The Fragility of Significance in the Hip Arthroscopy Literature: A Systematic Review

The Statistical Fragility of Marrow Stimulation for Cartilage Defects of the Knee: A Systematic Review of Randomized Controlled Trials

OBJECTIVE

Marrow stimulation is used to address knee cartilage defects. In this study, we used the fragility index (FI), reverse fragility index (rFI), and fragility quotient (FQ) to evaluate statistical fragility of outcomes reported in randomized controlled trials (RCTs) evaluating marrow stimulation.

DESIGN

PubMed, Embase, and MEDLINE were queried for recent RCTs (January 1, 2010-September 5, 2023) assessing marrow stimulation for cartilage defects of the knee. The FI and rFI were calculated as the number of outcome event reversals required to alter statistical significance for significant and nonsignificant outcomes, respectively. The FQ was determined by dividing the FI by the study sample size.

RESULTS

Across 155 total outcomes from 21 RCTs, the median FI was 3 (interquartile range [IQR], 2-5), with an associated median FQ of 0.067 (IQR, 0.033-0.010). Thirty-two outcomes were statistically significant, with a median FI of 2 (IQR, 1-3.25) and FQ of 0.050 (IQR, 0.025-0.069). Ten of the 32 (31.3%) outcomes reported as statistically significant had an FI of 1. In total, 123 outcomes were nonsignificant, with a median rFI of 3 (IQR, 2-5). Studies assessing stem cell augments were the most fragile, with a median FI of 2. In 55.5% of outcomes, the number of patients lost to follow-up was greater than or equal to the FI.

CONCLUSION

Statistical findings in RCTs evaluating marrow stimulation for cartilage defects of the knee are statistically fragile. We recommend combined reporting of P-values with FI and FQ metrics to aid in the interpretation of clinical findings in comparative trials assessing cartilage restoration.

The Statistical Fragility of Lateral Extra-articular Tenodesis Research: A Systematic Review

Background

A P value of <.05 is often used to denote statistical significance; however, in many scenarios, this threshold is vulnerable to a small number of outcome reversals. This study joins a body of studies within the orthopaedic literature that evaluate the statistical fragility of existing research via metrics such as fragility index (FI) and fragility quotient (FQ).

Purpose/Hypothesis

The purpose of this study was to investigate the statistical fragility of randomized controlled trials (RCTs) and comparative studies on the topic, given the resurgent interest in lateral extra-articular tenodesis (LET) to augment primary or revision anterior cruciate ligament reconstruction (ACLR). It was hypothesized that the outcomes reported in these studies would be statistically fragile.

Study Design

Systematic review; Level of evidence, 4.

Methods

Comparative studies and RCTs regarding LET as an adjunct procedure to ACLR published between 2000 and 2022 were analyzed. Descriptive characteristics, dichotomous outcomes, and continuous outcomes were extracted. The FI and continuous FI (CFI) were calculated by the number of event reversals to change significance; the FQ and continuous FQ (CFQ) were calculated to normalize the fragility metrics per sample size.

Results

Of 455 studies screened, 29 studies were included (9 RCTs, 20 comparative); 79.3% of included studies were published after 2020. A total of 48 dichotomous and 265 continuous outcomes were analyzed. The median FI was 9.0 (IQR, 7.0-13.3), with FQ of 0.1 (IQR, 0.04-0.17); the median CFI was 7.8 (IQR, 4.2-19.6), with CFQ of 0.12 (IQR, 0.08-0.19). The FQ and CFQ for studies on LET with revision ACLR were larger (0.117 and 0.113, respectively) than those focused on primary ACLR (0.042 and 0.095, respectively).

Conclusion

Studies focused on LET with primary ACLR were more fragile than those on LET with revision, which suggests that further research on the indications for LET with primary ACLR is necessary. Future orthopaedic comparative research should include fragility metrics alongside traditional P values.

