Risk Factors

The need for ACL revision surgery can be because a patient suffers an ACL graft tear similar to the original injury at some time after returning to sports or work activities. A patient usually knows that the ACL graft has torn because the injury feels the same as what he/she experienced previously. However, when instability is observed upon evaluation early during recovery or the patient experiences a giving-way episode with even minor activities, this would indicate that the ACL graft failed to incorporate, either due to technical error or biological conditions.

Among the primary risk factors for ACL graft injury are young age and involvement in competitive sports. Several studies have shown ACL graft tear rates to be higher in younger patients. Shelbourne et al. found the ACL graft tear rate within 5 years after primary ACL reconstruction in 1415 patients was 8.7% for patients less than 18 years old, compared with 2.6% for patients 18–25 years old and 1.1% for patients greater than 25 years old. Andernord et al. studied the Swedish National Knee Ligament Register of almost 17,000 patients between 2005 and 2013 and found the risk factors for subsequent revision surgery to be the sport of soccer and adolescent age, with these two predictors having almost 3 times higher risk than other patients. Two- to 6-year follow-up from the Multicenter Orthopaedics Outcomes Network group found the rate of revision surgery was 7.7% of 980 patients, and younger age and the use of allografts were risk factors for revision ACL surgery. In a study of 402 competitive basketball or soccer athletes under age 17 at the time of ACL reconstruction, the rate of ACL graft injury was 15.7% for soccer and 8.3% for basketball.

Another risk factor for ACL graft tear is the use of allografts. Several studies have shown much higher graft tear/failure rates with allografts than with either hamstring or patellar tendon autografts. Engelman et al. found a 29% ACL revision rate using allografts, compared with 11% for autografts for young adolescents. Pallis et al. studied 120 cadets at a military academy and found the ACL revision rate to be 44% with using allografts, compared with 11% for patellar tendon autograft and 13% for hamstring autografts.

Some studies have shown higher rates of ACL revision after primary ACL surgery with the use of hamstring autografts compared with patellar tendon autografts. In a study of the Kaiser Permanente ACLR Registry for 2005–2012, the 5 year survival rate of 17,436 surgeries was 95%, and the factors associated with the risk of revision were the use of allografts, the use of hamstring autografts, male sex, younger age, lower body mass index, and Caucasian race. Similarly, a study of 12,643 patients in the Norwegian Cruciate Ligament Registry between 2004 and 2012 found the rate of revision ACL surgery was twice as high with hamstring autografts than with patellar tendon autografts.

Technical Errors

Surgical technique error is another cause of ACL graft failure. Placing the graft too far anterior may cause the graft to stretch when full flexion is obtained. However, placing the graft too far posteriorly may cause increased tension on the graft with extension. Anterior tunnel placement on the tibia can cause impingement of the graft in the intercondylar notch and decreased extension ( Fig. 89.1 ). Arthroscopic ACL reconstruction, in which the transtibial technique is used for drilling the femoral tunnel, can often result in vertical orientation of the graft ( Fig. 89.2 ). It is difficult to place the ACL graft in the correct location without knowing normal knee anatomy. The intercondylar notch in normal knees contains the ACL and posterior cruciate ligament, with little space existing between the ligaments. A properly placed graft should fit in the intercondylar notch with the knee in full hyperextension, without impingement in the notch ( Fig. 89.3 ).

Lateral radiographic view of the knee showing anterior placement of the tibial tunnel.

Lateral radiographic view of the knee in full extension showing anterior graft placement with vertical alignment.

Arthroscopic view of the knee at 2 years after primary anterior cruciate ligament reconstruction with (A) the knee in about 20 degrees of flexion and (B) the knee in full extension that shows the graft fits into the intercondylar notch without impingement.

Graft Choice

Graft choices for revision ACL reconstruction are the same as what is available for primary ACL reconstruction. According to a panel of 35 orthopaedic surgeons from around the world, the most common graft source used for revision ACL surgery is allograft tissue (33%), followed by either patellar tendon autograft (29%) or hamstring autograft (28%). The Multicenter ACL Revision Study found that allografts were used for revision ACL surgery 54% of the time, compared with only 27% for primary ACL reconstruction. My preference of graft choice is the patellar tendon autograft for both primary and revision ACL surgery. Given that allografts have a higher failure rate with both primary and revision surgery, I believe the best and most reliable graft source should be used with revision surgery, to be able to give the patient the best possible chance for achieving good stability and overall good outcome. A patellar tendon autograft from the contralateral knee is my first choice, but in cases where the patient has undergone ACL reconstruction with patellar tendon autografts on both knees, a reharvested patellar tendon can be successfully used. My rationale for choosing patellar tendon autograft, especially from the contralateral normal knee, is explained further in Chapter 15 of this book.

