Rizzoli Over-The-Top ACL Reconstruction

https://pubmed.ncbi.nlm.nih.gov/9604189/

• 👥 Patient population: 40 sports-active patients, minimum 2-year follow-up (mean 36 months). 33 men/7 women; age 18–40 (mean 25). 16 acute cases; 24 chronic (injury-to-surgery 2–121 months, mean 22.5)
• ✅ 92.5% normal or nearly normal knees (IKDC A/B); mean Lysholm 95
• 📏 Instrumented stability: KT-2000 mean side-to-side difference 2.1 mm (range 0–8); 93.3% within 0–5 mm
• ⚽ Return to sport: 100% resumed sport; 90% at the same level. Timing: 67.5% at 3–4 months, 27.5% at 4–6 months
• 🦵 Low morbidity: full ROM in 95%; anterior knee pain 5%; no patellofemoral crepitus reported
• 🚀 Accelerated rehab didn’t compromise stability: earlier return (3–4 months) was not associated with worse IKDC/stability

https://pmc.ncbi.nlm.nih.gov/articles/PMC9520075/

• 👥 Patient context: Technical note describing single-stage revision ACL reconstruction using Achilles tendon allograft with bone block, combined with lateral extra-articular tenodesis (LET) — designed for failed primary ACL with rotatory instability and tunnel malposition/widening
• 🔧 Key surgical advantage: OTT technique eliminates need for a new femoral tunnel, bypassing tunnel overlap, widening, or hardware issues — useful in complex revision cases
• 🔁 Addresses rotatory instability: LET incorporated through the same graft, fixed just medial to Gerdy’s tubercle, enhancing pivot-shift control in high-risk revision patients
• 🦴 Versatile graft option: Achilles allograft with calcaneal bone block allows tibial fixation with interference screw and femoral fixation with staples; suitable when autograft options are limited
• 📊 Reported literature outcomes (revision OTT): ~52% return to preinjury sport level; ~8.4% failure rate; functional outcomes comparable to anatomic revision techniques
• 💰 Cost-efficient construct: Requires only three staples plus tibial interference screw; avoids staged bone grafting and prolonged two-stage recovery

https://www.sciencedirect.com/science/article/pii/S2212628725004256

• 👥 Indication:

Revision ACL cases with femoral tunnel malposition or enlargement, and tibial tunnels ≥8 mm — where traditional tunnel-based revision may require 2-stage surgery.

• 🔧 Key Innovation:

Classic OTT (hamstrings with preserved tibial insertion) is augmented with peroneus longus allograft, increasing graft diameter from 5.5–7 mm to >8 mm, making it suitable for revision settings.

• 🦴 Single-Stage Solution:

Avoids femoral tunnel drilling entirely → enables correction of femoral tunnel malposition without staged bone grafting.

• 🔄 Biomechanical Rationale:
• Larger graft diameter (>8 mm) improves strength and lowers failure risk
• Preserving tibial insertion may enhance biological integration
• Built-in LET improves rotational stability
• 💰 Practical Advantages:

Cost-effective staple fixation

Reduced morbidity vs 2-stage revision

Addresses intra- and extra-articular instability simultaneously

• ⚠️ Limitations:**

Extra lateral incision

Hardware-related symptoms possible

Allograft required if prior hamstrings used

Core Message

In complex revision ACL cases, augmented OTT provides a tunnel-free, >8 mm graft, single-stage solution — eliminating femoral malposition while restoring rotational stability.

https://pmc.ncbi.nlm.nih.gov/articles/PMC12322690/

• 👥 Population: 75 skeletally immature patients (mean age 13.9 ± 2.2 years) with acute ACL rupture.
• 🧮 6 Weighted Criteria (Score 0–10):

MRI factors

1. Bucket-handle or radial tear (3 pts)
2. Ramp/longitudinal tear (2 pts)
3. Lateral bone bruise pattern (1 pt)

Patient factors

4. Skeletal age ≥13 (boys) / ≥11 (girls) (2 pts)
5. Non-contact injury during preferred sport (1 pt)
6. Grade 3 pivot shift (1 pt)
• ⚖️ Interpretation:
• 0–2 points → Conservative treatment
• ≥3 points → Surgical treatment
• 📈 Predictive Performance:
• Positive predictive value (surgery needed) = 91.7%
• Negative predictive value (conservative success) = 87.5%
• 🎯 Purpose:

Provides a structured, MRI-based framework to predict failure of conservative care and guide early surgical decision-making in skeletally immature ACL injuries.

In short:

It predicts who will fail nonoperative treatment before instability causes secondary damage

https://pmc.ncbi.nlm.nih.gov/articles/PMC12459316/

• 👥 Indication: ACL injuries in skeletally immature patients; treatment tailored based on MRI bone age assessment, not chronological age.
• 📊 Three-stage OTT strategy based on skeletal maturity:

1️⃣ Prepubescents → Extra-physeal (no tunnels, no hardware)

2️⃣ Young adolescents → Supra-physeal (epiphyseal tibial tunnel, fixation above physes)

3️⃣ Older adolescents → Trans-physeal (adult-style technique)

• 🦴 Femoral fixation without tunnel in all stages (true OTT route), minimizing risk to distal femoral physis.
• 🔄 Single continuous graft + lateral tenodesis improves rotational control while preserving hamstring tibial insertion, potentially enhancing graft maturation.
• 📈 Clinical outcomes:

High return-to-sport rates, low growth disturbance rates, and durable long-term adult data supporting safety of the OTT construct.

Extraphyseal Technique

Supraphyseal Technique

Transphyseal Technique

https://pmc.ncbi.nlm.nih.gov/articles/PMC12620561/

• 👥 Patient population

Paediatric and skeletally immature athletes with ACL injuries, typically ages 12–14, where open physes make surgical management more complex.

• 📈 Incidence is increasing

ACL injuries in children are rising due to increased sport participation, with ~2.3% annual increase reported in the United States.

• ⚠️ Non-operative treatment carries risks

Conservative management may lead to secondary meniscal injury rates as high as 60–70%, potentially accelerating long-term joint degeneration.

• 🧠 Treatment must consider skeletal age, not chronological age

MRI-based skeletal maturity assessment (STEP method) helps guide technique selection and determine remaining growth and physeal risk.

• 🧭 BABY-Knee algorithm guides decision-making

A 10-point scoring system incorporating bone age, meniscal injury, bone bruising, laxity, and trauma mechanism helps determine conservative vs surgical treatment.

• 🔧 Technique selection depends on growth remaining

Surgical options include:

1. Extraphyseal (Over-the-Top) – preferred in prepubescent children
2. All-epiphyseal – tunnels within epiphysis
3. Partial transphyseal – hybrid approach
4. Transphyseal – used near skeletal maturity.

https://www.aaos.org/videos/video-detail-page/?id=17134__Videos

https://pmc.ncbi.nlm.nih.gov/articles/PMC12420572/

• 👦 Indication: Prepubescent skeletally immature patients with ≥5 years of growth remaining (bone age: boys <12, girls <10), open physes on MRI.
• 🦴 No tunnels. No hardware.

Hamstrings (gracilis + semitendinosus) left attached distally, passed over-the-top and fixed to periosteum — completely extraphyseal, avoiding femoral and tibial drilling.

• 🔄 Combined intra- + extra-articular construct

Single graft restores AP and rotational stability, incorporating a lateral extra-articular tenodesis (LET).

• 📉 Designed to minimize physeal risk

Graft passed under the intermeniscal ligament (not through a tibial tunnel) to protect the proximal tibial physis.

• 📚 Built on 25-year adult OTT data

Adult OTT + LET series show durable long-term results, supporting its adaptation to the pediatric extraphyseal setting.

https://pmc.ncbi.nlm.nih.gov/articles/PMC12712505/

• 👥 Indication:

Skeletally immature patients (Tanner stage 2–3) with 5–7 years of growth remaining, where preserving the femoral physis is critical.

• 🔧 Hybrid surgical concept:

Combines three principles in one construct:

1. Transphyseal tibial ACL tunnel
2. Over-the-top femoral fixation (physeal-sparing)
3. All-epiphyseal tibial fixation for ALL reconstruction
• 🦴 Single hamstring graft with preserved tibial insertion

Semitendinosus and gracilis are harvested while maintaining their tibial attachment, then routed through the tibial tunnel and over the lateral femoral condyle.

• 🔄 Built-in rotational control:

The remaining graft portion reconstructs the anterolateral ligament (ALL) and is fixed epiphyseally on the tibia, providing additional rotational stability.

• ⚠️ Rationale for OTT femoral fixation:

Femoral physeal injury carries greater risk of growth disturbance and angular deformity, making physeal-sparing approaches preferable in children.

• 📉 Failure reduction strategy:

Pediatric ACL reconstruction has failure rates up to 23% (or 32% including contralateral injury); adding anterolateral augmentation may improve stability and reduce graft rupture risk.

