Anterior Cervical Instrumentation Research Articles

Missing Screw as a Rare Complication of Anterior Cervical Instrumentation

Although anterior cervical arthrodesis is an effective procedure for the treatment of cervical disorders, the method has some complications. Here, we describe this rare complication of cervical instrumentation with a literature review. A 23-year-old male patient was operated for a C6-C7 dislocation. At postoperative month 10, he presented with hemoptysis and dysphagia. Cervical roentgenograms showed anterior migrations of one broken screw and a plate-locking screw at the C6 corpus. One screw was missing. We concluded that the missing screw had perforated the esophagus and had been eliminated spontaneously through the gastrointestinal tract. No screw should migrate. Even loose screws should be noted in follow-up X-ray studies. If such findings are detected, a second operation for revision should be considered as soon as possible to prevent potentially fatal complications.

Spontaneous expulsion of a screw: An unusual complication 3 years after internal fixation of posterior acetabular wall fracture

Although cases have been documented describing wires extracorporeal expulsion associated with osteosynthesis, interference screw disengaging from the tibial tunnel in anterior cruciate ligament reconstructions, screw migration from the symphysis to the bladder in pelvic fractures and oesophageal perforation from anterior cervical instrumentation, no reports have noted migration of a failed implant after acetabular fractures. In this report, we present a novel case in which an acetabular screw spontaneously migrated 3 years after the surgery, undergoing subsequent transcutaneous expulsion.

Esophageal perforation from anterior cervical screw migration

Background Esophageal perforation from anterior cervical instrumentation migration is an uncommon but potentially highly morbid or even fatal complication. Early recognition and aggressive investigation and treatment are essential to ensure good outcome. Case Description A 58-year-old man underwent C6 vertebrectomy and C5-7 interbody fusion with a cage and anterior cervical plate. After surgery he developed fever and recurrence of his symptoms and deficits, but was managed expectantly. He was then referred to the author's institution. A barium swallow demonstrated an esophageal fistula (a Gastrograffin swallow was falsely negative) caused by a migrated screw; serial radiographs confirmed its passage through the gastrointestinal tract. Revision surgery was required to repair the perforation and reconstruct the cervicothoracic spine. Intraoperative esophageal injection of methylene blue was helpful in demonstrating the site of leakage. Despite a prolonged postoperative course complicated by pulmonary embolus, the patient recovered with minimal residual deficit, and continues to do well 2 years later. Conclusions A high index of suspicion followed by aggressive investigation are crucial in the setting of unexpected neck pain, new neurologic deficit, fever, or swallowing difficulties in the early postoperative period after anterior cervical spine instrumentation. If esophageal perforation is suspected, a barium swallow is recommended over Gastrograffin, which, although less irritating to the surrounding tissues, may be falsely negative. Intraoperative methylene blue injection into the esophageal lumen is useful in identifying the site of perforation.

A Comparison of Retraction Pressure During Anterior Cervical Plate Surgery and Cervical Disc Replacement

Dysphagia is a well-recognized complication after anterior cervical discectomy and fusion, observed in as high as 50% of cases by videofluoroscopic evaluation postoperatively. Esophageal injury due to surgical retraction is a complication due to which swallowing difficulties may ensue. There are limited published data evaluating the effect of soft tissue retraction on intraesophageal pressures during anterior cervical instrumentation procedures. The purpose of this study was to (a) measure the intraesophageal pressure secondary to retraction during anterior instrumentation, (b) determine whether any pressure differences exist between plating and cervical disc replacement, and (c) determine whether the surgical level or length of the plate influences the magnitude of intraesophageal pressure during retraction. An analysis of soft tissue retraction pressure was performed for anterior single-level and 3-level cervical plating and cervical disc replacement procedures. Using a 4-cm transverse incision, a Smith-Robinson anterior approach to the cervical spine was performed on 7 fresh, frozen cadavers. The correct placement of an esophageal pressure-transducing catheter was confirmed by laryngoscopy, manual palpation of the esophagus, and fluoroscopic imaging. Three surgical instrumentation groups were used for comparisons: (a) single-level plate (b) single-level Porous Coated Motion cervical disc replacement, and (c) 3-level plate. Hand-held appendiceal retractors were used to retract the soft tissues during screw insertion into the plate and during application of the disc prosthesis into the interspace. Care was taken to exert just enough force on the retractors to allow the surgeon to move the desired implant into the correct position. In addition the individual performing the retraction was blinded to the procedure being performed-1-level plating, 3-level plating, or disk replacement. Fluoroscopy confirmed that the pressure sensors were directly behind the retractors during data acquisition. Significantly greater intraesophageal pressures were demonstrated for single-level cervical plating at C5-6 compared to that at C3-4 (P=0.036). Similarly, significantly greater pressures were recorded at C5-6 versus C3-4 for the 3-level plating group (P<0.001). In contrast, there was no statistically significant difference in pressures observed during disk replacement at C5-6 compared to that at C3-4 (P=0.084). Significantly greater pressures were recorded during single-level plating compared to disc replacement at both C3-4 (P=0.016) and C5-6 (P=0.016). Three-level plating demonstrated significantly greater pressures at C5-6 compared to disk replacement (P<0.001) but no statistically significant difference compared to disk replacement at C3-4 (P=0.333). The highest mean pressure, 154.5+/-49.5 mm Hg, was recorded at C5-6 level during insertion of the 3-level plates. On the basis of the data presented here, anterior cervical plating results in significantly greater intraesophageal pressures when performed at C5-6 compared to C3-4. This holds regardless of whether the plate spans the distance from C3 to C6 (3-level plate) or the single C5-6 level. In addition, the insertion of the cervical disc replacement seems to require less esophageal retraction and hence reduced intraesophageal pressures when compared to anterior cervical plating.

