Aim:. The aim of this study was test the amount of corrosion occurring at the (Ti) /cobalt chrome (CoCr) interface comparing this with Ti and Ti interfaces. This was compared with retrieved metal work visualised under a scanning electron microscope (SEM). Methods:. The interface of interest is the interface between rod and the screw. We investigated corrosion seen at that interface with a CoCr rod coupled to a Ti screw versus a Ti rod coupled to a Ti screw (6 screws were used) Implants were loaded according to the ASTM F2193 – 02 Standard Specifications and Test Methods for Components Used in the Surgical Fixation of the Spinal Skeletal System. Pitting potentials were monitored using cyclic potentiodynamic polarization tests (ASTM F2129 – 08 Standard Test Method for Conducting Cyclic Potentiodynamic Polarisation Measurements) to determine corrosion susceptibility. Retrieved implants were visualised under (SEM) to confirm corrosion. Results:. Mean fretting current for titanium and cobalt chrome was 7.94 (μA) and for titanium on titanium 5.89 (μA). The results of SEM showed evidence of fretting and galvanic corrosion. Discussion:. Cobalt chrome ions in hip implants have raised concern amongst the orthopaedic community. This study showed that metal ion production occurs due to fretting and galvanic corrosion. This corrosion is increased in cobalt chrome and titanium constructs but statistically more tests are required to confirm this. Further research is required to understand this interface as cobalt chrome ions pose a potential hazard to patients with their reproductive years ahead. Conflict Of Interest Statement: No conflict of interest

Aim:. To compare the degree of deformity correction achieved using cobalt chromium versus titanium alloy rods in patients with Adolescent Idiopathic Scoliosis. Method:. A retrospective comparison of two cohorts of patients with Adolescent Idiopathic Scoliosis treated with posterior segmental pedicle screw fixation using either Titanium or Cobalt Chromium rods. The radiographs of 50 patients treated before 2009 (Ti group) and 50 patients after 2009 (CoCr group) were reviewed for changes in: Main Coronal Curvature Sagittal Balance (C7 Plumb Line) Kyphosis (T5-12). Results:. Thirteen were excluded because of incomplete radiographs. 38 patients received CoCr, 45 Ti and 4 patients received hybrid constructs. Correction rate of curves measuring >50 was significantly improved with CoCr (81% vs 69%, p=0.02). Sagittal balance was improved in both groups (CoCr 27.8, Ti 28.0 mm) but no significant difference was seen (p=0.84). Within the Ti group 12 patients moved for normal kyphosis (20–40) to abnormal (<20, >40) while 9 patients moved from abnormal to normal (p=0.66). Within the CoCr Group 10 patients were normalised while only 2 patients moved from normal to abnormal (p=0.04). Mean change in kyphosis showed a trend towards improved correction with CoCr (4.2 vs 2.9) but failed to reach significance (p=0.62). Discussion:. We have demonstrated that CoCr rods significantly improve coronal correction in patient with >50 curves. No difference in overall sagittal balance was seen between metal alloys. There is a trend towards better restoration of T5-12 kyphosis with CoCr however it is unclear if this small difference is clinically relevant. Conflict Of Interest Statement: No conflict of interest

The purpose of this study was to evaluate whether concerns about the release of metal ions in metal-on-metal total hip replacements (THR) should be extended to patients with metal-bearing total disc replacements (TDR). Cobalt and chromium levels in whole blood and serum were measured in ten patients with a single-level TDR after a mean follow-up of 34.5 months (13 to 61) using inductively-coupled plasma mass spectrometry. These metal ion levels were compared with pre-operative control levels in 81 patients and with metal ion levels 12 months after metal-on-metal THR (n = 21) and resurfacing hip replacement (n = 36). Flexion-extension radiographs were used to verify movement of the TDR. Cobalt levels in whole blood and serum were significantly lower in the TDR group than in either the THR (p = 0.007) or the resurfacing group (p < 0.001). Both chromium levels were also significantly lower after TDR versus hip resurfacing (p < 0.001), whereas compared with THR this difference was only significant for serum levels (p = 0.008). All metal ion levels in the THR and resurfacing groups were significantly higher than in the control group (p < 0.001). In the TDR group only cobalt in whole blood appeared to be significantly higher (p < 0.001). The median range of movement of the TDR was 15.5° (10° to 22°). These results suggest that there is minimal cause for concern about high metal ion concentrations after TDR, as the levels appear to be only moderately elevated. However, spinal surgeons using a metal-on-metal TDR should still be aware of concerns expressed in the hip replacement literature about toxicity from elevated metal ion levels, and inform their patients appropriately

