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The article presents a college thesis which investigated the determinants of the outcomes of lumbar spinal stenosis surgery and is based on several papers previously published by F. G. Sigmundsson, B. Jönsson and B.Strömqvist, including papers which appeared in a 2013 issue of "Acta Orthopaedica", a 2012 issue of "Acta Orthopaedica" and a 2014 issue of "Spine".

Background and purpose — A shortened tibial stem could influence the early prosthetic fixation. We therefore compared the short stem to the standard-length stem using radiostereometric analysis (RSA) as primary outcome measure. Patients and methods — 60 patients were randomized to receive a cemented Triathlon total knee arthroplasty (TKA) with a tibial tray of either standard or short stem length. The patients were blinded regarding treatment allocation. The micromotion of the tibial component was measured by RSA postoperatively, at 3 months, and after 1 and 2 years; clinical outcome was measured with the American Knee Society score (AKSS) and the knee osteoarthritis and injury outcome score (KOOS). Results — The maximum total point motion (MTPM) for the standard stem was 0.36 (SD 0.16) mm at 3 months, 0.51 (SD 0.27) mm at 1 year, and 0.54 (SD 0.28) mm at 2 years. For the short stem, it was 0.42 (0.24) mm, 0.59 (0.43) mm, and 0.61 (0.39) mm. 4 short-stemmed components and 2 standard-stemmed components had more than 0.2 mm of migration between the first- and second-year follow-up, and were classified as continuously migrating. Interpretation — The short-stemmed cemented tibial prosthesis showed an early prosthetic migratory pattern similar to that of the standard-stemmed cemented Triathlon knee prosthesis. The number of continuously migrating tibial plates in each group is predictive of a lower revision rate than 5% at 10 years. [ABSTRACT FROM AUTHOR]

Background and purpose - Little is known about the characteristics of non-participants in epidemiological studies. We evaluated external validity by comparing fracture and mortality rate in participants and non-participants in a longitudinal study on risk factors for fracture. Methods - 1,604 randomly selected women, 75 years of age, were invited to attend a study on osteoporosis and fracture. 1,044 women attended the study (participants) and 560 women did not participate (non-participants). Fracture data for all were obtained prospectively from radiographic records. Mortality data were obtained through the population register. Mean follow-up was 13 (11-15) years. Cumulative survival was compared with the log-rank test. Fracture incidence rates per 1,000 person-years were compared with Mann-Whitney U-tests. In addition, fracture comparisons were made with the cumulative incidence function and Gray's test. Results - 454 participants (44%) died during the follow-up, as compared to 372 of the non-participants (66%) (p < 0.001). The fracture incidence rate for any type of fracture was 43 for participants and 47 for non-participants (p = 1.0). The fracture incidence rate for typical osteoporotic fracture was 36 for participants and 39 for non-participants (p = 0.6). The corresponding values for distal forearm fracture were 11 and 7 (p = 0.002), they were 8 and 9 for proximal humerus fracture (p = 0.9), 13 and 10 for vertebral fracture (p = 0.007), 15 and 18 for hip fracture (p = 0.8), and they were 6 and 5 for pelvic fracture (p = 0.3). The cumulative incidence function confirmed the results. Interpretation - Our findings suggest that participants had a lower mortality rate than non-participants. Distal forearm and vertebral fractures were more frequent in participants. However, the external validity for fractures in general appeared to be satisfactory. [ABSTRACT FROM AUTHOR]