Key Insight

Using over-the-top femoral fixation allows ACL reconstruction in children while protecting the femoral growth plate, making it a valuable option for skeletally immature athletes.

https://pmc.ncbi.nlm.nih.gov/articles/PMC9705769/

Single-Stage Strategy for Multiple Failures

• 👥 Paper type: Technical Note describing single-stage revision ACL reconstruction combined with slope-reducing high tibial osteotomy (HTO) in patients with multiple graft failures and posterior tibial slope (PTS) >12° (Arthrosc Tech 2022, Zsidai et al.)
• 📐 Why slope matters:

PTS ≥12° strongly associated with recurrent graft failure; slope reduction decreases anterior tibial translation and ACL graft forces (Arthrosc Tech 2022, Zsidai et al.)

• 🔧 Key surgical concept:

Combine anterior closing-wedge HTO (target PTS 7–10°) with OTT Achilles allograft ACL reconstruction in a single stage (Arthrosc Tech 2022, Zsidai et al.)

• 🔁 Revision advantage of OTT:

Bypasses widened or malpositioned femoral tunnels, avoids new femoral tunnel drilling, and simplifies complex revision scenarios (Arthrosc Tech 2022, Zsidai et al.)

• 🎯 Core principle:

Address both biologic and biomechanical failure drivers —correct the slope, eliminate tunnel error, restore stability (Arthrosc Tech 2022, Zsidai et al.)

https://pubmed.ncbi.nlm.nih.gov/9604189/

• 👥 Patient population: 40 sports-active patients, minimum 2-year follow-up (mean 36 months). 33 men/7 women; age 18–40 (mean 25). 16 acute cases; 24 chronic (injury-to-surgery 2–121 months, mean 22.5)
• ✅ 92.5% normal or nearly normal knees (IKDC A/B); mean Lysholm 95
• 📏 Instrumented stability: KT-2000 mean side-to-side difference 2.1 mm (range 0–8); 93.3% within 0–5 mm
• ⚽ Return to sport: 100% resumed sport; 90% at the same level. Timing: 67.5% at 3–4 months, 27.5% at 4–6 months
• 🦵 Low morbidity: full ROM in 95%; anterior knee pain 5%; no patellofemoral crepitus reported
• 🚀 Accelerated rehab didn’t compromise stability: earlier return (3–4 months) was not associated with worse IKDC/stability

https://pubmed.ncbi.nlm.nih.gov/33523751/

• 👥 Patient population: 267 consecutive primary ACL reconstructions (2007–2009); mean age 30.7 years; 77% male; mean follow-up 10.1 years. 44% medial meniscal lesions; 21% lateral meniscal lesions
• 🔁 Low revision rate: 3% ACL revision; 96.3% 10-year survivorship
• 📊 Strong PROMs at 10 years:
• Lysholm 94.1 ± 10.8
• KOOS Pain 95.7, Symptoms 92.5, ADL 98.4, Sport 90.7, QoL 91.2
• 81–99% achieved PASS across KOOS subscales
• ⚽ Return to sport: 82% resumed sport postoperatively; 57% still active at 10 years
• 📈 Risk factors for worse outcomes:
• Medial meniscal lesion → ↑ risk of revision/new meniscectomy
• Outerbridge ≥2 chondropathy → lower KOOS & higher pain
• Female sex → lower Sport & QoL scores
• 🦴 Overall reoperation rate 13% (mostly hardware removal); arthroplasty rare (≤1%)

https://pubmed.ncbi.nlm.nih.gov/31910045/

👥 Patient population

• 244 patients after primary ACL reconstruction
• All underwent single-bundle Over-the-Top ACL reconstruction + lateral plasty
• Mean follow-up: 10 years.

📊 Second ACL injury rates (10-year)

• Ipsilateral graft failure: 3.4% (8 patients)
• Contralateral ACL reconstruction: 7.8% (19 patients)

➡️ >2× higher risk of contralateral ACL injury vs graft failure

📈 Survival outcomes

• Ipsilateral graft survival: 96.3%
• Contralateral knee survival: 92.2%
• Overall survival (any ACL injury): 89.3%

📍 Timing of injuries

• Risk of contralateral injury becomes significantly higher after 6 years
• Mean time to injury:
• Ipsilateral: 3.7 years
• Contralateral: 3.5 years

⚠️ High-risk subgroup

• Age <18 + high activity (Tegner ≥7)
• 10-year survival of both knees: 61%

➡️ Up to ~40% risk of second ACL injury

🦴 Interpretation

• The reconstructed knee shows low failure rates after OTT + LET
• However, the contralateral knee remains vulnerable, especially in young active patients
• ACL injury risk is therefore not just a graft problem, but a patient-level / biomechanical issue

💡 Key message

• After OTT ACL reconstruction, contralateral ACL injury is more than twice as common as graft failure, highlighting excellent graft durability but persistent patient-level injury risk.

https://pubmed.ncbi.nlm.nih.gov/12548444/

• 👥 Patient population: 60 high-level athletes enrolled (1993–1995); 50 available at mean 6.4-year follow-up. 40 men, 10 women; professional/competitive cutting-sport athletes
• ✅ 92% normal or nearly normal knees (IKDC) at midterm follow-up
• 📊 Mean Lysholm score 94; mean Tegner 8.1, with high activity restoration
• ⚽ 90% returned to sport at the same level, many within 4–6 months
• 📏 76% had <3 mm laxity on KT-2000 testing; only 6% >5 mm
• 💪 No significant long-term quadriceps or hamstring strength deficit; low morbidity overall

https://pubmed.ncbi.nlm.nih.gov/19193599/

• 👥 Patient population: 60 consecutive high-level cutting-sport athletes (1993–1995); 54 available at mean 11-year follow-up (90% follow-up). 42 men, 12 women; 26 acute and 28 chronic ACL injuries
• ✅ 90.7% normal or nearly normal knees (IKDC A/B) at long-term follow-up
• 📊 Mean Lysholm score 97.3; mean subjective score 90% at 11 years
• 📏 74% had <3 mm laxity on KT-2000; only 6% >5 mm — stability maintained from 5 to 11 years
• 🦴 Medial joint-space narrowing associated with meniscectomy (P = .0095); no significant lateral compartment degeneration
• 🔧 Low complication profile: staple removal in 13%; no significant tunnel enlargement at long-term follow-up

https://pubmed.ncbi.nlm.nih.gov/28922015/

• 👥 Patient population: 60 consecutive patients (1993–1995); 52 available at mean 24-year follow-up (41 men, 11 women; mean age at surgery 25.5 years). 25 acute and 27 chronic ACL injuries
• ✅ 84–86% normal or nearly normal knees (IKDC A/B) at 20 years; mean Lysholm 85.7 ± 14.6
• 📏 Excellent long-term stability: Only 12% had >5 mm KT-2000 side-to-side difference; KiRA pivot-shift positive in the same 12%
• ⚽ 86% still practicing sport at 20 years, though Tegner activity level declined over time (lifestyle-related reduction)
• 🦴 Meniscectomy was the key driver of osteoarthritis: Significant medial joint-space narrowing in meniscectomized knees (P = .0114); no increased lateral or patellofemoral OA from lateral tenodesis
• 🔁 Low failure profile: 1 rerupture (2%); 4 clinical failures among 29 fully evaluated patients at final follow-up

https://pubmed.ncbi.nlm.nih.gov/35451640/

• 👥 Patient population: 28 professional male footballers (33 ACLRs), mean age 25.3 years; mean follow-up 12.6 years. All reconstructions used hamstrings with over-the-top techniques
• ⚽ Return to play:
• 97% returned to sport
• 94% played an official match
• First match at 8.0 ± 3.6 months
• 📊 Long-term function:

Mean Lysholm 94.2 ± 8.3 at >12 years

• 🔁 Re-rupture rate:

3/33 ACLRs (9%) overall; 6% ipsilateral revision at 1–5 years

• 🔄 Contralateral risk:

21% sustained contralateral ACL injury during follow-up; 32% had bilateral ACL injury across career

• 🏆 Career durability:

82% still competing professionally at 3 seasons; many sustained long careers despite high pivoting demands

https://pmc.ncbi.nlm.nih.gov/articles/PMC12678718/

📚 Study design

• Retrospective case series (Level IV)
• 58 elite professional soccer players undergoing ACL reconstruction at Rizzoli.

🔧 Technique

• Hamstring autograft ACL reconstruction
• Techniques included Over-the-Top (OTT) ± lateral tenodesis and double-bundle reconstructions.

⚽ Return to play

• 96.6% returned to play
• 6.4 months to training, 7.5 months to official match.

📈 Performance

• 53% played >20 matches in season 1
• 65% played >20 matches in season 2
• Most athletes recovered pre-injury participation by the second season.

⚠️ Second ACL injury

• 15.8% overall second ACL injury rate
• Contralateral injury (10.5%) > graft failure (5.3%).

⏱ Key risk factor

• Returning to match before 5 months significantly increased reinjury risk, especially in athletes <21 years.

