Anterior Cruciate Ligament Tears- ACL Reconstruction

 

ACL Tear (Image courtesy of orthoinfo.aaos.org)

Anterior cruciate ligament (ACL) ruptures or tears are a common injury among athletes. The ACL is an important ligament inside the knee that provides stability during certain motions. Many folks initially have significant pain and swelling after an ACL injury. The ACL does not have nerves that provide pain sensation. Most of the knee pain from an ACL injury occurs after the ACL ruptures and the bones bump or kiss one another as the knee shifts unrestrained. This generates a painful “bone bruise” that eventually resolves with time as swelling decreases. Often patients come to see me 2-3 weeks after the ACL injury questioning the role of surgery when their pain has all but resolved. While the ACL is not essential for walking in a straight line, the ACL is essential for any activity involving running, cutting, jumping, or twisting. A small proportion of patients may tolerate non-operative treatment for their ACL rupture, however, this treatment is generally reserved for less active individuals or ones that have no signs of instability with cutting, pivoting, or turning. The ACL stabilizes the knee and prevents repetitive shifting from instability of the knee that can cause further internal knee damage. Most active individuals are good candidates for ACL reconstruction.

Knee Stability and Anatomy

Every joint in the body has three core stabilizing components-

  • bony anatomy of the joint itself
  • peri-articular muscles
  • ligaments that restrain excessive joint movement

A well functioning healthy joint relies on all 3 to maintain stability. An ACL injury not only involves the ligamentous structure of the knee, but also impacts the muscle mass and coordination around the knee. Recovery and rehabilitation from ACL treatment must address muscle mass and coordination deficits.

Although isolated ACL injuries are the focus here, many times damage to other structures occur as well. In addition to the ACL, there are many other ligaments that help stabilize the knee. About half of ACL injuries have damage to other knee structures. Depending on what other structures are involved in the injury your proposed treatment may vary.

Collateral Ligaments

The collateral ligaments are found on the sides of the knee. The medial collateral ligament (MCL) is on the inside of the leg, and the lateral collateral ligament (LCL) is on the outside of the leg. The collateral ligaments help restrain side to side motion of the knee joint. If injured with the ACL they must be addressed otherwise the ACL treatment will fail.

Cruciate Ligaments

The cruciate ligaments are within the central part of the knee joint itself. The two cruciate ligaments cross each other to form an “X” with the anterior cruciate ligament in front and the posterior cruciate ligament in back. The cruciate ligaments restrain anterior, posterior, and rotational motion of the knee. In only the most severe ACL injuries are the anterior AND posterior cruciate ligaments affected.

Timing of Anterior Cruciate Ligament Reconstruction

Immediately after an ACL tear the instinct is to avoid weight bearing and motion of the injured knee. Knee swelling and spasm of muscles around the knee make it difficult to straighten and weight bear on the knee. Assuming there is no other injury in the knee contributing to the swelling or lack of knee motion, delaying any surgical intervention until after acute swelling has decreased and knee motion is restored is essential for a successful outcome from surgery. I tell my patients-

“Going into surgery with a stiff knee will only lead to a stiffer knee after surgery.”

ACL Tear (Image courtesy of orthoinfo.aaos.org)

Anterior cruciate ligament (ACL) ruptures or tears are a common injury among athletes. The ACL is an important ligament inside the knee that provides stability during certain motions. Many folks initially have significant pain and swelling after an ACL injury. The ACL does not have nerves that provide pain sensation. Most of the knee pain from an ACL injury occurs after the ACL ruptures and the bones bump or kiss one another as the knee shifts unrestrained. This generates a painful “bone bruise” that eventually resolves with time as swelling decreases. Often patients come to see me 2-3 weeks after the ACL injury questioning the role of surgery when their pain has all but resolved. While the ACL is not essential for walking in a straight line, the ACL is essential for any activity involving running, cutting, jumping, or twisting. A small proportion of patients may tolerate non-operative treatment for their ACL rupture, however, this treatment is generally reserved for less active individuals or ones that have no signs of instability with cutting, pivoting, or turning. The ACL stabilizes the knee and prevents repetitive shifting from instability of the knee that can cause further internal knee damage. Most active individuals are good candidates for ACL reconstruction.

