ACL Graft Choices

There are many methods for reconstructing a torn anterior cruciate ligament (ACL Graft Options). I will describe the most common method in detail – some have referred to it in the past as "the Gold Standard". In this technique, a segment of patellar tendon with attached bone blocks at each end is placed in the same position as the original anterior cruciate ligament, and fastened securely in place with two "interference fit" screws. This strong and stable construct allows early, safe, secure motion of the knee, and allows the rehabilitation process to proceed rapidly without fear of damaging the graft or impairing the healing process, culminating in a stable, fully-healed knee at approximately 6 months after surgery. Conceptually, ACL reconstruction using hamstring tendons or other graft tissues is a similar technique other than the graft procurement and sometimes fixation methods.

Overview and setting – outpatient vs. inpatient

Traditionally ACL reconstruction has been considered a "major" orthopedic procedure, but in recent years, the distinction between major and minor has changed. Bill Walton, the famous UCLA basketball player, used to joke that any surgical procedure was "major" if it was done on you. "Minor" procedures, he said, were done on someone else.

Typically, an ACL reconstruction takes 2 to 2½ hours, and involves a series of intricate and technical steps, most of which are done inside the joint using an arthroscope and small specialized instruments. Because so much of the procedure can now be done arthroscopically, without big incisions and excessive trauma to the tissues, it is really well-suited to be an outpatient procedure. Therefore, the vast majority of ACL reconstructions in the US are done either as inpatients with 1-2 nights in the hospital, or as outpatients. Since the major issues to deal with during the first 24-48 hours after surgery are patient comfort, not the risk of any serious side effects or complications, as long as pain can be controlled well, and as long as the patient can rest in a comfortable and convenient environment at home or in a motel, there is no real need for overnight hospitalization.

Overview of anesthesia and pain management

Without a doubt, controlling post-operative pain is every patient's initial primary concern. There has been much research and many new developments in the field of pain management over the last 5-10 years, particularly within the specialty of anesthesia, where pain management now has developed into a legitimate sub-specialty. We are fortunate in Portland to have some outstanding anesthesiologists who have been specially trained in these new methods, and who have helped develop some pain management protocols especially designed for patients undergoing ACL reconstruction. We have evaluated and refined these protocols as part of an ongoing study of outpatient post-operative pain management at the Orthopedic Surgery Center, and the results have been presented and published nationally. For those interested in reading these scientific articles in their entirety, see the original research articles on outpatient pain management as well as our pain and nausea protocols at the Orthopedic Surgery Center.

Overall, the strategy for optimally controlling pain calls for adhering to many small details. First is a thorough pre-operative briefing so patients understand exactly what is going to happen to them, and what they are supposed to do, including exactly what medications to use, in what doses and combinations, and when. There are 3 key medications which we use in combination, each operating by a different mechanism, so the effects are complimentary and synergistic. The baseline analgesics (pain relievers) are Tylenol and an anti-inflammatory medication (e.g. ibuprofen, Toradol, or Celebrex) – taken in appropriate doses (600 mg for the Motrin and 1000mg for the Tylenol) every 6 hours. Patients are told to take these drugs at the regular 6-hour intervals for the first 5-7 days, even if the pain is mild. We believe the combination of these 2 drugs, as long as they are taken consistently, will take care of 60-80% of most patient's pain after ACL reconstruction. The third drug, oxycodone, is a synthetic narcotic, which has a powerful pain relieving effect, but because it is a narcotic – and this is true of all narcotics from morphine to codeine – it also has a common side effect of nausea. Therefore, we recommend using the oxycodone (which requires a prescription) at doses of 5 to 10 mg as often as every 2 hours AS NEEDED. If patients don't think they need this extra boost of pain medication, we tell them to either not take it, or take only one 5mg tablet, or take it less frequently. Ultimately the patient determines the dose, and most patients really appreciate this kind of individualized control. The only rigid requirements are that they keep it under 10 mg every 2 hours.

