Harrington Compression Rods Research Articles

Results of lumbar pseudarthrosis repair.

Forty patients underwent 47 procedures for repair of a lumbar pseudarthrosis at the University of Minnesota, Twin Cities Scoliosis Center between 1973 and 1986. Forty-three procedures in 36 patients with a minimum follow-up of 2 years were reviewed. Symptoms at the time of surgery included back pain (100%), leg pain (61%), subjective neurologic symptoms (49%), and thigh pain (35%). The diagnosis was made most commonly on the basis of pain radiographs (70%). In 38 cases, posterolateral fusion was performed, using segmental sublaminar wiring in 37%, a variable screw plate in 29%, Harrington compression rods in 16%, and no implant in 18%. Anterior interbody fusion was performed in six cases, including one combined fusion. Follow-up averaged 4.4 years. Solid fusion was achieved in 49% of cases. Eighty-six percent of patients continued to have low-back pain. Clinical outcomes were graded as excellent in 7%, good in 35%, fair in 9%, and failure in 49%. Significantly improved results were seen in patients in whom a solid fusion was obtained (p less than 0.005), in patients who had undergone only one prior surgery on the lumbar spine (p less than 0.01), and in patients in whom the initial fusion had been performed for spondylolisthesis rather than a primarily degenerative disorder (p less than 0.025). A trend toward better results was seen in cases in which the patient did not complain of leg pain preoperatively, in which a Workers' Compensation claim was not involved, and in which a prior attempt at pseudarthrosis repair had not been performed.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomechanical Evaluation of Spinal Fixation Devices

The three-dimentional stability provided by six spinal fixation devices with or without interbody bone graft has been studied in an in vitro biomechanical model using five-vertebral (T11-L3) fresh cadaveric thoracolumbar specimens. An injury was created at T12-L1 by complete transection of the posterior elements and posterior half of the intervertebral disc, leaving the anterior half of the intervertebral disc and anterior longitudinal ligament intact. The three-dimensional rotations and translations, measures of biomechanical instabilities, were determined under physiologic loads for the intact spine and the spinal constructs, ie, injured spine plus instrumentation. The tested devices were: Harrington reverse ratchet rods (HR); Luque rectangle rod (LR); Kaneda device without transverse fixator (KD); Kaneda device with transverse fixators (KT); transpedicular external fixator (EF). In addition, stability tests were performed for KT, EF, and Harrington compression rods with interbody bone graft following a corpectomy (KTB, EFB, and HCB). The constructs were more stable than the intact spine under the four loads in the following order: flexion: EFB, HCB, EF, HR, LR, KTB, and KT; extension: EFB, LR, EF, KTB, HR, and KT; lateral bending: KTB, KT, EFB, KD, EF, HCB, and HR; and axial rotation: EFB.

A Modified Technique for Cervical Facet Fusions

Posterior facet fusion of the cervical spine has been described in the literature as a method of obtaining fusion when posterior elements are deficient because of previous laminectomy or trauma. The technique, as originally described, includes anchoring autologeneic struts of corticocancellous bone to the cervical spine with wires passed through drill holes in the inferior articular facets around the struts of bone graft. When long facet fusions are required, however, it may be impossible to obtain adequate length and shape of the grafts to bridge the desired fusion area. A technique is described that eliminates this problem by substituting thin Harrington compression rods for the autologeneic corticocancellous struts, and using cancellous and corticocancellous bone graft to achieve fusion.

Comparison of Lumbosacral Fixation Devices

Fusion of L4 and L5 to the sacrum has a high incidence of success. Using conventional methods, nonunion is common when long scoliosis fusions are extended to the sacrum. Three methods of instrumentation for fusing the lumbar spine to the sacrum were compared on a spine simulator test stand. Harrington distraction rods from the sacral ala to L1, Luque rods from L1 to the sacrum, and Harrington compression rods from L1 to the sacrum were tested. The use of a spine instrumentation test stand discounted biologic variation in spinal structure. Sequential loading of each test stand-instrumentation construct in torsion, flexion, extension, and lateral bending gave stiffness constants (Ks) for each test mode. Test values had reproducibility of greater than 94%. Ks illustrates the inability of Harrington distraction rods to the sacrum to resist flexion and torsion, but the ability to resist lateral bend and extension. Harrington compression rod and Luque rod constructs have equivalent stiffness in flexion and torsion. Harrington compression rods efficiently resist extension, and Luque rods resist lateral bending. Harrington distraction rods have limited use in lumbosacral junction fixation other than to correct and resist lateral bending.

Thoracic and lumbar spine fusion: postoperative radiologic evaluation.

A retrospective review of 206 consecutive thoracic and lumbar fusions revealed a variety of surgical procedures performed for instability and malalignment after severe trauma. Stabilization procedures included insertion of 103 Harrington distraction and 15 Harrington compression rods, 84 Weiss spings, six Luque rods, and 10 miscellaneous plates and wires as single or multiple devices in combination with anterior and/or posterior fusions. Complications of surgical fusion included nine unhooked rods, six fatigue fractures of rods and springs, five overdistractions of vertebrae, four cases of severe kyphosis, and two failures of reduction. A meaningful postoperative radiologic evaluation can be accomplished only when indications for surgical techniques, their radiologic appearance, and possible complications are known.

Reduction, Stability, and Strength Provided by Internal Fixation Systems for Thoracolumbar Spinal Injuries

Anterior, posterior, and combined thoracolumbar spinal injuries were simulated in human cadaver specimens and then stressed in flexion, before and after stabilization, with Weiss Springs, Roy-Camille plates, vertebral body plates, and Harrington compression and distraction rods. The reduction, stability, and strength were determined for each implant-injury combination. For posterior ligamentous injuries, the Harrington compression system on the laminae gave reduction in extension, stability to that of the intact spine, and failure at 87.6 Nm bending load with 14.1 J energy absorption. For anterior vertebral body fracture, Harrington distraction rods from three vertebrae above to three below the injury gave a reduction in extension with stability similar to that of the intact spine. Failure occurred at 81.6 Nm load, one-third greater than with rods two levels above to two below, and 14.0 J energy absorption, twice that for the short rod. The more unstable combined anterior and posterior injury was satisfactorily reduced only by the long distraction system, which failed at 44.1 Nm load, twice that for the short rod, and 5.7 J energy absorption. By accurately determining what structures have been injured, and appropriate fixation device can be selected and the strength of the stabilized spine estimated. A thorough understanding of the biomechanics of the spine is essential for successful clinical utilization of these experimental data.

Surgical treatment of severe angular kyphosis.

Five patients 10-21 years old were treated for severe angular kyphosis, ranging from 61 to 133 degrees, by a three-stage procedure: 1. distraction in a halo-pelvic apparatus, 2. anterior decompression and/or fusion and 3. posterior fusion with Harrington compression rods. An average correction of 68% and a good cosmetic result were obtained. A solid fusion was achieved in all patients. There were no neurological complications. A 12-year-old girl gained 20 cm in height and the spinal kyphosis was reduced from 133 to 27 degrees.