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Applied Anatomy of the Thoracolumbar Spine

Summary of Key Points The consideration of global anatomy, commonly referred to as spinal alignment or spinal balance, is important in achieving optimal surgical outcomes. Transverse pedicle width is the limiting variable in pedicle screw diameter. Width is usually smallest around T4‒T6, but it does not increase much until lower thoracic segments and the thoracolumbar junction. Lateral to medial angulation of the pedicle is greatest in…

Bone Physiology and Osteoporosis

Summary of Key Points Bone is important for structure, locomotion, protection of vital organs, and mineral metabolism. Osteoporosis is a common condition resulting from decreased bone mineral density and poor bone quality, increasing fracture risk. Osteomalacia results from poor bone mineralization, the most common cause being vitamin D deficiency. Fragility fractures of the spine are the most common manifestation of osteoporosis and result in significant increased…

Muscles and the Spine: Dynamic Stabilization

Summary of Key Points The muscles of the spine provide a “dynamic tension band” that is critical for optimum “balance” of the spine and a curvilinear plane that “loads” the discs, bones, and muscles. Optimum strength and fiber length provide balance through the spine and associated joints of shoulder girdle and pelvic girdle that allows optimum function. There is an absence of evidence that fitness of…

The Intervertebral Disc : Anatomy, Pathophysiology, and Aging

Summary of Key Points The intervertebral disc (IVD) is composed of the inner gelatinous nucleus pulposus (NP) and the outer annulus fibrosus (AF) and flanked by the cartilaginous end plates. The NP is composed primarily of various types of proteoglycans and type II collagen, which creates a hydrophilic environment that allows the NP to absorb water and buffer axial mechanical loads applied to the vertebral column.…

Biomechanical Modeling of the Spine

Summary of Key Points Computational spine models are valuable options for conducting comprehensive biomechanical analyses, especially when clinical and experimental approaches are difficult or impossible. Multibody models and finite element models are complementary techniques used to analyze the biomechanics of the spine and the treatment of pathologic conditions. Multibody models are adapted to assess loads and displacements along the spine and with surgical instrumentation constructs and…

Functional Anatomy of the Spine

Summary of Key Points The natural spinal curvature allows for horizontal gaze while standing in an upright position. The development and maintenance of spinal anatomy and posture are dynamic and vary by individual. Beyond the craniocervical junction, there are seven major spinal ligaments that work to stabilize the subaxial spine in its physiological range of motion. These ligaments also work to restrict the motion of the…

History of Spinal Instrumentation: The Modern Era

Summary of Key Points The development of instrumentation for internal fixation of the spine has dramatically improved the surgeon’s ability to successfully provide surgical intervention for a wide variety of spinal disorders. Internal fixation leads to higher fusion rates and provides more powerful means of correcting spinal deformity. Since the 1970s, there has been an amazing increase in the variety of instrumentation available to provide internal…

History of Spine Biomechanics

Summary of Key Points The field of spine biomechanics has evolved from the time of antiquity to the present. The first 2000 years provided the rich seeds with requisite advancements in spinal anatomy, neurophysiology, mathematics, and physics. Since the 20th century, we have seen the field of spinal biomechanics blossom and grow exponentially along with modern technology. Although the technology of today dwarfs historical feats of…

History of Spine Surgery

Summary of Key Points Although most advances in spine surgery occurred in the 19th and 20th centuries, their roots date back several thousand years. During the antique period, some special spine disorders were described and treated using drugs and orthotics. The Greco-Roman age was associated with a better understanding of spinal disorders and their treatment. Hippocrates and Galen were the most known figures of this period.…

The Surgical Technique of Vagus Nerve Stimulator Implantation

Introduction Vagus nerve stimulation (VNS) is a treatment option for a number of disorders. It is most commonly used to treat medically intractable seizures but has also been approved by the United States Food and Drug Administration (FDA) to treat severe depression ( ). It has been suggested (but not approved by the FDA) that VNS may also be used to treat tremor, obesity, and some…

Neuroprosthetic Surgical Strategies for Neuromuscular Stimulation

Introduction The provision of well-engineered, well-implanted neuroprostheses represents a major advance in the acceptability, safety, and durability of electronic controllers for paralyzed persons. Well-thought-out strategies and progressive understanding of the risks, benefits, and service and maintenance requirements of these devices have led to some experience-based criteria and advice. A stable neurologic physiology and functional level are requirements for a predictable functional reconstructive improvement. A changing responsiveness…

