Pivot Shift | Graft Selection | Tunnel Placement | Return to Sport
GRAFT OPTIONS
Critical Must-Knows
- ACL is PRIMARY restraint to anterior tibial translation
- Pivot shift is most specific clinical test
- Wait 3+ weeks post-injury to reduce arthrofibrosis risk
- Anatomic tunnel placement critical - avoid high noon position
- BTB autograft remains gold standard for young athletes
Clinical Pearls
- "Segond fracture = pathognomonic for ACL tear
- "Associated meniscal tears in 50%+ of acute injuries
- "Allograft failure 4x higher in patients under 25
- "STABILITY trial: LET reduces graft failure in high-risk
Critical Exam Concepts
Pivot Shift is KEY
Pivot shift test is most specific for ACL deficiency. Demonstrates rotational instability. Grade correlates with functional disability.
Tunnel Position Critical
Anatomic femoral tunnel at center of native footprint. Old high noon position is NON-ANATOMIC. Use anteromedial portal technique.
Graft Selection
BTB autograft = gold standard for young athletes. Fastest bone-to-bone healing. Avoid allograft in under 25 years old.
Timing Matters
Wait 3+ weeks before surgery. Regain full ROM first. Early surgery = arthrofibrosis risk.
Graft Selection Quick Guide
| Graft | Advantages | Disadvantages | Best For |
|---|---|---|---|
| BTB Autograft | Fastest integration | Anterior knee pain | Young athletes, contact sports |
| Hamstring | Less knee pain | Slower integration | Non-contact sports |
| Quadriceps | Strong graft | Quad weakness | Revision surgery |
| Allograft | No donor morbidity | 4x failure in young | Low-demand older than 35 |
PIVOTACL Injury Mechanism
| P | Planting foot Fixed foot on ground |
| I | Internal rotation Femur internally rotates |
| V | Valgus stress Knee collapses valgus |
| O | Off-balance Deceleration/cutting |
| T | Twisting motion Non-contact pivot |
| P | Planting foot Fixed foot on ground | O | Off-balance Deceleration/cutting |
| I | Internal rotation Femur internally rotates | T | Twisting motion Non-contact pivot |
| V | Valgus stress Knee collapses valgus |
Hook:PIVOT mechanism causes ACL tears - pivot shift tests for it!
GRAFTACL Reconstruction Principles
| G | Graft choice BTB vs hamstring vs quad |
| R | ROM before surgery Full extension essential |
| A | Anatomic tunnel Center of native footprint |
| F | Fixation secure Interference screws |
| T | Time to heal 9-12 months RTS |
| G | Graft choice BTB vs hamstring vs quad | F | Fixation secure Interference screws |
| R | ROM before surgery Full extension essential | T | Time to heal 9-12 months RTS |
| A | Anatomic tunnel Center of native footprint |
Hook:Get the GRAFT right for successful reconstruction!
LAPClinical Tests for ACL
| L | Lachman test Most sensitive 85-95% |
| A | Anterior drawer Less sensitive |
| P | Pivot shift Most specific |
| L | Lachman test Most sensitive 85-95% |
| A | Anterior drawer Less sensitive |
| P | Pivot shift Most specific |
Hook:LAP up the ACL tests!
Overview and Epidemiology
Female ACL Injury Risk
Females have 2-8x higher ACL injury rate than males in same sports. Factors: narrower notch, hormonal, neuromuscular patterns. Prevention programs reduce risk by 50%.
Epidemiology
- ACLR incidence ~46/100,000/year (German registry data)
- Peak age: 15-25 years
- Female greater than male (same sport)
- High-risk: soccer, basketball, skiing
- 70% non-contact injuries
Associated Injuries
- Meniscal tears: 50%+ acute
- MCL injury: contact mechanism
- Bone bruise pattern: posterolateral tibia
- Segond fracture: pathognomonic
- Lateral meniscus root tears
Pathophysiology and Mechanisms
ACL Anatomy
Origin: Posteromedial lateral femoral condyle in intercondylar notch.
Insertion: Anterior intercondylar tibia, anterolateral to medial tibial spine.
Two bundles:
- Anteromedial (AM): tight in flexion
- Posterolateral (PL): tight in extension
Blood supply: Middle genicular artery. Poor vascularity limits healing.
Length: 30-35mm. Width: 10-12mm.
Two-Bundle Anatomy
Understanding AM and PL bundles is important for anatomic reconstruction. Aim to recreate center of native footprint - double-bundle reconstruction has not shown superiority in most studies.
