Expansive Midline T-Saw (Modified Spinous Process-Splitting) Laminoplasty for the Treatment of Cervical Myelopathy

Abstract

Laminoplasty procedures for cervical myelopathy were evolved in Japan [1-5]. Open-door laminoplasty was introduced by Hirabayashi in 1978 [1]. Many variations have been described, including sagittal splitting of the spinous processes described Kurokawa et al. in 1982 [4]. In this procedure, spinal canal enlargement is achieved by sagittal splitting of the spinous process with a bur. After opening the hinged hemilaminae to the sides, several blocks of autograft bone are inserted between the two halves and stabilized with wire [4]. This procedure has a number of theoretical and practical advantages. First, the posterior arch can be reconstructed symmetrically as each hemilamina opens on its own hinge. Second, the enlargement of the spinal canal is constantly maintained by the bone grafts [4]. Third, troublesome hemorrhage from the arborizing lateral epidural veins is avoided since there are few veins in the dorsal midline epidural space. To date, the principal disadvantage of the midline spinous process splitting techniques has been the technical difficulty because of the high risk of cord injury during sagittal splitting with a bur. We have developed a safe sagittal splitting technique using a threadwire saw (T-saw, Fig. 1) [6] and called “expansive midline T-saw laminoplasty” [7].