Knee Stability and Anatomy

Every joint in the body has three core stabilizing components-

  • bony anatomy of the joint itself
  • peri-articular muscles
  • ligaments that restrain excessive joint movement

A well functioning healthy joint relies on all 3 to maintain stability. An ACL injury not only involves the ligamentous structure of the knee, but also impacts the muscle mass and coordination around the knee. Recovery and rehabilitation from ACL treatment must address muscle mass and coordination deficits.

Although isolated ACL injuries are the focus here, many times damage to other structures occur as well. In addition to the ACL, there are many other ligaments that help stabilize the knee. About half of ACL injuries have damage to other knee structures. Depending on what other structures are involved in the injury your proposed treatment may vary.

Collateral Ligaments

The collateral ligaments are found on the sides of the knee. The medial collateral ligament (MCL) is on the inside of the leg, and the lateral collateral ligament (LCL) is on the outside of the leg. The collateral ligaments help restrain side to side motion of the knee joint. If injured with the ACL they must be addressed otherwise the ACL treatment will fail.

Cruciate Ligaments

The cruciate ligaments are within the central part of the knee joint itself. The two cruciate ligaments cross each other to form an “X” with the anterior cruciate ligament in front and the posterior cruciate ligament in back. The cruciate ligaments restrain anterior, posterior, and rotational motion of the knee. In only the most severe ACL injuries are the anterior AND posterior cruciate ligaments affected.

Timing of Anterior Cruciate Ligament Reconstruction

Immediately after an ACL tear the instinct is to avoid weight bearing and motion of the injured knee. Knee swelling and spasm of muscles around the knee make it difficult to straighten and weight bear on the knee. Assuming there is no other injury in the knee contributing to the swelling or lack of knee motion, delaying any surgical intervention until after acute swelling has decreased and knee motion is restored is essential for a successful outcome from surgery. I tell my patients-

“Going into surgery with a stiff knee will only lead to a stiffer knee after surgery.”

Trainers or physical therapists can be enlisted for help in getting the knee swelling down and motion back in preparation for surgery. In addition to motion, muscle conditioning can be addressed immediately. Within days after an acute knee injury quadriceps atrophy begins to set in. A reoccurring theme in the human body is use it or loose it. Therefore, one important component of early ACL injury rehabilitation is promoting quadriceps neuromuscular stimulation and strengthening. Restoring natural gait and knee weight bearing with quadriceps activation is one way to help stem quadriceps atrophy and ensure smoother recovery from an ACL injury.

Once my patients have demonstrated full pain free knee range of motion and the ability to perform an almost normal gait, then only do I proceed with their ACL reconstruction. If you can maintain a less active lifestyle, and the knee is not unstable with day to day activities, one can schedule the ACL reconstruction at their convenience. Activity is restricted however until the ACL is reconstructed to avoid causing further damage to the knee.

ACL Reconstruction Surgery

After the ACL tears it does not heal itself. The remaining fragments of the ACL may scar in a new position, but without the appropriate tension the ACL is unable to provide the knee anterior and rotatory stability. Historically attempts were made to repair the torn fibers of the ACL directly with sutures and stitching. This however did not confer enough tension in the ACL and ultimately failed.

To restore knee stability, the current standard of care involves replacing your torn ligament with a substitute made of tendon. Tendon is similar in composition to ligament tissue and in this context is called a “graft”. The graft serves as a scaffold on which new ligament tissue can grow.

Types of ACL Reconstruction Grafts

ACL Graft sources (Image courtesy of orthoinfo.aaos.org)

Tissue to reconstruct the ACL can be obtained from the same knee at the time of surgery, and in some cases from the opposite knee. Common sources of graft used currently for ACL reconstruction include-

  • Patellar tendon autograft (autograft comes from the patient)
  • Hamstring tendon autograft
  • Quadriceps tendon autograft
  • Allograft (taken from a cadaver) patellar tendon, Achilles tendon, semitendinosus, gracilis, or posterior tibialis tendon

Choosing the correct graft for your reconstruction is part of the discussion when planning surgery. To learn more about the pros/cons of each graft type, and which one may be the best for you, check out my post on choosing the right ACL graft for your reconstruction.

