Spinal-Fusion Surgery — Advances and Concerns
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《新英格兰医药杂志》
Spinal arthrodesis (the creation of a fusion) was developed for the treatment of instability and deformity due to tuberculosis, scoliosis, and traumatic injury. Modern spinal surgery was helped by the introduction in 1911 of the tibial graft by Albee and the iliac-crest graft by Hibbs. These techniques required prolonged postoperative bed rest and the use of braces and casts for immobilization, and their use was complicated by a rate of pseudarthrosis of at least 20 percent. Surgical implants for the spine were developed later in the century in an attempt to improve the rate of fusion and hasten the recovery of patients after surgery. Today, the population of patients in whom surgeons use arthrodesis has changed greatly.
About two thirds of adults have low back pain at some time. Of the 65 million people in the United States with low back pain, approximately 151,000 undergo fusion of the lumbar spine each year. The traditional techniques used autologous bone to create a spinal fusion. The osteogenic potential of the donor bone and the prepared host site were relied on to produce successful fusion. In this issue of the Journal, Deyo et al. (pages 722–726) discuss spinal-fusion surgery and call for caution in its use.
Current surgical technology permits the use of surgical implants in the spine with the goals of correcting deformity, managing pain, and improving arthrodesis through the immobilization of the spine; it also allows osteoblastic activity to take place in a fusion mass that leads to the formation of new bony trabeculae. The use of pedicle-screw fixation, with intervertebral fixation using plates or rods, is relatively new and has already become commonplace. In addition, intervertebral cage devices have been developed that can be inserted by means of either an anterior or a posterior approach. The cage is metallic and is filled with bone-graft material in order to produce fusion between one vertebral body and the next. The cage itself distracts the intervertebral space, helps to immobilize the segment so as to promote fusion, and is perforated in order to allow the ingrowth of bone from the vertebral body to the graft within the cage.
The anatomy of a degenerative, anterior, L5–sacrum spondylolisthesis is shown in Figure 1. Neural decompression can be performed through a laminectomy, and a cage can be placed in the prepared intervertebral space for arthrodesis. With the use of a posterolateral approach, pedicle screws are placed bilaterally in the lumbar and sacral vertebrae. The screw connectors lie just dorsal to the transverse processes that arise from the pedicles. The transverse processes are decorticated on their dorsal aspect with the use of gouges, curettes, or power burs, as shown in Figure 2. Once decortication is complete and the screws have been placed, a bone graft is placed between one transverse process and the next. The intervertebral connecting rod or plate is then placed as shown in Figure 2B, and the wound is closed. The use of such surgical instrumentation always carries some risk of technical complications, increased operative time, greater blood loss, and higher costs.
Figure 1. Degenerative Spondylolisthesis at L5–S1.
As shown in Panel A, the intervertebral disk has lost height and bulges out. In Panel B, an intervertebral cage has been placed to correct the loss of height. Pedicle screws have been placed through a metal plate and into L5 and the sacrum.
Figure 2. Creation of an Instrumented Surgical Fusion of L5 and S1.
An intervertebral cage is in place between the decorticated endplates of L5 and S1. The L5 transverse process and the sacral alae have been decorticated, with one bone graft in place on the left (Panel A). An L5 laminectomy allows for decompression and cage placement. In Panel B, spine plates and bone graft have been placed to produce the fusion between L5 and the sacrum.
In order to achieve a successful arthrodesis, it is traditional to use an autologous bone graft, usually from the iliac crest, because of its substantial osteogenic activity. The goal is to produce a solid fusion mass connecting one vertebra to another. Bone-graft donor sites can be a source of pain, infection, and additional blood loss, and removing the bone takes extra time during surgery. Therefore, substitutes for autologous grafts have recently been developed. Successful fusion is biologically dependent on osteogenesis, which requires the stimulation of osteoblasts to produce bone tissue (osteoinduction) and to cause the growth of bony trabeculae (osteoconduction).
Recently introduced substitutes for autologous bone grafts include frozen or freeze-dried allografts from cadaveric sources. These materials have less osteoinductive potential, but they do retain their osteoconductive property, permitting the growth of bony trabeculae. Bone allografts do not tend to be rejected, but there is some risk of the transmission of infection, including human immunodeficiency virus infection. Other materials being used as bone-graft substitutes include hydroxyapatite, tricalcium phosphate, and collagen sponges with bone morphogenic protein. These substitutes are currently available and are being used in clinical series. The advances in spinal-fusion surgery are exciting, but they continue to provoke questions about the appropriate clinical place for this complex surgery.
