Spinopelvic fixation: indications, anatomical and biomechanical aspects and historical development of methods

A review of the literature on performing spinopelvic fixation for injuries and various pathologies of the spine and pelvis is presented. The review is analytical in nature and was carried out using databases of medical literature and search resources of PubMed and eLibrary. The following aspects are highlighted: the relevance and indications for performing spinopelvic fixation and its anatomical and biomechanical features. The historical aspects of the development of methods for performing spinopelvic fixation are considered and structured. The analysis of various methods of spinopelvic fixation (using hooks, screw insertion into the S2 sacral wings, L-shaped Luque rods, distractors, transiliac rods, Jackson, Harrington and Galveston techniques) was carried out. The features of surgical techniques, their advantages, disadvantages and complications are considered.

Decompression and Instrumentation without Fusion for Spinal Metastases: Loosening Rate and Consequences

Background/Purpose For patients with spinal metastases, decompression surgery was usually followed by instrumentation without fusion. Over time, mechanical stress would lead to loosening of implants. Yet, there is a lack of studies concerning the loosening rate, or the impact on patients when the implants are loosened. We aim at finding the postoperative loosening rate of implant, postoperative survivorship of patients, as well as their correlation with the mode of instrumentation. Methods A retrospective study including patients with metastatic spinal cord compression, who received decompression and instrumentation without fusion in a local hospital in Hong Kong from 2007 to 2014 was carried out. Patients with primary spinal tumour or prior spinal fusion were excluded. Demographics, tumour characteristics, mode of instrumentation, loosening rate of implants, as well as survivorship of patients were retrieved. Radiographs at 1 year postoperation were counter-examined by 2 Orthopaedic specialists on the Electronic Patient Record System. Results Total of 65 operations were retrieved. The age ranged from 27 to 84 years old. The most frequent primary source of malignancy was lung (26.5%), followed by breast (24.62%). Thoracic level (60%) was the most frequent site of spinal metastases. The survivorship at 1 year postoperation was 61.54%. The overall loosening rate of implants was 44.44%, with the Luque rods and sublaminar wire system being the most (70%). None of the cases required revision or removal of implants at 1 year postoperation. Conclusion The loosening rate of implants was high, and it is expected to grow even higher as oncological patients continue to improve in their survivorship with the medical advances such as target therapy. Yet there is still no definite evidence on how the implant loosening would affect patients’ quality of life and clinical performance.

KYPHECTOMY IN PATIENTS WITH MYELOMENINGOCELE: SURGICAL RESULTS AND COMPLICATIONS

Objectives:The lumbar kyphosis in patients with myelomeningocele is a complex deformity whose treatment is mainly surgical. The objective of this study is to summarize the results and complications obtained by the group in 2012 with respect to this group of patients.Method:Performed a retrospective analysis of the medical records and radiographs of patients consecutively operated in 2012. The technique was originally described by Dunn-McCarthy and consists of kyphectomy and posterior fixation using S-shaped Luque rods through the foramina of S1 associated with pedicle screws in the thoracic spine.Results:Six patients were included in the study. The age at surgery was 11 years and 7±22 months and the weight was 29.1±11.9 kg. The procedure lasted 271±87 minutes, with the removal of one or two (mean 1.5) vertebrae from the apex of the kyphosis. Hospitalization time was 10±9 days. The lumbar kyphosis measuring 116.3±37 degrees preoperatively was reduced to 62.5±21 degrees. All patients began to sit without support and to lie in the supine position. Four patients developed postoperative infection and required surgical debridement at the follow-up. One patient had the implant removed after a year due to loosening of the rod in the sacrum.Conclusion:The surgical technique allows excellent functional results in the correction of lumbar kyphosis in patients with myelomeningocele despite high complication rates. It is necessary to conduct studies with a larger number of patients and duration of follow-up to assess whether the use of pedicle screws will decrease the rate of loosening and pseudoarthrosis.

History of instrumentation for stabilization of the subaxial cervical spine

In the past several decades methods have been developed to stabilize the subaxial cervical spine both posteriorly and anteriorly. Methods of posterior stabilization have progressed from interspinous wiring, through facet wiring and sublaminar wiring, to the lateral mass screws with plates and rods that are in use today. Plates for anterior stabilization have evolved from rigid plates requiring bicortical screws through those used with unicortical locking screws, to dynamic load-sharing plates used with variable angle screws. The original description of spinous process wiring was published by Hadra in 1891. In 1942 Rogers described the interspinous wiring method used for trauma-induced cervical instability, which was modified by Bohlman in 1985 (triple wiring technique). Luque rods with sublaminar wires were introduced in the late 1970s to address multilevel and occipitocervical instability. Facet wiring was developed in 1977 by Callahan to address the problem of stabilization when laminae are not present. Wiring remained the method used until Roy-Camille introduced the lateral mass screw–plate construct in the 1980s. The first plate for anterior stabilization was designed by Orozco and Llovet in 1970 and was later refined by Caspar; this was a rigid plate with bicortical screws. Morscher devised unicortical locking screws in the 1980s. The latest concept of dynamic load-sharing plates with variable angle screws was developed in 2000. In this article historical landmarks in surgical methods for the stabilization of the subaxial cervical spine are reviewed.

Aneurysmal Bone Cyst of the Thoracic Spine: Treatment by Excision and Segmental Stabilization with Luque Rods

Preoperative radiological evaluation with magnetic resonance imaging and computed tomography was valuable in planning the surgical management of a destructive lesion of the posterior elements of the thoracic spine that was causing spinal cord compression in an 18-year-old woman. Preoperative recognition of bilateral involvement of the pedicles in addition to the laminae and spinous process led to use of prophylactic segmental stabilization of the spine with Luque rods after successful excision of an aneurysmal bone cyst. This case provides an example of the usefulness of computed tomographic scanning and magnetic resonance imaging in assessing the distribution and location of vertebral tumor and its potential effect on spinal stability. The efficacy of combining radical excision with stabilization for treatment of aneurysmal bone cysts of the spine is emphasized.

Comparison of the Failure Biomechanics of Spinal Fixation Devices

The failure biomechanics of Harrington distraction rods, modified Weiss springs, and Luque rods were studied in intact cadavers and isolated spinal columns using flexion-compression loading. Most spines fractured at T-11 or T-12 at applied loads ranging between 556 and 4220 newtons (mean = 1833 N). After Harrington distraction rod placement, the same spines failed at a mean load of 859 N (42% of control), always as a result of hook extrusion and often including lamina fracture (seven cases). When modified Weiss springs were used, the spines failed at a mean load of 1128 N (54% of control) by allowing the spine to bend to the initial failure angle; in most instances, deformities resolved when the load was reduced. Luque rods were tested in four specimens; these provided the most rigid stabilization and failed at 83% of control values. Modified Weiss springs often maintain spinal stability better than Harrington distraction rods.