PINAL cord injury is a devastating affliction that may produce lasting functional deficits due to irre- versible damage to both descending and ascending axonal pathways. 43 Laceration of the spinal cord may be caused by bone fragments, gunshot wounds, and stab in- juries. 2,33,35 Functional recovery after complete transection of the spinal cord can occur in mice if dural injury, reten- tion of the ends of the spinal cord, and fibroblastic infil- tration are minimized. 39 Several pathophysiological events occur following lac- eration-related SCI, including wallerian degeneration ros- tral and/or caudal to the injury, myelin loss, reactive glio- sis, infiltration of acute and chronic inflammatory cells, and the development of connective tissue scarring origi- nating from the intra- and extradural compartments. 18,28,29, 34,35,37 The primary injury causes a tear in the meninges, laceration of the spinal cord leading to the retraction of se- vered stumps, and hematoma formation within the lesion gap. Following laceration, a gap in the spinal cord is cre- ated by the tensile strength of the spinal cord, resulting from the nerve root–related tethering of the spinal cord as well as intrinsic spinal cord tissue tension. Shortening the spinal column by approximation of the transected spinal cord stumps 1 leads to regeneration of serotinergic axons across the lesion. 1,3,4 Unrepaired laceration injury of the dura/arachnoid/spi- nal cord leads to the development of scar tissue due to meningeal cells in the pia 13 and ingrowth of connective tis- sue from surrounding muscle and soft tissue. 10 Connective tissue scar and ECM accumulation within the spinal cord stumps have been shown to form a physical barrier that may 18,37 or may not 44 impair axonal sprouting. Adhesions between the spinal cord and dura may cause a tethered cord syndrome, characterized by progressive neurological deterioration in spinal cord–injured patients. 9,27 J. Neurosurg: Spine / Volume 100 / April, 2004 J Neurosurg (Spine 4) 100:343–352, 2004 Dural closure, cord approximation, and clot removal: enhancement of tissue sparing in a novel laceration spinal cord injury model YI PING ZHANG, M.D., CHRISTOPHER IANNOTTI, PH.D., LISA B. E. SHIELDS, M.D., YINGCHUN HAN, M.D., DARLENE A. BURKE, M.A., XIAO-MING XU, M.D., PH.D., AND CHRISTOPHER B. SHIELDS, M.D. Department of Neurological Surgery, Kentucky Spinal Cord Injury Research Center, University of Louisville School of Medicine, Louisville, Kentucky Object. Laceration-induced spinal cord injury (SCI) results in the invasion of a connective tissue scar, progressive damage to the spinal cord due to complex secondary injury mechanisms, and axonal dieback of descending motor path- ways. The authors propose that preparation of the spinal cord for repair strategies should include hematoma removal and dural closure, resulting in apposition of the severed ends of the spinal cord. Such procedures may reduce the size of the postinjury spinal cord cyst as well as limit scar formation. Methods. Using a novel device, the Vibraknife, the authors created a dorsal hemisection of the spinal cord at C-6 in the adult rat. In Group 1 (eight rats), the dura mater was repaired with apposition of the two stumps of the spinal cord to reduce the lesion gap. In Group 2 (10 rats), the dura was not closed and the two cord stumps were not approximat- ed. All rats were killed at 4 weeks postinjury, and the spinal cords from each group were removed and examined using histological, stereological, and immunohistochemical methods. In Group 1 rats a significant reduction of the total lesion volume and connective tissue scar was observed compared with those in Group 2 (Student t-test, p  0.05). Approximation of the stumps did not promote the regeneration of cor- ticospinal tract fibers or sensory axons through the lesion site. Conclusions. Apposition of the severed ends of the spinal cord by dural closure reduces the lesion gap, cystic cav- itation, and connective tissue scar formation. These outcomes may collectively reduce secondary tissue damage at the injury site and shorten the length of the lesion gap, which will facilitate transplantation-mediated axonal regeneration after laceration-induced SCI. KEY WORDS • connective tissue scar • cystic cavitation • dorsal hemisection • inflammation • spinal cord injury • Vibraknife S 343 Abbreviations used in this paper: AP = anteroposterior; BDA = biotinylated dextran amine; CGRP = calcitonin gene–related pro- tein; CTB = cholera toxin subunit-B; ECM = extracellular matrix; GFAP = glial fibrillary acidic protein; ML = mediolateral; PBS = phosphate-buffered saline; SCI = spinal cord injury.