Lateral mass plate fixation for severe cervical instability

Abstract

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.