Preoperative Planning

Preoperative assessment of knee stability, range of motion (ROM), and leg strength are needed to determine the need for preoperative rehabilitation. Physical examination includes the Lachman and pivot shift test to evaluate stability of the involved knee and should be compared with the opposite normal knee. If there is no endpoint upon Lachman examination, the ACL graft either tore or failed. KT-2000 arthrometer testing can be used to objectively evaluate stability, as a difference of greater than 5 mm on the manual maximum test signifies gross laxity.

Any deficit in knee ROM should be corrected before surgery, as any loss of normal knee ROM has been found to be a major determinant for a good outcome after surgery. Obtaining full ROM before surgery will make it easier to obtain full ROM after surgery. Quadriceps muscle strength should be evaluated with isokinetic testing to determine if the patient has gross strength loss that might affect recovery. The advantage of using the contralateral patellar tendon graft is that the graft is being harvested usually from the stronger leg. Leg strength will be more symmetrical after harvesting the graft, which will allow the patient to use both legs equally during rehabilitation and recovery. Patients should have full knee ROM, no effusion, good leg strength, and have a full understanding of the rehabilitation process before undergoing revision ACL surgery.

Bilateral posteroanterior, lateral, and Merchant view radiographs should be obtained preoperatively. A full knee extension lateral view is helpful for evaluating tibial tunnel alignment, which should show that the tunnel is parallel and posterior to Blumensaat line. Radiographs will show the location of existing hardware, and plans can be made for removal, if needed.

If a reharvested PTG is used, a Merchant view radiograph and magnetic resonance imaging (MRI) are obtained to confirm that the patella and patellar tendon are of good quality. During primary ACL reconstruction with a patellar tendon graft, bone grafting of the patellar and tibial bone harvest sites using the bone reamings from drilling the tunnels is advantageous for healing, in case future revision ACL surgery is needed. Also, closure of the patellar tendon defect allows for full regeneration of the harvest site.

Advantages of Open Procedure

Although doing surgery arthroscopically assisted has become popular, for the knee it is less important. With a medial arthrotomy, no muscle is being cut. There is no doubt that arthroscopy has made management of meniscus injuries easier and better; however, I do not believe there is any clear advantage for using arthroscopy for ligament reconstruction. Correct placement of the ACL graft is much easier seen through a medial arthrotomy with correct exposure. Visualization of the tibial and femoral attachment sites are seen better with exposure of the entire intercondylar notch and tibial plateau of the knee than through arthroscopy. It is much like trying to place a nose on a face; standing back and having total perspective of the area is easier than trying to accomplish the task a centimeter away.

For revision surgery, having a good overall perspective is even more important because the previous surgery has changed the normal anatomy. Hardware removal from the femur is more difficult arthroscopically as well. After failure from primary surgery, revision surgery needs to place the new tunnels in the correct position, which is not difficult with an open view of the notch.

Tunnel Placement Around Hardware

Placing correct tunnels for revision ACL surgery can be difficult if previous hardware is in place. Removal of hardware on the femur is more difficult than on the tibia, especially if metal screws were used for the primary surgery. Given that most hardware on the tibia is usually at the level of the tibial cortex, hardware can be easily found and removed. If the metal screws have been placed and recessed under the cortex in the tibia and are buried in the correct location for the tibial tunnel, old hardware can be removed when drilling the new tunnels.

A hardware located femur can be more of a problem because it is usually placed at the entrance to the tunnel. Many times the previous tunnel is so far off that the correct tunnel can be placed while ignoring the previous tunnel and hardware. If the previous hardware is metal and is easy to remove, I prefer to go ahead and remove it.