✅ Takeaway

• ACL reconstruction using hamstring grafts with OTT techniques enables near-universal return to elite sport with durable outcomes.

https://pubmed.ncbi.nlm.nih.gov/31549207/

• 👥 Patient population: 35 patients, mean follow-up 2.2 years
• 14 skeletally immature adolescents (primary ACLR; age 14±1)
• 21 skeletally mature adults (revision ACLR; age 25±8)
• No previous lateral extra-articular tenodesis performed
• 📏 Anterior laxity significantly improved:
• Adolescents: 3.9 → 1.2 mm SSD (p=0.040)
• Revision: 4.2 → 1.2 mm SSD (p<0.001)
• 🔄 Rotatory stability restored:

Significant improvement in Lachman and pivot-shift grades in both groups

• 💥 Graft failure rate:
• Adolescents: 14.3% (2/14)
• Revision: 4.8% (1/21)

All due to new trauma ≥1 year post-op

• 🦴 Key advantage:

Avoids femoral physeal violation in adolescents and enables one-stage revision in cases with tunnel widening or overlap

https://pubmed.ncbi.nlm.nih.gov/30209520/

• 👥 Patient population: 20 athletes (age 8–13 years, Tanner I–IV) with open proximal tibial physes; mean follow-up 54 months.
• 📊 Marked clinical improvement:
• Lysholm improved from 40 → 100
• KOOS improved from 59 → 99
• 19/20 IKDC A; 1 IKDC B
• 📏 Excellent objective stability:
• Median KT-1000 side-to-side difference: 0.0 mm
• All pivot shift grade I
• No patient with >5 mm laxity
• ⚽ Return to sport:
• 100% returned to sport
• 60% returned to pre-injury level
• 30% returned to competitive level
• 🦴 Growth disturbances:
• 3 minor cases (≤1 cm LLD or ≤4° varus)
• No graft failures reported
• 🎯 Takeaway:

The all-epiphyseal OTT + lateral tenodesis technique provides excellent stability, high return-to-sport, and minimal growth disturbance risk in pediatric patients.

https://pubmed.ncbi.nlm.nih.gov/31993711/

👥 Patient population

• 42 skeletally immature patients with ACL rupture
• 30 males, 12 females
• Mean age 12.5 years (range 11–14).

🔧 Technique

• Over-the-Top ACL reconstruction with lateral extra-articular tenodesis (LET)
• All surgeries performed by a single surgeon with standardized rehabilitation.

⏱ Follow-up

• Mean follow-up 96.1 months (~8 years).

📊 Clinical outcomes

• Tegner-Lysholm improved from 55 → 94.8
• Pedi-IKDC improved from 40 → 94.78
• Mean side-to-side laxity 1.2 mm (KT-1000).

⚽ Return to sport

• 22 patients returned to pre-injury sport level
• Average return to sport 7.3 months.

⚠️ Safety

• No instability or leg-length discrepancy reported
• Low complication rate and no hardware failure.

💡 Key message

• Physeal-sparing OTT ACL reconstruction with LET provides excellent long-term outcomes and appears safe and effective in skeletally immature patients.

https://pmc.ncbi.nlm.nih.gov/articles/PMC12673041/

👥 Patient population

• 43 skeletally immature patients (mean age 13.3 years)
• Treated with physeal-sparing OTT ACL reconstruction + LET
• Mean follow-up: 11 years (range 8–17 years).

📈 Graft survivorship

• 90% survivorship from ACL revision at 10 and 15 years
• Revision ACL reconstruction occurred in 9% of patients.

🔧 Reoperations

• 26% required ipsilateral reoperation
• Most common reason: staple removal due to local discomfort.

⚠️ Second ACL injuries

• 28% experienced a second ACL injury (including contralateral)
• Mean time to second injury ≈4 years after surgery.

📊 Functional outcomes

• KOOS scores exceeded Patient Acceptable Symptom State thresholds across all domains
• 84% achieved successful long-term clinical outcomes.

✅ Key message

• Physeal-sparing OTT ACL reconstruction with LET demonstrates excellent long-term durability and functional outcomes in skeletally immature patients.

https://pubmed.ncbi.nlm.nih.gov/31549207/

• 👥 Patient population: 35 patients, mean follow-up 2.2 years
• 14 skeletally immature adolescents (primary ACLR; age 14±1)
• 21 skeletally mature adults (revision ACLR; age 25±8)
• No previous lateral extra-articular tenodesis performed
• 📏 Anterior laxity significantly improved:
• Adolescents: 3.9 → 1.2 mm SSD (p=0.040)
• Revision: 4.2 → 1.2 mm SSD (p<0.001)
• 🔄 Rotatory stability restored:

Significant improvement in Lachman and pivot-shift grades in both groups

• 💥 Graft failure rate:
• Adolescents: 14.3% (2/14)
• Revision: 4.8% (1/21)

All due to new trauma ≥1 year post-op

• 🦴 Key advantage:

Avoids femoral physeal violation in adolescents and enables one-stage revision in cases with tunnel widening or overlap

https://pubmed.ncbi.nlm.nih.gov/23292987/

• 👥 Patient population:

24 male athletes (mean age 30 years) with ≥2 prior failed ACL reconstructions

1. 20 had 2 prior reconstructions
2. 4 had 3 prior reconstructions

Mean follow-up: 3.3 years

• 🛠 Technique:

Non-anatomic over-the-top femoral route + lateral extra-articular plasty

Achilles (37.5%) or tibialis posterior (62.5%) fresh-frozen allograft

Designed to avoid staged femoral tunnel grafting

• 📊 Clinical outcomes:
• IKDC subjective improved from 40.8 → 81.3 (P < .005)
• 83% IKDC objective A/B
• 📏 Stability:
• Mean KT-2000 side-to-side difference: 3.1 mm
• 8% objective failures (2 patients)
• 🏃 Return to sport:
• 71% returned to pre-injury level
• Traumatic failures had significantly better outcomes than atraumatic failures
• 🎯 Key insight:

OTT + LET allows single-stage revision in complex femoral tunnel situations with outcomes comparable to other revision series, though mild residual laxity was relatively common

https://pmc.ncbi.nlm.nih.gov/articles/PMC5738484/

• 👥 Patient population:

24 patients (mean age 31.9 ± 11.2 years) undergoing revision ACL reconstruction with the over-the-top (OTT) technique; mean follow-up 30.7 ± 18.9 months

• 📊 Objective stability improved significantly:
• 72% IKDC objective A/B postoperatively (vs 0% pre-op)
• Mean KT-1000 side-to-side difference: 3.1 ± 2.4 mm
• 📈 Subjective outcomes:
• IKDC subjective improved significantly (51.1 → 63.7, p = 0.0027)
• KOOS, Lysholm, Tegner improved (not statistically significant)
• ⚽ Return to sport:
• 81.8% returned to sport
• 44.4% returned to same pre-injury level
• ACL-RSI psychological readiness strongly associated with RTP (p = 0.0168)
• ⚠️ Complications & survivorship:
• 14.3% failure prevalence
• Kaplan–Meier survivorship ~81% at 60 months
• 21.5% required staple removal
• 🎯 Key advantage:

The main benefit highlighted: avoiding femoral tunnel management in revision cases with tunnel widening or malposition

https://pubmed.ncbi.nlm.nih.gov/31324964/

• 851 patients, mean age 28.8 years, mean follow-up 4.9 years; overall failure rate 3.6%, complication rate 8%.
• Three OTT series (Buda, Zaffagnini, Zanovello) used a femoral over-the-top graft passage, avoiding femoral tunnel management.
• OTT studies reported ~3 mm side-to-side laxity, high IKDC A/B rates, and acceptable mid-term survivorship (~80–85%).
• Other techniques (Lemaire, Coker-Arnold ITB tenodesis) required standard femoral tunnel drilling but showed similar pooled outcomes: 83% negative pivot shift and 2.6 mm mean arthrometric difference.
• No clear superiority demonstrated; however, OTT uniquely avoids femoral tunnel issues, making it particularly useful in complex revision cases.

https://pubmed.ncbi.nlm.nih.gov/37386198/

• 👥 32 varus, ACL-deficient knees with medial OA

Mean age at surgery: 38.6 years

72% available at final follow-up

Mean follow-up: 14.3 ± 2.2 years

• 🔧 Technique:

Lateral closing wedge HTO + Over-the-Top ACL reconstruction (Marcacci–Zaffagnini) using hamstrings with extra-articular ITB fixation.

• 📈 Clinical improvement sustained long term:

Significant improvement in VAS, WOMAC, Tegner, and IKDC from pre-op to mid-term (p < 0.001).

VAS and IKDC remained stable at long term; some decline in Tegner and WOMAC over time.

• 🦴 Alignment correction maintained:

Significant correction in HKA and MPTA, with lateral shift of mechanical axis maintained at final follow-up.

• 📉 OA progression expected but delayed:

Medial compartment degeneration progressed early; lateral and patellofemoral OA increased between mid- and long-term follow-up.

