Survival analysis is an important tool for assessing the outcome of total joint replacement. The Kaplan-Meier method is used to estimate the incidence of revision of a prosthesis over time, but does not account appropriately for competing events which preclude revision. In the presence of competing death, this method will lead to statistical bias and the curve will lose its interpretability. A valid comparison of survival results between studies using the method is impossible without accounting for different rates of competing events. An alternative and easily applicable approach, the cumulative incidence of competing risk, is proposed. Using three simulated data sets and realistic data from a cohort of 406 consecutive cementless total hip prostheses, followed up for a minimum of ten years, both approaches were compared and the magnitude of potential bias was highlighted. The Kaplan-Meier method overestimated the incidence of revision by almost 4% (60% relative difference) in the
The purpose of this study was to evaluate the
effect of various non-operative modalities of treatment (transcutaneous
electrical nerve stimulation (TENS); neuromuscular electrical stimulation
(NMES); insoles and bracing) on the pain of osteoarthritis (OA)
of the knee. We conducted a systematic review according to the Preferred Reporting
Items for Systematic Reviews and Meta-Analyses guidelines to identify
the therapeutic options which are commonly adopted for the management
of osteoarthritis (OA) of the knee. The outcome measurement tools used in the different studies were
the visual analogue scale and The Western Ontario and McMaster Universities
Arthritis Index pain index: all pain scores were converted to a
100-point scale. A total of 30 studies met our inclusion criteria: 13 on insoles,
seven on TENS, six on NMES, and four on bracing. The standardised
mean difference (SMD) in pain after treatment with TENS was 1.796,
which represented a significant reduction in pain. The significant
overall effect estimate for NMES on pain was similar to that of
TENS, with a SMD of 1.924. The overall effect estimate of insoles
on pain was a SMD of 0.992. The overall effect of bracing showed
a significant reduction in pain of 1.34. Overall, all four non-operative modalities of treatment were
found to have a significant effect on the reduction of pain in OA
of the knee. This study shows that non-operative physical modalities of treatment
are of benefit when treating OA of the knee. However, much of the
literature reviewed evaluates studies with follow-up of less than
six months: future work should aim to evaluate patients with longer
follow-up. Cite this article:
