Anterior Cruciate Ligament Surgery

Transcription

1 Anatomy Anterior Cruciate Ligament Surgery Roger Ostrander, MD Andrews Institute Anatomy Anatomy Function Primary restraint to anterior tibial translation Secondary restraint to internal tibial rotation Length: 32mm (range 22 to 41mm) Width: 10mm (range 7 to 12mm) Innervation: Tibialnerve (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 1

2 Epidemiology 30% of ACL injuries occur with direct contact» 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. Number of Cases Male Female Age in Years % of ACL injuries occur via non-contact mechanism Clinical Presentation» Feel a pop in the knee» Knee buckles» Difficulty with weight bearing» Cannot continue to participate» Large effusion 9 10 Associated Injuries Acute ACL tears can be associated with:» Meniscal tears» Meniscocapsular injuries» Chondral injury» Bone contusion» Other ligaments» Rest» Ice» Compression» Elevation» Physical Therapy» Arthrocentesis ** Initial Treatment

3 Treatment Non-operative versus Operative treatment Operative» Younger & Higher demand patients Treatment Non-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» Patellar Tendon» Quadrupled hamstring» Quadriceps tendon» Allograft 16 Patellar Tendon Graft Surgical Technique Graft Harvest» 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. 17 3

4 Graft Harvest Graft Prep Surgical Technique Closure and Bone Graft Closure & Bone Graft Notchplasty Notchplasty PCL 4

5 Diagnostic Scope Meniscus Repair Meniscocapsular Repair Lateral Meniscus Repair Drilling Tunnels Tibial Tunnel Guide Wire Drilling Tunnels Ream Tibial Tunnel Drilling Tunnels Ream Femoral Tunnel Drilling Tunnels 5

6 Graft Passing Pin Graft Pulled into Knee Screw in Femur Graft Passage Tibial Fixation Screw in Tibia Tibial Fixation 6

7 Outcomes ACL reconstruction successful >95% of time Complications are rare Stiffness Fractures Infection Thank You Tibial Fixation Screw in Tibia Thank You 7

8 Function Primary restraint to anterior tibial translation Posterior horn of medial meniscus is major secondary restraint Secondary restraint to internal tibial rotation Physical Exam Comprehensive Knee Exam» Range of Motion» Anterior Drawer» Posterior Drawer» Lachman» Pivot-shift» Varus / Valgus» Dial Test 45 Several theories have been proposed to explain the mechanism of non-contact ACL injury» Impingement on the intercondylar notch» Quadriceps contraction» Quadriceps-Hamstring force balance» Axial compressive forces Impingement» Impingement on the medial intercondylar notch proposed as an anatomic cause for ACL injury 10 (hyper-extension).» Most injuries occur with the knee in partial flexion. 11,

9 Quadriceps Contraction Hamstring Force Balance» 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 (10 o -25 o in ext)» 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.» Larger compressive force vector Axial Compressive Forces / Posterior Tibial Slope» Numerous authors axial compressive forces & increased tibial slope lead to anterior displacement of the tibia & ACL strain.» Meyer, et al 23 demonstrated that occult micro-cracks in subchondral bone were consistent with bone bruises found on MRI. Knee Abduction» 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 Male vs Female Gender as a risk factor» 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)

10 X-rays X-rays Segond Fragment Described by Paul Segond in Avulsion fracture of the anterolateral tibia. High association with ACL injury. Claes, et al. - Anterolateral Ligament (ALL) insertion Imaging (MRI) Confirm ACL disruption. Diagnosis of associated injuries. Allograft» 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 - 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 cadets - 11% BTB, 13% HS, 44% Allograft failure rates. 80 Hamstring (gracilis & semitendinosus) 83 Ultimate load to failure:» Semitendinosus: 1216N» Gracilis: 838N» Quadrupled: 4590N Allograft - Cost» Cooper, et al. - Mean total cost - $5,195 (allograft) & $4,072 (autograft). 81» OR time: avg 12mins longer with autograft

11 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? 61 Two functional bundles of ACL Anteromedial(AM) Tight in flexion Anterolateral stability Posterolateral(PL) Tight in extension Limits anterior translation, hyperextension, and rotation Anatomy Femoral Origin Footprint size:» Oval-shaped» Vertically oriented» 10mm x 18mm ACL Anatomy Posterior 64 Tibial Insertion ACL Anatomy Anterior tibial plateau Footprint size:» 10mm coronal plane» 18mm sagittal plane 65 11