• ⏳ Survivorship:

95.7% at 5 years

82.6% at 10 years

72.8% at 15 years

(Failures defined as arthroplasty, revision, or >5 mm laxity)

Takeaway

For young, varus, ACL-deficient knees with medial OA, OTT ACL + lateral closing wedge HTO provides durable stability and alignment correction, delaying arthroplasty for over a decade in most patients.

https://pubmed.ncbi.nlm.nih.gov/12486734/

• 👥 Study design: Anatomic cadaveric study (4 fresh knees injected with India ink) with histologic and computer-assisted vessel analysis of gracilis and semitendinosus tendons
• 🩸 Rich vascular supply at tibial insertion: An arterial arch from the inferior medial genicular artery (with contributions from inferior lateral genicular and anterior tibial recurrent arteries) surrounds the pes anserinus insertion
• 📊 Quantitative vascular findings: Mean vessel diameter decreased from ~2211 μm at insertion to ~662 μm mid-tendon, with increased caliber again near the myotendinous junction
• 🧠 Neural elements present: Ruffini endings, Pacinian corpuscles, and free nerve endings identified — demonstrating mechanoreceptive potential
• 🔬 No avascular zones observed along tendon length — vascular network continues proximally within connective septa
• ⚖️ Clinical implication: Unlike the patellar tendon (avascular at tibial insertion), the pes anserinus shows preserved neurovascularity — raising the question whether maintaining tibial attachment may have biologic advantages in ACL reconstruction

https://pubmed.ncbi.nlm.nih.gov/30285459/

• 👥 Study population: 64 skeletally mature New Zealand White rabbits undergoing unilateral ACL reconstruction.
• 32 with intact tibial insertion preserved
• 32 with free (detached) semitendinosus graft
• Sacrifice at 3, 6, 12, and 24 weeks for histology, micro-CT, and biomechanical testing
• 🩸 Preserved grafts bypassed avascular necrosis: No hypocellularity seen at early time points, while detached grafts showed classic necrosis → revascularization sequence (weeks 3–6)
• 🦴 Superior tendon-bone healing:
• Sharpey-like fibers present as early as 3 weeks
• Direct insertion–like fibrocartilage formed by 12 weeks
• Significantly higher histologic scores at weeks 6, 12, and 24
• 📊 Improved bone formation (micro-CT):
• Higher BV/TV at weeks 3 and 6 (P = .0026 and .0080)
• Smaller bone tunnel area at week 6 (P = .0096)
• 💪 Stronger biomechanics:
• Higher failure load at weeks 12 and 24 (P = .0313, .0343)
• Higher stiffness at week 24 (P = .0006)
• 🔬 Conclusion: Preserving the tibial insertion sustains graft blood supply, enhances tendon-bone integration, and improves biomechanical strength compared with a detached, avascular graft

https://pubmed.ncbi.nlm.nih.gov/17622515/

• 👥 Study population: 30 rabbits underwent ACL reconstruction using semitendinosus autograft without detaching the tibial insertion; 9 rabbits received free semitendinosus grafts as controls. Sacrifice at 3, 6, and 12 weeks
• 🩸 Viability preserved:

Grafts retaining tibial insertion showed no avascular–acellular necrosis at any time point

• ⚠️ Free grafts underwent classic necrosis phase:

At 3 weeks, free grafts demonstrated avascular necrosis, followed by progressive revascularization at 6–12 weeks

• 🦴 Earlier tendon–bone integration:

Rerouted grafts showed organized architecture and firm bone–graft bonding earlier than free grafts

• 🔬 Biologic implication:

Retaining tibial attachment sustains blood supply during the critical early weeks, potentially avoiding the mechanically vulnerable necrosis phase

• 🎯 Core conclusion:

“Harvesting semitendinosus without detachment of the tibial attachment preserves viability.” (KSSTA 2007, Papachristou et al.)

https://pubmed.ncbi.nlm.nih.gov/27388213/

• 👥 Patient population: 40 patients (mean age 27.5 ± 9.5 years) randomized
• 20 with preserved hamstring tibial insertion
• 20 with detached hamstring graft

24-month clinical follow-up; MRI at 6 months

• 📊 Clinical outcomes:

Excellent IKDC improvement in both groups; no significant differences at 12 and 24 months

• 🩻 Better intra-articular graft morphology (MRI):

Higher ligamentization score in preserved group

(2.1 ± 0.6 vs 1.7 ± 0.6, p < 0.05)

• 💧 Less hyperintense signal:

Hyperintensity seen in 15% (preserved) vs 40% (detached) — suggesting improved maturation

• 🦴 Tibial integration:

No significant difference in synovial fluid at bone–graft interface between groups

• 🎯 Conclusion:

Preserving hamstring tibial insertion improves early graft ligamentization on MRI, without compromising clinical outcomes

https://pubmed.ncbi.nlm.nih.gov/29443537/

• 👥 Patient population: 45 patients (age 18–45) randomized
• Insertion preserved (n=21)
• Insertion detached (n=24)

37 completed full 2-year follow-up

• 📊 Clinical outcomes:

Significant IKDC, Lysholm, and Tegner improvement in both groups;

no between-group difference in stability or KT-1000 laxity

• 🩸 MRI graft maturity (SNQ analysis):

Detached grafts showed rising signal intensity peaking at 6 months, then declining.

Preserved grafts maintained lower, stable signal intensity throughout 2 years

• 📈 Significant difference at key remodeling phase:

SNQ significantly lower in preserved group at

1. 6 months (P = .002)
2. 12 months (P = .02)
• 🔬 Interpretation:

Tibial insertion preservation may bypass the classic necrosis–revascularization phase, supporting earlier graft maturation

https://pubmed.ncbi.nlm.nih.gov/32266415/

• 👥 Patient population: 20 patients analyzed
• 10 Quadrupled Single-Bundle (detached hamstrings, 4SB)
• 10 Non-Detached Single-Bundle + Lateral Plasty (NDSB)

MRI at 4 and 18 months

• 🩸 Less intra-graft fluid (NDSB):

Significantly less reactive fluid within the graft at

1. 4 months (p=0.008)
2. 18 months (p=0.028)
• 🦴 Less tibial tunnel enlargement:

NDSB group had significantly smaller tunnel diameter and less widening at both follow-ups (p<0.01)

• 📉 Lower intra-tunnel SNQ at 18 months:

Suggesting improved graft maturation and lower water content (p=0.015)

• 🚀 Earlier overall MRI maturation:

Higher composite MRI score in NDSB already at 4 months (p=0.006), remaining stable at 18 months

• 🎯 Core implication:

Preserving the hamstring tibial insertion may help bypass the early “necrotizing” phase of graft remodeling

https://pubmed.ncbi.nlm.nih.gov/32909826/

👥 Patient population

• 45 patients with isolated ACL injury were randomized to ACL reconstruction using:

• Insertion-preserved hamstring tendon (IP-HT)

• Free hamstring tendon (FHT)

• Final 60-month follow-up included 18 IP-HT and 19 FHT patients. Zhang 2020 Zhang 2020

📊 What the study measured

• Serial 3D MRI at 6, 12, 24, and 60 months

• Signal/noise quotient (SNQ) measured separately at:

• Femoral tunnel graft (FTG)

• Intra-articular graft (IAG)

• Tibial tunnel graft (TTG)

• Lower SNQ = better graft maturity. Zhang 2020

📍 Key MRI finding

• SNQ progression differed by graft site

• In both groups, the femoral tunnel graft had the highest SNQ values

• All significantly changing SNQ values peaked at 6 months. Zhang 2020 Zhang 2020

📈 Comparison between graft types

• In the early postoperative period, all graft segments in the IP-HT group had lower SNQ values than FHT

• The femoral tunnel graft SNQ remained lower in IP-HT up to 24 months

• By 60 months, graft maturity was similar in both groups. Zhang 2020 Zhang 2020

⚠️ Clinical outcomes

• Both groups improved significantly after surgery

• At 60 months, clinical scores were similar between IP-HT and FHT

• No significant association was found between MRI graft maturity and clinical scores. Zhang 2020 Zhang 2020

🦴 Interpretation

• Preserving the tibial insertion may help the graft mature earlier and more stably in the first 2 years

• The femoral tunnel appears to be the slowest-maturing / most biologically vulnerable segment of the graft. Zhang 2020

💡 Key message

• Graft maturation varies by location, and the femoral tunnel shows the highest SNQ values, while insertion-preserved hamstring grafts demonstrate earlier and more stable early maturation than free hamstring grafts.

https://www.arthroscopyjournal.org/article/S0749-8063(21)00366-2/fulltext

• 🔄 Core message: Isolated ACL reconstruction is not sufficient to control rotational instability in chronic complex ACL injuries
• ➕ Lateral extra-articular tenodesis (LET) is necessary to restore rotational control, regardless of single- or double-bundle technique
• ⚖️ Caution against over-complexity: Double-bundle + LET may improve certain biomechanical parameters, but added technical complexity increases risk without proven clinical superiority
• 🧠 Philosophy: Neither single- nor double-bundle reconstruction is truly “anatomic.” The take-home principle:

“Keep it simple. Keep it safe.”

https://pubmed.ncbi.nlm.nih.gov/38296446/

• 👥 Paper type: Editorial commentary reviewing evidence on non-traumatic ACL graft failure and femoral tunnel malposition (Arthroscopy 2024, Lucidi et al.)
• 🎯 Main message: The number one cause of ACL reconstruction failure is a misplaced femoral tunnel, typically too anterior or too vertical (Arthroscopy 2024, Lucidi et al.)
• 📊 Technical error prevalence: In revision cohorts, technical errors account for ~60% of failures, and femoral tunnel malposition is implicated in up to 80% (Arthroscopy 2024, Lucidi et al.)
• ⚠️ Consequences of malposition:
• Increased anterior translation
• Residual pivot shift
• Higher postoperative meniscal tears
• Increased revision rates (Arthroscopy 2024, Lucidi et al.)
• 🔁 Proposed solution:

The Over-The-Top technique + lateral extra-articular tenodesis (LET) avoids femoral tunnel malposition and improves rotatory control, particularly in patients with narrow notch or high tibial slope (Arthroscopy 2024, Lucidi et al.)