P155. Intraesophageal retraction pressure during anterior cervical plating vs. cervical disc replacement

BACKGROUND CONTEXT: Dysphagia is a well-recognized complication following anterior cervical discectomy and fusion, observed as high as 50% by videofluoroscopic evaluation postoperatively. Esophageal injury due to surgical retraction is one mechanism by which swallowing difficulties may ensue. There are limited published data evaluating the effect of soft tissue retraction on intra-esophageal pressures during anterior cervical instrumentation procedures.

Anterior cervical plating

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.

Biomechanical Testing of an Artificial Cervical Joint and an Anterior Cervical Plate

An in vitro biomechanical study was conducted to determine the effects of fusion and nonfusion anterior cervical instrumentation on cervical spine biomechanics in a multilevel human cadaveric model. Three spine conditions were studied: harvested, single-level artificial cervical joint, and single-level graft with anterior cervical plate. A programmable testing apparatus was used that replicated physiologic flexion/extension and lateral bending. Measurements included vertebral motion, applied load, and bending moments. Relative rotations at the superior, implanted, and inferior motion segment units (MSUs) were normalized with respect to the overall rotation of those three MSUs and compared using a one-way analysis of variance (P < 0.05). Application of an anterior cervical plate decreased motion across the fusion site relative to the harvested and artificial joint spine conditions. The reduced motion was compensated for by an increase in motion at the adjacent segments. Use of an artificial cervical joint did not alter the motion patterns at either the instrumented level or the adjacent segments compared with the harvested condition for all modes of testing.

Advances in spinal instrumentation

New approaches to the spinal column and the use of spinal fixation have vastly improved our ability to treat spinal pathology. Over the last several decades there has been a rapid expansion in the availability of implants for use in the spine. The empetus behind these advancements is a combination of the ingenuity of surgeons in the drive for better results, a better understanding of bone healing, better biomechanically understanding and tes i g, and improved surgical techniques. The indications for surgery remain the most critical component in patient outcome and must be strictly defined before the optimum implant can be selected on the basis of advantages and potential risks. Many new systems and devices have been created or modified over the last several decades. Their' applic ations and results continue to evolve. This article hopes to update and acquaint readers on some of the progress over the past years. Because of the shear expanse of the topic, an exhaustive discourse is not possible. We will co er three concepts, anterior cervical instrumentation, transpedicular screw instrumentation, and interbody cage uevI c . While the same can be said for many innovative implants used in the spine, these relatively recent devices have been revolutionary, at times controversial, and remain at the forefront of spinal surgery.

Preliminary experience with the DOC dynamic cervical implant for the treatment of multilevel cervical spondylosis.

Despite the wide use of anterior cervical instrumentation in the management of multilevel cervical spondylosis, the incidences of pseudarthrosis and instrument-related failure remain high. The use of a dynamic implant may aid in the prevention of these complications. The purpose of this study was to evaluate the DOC dynamic cervical implant in the treatment of multilevel cervical spondylosis. The authors evaluated 34 cases in which anterior multilevel cervical decompression and fusion were performed using the DOC Ventral Cervical Stabilization System. Postoperatively, and at each follow-up visit, the sagittal angle and the degree of subsidence that developed were measured. Fusion rates and clinical outcomes were also evaluated. The mean postoperative sagittal angle was 14 degrees of lordosis. The mean change in the sagittal angle during the follow-up period was 0.4 degrees of lordosis. By 6 months postoperatively some subsidence had occurred in most patients, with no subsidence occurring in only 15%. By 3 months greater than or equal to 2 mm of subsidence was demonstrated in 61% of cases. The overall fusion rate was 91%. In the majority of patients (79%) symptoms were judged to be improved or resolved. The DOC dynamic cervical implant permitted controlled subsidence and prevented progression of kyphotic deformity. There was one construct failure (related to a motor vehicle accident) and an overall fusion rate of 91%. The DOC implant is a safe and effective cervical construct for multilevel spondylotic disease.

