Why graft choice matters in ACL reconstruction

Choosing to have ACL reconstruction is often straightforward; choosing which graft to use is considerably less so. Surgeons performing this procedure — one of the most common in orthopaedic practice — do not default to a single option, because the evidence consistently shows that patient profile, not surgical habit, should drive the decision.

Three graft families sit at the centre of that decision. Hamstring tendon autograft uses the patient's own semitendinosus and gracilis tendons. Bone-patellar tendon-bone autograft takes a strip of the patellar tendon with a bone block at each end. LARS (Ligament Advanced Reinforcement System) is a polyethylene terephthalate synthetic device, used either alone or to augment a biological graft. Each carries a distinct set of mechanical properties, healing biology, and donor-site considerations.

Data from national registries spanning tens of thousands of reconstructions confirm what most experienced knee surgeons observe in practice: the same graft is not right for every patient. Age, sex, the demands of the sport or occupation, knee anatomy, and whether this is a primary or revision procedure all shift the calculation.

The sections below work through each graft in turn, then bring together the factors that personalise the choice.

What hamstring tendon autograft offers

Hamstring tendon autograft draws its appeal primarily from what it does not do: it avoids the anterior knee pain and kneeling discomfort that accompany patellar tendon harvest. For patients whose work or daily life involves kneeling, that donor-site advantage is a meaningful practical consideration.

The trade-off is visible in large-scale registry data. Three independent national registries — Denmark (13,647 reconstructions), Norway (12,643), and Kaiser Permanente in the USA (9,817) — converge on hamstring graft carrying a 1.4 to 2.3 times higher revision risk than BPTB. Danish five-year figures put revision at 4.45% for hamstring versus 3.03% for patellar tendon. The gap is starkest in young female athletes: New Zealand registry data show hamstring failure reaching 7.7% in this group, against 1.1% for BPTB — a hazard ratio of 6.1.

The Swedish registry (13,102 patients) and a Cochrane review of 19 randomised trials found no statistically significant difference in rupture rates — a genuine divergence in the evidence that the field has not yet fully resolved.

Two anatomical factors compound the risk. A harvested graft diameter below 8 mm significantly elevates re-rupture likelihood. A posterior tibial slope of 12° or more does so further: a 2025 study found rupture rates of 19.4% with a steep slope versus 2.7% with a shallower one, rising to 26% where excess anterior tibial translation was also present. Preoperative imaging should assess both.

Hamstring autograft remains appropriate for many patients; the key is identifying whose anatomy and risk profile it suits.

When patellar tendon bone graft has the edge

Patellar tendon graft earns its reputation not through reputation alone but through a mechanical detail that distinguishes it from soft-tissue fixation: the bone blocks at each end of the harvested strip sit directly inside the tibial and femoral tunnels, where they heal bone-to-bone. That process — faster and mechanically more secure than the fibrous ingrowth by which hamstring tendons integrate — translates into earlier rotational stability during the period when the graft is most vulnerable to re-injury.

The clinical consequence shows clearly in a 2026 high-demand cohort, where BPTB recorded a re-rupture rate of 12.9% against 35.7% for hamstring graft (p=0.03). That gap is consistent with the national registry patterns discussed above, though worth noting that registry comparisons carry an inherent selection effect — surgeons already tend to direct higher-risk athletes towards BPTB, which may amplify the apparent advantage.

The trade-off patients must weigh is kneeling discomfort. Anterior knee pain at the harvest site affects approximately 29% of BPTB recipients, compared with around 7% after hamstring harvest. For tradespeople, athletes in contact sports, or anyone whose occupation involves prolonged kneeling, that figure warrants serious consideration before accepting this graft.

Anatomy is not irrelevant here either. In a prospective series of 2,439 primary BPTB reconstructions followed for a mean of 11.6 years, a posterior tibial slope of 10° or more was associated with a graft tear rate of 9.7% versus 4.8% below that threshold — a reminder that BPTB is not failure-proof in adverse anatomy.

The patients who benefit most from BPTB are typically young adults competing in pivoting and cutting sports, female athletes in whom hamstring failure rates are disproportionately high, and those undergoing revision surgery where tunnel position and fixation strength are at a premium.

Where LARS standalone and hybrid grafts fit

Synthetic grafts occupy a narrower but legitimate place in ACL reconstruction — provided the right construct is matched to the right patient.

