162 patient cohort with serial Metal Artefact Reduction Sequence MRI scans. Patients with normal initial scans can be followed up at 1 year. Those with abnormal scans should be followed up at a shorter interval of 6 months. Cross-sectional imaging is a key investigation in the assessment and surveillance of patients with metal-on-metal (MoM) hip arthroplasty. We present our experience of Metal Artefact Reduction Sequence (MARS) MRI scanning in metal on metal hip arthroplasty. We aimed to investigate the natural history and radiological disease progression from Adverse Reactions to Metallic Debris.Summary
Introduction
Common problems following total knee arthroplasty include tibial component malpositioning, ligament imbalance, and clinical and subclinical fat embolism associated with intramedullary alignment guides. Tibial component malaligment can lead to component loosening. Ligament imbalance can lead to dysfunction and the need for revision. Fat embolism had been shown to occur in 46% of unilateral and 65% of bilateral total knee arthroplasty patients with neurological sequelae in 2 and 4% of patients respectively (Kim YH, J. Arth. 1999). All three of these common problems can be addressed with the use of surgical navigation. Instruments designed for the Genesis II total knee arthroplasty (Smith-Nephew, Memphis, TN) are tracked optically using the ION virtual fluoroscopy surgical navigation system (Medtronics SNT, Louisville, CO). A software system specifically designed for TKR navigation is employed. Following exposure, reference frames are attached to the femur and tibia and fluoroscopic images of the knee are obtained. Hip and Ankle centres can be determined either kinematically or with images. Proper alignment and component rotation is determined using navigation without intramedullary alignment guides. Proper implant sizing is determined before the cuts are made by superimposing images of the proposed implants into the fluoroscopic images of the knee. Motion and ligament integrity can be quantified kinematically. The system was used to perform total knee arthroplasty on 14 cadavers. Post-operative alignment was measured radiographically. As compared to the mechanical axis measured radiographically, the coronal femoral alignment measured 0.03 degrees of valgus (95% confidence:−1.81 to 1.88 degrees). Coronal tibial aligment measured 0.88 degrees of valgus (95% confidence: −2.17 to 0.41 degrees). Sagittal tibial aligment measured 1.81 degrees of posterior slope (95% confidence: −0.14 to 3.76 degrees) The use of surgical navigation for TKA results in appropriately aligned implants. Surgical navigation has the potential to improve many of the most common problems encountered during and following total knee arthroplasty including component malaligment and malsizing, malrotation, ligament imbalance, and fat embolism.
