We tested whether our results were robust to alternative assumptions. Firstly, the base case model assumes that in the absence of a prosthesis failure, any differences in quality of life between prosthesis types are maintained over the patient’s lifetime. Here we assumed instead that any residual differences in quality of life between the prosthesis types are maintained for two years after the total hip replacement. Secondly, to consider an alternative way of addressing potential confounding, we estimated postoperative quality of life with ordinary least squares regression but without using GenMatch. Thirdly, we predicted revision rates beyond five years using a Gompertz rather than a Weibull hazard function. Fourthly, we created a “failed hip” state, whereas in the base case analysis we assumed that all patients with a prosthetic failure had a revision. Patients were assumed to move to this failed hip state if their prosthesis failed and their risk of operative mortality was predicted to exceed 10%. Quality of life for this failed hip state was assumed to be that for patients awaiting revision surgery. Fifthly, in the light of recent concerns over the use of metal-on-metal prostheses we undertook a sensitivity analysis in which quality of life and revision rates after total hip replacement were estimated after exclusion of patients with these prostheses.
Titanium, stainless steel, and cobalt chrome are the common metal used and the plastic is made of polyethylene. The implant is attached to the bone by either press-fit or cementing into place. With pressed in implants, new bone forms around the prosthetic securing it firmly. A special bone cement is used when the implant is cemented in. Both options securely hold the implant in place.
hip prosthesis has been estimated to be able save about 25% of the ..
We prefer to have the amputee simulate weight bearing during the plaster impression technique to create as precise a mold as possible. However, in contrast to the technique advocated by Otto Bock, we believe that careful attention to shaping the medial wall in the ischial region is important to improve control of the prosthesis for both walking and sitting.
The choice between hip prosthetic ..
The methods used to calculate revision and re-revision rates were reported clearly and were appropriate. A strength of the analysis was use of data from large national studies that provided detailed patient information representative of the target population of interest. However, some data were not available and some assumptions were required. A key assumption in the analysis concerned the duration of postoperative QoL differences between prosthesis types. The authors argued that although the sensitivity analysis demonstrated that if residual differences in postoperative QoL were assumed to last for only two years then the probability that cemented prostheses were cost-effective increased, evidence suggested that QoL improvements after hip replacement could persist for at least five years. Since the analysis did not include a scenario in which QoL differences were maintained for five years, it was not possible to assess how sensitive the results were to this alternative assumption.
hip prosthesis/ or total hip prosthesis/ or exp ..
A third type that has proved advantageous for this level of amputation is the polycentric (four-bar) knee. Although slightly heavier than the previous two types, this component offers maximum stance-phase stability. Because the stability is inherent in the multilinkage design, it does not erode as the knee mechanism wears during use. In addition, all polycentric mechanisms tend to "shorten" during swing phase, thus adding slightly to the toe clearance at that time. Many of the endoskeletal designs feature a readily adjustable knee extension stop. This permits significant changes to the biomechanical stability of the prosthesis, even in the definitive limb. Because of the powerful stability, good durability, and realignment capabilities of the endoskeletal polycentric mechanisms, they are particularly well suited for the bilateral amputee. Patients with all levels of amputation, up to and including translumbar (hemicorporectomy), have successfully ambulated with these components.
and cost-effectiveness of hip ..
For many years, the use of fluid-controlled knee mechanisms for high-level amputees was considered unwarranted since these individuals obviously walked at only one (slow) cadence. The development of hip flexion bias mechanisms and more propulsive foot designs have challenged this assumption. Furthermore, a more sophisticated understanding of the details of prosthetic locomotion has revealed an additional advantage of fluid control for the hip-level amputee.