Artificial total knee designs have revolutionized over time, yet 20% of the population still report dissatisfaction. The standard implants fail to replicate native knee kinematic functionality due to mismatch of condylar surfaces and non-anatomically placed implantation. (Daggett et al 2016; Saigo et al 2017). It is essential that the implant surface matches the native knee to prevent Instability and soft tissue impingement. Our goal is to use computational modeling to determine the ideal shapes and orientations of anatomically-shaped components and test the accuracy of fit of component surfaces. One hundred MRI scans of knees with early osteoarthritis were obtained from the NIH Osteoarthritis Initiative, converted into 3D meshes, and aligned via an anatomic coordinate system algorithm. Geomagic Design X software was used to determine the average anterior-posterior (AP) length. Each knee was then scaled in three dimensions to match the average AP length. Geomagic's least-squares algorithm was used to create an average surface model. This method was validated by generating a statistical shaped model using principal component analysis (PCA) to compare to the least square's method. The averaged knee surface was used to design component system sizing schemes of 1, 3, 5, and 7 (fig 1). A further fifty arthritic knees were modeled to test the accuracy of fit for all component sizing schemes. Standard deviation maps were created using Geomagic to analyze the error of fit of the implant surface compared to the native femur surface.Background
Methods
Diabetes is a poor prognostic indicator after an acute ankle fracture. Many surgeons avoid essential surgery due to their concerns regarding complications. We performed a retrospective analysis of complication rates for acute ankle fractures in diabetics with a control non-diabetic patient treated by all surgeons in our unit and assessed factors for success including long-segment fixation methodologies. Patient records were cross-referenced with departmental databases and a retrospective review of all ankle fractures managed in our department was conducted from 2014. All patients subjected to a retrospective review of their notes and assessment of their follow up for at least 6 months. Radiographs were assessed of the ankle before and at completion of treatment were reviewed independently (RA and FR). We identified all patients with a diabetic ankle fracture their HB1Ac (for diabetic control) and systematic co-morbidities. Fractures were classified into unimalleolar, bi malleolar and trimalleolar and surgery grouped into standard or long-segment-rigid fixation. Statistical analysis was conducted using absolute/relative risk (RR); numbers needed to treat (NNT) were calculated. We compared a control-group, a diabetic group managed conservatively, and undergoing surgery; comparing the concept of rigid fixation. Further sub-analysis conducted to assess differences between diabetic neuropathy, retinopathy and nephropathy. Ethics approval was granted as per our institutional policy by our governance lead. We identified 64 patients with a diabetic ankle fractures, their fracture pattern and a control group. Thirty-one had conservative treatment; 33 had operative fixation of which 13 had rigid fixation. Compared to the control (n=32) both diabetic groups had a higher risk of possible complication. The relative risk was between 3.1–3.4 (P<0.002) and linked to systematic complications of diabetes e.g. neuropathy 5.9 (P<0.003); HBA1c 4.6 P<0.004); and neuropathy and retinopathy 6.2 P<0.0003). We observed RR is reduced for a complication occurring following surgery with prolonged immobilization (0.86) and rigid fixation (0.65) and NNT required to see a benefit from rigid fixation was 7. The overall RR for a complication was similar between conservative and surgical management (4.6 vs.5.1). We agree diabetics have a higher risk for complications than non-diabetics, however the risk is not as great as previously reported. There is little difference in surgical or conservative treatment but strong evidence indicating rigid long-segment-fixation with prolonged-immobilization could improve the risk benefit ratio when compared to non- operative management alone but further evaluation is required.
