Harrington Implant
Encyclopedia
The Harrington implant is a stainless steel
surgical device. Historically, this rod was implanted along the spinal column to treat, among other conditions, a lateral or coronal-plane curvature of the spine, or scoliosis
. Up to one million people had Harrington rods implanted for scoliosis between the early 1960s and the late 1990s. The Harrington rod eventually became obsolete as newer, more effective types of spinal instrumentation were developed.
, an orthopedic surgeon in Houston, Texas
.
Harrington rods were intended to provide a means to reduce the curvature and to provide more stability to a spinal fusion. Before the Harrington rod was invented, scoliosis patients had their spines fused without any instrumentation to support it; such fusions required many months in plaster casts, and large curvatures could progress despite fusion.
, neurofibromatosis
, neuromuscular disease
s, severe injuries, and tumors. By far, the most common use for the Harrington rod was in the treatment of scoliosis, for which it was invented.
. It was used at the beginning without performing a spinal fusion
but early results proved fusion as part of the procedure was mandatory, as movement of the unfused spine would cause the metal to fatigue and eventually break. The procedure required the use of a postoperative plaster cast or bracing until vertebral fusion had occurred.
of the lower back (i.e. the backwaist curve), the spine is straightened out into an unnatural position. At first, the unfused spinal segments compensate for the straightening effects, but eventually the discs degenerate and wear down. The patient then develops back pain, has difficulty standing upright, and experiences limitations when walking. Eventually, the problem requires surgery to realign the spine.
As exemplified by Pecina and Dapic in the European Spine Journal (February 2007), flatback syndrome is not inevitable and does not happen to every person with a low Harrington rod instrumented fusion - there are many people who have had Harrington rods for decades with no adverse effects.
Stainless steel
In metallurgy, stainless steel, also known as inox steel or inox from French "inoxydable", is defined as a steel alloy with a minimum of 10.5 or 11% chromium content by mass....
surgical device. Historically, this rod was implanted along the spinal column to treat, among other conditions, a lateral or coronal-plane curvature of the spine, or scoliosis
Scoliosis
Scoliosis is a medical condition in which a person's spine is curved from side to side. Although it is a complex three-dimensional deformity, on an X-ray, viewed from the rear, the spine of an individual with scoliosis may look more like an "S" or a "C" than a straight line...
. Up to one million people had Harrington rods implanted for scoliosis between the early 1960s and the late 1990s. The Harrington rod eventually became obsolete as newer, more effective types of spinal instrumentation were developed.
History
The Harrington implant was developed in 1953 by Paul HarringtonPaul Randall Harrington
Paul Randall Harrington was an American orthopaedic surgeon. He is best known as the designer of the Harrington Rod, the first device for the straightening and immobilization of the spine inside the body. It entered common use in the early 1960s and remained the gold standard for scoliosis...
, an orthopedic surgeon in Houston, Texas
Houston, Texas
Houston is the fourth-largest city in the United States, and the largest city in the state of Texas. According to the 2010 U.S. Census, the city had a population of 2.1 million people within an area of . Houston is the seat of Harris County and the economic center of , which is the ...
.
Harrington rods were intended to provide a means to reduce the curvature and to provide more stability to a spinal fusion. Before the Harrington rod was invented, scoliosis patients had their spines fused without any instrumentation to support it; such fusions required many months in plaster casts, and large curvatures could progress despite fusion.
Purpose
Harrington rod instrumentation is used to treat instability and deformity of the spine. Instability occurs when the spine no longer maintains its normal shape during movement. Such instability results in nerve damage, spinal deformities, and disabling pain. Spinal deformities may be caused by birth defects, fractures, marfan syndromeMarfan syndrome
Marfan syndrome is a genetic disorder of the connective tissue. People with Marfan's tend to be unusually tall, with long limbs and long, thin fingers....
, neurofibromatosis
Neurofibromatosis
Neurofibromatosis is a genetically-inherited disorder in which the nerve tissue grows tumors that may be benign or may cause serious damage by compressing nerves and other tissues...
, neuromuscular disease
Neuromuscular disease
Neuromuscular disease is a very broad term that encompasses many diseases and ailments that either directly, via intrinsic muscle pathology, or indirectly, via nerve pathology, impair the functioning of the muscles....
s, severe injuries, and tumors. By far, the most common use for the Harrington rod was in the treatment of scoliosis, for which it was invented.
Description
The device itself was a stainless steel distraction rod fitted with hooks at both ends and a ratchet and was implanted through an extensive posterior spinal approach, the hooks being secured onto the vertebral laminaeLamina of the vertebral arch
The laminæ are two broad plates, extending dorsally and medially from the pedicles, fusing to complete the roof of the vertebral arch.Their upper borders and the lower parts of their anterior surfaces are rough for the attachment of the ligamenta flava....
. It was used at the beginning without performing a spinal fusion
Spinal fusion
Spinal fusion, also known as spondylodesis or spondylosyndesis, is a surgical technique used to join two or more vertebrae. Supplementary bone tissue, either from the patient or a donor , is used in conjunction with the body's natural bone growth processes to fuse the vertebrae.Fusing of the...
but early results proved fusion as part of the procedure was mandatory, as movement of the unfused spine would cause the metal to fatigue and eventually break. The procedure required the use of a postoperative plaster cast or bracing until vertebral fusion had occurred.
Flatback syndrome
Flatback syndrome is a problem that develops in some patients treated with Harrington rod instrumentation, where the rod extends down into lower part of the lumbar spine. Because the Harrington cannot follow the natural lordosisLordosis
Lordosis is a medical term used to describe an inward curvature of a portion of the lumbar and cervical vertebral column. Two segments of the vertebral column, namely cervical and lumbar, are normally lordotic, that is, they are set in a curve that has its convexity anteriorly and concavity...
of the lower back (i.e. the backwaist curve), the spine is straightened out into an unnatural position. At first, the unfused spinal segments compensate for the straightening effects, but eventually the discs degenerate and wear down. The patient then develops back pain, has difficulty standing upright, and experiences limitations when walking. Eventually, the problem requires surgery to realign the spine.
As exemplified by Pecina and Dapic in the European Spine Journal (February 2007), flatback syndrome is not inevitable and does not happen to every person with a low Harrington rod instrumented fusion - there are many people who have had Harrington rods for decades with no adverse effects.