Evaluation of Titanium Mesh Cages Used For Anterior Column Support Following Corpectomy in The Thoracic and Lumbar (T1-S1) Region with Minimum Three-Year Follow-up

Purpose: There are some studies on mesh cages used as interbody fusion devices after discectomy. To our knowledge, there is no clinical study analyzing titanium mesh cages (TMC) used for anterior column support following corpectomy. Our purpose was to evaluate the clinical and radiological results and complications after thoracic and lumbar level corpectomy and reconstruction using TMC with either anterior instrumentation, posterior instrumentation or a combination of all and to determine ideal configuration.

Methods: 34 adult patients who had thoracic and/or lumbar corpectomy for various reasons (24 fractures, 5 spinal tuberculosis, 5 deformity) were included. Average age was 48.6 (17-86) years and follow-up ranged from 38 to 68 (mean 32) months. Total 41 level corpectomy (min 1, max 4 levels) was performed. Structural TMC filled with autogenous bone graft was used for anterior column. In addition to TMC and on the same day, 2 had only anterior, 20 had only posterior and 12 had anterior and posterior instrumentation. Standing AP and lateral, supine AP, lateral and both oblique X-rays and high resolution CT reconstruction have been used to assess fusion status for TMC in the anterior column. Sagittal kyphosis angle and sagittal index measurements were made for all consecutive levels containing anterior TMC for every patient's preoperative, immediate postoperative, 6 weeks, 3 months, 6 months, 1 and 2 years and final follow-up postoperative radiographs. Besides the status of anterior and posterior instrumentation, anterior cage status was assessed for settling, migration and/or fatigue. Fusion status for TMC was assessed according to a previously published (Bridwell et al, 1995) fusion grading system. More than 2mm settling and 4º correction loss were accepted to be significant.

Results: Preoperative kyphosis angle was 23.4º on average. Mean preoperative sagittal index was 27.8º for trauma patients. Mean immediate postoperative sagittal correction rate was 96.8%. Mean correction loss was 0.9º (0º-8º). There was no failure of anterior and posterior instrumentations. No cage failure or migration was observed. There was no pseudarthrosis and fusion was achieved in all patients. 6 (17.6%) patients showed cage settling of more than 2mm. Of these 3 had more than 4º and 3 had less than 4º correction loss. These patients with significant settling and correction loss were either osteoporotic with damaged end-plates or no end-plate collar was used in the TMC.

Conclusions: The configuration consisting of TMC+anterior single rod instrumentation+short segment posterior instrumentation after corpectomy involves no correction loss and cage settling and seems to be the ideal solution. There is a risk of correction loss and cage settling in osteoporotic patients when only short segment posterior instrumentation is used, especially with no end-plate collar in the TMC.Posterior instrumentation after corpectomy should be two level above and below in patients with previous laminectomy and serious sagittal plane deformity.