Source Information
From the Department of Orthopedic Surgery, Harvard Medical School, Beth Israel Deaconess Medical Center, and Harvard Vanguard Medical Associates, Boston.(Stephen J. Lipson, M.D.)
About two thirds of adults have low back pain at some time. Of the 65 million people in the United States with low back pain, approximately 151,000 undergo fusion of the lumbar spine each year. The traditional techniques used autologous bone to create a spinal fusion. The osteogenic potential of the donor bone and the prepared host site were relied on to produce successful fusion. In this issue of the Journal, Deyo et al. (pages 722–726) discuss spinal-fusion surgery and call for caution in its use.
Current surgical technology permits the use of surgical implants in the spine with the goals of correcting deformity, managing pain, and improving arthrodesis through the immobilization of the spine; it also allows osteoblastic activity to take place in a fusion mass that leads to the formation of new bony trabeculae. The use of pedicle-screw fixation, with intervertebral fixation using plates or rods, is relatively new and has already become commonplace. In addition, intervertebral cage devices have been developed that can be inserted by means of either an anterior or a posterior approach. The cage is metallic and is filled with bone-graft material in order to produce fusion between one vertebral body and the next. The cage itself distracts the intervertebral space, helps to immobilize the segment so as to promote fusion, and is perforated in order to allow the ingrowth of bone from the vertebral body to the graft within the cage.
The anatomy of a degenerative, anterior, L5–sacrum spondylolisthesis is shown in Figure 1. Neural decompression can be performed through a laminectomy, and a cage can be placed in the prepared intervertebral space for arthrodesis. With the use of a posterolateral approach, pedicle screws are placed bilaterally in the lumbar and sacral vertebrae. The screw connectors lie just dorsal to the transverse processes that arise from the pedicles. The transverse processes are decorticated on their dorsal aspect with the use of gouges, curettes, or power burs, as shown in Figure 2. Once decortication is complete and the screws have been placed, a bone graft is placed between one transverse process and the next. The intervertebral connecting rod or plate is then placed as shown in Figure 2B, and the wound is closed. The use of such surgical instrumentation always carries some risk of technical complications, increased operative time, greater blood loss, and higher costs.
Figure 1. Degenerative Spondylolisthesis at L5–S1.
As shown in Panel A, the intervertebral disk has lost height and bulges out. In Panel B, an intervertebral cage has been placed to correct the loss of height. Pedicle screws have been placed through a metal plate and into L5 and the sacrum.
Figure 2. Creation of an Instrumented Surgical Fusion of L5 and S1.
An intervertebral cage is in place between the decorticated endplates of L5 and S1. The L5 transverse process and the sacral alae have been decorticated, with one bone graft in place on the left (Panel A). An L5 laminectomy allows for decompression and cage placement. In Panel B, spine plates and bone graft have been placed to produce the fusion between L5 and the sacrum.
In order to achieve a successful arthrodesis, it is traditional to use an autologous bone graft, usually from the iliac crest, because of its substantial osteogenic activity. The goal is to produce a solid fusion mass connecting one vertebra to another. Bone-graft donor sites can be a source of pain, infection, and additional blood loss, and removing the bone takes extra time during surgery. Therefore, substitutes for autologous grafts have recently been developed. Successful fusion is biologically dependent on osteogenesis, which requires the stimulation of osteoblasts to produce bone tissue (osteoinduction) and to cause the growth of bony trabeculae (osteoconduction).
Recently introduced substitutes for autologous bone grafts include frozen or freeze-dried allografts from cadaveric sources. These materials have less osteoinductive potential, but they do retain their osteoconductive property, permitting the growth of bony trabeculae. Bone allografts do not tend to be rejected, but there is some risk of the transmission of infection, including human immunodeficiency virus infection. Other materials being used as bone-graft substitutes include hydroxyapatite, tricalcium phosphate, and collagen sponges with bone morphogenic protein. These substitutes are currently available and are being used in clinical series. The advances in spinal-fusion surgery are exciting, but they continue to provoke questions about the appropriate clinical place for this complex surgery.
Source Information
From the Department of Orthopedic Surgery, Harvard Medical School, Beth Israel Deaconess Medical Center, and Harvard Vanguard Medical Associates, Boston.(Stephen J. Lipson, M.D.)