Our experience has been that the combination of these three drugs is extremely effective, and 96% of our patients have rated their pain control as either "good" or "excellent".

The anesthesia that we recommend is "general anesthesia" (i.e. asleep), although on rare occasions and under special circumstances it can be done under spinal anesthesia. With general anesthesia, a quick acting agent, Propofol, is given by IV in the OR, which almost immediately puts the patient to sleep. Immediately after going to sleep, appropriate anesthetic gasses are introduced, either by a mask or an endotracheal tube, or similar device, and these gasses keep the patient safely asleep throughout the procedure. The beauty of using anesthetic gasses is that the anesthesiologist can maintain minute by minute control of the depth of anesthesia simply by controlling the percentage of the gasses, and emerging from anesthesia at the end of the procedure can be managed easily, effectively, and safely.

With the newer agents used in anesthesia, and by carefully controlling the type and dose of all the agents used, the anesthesiologist can now either eliminate altogether or control quickly the nausea and vomiting which used to so frequently be associated with general anesthesia. These problems are still not completely eliminated, but they can be well-controlled and are much rarer now. To further reduce the risk of postoperative nausea, we start patients on a low dose of amitriptyline (Elavil) 25 mg. the night before surgery for a total of three nights.

Arthroscopy

As mentioned earlier, ACL reconstruction is now essentially an arthroscopic procedure from start to finish, but the exception to this is obtaining the graft tissue itself. In the case of the "bone-patellar tendon-bone autograft", this requires a 3-5 inch vertical incision in the front of the knee. Other than this skin incision and the incisions in the deeper tissues required to harvest the graft, all the rest of the surgery is done arthroscopically.

Before actually doing the reconstruction, the arthroscope is used to carefully survey the whole joint, looking at and evaluating each key structure. During this portion of the procedure, any additional damage to any of the other knee structures can be identified, and where appropriate, corrected surgically. For example, a torn meniscus cartilage, which occurs 65% of the time in association with an anterior cruciate ligament tear, can be easily identified and resected (menisectomy), or in certain instances, repaired. Some joint surface injuries or roughened areas of the joint can be smoothed with a special "shaver", and loose bodies or fragments of bone or other tissue can be easily removed, although this is fairly rare in these circumstances.

Harvesting the Patellar Tendon Graft

Through the anterior incision, the patellar tendon is exposed just beneath the skin.

A central strip, usually measuring 10mm in width, is outlined and removed, along with an attached segment of bone from the patella above and the tibia below. These bone blocks are carefully cut with a small oscillating saw and shaped to be either 9 or 10 mm in diameter and 20-25mm long. Because of their size, the patella above and the tibia below remain virtually unaffected by the removal of this amount of bone, and over time, these areas either partially of fully fill in with new bone, and the original strength of the patella and tibia are quickly restored by the body as well.

The remaining portions of the patellar tendon on either side of the graft are re-approximated (sutured) after its removal so that a single 10-30 mm strip of patellar tendon remains in place to continue the normal function of that tissue.

Once it is harvested in this manner, the graft is carefully shaped and prepared for "transplantation" into the appropriate location within the joint. Part of the preparation is the placement of 4 sutures, 2 in each bone block, which will be used to later pass the graft into its proper position and hold it while it is being fixed in place.

Preparing the graft sites

Meanwhile, within the joint, the old torn or scarred ACL tissue is trimmed out of the way with a special shaver device. This device which we call a "shaver" is essentially a steel tube revolving inside another steel tube with a window with sharp edges cut in the end of both tubes. Suction is applied through the center of the inner tube, and the combination of the suction gently pulling any loose tissue into the windows, and the revolving inner tube effectively cuts this tissue off with each revolution.