If the previous femoral tunnel is in a good position and a metal screw has been used, the open procedure allows for easy removal, except when the screw is recessed in the femoral tunnel. Since the screw was usually placed from the inside, we need to find the head of the screw to remove it if it is in the place of our new femoral tunnel. After removal of the screw, the open technique allows for placing the new femoral tunnel in the correct position. The new “bioabsorbable” screws are supposed to disappear; however, we have found some that have not. We usually are able to ream a new tunnel over and past the bioabsorbable screw if it is in our way.

Tunnel Placement Around Existing Tunnels (Bone Loss)

Bone tunnel expansion is a known problem that can happen with ACL surgery. In addition, previous primary surgery where double-bundle tunnels were drilled can be a challenge. If you use screw fixation, tunnel enlargement or bone loss can further complicate revision surgery. With the open ACL technique I use, whereby the bone plug in the tibia is placed at the level of the joint line and using button fixation on both the femoral and tibial side, tunnel enlargement present at the time of revision surgery is seldom a concern. The bone plug in the tibial tunnel fits tightly in the tunnel when two sides of the graft have bony contact, and the bone plug heals quickly and well after surgery, even if there is bone loss anterior to the bone plug. On the femoral side, we just need to place the entrance of the tunnel correctly, as the long end of the graft is taken up in the femoral tunnel and the bone plug will be 10–20 mm proximal to the entrance of the femoral tunnel. The patellar tendon autografts are much longer than the native ACL, and the femoral tunnel can be drilled to accommodate the length of the graft accordingly.

Button Fixation—Advantages

I have been using button fixation for all ACL reconstruction surgery since 1982 (over 6000 ACL surgeries). Button fixation is easy and simple, but many believe that button fixation is not strong enough. Even with using an “accelerated rehabilitation” protocol, during which patients achieve full ROM quickly after surgery and progress through a functional rehabilitation program as they are able, the use of button fixation has not caused graft failures. Most surgeons feel more comfortable with screw fixation in order to allow full ROM and quick return to activities. There is no doubt that interference screw fixation is the strongest, but is it really needed? The problem with choosing fixation is that we need to use something strong enough to allow full ROM and activities, but not too strong that it makes the ligament too tight so as to constrain the knee. If the graft is placed in the right spot, press-fit bone-to-bone healing can occur without any fixation.

Reharvest of the Patellar Tendon Autograft

Reharvest of the patellar tendon for use in revision ACL surgery can be performed successfully, and the graft has been shown to undergo ligamentization and be viable after surgery. Colosimo et al. reported on 13 patients with a mean follow-up of 39 months after reharvested central third patellar tendon autograft. They found that 11 patients had good or excellent results and two patients had fair results. The mean KT-1000 side-to-side difference was 1.9 mm for the group, and only one patient reported any patellofemoral problems.

O’Shea and Shelbourne reported 2-years objective follow-up of eight patients after reharvested patellar tendon autograft. They used MRI before surgery to determine the width of the tendon and the quality of the tissue. The graft was harvested to include 7–8 mm of regenerated tissue and 2–3 mm of previously untouched tissue, either medial or lateral to the original harvest. The mean manual maximum KT-1000 arthrometer difference between knees was 1.6 mm and mean quadriceps strength compared with the opposite knee after surgery was 103%.

Reharvest of the patellar tendon graft is best done when the primary surgery includes a repair of the patellar tendon defect and when bone grafting is done on the tibia and patella. These extra steps at the time of the primary ACL surgery take little time and allow the option for revision surgery in the future, if needed.

Advantages of Open Procedure

Although doing surgery arthroscopically assisted has become popular, for the knee it is less important. With a medial arthrotomy, no muscle is being cut. There is no doubt that arthroscopy has made management of meniscus injuries easier and better; however, I do not believe there is any clear advantage for using arthroscopy for ligament reconstruction. Correct placement of the ACL graft is much easier seen through a medial arthrotomy with correct exposure. Visualization of the tibial and femoral attachment sites are seen better with exposure of the entire intercondylar notch and tibial plateau of the knee than through arthroscopy. It is much like trying to place a nose on a face; standing back and having total perspective of the area is easier than trying to accomplish the task a centimeter away.

For revision surgery, having a good overall perspective is even more important because the previous surgery has changed the normal anatomy. Hardware removal from the femur is more difficult arthroscopically as well. After failure from primary surgery, revision surgery needs to place the new tunnels in the correct position, which is not difficult with an open view of the notch.