Classification Systems
ACL Injury Grading
| Grade | Pathology | Clinical Finding | Treatment |
|---|---|---|---|
| I Sprain | Microscopic tears | Firm endpoint | Conservative |
| II Partial | Partial macroscopic | Endpoint present | Variable |
| III Complete | Complete rupture | No endpoint, positive pivot | Reconstruction |
Most presentations are Grade III (complete tears).
Clinical Assessment
History
- Mechanism: Non-contact pivot, pop heard
- Immediate swelling: Hemarthrosis
- Instability: Giving way with pivoting
- Sport level: Determines treatment
- Previous injuries: Contralateral ACL
Examination
- Lachman test: Most sensitive (85-95%)
- Anterior drawer: Less sensitive
- Pivot shift: Most specific
- Associated injuries: MCL, meniscus
- Effusion: Hemarthrosis acute
Lachman Test Technique
Knee 20-30 degrees flexion. Stabilize femur. Translate tibia anteriorly. Positive: Increased translation AND soft/absent endpoint. Compare to contralateral side.
Key Clinical Pearls
Pivot shift: Best with patient relaxed (EUA). Demonstrates functional rotational instability causing giving way.
Associated injuries: Always check MCL, menisci, posterolateral corner.
Differential Diagnosis of the Acute Haemarthrotic Knee
Differentiating ACL Injury from Mimics
| Diagnosis | Distinguishing Feature | Confirming Test |
|---|---|---|
| ACL rupture | Non-contact pivot, pop, rapid effusion, positive Lachman/pivot shift | MRI; EUA |
| Patellar dislocation | Lateral patellar apprehension, medial tenderness (MPFL) | MRI - MPFL tear, lateral femoral/medial patellar bone bruise |
| Peripheral meniscal tear | True locking, joint-line tenderness, slower effusion | MRI |
| PCL injury | Dashboard/hyperflexion mechanism, positive posterior drawer/sag | Posterior drawer, MRI |
| Osteochondral fracture | Haemarthrosis with fat globules on aspiration | Radiograph/CT |
| Multiligament / knee dislocation | Gross instability in multiple planes, vascular concern | Vascular assessment, MRI |
A tense haemarthrosis after a twisting injury is ACL rupture until proven otherwise, but patellar dislocation and peripheral meniscal tears are the commonest mimics. Always exclude a spontaneously reduced knee dislocation when more than one ligament is involved.
Investigations
Standard Views
AP weight-bearing: Alignment, fractures.
Lateral: Segond fracture, tibial plateau.
Key findings:
- Segond fracture: Pathognomonic for ACL tear
- Tibial spine fracture: Common in children
- Deep lateral notch sign: Greater than 1.5mm
These radiographic signs should prompt further evaluation with MRI.
Segond Fracture
Segond fracture = small avulsion lateral tibial plateau = anterolateral ligament avulsion. Pathognomonic for ACL injury. Associated with high-grade pivot shift.
Management Algorithm
Management Pathway
ACL Injury Management
RICE, aspiration for comfort, brace, physiotherapy for ROM.
Consider: age, activity, sports demands, instability, associated injuries.
Low-demand, willing to avoid pivoting, no giving way, older patient.
Young active, pivoting sports, recurrent instability, repairable meniscus.
Surgical Technique
Anatomic Tunnel Position
Femoral tunnel:
- Center of native ACL footprint
- NOT high noon (non-anatomic)
- Use anteromedial portal technique
- Resident ridge as posterior landmark
Tibial tunnel:
- Anterolateral to medial tibial spine
- 1:30 (right) or 10:30 (left) position
Anatomic placement is essential for restoring rotational stability.
Avoid High Noon
Old transtibial technique placed femoral tunnel too vertically. This is non-anatomic with poor rotational control. Use anteromedial portal for anatomic placement (10:30 right knee).
Complications
| Complication | Risk Factors | Prevention | Management |
|---|---|---|---|
| Arthrofibrosis | Early surgery, poor ROM | Wait 3+ weeks, restore ROM | Aggressive PT, lysis |
| Graft failure | Allograft young, malposition | Autograft, anatomic tunnels | Revision ACLR |
| Anterior knee pain | BTB graft | Hamstring/quad graft | Usually settles |
| Infection | Any surgery | Aseptic technique | Washout, antibiotics |
Graft Failure Risk Factors
Highest failure risk: Allograft in under 25 (4x), RTS before 9 months, non-anatomic tunnels. BTB autograft + anatomic tunnels + delayed RTS minimizes failure.
Postoperative Care
Rehabilitation Protocol
Brace locked extension. WBAT with crutches. ROM 0-90 degrees. Quad sets, SLR.
