Current Concepts In ACL Reconstruction

1. Current Concepts In ACL Reconstruction Reviewed by Marc Rogers, D.O. September 1, 2000

2. Anatomy Of The ACL • Originates in a broad, irregular, diamond-shaped area just in front of the intercondylar eminence of the tibia (medial to the insertion of the anterior horn of lateral meniscus) and inserts in a semicircular area on the posteromedial aspect of the lateral femoral condyle • Approximately 33 mm long and 11 mm in diameter • Composed of 2 Bundles: - Anteromedial: tight in flexion - Posterolateral: tight in extension • Ultimate tensile load and stiffness is 2160 +/- 157 N and 242 +/- 28 N/mm • Blood Supply via branches of the middle geniculate artery

3. ACL Injury • Prevalence is approximately 1 per 3000 Americans • Most commonly the result of non-contact pivoting injuries and are commonly associated with an audible “pop” and immediate swelling • Lachman test is the most sensitive examination for acute ACL injuries • Controversy continues regarding development of late arthritis in ACL deficient vs. reconstructed knees • Chronic ACL deficiency is associated with a higher incidence of complex meniscal tears that are not amenable to repair • Treatment decisions should be individualized and based on age, activity level, instability, associated injuries, and other medical conditions (For more specifics, see Algorithm by IKDC in Review ofOrthopaedics by Miller)

4. ACL Surgery: Treatment Perspectives • Surgical options for the treatment of the ACL-deficient knee include: - Primary repair - Augmented primary repair - Prosthetic replacement - Reconstruction using graft material

5. Primary Repair • No longer recommended • Studies have shown that isolated primary repairs become functionally inadequate with failure rates as high as 50% • Approximately 20% require repeat surgery in 3-5 years

6. Augmented Primary Repair • Primary suture repair augmented by lateral extraarticular procedures • Artificial strut device placed in an over-the-top position on the lateral femoral condyle to provide additional stability • Most extraarticular procedures have failed to restore satisfactory stability to the knee • Overall, no real difference when compared to primary repair alone

7. Prosthetic Replacement • Not currently recommended for ACL reconstruction • 40-78% of 855 prosthetic ACL ligaments failed when assessed over a 15 year period • 83% of 55 knees reconstructed with a Dacron prosthesis had significant osteoarthritic changes at 9 year follow-up • Overall, appear to cause more complications than biologic grafts (partly due to increased wear debris) • Currently working on a prosthetic replacement that comes from tissue-engineered collagen scaffolds enriched with growth factors (would be strong enough to allow for achievement of solid fixation and early rehab)

8. Biologic Tissue Graft Reconstruction • Most popular treatment of the ACL-deficient knee • In most patients, properly performed ACL reconstruction with a biologic tissue graft improves the stability and function of the knee

9. Graft Options For ACL Reconstruction • Include biologic autograft and allograft materials: AUTOGRAFT OPTIONS: - Bone-Patellar Tendon-Bone - Quadrupled Semitendinosus/Gracilis Tendon - Bone-Quadriceps Tendon ALLOGRAFT OPTIONS: - Achilles Tendon - Bone-Patellar Tendon-Bone - Hamstring Tendon

10. Graft Options For ACL Reconstruction Con’t • Should choose the graft type most suitable for a given patient • With appropriate surgical technique and rehabilitation, all of these grafts are suitable for reconstruction • Currently, most commonly used grafts are: - Autograft Bone-Patellar Tendon-Bone - Autograft Hamstring Tendon • These have shown similar results at 2,3, and 5 year follow-up studies

11. Autograft vs. Allograft • Recent studies support use of allograft tissue as an alternative for ACL reconstruction (as with autograft, found to revascularize and become viable after implantation) • 5 and 7 year follow-up studies demonstrate similar outcomes of early ACL allograft reconstructions compared to autograft reconstructions • Allograft must be carefully screened for viral disease • Allograft must undergo appropriate harvesting, sterilization, and preservation techniques that do not weaken the graft • Some studies have demonstrated a slower rate of graft incorporation and remodeling for allografts

12. Current Trends In ACL Reconstruction • Bone-Patellar Tendon-Bone: - most commonly used today - central third of patellar tendon with its adjacent patellar and tibial bone blocks - young, high-demand athletes - allows for earliest return to high-demand activities - allows for good bony fixation, excellent load to failure and stiffness (2300 N and 620 N/mm), durability, and success at long-term follow-up

13. Current Trends Con’t • Hamstring Tendon: - quadruple-strand semitendinosus/gracilis tendon graft where both the semitendinosus and gracilis tendons are folded in half and combined - tensile strength as high as 4108 N - dimensions of 10mm graft is more comparable to intact ACL - smaller incision - theoretically less knee pain - avoid interference with extensor mechanism - thicker tendinous portion within the knee joint and bone tunnels - fixation site healing still under investigation