Surgical Procedure

ACL reconstruction is an outpatient day surgery procedure. On the day of surgery you are instructed to arrive a few hours before the actual surgery. Upon arrival you visit with the anesthesiologist. If you are a candidate for a nerve block the anesthesiologist places a catheter under ultrasound guidance adjacent to your nerves. This catheter is attached to a disposable pump that continuously provides numbing medication to keep you comfortable during and after your surgery. For surgery the anesthesiologist puts you to sleep.

The surgery itself takes between 1-2 hours to complete. The video above illustrates the principal steps involved in the reconstruction. The operation is highly technical and involves sophisticated minimally invasive instruments. Autografts are first harvested through an incision made on the front of the knee. The graft is prepared for implantation. The arthroscopic camera and instruments are inserted next through two other small 1 cm incisions over the front of the knee. Several pictures are taken inside the joint of the damaged structures. Associated meniscus and cartilage injuries are trimmed or repaired and the torn ACL stump is then removed. Next bone tunnels are drilled into the tibia and the femur to place the ACL graft in the same position as the former ACL. A suture is passed through the tunnels next, and this is used to help pull the previously prepared graft through the knee to its new home. The graft is held under tension and it is fixed using specialized screws. The devices used to hold the graft in place are generally not removed. Before the surgery is complete, I verify the graft tension feels appropriate on probing, and that anterior stability of the knee is restored with the new ACL graft. The skin is closed and dressings are applied.

In the recovery area the patient is allowed to gradually wake up. Once nausea and pain are well controlled, you are sent home with the appropriate medications for pain.

Outcome

Knee stability is maintained by the anterior cruciate ligament (ACL) in conjunction with other ligaments and muscles around the joint. After an ACL rupture, not only is the ligament torn, but muscles around the knee rapidly weaken as a result of the knee trauma. Ultimately, a successful outcome from surgery depends not only on the ligament reconstruction healing, but also restoring adequate muscle strength, coordination, and balance at the knee. Patients treated with surgical reconstruction of the ACL have long-term success rates of 82-95%. Recurrent instability and graft failure are seen in approximately 3.3% of patients. Graft failure rates vary depending on the source of the tissue used to reconstruct the ACL. ACL’s reconstructed from your own patellar tendon or hamstring tendon generally have the most predictable outcomes. Some studies suggest the patellar tendon graft may have a slightly lower failure rate than the hamstring tendon graft, however, patellar tendon grafts have a greater rate of postoperative patellofemoral pain (pain behind the kneecap). While in some circumstances a graft for ACL reconstruction from a cadaver may be considered, using your own tissue is more reliable and usually the first preference.

Recovery

The rehabilitation and physiotherapy after anterior cruciate ligament (ACL) reconstruction is long, grueling, and often harder than the actual surgery itself. Complete recovery from surgery can take well over a year. For the first two weeks after surgery we recommend avoiding strenuous activities and limiting activity. The initial emphasis of rehabilitation is restoration of knee motion and normal walking. Swelling usually persists up to 6 weeks after surgery. At 4-6 weeks after surgery strengthening of the knee is started. Jogging is permitted at approximately 2 months after surgery. Between 4-6 months after surgery agility drills and sports specific exercises are incorporated. Clearance for sports participation can be expected about 6-9 months after surgery. Improvement in knee function continues for up to a year after surgery as strength, agility, and neuromuscular control improve with increased sports participation. Patience and consistent physical therapy is critical for successful return to sport and stability of the knee.

Risks

Arthroscopic ACL reconstruction surgery is safe, with minimal complications. Risks of surgery include:

