Posterior keyhole corpectomy with percutaneous pedicle screw stabilization in the surgical management of lumbar burst fractures.

OBJECTIVE: The authors present a new method of minimally invasive surgical management of lumbar burst fractures through the posterior approach. The method includes minimally invasive corpectomy and interbody fusion, both of which are performed through a keyhole approach, and percutaneous pedicle screw fixation of the fracture. The technique of the posterior keyhole corpectomy presented in this report is a novel and original concept of the first author (AM). The percutaneous pedicle screw stabilization is performed with the use of a percutaneous instrumentation system (Sextant; Medtronic, Inc., Minneapolis, MN). The Sextant system has been dedicated and used in nontrauma degenerative cases; the novel aspect of this system is its application in spine fractures. Indications for the method include Denis classification subtype B or Magerl subtype A.3.1 burst fractures. Both subtypes represent fractures with failure and retropulsion of the upper part of the vertebral body.
METHODS: The clinical experience of this study includes four cases of burst fractures with significant retropulsion and occlusion of the spinal canal. Long-term results were assessed at a minimum follow-up period of 1 year (maximum, 3.5 yr). The follow-up assessments included: 1) the quality of decompression and reconstruction of the spinal canal (computed tomographic and magnetic resonance imaging scanning); 2) the stability of the operated segment (dynamic x-rays); 3) the quality of interbody fusion (computed tomographic scanning and dynamic x-rays); and 4) correction of the fracture kyphosis and its postoperative loss (measurements of Cobb angles for the assessment of sagittal plane deformity). The minimum armamentarium requirements for this method include a typical micro lumbar discectomy retractor set; a surgical microscope; two-plane intraoperative fluoroscopy; and a system for percutaneous pedicle screw stabilization (Sextant). "Posterior keyhole corpectomy" indicates corpectomy of the posterior upper half of the vertebral body or removal of the retropulsed bone fragment via two keyhole skin incisions on both sides of the spinous process (each skin incision measures 2 to 3 cm long). Exposure of the retropulsed fragment (the posterior upper part of the vertebral body) is achieved by medial or complete facetectomy along with complete or medial resection of the pedicle. This has to be performed bilaterally. Percutaneous stabilization requires four additional stab skin incisions.
RESULTS: We observed no surgery-related complications (neurological, hardware, dural tears, or deep or superficial wound infections); there was perfect decompression and clearance of the spinal canal (confirmed by computed tomographic and magnetic resonance imaging scanning); and there was solid stability at the affected segments (confirmed by dynamic x-rays). Healed fusion was noted in all patients but one. The latter patient had no clinical symptoms of spinal instability. Kyphotic deformity was corrected and reversed into lordosis in three patients. Loss of deformity correction was noted in all patients; however, all patients retained lordotic alignment of the affected segment.
CONCLUSION: The advantages of this method include sparing the posterior elements (lamina, spinous process, supraspinous and interspinous ligaments, and paravertebral muscles), safety of the decompression provided by the use of a surgical microscope, and perfect illumination of the operating field. The drawbacks of the method include limitation to certain types of burst fractures, the method is surgically demanding, and the method requires development of a special retractor system to eliminate the cumbersome alternate insertion and the reinsertions of the typical microdiscectomy retractor set.