• 🛠 Revision advantage:

If failure occurs, there is no femoral tunnel widening, osteolysis, or hardware conflict, simplifying revision surgery (Arthroscopy 2024, Lucidi et al.)

https://pubmed.ncbi.nlm.nih.gov/18982310/

• 👥 Patient population: 28 consecutive patients (mean age 30 years) undergoing single-bundle hamstring ACL reconstruction with over-the-top femoral fixation plus extra-articular plasty
• 📍 Study design:

In vivo, intra-operative computer-assisted navigation measured AP tibial translation at

1. 30° (Lachman)
2. 90° (drawer test)

across medial, central, and lateral compartments

• 📉 Effect of single-bundle (SB) graft:
• Reduced AP translation ~4.8 mm at 30°
• Reduced ~3.2 mm at 90°

Primary stabilizer for anterior translation

• ➕ Added effect of extra-articular (EA) plasty:
• Further reduced lateral compartment translation by 1.6 mm at 30°
• Reduced AP laxity by ~1 mm at 90°

Significant control of coupled tibial translation, especially in the lateral compartment

• 🔬 Key biomechanical insight:

Extra-articular plasty improves control of residual rotational/lateral laxity not fully addressed by single-bundle reconstruction alone

https://pubmed.ncbi.nlm.nih.gov/21710111/

• 👥 Patient population: 35 consecutive patients with isolated chronic ACL injury
• Anatomic Double-Bundle (ADB): 15 patients
• Over-the-Top Single-Bundle + Lateral Plasty (SBLP): 20 patients
• 📊 Static laxity (AP, VV, IE tests):

Both techniques significantly reduced anterior–posterior, varus/valgus, and rotational laxity.

Overall static stability was similar between groups.

• ➕ Lateral compartment control (SBLP advantage):

Extra-articular tenodesis better restrained:

1. Lateral compartment AP translation (especially at 90°)
2. Varus/valgus opening at 0° and 30°
3. Rotational displacement at 90°
• 🔄 Dynamic stability (ADB advantage):

Anatomic double-bundle reconstruction better controlled:

1. Pivot-shift phenomenon
2. Peak anterior displacement of lateral compartment
3. Hysteresis area during pivot-shift
4. Tibial reduction acceleration
• 🧠 Key insight:

Over-the-top + lateral plasty enhances peripheral/lateral compartment control

while anatomic double-bundle more closely restores dynamic rotational behavior.

https://pubmed.ncbi.nlm.nih.gov/31260843/

• 👥 Patient population: 42 patients (mean age 26 ± 8 years) with isolated ACL injury, randomized into:
• Single-Bundle (SB)
• Single-Bundle + Lateral Plasty (SBLP, over-the-top)
• Non-anatomic Double-Bundle (DB)
• 📉 All techniques reduced laxity compared to preoperative values across AP, IE, VV, and pivot-shift tests.
• 🥇 SBLP showed the greatest AP reduction at 90°

Superior to DB (p = 0.012); trend vs SB.

• 🔄 Superior rotational control (SBLP):

Greater reduction in internal–external rotation at 30° and 90° compared to both SB and DB (p < 0.05).

• 🦴 Lateral compartment restraint:

SBLP better controlled lateral tibial translation during drawer and rotational stress tests.

• 🎯 Pivot shift:

No significant difference among techniques for dynamic pivot-shift reduction.

https://pmc.ncbi.nlm.nih.gov/articles/PMC11780662/

• 👥 75 patients randomized (25 per group) to:
• BPTB
• SB Quadrupled HT (no LET)
• Over-the-Top

Mean follow-up: 23 years

• 📊 Clinical outcomes:

All three techniques showed comparable PROMs at 20+ years.

HT + LET had a slightly higher Tegner score vs BPTB (p = .023).

• 📉 Failure rates (revision):
• BPTB: 16%
• HT: 10%
• OTT: 5%

Trend toward fewer revisions with OTT + LET (not statistically significant).

• 🦴 Osteoarthritis:
• No increase in lateral OA with HT + LET
• BPTB showed significantly higher patellofemoral OA vs HT + LET (p = .029).
• 📏 Knee laxity:

BPTB had slightly less AP laxity than HT;

HT + LET was comparable and did not increase instability.

Bottom Line

At >20 years, Over-the-Top HT + LET performs at least as well as standard tunnel techniques, with a trend toward fewer failures and no evidence of lateral overconstraint or OA progression.

https://pubmed.ncbi.nlm.nih.gov/30078121/

• 👥 16 studies included (3 RCTs, 13 case series)
• Primary OTT: 453 patients (mean age 26.9 yrs)
• Revision OTT: 60 patients (mean age 31.4 yrs)
• Mean follow-up ≈ 5.8 years
• 📊 Clinical outcomes comparable to traditional techniques
• Mean Lysholm (primary): 89.9
• Mean subjective IKDC: ~82
• Mean Tegner: 6.5
• 🔄 Rotational stability strong
• Positive pivot shift only 7.8%

lower than many reported transtibial or AM portal series

• ⚽ Return to sport (primary cases):
• 94% returned to sport
• 69% returned to pre-injury level
• ❌ Failure rates low
• Primary graft failure: 3.7%
• Revision failure: 8.4%
• 🧠 Conclusion of the review:

OTT ACL reconstruction demonstrates clinically important outcomes comparable to traditional all-inside, transtibial, and anteromedial portal techniques, in both primary and revision settings.

https://pubmed.ncbi.nlm.nih.gov/8998862/

👥 Patient population

• 25 patients underwent revision ACL reconstruction after failure of a prior intra-articular ACL reconstruction
• Mean age at revision: 25 years
• Mean interval from primary to revision surgery: 30 months
• Mean follow-up after revision: 28 months.

📊 Etiology of primary graft failure

• After history, examination, radiographs, and review of prior operative records, the authors assigned a cause of failure for each case.
• The most common category was surgical technique
• Within this, tunnel placement accounted for 9 cases, making it the single most frequent technical error.

📍 Failure classification proposed by the Pittsburgh group

The paper’s classification of ACL graft failure included:

• Surgical technique
• Mechanical/biomechanical factors
• Failure of graft incorporation
• Trauma.

Within technical errors, the authors listed:

• Tunnel location
• Graft impingement
• Graft tension
• Graft fixation.

⚠️ Important nuance

• This paper does not report a specific percentage for femoral tunnel malposition alone
• It reports tunnel placement more broadly as the leading technical cause of failure.

🦴 Interpretation

• By 1996, the Pittsburgh group had already identified tunnel location as a central problem in failed ACL reconstruction
• This paper is therefore important as an early conceptual paper showing that technical tunnel errors were a major driver of graft failure.

💡 Key message

• Tunnel placement was the most frequent technical cause of failure in this revision ACL series, making this one of the early papers to highlight the tunnel-position problem in ACL reconstruction.

https://pubmed.ncbi.nlm.nih.gov/14967325/

👥 Patient population

• 20 patients undergoing revision ACL reconstruction
• All presented with persistent instability following primary ACL reconstruction
• Mid-term follow-up with clinical examination, KT-1000 testing, and functional assessment.

📊 Causes of primary ACL graft failure

• Technical errors were the most common cause of graft failure
• Femoral tunnel malposition identified as the leading technical error
• Other causes included:
• Tibial tunnel malposition
• Traumatic re-injury
• Graft stretching or rupture.

📍 Objective outcomes after revision surgery

• Residual anterior laxity remained common on KT-1000 testing
• However, many patients reported improved knee stability and function.

⚠️ Objective stability vs patient satisfaction

• Patient-reported outcomes were generally good despite measurable laxity
• Objective laxity did not correlate strongly with patient satisfaction.

🦴 Interpretation

• Malpositioned femoral tunnels can lead to persistent rotational instability and graft overload, resulting in graft failure.
• Accurate femoral positioning is therefore critical for successful ACL reconstruction.

💡 Key message

• Femoral tunnel malposition is a major technical cause of ACL reconstruction failure, emphasizing the importance of precise graft positioning in primary ACL surgery.

https://pubmed.ncbi.nlm.nih.gov/16458807/

👥 Patient population

• 31 patients underwent revision ACL reconstruction for recurrent instability
• 28 patients available for follow-up
• Mean follow-up: 4.2 years
• Mean age at revision surgery: 27 years.

📊 Tunnel malposition in failed ACL reconstructions

• 79% of failed ACL reconstructions showed radiographic FEMUR tunnel malposition
• Only 21% had anatomically positioned femoral and tibial tunnels on imaging (MRI/CT).

📍 Patterns of malposition

• Several cases showed excessively central femoral tunnel placement
• Malpositioned tunnels contributed to persistent instability and graft failure.

📈 Outcomes after revision surgery

• Revision ACL reconstruction corrected tunnel position
• Significant improvement in Lachman and pivot shift tests
• 97% of patients had ≤5 mm side-to-side difference on KT-1000 testing postoperatively.

🦴 Interpretation

• Incorrect tunnel placement is a major contributor to recurrent instability after ACL reconstruction.
• Revision surgery can improve stability when tunnel positioning is corrected.