14. Current Trends Con’t • Bone-Quadriceps tendon: - alternative for revision - knees with multiple ligament injuries - Advantages: wide tendinous portion along with a bone plug fixation at one end(tensile strength 2352 N) - Disadvantages: size and location of donor-site scar

15. Surgical Approaches • Less invasive techniques aimed at limiting extensor mechanism trauma, decreasing scarring on the knee, and avoiding exposure of the articular cartilage • Arthroscopically assisted procedures have shown minor improvement of early symptoms when compared to miniarthrotomy • No significant difference at 2 year follow-up

16. Surgical Approaches Con’t • Single-Incision vs. Two-Incision: - only minor short-term differences in subjective and objective outcomes - Potential benefits of single-incision technique include improved cosmesis, less post-op pain and potentially faster rehab - initial concerns of single –incision technique regarding difficulty of obtaining proper femoral tunnel placement has not been a problem (notchplasty and anteromedial portal of arthroscope may assist with femoral visualization)

17. Tunnel Placement • Placement of femoral and tibial tunnels aims to best restore the original anatomy • Attempts to limit permanent graft stretching, impingement, and overconstraint of the knee that would result in loss of motion and graft failure • Most common technical mistake is excessive anterior placement of either the tibial or femoral tunnel

18. Tibial Tunnel • Initiated at or slightly anterior to the midpoint between the anterior tibial tubercle and posteromedial border of the tibia • Directed between a 45-55 degree angle toward posterior aspect of ACL tibial footprint • Care must be taken to ensure that the ACL tibia guide is perpendicular to long axis of tibia during drilling to prevent excessive superior or inferior tunnel placement • Anterior tibial tunnel placement results in graft impingement against the intercondylar roof and limits knee extension • Therefore, drilling in the posterior aspect of ACL footprint avoids these problems and allows for satisfactory clinical outcomes

19. Femoral Tunnel • Right knee: 10 or 11 o’clock position • Left knee: 1 or 2 o’clock position • Both immediately anterior to the over-the –top position leaving a 1-2 mm posterior cortical wall • Mueller: anterior femoral tunnel places the graft under high tissue strains with knee flexion resulting in decreased knee flexion and/or increased graft stretching

20. Notchplasty And Roofplasty • Serves to increase the view of the posterior part of the notch and create clearance for the graft when the knee is in extension • If too large, may displace the femoral insertion to an abnormally lateral position resulting in abnormal knee kinematics • LaPrade et al: demonstrated histopathologic changes at 6 months consistent with those found in kness with early degenerstive arthosis • Cohen et al: study of 100 patients found no beneficial short term effect • Minimizing notchplasty reduced post-op bleeding, pain, and swelling • Should only be performed if deemed necessary after testing the graft clearance intraoperatively

21. Graft Preconditioning And Tensioning • Inadequate tension results in continued instability • Excessive tension results in restricted knee motion and accelerated arthrosis • Application of tension can influence graft performance • Yasuda et al: grafts tensioned at 80 N had significantly less knee laxity than those tensioned at 20 N (no reported differences in clinical symptoms • Graf et al: forces within the graft may decrease by as much as 30% soon after fixation unless graft has been cyclically preconditioned

22. Graft Fixation • Should ideally restore the original anatomy • Therefore, should be as close to the joint line as possible • In order to achieve Bone-Patellar Tendon-Bone graft fixation at both femoral and tibial joint lines, may supplement tibial fixation with a bone graft/bioabsorbsable screw in addition to placing an interference screw adjacent to more distal bone plug • Benedetto et al: no difference in clinical outcome when metallic, titanium, or biodegradable screws used for fixation/ screw divergence greater than 15 degrees from orientation of bone plug dramatically decreases fixation strength • Inserting femoral screw with knee flexed 100-120 degrees better approximates axis of femoral tunnel (may also insert screw into notch and place screwdriver through tibial tunnel • Best knee position to fix graft has yet to be determined

23. Donor Site Morbidity • Bone-Patellar Tendon-Bone: - Rarely have post-op arthrofibrosis, patellar fracture, tendon rupture - Patellar pain incidence relatively high (4-40%) - Thought to be due to development of patella baja postharvest - Control of patellar pain appears to be more dependent on rehabilitation than on technique of site closure or bone grafting - low incidence of tendon rupture • Hamstring Tendon: - at 3 years post-op strength 95% of pre-op values - mild harvest area soreness up to 3 months - no major functional impairment

24. Conclusions • Overall, follow-up studies reveal favorable results 80-90% of the time • Does appear to be a higher incidence of degenerative arthrosis compared to ACL-deficient patients

25. Future Directions • Advances in molecular biology, gene therapy and tissue engineering may accelerate and promote the soft tissue healing process of both the ACL graft and its insertion site • Combined with the use of robotic technology and computer assisted surgery, may be able to more successfully restore the ACL-injured knee to its preinjury state