The Statistical Fragility of Tranexamic Acid Use in the Orthopaedic Surgery Literature: A Systematic Review of Randomized Controlled Trials

INTRODUCTION

Randomized controlled trials (RCTs) represent the highest level of evidence in orthopaedic surgery literature, although the robustness of statistical findings in these trials may be unreliable. We used the fragility index (FI), reverse fragility index (rFI), and fragility quotient (FQ) to evaluate the statistical stability of outcomes reported in RCTs that assess the use of tranexamic acid (TXA) across orthopaedic subspecialties.

METHODS

PubMed, EMBASE, and MEDLINE were queried for RCTs (2010-present) reporting dichotomous outcomes with study groups stratified by TXA administration. The FI and rFI were defined as the number of outcome event reversals needed to alter the significance level of significant and nonsignificant outcomes, respectively. FQ was determined by dividing the FI or rFI by sample size. Subgroup analyses were conducted based on orthopaedic subspecialty.

RESULTS

Six hundred five RCTs were screened with 108 studies included for analysis comprising 192 total outcomes. The median FI of the 192 outcomes was 4 (IQR 2 to 5) with an associated FQ of 0.03 (IQR 0.019 to 0.050). 45 outcomes were reported as statistically significant with a median FI of 1 (IQR 1 to 5) and associated FQ of 0.02 (IQR 0.011 to 0.034). 147 outcomes were reported as nonsignificant with a median rFI of 4 (IQR 3 to 5) and associated FQ of 0.04 (IQR 0.023 to 0.051). The adult reconstruction, trauma, and spine subspecialties had a median FI of 4. Sports had a median FI of 3. Shoulder and elbow and foot and ankle had median FIs of 6.

DISCUSSION

Statistical outcomes reported in RCTs on the use of TXA in orthopaedic surgery are fragile. Reversal of a few outcomes is sufficient to alter statistical significance. We recommend reporting FI, rFI, and FQ metrics to aid in interpreting the outcomes reported in comparative trials.

Fragile Statistical Findings in Randomized Controlled Trials Evaluating Autograft Versus Allograft Use in Anterior Cruciate Ligament Reconstruction: A Systematic Review

PURPOSE

To analyze the statistical stability of randomized controlled trials (RCTs) evaluating the surgical management of autografts versus allografts in the anterior cruciate ligament reconstruction (ACLR) literature and calculate the fragility index (FI) and fragility quotient and explore a subgroup analysis by calculating the proportion of outcome events where the FI was less than the number of patients lost to follow-up.

METHODS

Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, we conducted a systematic search in the PubMed and Cochrane databases to identify RCTs published between 2000 and 2022 that investigated the use of autografts versus allografts in ACLR literature and reported dichotomous data. The fragility index of each dichotomous variable was calculated through the reversal of a single outcome event until significance was reversed. The fragility quotient was calculated by dividing each fragility index by the study sample size. The interquartile range also was calculated.

RESULTS

Of the 4407 articles screened, 23 met the search criteria, with 11 RCTs evaluating ALCR using autografts and allografts included for analysis. Two hundred and 18 outcome events with 32 significant (P < .05) outcomes and 186 nonsignificant (P ≥ .05) outcomes were identified. The overall fragility index and fragility quotient for all 218 outcomes were 6 subjects (interquartile range 5-8) and 0.058 (interquartile range 0.039-0.077). Fragility analysis of statistically significant outcomes and nonsignificant outcomes had a fragility index of 3.5 (interquartile range 1-5.5) and 6 (interquartile range 5-8), respectively. All of the studies reported a loss to follow-up where 45.5% (5) reported a loss to follow-up greater or equal to 6.

CONCLUSIONS

The RCTs in the ACLR peer-reviewed literature evaluating autograft versus allograft use are vulnerable to a small number of outcome event reversals and exemplify significant statistical fragility in statistically significant findings.

LEVEL OF EVIDENCE

Level I, systematic review of Level I studies.

