Letter to the Editor: Increased Risk of Revision, Reoperation, and Implant Constraint in TKA After Multiligament Knee Surgery
To the Editor,
In their study, Pancio and colleagues , retrospectively evaluated implant survival, complication rate, and long-term outcomes of knee arthroplasty in patients with a prior history of multiligament surgery. The authors found that patients with a prior history of multiligament surgery more frequently received varus-valgus constraint compared with patients undergoing primary knee arthroplasty for osteoarthritis. These results also showed large effect size estimates, but those estimates had wide confidence intervals (CI).
Previous studies [4, 5] showed that wide CIs around large effect-size estimates may indicate sparse-data bias, an estimate inflation that occurs “when the data lack adequate case numbers for some combination of risk factor and outcome levels” . When this occurs, “the resulting estimates of the regression coefficients can have bias away from the null (downward when the estimate is below 1, upward when it is above 1)” . Additionally, sparse-data bias can cause imprecise CIs .
Sparse-data bias is generally found if the sample size is relatively small or when there are different sample sizes in the exposure and intervention groups [1, 2, 3, 5, 7]. To address and adjust this bias, researchers developed the conventional method, which adds a half count to every strata in the table. Greenland and colleagues  introduced an alternative to the conventional method called penalization via data augmentation, an efficient method “in which external (or prior) information is used to improve accuracy over repeated studies” . Penalization via data augmentation better addresses bias compared to conventional methods by removing or correcting the bias .
Estimated odds ratios for multiligament group
Method to adjust bias
Estimated odds ratio (95% CI)
Conventional bias reduction method
Penalization via data augmentation method
- 3.Ayubi E, Safiri S. Profile and outcome of first 109 cases of paediatric acute liver failure at a specialized paediatric liver unit in India: Methodological issues. Liver Int. [Published online ahead of print April 9, 2017]. DOI: 10.1111/liv.13455.
- 7.Safiri S, Ayubi E. Dual photon microscopy based quantitation of fibrosis-related parameters (q-FP) to model disease progression in steatohepatitis: Methodological issues. Hepatology. [Published online ahead of print May 16, 2017]. DOI: 10.1002/hep.29261.