Anterior Cruciate Reconstruction
withHamstrings and BioScrews
Dr. Don JohnsonDirector Sports Medicine Clinic Carleton University
Assistant Professor Orthopedic Surgery University of Ottawa
Ottawa On Canada
Graft Choice in Anterior Cruciate Ligament Reconstruction
The debate over graft choice in anterior cruciate ligament reconstruction has been ongoing over the past 2 decades. There have been several papers to compare the ‘gold standard’ patellar tendon graft with the hamstring grafts. (1,2,3) The end functional result is the same for both grafts. A metanalysis by Yunes (27) of the four papers from the 1990's showed no significant difference in outcome. There was a slight trend for the patellar tendon graft to return to the same level of athletic competition. The difference is mainly in harvest site morbidity. The patellar tendon graft has more harvest site morbidity.(4) There is some increase in the 3-5 mm side to side instrumented measurement in follow-up with the hamstrings. This may be more related to the method of fixation; interference screws versus periosteal buttons.(5,6) The summary is that the patellar tendon graft is for the surgeon, and the hamstring graft is for the patient.
The technique of anterior cruciate reconstruction with the hamstrings has been well described by many authors (7,8,9,10,11,12,13,14)
The biomechanics of the patellar tendon graft compared to the semi-tendinosis has been reported by Noyes(15) The interest in multiple bundles of hamstring tendons has been stimulated by the biomechanical testing by Howell and Brown (16,17) Pinczweski described the use of interference screw fixation for the multiple bundles of semi-tendinosis and gracilus tendons. (18)At the present time this is the only long term follow up of the screw fixation of tendons.
The biomechanical testing of this method of fixation has been reported by Weiler.(19,20,21)
Semi-tendinosis and Gracilus - Harvest and Preparation
Graft Harvest
The graft harvest can be the most difficult aspect of this operation. There are video tapes on this technique available by Fowler and Fox from the AAOS library,. A video on the complete procedure is available from Linvatec.
The anatomic consideration of graft harvest has been described in the literature by Warren and by Ferrai.(22,23) The strength after harvest of the tendons was reported by Lipscomb.(24) The harvest site morbidity is described by Yasuda.(25) The possible regeneration of the tendons was described by Cross (26) In a recent study by Shino (28) et al there was some weakness of knee flexion in the inner range of motion.
SKIN INCISION
An oblique 3 cm skin incision is made over the pes anserine.
This should start 1 cm medial to the tibial tubercle and head postero-medial. It should be 5 cm below the joint line. Plan to harvest the graft and drill the tibial tunnel through this incision. Incise the subcutaneous fat, and strip the pes with a sponge
EXPOSURE OF THE TENDON
Identify the superior border of the pes with your finger and incise the fascia. Continue the incision medially, in a hockey stick fashion, down the tibia, to remove the attachment site. A kocker is used to traction this flap. Look for the most inferior tendon, the semi-t, lift it up with the tip of the scissors and grasp it with a kocker.
The top of the pes is turned down to visualize the tendons.
TENDON RELEASE
Free the distal end of the tendon with the scissors. Make sure you get the full length distally. Grasp it with a kocher, and traction it firmly. Many of the bands can be released with the traction and by blunt finger dissection.
The main band that goes to the medial head of the gastrocnemius will have to be cut with the scissors.
Pull firmly on the tendon and cut away from the tendon ( to avoid cutting the tendon with the scissors). The tendon should not retract proximally if all the bands are cut. Make sure that there is no dimpling posteriorly on the gastroc, when the tendon is pulled.
If the bands to the gastroc are not cut, then the stripper may cut the tendon short when it is advanced. This is demonstrated in the photo above.
STRIPPING OF THE TENDON
The tendon stripper is pushed up the tendon using short jerky strokes.
The key is to keep tension on the distal end, to prevent the tendon from folding over, and being cut off short. There is often resistance at the muscle tendon junction and the stripper should be rotated to slip it up along the surface of the muscle. This gives extra length. The total length is usually 28-30 cm. Strip the gracilus tendon in a similar fashion.
Click here for the Video of the harvest of the hamstring tendons-dial up
Click here for the video using a high speed connection
PREPARATION OF THE GRAFT
PREPARATION OF THE 4 BUNDLE SEMI-T AND GRACILIS GRAFT
The graft is taken to the graft master on the back table. It is laid out, measured, and the muscle removed with the periosteal elevator.
The semi-t and gracilus grafts are looped over a # 5 Ticron suture.
Sutures of #2 Ticron ( Krakow technique ) are placed through the distal end of all the tendons. Make sure that each tendon has a suture in it. This allows you to tension each bundle of the composite graft.
The Endopearl
The appropriate sized endopearl is attached with 2 no 5 Ticrons to the proximal end of the tendon. The endopearl prevents the graft from slipping out from under the screw.
The tendon is marked at the point that the screw abuts against the endopearl. The tendon is pulled into the femoral tunnel up to this mark.
The proximal edges of the tendons are whip stitched together. This prevents the graft from wrapping up when the screw is introduced. The stitch is done over 3 cm, to mark the length of graft in the femoral tunnel. Mark 3 cm from the end with a blue skin marker pen.
The completed 4 bundle semi-T and gracilus composite graft. Note that the overall length is 9 -10 cm. A mark is made at 3 cm from the looped end, to determine the depth to pull the graft into the femoral tunnel. The leader sutures of # 2 Ticron may be used to tie over a button on the tibial surface, if necessary.