Once the old ACL tissue is removed (resected, or debrided are the medical terms), the surgeon prepares the lateral wall of the intercondylar notch by carefully burring away 1-2mm of bone to create a slightly more spacious area for the new graft. Also, this wall preparation makes it much easier to locate the proper place for the graft to be attached into the femur, which is critical. One of the major advancements in recent years in the ACL reconstruction technique is the perfection of techniques and instruments to reliably locate and place the graft literally within a millimeter of where it should go. Graft position, it turns out is extremely critical. A graft placed more than 1-2mm from the correct location will be subjected to much higher forces and may eventually break.

Once the lateral inside wall of the notch has been prepared and all the old ACL tissue has been removed, everything is ready for making the critical 9 or 10mm drill holes – the first up unto the joint through the tibia below, and the second up into the femur.

To make the tibial hole (9mm if the graft and bone block size is 9mm and 10mm if they are 10mm - but almost always the size is 10mm, unless the patient is very small), a special drill guide is used to place a 2.7mm guide pin first. This pin goes in the exact center of where the eventual bone block will go and because of its size, it can be placed and replaced until the position is perfect. Once it is properly in place, an appropriate sized larger drill (again either 10mm or 9mm) with a hole in the center to fit over the guide pin is used to overdrill the final hole, exactly the right size for the graft bone block and in exactly the right position.

Once that hole is drilled and its edges smoothed, another guide device is used to place another guide pin up into the femur, and after that to overdrill it with a 9mm or 10mm drill, exactly like in the tibia. To do this properly, the knee must be flexed to 90 degrees, and the exact point must be chosen on the lateral wall of the notch so that the eventual larger hole will come right next to the back edge of the femur – but not break through it. We want the graft to lie as far back in the femur (and the notch) as we can without breaking out the back. Unlike the hole in the tibia which is a "through and through" hole, the femur hole is blind ended, usually about 30mm deep to allow a little flexibility in putting the 20mm graft bone block either a little further up into the femur or not depending on the overall graft length. Also, unlike the tibia, the guide pin in the femur is purposely long enough to drill not only up into the femur but out through the skin on the outside (lateral side) of the thigh. This long 2.7mm pin will also serve as the method of pulling the graft up into the knee and into its proper place in the femur, later on.

Placing and then attaching the graft

Once the 2 holes have been properly done and all the rough edges have been smoothed, the already-prepared graft, with its sutures in each end, is passed carefully up into the joint. This is done by threading the sutures in the top end of the graft into a small "eye" in the lower end of the pin which was previously used as the guide pin for drilling into the femur. Remember that the top end of this long pin was purposely drilled out through the thigh muscle and skin.

Therefore, by grasping the top end of this pin and by pulling it upward, the graft, guided by the sutures in its top end, can be pulled up through the tibial hole, through the central part of the joint and into the hole in the femur. Simultaneously, because generally the length of the tendon portion of the graft is appropriate, as the top end of the graft (the bone block) comes to rest up in the femur drill hole, the lower end of the graft (the other bone block) will come to rest in the hole in the tibia. In between, exactly where you want it to be, the central tendon portion of the graft will come to lie exactly where the ACL used to be. It now becomes simply a matter of fixing the 2 bone blocks rigidly in place within the holes that were prepared for them, and with the appropriate tension applied to the graft itself.

Fixing the graft in place first requires placing a suitable sized screw, either made of metal, or more recently of "bioabsorbable" material. These new bioabsorbable screws are constructed in exactly the same shape as the previously more commonly used metal screws. They are called "interference fit" because they literally wedge themselves between the bone block and the wall of the hole into which the bone block fits. Because the holes were drilled to be the same size as the bone block, there is very little space between the bone block and the wall anyway. The interference fit screws are designed with no heads to protrude and very large threads which will force their way into the surrounding bone and literally wedge the bone block firmly in place. The pull out strength has been carefully tested for these interference fit screws, and if the proper size is selected (usually a 7 or 8 mm screw with a 10mm bone block) the fixation is very secure – actually stronger than the breaking strength of the graft tissue itself.