Standalone LARS

LARS is a polyethylene terephthalate scaffold that provides immediate mechanical strength with no donor-site pain and no harvest morbidity. In theory, that combination should be ideal. In practice, the long-term data from active populations tell a sobering story: mid-to-long-term failure rates range from 33% to 50% in primary reconstructions. A 2014 report on elite AFL players found a 50% failure rate at three years alone, and that finding effectively ended routine standalone use in high-demand athletes.

The picture is meaningfully different in lower-demand patients. A 2024 cohort study (Moretti) of middle-aged patients reported a graft failure rate of just 3.8%, with no infections or implant complications — a result that supports standalone LARS as a reasonable option where faster recovery and the avoidance of harvest surgery matter more than long-term mechanical demands.

LARS hybrid (augmented hamstring)

The hybrid construct pairs a biological hamstring autograft with a LARS scaffold that acts as a protective reinforcement during the early high-load healing phase — not as a structural replacement. Studies consistently show significantly better short-term Lysholm, IKDC, Tegner, and psychological readiness (ACL-RSI) scores compared with hamstring autograft alone. By medium-term, KT-1000 laxity measurements converge between the two approaches, and Qurashi's 8–11 year follow-up data (2025) confirm the hybrid remains safe and durable over time.

The hybrid is best justified when the harvested hamstring is small in diameter, the patient is aged over 40, or an accelerated return to function is a genuine clinical priority. Head-to-head RCT data comparing hybrid with autograft at scale remain limited, and that evidence gap should inform expectations on both sides.

The factors that personalise graft choice

No single variable determines graft choice on its own — the factors interact. A 17-year-old female footballer playing pivoting sport at regional level brings together three of the most powerful risk modifiers for hamstring failure: youth, sex, and high sport demand. If preoperative imaging then reveals a steep tibial slope, the evidence discussed above consistently points away from hamstring graft without further adjuncts. The combination overrides what any single factor would suggest in isolation.

It helps to think of the decision variables in two clusters. Patient-level factors — age, sex, and the intensity of sport or occupational demand — set the baseline risk profile; the anatomical factors established by imaging (tibial slope, predicted tendon diameter) modify it up or down. A middle-aged recreational patient with a steep slope still needs that slope considered, even if the overall risk picture differs markedly from a younger athlete's. Neither cluster overrides the other in isolation.

Revision surgery adds a constraint that primary cases do not face: previous tunnel position and residual bone stock from the original reconstruction can limit which graft configurations are mechanically feasible, independent of what might otherwise be preferred. Allograft is generally disfavoured in younger patients undergoing revision, though what is achievable depends on what the surgeon finds at the time.

Because these variables compound rather than simply add, working out where a given patient sits across all of them — and which trade-offs are acceptable given anatomy, lifestyle, and surgical history — is the work of a specialist assessment, not a checklist.

Getting an assessment at Lincolnshire Knee

The evidence, taken together, points to one consistent conclusion: graft selection that accounts for age, sex, tibial slope, sport demand, and achievable graft diameter produces meaningfully better outcomes than any single default choice. For patients approaching this decision, that individualisation begins with a structured specialist assessment — clinical examination, imaging review, and a careful discussion of anatomy, activity level, and personal priorities.

At Lincolnshire Knee, objective lower-limb biomechanical data from MAI Motion® assessment can contribute relevant information on movement mechanics as part of surgical planning. The clinic is consultant-led and accepts patients without a GP referral, with appointments available at Sleaford (NG34) and Grantham (NG31).

To book, visit lincolnshireknee.co.uk.

1. [1] Emerging Topics in ACL Graft Selection: Best Evidence for the Use of Quadriceps Tendon Graft (2021). (2021). https://doi.org/10.1016/j.otsm.2021.150835 https://doi.org/10.1016/j.otsm.2021.150835
2. [2] The Impact of Posterior Tibial Slope and Static Anterior Tibial Translation on ACL Graft Rupture Rates After Hamstring Autograft + LET (AJSM 2025). (2025). https://doi.org/10.1177/03635465251350397 https://doi.org/10.1177/03635465251350397
3. [3] Posterior Tibial Slope in Patients Undergoing ACL Reconstruction with Patellar Tendon Autograft (AJSM 2021). (2021). https://doi.org/10.1177/0363546520982241 https://doi.org/10.1177/0363546520982241