Assessment of corrosion in retrieved spine implants.

Recently the use of dissimilar metals in spine instrumentation has increased, especially in the case of adult deformities, where rods made from Cobalt Chrome alloys (CoCr) are used with Titanium (Ti) screws. The use of dissimilar metals increases the risk of galvanic corrosion and patients have required revision spine surgery due to severe metallosis that may have been caused by corrosion. We aimed to assess the presence of corrosion in spine implant retrievals from constructs with two types of material combinations: similar (Ti/Ti) and dissimilar (CoCr/Ti). First, we devised a grading score for corrosion of the rod-fixture junctions. Then, we applied this score to a collection of retrieved spine implants. Our proposed corrosion grading score was proven reliable (kappa > 0.7). We found no significant difference in the scores between 4 CoCr and 11 Ti rods (p = 0.0642). There was no indication that time of implantation had an effect on the corrosion score (p = 0.9361). We recommend surgeons avoid using implants designs with dissimilar metals to reduce the risk of corrosion whilst a larger scale study of retrieved spine implants is conducted. Future studies can now use our scoring system for spine implant corrosion. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 632-638, 2018.

Clinically orientated classification incorporating shoulder balance for the surgical treatment of adolescent idiopathic scoliosis.

PURPOSE: The achievement of shoulder balance is an important measure of successful scoliosis surgery. No previously described classification system has taken shoulder balance into account. We propose a simple classification system for AIS based on two components which include the curve type and shoulder level. METHODS: Altogether, three curve types have been defined according to the size and location of the curves, each curve pattern is subdivided into type A or B depending on the shoulder level. This classification was tested for interobserver reproducibility and intraobserver reliability. A retrospective analysis of the radiographs of 232 consecutive cases of AIS patients treated surgically between 2005 and 2009 was also performed. RESULTS: Three major types and six subtypes were identified. Type I accounted for 30 %, type II 28 % and type III 42 %. The retrospective analysis showed three patients developed a decompensation that required extension of the fusion. One case developed worsening of shoulder balance requiring further surgery. This classification was tested for interobserver and intraobserver reliability. The mean kappa coefficients for interobserver reproducibility ranged from 0.89 to 0.952, while the mean kappa value for intraobserver reliability was 0.964 indicating a good-to-excellent reliability. CONCLUSIONS: The treatment algorithm guides the spinal surgeon to achieve optimal curve correction and postoperative shoulder balance whilst fusing the smallest number of spinal segments. The high interobserver reproducibility and intraobserver reliability makes it an invaluable tool to describe scoliosis curves in everyday clinical practice.

Early results of a remotely-operated magnetic growth rod in early-onset scoliosis.

Conventional growing rods are the most commonly used distraction-based devices in the treatment of progressive early-onset scoliosis. This technique requires repeated lengthenings with the patient anaesthetised in the operating theatre. We describe the outcomes and complications of using a non-invasive magnetically controlled growing rod (MCGR) in children with early-onset scoliosis. Lengthening is performed on an outpatient basis using an external remote control with the patient awake.Between November 2009 and March 2011, 34 children with a mean age of eight years (5 to 12) underwent treatment. The mean length of follow-up was 15 months (12 to 18). In total, 22 children were treated with dual rod constructs and 12 with a single rod. The mean number of distractions per patient was 4.8 (3 to 6). The mean pre-operative Cobb angle was 69° (46° to 108°); this was corrected to a mean 47° (28° to 91°) post-operatively. The mean Cobb angle at final review was 41° (27° to 86°). The mean pre-operative distance from T1 to S1 was 304 mm (243 to 380) and increased to 335 mm (253 to 400) in the immediate post-operative period. At final review the mean distance from T1 to S1 had increased to 348 mm (260 to 420).Two patients developed a superficial wound infection and a further two patients in the single rod group developed a loss of distraction. In the dual rod group, one patient had pull-out of a hook and one developed prominent metalwork. Two patients had a rod breakage; one patient in the single rod group and one patient in the dual rod group. Our early results show that the MCGR is safe and effective in the treatment of progressive early-onset scoliosis with the avoidance of repeated surgical lengthenings.

