CPT Code: 29888
Anterior cruciate ligament reconstruction (ACL reconstruction) is a surgical tissue graft replacement of the anterior cruciate ligament, located in the knee, to restore its function after anterior cruciate ligament injury. The torn ligament is removed from the knee before the graft is inserted through a hole created by a single hole punch. The surgery is performed arthroscopically.
An ACL reconstruction is sometimes referred to, incorrectly, as an ACL repair. A torn anterior cruciate ligament cannot be “repaired”, and must instead be reconstructed with a tissue graft replacement.
Two alternative sources of replacement material for ACL reconstruction are commonly utilized:
- Autografts (employing bone or tissue harvested from the patient’s body), and
- Allografts (using bone or tissue from a donor’s body, typically a cadaver’s or a live donor).
Since the tissue is one’s own in an autograft the probability of rejection (sans infection) is minimal.
Sterilization and redundant donor screening process make allografts a generally safe choice for patients; however, risks remain. Irradiation of donor content to remove infectious agents potentially weakens the selected tendon, although for ACL surgery the weakened tendon is generally as strong as the replaced ligament. Infection may also require removal of the graft.
- Synthetic tissue tissue suitable to ACL reconstruction has also been developed. Few data exist on its strength or reliability.
The patellar tendon, anterior tibialis tendon, or Achilles tendon may be recovered from a cadaver and used as an allograft in reconstruction. The Achilles tendon, due to its large size, must be shaved to fit within the joint cavity. There is a slight chance of rejection, which would lead to more surgery to remove the graft and replace it.
An accessory hamstring or part of the patellar tendon are the most common donor tissues used in autografts.
Unlike the patellar tendon, the hamstring tendon’s fixation to the bone can be affected by motion in the post-operative phase. Therefore, following surgery, a brace is often used to immobilize the knee for one to two weeks while the most critical healing takes place. Evidence suggests that the hamstring tendon graft does just as well, or nearly as well, as the patellar tendon graft in the long-term.
Many patients struggle with recovery after a hamstring graft procedure. Problems include strengthening of the quadriceps, T-band and calf. Proper healing procedures and medical care (physical therapy) are essential to regain strength.
The main surgical wound is over the upper proximal tibia, avoiding the typical pain sensation when one kneels down. The wound is typically smaller than the patellar tendon graft and hence less pain after the operation. A new technique for minimal-invasive harvesting from the back of the knee has been developed in the last years. This technique is faster, easier and produces a significantly smaller wound. his procedure is typically an outpatient procedure.
There seems to be some controversy as to how well a hamstring tendon regenerates after the harvesting. Most studies suggest that the tendon can be regenerated at least partially, while still being inferior in strength to the original tendon.
The patellar tendon connects the patella (kneecap) to the tibia (shin). The graft is taken from the injured knee, but in some circumstances, such as a second operation, the other knee may be used. The middle third of the tendon is used, with bone fragments removed on each end. The graft is then threaded through holes drilled in the tibia and femur, and finally screwed into place.
The graft is slightly larger than a hamstring graft, however graft size is not a determinant of outcome. The most important factor in determining the outcome is correct graft placement.
The disadvantages include: 1. Increased wound pain. 2. Increased scar formation as compared to a hamstring tendon operation. 3. Risk of fracturing the patella during harvesting of the graft. 4. Increased risk of tendinitis. 5. Increased levels of pain with activities that require kneeling years after post op.
Choice of graft
Typically, age and lifestyle choices help decide the type of graft to be used for ACL reconstruction. The overall factors in knee stability are correct graft placement by the surgeon and treatment of other menisco-ligament injuries in the knee, rather than type of graft.
The advantage of an allograft is the patient does not sustain additional injury through removing a tendon, thus making it faster to recover. Disadvantage are the risk of infection from foreign bodily materials and a typically slightly weaker graft.
No ideal graft site for ACL reconstruction exists. Surgeons have historically regarded patella tendon grafts as the “gold standard” for knee stability, however the procedure suffers a slightly higher complication rate, including knee pain when lunging.
Hamstring grafts historically had problems with fixation slippage and stretching out over time. Modern fixation methods avoid graft slippage produce similarly stable outcomes with easier rehabilitation, less anterior knee pain and less joint stiffness.
Initial physical therapy consists of range of motion (ROM) exercises, often with the guidance of a physical therapist. Range of motion exercises are used to regain the flexibility of the ligament, prevent or break down scar tissue from forming and reduce loss of muscle tone. Range of motion exercise examples include: quadriceps contractions and straight leg raises. In some cases, a continuous passive motion (CPM) device is used immediately after surgery to help with flexibility. The preferred method of preventing muscle loss is isometric exercises that put zero strain on the knee. Knee extension within two weeks is important with many rehab guidelines.
Approximately six weeks is required for the bone to attach to the graft. However, the patient can typically walk on their own and perform simple physical tasks prior to this with caution, relying on the surgical fixation of the graft until true healing (graft attachment to bone) has taken place. At this stage the first round of physical therapy can begin. This usually consists of careful exercises to regain flexibility and small amounts of strength. One of the more important benchmarks in recovery is the twelve weeks post-surgery period. After this, the patient can typically begin a more aggressive regimen of exercises involving stress on the knee, and increasing resistance. Jogging may be incorporated as well.
After four months, more intense activities such as running are possible without risk. After five months, light ball work may commence as the ligament is nearly regenerated. After six months, the reconstructed ACL is generally at full strength (ligament tissue has fully regrown), and the patient may return to activities involving cutting and twisting if a brace is worn. Recovery varies highly from case to case, and sometimes resumption of stressful activities may take a year or longer.
The reconstructed ACL has a high success rate. Studies show that cases in which the ACL retears are generally caused by a traumatic impact. Some studies indicate that wearing a brace during athletic activity does not reduce probability of re-injury to the ACL&llt;sup>, but a study of active post-ACL replacement skiers shows a 300% reduction in re-injury likelihood by using a knee brace after recovery. A sufficiently traumatic impact to retear the ACL is unlikely to be mitigated by the use of a brace.[citation