PubMed · 10441892
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A Isdale, P Helliwell. 1998. Key developments in knee surgery.. https://pubmed.ncbi.nlm.nih.gov/10441892/
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Total knee replacements using intercondylar cams, such as posterior stabilized types, have been in use for many years. In a previous study, software was written to analyze an alternative shape of the intercondylar cams. The goal of the current study was to investigate in a more general way the potential of intercondylar cams, or guide surfaces, for reproducing the anterior-posterior motion of the natural knee throughout the flexion range. Typical sagittal outlines for the femoral and tibial bearing surfaces were defined, and a parametrized shape for the femoral guide surface was defined to produce a wide range of shapes. Software was written in which the femoral component was flexed in increments, with the posterior translation defined as a function of the flexion angle. The shape of the tibial guide surface was derived from the locus of the femoral guide surface at its multiple flexion positions. By iterating methodically through possible shapes of femoral guide surfaces, several types of total knee replacement components in common use today were identified, as well as other configurations of potential interest. For quantification of a given design, the software calculated the anterior and posterior laxity at each flexion angle. Laxity was defined as the motion before the femoral guide surface impacted the tibial guide surface or until the contact point of the bearing surfaces reached a specified slope. Convex femoral and concave saddle-shaped tibial guide surfaces produced small laxities in both directions over most of the flexion range. A saddle design with small laxities in the first half of flexion, combined with a posterior stabilized feature, was an interesting combination. Potential improvements to the currently used designs were shown in this study, and new shapes of intercondylar guide surfaces were derived that could be considered for application.
The nerve distribution to the knee joints was analyzed in 5 cadavers and 10 joint capsules specimens were resected during total knee arthroplasty. We found nerve fibers immunoreactive for anti-substance P antibody in the articular capsule. By confocal laser scanning microscopy, we evaluated the three-dimensional structures of the Ruffini's corpuscles and the free nerve endings, both of which were immunoreactive for anti-protein gene product 9.5.
The purpose of the present study was to illustrate the use of computer-assisted decision analysis in making decisions in the field of orthopaedic surgery, using the choice between resurfacing and not resurfacing the patella in total knee arthroplasty as an example. We used a decision analysis technique based on probability theory and on Bayesian logic, with the help of an especially developed computer software. The process involves building a decision tree, searching for probabilities and utilities in the literature, folding back the tree to compute the baseline result, and running sensitivity analyses. Our literature search provided 26 useful articles, only 3 of which were randomized controlled trials. In the baseline analysis, both options were rated similarly, with resurfacing the patella faring slightly better. Sensitivity analyses revealed that not resurfacing becomes the procedure of choice if the probability of postoperative anterior knee pain with an unresurfaced patella falls below 14%, or if the probability of having pain with a resurfaced patella rises above 8% or if the utility of patellar implant failure falls below 80% of the utility of a perfect health state. Computer-assisted decision analysis is a promising, evidence-based tool to assist clinical decision making in orthopaedic surgery. However, its validity is limited by the poor quality of data found in the orthopaedic literature, especially the scarcity of randomized controlled trials.