Lateral mass plate fixation for severe cervical instability

Jed Vanichkachorn, MD, Paul C. McAfee, MD, Ira L. Fedder, MD, Michael A. Catino, MD, Towson, MD, USA; Alexander R. Vaccaro, MD, Todd J. Albert, MD, Philadelphia, PA, USA; Marshall D. Paris, MD, Pittsburgh, PA, USAIntroduction: Segmental fixation of the posterior cervical spine can significantly enhance the stability of the unstable cervical spine. Used either alone or in conjunction with complex anterior cervical reconstructions, lateral mass plates provide significantly more stability and more reliability than stand-alone anterior cervical instrumentations, especially over three or more vertebral levels. This posterior segmental fixation can also protect long anterior cervical instrumentations from the significant displacing forces that are often present with severe cervical instability, even after reconstruction. This study presents the lateral mass plating experience from three separate academic institutions and demonstrates the enhanced cervical stability provided by this valuable technique.Methods: This is a 6-year retrospective study of 66 patients who underwent an instrumented posterior cervical fusion (PCF) using lateral mass plates over three or more vertebral levels. Data were obtained for analysis by a retrospective patient chart review at the University of Pittsburgh Medical Center, Pittsburgh, PA, Thomas Jefferson University Hospital, Philadelphia, PA, and the Spine and Scoliosis Center, Baltimore, MD. Of the 66 patients entered into the study, 50 patients had a concurrent anterior cervical fusion (ACF) performed, 34 using anterior instrumentation. The anterior instrumentation varied from a one-level anterior junctional plate to a contoured four-level long anterior cervical plate. Of the patients with a combined anterior and posterior cervical fusion, 47 were performed in a one-stage procedure. Seventeen patients had a prior anterior cervical fusion, six that required a revision anterior cervical fusion at the time of their posterior cervical fusion. The indications for the instrumented posterior cervical fusions were as follows: 6 patients with acute trauma with a concurrent ACF, 1 patient with ankylosing spondylitis with fracture, 9 patients with neoplasms with pathologic fractures (7 concurrent ACF), 15 patients with congenital stenosis (13 concurrent ACF), 19 patients with cervical kyphosis greater that 40 degrees (14 concurrent ACF) and 39 patients with cervical spondylitic myelopathy (27 concurrent ACF).Results: The 66 patients in the study had an average age of 54.8 years (range, 11 to 76 years) at the time of surgery. The patients in the study had an average follow-up of 39 months (range, 9 to 81 months). An average of 5.02 posterior cervical levels were instrumented (range, 3 to 9). The posterior fusion with iliac crest bond graft was extended the entire length of the lateral mass plates. The preoperative Frankel grade generally improved in the patient population from C (13), D (44) and E (9) preoperatively to C (2), D (19) and E (45) in the postoperative period. Fifty-four PCFs used Axis plates (Sofamor-Danek, Memphis, TN), and 12 used Synthes (Synthes, Paoli, PA) instrumentation. Three cases of asymptomatic screw breakage or back out at the third cervical vertebrae occurred after the posterior cervical fusions. Three cases of postoperative C5 nerve palsies following anterior three-level cervical corpectomies were noted in patients undergoing complex revisions ACF, resolving in 4 weeks, 4 months and 6 months. One patient developed a posterior cervical wound infection requiring debridement and plastic surgery closure. There were three deaths related to complications of multiple myeloma and progression of the patients' underlying metastatic disease. There were no cases of iatrogenic spinal cord injury, progressive neurologic deficit or progressive kyphotic deformity. No cases had failure of the anterior cervical instrumentation, and no anterior cervical construct needed revision. No cases required additional surgery for revision of the instrumented posterior cervical fusions.Discussion: Long anterior cervical plate instrumentation has a high published incidence of failure [1], a 53% pseudarthrosis rate [2], graft displacement in 3 of 33 patients with two-level corpectomy and long plate fixation [3], anterior hardware failure in 11 of 49 patients with anterior plates and anterior hardware failure in 4 of 39 patients who underwent multilevel cervical corpectomy [4]. Posterior segmental fixation with lateral mass plates provides excellent stability and a reliable fixation of the cervical spine in cases of cervical instability involving three or more vertebral levels. Although useful as a stand-alone technique, multilevel posterior cervical lateral mass plating can have a significant protective effect on complex anterior reconstructions, especially those requiring long anterior cervical instrumentation. This series of 66 consecutive patients from three major spinal centers illustrated that posterior lateral mass fixation can be done safely with minimal morbidity while significantly enhancing the stability and durability of complex cervical reconstructions. There was no incidence of postoperative cervical kyphosis or failure of the posterior cervical fusion requiring revision. More importantly, no patient in the study had a failure of his or her anterior cervical constructs.