💡 Key message

• Tunnel malposition was present in nearly 80% of failed ACL reconstructions, highlighting the importance of accurate graft positioning in primary ACL surgery.

https://pubmed.ncbi.nlm.nih.gov/20889962/

• 👥 460 patients enrolled across 87 surgeons (52 sites); median age 26 years, 57% male; 89% undergoing their first revision.
• ⚠️ Mode of failure:
• Traumatic: 32%
• Technical: 24%
• Biologic: 7%
• Combination of factors: 37% (most common overall category).
• 🎯 Technical failure details:
• Femoral tunnel malposition = 80% of technical failures (most common cause).
• Tibial tunnel malposition = 37%.
• 🦴 Graft choice in revision:
• 54% allograft
• 45% autograft
• Bone–patellar tendon–bone most common graft overall.
• 📉 Concomitant pathology common:
• 74% meniscal injury
• 73% chondral damage (Outerbridge ≥2)
• Only 10% had neither meniscal nor cartilage injury.

Key Insight

Revision ACL failure is rarely isolated — it is often multifactorial, with femoral tunnel malposition emerging as the dominant technical contributor.

https://pubmed.ncbi.nlm.nih.gov/20644911/

👥 Patient population

• Multicenter retrospective study across 10 French orthopaedic centers
• 293 patients undergoing revision ACL reconstruction
• Failures of primary ACL reconstruction analyzed over a 12-year period (1994–2005).

📊 Main causes of ACL reconstruction failure

• Femoral tunnel malposition: 36% (most common cause)
• Other causes included:
• Untreated laxity
• Tibial tunnel malposition
• Impingement
• Fixation failure
• New trauma
• Infection.

📍 Typical pattern of femoral tunnel malposition

• Failures were frequently associated with anterior placement of the femoral tunnel
• This produces a vertical graft orientation and inadequate rotational stability.

⚠️ Outcomes after revision surgery

• When failure was caused by anterior femoral tunnel malposition, revision surgery produced better outcomes:
• 44% IKDC A after revision
• compared with 24% IKDC A when failure was due to other causes.

🦴 Additional finding — meniscus preservation

• Total meniscectomy worsened outcomes after revision ACL reconstruction
• Patients with preserved menisci had better knee stability and function.

💡 Key message

• Anterior femoral tunnel malposition was the most common cause of ACL reconstruction failure (36%), highlighting the critical importance of accurate femoral tunnel placement.

https://pubmed.ncbi.nlm.nih.gov/23150344/

• 👥 Population:

Subset analysis of the MARS cohort (460 revision ACLRs).

Femoral tunnel malposition identified in 219 cases (47.6%), and as the sole cause in 117 patients (mean age 28.7 years).

• 📍 Most common technical error:

Femoral tunnel malposition was the leading technical cause of failure in revision ACLR.

• 📐 Type of malposition:
• Too vertical – 36%
• Too anterior – 30%
• Vertical + anterior – 27%

→ Vertical/anterior errors dominate.

• 🔧 Revision strategy:
• 82% required drilling an entirely new femoral tunnel
• Tibial tunnel could be reused in ~50%
• Both transtibial and AM portal techniques were used in revision
• 🦴 Graft choice highly variable:

No clear consensus—mix of autograft and allograft used in revision, reflecting surgeon preference rather than standardized algorithm.

Core Insight

In revision ACL surgery, femoral tunnel malposition—especially vertical/anterior placement—is the dominant preventable cause of failure, and most cases require creation of a new anatomic femoral tunnel.

https://pubmed.ncbi.nlm.nih.gov/28721590/

• 👥 110 revision ACL patients (mean age 28.7 yrs); failures classified as:
• Technical (non-traumatic): 64.5%
• Traumatic: 29.1%
• Biological: 6.4%
• 📍 Non-anatomic femoral tunnel = most common cause of technical failure (83.1%)

Tibial malposition also common (45.1%), but femoral malposition showed the strongest correlation with non-traumatic failure (p ≤ 0.05).

• 🔧 Technique matters:

Transtibial femoral drilling and femoral transfixation fixation were significantly associated with non-traumatic technical failure (p < 0.05).

• ⏱ Earlier failure in technical cases:

Non-traumatic failures occurred significantly earlier (mean 40 months) than traumatic failures (75 months).

• ⚠️ Important nuance:

High rates of non-anatomic tunnels were also seen in traumatic failures, suggesting tunnel error may predispose grafts to rupture under stress.

Core Message

Most revision ACL failures are technical rather than traumatic, and femoral tunnel malposition remains the dominant preventable factor.

https://pubmed.ncbi.nlm.nih.gov/33983487/

• 👥 117 patients total
• 58 successful primary ACLR
• 59 revision ACLR

Strict lateral radiographs used with Bernard quadrant method.

• 📍 Revision group had significantly more anterior femoral tunnels
• 38% ± 11% vs 28% ± 6% (p < 0.01)

Native center = 25% (PA dimension).

• 📐 Revision group also had more proximal (high) tunnels
• 30% ± 9% vs 38% ± 9% (p < 0.01)

Native center = 29% (PD dimension).

• ⚠️ Risk thresholds:
• ≥30% anterior → OR 6 for revision
• ≥40% anterior → OR 39
• PD ≤25% (high tunnel) → OR 13
• 🔄 Non-traumatic failures were the most anterior

Chronic failures averaged 41% PA vs 35% in traumatic failures.

Core Message

Anterior and proximal (high) femoral tunnel placement independently predicts revision ACL reconstruction — reinforcing that anatomic femoral positioning reduces revision risk.

https://pmc.ncbi.nlm.nih.gov/articles/PMC9165258/

👥 Patient population

• 78 patients from a prior randomized trial
• Mean follow-up 11.4 years
• All underwent primary transtibial ACL reconstruction.

📍 Main finding

• More anterior femoral tunnels were associated with higher long-term failure
• No-failure group: femoral tunnel at 37.7% posterior-to-anterior
• Failure group: 44.1% posterior-to-anterior.

⚠️ Safe zone identified

• A femoral tunnel placed within the most posterior 35% of the femoral condyle (parallel to Blumensaat) was associated with lower failure
• 15 of 16 failures (93.8%) were anterior to this cut-off.

📊 What tunnel position did not affect

• No significant relationship between femoral or tibial tunnel position and:
• IKDC subjective score
• Radiographic osteoarthritis.

🦴 Failure and OA rates

• 24.6% overall failure at 10 years
• 28.2% developed radiographic osteoarthritis.

✅ Key message

• Anterior femoral tunnel placement increases long-term ACL failure risk, while a more posterior femoral position is protective.

https://pubmed.ncbi.nlm.nih.gov/35219217/

👥 Patient population

• 244 patients undergoing primary ACL reconstruction
• Single surgeon, quadrupled semitendinosus autograft
• Compared two femoral tunnel positions using the anteromedial portal technique.

📍 Study groups

• Group A (117 patients): femoral tunnel at central ACL footprint
• Group B (127 patients): femoral tunnel placed closer to the AM bundle footprint.

⚠️ Failure rates differed significantly

• Central tunnel position: 10.3% failure (12/117)
• AM bundle position: 2.3% failure (3/127).

📊 Clinical outcomes

• AM bundle tunnel position showed:
• Higher Lysholm scores
• Better subjective IKDC scores
• Lower anterior knee laxity.

🦴 Knee stability findings

• Less anterior tibial translation in the AM bundle group
• Greater improvement in KT-1000 measurements compared with central tunnel placement.

💡 Key message

• Femoral tunnel position significantly affects ACL reconstruction outcomes, with central footprint tunnels showing up to 4× higher failure rates than tunnels placed closer to the AM bundle footprint.

https://pubmed.ncbi.nlm.nih.gov/37422027/

• 👥 104 patients (Level III study)
• 52 non-traumatic ACLR failures
• 52 matched controls (≥48-month follow-up)
• Mean age ≈ 32 years
• 📍 Femoral tunnel malposition matters
• Failed grafts had significantly more anterior & superior femoral tunnels
• DS ratio > 37.4% independently predicted failure (OR 1.09 per % increase)
• 📐 Lateral tibial slope (LTS) is the strongest predictor
• LTS > 6.7° → AUC 0.804
• OR 1.31 per degree increase
• 🦴 Narrow notch increases risk
• NWI < 26.4% independently associated with failure
• OR 0.81 (protective effect decreases as notch narrows)
• ⚠️ Multifactorial risk
• 73% of failed cases had ≥2 risk factors
• All patients with 3 risk factors failed
• Combination of anatomy + tunnel error dramatically increases risk

https://pmc.ncbi.nlm.nih.gov/articles/PMC11813002/

👥 Patient population

• 65 patients undergoing revision ACL reconstruction
• Mean age 30 years
• Retrospective analysis of failures between 2014–2022.

📊 Most common cause of failure

• Traumatic reinjury: 54.7% of failures
• 24 high-energy injuries (sports, collisions)
• 11 low-energy injuries (slips, falls).

📍 Technical failure: tunnel malposition

• Inappropriate tunnel placement: 18.8% of failures
• Femoral tunnel errors included anterior and posterior malposition, while some involved anterior tibial tunnel placement.

⚠️ Other causes of failure

• Graft failure: 12.5%
• Fixation problems: 6.3%
• Infection: 7.8%
• Multiple ligament injuries: 1.6%.

