Medical Apparatus: Imaging Guide to Orthopedic Devices
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Neck & Spine

Overlying Materials

Neck Apparatus

Cervical Spine

Thoracic & Lumbar Spine

References

 

 

 

Medical Devices of the Neck & Spine continued


by Tim B Hunter, MD, MSc and Mihra S Taljanovic, MD, PhD

 

Thoracic and Lumbar Spine Instrumentation continued...

 

Metal-on-polyethylene total disk replacement at L4-5 Metal-on-polyethylene total disk replacement at L4-5 and L5-S1
Metal-on-polyethylene disk replacement Metal-on-polyethylene disk replacement Lumbar spine total disk replacements at L4-5 and L5-S1 Lumbar spine total disk replacements at L4-5 and L5-S1
46 year-old woman with degenerative disk disease. There is also a ligamentous fixation screw at L4. 47 year-old man
Lumbar spine fusion and metal-on-polyethylene disk replacement at L4-5 and L5-S1 Thoracic insufficiency syndrome (TIS) devices
Lumbar spine fusion and metal-on-polyethylene disks Lumbar spine fusion and metal-on-polyethylene disks Vertebral titanium expandable rib Expandable titanium rib
31 year-old man with chronic low back pain. In addition to the total disk replacements at L4-5 and L5-S1 there is also a laminectomy from L4 to S1 with posterolateral bony fusion masses and pedicle screws with connecting rods on each side. These are two examples of VEPTR-VEPTRII Vertical Expandable Prosthetic Titanium Rib (DePuy Synthes). © DePuy Synthes 2016.  All rights reserved. VEPTRII™ is a trademark of DePuy Synthes.
Patient with severe spinal deformity treated by expandable rib devices    
Severe congenital scoliosis before therapy Expandable ribs    
Young child with congenital spinal anomaly and progressive scoliosis. Two expandable ribs were placed to stabilize and reduce the scoliosis.    

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Thoracic Insufficiency Syndrome (TIS) Devices; Expandable ribs

TIS devices devices are designed for skeletally immature patients who have severe, progressive spinal deformity or thoracic deformity and who are at risk for developing thoracic insufficiency syndrome in which the thorax and spine cannot support normal respiration or lung growth. This includes patients with progressive congenital, neuromuscular, or idiopathic scoliosis (figure: congenital spinal deformity and expandable ribs). Such devices expand the rib cage or slow progressive deformity of the thorax by mechanically stabilizing the thorax and distracting a portion of the rib cage. TIS apparatus consists of rib to rib, rib to spinal lamina, or rib to pelvis expandable bars which can adjust to patient growth (figure: TIS devices). There is limited experience with the use of expandable ribs and similar devices. There does seem to be a high rate of complications, and it is possible many patients with congenital scoliosis may do well with advanced bracing rather than spinal or thoracic cage surgery (Weiss, 2016).

 

Spinal Column Stimulators; Bone Stimulators; Intrathecal Drug Delivery Pumps; Spinal Braces; and Sacral Stimulators

Patients with intractable pain and muscle spasms are difficult to treat. They often become dependent on large doses of pain medication and cannot perform normal activities of daily living. Some patients receive considerable pain relief through electrical stimulation of the spinal cord or dorsal nerve roots. Devices designed for this function are the transcutaneous electrical neural stimulation (TENS) and dorsal column stimulation (DCS) units (Burton, 1975; Campos, 1987; Mundinger, 1982; Ray, 1981; Richardson, 1979). The TENS unit consists of stimulating electrodes in externally placed patches similar to those used in electrocardiography.

A DCS unit is placed percutaneously or surgically in the dorsal epidural space or subarachnoid space near a dorsal root ganglion, with a battery pack (pulse generator) placed in the subcutaneous tissues of the back. The battery pack, stimulator wires, and electrodes are partially metallic and easily seen on radiographs (figure: dorsal column stimulator in cervical spine; figure: dorsal column stimulator in thoracic spine). The electrodes are often enmeshed in Teflon or a plastic matrix, and they look like a set of unconnected metallic dots on radiographs. Unfortunately, in many patients the relief from pain and spasticity provided by these devices decreases with time, possibly because the electrodes are eventually enveloped by reactive fibrous tissues.

Bone stimulator devices appear similar to TENS and DCS units, and they may be confused with them. They have a completely different function, however, and are located on bony fusion masses and not in the epidural space (figure: bone stimulator). Bone stimulators are designed to stimulate bone growth to increase the likelihood of solid postoperative bone fusion at the operative sites, especially in smokers. These devices are often used in lower lumbar spine surgery, which frequently consists of a laminectomy and placement of a metallic spinal fixation system and posterolateral bony fusion masses. These masses consist of multiple packed together pieces of bone harvested from one of the iliac crests. Solid fusion of the bone masses is very important for the long-term success of the spinal fixation system.