First the femoral bone block is fixed with an interference fit screw. Then, with the knee almost straight, and with firm tension applied to the lower half of the graft using the sutures that were previously placed through drill holes in the lower (tibial) bone block, a second interference fit screw is placed up into the tibial drill hole from below. If the scope is kept focused on the graft inside the knee during this process you can easily see when the graft is appropriately tightened. You can also check it with a small instrument and watch the graft function throughout a full range of motion of the knee. Sometimes, if the length of the graft needs to be adjusted a little, this can be done by twisting the graft (which effectively shortens it while maintaining or possibly even increasing its strength slightly. Incidentally, a 10mm graft has been shown to be 175% as strong as a normal ACL. In other words, it's almost twice as strong, which accounts in part for why these knees can be safely moved and walked on during the very early phases of the recovery. The strength of the interference fit screws locking the bone blocks in place obviously are equally important.

Finishing up – closure

Once the graft is in place and the screws holding the bone blocks at each end are also seated, there is nothing left to do except thoroughly irrigate out the joint to be sure that all the tiny pieces of tissue which might have escaped into the joint during all the tissue shaving, trimming, and drilling are flushed out. The sutures used to pull the graft and tension it are simply cut off and pulled out. Then the small holes into the joint where the arthroscope and instruments (usually there are 2) are sutured beneath the skin, and the bone "shavings" collected during the large hole drilling process are carefully packed into the defects in the patella where the original graft was harvested (this helps stimulate new bone formation during healing). Then the skin incision is carefully re-approximated with sutures buried under the skin surface to minimize scarring. Usually 1 or 2 small drains are placed, one in the joint itself, and another just beneath the skin to help collect any excessive bleeding over the first 24 hours. These drains are removed in the office. Finally, before waking the patient up to go to the Recovery Room, a measured dose of long acting local anesthetic (Marcaine) which should last about 6-8 hours is injected into the joint and around all of the tissue that was previously cut, manipulated, or sutured. This is also part of the Pain Management Protocol and makes a huge difference in pain on awakening in the Recovery Room. It's another small detail that makes a big difference.

The knee is wrapped with sterile dressings, the drains are connected to a spring activated suction collection container (that can be emptied by the patient if necessary during the time the drains are in place), and a unique cold and compression Cryo/Cuff® is placed around the knee to help reduce bleeding and swelling. A removable knee immobilizer goes over that to help stabilize the knee and leg, making walking and moving about out of bed easier.

Recovery Room

Usually, it takes about 90-120 minutes in the Recovery Room for an average patient to recover enough to be able to sit up, eat some light food, use the bathroom (with crutches), and feel ready to go home. The basic pain protocol medications mentioned in the beginning are started, and can be supplemented with some IV narcotic analgesic if it is necessary. Also, IV medications to combat nausea and vomiting can be added as necessary. Usually, after approximately 4 – 5 hours of total time in the Outpatient Surgery Center the patient is able to go home.

The first night

Using the 3 oral pain medications – Tylenol, an anti-inflammatory, and oxycodone – most patients are quite comfortable and sleeping through the night is the rule, not the exception. The Pain Management Protocol also calls for taking a low dose of amitriptyline (Elavil) 25 mg. for the first 2 nights after surgery (and the night before surgery as well). This helps decrease any tendency towards nausea, and in our studies reduced nausea by as much as 30-50%.

The next day and beyond

Typically the day after surgery is statistically a little more uncomfortable than the day of surgery according to our studies in more than 300 patients. Still the 3 analgesic medications are very effective when used in combination. During the first follow-up visit which occurs on the first day post-op, the dressing is changed and the drains are removed. The rehab program officially begins immediately after surgery with patients walking with crutches and contracting the thigh muscles and attempting to lift the leg independently.

By one week post op, most patients are able to walk quite easily with crutches, can lift their leg without assistance from a position lying on their back, and by the end of the second week post-op can walk without crutches and without any need for the leg immobilizer.