anterior cervical instrumentation was initially used in cervical trauma, because of obvious benefits, indications for its use have been expanded over time to degenerative cases as well as tumor and infection of the cervical spine. Along with a threefold increase in incidence of cervical fusion surgery, implant designs have evolved over the last three decades. Observation of graft subsidence and phenomenon of stress shielding led to the development of the new generation dynamic anterior cervical plating systems. Anterior cervical plating does not conclusively improve clinical outcome of the patients, but certainly enhances the efficacy of autograft and allograft fusion and lessens the rate of pseudoarthrosis and kyphosis after multilevel discectomy and fusions. A review of biomechanics, surgical technique, indications, complications and results of various anterior cervical plating systems is presented here to enable clinicians to select the appropriate construct design.
Clinical experience with a new load-sharing anterior cervical plate
International Congress Series, 2002
Purpose of study: Anterior plate fixation is widely accepted as an adjunct to surgical correction of traumatic or degenerative conditions of the cervical spine. The various systems have evolved from nonconstrained constructs to rigid plate screw constructs. With the popularity of the latter, concerns have increased on both the biomechanical and clinical levels regarding the adverse effects of graft stress shielding which can result in delayed bony union or nonunion. This ultimately can result in hardware or construct failure. A new dynamic plating system (ABC plate) has been developed which seeks to avoid stress shielding of the graft by allowing vertical migration of the fixation screws within the plate. This design can prevent screw back-out and effectively stabilize the spine while allowing full load sharing, thus promoting early fusion and restoring or preserving lordosis. Methods: This study reports on our experience with 486 patients at two different centers over a 3-1/2-year interval utilizing the ABC system. Indications for surgery were herniated disks in 36%, degenerative disease in 45%, trauma in 14%, failed fusion in 2%, and deformity, tumors and OPLL in 1% each. Patients ranged in age from 10 to 80 years (average 47 years). Unicortical screw placement was used in 68%, bicortical in 28%, and a combination of these in 4%, according to the surgeon's preference and judgment. Single-level plates were used in 47%, two-level plates in 39%, and three or more levels were plated in 14%. Corpectomies were used in 19% with the remainder being interbody fusions. Allograft iliac crest bone was used in 61% and autograft iliac crest bone in 39%. Patients were seen in follow-up and radiographs, which include lateral flexion/extension views, were taken at the 1-, 3-, 6-, 12and 24-month intervals after surgery. Settling was measured and corrected for magnification. Cobb angles were measured to determine changes in angulation from immediately preoperatively to subsequent interval films. Fusion was determined using the rigid criteria of bridging trabecular bone and the absence of motion at the tips of the spinous processes on flexion and 0531-5131/02 D 2002 Published by Elsevier Science B.V.
A Biomechanical Comparison of Modern Anterior and Posterior Plate Fixation of the Cervical Spine
Spine, 2001
Study Design. 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. Objectives. 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. Summary of Background Data. 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. Methods. Biomechanical flexibility tests were performed using cervical spines (C2-T1) obtained from 10 fresh human cadavers. In group I (5 specimens), onelevel, 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. Results. 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. Conclusions. 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.
Anterior cervical fusion: a comparison of cage, dowel and dowel-plate constructs
The Spine Journal, 2003
Background context: Threaded lumbar cages have been used as a safe and effective surgical fusion method for a decade. Smaller versions have now been developed for the cervical spine to obviate the need for allograft use or iliac autograft harvest and to provide initial stability before fusion. Purpose: To compare anterior cervical interbody fusion with the BAK/C Cervical Interbody Fusion System, cage (Centerpulse Spine-Tech Inc., Minneapolis, MN), conventional anterior cervical discectomy and fusion (ACDF) and plate constructs (anterior cervical locking plates). Study design/setting: Radiological and clinical outcomes of patients who underwent cervical fusion with the BAK/C (filled with local autograft reamings) are compared with ACDF and plate fusion constructs (anterior cervical locking plates). One surgeon performed 88 fusions: BAK/C (n ϭ 30), ACDF (n ϭ 32), plate (n ϭ 26). There were 43 one-level and 45 two-level fusions from C3-C4 to C7-T1. Patient sample: The patients represented a wide range of diagnoses as indications for cervical fusion. Patients (n ϭ 88) were 40 men (45%) and 48 women (55%) with a mean age of 51 years (range, 30 to 70 years). Thirty-five percent of patients were smokers, and 26% had known workers' or other compensation issues. Outcome measures: Hospital records were examined for data from operative reports and discharge summaries. An independent spine radiologist performed a radiological review of cervical flexion and extension films, noting fusion status, graft position and cage subsidence. Short Form (SF)-36 inventories for physical/mental functioning and visual analog scales (VAS) for pain were administered. Methods: A retrospective clinical and radiological review was performed. Hospital and clinic chart data, flexion-extension X-rays and self-assessments (SF-36, VAS) were evaluated. Follow-up at X-ray was 2.4 years (range, 1.0 to 5.5 years). Results: Iliac crest harvesting was least likely for BAK/C patients (2 of 30; 6.7%) compared with ACDF (30 of 32; 93.8%) and plate patients (13 of 26; 50.0%; p Ͻ .0001). Plate surgeries took longest (3.5 hours), followed by ACDF (2.3 hours) and BAK/C (2.2 hours; p Ͻ .0001). Blood loss was greatest for plate procedures (289 cc), followed by BAK/C (142 cc) and ACDF (121 cc; p Ͻ .01). No BAK/C patient stayed in the hospital more than 1 day; ACDF, 1 to 2 days; plate, 1 to 5 days (p Ͻ .02). BAK/C patients were most likely to have a successful fusion: BAK/C, 29 of 30, 97%; ACDF, 26 of 31, 84% (one X-ray fusion status indeterminate); plate, 22 of 26, 85% (p Ͻ .0585). No BAK/C patient experienced prolonged donor-site pain (0%) compared with ACDF (25.0%) and plate (23.0%) patients. SF-36 and VAS scores, influenced by compensation, were comparable for all groups. Revisions were as follows: ACDF, 4 of 32, 13%; plate, 2 of 26, 8%); BAK/C, 1 of 30, 3%). Conclusions: In this study, the BAK/C cage group had the lowest graft requirements/risks, generally required fewer hospital resources, achieved similar patient outcomes and fused at a higher rate than ACDF and plate groups.