A new anterior cervical instrumentation system combining an intradiscal cage with an integrated plate: an early technical report.

To provide a technical report on a new device. Early outcome assessment of patients undergoing anterior cervical decompression and stabilization with the described technique. To detail the operative and technical aspects of the new anterior cervical instrumentation and to identify its suitability for an extensive clinical study. The controversy over the need for fusion in the surgery of cervical disc disease is in part fueled by the absence of an ideal technique. However, the design of the integrated anterior cervical plate and cage device (PCB) appears to provide immediate stability and to restore disc height and cervical lordosis in addition to reducing graft recipient and donor site-related complications. After a standard anterior cervical discectomy and preparation of the disc space, the correct size of the cage with integrated plate is inserted. Self-tapping screws are inserted without image intensifier. Cancellous bone chips are used. The technique was used in 29 patients that were followed prospectively from 5 to 24 months (median 8 months, interquartile range 6-15 months). The technique was easy to learn and implement. The authors' experience has been free of intraoperative complications. After surgery no screw backout or device failure was identified. Twenty-seven patients improved clinically. Donor site morbidity was trivial. No collars were applied after surgery. The design of the system appears to prevent bone-graft recipient site and donor site complications, provides immediate biomechanical stability, prevents screw backout or breakage, and restores posterior interbody height and lordosis. The device is of sufficient promise to warrant further close evaluation focusing on long-term outcome. The new radiolucent version has potential advantages for the assessment of fusion.

Anterior Plate Instrumentation for Disorders of the Subaxial Cervical Spine

Anterior cervical plate instrumentation is useful in the maintenance of cervical alignment, the prevention of graft extrusion, and the development of late deformity as well as potentially avoiding the need for a secondary posterior cervical procedure in the setting of cervical trauma. Its role in cervical reconstruction after decompression for cervical spondylosis is evolving. The definite risks of anterior cervical instrumentation should be considered, that is, screw and plate displacement or screw violation of neurologic structures, before the implementation of this form of fixation.

Anterior instrumentation in thetreatment of lower cervical spine injuries

Anterior cervical instrumentation is a valuable adjunct to bony fusion techniques in obtaining internal stability to thecervical spine following trauma. Anterior plate fixator may obviate the need for a subsequent posterior procedure in cases of associated posterior cervical ligamentous instability, decrease the potential for loss of alignment or deformity, prevent graft dislodgment, and minimize the need for restrictive external immobilization for easier rehabilitation.

Biomechanical Evaluation of Caspar Cervical Screws

Anterior cervical instrumentation is used as an adjunct to bone fusion; however, definitive biomechanical data to support some applications and techniques are lacking. In the absence of supportive experimental data, posterior cortical penetration has been recommended with the Caspar system. Previously, we compared the axial pull-out strength of Caspar screws with and without posterior cortical penetration. This study compares the stability of unicortical versus bicortical screw penetration groups under cyclical loading simulating physiological flexion-extension. Caspar screws were placed in human cadaveric vertebrae with or without posterior cortical purchase. Each screw was separately tested, simulating flexion-extension to 200 cycles. Deformation time data allowed a direct comparison of screw "wobble" with and without posterior cortical purchase. The mean deformation differences between subcortical and bicortical groups were statistically significant and increased over time within both groups. Enhanced stability was noted with bicortical purchase throughout most of the examined range, becoming more pronounced over longer periods of cyclical loading. Significant (P < 0.05) increases in deformation over time were noted for both groups, suggesting potentially significant deterioration at the screw-bone interface, despite bicortical purchase. Such deterioration with repeated flexion-extension loading may be of concern in the use of Caspar plates in the presence of multicolumn instability.

Pull-out strength of Caspar cervical screws.

Anterior cervical instrumentation as an adjunct to bone fusion has an important role in cervical spine surgery. Posterior vertebral body cortex purchase is strongly recommended in the use of the Caspar system, although few biomechanical data exist to validate this requirement. In this study, Caspar screws were placed in 43 human cadaveric cervical vertebral bodies, either putting them into the posterior vertebral cortex as identified radiographically or penetrating it by 2 mm as recommended in the literature. Pull-out tests were conducted with tension applied to a connected plate at 0.25 mm/s, and force-deformation data were obtained. Failure typically occurred with clean pull-out; in most instances, cancellous bone remained attached to screw threads. Mean load without posterior cortical purchase was 375 +/- 53 N; with penetration it was 411 +/- 70 N. These differences were nonsignificant. Average deformation to failure was 1.41 +/- 0.10 mm in the group without posterior cortical penetration. In the posterior penetration group, mean deformation was 1.56 +/- 0.16 mm. Again, differences were not significant. Posterior cortical penetration does not improve the pull-out strength of Caspar screws in an isolated vertebral body model, but other biomechanical studies need to be done before insertion methods are altered.