Surgical Technique: Intrathecal Medication Delivery System Implantation

Surgical Planning/Preoperative Considerations Planning for the implantation of an implantable drug delivery system (IDDS) requires considerations for the prevention of hardware infection, ergonomics of system function and comfort of the patient, prevention of pump pocket and catheter complications, and prevention of cerebrospinal fluid (CSF) leak. An IDDS consists of an intrathecal (IT) segment of catheter, a subcutaneous segment of catheter, and an implanted pump. The IT…

Surgical Placement of Leads for Occipital Nerve Stimulation

Introduction Occipital electrode placement into the subcutaneous tissues, innervated by and adjacent to the greater, lesser, and/or third occipital nerves from the C2-3 nerve roots for intractable occipital headache syndromes, continues to be an evolving methodology since the first cases were performed in 1993 and reported in 1999 ( ). These initial cases described a percutaneous method of wire electrode lead placement, which has been verified…

Subcutaneous Peripheral Nerve Field Stimulation for Intractable Pain

Introduction Spinal cord stimulation (SCS) has been accepted as a therapeutic modality for chronic complex pain conditions of the lumbar and cervical spine ( ). Although conventional SCS has been successful for the treatment of radicular pain, either upper extremity or lower extremity, it has been less effective for the relief of axial pain such as chronic low back pain (CLBP). The main reason for this…

Spinal Cord Stimulation: Placement of Surgical Leads via Laminotomy: Techniques and Benefits

Introduction Spinal cord stimulation (SCS) provides a nondestructive and adjustable method of providing symptomatic relief of neuropathic pain across several indications. Based on Melzak and Wall’s Gate Control Theory of Pain ( ), electrical stimulation of dorsal column fibers within the spinal cord replaces painful dysesthesia with a more tolerable tingling paresthesia ( ). Recently, paresthesia-free SCS has been explored, and perhaps a new mechanism of…

Deep Brain Stimulation: Surgical Technique

Introduction Traditionally, deep brain stimulation (DBS) has been performed by using frame-based stereotaxy in an awake patient. Frame-based stereotaxy has been the technique of choice due to its perceived superior accuracy over “frameless” approaches, while awake testing was deemed essential to both confirm clinical efficacy and ensure a well-tolerated side effect profile. In recent years, the tide has shifted toward the use of targeting devices other…

Neuromodulation Using Optogenetics and Related Technologies

Introduction Optogenetics is defined as the use of light-based technologies that are genetically targeted to certain cellular groups or proteins ( ). In practice, optogenetics most often refers to the use of genetically modified, microbial rhodopsins (pigmented light-sensitive membrane proteins) to manipulate the excitability of genetically targeted neurons. Given this high degree of temporal control over targeted neurons, with a well-understood mechanism of action, these techniques…

The Use of New Surgical Technologies for Deep Brain Stimulation

Introduction Deep brain stimulation (DBS) is an established treatment for movement disorders with distinct advantages over best medical therapy and lesioning procedures ( ). In Parkinson disease (PD), for example, in addition to improving motor symptoms, DBS improves the overall quality of life ( ) and is more cost effective than medical therapy alone in younger patients ( ). While the efficacy of lesioning (thalamotomy) may…

Gaming for the Brain: Video Gaming to Rehabilitate the Upper Extremity After Stroke

Rehabilitation Gaming Can Address Major Care Disparities Upper extremity motor disability following damage to the brain makes everyday tasks such as dressing and preparing meals extremely challenging and time-consuming to accomplish. These difficulties exert notable effects on a person’s quality of life ( ). Upper extremity disability is also hugely costly to society. There are an estimated 2.4 million chronic stroke survivors in the United States…

Implanted Sensors in Neuromodulation via Electrical Stimulation

Introduction Neuromodulation systems rely on external control systems to adjust parameters, which control their output. Observation of the patient’s response to stimulation, or the patient’s own perception of stimulation, is used to manually adjust stimulation levels or other parameters to optimize the benefit from the device. Sensor technology can provide data that speed up the optimization process and, in some instances, eliminate the need for user…