Table 2

Quality rating of studies included in the review according to the SIGN scale, which assesses the risk of bias and confounding present and the ability of the study to establish a causal relationship between the variables of interest and recurrent shoulder instability

SIGN21Clear focused questionSelection biasSelection biasPerformance biasAttrition biasAttrition biasDetection biasDetection biasDetection biasDetection biasDetection biasDetection biasConfoundingCILimitation of bias
teSlaa et al311011001N+Acceptable5
Simonet and Cofield1611110001N+Acceptable5
Safran et al32110111001010YLow7
Sachs et al8111101110011Y+High9
Robinson et al11111111001111Y+High10
Kralinger et al1510000111NLow4
Vermeiren et al3111000000NLow2
Hoelen et al3011100000NLow3
Salomonsson et al2811111101N+Acceptable7
Pevny et al2911110100NLow5
  • *Grey shading indicates retrospective studies where it was not possible to evaluate criteria.

  • †Rating scales refer to how well the study has minimised the risk of bias or confounding and establish a causal relationship between the risk factor and recurrent instability. High-quality studies have little or no risk of bias, and the results from these studies are unlikely to change with further research. Acceptable quality studies have some associate risk of bias and the conclusions may change in light of further studies. Low-quality studies have significant flaws related to study design and the conclusions drawn from these studies are likely to change in the light of further studies.

  • ‡Total scores can range from 0 to 13 with lower number representing increased risk of bias and higher numbers representing prospective cohort studies with minimal risk of bias.

  • N, no; SIGN, Scottish Intercollegiate Guidelines Network; Y, yes.