Virtual trial to evaluate the robustness of cementless femoral stems to patient and surgical variation

Primary stability is essential for the success of cementless femoral stems. In this study, patient specific finite element (FE) models were used to assess changes in primary stability due to variability in patient anatomy, bone properties and stem alignment for two commonly used cementless femoral stems, Corail® and Summit® (DePuy Synthes, Warsaw, USA). Computed-tomography images of the femur were obtained for 8 males and 8 females. An automated algorithm was used to determine the stem position and size which minimized the endo-cortical space, and then span the plausible surgical envelope of implant positions constrained by the endo-cortical boundary. A total of 1952 models were generated and ran, each with a unique alignment scenario. Peak hip contact and muscle forces for stair climbing were scaled to the donor’s body weight and applied to the model. The primary stability was assessed by comparing the implant micromotion and peri-prosthetic strains to thresholds (150 μm and 7000 µε, respectively) above which fibrous tissue differentiation and bone damage are expected to prevail. Despite the wide range of implant positions included, FE prediction were mostly below the thresholds (medians: Corail®: 20–74 µm and 1150–2884 µε, Summit®: 25–111 µm and 860–3010 µε), but sensitivity of micromotion and interfacial strains varied across femora, with the majority being sensitive (p < 0.0029) to average bone mineral density, cranio-caudal angle, post-implantation anteversion angle and lateral offset of the femur. The results confirm the relationship between implant position and primary stability was highly dependent on the patient and the stem design used.     

Implant therapy alternatives for geriatric edentulous patients

The predicament of being both elderly and edentulous undermines life quality for both patient and dentist. The former suffer because of morphological and functional compromises, the latter because of a dearth of safe and predictably successful clinical techniques. The introduction of the osseointegration technique suggested great promise for profoundly changing this predicament, but the specific merits of this approach have been mainly extrapolated ones. The purpose of this study was to examine the clinical success of treatment with osseointegration for patients who were 65 or older at the time of implant insertion. A second group of patients, who became 65 during the course of the study was also studied and the results recorded separately. Data regarding the longevity of implants and prosthodontic restorations and the numbers and types of problems encountered were recorded. The evidence suggests that the biological anchorage of tooth root analogues in elderly jaws is predicatbly successful and enhances the quality of life for geriatric patients who are edentulous.