ACL Reconstruction with Autogenous Semitendonsis and Gracilis William R. Beach, M.D.

Graft Harvest, Fixation and Tensioning

Graft Harvest Most important and “stressful” portion Incision – two finger breadths distal and one medial to the tibial tubercle Palpate the “speed bumps” Longitudinal incision down to bone Elevate the tendons and view the tendinous “raphe” from “inside” the fascia

Graft Harvest “Whip-stitch” the free ends of the semi-t and gracilis with #5 suture Carefully and completely release the tendinous connections to the gastrocnemius

Graft Harvest “Blunt” tendon stripper to avoid premature tendon amputation “Sharp” tendon stripper

Tibial Tunnel Placement and Notchplasty Notchplasty required because we are replacing an “hourglass with a cylinder” Howell Guide couples tibial tunnel placement and the notchplasty

Howell Guide References the tibial tunnel placement off the roof of the intercondylar notch Ideal for acute tears and reconstruction Less suited for the chronic “overgrown” intercondylar notch The guide is positioned and the pin is drilled in full extension

Marking The Roof While the knee is in full extension the drill can be advanced into and under the roof This will outline the minimum amount of roof which must be removed to avoid graft impingement

Avoiding Lateral Wall Abrasion Advance the drill slightly past the entrance of the tibial tunnel By carefully flexing the knee the minimum amount of lateral wall is removed to avoid abrasion

Femoral Tunnel Is the cortex or bony cylinder intact ? If the posterior cortex is intact then compression or interference fixation is possible If the posterior cortex is incompetent then suspension fixation is necessary

Fixation Types Compression or interference –ex. Metal or resorbable screws Suspension –ex. Endobutton, LinX HT or Cross-pin

Tunnel Requirements for Compression Device Competent bony cylinder Protected posterior cortex Usually requires creation of this tunnel in greater degrees of flexion – avoid the “over the top position”

Tunnel Requirements for Suspension Device Competent bony cortex in the proximal portion of the tunnel – Endobutton and LinX An intact or defined cortical breach – Endobutton and LinX Adequate bone strength to support the cross-pin device

Peak Loads for Femoral Interference/Compression Fixation Metal RCI screw - 214N Bioscrew (8mm) - 341N (Brown CH et al /-68 N) Half millimeter drilling and “over-sized” screw - increased ultimate strength to 530N JC Richmond and MJ Friedman, Fall AANA Meeting, 1999.

Peak Loads for Suspension Fixation Devices Lynx HT Newtons –Innovasive data EndoButton (Deknatel tape) Newtons –Rowden et al. AmJSM, EndoButton (continous loop) – two times “stronger and stiffer” than with tape – M.J. Friedman, Fall AANA Meeting, Cross-pins – 850 to 1150N ultimate tensile strength with stiffness of 224N/mm –M.J. Friedman, Fall AANA Meeting, 1999.

Peak Loads for Tibial Fixation Tandem AO Screw and Washer N WasherLoc - 905N Screw and Post - 768N RCI screw (metal) - 241N Resorbable screw - 341N (over-sized screw - 420N)

ACL TENSIONING How ? When ? How much ?

ACL Reconstruction and Tensioning Underload - Instability Overload - Constrains motion

Variable Factors Viscoelastic Properties –Pretension –Preoperative tension –Postoperative tension

Literature Review

Human Studies - In Vivo Tension on the ACL/PCL changes throughout the arc of motion FG Girgis et. al. Clin Orth 1975

ACL Biomechanics Doubled gracilis and semitendinosus strength N –JC Richmond - AANA Fall Meeting, the ACL get tighter in extension the ACL is more lax in 30 degrees of flexion

Review On Tension In The Natural And Reconstructed Anterior Cruciate Ligament H.N. Andersen, D.A. Amis Knee Surg Sports Trauma Arthroscopy 2: (1994)

Andersen and Amis Different grafts will require different tensions to restore normal stability The joint position (flexion angle) and graft placement are critical Little firm evidence for which to base a consistent protocol

Determination of Graft Tension before Fixation in ACL Reconstruction Burks RT, Leland R. Arthroscopy 4:260-6 (1988)

Human Study - In Vitro Determination of Graft Tension Before Fixation in Anterior Cruciate Ligament Reconstruction –Ten cadaveric knees –KT 1000 (Medmetric) –Measured anterior tibial translation with a 20 lb load Burks and Leland Arthroscopy 1988

Burks and Leland Goal - to determine the tension needed before graft fixation to restore normal anteroposterior translation Arthrometer testing until the 20 lb. anterior drawer equalled the ACL intact drawer

Burks and Leland Graft and tension bone-tendon-bone pounds semitendinosus pounds iliotibial band pounds The required tension to return anterior translation to normal seems to be tissue specific.

Tuckahoe Orthopaedics Caspari, Meyers, Beach and Galbraith Study to determine tensioning affects Tensioned and non-tensioned group Not completed because of the early identifiable benefits in tensioning

ACL Pretensioning B-T-B complexes were tensioned initially with 16 lbs. via an Instrom device Measured 3 min. later the tension was 8 lbs. This “creep” stabilized at 3 minutes M.Goble 1997 Metcalf Mem. Sun Valley, ID

ACL Pretensioning Goble suggests –Tensioning the graft and femoral fixation complex –Cycle the knee through a full ROM and repeat several cycles –Re-tension the graft after 3 minutes and fixate the graft to the tibia

Practical Tensioning Tension Boot

Allows up to 20 lbs. of tension to be applied to the graft Allows cycling of the graft under tension Frees the surgeons hands to fixate the graft to the tibia

Conclusions Graft placement is crucial Notchoplasty is important Graft type is minimally important

Conclusions Graft fixation construct should have minimal strain Angle of tensioning 0° - 30°

Conclusions Operative graft tension lbs. Specific to graft type Pretension (??)

Conclusions Well controlled clinical studies hold the answers.

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