  • ACL re-rupture- 5-20% re-rupture rate, depends on graft type for ACL reconstruction; lowest rate of revision with autograft tissue compared to ACLs reconstructed with allograft cadaver tissue
  • Stiffness- Some patients in spite of aggressive physical therapy after surgery may produce more scar tissue than average leading to stiffness. If by 6 weeks after surgery knee motion is not restored may have to consider arthroscopic surgery to remove the scar tissue.
  • Anterior knee pain- Some patients may experience persistent soreness on the front of their knee from where the ACL graft was taken for surgery. Patients that have to kneel frequently for their occupation or praying may want to consider an alternative graft source such as the hamstring tendons.
  • Graft loosening- On rare occasion hardware used to secure the reconstructed graft can fail or loosen prematurely. This may require a subsequent surgery to re-tension/tighten the graft.
  • Infection- The incidence of superficial (skin) and deep (joint) infection is <0.5%. Steps are taken at time of surgery to minimize the risk of infection including peri-operative intravenous antibiotic administration, aseptic skin preparation/cleaning, and observation of stringent sterile surgical protocols. In the unlikely event of infection oral antibiotics or even additional surgery may be necessary to wash and eradicate any infectious organisms such as bacteria.
  • Blood clots- Deep vein thrombosis or blood clots are uncommon after arthroscopic surgery. Please let our office know if you have a previous history or family history of blood clots that may increase your risk of developing them. In the unlikely event of a blood clot, blood thinners will be prescribed for a period of time to prevent the clot from propagating.
  • Temporary nerve irritation- Small sensory nerves at the skin level sometimes cannot be avoided when making incisions for the surgery. This can result in a small numb patch adjacent to the surgical incisions and rarely, nerve irritation and pain near the incisions.
  • Swelling- Persistent swelling or fluid in the joint may require aspiration (removal) in the office postoperatively.

Extremely rare but serious complications from Arthroscopic ACL reconstruction include:

  • Patella fracture- Rare complication that can occur during surgery when obtaining the ACL graft from the patellar tendon or in rehabilitation from a weakened patella. Most often the fracture (or bone break) remains non-displaced and can be treated with immobilization of the knee locked in full extension for 4 weeks. While this delays the ACL rehabilitation schedule, the ultimate outcome is generally unaffected.
  • Bleeding- There are no major blood vessels typically encountered during this surgery. If a major injury to the blood vessels in the back of the knee occurred, a vascular repair by a vascular surgeon is required with a subsequent hospitalization. Very rarely, vascular injuries have resulted in an amputation of the extremity.
  • Permanent nerve damage- No major nerves are typically encountered during this surgery, however, rare but serious injuries to the saphenous and common peroneal nerves have been reported. The saphenous nerve runs along the inner aspect of the knee. Permanent injury would result in numbness along the side of the lower leg into foot area. The common peroneal nerve courses around the outside of the knee and provides protective sensation and control of muscles that raise our foot and ankle. If this nerve is injured a “foot drop” occurs and would require a brace and/or surgery.
  • Pulmonary embolus- When a blood clot develops in the lungs, it results in difficulty breathing, rapid heart rate, and in rare situations, sudden death.
  • Broken instruments- This is an extremely rare occurence. Most often the broken piece is recovered from the joint uneventfully. Sometimes the arthroscopic surgery has to be converted to an open surgery with a larger surgical incision to allow safe removal of the broken instrument.
  • Fistula- This is a rare complication that occurs when the skin wound incompletely heals and knee fluid leaks from the joint.
  • Pain- Pain is anticipated after surgery and is managed using medication, local numbing medication, cold compressess, and injections after surgery. While the majority of people get relief after recovering from surgery, in rare circumstances, complex regional pain syndrome may develop. Treatment for this could entail referral to a pain clinic, prolonged rehabilitation, and spinal injections.
  • Compartment syndrome- This rare complication occurs when fluid leaks out of the joint into the muscle compartment(s). Massive swelling could result in compromise of the neurovascular structures. If this were suspected emergency surgical decompression of the muscular compartments are required.
  • Anesthesia complications- To ensure anesthesia is safe we will discuss health risks in advance with anesthesia and other specialists as needed. Anesthesia can put stress on your heart and lungs and increase the risk of heart attack, respiratory failure, and even death. Permanent nerve damage from nerve blocks is exceedingly rare, but can cause paralysis, pain, or sensory distrubances in the operative extremity.

Sources:

http://www.ncbi.nlm.nih.gov/pubmed/15572332

http://www.ncbi.nlm.nih.gov/pubmed/12531750

http://www.ncbi.nlm.nih.gov/pubmed/11912091

http://orthoinfo.aaos.org/topic.cfm?topic=a00297

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