Anterior cruciate ligament reconstruction

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Knees following ACL reconstruction surgery. A patellar tendon graft was used. Discoloration of the left leg is from swelling that drained from the knee to the shin.
Knees following ACL reconstruction surgery. A patellar tendon graft was used. Discoloration of the left leg is from swelling that drained from the knee to the shin.

Anterior cruciate ligament reconstruction (ACL reconstruction) is surgical graft replacement of a torn anterior cruciate ligament in the knee. Because the ACL does not heal on its own, an ACL reconstruction requires a tissue graft. The torn ligament is removed from the knee before the graft is inserted. The types of surgery differ mainly in the type of graft that is used. In all cases, the surgery is done arthroscopically.

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[edit] Types of grafts

[edit] Patellar tendon

The patellar tendon connects the patella (kneecap) to the tibia (shin). Generally 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 on each end removed. 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. more wound pain , 2. more prominent scar as compared to hamstring tendon operation , 3. risk of fracture of patella during harvesting of this graft resulting in significant complication , 4. increased risk of tendinitis.

[edit] Hamstring tendon

For this procedure, the gracilis and semitendinosus tendons from the hamstring of the injured knee are the source of the graft. A long piece (about 25 cm) is removed from each of two tendons. The tendon segments are folded and braided together to form a quadruple thickness strand for the replacement graft. The braided segment is threaded through the heads of tibia and femur and its ends fixated with screws on the opposite sides of the two bones.

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[citation needed].

This main surgical wound is over the upper proximal shin which would avoid the typical pain sensation when one kneel down. Besides, the wound is typically smaller than the patellar tendon graft and hence less pain after the operation. As a result, patient undergone this operation typically discharge from hospital within 2 days after surgery.

[edit] Allograft

An ACL, patellar tendon, or achilles tendon may be harvested from a cadaver and used as an allograft in reconstruction. The achilles tendon is so large it needs to be shaved to fit within the cavity inside the knee. This method has the benefit that the most painful part of the surgery, the harvesting of tendon tissue, is avoided. However, there is a slight chance of rejection which would lead to another surgery to remove the graft and replace it again. Allografts are often irradiated to remove infectious agents. There is a risk of weakening the selected tendon, although for ACL surgery the weakened tendon is still as strong or about as strong as the ligament being replaced. [1] Even with the extensive and redundant screening process for donor grafts, there is still a risk of infection, which would be grounds to remove the graft. Therefore, this option runs the largest health risk.

[edit] Choice of Graft

No ideal graft for ACL reconstruction exists. All graft choices have advantages and disadvantages. Patella tendon grafts are still considered the historical "gold standard" for knee stability by surgeons, however they suffer a slightly higher complication rate. Hamstring grafts had initial problems with fixation slippage. Modern fixation methods of hamstrings avoid graft slippage, producing outcomes that are the same in terms of knee stability with easier rehabilitation, less anterior knee pain and less joint stiffness. The main factors in knee stability are correct graft placement by the surgeon and treatment of other menisco-ligament injuries in the knee, rather than choice of graft.

[edit] Recovery

All surgeries have a similar long-term recovery time frame. After surgery, motion of the knee joint recovers fairly quickly. Initial therapy consists of range of motion exercises, often with the guidance of a physical therapist, to regain the flexibility and prevent scar tissue from forming, and simple exercises to reduce loss of muscle (for example, quadriceps contractions, and straight leg raises). Often a continuous passive motion machine is used immediately after surgery to help with flexibility; and the preferred method of preventing muscle loss is isometric exercises that put no strain on the knee.

About six weeks are 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 back.

One of the more important benchmarks in recovery is the 12 weeks period. After this the patient can typically begin a more aggressive regimine of exercises involving stress on the knee, and increasing resistance. Jogging is often incorporated at or around this time.

After four months, more intense activities such as running are possible without risk. 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. Statistically, it does not appear to matter if the patient uses a brace after recovery. A sufficiently traumatic impact to retear the ACL is unlikely to be mitigated by the use of a brace.

[edit] Future Treatments

Like any other ligament of the human body when the ACL gets torn a blood clot is formed. In other ligaments this blood clot would be used by the cells as a bridge that would connect the ligament ends together and would help to heal the ligament.The same would apply for the ACL if it weren't for the knee fluids that dissolve the blood clots. Even though ACL cells try to repair the damage there is no "bridge" for them to use and as a result a tissue graft is required to replace the damaged ACL.

Martha Murray an orthopedic surgeon after various failed trials managed to find a collagen hydrogel which mixed with platelet-rich blood plasma can be used from the human body as that bridge that was missing in order for the ACL to heal itself.

Even though ACL cells are happy to participate in the repair process, there's no place for them to do it," Murray says. "Our big finding was recognizing that the cells are fine--they just need a bridge that they like."

Murray has used this method with success on animals.Knees that were treated with the collagen had a 40 % increase in mechanical strenth compared to the 14 for untreated defects in a period of six weeks

She claims that her arthroscopic approach will insert the gel into the wound using two small knee-incisions.This arthroscopic procedure will be a lot less traumatic for the joint compared to the existing ACL reconstruction treatments as a result recovery time will be severely decreased. She has yet to perform such an operation on a human subject though.

Murray's work is funded by the National Football League, the Orthopedic Research and Education FOundation and the Center for minimally invasice Technology.

[edit] References

[edit] External links

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