The graft is pre-tensioned by tying the sutures over the posts on the graft master. 15 # are applied for 10-15 minutes. I think that this allows the sutures to settle into the tendon. It obviously stretches out the tendon, before it is implanted. If you do not have a graft master, manual tensioning, to settle the sutures, is sufficient.
This 4 bundle graft will be 4 times the strength of a single strand of semi-t, as long as all bundles are tensioned. The graft is incorporated into the bone tunnel by tendon ingrowth, by Sharpey’s fibres. This will take about 10-12 weeks to heal. This graft will have at least 3 cm of graft in each tunnel. The depth of graft in the tunnel can be determined by the suture marks at each end.
Click here for streaming video of hamstring graft preparation
Graft Sizing
The size of the composite graft is measured to the nearest .5 cm, i.e. 7.5 mm and 8 mm are the commonest sizes.
The composite graft is sized to the nearest 0.5 centimeter.
Do not leave the graft soaking in saline. It may swell and make passing difficult. Simply wrap the graft in a damp surgical sponge.
Portals
The 3 portals are demonstrated above. The high anterolateral portal, the mid anteromedial portal, and the low anteromedial portal. The low anteromedial portal is essential for insertion of the femoral screw parallel to the femoral tunnel.
Tunnel PreparationThe tibial and femoral tunnels are prepared with the Linvatec Paramax system (Linvatec Corp Largo Fl). The low antero-medial portal is used to insert the tibial guide.
The 18 gauge needle is used to localize the position of the low antero-medial portal.
The knife is introduced along the same angle as the spinal needle. The blade should be up to avoid cutting the anterior horn of the lateral meniscus.
The exterior position of the Linvatec tibial guide is 5 cm distal to the joint line and 2 cm from the crest of the tibia. When placed at this site with the angle set at 55*, the length of the tibial tunnel will usually be 4 cm.
The Linvatec tibial guide is used to drill a k-wire 7 mm anterior to the PCL in the midline.
The K-wire is then over reamed with the appropriate sized drill bit. If the bone is osteopenic, it is recommended that the tunnel be drilled 2 sizes smaller, and then dilated to the correct size using the bone dilators.
Femoral Tunnel
With the knee flexed at 90*, the Bullseye femoral aiming guide is inserted through the tibial tunnel to drill the femoral tunnel.
The tunnels are drilled according to the graft measurement, i.e. 7, or 8 mm.
The Bullseye guide is inserted through the tibial tunnel. The knee must be flexed to 70-90*.
The arthroscopic view of the Bullseye guide hooked over the back of the over the top position. The guide should aim towards the 1 o’clock position. The K-wire is passed through the femur and retrieved from the anterolateral thigh.
The graft passing wire retrieved from the anterolateral thigh.
The Bullseye guide is used to place a k-wire 7 mm anterior to the over the top position on the femur. The C-reamer is then used to make a footprint on the femur by push pull drilling. When it has been determined that the footprint is in the correct position, then the femoral tunnel is drilled to a depth of 35 mm.
Click here for a streaming video of tunnel creation
Graft Passage
The 2.4 mm graft passing wire is used to pull the # 5 Ticron sutures and graft into the femoral tunnel. The graft is pulled into the femoral tunnel to the 3 cm mark on the proximal end of the graft.
The 4 bundle graft has been pulled 30 mm into the femoral tunnel. The tunnel has been notched at the 1 o’clock position to accept the BioScrew.
Graft Fixation
The femoral tunnel is notched, and the guide wire for the BioScrew is passed into the notch. The appropriate sized screw (same size screw as tunnel size) is inserted along the guide wire. The screw guide wire is passed into the notched edge of the femoral tunnel.
The diagrammatic view of the BioScrew insertion into the femoral tunnel.
Click here for a streaming video of hamstring graft passage and screw fixation
Tibial Tunnel Fixation
The tibial BioScrew is inserted into the tibial tunnel with the knee flexed at 30*, and maintaining tension on the distal leader sutures. The screw should be inserted flush with the cortex, but not beyond. The screw size is one size larger than the tunnel.
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The newest version of the tibial BioScrew, ExtraLoc, flares up one size at the distal end to provide improved cortical purchase. The four bundles of the hamstring graft are separated and the screw placed up the middle of the bundle as seen in the photo above. The screw is also beveled at the distal end to sit flush at the cortex. We are currently conducted a clinical trial comparing this to the previous type of screw fixation, and to the Intrafix device. In the video below the 4 bundles of the hamstring graft are separated and tensioned.
Click here for a streaming video of the ExtraLoc screw insertion.
Graft tensioning
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There is very little known about the amount of tension to apply to the graft before the tibial fixation. Previous studies have indicated that approximately 15 pounds of tension should be applied to the graft as the screw is inserted. We are currently comparing methods of tension of the graft. The Mitek tensioner is shown above.
Confirm the stability after the reconstruction by measuring the a-p displacement with the KT-S at the end of the operative procedure.
Important points:
When there is any doubt about the tibial tunnel fixation, tie the leader sutures from the distal end over a button or screw post.
The tibial end is the worrisome site to obtain adequate fixation. Chose to use a larger screw.
Dr. David Caborn from the Kentucky Sports Medicine Clinic did pull out strength studies on cadavers. He confirmed that the 7 mm BioScrew in a 8 mm tunnel had adequate pull out strength. ( Average 340 N )
Andreas Weiler has also confirmed the pullout strength of the BioScrew. However, the tibial tunnel is the problematic fixation. Always augment the tibial side if the purchase of the tibial screw is inadequate.
References
Different HamstringTendon Graft
Fixation Techniques under Incremental Cyclic Loading Conditions: AANA Spring Meeting
Orlando 1998