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 - 566 +/-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 - 673 Newtons– Innovasive data

• EndoButton (Deknatel tape) - 610-700 Newtons– Rowden et al. AmJSM, 1996.

• EndoButton (continous loop) – two times “stronger and stiffer” than with tape– M.J. Friedman, Fall AANA Meeting, 1999.

• 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 - 1159N

• WasherLoc - 905N

• Screw and Post - 768N

• RCI screw (metal) - 241N

• Resorbable screw - 341N (over-sized screw - 420N)

ACL TENSIONINGACL 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 - 4400N– JC Richmond - AANA Fall Meeting,

1999.

• 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. AmisKnee Surg Sports Trauma

Arthroscopy 2:192 - 202 (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

loadBurks 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 - 3.6 pounds

• semitendinosus - 8.5 pounds

• iliotibial band - 13.6 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.Goble1997 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 TensioningTension Boot

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 5 - 15 lbs.

• Specific to graft type

• Pretension (??)

Conclusions

Well controlled clinical studies

hold the answers.

Thank You

Orthopaedic Research of Virginia

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ORV 2000