Repair of spondylolysis using compression with a modular link and screws.

We describe the results of a prospective case series of patients with spondylolysis, evaluating a technique of direct stabilisation of the pars interarticularis with a construct that consists of a pair of pedicle screws connected by a U-shaped modular link passing beneath the spinous process. Tightening the link to the screws compresses bone graft in the defect in the pars, providing rigid intrasegmental fixation. We have carried out this procedure on 20 patients aged between nine and 21 years with a defect of the pars at L5, confirmed on CT. The mean age of the patients was 13.9 years (9 to 21). They had a grade I or less spondylolisthesis and no evidence of intervertebral degeneration on MRI. The mean follow-up was four years (2.3 to 7.3). The patients were assessed by the Oswestry Disability Index (ODI) and a visual analogue scale (VAS). At the latest follow-up, 18 patients had an excellent clinical outcome, with a significant (p < 0.001) improvement in their ODI and VAS scores. The mean ODI score at final follow-up was 8%. Assessment of the defect by CT showed a rate of union of 80%. There were no complications involving the internal fixation. The strength of the construct removes the need for post-operative immobilisation.

Short anterior instrumented fusion and posterior convex non-instrumented fusion of hemivertebra for congenital scoliosis in very young children.

A variety of treatments has been described in the literature for the treatment of HV. We report the results of early surgical anterior instrumented fusion with partial preservation of the HV and posterior non-instrumented fusion in the treatment of progressive congenital scoliosis in children below the age of six. Between 1996 and 2006, 31 consecutive patients with 33 lateral HV and progressive scoliosis underwent short segment fusions. Mean age at surgery was 2 years and 10 months. Mean follow-up period was 6.1 years. The major scoliotic curve improved from 41 degrees preoperatively to 17 degrees on follow-up. Preoperative segmental Cobb angle averaging 39 degrees was corrected to 15 degrees after surgery, being 15 degrees at the last follow-up (62% of improvement). Compensatory cranial and caudal curves corrected by 47 and 45%, respectively. The angle of segmental kyphosis averaged 16 degrees before surgery, 11 degrees after surgery, and 11 degrees at follow-up. There were two wound infections requiring surgical debridment, one intraoperative fracture of the vertebral body and one case lost correction due to implant failure. All went on to stable bony union. There were no neurological complications. Early diagnosis and early and aggressive surgical treatment are mandatory for a successful treatment of congenital scoliosis and prevention of the development of secondary compensatory deformities. Anterior instrumentation is a safe and effective technique capable of transmitting a high amount of convex compression allowing short segment fusion, which is of great importance in the growing spine.

The role of imaging in the diagnosis and management of thoracolumbar burst fractures: current concepts and a review of the literature.

The burst fracture of the spine was first described by Holdsworth in 1963 and redefined by Denis in 1983 as being a fracture of the anterior and middle columns of the spine with or without an associated posterior column fracture. This injury has received much attention in the literature as regards its radiological diagnosis and also its clinical management. The purpose of this article is to review the way that imaging has been used both to diagnose the injury and to guide management. Current concepts of the stability of this fracture are presented and our experience in the use of magnetic resonance imaging in deciding treatment options is discussed.

MRI of 'idiopathic' juvenile scoliosis. A prospective study.

In a prospective trial we performed MRI of the spine and hind brain in 31 patients with scoliosis of onset between the ages of four and 12 years. In eight patients (26%) there was a significant neuroanatomical abnormality; there were six cases of Chiari-1 malformation associated with a syrinx, one isolated Chiari-1 malformation and one astrocytoma of the cervical spine. Four of these patients had left-sided curves. There were no clinical features which could reliably identify those patients with abnormalities on MRI. In particular, the unilateral absence of abdominal reflexes was found to be non-specific (1 of 8 of patients with neuroanatomical abnormalities (12.5%) v 2 of 23 with normal scans (8.7%). In view of the established risks of surgical correction of scoliosis in the presence of undecompressed syringomyelia and the possible improvement that may follow decompression of the foramen magnum, we feel that MRI of all patients with scoliosis of juvenile onset should be obligatory.