Aim:. To evaluate the effect of a stiffer rod in normalising thoracic hypokyphosis in adolescent idiopathic scoliosis (AIS). Methods:. A retrospective review of AIS cases performed at our institution was carried out. In order to reduce variability, the analysis included only Lenke 1 cases which had all pedicle screw constructs, with similar constructs and implant density. Cases that underwent anterior release were excluded. All cases had the same implant (Expedium 5.5, Depuy-Synthes, Raynham, USA). The rod material differed in that some cases had 5.5 titanium, whilst others had 5.5 cobalt chrome. The preoperative and postoperative sagittal Cobb angle was measured. Results:. 35 patients met the inclusion criteria. 15 had titanium rods and 20 had cobalt chrome rods. The mean fulcrum correction index was similar between groups. The preoperative coronal and sagittal Cobb was similar between the two groups. There was no statistically significant difference in the postoperative sagittal Cobb between the two groups (ANOVA one way test). Discussion:. Despite the theoretical advantage of a stiffer construct improving the sagittal profile in AIS, this study identified no such benefit despite closely matching the two groups. All pedicle screw constructs do not seem to improve the sagittal profile despite the use of a stiffer rod. Conflict of interest:. Depuy-Synthes fund a fellow in this unit. Conflict Of Interest Statement: No conflict of interest

Pedicle screw constructs (PSC) in scoliosis are a recently established and widely accepted method of managing scoliotic curves posteriorly. There is a perceived improved coronal and rotational correction when compared to other posterior only constructs. With continued use of this method, the authors and deformity surgeons in general have become aware of persistent thoracic hypokyphosis. This review of 3 years of scoliosis cases using PSC looks at four different implant strategies utilised to manage this problem and our current practice. These strategies were:. All titanium 5.5 mm rod diameter (Expedium, Depuy spine). All titanium 5.5 mm rod diameter with periapical washers (Expedium, Depuy spine). All titanium 6.0 mm rod diameter (Pangea, Synthes). Titanium pedicle screws with 5.5 mm diameter cobalt chrome rods (Expedium Depuy spine). We have reviewed our outcomes with these strategies with respect to thoracic hypokyphosis. Strategy 1 had the highest rate of hypokyphosis on postoperative radiographs. Strategy 4 seems to have the best correction of coronal and sagittal plane abnormality post operatively. As a consequence, our current practice is the use of titanium pedicle screws and 5.5 mm diameter cobalt chrome rods when managing scoliosis with a pedicle screw construct

School of Mechanical Engineering, University of Birmingham, Birmingham, UK. This study investigated the effects on friction of changing the dimensions of a ball-and-socket Total Disc Arthroplasty (TDA). A generic ball-and-socket model was designed and manufactured based on the dimensions and geometry of a metal-on-metal Maverick (Medtronic, Minneapolis, USA) device. Keeping the radial clearance similar to the Maverick, the ball and socket dimensions varied between 10 to 16 mm and 10.015 to 16.015 mm, respectively, in order to enable the comparison between different dimensions. The implants were made out of Cobalt Chrome Molybdenum alloy, with a surface roughness of 0.05 μm. A Bose spine simulator (Bose Corporation, ElectroForce Systems Group, Minnesota, USA) was used to apply an axial compressive force to the TDA. Axial rotation of ±2° was then applied at various frequencies and the resulting frictional torque measured. The tests were performed under an axial load of 50, 600 and 1200 N and frequencies of 0.5, 1.0, 1.5 and 2.0 Hz, for four different samples of radii 10, 12, 14 and 16 mm (48 combinations in total). The results showed variation of frictional torque in different frequencies for all four samples under constant axial load. It was observed that the frictional torque had the lowest value for the implant with ball radius of 16mm. It might be concluded that the implant with larger ball radius may create less friction and hence offer a longer life

To determine the current practice of scoliosis surgery in the UK. A 10 point questionnaire was constructed to identify the philosophy of surgeons on various aspects of scoliosis surgery such as choice of implant, bone graft, autologous blood transfusion (ABT), cord monitoring and computer assisted surgery. Results are compared with the current best evidence. Consultants and Fellows attending the 2009 British Scoliosis Society meeting. 50 questionnaires were completed: 45 Consultants and 5 Fellows. All pedicle screw construct favored by 25/50, hybrid 24/50 (one undecided). Posterior construct of less than 10 levels, 20/50 would not cross-link, 11/50 used one and 19/20 used two or more. More than ten levels 17/50 considered cross-links unnecessary, 4/50 used one and 29/50 used two or more. 88% preferred titanium alloy implants, while a mixture of stainless steel and cobalt chrome was used by others. For bone graft, substitutes (24), iliac crest (14), allograft (12) and demineralised bone matrix (9) in addition to local bone. 10/50 would use recombinant bone morphogenetic protein (3 for revision cases only). 39/50 routinely used intra-operative cell salvage or ABT drains and 4/50 never used autologous blood. All used cord monitoring, Sensory (19/50), Motor (2/50) and combined (29/50). None used computer-aided surgery. 26 operated alone 12 operated in pairs and 12 varied depending on type of case. This survey has brought to light interesting variations in scoliosis surgery in UK. It may reflect the conflicting evidence in the literature

Aims

The direct posterior approach with subperiosteal dissection of the paraspinal muscles from the vertebrae is considered to be the standard approach for the surgical treatment of adolescent idiopathic scoliosis (AIS). We investigated whether or not a minimally-invasive surgery (MIS) technique could offer improved results.