The battery pack generator of the bone stimulator is placed in the subcutaneous tissues of the lower back. Wires extend from the battery pack to the bony fusion masses on each side. At the end of the wires are stimulating electrodes. A bone stimulator does not hasten bone fusion, but it may promote a higher percentage of eventual fusion of the bone mass. Usually, the battery pack generator is removed after several months, and the electrodes are left embedded in the fusion mass.

Intrathecal drug delivery pumps are another technique for treating patients with intractable pain and muscle spasticity (Ray, 1981; Deer, 2011). These pumps consist of a catheter placed in the spinal subarachnoid space, usually in the lumbar area, and a battery-operated pump located in a nearby subcutaneous pocket (figure: intrathecal drug delivery catheter). There is usually infusion of opiods and other analgesics in direct proximity to opiod receptors in the dorsal horn of the spinal cord where small doses can produce marked analgesic effects with fewer side effects than with systemic opiods. The pump is attached to the catheter, and it delivers a carefully controlled volume of medication to the CSF. Because the pump lies in a convenient subcutaneous location, it can easily be refilled via a needle inserted into its access port through the skin.

Intrathecal drug delivery pumps are most commonly used to deliver intrathecal morphine to ameliorate intractable pain in cancer patients. Other medications, such as local anesthetics and chemotherapeutic agents, may be infused in a similar manner. Similar chemotherapeutic infusion pumps are sometimes used in the abdomen and pelvis to deliver chemotherapeutic agents into the vascular system that feeds an abdominal or pelvic tumor mass.

Baclofen is a medication used to treat spasticity seen with multiple sclerosis, spinal cord injuries, various neurological diseases, and assorted muscular conditions. It may be taken orally but is sometimes instilled via an intrathecal pump similar to instillation of intrathecal morphine, local anesthetics, or chemotherapeutic agents (figure: Baclofen intrathecal pump). Similar to other intrathecal pumps, the Baclofen pump lies in a convenient subcutaneous position usually over the upper abdomen.

After spinal surgery or after the patient has suffered a vertebral compression fracture, a close fitting brace is often worn for several weeks to give support to the spinal column and ease the patient's pain. This allows for ambulation and stabilization of the spine for healing and protection of the spinal cord. Frequently seen are Boston or TLSO (thoracolumbar sacral orthosis) braces. These are form fitting rigid braces composed mainly of plastic and worn around the thoracolumbar region limiting back motion (figure: TLSO brace).

Milwaukee or CTLSO (cervico-thoracoc-lumbar sacral orthosis) braces are also sometimes used for postoperative or post-injury immobilization of the cervicothoracic region. They are most commonly seen in skeletally immature individuals and are used to treat scoliosis and kyphosis as opposed to the TLSO brace being most commonly used to treat vertebral injuries. A Milwaukee brace is a full torso brace that extends from the base of the skull to the pelvis, while a TLSO brace is more limited to the thoracolumbar region.

A recent study concluded brace treatment was associated with better outcomes in patients with adolescent scoliosis (Weinstein, 2013). However, it remains uncertain which patients would benefit from such braces as the decision to commit an adolescent patient to several years of wearing a brace should not be taking lightly (Carragee, 2013). The braces are often uncomfortable and suffer from poor patient acceptance in young adolescent women who constitute the majority of adolescent scoliosis patients. Many patients with adolescent scoliosis do well with no treatment. The challenge is determining which patients would benefit from bracing and which would not benefit from it (Carragee, 2013; Weinstein, 2013).

Sacral plexus nerve stimulation (also known as sacral neuromodulation therapy) is for long-term treatment of patients with bladder dysfunction, such as urinary urge incontinence, urinary frequency, or urinary retention (van Kerrebroeck, 1984; Steele, 2012; Noblett, 2014). It may also be effective for rectal dysfunction with fecal incontinence or chronic constipation. One or more wire electrodes are placed in the vicinity of the sacral roots at the level of the sacral foramina (figures: sacral nerve stimulation). The wires are connected to an external stimulator. Proper placement of the stimulating wires varies depending on the patient and the problem being addressed. S3 nerve root stimulation, for example, sometimes produces a contraction of the levator muscles, the detrusor musculature, the urethral sphincter, and plantar flexion of the great toes. The sacral root on each side that gives the best subjective patient response is used for the stimulation.

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Devices of the Neck and Spine References


Author contact information

Tim Hunter
Email: hunter@radiology.arizona.edu


COPYRIGHT 2013: TBH
All Rights Reserved

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