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