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3/6/2017
1
Anterior Cruciate LigamentSurgery
Roger Ostrander, MD
Andrews Institute
Anatomy
Anatomy
Function• Primary restraint to
anterior tibial
translation
• Secondary restraint to
internal tibial rotation
Anatomy
• Length: 32mm (range 22 to
41mm)
• Width: 10mm (range 7 to
12mm)
• Innervation: Tibial nerve
(posterior articular nerve)
– Infiltrates capsule
posteriorly
– Golgi tendon receptors
• Blood supply: middle genicular
artery
• Strength: 2200N
Anatomy Background
• Incidence of ACL
rupture:
• 50 per 100,000 persons
per year
– ~200,000 ACL ruptures in
USA per year
– ~175,000 ACL recons per
year in USA
– Initial cost of ACL recon
exceeds 2 billion dollars
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7
Epidemiology
» 70% of ACL injuries occur during sport participation.
» Peak age group: 15-30
» Females: 4-6 times rate of ACL injury when compared to males.
0
150
300
450
600
10-14 15-19 20-24 25-29 30-34 35-39 40-44 45-49 50-54
Num
ber
of C
ases
Age in Years
Male Female
8
Mechanism of Injury30% of ACL injuries occur with direct contact
9
Mechanism of Injury
70% of ACL injuries occur via non-contact mechanism
10
Clinical Presentation
» Feel a pop in the knee
» Knee buckles
» Difficulty with weight bearing
» Cannot continue to participate
» Large effusion
11
Associated Injuries
» Meniscal tears
» Meniscocapsular injuries
» Chondral injury
» Bone contusion
» Other ligaments
Acute ACL tears can be associated with:
12
Initial Treatment
» Rest
» Ice
» Compression
» Elevation
» Physical Therapy
» Arthrocentesis **
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13
TreatmentNon-operative versus Operative treatment
Operative
» Younger & Higher demand patients
14
TreatmentNon-operative versus Operative treatment
Non-operative
» Lower demand and sedentary patients
» No concomitant injury
Goals of Reconstruction
• Reproduce the normal
anatomy of the native ACL
• Restore knee stability
– Eliminate anterior translation
– Improve rotatory function
• Improve long term outcomes
16
Graft Options
» Patellar Tendon
» Quadrupled hamstring
» Quadriceps tendon
» Allograft
17
Graft Options
Patellar Tendon Graft
» Dimension: 9,10 or 11 mm width x 4mm thick
» Ultimate load to failure: 2,977N
» Advantages: Good biomechanical tensile strength, bone-to-bone healing (6-8wks), stiffer graft.
» Disadvantages: Increased risk of anterior knee pain, patellar fracture.
Surgical TechniqueGraft Harvest
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Graft Harvest Graft Prep
Surgical TechniqueClosure and Bone Graft
Closure & Bone Graft
Notchplasty
PCL
Notchplasty
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Diagnostic ScopeMeniscus Repair
Meniscocapsular Repair
Lateral Meniscus Repair
Drilling Tunnels
Tibial Tunnel Guide Wire
Drilling Tunnels
Ream Tibial Tunnel
Drilling Tunnels
Ream Femoral Tunnel
Drilling Tunnels
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Graft Passing Pin Graft Pulled into Knee
Screw in FemurGraft Passage
Tibial Fixation
Screw in TibiaTibial Fixation
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Outcomes
• ACL reconstruction
successful >95% of time
• Complications are rare
– Stiffness
– Fractures
– Infection
Thank You
Tibial Fixation
Screw in Tibia
Thank You
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Function
• Primary restraint to anterior tibial translation
– Posterior horn of medial meniscus is major secondary restraint
• Secondary restraint to internal tibial rotation
45
Physical Exam
Comprehensive Knee Exam
» Range of Motion
» Anterior Drawer
» Posterior Drawer
» Lachman
» Pivot-shift
» Varus / Valgus
» Dial Test
Graft Options
47
Mechanism of Injury
» Impingement on the intercondylar notch
» Quadriceps contraction
» Quadriceps-Hamstring force balance
» Axial compressive forces
Several theories have been proposed to explain the
mechanism of non-contact ACL injury
48
Mechanism of Injury
» Impingement on the medial intercondylar
notch proposed as an anatomic cause for ACL
injury10 (hyper-extension).