Randomized Controlled Trials Comparing Bone-Patellar Tendon-Bone Versus Hamstring Tendon Autografts in Anterior Cruciate Ligament Reconstruction Surgery Are Statistically Fragile: A Systematic Review

PURPOSE

To assess the statistical fragility of recently published randomized controlled trials (RCTs) comparing the use of hamstring tendon autograft with bone-patellar tendon-bone autograft for anterior cruciate ligament (ACL) reconstruction.

METHODS

The PubMed, Embase, and MEDLINE databases were queried for RCTs published since 2010 comparing autograft type (bone-patellar tendon-bone vs hamstring tendon) in ACL reconstruction surgery. The fragility index (FI) and reverse FI (rFI) were determined for significant and nonsignificant outcomes, respectively, as the number of outcome reversals required to change statistical significance. The fragility quotient (FQ) and reverse FQ, representing fragility as a proportion of the study population, were calculated by dividing the FI and rFI, respectively, by the sample size.

RESULTS

We identified 19 RCTs reporting 55 total dichotomous outcomes. The median FI of the 55 total outcomes was 5 (interquartile range [IQR], 4-7), meaning a median of 5 outcome event reversals would alter the outcomes' significance. Five outcomes were reported as statistically significant with a median FI of 4 (IQR, 2-6), meaning a median of 4 outcome event reversals would change outcomes to be nonsignificant. Fifty outcomes were reported as nonsignificant with a median rFI of 5 (IQR, 4-7), meaning a median of 5 outcome event reversals would change outcomes to be significant. The FQ and reverse FQ for significant and nonsignificant outcomes were 0.025 (IQR, 0.018-0.045) and 0.082 (IQR, 0.041-0.106), respectively. For 61.8% of outcomes, patients lost to follow-up exceeded the corresponding FI or rFI.

CONCLUSIONS

There is substantial statistical fragility in recent RCTs on autograft choice in ACL reconstruction surgery given that altering a few outcome events is sufficient to reverse study findings. For over half of outcomes, maintaining patients lost to follow-up may have been sufficient to reverse study conclusions.

CLINICAL RELEVANCE

We recommend co-reporting FIs and P values to provide a more comprehensive representation of a study's conclusions when conducting an RCT.

The fragility of statistical significance in distal femur fractures: systematic review of randomized controlled trials

PURPOSE

The purpose of this study was to apply both the fragility index (FI) and fragility quotient (FQ) to evaluate the degree of statistical fragility in the distal femur fracture (DFF) literature. We hypothesized that the dichotomous outcomes within the DFF literature are statistically fragile.

METHODS

Using preferred reporting items for systematic reviews and meta-analyses, we performed a PubMed search for distal femur fractures clinical trials from 2000 to 2022 reporting dichotomous outcomes. The FI of each outcome was calculated through the reversal of a single outcome event until significance was reversed. The FQ was calculated by dividing each fragility index by study sample size. The interquartile range (IQR) was also calculated for the FI and FQ.

RESULTS

Of the 4258 articles screened, 92 met the search criteria, with eleven RCTs included for analysis. Ninety eight outcome events with 25 significant (P < 0.05) outcomes and 73 nonsignificant (P > 0.05) outcomes were identified. The overall FI and FQ for all 98 outcomes were 5 (IQR 4-6) and 0.130 (IQR 0.087-0.174), respectively. Three studies (33.3%) reported loss to follow (LTF) greater than 5.

CONCLUSIONS

The randomized controlled trials in the peer-reviewed distal femur fracture literature may not be as robust as previously thought, as incorporating statistical analyses solely on a P value threshold is misleading. Standardized reporting of the P value, FI and FQ can help the clinician reliably draw conclusions based on the fragility of outcome measures.

