Are Comparable Short-term Outcomes Between Hamstring and Quadriceps Tendon Autografts for ACL Reconstruction Statistically Robust? A Reverse Continuous Fragility Index Analysis of Randomized Controlled Trials
Orthopaedic journal of sports medicine · 2026
The 'no difference' between hamstring and quad tendon ACL grafts holds up statistically, but robust-null doesn't mean proven-equivalent.
The paper
Systematic review (meta-research/statistical re-analysis), 8 RCTs, 562 allocated patients, adult primary ACL reconstruction comparing hamstring tendon vs quadriceps tendon autografts.
What they found
Across 6 studies with nonsignificant primary continuous outcomes, the mean reverse continuous fragility index (rCFI) was 17.4 ± 7.3 and the mean reverse fragility quotient was 0.296 ± 0.069; every eligible primary outcome had an rCFI exceeding its trial's loss to follow-up (80 of 562 patients overall), and 19 of 21 secondary outcomes did too.
Study design
This is not a clinical outcomes trial but a PRISMA-guided systematic review applying a novel fragility metric to existing Level 1 RCTs (n=8, 562 patients) comparing HT and QT autografts for ACLR; it sits at the meta-research/methods level above the primary trials it re-analyzes.
Methodology
rCFI was calculated from pseudo-individual patient datasets reconstructed from published summary statistics rather than true IPD, which is an approximation clinicians should note before trusting the exact numbers. The abstract gives no mention of formal risk-of-bias grading (e.g. Cochrane RoB2 or GRADE) of the underlying trials, and heterogeneity in graft fixation, sample size, and follow-up across the 8 source RCTs isn't addressed; publication bias also applies since only published RCTs with sufficient summary statistics could be included, and a sensitivity analysis across 20 simulation seeds is the main internal check on stability.
The appraisal
The fragility metric is a statistical concept, not a clinical effect size, so this tells you the 'no difference' conclusions in the source RCTs are unlikely to flip with small numbers of patient reclassifications, but it does not establish that HT and QT grafts are clinically equivalent, only that the individual trials' null findings aren't fragile artifacts of chance or dropout. Worth flagging: rCFI wasn't calculated from real patient-level data but from pseudo-individual datasets simulated from each trial's published means and SDs, and the headline mean rCFI of 17.4 rests on just 6 primary outcomes across 6 studies, so treat it as indicative rather than precise. None of this addresses whether those trials were adequately powered as equivalence or non-inferiority studies in the first place, which is a different and unanswered question.
The gap
A robust null result in underpowered superiority trials is not the same as proof of equivalence; you'd need adequately powered non-inferiority RCTs with individual patient data and standardized outcome definitions before treating this as settled.
Landmark context
This extends the fragility index concept (originally developed for binary outcomes in RCTs, later adapted to continuous outcomes) to the specific HT vs QT graft debate, building on the existing body of RCTs and meta-analyses that have generally reported comparable short-term outcomes between these grafts.
What to do Monday
No change to Monday practice. It offers reassurance that the existing 'comparable outcomes' literature for HT vs QT grafts isn't just statistical noise, but graft choice should still be individualized based on donor-site morbidity, patient activity, and surgeon experience as before.
In practice
This doesn't change graft selection, which stays a shared surgeon-patient decision weighing donor-site trade-offs: HT carries more risk of residual hamstring strength deficit and graft laxity, QT more anterior knee pain and early quad inhibition. In clinic, keep rehab graft-specific rather than generic, front-load quad activation work after QT harvest and prioritise eccentric hamstring loading (Nordics progression) after HT harvest. On the S&C floor, when clearing an athlete for return to sprinting or cutting, test the deficit that matches their graft, Single Leg Extension or Single Leg Press for QT-harvested quad strength, Single Leg Seated Leg Curl for HT-harvested hamstring strength, alongside Single leg jump or Countermovement jump for power symmetry, rather than assuming this paper's statistical reassurance means equal readiness timelines. The caveat in applying it: this study says the trials' 'no difference' conclusions are statistically sound, not that any individual athlete's recovery curve will match the average, so keep progressing by the numbers you re-test, not by the literature alone.
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