🦴 Associated intra-articular pathology

• Meniscal injuries present in 77% of revision cases.

💡 Key takeaway

• ACL reconstruction failure is multifactorial, but technical factors—particularly bone tunnel positioning—remain a critical determinant of surgical success.

https://pubmed.ncbi.nlm.nih.gov/16897068/

👥 Study population

• Cadaveric anatomical study analyzing the femoral insertion of the anterior cruciate ligament
• Detailed dissection performed to evaluate the anteromedial (AM) and posterolateral (PL) bundle insertions.

📊 Distinct bundle insertions

• The ACL femoral footprint consists of two distinct functional bundles:
• Anteromedial (AM) bundle
• Posterolateral (PL) bundle

These bundles have separate femoral attachment areas.

📍 Different functional roles

• AM bundle
• Tight in knee flexion
• Primarily controls anterior tibial translation
• PL bundle
• Tight in knee extension
• Contributes more to rotational stability

⚠️ Implications for ACL reconstruction

• A single round femoral tunnel cannot reproduce the distinct insertion areas of both bundles
• This anatomical complexity partly explains the interest in double-bundle reconstruction techniques.

🦴 Interpretation

• The femoral ACL insertion is not a single point but a complex anatomical region composed of functionally distinct bundle insertions.
• Simplified reconstruction techniques may therefore fail to replicate native ACL anatomy.

💡 Key message

• The ACL femoral footprint contains separate functional bundle insertions, highlighting the anatomical complexity that reconstruction techniques attempt to reproduce.

https://www.sciencedirect.com/science/article/abs/pii/S0749806311013429

👥 Study population

• Cadaveric knee specimens analyzed to evaluate arthroscopic landmarks used for femoral tunnel placement
• Aim: determine whether commonly used landmarks reliably identify the anatomic femoral ACL footprint.

📊 Key finding — variability of femoral anatomy

• Significant variability in femoral condyle size and morphology was observed across specimens
• This variability makes consistent identification of the ACL femoral footprint difficult using fixed arthroscopic landmarks.

📍 Limitations of arthroscopic visualization

• Arthroscopic viewing introduces parallax error, meaning the apparent location of structures changes depending on camera position
• Because of this optical effect, the anatomic center of the ACL footprint cannot be reliably quantified arthroscopically.

⚠️ Implications for femoral tunnel placement

• Surgeons relying on visual landmarks may misidentify the true femoral footprint
• This contributes to variability and potential malposition of femoral tunnels in ACL reconstruction.

🦴 Interpretation

• Femoral tunnel placement is technically challenging because:
• Arthroscopic visualization introduces parallax distortion
• Femoral anatomy varies significantly between patients.

💡 Key message

• Arthroscopic landmarks alone cannot reliably identify the anatomic femoral ACL footprint, contributing to variability in femoral tunnel placement.

https://pubmed.ncbi.nlm.nih.gov/20847222/

👥 Study population

• 137 knees analyzed

• Detailed measurements of femoral and tibial ACL insertion sites

• Aim: quantify size variability of the ACL footprints.

📊 Substantial variability in ACL insertion size

• Mean femoral ACL insertion length: ~16 mm

• Mean tibial ACL insertion length: ~18 mm

However, large variability was observed:

• Femoral insertion length ranged approximately 11–19 mm

• Tibial insertion length ranged approximately 9–24 mm

📍 Clinical relevance for ACL reconstruction

• In two-thirds of knees, the ACL insertion length was ≤16 mm

• Smaller insertion sites may not accommodate larger grafts or double-bundle reconstructions.

⚠️ Implications for surgical techniques

• A single standardized tunnel size or position may not reproduce native ACL anatomy in all patients

• Surgeons should measure the native footprint intraoperatively to guide reconstruction strategy.

🦴 Interpretation

• The ACL insertion sites demonstrate considerable inter-individual variability in size

• Reconstruction techniques should therefore be adapted to patient-specific anatomy.

💡 Key message

• ACL insertion site size varies substantially between individuals, meaning a standardized tunnel strategy may not reproduce native anatomy in all knees.

https://pubmed.ncbi.nlm.nih.gov/24972997/

👥 Study population

• 111 cadaveric knees analyzed to study native ACL femoral anatomy
• Detailed dissection of ACL insertion morphology.

📊 Key anatomical finding

• The ACL is not cylindrical or round
• The femoral attachment is a flat ribbon-like structure.

Typical dimensions reported:

• Width ≈ 16–18 mm
• Thickness ≈ 3–4 mm

This produces a flat, elongated insertion along the femoral wall.

📍 Implications for ACL reconstruction

• Conventional ACL reconstruction uses round reamers (7–10 mm)
• These create circular femoral tunnels.

However:

• A round tunnel cannot reproduce the flat ribbon-like femoral insertion of the native ACL.

⚠️ Geometric mismatch

This creates a fundamental mismatch:

Native ACL insertion

→ flat ribbon structure

Reconstruction tunnel

→ cylindrical bone tunnel.

Even if placed “anatomically”, the graft cannot replicate the native insertion geometry.

🦴 Interpretation

• ACL reconstruction techniques based on round tunnels inherently simplify native anatomy
• This may partly explain why reconstructed grafts often appear more cylindrical and vertical than the native ligament.

💡 Key message

• The native ACL femoral attachment is flat and ribbon-like, whereas ACL reconstruction relies on round tunnels, creating a fundamental mismatch between native anatomy and reconstruction geometry.

https://pubmed.ncbi.nlm.nih.gov/32613337/

• 👥 95 ACL-ruptured patients (mean age 26 yrs) underwent 3D MRI-based femoral footprint analysis.
• 📍 Marked intersubject variability

Femoral ACL center ranged:

1. 1.8–12.3 mm posterior
2. 7.7 mm distal to 4.8 mm proximal

(posterior condyle reference system).

• 📏 Distance from Over-the-Top (OTT) position:

Mean 1.9 ± 1.5 mm posterior and 13.8 ± 2.7 mm distal.

• ⚠️ Contemporary OTT femoral guides (4–10 mm offset) could restore the true femoral center in only 6.5% of patients.
• 🔧 Authors suggest AM-portal femoral guides with 10–18 mm proximal–distal offset may be required for true anatomic restoration.

Core Insight

The native femoral ACL center varies widely between patients — and standard over-the-top offset guides are insufficient to consistently reproduce it anatomically.

https://pubmed.ncbi.nlm.nih.gov/41426266/

👥 Study population

• 50 anatomical studies included
• 1652 knees analyzed in total

The meta-analysis compared ACL femoral and tibial footprint anatomy between the two populations.

📊 Femoral ACL footprint location

Location measured relative to the posterior edge of the lateral femoral condyle:

• Asian population: 35.2%
• Western population: 27.3%
• Statistically significant difference (P < 0.001)

Location relative to the Blumensaat line:

• Asian population: 39.4%
• Western population: 33%
• Statistically significant difference (P = 0.049)

➡️ This indicates the ACL femoral footprint lies more anterior and distal in Asian knees.

📐 Femoral footprint size

• Asian population:

96.3 mm² (95% CI 81.1–111.4)

• Western population:

126.8 mm² (95% CI 103.5–150)

• Significant difference (P = 0.03)

➡️ Asian knees have a smaller femoral ACL footprint.

📍 Tibial footprint

• No significant difference between Asian and Western populations for:
• Tibial footprint size
• Tibial footprint location

⚠️ Key implication

The femoral ACL footprint differs significantly between populations in both:

• Location
• Size

This demonstrates that the “anatomic footprint” is not universal.

🦴 Interpretation

If the ACL femoral footprint varies between populations, then:

• A single standardized femoral tunnel position may not reproduce native anatomy in every patient.

This variability partly explains why consistent anatomic femoral tunnel placement is challenging in clinical practice.

💡 Key message

• Meta-analysis of 50 studies (1652 knees) shows significant population differences in ACL femoral footprint size and location, highlighting the variability surgeons must contend with when drilling femoral tunnels.

https://pubmed.ncbi.nlm.nih.gov/32875301/

• 👥 12 sports fellowship–trained surgeons evaluated 10 patient-specific 3D printed femoral models derived from MRI.
• 📍 None could consistently identify the junction of the intercondylar and bifurcate ridges.

Mean ridge identification error:

1. 2.8–7.3 mm (proximal)
2. 2.4–8.0 mm (posterior) (p < .05).
• 🎯 None accurately identified the true femoral footprint center on bony models.

Mean tunnel error ranged:

1. 1.3–5.9 mm (proximal)
2. up to 4.3 mm posterior deviation (p < .05).
• 🔬 Intraoperative tunnels were more accurate than model-based placement.
• Surgical error: 3.7 ± 2.4 mm
• 3D model error: 5.8 ± 2.0 mm

(p = .0046).

• 🧠 Implication:

Osseous ridges alone are unreliable landmarks. Soft tissue cues and arthroscopic visualization significantly improve femoral tunnel localization.