Unlock brace. Progressive ROM. Stationary bike. Patellar mobilization.
Wean crutches. Pool running. Closed chain exercises. Proprioception.
Running program (straight). Progressive resistance. Late agility.
Cutting/pivoting. Sport drills. Psychological readiness.
Full competition after functional tests. Hop tests, strength greater than 90%.
Return to Sport Criteria
Before RTS: Hop test LSI greater than 90%, quad strength greater than 90%, no effusion, full ROM, ACL-RSI passed, minimum 9 months. Each month delay reduces re-injury risk.
Outcomes and Prognosis
Outcome Factors
Good: Anatomic reconstruction, appropriate graft, compliant rehab, adequate time, isolated injury.
Poor: Malposition, early RTS, cartilage injury, meniscectomy, non-compliance.
Long-Term
OA: 50% develop radiographic OA by 10-15 years regardless of treatment. Higher if meniscectomy.
Contralateral ACL: 10-25% lifetime risk, especially young females.
Evidence Base and Key Studies
KANON Trial - Early ACLR vs Rehab + Optional Delayed
- RCT, 121 young active adults with acute ACL tear
- Early ACLR + rehab vs rehab + optional delayed ACLR
- No difference in 2-year KOOS (between-group 0.2 points)
- 61% of the optional-delayed group avoided surgery
MARS Cohort - Graft Choice in Revision ACLR
- 1205 revision ACLRs, 83 surgeons, 52 sites
- Autograft predicted better 2-year IKDC and KOOS sport/QoL
- Graft re-rupture 3.3% at 2 years
- Autograft 2.78x less likely to re-rupture vs allograft
Timing of ACL Reconstruction (Hamstring)
- RCT, 69 patients, early (within 21 days) vs delayed (beyond 6 weeks)
- Hamstring autograft, identical extension-focused rehab in both arms
- No difference in postoperative range of motion lost
- No difference in KT-1000 stability or subjective scores
STABILITY Trial - LET
- RCT ACLR +/- lateral extra-articular tenodesis
- 618 patients randomized
- ACLR + LET: 4% graft rupture
- ACLR alone: 11% graft rupture
Return to Sport Timing
- 106 elite athletes prospective
- Each month delay = 51% reduced re-injury
- Less than 9 months RTS: higher failure
- Passing functional tests protective
Allograft Failure in Young
- MOON cohort analysis
- Under 25 with allograft: 4x failure vs autograft
- No difference in over 35
- Activity level also affects outcome
Exam Viva Scenarios
Use these scenarios to practise clinical reasoning and management decisions
Scenario 1: Young Athlete ACL Injury
"A 20-year-old male soccer player presents 2 weeks after a non-contact pivoting injury. He heard a pop and had immediate swelling. Examination shows positive Lachman and pivot shift. MRI confirms complete ACL tear without meniscal injury. How would you manage this?"
Scenario 2: Graft Selection in Female
"A 30-year-old female recreational skier needs ACL reconstruction but is concerned about anterior knee pain as she kneels frequently for work. She asks about graft options. What would you discuss?"
Scenario 3: Failed ACL Reconstruction
"A 23-year-old presents 18 months after hamstring ACL reconstruction. He returned to soccer at 7 months and now has recurrent instability. MRI shows graft rupture. CT shows vertical femoral tunnel. How would you approach this?"
MCQ Practice Points
Primary ACL Function
Q: Primary function of ACL? A: Restraint to anterior tibial translation - 85% of restraint at 30 degrees. Also resists internal rotation and hyperextension.
Most Sensitive Test
Q: Most sensitive clinical test for ACL? A: Lachman test (85-95% sensitive). At 20-30 degrees flexion. Assess translation AND endpoint quality.
Most Specific Test
Q: Most specific clinical test for ACL? A: Pivot shift test. Demonstrates rotational instability causing functional giving way.
Segond Fracture
Q: What does Segond fracture indicate? A: ACL rupture (pathognomonic). Avulsion lateral tibial plateau. Associated high-grade pivot shift.
Allograft in Young
Q: Why avoid allograft in young athletes? A: 4x higher failure rate in under 25. Slower incorporation, remodeling issues.
Early Surgery Risk
Q: Primary risk of ACL surgery within 3 weeks? A: Arthrofibrosis. Wait for ROM recovery. Optimal timing 4-12 weeks.