Fragility Part I: a guide to understanding statistical power

The aim of this paper is to close the knowledge-to-practice gap around statistical power. We demonstrate how four factors affect power: p value, effect size, sample size, and variance. This article further delves into the advantages and disadvantages of a priori versus post hoc power analyses, though we believe only understanding of the former is essential to addressing the present-day issue of reproducibility in research. Upon reading this paper, physician-scientists should have expanded their arsenal of statistical tools and have the necessary context to understand statistical fragility.

The Statistical Fragility of Operative vs Nonoperative Management for Achilles Tendon Rupture: A Systematic Review of Comparative Studies

BACKGROUND

The statistical significance of randomized controlled trials (RCTs) and comparative studies is often conveyed utilizing the P value. However, P values are an imperfect measure and may be vulnerable to a small number of outcome reversals to alter statistical significance. The interpretation of the statistical strength of these studies may be aided by the inclusion of a Fragility Index (FI) and Fragility Quotient (FQ). This study examines the statistical stability of studies comparing operative vs nonoperative management for Achilles tendon rupture.

METHODS

A systematic search was performed of 10 orthopaedic journals between 2000 and 2021 for comparative studies focusing on management of Achilles tendon rupture reporting dichotomous outcome measures. FI for each outcome was determined by the number of event reversals necessary to alter significance (P < .05). FQ was calculated by dividing the FI by the respective sample size. Additional subgroup analyses were performed.

RESULTS

Of 8020 studies screened, 1062 met initial search criteria with 17 comparative studies ultimately included for analysis, 10 of which were RCTs. A total of 40 outcomes were examined. Overall, the median FI was 2.5 (interquartile range [IQR] 2-4), the mean FI was 2.90 (±1.58), the median FQ was 0.032 (IQR 0.012-0.069), and the mean FQ was 0.049 (±0.062). The FI was less than the number of patients lost to follow-up for 78% of outcomes.

CONCLUSION

Studies examining the efficacy of operative vs nonoperative management of Achilles tendon rupture may not be as statistically stable as previously thought. The average number of outcome reversals needed to alter the significance of a given study was 2.90. Future analyses may benefit from the inclusion of a fragility index and a fragility quotient in their statistical analyses.

The Fragility of Statistical Findings in Distal Radius Fractures: A Systematic Review of Randomized Controlled Trials

PURPOSE

Probability analysis with reporting of P values is often used to determine the statistical significance of study findings in the orthopedic literature. The fragility index (FI) has been used to evaluate the robustness of a significant result. The purpose of this study was to determine the utility of applying a fragility analysis to randomized controlled trials (RCTs) evaluating distal radius fractures (DRFs).

METHODS

We identified all dichotomous outcome data for randomized controlled trials of distal radius fractures (DRFs) published in 13 orthopedic journals from 2000 to 2020. The fragility index (FI) was determined by the number of event reversals required to change a P value from less than 0.05 to greater than 0.05, or vice-versa. The associated fragility quotient (FQ) was determined by dividing the FI by the sample size. The interquartile ranges (IQR) for the FI and FQ were calculated as the difference between the 25th and 75th percentiles for the overall study.

RESULTS

Of the 7352 studies screened, 221 met the search criteria, with 34 randomized controlled trials evaluating distal radius fractures and 151 total outcome events included for analysis. The overall FI was 9 (IQR 6.5-11) with an associated fragility quotient of 0.097 (IQR 0.060-0.140). However, a majority of outcomes (78.8%) were not significant. Fragility analysis of statistically significant outcomes had an FI of 4 (IQR 1-10). All of the studies reported lost to follow-up (LTF) data where 20.6% reported lost to follow-up of greater or equal to 9.

CONCLUSION

The RCTs in distal radius fracture outcomes have comparable statistical robustness to literature in other orthopedic surgical specialties, are not as statistically stable as previously thought and should be interpreted with caution. We recommend that orthopedic literature report the FI and FQ along with the P values to help the reader draw reliable conclusions based on the fragility of outcome measures.

LEVEL OF EVIDENCE

Level I.