Core Insight

Even experienced ACL surgeons cannot reliably identify femoral ridges on bone-only models — highlighting how dependent tunnel placement is on intraoperative soft-tissue landmarks.

https://pubmed.ncbi.nlm.nih.gov/28972789/

• 👥 41 patients underwent pre- and postoperative 3D MRI; 4 experienced sports surgeons using contemporary “anatomic” techniques (AM portal + transtibial).
• 📍 Mean femoral tunnel error distance:

3.6 ± 2.6 mm from the native footprint center (range 0–9.3 mm).

• 📉 29% of grafts had >50% of their footprint outside the native ACL footprint.
• 📐 Native footprint center (contralateral knee reference):

12.0 mm distal and 9.3 mm anterior to apex of deep cartilage.

Reconstructed tunnels were significantly different in both axes (P = .02, P = .01).

• 🔧 No difference between techniques or surgeons

Independent drilling vs transtibial → similar error (P = .07).

Error distribution similar across all 4 surgeons.

Core Message

Even with modern “anatomic” techniques and experienced surgeons, femoral tunnel placement frequently fails to reproduce the patient’s true native footprint, with clinically meaningful deviation.

https://pubmed.ncbi.nlm.nih.gov/34049511/

👥 Study population

• 20 patients with confirmed ACL rupture
• MRI scans evaluated by 8 observers:
• Orthopaedic surgeons
• Orthopaedic residents
• Musculoskeletal radiologists
• Observers identified the center of the femoral ACL footprint twice using MRI with 3D femur models.

📊 Intra-observer reliability (same observer repeating measurement)

• Mean 3D difference: 3.82 mm
• Indicates good repeatability when the same person performs the measurement.

📍 Inter-observer variability (between different observers)

• Mean 3D difference: 8.67 mm between observers
• Indicates substantial disagreement on where the femoral ACL footprint is located.

⚠️ Influence of observer experience

• Orthopaedic surgeons showed higher agreement than residents and radiologists
• Identifying the femoral footprint remains experience-dependent.

🦴 Interpretation

• Even with MRI and 3D modeling, there is considerable variability between observers in identifying the femoral ACL origin.
• Determining the correct femoral tunnel position therefore remains technically challenging and subjective.

💡 Key message

• Different observers identify the femoral ACL footprint up to ~9 mm apart on MRI, highlighting the variability and difficulty in defining the exact femoral tunnel position.

https://pubmed.ncbi.nlm.nih.gov/10524823/

👥 Study population

• 30 cadaver knees from 15 fresh male cadavers
• Compared 3 femoral tunnel drilling techniques:
• Double-incision (DI)
• Transtibial (TT)
• Anteromedial portal (AM).

📊 Study aim

• To test whether a correct deep femoral tunnel position could be achieved equally with the 3 techniques
• The reference point was placed just deep to the insertion of the anteromedial bundle of the ACL.

📍 Main radiographic findings

• Mean position of the superficial aspect of the intra-articular tunnel exit along Blumensaat’s line:
• DI: 36%
• TT: 36%
• AM: 34%
• No statistically significant difference between techniques
• None of the femoral holes was more anterior than 40%.

⚠️ Clinical background highlighted by the authors

• The paper cites prior clinical work showing that 88% of knees with correct deep femoral tunnel placement had satisfactory stability
• In contrast, superficial placement in the anterior 50% of the condylar width was associated with graft failure in 62.5% of knees.

🦴 Interpretation

• The key message of this paper is not that one technique was superior, but that all 3 techniques were capable of reaching a deep femoral position in the cadaver model
• The authors conclude that technique choice should depend on surgeon preference and clinical results.

💡 Key message

• Deep femoral tunnel placement could be achieved with DI, TT, and AM techniques in a cadaver model, reinforcing the importance of femoral tunnel position rather than simply the drilling approach.

https://pubmed.ncbi.nlm.nih.gov/23276417/

👥 Patient population

• 8,375 primary ACL reconstructions from the Danish Knee Ligament Reconstruction Register
• Compared anteromedial (AM) portal drilling vs transtibial (TT) drilling for femoral tunnel placement.

📊 Revision risk

• AM technique: 5.16% revision at 4 years
• TT technique: 3.20% revision at 4 years.

📈 Relative risk of revision

• AM drilling doubled the risk of revision ACL surgery
• Adjusted RR = 2.04 compared with transtibial drilling.

⚠️ Objective instability findings

• AM technique associated with:
• Higher pivot shift risk (RR 2.86)
• Higher sagittal instability >2 mm (RR 3.70).

📊 Patient-reported outcomes

• KOOS and Tegner scores were similar between techniques despite differences in revision risk.

💡 Key message

• Femoral drilling technique significantly affects revision risk, with anteromedial portal drilling showing higher revision rates than transtibial techniques in registry data.

https://pubmed.ncbi.nlm.nih.gov/28721590/

👥 Patient population

• 101 patients undergoing revision ACL reconstruction
• Prior primary ACL reconstructions performed using:
• Transtibial (TT): 64 cases
• Anteromedial (AM): 37 cases.

📊 Non-anatomic tunnel positioning

• 77.2% had non-anatomic femoral tunnel positions
• 40.1% had non-anatomic tibial tunnel positions on CT analysis.

📍 Comparison between drilling techniques

• TT technique:
• Non-anatomic femoral tunnels 79.7%
• AM technique:
• Non-anatomic femoral tunnels 73%.

⚠️ No significant difference between techniques

• Rates of malposition were similar between TT and AM techniques (p > 0.05).

🦴 Interpretation

• Even with techniques designed to improve anatomical placement (AM drilling), accurate femoral tunnel positioning remains difficult in clinical practice.

💡 Key message

• Most failed ACL reconstructions show non-anatomic tunnel placement, and changing drilling technique alone does not reliably prevent femoral tunnel malposition.

https://pubmed.ncbi.nlm.nih.gov/36435433/

• 🏷️ Stop using the word “anatomic.”

A single cylindrical graft cannot recreate a ribbon-like ACL that is ~3.5× wider at its insertions than its midsubstance. The term is vague, misleading, and implies superiority without precision.

• 📍 Femoral tunnel: restore the direct fibers.

The direct fibers (just posterior to the lateral intercondylar ridge) bear 85–95% of load and are most critical for resisting anterior translation and pivot shift.

• 🦴 Tibial tunnel precision matters.

The native ACL tibial insertion is C-shaped and large; any tunnel within it could be labeled “anatomic.” Authors prefer placement in the central footprint without impingement, with clear description of exact position.

• 🔄 Address associated lesions.

Rotational control often depends on the IT band / anterolateral complex, not just ACL graft position. High-grade pivot shift may require lateral extra-articular tenodesis.

• 🔬 Future direction:

Techniques should be described with precise anatomical tunnel coordinates, not marketing terminology — and validated with patient outcomes and return-to-play data.

Core Message

Don’t call it “anatomic.”

Describe it precisely. Restore the load-bearing fibers. Validate it clinically.

https://pmc.ncbi.nlm.nih.gov/articles/PMC12575944/

• 🎯 Core Argument:

Many procedures labeled “anatomic” are actually pseudo-anatomic and may not be biomechanically superior. The term can be misleading and used as a proxy for “better.”

• 🦴 ACL Example:

Moving the femoral tunnel from the traditional AM bundle position to the so-called “central footprint anatomic” position increased graft rerupture rates in professional soccer players (up to 18.5% with hamstrings). The author reverted to AM placement.

• 🔄 LET Example:

Lateral extra-articular tenodesis (LET) is clearly not anatomic, yet significantly reduces ACL graft rerupture (as low as 2% in elite athletes when combined with patellar tendon graft + AM position).

• ⚖️ PLC & MCL Reconstructions:

Several “anatomic” techniques fail to reproduce true dynamic biomechanics and may not restore rotational stability as effectively as simpler, biomechanically optimized constructs.

• 🔬 Philosophical Shift:

Authors advocate for:

1️⃣ Biomechanical validation over cosmetic anatomy

2️⃣ Abandoning the misleading “anatomic” label

3️⃣ Laboratory testing + clinical outcomes as the gold standard

Core Message

Biomechanical function—not visual resemblance to native anatomy—should define successful ligament reconstruction.

https://www.sciencedirect.com/science/article/abs/pii/S074980632300587X

• 👥 Paper type: Editorial commentary reviewing evidence on non-traumatic ACL graft failure and femoral tunnel malposition (Arthroscopy 2024, Lucidi et al.)
• 🎯 Main message: The number one cause of ACL reconstruction failure is a misplaced femoral tunnel, typically too anterior or too vertical (Arthroscopy 2024, Lucidi et al.)
• 📊 Technical error prevalence: In revision cohorts, technical errors account for ~60% of failures, and femoral tunnel malposition is implicated in up to 80% (Arthroscopy 2024, Lucidi et al.)
• ⚠️ Consequences of malposition:
• Increased anterior translation
• Residual pivot shift
• Higher postoperative meniscal tears
• Increased revision rates (Arthroscopy 2024, Lucidi et al.)
• 🔁 Proposed solution:

The Over-The-Top technique + lateral extra-articular tenodesis (LET) avoids femoral tunnel malposition and improves rotatory control, particularly in patients with narrow notch or high tibial slope (Arthroscopy 2024, Lucidi et al.)

• 🛠 Revision advantage:

If failure occurs, there is no femoral tunnel widening, osteolysis, or hardware conflict, simplifying revision surgery (Arthroscopy 2024, Lucidi et al.)