» Most injuries occur with the knee in partial
flexion.11,12
Impingement
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9
49
Mechanism of Injury
» The quadricep is the primary producer of anterior force with the knee at/near full extension.13
» Anterior vector of the quadriceps is the primary
contributing force to ACL injury.14
» Angle of the patellar tendon is shallow.15
(10o-25o in ext)
» Larger compressive force vector.
Quadriceps Contraction
50
Mechanism of Injury
» Hamstrings co-contraction provides a protective mechanism for the ACL.16
» Several authors have demonstrated that the hamstrings produce a small protective force vector.17,18
» Hamstrings contribute to knee compressive forces.
Hamstring Force Balance
51
Mechanism of Injury
» Numerous authors19-22 - axial compressive forces & increased tibial slope lead to anterior displacement of the tibia & ACL strain.
» Meyer, et al23 demonstrated that occult micro-cracks in subchondral bone were consistent with bone bruises found on MRI.
Axial Compressive Forces / Posterior Tibial Slope
52
Mechanism of Injury
» Hewett, et al. - landing with the knee in valgus as a factor contributing to ACL injury.24
» Chaudhari, et al. - valgus alignment compounds effect of axial compressive loading.25
Knee Abduction
54
Male vs Female
» 2 to 8 times risk for ACL injury in females.
» Risk of ACL injury in female collegiate soccer and basketball players is 5% per year (<2% for males).43
Gender as a risk factor
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55
X-rays
56
X-rays
Segond Fragment
Described by Paul Segond in 1879.66
Avulsion fracture of the anterolateral tibia.
High association with ACL injury.
Claes, et al. - Anterolateral Ligament (ALL) insertion.67
57
Imaging (MRI)
Confirm ACL disruption.
Diagnosis of associated injuries.
58
Graft Options
» Advantages: multiple sources, eliminates donor site morbidity, decreased OR time.
» Disadvantages: increased cost, slower rate of incorporation, increased risk of disease transmission, higher rate of failure.
» Good choice for older/lower demand population, revision cases.
Allograft
59
Graft Options
Allograft - Increased Failure Rate
» Kaeding, et al. - ACLr - 4x greater failure rate w/ allograft.78
» Krych, et al. - BPTB auto vs BPTB allo - 5x greater failure rate w/ allograft.79
» Keller, et al. - 120 cadets - 11% BTB, 13% HS, 44% Allograft failure rates.80
» Cooper, et al. - Mean total cost - $5,195 (allograft) & $4,072 (autograft).81
» OR time: avg 12mins longer with autograft.81
Allograft - Cost
60
Graft Options
Hamstring (gracilis & semitendinosus)83
Ultimate load to failure:
» Semitendinosus: 1216N
» Gracilis: 838N
» Quadrupled: 4590N
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61
Graft Options
Hamstring (gracilis & semitendinosus)83
» Advantages: Highest ultimate tensile strength (4090N), decreased risk of anterior knee pain.
» Disadvantages: Tissue-to-bone fixation & healing (10-12wks), tunnel widening, loosening of graft, hamstring weakness.
» Must be at least 8mm in diameter
Goals for Graft
Tensioning• Provide a Stable Graft that Functions
Biomechanically
• “ISOMETRIC” Vs “ANATOMIC” tension
– ISOMETRIC=Equal tension throughout ROM
– ANATOMIC=Most tension in extension with less in flexion
• Allow full physiologic range of motion
• Potential for over constraint of the joint?
Anatomy
• Two functional bundles of ACL
– Anteromedial (AM)
• Tight in flexion
• Anterolateral stability
– Posterolateral (PL)
• Tight in extension
• Limits anterior
translation,
hyperextension, and
rotation
64
ACL Anatomy
Femoral Origin
Footprint size:
» Oval-shaped
» Vertically oriented
» 10mm x 18mm
Posterior
65
ACL Anatomy
Tibial Insertion
Anterior tibial plateau
Footprint size:
» 10mm coronal plane
» 18mm sagittal plane