Tunnel Placement Around Hardware

Placing correct tunnels for revision ACL surgery can be difficult if previous hardware is in place. Removal of hardware on the femur is more difficult than on the tibia, especially if metal screws were used for the primary surgery. Given that most hardware on the tibia is usually at the level of the tibial cortex, hardware can be easily found and removed. If the metal screws have been placed and recessed under the cortex in the tibia and are buried in the correct location for the tibial tunnel, old hardware can be removed when drilling the new tunnels.

A hardware located femur can be more of a problem because it is usually placed at the entrance to the tunnel. Many times the previous tunnel is so far off that the correct tunnel can be placed while ignoring the previous tunnel and hardware. If the previous hardware is metal and is easy to remove, I prefer to go ahead and remove it.

If the previous femoral tunnel is in a good position and a metal screw has been used, the open procedure allows for easy removal, except when the screw is recessed in the femoral tunnel. Since the screw was usually placed from the inside, we need to find the head of the screw to remove it if it is in the place of our new femoral tunnel. After removal of the screw, the open technique allows for placing the new femoral tunnel in the correct position. The new “bioabsorbable” screws are supposed to disappear; however, we have found some that have not. We usually are able to ream a new tunnel over and past the bioabsorbable screw if it is in our way.

Tunnel Placement Around Existing Tunnels (Bone Loss)

Bone tunnel expansion is a known problem that can happen with ACL surgery. In addition, previous primary surgery where double-bundle tunnels were drilled can be a challenge. If you use screw fixation, tunnel enlargement or bone loss can further complicate revision surgery. With the open ACL technique I use, whereby the bone plug in the tibia is placed at the level of the joint line and using button fixation on both the femoral and tibial side, tunnel enlargement present at the time of revision surgery is seldom a concern. The bone plug in the tibial tunnel fits tightly in the tunnel when two sides of the graft have bony contact, and the bone plug heals quickly and well after surgery, even if there is bone loss anterior to the bone plug. On the femoral side, we just need to place the entrance of the tunnel correctly, as the long end of the graft is taken up in the femoral tunnel and the bone plug will be 10–20 mm proximal to the entrance of the femoral tunnel. The patellar tendon autografts are much longer than the native ACL, and the femoral tunnel can be drilled to accommodate the length of the graft accordingly.

Button Fixation—Advantages

I have been using button fixation for all ACL reconstruction surgery since 1982 (over 6000 ACL surgeries). Button fixation is easy and simple, but many believe that button fixation is not strong enough. Even with using an “accelerated rehabilitation” protocol, during which patients achieve full ROM quickly after surgery and progress through a functional rehabilitation program as they are able, the use of button fixation has not caused graft failures. Most surgeons feel more comfortable with screw fixation in order to allow full ROM and quick return to activities. There is no doubt that interference screw fixation is the strongest, but is it really needed? The problem with choosing fixation is that we need to use something strong enough to allow full ROM and activities, but not too strong that it makes the ligament too tight so as to constrain the knee. If the graft is placed in the right spot, press-fit bone-to-bone healing can occur without any fixation.

Reharvest of the Patellar Tendon Autograft

Reharvest of the patellar tendon for use in revision ACL surgery can be performed successfully, and the graft has been shown to undergo ligamentization and be viable after surgery. Colosimo et al. reported on 13 patients with a mean follow-up of 39 months after reharvested central third patellar tendon autograft. They found that 11 patients had good or excellent results and two patients had fair results. The mean KT-1000 side-to-side difference was 1.9 mm for the group, and only one patient reported any patellofemoral problems.

O’Shea and Shelbourne reported 2-years objective follow-up of eight patients after reharvested patellar tendon autograft. They used MRI before surgery to determine the width of the tendon and the quality of the tissue. The graft was harvested to include 7–8 mm of regenerated tissue and 2–3 mm of previously untouched tissue, either medial or lateral to the original harvest. The mean manual maximum KT-1000 arthrometer difference between knees was 1.6 mm and mean quadriceps strength compared with the opposite knee after surgery was 103%.

Reharvest of the patellar tendon graft is best done when the primary surgery includes a repair of the patellar tendon defect and when bone grafting is done on the tibia and patella. These extra steps at the time of the primary ACL surgery take little time and allow the option for revision surgery in the future, if needed.