Harrington implant

The Harrington Implant (or Harrington Rod) 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.

History

This treatment was developed in 1953 by Dr. Paul Harrington, an orthopedic surgeon in Houston, Texas. It was 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 syndrome, neurofibromatosis, neuromuscular diseases, 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 laminae. 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.

Flatback Syndrome caused by lumbar fusion using a Harrington Rod

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 could not follow the natural lordosis of the lower back (ie the backwaist curve), the spine was straightened out into an unnatural position. At first, the unfused spinal segments would compensate for the straightening effects, but eventually the discs would degenerate and wear down. The patient then develops back pain, difficulty standing upright, and experiences limitations when walking. Eventually, the problem requires surgery to realign the spine. As exemplified by Pecina & Dapic in the European Spine Journal Feb 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 Harringtons for decades with no adverse effects.

A patient's experience of spinal fusion surgery in the 1960s

These notes refer to the timescales in 1966-70, and are based on the experience of a patient. This information is of historical interest but does not reflect the experiences of everyone who had Harrington Rods implanted, as surgical and nursing techniques improved over the course of time.

Patients were initially admitted for two days' observation to ensure they were in good general health. On the third day, they underwent the operation, under full anaesthetic. The rod was fixed in the optimum position for the degree and place of curvature, and fixed securely using a pair of hooks that linked it to the spine. The rod had ratchet ends that fitted through holes in the hooks, and the compression of the spine kept the whole thing in place.

Under anaesthetic, the patient was stretched to straighten the spine, and the ratchet system held everything in its new position. The design also allowed for additional growth in the patient, or post-operative straightening, because as the spine got longer, the ratchet allowed the rod to move in only one direction. Rods came in a variety of lengths from around 10 to 30 cm, depending on the patient's need.

The first stage of post-operative treatment took place at the unit because patients needed to be kept as immobile as possible. They spent two weeks on a "Stryker" bed that allowed the patient to be either flat on their back, or flat on their front. (Stryker is a Canadian trademark covering a variety of specialist orthopaedic beds.) Lying on a side was not allowed, nor was turning from front to back. The bed was designed to allow nursing staff to roll the patient every four hours by strapping on a new section and rotating the whole structure.

At the end of two weeks, or longer, if the surgeon felt it was necessary, the patient was put into a surgical plaster cast, covering at least the length of the spine, and sometimes the neck. After the cast set, the patient was allowed to go home where they spent a further 12 weeks on full bed rest, and told to operate "log roll" conditions. That meant being horizontal at all times — no sitting or standing, no more than one pillow, and only bending one leg at once, when lying on the back.

At the end of the 12 weeks, the patient was returned to the unit to spend the next 10 days to 2 weeks learning to walk again. They faced two main problems:
* Having spent more than 3 months in bed, the patient was weak and frequently carrying 10-15 kilograms of plaster;
* The patient's spine was frequently a very different shape from before the operation, so balance was difficult. Many felt that they were falling over because they had spent many years, leaning sideways before the operation.

After learning to walk again, the patient was fitted with a surgical corset that had steel-reinforcing rods down the back. This had to be worn for 24 hours a day, and could be removed only for bathing. The time-scale for this stage of the treatment was extremely variable, but rarely less than a year. Termination of the corset-stage began with removal during sleep for a few months, before the patient was allowed to abandon it altogether.

During the treatment, and up to losing the corset, patients were forbidden to undergo any form of physical exercise, including swimming, at least in the late 1960s and early 1970s. As doctors realised that the treatment was quite robust, the restrictions began to be lifted, and the timescale for the whole process reduced.

References

* [http://www.livingwithcerebralpalsy.com/page.php?pg=140 Living with cerebral palsy]
* [http://www.medscape.com/viewarticle/468467_3 Medscape - Modern Posterior Thoracic Instrumentation]
* [http://www.ingentaconnect.com/content/klu/586/2007/00000016/00000002/00000223 - 20-year follow-up of Harrington instrumentation in the treatment of severe Idiopathic Scoliosis, Pecina & Dapic, European Spine Journal Vol 16 No 2 Feb 2007(subscription only)]
* [http://www.spineuniverse.com/displayarticle.php/article2052.html - Scoliosis Surgery: Flatback Syndrome and Surgery, by Baron S. Lonner MD, Director of Scoliosis Associates in New York]