Guidelines, Registries & Global Practice
Global Epidemiology
Incidence & Demographics
- ACLR incidence ~46/100,000/year (German inpatient data, Domnick 2017)
- Peak age: 15-25 years; second mid-life peak in women
- Males higher absolute volume; females higher per-exposure risk
- Highest-risk sports: football/soccer, basketball, skiing, handball
- ~70% of injuries are non-contact (cutting/landing)
Risk Factors
- Female sex (per-exposure), narrow intercondylar notch
- Increased posterior tibial slope
- Generalised ligamentous laxity
- Neuromuscular control (dynamic valgus on landing)
- Prior ACL injury (ipsi- or contralateral)
Major Guidelines, Side by Side
Guideline Positions on Key ACL Questions
| Question | AAOS CPG 2023 | NICE / UK practice | Evidence |
|---|---|---|---|
| Reconstruction vs rehab | Reconstruction improves activity/stability in active patients; rehab reasonable in lower-demand | Trial of rehab acceptable; reconstruct if instability persists or high demand | Moderate (KANON, AAOS systematic review) |
| Graft choice (adult) | Autograft (BTB or hamstring) over allograft, especially in young/active | Autograft preferred in young; allograft reserved for selected older/low-demand | Strong for autograft in young (MOON/MARS) |
| Adding LET / anterolateral procedure | Option in high-risk revision/young pivoting patients | Increasingly offered to high-risk young pivoting patients | Level 1 (STABILITY) |
| Return to sport | Delay and use objective criteria, not time alone | Criteria-based RTS, typically not before 9 months | Level 3 (Grindem/Delaware-Oslo) |
Guideline Anchor
The AAOS 2023 ACL Clinical Practice Guideline (Brophy & Lowry, J Am Acad Orthop Surg) gives 8 recommendations plus 7 options: autograft over allograft in young/active patients, anatomic single-bundle reconstruction, and criteria-based (not purely time-based) return to sport.
Landmark Trials That Shape Practice
Key ACL Evidence
| Trial / Cohort | Design | Take-home |
|---|---|---|
| KANON (Frobell 2010) | RCT 121 acute tears | Rehab + optional delayed ACLR equals early ACLR at 2-5y; many avoid surgery |
| STABILITY (Getgood 2020) | RCT 618, ACLR +/- LET | LET cut graft rupture 11% to 4% in high-risk young patients |
| MOON cohort (Kaeding 2011) | Prospective cohort | Allograft 4x failure vs autograft in young patients |
| MARS (Wright 2014) | 1205 revision ACLRs | Autograft 2.78x lower re-rupture than allograft at revision |
| Delaware-Oslo (Grindem 2016) | Prospective cohort | Each month RTS delay to 9 months cut re-injury 51% |
Global Practice Variation
Where Practice Differs
- Graft default: hamstring dominant in Europe/Scandinavia (~90% in German data); BTB/quadriceps more favoured for high-demand contact athletes elsewhere
- Timing: early reconstruction common in athlete-focused systems; rehab-first with optional delayed ACLR (KANON model) used widely in Scandinavia
- LET use: rising globally after STABILITY, fastest in young pivoting and revision cases
Why It Differs
- Surgeon training and registry feedback (e.g. Scandinavian, NZ knee-ligament registries)
- Patient demand profile and sport culture
- Access, theatre capacity and rehab resourcing
- Interpretation of equivalence trials (KANON) vs failure-reduction trials (STABILITY)
Orthopaedic Exam Relevance
ACL injuries are an extremely common viva topic across FRCS (Tr & Orth), FRACS, EBOT and ABOS. Know graft selection, the rehab-vs-reconstruct debate (KANON), surgical timing, anatomic tunnel placement, LET indications (STABILITY) and criteria-based RTS (Grindem).
ANTERIOR CRUCIATE LIGAMENT INJURIES
Clinical summary
Clinical Tests (LAP)
- •Lachman: Most sensitive 85-95%
- •Anterior drawer: Less sensitive
- •Pivot shift: Most specific
- •Compare endpoint quality
Graft Selection
- •BTB: Gold standard young athletes
- •Hamstring: Less anterior knee pain
- •Quad: Growing popularity
- •Allograft: Over 35 only (4x failure young)
Surgical Timing
- •Wait 3+ weeks post-injury
- •Regain full ROM extension
- •Early surgery = arthrofibrosis
- •Optimal: 4-12 weeks
Tunnel Placement
- •Anatomic = center of footprint
- •Avoid high noon non-anatomic
- •Use anteromedial portal
- •10:30 right or 1:30 left
Return to Sport
- •Minimum 9 months post-op
- •Hop test LSI greater than 90%
- •Quad strength greater than 90%
- •Each month delay = 51% less re-injury